1use super::plumbing::*;
2use super::*;
3use std::iter;
4use std::ops::Range;
5use std::usize;
6
7/// `Enumerate` is an iterator that returns the current count along with the element.
8/// This struct is created by the [`enumerate()`] method on [`IndexedParallelIterator`]
9///
10/// [`enumerate()`]: trait.IndexedParallelIterator.html#method.enumerate
11/// [`IndexedParallelIterator`]: trait.IndexedParallelIterator.html
12#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
13#[derive(Debug, Clone)]
14pub struct Enumerate<I: IndexedParallelIterator> {
15 base: I,
16}
17
18impl<I> Enumerate<I>
19where
20 I: IndexedParallelIterator,
21{
22 /// Creates a new `Enumerate` iterator.
23 pub(super) fn new(base: I) -> Self {
24 Enumerate { base }
25 }
26}
27
28impl<I> ParallelIterator for Enumerate<I>
29where
30 I: IndexedParallelIterator,
31{
32 type Item = (usize, 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 Enumerate<I>
47where
48 I: IndexedParallelIterator,
49{
50 fn drive<C: Consumer<Self::Item>>(self, consumer: C) -> C::Result {
51 bridge(self, consumer)
52 }
53
54 fn len(&self) -> usize {
55 self.base.len()
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 { callback });
63
64 struct Callback<CB> {
65 callback: CB,
66 }
67
68 impl<I, CB> ProducerCallback<I> for Callback<CB>
69 where
70 CB: ProducerCallback<(usize, I)>,
71 {
72 type Output = CB::Output;
73 fn callback<P>(self, base: P) -> CB::Output
74 where
75 P: Producer<Item = I>,
76 {
77 let producer = EnumerateProducer { base, offset: 0 };
78 self.callback.callback(producer)
79 }
80 }
81 }
82}
83
84/// ////////////////////////////////////////////////////////////////////////
85/// Producer implementation
86
87struct EnumerateProducer<P> {
88 base: P,
89 offset: usize,
90}
91
92impl<P> Producer for EnumerateProducer<P>
93where
94 P: Producer,
95{
96 type Item = (usize, P::Item);
97 type IntoIter = iter::Zip<Range<usize>, P::IntoIter>;
98
99 fn into_iter(self) -> Self::IntoIter {
100 // Enumerate only works for IndexedParallelIterators. Since those
101 // have a max length of usize::MAX, their max index is
102 // usize::MAX - 1, so the range 0..usize::MAX includes all
103 // possible indices.
104 //
105 // However, we should to use a precise end to the range, otherwise
106 // reversing the iterator may have to walk back a long ways before
107 // `Zip::next_back` can produce anything.
108 let base = self.base.into_iter();
109 let end = self.offset + base.len();
110 (self.offset..end).zip(base)
111 }
112
113 fn min_len(&self) -> usize {
114 self.base.min_len()
115 }
116 fn max_len(&self) -> usize {
117 self.base.max_len()
118 }
119
120 fn split_at(self, index: usize) -> (Self, Self) {
121 let (left, right) = self.base.split_at(index);
122 (
123 EnumerateProducer {
124 base: left,
125 offset: self.offset,
126 },
127 EnumerateProducer {
128 base: right,
129 offset: self.offset + index,
130 },
131 )
132 }
133}
134