rayon/
option.rs

1//! Parallel iterator types for [options][std::option]
2//!
3//! You will rarely need to interact with this module directly unless you need
4//! to name one of the iterator types.
5//!
6//! [std::option]: https://doc.rust-lang.org/stable/std/option/
7
8use crate::iter::plumbing::*;
9use crate::iter::*;
10use std::sync::atomic::{AtomicBool, Ordering};
11
12/// A parallel iterator over the value in [`Some`] variant of an [`Option`].
13///
14/// The iterator yields one value if the [`Option`] is a [`Some`], otherwise none.
15///
16/// This `struct` is created by the [`into_par_iter`] function.
17///
18/// [`Option`]: https://doc.rust-lang.org/std/option/enum.Option.html
19/// [`Some`]: https://doc.rust-lang.org/std/option/enum.Option.html#variant.Some
20/// [`into_par_iter`]: ../iter/trait.IntoParallelIterator.html#tymethod.into_par_iter
21#[derive(Debug, Clone)]
22pub struct IntoIter<T: Send> {
23    opt: Option<T>,
24}
25
26impl<T: Send> IntoParallelIterator for Option<T> {
27    type Item = T;
28    type Iter = IntoIter<T>;
29
30    fn into_par_iter(self) -> Self::Iter {
31        IntoIter { opt: self }
32    }
33}
34
35impl<T: Send> ParallelIterator for IntoIter<T> {
36    type Item = T;
37
38    fn drive_unindexed<C>(self, consumer: C) -> C::Result
39    where
40        C: UnindexedConsumer<Self::Item>,
41    {
42        self.drive(consumer)
43    }
44
45    fn opt_len(&self) -> Option<usize> {
46        Some(self.len())
47    }
48}
49
50impl<T: Send> IndexedParallelIterator for IntoIter<T> {
51    fn drive<C>(self, consumer: C) -> C::Result
52    where
53        C: Consumer<Self::Item>,
54    {
55        let mut folder = consumer.into_folder();
56        if let Some(item) = self.opt {
57            folder = folder.consume(item);
58        }
59        folder.complete()
60    }
61
62    fn len(&self) -> usize {
63        match self.opt {
64            Some(_) => 1,
65            None => 0,
66        }
67    }
68
69    fn with_producer<CB>(self, callback: CB) -> CB::Output
70    where
71        CB: ProducerCallback<Self::Item>,
72    {
73        callback.callback(OptionProducer { opt: self.opt })
74    }
75}
76
77/// A parallel iterator over a reference to the [`Some`] variant of an [`Option`].
78///
79/// The iterator yields one value if the [`Option`] is a [`Some`], otherwise none.
80///
81/// This `struct` is created by the [`par_iter`] function.
82///
83/// [`Option`]: https://doc.rust-lang.org/std/option/enum.Option.html
84/// [`Some`]: https://doc.rust-lang.org/std/option/enum.Option.html#variant.Some
85/// [`par_iter`]: ../iter/trait.IntoParallelRefIterator.html#tymethod.par_iter
86#[derive(Debug)]
87pub struct Iter<'a, T: Sync> {
88    inner: IntoIter<&'a T>,
89}
90
91impl<'a, T: Sync> Clone for Iter<'a, T> {
92    fn clone(&self) -> Self {
93        Iter {
94            inner: self.inner.clone(),
95        }
96    }
97}
98
99impl<'a, T: Sync> IntoParallelIterator for &'a Option<T> {
100    type Item = &'a T;
101    type Iter = Iter<'a, T>;
102
103    fn into_par_iter(self) -> Self::Iter {
104        Iter {
105            inner: self.as_ref().into_par_iter(),
106        }
107    }
108}
109
110delegate_indexed_iterator! {
111    Iter<'a, T> => &'a T,
112    impl<'a, T: Sync + 'a>
113}
114
115/// A parallel iterator over a mutable reference to the [`Some`] variant of an [`Option`].
116///
117/// The iterator yields one value if the [`Option`] is a [`Some`], otherwise none.
118///
119/// This `struct` is created by the [`par_iter_mut`] function.
120///
121/// [`Option`]: https://doc.rust-lang.org/std/option/enum.Option.html
122/// [`Some`]: https://doc.rust-lang.org/std/option/enum.Option.html#variant.Some
123/// [`par_iter_mut`]: ../iter/trait.IntoParallelRefMutIterator.html#tymethod.par_iter_mut
124#[derive(Debug)]
125pub struct IterMut<'a, T: Send> {
126    inner: IntoIter<&'a mut T>,
127}
128
129impl<'a, T: Send> IntoParallelIterator for &'a mut Option<T> {
130    type Item = &'a mut T;
131    type Iter = IterMut<'a, T>;
132
133    fn into_par_iter(self) -> Self::Iter {
134        IterMut {
135            inner: self.as_mut().into_par_iter(),
136        }
137    }
138}
139
140delegate_indexed_iterator! {
141    IterMut<'a, T> => &'a mut T,
142    impl<'a, T: Send + 'a>
143}
144
145/// Private producer for an option
146struct OptionProducer<T: Send> {
147    opt: Option<T>,
148}
149
150impl<T: Send> Producer for OptionProducer<T> {
151    type Item = T;
152    type IntoIter = std::option::IntoIter<T>;
153
154    fn into_iter(self) -> Self::IntoIter {
155        self.opt.into_iter()
156    }
157
158    fn split_at(self, index: usize) -> (Self, Self) {
159        debug_assert!(index <= 1);
160        let none = OptionProducer { opt: None };
161        if index == 0 {
162            (none, self)
163        } else {
164            (self, none)
165        }
166    }
167}
168
169/// Collect an arbitrary `Option`-wrapped collection.
170///
171/// If any item is `None`, then all previous items collected are discarded,
172/// and it returns only `None`.
173impl<C, T> FromParallelIterator<Option<T>> for Option<C>
174where
175    C: FromParallelIterator<T>,
176    T: Send,
177{
178    fn from_par_iter<I>(par_iter: I) -> Self
179    where
180        I: IntoParallelIterator<Item = Option<T>>,
181    {
182        fn check<T>(found_none: &AtomicBool) -> impl Fn(&Option<T>) + '_ {
183            move |item| {
184                if item.is_none() {
185                    found_none.store(true, Ordering::Relaxed);
186                }
187            }
188        }
189
190        let found_none = AtomicBool::new(false);
191        let collection = par_iter
192            .into_par_iter()
193            .inspect(check(&found_none))
194            .while_some()
195            .collect();
196
197        if found_none.load(Ordering::Relaxed) {
198            None
199        } else {
200            Some(collection)
201        }
202    }
203}
rayon/option.rs

rayon/
option.rs
