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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-17 12:03:36 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-17 12:03:36 +0000 |
commit | 17d40c6057c88f4c432b0d7bac88e1b84cb7e67f (patch) | |
tree | 3f66c4a5918660bb8a758ab6cda5ff8ee4f6cdcd /library/alloc/src/collections/vec_deque/drain.rs | |
parent | Adding upstream version 1.64.0+dfsg1. (diff) | |
download | rustc-upstream/1.65.0+dfsg1.tar.xz rustc-upstream/1.65.0+dfsg1.zip |
Adding upstream version 1.65.0+dfsg1.upstream/1.65.0+dfsg1
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'library/alloc/src/collections/vec_deque/drain.rs')
-rw-r--r-- | library/alloc/src/collections/vec_deque/drain.rs | 44 |
1 files changed, 35 insertions, 9 deletions
diff --git a/library/alloc/src/collections/vec_deque/drain.rs b/library/alloc/src/collections/vec_deque/drain.rs index 05f94da6d..41baa7102 100644 --- a/library/alloc/src/collections/vec_deque/drain.rs +++ b/library/alloc/src/collections/vec_deque/drain.rs @@ -1,10 +1,12 @@ +use core::fmt; use core::iter::FusedIterator; +use core::marker::PhantomData; +use core::mem::{self, MaybeUninit}; use core::ptr::{self, NonNull}; -use core::{fmt, mem}; use crate::alloc::{Allocator, Global}; -use super::{count, Iter, VecDeque}; +use super::{count, wrap_index, VecDeque}; /// A draining iterator over the elements of a `VecDeque`. /// @@ -20,18 +22,24 @@ pub struct Drain< > { after_tail: usize, after_head: usize, - iter: Iter<'a, T>, + ring: NonNull<[T]>, + tail: usize, + head: usize, deque: NonNull<VecDeque<T, A>>, + _phantom: PhantomData<&'a T>, } impl<'a, T, A: Allocator> Drain<'a, T, A> { pub(super) unsafe fn new( after_tail: usize, after_head: usize, - iter: Iter<'a, T>, + ring: &'a [MaybeUninit<T>], + tail: usize, + head: usize, deque: NonNull<VecDeque<T, A>>, ) -> Self { - Drain { after_tail, after_head, iter, deque } + let ring = unsafe { NonNull::new_unchecked(ring as *const [MaybeUninit<T>] as *mut _) }; + Drain { after_tail, after_head, ring, tail, head, deque, _phantom: PhantomData } } } @@ -41,7 +49,9 @@ impl<T: fmt::Debug, A: Allocator> fmt::Debug for Drain<'_, T, A> { f.debug_tuple("Drain") .field(&self.after_tail) .field(&self.after_head) - .field(&self.iter) + .field(&self.ring) + .field(&self.tail) + .field(&self.head) .finish() } } @@ -118,12 +128,21 @@ impl<T, A: Allocator> Iterator for Drain<'_, T, A> { #[inline] fn next(&mut self) -> Option<T> { - self.iter.next().map(|elt| unsafe { ptr::read(elt) }) + if self.tail == self.head { + return None; + } + let tail = self.tail; + self.tail = wrap_index(self.tail.wrapping_add(1), self.ring.len()); + // Safety: + // - `self.tail` in a ring buffer is always a valid index. + // - `self.head` and `self.tail` equality is checked above. + unsafe { Some(ptr::read(self.ring.as_ptr().get_unchecked_mut(tail))) } } #[inline] fn size_hint(&self) -> (usize, Option<usize>) { - self.iter.size_hint() + let len = count(self.tail, self.head, self.ring.len()); + (len, Some(len)) } } @@ -131,7 +150,14 @@ impl<T, A: Allocator> Iterator for Drain<'_, T, A> { impl<T, A: Allocator> DoubleEndedIterator for Drain<'_, T, A> { #[inline] fn next_back(&mut self) -> Option<T> { - self.iter.next_back().map(|elt| unsafe { ptr::read(elt) }) + if self.tail == self.head { + return None; + } + self.head = wrap_index(self.head.wrapping_sub(1), self.ring.len()); + // Safety: + // - `self.head` in a ring buffer is always a valid index. + // - `self.head` and `self.tail` equality is checked above. + unsafe { Some(ptr::read(self.ring.as_ptr().get_unchecked_mut(self.head))) } } } |