rayon/iter/
enumerate.rs

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}
rayon/iter/enumerate.rs

rayon/iter/
enumerate.rs
