Vendor dependencies for 0.3.0 release

vendor/cpal/src/error.rs

@@ -0,0 +1,292 @@
+use std::error::Error;
+use std::fmt::{Display, Formatter};
+
+/// The requested host, although supported on this platform, is unavailable.
+#[derive(Copy, Clone, Debug)]
+pub struct HostUnavailable;
+
+impl Display for HostUnavailable {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        f.write_str("the requested host is unavailable")
+    }
+}
+
+impl Error for HostUnavailable {}
+
+/// Some error has occurred that is specific to the backend from which it was produced.
+///
+/// This error is often used as a catch-all in cases where:
+///
+/// - It is unclear exactly what error might be produced by the backend API.
+/// - It does not make sense to add a variant to the enclosing error type.
+/// - No error was expected to occur at all, but we return an error to avoid the possibility of a
+///   `panic!` caused by some unforeseen or unknown reason.
+///
+/// **Note:** If you notice a `BackendSpecificError` that you believe could be better handled in a
+/// cross-platform manner, please create an issue or submit a pull request with a patch that adds
+/// the necessary error variant to the appropriate error enum.
+#[derive(Clone, Debug)]
+pub struct BackendSpecificError {
+    pub description: String,
+}
+
+impl Display for BackendSpecificError {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        write!(
+            f,
+            "A backend-specific error has occurred: {}",
+            self.description
+        )
+    }
+}
+
+impl Error for BackendSpecificError {}
+
+/// An error that might occur while attempting to enumerate the available devices on a system.
+#[derive(Clone, Debug)]
+pub enum DevicesError {
+    /// See the [`BackendSpecificError`] docs for more information about this error variant.
+    BackendSpecific { err: BackendSpecificError },
+}
+
+impl Display for DevicesError {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Self::BackendSpecific { err } => err.fmt(f),
+        }
+    }
+}
+
+impl Error for DevicesError {}
+
+impl From<BackendSpecificError> for DevicesError {
+    fn from(err: BackendSpecificError) -> Self {
+        Self::BackendSpecific { err }
+    }
+}
+
+/// An error that may occur while attempting to retrieve a device name.
+#[derive(Clone, Debug)]
+pub enum DeviceNameError {
+    /// See the [`BackendSpecificError`] docs for more information about this error variant.
+    BackendSpecific { err: BackendSpecificError },
+}
+
+impl Display for DeviceNameError {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Self::BackendSpecific { err } => err.fmt(f),
+        }
+    }
+}
+
+impl Error for DeviceNameError {}
+
+impl From<BackendSpecificError> for DeviceNameError {
+    fn from(err: BackendSpecificError) -> Self {
+        Self::BackendSpecific { err }
+    }
+}
+
+/// Error that can happen when enumerating the list of supported formats.
+#[derive(Debug)]
+pub enum SupportedStreamConfigsError {
+    /// The device no longer exists. This can happen if the device is disconnected while the
+    /// program is running.
+    DeviceNotAvailable,
+    /// We called something the C-Layer did not understand
+    InvalidArgument,
+    /// See the [`BackendSpecificError`] docs for more information about this error variant.
+    BackendSpecific { err: BackendSpecificError },
+}
+
+impl Display for SupportedStreamConfigsError {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Self::BackendSpecific { err } => err.fmt(f),
+            Self::DeviceNotAvailable => f.write_str("The requested device is no longer available. For example, it has been unplugged."),
+            Self::InvalidArgument => f.write_str("Invalid argument passed to the backend. For example, this happens when trying to read capture capabilities when the device does not support it.")
+        }
+    }
+}
+
+impl Error for SupportedStreamConfigsError {}
+
+impl From<BackendSpecificError> for SupportedStreamConfigsError {
+    fn from(err: BackendSpecificError) -> Self {
+        Self::BackendSpecific { err }
+    }
+}
+
+/// May occur when attempting to request the default input or output stream format from a [`Device`](crate::Device).
+#[derive(Debug)]
+pub enum DefaultStreamConfigError {
+    /// The device no longer exists. This can happen if the device is disconnected while the
+    /// program is running.
+    DeviceNotAvailable,
+    /// Returned if e.g. the default input format was requested on an output-only audio device.
+    StreamTypeNotSupported,
+    /// See the [`BackendSpecificError`] docs for more information about this error variant.
+    BackendSpecific { err: BackendSpecificError },
+}
+
+impl Display for DefaultStreamConfigError {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Self::BackendSpecific { err } => err.fmt(f),
+            DefaultStreamConfigError::DeviceNotAvailable => f.write_str(
+                "The requested device is no longer available. For example, it has been unplugged.",
+            ),
+            DefaultStreamConfigError::StreamTypeNotSupported => {
+                f.write_str("The requested stream type is not supported by the device.")
+            }
+        }
+    }
+}
+
+impl Error for DefaultStreamConfigError {}
+
+impl From<BackendSpecificError> for DefaultStreamConfigError {
+    fn from(err: BackendSpecificError) -> Self {
+        Self::BackendSpecific { err }
+    }
+}
+/// Error that can happen when creating a [`Stream`](crate::Stream).
+#[derive(Debug)]
+pub enum BuildStreamError {
+    /// The device no longer exists. This can happen if the device is disconnected while the
+    /// program is running.
+    DeviceNotAvailable,
+    /// The specified stream configuration is not supported.
+    StreamConfigNotSupported,
+    /// We called something the C-Layer did not understand
+    ///
+    /// On ALSA device functions called with a feature they do not support will yield this. E.g.
+    /// Trying to use capture capabilities on an output only format yields this.
+    InvalidArgument,
+    /// Occurs if adding a new Stream ID would cause an integer overflow.
+    StreamIdOverflow,
+    /// See the [`BackendSpecificError`] docs for more information about this error variant.
+    BackendSpecific { err: BackendSpecificError },
+}
+
+impl Display for BuildStreamError {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Self::BackendSpecific { err } => err.fmt(f),
+            BuildStreamError::DeviceNotAvailable => f.write_str(
+                "The requested device is no longer available. For example, it has been unplugged.",
+            ),
+            BuildStreamError::StreamConfigNotSupported => {
+                f.write_str("The requested stream configuration is not supported by the device.")
+            }
+            BuildStreamError::InvalidArgument => f.write_str(
+                "The requested device does not support this capability (invalid argument)",
+            ),
+            BuildStreamError::StreamIdOverflow => {
+                f.write_str("Adding a new stream ID would cause an overflow")
+            }
+        }
+    }
+}
+
+impl Error for BuildStreamError {}
+
+impl From<BackendSpecificError> for BuildStreamError {
+    fn from(err: BackendSpecificError) -> Self {
+        Self::BackendSpecific { err }
+    }
+}
+
+/// Errors that might occur when calling [`Stream::play()`](crate::traits::StreamTrait::play).
+///
+/// As of writing this, only macOS may immediately return an error while calling this method. This
+/// is because both the alsa and wasapi backends only enqueue these commands and do not process
+/// them immediately.
+#[derive(Debug)]
+pub enum PlayStreamError {
+    /// The device associated with the stream is no longer available.
+    DeviceNotAvailable,
+    /// See the [`BackendSpecificError`] docs for more information about this error variant.
+    BackendSpecific { err: BackendSpecificError },
+}
+
+impl Display for PlayStreamError {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Self::BackendSpecific { err } => err.fmt(f),
+            PlayStreamError::DeviceNotAvailable => {
+                f.write_str("the device associated with the stream is no longer available")
+            }
+        }
+    }
+}
+
+impl Error for PlayStreamError {}
+
+impl From<BackendSpecificError> for PlayStreamError {
+    fn from(err: BackendSpecificError) -> Self {
+        Self::BackendSpecific { err }
+    }
+}
+
+/// Errors that might occur when calling [`Stream::pause()`](crate::traits::StreamTrait::pause).
+///
+/// As of writing this, only macOS may immediately return an error while calling this method. This
+/// is because both the alsa and wasapi backends only enqueue these commands and do not process
+/// them immediately.
+#[derive(Debug)]
+pub enum PauseStreamError {
+    /// The device associated with the stream is no longer available.
+    DeviceNotAvailable,
+    /// See the [`BackendSpecificError`] docs for more information about this error variant.
+    BackendSpecific { err: BackendSpecificError },
+}
+
+impl Display for PauseStreamError {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Self::BackendSpecific { err } => err.fmt(f),
+            PauseStreamError::DeviceNotAvailable => {
+                f.write_str("the device associated with the stream is no longer available")
+            }
+        }
+    }
+}
+
+impl Error for PauseStreamError {}
+
+impl From<BackendSpecificError> for PauseStreamError {
+    fn from(err: BackendSpecificError) -> Self {
+        Self::BackendSpecific { err }
+    }
+}
+
+/// Errors that might occur while a stream is running.
+#[derive(Debug)]
+pub enum StreamError {
+    /// The device no longer exists. This can happen if the device is disconnected while the
+    /// program is running.
+    DeviceNotAvailable,
+    /// See the [`BackendSpecificError`] docs for more information about this error variant.
+    BackendSpecific { err: BackendSpecificError },
+}
+
+impl Display for StreamError {
+    fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Self::BackendSpecific { err } => err.fmt(f),
+            StreamError::DeviceNotAvailable => f.write_str(
+                "The requested device is no longer available. For example, it has been unplugged.",
+            ),
+        }
+    }
+}
+
+impl Error for StreamError {}
+
+impl From<BackendSpecificError> for StreamError {
+    fn from(err: BackendSpecificError) -> Self {
+        Self::BackendSpecific { err }
+    }
+}

vendor/cpal/src/host/alsa/enumerate.rs

@@ -0,0 +1,70 @@
+use super::alsa;
+use super::{Device, DeviceHandles};
+use crate::{BackendSpecificError, DevicesError};
+use std::sync::{Arc, Mutex};
+
+/// ALSA's implementation for `Devices`.
+pub struct Devices {
+    hint_iter: alsa::device_name::HintIter,
+}
+
+impl Devices {
+    pub fn new() -> Result<Self, DevicesError> {
+        Ok(Devices {
+            hint_iter: alsa::device_name::HintIter::new_str(None, "pcm")?,
+        })
+    }
+}
+
+unsafe impl Send for Devices {}
+unsafe impl Sync for Devices {}
+
+impl Iterator for Devices {
+    type Item = Device;
+
+    fn next(&mut self) -> Option<Device> {
+        loop {
+            match self.hint_iter.next() {
+                None => return None,
+                Some(hint) => {
+                    let name = match hint.name {
+                        None => continue,
+                        // Ignoring the `null` device.
+                        Some(name) if name == "null" => continue,
+                        Some(name) => name,
+                    };
+
+                    if let Ok(handles) = DeviceHandles::open(&name) {
+                        return Some(Device {
+                            name,
+                            handles: Arc::new(Mutex::new(handles)),
+                        });
+                    }
+                }
+            }
+        }
+    }
+}
+
+#[inline]
+pub fn default_input_device() -> Option<Device> {
+    Some(Device {
+        name: "default".to_owned(),
+        handles: Arc::new(Mutex::new(Default::default())),
+    })
+}
+
+#[inline]
+pub fn default_output_device() -> Option<Device> {
+    Some(Device {
+        name: "default".to_owned(),
+        handles: Arc::new(Mutex::new(Default::default())),
+    })
+}
+
+impl From<alsa::Error> for DevicesError {
+    fn from(err: alsa::Error) -> Self {
+        let err: BackendSpecificError = err.into();
+        err.into()
+    }
+}

vendor/cpal/src/host/asio/device.rs

@@ -0,0 +1,232 @@
+pub type SupportedInputConfigs = std::vec::IntoIter<SupportedStreamConfigRange>;
+pub type SupportedOutputConfigs = std::vec::IntoIter<SupportedStreamConfigRange>;
+
+use super::sys;
+use crate::BackendSpecificError;
+use crate::DefaultStreamConfigError;
+use crate::DeviceNameError;
+use crate::DevicesError;
+use crate::SampleFormat;
+use crate::SampleRate;
+use crate::SupportedBufferSize;
+use crate::SupportedStreamConfig;
+use crate::SupportedStreamConfigRange;
+use crate::SupportedStreamConfigsError;
+use std::hash::{Hash, Hasher};
+use std::sync::atomic::AtomicI32;
+use std::sync::{Arc, Mutex};
+
+/// A ASIO Device
+#[derive(Clone)]
+pub struct Device {
+    /// The driver represented by this device.
+    pub driver: Arc<sys::Driver>,
+
+    // Input and/or Output stream.
+    // A driver can only have one of each.
+    // They need to be created at the same time.
+    pub asio_streams: Arc<Mutex<sys::AsioStreams>>,
+    pub current_buffer_index: Arc<AtomicI32>,
+}
+
+/// All available devices.
+pub struct Devices {
+    asio: Arc<sys::Asio>,
+    drivers: std::vec::IntoIter<String>,
+}
+
+impl PartialEq for Device {
+    fn eq(&self, other: &Self) -> bool {
+        self.driver.name() == other.driver.name()
+    }
+}
+
+impl Eq for Device {}
+
+impl Hash for Device {
+    fn hash<H: Hasher>(&self, state: &mut H) {
+        self.driver.name().hash(state);
+    }
+}
+
+impl Device {
+    pub fn name(&self) -> Result<String, DeviceNameError> {
+        Ok(self.driver.name().to_string())
+    }
+
+    /// Gets the supported input configs.
+    /// TODO currently only supports the default.
+    /// Need to find all possible configs.
+    pub fn supported_input_configs(
+        &self,
+    ) -> Result<SupportedInputConfigs, SupportedStreamConfigsError> {
+        // Retrieve the default config for the total supported channels and supported sample
+        // format.
+        let f = match self.default_input_config() {
+            Err(_) => return Err(SupportedStreamConfigsError::DeviceNotAvailable),
+            Ok(f) => f,
+        };
+
+        // Collect a config for every combination of supported sample rate and number of channels.
+        let mut supported_configs = vec![];
+        for &rate in crate::COMMON_SAMPLE_RATES {
+            if !self
+                .driver
+                .can_sample_rate(rate.0.into())
+                .ok()
+                .unwrap_or(false)
+            {
+                continue;
+            }
+            for channels in 1..f.channels + 1 {
+                supported_configs.push(SupportedStreamConfigRange {
+                    channels,
+                    min_sample_rate: rate,
+                    max_sample_rate: rate,
+                    buffer_size: f.buffer_size,
+                    sample_format: f.sample_format,
+                })
+            }
+        }
+        Ok(supported_configs.into_iter())
+    }
+
+    /// Gets the supported output configs.
+    /// TODO currently only supports the default.
+    /// Need to find all possible configs.
+    pub fn supported_output_configs(
+        &self,
+    ) -> Result<SupportedOutputConfigs, SupportedStreamConfigsError> {
+        // Retrieve the default config for the total supported channels and supported sample
+        // format.
+        let f = match self.default_output_config() {
+            Err(_) => return Err(SupportedStreamConfigsError::DeviceNotAvailable),
+            Ok(f) => f,
+        };
+
+        // Collect a config for every combination of supported sample rate and number of channels.
+        let mut supported_configs = vec![];
+        for &rate in crate::COMMON_SAMPLE_RATES {
+            if !self
+                .driver
+                .can_sample_rate(rate.0.into())
+                .ok()
+                .unwrap_or(false)
+            {
+                continue;
+            }
+            for channels in 1..f.channels + 1 {
+                supported_configs.push(SupportedStreamConfigRange {
+                    channels,
+                    min_sample_rate: rate,
+                    max_sample_rate: rate,
+                    buffer_size: f.buffer_size,
+                    sample_format: f.sample_format,
+                })
+            }
+        }
+        Ok(supported_configs.into_iter())
+    }
+
+    /// Returns the default input config
+    pub fn default_input_config(&self) -> Result<SupportedStreamConfig, DefaultStreamConfigError> {
+        let channels = self.driver.channels().map_err(default_config_err)?.ins as u16;
+        let sample_rate = SampleRate(self.driver.sample_rate().map_err(default_config_err)? as _);
+        let (min, max) = self.driver.buffersize_range().map_err(default_config_err)?;
+        let buffer_size = SupportedBufferSize::Range {
+            min: min as u32,
+            max: max as u32,
+        };
+        // Map th ASIO sample type to a CPAL sample type
+        let data_type = self.driver.input_data_type().map_err(default_config_err)?;
+        let sample_format = convert_data_type(&data_type)
+            .ok_or(DefaultStreamConfigError::StreamTypeNotSupported)?;
+        Ok(SupportedStreamConfig {
+            channels,
+            sample_rate,
+            buffer_size,
+            sample_format,
+        })
+    }
+
+    /// Returns the default output config
+    pub fn default_output_config(&self) -> Result<SupportedStreamConfig, DefaultStreamConfigError> {
+        let channels = self.driver.channels().map_err(default_config_err)?.outs as u16;
+        let sample_rate = SampleRate(self.driver.sample_rate().map_err(default_config_err)? as _);
+        let (min, max) = self.driver.buffersize_range().map_err(default_config_err)?;
+        let buffer_size = SupportedBufferSize::Range {
+            min: min as u32,
+            max: max as u32,
+        };
+        let data_type = self.driver.output_data_type().map_err(default_config_err)?;
+        let sample_format = convert_data_type(&data_type)
+            .ok_or(DefaultStreamConfigError::StreamTypeNotSupported)?;
+        Ok(SupportedStreamConfig {
+            channels,
+            sample_rate,
+            buffer_size,
+            sample_format,
+        })
+    }
+}
+
+impl Devices {
+    pub fn new(asio: Arc<sys::Asio>) -> Result<Self, DevicesError> {
+        let drivers = asio.driver_names().into_iter();
+        Ok(Devices { asio, drivers })
+    }
+}
+
+impl Iterator for Devices {
+    type Item = Device;
+
+    /// Load drivers and return device
+    fn next(&mut self) -> Option<Device> {
+        loop {
+            match self.drivers.next() {
+                Some(name) => match self.asio.load_driver(&name) {
+                    Ok(driver) => {
+                        let driver = Arc::new(driver);
+                        let asio_streams = Arc::new(Mutex::new(sys::AsioStreams {
+                            input: None,
+                            output: None,
+                        }));
+                        return Some(Device {
+                            driver,
+                            asio_streams,
+                            current_buffer_index: Arc::new(AtomicI32::new(-1)),
+                        });
+                    }
+                    Err(_) => continue,
+                },
+                None => return None,
+            }
+        }
+    }
+}
+
+pub(crate) fn convert_data_type(ty: &sys::AsioSampleType) -> Option<SampleFormat> {
+    let fmt = match *ty {
+        sys::AsioSampleType::ASIOSTInt16MSB => SampleFormat::I16,
+        sys::AsioSampleType::ASIOSTInt16LSB => SampleFormat::I16,
+        sys::AsioSampleType::ASIOSTFloat32MSB => SampleFormat::F32,
+        sys::AsioSampleType::ASIOSTFloat32LSB => SampleFormat::F32,
+        sys::AsioSampleType::ASIOSTInt32MSB => SampleFormat::I32,
+        sys::AsioSampleType::ASIOSTInt32LSB => SampleFormat::I32,
+        _ => return None,
+    };
+    Some(fmt)
+}
+
+fn default_config_err(e: sys::AsioError) -> DefaultStreamConfigError {
+    match e {
+        sys::AsioError::NoDrivers | sys::AsioError::HardwareMalfunction => {
+            DefaultStreamConfigError::DeviceNotAvailable
+        }
+        sys::AsioError::NoRate => DefaultStreamConfigError::StreamTypeNotSupported,
+        err => {
+            let description = format!("{}", err);
+            BackendSpecificError { description }.into()
+        }
+    }
+}

vendor/cpal/src/host/asio/mod.rs

@@ -0,0 +1,138 @@
+extern crate asio_sys as sys;
+
+use crate::traits::{DeviceTrait, HostTrait, StreamTrait};
+use crate::{
+    BuildStreamError, Data, DefaultStreamConfigError, DeviceNameError, DevicesError,
+    InputCallbackInfo, OutputCallbackInfo, PauseStreamError, PlayStreamError, SampleFormat,
+    StreamConfig, StreamError, SupportedStreamConfig, SupportedStreamConfigsError,
+};
+
+pub use self::device::{Device, Devices, SupportedInputConfigs, SupportedOutputConfigs};
+pub use self::stream::Stream;
+use std::sync::Arc;
+use std::time::Duration;
+
+mod device;
+mod stream;
+
+/// The host for ASIO.
+#[derive(Debug)]
+pub struct Host {
+    asio: Arc<sys::Asio>,
+}
+
+impl Host {
+    pub fn new() -> Result<Self, crate::HostUnavailable> {
+        let asio = Arc::new(sys::Asio::new());
+        let host = Host { asio };
+        Ok(host)
+    }
+}
+
+impl HostTrait for Host {
+    type Devices = Devices;
+    type Device = Device;
+
+    fn is_available() -> bool {
+        true
+        //unimplemented!("check how to do this using asio-sys")
+    }
+
+    fn devices(&self) -> Result<Self::Devices, DevicesError> {
+        Devices::new(self.asio.clone())
+    }
+
+    fn default_input_device(&self) -> Option<Self::Device> {
+        // ASIO has no concept of a default device, so just use the first.
+        self.input_devices().ok().and_then(|mut ds| ds.next())
+    }
+
+    fn default_output_device(&self) -> Option<Self::Device> {
+        // ASIO has no concept of a default device, so just use the first.
+        self.output_devices().ok().and_then(|mut ds| ds.next())
+    }
+}
+
+impl DeviceTrait for Device {
+    type SupportedInputConfigs = SupportedInputConfigs;
+    type SupportedOutputConfigs = SupportedOutputConfigs;
+    type Stream = Stream;
+
+    fn name(&self) -> Result<String, DeviceNameError> {
+        Device::name(self)
+    }
+
+    fn supported_input_configs(
+        &self,
+    ) -> Result<Self::SupportedInputConfigs, SupportedStreamConfigsError> {
+        Device::supported_input_configs(self)
+    }
+
+    fn supported_output_configs(
+        &self,
+    ) -> Result<Self::SupportedOutputConfigs, SupportedStreamConfigsError> {
+        Device::supported_output_configs(self)
+    }
+
+    fn default_input_config(&self) -> Result<SupportedStreamConfig, DefaultStreamConfigError> {
+        Device::default_input_config(self)
+    }
+
+    fn default_output_config(&self) -> Result<SupportedStreamConfig, DefaultStreamConfigError> {
+        Device::default_output_config(self)
+    }
+
+    fn build_input_stream_raw<D, E>(
+        &self,
+        config: &StreamConfig,
+        sample_format: SampleFormat,
+        data_callback: D,
+        error_callback: E,
+        timeout: Option<Duration>,
+    ) -> Result<Self::Stream, BuildStreamError>
+    where
+        D: FnMut(&Data, &InputCallbackInfo) + Send + 'static,
+        E: FnMut(StreamError) + Send + 'static,
+    {
+        Device::build_input_stream_raw(
+            self,
+            config,
+            sample_format,
+            data_callback,
+            error_callback,
+            timeout,
+        )
+    }
+
+    fn build_output_stream_raw<D, E>(
+        &self,
+        config: &StreamConfig,
+        sample_format: SampleFormat,
+        data_callback: D,
+        error_callback: E,
+        timeout: Option<Duration>,
+    ) -> Result<Self::Stream, BuildStreamError>
+    where
+        D: FnMut(&mut Data, &OutputCallbackInfo) + Send + 'static,
+        E: FnMut(StreamError) + Send + 'static,
+    {
+        Device::build_output_stream_raw(
+            self,
+            config,
+            sample_format,
+            data_callback,
+            error_callback,
+            timeout,
+        )
+    }
+}
+
+impl StreamTrait for Stream {
+    fn play(&self) -> Result<(), PlayStreamError> {
+        Stream::play(self)
+    }
+
+    fn pause(&self) -> Result<(), PauseStreamError> {
+        Stream::pause(self)
+    }
+}

vendor/cpal/src/host/asio/stream.rs

@@ -0,0 +1,718 @@
+extern crate asio_sys as sys;
+extern crate num_traits;
+
+use self::num_traits::PrimInt;
+use super::Device;
+use crate::{
+    BackendSpecificError, BufferSize, BuildStreamError, Data, InputCallbackInfo,
+    OutputCallbackInfo, PauseStreamError, PlayStreamError, SampleFormat, StreamConfig, StreamError,
+};
+use std::sync::atomic::{AtomicBool, Ordering};
+use std::sync::{Arc, Mutex};
+use std::time::Duration;
+
+pub struct Stream {
+    playing: Arc<AtomicBool>,
+    // Ensure the `Driver` does not terminate until the last stream is dropped.
+    driver: Arc<sys::Driver>,
+    #[allow(dead_code)]
+    asio_streams: Arc<Mutex<sys::AsioStreams>>,
+    callback_id: sys::CallbackId,
+}
+
+impl Stream {
+    pub fn play(&self) -> Result<(), PlayStreamError> {
+        self.playing.store(true, Ordering::SeqCst);
+        Ok(())
+    }
+
+    pub fn pause(&self) -> Result<(), PauseStreamError> {
+        self.playing.store(false, Ordering::SeqCst);
+        Ok(())
+    }
+}
+
+impl Device {
+    pub fn build_input_stream_raw<D, E>(
+        &self,
+        config: &StreamConfig,
+        sample_format: SampleFormat,
+        mut data_callback: D,
+        _error_callback: E,
+        _timeout: Option<Duration>,
+    ) -> Result<Stream, BuildStreamError>
+    where
+        D: FnMut(&Data, &InputCallbackInfo) + Send + 'static,
+        E: FnMut(StreamError) + Send + 'static,
+    {
+        let stream_type = self.driver.input_data_type().map_err(build_stream_err)?;
+
+        // Ensure that the desired sample type is supported.
+        let expected_sample_format = super::device::convert_data_type(&stream_type)
+            .ok_or(BuildStreamError::StreamConfigNotSupported)?;
+        if sample_format != expected_sample_format {
+            return Err(BuildStreamError::StreamConfigNotSupported);
+        }
+
+        let num_channels = config.channels;
+        let buffer_size = self.get_or_create_input_stream(config, sample_format)?;
+        let cpal_num_samples = buffer_size * num_channels as usize;
+
+        // Create the buffer depending on the size of the data type.
+        let len_bytes = cpal_num_samples * sample_format.sample_size();
+        let mut interleaved = vec![0u8; len_bytes];
+
+        let stream_playing = Arc::new(AtomicBool::new(false));
+        let playing = Arc::clone(&stream_playing);
+        let asio_streams = self.asio_streams.clone();
+
+        // Set the input callback.
+        // This is most performance critical part of the ASIO bindings.
+        let config = config.clone();
+        let callback_id = self.driver.add_callback(move |callback_info| unsafe {
+            // If not playing return early.
+            if !playing.load(Ordering::SeqCst) {
+                return;
+            }
+
+            // There is 0% chance of lock contention the host only locks when recreating streams.
+            let stream_lock = asio_streams.lock().unwrap();
+            let asio_stream = match stream_lock.input {
+                Some(ref asio_stream) => asio_stream,
+                None => return,
+            };
+
+            /// 1. Write from the ASIO buffer to the interleaved CPAL buffer.
+            /// 2. Deliver the CPAL buffer to the user callback.
+            unsafe fn process_input_callback<A, D, F>(
+                data_callback: &mut D,
+                interleaved: &mut [u8],
+                asio_stream: &sys::AsioStream,
+                asio_info: &sys::CallbackInfo,
+                sample_rate: crate::SampleRate,
+                format: SampleFormat,
+                from_endianness: F,
+            ) where
+                A: Copy,
+                D: FnMut(&Data, &InputCallbackInfo) + Send + 'static,
+                F: Fn(A) -> A,
+            {
+                // 1. Write the ASIO channels to the CPAL buffer.
+                let interleaved: &mut [A] = cast_slice_mut(interleaved);
+                let n_frames = asio_stream.buffer_size as usize;
+                let n_channels = interleaved.len() / n_frames;
+                let buffer_index = asio_info.buffer_index as usize;
+                for ch_ix in 0..n_channels {
+                    let asio_channel = asio_channel_slice::<A>(asio_stream, buffer_index, ch_ix);
+                    for (frame, s_asio) in interleaved.chunks_mut(n_channels).zip(asio_channel) {
+                        frame[ch_ix] = from_endianness(*s_asio);
+                    }
+                }
+
+                // 2. Deliver the interleaved buffer to the callback.
+                let data = interleaved.as_mut_ptr() as *mut ();
+                let len = interleaved.len();
+                let data = Data::from_parts(data, len, format);
+                let callback = system_time_to_stream_instant(asio_info.system_time);
+                let delay = frames_to_duration(n_frames, sample_rate);
+                let capture = callback
+                    .sub(delay)
+                    .expect("`capture` occurs before origin of alsa `StreamInstant`");
+                let timestamp = crate::InputStreamTimestamp { callback, capture };
+                let info = InputCallbackInfo { timestamp };
+                data_callback(&data, &info);
+            }
+
+            match (&stream_type, sample_format) {
+                (&sys::AsioSampleType::ASIOSTInt16LSB, SampleFormat::I16) => {
+                    process_input_callback::<i16, _, _>(
+                        &mut data_callback,
+                        &mut interleaved,
+                        asio_stream,
+                        callback_info,
+                        config.sample_rate,
+                        SampleFormat::I16,
+                        from_le,
+                    );
+                }
+                (&sys::AsioSampleType::ASIOSTInt16MSB, SampleFormat::I16) => {
+                    process_input_callback::<i16, _, _>(
+                        &mut data_callback,
+                        &mut interleaved,
+                        asio_stream,
+                        callback_info,
+                        config.sample_rate,
+                        SampleFormat::I16,
+                        from_be,
+                    );
+                }
+
+                (&sys::AsioSampleType::ASIOSTFloat32LSB, SampleFormat::F32) => {
+                    process_input_callback::<u32, _, _>(
+                        &mut data_callback,
+                        &mut interleaved,
+                        asio_stream,
+                        callback_info,
+                        config.sample_rate,
+                        SampleFormat::F32,
+                        from_le,
+                    );
+                }
+                (&sys::AsioSampleType::ASIOSTFloat32MSB, SampleFormat::F32) => {
+                    process_input_callback::<u32, _, _>(
+                        &mut data_callback,
+                        &mut interleaved,
+                        asio_stream,
+                        callback_info,
+                        config.sample_rate,
+                        SampleFormat::F32,
+                        from_be,
+                    );
+                }
+
+                (&sys::AsioSampleType::ASIOSTInt32LSB, SampleFormat::I32) => {
+                    process_input_callback::<i32, _, _>(
+                        &mut data_callback,
+                        &mut interleaved,
+                        asio_stream,
+                        callback_info,
+                        config.sample_rate,
+                        SampleFormat::I32,
+                        from_le,
+                    );
+                }
+                (&sys::AsioSampleType::ASIOSTInt32MSB, SampleFormat::I32) => {
+                    process_input_callback::<i32, _, _>(
+                        &mut data_callback,
+                        &mut interleaved,
+                        asio_stream,
+                        callback_info,
+                        config.sample_rate,
+                        SampleFormat::I32,
+                        from_be,
+                    );
+                }
+
+                (&sys::AsioSampleType::ASIOSTFloat64LSB, SampleFormat::F64) => {
+                    process_input_callback::<u64, _, _>(
+                        &mut data_callback,
+                        &mut interleaved,
+                        asio_stream,
+                        callback_info,
+                        config.sample_rate,
+                        SampleFormat::F64,
+                        from_le,
+                    );
+                }
+                (&sys::AsioSampleType::ASIOSTFloat64MSB, SampleFormat::F64) => {
+                    process_input_callback::<u64, _, _>(
+                        &mut data_callback,
+                        &mut interleaved,
+                        asio_stream,
+                        callback_info,
+                        config.sample_rate,
+                        SampleFormat::F64,
+                        from_be,
+                    );
+                }
+
+                unsupported_format_pair => unreachable!(
+                    "`build_input_stream_raw` should have returned with unsupported \
+                     format {:?}",
+                    unsupported_format_pair
+                ),
+            }
+        });
+
+        let driver = self.driver.clone();
+        let asio_streams = self.asio_streams.clone();
+
+        // Immediately start the device?
+        self.driver.start().map_err(build_stream_err)?;
+
+        Ok(Stream {
+            playing: stream_playing,
+            driver,
+            asio_streams,
+            callback_id,
+        })
+    }
+
+    pub fn build_output_stream_raw<D, E>(
+        &self,
+        config: &StreamConfig,
+        sample_format: SampleFormat,
+        mut data_callback: D,
+        _error_callback: E,
+        _timeout: Option<Duration>,
+    ) -> Result<Stream, BuildStreamError>
+    where
+        D: FnMut(&mut Data, &OutputCallbackInfo) + Send + 'static,
+        E: FnMut(StreamError) + Send + 'static,
+    {
+        let stream_type = self.driver.output_data_type().map_err(build_stream_err)?;
+
+        // Ensure that the desired sample type is supported.
+        let expected_sample_format = super::device::convert_data_type(&stream_type)
+            .ok_or(BuildStreamError::StreamConfigNotSupported)?;
+        if sample_format != expected_sample_format {
+            return Err(BuildStreamError::StreamConfigNotSupported);
+        }
+
+        let num_channels = config.channels;
+        let buffer_size = self.get_or_create_output_stream(config, sample_format)?;
+        let cpal_num_samples = buffer_size * num_channels as usize;
+
+        // Create buffers depending on data type.
+        let len_bytes = cpal_num_samples * sample_format.sample_size();
+        let mut interleaved = vec![0u8; len_bytes];
+        let current_buffer_index = self.current_buffer_index.clone();
+
+        let stream_playing = Arc::new(AtomicBool::new(false));
+        let playing = Arc::clone(&stream_playing);
+        let asio_streams = self.asio_streams.clone();
+
+        let config = config.clone();
+        let callback_id = self.driver.add_callback(move |callback_info| unsafe {
+            // If not playing, return early.
+            if !playing.load(Ordering::SeqCst) {
+                return;
+            }
+
+            // There is 0% chance of lock contention the host only locks when recreating streams.
+            let mut stream_lock = asio_streams.lock().unwrap();
+            let asio_stream = match stream_lock.output {
+                Some(ref mut asio_stream) => asio_stream,
+                None => return,
+            };
+
+            // Silence the ASIO buffer that is about to be used.
+            //
+            // This checks if any other callbacks have already silenced the buffer associated with
+            // the current `buffer_index`.
+            let silence =
+                current_buffer_index.load(Ordering::Acquire) != callback_info.buffer_index;
+
+            if silence {
+                current_buffer_index.store(callback_info.buffer_index, Ordering::Release);
+            }
+
+            /// 1. Render the given callback to the given buffer of interleaved samples.
+            /// 2. If required, silence the ASIO buffer.
+            /// 3. Finally, write the interleaved data to the non-interleaved ASIO buffer,
+            ///    performing endianness conversions as necessary.
+            unsafe fn process_output_callback<A, D, F>(
+                data_callback: &mut D,
+                interleaved: &mut [u8],
+                silence_asio_buffer: bool,
+                asio_stream: &mut sys::AsioStream,
+                asio_info: &sys::CallbackInfo,
+                sample_rate: crate::SampleRate,
+                format: SampleFormat,
+                mix_samples: F,
+            ) where
+                A: Copy,
+                D: FnMut(&mut Data, &OutputCallbackInfo) + Send + 'static,
+                F: Fn(A, A) -> A,
+            {
+                // 1. Render interleaved buffer from callback.
+                let interleaved: &mut [A] = cast_slice_mut(interleaved);
+                let data = interleaved.as_mut_ptr() as *mut ();
+                let len = interleaved.len();
+                let mut data = Data::from_parts(data, len, format);
+                let callback = system_time_to_stream_instant(asio_info.system_time);
+                let n_frames = asio_stream.buffer_size as usize;
+                let delay = frames_to_duration(n_frames, sample_rate);
+                let playback = callback
+                    .add(delay)
+                    .expect("`playback` occurs beyond representation supported by `StreamInstant`");
+                let timestamp = crate::OutputStreamTimestamp { callback, playback };
+                let info = OutputCallbackInfo { timestamp };
+                data_callback(&mut data, &info);
+
+                // 2. Silence ASIO channels if necessary.
+                let n_channels = interleaved.len() / n_frames;
+                let buffer_index = asio_info.buffer_index as usize;
+                if silence_asio_buffer {
+                    for ch_ix in 0..n_channels {
+                        let asio_channel =
+                            asio_channel_slice_mut::<A>(asio_stream, buffer_index, ch_ix);
+                        asio_channel.align_to_mut::<u8>().1.fill(0);
+                    }
+                }
+
+                // 3. Write interleaved samples to ASIO channels, one channel at a time.
+                for ch_ix in 0..n_channels {
+                    let asio_channel =
+                        asio_channel_slice_mut::<A>(asio_stream, buffer_index, ch_ix);
+                    for (frame, s_asio) in interleaved.chunks(n_channels).zip(asio_channel) {
+                        *s_asio = mix_samples(*s_asio, frame[ch_ix]);
+                    }
+                }
+            }
+
+            match (sample_format, &stream_type) {
+                (SampleFormat::I16, &sys::AsioSampleType::ASIOSTInt16LSB) => {
+                    process_output_callback::<i16, _, _>(
+                        &mut data_callback,
+                        &mut interleaved,
+                        silence,
+                        asio_stream,
+                        callback_info,
+                        config.sample_rate,
+                        SampleFormat::I16,
+                        |old_sample, new_sample| {
+                            from_le(old_sample).saturating_add(new_sample).to_le()
+                        },
+                    );
+                }
+                (SampleFormat::I16, &sys::AsioSampleType::ASIOSTInt16MSB) => {
+                    process_output_callback::<i16, _, _>(
+                        &mut data_callback,
+                        &mut interleaved,
+                        silence,
+                        asio_stream,
+                        callback_info,
+                        config.sample_rate,
+                        SampleFormat::I16,
+                        |old_sample, new_sample| {
+                            from_be(old_sample).saturating_add(new_sample).to_be()
+                        },
+                    );
+                }
+                (SampleFormat::F32, &sys::AsioSampleType::ASIOSTFloat32LSB) => {
+                    process_output_callback::<u32, _, _>(
+                        &mut data_callback,
+                        &mut interleaved,
+                        silence,
+                        asio_stream,
+                        callback_info,
+                        config.sample_rate,
+                        SampleFormat::F32,
+                        |old_sample, new_sample| {
+                            (f32::from_bits(from_le(old_sample)) + f32::from_bits(new_sample))
+                                .to_bits()
+                                .to_le()
+                        },
+                    );
+                }
+
+                (SampleFormat::F32, &sys::AsioSampleType::ASIOSTFloat32MSB) => {
+                    process_output_callback::<u32, _, _>(
+                        &mut data_callback,
+                        &mut interleaved,
+                        silence,
+                        asio_stream,
+                        callback_info,
+                        config.sample_rate,
+                        SampleFormat::F32,
+                        |old_sample, new_sample| {
+                            (f32::from_bits(from_be(old_sample)) + f32::from_bits(new_sample))
+                                .to_bits()
+                                .to_be()
+                        },
+                    );
+                }
+
+                (SampleFormat::I32, &sys::AsioSampleType::ASIOSTInt32LSB) => {
+                    process_output_callback::<i32, _, _>(
+                        &mut data_callback,
+                        &mut interleaved,
+                        silence,
+                        asio_stream,
+                        callback_info,
+                        config.sample_rate,
+                        SampleFormat::I32,
+                        |old_sample, new_sample| {
+                            from_le(old_sample).saturating_add(new_sample).to_le()
+                        },
+                    );
+                }
+                (SampleFormat::I32, &sys::AsioSampleType::ASIOSTInt32MSB) => {
+                    process_output_callback::<i32, _, _>(
+                        &mut data_callback,
+                        &mut interleaved,
+                        silence,
+                        asio_stream,
+                        callback_info,
+                        config.sample_rate,
+                        SampleFormat::I32,
+                        |old_sample, new_sample| {
+                            from_be(old_sample).saturating_add(new_sample).to_be()
+                        },
+                    );
+                }
+
+                (SampleFormat::F64, &sys::AsioSampleType::ASIOSTFloat64LSB) => {
+                    process_output_callback::<u64, _, _>(
+                        &mut data_callback,
+                        &mut interleaved,
+                        silence,
+                        asio_stream,
+                        callback_info,
+                        config.sample_rate,
+                        SampleFormat::F64,
+                        |old_sample, new_sample| {
+                            (f64::from_bits(from_le(old_sample)) + f64::from_bits(new_sample))
+                                .to_bits()
+                                .to_le()
+                        },
+                    );
+                }
+
+                (SampleFormat::F64, &sys::AsioSampleType::ASIOSTFloat64MSB) => {
+                    process_output_callback::<u64, _, _>(
+                        &mut data_callback,
+                        &mut interleaved,
+                        silence,
+                        asio_stream,
+                        callback_info,
+                        config.sample_rate,
+                        SampleFormat::F64,
+                        |old_sample, new_sample| {
+                            (f64::from_bits(from_be(old_sample)) + f64::from_bits(new_sample))
+                                .to_bits()
+                                .to_be()
+                        },
+                    );
+                }
+
+                unsupported_format_pair => unreachable!(
+                    "`build_output_stream_raw` should have returned with unsupported \
+                     format {:?}",
+                    unsupported_format_pair
+                ),
+            }
+        });
+
+        let driver = self.driver.clone();
+        let asio_streams = self.asio_streams.clone();
+
+        // Immediately start the device?
+        self.driver.start().map_err(build_stream_err)?;
+
+        Ok(Stream {
+            playing: stream_playing,
+            driver,
+            asio_streams,
+            callback_id,
+        })
+    }
+
+    /// Create a new CPAL Input Stream.
+    ///
+    /// If there is no existing ASIO Input Stream it will be created.
+    ///
+    /// On success, the buffer size of the stream is returned.
+    fn get_or_create_input_stream(
+        &self,
+        config: &StreamConfig,
+        sample_format: SampleFormat,
+    ) -> Result<usize, BuildStreamError> {
+        match self.default_input_config() {
+            Ok(f) => {
+                let num_asio_channels = f.channels;
+                check_config(&self.driver, config, sample_format, num_asio_channels)
+            }
+            Err(_) => Err(BuildStreamError::StreamConfigNotSupported),
+        }?;
+        let num_channels = config.channels as usize;
+        let mut streams = self.asio_streams.lock().unwrap();
+
+        let buffer_size = match config.buffer_size {
+            BufferSize::Fixed(v) => Some(v as i32),
+            BufferSize::Default => None,
+        };
+
+        // Either create a stream if thers none or had back the
+        // size of the current one.
+        match streams.input {
+            Some(ref input) => Ok(input.buffer_size as usize),
+            None => {
+                let output = streams.output.take();
+                self.driver
+                    .prepare_input_stream(output, num_channels, buffer_size)
+                    .map(|new_streams| {
+                        let bs = match new_streams.input {
+                            Some(ref inp) => inp.buffer_size as usize,
+                            None => unreachable!(),
+                        };
+                        *streams = new_streams;
+                        bs
+                    })
+                    .map_err(|ref e| {
+                        println!("Error preparing stream: {}", e);
+                        BuildStreamError::DeviceNotAvailable
+                    })
+            }
+        }
+    }
+
+    /// Create a new CPAL Output Stream.
+    ///
+    /// If there is no existing ASIO Output Stream it will be created.
+    fn get_or_create_output_stream(
+        &self,
+        config: &StreamConfig,
+        sample_format: SampleFormat,
+    ) -> Result<usize, BuildStreamError> {
+        match self.default_output_config() {
+            Ok(f) => {
+                let num_asio_channels = f.channels;
+                check_config(&self.driver, config, sample_format, num_asio_channels)
+            }
+            Err(_) => Err(BuildStreamError::StreamConfigNotSupported),
+        }?;
+        let num_channels = config.channels as usize;
+        let mut streams = self.asio_streams.lock().unwrap();
+
+        let buffer_size = match config.buffer_size {
+            BufferSize::Fixed(v) => Some(v as i32),
+            BufferSize::Default => None,
+        };
+
+        // Either create a stream if thers none or had back the
+        // size of the current one.
+        match streams.output {
+            Some(ref output) => Ok(output.buffer_size as usize),
+            None => {
+                let input = streams.input.take();
+                self.driver
+                    .prepare_output_stream(input, num_channels, buffer_size)
+                    .map(|new_streams| {
+                        let bs = match new_streams.output {
+                            Some(ref out) => out.buffer_size as usize,
+                            None => unreachable!(),
+                        };
+                        *streams = new_streams;
+                        bs
+                    })
+                    .map_err(|ref e| {
+                        println!("Error preparing stream: {}", e);
+                        BuildStreamError::DeviceNotAvailable
+                    })
+            }
+        }
+    }
+}
+
+impl Drop for Stream {
+    fn drop(&mut self) {
+        self.driver.remove_callback(self.callback_id);
+    }
+}
+
+fn asio_ns_to_double(val: sys::bindings::asio_import::ASIOTimeStamp) -> f64 {
+    let two_raised_to_32 = 4294967296.0;
+    val.lo as f64 + val.hi as f64 * two_raised_to_32
+}
+
+/// Asio retrieves system time via `timeGetTime` which returns the time in milliseconds.
+fn system_time_to_stream_instant(
+    system_time: sys::bindings::asio_import::ASIOTimeStamp,
+) -> crate::StreamInstant {
+    let systime_ns = asio_ns_to_double(system_time);
+    let secs = systime_ns as i64 / 1_000_000_000;
+    let nanos = (systime_ns as i64 - secs * 1_000_000_000) as u32;
+    crate::StreamInstant::new(secs, nanos)
+}
+
+/// Convert the given duration in frames at the given sample rate to a `std::time::Duration`.
+fn frames_to_duration(frames: usize, rate: crate::SampleRate) -> std::time::Duration {
+    let secsf = frames as f64 / rate.0 as f64;
+    let secs = secsf as u64;
+    let nanos = ((secsf - secs as f64) * 1_000_000_000.0) as u32;
+    std::time::Duration::new(secs, nanos)
+}
+
+/// Check whether or not the desired config is supported by the stream.
+///
+/// Checks sample rate, data type and then finally the number of channels.
+fn check_config(
+    driver: &sys::Driver,
+    config: &StreamConfig,
+    sample_format: SampleFormat,
+    num_asio_channels: u16,
+) -> Result<(), BuildStreamError> {
+    let StreamConfig {
+        channels,
+        sample_rate,
+        buffer_size: _,
+    } = config;
+    // Try and set the sample rate to what the user selected.
+    let sample_rate = sample_rate.0.into();
+    if sample_rate != driver.sample_rate().map_err(build_stream_err)? {
+        if driver
+            .can_sample_rate(sample_rate)
+            .map_err(build_stream_err)?
+        {
+            driver
+                .set_sample_rate(sample_rate)
+                .map_err(build_stream_err)?;
+        } else {
+            return Err(BuildStreamError::StreamConfigNotSupported);
+        }
+    }
+    // unsigned formats are not supported by asio
+    match sample_format {
+        SampleFormat::I16 | SampleFormat::I32 | SampleFormat::F32 => (),
+        _ => return Err(BuildStreamError::StreamConfigNotSupported),
+    }
+    if *channels > num_asio_channels {
+        return Err(BuildStreamError::StreamConfigNotSupported);
+    }
+    Ok(())
+}
+
+/// Cast a byte slice into a mutable slice of desired type.
+///
+/// Safety: it's up to the caller to ensure that the input slice has valid bit representations.
+unsafe fn cast_slice_mut<T>(v: &mut [u8]) -> &mut [T] {
+    debug_assert!(v.len() % std::mem::size_of::<T>() == 0);
+    std::slice::from_raw_parts_mut(v.as_mut_ptr() as *mut T, v.len() / std::mem::size_of::<T>())
+}
+
+/// Helper function to convert from little endianness.
+fn from_le<T: PrimInt>(t: T) -> T {
+    T::from_le(t)
+}
+
+/// Helper function to convert from little endianness.
+fn from_be<T: PrimInt>(t: T) -> T {
+    T::from_be(t)
+}
+
+/// Shorthand for retrieving the asio buffer slice associated with a channel.
+unsafe fn asio_channel_slice<T>(
+    asio_stream: &sys::AsioStream,
+    buffer_index: usize,
+    channel_index: usize,
+) -> &[T] {
+    let buff_ptr: *const T =
+        asio_stream.buffer_infos[channel_index].buffers[buffer_index as usize] as *const _;
+    std::slice::from_raw_parts(buff_ptr, asio_stream.buffer_size as usize)
+}
+
+/// Shorthand for retrieving the asio buffer slice associated with a channel.
+unsafe fn asio_channel_slice_mut<T>(
+    asio_stream: &mut sys::AsioStream,
+    buffer_index: usize,
+    channel_index: usize,
+) -> &mut [T] {
+    let buff_ptr: *mut T =
+        asio_stream.buffer_infos[channel_index].buffers[buffer_index as usize] as *mut _;
+    std::slice::from_raw_parts_mut(buff_ptr, asio_stream.buffer_size as usize)
+}
+
+fn build_stream_err(e: sys::AsioError) -> BuildStreamError {
+    match e {
+        sys::AsioError::NoDrivers | sys::AsioError::HardwareMalfunction => {
+            BuildStreamError::DeviceNotAvailable
+        }
+        sys::AsioError::InvalidInput | sys::AsioError::BadMode => BuildStreamError::InvalidArgument,
+        err => {
+            let description = format!("{}", err);
+            BackendSpecificError { description }.into()
+        }
+    }
+}

