par_iter/iter/
step_by.rs

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

par_iter/iter/
step_by.rs
