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use std::cmp::min;
use super::plumbing::*;
use super::*;
use crate::math::div_round_up;
/// `Chunks` is an iterator that groups elements of an underlying iterator.
///
/// This struct is created by the [`chunks()`] method on [`IndexedParallelIterator`]
///
/// [`chunks()`]: trait.IndexedParallelIterator.html#method.chunks
/// [`IndexedParallelIterator`]: trait.IndexedParallelIterator.html
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
#[derive(Debug, Clone)]
pub struct Chunks<I>
where
I: IndexedParallelIterator,
{
size: usize,
i: I,
}
impl<I> Chunks<I>
where
I: IndexedParallelIterator,
{
/// Creates a new `Chunks` iterator
pub(super) fn new(i: I, size: usize) -> Self {
Chunks { i, size }
}
}
impl<I> ParallelIterator for Chunks<I>
where
I: IndexedParallelIterator,
{
type Item = Vec<I::Item>;
fn drive_unindexed<C>(self, consumer: C) -> C::Result
where
C: Consumer<Vec<I::Item>>,
{
bridge(self, consumer)
}
fn opt_len(&self) -> Option<usize> {
Some(self.len())
}
}
impl<I> IndexedParallelIterator for Chunks<I>
where
I: IndexedParallelIterator,
{
fn drive<C>(self, consumer: C) -> C::Result
where
C: Consumer<Self::Item>,
{
bridge(self, consumer)
}
fn len(&self) -> usize {
div_round_up(self.i.len(), self.size)
}
fn with_producer<CB>(self, callback: CB) -> CB::Output
where
CB: ProducerCallback<Self::Item>,
{
let len = self.i.len();
return self.i.with_producer(Callback {
size: self.size,
len,
callback,
});
struct Callback<CB> {
size: usize,
len: usize,
callback: CB,
}
impl<T, CB> ProducerCallback<T> for Callback<CB>
where
CB: ProducerCallback<Vec<T>>,
{
type Output = CB::Output;
fn callback<P>(self, base: P) -> CB::Output
where
P: Producer<Item = T>,
{
let producer = ChunkProducer::new(self.size, self.len, base, Vec::from_iter);
self.callback.callback(producer)
}
}
}
}
pub(super) struct ChunkProducer<P, F> {
chunk_size: usize,
len: usize,
base: P,
map: F,
}
impl<P, F> ChunkProducer<P, F> {
pub(super) fn new(chunk_size: usize, len: usize, base: P, map: F) -> Self {
Self {
chunk_size,
len,
base,
map,
}
}
}
impl<P, F, T> Producer for ChunkProducer<P, F>
where
P: Producer,
F: Fn(P::IntoIter) -> T + Send + Clone,
{
type Item = T;
type IntoIter = std::iter::Map<ChunkSeq<P>, F>;
fn into_iter(self) -> Self::IntoIter {
let chunks = ChunkSeq {
chunk_size: self.chunk_size,
len: self.len,
inner: if self.len > 0 { Some(self.base) } else { None },
};
chunks.map(self.map)
}
fn split_at(self, index: usize) -> (Self, Self) {
let elem_index = min(index * self.chunk_size, self.len);
let (left, right) = self.base.split_at(elem_index);
(
ChunkProducer {
chunk_size: self.chunk_size,
len: elem_index,
base: left,
map: self.map.clone(),
},
ChunkProducer {
chunk_size: self.chunk_size,
len: self.len - elem_index,
base: right,
map: self.map,
},
)
}
fn min_len(&self) -> usize {
div_round_up(self.base.min_len(), self.chunk_size)
}
fn max_len(&self) -> usize {
self.base.max_len() / self.chunk_size
}
}
pub(super) struct ChunkSeq<P> {
chunk_size: usize,
len: usize,
inner: Option<P>,
}
impl<P> Iterator for ChunkSeq<P>
where
P: Producer,
{
type Item = P::IntoIter;
fn next(&mut self) -> Option<Self::Item> {
let producer = self.inner.take()?;
if self.len > self.chunk_size {
let (left, right) = producer.split_at(self.chunk_size);
self.inner = Some(right);
self.len -= self.chunk_size;
Some(left.into_iter())
} else {
debug_assert!(self.len > 0);
self.len = 0;
Some(producer.into_iter())
}
}
fn size_hint(&self) -> (usize, Option<usize>) {
let len = self.len();
(len, Some(len))
}
}
impl<P> ExactSizeIterator for ChunkSeq<P>
where
P: Producer,
{
#[inline]
fn len(&self) -> usize {
div_round_up(self.len, self.chunk_size)
}
}
impl<P> DoubleEndedIterator for ChunkSeq<P>
where
P: Producer,
{
fn next_back(&mut self) -> Option<Self::Item> {
let producer = self.inner.take()?;
if self.len > self.chunk_size {
let mut size = self.len % self.chunk_size;
if size == 0 {
size = self.chunk_size;
}
let (left, right) = producer.split_at(self.len - size);
self.inner = Some(left);
self.len -= size;
Some(right.into_iter())
} else {
debug_assert!(self.len > 0);
self.len = 0;
Some(producer.into_iter())
}
}
}