vendor/cpal/src/host/coreaudio/ios/enumerate.rs

@@ -0,0 +1,43 @@
+use std::vec::IntoIter as VecIntoIter;
+
+use crate::DevicesError;
+use crate::SupportedStreamConfigRange;
+
+use super::Device;
+
+pub type SupportedInputConfigs = ::std::vec::IntoIter<SupportedStreamConfigRange>;
+pub type SupportedOutputConfigs = ::std::vec::IntoIter<SupportedStreamConfigRange>;
+
+// TODO: Support enumerating earpiece vs headset vs speaker etc?
+pub struct Devices(VecIntoIter<Device>);
+
+impl Devices {
+    pub fn new() -> Result<Self, DevicesError> {
+        Ok(Self::default())
+    }
+}
+
+impl Default for Devices {
+    fn default() -> Devices {
+        Devices(vec![Device].into_iter())
+    }
+}
+
+impl Iterator for Devices {
+    type Item = Device;
+
+    #[inline]
+    fn next(&mut self) -> Option<Device> {
+        self.0.next()
+    }
+}
+
+#[inline]
+pub fn default_input_device() -> Option<Device> {
+    Some(Device)
+}
+
+#[inline]
+pub fn default_output_device() -> Option<Device> {
+    Some(Device)
+}

vendor/cpal/src/host/coreaudio/ios/mod.rs

@@ -0,0 +1,434 @@
+//!
+//! coreaudio on iOS looks a bit different from macOS. A lot of configuration needs to use
+//! the AVAudioSession objc API which doesn't exist on macOS.
+//!
+//! TODO:
+//! - Use AVAudioSession to enumerate buffer size / sample rate / number of channels and set
+//!   buffer size.
+//!
+
+extern crate core_foundation_sys;
+extern crate coreaudio;
+
+use std::cell::RefCell;
+
+use self::coreaudio::audio_unit::render_callback::data;
+use self::coreaudio::audio_unit::{render_callback, AudioUnit, Element, Scope};
+use self::coreaudio::sys::{
+    kAudioOutputUnitProperty_EnableIO, kAudioUnitProperty_StreamFormat, AudioBuffer,
+    AudioStreamBasicDescription,
+};
+
+use super::{asbd_from_config, frames_to_duration, host_time_to_stream_instant};
+use crate::traits::{DeviceTrait, HostTrait, StreamTrait};
+
+use crate::{
+    BackendSpecificError, BufferSize, BuildStreamError, Data, DefaultStreamConfigError,
+    DeviceNameError, DevicesError, InputCallbackInfo, OutputCallbackInfo, PauseStreamError,
+    PlayStreamError, SampleFormat, SampleRate, StreamConfig, StreamError, SupportedBufferSize,
+    SupportedStreamConfig, SupportedStreamConfigRange, SupportedStreamConfigsError,
+};
+
+use self::enumerate::{
+    default_input_device, default_output_device, Devices, SupportedInputConfigs,
+    SupportedOutputConfigs,
+};
+use std::slice;
+use std::time::Duration;
+
+pub mod enumerate;
+
+// These days the default of iOS is now F32 and no longer I16
+const SUPPORTED_SAMPLE_FORMAT: SampleFormat = SampleFormat::F32;
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct Device;
+
+pub struct Host;
+
+impl Host {
+    pub fn new() -> Result<Self, crate::HostUnavailable> {
+        Ok(Host)
+    }
+}
+
+impl HostTrait for Host {
+    type Devices = Devices;
+    type Device = Device;
+
+    fn is_available() -> bool {
+        true
+    }
+
+    fn devices(&self) -> Result<Self::Devices, DevicesError> {
+        Devices::new()
+    }
+
+    fn default_input_device(&self) -> Option<Self::Device> {
+        default_input_device()
+    }
+
+    fn default_output_device(&self) -> Option<Self::Device> {
+        default_output_device()
+    }
+}
+
+impl Device {
+    #[inline]
+    fn name(&self) -> Result<String, DeviceNameError> {
+        Ok("Default Device".to_owned())
+    }
+
+    #[inline]
+    fn supported_input_configs(
+        &self,
+    ) -> Result<SupportedInputConfigs, SupportedStreamConfigsError> {
+        // TODO: query AVAudioSession for parameters, some values like sample rate and buffer size
+        // probably need to actually be set to see if it works, but channels can be enumerated.
+
+        let asbd: AudioStreamBasicDescription = default_input_asbd()?;
+        let stream_config = stream_config_from_asbd(asbd);
+        Ok(vec![SupportedStreamConfigRange {
+            channels: stream_config.channels,
+            min_sample_rate: stream_config.sample_rate,
+            max_sample_rate: stream_config.sample_rate,
+            buffer_size: stream_config.buffer_size.clone(),
+            sample_format: SUPPORTED_SAMPLE_FORMAT,
+        }]
+        .into_iter())
+    }
+
+    #[inline]
+    fn supported_output_configs(
+        &self,
+    ) -> Result<SupportedOutputConfigs, SupportedStreamConfigsError> {
+        // TODO: query AVAudioSession for parameters, some values like sample rate and buffer size
+        // probably need to actually be set to see if it works, but channels can be enumerated.
+
+        let asbd: AudioStreamBasicDescription = default_output_asbd()?;
+        let stream_config = stream_config_from_asbd(asbd);
+
+        let configs: Vec<_> = (1..=asbd.mChannelsPerFrame as u16)
+            .map(|channels| SupportedStreamConfigRange {
+                channels,
+                min_sample_rate: stream_config.sample_rate,
+                max_sample_rate: stream_config.sample_rate,
+                buffer_size: stream_config.buffer_size.clone(),
+                sample_format: SUPPORTED_SAMPLE_FORMAT,
+            })
+            .collect();
+        Ok(configs.into_iter())
+    }
+
+    #[inline]
+    fn default_input_config(&self) -> Result<SupportedStreamConfig, DefaultStreamConfigError> {
+        let asbd: AudioStreamBasicDescription = default_input_asbd()?;
+        let stream_config = stream_config_from_asbd(asbd);
+        Ok(stream_config)
+    }
+
+    #[inline]
+    fn default_output_config(&self) -> Result<SupportedStreamConfig, DefaultStreamConfigError> {
+        let asbd: AudioStreamBasicDescription = default_output_asbd()?;
+        let stream_config = stream_config_from_asbd(asbd);
+        Ok(stream_config)
+    }
+}
+
+impl DeviceTrait for Device {
+    type SupportedInputConfigs = SupportedInputConfigs;
+    type SupportedOutputConfigs = SupportedOutputConfigs;
+    type Stream = Stream;
+
+    #[inline]
+    fn name(&self) -> Result<String, DeviceNameError> {
+        Device::name(self)
+    }
+
+    #[inline]
+    fn supported_input_configs(
+        &self,
+    ) -> Result<Self::SupportedInputConfigs, SupportedStreamConfigsError> {
+        Device::supported_input_configs(self)
+    }
+
+    #[inline]
+    fn supported_output_configs(
+        &self,
+    ) -> Result<Self::SupportedOutputConfigs, SupportedStreamConfigsError> {
+        Device::supported_output_configs(self)
+    }
+
+    #[inline]
+    fn default_input_config(&self) -> Result<SupportedStreamConfig, DefaultStreamConfigError> {
+        Device::default_input_config(self)
+    }
+
+    #[inline]
+    fn default_output_config(&self) -> Result<SupportedStreamConfig, DefaultStreamConfigError> {
+        Device::default_output_config(self)
+    }
+
+    fn build_input_stream_raw<D, E>(
+        &self,
+        config: &StreamConfig,
+        sample_format: SampleFormat,
+        mut data_callback: D,
+        mut error_callback: E,
+        _timeout: Option<Duration>,
+    ) -> Result<Self::Stream, BuildStreamError>
+    where
+        D: FnMut(&Data, &InputCallbackInfo) + Send + 'static,
+        E: FnMut(StreamError) + Send + 'static,
+    {
+        // The scope and element for working with a device's input stream.
+        let scope = Scope::Output;
+        let element = Element::Input;
+
+        let mut audio_unit = create_audio_unit()?;
+        audio_unit.uninitialize()?;
+        configure_for_recording(&mut audio_unit)?;
+        audio_unit.initialize()?;
+
+        // Set the stream in interleaved mode.
+        let asbd = asbd_from_config(config, sample_format);
+        audio_unit.set_property(kAudioUnitProperty_StreamFormat, scope, element, Some(&asbd))?;
+
+        // Set the buffersize
+        match config.buffer_size {
+            BufferSize::Fixed(_) => {
+                return Err(BuildStreamError::StreamConfigNotSupported);
+            }
+            BufferSize::Default => (),
+        }
+
+        // Register the callback that is being called by coreaudio whenever it needs data to be
+        // fed to the audio buffer.
+        let bytes_per_channel = sample_format.sample_size();
+        let sample_rate = config.sample_rate;
+        type Args = render_callback::Args<data::Raw>;
+        audio_unit.set_input_callback(move |args: Args| unsafe {
+            let ptr = (*args.data.data).mBuffers.as_ptr() as *const AudioBuffer;
+            let len = (*args.data.data).mNumberBuffers as usize;
+            let buffers: &[AudioBuffer] = slice::from_raw_parts(ptr, len);
+
+            // There is only 1 buffer when using interleaved channels
+            let AudioBuffer {
+                mNumberChannels: channels,
+                mDataByteSize: data_byte_size,
+                mData: data,
+            } = buffers[0];
+
+            let data = data as *mut ();
+            let len = (data_byte_size as usize / bytes_per_channel) as usize;
+            let data = Data::from_parts(data, len, sample_format);
+
+            // TODO: Need a better way to get delay, for now we assume a double-buffer offset.
+            let callback = match host_time_to_stream_instant(args.time_stamp.mHostTime) {
+                Err(err) => {
+                    error_callback(err.into());
+                    return Err(());
+                }
+                Ok(cb) => cb,
+            };
+            let buffer_frames = len / channels as usize;
+            let delay = frames_to_duration(buffer_frames, sample_rate);
+            let capture = callback
+                .sub(delay)
+                .expect("`capture` occurs before origin of alsa `StreamInstant`");
+            let timestamp = crate::InputStreamTimestamp { callback, capture };
+
+            let info = InputCallbackInfo { timestamp };
+            data_callback(&data, &info);
+            Ok(())
+        })?;
+
+        audio_unit.start()?;
+
+        Ok(Stream::new(StreamInner {
+            playing: true,
+            audio_unit,
+        }))
+    }
+
+    /// Create an output stream.
+    fn build_output_stream_raw<D, E>(
+        &self,
+        config: &StreamConfig,
+        sample_format: SampleFormat,
+        mut data_callback: D,
+        mut error_callback: E,
+        _timeout: Option<Duration>,
+    ) -> Result<Self::Stream, BuildStreamError>
+    where
+        D: FnMut(&mut Data, &OutputCallbackInfo) + Send + 'static,
+        E: FnMut(StreamError) + Send + 'static,
+    {
+        match config.buffer_size {
+            BufferSize::Fixed(_) => {
+                return Err(BuildStreamError::StreamConfigNotSupported);
+            }
+            BufferSize::Default => (),
+        };
+
+        let mut audio_unit = create_audio_unit()?;
+
+        // The scope and element for working with a device's output stream.
+        let scope = Scope::Input;
+        let element = Element::Output;
+
+        // Set the stream in interleaved mode.
+        let asbd = asbd_from_config(config, sample_format);
+        audio_unit.set_property(kAudioUnitProperty_StreamFormat, scope, element, Some(&asbd))?;
+
+        // Register the callback that is being called by coreaudio whenever it needs data to be
+        // fed to the audio buffer.
+        let bytes_per_channel = sample_format.sample_size();
+        let sample_rate = config.sample_rate;
+        type Args = render_callback::Args<data::Raw>;
+        audio_unit.set_render_callback(move |args: Args| unsafe {
+            // If `run()` is currently running, then a callback will be available from this list.
+            // Otherwise, we just fill the buffer with zeroes and return.
+
+            let AudioBuffer {
+                mNumberChannels: channels,
+                mDataByteSize: data_byte_size,
+                mData: data,
+            } = (*args.data.data).mBuffers[0];
+
+            let data = data as *mut ();
+            let len = (data_byte_size as usize / bytes_per_channel) as usize;
+            let mut data = Data::from_parts(data, len, sample_format);
+
+            let callback = match host_time_to_stream_instant(args.time_stamp.mHostTime) {
+                Err(err) => {
+                    error_callback(err.into());
+                    return Err(());
+                }
+                Ok(cb) => cb,
+            };
+            // TODO: Need a better way to get delay, for now we assume a double-buffer offset.
+            let buffer_frames = len / channels as usize;
+            let delay = frames_to_duration(buffer_frames, sample_rate);
+            let playback = callback
+                .add(delay)
+                .expect("`playback` occurs beyond representation supported by `StreamInstant`");
+            let timestamp = crate::OutputStreamTimestamp { callback, playback };
+
+            let info = OutputCallbackInfo { timestamp };
+            data_callback(&mut data, &info);
+            Ok(())
+        })?;
+
+        audio_unit.start()?;
+
+        Ok(Stream::new(StreamInner {
+            playing: true,
+            audio_unit,
+        }))
+    }
+}
+
+pub struct Stream {
+    inner: RefCell<StreamInner>,
+}
+
+impl Stream {
+    fn new(inner: StreamInner) -> Self {
+        Self {
+            inner: RefCell::new(inner),
+        }
+    }
+}
+
+impl StreamTrait for Stream {
+    fn play(&self) -> Result<(), PlayStreamError> {
+        let mut stream = self.inner.borrow_mut();
+
+        if !stream.playing {
+            if let Err(e) = stream.audio_unit.start() {
+                let description = format!("{}", e);
+                let err = BackendSpecificError { description };
+                return Err(err.into());
+            }
+            stream.playing = true;
+        }
+        Ok(())
+    }
+
+    fn pause(&self) -> Result<(), PauseStreamError> {
+        let mut stream = self.inner.borrow_mut();
+
+        if stream.playing {
+            if let Err(e) = stream.audio_unit.stop() {
+                let description = format!("{}", e);
+                let err = BackendSpecificError { description };
+                return Err(err.into());
+            }
+
+            stream.playing = false;
+        }
+        Ok(())
+    }
+}
+
+struct StreamInner {
+    playing: bool,
+    audio_unit: AudioUnit,
+}
+
+fn create_audio_unit() -> Result<AudioUnit, coreaudio::Error> {
+    AudioUnit::new(coreaudio::audio_unit::IOType::RemoteIO)
+}
+
+fn configure_for_recording(audio_unit: &mut AudioUnit) -> Result<(), coreaudio::Error> {
+    // Enable mic recording
+    let enable_input = 1u32;
+    audio_unit.set_property(
+        kAudioOutputUnitProperty_EnableIO,
+        Scope::Input,
+        Element::Input,
+        Some(&enable_input),
+    )?;
+
+    // Disable output
+    let disable_output = 0u32;
+    audio_unit.set_property(
+        kAudioOutputUnitProperty_EnableIO,
+        Scope::Output,
+        Element::Output,
+        Some(&disable_output),
+    )?;
+
+    Ok(())
+}
+
+fn default_output_asbd() -> Result<AudioStreamBasicDescription, coreaudio::Error> {
+    let audio_unit = create_audio_unit()?;
+    let id = kAudioUnitProperty_StreamFormat;
+    let asbd: AudioStreamBasicDescription =
+        audio_unit.get_property(id, Scope::Output, Element::Output)?;
+    Ok(asbd)
+}
+
+fn default_input_asbd() -> Result<AudioStreamBasicDescription, coreaudio::Error> {
+    let mut audio_unit = create_audio_unit()?;
+    audio_unit.uninitialize()?;
+    configure_for_recording(&mut audio_unit)?;
+    audio_unit.initialize()?;
+
+    let id = kAudioUnitProperty_StreamFormat;
+    let asbd: AudioStreamBasicDescription =
+        audio_unit.get_property(id, Scope::Input, Element::Input)?;
+    Ok(asbd)
+}
+
+fn stream_config_from_asbd(asbd: AudioStreamBasicDescription) -> SupportedStreamConfig {
+    let buffer_size = SupportedBufferSize::Range { min: 0, max: 0 };
+    SupportedStreamConfig {
+        channels: asbd.mChannelsPerFrame as u16,
+        sample_rate: SampleRate(asbd.mSampleRate as u32),
+        buffer_size: buffer_size.clone(),
+        sample_format: SUPPORTED_SAMPLE_FORMAT,
+    }
+}

vendor/cpal/src/host/coreaudio/macos/enumerate.rs

@@ -0,0 +1,152 @@
+extern crate coreaudio;
+
+use self::coreaudio::sys::{
+    kAudioHardwareNoError, kAudioHardwarePropertyDefaultInputDevice,
+    kAudioHardwarePropertyDefaultOutputDevice, kAudioHardwarePropertyDevices,
+    kAudioObjectPropertyElementMaster, kAudioObjectPropertyScopeGlobal, kAudioObjectSystemObject,
+    AudioDeviceID, AudioObjectGetPropertyData, AudioObjectGetPropertyDataSize,
+    AudioObjectPropertyAddress, OSStatus,
+};
+use super::Device;
+use crate::{BackendSpecificError, DevicesError, SupportedStreamConfigRange};
+use std::mem;
+use std::ptr::null;
+use std::vec::IntoIter as VecIntoIter;
+
+unsafe fn audio_devices() -> Result<Vec<AudioDeviceID>, OSStatus> {
+    let property_address = AudioObjectPropertyAddress {
+        mSelector: kAudioHardwarePropertyDevices,
+        mScope: kAudioObjectPropertyScopeGlobal,
+        mElement: kAudioObjectPropertyElementMaster,
+    };
+
+    macro_rules! try_status_or_return {
+        ($status:expr) => {
+            if $status != kAudioHardwareNoError as i32 {
+                return Err($status);
+            }
+        };
+    }
+
+    let data_size = 0u32;
+    let status = AudioObjectGetPropertyDataSize(
+        kAudioObjectSystemObject,
+        &property_address as *const _,
+        0,
+        null(),
+        &data_size as *const _ as *mut _,
+    );
+    try_status_or_return!(status);
+
+    let device_count = data_size / mem::size_of::<AudioDeviceID>() as u32;
+    let mut audio_devices = vec![];
+    audio_devices.reserve_exact(device_count as usize);
+
+    let status = AudioObjectGetPropertyData(
+        kAudioObjectSystemObject,
+        &property_address as *const _,
+        0,
+        null(),
+        &data_size as *const _ as *mut _,
+        audio_devices.as_mut_ptr() as *mut _,
+    );
+    try_status_or_return!(status);
+
+    audio_devices.set_len(device_count as usize);
+
+    Ok(audio_devices)
+}
+
+pub struct Devices(VecIntoIter<AudioDeviceID>);
+
+impl Devices {
+    pub fn new() -> Result<Self, DevicesError> {
+        let devices = unsafe {
+            match audio_devices() {
+                Ok(devices) => devices,
+                Err(os_status) => {
+                    let description = format!("{}", os_status);
+                    let err = BackendSpecificError { description };
+                    return Err(err.into());
+                }
+            }
+        };
+        Ok(Devices(devices.into_iter()))
+    }
+}
+
+unsafe impl Send for Devices {}
+unsafe impl Sync for Devices {}
+
+impl Iterator for Devices {
+    type Item = Device;
+    fn next(&mut self) -> Option<Device> {
+        self.0.next().map(|id| Device {
+            audio_device_id: id,
+            is_default: false,
+        })
+    }
+}
+
+pub fn default_input_device() -> Option<Device> {
+    let property_address = AudioObjectPropertyAddress {
+        mSelector: kAudioHardwarePropertyDefaultInputDevice,
+        mScope: kAudioObjectPropertyScopeGlobal,
+        mElement: kAudioObjectPropertyElementMaster,
+    };
+
+    let audio_device_id: AudioDeviceID = 0;
+    let data_size = mem::size_of::<AudioDeviceID>();
+    let status = unsafe {
+        AudioObjectGetPropertyData(
+            kAudioObjectSystemObject,
+            &property_address as *const _,
+            0,
+            null(),
+            &data_size as *const _ as *mut _,
+            &audio_device_id as *const _ as *mut _,
+        )
+    };
+    if status != kAudioHardwareNoError as i32 {
+        return None;
+    }
+
+    let device = Device {
+        audio_device_id,
+        is_default: true,
+    };
+    Some(device)
+}
+
+pub fn default_output_device() -> Option<Device> {
+    let property_address = AudioObjectPropertyAddress {
+        mSelector: kAudioHardwarePropertyDefaultOutputDevice,
+        mScope: kAudioObjectPropertyScopeGlobal,
+        mElement: kAudioObjectPropertyElementMaster,
+    };
+
+    let audio_device_id: AudioDeviceID = 0;
+    let data_size = mem::size_of::<AudioDeviceID>();
+    let status = unsafe {
+        AudioObjectGetPropertyData(
+            kAudioObjectSystemObject,
+            &property_address as *const _,
+            0,
+            null(),
+            &data_size as *const _ as *mut _,
+            &audio_device_id as *const _ as *mut _,
+        )
+    };
+    if status != kAudioHardwareNoError as i32 {
+        return None;
+    }
+
+    let device = Device {
+        audio_device_id,
+        is_default: true,
+    };
+    Some(device)
+}
+
+pub type SupportedInputConfigs = VecIntoIter<SupportedStreamConfigRange>;
+pub type SupportedOutputConfigs = VecIntoIter<SupportedStreamConfigRange>;

