Jakub Kotur | 041839c | 2020-12-21 17:28:15 +0100 | [diff] [blame] | 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 | |
| 8 | use crate::iter::plumbing::*; |
| 9 | use crate::iter::*; |
| 10 | use 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)] |
| 22 | pub struct IntoIter<T: Send> { |
| 23 | opt: Option<T>, |
| 24 | } |
| 25 | |
| 26 | impl<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 | |
| 35 | impl<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 | |
| 50 | impl<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)] |
| 87 | pub struct Iter<'a, T: Sync> { |
| 88 | inner: IntoIter<&'a T>, |
| 89 | } |
| 90 | |
| 91 | impl<'a, T: Sync> Clone for Iter<'a, T> { |
| 92 | fn clone(&self) -> Self { |
| 93 | Iter { |
| 94 | inner: self.inner.clone(), |
| 95 | } |
| 96 | } |
| 97 | } |
| 98 | |
| 99 | impl<'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 | |
| 110 | delegate_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)] |
| 125 | pub struct IterMut<'a, T: Send> { |
| 126 | inner: IntoIter<&'a mut T>, |
| 127 | } |
| 128 | |
| 129 | impl<'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 | |
| 140 | delegate_indexed_iterator! { |
| 141 | IterMut<'a, T> => &'a mut T, |
| 142 | impl<'a, T: Send + 'a> |
| 143 | } |
| 144 | |
| 145 | /// Private producer for an option |
| 146 | struct OptionProducer<T: Send> { |
| 147 | opt: Option<T>, |
| 148 | } |
| 149 | |
| 150 | impl<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`. |
| 173 | impl<C, T> FromParallelIterator<Option<T>> for Option<C> |
| 174 | where |
| 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 | } |