| use std::cmp::min; |
| |
| use super::plumbing::*; |
| use super::*; |
| use crate::math::div_round_up; |
| use std::iter; |
| use std::usize; |
| |
| /// `StepBy` is an iterator that skips `n` elements between each yield, where `n` is the given step. |
| /// This struct is created by the [`step_by()`] method on [`IndexedParallelIterator`] |
| /// |
| /// [`step_by()`]: trait.IndexedParallelIterator.html#method.step_by |
| /// [`IndexedParallelIterator`]: trait.IndexedParallelIterator.html |
| #[must_use = "iterator adaptors are lazy and do nothing unless consumed"] |
| #[derive(Debug, Clone)] |
| pub struct StepBy<I: IndexedParallelIterator> { |
| base: I, |
| step: usize, |
| } |
| |
| impl<I> StepBy<I> |
| where |
| I: IndexedParallelIterator, |
| { |
| /// Creates a new `StepBy` iterator. |
| pub(super) fn new(base: I, step: usize) -> Self { |
| StepBy { base, step } |
| } |
| } |
| |
| impl<I> ParallelIterator for StepBy<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 StepBy<I> |
| where |
| I: IndexedParallelIterator, |
| { |
| fn drive<C: Consumer<Self::Item>>(self, consumer: C) -> C::Result { |
| bridge(self, consumer) |
| } |
| |
| fn len(&self) -> usize { |
| div_round_up(self.base.len(), self.step) |
| } |
| |
| fn with_producer<CB>(self, callback: CB) -> CB::Output |
| where |
| CB: ProducerCallback<Self::Item>, |
| { |
| let len = self.base.len(); |
| return self.base.with_producer(Callback { |
| callback, |
| step: self.step, |
| len, |
| }); |
| |
| struct Callback<CB> { |
| callback: CB, |
| step: usize, |
| len: 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 = StepByProducer { |
| base, |
| step: self.step, |
| len: self.len, |
| }; |
| self.callback.callback(producer) |
| } |
| } |
| } |
| } |
| |
| /// //////////////////////////////////////////////////////////////////////// |
| /// Producer implementation |
| |
| struct StepByProducer<P> { |
| base: P, |
| step: usize, |
| len: usize, |
| } |
| |
| impl<P> Producer for StepByProducer<P> |
| where |
| P: Producer, |
| { |
| type Item = P::Item; |
| type IntoIter = iter::StepBy<P::IntoIter>; |
| |
| fn into_iter(self) -> Self::IntoIter { |
| self.base.into_iter().step_by(self.step) |
| } |
| |
| fn split_at(self, index: usize) -> (Self, Self) { |
| let elem_index = min(index * self.step, self.len); |
| |
| let (left, right) = self.base.split_at(elem_index); |
| ( |
| StepByProducer { |
| base: left, |
| step: self.step, |
| len: elem_index, |
| }, |
| StepByProducer { |
| base: right, |
| step: self.step, |
| len: self.len - elem_index, |
| }, |
| ) |
| } |
| |
| fn min_len(&self) -> usize { |
| div_round_up(self.base.min_len(), self.step) |
| } |
| |
| fn max_len(&self) -> usize { |
| self.base.max_len() / self.step |
| } |
| } |