| use super::plumbing::*; |
| use super::*; |
| use rayon_core::join; |
| use std::cmp; |
| use std::iter; |
| |
| /// `Chain` is an iterator that joins `b` after `a` in one continuous iterator. |
| /// This struct is created by the [`chain()`] method on [`ParallelIterator`] |
| /// |
| /// [`chain()`]: trait.ParallelIterator.html#method.chain |
| /// [`ParallelIterator`]: trait.ParallelIterator.html |
| #[must_use = "iterator adaptors are lazy and do nothing unless consumed"] |
| #[derive(Debug, Clone)] |
| pub struct Chain<A, B> |
| where |
| A: ParallelIterator, |
| B: ParallelIterator<Item = A::Item>, |
| { |
| a: A, |
| b: B, |
| } |
| |
| impl<A, B> Chain<A, B> |
| where |
| A: ParallelIterator, |
| B: ParallelIterator<Item = A::Item>, |
| { |
| /// Creates a new `Chain` iterator. |
| pub(super) fn new(a: A, b: B) -> Self { |
| Chain { a, b } |
| } |
| } |
| |
| impl<A, B> ParallelIterator for Chain<A, B> |
| where |
| A: ParallelIterator, |
| B: ParallelIterator<Item = A::Item>, |
| { |
| type Item = A::Item; |
| |
| fn drive_unindexed<C>(self, consumer: C) -> C::Result |
| where |
| C: UnindexedConsumer<Self::Item>, |
| { |
| let Chain { a, b } = self; |
| |
| // If we returned a value from our own `opt_len`, then the collect consumer in particular |
| // will balk at being treated like an actual `UnindexedConsumer`. But when we do know the |
| // length, we can use `Consumer::split_at` instead, and this is still harmless for other |
| // truly-unindexed consumers too. |
| let (left, right, reducer) = if let Some(len) = a.opt_len() { |
| consumer.split_at(len) |
| } else { |
| let reducer = consumer.to_reducer(); |
| (consumer.split_off_left(), consumer, reducer) |
| }; |
| |
| let (a, b) = join(|| a.drive_unindexed(left), || b.drive_unindexed(right)); |
| reducer.reduce(a, b) |
| } |
| |
| fn opt_len(&self) -> Option<usize> { |
| self.a.opt_len()?.checked_add(self.b.opt_len()?) |
| } |
| } |
| |
| impl<A, B> IndexedParallelIterator for Chain<A, B> |
| where |
| A: IndexedParallelIterator, |
| B: IndexedParallelIterator<Item = A::Item>, |
| { |
| fn drive<C>(self, consumer: C) -> C::Result |
| where |
| C: Consumer<Self::Item>, |
| { |
| let Chain { a, b } = self; |
| let (left, right, reducer) = consumer.split_at(a.len()); |
| let (a, b) = join(|| a.drive(left), || b.drive(right)); |
| reducer.reduce(a, b) |
| } |
| |
| fn len(&self) -> usize { |
| self.a.len().checked_add(self.b.len()).expect("overflow") |
| } |
| |
| fn with_producer<CB>(self, callback: CB) -> CB::Output |
| where |
| CB: ProducerCallback<Self::Item>, |
| { |
| let a_len = self.a.len(); |
| return self.a.with_producer(CallbackA { |
| callback, |
| a_len, |
| b: self.b, |
| }); |
| |
| struct CallbackA<CB, B> { |
| callback: CB, |
| a_len: usize, |
| b: B, |
| } |
| |
| impl<CB, B> ProducerCallback<B::Item> for CallbackA<CB, B> |
| where |
| B: IndexedParallelIterator, |
| CB: ProducerCallback<B::Item>, |
| { |
| type Output = CB::Output; |
| |
| fn callback<A>(self, a_producer: A) -> Self::Output |
| where |
| A: Producer<Item = B::Item>, |
| { |
| self.b.with_producer(CallbackB { |
| callback: self.callback, |
| a_len: self.a_len, |
| a_producer, |
| }) |
| } |
| } |
| |
| struct CallbackB<CB, A> { |
| callback: CB, |
| a_len: usize, |
