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: usize = Ord::min(self:base.len(), other: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}
95