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use super::plumbing::*;
use super::*;
use std::iter;
use std::ops::Range;
use std::usize;
/// `Enumerate` is an iterator that returns the current count along with the element.
/// This struct is created by the [`enumerate()`] method on [`IndexedParallelIterator`]
///
/// [`enumerate()`]: trait.IndexedParallelIterator.html#method.enumerate
/// [`IndexedParallelIterator`]: trait.IndexedParallelIterator.html
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
#[derive(Debug, Clone)]
pub struct Enumerate<I: IndexedParallelIterator> {
base: I,
}
impl<I> Enumerate<I>
where
I: IndexedParallelIterator,
{
/// Creates a new `Enumerate` iterator.
pub(super) fn new(base: I) -> Self {
Enumerate { base }
}
}
impl<I> ParallelIterator for Enumerate<I>
where
I: IndexedParallelIterator,
{
type Item = (usize, 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 Enumerate<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>,
{
return self.base.with_producer(Callback { callback });
struct Callback<CB> {
callback: CB,
}
impl<I, CB> ProducerCallback<I> for Callback<CB>
where
CB: ProducerCallback<(usize, I)>,
{
type Output = CB::Output;
fn callback<P>(self, base: P) -> CB::Output
where
P: Producer<Item = I>,
{
let producer = EnumerateProducer { base, offset: 0 };
self.callback.callback(producer)
}
}
}
}
/// ////////////////////////////////////////////////////////////////////////
/// Producer implementation
struct EnumerateProducer<P> {
base: P,
offset: usize,
}
impl<P> Producer for EnumerateProducer<P>
where
P: Producer,
{
type Item = (usize, P::Item);
type IntoIter = iter::Zip<Range<usize>, P::IntoIter>;
fn into_iter(self) -> Self::IntoIter {
// Enumerate only works for IndexedParallelIterators. Since those
// have a max length of usize::MAX, their max index is
// usize::MAX - 1, so the range 0..usize::MAX includes all
// possible indices.
//
// However, we should to use a precise end to the range, otherwise
// reversing the iterator may have to walk back a long ways before
// `Zip::next_back` can produce anything.
let base = self.base.into_iter();
let end = self.offset + base.len();
(self.offset..end).zip(base)
}
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(index);
(
EnumerateProducer {
base: left,
offset: self.offset,
},
EnumerateProducer {
base: right,
offset: self.offset + index,
},
)
}
}