vendor/cpal/src/host/coreaudio/macos/mod.rs

@@ -0,0 +1,941 @@
+extern crate core_foundation_sys;
+extern crate coreaudio;
+
+use super::{asbd_from_config, check_os_status, frames_to_duration, host_time_to_stream_instant};
+
+use self::core_foundation_sys::string::{CFStringGetCString, CFStringGetCStringPtr, CFStringRef};
+use self::coreaudio::audio_unit::render_callback::{self, data};
+use self::coreaudio::audio_unit::{AudioUnit, Element, Scope};
+use self::coreaudio::sys::{
+    kAudioDevicePropertyAvailableNominalSampleRates, kAudioDevicePropertyBufferFrameSize,
+    kAudioDevicePropertyBufferFrameSizeRange, kAudioDevicePropertyDeviceIsAlive,
+    kAudioDevicePropertyDeviceNameCFString, kAudioDevicePropertyNominalSampleRate,
+    kAudioDevicePropertyScopeOutput, kAudioDevicePropertyStreamConfiguration,
+    kAudioDevicePropertyStreamFormat, kAudioObjectPropertyElementMaster,
+    kAudioObjectPropertyScopeGlobal, kAudioObjectPropertyScopeInput,
+    kAudioObjectPropertyScopeOutput, kAudioOutputUnitProperty_CurrentDevice,
+    kAudioOutputUnitProperty_EnableIO, kAudioUnitProperty_StreamFormat, kCFStringEncodingUTF8,
+    AudioBuffer, AudioBufferList, AudioDeviceID, AudioObjectGetPropertyData,
+    AudioObjectGetPropertyDataSize, AudioObjectID, AudioObjectPropertyAddress,
+    AudioObjectPropertyScope, AudioObjectSetPropertyData, AudioStreamBasicDescription,
+    AudioValueRange, OSStatus,
+};
+use crate::traits::{DeviceTrait, HostTrait, StreamTrait};
+use crate::{
+    BackendSpecificError, BufferSize, BuildStreamError, ChannelCount, Data,
+    DefaultStreamConfigError, DeviceNameError, DevicesError, InputCallbackInfo, OutputCallbackInfo,
+    PauseStreamError, PlayStreamError, SampleFormat, SampleRate, StreamConfig, StreamError,
+    SupportedBufferSize, SupportedStreamConfig, SupportedStreamConfigRange,
+    SupportedStreamConfigsError,
+};
+use std::ffi::CStr;
+use std::fmt;
+use std::mem;
+use std::os::raw::c_char;
+use std::ptr::null;
+use std::rc::Rc;
+use std::slice;
+use std::sync::mpsc::{channel, RecvTimeoutError};
+use std::sync::{Arc, Mutex};
+use std::time::{Duration, Instant};
+
+pub use self::enumerate::{
+    default_input_device, default_output_device, Devices, SupportedInputConfigs,
+    SupportedOutputConfigs,
+};
+
+use property_listener::AudioObjectPropertyListener;
+
+pub mod enumerate;
+mod property_listener;
+
+/// Coreaudio host, the default host on macOS.
+#[derive(Debug)]
+pub struct Host;
+
+impl Host {
+    pub fn new() -> Result<Self, crate::HostUnavailable> {
+        Ok(Host)
+    }
+}
+
+impl HostTrait for Host {
+    type Devices = Devices;
+    type Device = Device;
+
+    fn is_available() -> bool {
+        // Assume coreaudio is always available
+        true
+    }
+
+    fn devices(&self) -> Result<Self::Devices, DevicesError> {
+        Devices::new()
+    }
+
+    fn default_input_device(&self) -> Option<Self::Device> {
+        default_input_device()
+    }
+
+    fn default_output_device(&self) -> Option<Self::Device> {
+        default_output_device()
+    }
+}
+
+impl DeviceTrait for Device {
+    type SupportedInputConfigs = SupportedInputConfigs;
+    type SupportedOutputConfigs = SupportedOutputConfigs;
+    type Stream = Stream;
+
+    fn name(&self) -> Result<String, DeviceNameError> {
+        Device::name(self)
+    }
+
+    fn supported_input_configs(
+        &self,
+    ) -> Result<Self::SupportedInputConfigs, SupportedStreamConfigsError> {
+        Device::supported_input_configs(self)
+    }
+
+    fn supported_output_configs(
+        &self,
+    ) -> Result<Self::SupportedOutputConfigs, SupportedStreamConfigsError> {
+        Device::supported_output_configs(self)
+    }
+
+    fn default_input_config(&self) -> Result<SupportedStreamConfig, DefaultStreamConfigError> {
+        Device::default_input_config(self)
+    }
+
+    fn default_output_config(&self) -> Result<SupportedStreamConfig, DefaultStreamConfigError> {
+        Device::default_output_config(self)
+    }
+
+    fn build_input_stream_raw<D, E>(
+        &self,
+        config: &StreamConfig,
+        sample_format: SampleFormat,
+        data_callback: D,
+        error_callback: E,
+        timeout: Option<Duration>,
+    ) -> Result<Self::Stream, BuildStreamError>
+    where
+        D: FnMut(&Data, &InputCallbackInfo) + Send + 'static,
+        E: FnMut(StreamError) + Send + 'static,
+    {
+        Device::build_input_stream_raw(
+            self,
+            config,
+            sample_format,
+            data_callback,
+            error_callback,
+            timeout,
+        )
+    }
+
+    fn build_output_stream_raw<D, E>(
+        &self,
+        config: &StreamConfig,
+        sample_format: SampleFormat,
+        data_callback: D,
+        error_callback: E,
+        timeout: Option<Duration>,
+    ) -> Result<Self::Stream, BuildStreamError>
+    where
+        D: FnMut(&mut Data, &OutputCallbackInfo) + Send + 'static,
+        E: FnMut(StreamError) + Send + 'static,
+    {
+        Device::build_output_stream_raw(
+            self,
+            config,
+            sample_format,
+            data_callback,
+            error_callback,
+            timeout,
+        )
+    }
+}
+
+#[derive(Clone, PartialEq, Eq)]
+pub struct Device {
+    pub(crate) audio_device_id: AudioDeviceID,
+    is_default: bool,
+}
+
+impl Device {
+    fn name(&self) -> Result<String, DeviceNameError> {
+        let property_address = AudioObjectPropertyAddress {
+            mSelector: kAudioDevicePropertyDeviceNameCFString,
+            mScope: kAudioDevicePropertyScopeOutput,
+            mElement: kAudioObjectPropertyElementMaster,
+        };
+        let device_name: CFStringRef = null();
+        let data_size = mem::size_of::<CFStringRef>();
+        let c_str = unsafe {
+            let status = AudioObjectGetPropertyData(
+                self.audio_device_id,
+                &property_address as *const _,
+                0,
+                null(),
+                &data_size as *const _ as *mut _,
+                &device_name as *const _ as *mut _,
+            );
+            check_os_status(status)?;
+
+            let c_string: *const c_char = CFStringGetCStringPtr(device_name, kCFStringEncodingUTF8);
+            if c_string.is_null() {
+                let status = AudioObjectGetPropertyData(
+                    self.audio_device_id,
+                    &property_address as *const _,
+                    0,
+                    null(),
+                    &data_size as *const _ as *mut _,
+                    &device_name as *const _ as *mut _,
+                );
+                check_os_status(status)?;
+                let mut buf: [i8; 255] = [0; 255];
+                let result = CFStringGetCString(
+                    device_name,
+                    buf.as_mut_ptr(),
+                    buf.len() as _,
+                    kCFStringEncodingUTF8,
+                );
+                if result == 0 {
+                    let description =
+                        "core foundation failed to return device name string".to_string();
+                    let err = BackendSpecificError { description };
+                    return Err(err.into());
+                }
+                let name: &CStr = CStr::from_ptr(buf.as_ptr());
+                return Ok(name.to_str().unwrap().to_owned());
+            }
+            CStr::from_ptr(c_string as *mut _)
+        };
+        Ok(c_str.to_string_lossy().into_owned())
+    }
+
+    // Logic re-used between `supported_input_configs` and `supported_output_configs`.
+    #[allow(clippy::cast_ptr_alignment)]
+    fn supported_configs(
+        &self,
+        scope: AudioObjectPropertyScope,
+    ) -> Result<SupportedOutputConfigs, SupportedStreamConfigsError> {
+        let mut property_address = AudioObjectPropertyAddress {
+            mSelector: kAudioDevicePropertyStreamConfiguration,
+            mScope: scope,
+            mElement: kAudioObjectPropertyElementMaster,
+        };
+
+        unsafe {
+            // Retrieve the devices audio buffer list.
+            let data_size = 0u32;
+            let status = AudioObjectGetPropertyDataSize(
+                self.audio_device_id,
+                &property_address as *const _,
+                0,
+                null(),
+                &data_size as *const _ as *mut _,
+            );
+            check_os_status(status)?;
+
+            let mut audio_buffer_list: Vec<u8> = vec![];
+            audio_buffer_list.reserve_exact(data_size as usize);
+            let status = AudioObjectGetPropertyData(
+                self.audio_device_id,
+                &property_address as *const _,
+                0,
+                null(),
+                &data_size as *const _ as *mut _,
+                audio_buffer_list.as_mut_ptr() as *mut _,
+            );
+            check_os_status(status)?;
+
+            let audio_buffer_list = audio_buffer_list.as_mut_ptr() as *mut AudioBufferList;
+
+            // If there's no buffers, skip.
+            if (*audio_buffer_list).mNumberBuffers == 0 {
+                return Ok(vec![].into_iter());
+            }
+
+            // Count the number of channels as the sum of all channels in all output buffers.
+            let n_buffers = (*audio_buffer_list).mNumberBuffers as usize;
+            let first: *const AudioBuffer = (*audio_buffer_list).mBuffers.as_ptr();
+            let buffers: &'static [AudioBuffer] = slice::from_raw_parts(first, n_buffers);
+            let mut n_channels = 0;
+            for buffer in buffers {
+                n_channels += buffer.mNumberChannels as usize;
+            }
+
+            // TODO: macOS should support U8, I16, I32, F32 and F64. This should allow for using
+            // I16 but just use F32 for now as it's the default anyway.
+            let sample_format = SampleFormat::F32;
+
+            // Get available sample rate ranges.
+            property_address.mSelector = kAudioDevicePropertyAvailableNominalSampleRates;
+            let data_size = 0u32;
+            let status = AudioObjectGetPropertyDataSize(
+                self.audio_device_id,
+                &property_address as *const _,
+                0,
+                null(),
+                &data_size as *const _ as *mut _,
+            );
+            check_os_status(status)?;
+
+            let n_ranges = data_size as usize / mem::size_of::<AudioValueRange>();
+            let mut ranges: Vec<u8> = vec![];
+            ranges.reserve_exact(data_size as usize);
+            let status = AudioObjectGetPropertyData(
+                self.audio_device_id,
+                &property_address as *const _,
+                0,
+                null(),
+                &data_size as *const _ as *mut _,
+                ranges.as_mut_ptr() as *mut _,
+            );
+            check_os_status(status)?;
+
+            let ranges: *mut AudioValueRange = ranges.as_mut_ptr() as *mut _;
+            let ranges: &'static [AudioValueRange] = slice::from_raw_parts(ranges, n_ranges);
+
+            let audio_unit = audio_unit_from_device(self, true)?;
+            let buffer_size = get_io_buffer_frame_size_range(&audio_unit)?;
+
+            // Collect the supported formats for the device.
+            let mut fmts = vec![];
+            for range in ranges {
+                let fmt = SupportedStreamConfigRange {
+                    channels: n_channels as ChannelCount,
+                    min_sample_rate: SampleRate(range.mMinimum as _),
+                    max_sample_rate: SampleRate(range.mMaximum as _),
+                    buffer_size,
+                    sample_format,
+                };
+                fmts.push(fmt);
+            }
+
+            Ok(fmts.into_iter())
+        }
+    }
+
+    fn supported_input_configs(
+        &self,
+    ) -> Result<SupportedOutputConfigs, SupportedStreamConfigsError> {
+        self.supported_configs(kAudioObjectPropertyScopeInput)
+    }
+
+    fn supported_output_configs(
+        &self,
+    ) -> Result<SupportedOutputConfigs, SupportedStreamConfigsError> {
+        self.supported_configs(kAudioObjectPropertyScopeOutput)
+    }
+
+    fn default_config(
+        &self,
+        scope: AudioObjectPropertyScope,
+    ) -> Result<SupportedStreamConfig, DefaultStreamConfigError> {
+        fn default_config_error_from_os_status(
+            status: OSStatus,
+        ) -> Result<(), DefaultStreamConfigError> {
+            let err = match coreaudio::Error::from_os_status(status) {
+                Err(err) => err,
+                Ok(_) => return Ok(()),
+            };
+            match err {
+                coreaudio::Error::AudioUnit(
+                    coreaudio::error::AudioUnitError::FormatNotSupported,
+                )
+                | coreaudio::Error::AudioCodec(_)
+                | coreaudio::Error::AudioFormat(_) => {
+                    Err(DefaultStreamConfigError::StreamTypeNotSupported)
+                }
+                coreaudio::Error::AudioUnit(coreaudio::error::AudioUnitError::NoConnection) => {
+                    Err(DefaultStreamConfigError::DeviceNotAvailable)
+                }
+                err => {
+                    let description = format!("{}", err);
+                    let err = BackendSpecificError { description };
+                    Err(err.into())
+                }
+            }
+        }
+
+        let property_address = AudioObjectPropertyAddress {
+            mSelector: kAudioDevicePropertyStreamFormat,
+            mScope: scope,
+            mElement: kAudioObjectPropertyElementMaster,
+        };
+
+        unsafe {
+            let asbd: AudioStreamBasicDescription = mem::zeroed();
+            let data_size = mem::size_of::<AudioStreamBasicDescription>() as u32;
+            let status = AudioObjectGetPropertyData(
+                self.audio_device_id,
+                &property_address as *const _,
+                0,
+                null(),
+                &data_size as *const _ as *mut _,
+                &asbd as *const _ as *mut _,
+            );
+            default_config_error_from_os_status(status)?;
+
+            let sample_format = {
+                let audio_format = coreaudio::audio_unit::AudioFormat::from_format_and_flag(
+                    asbd.mFormatID,
+                    Some(asbd.mFormatFlags),
+                );
+                let flags = match audio_format {
+                    Some(coreaudio::audio_unit::AudioFormat::LinearPCM(flags)) => flags,
+                    _ => return Err(DefaultStreamConfigError::StreamTypeNotSupported),
+                };
+                let maybe_sample_format =
+                    coreaudio::audio_unit::SampleFormat::from_flags_and_bits_per_sample(
+                        flags,
+                        asbd.mBitsPerChannel,
+                    );
+                match maybe_sample_format {
+                    Some(coreaudio::audio_unit::SampleFormat::F32) => SampleFormat::F32,
+                    Some(coreaudio::audio_unit::SampleFormat::I16) => SampleFormat::I16,
+                    _ => return Err(DefaultStreamConfigError::StreamTypeNotSupported),
+                }
+            };
+
+            let audio_unit = audio_unit_from_device(self, true)?;
+            let buffer_size = get_io_buffer_frame_size_range(&audio_unit)?;
+
+            let config = SupportedStreamConfig {
+                sample_rate: SampleRate(asbd.mSampleRate as _),
+                channels: asbd.mChannelsPerFrame as _,
+                buffer_size,
+                sample_format,
+            };
+            Ok(config)
+        }
+    }
+
+    fn default_input_config(&self) -> Result<SupportedStreamConfig, DefaultStreamConfigError> {
+        self.default_config(kAudioObjectPropertyScopeInput)
+    }
+
+    fn default_output_config(&self) -> Result<SupportedStreamConfig, DefaultStreamConfigError> {
+        self.default_config(kAudioObjectPropertyScopeOutput)
+    }
+}
+
+impl fmt::Debug for Device {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        f.debug_struct("Device")
+            .field("audio_device_id", &self.audio_device_id)
+            .field("name", &self.name())
+            .finish()
+    }
+}
+
+struct StreamInner {
+    playing: bool,
+    audio_unit: AudioUnit,
+    /// Manage the lifetime of the closure that handles device disconnection.
+    _disconnect_listener: Option<AudioObjectPropertyListener>,
+    // Track the device with which the audio unit was spawned.
+    //
+    // We must do this so that we can avoid changing the device sample rate if there is already
+    // a stream associated with the device.
+    #[allow(dead_code)]
+    device_id: AudioDeviceID,
+}
+
+/// Register the on-disconnect callback.
+/// This will both stop the stream and call the error callback with DeviceNotAvailable.
+/// This function should only be called once per stream.
+fn add_disconnect_listener<E>(
+    stream: &Stream,
+    error_callback: Arc<Mutex<E>>,
+) -> Result<(), BuildStreamError>
+where
+    E: FnMut(StreamError) + Send + 'static,
+{
+    let stream_copy = stream.clone();
+    let mut stream_inner = stream.inner.lock().unwrap();
+    stream_inner._disconnect_listener = Some(AudioObjectPropertyListener::new(
+        stream_inner.device_id,
+        AudioObjectPropertyAddress {
+            mSelector: kAudioDevicePropertyDeviceIsAlive,
+            mScope: kAudioObjectPropertyScopeGlobal,
+            mElement: kAudioObjectPropertyElementMaster,
+        },
+        move || {
+            let _ = stream_copy.pause();
+            (error_callback.lock().unwrap())(StreamError::DeviceNotAvailable);
+        },
+    )?);
+    Ok(())
+}
+
+fn audio_unit_from_device(device: &Device, input: bool) -> Result<AudioUnit, coreaudio::Error> {
+    let output_type = if device.is_default && !input {
+        coreaudio::audio_unit::IOType::DefaultOutput
+    } else {
+        coreaudio::audio_unit::IOType::HalOutput
+    };
+    let mut audio_unit = AudioUnit::new(output_type)?;
+
+    if input {
+        // Enable input processing.
+        let enable_input = 1u32;
+        audio_unit.set_property(
+            kAudioOutputUnitProperty_EnableIO,
+            Scope::Input,
+            Element::Input,
+            Some(&enable_input),
+        )?;
+
+        // Disable output processing.
+        let disable_output = 0u32;
+        audio_unit.set_property(
+            kAudioOutputUnitProperty_EnableIO,
+            Scope::Output,
+            Element::Output,
+            Some(&disable_output),
+        )?;
+    }
+
+    audio_unit.set_property(
+        kAudioOutputUnitProperty_CurrentDevice,
+        Scope::Global,
+        Element::Output,
+        Some(&device.audio_device_id),
+    )?;
+
+    Ok(audio_unit)
+}
+
+impl Device {
+    #[allow(clippy::cast_ptr_alignment)]
+    #[allow(clippy::while_immutable_condition)]
+    #[allow(clippy::float_cmp)]
+    fn build_input_stream_raw<D, E>(
+        &self,
+        config: &StreamConfig,
+        sample_format: SampleFormat,
+        mut data_callback: D,
+        error_callback: E,
+        _timeout: Option<Duration>,
+    ) -> Result<Stream, BuildStreamError>
+    where
+        D: FnMut(&Data, &InputCallbackInfo) + Send + 'static,
+        E: FnMut(StreamError) + Send + 'static,
+    {
+        // The scope and element for working with a device's input stream.
+        let scope = Scope::Output;
+        let element = Element::Input;
+
+        // Potentially change the device sample rate to match the config.
+        set_sample_rate(self.audio_device_id, config.sample_rate)?;
+
+        let mut audio_unit = audio_unit_from_device(self, true)?;
+
+        // Set the stream in interleaved mode.
+        let asbd = asbd_from_config(config, sample_format);
+        audio_unit.set_property(kAudioUnitProperty_StreamFormat, scope, element, Some(&asbd))?;
+
+        // Set the buffersize
+        match config.buffer_size {
+            BufferSize::Fixed(v) => {
+                let buffer_size_range = get_io_buffer_frame_size_range(&audio_unit)?;
+                match buffer_size_range {
+                    SupportedBufferSize::Range { min, max } => {
+                        if v >= min && v <= max {
+                            audio_unit.set_property(
+                                kAudioDevicePropertyBufferFrameSize,
+                                scope,
+                                element,
+                                Some(&v),
+                            )?
+                        } else {
+                            return Err(BuildStreamError::StreamConfigNotSupported);
+                        }
+                    }
+                    SupportedBufferSize::Unknown => (),
+                }
+            }
+            BufferSize::Default => (),
+        }
+
+        let error_callback = Arc::new(Mutex::new(error_callback));
+        let error_callback_disconnect = error_callback.clone();
+
+        // Register the callback that is being called by coreaudio whenever it needs data to be
+        // fed to the audio buffer.
+        let bytes_per_channel = sample_format.sample_size();
+        let sample_rate = config.sample_rate;
+        type Args = render_callback::Args<data::Raw>;
+        audio_unit.set_input_callback(move |args: Args| unsafe {
+            let ptr = (*args.data.data).mBuffers.as_ptr();
+            let len = (*args.data.data).mNumberBuffers as usize;
+            let buffers: &[AudioBuffer] = slice::from_raw_parts(ptr, len);
+
+            // TODO: Perhaps loop over all buffers instead?
+            let AudioBuffer {
+                mNumberChannels: channels,
+                mDataByteSize: data_byte_size,
+                mData: data,
+            } = buffers[0];
+
+            let data = data as *mut ();
+            let len = data_byte_size as usize / bytes_per_channel;
+            let data = Data::from_parts(data, len, sample_format);
+
+            // TODO: Need a better way to get delay, for now we assume a double-buffer offset.
+            let callback = match host_time_to_stream_instant(args.time_stamp.mHostTime) {
+                Err(err) => {
+                    (error_callback.lock().unwrap())(err.into());
+                    return Err(());
+                }
+                Ok(cb) => cb,
+            };
+            let buffer_frames = len / channels as usize;
+            let delay = frames_to_duration(buffer_frames, sample_rate);
+            let capture = callback
+                .sub(delay)
+                .expect("`capture` occurs before origin of alsa `StreamInstant`");
+            let timestamp = crate::InputStreamTimestamp { callback, capture };
+
+            let info = InputCallbackInfo { timestamp };
+            data_callback(&data, &info);
+            Ok(())
+        })?;
+
+        let stream = Stream::new(StreamInner {
+            playing: true,
+            _disconnect_listener: None,
+            audio_unit,
+            device_id: self.audio_device_id,
+        });
+
+        // If we didn't request the default device, stop the stream if the
+        // device disconnects.
+        if !self.is_default {
+            add_disconnect_listener(&stream, error_callback_disconnect)?;
+        }
+
+        stream.inner.lock().unwrap().audio_unit.start()?;
+
+        Ok(stream)
+    }
+
+    fn build_output_stream_raw<D, E>(
+        &self,
+        config: &StreamConfig,
+        sample_format: SampleFormat,
+        mut data_callback: D,
+        error_callback: E,
+        _timeout: Option<Duration>,
+    ) -> Result<Stream, BuildStreamError>
+    where
+        D: FnMut(&mut Data, &OutputCallbackInfo) + Send + 'static,
+        E: FnMut(StreamError) + Send + 'static,
+    {
+        let mut audio_unit = audio_unit_from_device(self, false)?;
+
+        // The scope and element for working with a device's output stream.
+        let scope = Scope::Input;
+        let element = Element::Output;
+
+        // Set the stream in interleaved mode.
+        let asbd = asbd_from_config(config, sample_format);
+        audio_unit.set_property(kAudioUnitProperty_StreamFormat, scope, element, Some(&asbd))?;
+
+        // Set the buffersize
+        match config.buffer_size {
+            BufferSize::Fixed(v) => {
+                let buffer_size_range = get_io_buffer_frame_size_range(&audio_unit)?;
+                match buffer_size_range {
+                    SupportedBufferSize::Range { min, max } => {
+                        if v >= min && v <= max {
+                            audio_unit.set_property(
+                                kAudioDevicePropertyBufferFrameSize,
+                                scope,
+                                element,
+                                Some(&v),
+                            )?
+                        } else {
+                            return Err(BuildStreamError::StreamConfigNotSupported);
+                        }
+                    }
+                    SupportedBufferSize::Unknown => (),
+                }
+            }
+            BufferSize::Default => (),
+        }
+
+        let error_callback = Arc::new(Mutex::new(error_callback));
+        let error_callback_disconnect = error_callback.clone();
+
+        // Register the callback that is being called by coreaudio whenever it needs data to be
+        // fed to the audio buffer.
+        let bytes_per_channel = sample_format.sample_size();
+        let sample_rate = config.sample_rate;
+        type Args = render_callback::Args<data::Raw>;
+        audio_unit.set_render_callback(move |args: Args| unsafe {
+            // If `run()` is currently running, then a callback will be available from this list.
+            // Otherwise, we just fill the buffer with zeroes and return.
+
+            let AudioBuffer {
+                mNumberChannels: channels,
+                mDataByteSize: data_byte_size,
+                mData: data,
+            } = (*args.data.data).mBuffers[0];
+
+            let data = data as *mut ();
+            let len = data_byte_size as usize / bytes_per_channel;
+            let mut data = Data::from_parts(data, len, sample_format);
+
+            let callback = match host_time_to_stream_instant(args.time_stamp.mHostTime) {
+                Err(err) => {
+                    (error_callback.lock().unwrap())(err.into());
+                    return Err(());
+                }
+                Ok(cb) => cb,
+            };
+            // TODO: Need a better way to get delay, for now we assume a double-buffer offset.
+            let buffer_frames = len / channels as usize;
+            let delay = frames_to_duration(buffer_frames, sample_rate);
+            let playback = callback
+                .add(delay)
+                .expect("`playback` occurs beyond representation supported by `StreamInstant`");
+            let timestamp = crate::OutputStreamTimestamp { callback, playback };
+
+            let info = OutputCallbackInfo { timestamp };
+            data_callback(&mut data, &info);
+            Ok(())
+        })?;
+
+        let stream = Stream::new(StreamInner {
+            playing: true,
+            _disconnect_listener: None,
+            audio_unit,
+            device_id: self.audio_device_id,
+        });
+
+        // If we didn't request the default device, stop the stream if the
+        // device disconnects.
+        if !self.is_default {
+            add_disconnect_listener(&stream, error_callback_disconnect)?;
+        }
+
+        stream.inner.lock().unwrap().audio_unit.start()?;
+
+        Ok(stream)
+    }
+}
+
+/// Attempt to set the device sample rate to the provided rate.
+/// Return an error if the requested sample rate is not supported by the device.
+fn set_sample_rate(
+    audio_device_id: AudioObjectID,
+    target_sample_rate: SampleRate,
+) -> Result<(), BuildStreamError> {
+    // Get the current sample rate.
+    let mut property_address = AudioObjectPropertyAddress {
+        mSelector: kAudioDevicePropertyNominalSampleRate,
+        mScope: kAudioObjectPropertyScopeGlobal,
+        mElement: kAudioObjectPropertyElementMaster,
+    };
+    let sample_rate: f64 = 0.0;
+    let data_size = mem::size_of::<f64>() as u32;
+    let status = unsafe {
+        AudioObjectGetPropertyData(
+            audio_device_id,
+            &property_address as *const _,
+            0,
+            null(),
+            &data_size as *const _ as *mut _,
+            &sample_rate as *const _ as *mut _,
+        )
+    };
+    coreaudio::Error::from_os_status(status)?;
+
+    // If the requested sample rate is different to the device sample rate, update the device.
+    if sample_rate as u32 != target_sample_rate.0 {
+        // Get available sample rate ranges.
+        property_address.mSelector = kAudioDevicePropertyAvailableNominalSampleRates;
+        let data_size = 0u32;
+        let status = unsafe {
+            AudioObjectGetPropertyDataSize(
+                audio_device_id,
+                &property_address as *const _,
+                0,
+                null(),
+                &data_size as *const _ as *mut _,
+            )
+        };
+        coreaudio::Error::from_os_status(status)?;
+        let n_ranges = data_size as usize / mem::size_of::<AudioValueRange>();
+        let mut ranges: Vec<u8> = vec![];
+        ranges.reserve_exact(data_size as usize);
+        let status = unsafe {
+            AudioObjectGetPropertyData(
+                audio_device_id,
+                &property_address as *const _,
+                0,
+                null(),
+                &data_size as *const _ as *mut _,
+                ranges.as_mut_ptr() as *mut _,
+            )
+        };
+        coreaudio::Error::from_os_status(status)?;
+        let ranges: *mut AudioValueRange = ranges.as_mut_ptr() as *mut _;
+        let ranges: &'static [AudioValueRange] = unsafe { slice::from_raw_parts(ranges, n_ranges) };
+
+        // Now that we have the available ranges, pick the one matching the desired rate.
+        let sample_rate = target_sample_rate.0;
+        let maybe_index = ranges
+            .iter()
+            .position(|r| r.mMinimum as u32 == sample_rate && r.mMaximum as u32 == sample_rate);
+        let range_index = match maybe_index {
+            None => return Err(BuildStreamError::StreamConfigNotSupported),
+            Some(i) => i,
+        };
+
+        let (send, recv) = channel::<Result<f64, coreaudio::Error>>();
+        let sample_rate_address = AudioObjectPropertyAddress {
+            mSelector: kAudioDevicePropertyNominalSampleRate,
+            mScope: kAudioObjectPropertyScopeGlobal,
+            mElement: kAudioObjectPropertyElementMaster,
+        };
+        // Send sample rate updates back on a channel.
+        let sample_rate_handler = move || {
+            let mut rate: f64 = 0.0;
+            let data_size = mem::size_of::<f64>();
+
+            let result = unsafe {
+                AudioObjectGetPropertyData(
+                    audio_device_id,
+                    &sample_rate_address as *const _,
+                    0,
+                    null(),
+                    &data_size as *const _ as *mut _,
+                    &mut rate as *const _ as *mut _,
+                )
+            };
+            send.send(coreaudio::Error::from_os_status(result).map(|_| rate))
+                .ok();
+        };
+
+        let listener = AudioObjectPropertyListener::new(
+            audio_device_id,
+            sample_rate_address,
+            sample_rate_handler,
+        )?;
+
+        // Finally, set the sample rate.
+        property_address.mSelector = kAudioDevicePropertyNominalSampleRate;
+        let status = unsafe {
+            AudioObjectSetPropertyData(
+                audio_device_id,
+                &property_address as *const _,
+                0,
+                null(),
+                data_size,
+                &ranges[range_index] as *const _ as *const _,
+            )
+        };
+        coreaudio::Error::from_os_status(status)?;
+
+        // Wait for the reported_rate to change.
+        //
+        // This should not take longer than a few ms, but we timeout after 1 sec just in case.
+        // We loop over potentially several events from the channel to ensure
+        // that we catch the expected change in sample rate.
+        let mut timeout = Duration::from_secs(1);
+        let start = Instant::now();
+
+        loop {
+            match recv.recv_timeout(timeout) {
+                Err(err) => {
+                    let description = match err {
+                        RecvTimeoutError::Disconnected => {
+                            "sample rate listener channel disconnected unexpectedly"
+                        }
+                        RecvTimeoutError::Timeout => {
+                            "timeout waiting for sample rate update for device"
+                        }
+                    }
+                    .to_string();
+                    return Err(BackendSpecificError { description }.into());
+                }
+                Ok(Ok(reported_sample_rate)) => {
+                    if reported_sample_rate == target_sample_rate.0 as f64 {
+                        break;
+                    }
+                }
+                Ok(Err(_)) => {
+                    // TODO: should we consider collecting this error?
+                }
+            };
+            timeout = timeout
+                .checked_sub(start.elapsed())
+                .unwrap_or(Duration::ZERO);
+        }
+        listener.remove()?;
+    }
+    Ok(())
+}
+
+#[derive(Clone)]
+pub struct Stream {
+    inner: Arc<Mutex<StreamInner>>,
+}
+
+impl Stream {
+    fn new(inner: StreamInner) -> Self {
+        Self {
+            inner: Arc::new(Mutex::new(inner)),
+        }
+    }
+}
+
+impl StreamTrait for Stream {
+    fn play(&self) -> Result<(), PlayStreamError> {
+        let mut stream = self.inner.lock().unwrap();
+
+        if !stream.playing {
+            if let Err(e) = stream.audio_unit.start() {
+                let description = format!("{}", e);
+                let err = BackendSpecificError { description };
+                return Err(err.into());
+            }
+            stream.playing = true;
+        }
+        Ok(())
+    }
+
+    fn pause(&self) -> Result<(), PauseStreamError> {
+        let mut stream = self.inner.lock().unwrap();
+
+        if stream.playing {
+            if let Err(e) = stream.audio_unit.stop() {
+                let description = format!("{}", e);
+                let err = BackendSpecificError { description };
+                return Err(err.into());
+            }
+
+            stream.playing = false;
+        }
+        Ok(())
+    }
+}
+
+fn get_io_buffer_frame_size_range(
+    audio_unit: &AudioUnit,
+) -> Result<SupportedBufferSize, coreaudio::Error> {
+    let buffer_size_range: AudioValueRange = audio_unit.get_property(
+        kAudioDevicePropertyBufferFrameSizeRange,
+        Scope::Global,
+        Element::Output,
+    )?;
+
+    Ok(SupportedBufferSize::Range {
+        min: buffer_size_range.mMinimum as u32,
+        max: buffer_size_range.mMaximum as u32,
+    })
+}

vendor/cpal/src/host/coreaudio/macos/property_listener.rs

@@ -0,0 +1,85 @@
+//! Helper code for registering audio object property listeners.
+use super::coreaudio::sys::{
+    AudioObjectAddPropertyListener, AudioObjectID, AudioObjectPropertyAddress,
+    AudioObjectRemovePropertyListener, OSStatus,
+};
+
+use crate::BuildStreamError;
+
+/// A double-indirection to be able to pass a closure (a fat pointer)
+/// via a single c_void.
+struct PropertyListenerCallbackWrapper(Box<dyn FnMut()>);
+
+/// Maintain an audio object property listener.
+/// The listener will be removed when this type is dropped.
+pub struct AudioObjectPropertyListener {
+    callback: Box<PropertyListenerCallbackWrapper>,
+    property_address: AudioObjectPropertyAddress,
+    audio_object_id: AudioObjectID,
+    removed: bool,
+}
+
+impl AudioObjectPropertyListener {
+    /// Attach the provided callback as a audio object property listener.
+    pub fn new<F: FnMut() + 'static>(
+        audio_object_id: AudioObjectID,
+        property_address: AudioObjectPropertyAddress,
+        callback: F,
+    ) -> Result<Self, BuildStreamError> {
+        let callback = Box::new(PropertyListenerCallbackWrapper(Box::new(callback)));
+        unsafe {
+            coreaudio::Error::from_os_status(AudioObjectAddPropertyListener(
+                audio_object_id,
+                &property_address as *const _,
+                Some(property_listener_handler_shim),
+                &*callback as *const _ as *mut _,
+            ))?;
+        };
+        Ok(Self {
+            callback,
+            audio_object_id,
+            property_address,
+            removed: false,
+        })
+    }
+
+    /// Explicitly remove the property listener.
+    /// Use this method if you need to explicitly handle failure to remove
+    /// the property listener.
+    pub fn remove(mut self) -> Result<(), BuildStreamError> {
+        self.remove_inner()
+    }
+
+    fn remove_inner(&mut self) -> Result<(), BuildStreamError> {
+        unsafe {
+            coreaudio::Error::from_os_status(AudioObjectRemovePropertyListener(
+                self.audio_object_id,
+                &self.property_address as *const _,
+                Some(property_listener_handler_shim),
+                &*self.callback as *const _ as *mut _,
+            ))?;
+        }
+        self.removed = true;
+        Ok(())
+    }
+}
+
+impl Drop for AudioObjectPropertyListener {
+    fn drop(&mut self) {
+        if !self.removed {
+            let _ = self.remove_inner();
+        }
+    }
+}
+
+/// Callback used to call user-provided closure as a property listener.
+unsafe extern "C" fn property_listener_handler_shim(
+    _: AudioObjectID,
+    _: u32,
+    _: *const AudioObjectPropertyAddress,
+    callback: *mut ::std::os::raw::c_void,
+) -> OSStatus {
+    let wrapper = callback as *mut PropertyListenerCallbackWrapper;
+    (*wrapper).0();
+    0
+}

vendor/cpal/src/host/coreaudio/mod.rs

@@ -0,0 +1,121 @@
+extern crate coreaudio;
+
+use self::coreaudio::sys::{
+    kAudioFormatFlagIsFloat, kAudioFormatFlagIsPacked, kAudioFormatLinearPCM,
+    AudioStreamBasicDescription, OSStatus,
+};
+
+use crate::DefaultStreamConfigError;
+use crate::{BuildStreamError, SupportedStreamConfigsError};
+
+use crate::{BackendSpecificError, SampleFormat, StreamConfig};
+
+#[cfg(target_os = "ios")]
+mod ios;
+#[cfg(target_os = "macos")]
+mod macos;
+
+#[cfg(target_os = "ios")]
+pub use self::ios::{
+    enumerate::{Devices, SupportedInputConfigs, SupportedOutputConfigs},
+    Device, Host, Stream,
+};
+
+#[cfg(target_os = "macos")]
+pub use self::macos::{
+    enumerate::{Devices, SupportedInputConfigs, SupportedOutputConfigs},
+    Device, Host, Stream,
+};
+
+/// Common helper methods used by both macOS and iOS
+
+fn check_os_status(os_status: OSStatus) -> Result<(), BackendSpecificError> {
+    match coreaudio::Error::from_os_status(os_status) {
+        Ok(()) => Ok(()),
+        Err(err) => {
+            let description = err.to_string();
+            Err(BackendSpecificError { description })
+        }
+    }
+}
+
+// Create a coreaudio AudioStreamBasicDescription from a CPAL Format.
+fn asbd_from_config(
+    config: &StreamConfig,
+    sample_format: SampleFormat,
+) -> AudioStreamBasicDescription {
+    let n_channels = config.channels as usize;
+    let sample_rate = config.sample_rate.0;
+    let bytes_per_channel = sample_format.sample_size();
+    let bits_per_channel = bytes_per_channel * 8;
+    let bytes_per_frame = n_channels * bytes_per_channel;
+    let frames_per_packet = 1;
+    let bytes_per_packet = frames_per_packet * bytes_per_frame;
+    let format_flags = match sample_format {
+        SampleFormat::F32 => kAudioFormatFlagIsFloat | kAudioFormatFlagIsPacked,
+        _ => kAudioFormatFlagIsPacked,
+    };
+    AudioStreamBasicDescription {
+        mBitsPerChannel: bits_per_channel as _,
+        mBytesPerFrame: bytes_per_frame as _,
+        mChannelsPerFrame: n_channels as _,
+        mBytesPerPacket: bytes_per_packet as _,
+        mFramesPerPacket: frames_per_packet as _,
+        mFormatFlags: format_flags,
+        mFormatID: kAudioFormatLinearPCM,
+        mSampleRate: sample_rate as _,
+        ..Default::default()
+    }
+}
+
+fn host_time_to_stream_instant(
+    m_host_time: u64,
+) -> Result<crate::StreamInstant, BackendSpecificError> {
+    let mut info: mach2::mach_time::mach_timebase_info = Default::default();
+    let res = unsafe { mach2::mach_time::mach_timebase_info(&mut info) };
+    check_os_status(res)?;
+    let nanos = m_host_time * info.numer as u64 / info.denom as u64;
+    let secs = nanos / 1_000_000_000;
+    let subsec_nanos = nanos - secs * 1_000_000_000;
+    Ok(crate::StreamInstant::new(secs as i64, subsec_nanos as u32))
+}
+
+// Convert the given duration in frames at the given sample rate to a `std::time::Duration`.
+fn frames_to_duration(frames: usize, rate: crate::SampleRate) -> std::time::Duration {
+    let secsf = frames as f64 / rate.0 as f64;
+    let secs = secsf as u64;
+    let nanos = ((secsf - secs as f64) * 1_000_000_000.0) as u32;
+    std::time::Duration::new(secs, nanos)
+}
+
+// TODO need stronger error identification
+impl From<coreaudio::Error> for BuildStreamError {
+    fn from(err: coreaudio::Error) -> BuildStreamError {
+        match err {
+            coreaudio::Error::RenderCallbackBufferFormatDoesNotMatchAudioUnitStreamFormat
+            | coreaudio::Error::NoKnownSubtype
+            | coreaudio::Error::AudioUnit(coreaudio::error::AudioUnitError::FormatNotSupported)
+            | coreaudio::Error::AudioCodec(_)
+            | coreaudio::Error::AudioFormat(_) => BuildStreamError::StreamConfigNotSupported,
+            _ => BuildStreamError::DeviceNotAvailable,
+        }
+    }
+}
+
+impl From<coreaudio::Error> for SupportedStreamConfigsError {
+    fn from(err: coreaudio::Error) -> SupportedStreamConfigsError {
+        let description = format!("{}", err);
+        let err = BackendSpecificError { description };
+        // Check for possible DeviceNotAvailable variant
+        SupportedStreamConfigsError::BackendSpecific { err }
+    }
+}
+
+impl From<coreaudio::Error> for DefaultStreamConfigError {
+    fn from(err: coreaudio::Error) -> DefaultStreamConfigError {
+        let description = format!("{}", err);
+        let err = BackendSpecificError { description };
+        // Check for possible DeviceNotAvailable variant
+        DefaultStreamConfigError::BackendSpecific { err }
+    }
+}

