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
138
139
140
141
142
143
144
145
146
147
148
149
150

//! Parallel iterator types for [vectors][std::vec] (`Vec<T>`)
//!
//! You will rarely need to interact with this module directly unless you need
//! to name one of the iterator types.
//!
//! [std::vec]: https://doc.rust-lang.org/stable/std/vec/

use iter::plumbing::*;
use iter::*;
use std;

/// Parallel iterator that moves out of a vector.
#[derive(Debug, Clone)]
pub struct IntoIter<T: Send> {
    vec: Vec<T>,
}

impl<T: Send> IntoParallelIterator for Vec<T> {
    type Item = T;
    type Iter = IntoIter<T>;

    fn into_par_iter(self) -> Self::Iter {
        IntoIter { vec: self }
    }
}

impl<T: Send> ParallelIterator for IntoIter<T> {
    type Item = T;

    fn drive_unindexed<C>(self, consumer: C) -> C::Result
    where
        C: UnindexedConsumer<Self::Item>,
    {
        bridge(self, consumer)
    }

    fn opt_len(&self) -> Option<usize> {
        Some(self.len())
    }
}

impl<T: Send> IndexedParallelIterator for IntoIter<T> {
    fn drive<C>(self, consumer: C) -> C::Result
    where
        C: Consumer<Self::Item>,
    {
        bridge(self, consumer)
    }

    fn len(&self) -> usize {
        self.vec.len()
    }

    fn with_producer<CB>(mut self, callback: CB) -> CB::Output
    where
        CB: ProducerCallback<Self::Item>,
    {
        // The producer will move or drop each item from its slice, effectively taking ownership of
        // them.  When we're done, the vector only needs to free its buffer.
        unsafe {
            // Make the vector forget about the actual items.
            let len = self.vec.len();
            self.vec.set_len(0);

            // Get a correct borrow, then extend it to the original length.
            let mut slice = self.vec.as_mut_slice();
            slice = std::slice::from_raw_parts_mut(slice.as_mut_ptr(), len);

            callback.callback(VecProducer { slice })
        }
    }
}

/// ////////////////////////////////////////////////////////////////////////

struct VecProducer<'data, T: 'data + Send> {
    slice: &'data mut [T],
}

impl<'data, T: 'data + Send> Producer for VecProducer<'data, T> {
    type Item = T;
    type IntoIter = SliceDrain<'data, T>;

    fn into_iter(mut self) -> Self::IntoIter {
        // replace the slice so we don't drop it twice
        let slice = std::mem::replace(&mut self.slice, &mut []);
        SliceDrain {
            iter: slice.iter_mut(),
        }
    }

    fn split_at(mut self, index: usize) -> (Self, Self) {
        // replace the slice so we don't drop it twice
        let slice = std::mem::replace(&mut self.slice, &mut []);
        let (left, right) = slice.split_at_mut(index);
        (VecProducer { slice: left }, VecProducer { slice: right })
    }
}

impl<'data, T: 'data + Send> Drop for VecProducer<'data, T> {
    fn drop(&mut self) {
        SliceDrain {
            iter: self.slice.iter_mut(),
        };
    }
}

/// ////////////////////////////////////////////////////////////////////////

// like std::vec::Drain, without updating a source Vec
struct SliceDrain<'data, T: 'data> {
    iter: std::slice::IterMut<'data, T>,
}

impl<'data, T: 'data> Iterator for SliceDrain<'data, T> {
    type Item = T;

    fn next(&mut self) -> Option<T> {
        let ptr = self.iter.next()?;
        Some(unsafe { std::ptr::read(ptr) })
    }

    fn size_hint(&self) -> (usize, Option<usize>) {
        let len = self.len();
        (len, Some(len))
    }
}

impl<'data, T: 'data> DoubleEndedIterator for SliceDrain<'data, T> {
    fn next_back(&mut self) -> Option<Self::Item> {
        let ptr = self.iter.next_back()?;
        Some(unsafe { std::ptr::read(ptr) })
    }
}

impl<'data, T: 'data> ExactSizeIterator for SliceDrain<'data, T> {
    fn len(&self) -> usize {
        self.iter.len()
    }
}

impl<'data, T: 'data> Drop for SliceDrain<'data, T> {
    fn drop(&mut self) {
        for ptr in &mut self.iter {
            unsafe {
                std::ptr::drop_in_place(ptr);
            }
        }
    }
}