| a_producer: A, |
| } |
| |
| impl<CB, A> ProducerCallback<A::Item> for CallbackB<CB, A> |
| where |
| A: Producer, |
| CB: ProducerCallback<A::Item>, |
| { |
| type Output = CB::Output; |
| |
| fn callback<B>(self, b_producer: B) -> Self::Output |
| where |
| B: Producer<Item = A::Item>, |
| { |
| let producer = ChainProducer::new(self.a_len, self.a_producer, b_producer); |
| self.callback.callback(producer) |
| } |
| } |
| } |
| } |
| |
| /// //////////////////////////////////////////////////////////////////////// |
| |
| struct ChainProducer<A, B> |
| where |
| A: Producer, |
| B: Producer<Item = A::Item>, |
| { |
| a_len: usize, |
| a: A, |
| b: B, |
| } |
| |
| impl<A, B> ChainProducer<A, B> |
| where |
| A: Producer, |
| B: Producer<Item = A::Item>, |
| { |
| fn new(a_len: usize, a: A, b: B) -> Self { |
| ChainProducer { a_len, a, b } |
| } |
| } |
| |
| impl<A, B> Producer for ChainProducer<A, B> |
| where |
| A: Producer, |
| B: Producer<Item = A::Item>, |
| { |
| type Item = A::Item; |
| type IntoIter = ChainSeq<A::IntoIter, B::IntoIter>; |
| |
| fn into_iter(self) -> Self::IntoIter { |
| ChainSeq::new(self.a.into_iter(), self.b.into_iter()) |
| } |
| |
| fn min_len(&self) -> usize { |
| cmp::max(self.a.min_len(), self.b.min_len()) |
| } |
| |
| fn max_len(&self) -> usize { |
| cmp::min(self.a.max_len(), self.b.max_len()) |
| } |
| |
| fn split_at(self, index: usize) -> (Self, Self) { |
| if index <= self.a_len { |
| let a_rem = self.a_len - index; |
| let (a_left, a_right) = self.a.split_at(index); |
| let (b_left, b_right) = self.b.split_at(0); |
| ( |
| ChainProducer::new(index, a_left, b_left), |
| ChainProducer::new(a_rem, a_right, b_right), |
| ) |
| } else { |
| let (a_left, a_right) = self.a.split_at(self.a_len); |
| let (b_left, b_right) = self.b.split_at(index - self.a_len); |
| ( |
| ChainProducer::new(self.a_len, a_left, b_left), |
| ChainProducer::new(0, a_right, b_right), |
| ) |
| } |
| } |
| |
| fn fold_with<F>(self, mut folder: F) -> F |
| where |
| F: Folder<A::Item>, |
| { |
| folder = self.a.fold_with(folder); |
| if folder.full() { |
| folder |
| } else { |
| self.b.fold_with(folder) |
| } |
| } |
| } |
| |
| /// //////////////////////////////////////////////////////////////////////// |
| /// Wrapper for Chain to implement ExactSizeIterator |
| |
| struct ChainSeq<A, B> { |
| chain: iter::Chain<A, B>, |
| } |
| |
| impl<A, B> ChainSeq<A, B> { |
| fn new(a: A, b: B) -> ChainSeq<A, B> |
| where |
| A: ExactSizeIterator, |
| B: ExactSizeIterator<Item = A::Item>, |
| { |
| ChainSeq { chain: a.chain(b) } |
| } |
| } |
| |
| impl<A, B> Iterator for ChainSeq<A, B> |
| where |
| A: Iterator, |
| B: Iterator<Item = A::Item>, |
| { |
| type Item = A::Item; |
| |
| fn next(&mut self) -> Option<Self::Item> { |
| self.chain.next() |
| } |
| |
| fn size_hint(&self) -> (usize, Option<usize>) { |
| self.chain.size_hint() |
| } |
| } |
| |
| impl<A, B> ExactSizeIterator for ChainSeq<A, B> |
| where |
| A: ExactSizeIterator, |
| B: ExactSizeIterator<Item = A::Item>, |
| { |
| } |
| |
| impl<A, B> DoubleEndedIterator for ChainSeq<A, B> |
| where |
| A: DoubleEndedIterator, |
| B: DoubleEndedIterator<Item = A::Item>, |
| { |
| fn next_back(&mut self) -> Option<Self::Item> { |
| self.chain.next_back() |
| } |
| } |