126 lines
4.0 KiB
Rust
126 lines
4.0 KiB
Rust
use std::{fmt, ops::Range};
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use crate::{
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Buffer, ParseError,
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err::{perr, ParseErrorKind::*},
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escape::{scan_raw_string, unescape_string},
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parse::first_byte_or_empty,
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};
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/// A string or raw string literal, e.g. `"foo"`, `"Grüße"` or `r#"a🦊c"d🦀f"#`.
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///
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/// See [the reference][ref] for more information.
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///
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/// [ref]: https://doc.rust-lang.org/reference/tokens.html#string-literals
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#[derive(Debug, Clone, PartialEq, Eq)]
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pub struct StringLit<B: Buffer> {
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/// The raw input.
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raw: B,
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/// The string value (with all escapes unescaped), or `None` if there were
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/// no escapes. In the latter case, the string value is in `raw`.
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value: Option<String>,
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/// The number of hash signs in case of a raw string literal, or `None` if
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/// it's not a raw string literal.
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num_hashes: Option<u32>,
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/// Start index of the suffix or `raw.len()` if there is no suffix.
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start_suffix: usize,
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}
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impl<B: Buffer> StringLit<B> {
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/// Parses the input as a (raw) string literal. Returns an error if the
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/// input is invalid or represents a different kind of literal.
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pub fn parse(input: B) -> Result<Self, ParseError> {
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match first_byte_or_empty(&input)? {
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b'r' | b'"' => {
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let (value, num_hashes, start_suffix) = parse_impl(&input)?;
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Ok(Self { raw: input, value, num_hashes, start_suffix })
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}
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_ => Err(perr(0, InvalidStringLiteralStart)),
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}
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}
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/// Returns the string value this literal represents (where all escapes have
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/// been turned into their respective values).
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pub fn value(&self) -> &str {
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self.value.as_deref().unwrap_or(&self.raw[self.inner_range()])
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}
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/// Like `value` but returns a potentially owned version of the value.
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///
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/// The return value is either `Cow<'static, str>` if `B = String`, or
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/// `Cow<'a, str>` if `B = &'a str`.
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pub fn into_value(self) -> B::Cow {
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let inner_range = self.inner_range();
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let Self { raw, value, .. } = self;
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value.map(B::Cow::from).unwrap_or_else(|| raw.cut(inner_range).into_cow())
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}
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/// The optional suffix. Returns `""` if the suffix is empty/does not exist.
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pub fn suffix(&self) -> &str {
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&(*self.raw)[self.start_suffix..]
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}
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/// Returns whether this literal is a raw string literal (starting with
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/// `r`).
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pub fn is_raw_string(&self) -> bool {
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self.num_hashes.is_some()
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}
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/// Returns the raw input that was passed to `parse`.
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pub fn raw_input(&self) -> &str {
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&self.raw
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}
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/// Returns the raw input that was passed to `parse`, potentially owned.
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pub fn into_raw_input(self) -> B {
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self.raw
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}
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/// The range within `self.raw` that excludes the quotes and potential `r#`.
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fn inner_range(&self) -> Range<usize> {
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match self.num_hashes {
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None => 1..self.start_suffix - 1,
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Some(n) => 1 + n as usize + 1..self.start_suffix - n as usize - 1,
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}
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}
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}
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impl StringLit<&str> {
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/// Makes a copy of the underlying buffer and returns the owned version of
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/// `Self`.
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pub fn into_owned(self) -> StringLit<String> {
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StringLit {
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raw: self.raw.to_owned(),
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value: self.value,
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num_hashes: self.num_hashes,
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start_suffix: self.start_suffix,
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}
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}
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}
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impl<B: Buffer> fmt::Display for StringLit<B> {
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fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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f.pad(&self.raw)
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}
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}
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/// Precondition: input has to start with either `"` or `r`.
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#[inline(never)]
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pub(crate) fn parse_impl(input: &str) -> Result<(Option<String>, Option<u32>, usize), ParseError> {
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if input.starts_with('r') {
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scan_raw_string::<char>(&input, 1, true)
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.map(|(hashes, start_suffix)| (None, Some(hashes), start_suffix))
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} else {
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unescape_string::<char>(&input, 1, true, false)
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.map(|(v, start_suffix)| (v, None, start_suffix))
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}
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}
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#[cfg(test)]
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mod tests;
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