vendor/cpal/src/host/emscripten/mod.rs

@@ -0,0 +1,422 @@
+use js_sys::Float32Array;
+use std::time::Duration;
+use wasm_bindgen::prelude::*;
+use wasm_bindgen::JsCast;
+use wasm_bindgen_futures::{spawn_local, JsFuture};
+use web_sys::AudioContext;
+
+use crate::traits::{DeviceTrait, HostTrait, StreamTrait};
+use crate::{
+    BufferSize, BuildStreamError, Data, DefaultStreamConfigError, DeviceNameError, DevicesError,
+    InputCallbackInfo, OutputCallbackInfo, PauseStreamError, PlayStreamError, SampleFormat,
+    SampleRate, StreamConfig, StreamError, SupportedBufferSize, SupportedStreamConfig,
+    SupportedStreamConfigRange, SupportedStreamConfigsError,
+};
+
+// The emscripten backend currently works by instantiating an `AudioContext` object per `Stream`.
+// Creating a stream creates a new `AudioContext`. Destroying a stream destroys it. Creation of a
+// `Host` instance initializes the `stdweb` context.
+
+/// The default emscripten host type.
+#[derive(Debug)]
+pub struct Host;
+
+/// Content is false if the iterator is empty.
+pub struct Devices(bool);
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct Device;
+
+#[wasm_bindgen]
+#[derive(Clone)]
+pub struct Stream {
+    // A reference to an `AudioContext` object.
+    audio_ctxt: AudioContext,
+}
+
+// Index within the `streams` array of the events loop.
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+pub struct StreamId(usize);
+
+pub type SupportedInputConfigs = ::std::vec::IntoIter<SupportedStreamConfigRange>;
+pub type SupportedOutputConfigs = ::std::vec::IntoIter<SupportedStreamConfigRange>;
+
+const MIN_CHANNELS: u16 = 1;
+const MAX_CHANNELS: u16 = 32;
+const MIN_SAMPLE_RATE: SampleRate = SampleRate(8_000);
+const MAX_SAMPLE_RATE: SampleRate = SampleRate(96_000);
+const DEFAULT_SAMPLE_RATE: SampleRate = SampleRate(44_100);
+const MIN_BUFFER_SIZE: u32 = 1;
+const MAX_BUFFER_SIZE: u32 = u32::MAX;
+const DEFAULT_BUFFER_SIZE: usize = 2048;
+const SUPPORTED_SAMPLE_FORMAT: SampleFormat = SampleFormat::F32;
+
+impl Host {
+    pub fn new() -> Result<Self, crate::HostUnavailable> {
+        Ok(Host)
+    }
+}
+
+impl Devices {
+    fn new() -> Result<Self, DevicesError> {
+        Ok(Self::default())
+    }
+}
+
+impl Device {
+    #[inline]
+    fn name(&self) -> Result<String, DeviceNameError> {
+        Ok("Default Device".to_owned())
+    }
+
+    #[inline]
+    fn supported_input_configs(
+        &self,
+    ) -> Result<SupportedInputConfigs, SupportedStreamConfigsError> {
+        unimplemented!();
+    }
+
+    #[inline]
+    fn supported_output_configs(
+        &self,
+    ) -> Result<SupportedOutputConfigs, SupportedStreamConfigsError> {
+        let buffer_size = SupportedBufferSize::Range {
+            min: MIN_BUFFER_SIZE,
+            max: MAX_BUFFER_SIZE,
+        };
+        let configs: Vec<_> = (MIN_CHANNELS..=MAX_CHANNELS)
+            .map(|channels| SupportedStreamConfigRange {
+                channels,
+                min_sample_rate: MIN_SAMPLE_RATE,
+                max_sample_rate: MAX_SAMPLE_RATE,
+                buffer_size: buffer_size.clone(),
+                sample_format: SUPPORTED_SAMPLE_FORMAT,
+            })
+            .collect();
+        Ok(configs.into_iter())
+    }
+
+    fn default_input_config(&self) -> Result<SupportedStreamConfig, DefaultStreamConfigError> {
+        unimplemented!();
+    }
+
+    fn default_output_config(&self) -> Result<SupportedStreamConfig, DefaultStreamConfigError> {
+        const EXPECT: &str = "expected at least one valid webaudio stream config";
+        let config = self
+            .supported_output_configs()
+            .expect(EXPECT)
+            .max_by(|a, b| a.cmp_default_heuristics(b))
+            .unwrap()
+            .with_sample_rate(DEFAULT_SAMPLE_RATE);
+
+        Ok(config)
+    }
+}
+
+impl HostTrait for Host {
+    type Devices = Devices;
+    type Device = Device;
+
+    fn is_available() -> bool {
+        // Assume this host is always available on emscripten.
+        true
+    }
+
+    fn devices(&self) -> Result<Self::Devices, DevicesError> {
+        Devices::new()
+    }
+
+    fn default_input_device(&self) -> Option<Self::Device> {
+        default_input_device()
+    }
+
+    fn default_output_device(&self) -> Option<Self::Device> {
+        default_output_device()
+    }
+}
+
+impl DeviceTrait for Device {
+    type SupportedInputConfigs = SupportedInputConfigs;
+    type SupportedOutputConfigs = SupportedOutputConfigs;
+    type Stream = Stream;
+
+    fn name(&self) -> Result<String, DeviceNameError> {
+        Device::name(self)
+    }
+
+    fn supported_input_configs(
+        &self,
+    ) -> Result<Self::SupportedInputConfigs, SupportedStreamConfigsError> {
+        Device::supported_input_configs(self)
+    }
+
+    fn supported_output_configs(
+        &self,
+    ) -> Result<Self::SupportedOutputConfigs, SupportedStreamConfigsError> {
+        Device::supported_output_configs(self)
+    }
+
+    fn default_input_config(&self) -> Result<SupportedStreamConfig, DefaultStreamConfigError> {
+        Device::default_input_config(self)
+    }
+
+    fn default_output_config(&self) -> Result<SupportedStreamConfig, DefaultStreamConfigError> {
+        Device::default_output_config(self)
+    }
+
+    fn build_input_stream_raw<D, E>(
+        &self,
+        _config: &StreamConfig,
+        _sample_format: SampleFormat,
+        _data_callback: D,
+        _error_callback: E,
+        _timeout: Option<Duration>,
+    ) -> Result<Self::Stream, BuildStreamError>
+    where
+        D: FnMut(&Data, &InputCallbackInfo) + Send + 'static,
+        E: FnMut(StreamError) + Send + 'static,
+    {
+        unimplemented!()
+    }
+
+    fn build_output_stream_raw<D, E>(
+        &self,
+        config: &StreamConfig,
+        sample_format: SampleFormat,
+        data_callback: D,
+        _error_callback: E,
+        _timeout: Option<Duration>,
+    ) -> Result<Self::Stream, BuildStreamError>
+    where
+        D: FnMut(&mut Data, &OutputCallbackInfo) + Send + 'static,
+        E: FnMut(StreamError) + Send + 'static,
+    {
+        if !valid_config(config, sample_format) {
+            return Err(BuildStreamError::StreamConfigNotSupported);
+        }
+
+        let buffer_size_frames = match config.buffer_size {
+            BufferSize::Fixed(v) => {
+                if v == 0 {
+                    return Err(BuildStreamError::StreamConfigNotSupported);
+                } else {
+                    v as usize
+                }
+            }
+            BufferSize::Default => DEFAULT_BUFFER_SIZE,
+        };
+
+        // Create the stream.
+        let audio_ctxt = AudioContext::new().expect("webaudio is not present on this system");
+        let stream = Stream { audio_ctxt };
+
+        // Use `set_timeout` to invoke a Rust callback repeatedly.
+        //
+        // The job of this callback is to fill the content of the audio buffers.
+        //
+        // See also: The call to `set_timeout` at the end of the `audio_callback_fn` which creates
+        // the loop.
+        set_timeout(
+            10,
+            stream.clone(),
+            data_callback,
+            config,
+            sample_format,
+            buffer_size_frames as u32,
+        );
+
+        Ok(stream)
+    }
+}
+
+impl StreamTrait for Stream {
+    fn play(&self) -> Result<(), PlayStreamError> {
+        let future = JsFuture::from(
+            self.audio_ctxt
+                .resume()
+                .expect("Could not resume the stream"),
+        );
+        spawn_local(async {
+            match future.await {
+                Ok(value) => assert!(value.is_undefined()),
+                Err(value) => panic!("AudioContext.resume() promise was rejected: {:?}", value),
+            }
+        });
+        Ok(())
+    }
+
+    fn pause(&self) -> Result<(), PauseStreamError> {
+        let future = JsFuture::from(
+            self.audio_ctxt
+                .suspend()
+                .expect("Could not suspend the stream"),
+        );
+        spawn_local(async {
+            match future.await {
+                Ok(value) => assert!(value.is_undefined()),
+                Err(value) => panic!("AudioContext.suspend() promise was rejected: {:?}", value),
+            }
+        });
+        Ok(())
+    }
+}
+
+fn audio_callback_fn<D>(
+    mut data_callback: D,
+) -> impl FnOnce(Stream, StreamConfig, SampleFormat, u32)
+where
+    D: FnMut(&mut Data, &OutputCallbackInfo) + Send + 'static,
+{
+    |stream, config, sample_format, buffer_size_frames| {
+        let sample_rate = config.sample_rate.0;
+        let buffer_size_samples = buffer_size_frames * config.channels as u32;
+        let audio_ctxt = &stream.audio_ctxt;
+
+        // TODO: We should be re-using a buffer.
+        let mut temporary_buffer = vec![0f32; buffer_size_samples as usize];
+
+        {
+            let len = temporary_buffer.len();
+            let data = temporary_buffer.as_mut_ptr() as *mut ();
+            let mut data = unsafe { Data::from_parts(data, len, sample_format) };
+            let now_secs: f64 = audio_ctxt.current_time();
+            let callback = crate::StreamInstant::from_secs_f64(now_secs);
+            // TODO: Use proper latency instead. Currently, unsupported on most browsers though, so
+            // we estimate based on buffer size instead. Probably should use this, but it's only
+            // supported by firefox (2020-04-28).
+            // let latency_secs: f64 = audio_ctxt.outputLatency.try_into().unwrap();
+            let buffer_duration = frames_to_duration(len, sample_rate as usize);
+            let playback = callback
+                .add(buffer_duration)
+                .expect("`playback` occurs beyond representation supported by `StreamInstant`");
+            let timestamp = crate::OutputStreamTimestamp { callback, playback };
+            let info = OutputCallbackInfo { timestamp };
+            data_callback(&mut data, &info);
+        }
+
+        let typed_array: Float32Array = temporary_buffer.as_slice().into();
+
+        debug_assert_eq!(temporary_buffer.len() % config.channels as usize, 0);
+
+        let src_buffer = Float32Array::new(typed_array.buffer().as_ref());
+        let context = audio_ctxt;
+        let buffer = context
+            .create_buffer(
+                config.channels as u32,
+                buffer_size_frames as u32,
+                sample_rate as f32,
+            )
+            .expect("Buffer could not be created");
+        for channel in 0..config.channels {
+            let mut buffer_content = buffer
+                .get_channel_data(channel as u32)
+                .expect("Should be impossible");
+            for (i, buffer_content_item) in buffer_content.iter_mut().enumerate() {
+                *buffer_content_item =
+                    src_buffer.get_index(i as u32 * config.channels as u32 + channel as u32);
+            }
+        }
+
+        let node = context
+            .create_buffer_source()
+            .expect("The buffer source node could not be created");
+        node.set_buffer(Some(&buffer));
+        context
+            .destination()
+            .connect_with_audio_node(&node)
+            .expect("Could not connect the audio node to the destination");
+        node.start().expect("Could not start the audio node");
+
+        // TODO: handle latency better ; right now we just use setInterval with the amount of sound
+        // data that is in each buffer ; this is obviously bad, and also the schedule is too tight
+        // and there may be underflows
+        set_timeout(
+            1000 * buffer_size_frames as i32 / sample_rate as i32,
+            stream.clone().clone(),
+            data_callback,
+            &config,
+            sample_format,
+            buffer_size_frames as u32,
+        );
+    }
+}
+
+fn set_timeout<D>(
+    time: i32,
+    stream: Stream,
+    data_callback: D,
+    config: &StreamConfig,
+    sample_format: SampleFormat,
+    buffer_size_frames: u32,
+) where
+    D: FnMut(&mut Data, &OutputCallbackInfo) + Send + 'static,
+{
+    let window = web_sys::window().expect("Not in a window somehow?");
+    window
+        .set_timeout_with_callback_and_timeout_and_arguments_4(
+            &Closure::once_into_js(audio_callback_fn(data_callback))
+                .dyn_ref::<js_sys::Function>()
+                .expect("The function was somehow not a function"),
+            time,
+            &stream.into(),
+            &((*config).clone()).into(),
+            &Closure::once_into_js(move || sample_format),
+            &buffer_size_frames.into(),
+        )
+        .expect("The timeout could not be set");
+}
+
+impl Default for Devices {
+    fn default() -> Devices {
+        // We produce an empty iterator if the WebAudio API isn't available.
+        Devices(is_webaudio_available())
+    }
+}
+impl Iterator for Devices {
+    type Item = Device;
+    #[inline]
+    fn next(&mut self) -> Option<Device> {
+        if self.0 {
+            self.0 = false;
+            Some(Device)
+        } else {
+            None
+        }
+    }
+}
+
+#[inline]
+fn default_input_device() -> Option<Device> {
+    unimplemented!();
+}
+
+#[inline]
+fn default_output_device() -> Option<Device> {
+    if is_webaudio_available() {
+        Some(Device)
+    } else {
+        None
+    }
+}
+
+// Detects whether the `AudioContext` global variable is available.
+fn is_webaudio_available() -> bool {
+    AudioContext::new().is_ok()
+}
+
+// Whether or not the given stream configuration is valid for building a stream.
+fn valid_config(conf: &StreamConfig, sample_format: SampleFormat) -> bool {
+    conf.channels <= MAX_CHANNELS
+        && conf.channels >= MIN_CHANNELS
+        && conf.sample_rate <= MAX_SAMPLE_RATE
+        && conf.sample_rate >= MIN_SAMPLE_RATE
+        && sample_format == SUPPORTED_SAMPLE_FORMAT
+}
+
+// Convert the given duration in frames at the given sample rate to a `std::time::Duration`.
+fn frames_to_duration(frames: usize, rate: usize) -> std::time::Duration {
+    let secsf = frames as f64 / rate as f64;
+    let secs = secsf as u64;
+    let nanos = ((secsf - secs as f64) * 1_000_000_000.0) as u32;
+    std::time::Duration::new(secs, nanos)
+}

vendor/cpal/src/host/jack/device.rs

@@ -0,0 +1,268 @@
+use crate::traits::DeviceTrait;
+use crate::{
+    BackendSpecificError, BuildStreamError, Data, DefaultStreamConfigError, DeviceNameError,
+    InputCallbackInfo, OutputCallbackInfo, SampleFormat, SampleRate, StreamConfig, StreamError,
+    SupportedBufferSize, SupportedStreamConfig, SupportedStreamConfigRange,
+    SupportedStreamConfigsError,
+};
+use std::hash::{Hash, Hasher};
+use std::time::Duration;
+
+use super::stream::Stream;
+use super::JACK_SAMPLE_FORMAT;
+
+pub type SupportedInputConfigs = std::vec::IntoIter<SupportedStreamConfigRange>;
+pub type SupportedOutputConfigs = std::vec::IntoIter<SupportedStreamConfigRange>;
+
+const DEFAULT_NUM_CHANNELS: u16 = 2;
+const DEFAULT_SUPPORTED_CHANNELS: [u16; 10] = [1, 2, 4, 6, 8, 16, 24, 32, 48, 64];
+
+/// If a device is for input or output.
+/// Until we have duplex stream support JACK clients and CPAL devices for JACK will be either input or output.
+#[derive(Clone, Debug)]
+pub enum DeviceType {
+    InputDevice,
+    OutputDevice,
+}
+#[derive(Clone, Debug)]
+pub struct Device {
+    name: String,
+    sample_rate: SampleRate,
+    buffer_size: SupportedBufferSize,
+    device_type: DeviceType,
+    start_server_automatically: bool,
+    connect_ports_automatically: bool,
+}
+
+impl Device {
+    fn new_device(
+        name: String,
+        connect_ports_automatically: bool,
+        start_server_automatically: bool,
+        device_type: DeviceType,
+    ) -> Result<Self, String> {
+        // ClientOptions are bit flags that you can set with the constants provided
+        let client_options = super::get_client_options(start_server_automatically);
+
+        // Create a dummy client to find out the sample rate of the server to be able to provide it as a possible config.
+        // This client will be dropped, and a new one will be created when making the stream.
+        // This is a hack due to the fact that the Client must be moved to create the AsyncClient.
+        match super::get_client(&name, client_options) {
+            Ok(client) => Ok(Device {
+                // The name given to the client by JACK, could potentially be different from the name supplied e.g.if there is a name collision
+                name: client.name().to_string(),
+                sample_rate: SampleRate(client.sample_rate() as u32),
+                buffer_size: SupportedBufferSize::Range {
+                    min: client.buffer_size(),
+                    max: client.buffer_size(),
+                },
+                device_type,
+                start_server_automatically,
+                connect_ports_automatically,
+            }),
+            Err(e) => Err(e),
+        }
+    }
+
+    pub fn default_output_device(
+        name: &str,
+        connect_ports_automatically: bool,
+        start_server_automatically: bool,
+    ) -> Result<Self, String> {
+        let output_client_name = format!("{}_out", name);
+        Device::new_device(
+            output_client_name,
+            connect_ports_automatically,
+            start_server_automatically,
+            DeviceType::OutputDevice,
+        )
+    }
+
+    pub fn default_input_device(
+        name: &str,
+        connect_ports_automatically: bool,
+        start_server_automatically: bool,
+    ) -> Result<Self, String> {
+        let input_client_name = format!("{}_in", name);
+        Device::new_device(
+            input_client_name,
+            connect_ports_automatically,
+            start_server_automatically,
+            DeviceType::InputDevice,
+        )
+    }
+
+    pub fn default_config(&self) -> Result<SupportedStreamConfig, DefaultStreamConfigError> {
+        let channels = DEFAULT_NUM_CHANNELS;
+        let sample_rate = self.sample_rate;
+        let buffer_size = self.buffer_size.clone();
+        // The sample format for JACK audio ports is always "32-bit float mono audio" in the current implementation.
+        // Custom formats are allowed within JACK, but this is of niche interest.
+        // The format can be found programmatically by calling jack::PortSpec::port_type() on a created port.
+        let sample_format = JACK_SAMPLE_FORMAT;
+        Ok(SupportedStreamConfig {
+            channels,
+            sample_rate,
+            buffer_size,
+            sample_format,
+        })
+    }
+
+    pub fn supported_configs(&self) -> Vec<SupportedStreamConfigRange> {
+        let f = match self.default_config() {
+            Err(_) => return vec![],
+            Ok(f) => f,
+        };
+
+        let mut supported_configs = vec![];
+
+        for &channels in DEFAULT_SUPPORTED_CHANNELS.iter() {
+            supported_configs.push(SupportedStreamConfigRange {
+                channels,
+                min_sample_rate: f.sample_rate,
+                max_sample_rate: f.sample_rate,
+                buffer_size: f.buffer_size.clone(),
+                sample_format: f.sample_format,
+            });
+        }
+        supported_configs
+    }
+
+    pub fn is_input(&self) -> bool {
+        matches!(self.device_type, DeviceType::InputDevice)
+    }
+
+    pub fn is_output(&self) -> bool {
+        matches!(self.device_type, DeviceType::OutputDevice)
+    }
+}
+
+impl DeviceTrait for Device {
+    type SupportedInputConfigs = SupportedInputConfigs;
+    type SupportedOutputConfigs = SupportedOutputConfigs;
+    type Stream = Stream;
+
+    fn name(&self) -> Result<String, DeviceNameError> {
+        Ok(self.name.clone())
+    }
+
+    fn supported_input_configs(
+        &self,
+    ) -> Result<Self::SupportedInputConfigs, SupportedStreamConfigsError> {
+        Ok(self.supported_configs().into_iter())
+    }
+
+    fn supported_output_configs(
+        &self,
+    ) -> Result<Self::SupportedOutputConfigs, SupportedStreamConfigsError> {
+        Ok(self.supported_configs().into_iter())
+    }
+
+    /// Returns the default input config
+    /// The sample format for JACK audio ports is always "32-bit float mono audio" unless using a custom type.
+    /// The sample rate is set by the JACK server.
+    fn default_input_config(&self) -> Result<SupportedStreamConfig, DefaultStreamConfigError> {
+        self.default_config()
+    }
+
+    /// Returns the default output config
+    /// The sample format for JACK audio ports is always "32-bit float mono audio" unless using a custom type.
+    /// The sample rate is set by the JACK server.
+    fn default_output_config(&self) -> Result<SupportedStreamConfig, DefaultStreamConfigError> {
+        self.default_config()
+    }
+
+    fn build_input_stream_raw<D, E>(
+        &self,
+        conf: &StreamConfig,
+        sample_format: SampleFormat,
+        data_callback: D,
+        error_callback: E,
+        _timeout: Option<Duration>,
+    ) -> Result<Self::Stream, BuildStreamError>
+    where
+        D: FnMut(&Data, &InputCallbackInfo) + Send + 'static,
+        E: FnMut(StreamError) + Send + 'static,
+    {
+        if let DeviceType::OutputDevice = &self.device_type {
+            // Trying to create an input stream from an output device
+            return Err(BuildStreamError::StreamConfigNotSupported);
+        }
+        if conf.sample_rate != self.sample_rate || sample_format != JACK_SAMPLE_FORMAT {
+            return Err(BuildStreamError::StreamConfigNotSupported);
+        }
+        // The settings should be fine, create a Client
+        let client_options = super::get_client_options(self.start_server_automatically);
+        let client;
+        match super::get_client(&self.name, client_options) {
+            Ok(c) => client = c,
+            Err(e) => {
+                return Err(BuildStreamError::BackendSpecific {
+                    err: BackendSpecificError { description: e },
+                })
+            }
+        };
+        let mut stream = Stream::new_input(client, conf.channels, data_callback, error_callback);
+
+        if self.connect_ports_automatically {
+            stream.connect_to_system_inputs();
+        }
+
+        Ok(stream)
+    }
+
+    fn build_output_stream_raw<D, E>(
+        &self,
+        conf: &StreamConfig,
+        sample_format: SampleFormat,
+        data_callback: D,
+        error_callback: E,
+        _timeout: Option<Duration>,
+    ) -> Result<Self::Stream, BuildStreamError>
+    where
+        D: FnMut(&mut Data, &OutputCallbackInfo) + Send + 'static,
+        E: FnMut(StreamError) + Send + 'static,
+    {
+        if let DeviceType::InputDevice = &self.device_type {
+            // Trying to create an output stream from an input device
+            return Err(BuildStreamError::StreamConfigNotSupported);
+        }
+        if conf.sample_rate != self.sample_rate || sample_format != JACK_SAMPLE_FORMAT {
+            return Err(BuildStreamError::StreamConfigNotSupported);
+        }
+
+        // The settings should be fine, create a Client
+        let client_options = super::get_client_options(self.start_server_automatically);
+        let client;
+        match super::get_client(&self.name, client_options) {
+            Ok(c) => client = c,
+            Err(e) => {
+                return Err(BuildStreamError::BackendSpecific {
+                    err: BackendSpecificError { description: e },
+                })
+            }
+        };
+        let mut stream = Stream::new_output(client, conf.channels, data_callback, error_callback);
+
+        if self.connect_ports_automatically {
+            stream.connect_to_system_outputs();
+        }
+
+        Ok(stream)
+    }
+}
+
+impl PartialEq for Device {
+    fn eq(&self, other: &Self) -> bool {
+        // Device::name() can never fail in this implementation
+        self.name().unwrap() == other.name().unwrap()
+    }
+}
+
+impl Eq for Device {}
+
+impl Hash for Device {
+    fn hash<H: Hasher>(&self, state: &mut H) {
+        self.name().unwrap().hash(state);
+    }
+}

vendor/cpal/src/host/jack/mod.rs

@@ -0,0 +1,180 @@
+extern crate jack;
+
+use crate::traits::HostTrait;
+use crate::{DevicesError, SampleFormat, SupportedStreamConfigRange};
+
+mod device;
+pub use self::device::Device;
+pub use self::stream::Stream;
+mod stream;
+
+const JACK_SAMPLE_FORMAT: SampleFormat = SampleFormat::F32;
+
+pub type SupportedInputConfigs = std::vec::IntoIter<SupportedStreamConfigRange>;
+pub type SupportedOutputConfigs = std::vec::IntoIter<SupportedStreamConfigRange>;
+pub type Devices = std::vec::IntoIter<Device>;
+
+/// The JACK Host type
+#[derive(Debug)]
+pub struct Host {
+    /// The name that the client will have in JACK.
+    /// Until we have duplex streams two clients will be created adding "out" or "in" to the name
+    /// since names have to be unique.
+    name: String,
+    /// If ports are to be connected to the system (soundcard) ports automatically (default is true).
+    connect_ports_automatically: bool,
+    /// If the JACK server should be started automatically if it isn't already when creating a Client (default is false).
+    start_server_automatically: bool,
+    /// A list of the devices that have been created from this Host.
+    devices_created: Vec<Device>,
+}
+
+impl Host {
+    pub fn new() -> Result<Self, crate::HostUnavailable> {
+        let mut host = Host {
+            name: "cpal_client".to_owned(),
+            connect_ports_automatically: true,
+            start_server_automatically: false,
+            devices_created: vec![],
+        };
+        // Devices don't exist for JACK, they have to be created
+        host.initialize_default_devices();
+        Ok(host)
+    }
+    /// Set whether the ports should automatically be connected to system
+    /// (default is true)
+    pub fn set_connect_automatically(&mut self, do_connect: bool) {
+        self.connect_ports_automatically = do_connect;
+    }
+    /// Set whether a JACK server should be automatically started if it isn't already.
+    /// (default is false)
+    pub fn set_start_server_automatically(&mut self, do_start_server: bool) {
+        self.start_server_automatically = do_start_server;
+    }
+
+    pub fn input_device_with_name(&mut self, name: &str) -> Option<Device> {
+        self.name = name.to_owned();
+        self.default_input_device()
+    }
+
+    pub fn output_device_with_name(&mut self, name: &str) -> Option<Device> {
+        self.name = name.to_owned();
+        self.default_output_device()
+    }
+
+    fn initialize_default_devices(&mut self) {
+        let in_device_res = Device::default_input_device(
+            &self.name,
+            self.connect_ports_automatically,
+            self.start_server_automatically,
+        );
+
+        match in_device_res {
+            Ok(device) => self.devices_created.push(device),
+            Err(err) => {
+                println!("{}", err);
+            }
+        }
+
+        let out_device_res = Device::default_output_device(
+            &self.name,
+            self.connect_ports_automatically,
+            self.start_server_automatically,
+        );
+        match out_device_res {
+            Ok(device) => self.devices_created.push(device),
+            Err(err) => {
+                println!("{}", err);
+            }
+        }
+    }
+}
+
+impl HostTrait for Host {
+    type Devices = Devices;
+    type Device = Device;
+
+    /// JACK is available if
+    /// - the jack feature flag is set
+    /// - libjack is installed (wouldn't compile without it)
+    /// - the JACK server can be started
+    ///
+    /// If the code compiles the necessary jack libraries are installed.
+    /// There is no way to know if the user has set up a correct JACK configuration e.g. with qjackctl.
+    /// Users can choose to automatically start the server if it isn't already started when creating a client
+    /// so checking if the server is running could give a false negative in some use cases.
+    /// For these reasons this function should always return true.
+    fn is_available() -> bool {
+        true
+    }
+
+    fn devices(&self) -> Result<Self::Devices, DevicesError> {
+        Ok(self.devices_created.clone().into_iter())
+    }
+
+    fn default_input_device(&self) -> Option<Self::Device> {
+        for device in &self.devices_created {
+            if device.is_input() {
+                return Some(device.clone());
+            }
+        }
+        None
+    }
+
+    fn default_output_device(&self) -> Option<Self::Device> {
+        for device in &self.devices_created {
+            if device.is_output() {
+                return Some(device.clone());
+            }
+        }
+        None
+    }
+}
+
+fn get_client_options(start_server_automatically: bool) -> jack::ClientOptions {
+    let mut client_options = jack::ClientOptions::empty();
+    client_options.set(
+        jack::ClientOptions::NO_START_SERVER,
+        !start_server_automatically,
+    );
+    client_options
+}
+
+fn get_client(name: &str, client_options: jack::ClientOptions) -> Result<jack::Client, String> {
+    let c_res = jack::Client::new(name, client_options);
+    match c_res {
+        Ok((client, status)) => {
+            // The ClientStatus can tell us many things
+            if status.intersects(jack::ClientStatus::SERVER_ERROR) {
+                return Err(String::from(
+                    "There was an error communicating with the JACK server!",
+                ));
+            } else if status.intersects(jack::ClientStatus::SERVER_FAILED) {
+                return Err(String::from("Could not connect to the JACK server!"));
+            } else if status.intersects(jack::ClientStatus::VERSION_ERROR) {
+                return Err(String::from(
+                    "Error connecting to JACK server: Client's protocol version does not match!",
+                ));
+            } else if status.intersects(jack::ClientStatus::INIT_FAILURE) {
+                return Err(String::from(
+                    "Error connecting to JACK server: Unable to initialize client!",
+                ));
+            } else if status.intersects(jack::ClientStatus::SHM_FAILURE) {
+                return Err(String::from(
+                    "Error connecting to JACK server: Unable to access shared memory!",
+                ));
+            } else if status.intersects(jack::ClientStatus::NO_SUCH_CLIENT) {
+                return Err(String::from(
+                    "Error connecting to JACK server: Requested client does not exist!",
+                ));
+            } else if status.intersects(jack::ClientStatus::INVALID_OPTION) {
+                return Err(String::from("Error connecting to JACK server: The operation contained an invalid or unsupported option!"));
+            }
+
+            return Ok(client);
+        }
+        Err(e) => {
+            return Err(format!("Failed to open client because of error: {:?}", e));
+        }
+    }
+}

vendor/cpal/src/host/jack/stream.rs

@@ -0,0 +1,463 @@
+use crate::traits::StreamTrait;
+use crate::ChannelCount;
+use std::sync::atomic::{AtomicBool, Ordering};
+use std::sync::{Arc, Mutex};
+
+use crate::{
+    BackendSpecificError, Data, InputCallbackInfo, OutputCallbackInfo, PauseStreamError,
+    PlayStreamError, SampleRate, StreamError,
+};
+
+use super::JACK_SAMPLE_FORMAT;
+
+type ErrorCallbackPtr = Arc<Mutex<dyn FnMut(StreamError) + Send + 'static>>;
+
+pub struct Stream {
+    // TODO: It might be faster to send a message when playing/pausing than to check this every iteration
+    playing: Arc<AtomicBool>,
+    async_client: jack::AsyncClient<JackNotificationHandler, LocalProcessHandler>,
+    // Port names are stored in order to connect them to other ports in jack automatically
+    input_port_names: Vec<String>,
+    output_port_names: Vec<String>,
+}
+
+impl Stream {
+    // TODO: Return error messages
+    pub fn new_input<D, E>(
+        client: jack::Client,
+        channels: ChannelCount,
+        data_callback: D,
+        mut error_callback: E,
+    ) -> Stream
+    where
+        D: FnMut(&Data, &InputCallbackInfo) + Send + 'static,
+        E: FnMut(StreamError) + Send + 'static,
+    {
+        let mut ports = vec![];
+        let mut port_names: Vec<String> = vec![];
+        // Create ports
+        for i in 0..channels {
+            let port_try = client.register_port(&format!("in_{}", i), jack::AudioIn::default());
+            match port_try {
+                Ok(port) => {
+                    // Get the port name in order to later connect it automatically
+                    if let Ok(port_name) = port.name() {
+                        port_names.push(port_name);
+                    }
+                    // Store the port into a Vec to move to the ProcessHandler
+                    ports.push(port);
+                }
+                Err(e) => {
+                    // If port creation failed, send the error back via the error_callback
+                    error_callback(
+                        BackendSpecificError {
+                            description: e.to_string(),
+                        }
+                        .into(),
+                    );
+                }
+            }
+        }
+
+        let playing = Arc::new(AtomicBool::new(true));
+
+        let error_callback_ptr = Arc::new(Mutex::new(error_callback)) as ErrorCallbackPtr;
+
+        let input_process_handler = LocalProcessHandler::new(
+            vec![],
+            ports,
+            SampleRate(client.sample_rate() as u32),
+            client.buffer_size() as usize,
+            Some(Box::new(data_callback)),
+            None,
+            playing.clone(),
+            Arc::clone(&error_callback_ptr),
+        );
+
+        let notification_handler = JackNotificationHandler::new(error_callback_ptr);
+
+        let async_client = client
+            .activate_async(notification_handler, input_process_handler)
+            .unwrap();
+
+        Stream {
+            playing,
+            async_client,
+            input_port_names: port_names,
+            output_port_names: vec![],
+        }
+    }
+
+    pub fn new_output<D, E>(
+        client: jack::Client,
+        channels: ChannelCount,
+        data_callback: D,
+        mut error_callback: E,
+    ) -> Stream
+    where
+        D: FnMut(&mut Data, &OutputCallbackInfo) + Send + 'static,
+        E: FnMut(StreamError) + Send + 'static,
+    {
+        let mut ports = vec![];
+        let mut port_names: Vec<String> = vec![];
+        // Create ports
+        for i in 0..channels {
+            let port_try = client.register_port(&format!("out_{}", i), jack::AudioOut::default());
+            match port_try {
+                Ok(port) => {
+                    // Get the port name in order to later connect it automatically
+                    if let Ok(port_name) = port.name() {
+                        port_names.push(port_name);
+                    }
+                    // Store the port into a Vec to move to the ProcessHandler
+                    ports.push(port);
+                }
+                Err(e) => {
+                    // If port creation failed, send the error back via the error_callback
+                    error_callback(
+                        BackendSpecificError {
+                            description: e.to_string(),
+                        }
+                        .into(),
+                    );
+                }
+            }
+        }
+
+        let playing = Arc::new(AtomicBool::new(true));
+
+        let error_callback_ptr = Arc::new(Mutex::new(error_callback)) as ErrorCallbackPtr;
+
+        let output_process_handler = LocalProcessHandler::new(
+            ports,
+            vec![],
+            SampleRate(client.sample_rate() as u32),
+            client.buffer_size() as usize,
+            None,
+            Some(Box::new(data_callback)),
+            playing.clone(),
+            Arc::clone(&error_callback_ptr),
+        );
+
+        let notification_handler = JackNotificationHandler::new(error_callback_ptr);
+
+        let async_client = client
+            .activate_async(notification_handler, output_process_handler)
+            .unwrap();
+
+        Stream {
+            playing,
+            async_client,
+            input_port_names: vec![],
+            output_port_names: port_names,
+        }
+    }
+
+    /// Connect to the standard system outputs in jack, system:playback_1 and system:playback_2
+    /// This has to be done after the client is activated, doing it just after creating the ports doesn't work.
+    pub fn connect_to_system_outputs(&mut self) {
+        // Get the system ports
+        let system_ports = self.async_client.as_client().ports(
+            Some("system:playback_.*"),
+            None,
+            jack::PortFlags::empty(),
+        );
+
+        // Connect outputs from this client to the system playback inputs
+        for i in 0..self.output_port_names.len() {
+            if i >= system_ports.len() {
+                break;
+            }
+            match self
+                .async_client
+                .as_client()
+                .connect_ports_by_name(&self.output_port_names[i], &system_ports[i])
+            {
+                Ok(_) => (),
+                Err(e) => println!("Unable to connect to port with error {}", e),
+            }
+        }
+    }
+
+    /// Connect to the standard system outputs in jack, system:capture_1 and system:capture_2
+    /// This has to be done after the client is activated, doing it just after creating the ports doesn't work.
+    pub fn connect_to_system_inputs(&mut self) {
+        // Get the system ports
+        let system_ports = self.async_client.as_client().ports(
+            Some("system:capture_.*"),
+            None,
+            jack::PortFlags::empty(),
+        );
+
+        // Connect outputs from this client to the system playback inputs
+        for i in 0..self.input_port_names.len() {
+            if i >= system_ports.len() {
+                break;
+            }
+            match self
+                .async_client
+                .as_client()
+                .connect_ports_by_name(&system_ports[i], &self.input_port_names[i])
+            {
+                Ok(_) => (),
+                Err(e) => println!("Unable to connect to port with error {}", e),
+            }
+        }
+    }
+}
+
+impl StreamTrait for Stream {
+    fn play(&self) -> Result<(), PlayStreamError> {
+        self.playing.store(true, Ordering::SeqCst);
+        Ok(())
+    }
+
+    fn pause(&self) -> Result<(), PauseStreamError> {
+        self.playing.store(false, Ordering::SeqCst);
+        Ok(())
+    }
+}
+
+struct LocalProcessHandler {
+    /// No new ports are allowed to be created after the creation of the LocalProcessHandler as that would invalidate the buffer sizes
+    out_ports: Vec<jack::Port<jack::AudioOut>>,
+    in_ports: Vec<jack::Port<jack::AudioIn>>,
+
+    sample_rate: SampleRate,
+    buffer_size: usize,
+    input_data_callback: Option<Box<dyn FnMut(&Data, &InputCallbackInfo) + Send + 'static>>,
+    output_data_callback: Option<Box<dyn FnMut(&mut Data, &OutputCallbackInfo) + Send + 'static>>,
+
+    // JACK audio samples are 32-bit float (unless you do some custom dark magic)
+    temp_input_buffer: Vec<f32>,
+    temp_output_buffer: Vec<f32>,
+    playing: Arc<AtomicBool>,
+    creation_timestamp: std::time::Instant,
+    /// This should not be called on `process`, only on `buffer_size` because it can block.
+    error_callback_ptr: ErrorCallbackPtr,
+}
+
+impl LocalProcessHandler {
+    fn new(
+        out_ports: Vec<jack::Port<jack::AudioOut>>,
+        in_ports: Vec<jack::Port<jack::AudioIn>>,
+        sample_rate: SampleRate,
+        buffer_size: usize,
+        input_data_callback: Option<Box<dyn FnMut(&Data, &InputCallbackInfo) + Send + 'static>>,
+        output_data_callback: Option<
+            Box<dyn FnMut(&mut Data, &OutputCallbackInfo) + Send + 'static>,
+        >,
+        playing: Arc<AtomicBool>,
+        error_callback_ptr: ErrorCallbackPtr,
+    ) -> Self {
+        // These may be reallocated in the `buffer_size` callback.
+        let temp_input_buffer = vec![0.0; in_ports.len() * buffer_size];
+        let temp_output_buffer = vec![0.0; out_ports.len() * buffer_size];
+
+        LocalProcessHandler {
+            out_ports,
+            in_ports,
+            sample_rate,
+            buffer_size,
+            input_data_callback,
+            output_data_callback,
+            temp_input_buffer,
+            temp_output_buffer,
+            playing,
+            creation_timestamp: std::time::Instant::now(),
+            error_callback_ptr,
+        }
+    }
+}
+
+fn temp_buffer_to_data(temp_input_buffer: &mut Vec<f32>, total_buffer_size: usize) -> Data {
+    let slice = &temp_input_buffer[0..total_buffer_size];
+    let data = slice.as_ptr() as *mut ();
+    let len = total_buffer_size;
+    let data = unsafe { Data::from_parts(data, len, JACK_SAMPLE_FORMAT) };
+    data
+}
+
+impl jack::ProcessHandler for LocalProcessHandler {
+    fn process(&mut self, _: &jack::Client, process_scope: &jack::ProcessScope) -> jack::Control {
+        if !self.playing.load(Ordering::SeqCst) {
+            return jack::Control::Continue;
+        }
+
+        // This should be equal to self.buffer_size, but the implementation will
+        // work even if it is less. Will panic in `temp_buffer_to_data` if greater.
+        let current_frame_count = process_scope.n_frames() as usize;
+
+        // Get timestamp data
+        let cycle_times = process_scope.cycle_times();
+        let current_start_usecs = match cycle_times {
+            Ok(times) => times.current_usecs,
+            Err(_) => {
+                // jack was unable to get the current time information
+                // Fall back to using Instants
+                let now = std::time::Instant::now();
+                let duration = now.duration_since(self.creation_timestamp);
+                duration.as_micros() as u64
+            }
+        };
+        let start_cycle_instant = micros_to_stream_instant(current_start_usecs);
+        let start_callback_instant = start_cycle_instant
+            .add(frames_to_duration(
+                process_scope.frames_since_cycle_start() as usize,
+                self.sample_rate,
+            ))
+            .expect("`playback` occurs beyond representation supported by `StreamInstant`");
+
+        if let Some(input_callback) = &mut self.input_data_callback {
+            // Let's get the data from the input ports and run the callback
+
+            let num_in_channels = self.in_ports.len();
+
+            // Read the data from the input ports into the temporary buffer
+            // Go through every channel and store its data in the temporary input buffer
+            for ch_ix in 0..num_in_channels {
+                let input_channel = &self.in_ports[ch_ix].as_slice(process_scope);
+                for i in 0..current_frame_count {
+                    self.temp_input_buffer[ch_ix + i * num_in_channels] = input_channel[i];
+                }
+            }
+            // Create a slice of exactly current_frame_count frames
+            let data = temp_buffer_to_data(
+                &mut self.temp_input_buffer,
+                current_frame_count * num_in_channels,
+            );
+            // Create timestamp
+            let frames_since_cycle_start = process_scope.frames_since_cycle_start() as usize;
+            let duration_since_cycle_start =
+                frames_to_duration(frames_since_cycle_start, self.sample_rate);
+            let callback = start_callback_instant
+                .add(duration_since_cycle_start)
+                .expect("`playback` occurs beyond representation supported by `StreamInstant`");
+            let capture = start_callback_instant;
+            let timestamp = crate::InputStreamTimestamp { callback, capture };
+            let info = crate::InputCallbackInfo { timestamp };
+            input_callback(&data, &info);
+        }
+
+        if let Some(output_callback) = &mut self.output_data_callback {
+            let num_out_channels = self.out_ports.len();
+
+            // Create a slice of exactly current_frame_count frames
+            let mut data = temp_buffer_to_data(
+                &mut self.temp_output_buffer,
+                current_frame_count * num_out_channels,
+            );
+            // Create timestamp
+            let frames_since_cycle_start = process_scope.frames_since_cycle_start() as usize;
+            let duration_since_cycle_start =
+                frames_to_duration(frames_since_cycle_start, self.sample_rate);
+            let callback = start_callback_instant
+                .add(duration_since_cycle_start)
+                .expect("`playback` occurs beyond representation supported by `StreamInstant`");
+            let buffer_duration = frames_to_duration(current_frame_count, self.sample_rate);
+            let playback = start_cycle_instant
+                .add(buffer_duration)
+                .expect("`playback` occurs beyond representation supported by `StreamInstant`");
+            let timestamp = crate::OutputStreamTimestamp { callback, playback };
+            let info = crate::OutputCallbackInfo { timestamp };
+            output_callback(&mut data, &info);
+
+            // Deinterlace
+            for ch_ix in 0..num_out_channels {
+                let output_channel = &mut self.out_ports[ch_ix].as_mut_slice(process_scope);
+                for i in 0..current_frame_count {
+                    output_channel[i] = self.temp_output_buffer[ch_ix + i * num_out_channels];
+                }
+            }
+        }
+
+        // Continue as normal
+        jack::Control::Continue
+    }
+
+    fn buffer_size(&mut self, _: &jack::Client, size: jack::Frames) -> jack::Control {
+        // The `buffer_size` callback is actually called on the process thread, but
+        // it does not need to be suitable for real-time use. Thus we can simply allocate
+        // new buffers here. It is also fine to call the error callback.
+        // Details: https://github.com/RustAudio/rust-jack/issues/137
+        let new_size = size as usize;
+        if new_size != self.buffer_size {
+            self.buffer_size = new_size;
+            self.temp_input_buffer = vec![0.0; self.in_ports.len() * new_size];
+            self.temp_output_buffer = vec![0.0; self.out_ports.len() * new_size];
+            let description = format!("buffer size changed to: {}", new_size);
+            if let Ok(mut mutex_guard) = self.error_callback_ptr.lock() {
+                let err = &mut *mutex_guard;
+                err(BackendSpecificError { description }.into());
+            }
+        }
+
+        jack::Control::Continue
+    }
+}
+
+fn micros_to_stream_instant(micros: u64) -> crate::StreamInstant {
+    let nanos = micros * 1000;
+    let secs = micros / 1_000_000;
+    let subsec_nanos = nanos - secs * 1_000_000_000;
+    crate::StreamInstant::new(secs as i64, subsec_nanos as u32)
+}
+
+// Convert the given duration in frames at the given sample rate to a `std::time::Duration`.
+fn frames_to_duration(frames: usize, rate: crate::SampleRate) -> std::time::Duration {
+    let secsf = frames as f64 / rate.0 as f64;
+    let secs = secsf as u64;
+    let nanos = ((secsf - secs as f64) * 1_000_000_000.0) as u32;
+    std::time::Duration::new(secs, nanos)
+}
+
+/// Receives notifications from the JACK server. It is unclear if this may be run concurrent with itself under JACK2 specs
+/// so it needs to be Sync.
+struct JackNotificationHandler {
+    error_callback_ptr: ErrorCallbackPtr,
+    init_sample_rate_flag: Arc<AtomicBool>,
+}
+
+impl JackNotificationHandler {
+    pub fn new(error_callback_ptr: ErrorCallbackPtr) -> Self {
+        JackNotificationHandler {
+            error_callback_ptr,
+            init_sample_rate_flag: Arc::new(AtomicBool::new(false)),
+        }
+    }
+
+    fn send_error(&mut self, description: String) {
+        // This thread isn't the audio thread, it's fine to block
+        if let Ok(mut mutex_guard) = self.error_callback_ptr.lock() {
+            let err = &mut *mutex_guard;
+            err(BackendSpecificError { description }.into());
+        }
+    }
+}
+
+impl jack::NotificationHandler for JackNotificationHandler {
+    fn shutdown(&mut self, _status: jack::ClientStatus, reason: &str) {
+        self.send_error(format!("JACK was shut down for reason: {}", reason));
+    }
+
+    fn sample_rate(&mut self, _: &jack::Client, srate: jack::Frames) -> jack::Control {
+        match self.init_sample_rate_flag.load(Ordering::SeqCst) {
+            false => {
+                // One of these notifications is sent every time a client is started.
+                self.init_sample_rate_flag.store(true, Ordering::SeqCst);
+                jack::Control::Continue
+            }
+            true => {
+                self.send_error(format!("sample rate changed to: {}", srate));
+                // Since CPAL currently has no way of signaling a sample rate change in order to make
+                // all necessary changes that would bring we choose to quit.
+                jack::Control::Quit
+            }
+        }
+    }
+
+    fn xrun(&mut self, _: &jack::Client) -> jack::Control {
+        self.send_error(String::from("xrun (buffer over or under run)"));
+        jack::Control::Continue
+    }
+}

