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

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

/// `FlattenIter` turns each element to a serial iterator, then flattens these iterators
/// together. This struct is created by the [`flatten_iter()`] method on [`ParallelIterator`].
///
/// [`flatten_iter()`]: trait.ParallelIterator.html#method.flatten_iter
/// [`ParallelIterator`]: trait.ParallelIterator.html
#[must_use = "iterator adaptors are lazy and do nothing unless consumed"]
#[derive(Debug, Clone)]
pub struct FlattenIter<I: ParallelIterator> {
    base: I,
}

impl<I> FlattenIter<I>
where
    I: ParallelIterator,
    I::Item: IntoIterator,
    <I::Item as IntoIterator>::Item: Send,
{
    /// Creates a new `FlattenIter` iterator.
    pub(super) fn new(base: I) -> Self {
        FlattenIter { base }
    }
}

impl<I> ParallelIterator for FlattenIter<I>
where
    I: ParallelIterator,
    I::Item: IntoIterator,
    <I::Item as IntoIterator>::Item: Send,
{
    type Item = <I::Item as IntoIterator>::Item;

    fn drive_unindexed<C>(self, consumer: C) -> C::Result
    where
        C: UnindexedConsumer<Self::Item>,
    {
        let consumer = FlattenIterConsumer::new(consumer);
        self.base.drive_unindexed(consumer)
    }
}

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

struct FlattenIterConsumer<C> {
    base: C,
}

impl<C> FlattenIterConsumer<C> {
    fn new(base: C) -> Self {
        FlattenIterConsumer { base }
    }
}

impl<T, C> Consumer<T> for FlattenIterConsumer<C>
where
    C: UnindexedConsumer<T::Item>,
    T: IntoIterator,
{
    type Folder = FlattenIterFolder<C::Folder>;
    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);
        (
            FlattenIterConsumer::new(left),
            FlattenIterConsumer::new(right),
            reducer,
        )
    }

    fn into_folder(self) -> Self::Folder {
        FlattenIterFolder {
            base: self.base.into_folder(),
        }
    }

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

impl<T, C> UnindexedConsumer<T> for FlattenIterConsumer<C>
where
    C: UnindexedConsumer<T::Item>,
    T: IntoIterator,
{
    fn split_off_left(&self) -> Self {
        FlattenIterConsumer::new(self.base.split_off_left())
    }

    fn to_reducer(&self) -> Self::Reducer {
        self.base.to_reducer()
    }
}

struct FlattenIterFolder<C> {
    base: C,
}

impl<T, C> Folder<T> for FlattenIterFolder<C>
where
    C: Folder<T::Item>,
    T: IntoIterator,
{
    type Result = C::Result;

    fn consume(self, item: T) -> Self {
        let base = self.base.consume_iter(item);
        FlattenIterFolder { base }
    }

    fn consume_iter<I>(self, iter: I) -> Self
    where
        I: IntoIterator<Item = T>,
    {
        let iter = iter.into_iter().flatten();
        let base = self.base.consume_iter(iter);
        FlattenIterFolder { base }
    }

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

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