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//! Parallel iterator types for [options][std::option]
//!
//! You will rarely need to interact with this module directly unless you need
//! to name one of the iterator types.
//!
use crate::iter::plumbing::*;
use crate::iter::*;
use std::sync::atomic::{AtomicBool, Ordering};
/// A parallel iterator over the value in [`Some`] variant of an [`Option`].
///
/// The iterator yields one value if the [`Option`] is a [`Some`], otherwise none.
///
/// This `struct` is created by the [`into_par_iter`] function.
///
/// [`into_par_iter`]: ../iter/trait.IntoParallelIterator.html#tymethod.into_par_iter
#[derive(Debug, Clone)]
pub struct IntoIter<T: Send> {
opt: Option<T>,
}
impl<T: Send> IntoParallelIterator for Option<T> {
type Item = T;
type Iter = IntoIter<T>;
fn into_par_iter(self) -> Self::Iter {
IntoIter { opt: self }
}
}
impl<T: Send> ParallelIterator for IntoIter<T> {
type Item = T;
fn drive_unindexed<C>(self, consumer: C) -> C::Result
where
C: UnindexedConsumer<Self::Item>,
{
self.drive(consumer)
}
fn opt_len(&self) -> Option<usize> {
Some(self.len())
}
}
impl<T: Send> IndexedParallelIterator for IntoIter<T> {
fn drive<C>(self, consumer: C) -> C::Result
where
C: Consumer<Self::Item>,
{
let mut folder = consumer.into_folder();
if let Some(item) = self.opt {
folder = folder.consume(item);
}
folder.complete()
}
fn len(&self) -> usize {
match self.opt {
Some(_) => 1,
None => 0,
}
}
fn with_producer<CB>(self, callback: CB) -> CB::Output
where
CB: ProducerCallback<Self::Item>,
{
callback.callback(OptionProducer { opt: self.opt })
}
}
/// A parallel iterator over a reference to the [`Some`] variant of an [`Option`].
///
/// The iterator yields one value if the [`Option`] is a [`Some`], otherwise none.
///
/// This `struct` is created by the [`par_iter`] function.
///
/// [`par_iter`]: ../iter/trait.IntoParallelRefIterator.html#tymethod.par_iter
#[derive(Debug)]
pub struct Iter<'a, T: Sync> {
inner: IntoIter<&'a T>,
}
impl<'a, T: Sync> Clone for Iter<'a, T> {
fn clone(&self) -> Self {
Iter {
inner: self.inner.clone(),
}
}
}
impl<'a, T: Sync> IntoParallelIterator for &'a Option<T> {
type Item = &'a T;
type Iter = Iter<'a, T>;
fn into_par_iter(self) -> Self::Iter {
Iter {
inner: self.as_ref().into_par_iter(),
}
}
}
delegate_indexed_iterator! {
Iter<'a, T> => &'a T,
impl<'a, T: Sync + 'a>
}
/// A parallel iterator over a mutable reference to the [`Some`] variant of an [`Option`].
///
/// The iterator yields one value if the [`Option`] is a [`Some`], otherwise none.
///
/// This `struct` is created by the [`par_iter_mut`] function.
///
/// [`par_iter_mut`]: ../iter/trait.IntoParallelRefMutIterator.html#tymethod.par_iter_mut
#[derive(Debug)]
pub struct IterMut<'a, T: Send> {
inner: IntoIter<&'a mut T>,
}
impl<'a, T: Send> IntoParallelIterator for &'a mut Option<T> {
type Item = &'a mut T;
type Iter = IterMut<'a, T>;
fn into_par_iter(self) -> Self::Iter {
IterMut {
inner: self.as_mut().into_par_iter(),
}
}
}
delegate_indexed_iterator! {
IterMut<'a, T> => &'a mut T,
impl<'a, T: Send + 'a>
}
/// Private producer for an option
struct OptionProducer<T: Send> {
opt: Option<T>,
}
impl<T: Send> Producer for OptionProducer<T> {
type Item = T;
type IntoIter = std::option::IntoIter<T>;
fn into_iter(self) -> Self::IntoIter {
self.opt.into_iter()
}
fn split_at(self, index: usize) -> (Self, Self) {
debug_assert!(index <= 1);
let none = OptionProducer { opt: None };
if index == 0 {
(none, self)
} else {
(self, none)
}
}
}
/// Collect an arbitrary `Option`-wrapped collection.
///
/// If any item is `None`, then all previous items collected are discarded,
/// and it returns only `None`.
impl<C, T> FromParallelIterator<Option<T>> for Option<C>
where
C: FromParallelIterator<T>,
T: Send,
{
fn from_par_iter<I>(par_iter: I) -> Self
where
I: IntoParallelIterator<Item = Option<T>>,
{
fn check<T>(found_none: &AtomicBool) -> impl Fn(&Option<T>) + '_ {
move |item| {
if item.is_none() {
found_none.store(true, Ordering::Relaxed);
}
}
}
let found_none = AtomicBool::new(false);
let collection = par_iter
.into_par_iter()
.inspect(check(&found_none))
.while_some()
.collect();
if found_none.load(Ordering::Relaxed) {
None
} else {
Some(collection)
}
}
}