vendor/cpal/src/host/mod.rs

@@ -0,0 +1,30 @@
+#[cfg(any(
+    target_os = "linux",
+    target_os = "dragonfly",
+    target_os = "freebsd",
+    target_os = "netbsd"
+))]
+pub(crate) mod alsa;
+#[cfg(all(windows, feature = "asio"))]
+pub(crate) mod asio;
+#[cfg(any(target_os = "macos", target_os = "ios"))]
+pub(crate) mod coreaudio;
+#[cfg(target_os = "emscripten")]
+pub(crate) mod emscripten;
+#[cfg(all(
+    any(
+        target_os = "linux",
+        target_os = "dragonfly",
+        target_os = "freebsd",
+        target_os = "netbsd"
+    ),
+    feature = "jack"
+))]
+pub(crate) mod jack;
+pub(crate) mod null;
+#[cfg(target_os = "android")]
+pub(crate) mod oboe;
+#[cfg(windows)]
+pub(crate) mod wasapi;
+#[cfg(all(target_arch = "wasm32", feature = "wasm-bindgen"))]
+pub(crate) mod webaudio;

vendor/cpal/src/host/null/mod.rs

@@ -0,0 +1,160 @@
+use std::time::Duration;
+
+use crate::traits::{DeviceTrait, HostTrait, StreamTrait};
+use crate::{
+    BuildStreamError, Data, DefaultStreamConfigError, DeviceNameError, DevicesError,
+    InputCallbackInfo, OutputCallbackInfo, PauseStreamError, PlayStreamError, SampleFormat,
+    StreamConfig, StreamError, SupportedStreamConfig, SupportedStreamConfigRange,
+    SupportedStreamConfigsError,
+};
+
+#[derive(Default)]
+pub struct Devices;
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct Device;
+
+pub struct Host;
+
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
+pub struct Stream;
+
+pub struct SupportedInputConfigs;
+pub struct SupportedOutputConfigs;
+
+impl Host {
+    #[allow(dead_code)]
+    pub fn new() -> Result<Self, crate::HostUnavailable> {
+        Ok(Host)
+    }
+}
+
+impl Devices {
+    pub fn new() -> Result<Self, DevicesError> {
+        Ok(Devices)
+    }
+}
+
+impl DeviceTrait for Device {
+    type SupportedInputConfigs = SupportedInputConfigs;
+    type SupportedOutputConfigs = SupportedOutputConfigs;
+    type Stream = Stream;
+
+    #[inline]
+    fn name(&self) -> Result<String, DeviceNameError> {
+        Ok("null".to_owned())
+    }
+
+    #[inline]
+    fn supported_input_configs(
+        &self,
+    ) -> Result<SupportedInputConfigs, SupportedStreamConfigsError> {
+        unimplemented!()
+    }
+
+    #[inline]
+    fn supported_output_configs(
+        &self,
+    ) -> Result<SupportedOutputConfigs, SupportedStreamConfigsError> {
+        unimplemented!()
+    }
+
+    #[inline]
+    fn default_input_config(&self) -> Result<SupportedStreamConfig, DefaultStreamConfigError> {
+        unimplemented!()
+    }
+
+    #[inline]
+    fn default_output_config(&self) -> Result<SupportedStreamConfig, DefaultStreamConfigError> {
+        unimplemented!()
+    }
+
+    fn build_input_stream_raw<D, E>(
+        &self,
+        _config: &StreamConfig,
+        _sample_format: SampleFormat,
+        _data_callback: D,
+        _error_callback: E,
+        _timeout: Option<Duration>,
+    ) -> Result<Self::Stream, BuildStreamError>
+    where
+        D: FnMut(&Data, &InputCallbackInfo) + Send + 'static,
+        E: FnMut(StreamError) + Send + 'static,
+    {
+        unimplemented!()
+    }
+
+    /// Create an output stream.
+    fn build_output_stream_raw<D, E>(
+        &self,
+        _config: &StreamConfig,
+        _sample_format: SampleFormat,
+        _data_callback: D,
+        _error_callback: E,
+        _timeout: Option<Duration>,
+    ) -> Result<Self::Stream, BuildStreamError>
+    where
+        D: FnMut(&mut Data, &OutputCallbackInfo) + Send + 'static,
+        E: FnMut(StreamError) + Send + 'static,
+    {
+        unimplemented!()
+    }
+}
+
+impl HostTrait for Host {
+    type Devices = Devices;
+    type Device = Device;
+
+    fn is_available() -> bool {
+        false
+    }
+
+    fn devices(&self) -> Result<Self::Devices, DevicesError> {
+        Devices::new()
+    }
+
+    fn default_input_device(&self) -> Option<Device> {
+        None
+    }
+
+    fn default_output_device(&self) -> Option<Device> {
+        None
+    }
+}
+
+impl StreamTrait for Stream {
+    fn play(&self) -> Result<(), PlayStreamError> {
+        unimplemented!()
+    }
+
+    fn pause(&self) -> Result<(), PauseStreamError> {
+        unimplemented!()
+    }
+}
+
+impl Iterator for Devices {
+    type Item = Device;
+
+    #[inline]
+    fn next(&mut self) -> Option<Device> {
+        None
+    }
+}
+
+impl Iterator for SupportedInputConfigs {
+    type Item = SupportedStreamConfigRange;
+
+    #[inline]
+    fn next(&mut self) -> Option<SupportedStreamConfigRange> {
+        None
+    }
+}
+
+impl Iterator for SupportedOutputConfigs {
+    type Item = SupportedStreamConfigRange;
+
+    #[inline]
+    fn next(&mut self) -> Option<SupportedStreamConfigRange> {
+        None
+    }
+}

vendor/cpal/src/host/oboe/android_media.rs

@@ -0,0 +1,62 @@
+use std::sync::Arc;
+
+extern crate jni;
+
+use self::jni::Executor;
+use self::jni::{errors::Result as JResult, JNIEnv, JavaVM};
+
+// constants from android.media.AudioFormat
+pub const ENCODING_PCM_16BIT: i32 = 2;
+pub const ENCODING_PCM_FLOAT: i32 = 4;
+pub const CHANNEL_OUT_MONO: i32 = 4;
+pub const CHANNEL_OUT_STEREO: i32 = 12;
+
+fn with_attached<F, R>(closure: F) -> JResult<R>
+where
+    F: FnOnce(&mut JNIEnv) -> JResult<R>,
+{
+    let android_context = ndk_context::android_context();
+    let vm = Arc::new(unsafe { JavaVM::from_raw(android_context.vm().cast())? });
+    Executor::new(vm).with_attached(|env| closure(env))
+}
+
+fn get_min_buffer_size(
+    class: &'static str,
+    sample_rate: i32,
+    channel_mask: i32,
+    format: i32,
+) -> i32 {
+    // Unwrapping everything because these operations are not expected to fail
+    // or throw exceptions. Android returns negative values for invalid parameters,
+    // which is what we expect.
+    with_attached(|env| {
+        let class = env.find_class(class).unwrap();
+        env.call_static_method(
+            class,
+            "getMinBufferSize",
+            "(III)I",
+            &[sample_rate.into(), channel_mask.into(), format.into()],
+        )
+        .unwrap()
+        .i()
+    })
+    .unwrap()
+}
+
+pub fn get_audio_track_min_buffer_size(sample_rate: i32, channel_mask: i32, format: i32) -> i32 {
+    get_min_buffer_size(
+        "android/media/AudioTrack",
+        sample_rate,
+        channel_mask,
+        format,
+    )
+}
+
+pub fn get_audio_record_min_buffer_size(sample_rate: i32, channel_mask: i32, format: i32) -> i32 {
+    get_min_buffer_size(
+        "android/media/AudioRecord",
+        sample_rate,
+        channel_mask,
+        format,
+    )
+}

vendor/cpal/src/host/oboe/convert.rs

@@ -0,0 +1,82 @@
+use std::convert::TryInto;
+use std::time::Duration;
+
+extern crate oboe;
+
+use crate::{
+    BackendSpecificError, BuildStreamError, PauseStreamError, PlayStreamError, StreamError,
+    StreamInstant,
+};
+
+pub fn to_stream_instant(duration: Duration) -> StreamInstant {
+    StreamInstant::new(
+        duration.as_secs().try_into().unwrap(),
+        duration.subsec_nanos(),
+    )
+}
+
+pub fn stream_instant<T: oboe::AudioStreamSafe + ?Sized>(stream: &mut T) -> StreamInstant {
+    const CLOCK_MONOTONIC: i32 = 1;
+    let ts = stream
+        .get_timestamp(CLOCK_MONOTONIC)
+        .unwrap_or(oboe::FrameTimestamp {
+            position: 0,
+            timestamp: 0,
+        });
+    to_stream_instant(Duration::from_nanos(ts.timestamp as u64))
+}
+
+impl From<oboe::Error> for StreamError {
+    fn from(error: oboe::Error) -> Self {
+        use self::oboe::Error::*;
+        match error {
+            Disconnected | Unavailable | Closed => Self::DeviceNotAvailable,
+            e => (BackendSpecificError {
+                description: e.to_string(),
+            })
+            .into(),
+        }
+    }
+}
+
+impl From<oboe::Error> for PlayStreamError {
+    fn from(error: oboe::Error) -> Self {
+        use self::oboe::Error::*;
+        match error {
+            Disconnected | Unavailable | Closed => Self::DeviceNotAvailable,
+            e => (BackendSpecificError {
+                description: e.to_string(),
+            })
+            .into(),
+        }
+    }
+}
+
+impl From<oboe::Error> for PauseStreamError {
+    fn from(error: oboe::Error) -> Self {
+        use self::oboe::Error::*;
+        match error {
+            Disconnected | Unavailable | Closed => Self::DeviceNotAvailable,
+            e => (BackendSpecificError {
+                description: e.to_string(),
+            })
+            .into(),
+        }
+    }
+}
+
+impl From<oboe::Error> for BuildStreamError {
+    fn from(error: oboe::Error) -> Self {
+        use self::oboe::Error::*;
+        match error {
+            Disconnected | Unavailable | Closed => Self::DeviceNotAvailable,
+            NoFreeHandles => Self::StreamIdOverflow,
+            InvalidFormat | InvalidRate => Self::StreamConfigNotSupported,
+            IllegalArgument => Self::InvalidArgument,
+            e => (BackendSpecificError {
+                description: e.to_string(),
+            })
+            .into(),
+        }
+    }
+}

vendor/cpal/src/host/oboe/input_callback.rs

@@ -0,0 +1,90 @@
+use std::marker::PhantomData;
+use std::time::Instant;
+
+extern crate oboe;
+
+use super::convert::{stream_instant, to_stream_instant};
+use crate::{Data, InputCallbackInfo, InputStreamTimestamp, SizedSample, StreamError};
+
+pub struct CpalInputCallback<I, C> {
+    data_cb: Box<dyn FnMut(&Data, &InputCallbackInfo) + Send + 'static>,
+    error_cb: Box<dyn FnMut(StreamError) + Send + 'static>,
+    created: Instant,
+    phantom_channel: PhantomData<C>,
+    phantom_input: PhantomData<I>,
+}
+
+impl<I, C> CpalInputCallback<I, C> {
+    pub fn new<D, E>(data_cb: D, error_cb: E) -> Self
+    where
+        D: FnMut(&Data, &InputCallbackInfo) + Send + 'static,
+        E: FnMut(StreamError) + Send + 'static,
+    {
+        Self {
+            data_cb: Box::new(data_cb),
+            error_cb: Box::new(error_cb),
+            created: Instant::now(),
+            phantom_channel: PhantomData,
+            phantom_input: PhantomData,
+        }
+    }
+
+    fn make_callback_info(
+        &self,
+        audio_stream: &mut dyn oboe::AudioInputStreamSafe,
+    ) -> InputCallbackInfo {
+        InputCallbackInfo {
+            timestamp: InputStreamTimestamp {
+                callback: to_stream_instant(self.created.elapsed()),
+                capture: stream_instant(audio_stream),
+            },
+        }
+    }
+}
+
+impl<T: SizedSample, C: oboe::IsChannelCount> oboe::AudioInputCallback for CpalInputCallback<T, C>
+where
+    (T, C): oboe::IsFrameType,
+{
+    type FrameType = (T, C);
+
+    fn on_error_before_close(
+        &mut self,
+        _audio_stream: &mut dyn oboe::AudioInputStreamSafe,
+        error: oboe::Error,
+    ) {
+        (self.error_cb)(StreamError::from(error))
+    }
+
+    fn on_error_after_close(
+        &mut self,
+        _audio_stream: &mut dyn oboe::AudioInputStreamSafe,
+        error: oboe::Error,
+    ) {
+        (self.error_cb)(StreamError::from(error))
+    }
+
+    fn on_audio_ready(
+        &mut self,
+        audio_stream: &mut dyn oboe::AudioInputStreamSafe,
+        audio_data: &[<<Self as oboe::AudioInputCallback>::FrameType as oboe::IsFrameType>::Type],
+    ) -> oboe::DataCallbackResult {
+        let cb_info = self.make_callback_info(audio_stream);
+        let channel_count = if C::CHANNEL_COUNT == oboe::ChannelCount::Mono {
+            1
+        } else {
+            2
+        };
+        (self.data_cb)(
+            &unsafe {
+                Data::from_parts(
+                    audio_data.as_ptr() as *mut _,
+                    audio_data.len() * channel_count,
+                    T::FORMAT,
+                )
+            },
+            &cb_info,
+        );
+        oboe::DataCallbackResult::Continue
+    }
+}

vendor/cpal/src/host/oboe/mod.rs

@@ -0,0 +1,499 @@
+use std::cell::RefCell;
+use std::cmp;
+use std::convert::TryInto;
+use std::time::Duration;
+use std::vec::IntoIter as VecIntoIter;
+
+extern crate oboe;
+
+use crate::traits::{DeviceTrait, HostTrait, StreamTrait};
+use crate::{
+    BackendSpecificError, BufferSize, BuildStreamError, Data, DefaultStreamConfigError,
+    DeviceNameError, DevicesError, InputCallbackInfo, OutputCallbackInfo, PauseStreamError,
+    PlayStreamError, SampleFormat, SampleRate, SizedSample, StreamConfig, StreamError,
+    SupportedBufferSize, SupportedStreamConfig, SupportedStreamConfigRange,
+    SupportedStreamConfigsError,
+};
+
+mod android_media;
+mod convert;
+mod input_callback;
+mod output_callback;
+
+use self::android_media::{get_audio_record_min_buffer_size, get_audio_track_min_buffer_size};
+use self::input_callback::CpalInputCallback;
+use self::oboe::{AudioInputStream, AudioOutputStream};
+use self::output_callback::CpalOutputCallback;
+
+// Android Java API supports up to 8 channels, but oboe API
+// only exposes mono and stereo.
+const CHANNEL_MASKS: [i32; 2] = [
+    android_media::CHANNEL_OUT_MONO,
+    android_media::CHANNEL_OUT_STEREO,
+];
+
+const SAMPLE_RATES: [i32; 13] = [
+    5512, 8000, 11025, 16000, 22050, 32000, 44100, 48000, 64000, 88200, 96000, 176_400, 192_000,
+];
+
+pub struct Host;
+#[derive(Clone)]
+pub struct Device(Option<oboe::AudioDeviceInfo>);
+pub enum Stream {
+    Input(Box<RefCell<dyn AudioInputStream>>),
+    Output(Box<RefCell<dyn AudioOutputStream>>),
+}
+pub type SupportedInputConfigs = VecIntoIter<SupportedStreamConfigRange>;
+pub type SupportedOutputConfigs = VecIntoIter<SupportedStreamConfigRange>;
+pub type Devices = VecIntoIter<Device>;
+
+impl Host {
+    pub fn new() -> Result<Self, crate::HostUnavailable> {
+        Ok(Host)
+    }
+}
+
+impl HostTrait for Host {
+    type Devices = Devices;
+    type Device = Device;
+
+    fn is_available() -> bool {
+        true
+    }
+
+    fn devices(&self) -> Result<Self::Devices, DevicesError> {
+        if let Ok(devices) = oboe::AudioDeviceInfo::request(oboe::AudioDeviceDirection::InputOutput)
+        {
+            Ok(devices
+                .into_iter()
+                .map(|d| Device(Some(d)))
+                .collect::<Vec<_>>()
+                .into_iter())
+        } else {
+            Ok(vec![Device(None)].into_iter())
+        }
+    }
+
+    fn default_input_device(&self) -> Option<Self::Device> {
+        Some(Device(None))
+    }
+
+    fn default_output_device(&self) -> Option<Self::Device> {
+        Some(Device(None))
+    }
+}
+
+fn buffer_size_range_for_params(
+    is_output: bool,
+    sample_rate: i32,
+    channel_mask: i32,
+    android_format: i32,
+) -> SupportedBufferSize {
+    let min_buffer_size = if is_output {
+        get_audio_track_min_buffer_size(sample_rate, channel_mask, android_format)
+    } else {
+        get_audio_record_min_buffer_size(sample_rate, channel_mask, android_format)
+    };
+    if min_buffer_size > 0 {
+        SupportedBufferSize::Range {
+            min: min_buffer_size as u32,
+            max: i32::MAX as u32,
+        }
+    } else {
+        SupportedBufferSize::Unknown
+    }
+}
+
+fn default_supported_configs(is_output: bool) -> VecIntoIter<SupportedStreamConfigRange> {
+    // Have to "brute force" the parameter combinations with getMinBufferSize
+    const FORMATS: [SampleFormat; 2] = [SampleFormat::I16, SampleFormat::F32];
+
+    let mut output = Vec::with_capacity(SAMPLE_RATES.len() * CHANNEL_MASKS.len() * FORMATS.len());
+    for sample_format in &FORMATS {
+        let android_format = if *sample_format == SampleFormat::I16 {
+            android_media::ENCODING_PCM_16BIT
+        } else {
+            android_media::ENCODING_PCM_FLOAT
+        };
+        for (mask_idx, channel_mask) in CHANNEL_MASKS.iter().enumerate() {
+            let channel_count = mask_idx + 1;
+            for sample_rate in &SAMPLE_RATES {
+                if let SupportedBufferSize::Range { min, max } = buffer_size_range_for_params(
+                    is_output,
+                    *sample_rate,
+                    *channel_mask,
+                    android_format,
+                ) {
+                    output.push(SupportedStreamConfigRange {
+                        channels: channel_count as u16,
+                        min_sample_rate: SampleRate(*sample_rate as u32),
+                        max_sample_rate: SampleRate(*sample_rate as u32),
+                        buffer_size: SupportedBufferSize::Range { min, max },
+                        sample_format: *sample_format,
+                    });
+                }
+            }
+        }
+    }
+
+    output.into_iter()
+}
+
+fn device_supported_configs(
+    device: &oboe::AudioDeviceInfo,
+    is_output: bool,
+) -> VecIntoIter<SupportedStreamConfigRange> {
+    let sample_rates = if !device.sample_rates.is_empty() {
+        device.sample_rates.as_slice()
+    } else {
+        &SAMPLE_RATES
+    };
+
+    const ALL_CHANNELS: [i32; 2] = [1, 2];
+    let channel_counts = if !device.channel_counts.is_empty() {
+        device.channel_counts.as_slice()
+    } else {
+        &ALL_CHANNELS
+    };
+
+    const ALL_FORMATS: [oboe::AudioFormat; 2] = [oboe::AudioFormat::I16, oboe::AudioFormat::F32];
+    let formats = if !device.formats.is_empty() {
+        device.formats.as_slice()
+    } else {
+        &ALL_FORMATS
+    };
+
+    let mut output = Vec::with_capacity(sample_rates.len() * channel_counts.len() * formats.len());
+    for sample_rate in sample_rates {
+        for channel_count in channel_counts {
+            assert!(*channel_count > 0);
+            if *channel_count > 2 {
+                // could be supported by the device, but oboe does not support more than 2 channels
+                continue;
+            }
+            let channel_mask = CHANNEL_MASKS[*channel_count as usize - 1];
+            for format in formats {
+                let (android_format, sample_format) = match format {
+                    oboe::AudioFormat::I16 => {
+                        (android_media::ENCODING_PCM_16BIT, SampleFormat::I16)
+                    }
+                    oboe::AudioFormat::F32 => {
+                        (android_media::ENCODING_PCM_FLOAT, SampleFormat::F32)
+                    }
+                    _ => panic!("Unexpected format"),
+                };
+                let buffer_size = buffer_size_range_for_params(
+                    is_output,
+                    *sample_rate,
+                    channel_mask,
+                    android_format,
+                );
+                output.push(SupportedStreamConfigRange {
+                    channels: cmp::min(*channel_count as u16, 2u16),
+                    min_sample_rate: SampleRate(*sample_rate as u32),
+                    max_sample_rate: SampleRate(*sample_rate as u32),
+                    buffer_size,
+                    sample_format,
+                });
+            }
+        }
+    }
+
+    output.into_iter()
+}
+
+fn configure_for_device<D, C, I>(
+    builder: oboe::AudioStreamBuilder<D, C, I>,
+    device: &Device,
+    config: &StreamConfig,
+) -> oboe::AudioStreamBuilder<D, C, I> {
+    let mut builder = if let Some(info) = &device.0 {
+        builder.set_device_id(info.id)
+    } else {
+        builder
+    };
+    builder = builder.set_sample_rate(config.sample_rate.0.try_into().unwrap());
+    match &config.buffer_size {
+        BufferSize::Default => builder,
+        BufferSize::Fixed(size) => builder.set_buffer_capacity_in_frames(*size as i32),
+    }
+}
+
+fn build_input_stream<D, E, C, T>(
+    device: &Device,
+    config: &StreamConfig,
+    data_callback: D,
+    error_callback: E,
+    builder: oboe::AudioStreamBuilder<oboe::Input, C, T>,
+) -> Result<Stream, BuildStreamError>
+where
+    T: SizedSample + oboe::IsFormat + Send + 'static,
+    C: oboe::IsChannelCount + Send + 'static,
+    (T, C): oboe::IsFrameType,
+    D: FnMut(&Data, &InputCallbackInfo) + Send + 'static,
+    E: FnMut(StreamError) + Send + 'static,
+{
+    let builder = configure_for_device(builder, device, config);
+    let stream = builder
+        .set_callback(CpalInputCallback::<T, C>::new(
+            data_callback,
+            error_callback,
+        ))
+        .open_stream()?;
+    Ok(Stream::Input(Box::new(RefCell::new(stream))))
+}
+
+fn build_output_stream<D, E, C, T>(
+    device: &Device,
+    config: &StreamConfig,
+    data_callback: D,
+    error_callback: E,
+    builder: oboe::AudioStreamBuilder<oboe::Output, C, T>,
+) -> Result<Stream, BuildStreamError>
+where
+    T: SizedSample + oboe::IsFormat + Send + 'static,
+    C: oboe::IsChannelCount + Send + 'static,
+    (T, C): oboe::IsFrameType,
+    D: FnMut(&mut Data, &OutputCallbackInfo) + Send + 'static,
+    E: FnMut(StreamError) + Send + 'static,
+{
+    let builder = configure_for_device(builder, device, config);
+    let stream = builder
+        .set_callback(CpalOutputCallback::<T, C>::new(
+            data_callback,
+            error_callback,
+        ))
+        .open_stream()?;
+    Ok(Stream::Output(Box::new(RefCell::new(stream))))
+}
+
+impl DeviceTrait for Device {
+    type SupportedInputConfigs = SupportedInputConfigs;
+    type SupportedOutputConfigs = SupportedOutputConfigs;
+    type Stream = Stream;
+
+    fn name(&self) -> Result<String, DeviceNameError> {
+        match &self.0 {
+            None => Ok("default".to_owned()),
+            Some(info) => Ok(info.product_name.clone()),
+        }
+    }
+
+    fn supported_input_configs(
+        &self,
+    ) -> Result<Self::SupportedInputConfigs, SupportedStreamConfigsError> {
+        if let Some(info) = &self.0 {
+            Ok(device_supported_configs(info, false))
+        } else {
+            Ok(default_supported_configs(false))
+        }
+    }
+
+    fn supported_output_configs(
+        &self,
+    ) -> Result<Self::SupportedOutputConfigs, SupportedStreamConfigsError> {
+        if let Some(info) = &self.0 {
+            Ok(device_supported_configs(info, true))
+        } else {
+            Ok(default_supported_configs(true))
+        }
+    }
+
+    fn default_input_config(&self) -> Result<SupportedStreamConfig, DefaultStreamConfigError> {
+        let mut configs: Vec<_> = self.supported_input_configs().unwrap().collect();
+        configs.sort_by(|a, b| b.cmp_default_heuristics(a));
+        let config = configs
+            .into_iter()
+            .next()
+            .ok_or(DefaultStreamConfigError::StreamTypeNotSupported)?
+            .with_max_sample_rate();
+        Ok(config)
+    }
+
+    fn default_output_config(&self) -> Result<SupportedStreamConfig, DefaultStreamConfigError> {
+        let mut configs: Vec<_> = self.supported_output_configs().unwrap().collect();
+        configs.sort_by(|a, b| b.cmp_default_heuristics(a));
+        let config = configs
+            .into_iter()
+            .next()
+            .ok_or(DefaultStreamConfigError::StreamTypeNotSupported)?
+            .with_max_sample_rate();
+        Ok(config)
+    }
+
+    fn build_input_stream_raw<D, E>(
+        &self,
+        config: &StreamConfig,
+        sample_format: SampleFormat,
+        data_callback: D,
+        error_callback: E,
+        _timeout: Option<Duration>,
+    ) -> Result<Self::Stream, BuildStreamError>
+    where
+        D: FnMut(&Data, &InputCallbackInfo) + Send + 'static,
+        E: FnMut(StreamError) + Send + 'static,
+    {
+        match sample_format {
+            SampleFormat::I16 => {
+                let builder = oboe::AudioStreamBuilder::default()
+                    .set_input()
+                    .set_format::<i16>();
+                if config.channels == 1 {
+                    build_input_stream(
+                        self,
+                        config,
+                        data_callback,
+                        error_callback,
+                        builder.set_mono(),
+                    )
+                } else if config.channels == 2 {
+                    build_input_stream(
+                        self,
+                        config,
+                        data_callback,
+                        error_callback,
+                        builder.set_stereo(),
+                    )
+                } else {
+                    Err(BackendSpecificError {
+                        description: "More than 2 channels are not supported by Oboe.".to_owned(),
+                    }
+                    .into())
+                }
+            }
+            SampleFormat::F32 => {
+                let builder = oboe::AudioStreamBuilder::default()
+                    .set_input()
+                    .set_format::<f32>();
+                if config.channels == 1 {
+                    build_input_stream(
+                        self,
+                        config,
+                        data_callback,
+                        error_callback,
+                        builder.set_mono(),
+                    )
+                } else if config.channels == 2 {
+                    build_input_stream(
+                        self,
+                        config,
+                        data_callback,
+                        error_callback,
+                        builder.set_stereo(),
+                    )
+                } else {
+                    Err(BackendSpecificError {
+                        description: "More than 2 channels are not supported by Oboe.".to_owned(),
+                    }
+                    .into())
+                }
+            }
+            sample_format => Err(BackendSpecificError {
+                description: format!("{} format is not supported on Android.", sample_format),
+            }
+            .into()),
+        }
+    }
+
+    fn build_output_stream_raw<D, E>(
+        &self,
+        config: &StreamConfig,
+        sample_format: SampleFormat,
+        data_callback: D,
+        error_callback: E,
+        _timeout: Option<Duration>,
+    ) -> Result<Self::Stream, BuildStreamError>
+    where
+        D: FnMut(&mut Data, &OutputCallbackInfo) + Send + 'static,
+        E: FnMut(StreamError) + Send + 'static,
+    {
+        match sample_format {
+            SampleFormat::I16 => {
+                let builder = oboe::AudioStreamBuilder::default()
+                    .set_output()
+                    .set_format::<i16>();
+                if config.channels == 1 {
+                    build_output_stream(
+                        self,
+                        config,
+                        data_callback,
+                        error_callback,
+                        builder.set_mono(),
+                    )
+                } else if config.channels == 2 {
+                    build_output_stream(
+                        self,
+                        config,
+                        data_callback,
+                        error_callback,
+                        builder.set_stereo(),
+                    )
+                } else {
+                    Err(BackendSpecificError {
+                        description: "More than 2 channels are not supported by Oboe.".to_owned(),
+                    }
+                    .into())
+                }
+            }
+            SampleFormat::F32 => {
+                let builder = oboe::AudioStreamBuilder::default()
+                    .set_output()
+                    .set_format::<f32>();
+                if config.channels == 1 {
+                    build_output_stream(
+                        self,
+                        config,
+                        data_callback,
+                        error_callback,
+                        builder.set_mono(),
+                    )
+                } else if config.channels == 2 {
+                    build_output_stream(
+                        self,
+                        config,
+                        data_callback,
+                        error_callback,
+                        builder.set_stereo(),
+                    )
+                } else {
+                    Err(BackendSpecificError {
+                        description: "More than 2 channels are not supported by Oboe.".to_owned(),
+                    }
+                    .into())
+                }
+            }
+            sample_format => Err(BackendSpecificError {
+                description: format!("{} format is not supported on Android.", sample_format),
+            }
+            .into()),
+        }
+    }
+}
+
+impl StreamTrait for Stream {
+    fn play(&self) -> Result<(), PlayStreamError> {
+        match self {
+            Self::Input(stream) => stream
+                .borrow_mut()
+                .request_start()
+                .map_err(PlayStreamError::from),
+            Self::Output(stream) => stream
+                .borrow_mut()
+                .request_start()
+                .map_err(PlayStreamError::from),
+        }
+    }
+
+    fn pause(&self) -> Result<(), PauseStreamError> {
+        match self {
+            Self::Input(_) => Err(BackendSpecificError {
+                description: "Pause called on the input stream.".to_owned(),
+            }
+            .into()),
+            Self::Output(stream) => stream
+                .borrow_mut()
+                .request_pause()
+                .map_err(PauseStreamError::from),
+        }
+    }
+}

vendor/cpal/src/host/oboe/output_callback.rs

@@ -0,0 +1,90 @@
+use std::marker::PhantomData;
+use std::time::Instant;
+
+extern crate oboe;
+
+use super::convert::{stream_instant, to_stream_instant};
+use crate::{Data, OutputCallbackInfo, OutputStreamTimestamp, SizedSample, StreamError};
+
+pub struct CpalOutputCallback<I, C> {
+    data_cb: Box<dyn FnMut(&mut Data, &OutputCallbackInfo) + Send + 'static>,
+    error_cb: Box<dyn FnMut(StreamError) + Send + 'static>,
+    created: Instant,
+    phantom_channel: PhantomData<C>,
+    phantom_input: PhantomData<I>,
+}
+
+impl<I, C> CpalOutputCallback<I, C> {
+    pub fn new<D, E>(data_cb: D, error_cb: E) -> Self
+    where
+        D: FnMut(&mut Data, &OutputCallbackInfo) + Send + 'static,
+        E: FnMut(StreamError) + Send + 'static,
+    {
+        Self {
+            data_cb: Box::new(data_cb),
+            error_cb: Box::new(error_cb),
+            created: Instant::now(),
+            phantom_channel: PhantomData,
+            phantom_input: PhantomData,
+        }
+    }
+
+    fn make_callback_info(
+        &self,
+        audio_stream: &mut dyn oboe::AudioOutputStreamSafe,
+    ) -> OutputCallbackInfo {
+        OutputCallbackInfo {
+            timestamp: OutputStreamTimestamp {
+                callback: to_stream_instant(self.created.elapsed()),
+                playback: stream_instant(audio_stream),
+            },
+        }
+    }
+}
+
+impl<T: SizedSample, C: oboe::IsChannelCount> oboe::AudioOutputCallback for CpalOutputCallback<T, C>
+where
+    (T, C): oboe::IsFrameType,
+{
+    type FrameType = (T, C);
+
+    fn on_error_before_close(
+        &mut self,
+        _audio_stream: &mut dyn oboe::AudioOutputStreamSafe,
+        error: oboe::Error,
+    ) {
+        (self.error_cb)(StreamError::from(error))
+    }
+
+    fn on_error_after_close(
+        &mut self,
+        _audio_stream: &mut dyn oboe::AudioOutputStreamSafe,
+        error: oboe::Error,
+    ) {
+        (self.error_cb)(StreamError::from(error))
+    }
+
+    fn on_audio_ready(
+        &mut self,
+        audio_stream: &mut dyn oboe::AudioOutputStreamSafe,
+        audio_data: &mut [<<Self as oboe::AudioOutputCallback>::FrameType as oboe::IsFrameType>::Type],
+    ) -> oboe::DataCallbackResult {
+        let cb_info = self.make_callback_info(audio_stream);
+        let channel_count = if C::CHANNEL_COUNT == oboe::ChannelCount::Mono {
+            1
+        } else {
+            2
+        };
+        (self.data_cb)(
+            &mut unsafe {
+                Data::from_parts(
+                    audio_data.as_mut_ptr() as *mut _,
+                    audio_data.len() * channel_count,
+                    T::FORMAT,
+                )
+            },
+            &cb_info,
+        );
+        oboe::DataCallbackResult::Continue
+    }
+}

