rayon/iter/
chunks.rs

1use super::plumbing::*;
2use super::*;
3
4/// `Chunks` is an iterator that groups elements of an underlying iterator.
5///
6/// This struct is created by the [`chunks()`] method on [`IndexedParallelIterator`]
7///
8/// [`chunks()`]: IndexedParallelIterator::chunks()
9#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
10#[derive(Debug, Clone)]
11pub struct Chunks<I> {
12    size: usize,
13    i: I,
14}
15
16impl<I> Chunks<I> {
17    /// Creates a new `Chunks` iterator
18    pub(super) fn new(i: I, size: usize) -> Self {
19        Chunks { i, size }
20    }
21}
22
23impl<I> ParallelIterator for Chunks<I>
24where
25    I: IndexedParallelIterator,
26{
27    type Item = Vec<I::Item>;
28
29    fn drive_unindexed<C>(self, consumer: C) -> C::Result
30    where
31        C: Consumer<Vec<I::Item>>,
32    {
33        bridge(self, consumer)
34    }
35
36    fn opt_len(&self) -> Option<usize> {
37        Some(self.len())
38    }
39}
40
41impl<I> IndexedParallelIterator for Chunks<I>
42where
43    I: IndexedParallelIterator,
44{
45    fn drive<C>(self, consumer: C) -> C::Result
46    where
47        C: Consumer<Self::Item>,
48    {
49        bridge(self, consumer)
50    }
51
52    fn len(&self) -> usize {
53        self.i.len().div_ceil(self.size)
54    }
55
56    fn with_producer<CB>(self, callback: CB) -> CB::Output
57    where
58        CB: ProducerCallback<Self::Item>,
59    {
60        let len = self.i.len();
61        return self.i.with_producer(Callback {
62            size: self.size,
63            len,
64            callback,
65        });
66
67        struct Callback<CB> {
68            size: usize,
69            len: usize,
70            callback: CB,
71        }
72
73        impl<T, CB> ProducerCallback<T> for Callback<CB>
74        where
75            CB: ProducerCallback<Vec<T>>,
76        {
77            type Output = CB::Output;
78
79            fn callback<P>(self, base: P) -> CB::Output
80            where
81                P: Producer<Item = T>,
82            {
83                let producer = ChunkProducer::new(self.size, self.len, base, Vec::from_iter);
84                self.callback.callback(producer)
85            }
86        }
87    }
88}
89
90pub(super) struct ChunkProducer<P, F> {
91    chunk_size: usize,
92    len: usize,
93    base: P,
94    map: F,
95}
96
97impl<P, F> ChunkProducer<P, F> {
98    pub(super) fn new(chunk_size: usize, len: usize, base: P, map: F) -> Self {
99        Self {
100            chunk_size,
101            len,
102            base,
103            map,
104        }
105    }
106}
107
108impl<P, F, T> Producer for ChunkProducer<P, F>
109where
110    P: Producer,
111    F: Fn(P::IntoIter) -> T + Send + Clone,
112{
113    type Item = T;
114    type IntoIter = std::iter::Map<ChunkSeq<P>, F>;
115
116    fn into_iter(self) -> Self::IntoIter {
117        let chunks = ChunkSeq {
118            chunk_size: self.chunk_size,
119            len: self.len,
120            inner: if self.len > 0 { Some(self.base) } else { None },
121        };
122        chunks.map(self.map)
123    }
124
125    fn split_at(self, index: usize) -> (Self, Self) {
126        let elem_index = Ord::min(index * self.chunk_size, self.len);
127        let (left, right) = self.base.split_at(elem_index);
128        (
129            ChunkProducer {
130                chunk_size: self.chunk_size,
131                len: elem_index,
132                base: left,
133                map: self.map.clone(),
134            },
135            ChunkProducer {
136                chunk_size: self.chunk_size,
137                len: self.len - elem_index,
138                base: right,
139                map: self.map,
140            },
141        )
142    }
143
144    fn min_len(&self) -> usize {
145        self.base.min_len().div_ceil(self.chunk_size)
146    }
147
148    fn max_len(&self) -> usize {
149        self.base.max_len() / self.chunk_size
150    }
151}
152
153pub(super) struct ChunkSeq<P> {
154    chunk_size: usize,
155    len: usize,
156    inner: Option<P>,
157}
158
159impl<P> Iterator for ChunkSeq<P>
160where
161    P: Producer,
162{
163    type Item = P::IntoIter;
164
165    fn next(&mut self) -> Option<Self::Item> {
166        let producer = self.inner.take()?;
167        if self.len > self.chunk_size {
168            let (left, right) = producer.split_at(self.chunk_size);
169            self.inner = Some(right);
170            self.len -= self.chunk_size;
171            Some(left.into_iter())
172        } else {
173            debug_assert!(self.len > 0);
174            self.len = 0;
175            Some(producer.into_iter())
176        }
177    }
178
179    fn size_hint(&self) -> (usize, Option<usize>) {
180        let len = self.len();
181        (len, Some(len))
182    }
183}
184
185impl<P> ExactSizeIterator for ChunkSeq<P>
186where
187    P: Producer,
188{
189    #[inline]
190    fn len(&self) -> usize {
191        self.len.div_ceil(self.chunk_size)
192    }
193}
194
195impl<P> DoubleEndedIterator for ChunkSeq<P>
196where
197    P: Producer,
198{
199    fn next_back(&mut self) -> Option<Self::Item> {
200        let producer = self.inner.take()?;
201        if self.len > self.chunk_size {
202            let mut size = self.len % self.chunk_size;
203            if size == 0 {
204                size = self.chunk_size;
205            }
206            let (left, right) = producer.split_at(self.len - size);
207            self.inner = Some(left);
208            self.len -= size;
209            Some(right.into_iter())
210        } else {
211            debug_assert!(self.len > 0);
212            self.len = 0;
213            Some(producer.into_iter())
214        }
215    }
216}
rayon/iter/chunks.rs

rayon/iter/
chunks.rs
