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()`]: trait.IndexedParallelIterator.html#method.take
8/// [`IndexedParallelIterator`]: trait.IndexedParallelIterator.html
9#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
10#[derive(Debug, Clone)]
11pub struct Take<I> {
12 base: I,
13 n: usize,
14}
15
16impl<I> Take<I>
17where
18 I: IndexedParallelIterator,
19{
20 /// Creates a new `Take` iterator.
21 pub(super) fn new(base: I, n: usize) -> Self {
22 let n: usize = Ord::min(self:base.len(), other:n);
23 Take { base, n }
24 }
25}
26
27impl<I> ParallelIterator for Take<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 Take<I>
46where
47 I: IndexedParallelIterator,
48{
49 fn len(&self) -> usize {
50 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 let (producer, _) = base.split_at(self.n);
81 self.callback.callback(producer)
82 }
83 }
84 }
85}
86