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()`]: IndexedParallelIterator::skip()
9#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
10#[derive(Debug, Clone)]
11pub struct Skip<I> {
12    base: I,
13    n: usize,
14}
15
16impl<I> Skip<I>
17where
18    I: IndexedParallelIterator,
19{
20    /// Creates a new `Skip` iterator.
21    pub(super) fn new(base: I, n: usize) -> Self {
22        let n = Ord::min(base.len(), n);
23        Skip { base, n }
24    }
25}
26
27impl<I> ParallelIterator for Skip<I>
28where
29    I: IndexedParallelIterator,
30{
31    type Item = I::Item;
32
33    fn drive_unindexed<C>(self, consumer: C) -> C::Result
34    where
35        C: UnindexedConsumer<Self::Item>,
36    {
37        bridge(self, consumer)
38    }
39
40    fn opt_len(&self) -> Option<usize> {
41        Some(self.len())
42    }
43}
44
45impl<I> IndexedParallelIterator for Skip<I>
46where
47    I: IndexedParallelIterator,
48{
49    fn len(&self) -> usize {
50        self.base.len() - self.n
51    }
52
53    fn drive<C: Consumer<Self::Item>>(self, consumer: C) -> C::Result {
54        bridge(self, consumer)
55    }
56
57    fn with_producer<CB>(self, callback: CB) -> CB::Output
58    where
59        CB: ProducerCallback<Self::Item>,
60    {
61        return self.base.with_producer(Callback {
62            callback,
63            n: self.n,
64        });
65
66        struct Callback<CB> {
67            callback: CB,
68            n: usize,
69        }
70
71        impl<T, CB> ProducerCallback<T> for Callback<CB>
72        where
73            CB: ProducerCallback<T>,
74        {
75            type Output = CB::Output;
76            fn callback<P>(self, base: P) -> CB::Output
77            where
78                P: Producer<Item = T>,
79            {
80                crate::in_place_scope(|scope| {
81                    let Self { callback, n } = self;
82                    let (before_skip, after_skip) = base.split_at(n);
83
84                    // Run the skipped part separately for side effects.
85                    // We'll still get any panics propagated back by the scope.
86                    scope.spawn(move |_| bridge_producer_consumer(n, before_skip, NoopConsumer));
87
88                    callback.callback(after_skip)
89                })
90            }
91        }
92    }
93}
rayon/iter/skip.rs

rayon/iter/
skip.rs
