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//! Parallel iterator types for [standard collections][std::collections]
//!
//! You will rarely need to interact with this module directly unless you need
//! to name one of the iterator types.
//!
//! [std::collections]: https://doc.rust-lang.org/stable/std/collections/
/// Convert an iterable collection into a parallel iterator by first
/// collecting into a temporary `Vec`, then iterating that.
macro_rules! into_par_vec {
($t:ty => $iter:ident<$($i:tt),*>, impl $($args:tt)*) => {
impl $($args)* IntoParallelIterator for $t {
type Item = <$t as IntoIterator>::Item;
type Iter = $iter<$($i),*>;
fn into_par_iter(self) -> Self::Iter {
use std::iter::FromIterator;
$iter { inner: Vec::from_iter(self).into_par_iter() }
}
}
};
}
pub mod binary_heap;
pub mod btree_map;
pub mod btree_set;
pub mod hash_map;
pub mod hash_set;
pub mod linked_list;
pub mod vec_deque;
use self::drain_guard::DrainGuard;
mod drain_guard {
use crate::iter::ParallelDrainRange;
use std::mem;
use std::ops::RangeBounds;
/// A proxy for draining a collection by converting to a `Vec` and back.
///
/// This is used for draining `BinaryHeap` and `VecDeque`, which both have
/// zero-allocation conversions to/from `Vec`, though not zero-cost:
/// - `BinaryHeap` will heapify from `Vec`, but at least that will be empty.
/// - `VecDeque` has to shift items to offset 0 when converting to `Vec`.
#[allow(missing_debug_implementations)]
pub(super) struct DrainGuard<'a, T, C: From<Vec<T>>> {
collection: &'a mut C,
vec: Vec<T>,
}
impl<'a, T, C> DrainGuard<'a, T, C>
where
C: Default + From<Vec<T>>,
Vec<T>: From<C>,
{
pub(super) fn new(collection: &'a mut C) -> Self {
Self {
// Temporarily steal the inner `Vec` so we can drain in place.
vec: Vec::from(mem::take(collection)),
collection,
}
}
}
impl<'a, T, C: From<Vec<T>>> Drop for DrainGuard<'a, T, C> {
fn drop(&mut self) {
// Restore the collection from the `Vec` with its original capacity.
*self.collection = C::from(mem::take(&mut self.vec));
}
}
impl<'a, T, C> ParallelDrainRange<usize> for &'a mut DrainGuard<'_, T, C>
where
T: Send,
C: From<Vec<T>>,
{
type Iter = crate::vec::Drain<'a, T>;
type Item = T;
fn par_drain<R: RangeBounds<usize>>(self, range: R) -> Self::Iter {
self.vec.par_drain(range)
}
}
}
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