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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. | |
10 | macro_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 | ||
24 | pub mod binary_heap; | |
25 | pub mod btree_map; | |
26 | pub mod btree_set; | |
27 | pub mod hash_map; | |
28 | pub mod hash_set; | |
29 | pub mod linked_list; | |
30 | pub mod vec_deque; | |
923072b8 FG |
31 | |
32 | use self::drain_guard::DrainGuard; | |
33 | ||
34 | mod 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. | |
353b0b11 | 59 | vec: Vec::from(mem::take(collection)), |
923072b8 FG |
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. | |
353b0b11 | 68 | *self.collection = C::from(mem::take(&mut self.vec)); |
923072b8 FG |
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 | } |