rayon/iter/
take.rs

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

rayon/iter/
take.rs
