rayon/iter/
skip.rs

1use super::noop::NoopConsumer;
2use super::plumbing::*;
3use super::*;
4
5/// `Skip` is an iterator that skips over the first `n` elements.
6/// This struct is created by the [`skip()`] method on [`IndexedParallelIterator`]
7///
8/// [`skip()`]: trait.IndexedParallelIterator.html#method.skip
9/// [`IndexedParallelIterator`]: trait.IndexedParallelIterator.html
10#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
11#[derive(Debug, Clone)]
12pub struct Skip<I> {
13    base: I,
14    n: usize,
15}
16
17impl<I> Skip<I>
18where
19    I: IndexedParallelIterator,
20{
21    /// Creates a new `Skip` iterator.
22    pub(super) fn new(base: I, n: usize) -> Self {
23        let n = Ord::min(base.len(), n);
24        Skip { base, n }
25    }
26}
27
28impl<I> ParallelIterator for Skip<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 Skip<I>
47where
48    I: IndexedParallelIterator,
49{
50    fn len(&self) -> usize {
51        self.base.len() - 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                crate::in_place_scope(|scope| {
82                    let Self { callback, n } = self;
83                    let (before_skip, after_skip) = base.split_at(n);
84
85                    // Run the skipped part separately for side effects.
86                    // We'll still get any panics propagated back by the scope.
87                    scope.spawn(move |_| bridge_producer_consumer(n, before_skip, NoopConsumer));
88
89                    callback.callback(after_skip)
90                })
91            }
92        }
93    }
94}
rayon/iter/skip.rs

rayon/iter/
skip.rs
