| use super::plumbing::*; |
| use super::*; |
| use std::cmp::min; |
| |
| /// `Take` is an iterator that iterates over the first `n` elements. |
| /// This struct is created by the [`take()`] method on [`IndexedParallelIterator`] |
| /// |
| /// [`take()`]: trait.IndexedParallelIterator.html#method.take |
| /// [`IndexedParallelIterator`]: trait.IndexedParallelIterator.html |
| #[must_use = "iterator adaptors are lazy and do nothing unless consumed"] |
| #[derive(Debug, Clone)] |
| pub struct Take<I> { |
| base: I, |
| n: usize, |
| } |
| |
| /// Create a new `Take` iterator. |
| /// |
| /// NB: a free fn because it is NOT part of the end-user API. |
| pub fn new<I>(base: I, n: usize) -> Take<I> |
| where I: IndexedParallelIterator |
| { |
| let n = min(base.len(), n); |
| Take { base: base, n: n } |
| } |
| |
| impl<I> ParallelIterator for Take<I> |
| where I: IndexedParallelIterator |
| { |
| type Item = I::Item; |
| |
| fn drive_unindexed<C>(self, consumer: C) -> C::Result |
| where C: UnindexedConsumer<Self::Item> |
| { |
| bridge(self, consumer) |
| } |
| |
| fn opt_len(&self) -> Option<usize> { |
| Some(self.len()) |
| } |
| } |
| |
| impl<I> IndexedParallelIterator for Take<I> |
| where I: IndexedParallelIterator |
| { |
| fn len(&self) -> usize { |
| self.n |
| } |
| |
| fn drive<C: Consumer<Self::Item>>(self, consumer: C) -> C::Result { |
| bridge(self, consumer) |
| } |
| |
| fn with_producer<CB>(self, callback: CB) -> CB::Output |
| where CB: ProducerCallback<Self::Item> |
| { |
| return self.base.with_producer(Callback { |
| callback: callback, |
| n: self.n, |
| }); |
| |
| struct Callback<CB> { |
| callback: CB, |
| n: usize, |
| } |
| |
| 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 (producer, _) = base.split_at(self.n); |
| self.callback.callback(producer) |
| } |
| } |
| } |
| } |