rayon/iter/
skip.rs

1use super::noop::NoopConsumer;
2use super::plumbing::*;
3use super::*;
4use std::cmp::min;
5
6/// `Skip` is an iterator that skips over the first `n` elements.
7/// This struct is created by the [`skip()`] method on [`IndexedParallelIterator`]
8///
9/// [`skip()`]: trait.IndexedParallelIterator.html#method.skip
10/// [`IndexedParallelIterator`]: trait.IndexedParallelIterator.html
11#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
12#[derive(Debug, Clone)]
13pub struct Skip<I> {
14    base: I,
15    n: usize,
16}
17
18impl<I> Skip<I>
19where
20    I: IndexedParallelIterator,
21{
22    /// Creates a new `Skip` iterator.
23    pub(super) fn new(base: I, n: usize) -> Self {
24        let n = min(base.len(), n);
25        Skip { base, n }
26    }
27}
28
29impl<I> ParallelIterator for Skip<I>
30where
31    I: IndexedParallelIterator,
32{
33    type Item = I::Item;
34
35    fn drive_unindexed<C>(self, consumer: C) -> C::Result
36    where
37        C: UnindexedConsumer<Self::Item>,
38    {
39        bridge(self, consumer)
40    }
41
42    fn opt_len(&self) -> Option<usize> {
43        Some(self.len())
44    }
45}
46
47impl<I> IndexedParallelIterator for Skip<I>
48where
49    I: IndexedParallelIterator,
50{
51    fn len(&self) -> usize {
52        self.base.len() - self.n
53    }
54
55    fn drive<C: Consumer<Self::Item>>(self, consumer: C) -> C::Result {
56        bridge(self, consumer)
57    }
58
59    fn with_producer<CB>(self, callback: CB) -> CB::Output
60    where
61        CB: ProducerCallback<Self::Item>,
62    {
63        return self.base.with_producer(Callback {
64            callback,
65            n: self.n,
66        });
67
68        struct Callback<CB> {
69            callback: CB,
70            n: usize,
71        }
72
73        impl<T, CB> ProducerCallback<T> for Callback<CB>
74        where
75            CB: ProducerCallback<T>,
76        {
77            type Output = CB::Output;
78            fn callback<P>(self, base: P) -> CB::Output
79            where
80                P: Producer<Item = T>,
81            {
82                crate::in_place_scope(|scope| {
83                    let Self { callback, n } = self;
84                    let (before_skip, after_skip) = base.split_at(n);
85
86                    // Run the skipped part separately for side effects.
87                    // We'll still get any panics propagated back by the scope.
88                    scope.spawn(move |_| bridge_producer_consumer(n, before_skip, NoopConsumer));
89
90                    callback.callback(after_skip)
91                })
92            }
93        }
94    }
95}
rayon/iter/skip.rs

rayon/iter/
skip.rs
