rayon/iter/
take.rs

1use super::plumbing::*;
2use super::*;
3use std::cmp::min;
4
5/// `Take` is an iterator that iterates over the first `n` elements.
6/// This struct is created by the [`take()`] method on [`IndexedParallelIterator`]
7///
8/// [`take()`]: trait.IndexedParallelIterator.html#method.take
9/// [`IndexedParallelIterator`]: trait.IndexedParallelIterator.html
10#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
11#[derive(Debug, Clone)]
12pub struct Take<I> {
13    base: I,
14    n: usize,
15}
16
17impl<I> Take<I>
18where
19    I: IndexedParallelIterator,
20{
21    /// Creates a new `Take` iterator.
22    pub(super) fn new(base: I, n: usize) -> Self {
23        let n = min(base.len(), n);
24        Take { base, n }
25    }
26}
27
28impl<I> ParallelIterator for Take<I>
29where
30    I: IndexedParallelIterator,
31{
32    type Item = I::Item;
33
34    fn drive_unindexed<C>(self, consumer: C) -> C::Result
35    where
36        C: UnindexedConsumer<Self::Item>,
37    {
38        bridge(self, consumer)
39    }
40
41    fn opt_len(&self) -> Option<usize> {
42        Some(self.len())
43    }
44}
45
46impl<I> IndexedParallelIterator for Take<I>
47where
48    I: IndexedParallelIterator,
49{
50    fn len(&self) -> usize {
51        self.n
52    }
53
54    fn drive<C: Consumer<Self::Item>>(self, consumer: C) -> C::Result {
55        bridge(self, consumer)
56    }
57
58    fn with_producer<CB>(self, callback: CB) -> CB::Output
59    where
60        CB: ProducerCallback<Self::Item>,
61    {
62        return self.base.with_producer(Callback {
63            callback,
64            n: self.n,
65        });
66
67        struct Callback<CB> {
68            callback: CB,
69            n: usize,
70        }
71
72        impl<T, CB> ProducerCallback<T> for Callback<CB>
73        where
74            CB: ProducerCallback<T>,
75        {
76            type Output = CB::Output;
77            fn callback<P>(self, base: P) -> CB::Output
78            where
79                P: Producer<Item = T>,
80            {
81                let (producer, _) = base.split_at(self.n);
82                self.callback.callback(producer)
83            }
84        }
85    }
86}
rayon/iter/take.rs

rayon/iter/
take.rs
