154 lines
3.7 KiB
Rust
154 lines
3.7 KiB
Rust
use super::plumbing::*;
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use super::*;
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use std::fmt::{self, Debug};
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/// `FlatMap` maps each element to a parallel iterator, then flattens these iterators together.
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/// This struct is created by the [`flat_map()`] method on [`ParallelIterator`]
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///
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/// [`flat_map()`]: ParallelIterator::flat_map()
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#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
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#[derive(Clone)]
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pub struct FlatMap<I, F> {
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base: I,
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map_op: F,
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}
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impl<I: Debug, F> Debug for FlatMap<I, F> {
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fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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f.debug_struct("FlatMap").field("base", &self.base).finish()
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}
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}
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impl<I, F> FlatMap<I, F> {
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/// Creates a new `FlatMap` iterator.
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pub(super) fn new(base: I, map_op: F) -> Self {
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FlatMap { base, map_op }
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}
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}
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impl<I, F, PI> ParallelIterator for FlatMap<I, F>
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where
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I: ParallelIterator,
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F: Fn(I::Item) -> PI + Sync + Send,
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PI: IntoParallelIterator,
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{
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type Item = PI::Item;
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fn drive_unindexed<C>(self, consumer: C) -> C::Result
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where
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C: UnindexedConsumer<Self::Item>,
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{
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let consumer = FlatMapConsumer::new(consumer, &self.map_op);
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self.base.drive_unindexed(consumer)
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}
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}
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// ////////////////////////////////////////////////////////////////////////
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// Consumer implementation
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struct FlatMapConsumer<'f, C, F> {
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base: C,
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map_op: &'f F,
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}
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impl<'f, C, F> FlatMapConsumer<'f, C, F> {
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fn new(base: C, map_op: &'f F) -> Self {
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FlatMapConsumer { base, map_op }
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}
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}
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impl<'f, T, U, C, F> Consumer<T> for FlatMapConsumer<'f, C, F>
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where
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C: UnindexedConsumer<U::Item>,
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F: Fn(T) -> U + Sync,
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U: IntoParallelIterator,
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{
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type Folder = FlatMapFolder<'f, C, F, C::Result>;
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type Reducer = C::Reducer;
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type Result = C::Result;
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fn split_at(self, index: usize) -> (Self, Self, C::Reducer) {
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let (left, right, reducer) = self.base.split_at(index);
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(
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FlatMapConsumer::new(left, self.map_op),
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FlatMapConsumer::new(right, self.map_op),
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reducer,
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)
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}
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fn into_folder(self) -> Self::Folder {
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FlatMapFolder {
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base: self.base,
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map_op: self.map_op,
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previous: None,
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}
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}
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fn full(&self) -> bool {
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self.base.full()
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}
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}
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impl<'f, T, U, C, F> UnindexedConsumer<T> for FlatMapConsumer<'f, C, F>
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where
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C: UnindexedConsumer<U::Item>,
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F: Fn(T) -> U + Sync,
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U: IntoParallelIterator,
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{
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fn split_off_left(&self) -> Self {
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FlatMapConsumer::new(self.base.split_off_left(), self.map_op)
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}
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fn to_reducer(&self) -> Self::Reducer {
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self.base.to_reducer()
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}
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}
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struct FlatMapFolder<'f, C, F, R> {
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base: C,
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map_op: &'f F,
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previous: Option<R>,
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}
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impl<'f, T, U, C, F> Folder<T> for FlatMapFolder<'f, C, F, C::Result>
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where
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C: UnindexedConsumer<U::Item>,
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F: Fn(T) -> U + Sync,
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U: IntoParallelIterator,
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{
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type Result = C::Result;
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fn consume(self, item: T) -> Self {
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let map_op = self.map_op;
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let par_iter = map_op(item).into_par_iter();
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let consumer = self.base.split_off_left();
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let result = par_iter.drive_unindexed(consumer);
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let previous = match self.previous {
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None => Some(result),
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Some(previous) => {
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let reducer = self.base.to_reducer();
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Some(reducer.reduce(previous, result))
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}
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};
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FlatMapFolder {
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base: self.base,
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map_op,
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previous,
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}
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}
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fn complete(self) -> Self::Result {
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match self.previous {
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Some(previous) => previous,
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None => self.base.into_folder().complete(),
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}
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}
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fn full(&self) -> bool {
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self.base.full()
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}
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}
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