vendor/cpal/src/host/wasapi/com.rs

@@ -0,0 +1,57 @@
+//! Handles COM initialization and cleanup.
+
+use super::IoError;
+use std::marker::PhantomData;
+
+use windows::Win32::Foundation::RPC_E_CHANGED_MODE;
+use windows::Win32::System::Com::{CoInitializeEx, CoUninitialize, COINIT_APARTMENTTHREADED};
+
+thread_local!(static COM_INITIALIZED: ComInitialized = {
+    unsafe {
+        // Try to initialize COM with STA by default to avoid compatibility issues with the ASIO
+        // backend (where CoInitialize() is called by the ASIO SDK) or winit (where drag and drop
+        // requires STA).
+        // This call can fail with RPC_E_CHANGED_MODE if another library initialized COM with MTA.
+        // That's OK though since COM ensures thread-safety/compatibility through marshalling when
+        // necessary.
+        let result = CoInitializeEx(None, COINIT_APARTMENTTHREADED);
+        if result.is_ok() || result == RPC_E_CHANGED_MODE {
+            ComInitialized {
+                result,
+                _ptr: PhantomData,
+            }
+        } else {
+            // COM initialization failed in another way, something is really wrong.
+            panic!(
+                "Failed to initialize COM: {}",
+                IoError::from_raw_os_error(result.0)
+            );
+        }
+    }
+});
+
+/// RAII object that guards the fact that COM is initialized.
+///
+// We store a raw pointer because it's the only way at the moment to remove `Send`/`Sync` from the
+// object.
+struct ComInitialized {
+    result: windows::core::HRESULT,
+    _ptr: PhantomData<*mut ()>,
+}
+
+impl Drop for ComInitialized {
+    #[inline]
+    fn drop(&mut self) {
+        // Need to avoid calling CoUninitialize() if CoInitializeEx failed since it may have
+        // returned RPC_E_MODE_CHANGED - which is OK, see above.
+        if self.result.is_ok() {
+            unsafe { CoUninitialize() };
+        }
+    }
+}
+
+/// Ensures that COM is initialized in this thread.
+#[inline]
+pub fn com_initialized() {
+    COM_INITIALIZED.with(|_| {});
+}

vendor/cpal/src/host/wasapi/mod.rs

@@ -0,0 +1,104 @@
+pub use self::device::{
+    default_input_device, default_output_device, Device, Devices, SupportedInputConfigs,
+    SupportedOutputConfigs,
+};
+pub use self::stream::Stream;
+use crate::traits::HostTrait;
+use crate::BackendSpecificError;
+use crate::DevicesError;
+use std::io::Error as IoError;
+use windows::Win32::Media::Audio;
+
+mod com;
+mod device;
+mod stream;
+
+/// The WASAPI host, the default windows host type.
+///
+/// Note: If you use a WASAPI output device as an input device it will
+/// transparently enable loopback mode (see
+/// https://docs.microsoft.com/en-us/windows/win32/coreaudio/loopback-recording).
+#[derive(Debug)]
+pub struct Host;
+
+impl Host {
+    pub fn new() -> Result<Self, crate::HostUnavailable> {
+        Ok(Host)
+    }
+}
+
+impl HostTrait for Host {
+    type Devices = Devices;
+    type Device = Device;
+
+    fn is_available() -> bool {
+        // Assume WASAPI is always available on Windows.
+        true
+    }
+
+    fn devices(&self) -> Result<Self::Devices, DevicesError> {
+        Devices::new()
+    }
+
+    fn default_input_device(&self) -> Option<Self::Device> {
+        default_input_device()
+    }
+
+    fn default_output_device(&self) -> Option<Self::Device> {
+        default_output_device()
+    }
+}
+
+impl From<windows::core::Error> for BackendSpecificError {
+    fn from(error: windows::core::Error) -> Self {
+        BackendSpecificError {
+            description: format!("{}", IoError::from(error)),
+        }
+    }
+}
+
+trait ErrDeviceNotAvailable: From<BackendSpecificError> {
+    fn device_not_available() -> Self;
+}
+
+impl ErrDeviceNotAvailable for crate::BuildStreamError {
+    fn device_not_available() -> Self {
+        Self::DeviceNotAvailable
+    }
+}
+
+impl ErrDeviceNotAvailable for crate::SupportedStreamConfigsError {
+    fn device_not_available() -> Self {
+        Self::DeviceNotAvailable
+    }
+}
+
+impl ErrDeviceNotAvailable for crate::DefaultStreamConfigError {
+    fn device_not_available() -> Self {
+        Self::DeviceNotAvailable
+    }
+}
+
+impl ErrDeviceNotAvailable for crate::StreamError {
+    fn device_not_available() -> Self {
+        Self::DeviceNotAvailable
+    }
+}
+
+fn windows_err_to_cpal_err<E: ErrDeviceNotAvailable>(e: windows::core::Error) -> E {
+    windows_err_to_cpal_err_message::<E>(e, "")
+}
+
+fn windows_err_to_cpal_err_message<E: ErrDeviceNotAvailable>(
+    e: windows::core::Error,
+    message: &str,
+) -> E {
+    match e.code() {
+        Audio::AUDCLNT_E_DEVICE_INVALIDATED => E::device_not_available(),
+        _ => {
+            let description = format!("{}{}", message, e);
+            let err = BackendSpecificError { description };
+            err.into()
+        }
+    }
+}

vendor/cpal/src/host/wasapi/stream.rs

@@ -0,0 +1,559 @@
+use super::windows_err_to_cpal_err;
+use crate::traits::StreamTrait;
+use crate::{
+    BackendSpecificError, Data, InputCallbackInfo, OutputCallbackInfo, PauseStreamError,
+    PlayStreamError, SampleFormat, StreamError,
+};
+use std::mem;
+use std::ptr;
+use std::sync::mpsc::{channel, Receiver, SendError, Sender};
+use std::thread::{self, JoinHandle};
+use windows::Win32::Foundation;
+use windows::Win32::Foundation::HANDLE;
+use windows::Win32::Foundation::WAIT_OBJECT_0;
+use windows::Win32::Media::Audio;
+use windows::Win32::System::SystemServices;
+use windows::Win32::System::Threading;
+
+pub struct Stream {
+    /// The high-priority audio processing thread calling callbacks.
+    /// Option used for moving out in destructor.
+    ///
+    /// TODO: Actually set the thread priority.
+    thread: Option<JoinHandle<()>>,
+
+    // Commands processed by the `run()` method that is currently running.
+    // `pending_scheduled_event` must be signalled whenever a command is added here, so that it
+    // will get picked up.
+    commands: Sender<Command>,
+
+    // This event is signalled after a new entry is added to `commands`, so that the `run()`
+    // method can be notified.
+    pending_scheduled_event: Foundation::HANDLE,
+}
+
+struct RunContext {
+    // Streams that have been created in this event loop.
+    stream: StreamInner,
+
+    // Handles corresponding to the `event` field of each element of `voices`. Must always be in
+    // sync with `voices`, except that the first element is always `pending_scheduled_event`.
+    handles: Vec<Foundation::HANDLE>,
+
+    commands: Receiver<Command>,
+}
+
+// Once we start running the eventloop, the RunContext will not be moved.
+unsafe impl Send for RunContext {}
+
+pub enum Command {
+    PlayStream,
+    PauseStream,
+    Terminate,
+}
+
+pub enum AudioClientFlow {
+    Render {
+        render_client: Audio::IAudioRenderClient,
+    },
+    Capture {
+        capture_client: Audio::IAudioCaptureClient,
+    },
+}
+
+pub struct StreamInner {
+    pub audio_client: Audio::IAudioClient,
+    pub audio_clock: Audio::IAudioClock,
+    pub client_flow: AudioClientFlow,
+    // Event that is signalled by WASAPI whenever audio data must be written.
+    pub event: Foundation::HANDLE,
+    // True if the stream is currently playing. False if paused.
+    pub playing: bool,
+    // Number of frames of audio data in the underlying buffer allocated by WASAPI.
+    pub max_frames_in_buffer: u32,
+    // Number of bytes that each frame occupies.
+    pub bytes_per_frame: u16,
+    // The configuration with which the stream was created.
+    pub config: crate::StreamConfig,
+    // The sample format with which the stream was created.
+    pub sample_format: SampleFormat,
+}
+
+impl Stream {
+    pub(crate) fn new_input<D, E>(
+        stream_inner: StreamInner,
+        mut data_callback: D,
+        mut error_callback: E,
+    ) -> Stream
+    where
+        D: FnMut(&Data, &InputCallbackInfo) + Send + 'static,
+        E: FnMut(StreamError) + Send + 'static,
+    {
+        let pending_scheduled_event = unsafe {
+            Threading::CreateEventA(None, false, false, windows::core::PCSTR(ptr::null()))
+        }
+        .expect("cpal: could not create input stream event");
+        let (tx, rx) = channel();
+
+        let run_context = RunContext {
+            handles: vec![pending_scheduled_event, stream_inner.event],
+            stream: stream_inner,
+            commands: rx,
+        };
+
+        let thread = thread::Builder::new()
+            .name("cpal_wasapi_in".to_owned())
+            .spawn(move || run_input(run_context, &mut data_callback, &mut error_callback))
+            .unwrap();
+
+        Stream {
+            thread: Some(thread),
+            commands: tx,
+            pending_scheduled_event,
+        }
+    }
+
+    pub(crate) fn new_output<D, E>(
+        stream_inner: StreamInner,
+        mut data_callback: D,
+        mut error_callback: E,
+    ) -> Stream
+    where
+        D: FnMut(&mut Data, &OutputCallbackInfo) + Send + 'static,
+        E: FnMut(StreamError) + Send + 'static,
+    {
+        let pending_scheduled_event = unsafe {
+            Threading::CreateEventA(None, false, false, windows::core::PCSTR(ptr::null()))
+        }
+        .expect("cpal: could not create output stream event");
+        let (tx, rx) = channel();
+
+        let run_context = RunContext {
+            handles: vec![pending_scheduled_event, stream_inner.event],
+            stream: stream_inner,
+            commands: rx,
+        };
+
+        let thread = thread::Builder::new()
+            .name("cpal_wasapi_out".to_owned())
+            .spawn(move || run_output(run_context, &mut data_callback, &mut error_callback))
+            .unwrap();
+
+        Stream {
+            thread: Some(thread),
+            commands: tx,
+            pending_scheduled_event,
+        }
+    }
+
+    #[inline]
+    fn push_command(&self, command: Command) -> Result<(), SendError<Command>> {
+        self.commands.send(command)?;
+        unsafe {
+            Threading::SetEvent(self.pending_scheduled_event).unwrap();
+        }
+        Ok(())
+    }
+}
+
+impl Drop for Stream {
+    #[inline]
+    fn drop(&mut self) {
+        if self.push_command(Command::Terminate).is_ok() {
+            self.thread.take().unwrap().join().unwrap();
+            unsafe {
+                let _ = Foundation::CloseHandle(self.pending_scheduled_event);
+            }
+        }
+    }
+}
+
+impl StreamTrait for Stream {
+    fn play(&self) -> Result<(), PlayStreamError> {
+        self.push_command(Command::PlayStream)
+            .map_err(|_| crate::error::PlayStreamError::DeviceNotAvailable)?;
+        Ok(())
+    }
+    fn pause(&self) -> Result<(), PauseStreamError> {
+        self.push_command(Command::PauseStream)
+            .map_err(|_| crate::error::PauseStreamError::DeviceNotAvailable)?;
+        Ok(())
+    }
+}
+
+impl Drop for StreamInner {
+    #[inline]
+    fn drop(&mut self) {
+        unsafe {
+            let _ = Foundation::CloseHandle(self.event);
+        }
+    }
+}
+
+// Process any pending commands that are queued within the `RunContext`.
+// Returns `true` if the loop should continue running, `false` if it should terminate.
+fn process_commands(run_context: &mut RunContext) -> Result<bool, StreamError> {
+    // Process the pending commands.
+    for command in run_context.commands.try_iter() {
+        match command {
+            Command::PlayStream => unsafe {
+                if !run_context.stream.playing {
+                    run_context
+                        .stream
+                        .audio_client
+                        .Start()
+                        .map_err(windows_err_to_cpal_err::<StreamError>)?;
+                    run_context.stream.playing = true;
+                }
+            },
+            Command::PauseStream => unsafe {
+                if run_context.stream.playing {
+                    run_context
+                        .stream
+                        .audio_client
+                        .Stop()
+                        .map_err(windows_err_to_cpal_err::<StreamError>)?;
+                    run_context.stream.playing = false;
+                }
+            },
+            Command::Terminate => {
+                return Ok(false);
+            }
+        }
+    }
+
+    Ok(true)
+}
+// Wait for any of the given handles to be signalled.
+//
+// Returns the index of the `handle` that was signalled, or an `Err` if
+// `WaitForMultipleObjectsEx` fails.
+//
+// This is called when the `run` thread is ready to wait for the next event. The
+// next event might be some command submitted by the user (the first handle) or
+// might indicate that one of the streams is ready to deliver or receive audio.
+fn wait_for_handle_signal(handles: &[Foundation::HANDLE]) -> Result<usize, BackendSpecificError> {
+    debug_assert!(handles.len() <= SystemServices::MAXIMUM_WAIT_OBJECTS as usize);
+    let result = unsafe {
+        Threading::WaitForMultipleObjectsEx(
+            handles,
+            false,               // Don't wait for all, just wait for the first
+            Threading::INFINITE, // TODO: allow setting a timeout
+            false,               // irrelevant parameter here
+        )
+    };
+    if result == Foundation::WAIT_FAILED {
+        let err = unsafe { Foundation::GetLastError() };
+        let description = format!("`WaitForMultipleObjectsEx failed: {:?}", err);
+        let err = BackendSpecificError { description };
+        return Err(err);
+    }
+    // Notifying the corresponding task handler.
+    let handle_idx = (result.0 - WAIT_OBJECT_0.0) as usize;
+    Ok(handle_idx)
+}
+
+// Get the number of available frames that are available for writing/reading.
+fn get_available_frames(stream: &StreamInner) -> Result<u32, StreamError> {
+    unsafe {
+        let padding = stream
+            .audio_client
+            .GetCurrentPadding()
+            .map_err(windows_err_to_cpal_err::<StreamError>)?;
+        Ok(stream.max_frames_in_buffer - padding)
+    }
+}
+
+fn run_input(
+    mut run_ctxt: RunContext,
+    data_callback: &mut dyn FnMut(&Data, &InputCallbackInfo),
+    error_callback: &mut dyn FnMut(StreamError),
+) {
+    boost_current_thread_priority();
+
+    loop {
+        match process_commands_and_await_signal(&mut run_ctxt, error_callback) {
+            Some(ControlFlow::Break) => break,
+            Some(ControlFlow::Continue) => continue,
+            None => (),
+        }
+        let capture_client = match run_ctxt.stream.client_flow {
+            AudioClientFlow::Capture { ref capture_client } => capture_client.clone(),
+            _ => unreachable!(),
+        };
+        match process_input(
+            &run_ctxt.stream,
+            capture_client,
+            data_callback,
+            error_callback,
+        ) {
+            ControlFlow::Break => break,
+            ControlFlow::Continue => continue,
+        }
+    }
+}
+
+fn run_output(
+    mut run_ctxt: RunContext,
+    data_callback: &mut dyn FnMut(&mut Data, &OutputCallbackInfo),
+    error_callback: &mut dyn FnMut(StreamError),
+) {
+    boost_current_thread_priority();
+
+    loop {
+        match process_commands_and_await_signal(&mut run_ctxt, error_callback) {
+            Some(ControlFlow::Break) => break,
+            Some(ControlFlow::Continue) => continue,
+            None => (),
+        }
+        let render_client = match run_ctxt.stream.client_flow {
+            AudioClientFlow::Render { ref render_client } => render_client.clone(),
+            _ => unreachable!(),
+        };
+        match process_output(
+            &run_ctxt.stream,
+            render_client,
+            data_callback,
+            error_callback,
+        ) {
+            ControlFlow::Break => break,
+            ControlFlow::Continue => continue,
+        }
+    }
+}
+
+fn boost_current_thread_priority() {
+    unsafe {
+        let thread_id = Threading::GetCurrentThreadId();
+
+        let _ = Threading::SetThreadPriority(
+            HANDLE(thread_id as isize),
+            Threading::THREAD_PRIORITY_TIME_CRITICAL,
+        );
+    }
+}
+
+enum ControlFlow {
+    Break,
+    Continue,
+}
+
+fn process_commands_and_await_signal(
+    run_context: &mut RunContext,
+    error_callback: &mut dyn FnMut(StreamError),
+) -> Option<ControlFlow> {
+    // Process queued commands.
+    match process_commands(run_context) {
+        Ok(true) => (),
+        Ok(false) => return Some(ControlFlow::Break),
+        Err(err) => {
+            error_callback(err);
+            return Some(ControlFlow::Break);
+        }
+    };
+
+    // Wait for any of the handles to be signalled.
+    let handle_idx = match wait_for_handle_signal(&run_context.handles) {
+        Ok(idx) => idx,
+        Err(err) => {
+            error_callback(err.into());
+            return Some(ControlFlow::Break);
+        }
+    };
+
+    // If `handle_idx` is 0, then it's `pending_scheduled_event` that was signalled in
+    // order for us to pick up the pending commands. Otherwise, a stream needs data.
+    if handle_idx == 0 {
+        return Some(ControlFlow::Continue);
+    }
+
+    None
+}
+
+// The loop for processing pending input data.
+fn process_input(
+    stream: &StreamInner,
+    capture_client: Audio::IAudioCaptureClient,
+    data_callback: &mut dyn FnMut(&Data, &InputCallbackInfo),
+    error_callback: &mut dyn FnMut(StreamError),
+) -> ControlFlow {
+    unsafe {
+        // Get the available data in the shared buffer.
+        let mut buffer: *mut u8 = ptr::null_mut();
+        let mut flags = mem::MaybeUninit::uninit();
+        loop {
+            let mut frames_available = match capture_client.GetNextPacketSize() {
+                Ok(0) => return ControlFlow::Continue,
+                Ok(f) => f,
+                Err(err) => {
+                    error_callback(windows_err_to_cpal_err(err));
+                    return ControlFlow::Break;
+                }
+            };
+            let mut qpc_position: u64 = 0;
+            let result = capture_client.GetBuffer(
+                &mut buffer,
+                &mut frames_available,
+                flags.as_mut_ptr(),
+                None,
+                Some(&mut qpc_position),
+            );
+
+            match result {
+                // TODO: Can this happen?
+                Err(e) if e.code() == Audio::AUDCLNT_S_BUFFER_EMPTY => continue,
+                Err(e) => {
+                    error_callback(windows_err_to_cpal_err(e));
+                    return ControlFlow::Break;
+                }
+                Ok(_) => (),
+            }
+
+            debug_assert!(!buffer.is_null());
+
+            let data = buffer as *mut ();
+            let len = frames_available as usize * stream.bytes_per_frame as usize
+                / stream.sample_format.sample_size();
+            let data = Data::from_parts(data, len, stream.sample_format);
+
+            // The `qpc_position` is in 100 nanosecond units. Convert it to nanoseconds.
+            let timestamp = match input_timestamp(stream, qpc_position) {
+                Ok(ts) => ts,
+                Err(err) => {
+                    error_callback(err);
+                    return ControlFlow::Break;
+                }
+            };
+            let info = InputCallbackInfo { timestamp };
+            data_callback(&data, &info);
+
+            // Release the buffer.
+            let result = capture_client
+                .ReleaseBuffer(frames_available)
+                .map_err(windows_err_to_cpal_err);
+            if let Err(err) = result {
+                error_callback(err);
+                return ControlFlow::Break;
+            }
+        }
+    }
+}
+
+// The loop for writing output data.
+fn process_output(
+    stream: &StreamInner,
+    render_client: Audio::IAudioRenderClient,
+    data_callback: &mut dyn FnMut(&mut Data, &OutputCallbackInfo),
+    error_callback: &mut dyn FnMut(StreamError),
+) -> ControlFlow {
+    // The number of frames available for writing.
+    let frames_available = match get_available_frames(stream) {
+        Ok(0) => return ControlFlow::Continue, // TODO: Can this happen?
+        Ok(n) => n,
+        Err(err) => {
+            error_callback(err);
+            return ControlFlow::Break;
+        }
+    };
+
+    unsafe {
+        let buffer = match render_client.GetBuffer(frames_available) {
+            Ok(b) => b,
+            Err(e) => {
+                error_callback(windows_err_to_cpal_err(e));
+                return ControlFlow::Break;
+            }
+        };
+
+        debug_assert!(!buffer.is_null());
+
+        let data = buffer as *mut ();
+        let len = frames_available as usize * stream.bytes_per_frame as usize
+            / stream.sample_format.sample_size();
+        let mut data = Data::from_parts(data, len, stream.sample_format);
+        let sample_rate = stream.config.sample_rate;
+        let timestamp = match output_timestamp(stream, frames_available, sample_rate) {
+            Ok(ts) => ts,
+            Err(err) => {
+                error_callback(err);
+                return ControlFlow::Break;
+            }
+        };
+        let info = OutputCallbackInfo { timestamp };
+        data_callback(&mut data, &info);
+
+        if let Err(err) = render_client.ReleaseBuffer(frames_available, 0) {
+            error_callback(windows_err_to_cpal_err(err));
+            return ControlFlow::Break;
+        }
+    }
+
+    ControlFlow::Continue
+}
+
+/// Convert the given duration in frames at the given sample rate to a `std::time::Duration`.
+fn frames_to_duration(frames: u32, rate: crate::SampleRate) -> std::time::Duration {
+    let secsf = frames as f64 / rate.0 as f64;
+    let secs = secsf as u64;
+    let nanos = ((secsf - secs as f64) * 1_000_000_000.0) as u32;
+    std::time::Duration::new(secs, nanos)
+}
+
+/// Use the stream's `IAudioClock` to produce the current stream instant.
+///
+/// Uses the QPC position produced via the `GetPosition` method.
+fn stream_instant(stream: &StreamInner) -> Result<crate::StreamInstant, StreamError> {
+    let mut position: u64 = 0;
+    let mut qpc_position: u64 = 0;
+    unsafe {
+        stream
+            .audio_clock
+            .GetPosition(&mut position, Some(&mut qpc_position))
+            .map_err(windows_err_to_cpal_err::<StreamError>)?;
+    };
+    // The `qpc_position` is in 100 nanosecond units. Convert it to nanoseconds.
+    let qpc_nanos = qpc_position as i128 * 100;
+    let instant = crate::StreamInstant::from_nanos_i128(qpc_nanos)
+        .expect("performance counter out of range of `StreamInstant` representation");
+    Ok(instant)
+}
+
+/// Produce the input stream timestamp.
+///
+/// `buffer_qpc_position` is the `qpc_position` returned via the `GetBuffer` call on the capture
+/// client. It represents the instant at which the first sample of the retrieved buffer was
+/// captured.
+fn input_timestamp(
+    stream: &StreamInner,
+    buffer_qpc_position: u64,
+) -> Result<crate::InputStreamTimestamp, StreamError> {
+    // The `qpc_position` is in 100 nanosecond units. Convert it to nanoseconds.
+    let qpc_nanos = buffer_qpc_position as i128 * 100;
+    let capture = crate::StreamInstant::from_nanos_i128(qpc_nanos)
+        .expect("performance counter out of range of `StreamInstant` representation");
+    let callback = stream_instant(stream)?;
+    Ok(crate::InputStreamTimestamp { capture, callback })
+}
+
+/// Produce the output stream timestamp.
+///
+/// `frames_available` is the number of frames available for writing as reported by subtracting the
+/// result of `GetCurrentPadding` from the maximum buffer size.
+///
+/// `sample_rate` is the rate at which audio frames are processed by the device.
+///
+/// TODO: The returned `playback` is an estimate that assumes audio is delivered immediately after
+/// `frames_available` are consumed. The reality is that there is likely a tiny amount of latency
+/// after this, but not sure how to determine this.
+fn output_timestamp(
+    stream: &StreamInner,
+    frames_available: u32,
+    sample_rate: crate::SampleRate,
+) -> Result<crate::OutputStreamTimestamp, StreamError> {
+    let callback = stream_instant(stream)?;
+    let buffer_duration = frames_to_duration(frames_available, sample_rate);
+    let playback = callback
+        .add(buffer_duration)
+        .expect("`playback` occurs beyond representation supported by `StreamInstant`");
+    Ok(crate::OutputStreamTimestamp { callback, playback })
+}

vendor/cpal/src/host/webaudio/mod.rs

@@ -0,0 +1,528 @@
+extern crate js_sys;
+extern crate wasm_bindgen;
+extern crate web_sys;
+
+use self::js_sys::eval;
+use self::wasm_bindgen::prelude::*;
+use self::wasm_bindgen::JsCast;
+use self::web_sys::{AudioContext, AudioContextOptions};
+use crate::traits::{DeviceTrait, HostTrait, StreamTrait};
+use crate::{
+    BackendSpecificError, BufferSize, BuildStreamError, Data, DefaultStreamConfigError,
+    DeviceNameError, DevicesError, InputCallbackInfo, OutputCallbackInfo, PauseStreamError,
+    PlayStreamError, SampleFormat, SampleRate, StreamConfig, StreamError, SupportedBufferSize,
+    SupportedStreamConfig, SupportedStreamConfigRange, SupportedStreamConfigsError,
+};
+use std::ops::DerefMut;
+use std::sync::{Arc, Mutex, RwLock};
+use std::time::Duration;
+
+/// Content is false if the iterator is empty.
+pub struct Devices(bool);
+
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct Device;
+
+pub struct Host;
+
+pub struct Stream {
+    ctx: Arc<AudioContext>,
+    on_ended_closures: Vec<Arc<RwLock<Option<Closure<dyn FnMut()>>>>>,
+    config: StreamConfig,
+    buffer_size_frames: usize,
+}
+
+pub type SupportedInputConfigs = ::std::vec::IntoIter<SupportedStreamConfigRange>;
+pub type SupportedOutputConfigs = ::std::vec::IntoIter<SupportedStreamConfigRange>;
+
+const MIN_CHANNELS: u16 = 1;
+const MAX_CHANNELS: u16 = 32;
+const MIN_SAMPLE_RATE: SampleRate = SampleRate(8_000);
+const MAX_SAMPLE_RATE: SampleRate = SampleRate(96_000);
+const DEFAULT_SAMPLE_RATE: SampleRate = SampleRate(44_100);
+const MIN_BUFFER_SIZE: u32 = 1;
+const MAX_BUFFER_SIZE: u32 = u32::MAX;
+const DEFAULT_BUFFER_SIZE: usize = 2048;
+const SUPPORTED_SAMPLE_FORMAT: SampleFormat = SampleFormat::F32;
+
+impl Host {
+    pub fn new() -> Result<Self, crate::HostUnavailable> {
+        Ok(Host)
+    }
+}
+
+impl HostTrait for Host {
+    type Devices = Devices;
+    type Device = Device;
+
+    fn is_available() -> bool {
+        // Assume this host is always available on webaudio.
+        true
+    }
+
+    fn devices(&self) -> Result<Self::Devices, DevicesError> {
+        Devices::new()
+    }
+
+    fn default_input_device(&self) -> Option<Self::Device> {
+        default_input_device()
+    }
+
+    fn default_output_device(&self) -> Option<Self::Device> {
+        default_output_device()
+    }
+}
+
+impl Devices {
+    fn new() -> Result<Self, DevicesError> {
+        Ok(Self::default())
+    }
+}
+
+impl Device {
+    #[inline]
+    fn name(&self) -> Result<String, DeviceNameError> {
+        Ok("Default Device".to_owned())
+    }
+
+    #[inline]
+    fn supported_input_configs(
+        &self,
+    ) -> Result<SupportedInputConfigs, SupportedStreamConfigsError> {
+        // TODO
+        Ok(Vec::new().into_iter())
+    }
+
+    #[inline]
+    fn supported_output_configs(
+        &self,
+    ) -> Result<SupportedOutputConfigs, SupportedStreamConfigsError> {
+        let buffer_size = SupportedBufferSize::Range {
+            min: MIN_BUFFER_SIZE,
+            max: MAX_BUFFER_SIZE,
+        };
+        let configs: Vec<_> = (MIN_CHANNELS..=MAX_CHANNELS)
+            .map(|channels| SupportedStreamConfigRange {
+                channels,
+                min_sample_rate: MIN_SAMPLE_RATE,
+                max_sample_rate: MAX_SAMPLE_RATE,
+                buffer_size: buffer_size.clone(),
+                sample_format: SUPPORTED_SAMPLE_FORMAT,
+            })
+            .collect();
+        Ok(configs.into_iter())
+    }
+
+    #[inline]
+    fn default_input_config(&self) -> Result<SupportedStreamConfig, DefaultStreamConfigError> {
+        // TODO
+        Err(DefaultStreamConfigError::StreamTypeNotSupported)
+    }
+
+    #[inline]
+    fn default_output_config(&self) -> Result<SupportedStreamConfig, DefaultStreamConfigError> {
+        const EXPECT: &str = "expected at least one valid webaudio stream config";
+        let config = self
+            .supported_output_configs()
+            .expect(EXPECT)
+            .max_by(|a, b| a.cmp_default_heuristics(b))
+            .unwrap()
+            .with_sample_rate(DEFAULT_SAMPLE_RATE);
+
+        Ok(config)
+    }
+}
+
+impl DeviceTrait for Device {
+    type SupportedInputConfigs = SupportedInputConfigs;
+    type SupportedOutputConfigs = SupportedOutputConfigs;
+    type Stream = Stream;
+
+    #[inline]
+    fn name(&self) -> Result<String, DeviceNameError> {
+        Device::name(self)
+    }
+
+    #[inline]
+    fn supported_input_configs(
+        &self,
+    ) -> Result<Self::SupportedInputConfigs, SupportedStreamConfigsError> {
+        Device::supported_input_configs(self)
+    }
+
+    #[inline]
+    fn supported_output_configs(
+        &self,
+    ) -> Result<Self::SupportedOutputConfigs, SupportedStreamConfigsError> {
+        Device::supported_output_configs(self)
+    }
+
+    #[inline]
+    fn default_input_config(&self) -> Result<SupportedStreamConfig, DefaultStreamConfigError> {
+        Device::default_input_config(self)
+    }
+
+    #[inline]
+    fn default_output_config(&self) -> Result<SupportedStreamConfig, DefaultStreamConfigError> {
+        Device::default_output_config(self)
+    }
+
+    fn build_input_stream_raw<D, E>(
+        &self,
+        _config: &StreamConfig,
+        _sample_format: SampleFormat,
+        _data_callback: D,
+        _error_callback: E,
+        _timeout: Option<Duration>,
+    ) -> Result<Self::Stream, BuildStreamError>
+    where
+        D: FnMut(&Data, &InputCallbackInfo) + Send + 'static,
+        E: FnMut(StreamError) + Send + 'static,
+    {
+        // TODO
+        Err(BuildStreamError::StreamConfigNotSupported)
+    }
+
+    /// Create an output stream.
+    fn build_output_stream_raw<D, E>(
+        &self,
+        config: &StreamConfig,
+        sample_format: SampleFormat,
+        data_callback: D,
+        _error_callback: E,
+        _timeout: Option<Duration>,
+    ) -> Result<Self::Stream, BuildStreamError>
+    where
+        D: FnMut(&mut Data, &OutputCallbackInfo) + Send + 'static,
+        E: FnMut(StreamError) + Send + 'static,
+    {
+        if !valid_config(config, sample_format) {
+            return Err(BuildStreamError::StreamConfigNotSupported);
+        }
+
+        let n_channels = config.channels as usize;
+
+        let buffer_size_frames = match config.buffer_size {
+            BufferSize::Fixed(v) => {
+                if v == 0 {
+                    return Err(BuildStreamError::StreamConfigNotSupported);
+                } else {
+                    v as usize
+                }
+            }
+            BufferSize::Default => DEFAULT_BUFFER_SIZE,
+        };
+        let buffer_size_samples = buffer_size_frames * n_channels;
+        let buffer_time_step_secs = buffer_time_step_secs(buffer_size_frames, config.sample_rate);
+
+        let data_callback = Arc::new(Mutex::new(Box::new(data_callback)));
+
+        // Create the WebAudio stream.
+        let mut stream_opts = AudioContextOptions::new();
+        stream_opts.sample_rate(config.sample_rate.0 as f32);
+        let ctx = AudioContext::new_with_context_options(&stream_opts).map_err(
+            |err| -> BuildStreamError {
+                let description = format!("{:?}", err);
+                let err = BackendSpecificError { description };
+                err.into()
+            },
+        )?;
+
+        let destination = ctx.destination();
+
+        // If possible, set the destination's channel_count to the given config.channel.
+        // If not, fallback on the default destination channel_count to keep previous behavior
+        // and do not return an error.
+        if config.channels as u32 <= destination.max_channel_count() {
+            destination.set_channel_count(config.channels as u32);
+        }
+
+        let ctx = Arc::new(ctx);
+
+        // A container for managing the lifecycle of the audio callbacks.
+        let mut on_ended_closures: Vec<Arc<RwLock<Option<Closure<dyn FnMut()>>>>> = Vec::new();
+
+        // A cursor keeping track of the current time at which new frames should be scheduled.
+        let time = Arc::new(RwLock::new(0f64));
+
+        // Create a set of closures / callbacks which will continuously fetch and schedule sample
+        // playback. Starting with two workers, e.g. a front and back buffer so that audio frames
+        // can be fetched in the background.
+        for _i in 0..2 {
+            let data_callback_handle = data_callback.clone();
+            let ctx_handle = ctx.clone();
+            let time_handle = time.clone();
+
+            // A set of temporary buffers to be used for intermediate sample transformation steps.
+            let mut temporary_buffer = vec![0f32; buffer_size_samples];
+            let mut temporary_channel_buffer = vec![0f32; buffer_size_frames];
+
+            #[cfg(target_feature = "atomics")]
+            let temporary_channel_array_view: js_sys::Float32Array;
+            #[cfg(target_feature = "atomics")]
+            {
+                let temporary_channel_array = js_sys::ArrayBuffer::new(
+                    (std::mem::size_of::<f32>() * buffer_size_frames) as u32,
+                );
+                temporary_channel_array_view = js_sys::Float32Array::new(&temporary_channel_array);
+            }
+
+            // Create a webaudio buffer which will be reused to avoid allocations.
+            let ctx_buffer = ctx
+                .create_buffer(
+                    config.channels as u32,
+                    buffer_size_frames as u32,
+                    config.sample_rate.0 as f32,
+                )
+                .map_err(|err| -> BuildStreamError {
+                    let description = format!("{:?}", err);
+                    let err = BackendSpecificError { description };
+                    err.into()
+                })?;
+
+            // A self reference to this closure for passing to future audio event calls.
+            let on_ended_closure: Arc<RwLock<Option<Closure<dyn FnMut()>>>> =
+                Arc::new(RwLock::new(None));
+            let on_ended_closure_handle = on_ended_closure.clone();
+
+            on_ended_closure
+                .write()
+                .unwrap()
+                .replace(Closure::wrap(Box::new(move || {
+                    let now = ctx_handle.current_time();
+                    let time_at_start_of_buffer = {
+                        let time_at_start_of_buffer = time_handle
+                            .read()
+                            .expect("Unable to get a read lock on the time cursor");
+                        // Synchronise first buffer as necessary (eg. keep the time value
+                        // referenced to the context clock).
+                        if *time_at_start_of_buffer > 0.001 {
+                            *time_at_start_of_buffer
+                        } else {
+                            // 25ms of time to fetch the first sample data, increase to avoid
+                            // initial underruns.
+                            now + 0.025
+                        }
+                    };
+
+                    // Populate the sample data into an interleaved temporary buffer.
+                    {
+                        let len = temporary_buffer.len();
+                        let data = temporary_buffer.as_mut_ptr() as *mut ();
+                        let mut data = unsafe { Data::from_parts(data, len, sample_format) };
+                        let mut data_callback = data_callback_handle.lock().unwrap();
+                        let callback = crate::StreamInstant::from_secs_f64(now);
+                        let playback = crate::StreamInstant::from_secs_f64(time_at_start_of_buffer);
+                        let timestamp = crate::OutputStreamTimestamp { callback, playback };
+                        let info = OutputCallbackInfo { timestamp };
+                        (data_callback.deref_mut())(&mut data, &info);
+                    }
+
+                    // Deinterleave the sample data and copy into the audio context buffer.
+                    // We do not reference the audio context buffer directly e.g. getChannelData.
+                    // As wasm-bindgen only gives us a copy, not a direct reference.
+                    for channel in 0..n_channels {
+                        for i in 0..buffer_size_frames {
+                            temporary_channel_buffer[i] =
+                                temporary_buffer[n_channels * i + channel];
+                        }
+
+                        #[cfg(not(target_feature = "atomics"))]
+                        {
+                            ctx_buffer
+                                .copy_to_channel(&mut temporary_channel_buffer, channel as i32)
+                                .expect(
+                                    "Unable to write sample data into the audio context buffer",
+                                );
+                        }
+
+                        // copyToChannel cannot be directly copied into from a SharedArrayBuffer,
+                        // which WASM memory is backed by if the 'atomics' flag is enabled.
+                        // This workaround copies the data into an intermediary buffer first.
+                        // There's a chance browsers may eventually relax that requirement.
+                        // See this issue: https://github.com/WebAudio/web-audio-api/issues/2565
+                        #[cfg(target_feature = "atomics")]
+                        {
+                            temporary_channel_array_view.copy_from(&mut temporary_channel_buffer);
+                            ctx_buffer
+                                .unchecked_ref::<ExternalArrayAudioBuffer>()
+                                .copy_to_channel(&temporary_channel_array_view, channel as i32)
+                                .expect(
+                                    "Unable to write sample data into the audio context buffer",
+                                );
+                        }
+                    }
+
+                    // Create an AudioBufferSourceNode, schedule it to playback the reused buffer
+                    // in the future.
+                    let source = ctx_handle
+                        .create_buffer_source()
+                        .expect("Unable to create a webaudio buffer source");
+                    source.set_buffer(Some(&ctx_buffer));
+                    source
+                        .connect_with_audio_node(&ctx_handle.destination())
+                        .expect(
+                        "Unable to connect the web audio buffer source to the context destination",
+                    );
+                    source.set_onended(Some(
+                        on_ended_closure_handle
+                            .read()
+                            .unwrap()
+                            .as_ref()
+                            .unwrap()
+                            .as_ref()
+                            .unchecked_ref(),
+                    ));
+
+                    source
+                        .start_with_when(time_at_start_of_buffer)
+                        .expect("Unable to start the webaudio buffer source");
+
+                    // Keep track of when the next buffer worth of samples should be played.
+                    *time_handle.write().unwrap() = time_at_start_of_buffer + buffer_time_step_secs;
+                }) as Box<dyn FnMut()>));
+
+            on_ended_closures.push(on_ended_closure);
+        }
+
+        Ok(Stream {
+            ctx,
+            on_ended_closures,
+            config: config.clone(),
+            buffer_size_frames,
+        })
+    }
+}
+
+impl Stream {
+    /// Return the [`AudioContext`](https://developer.mozilla.org/docs/Web/API/AudioContext) used
+    /// by this stream.
+    pub fn audio_context(&self) -> &AudioContext {
+        &*self.ctx
+    }
+}
+
+impl StreamTrait for Stream {
+    fn play(&self) -> Result<(), PlayStreamError> {
+        let window = web_sys::window().unwrap();
+        match self.ctx.resume() {
+            Ok(_) => {
+                // Begin webaudio playback, initially scheduling the closures to fire on a timeout
+                // event.
+                let mut offset_ms = 10;
+                let time_step_secs =
+                    buffer_time_step_secs(self.buffer_size_frames, self.config.sample_rate);
+                let time_step_ms = (time_step_secs * 1_000.0) as i32;
+                for on_ended_closure in self.on_ended_closures.iter() {
+                    window
+                        .set_timeout_with_callback_and_timeout_and_arguments_0(
+                            on_ended_closure
+                                .read()
+                                .unwrap()
+                                .as_ref()
+                                .unwrap()
+                                .as_ref()
+                                .unchecked_ref(),
+                            offset_ms,
+                        )
+                        .unwrap();
+                    offset_ms += time_step_ms;
+                }
+                Ok(())
+            }
+            Err(err) => {
+                let description = format!("{:?}", err);
+                let err = BackendSpecificError { description };
+                Err(err.into())
+            }
+        }
+    }
+
+    fn pause(&self) -> Result<(), PauseStreamError> {
+        match self.ctx.suspend() {
+            Ok(_) => Ok(()),
+            Err(err) => {
+                let description = format!("{:?}", err);
+                let err = BackendSpecificError { description };
+                Err(err.into())
+            }
+        }
+    }
+}
+
+impl Drop for Stream {
+    fn drop(&mut self) {
+        let _ = self.ctx.close();
+    }
+}
+
+impl Default for Devices {
+    fn default() -> Devices {
+        // We produce an empty iterator if the WebAudio API isn't available.
+        Devices(is_webaudio_available())
+    }
+}
+
+impl Iterator for Devices {
+    type Item = Device;
+    #[inline]
+    fn next(&mut self) -> Option<Device> {
+        if self.0 {
+            self.0 = false;
+            Some(Device)
+        } else {
+            None
+        }
+    }
+}
+
+#[inline]
+fn default_input_device() -> Option<Device> {
+    // TODO
+    None
+}
+
+#[inline]
+fn default_output_device() -> Option<Device> {
+    if is_webaudio_available() {
+        Some(Device)
+    } else {
+        None
+    }
+}
+
+// Detects whether the `AudioContext` global variable is available.
+fn is_webaudio_available() -> bool {
+    if let Ok(audio_context_is_defined) = eval("typeof AudioContext !== 'undefined'") {
+        audio_context_is_defined.as_bool().unwrap()
+    } else {
+        false
+    }
+}
+
+// Whether or not the given stream configuration is valid for building a stream.
+fn valid_config(conf: &StreamConfig, sample_format: SampleFormat) -> bool {
+    conf.channels <= MAX_CHANNELS
+        && conf.channels >= MIN_CHANNELS
+        && conf.sample_rate <= MAX_SAMPLE_RATE
+        && conf.sample_rate >= MIN_SAMPLE_RATE
+        && sample_format == SUPPORTED_SAMPLE_FORMAT
+}
+
+fn buffer_time_step_secs(buffer_size_frames: usize, sample_rate: SampleRate) -> f64 {
+    buffer_size_frames as f64 / sample_rate.0 as f64
+}
+
+#[cfg(target_feature = "atomics")]
+#[wasm_bindgen]
+extern "C" {
+    #[wasm_bindgen(js_name = AudioBuffer)]
+    type ExternalArrayAudioBuffer;
+
+    # [wasm_bindgen(catch, method, structural, js_class = "AudioBuffer", js_name = copyToChannel)]
+    pub fn copy_to_channel(
+        this: &ExternalArrayAudioBuffer,
+        source: &js_sys::Float32Array,
+        channel_number: i32,
+    ) -> Result<(), JsValue>;
+}

