par_iter/iter/
enumerate.rs

1use std::{iter, ops::Range};
2
3use super::{plumbing::*, *};
4
5/// `Enumerate` is an iterator that returns the current count along with the
6/// element. This struct is created by the [`enumerate()`] method on
7/// [`IndexedParallelIterator`]
8///
9/// [`enumerate()`]: trait.IndexedParallelIterator.html#method.enumerate
10/// [`IndexedParallelIterator`]: trait.IndexedParallelIterator.html
11#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
12#[derive(Debug, Clone)]
13pub struct Enumerate<I: IndexedParallelIterator> {
14    base: I,
15}
16
17impl<I> Enumerate<I>
18where
19    I: IndexedParallelIterator,
20{
21    /// Creates a new `Enumerate` iterator.
22    pub(super) fn new(base: I) -> Self {
23        Enumerate { base }
24    }
25}
26
27impl<I> ParallelIterator for Enumerate<I>
28where
29    I: IndexedParallelIterator,
30{
31    type Item = (usize, 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 Enumerate<I>
46where
47    I: IndexedParallelIterator,
48{
49    fn drive<C: Consumer<Self::Item>>(self, consumer: C) -> C::Result {
50        bridge(self, consumer)
51    }
52
53    fn len(&self) -> usize {
54        self.base.len()
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 { callback });
62
63        struct Callback<CB> {
64            callback: CB,
65        }
66
67        impl<I, CB> ProducerCallback<I> for Callback<CB>
68        where
69            CB: ProducerCallback<(usize, I)>,
70        {
71            type Output = CB::Output;
72
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 IntoIter = iter::Zip<Range<usize>, P::IntoIter>;
97    type Item = (usize, P::Item);
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
117    fn max_len(&self) -> usize {
118        self.base.max_len()
119    }
120
121    fn split_at(self, index: usize) -> (Self, Self) {
122        let (left, right) = self.base.split_at(index);
123        (
124            EnumerateProducer {
125                base: left,
126                offset: self.offset,
127            },
128            EnumerateProducer {
129                base: right,
130                offset: self.offset + index,
131            },
132        )
133    }
134}
par_iter/iter/enumerate.rs

par_iter/iter/
enumerate.rs
