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use super::plumbing::*;
use super::*;
use std::sync::atomic::{AtomicUsize, Ordering};
/// `TakeAny` is an iterator that iterates over `n` elements from anywhere in `I`.
/// This struct is created by the [`take_any()`] method on [`ParallelIterator`]
///
/// [`take_any()`]: trait.ParallelIterator.html#method.take_any
/// [`ParallelIterator`]: trait.ParallelIterator.html
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
#[derive(Clone, Debug)]
pub struct TakeAny<I: ParallelIterator> {
base: I,
count: usize,
}
impl<I> TakeAny<I>
where
I: ParallelIterator,
{
/// Creates a new `TakeAny` iterator.
pub(super) fn new(base: I, count: usize) -> Self {
TakeAny { base, count }
}
}
impl<I> ParallelIterator for TakeAny<I>
where
I: ParallelIterator,
{
type Item = I::Item;
fn drive_unindexed<C>(self, consumer: C) -> C::Result
where
C: UnindexedConsumer<Self::Item>,
{
let consumer1 = TakeAnyConsumer {
base: consumer,
count: &AtomicUsize::new(self.count),
};
self.base.drive_unindexed(consumer1)
}
}
/// ////////////////////////////////////////////////////////////////////////
/// Consumer implementation
struct TakeAnyConsumer<'f, C> {
base: C,
count: &'f AtomicUsize,
}
impl<'f, T, C> Consumer<T> for TakeAnyConsumer<'f, C>
where
C: Consumer<T>,
T: Send,
{
type Folder = TakeAnyFolder<'f, C::Folder>;
type Reducer = C::Reducer;
type Result = C::Result;
fn split_at(self, index: usize) -> (Self, Self, Self::Reducer) {
let (left, right, reducer) = self.base.split_at(index);
(
TakeAnyConsumer { base: left, ..self },
TakeAnyConsumer {
base: right,
..self
},
reducer,
)
}
fn into_folder(self) -> Self::Folder {
TakeAnyFolder {
base: self.base.into_folder(),
count: self.count,
}
}
fn full(&self) -> bool {
self.count.load(Ordering::Relaxed) == 0 || self.base.full()
}
}
impl<'f, T, C> UnindexedConsumer<T> for TakeAnyConsumer<'f, C>
where
C: UnindexedConsumer<T>,
T: Send,
{
fn split_off_left(&self) -> Self {
TakeAnyConsumer {
base: self.base.split_off_left(),
..*self
}
}
fn to_reducer(&self) -> Self::Reducer {
self.base.to_reducer()
}
}
struct TakeAnyFolder<'f, C> {
base: C,
count: &'f AtomicUsize,
}
fn checked_decrement(u: &AtomicUsize) -> bool {
u.fetch_update(Ordering::Relaxed, Ordering::Relaxed, |u| u.checked_sub(1))
.is_ok()
}
impl<'f, T, C> Folder<T> for TakeAnyFolder<'f, C>
where
C: Folder<T>,
{
type Result = C::Result;
fn consume(mut self, item: T) -> Self {
if checked_decrement(self.count) {
self.base = self.base.consume(item);
}
self
}
fn consume_iter<I>(mut self, iter: I) -> Self
where
I: IntoIterator<Item = T>,
{
self.base = self.base.consume_iter(
iter.into_iter()
.take_while(move |_| checked_decrement(self.count)),
);
self
}
fn complete(self) -> C::Result {
self.base.complete()
}
fn full(&self) -> bool {
self.count.load(Ordering::Relaxed) == 0 || self.base.full()
}
}