vendor/cpal/src/lib.rs

@@ -0,0 +1,871 @@
+//! # How to use cpal
+//!
+//! Here are some concepts cpal exposes:
+//!
+//! - A [`Host`] provides access to the available audio devices on the system.
+//!   Some platforms have more than one host available, but every platform supported by CPAL has at
+//!   least one [default_host] that is guaranteed to be available.
+//! - A [`Device`] is an audio device that may have any number of input and
+//!   output streams.
+//! - A [`Stream`] is an open flow of audio data. Input streams allow you to
+//!   receive audio data, output streams allow you to play audio data. You must choose which
+//!   [Device] will run your stream before you can create one. Often, a default device can be
+//!   retrieved via the [Host].
+//!
+//! The first step is to initialise the [`Host`]:
+//!
+//! ```
+//! use cpal::traits::HostTrait;
+//! let host = cpal::default_host();
+//! ```
+//!
+//! Then choose an available [`Device`]. The easiest way is to use the default input or output
+//! `Device` via the [`default_input_device()`] or [`default_output_device()`] methods on `host`.
+//!
+//! Alternatively, you can enumerate all the available devices with the [`devices()`] method.
+//! Beware that the `default_*_device()` functions return an `Option<Device>` in case no device
+//! is available for that stream type on the system.
+//!
+//! ```no_run
+//! # use cpal::traits::HostTrait;
+//! # let host = cpal::default_host();
+//! let device = host.default_output_device().expect("no output device available");
+//! ```
+//!
+//! Before we can create a stream, we must decide what the configuration of the audio stream is
+//! going to be.    
+//! You can query all the supported configurations with the
+//! [`supported_input_configs()`] and [`supported_output_configs()`] methods.
+//! These produce a list of [`SupportedStreamConfigRange`] structs which can later be turned into
+//! actual [`SupportedStreamConfig`] structs.
+//!
+//! If you don't want to query the list of configs,
+//! you can also build your own [`StreamConfig`] manually, but doing so could lead to an error when
+//! building the stream if the config is not supported by the device.
+//!
+//! > **Note**: the `supported_input/output_configs()` methods
+//! > could return an error for example if the device has been disconnected.
+//!
+//! ```no_run
+//! use cpal::traits::{DeviceTrait, HostTrait};
+//! # let host = cpal::default_host();
+//! # let device = host.default_output_device().unwrap();
+//! let mut supported_configs_range = device.supported_output_configs()
+//!     .expect("error while querying configs");
+//! let supported_config = supported_configs_range.next()
+//!     .expect("no supported config?!")
+//!     .with_max_sample_rate();
+//! ```
+//!
+//! Now that we have everything for the stream, we are ready to create it from our selected device:
+//!
+//! ```no_run
+//! use cpal::Data;
+//! use cpal::traits::{DeviceTrait, HostTrait, StreamTrait};
+//! # let host = cpal::default_host();
+//! # let device = host.default_output_device().unwrap();
+//! # let config = device.default_output_config().unwrap().into();
+//! let stream = device.build_output_stream(
+//!     &config,
+//!     move |data: &mut [f32], _: &cpal::OutputCallbackInfo| {
+//!         // react to stream events and read or write stream data here.
+//!     },
+//!     move |err| {
+//!         // react to errors here.
+//!     },
+//!     None // None=blocking, Some(Duration)=timeout
+//! );
+//! ```
+//!
+//! While the stream is running, the selected audio device will periodically call the data callback
+//! that was passed to the function. The callback is passed an instance of either [`&Data` or
+//! `&mut Data`](Data) depending on whether the stream is an input stream or output stream respectively.
+//!
+//! > **Note**: Creating and running a stream will *not* block the thread. On modern platforms, the
+//! > given callback is called by a dedicated, high-priority thread responsible for delivering
+//! > audio data to the system's audio device in a timely manner. On older platforms that only
+//! > provide a blocking API (e.g. ALSA), CPAL will create a thread in order to consistently
+//! > provide non-blocking behaviour (currently this is a thread per stream, but this may change to
+//! > use a single thread for all streams). *If this is an issue for your platform or design,
+//! > please share your issue and use-case with the CPAL team on the GitHub issue tracker for
+//! > consideration.*
+//!
+//! In this example, we simply fill the given output buffer with silence.
+//!
+//! ```no_run
+//! use cpal::{Data, Sample, SampleFormat, FromSample};
+//! use cpal::traits::{DeviceTrait, HostTrait, StreamTrait};
+//! # let host = cpal::default_host();
+//! # let device = host.default_output_device().unwrap();
+//! # let supported_config = device.default_output_config().unwrap();
+//! let err_fn = |err| eprintln!("an error occurred on the output audio stream: {}", err);
+//! let sample_format = supported_config.sample_format();
+//! let config = supported_config.into();
+//! let stream = match sample_format {
+//!     SampleFormat::F32 => device.build_output_stream(&config, write_silence::<f32>, err_fn, None),
+//!     SampleFormat::I16 => device.build_output_stream(&config, write_silence::<i16>, err_fn, None),
+//!     SampleFormat::U16 => device.build_output_stream(&config, write_silence::<u16>, err_fn, None),
+//!     sample_format => panic!("Unsupported sample format '{sample_format}'")
+//! }.unwrap();
+//!
+//! fn write_silence<T: Sample>(data: &mut [T], _: &cpal::OutputCallbackInfo) {
+//!     for sample in data.iter_mut() {
+//!         *sample = Sample::EQUILIBRIUM;
+//!     }
+//! }
+//! ```
+//!
+//! Not all platforms automatically run the stream upon creation. To ensure the stream has started,
+//! we can use [`Stream::play`](traits::StreamTrait::play).
+//!
+//! ```no_run
+//! # use cpal::traits::{DeviceTrait, HostTrait, StreamTrait};
+//! # let host = cpal::default_host();
+//! # let device = host.default_output_device().unwrap();
+//! # let supported_config = device.default_output_config().unwrap();
+//! # let sample_format = supported_config.sample_format();
+//! # let config = supported_config.into();
+//! # let data_fn = move |_data: &mut cpal::Data, _: &cpal::OutputCallbackInfo| {};
+//! # let err_fn = move |_err| {};
+//! # let stream = device.build_output_stream_raw(&config, sample_format, data_fn, err_fn, None).unwrap();
+//! stream.play().unwrap();
+//! ```
+//!
+//! Some devices support pausing the audio stream. This can be useful for saving energy in moments
+//! of silence.
+//!
+//! ```no_run
+//! # use cpal::traits::{DeviceTrait, HostTrait, StreamTrait};
+//! # let host = cpal::default_host();
+//! # let device = host.default_output_device().unwrap();
+//! # let supported_config = device.default_output_config().unwrap();
+//! # let sample_format = supported_config.sample_format();
+//! # let config = supported_config.into();
+//! # let data_fn = move |_data: &mut cpal::Data, _: &cpal::OutputCallbackInfo| {};
+//! # let err_fn = move |_err| {};
+//! # let stream = device.build_output_stream_raw(&config, sample_format, data_fn, err_fn, None).unwrap();
+//! stream.pause().unwrap();
+//! ```
+//!
+//! [`default_input_device()`]: traits::HostTrait::default_input_device
+//! [`default_output_device()`]: traits::HostTrait::default_output_device
+//! [`devices()`]: traits::HostTrait::devices
+//! [`supported_input_configs()`]: traits::DeviceTrait::supported_input_configs
+//! [`supported_output_configs()`]: traits::DeviceTrait::supported_output_configs
+
+#![recursion_limit = "2048"]
+
+// Extern crate declarations with `#[macro_use]` must unfortunately be at crate root.
+#[cfg(target_os = "emscripten")]
+#[macro_use]
+extern crate wasm_bindgen;
+#[cfg(target_os = "emscripten")]
+extern crate js_sys;
+#[cfg(target_os = "emscripten")]
+extern crate web_sys;
+
+pub use error::*;
+pub use platform::{
+    available_hosts, default_host, host_from_id, Device, Devices, Host, HostId, Stream,
+    SupportedInputConfigs, SupportedOutputConfigs, ALL_HOSTS,
+};
+pub use samples_formats::{FromSample, Sample, SampleFormat, SizedSample, I24, I48, U24, U48};
+use std::convert::TryInto;
+use std::ops::{Div, Mul};
+use std::time::Duration;
+#[cfg(target_os = "emscripten")]
+use wasm_bindgen::prelude::*;
+
+mod error;
+mod host;
+pub mod platform;
+mod samples_formats;
+pub mod traits;
+
+/// A host's device iterator yielding only *input* devices.
+pub type InputDevices<I> = std::iter::Filter<I, fn(&<I as Iterator>::Item) -> bool>;
+
+/// A host's device iterator yielding only *output* devices.
+pub type OutputDevices<I> = std::iter::Filter<I, fn(&<I as Iterator>::Item) -> bool>;
+
+/// Number of channels.
+pub type ChannelCount = u16;
+
+/// The number of samples processed per second for a single channel of audio.
+#[cfg_attr(target_os = "emscripten", wasm_bindgen)]
+#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
+pub struct SampleRate(pub u32);
+
+impl<T> Mul<T> for SampleRate
+where
+    u32: Mul<T, Output = u32>,
+{
+    type Output = Self;
+    fn mul(self, rhs: T) -> Self {
+        SampleRate(self.0 * rhs)
+    }
+}
+
+impl<T> Div<T> for SampleRate
+where
+    u32: Div<T, Output = u32>,
+{
+    type Output = Self;
+    fn div(self, rhs: T) -> Self {
+        SampleRate(self.0 / rhs)
+    }
+}
+
+/// The desired number of frames for the hardware buffer.
+pub type FrameCount = u32;
+
+/// The buffer size used by the device.
+///
+/// [`Default`] is used when no specific buffer size is set and uses the default
+/// behavior of the given host. Note, the default buffer size may be surprisingly
+/// large, leading to latency issues. If low latency is desired, [`Fixed(FrameCount)`]
+/// should be used in accordance with the [`SupportedBufferSize`] range produced by
+/// the [`SupportedStreamConfig`] API.  
+///
+/// [`Default`]: BufferSize::Default
+/// [`Fixed(FrameCount)`]: BufferSize::Fixed
+/// [`SupportedStreamConfig`]: SupportedStreamConfig::buffer_size
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+pub enum BufferSize {
+    Default,
+    Fixed(FrameCount),
+}
+
+#[cfg(target_os = "emscripten")]
+impl wasm_bindgen::describe::WasmDescribe for BufferSize {
+    fn describe() {}
+}
+
+#[cfg(target_os = "emscripten")]
+impl wasm_bindgen::convert::IntoWasmAbi for BufferSize {
+    type Abi = Option<u32>;
+    fn into_abi(self) -> Self::Abi {
+        match self {
+            Self::Default => None,
+            Self::Fixed(fc) => Some(fc),
+        }
+        .into_abi()
+    }
+}
+
+/// The set of parameters used to describe how to open a stream.
+///
+/// The sample format is omitted in favour of using a sample type.
+#[cfg_attr(target_os = "emscripten", wasm_bindgen)]
+#[derive(Clone, Debug, Eq, PartialEq)]
+pub struct StreamConfig {
+    pub channels: ChannelCount,
+    pub sample_rate: SampleRate,
+    pub buffer_size: BufferSize,
+}
+
+/// Describes the minimum and maximum supported buffer size for the device
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+pub enum SupportedBufferSize {
+    Range {
+        min: FrameCount,
+        max: FrameCount,
+    },
+    /// In the case that the platform provides no way of getting the default
+    /// buffersize before starting a stream.
+    Unknown,
+}
+
+/// Describes a range of supported stream configurations, retrieved via the
+/// [`Device::supported_input/output_configs`](traits::DeviceTrait#required-methods) method.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub struct SupportedStreamConfigRange {
+    pub(crate) channels: ChannelCount,
+    /// Minimum value for the samples rate of the supported formats.
+    pub(crate) min_sample_rate: SampleRate,
+    /// Maximum value for the samples rate of the supported formats.
+    pub(crate) max_sample_rate: SampleRate,
+    /// Buffersize ranges supported by the device
+    pub(crate) buffer_size: SupportedBufferSize,
+    /// Type of data expected by the device.
+    pub(crate) sample_format: SampleFormat,
+}
+
+/// Describes a single supported stream configuration, retrieved via either a
+/// [`SupportedStreamConfigRange`] instance or one of the
+/// [`Device::default_input/output_config`](traits::DeviceTrait#required-methods) methods.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct SupportedStreamConfig {
+    channels: ChannelCount,
+    sample_rate: SampleRate,
+    buffer_size: SupportedBufferSize,
+    sample_format: SampleFormat,
+}
+
+/// A buffer of dynamically typed audio data, passed to raw stream callbacks.
+///
+/// Raw input stream callbacks receive `&Data`, while raw output stream callbacks expect `&mut
+/// Data`.
+#[cfg_attr(target_os = "emscripten", wasm_bindgen)]
+#[derive(Debug)]
+pub struct Data {
+    data: *mut (),
+    len: usize,
+    sample_format: SampleFormat,
+}
+
+/// A monotonic time instance associated with a stream, retrieved from either:
+///
+/// 1. A timestamp provided to the stream's underlying audio data callback or
+/// 2. The same time source used to generate timestamps for a stream's underlying audio data
+///    callback.
+///
+/// `StreamInstant` represents a duration since some unspecified origin occurring either before
+/// or equal to the moment the stream from which it was created begins.
+///
+/// ## Host `StreamInstant` Sources
+///
+/// | Host | Source |
+/// | ---- | ------ |
+/// | alsa | `snd_pcm_status_get_htstamp` |
+/// | coreaudio | `mach_absolute_time` |
+/// | wasapi | `QueryPerformanceCounter` |
+/// | asio | `timeGetTime` |
+/// | emscripten | `AudioContext.getOutputTimestamp` |
+#[derive(Copy, Clone, Debug, Eq, Hash, PartialEq, PartialOrd, Ord)]
+pub struct StreamInstant {
+    secs: i64,
+    nanos: u32,
+}
+
+/// A timestamp associated with a call to an input stream's data callback.
+#[derive(Copy, Clone, Debug, Eq, Hash, PartialEq)]
+pub struct InputStreamTimestamp {
+    /// The instant the stream's data callback was invoked.
+    pub callback: StreamInstant,
+    /// The instant that data was captured from the device.
+    ///
+    /// E.g. The instant data was read from an ADC.
+    pub capture: StreamInstant,
+}
+
+/// A timestamp associated with a call to an output stream's data callback.
+#[derive(Copy, Clone, Debug, Eq, Hash, PartialEq)]
+pub struct OutputStreamTimestamp {
+    /// The instant the stream's data callback was invoked.
+    pub callback: StreamInstant,
+    /// The predicted instant that data written will be delivered to the device for playback.
+    ///
+    /// E.g. The instant data will be played by a DAC.
+    pub playback: StreamInstant,
+}
+
+/// Information relevant to a single call to the user's input stream data callback.
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct InputCallbackInfo {
+    timestamp: InputStreamTimestamp,
+}
+
+/// Information relevant to a single call to the user's output stream data callback.
+#[cfg_attr(target_os = "emscripten", wasm_bindgen)]
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub struct OutputCallbackInfo {
+    timestamp: OutputStreamTimestamp,
+}
+
+impl SupportedStreamConfig {
+    pub fn new(
+        channels: ChannelCount,
+        sample_rate: SampleRate,
+        buffer_size: SupportedBufferSize,
+        sample_format: SampleFormat,
+    ) -> Self {
+        Self {
+            channels,
+            sample_rate,
+            buffer_size,
+            sample_format,
+        }
+    }
+
+    pub fn channels(&self) -> ChannelCount {
+        self.channels
+    }
+
+    pub fn sample_rate(&self) -> SampleRate {
+        self.sample_rate
+    }
+
+    pub fn buffer_size(&self) -> &SupportedBufferSize {
+        &self.buffer_size
+    }
+
+    pub fn sample_format(&self) -> SampleFormat {
+        self.sample_format
+    }
+
+    pub fn config(&self) -> StreamConfig {
+        StreamConfig {
+            channels: self.channels,
+            sample_rate: self.sample_rate,
+            buffer_size: BufferSize::Default,
+        }
+    }
+}
+
+impl StreamInstant {
+    /// The amount of time elapsed from another instant to this one.
+    ///
+    /// Returns `None` if `earlier` is later than self.
+    pub fn duration_since(&self, earlier: &Self) -> Option<Duration> {
+        if self < earlier {
+            None
+        } else {
+            (self.as_nanos() - earlier.as_nanos())
+                .try_into()
+                .ok()
+                .map(Duration::from_nanos)
+        }
+    }
+
+    /// Returns the instant in time after the given duration has passed.
+    ///
+    /// Returns `None` if the resulting instant would exceed the bounds of the underlying data
+    /// structure.
+    pub fn add(&self, duration: Duration) -> Option<Self> {
+        self.as_nanos()
+            .checked_add(duration.as_nanos() as i128)
+            .and_then(Self::from_nanos_i128)
+    }
+
+    /// Returns the instant in time one `duration` ago.
+    ///
+    /// Returns `None` if the resulting instant would underflow. As a result, it is important to
+    /// consider that on some platforms the [`StreamInstant`] may begin at `0` from the moment the
+    /// source stream is created.
+    pub fn sub(&self, duration: Duration) -> Option<Self> {
+        self.as_nanos()
+            .checked_sub(duration.as_nanos() as i128)
+            .and_then(Self::from_nanos_i128)
+    }
+
+    fn as_nanos(&self) -> i128 {
+        (self.secs as i128 * 1_000_000_000) + self.nanos as i128
+    }
+
+    #[allow(dead_code)]
+    fn from_nanos(nanos: i64) -> Self {
+        let secs = nanos / 1_000_000_000;
+        let subsec_nanos = nanos - secs * 1_000_000_000;
+        Self::new(secs, subsec_nanos as u32)
+    }
+
+    #[allow(dead_code)]
+    fn from_nanos_i128(nanos: i128) -> Option<Self> {
+        let secs = nanos / 1_000_000_000;
+        if secs > i64::MAX as i128 || secs < i64::MIN as i128 {
+            None
+        } else {
+            let subsec_nanos = nanos - secs * 1_000_000_000;
+            debug_assert!(subsec_nanos < u32::MAX as i128);
+            Some(Self::new(secs as i64, subsec_nanos as u32))
+        }
+    }
+
+    #[allow(dead_code)]
+    fn from_secs_f64(secs: f64) -> crate::StreamInstant {
+        let s = secs.floor() as i64;
+        let ns = ((secs - s as f64) * 1_000_000_000.0) as u32;
+        Self::new(s, ns)
+    }
+
+    fn new(secs: i64, nanos: u32) -> Self {
+        StreamInstant { secs, nanos }
+    }
+}
+
+impl InputCallbackInfo {
+    /// The timestamp associated with the call to an input stream's data callback.
+    pub fn timestamp(&self) -> InputStreamTimestamp {
+        self.timestamp
+    }
+}
+
+impl OutputCallbackInfo {
+    /// The timestamp associated with the call to an output stream's data callback.
+    pub fn timestamp(&self) -> OutputStreamTimestamp {
+        self.timestamp
+    }
+}
+
+#[allow(clippy::len_without_is_empty)]
+impl Data {
+    // Internal constructor for host implementations to use.
+    //
+    // The following requirements must be met in order for the safety of `Data`'s public API.
+    //
+    // - The `data` pointer must point to the first sample in the slice containing all samples.
+    // - The `len` must describe the length of the buffer as a number of samples in the expected
+    //   format specified via the `sample_format` argument.
+    // - The `sample_format` must correctly represent the underlying sample data delivered/expected
+    //   by the stream.
+    pub(crate) unsafe fn from_parts(
+        data: *mut (),
+        len: usize,
+        sample_format: SampleFormat,
+    ) -> Self {
+        Data {
+            data,
+            len,
+            sample_format,
+        }
+    }
+
+    /// The sample format of the internal audio data.
+    pub fn sample_format(&self) -> SampleFormat {
+        self.sample_format
+    }
+
+    /// The full length of the buffer in samples.
+    ///
+    /// The returned length is the same length as the slice of type `T` that would be returned via
+    /// [`as_slice`](Self::as_slice) given a sample type that matches the inner sample format.
+    pub fn len(&self) -> usize {
+        self.len
+    }
+
+    /// The raw slice of memory representing the underlying audio data as a slice of bytes.
+    ///
+    /// It is up to the user to interpret the slice of memory based on [`Data::sample_format`].
+    pub fn bytes(&self) -> &[u8] {
+        let len = self.len * self.sample_format.sample_size();
+        // The safety of this block relies on correct construction of the `Data` instance.
+        // See the unsafe `from_parts` constructor for these requirements.
+        unsafe { std::slice::from_raw_parts(self.data as *const u8, len) }
+    }
+
+    /// The raw slice of memory representing the underlying audio data as a slice of bytes.
+    ///
+    /// It is up to the user to interpret the slice of memory based on [`Data::sample_format`].
+    pub fn bytes_mut(&mut self) -> &mut [u8] {
+        let len = self.len * self.sample_format.sample_size();
+        // The safety of this block relies on correct construction of the `Data` instance. See
+        // the unsafe `from_parts` constructor for these requirements.
+        unsafe { std::slice::from_raw_parts_mut(self.data as *mut u8, len) }
+    }
+
+    /// Access the data as a slice of sample type `T`.
+    ///
+    /// Returns `None` if the sample type does not match the expected sample format.
+    pub fn as_slice<T>(&self) -> Option<&[T]>
+    where
+        T: SizedSample,
+    {
+        if T::FORMAT == self.sample_format {
+            // The safety of this block relies on correct construction of the `Data` instance. See
+            // the unsafe `from_parts` constructor for these requirements.
+            unsafe { Some(std::slice::from_raw_parts(self.data as *const T, self.len)) }
+        } else {
+            None
+        }
+    }
+
+    /// Access the data as a slice of sample type `T`.
+    ///
+    /// Returns `None` if the sample type does not match the expected sample format.
+    pub fn as_slice_mut<T>(&mut self) -> Option<&mut [T]>
+    where
+        T: SizedSample,
+    {
+        if T::FORMAT == self.sample_format {
+            // The safety of this block relies on correct construction of the `Data` instance. See
+            // the unsafe `from_parts` constructor for these requirements.
+            unsafe {
+                Some(std::slice::from_raw_parts_mut(
+                    self.data as *mut T,
+                    self.len,
+                ))
+            }
+        } else {
+            None
+        }
+    }
+}
+
+impl SupportedStreamConfigRange {
+    pub fn new(
+        channels: ChannelCount,
+        min_sample_rate: SampleRate,
+        max_sample_rate: SampleRate,
+        buffer_size: SupportedBufferSize,
+        sample_format: SampleFormat,
+    ) -> Self {
+        Self {
+            channels,
+            min_sample_rate,
+            max_sample_rate,
+            buffer_size,
+            sample_format,
+        }
+    }
+
+    pub fn channels(&self) -> ChannelCount {
+        self.channels
+    }
+
+    pub fn min_sample_rate(&self) -> SampleRate {
+        self.min_sample_rate
+    }
+
+    pub fn max_sample_rate(&self) -> SampleRate {
+        self.max_sample_rate
+    }
+
+    pub fn buffer_size(&self) -> &SupportedBufferSize {
+        &self.buffer_size
+    }
+
+    pub fn sample_format(&self) -> SampleFormat {
+        self.sample_format
+    }
+
+    /// Retrieve a [`SupportedStreamConfig`] with the given sample rate and buffer size.
+    ///
+    /// # Panics
+    ///
+    /// Panics if the given `sample_rate` is outside the range specified within
+    /// this [`SupportedStreamConfigRange`] instance. For a non-panicking
+    /// variant, use [`try_with_sample_rate`](#method.try_with_sample_rate).
+    pub fn with_sample_rate(self, sample_rate: SampleRate) -> SupportedStreamConfig {
+        self.try_with_sample_rate(sample_rate)
+            .expect("sample rate out of range")
+    }
+
+    /// Retrieve a [`SupportedStreamConfig`] with the given sample rate and buffer size.
+    ///
+    /// Returns `None` if the given sample rate is outside the range specified
+    /// within this [`SupportedStreamConfigRange`] instance.
+    pub fn try_with_sample_rate(self, sample_rate: SampleRate) -> Option<SupportedStreamConfig> {
+        if self.min_sample_rate <= sample_rate && sample_rate <= self.max_sample_rate {
+            Some(SupportedStreamConfig {
+                channels: self.channels,
+                sample_rate,
+                sample_format: self.sample_format,
+                buffer_size: self.buffer_size,
+            })
+        } else {
+            None
+        }
+    }
+
+    /// Turns this [`SupportedStreamConfigRange`] into a [`SupportedStreamConfig`] corresponding to the maximum samples rate.
+    #[inline]
+    pub fn with_max_sample_rate(self) -> SupportedStreamConfig {
+        SupportedStreamConfig {
+            channels: self.channels,
+            sample_rate: self.max_sample_rate,
+            sample_format: self.sample_format,
+            buffer_size: self.buffer_size,
+        }
+    }
+
+    /// A comparison function which compares two [`SupportedStreamConfigRange`]s in terms of their priority of
+    /// use as a default stream format.
+    ///
+    /// Some backends do not provide a default stream format for their audio devices. In these
+    /// cases, CPAL attempts to decide on a reasonable default format for the user. To do this we
+    /// use the "greatest" of all supported stream formats when compared with this method.
+    ///
+    /// SupportedStreamConfigs are prioritised by the following heuristics:
+    ///
+    /// **Channels**:
+    ///
+    /// - Stereo
+    /// - Mono
+    /// - Max available channels
+    ///
+    /// **Sample format**:
+    /// - f32
+    /// - i16
+    /// - u16
+    ///
+    /// **Sample rate**:
+    ///
+    /// - 44100 (cd quality)
+    /// - Max sample rate
+    pub fn cmp_default_heuristics(&self, other: &Self) -> std::cmp::Ordering {
+        use std::cmp::Ordering::Equal;
+        use SampleFormat::{F32, I16, U16};
+
+        let cmp_stereo = (self.channels == 2).cmp(&(other.channels == 2));
+        if cmp_stereo != Equal {
+            return cmp_stereo;
+        }
+
+        let cmp_mono = (self.channels == 1).cmp(&(other.channels == 1));
+        if cmp_mono != Equal {
+            return cmp_mono;
+        }
+
+        let cmp_channels = self.channels.cmp(&other.channels);
+        if cmp_channels != Equal {
+            return cmp_channels;
+        }
+
+        let cmp_f32 = (self.sample_format == F32).cmp(&(other.sample_format == F32));
+        if cmp_f32 != Equal {
+            return cmp_f32;
+        }
+
+        let cmp_i16 = (self.sample_format == I16).cmp(&(other.sample_format == I16));
+        if cmp_i16 != Equal {
+            return cmp_i16;
+        }
+
+        let cmp_u16 = (self.sample_format == U16).cmp(&(other.sample_format == U16));
+        if cmp_u16 != Equal {
+            return cmp_u16;
+        }
+
+        const HZ_44100: SampleRate = SampleRate(44_100);
+        let r44100_in_self = self.min_sample_rate <= HZ_44100 && HZ_44100 <= self.max_sample_rate;
+        let r44100_in_other =
+            other.min_sample_rate <= HZ_44100 && HZ_44100 <= other.max_sample_rate;
+        let cmp_r44100 = r44100_in_self.cmp(&r44100_in_other);
+        if cmp_r44100 != Equal {
+            return cmp_r44100;
+        }
+
+        self.max_sample_rate.cmp(&other.max_sample_rate)
+    }
+}
+
+#[test]
+fn test_cmp_default_heuristics() {
+    let mut formats = [
+        SupportedStreamConfigRange {
+            buffer_size: SupportedBufferSize::Range { min: 256, max: 512 },
+            channels: 2,
+            min_sample_rate: SampleRate(1),
+            max_sample_rate: SampleRate(96000),
+            sample_format: SampleFormat::F32,
+        },
+        SupportedStreamConfigRange {
+            buffer_size: SupportedBufferSize::Range { min: 256, max: 512 },
+            channels: 1,
+            min_sample_rate: SampleRate(1),
+            max_sample_rate: SampleRate(96000),
+            sample_format: SampleFormat::F32,
+        },
+        SupportedStreamConfigRange {
+            buffer_size: SupportedBufferSize::Range { min: 256, max: 512 },
+            channels: 2,
+            min_sample_rate: SampleRate(1),
+            max_sample_rate: SampleRate(96000),
+            sample_format: SampleFormat::I16,
+        },
+        SupportedStreamConfigRange {
+            buffer_size: SupportedBufferSize::Range { min: 256, max: 512 },
+            channels: 2,
+            min_sample_rate: SampleRate(1),
+            max_sample_rate: SampleRate(96000),
+            sample_format: SampleFormat::U16,
+        },
+        SupportedStreamConfigRange {
+            buffer_size: SupportedBufferSize::Range { min: 256, max: 512 },
+            channels: 2,
+            min_sample_rate: SampleRate(1),
+            max_sample_rate: SampleRate(22050),
+            sample_format: SampleFormat::F32,
+        },
+    ];
+
+    formats.sort_by(|a, b| a.cmp_default_heuristics(b));
+
+    // lowest-priority first:
+    assert_eq!(formats[0].sample_format(), SampleFormat::F32);
+    assert_eq!(formats[0].min_sample_rate(), SampleRate(1));
+    assert_eq!(formats[0].max_sample_rate(), SampleRate(96000));
+    assert_eq!(formats[0].channels(), 1);
+
+    assert_eq!(formats[1].sample_format(), SampleFormat::U16);
+    assert_eq!(formats[1].min_sample_rate(), SampleRate(1));
+    assert_eq!(formats[1].max_sample_rate(), SampleRate(96000));
+    assert_eq!(formats[1].channels(), 2);
+
+    assert_eq!(formats[2].sample_format(), SampleFormat::I16);
+    assert_eq!(formats[2].min_sample_rate(), SampleRate(1));
+    assert_eq!(formats[2].max_sample_rate(), SampleRate(96000));
+    assert_eq!(formats[2].channels(), 2);
+
+    assert_eq!(formats[3].sample_format(), SampleFormat::F32);
+    assert_eq!(formats[3].min_sample_rate(), SampleRate(1));
+    assert_eq!(formats[3].max_sample_rate(), SampleRate(22050));
+    assert_eq!(formats[3].channels(), 2);
+
+    assert_eq!(formats[4].sample_format(), SampleFormat::F32);
+    assert_eq!(formats[4].min_sample_rate(), SampleRate(1));
+    assert_eq!(formats[4].max_sample_rate(), SampleRate(96000));
+    assert_eq!(formats[4].channels(), 2);
+}
+
+impl From<SupportedStreamConfig> for StreamConfig {
+    fn from(conf: SupportedStreamConfig) -> Self {
+        conf.config()
+    }
+}
+
+// If a backend does not provide an API for retrieving supported formats, we query it with a bunch
+// of commonly used rates. This is always the case for wasapi and is sometimes the case for alsa.
+//
+// If a rate you desire is missing from this list, feel free to add it!
+#[cfg(target_os = "windows")]
+const COMMON_SAMPLE_RATES: &[SampleRate] = &[
+    SampleRate(5512),
+    SampleRate(8000),
+    SampleRate(11025),
+    SampleRate(16000),
+    SampleRate(22050),
+    SampleRate(32000),
+    SampleRate(44100),
+    SampleRate(48000),
+    SampleRate(64000),
+    SampleRate(88200),
+    SampleRate(96000),
+    SampleRate(176400),
+    SampleRate(192000),
+];
+
+#[test]
+fn test_stream_instant() {
+    let a = StreamInstant::new(2, 0);
+    let b = StreamInstant::new(-2, 0);
+    let min = StreamInstant::new(i64::MIN, 0);
+    let max = StreamInstant::new(i64::MAX, 0);
+    assert_eq!(
+        a.sub(Duration::from_secs(1)),
+        Some(StreamInstant::new(1, 0))
+    );
+    assert_eq!(
+        a.sub(Duration::from_secs(2)),
+        Some(StreamInstant::new(0, 0))
+    );
+    assert_eq!(
+        a.sub(Duration::from_secs(3)),
+        Some(StreamInstant::new(-1, 0))
+    );
+    assert_eq!(min.sub(Duration::from_secs(1)), None);
+    assert_eq!(
+        b.add(Duration::from_secs(1)),
+        Some(StreamInstant::new(-1, 0))
+    );
+    assert_eq!(
+        b.add(Duration::from_secs(2)),
+        Some(StreamInstant::new(0, 0))
+    );
+    assert_eq!(
+        b.add(Duration::from_secs(3)),
+        Some(StreamInstant::new(1, 0))
+    );
+    assert_eq!(max.add(Duration::from_secs(1)), None);
+}

