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| 1 | +use core::fmt; |
| 2 | +use core::iter::FusedIterator; |
| 3 | +use core::ops::Try; |
| 4 | + |
| 5 | +use super::{count, wrap_index, RingSlices}; |
| 6 | + |
| 7 | +/// An iterator over the elements of a `VecDeque`. |
| 8 | +/// |
| 9 | +/// This `struct` is created by the [`iter`] method on [`super::VecDeque`]. See its |
| 10 | +/// documentation for more. |
| 11 | +/// |
| 12 | +/// [`iter`]: super::VecDeque::iter |
| 13 | +#[stable(feature = "rust1", since = "1.0.0")] |
| 14 | +pub struct Iter<'a, T: 'a> { |
| 15 | + pub(crate) ring: &'a [T], |
| 16 | + pub(crate) tail: usize, |
| 17 | + pub(crate) head: usize, |
| 18 | +} |
| 19 | + |
| 20 | +#[stable(feature = "collection_debug", since = "1.17.0")] |
| 21 | +impl<T: fmt::Debug> fmt::Debug for Iter<'_, T> { |
| 22 | + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
| 23 | + let (front, back) = RingSlices::ring_slices(self.ring, self.head, self.tail); |
| 24 | + f.debug_tuple("Iter").field(&front).field(&back).finish() |
| 25 | + } |
| 26 | +} |
| 27 | + |
| 28 | +// FIXME(#26925) Remove in favor of `#[derive(Clone)]` |
| 29 | +#[stable(feature = "rust1", since = "1.0.0")] |
| 30 | +impl<T> Clone for Iter<'_, T> { |
| 31 | + fn clone(&self) -> Self { |
| 32 | + Iter { ring: self.ring, tail: self.tail, head: self.head } |
| 33 | + } |
| 34 | +} |
| 35 | + |
| 36 | +#[stable(feature = "rust1", since = "1.0.0")] |
| 37 | +impl<'a, T> Iterator for Iter<'a, T> { |
| 38 | + type Item = &'a T; |
| 39 | + |
| 40 | + #[inline] |
| 41 | + fn next(&mut self) -> Option<&'a T> { |
| 42 | + if self.tail == self.head { |
| 43 | + return None; |
| 44 | + } |
| 45 | + let tail = self.tail; |
| 46 | + self.tail = wrap_index(self.tail.wrapping_add(1), self.ring.len()); |
| 47 | + unsafe { Some(self.ring.get_unchecked(tail)) } |
| 48 | + } |
| 49 | + |
| 50 | + #[inline] |
| 51 | + fn size_hint(&self) -> (usize, Option<usize>) { |
| 52 | + let len = count(self.tail, self.head, self.ring.len()); |
| 53 | + (len, Some(len)) |
| 54 | + } |
| 55 | + |
| 56 | + fn fold<Acc, F>(self, mut accum: Acc, mut f: F) -> Acc |
| 57 | + where |
| 58 | + F: FnMut(Acc, Self::Item) -> Acc, |
| 59 | + { |
| 60 | + let (front, back) = RingSlices::ring_slices(self.ring, self.head, self.tail); |
| 61 | + accum = front.iter().fold(accum, &mut f); |
| 62 | + back.iter().fold(accum, &mut f) |
| 63 | + } |
| 64 | + |
| 65 | + fn try_fold<B, F, R>(&mut self, init: B, mut f: F) -> R |
| 66 | + where |
| 67 | + Self: Sized, |
| 68 | + F: FnMut(B, Self::Item) -> R, |
| 69 | + R: Try<Ok = B>, |
| 70 | + { |
| 71 | + let (mut iter, final_res); |
| 72 | + if self.tail <= self.head { |
| 73 | + // single slice self.ring[self.tail..self.head] |
| 74 | + iter = self.ring[self.tail..self.head].iter(); |
| 75 | + final_res = iter.try_fold(init, &mut f); |
| 76 | + } else { |
| 77 | + // two slices: self.ring[self.tail..], self.ring[..self.head] |
| 78 | + let (front, back) = self.ring.split_at(self.tail); |
