rayon/iter/
step_by.rs

1use std::cmp::min;
2
3use super::plumbing::*;
4use super::*;
5use crate::math::div_round_up;
6use std::iter;
7use std::usize;
8
9/// `StepBy` is an iterator that skips `n` elements between each yield, where `n` is the given step.
10/// This struct is created by the [`step_by()`] method on [`IndexedParallelIterator`]
11///
12/// [`step_by()`]: trait.IndexedParallelIterator.html#method.step_by
13/// [`IndexedParallelIterator`]: trait.IndexedParallelIterator.html
14#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
15#[derive(Debug, Clone)]
16pub struct StepBy<I: IndexedParallelIterator> {
17    base: I,
18    step: usize,
19}
20
21impl<I> StepBy<I>
22where
23    I: IndexedParallelIterator,
24{
25    /// Creates a new `StepBy` iterator.
26    pub(super) fn new(base: I, step: usize) -> Self {
27        StepBy { base, step }
28    }
29}
30
31impl<I> ParallelIterator for StepBy<I>
32where
33    I: IndexedParallelIterator,
34{
35    type Item = I::Item;
36
37    fn drive_unindexed<C>(self, consumer: C) -> C::Result
38    where
39        C: UnindexedConsumer<Self::Item>,
40    {
41        bridge(self, consumer)
42    }
43
44    fn opt_len(&self) -> Option<usize> {
45        Some(self.len())
46    }
47}
48
49impl<I> IndexedParallelIterator for StepBy<I>
50where
51    I: IndexedParallelIterator,
52{
53    fn drive<C: Consumer<Self::Item>>(self, consumer: C) -> C::Result {
54        bridge(self, consumer)
55    }
56
57    fn len(&self) -> usize {
58        div_round_up(self.base.len(), self.step)
59    }
60
61    fn with_producer<CB>(self, callback: CB) -> CB::Output
62    where
63        CB: ProducerCallback<Self::Item>,
64    {
65        let len = self.base.len();
66        return self.base.with_producer(Callback {
67            callback,
68            step: self.step,
69            len,
70        });
71
72        struct Callback<CB> {
73            callback: CB,
74            step: usize,
75            len: usize,
76        }
77
78        impl<T, CB> ProducerCallback<T> for Callback<CB>
79        where
80            CB: ProducerCallback<T>,
81        {
82            type Output = CB::Output;
83            fn callback<P>(self, base: P) -> CB::Output
84            where
85                P: Producer<Item = T>,
86            {
87                let producer = StepByProducer {
88                    base,
89                    step: self.step,
90                    len: self.len,
91                };
92                self.callback.callback(producer)
93            }
94        }
95    }
96}
97
98/// ////////////////////////////////////////////////////////////////////////
99/// Producer implementation
100
101struct StepByProducer<P> {
102    base: P,
103    step: usize,
104    len: usize,
105}
106
107impl<P> Producer for StepByProducer<P>
108where
109    P: Producer,
110{
111    type Item = P::Item;
112    type IntoIter = iter::StepBy<P::IntoIter>;
113
114    fn into_iter(self) -> Self::IntoIter {
115        self.base.into_iter().step_by(self.step)
116    }
117
118    fn split_at(self, index: usize) -> (Self, Self) {
119        let elem_index = min(index * self.step, self.len);
120
121        let (left, right) = self.base.split_at(elem_index);
122        (
123            StepByProducer {
124                base: left,
125                step: self.step,
126                len: elem_index,
127            },
128            StepByProducer {
129                base: right,
130                step: self.step,
131                len: self.len - elem_index,
132            },
133        )
134    }
135
136    fn min_len(&self) -> usize {
137        div_round_up(self.base.min_len(), self.step)
138    }
139
140    fn max_len(&self) -> usize {
141        self.base.max_len() / self.step
142    }
143}
rayon/iter/step_by.rs

rayon/iter/
step_by.rs
