1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137

use super::plumbing::*;
use super::*;

use std::fmt::{self, Debug};

/// `Positions` takes a predicate `predicate` and filters out elements that match,
/// yielding their indices.
///
/// This struct is created by the [`positions()`] method on [`IndexedParallelIterator`]
///
/// [`positions()`]: trait.IndexedParallelIterator.html#method.positions
/// [`IndexedParallelIterator`]: trait.IndexedParallelIterator.html
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
#[derive(Clone)]
pub struct Positions<I: IndexedParallelIterator, P> {
    base: I,
    predicate: P,
}

impl<I: IndexedParallelIterator + Debug, P> Debug for Positions<I, P> {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_struct("Positions")
            .field("base", &self.base)
            .finish()
    }
}

impl<I, P> Positions<I, P>
where
    I: IndexedParallelIterator,
{
    /// Create a new `Positions` iterator.
    pub(super) fn new(base: I, predicate: P) -> Self {
        Positions { base, predicate }
    }
}

impl<I, P> ParallelIterator for Positions<I, P>
where
    I: IndexedParallelIterator,
    P: Fn(I::Item) -> bool + Sync + Send,
{
    type Item = usize;

    fn drive_unindexed<C>(self, consumer: C) -> C::Result
    where
        C: UnindexedConsumer<Self::Item>,
    {
        let consumer1 = PositionsConsumer::new(consumer, &self.predicate, 0);
        self.base.drive(consumer1)
    }
}

/// ////////////////////////////////////////////////////////////////////////
/// Consumer implementation

struct PositionsConsumer<'p, C, P> {
    base: C,
    predicate: &'p P,
    offset: usize,
}

impl<'p, C, P> PositionsConsumer<'p, C, P> {
    fn new(base: C, predicate: &'p P, offset: usize) -> Self {
        PositionsConsumer {
            base,
            predicate,
            offset,
        }
    }
}

impl<'p, T, C, P> Consumer<T> for PositionsConsumer<'p, C, P>
where
    C: Consumer<usize>,
    P: Fn(T) -> bool + Sync,
{
    type Folder = PositionsFolder<'p, C::Folder, P>;
    type Reducer = C::Reducer;
    type Result = C::Result;

    fn split_at(self, index: usize) -> (Self, Self, C::Reducer) {
        let (left, right, reducer) = self.base.split_at(index);
        (
            PositionsConsumer::new(left, self.predicate, self.offset),
            PositionsConsumer::new(right, self.predicate, self.offset + index),
            reducer,
        )
    }

    fn into_folder(self) -> Self::Folder {
        PositionsFolder {
            base: self.base.into_folder(),
            predicate: self.predicate,
            offset: self.offset,
        }
    }

    fn full(&self) -> bool {
        self.base.full()
    }
}

struct PositionsFolder<'p, F, P> {
    base: F,
    predicate: &'p P,
    offset: usize,
}

impl<F, P, T> Folder<T> for PositionsFolder<'_, F, P>
where
    F: Folder<usize>,
    P: Fn(T) -> bool,
{
    type Result = F::Result;

    fn consume(mut self, item: T) -> Self {
        let index = self.offset;
        self.offset += 1;
        if (self.predicate)(item) {
            self.base = self.base.consume(index);
        }
        self
    }

    // This cannot easily specialize `consume_iter` to be better than
    // the default, because that requires checking `self.base.full()`
    // during a call to `self.base.consume_iter()`. (#632)

    fn complete(self) -> Self::Result {
        self.base.complete()
    }

    fn full(&self) -> bool {
        self.base.full()
    }
}