rayon/collections/
mod.rs

1//! Parallel iterator types for [standard collections][std::collections]
2//!
3//! You will rarely need to interact with this module directly unless you need
4//! to name one of the iterator types.
5//!
6//! [std::collections]: https://doc.rust-lang.org/stable/std/collections/
7
8/// Convert an iterable collection into a parallel iterator by first
9/// collecting into a temporary `Vec`, then iterating that.
10macro_rules! into_par_vec {
11    ($t:ty => $iter:ident<$($i:tt),*>, impl $($args:tt)*) => {
12        impl $($args)* IntoParallelIterator for $t {
13            type Item = <$t as IntoIterator>::Item;
14            type Iter = $iter<$($i),*>;
15
16            fn into_par_iter(self) -> Self::Iter {
17                use std::iter::FromIterator;
18                $iter { inner: Vec::from_iter(self).into_par_iter() }
19            }
20        }
21    };
22}
23
24pub mod binary_heap;
25pub mod btree_map;
26pub mod btree_set;
27pub mod hash_map;
28pub mod hash_set;
29pub mod linked_list;
30pub mod vec_deque;
31
32use self::drain_guard::DrainGuard;
33
34mod drain_guard {
35    use crate::iter::ParallelDrainRange;
36    use std::mem;
37    use std::ops::RangeBounds;
38
39    /// A proxy for draining a collection by converting to a `Vec` and back.
40    ///
41    /// This is used for draining `BinaryHeap` and `VecDeque`, which both have
42    /// zero-allocation conversions to/from `Vec`, though not zero-cost:
43    /// - `BinaryHeap` will heapify from `Vec`, but at least that will be empty.
44    /// - `VecDeque` has to shift items to offset 0 when converting to `Vec`.
45    #[allow(missing_debug_implementations)]
46    pub(super) struct DrainGuard<'a, T, C: From<Vec<T>>> {
47        collection: &'a mut C,
48        vec: Vec<T>,
49    }
50
51    impl<'a, T, C> DrainGuard<'a, T, C>
52    where
53        C: Default + From<Vec<T>>,
54        Vec<T>: From<C>,
55    {
56        pub(super) fn new(collection: &'a mut C) -> Self {
57            Self {
58                // Temporarily steal the inner `Vec` so we can drain in place.
59                vec: Vec::from(mem::take(collection)),
60                collection,
61            }
62        }
63    }
64
65    impl<'a, T, C: From<Vec<T>>> Drop for DrainGuard<'a, T, C> {
66        fn drop(&mut self) {
67            // Restore the collection from the `Vec` with its original capacity.
68            *self.collection = C::from(mem::take(&mut self.vec));
69        }
70    }
71
72    impl<'a, T, C> ParallelDrainRange<usize> for &'a mut DrainGuard<'_, T, C>
73    where
74        T: Send,
75        C: From<Vec<T>>,
76    {
77        type Iter = crate::vec::Drain<'a, T>;
78        type Item = T;
79
80        fn par_drain<R: RangeBounds<usize>>(self, range: R) -> Self::Iter {
81            self.vec.par_drain(range)
82        }
83    }
84}
rayon/collections/mod.rs

rayon/collections/
mod.rs
