vendor/rustc-rayon/src/iter/positions.rs

   1 use super::plumbing::*;
   2 use super::*;
   3
   4 use std::fmt::{self, Debug};
   5
   6 /// `Positions` takes a predicate `predicate` and filters out elements that match,
   7 /// yielding their indices.
   8 ///
   9 /// This struct is created by the [`positions()`] method on [`IndexedParallelIterator`]
  10 ///
  11 /// [`positions()`]: trait.IndexedParallelIterator.html#method.positions
  12 /// [`IndexedParallelIterator`]: trait.IndexedParallelIterator.html
  13 #[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
  14 #[derive(Clone)]
  15 pub struct Positions<I: IndexedParallelIterator, P> {
  16     base: I,
  17     predicate: P,
  18 }
  19
  20 impl<I: IndexedParallelIterator + Debug, P> Debug for Positions<I, P> {
  21     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
  22         f.debug_struct("Positions")
  23             .field("base", &self.base)
  24             .finish()
  25     }
  26 }
  27
  28 impl<I, P> Positions<I, P>
  29 where
  30     I: IndexedParallelIterator,
  31 {
  32     /// Create a new `Positions` iterator.
  33     pub(super) fn new(base: I, predicate: P) -> Self {
  34         Positions { base, predicate }
  35     }
  36 }
  37
  38 impl<I, P> ParallelIterator for Positions<I, P>
  39 where
  40     I: IndexedParallelIterator,
  41     P: Fn(I::Item) -> bool + Sync + Send,
  42 {
  43     type Item = usize;
  44
  45     fn drive_unindexed<C>(self, consumer: C) -> C::Result
  46     where
  47         C: UnindexedConsumer<Self::Item>,
  48     {
  49         let consumer1 = PositionsConsumer::new(consumer, &self.predicate, 0);
  50         self.base.drive(consumer1)
  51     }
  52 }
  53
  54 /// ////////////////////////////////////////////////////////////////////////
  55 /// Consumer implementation
  56
  57 struct PositionsConsumer<'p, C, P> {
  58     base: C,
  59     predicate: &'p P,
  60     offset: usize,
  61 }
  62
  63 impl<'p, C, P> PositionsConsumer<'p, C, P> {
  64     fn new(base: C, predicate: &'p P, offset: usize) -> Self {
  65         PositionsConsumer {
  66             base,
  67             predicate,
  68             offset,
  69         }
  70     }
  71 }
  72
  73 impl<'p, T, C, P> Consumer<T> for PositionsConsumer<'p, C, P>
  74 where
  75     C: Consumer<usize>,
  76     P: Fn(T) -> bool + Sync,
  77 {
  78     type Folder = PositionsFolder<'p, C::Folder, P>;
  79     type Reducer = C::Reducer;
  80     type Result = C::Result;
  81
  82     fn split_at(self, index: usize) -> (Self, Self, C::Reducer) {
  83         let (left, right, reducer) = self.base.split_at(index);
  84         (
  85             PositionsConsumer::new(left, self.predicate, self.offset),
  86             PositionsConsumer::new(right, self.predicate, self.offset + index),
  87             reducer,
  88         )
  89     }
  90
  91     fn into_folder(self) -> Self::Folder {
  92         PositionsFolder {
  93             base: self.base.into_folder(),
  94             predicate: self.predicate,
  95             offset: self.offset,
  96         }
  97     }
  98
  99     fn full(&self) -> bool {
 100         self.base.full()
 101     }
 102 }
 103
 104 struct PositionsFolder<'p, F, P> {
 105     base: F,
 106     predicate: &'p P,
 107     offset: usize,
 108 }
 109
 110 impl<F, P, T> Folder<T> for PositionsFolder<'_, F, P>
 111 where
 112     F: Folder<usize>,
 113     P: Fn(T) -> bool,
 114 {
 115     type Result = F::Result;
 116
 117     fn consume(mut self, item: T) -> Self {
 118         let index = self.offset;
 119         self.offset += 1;
 120         if (self.predicate)(item) {
 121             self.base = self.base.consume(index);
 122         }
 123         self
 124     }
 125
 126     // This cannot easily specialize `consume_iter` to be better than
 127     // the default, because that requires checking `self.base.full()`
 128     // during a call to `self.base.consume_iter()`. (#632)
 129
 130     fn complete(self) -> Self::Result {
 131         self.base.complete()
 132     }
 133
 134     fn full(&self) -> bool {
 135         self.base.full()
 136     }
 137 }