| 79 | + let mut back_iter = back.iter(); |
| 80 | + let res = back_iter.try_fold(init, &mut f); |
| 81 | + let len = self.ring.len(); |
| 82 | + self.tail = (self.ring.len() - back_iter.len()) & (len - 1); |
| 83 | + iter = front[..self.head].iter(); |
| 84 | + final_res = iter.try_fold(res?, &mut f); |
| 85 | + } |
| 86 | + self.tail = self.head - iter.len(); |
| 87 | + final_res |
| 88 | + } |
| 89 | + |
| 90 | + fn nth(&mut self, n: usize) -> Option<Self::Item> { |
| 91 | + if n >= count(self.tail, self.head, self.ring.len()) { |
| 92 | + self.tail = self.head; |
| 93 | + None |
| 94 | + } else { |
| 95 | + self.tail = wrap_index(self.tail.wrapping_add(n), self.ring.len()); |
| 96 | + self.next() |
| 97 | + } |
| 98 | + } |
| 99 | + |
| 100 | + #[inline] |
| 101 | + fn last(mut self) -> Option<&'a T> { |
| 102 | + self.next_back() |
| 103 | + } |
| 104 | +} |
| 105 | + |
| 106 | +#[stable(feature = "rust1", since = "1.0.0")] |
| 107 | +impl<'a, T> DoubleEndedIterator for Iter<'a, T> { |
| 108 | + #[inline] |
| 109 | + fn next_back(&mut self) -> Option<&'a T> { |
| 110 | + if self.tail == self.head { |
| 111 | + return None; |
| 112 | + } |
| 113 | + self.head = wrap_index(self.head.wrapping_sub(1), self.ring.len()); |
| 114 | + unsafe { Some(self.ring.get_unchecked(self.head)) } |
| 115 | + } |
| 116 | + |
| 117 | + fn rfold<Acc, F>(self, mut accum: Acc, mut f: F) -> Acc |
| 118 | + where |
| 119 | + F: FnMut(Acc, Self::Item) -> Acc, |
| 120 | + { |
| 121 | + let (front, back) = RingSlices::ring_slices(self.ring, self.head, self.tail); |
| 122 | + accum = back.iter().rfold(accum, &mut f); |
| 123 | + front.iter().rfold(accum, &mut f) |
| 124 | + } |
| 125 | + |
| 126 | + fn try_rfold<B, F, R>(&mut self, init: B, mut f: F) -> R |
| 127 | + where |
| 128 | + Self: Sized, |
| 129 | + F: FnMut(B, Self::Item) -> R, |
| 130 | + R: Try<Ok = B>, |
| 131 | + { |
| 132 | + let (mut iter, final_res); |
| 133 | + if self.tail <= self.head { |
| 134 | + // single slice self.ring[self.tail..self.head] |
| 135 | + iter = self.ring[self.tail..self.head].iter(); |
| 136 | + final_res = iter.try_rfold(init, &mut f); |
| 137 | + } else { |
| 138 | + // two slices: self.ring[self.tail..], self.ring[..self.head] |
| 139 | + let (front, back) = self.ring.split_at(self.tail); |
| 140 | + let mut front_iter = front[..self.head].iter(); |
| 141 | + let res = front_iter.try_rfold(init, &mut f); |
| 142 | + self.head = front_iter.len(); |
| 143 | + iter = back.iter(); |
| 144 | + final_res = iter.try_rfold(res?, &mut f); |
| 145 | + } |
| 146 | + self.head = self.tail + iter.len(); |
| 147 | + final_res |
| 148 | + } |
| 149 | +} |
| 150 | + |
| 151 | +#[stable(feature = "rust1", since = "1.0.0")] |
| 152 | +impl<T> ExactSizeIterator for Iter<'_, T> { |
| 153 | + fn is_empty(&self) -> bool { |
| 154 | + self.head == self.tail |
| 155 | + } |
| 156 | +} |
| 157 | + |
| 158 | +#[stable(feature = "fused", since = "1.26.0")] |
| 159 | +impl<T> FusedIterator for Iter<'_, T> {} |
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