rayon/iter/
positions.rs

1use super::plumbing::*;
2use super::*;
3
4use std::fmt::{self, Debug};
5
6/// `Positions` takes a predicate `predicate` and filters out elements that match,
7/// yielding their indices.
8///
9/// This struct is created by the [`positions()`] method on [`IndexedParallelIterator`]
10///
11/// [`positions()`]: trait.IndexedParallelIterator.html#method.positions
12/// [`IndexedParallelIterator`]: trait.IndexedParallelIterator.html
13#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
14#[derive(Clone)]
15pub struct Positions<I: IndexedParallelIterator, P> {
16    base: I,
17    predicate: P,
18}
19
20impl<I: IndexedParallelIterator + Debug, P> Debug for Positions<I, P> {
21    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
22        f.debug_struct("Positions")
23            .field("base", &self.base)
24            .finish()
25    }
26}
27
28impl<I, P> Positions<I, P>
29where
30    I: IndexedParallelIterator,
31{
32    /// Create a new `Positions` iterator.
33    pub(super) fn new(base: I, predicate: P) -> Self {
34        Positions { base, predicate }
35    }
36}
37
38impl<I, P> ParallelIterator for Positions<I, P>
39where
40    I: IndexedParallelIterator,
41    P: Fn(I::Item) -> bool + Sync + Send,
42{
43    type Item = usize;
44
45    fn drive_unindexed<C>(self, consumer: C) -> C::Result
46    where
47        C: UnindexedConsumer<Self::Item>,
48    {
49        let consumer1 = PositionsConsumer::new(consumer, &self.predicate, 0);
50        self.base.drive(consumer1)
51    }
52}
53
54/// ////////////////////////////////////////////////////////////////////////
55/// Consumer implementation
56
57struct PositionsConsumer<'p, C, P> {
58    base: C,
59    predicate: &'p P,
60    offset: usize,
61}
62
63impl<'p, C, P> PositionsConsumer<'p, C, P> {
64    fn new(base: C, predicate: &'p P, offset: usize) -> Self {
65        PositionsConsumer {
66            base,
67            predicate,
68            offset,
69        }
70    }
71}
72
73impl<'p, T, C, P> Consumer<T> for PositionsConsumer<'p, C, P>
74where
75    C: Consumer<usize>,
76    P: Fn(T) -> bool + Sync,
77{
78    type Folder = PositionsFolder<'p, C::Folder, P>;
79    type Reducer = C::Reducer;
80    type Result = C::Result;
81
82    fn split_at(self, index: usize) -> (Self, Self, C::Reducer) {
83        let (left, right, reducer) = self.base.split_at(index);
84        (
85            PositionsConsumer::new(left, self.predicate, self.offset),
86            PositionsConsumer::new(right, self.predicate, self.offset + index),
87            reducer,
88        )
89    }
90
91    fn into_folder(self) -> Self::Folder {
92        PositionsFolder {
93            base: self.base.into_folder(),
94            predicate: self.predicate,
95            offset: self.offset,
96        }
97    }
98
99    fn full(&self) -> bool {
100        self.base.full()
101    }
102}
103
104struct PositionsFolder<'p, F, P> {
105    base: F,
106    predicate: &'p P,
107    offset: usize,
108}
109
110impl<F, P, T> Folder<T> for PositionsFolder<'_, F, P>
111where
112    F: Folder<usize>,
113    P: Fn(T) -> bool,
114{
115    type Result = F::Result;
116
117    fn consume(mut self, item: T) -> Self {
118        let index = self.offset;
119        self.offset += 1;
120        if (self.predicate)(item) {
121            self.base = self.base.consume(index);
122        }
123        self
124    }
125
126    // This cannot easily specialize `consume_iter` to be better than
127    // the default, because that requires checking `self.base.full()`
128    // during a call to `self.base.consume_iter()`. (#632)
129
130    fn complete(self) -> Self::Result {
131        self.base.complete()
132    }
133
134    fn full(&self) -> bool {
135        self.base.full()
136    }
137}
rayon/iter/positions.rs

rayon/iter/
positions.rs