vendor/cpal/src/platform/mod.rs

@@ -0,0 +1,742 @@
+//! Platform-specific items.
+//!
+//! This module also contains the implementation of the platform's dynamically dispatched [`Host`]
+//! type and its associated [`Device`], [`Stream`] and other associated types. These
+//! types are useful in the case that users require switching between audio host APIs at runtime.
+
+#[doc(inline)]
+pub use self::platform_impl::*;
+
+/// A macro to assist with implementing a platform's dynamically dispatched [`Host`] type.
+///
+/// These dynamically dispatched types are necessary to allow for users to switch between hosts at
+/// runtime.
+///
+/// For example the invocation `impl_platform_host(Wasapi wasapi "WASAPI", Asio asio "ASIO")`,
+/// this macro should expand to:
+///
+// This sample code block is marked as text because it's not a valid test,
+// it's just illustrative. (see rust issue #96573)
+/// ```text
+/// pub enum HostId {
+///     Wasapi,
+///     Asio,
+/// }
+///
+/// pub enum Host {
+///     Wasapi(crate::host::wasapi::Host),
+///     Asio(crate::host::asio::Host),
+/// }
+/// ```
+///
+/// And so on for Device, Devices, Host, Stream, SupportedInputConfigs,
+/// SupportedOutputConfigs and all their necessary trait implementations.
+///
+macro_rules! impl_platform_host {
+    ($($(#[cfg($feat: meta)])? $HostVariant:ident $host_mod:ident $host_name:literal),*) => {
+        /// All hosts supported by CPAL on this platform.
+        pub const ALL_HOSTS: &'static [HostId] = &[
+            $(
+                $(#[cfg($feat)])?
+                HostId::$HostVariant,
+            )*
+        ];
+
+        /// The platform's dynamically dispatched `Host` type.
+        ///
+        /// An instance of this `Host` type may represent one of the `Host`s available
+        /// on the platform.
+        ///
+        /// Use this type if you require switching between available hosts at runtime.
+        ///
+        /// This type may be constructed via the [`host_from_id`] function. [`HostId`]s may
+        /// be acquired via the [`ALL_HOSTS`] const, and the [`available_hosts`] function.
+        pub struct Host(HostInner);
+
+        /// The `Device` implementation associated with the platform's dynamically dispatched
+        /// [`Host`] type.
+        #[derive(Clone)]
+        pub struct Device(DeviceInner);
+
+        /// The `Devices` iterator associated with the platform's dynamically dispatched [`Host`]
+        /// type.
+        pub struct Devices(DevicesInner);
+
+        /// The `Stream` implementation associated with the platform's dynamically dispatched
+        /// [`Host`] type.
+        // Streams cannot be `Send` or `Sync` if we plan to support Android's AAudio API. This is
+        // because the stream API is not thread-safe, and the API prohibits calling certain
+        // functions within the callback.
+        //
+        // TODO: Confirm this and add more specific detail and references.
+        #[must_use = "If the stream is not stored it will not play."]
+        pub struct Stream(StreamInner, crate::platform::NotSendSyncAcrossAllPlatforms);
+
+        /// The `SupportedInputConfigs` iterator associated with the platform's dynamically
+        /// dispatched [`Host`] type.
+        pub struct SupportedInputConfigs(SupportedInputConfigsInner);
+
+        /// The `SupportedOutputConfigs` iterator associated with the platform's dynamically
+        /// dispatched [`Host`] type.
+        pub struct SupportedOutputConfigs(SupportedOutputConfigsInner);
+
+        /// Unique identifier for available hosts on the platform.
+        #[derive(Copy, Clone, Debug, Eq, Hash, PartialEq)]
+        pub enum HostId {
+            $(
+                $(#[cfg($feat)])?
+                $HostVariant,
+            )*
+        }
+
+        /// Contains a platform specific [`Device`] implementation.
+        #[derive(Clone)]
+        pub enum DeviceInner {
+            $(
+                $(#[cfg($feat)])?
+                $HostVariant(crate::host::$host_mod::Device),
+            )*
+        }
+
+        /// Contains a platform specific [`Devices`] implementation.
+        pub enum DevicesInner {
+            $(
+                $(#[cfg($feat)])?
+                $HostVariant(crate::host::$host_mod::Devices),
+            )*
+        }
+
+        /// Contains a platform specific [`Host`] implementation.
+        pub enum HostInner {
+            $(
+                $(#[cfg($feat)])?
+                $HostVariant(crate::host::$host_mod::Host),
+            )*
+        }
+
+        /// Contains a platform specific [`Stream`] implementation.
+        pub enum StreamInner {
+            $(
+                $(#[cfg($feat)])?
+                $HostVariant(crate::host::$host_mod::Stream),
+            )*
+        }
+
+        enum SupportedInputConfigsInner {
+            $(
+                $(#[cfg($feat)])?
+                $HostVariant(crate::host::$host_mod::SupportedInputConfigs),
+            )*
+        }
+
+        enum SupportedOutputConfigsInner {
+            $(
+                $(#[cfg($feat)])?
+                $HostVariant(crate::host::$host_mod::SupportedOutputConfigs),
+            )*
+        }
+
+        impl HostId {
+            pub fn name(&self) -> &'static str {
+                match self {
+                    $(
+                        $(#[cfg($feat)])?
+                        HostId::$HostVariant => $host_name,
+                    )*
+                }
+            }
+        }
+
+        impl Devices {
+            /// Returns a reference to the underlying platform specific implementation of this
+            /// `Devices`.
+            pub fn as_inner(&self) -> &DevicesInner {
+                &self.0
+            }
+
+            /// Returns a mutable reference to the underlying platform specific implementation of
+            /// this `Devices`.
+            pub fn as_inner_mut(&mut self) -> &mut DevicesInner {
+                &mut self.0
+            }
+
+            /// Returns the underlying platform specific implementation of this `Devices`.
+            pub fn into_inner(self) -> DevicesInner {
+                self.0
+            }
+        }
+
+        impl Device {
+            /// Returns a reference to the underlying platform specific implementation of this
+            /// `Device`.
+            pub fn as_inner(&self) -> &DeviceInner {
+                &self.0
+            }
+
+            /// Returns a mutable reference to the underlying platform specific implementation of
+            /// this `Device`.
+            pub fn as_inner_mut(&mut self) -> &mut DeviceInner {
+                &mut self.0
+            }
+
+            /// Returns the underlying platform specific implementation of this `Device`.
+            pub fn into_inner(self) -> DeviceInner {
+                self.0
+            }
+        }
+
+        impl Host {
+            /// The unique identifier associated with this `Host`.
+            pub fn id(&self) -> HostId {
+                match self.0 {
+                    $(
+                        $(#[cfg($feat)])?
+                        HostInner::$HostVariant(_) => HostId::$HostVariant,
+                    )*
+                }
+            }
+
+            /// Returns a reference to the underlying platform specific implementation of this
+            /// `Host`.
+            pub fn as_inner(&self) -> &HostInner {
+                &self.0
+            }
+
+            /// Returns a mutable reference to the underlying platform specific implementation of
+            /// this `Host`.
+            pub fn as_inner_mut(&mut self) -> &mut HostInner {
+                &mut self.0
+            }
+
+            /// Returns the underlying platform specific implementation of this `Host`.
+            pub fn into_inner(self) -> HostInner {
+                self.0
+            }
+        }
+
+        impl Stream {
+            /// Returns a reference to the underlying platform specific implementation of this
+            /// `Stream`.
+            pub fn as_inner(&self) -> &StreamInner {
+                &self.0
+            }
+
+            /// Returns a mutable reference to the underlying platform specific implementation of
+            /// this `Stream`.
+            pub fn as_inner_mut(&mut self) -> &mut StreamInner {
+                &mut self.0
+            }
+
+            /// Returns the underlying platform specific implementation of this `Stream`.
+            pub fn into_inner(self) -> StreamInner {
+                self.0
+            }
+        }
+
+        impl Iterator for Devices {
+            type Item = Device;
+
+            fn next(&mut self) -> Option<Self::Item> {
+                match self.0 {
+                    $(
+                        $(#[cfg($feat)])?
+                        DevicesInner::$HostVariant(ref mut d) => {
+                            d.next().map(DeviceInner::$HostVariant).map(Device::from)
+                        }
+                    )*
+                }
+            }
+
+            fn size_hint(&self) -> (usize, Option<usize>) {
+                match self.0 {
+                    $(
+                        $(#[cfg($feat)])?
+                        DevicesInner::$HostVariant(ref d) => d.size_hint(),
+                    )*
+                }
+            }
+        }
+
+        impl Iterator for SupportedInputConfigs {
+            type Item = crate::SupportedStreamConfigRange;
+
+            fn next(&mut self) -> Option<Self::Item> {
+                match self.0 {
+                    $(
+                        $(#[cfg($feat)])?
+                        SupportedInputConfigsInner::$HostVariant(ref mut s) => s.next(),
+                    )*
+                }
+            }
+
+            fn size_hint(&self) -> (usize, Option<usize>) {
+                match self.0 {
+                    $(
+                        $(#[cfg($feat)])?
+                        SupportedInputConfigsInner::$HostVariant(ref d) => d.size_hint(),
+                    )*
+                }
+            }
+        }
+
+        impl Iterator for SupportedOutputConfigs {
+            type Item = crate::SupportedStreamConfigRange;
+
+            fn next(&mut self) -> Option<Self::Item> {
+                match self.0 {
+                    $(
+                        $(#[cfg($feat)])?
+                        SupportedOutputConfigsInner::$HostVariant(ref mut s) => s.next(),
+                    )*
+                }
+            }
+
+            fn size_hint(&self) -> (usize, Option<usize>) {
+                match self.0 {
+                    $(
+                        $(#[cfg($feat)])?
+                        SupportedOutputConfigsInner::$HostVariant(ref d) => d.size_hint(),
+                    )*
+                }
+            }
+        }
+
+        impl crate::traits::DeviceTrait for Device {
+            type SupportedInputConfigs = SupportedInputConfigs;
+            type SupportedOutputConfigs = SupportedOutputConfigs;
+            type Stream = Stream;
+
+            fn name(&self) -> Result<String, crate::DeviceNameError> {
+                match self.0 {
+                    $(
+                        $(#[cfg($feat)])?
+                        DeviceInner::$HostVariant(ref d) => d.name(),
+                    )*
+                }
+            }
+
+            fn supported_input_configs(&self) -> Result<Self::SupportedInputConfigs, crate::SupportedStreamConfigsError> {
+                match self.0 {
+                    $(
+                        $(#[cfg($feat)])?
+                        DeviceInner::$HostVariant(ref d) => {
+                            d.supported_input_configs()
+                                .map(SupportedInputConfigsInner::$HostVariant)
+                                .map(SupportedInputConfigs)
+                        }
+                    )*
+                }
+            }
+
+            fn supported_output_configs(&self) -> Result<Self::SupportedOutputConfigs, crate::SupportedStreamConfigsError> {
+                match self.0 {
+                    $(
+                        $(#[cfg($feat)])?
+                        DeviceInner::$HostVariant(ref d) => {
+                            d.supported_output_configs()
+                                .map(SupportedOutputConfigsInner::$HostVariant)
+                                .map(SupportedOutputConfigs)
+                        }
+                    )*
+                }
+            }
+
+            fn default_input_config(&self) -> Result<crate::SupportedStreamConfig, crate::DefaultStreamConfigError> {
+                match self.0 {
+                    $(
+                        $(#[cfg($feat)])?
+                        DeviceInner::$HostVariant(ref d) => d.default_input_config(),
+                    )*
+                }
+            }
+
+            fn default_output_config(&self) -> Result<crate::SupportedStreamConfig, crate::DefaultStreamConfigError> {
+                match self.0 {
+                    $(
+                        $(#[cfg($feat)])?
+                        DeviceInner::$HostVariant(ref d) => d.default_output_config(),
+                    )*
+                }
+            }
+
+            fn build_input_stream_raw<D, E>(
+                &self,
+                config: &crate::StreamConfig,
+                sample_format: crate::SampleFormat,
+                data_callback: D,
+                error_callback: E,
+                timeout: Option<std::time::Duration>,
+            ) -> Result<Self::Stream, crate::BuildStreamError>
+            where
+                D: FnMut(&crate::Data, &crate::InputCallbackInfo) + Send + 'static,
+                E: FnMut(crate::StreamError) + Send + 'static,
+            {
+                match self.0 {
+                    $(
+                        $(#[cfg($feat)])?
+                        DeviceInner::$HostVariant(ref d) => d
+                            .build_input_stream_raw(
+                                config,
+                                sample_format,
+                                data_callback,
+                                error_callback,
+                                timeout,
+                            )
+                            .map(StreamInner::$HostVariant)
+                            .map(Stream::from),
+                    )*
+                }
+            }
+
+            fn build_output_stream_raw<D, E>(
+                &self,
+                config: &crate::StreamConfig,
+                sample_format: crate::SampleFormat,
+                data_callback: D,
+                error_callback: E,
+                timeout: Option<std::time::Duration>,
+            ) -> Result<Self::Stream, crate::BuildStreamError>
+            where
+                D: FnMut(&mut crate::Data, &crate::OutputCallbackInfo) + Send + 'static,
+                E: FnMut(crate::StreamError) + Send + 'static,
+            {
+                match self.0 {
+                    $(
+                        $(#[cfg($feat)])?
+                        DeviceInner::$HostVariant(ref d) => d
+                            .build_output_stream_raw(
+                                config,
+                                sample_format,
+                                data_callback,
+                                error_callback,
+                                timeout,
+                            )
+                            .map(StreamInner::$HostVariant)
+                            .map(Stream::from),
+                    )*
+                }
+            }
+        }
+
+        impl crate::traits::HostTrait for Host {
+            type Devices = Devices;
+            type Device = Device;
+
+            fn is_available() -> bool {
+                $(
+                    $(#[cfg($feat)])?
+                    if crate::host::$host_mod::Host::is_available() { return true; }
+                )*
+                false
+            }
+
+            fn devices(&self) -> Result<Self::Devices, crate::DevicesError> {
+                match self.0 {
+                    $(
+                        $(#[cfg($feat)])?
+                        HostInner::$HostVariant(ref h) => {
+                            h.devices().map(DevicesInner::$HostVariant).map(Devices::from)
+                        }
+                    )*
+                }
+            }
+
+            fn default_input_device(&self) -> Option<Self::Device> {
+                match self.0 {
+                    $(
+                        $(#[cfg($feat)])?
+                        HostInner::$HostVariant(ref h) => {
+                            h.default_input_device().map(DeviceInner::$HostVariant).map(Device::from)
+                        }
+                    )*
+                }
+            }
+
+            fn default_output_device(&self) -> Option<Self::Device> {
+                match self.0 {
+                    $(
+                        $(#[cfg($feat)])?
+                        HostInner::$HostVariant(ref h) => {
+                            h.default_output_device().map(DeviceInner::$HostVariant).map(Device::from)
+                        }
+                    )*
+                }
+            }
+        }
+
+        impl crate::traits::StreamTrait for Stream {
+            fn play(&self) -> Result<(), crate::PlayStreamError> {
+                match self.0 {
+                    $(
+                        $(#[cfg($feat)])?
+                        StreamInner::$HostVariant(ref s) => {
+                            s.play()
+                        }
+                    )*
+                }
+            }
+
+            fn pause(&self) -> Result<(), crate::PauseStreamError> {
+                match self.0 {
+                    $(
+                        $(#[cfg($feat)])?
+                        StreamInner::$HostVariant(ref s) => {
+                            s.pause()
+                        }
+                    )*
+                }
+            }
+        }
+
+        impl From<DeviceInner> for Device {
+            fn from(d: DeviceInner) -> Self {
+                Device(d)
+            }
+        }
+
+        impl From<DevicesInner> for Devices {
+            fn from(d: DevicesInner) -> Self {
+                Devices(d)
+            }
+        }
+
+        impl From<HostInner> for Host {
+            fn from(h: HostInner) -> Self {
+                Host(h)
+            }
+        }
+
+        impl From<StreamInner> for Stream {
+            fn from(s: StreamInner) -> Self {
+                Stream(s, Default::default())
+            }
+        }
+
+        $(
+            $(#[cfg($feat)])?
+            impl From<crate::host::$host_mod::Device> for Device {
+                fn from(h: crate::host::$host_mod::Device) -> Self {
+                    DeviceInner::$HostVariant(h).into()
+                }
+            }
+
+            $(#[cfg($feat)])?
+            impl From<crate::host::$host_mod::Devices> for Devices {
+                fn from(h: crate::host::$host_mod::Devices) -> Self {
+                    DevicesInner::$HostVariant(h).into()
+                }
+            }
+
+            $(#[cfg($feat)])?
+            impl From<crate::host::$host_mod::Host> for Host {
+                fn from(h: crate::host::$host_mod::Host) -> Self {
+                    HostInner::$HostVariant(h).into()
+                }
+            }
+
+            $(#[cfg($feat)])?
+            impl From<crate::host::$host_mod::Stream> for Stream {
+                fn from(h: crate::host::$host_mod::Stream) -> Self {
+                    StreamInner::$HostVariant(h).into()
+                }
+            }
+        )*
+
+        /// Produces a list of hosts that are currently available on the system.
+        pub fn available_hosts() -> Vec<HostId> {
+            let mut host_ids = vec![];
+            $(
+                $(#[cfg($feat)])?
+                if <crate::host::$host_mod::Host as crate::traits::HostTrait>::is_available() {
+                    host_ids.push(HostId::$HostVariant);
+                }
+            )*
+            host_ids
+        }
+
+        /// Given a unique host identifier, initialise and produce the host if it is available.
+        pub fn host_from_id(id: HostId) -> Result<Host, crate::HostUnavailable> {
+            match id {
+                $(
+                    $(#[cfg($feat)])?
+                    HostId::$HostVariant => {
+                        crate::host::$host_mod::Host::new()
+                            .map(HostInner::$HostVariant)
+                            .map(Host::from)
+                    }
+                )*
+            }
+        }
+    };
+}
+
+// TODO: Add pulseaudio and jack here eventually.
+#[cfg(any(
+    target_os = "linux",
+    target_os = "dragonfly",
+    target_os = "freebsd",
+    target_os = "netbsd"
+))]
+mod platform_impl {
+    pub use crate::host::alsa::{
+        Device as AlsaDevice, Devices as AlsaDevices, Host as AlsaHost, Stream as AlsaStream,
+        SupportedInputConfigs as AlsaSupportedInputConfigs,
+        SupportedOutputConfigs as AlsaSupportedOutputConfigs,
+    };
+    #[cfg(feature = "jack")]
+    pub use crate::host::jack::{
+        Device as JackDevice, Devices as JackDevices, Host as JackHost, Stream as JackStream,
+        SupportedInputConfigs as JackSupportedInputConfigs,
+        SupportedOutputConfigs as JackSupportedOutputConfigs,
+    };
+
+    impl_platform_host!(#[cfg(feature = "jack")] Jack jack "JACK", Alsa alsa "ALSA");
+
+    /// The default host for the current compilation target platform.
+    pub fn default_host() -> Host {
+        AlsaHost::new()
+            .expect("the default host should always be available")
+            .into()
+    }
+}
+
+#[cfg(any(target_os = "macos", target_os = "ios"))]
+mod platform_impl {
+    pub use crate::host::coreaudio::{
+        Device as CoreAudioDevice, Devices as CoreAudioDevices, Host as CoreAudioHost,
+        Stream as CoreAudioStream, SupportedInputConfigs as CoreAudioSupportedInputConfigs,
+        SupportedOutputConfigs as CoreAudioSupportedOutputConfigs,
+    };
+
+    impl_platform_host!(CoreAudio coreaudio "CoreAudio");
+
+    /// The default host for the current compilation target platform.
+    pub fn default_host() -> Host {
+        CoreAudioHost::new()
+            .expect("the default host should always be available")
+            .into()
+    }
+}
+
+#[cfg(target_os = "emscripten")]
+mod platform_impl {
+    pub use crate::host::emscripten::{
+        Device as EmscriptenDevice, Devices as EmscriptenDevices, Host as EmscriptenHost,
+        Stream as EmscriptenStream, SupportedInputConfigs as EmscriptenSupportedInputConfigs,
+        SupportedOutputConfigs as EmscriptenSupportedOutputConfigs,
+    };
+
+    impl_platform_host!(Emscripten emscripten "Emscripten");
+
+    /// The default host for the current compilation target platform.
+    pub fn default_host() -> Host {
+        EmscriptenHost::new()
+            .expect("the default host should always be available")
+            .into()
+    }
+}
+
+#[cfg(all(target_arch = "wasm32", feature = "wasm-bindgen"))]
+mod platform_impl {
+    pub use crate::host::webaudio::{
+        Device as WebAudioDevice, Devices as WebAudioDevices, Host as WebAudioHost,
+        Stream as WebAudioStream, SupportedInputConfigs as WebAudioSupportedInputConfigs,
+        SupportedOutputConfigs as WebAudioSupportedOutputConfigs,
+    };
+
+    impl_platform_host!(WebAudio webaudio "WebAudio");
+
+    /// The default host for the current compilation target platform.
+    pub fn default_host() -> Host {
+        WebAudioHost::new()
+            .expect("the default host should always be available")
+            .into()
+    }
+}
+
+#[cfg(windows)]
+mod platform_impl {
+    #[cfg(feature = "asio")]
+    pub use crate::host::asio::{
+        Device as AsioDevice, Devices as AsioDevices, Host as AsioHost, Stream as AsioStream,
+        SupportedInputConfigs as AsioSupportedInputConfigs,
+        SupportedOutputConfigs as AsioSupportedOutputConfigs,
+    };
+    pub use crate::host::wasapi::{
+        Device as WasapiDevice, Devices as WasapiDevices, Host as WasapiHost,
+        Stream as WasapiStream, SupportedInputConfigs as WasapiSupportedInputConfigs,
+        SupportedOutputConfigs as WasapiSupportedOutputConfigs,
+    };
+
+    impl_platform_host!(#[cfg(feature = "asio")] Asio asio "ASIO", Wasapi wasapi "WASAPI");
+
+    /// The default host for the current compilation target platform.
+    pub fn default_host() -> Host {
+        WasapiHost::new()
+            .expect("the default host should always be available")
+            .into()
+    }
+}
+
+#[cfg(target_os = "android")]
+mod platform_impl {
+    pub use crate::host::oboe::{
+        Device as OboeDevice, Devices as OboeDevices, Host as OboeHost, Stream as OboeStream,
+        SupportedInputConfigs as OboeSupportedInputConfigs,
+        SupportedOutputConfigs as OboeSupportedOutputConfigs,
+    };
+
+    impl_platform_host!(Oboe oboe "Oboe");
+
+    /// The default host for the current compilation target platform.
+    pub fn default_host() -> Host {
+        OboeHost::new()
+            .expect("the default host should always be available")
+            .into()
+    }
+}
+
+#[cfg(not(any(
+    windows,
+    target_os = "linux",
+    target_os = "dragonfly",
+    target_os = "freebsd",
+    target_os = "netbsd",
+    target_os = "macos",
+    target_os = "ios",
+    target_os = "emscripten",
+    target_os = "android",
+    all(target_arch = "wasm32", feature = "wasm-bindgen"),
+)))]
+mod platform_impl {
+    pub use crate::host::null::{
+        Device as NullDevice, Devices as NullDevices, Host as NullHost,
+        SupportedInputConfigs as NullSupportedInputConfigs,
+        SupportedOutputConfigs as NullSupportedOutputConfigs,
+    };
+
+    impl_platform_host!(Null null "Null");
+
+    /// The default host for the current compilation target platform.
+    pub fn default_host() -> Host {
+        NullHost::new()
+            .expect("the default host should always be available")
+            .into()
+    }
+}
+
+// The following zero-sized types are for applying Send/Sync restrictions to ensure
+// consistent behaviour across different platforms. These verbosely named types are used
+// (rather than using the markers directly) in the hope of making the compile errors
+// slightly more helpful.
+//
+// TODO: Remove these in favour of using negative trait bounds if they stabilise.
+
+// A marker used to remove the `Send` and `Sync` traits.
+struct NotSendSyncAcrossAllPlatforms(std::marker::PhantomData<*mut ()>);
+
+impl Default for NotSendSyncAcrossAllPlatforms {
+    fn default() -> Self {
+        NotSendSyncAcrossAllPlatforms(std::marker::PhantomData)
+    }
+}

vendor/cpal/src/samples_formats.rs

@@ -0,0 +1,167 @@
+use std::{fmt::Display, mem};
+#[cfg(target_os = "emscripten")]
+use wasm_bindgen::prelude::*;
+
+pub use dasp_sample::{FromSample, Sample, I24, I48, U24, U48};
+
+/// Format that each sample has.
+#[cfg_attr(target_os = "emscripten", wasm_bindgen)]
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+#[non_exhaustive]
+pub enum SampleFormat {
+    /// `i8` with a valid range of 'u8::MIN..=u8::MAX' with `0` being the origin
+    I8,
+
+    /// `i16` with a valid range of 'u16::MIN..=u16::MAX' with `0` being the origin
+    I16,
+
+    // /// `I24` with a valid range of '-(1 << 23)..(1 << 23)' with `0` being the origin
+    // I24,
+    /// `i32` with a valid range of 'u32::MIN..=u32::MAX' with `0` being the origin
+    I32,
+
+    // /// `I24` with a valid range of '-(1 << 47)..(1 << 47)' with `0` being the origin
+    // I48,
+    /// `i64` with a valid range of 'u64::MIN..=u64::MAX' with `0` being the origin
+    I64,
+
+    /// `u8` with a valid range of 'u8::MIN..=u8::MAX' with `1 << 7 == 128` being the origin
+    U8,
+
+    /// `u16` with a valid range of 'u16::MIN..=u16::MAX' with `1 << 15 == 32768` being the origin
+    U16,
+
+    // /// `U24` with a valid range of '0..16777216' with `1 << 23 == 8388608` being the origin
+    // U24,
+    /// `u32` with a valid range of 'u32::MIN..=u32::MAX' with `1 << 31` being the origin
+    U32,
+
+    // /// `U48` with a valid range of '0..(1 << 48)' with `1 << 47` being the origin
+    // U48,
+    /// `u64` with a valid range of 'u64::MIN..=u64::MAX' with `1 << 63` being the origin
+    U64,
+
+    /// `f32` with a valid range of `-1.0..1.0` with `0.0` being the origin
+    F32,
+
+    /// `f64` with a valid range of -1.0..1.0 with 0.0 being the origin
+    F64,
+}
+
+impl SampleFormat {
+    /// Returns the size in bytes of a sample of this format.
+    #[inline]
+    #[must_use]
+    pub fn sample_size(&self) -> usize {
+        match *self {
+            SampleFormat::I8 | SampleFormat::U8 => mem::size_of::<i8>(),
+            SampleFormat::I16 | SampleFormat::U16 => mem::size_of::<i16>(),
+            // SampleFormat::I24 | SampleFormat::U24 => 3,
+            SampleFormat::I32 | SampleFormat::U32 => mem::size_of::<i32>(),
+            // SampleFormat::I48 | SampleFormat::U48 => 6,
+            SampleFormat::I64 | SampleFormat::U64 => mem::size_of::<i64>(),
+            SampleFormat::F32 => mem::size_of::<f32>(),
+            SampleFormat::F64 => mem::size_of::<f64>(),
+        }
+    }
+
+    #[inline]
+    #[must_use]
+    pub fn is_int(&self) -> bool {
+        //matches!(*self, SampleFormat::I8 | SampleFormat::I16 | SampleFormat::I24 | SampleFormat::I32 | SampleFormat::I48 | SampleFormat::I64)
+        matches!(
+            *self,
+            SampleFormat::I8 | SampleFormat::I16 | SampleFormat::I32 | SampleFormat::I64
+        )
+    }
+
+    #[inline]
+    #[must_use]
+    pub fn is_uint(&self) -> bool {
+        //matches!(*self, SampleFormat::U8 | SampleFormat::U16 | SampleFormat::U24 | SampleFormat::U32 | SampleFormat::U48 | SampleFormat::U64)
+        matches!(
+            *self,
+            SampleFormat::U8 | SampleFormat::U16 | SampleFormat::U32 | SampleFormat::U64
+        )
+    }
+
+    #[inline]
+    #[must_use]
+    pub fn is_float(&self) -> bool {
+        matches!(*self, SampleFormat::F32 | SampleFormat::F64)
+    }
+}
+
+impl Display for SampleFormat {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match *self {
+            SampleFormat::I8 => "i8",
+            SampleFormat::I16 => "i16",
+            // SampleFormat::I24 => "i24",
+            SampleFormat::I32 => "i32",
+            // SampleFormat::I48 => "i48",
+            SampleFormat::I64 => "i64",
+            SampleFormat::U8 => "u8",
+            SampleFormat::U16 => "u16",
+            // SampleFormat::U24 => "u24",
+            SampleFormat::U32 => "u32",
+            // SampleFormat::U48 => "u48",
+            SampleFormat::U64 => "u64",
+            SampleFormat::F32 => "f32",
+            SampleFormat::F64 => "f64",
+        }
+        .fmt(f)
+    }
+}
+
+pub trait SizedSample: Sample {
+    const FORMAT: SampleFormat;
+}
+
+impl SizedSample for i8 {
+    const FORMAT: SampleFormat = SampleFormat::I8;
+}
+
+impl SizedSample for i16 {
+    const FORMAT: SampleFormat = SampleFormat::I16;
+}
+
+// impl SizedSample for I24 { const FORMAT: SampleFormat = SampleFormat::I24; }
+
+impl SizedSample for i32 {
+    const FORMAT: SampleFormat = SampleFormat::I32;
+}
+
+// impl SizedSample for I48 { const FORMAT: SampleFormat = SampleFormat::I48; }
+
+impl SizedSample for i64 {
+    const FORMAT: SampleFormat = SampleFormat::I64;
+}
+
+impl SizedSample for u8 {
+    const FORMAT: SampleFormat = SampleFormat::U8;
+}
+
+impl SizedSample for u16 {
+    const FORMAT: SampleFormat = SampleFormat::U16;
+}
+
+// impl SizedSample for U24 { const FORMAT: SampleFormat = SampleFormat::U24; }
+
+impl SizedSample for u32 {
+    const FORMAT: SampleFormat = SampleFormat::U32;
+}
+
+// impl SizedSample for U48 { const FORMAT: SampleFormat = SampleFormat::U48; }
+
+impl SizedSample for u64 {
+    const FORMAT: SampleFormat = SampleFormat::U64;
+}
+
+impl SizedSample for f32 {
+    const FORMAT: SampleFormat = SampleFormat::F32;
+}
+
+impl SizedSample for f64 {
+    const FORMAT: SampleFormat = SampleFormat::F64;
+}

vendor/cpal/src/traits.rs

@@ -0,0 +1,221 @@
+//! The suite of traits allowing CPAL to abstract over hosts, devices, event loops and stream IDs.
+
+use std::time::Duration;
+
+use crate::{
+    BuildStreamError, Data, DefaultStreamConfigError, DeviceNameError, DevicesError,
+    InputCallbackInfo, InputDevices, OutputCallbackInfo, OutputDevices, PauseStreamError,
+    PlayStreamError, SampleFormat, SizedSample, StreamConfig, StreamError, SupportedStreamConfig,
+    SupportedStreamConfigRange, SupportedStreamConfigsError,
+};
+
+/// A [`Host`] provides access to the available audio devices on the system.
+///
+/// Each platform may have a number of available hosts depending on the system, each with their own
+/// pros and cons.
+///
+/// For example, WASAPI is the standard audio host API that ships with the Windows operating
+/// system. However, due to historical limitations with respect to performance and flexibility,
+/// Steinberg created the ASIO API providing better audio device support for pro audio and
+/// low-latency applications. As a result, it is common for some devices and device capabilities to
+/// only be available via ASIO, while others are only available via WASAPI.
+///
+/// Another great example is the Linux platform. While the ALSA host API is the lowest-level API
+/// available to almost all distributions of Linux, its flexibility is limited as it requires that
+/// each process have exclusive access to the devices with which they establish streams. PulseAudio
+/// is another popular host API that aims to solve this issue by providing user-space mixing,
+/// however it has its own limitations w.r.t. low-latency and high-performance audio applications.
+/// JACK is yet another host API that is more suitable to pro-audio applications, however it is
+/// less readily available by default in many Linux distributions and is known to be tricky to
+/// set up.
+///
+/// [`Host`]: crate::Host
+pub trait HostTrait {
+    /// The type used for enumerating available devices by the host.
+    type Devices: Iterator<Item = Self::Device>;
+    /// The `Device` type yielded by the host.
+    type Device: DeviceTrait;
+
+    /// Whether or not the host is available on the system.
+    fn is_available() -> bool;
+
+    /// An iterator yielding all [`Device`](DeviceTrait)s currently available to the host on the system.
+    ///
+    /// Can be empty if the system does not support audio in general.
+    fn devices(&self) -> Result<Self::Devices, DevicesError>;
+
+    /// The default input audio device on the system.
+    ///
+    /// Returns `None` if no input device is available.
+    fn default_input_device(&self) -> Option<Self::Device>;
+
+    /// The default output audio device on the system.
+    ///
+    /// Returns `None` if no output device is available.
+    fn default_output_device(&self) -> Option<Self::Device>;
+
+    /// An iterator yielding all `Device`s currently available to the system that support one or more
+    /// input stream formats.
+    ///
+    /// Can be empty if the system does not support audio input.
+    fn input_devices(&self) -> Result<InputDevices<Self::Devices>, DevicesError> {
+        fn supports_input<D: DeviceTrait>(device: &D) -> bool {
+            device
+                .supported_input_configs()
+                .map(|mut iter| iter.next().is_some())
+                .unwrap_or(false)
+        }
+        Ok(self.devices()?.filter(supports_input::<Self::Device>))
+    }
+
+    /// An iterator yielding all `Device`s currently available to the system that support one or more
+    /// output stream formats.
+    ///
+    /// Can be empty if the system does not support audio output.
+    fn output_devices(&self) -> Result<OutputDevices<Self::Devices>, DevicesError> {
+        fn supports_output<D: DeviceTrait>(device: &D) -> bool {
+            device
+                .supported_output_configs()
+                .map(|mut iter| iter.next().is_some())
+                .unwrap_or(false)
+        }
+        Ok(self.devices()?.filter(supports_output::<Self::Device>))
+    }
+}
+
+/// A device that is capable of audio input and/or output.
+///
+/// Please note that `Device`s may become invalid if they get disconnected. Therefore, all the
+/// methods that involve a device return a `Result` allowing the user to handle this case.
+pub trait DeviceTrait {
+    /// The iterator type yielding supported input stream formats.
+    type SupportedInputConfigs: Iterator<Item = SupportedStreamConfigRange>;
+    /// The iterator type yielding supported output stream formats.
+    type SupportedOutputConfigs: Iterator<Item = SupportedStreamConfigRange>;
+    /// The stream type created by [`build_input_stream_raw`] and [`build_output_stream_raw`].
+    ///
+    /// [`build_input_stream_raw`]: Self::build_input_stream_raw
+    /// [`build_output_stream_raw`]: Self::build_output_stream_raw
+    type Stream: StreamTrait;
+
+    /// The human-readable name of the device.
+    fn name(&self) -> Result<String, DeviceNameError>;
+
+    /// An iterator yielding formats that are supported by the backend.
+    ///
+    /// Can return an error if the device is no longer valid (e.g. it has been disconnected).
+    fn supported_input_configs(
+        &self,
+    ) -> Result<Self::SupportedInputConfigs, SupportedStreamConfigsError>;
+
+    /// An iterator yielding output stream formats that are supported by the device.
+    ///
+    /// Can return an error if the device is no longer valid (e.g. it has been disconnected).
+    fn supported_output_configs(
+        &self,
+    ) -> Result<Self::SupportedOutputConfigs, SupportedStreamConfigsError>;
+
+    /// The default input stream format for the device.
+    fn default_input_config(&self) -> Result<SupportedStreamConfig, DefaultStreamConfigError>;
+
+    /// The default output stream format for the device.
+    fn default_output_config(&self) -> Result<SupportedStreamConfig, DefaultStreamConfigError>;
+
+    /// Create an input stream.
+    fn build_input_stream<T, D, E>(
+        &self,
+        config: &StreamConfig,
+        mut data_callback: D,
+        error_callback: E,
+        timeout: Option<Duration>,
+    ) -> Result<Self::Stream, BuildStreamError>
+    where
+        T: SizedSample,
+        D: FnMut(&[T], &InputCallbackInfo) + Send + 'static,
+        E: FnMut(StreamError) + Send + 'static,
+    {
+        self.build_input_stream_raw(
+            config,
+            T::FORMAT,
+            move |data, info| {
+                data_callback(
+                    data.as_slice()
+                        .expect("host supplied incorrect sample type"),
+                    info,
+                )
+            },
+            error_callback,
+            timeout,
+        )
+    }
+
+    /// Create an output stream.
+    fn build_output_stream<T, D, E>(
+        &self,
+        config: &StreamConfig,
+        mut data_callback: D,
+        error_callback: E,
+        timeout: Option<Duration>,
+    ) -> Result<Self::Stream, BuildStreamError>
+    where
+        T: SizedSample,
+        D: FnMut(&mut [T], &OutputCallbackInfo) + Send + 'static,
+        E: FnMut(StreamError) + Send + 'static,
+    {
+        self.build_output_stream_raw(
+            config,
+            T::FORMAT,
+            move |data, info| {
+                data_callback(
+                    data.as_slice_mut()
+                        .expect("host supplied incorrect sample type"),
+                    info,
+                )
+            },
+            error_callback,
+            timeout,
+        )
+    }
+
+    /// Create a dynamically typed input stream.
+    fn build_input_stream_raw<D, E>(
+        &self,
+        config: &StreamConfig,
+        sample_format: SampleFormat,
+        data_callback: D,
+        error_callback: E,
+        timeout: Option<Duration>,
+    ) -> Result<Self::Stream, BuildStreamError>
+    where
+        D: FnMut(&Data, &InputCallbackInfo) + Send + 'static,
+        E: FnMut(StreamError) + Send + 'static;
+
+    /// Create a dynamically typed output stream.
+    fn build_output_stream_raw<D, E>(
+        &self,
+        config: &StreamConfig,
+        sample_format: SampleFormat,
+        data_callback: D,
+        error_callback: E,
+        timeout: Option<Duration>,
+    ) -> Result<Self::Stream, BuildStreamError>
+    where
+        D: FnMut(&mut Data, &OutputCallbackInfo) + Send + 'static,
+        E: FnMut(StreamError) + Send + 'static;
+}
+
+/// A stream created from [`Device`](DeviceTrait), with methods to control playback.
+pub trait StreamTrait {
+    /// Run the stream.
+    ///
+    /// Note: Not all platforms automatically run the stream upon creation, so it is important to
+    /// call `play` after creation if it is expected that the stream should run immediately.
+    fn play(&self) -> Result<(), PlayStreamError>;
+
+    /// Some devices support pausing the audio stream. This can be useful for saving energy in
+    /// moments of silence.
+    ///
+    /// Note: Not all devices support suspending the stream at the hardware level. This method may
+    /// fail in these cases.
+    fn pause(&self) -> Result<(), PauseStreamError>;
+}