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Implement parallel sources over ranges.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,151 @@ | ||
| // Copyright 2024 Google LLC | ||
| // | ||
| // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or | ||
| // https://www.apache.org/licenses/LICENSE-2.0> or the MIT license | ||
| // <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your | ||
| // option. This file may not be copied, modified, or distributed | ||
| // except according to those terms. | ||
|
|
||
| use super::{IntoParallelSource, ParallelSource, SourceDescriptor}; | ||
| #[cfg(feature = "nightly")] | ||
| use std::iter::Step; | ||
| use std::ops::{Range, RangeInclusive}; | ||
|
|
||
| /// A parallel source over a [`Range`]. This struct is created by the | ||
| /// [`into_par_iter()`](IntoParallelSource::into_par_iter) method on | ||
| /// [`IntoParallelSource`]. | ||
| #[must_use = "iterator adaptors are lazy"] | ||
| pub struct RangeParallelSource<T> { | ||
| range: Range<T>, | ||
| } | ||
|
|
||
| #[cfg(feature = "nightly")] | ||
| impl<T: Step + Copy + Send + Sync> IntoParallelSource for Range<T> { | ||
| type Item = T; | ||
| type Source = RangeParallelSource<T>; | ||
|
|
||
| fn into_par_iter(self) -> Self::Source { | ||
| RangeParallelSource { range: self } | ||
| } | ||
| } | ||
|
|
||
| #[cfg(feature = "nightly")] | ||
| impl<T: Step + Copy + Send + Sync> ParallelSource for RangeParallelSource<T> { | ||
| type Item = T; | ||
|
|
||
| fn descriptor(self) -> SourceDescriptor<Self::Item, impl Fn(usize) -> Self::Item + Sync> { | ||
| let range = self.range; | ||
| let len = T::steps_between(&range.start, &range.end).unwrap_or_else(|| { | ||
| panic!( | ||
| "cannot iterate over a range with more than usize::MAX ({}) items", | ||
| usize::MAX | ||
| ); | ||
| }); | ||
| SourceDescriptor { | ||
| len, | ||
| fetch_item: move |index| T::forward(range.start, index), | ||
| } | ||
| } | ||
| } | ||
|
|
||
| #[cfg(not(feature = "nightly"))] | ||
| impl IntoParallelSource for Range<usize> { | ||
| type Item = usize; | ||
| type Source = RangeParallelSource<usize>; | ||
|
|
||
| fn into_par_iter(self) -> Self::Source { | ||
| RangeParallelSource { range: self } | ||
| } | ||
| } | ||
|
|
||
| #[cfg(not(feature = "nightly"))] | ||
| impl ParallelSource for RangeParallelSource<usize> { | ||
| type Item = usize; | ||
|
|
||
| fn descriptor(self) -> SourceDescriptor<Self::Item, impl Fn(usize) -> Self::Item + Sync> { | ||
| let range = self.range; | ||
| let len = range | ||
| .end | ||
| .checked_sub(range.start) | ||
| .expect("cannot iterate over a backward range"); | ||
| SourceDescriptor { | ||
| len, | ||
| fetch_item: move |index| range.start + index, | ||
| } | ||
| } | ||
| } | ||
|
|
||
| /// A parallel source over a [`RangeInclusive`]. This struct is created by the | ||
| /// [`into_par_iter()`](IntoParallelSource::into_par_iter) method on | ||
| /// [`IntoParallelSource`]. | ||
| #[must_use = "iterator adaptors are lazy"] | ||
| pub struct RangeInclusiveParallelSource<T> { | ||
| range: RangeInclusive<T>, | ||
| } | ||
|
|
||
| #[cfg(feature = "nightly")] | ||
| impl<T: Step + Copy + Send + Sync> IntoParallelSource for RangeInclusive<T> { | ||
| type Item = T; | ||
| type Source = RangeInclusiveParallelSource<T>; | ||
|
|
||
| fn into_par_iter(self) -> Self::Source { | ||
| RangeInclusiveParallelSource { range: self } | ||
| } | ||
| } | ||
|
|
||
| #[cfg(feature = "nightly")] | ||
| impl<T: Step + Copy + Send + Sync> ParallelSource for RangeInclusiveParallelSource<T> { | ||
| type Item = T; | ||
|
|
||
| fn descriptor(self) -> SourceDescriptor<Self::Item, impl Fn(usize) -> Self::Item + Sync> { | ||
| let (start, end) = self.range.into_inner(); | ||
| let len = T::steps_between(&start, &end).unwrap_or_else(|| { | ||
| panic!( | ||
| "cannot iterate over a range with more than usize::MAX ({}) items", | ||
| usize::MAX | ||
| ); | ||
| }); | ||
| let len = len.checked_add(1).unwrap_or_else(|| { | ||
| panic!( | ||
| "cannot iterate over a range with more than usize::MAX ({}) items", | ||
| usize::MAX | ||
| ); | ||
| }); | ||
| SourceDescriptor { | ||
| len, | ||
| fetch_item: move |index| T::forward(start, index), | ||
| } | ||
| } | ||
| } | ||
|
|
||
| #[cfg(not(feature = "nightly"))] | ||
| impl IntoParallelSource for RangeInclusive<usize> { | ||
| type Item = usize; | ||
| type Source = RangeInclusiveParallelSource<usize>; | ||
|
|
||
| fn into_par_iter(self) -> Self::Source { | ||
| RangeInclusiveParallelSource { range: self } | ||
| } | ||
| } | ||
|
|
||
| #[cfg(not(feature = "nightly"))] | ||
| impl ParallelSource for RangeInclusiveParallelSource<usize> { | ||
| type Item = usize; | ||
|
|
||
| fn descriptor(self) -> SourceDescriptor<Self::Item, impl Fn(usize) -> Self::Item + Sync> { | ||
| let (start, end) = self.range.into_inner(); | ||
| let len = end | ||
| .checked_sub(start) | ||
| .expect("cannot iterate over a backward range"); | ||
| let len = len.checked_add(1).unwrap_or_else(|| { | ||
| panic!( | ||
| "cannot iterate over a range with more than usize::MAX ({}) items", | ||
| usize::MAX | ||
| ); | ||
| }); | ||
| SourceDescriptor { | ||
| len, | ||
| fetch_item: move |index| start + index, | ||
| } | ||
| } | ||
| } |
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