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use super::plumbing::*;
use super::*;
use std::iter;
/// `Rev` is an iterator that produces elements in reverse order. This struct
/// is created by the [`rev()`] method on [`IndexedParallelIterator`]
///
/// [`rev()`]: trait.IndexedParallelIterator.html#method.rev
/// [`IndexedParallelIterator`]: trait.IndexedParallelIterator.html
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
#[derive(Debug, Clone)]
pub struct Rev<I: IndexedParallelIterator> {
base: I,
}
impl<I> Rev<I>
where
I: IndexedParallelIterator,
{
/// Creates a new `Rev` iterator.
pub(super) fn new(base: I) -> Self {
Rev { base }
}
}
impl<I> ParallelIterator for Rev<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 Rev<I>
where
I: IndexedParallelIterator,
{
fn drive<C: Consumer<Self::Item>>(self, consumer: C) -> C::Result {
bridge(self, consumer)
}
fn len(&self) -> usize {
self.base.len()
}
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, len });
struct Callback<CB> {
callback: CB,
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 = RevProducer {
base,
len: self.len,
};
self.callback.callback(producer)
}
}
}
}
struct RevProducer<P> {
base: P,
len: usize,
}
impl<P> Producer for RevProducer<P>
where
P: Producer,
{
type Item = P::Item;
type IntoIter = iter::Rev<P::IntoIter>;
fn into_iter(self) -> Self::IntoIter {
self.base.into_iter().rev()
}
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(self.len - index);
(
RevProducer {
base: right,
len: index,
},
RevProducer {
base: left,
len: self.len - index,
},
)
}
}