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Diffstat (limited to 'src/iter/panic_fuse.rs')
| -rw-r--r-- | src/iter/panic_fuse.rs | 342 |
1 files changed, 342 insertions, 0 deletions
diff --git a/src/iter/panic_fuse.rs b/src/iter/panic_fuse.rs new file mode 100644 index 0000000..7487230 --- /dev/null +++ b/src/iter/panic_fuse.rs @@ -0,0 +1,342 @@ +use super::plumbing::*; +use super::*; +use std::sync::atomic::{AtomicBool, Ordering}; +use std::thread; + +/// `PanicFuse` is an adaptor that wraps an iterator with a fuse in case +/// of panics, to halt all threads as soon as possible. +/// +/// This struct is created by the [`panic_fuse()`] method on [`ParallelIterator`] +/// +/// [`panic_fuse()`]: trait.ParallelIterator.html#method.panic_fuse +/// [`ParallelIterator`]: trait.ParallelIterator.html +#[must_use = "iterator adaptors are lazy and do nothing unless consumed"] +#[derive(Debug, Clone)] +pub struct PanicFuse<I: ParallelIterator> { + base: I, +} + +/// Helper that sets a bool to `true` if dropped while unwinding. +#[derive(Clone)] +struct Fuse<'a>(&'a AtomicBool); + +impl<'a> Drop for Fuse<'a> { + #[inline] + fn drop(&mut self) { + if thread::panicking() { + self.0.store(true, Ordering::Relaxed); + } + } +} + +impl<'a> Fuse<'a> { + #[inline] + fn panicked(&self) -> bool { + self.0.load(Ordering::Relaxed) + } +} + +impl<I> PanicFuse<I> +where + I: ParallelIterator, +{ + /// Creates a new `PanicFuse` iterator. + pub(super) fn new(base: I) -> PanicFuse<I> { + PanicFuse { base } + } +} + +impl<I> ParallelIterator for PanicFuse<I> +where + I: ParallelIterator, +{ + type Item = I::Item; + + fn drive_unindexed<C>(self, consumer: C) -> C::Result + where + C: UnindexedConsumer<Self::Item>, + { + let panicked = AtomicBool::new(false); + let consumer1 = PanicFuseConsumer { + base: consumer, + fuse: Fuse(&panicked), + }; + self.base.drive_unindexed(consumer1) + } + + fn opt_len(&self) -> Option<usize> { + self.base.opt_len() + } +} + +impl<I> IndexedParallelIterator for PanicFuse<I> +where + I: IndexedParallelIterator, +{ + fn drive<C>(self, consumer: C) -> C::Result + where + C: Consumer<Self::Item>, + { + let panicked = AtomicBool::new(false); + let consumer1 = PanicFuseConsumer { + base: consumer, + fuse: Fuse(&panicked), + }; + self.base.drive(consumer1) + } + + fn len(&self) -> usize { + self.base.len() + } + + fn with_producer<CB>(self, callback: CB) -> CB::Output + where + CB: ProducerCallback<Self::Item>, + { + return self.base.with_producer(Callback { callback }); + + struct Callback<CB> { + callback: CB, + } + + impl<T, CB> ProducerCallback<T> for Callback<CB> + where + CB: ProducerCallback<T>, + { + type Output = CB::Output; + + fn callback<P>(self, base: P) -> CB::Output + where + P: Producer<Item = T>, + { + let panicked = AtomicBool::new(false); + let producer = PanicFuseProducer { + base, + fuse: Fuse(&panicked), + }; + self.callback.callback(producer) + } + } + } +} + +/// //////////////////////////////////////////////////////////////////////// +/// Producer implementation + +struct PanicFuseProducer<'a, P> { + base: P, + fuse: Fuse<'a>, +} + +impl<'a, P> Producer for PanicFuseProducer<'a, P> +where + P: Producer, +{ + type Item = P::Item; + type IntoIter = PanicFuseIter<'a, P::IntoIter>; + + fn into_iter(self) -> Self::IntoIter { + PanicFuseIter { + base: self.base.into_iter(), + fuse: self.fuse, + } + } + + fn min_len(&self) -> usize { + self.base.min_len() + } + fn max_len(&self) -> usize { + self.base.max_len() + } + + fn split_at(self, index: usize) -> (Self, Self) { + let (left, right) = self.base.split_at(index); + ( + PanicFuseProducer { + base: left, + fuse: self.fuse.clone(), + }, + PanicFuseProducer { + base: right, + fuse: self.fuse, + }, + ) + } + + fn fold_with<G>(self, folder: G) -> G + where + G: Folder<Self::Item>, + { + let folder1 = PanicFuseFolder { + base: folder, + fuse: self.fuse, + }; + self.base.fold_with(folder1).base + } +} + +struct PanicFuseIter<'a, I> { + base: I, + fuse: Fuse<'a>, +} + +impl<'a, I> Iterator for PanicFuseIter<'a, I> +where + I: Iterator, +{ + type Item = I::Item; + + fn next(&mut self) -> Option<Self::Item> { + if self.fuse.panicked() { + None + } else { + self.base.next() + } + } + + fn size_hint(&self) -> (usize, Option<usize>) { + self.base.size_hint() + } +} + +impl<'a, I> DoubleEndedIterator for PanicFuseIter<'a, I> +where + I: DoubleEndedIterator, +{ + fn next_back(&mut self) -> Option<Self::Item> { + if self.fuse.panicked() { + None + } else { + self.base.next_back() + } + } +} + +impl<'a, I> ExactSizeIterator for PanicFuseIter<'a, I> +where + I: ExactSizeIterator, +{ + fn len(&self) -> usize { + self.base.len() + } +} + +/// //////////////////////////////////////////////////////////////////////// +/// Consumer implementation + +struct PanicFuseConsumer<'a, C> { + base: C, + fuse: Fuse<'a>, +} + +impl<'a, T, C> Consumer<T> for PanicFuseConsumer<'a, C> +where + C: Consumer<T>, +{ + type Folder = PanicFuseFolder<'a, C::Folder>; + type Reducer = PanicFuseReducer<'a, C::Reducer>; + type Result = C::Result; + + fn split_at(self, index: usize) -> (Self, Self, Self::Reducer) { + let (left, right, reducer) = self.base.split_at(index); + ( + PanicFuseConsumer { + base: left, + fuse: self.fuse.clone(), + }, + PanicFuseConsumer { + base: right, + fuse: self.fuse.clone(), + }, + PanicFuseReducer { + base: reducer, + _fuse: self.fuse, + }, + ) + } + + fn into_folder(self) -> Self::Folder { + PanicFuseFolder { + base: self.base.into_folder(), + fuse: self.fuse, + } + } + + fn full(&self) -> bool { + self.fuse.panicked() || self.base.full() + } +} + +impl<'a, T, C> UnindexedConsumer<T> for PanicFuseConsumer<'a, C> +where + C: UnindexedConsumer<T>, +{ + fn split_off_left(&self) -> Self { + PanicFuseConsumer { + base: self.base.split_off_left(), + fuse: self.fuse.clone(), + } + } + + fn to_reducer(&self) -> Self::Reducer { + PanicFuseReducer { + base: self.base.to_reducer(), + _fuse: self.fuse.clone(), + } + } +} + +struct PanicFuseFolder<'a, C> { + base: C, + fuse: Fuse<'a>, +} + +impl<'a, T, C> Folder<T> for PanicFuseFolder<'a, C> +where + C: Folder<T>, +{ + type Result = C::Result; + + fn consume(mut self, item: T) -> Self { + self.base = self.base.consume(item); + self + } + + fn consume_iter<I>(mut self, iter: I) -> Self + where + I: IntoIterator<Item = T>, + { + fn cool<'a, T>(fuse: &'a Fuse<'_>) -> impl Fn(&T) -> bool + 'a { + move |_| !fuse.panicked() + } + + self.base = { + let fuse = &self.fuse; + let iter = iter.into_iter().take_while(cool(fuse)); + self.base.consume_iter(iter) + }; + self + } + + fn complete(self) -> C::Result { + self.base.complete() + } + + fn full(&self) -> bool { + self.fuse.panicked() || self.base.full() + } +} + +struct PanicFuseReducer<'a, C> { + base: C, + _fuse: Fuse<'a>, +} + +impl<'a, T, C> Reducer<T> for PanicFuseReducer<'a, C> +where + C: Reducer<T>, +{ + fn reduce(self, left: T, right: T) -> T { + self.base.reduce(left, right) + } +} |