iter.rs - source
Description: Source of the Rust file `library/alloc/src/collections/vec_deque/iter.rs`.
Keywords: rust, rustlang, rust-lang

      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
    151
    152
    153
    154
    155
    156
    157
    158
    159

    use core::fmt;
    use core::iter::FusedIterator;
    use core::ops::Try;

    use super::{count, wrap_index, RingSlices};

    /// An iterator over the elements of a `VecDeque`.
    ///
    /// This `struct` is created by the [`iter`] method on [`super::VecDeque`]. See its
    /// documentation for more.
    ///
    /// [`iter`]: super::VecDeque::iter
    #[stable(feature = "rust1", since = "1.0.0")]
    pub struct Iter<'a, T: 'a> {
        pub(crate) ring: &'a [T],
        pub(crate) tail: usize,
        pub(crate) head: usize,
    }

    #[stable(feature = "collection_debug", since = "1.17.0")]
    impl<T: fmt::Debug> fmt::Debug for Iter<'_, T> {
        fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
            let (front, back) = RingSlices::ring_slices(self.ring, self.head, self.tail);
            f.debug_tuple("Iter").field(&front).field(&back).finish()
        }
    }

    // FIXME(#26925) Remove in favor of `#[derive(Clone)]`
    #[stable(feature = "rust1", since = "1.0.0")]
    impl<T> Clone for Iter<'_, T> {
        fn clone(&self) -> Self {
            Iter { ring: self.ring, tail: self.tail, head: self.head }
        }
    }

    #[stable(feature = "rust1", since = "1.0.0")]
    impl<'a, T> Iterator for Iter<'a, T> {
        type Item = &'a T;

        #[inline]
        fn next(&mut self) -> Option<&'a T> {
            if self.tail == self.head {
                return None;
            }
            let tail = self.tail;
            self.tail = wrap_index(self.tail.wrapping_add(1), self.ring.len());
            unsafe { Some(self.ring.get_unchecked(tail)) }
        }

        #[inline]
        fn size_hint(&self) -> (usize, Option<usize>) {
            let len = count(self.tail, self.head, self.ring.len());
            (len, Some(len))
        }

        fn fold<Acc, F>(self, mut accum: Acc, mut f: F) -> Acc
        where
            F: FnMut(Acc, Self::Item) -> Acc,
        {
            let (front, back) = RingSlices::ring_slices(self.ring, self.head, self.tail);
            accum = front.iter().fold(accum, &mut f);
            back.iter().fold(accum, &mut f)
        }

        fn try_fold<B, F, R>(&mut self, init: B, mut f: F) -> R
        where
            Self: Sized,
            F: FnMut(B, Self::Item) -> R,
            R: Try<Ok = B>,
        {
            let (mut iter, final_res);
            if self.tail <= self.head {
                // single slice self.ring[self.tail..self.head]
                iter = self.ring[self.tail..self.head].iter();
                final_res = iter.try_fold(init, &mut f);
            } else {
                // two slices: self.ring[self.tail..], self.ring[..self.head]
                let (front, back) = self.ring.split_at(self.tail);
                let mut back_iter = back.iter();
                let res = back_iter.try_fold(init, &mut f);
                let len = self.ring.len();
                self.tail = (self.ring.len() - back_iter.len()) & (len - 1);
                iter = front[..self.head].iter();
                final_res = iter.try_fold(res?, &mut f);
            }
            self.tail = self.head - iter.len();
            final_res
        }

        fn nth(&mut self, n: usize) -> Option<Self::Item> {
            if n >= count(self.tail, self.head, self.ring.len()) {
                self.tail = self.head;
                None
            } else {
                self.tail = wrap_index(self.tail.wrapping_add(n), self.ring.len());
                self.next()
            }
        }

        #[inline]
        fn last(mut self) -> Option<&'a T> {
            self.next_back()
        }
    }

    #[stable(feature = "rust1", since = "1.0.0")]
    impl<'a, T> DoubleEndedIterator for Iter<'a, T> {
        #[inline]
        fn next_back(&mut self) -> Option<&'a T> {
            if self.tail == self.head {
                return None;
            }
            self.head = wrap_index(self.head.wrapping_sub(1), self.ring.len());
            unsafe { Some(self.ring.get_unchecked(self.head)) }
        }

        fn rfold<Acc, F>(self, mut accum: Acc, mut f: F) -> Acc
        where
            F: FnMut(Acc, Self::Item) -> Acc,
        {
            let (front, back) = RingSlices::ring_slices(self.ring, self.head, self.tail);
            accum = back.iter().rfold(accum, &mut f);
            front.iter().rfold(accum, &mut f)
        }

        fn try_rfold<B, F, R>(&mut self, init: B, mut f: F) -> R
        where
            Self: Sized,
            F: FnMut(B, Self::Item) -> R,
            R: Try<Ok = B>,
        {
            let (mut iter, final_res);
            if self.tail <= self.head {
                // single slice self.ring[self.tail..self.head]
                iter = self.ring[self.tail..self.head].iter();
                final_res = iter.try_rfold(init, &mut f);
            } else {
                // two slices: self.ring[self.tail..], self.ring[..self.head]
                let (front, back) = self.ring.split_at(self.tail);
                let mut front_iter = front[..self.head].iter();
                let res = front_iter.try_rfold(init, &mut f);
                self.head = front_iter.len();
                iter = back.iter();
                final_res = iter.try_rfold(res?, &mut f);
            }
            self.head = self.tail + iter.len();
            final_res
        }
    }

    #[stable(feature = "rust1", since = "1.0.0")]
    impl<T> ExactSizeIterator for Iter<'_, T> {
        fn is_empty(&self) -> bool {
            self.head == self.tail
        }
    }

    #[stable(feature = "fused", since = "1.26.0")]
    impl<T> FusedIterator for Iter<'_, T> {}