Revision control
Copy as Markdown
Other Tools
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
}
}