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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-17 12:11:38 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-17 12:12:43 +0000 |
commit | cf94bdc0742c13e2a0cac864c478b8626b266e1b (patch) | |
tree | 044670aa50cc5e2b4229aa0b6b3df6676730c0a6 /library/core/src/iter/adapters/copied.rs | |
parent | Adding debian version 1.65.0+dfsg1-2. (diff) | |
download | rustc-cf94bdc0742c13e2a0cac864c478b8626b266e1b.tar.xz rustc-cf94bdc0742c13e2a0cac864c478b8626b266e1b.zip |
Merging upstream version 1.66.0+dfsg1.
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to '')
-rw-r--r-- | library/core/src/iter/adapters/copied.rs | 74 |
1 files changed, 74 insertions, 0 deletions
diff --git a/library/core/src/iter/adapters/copied.rs b/library/core/src/iter/adapters/copied.rs index f9bfd77d7..62d3afb81 100644 --- a/library/core/src/iter/adapters/copied.rs +++ b/library/core/src/iter/adapters/copied.rs @@ -2,7 +2,10 @@ use crate::iter::adapters::{ zip::try_get_unchecked, TrustedRandomAccess, TrustedRandomAccessNoCoerce, }; use crate::iter::{FusedIterator, TrustedLen}; +use crate::mem::MaybeUninit; +use crate::mem::SizedTypeProperties; use crate::ops::Try; +use crate::{array, ptr}; /// An iterator that copies the elements of an underlying iterator. /// @@ -44,6 +47,15 @@ where self.it.next().copied() } + fn next_chunk<const N: usize>( + &mut self, + ) -> Result<[Self::Item; N], array::IntoIter<Self::Item, N>> + where + Self: Sized, + { + <I as SpecNextChunk<'_, N, T>>::spec_next_chunk(&mut self.it) + } + fn size_hint(&self) -> (usize, Option<usize>) { self.it.size_hint() } @@ -166,3 +178,65 @@ where T: Copy, { } + +trait SpecNextChunk<'a, const N: usize, T: 'a>: Iterator<Item = &'a T> +where + T: Copy, +{ + fn spec_next_chunk(&mut self) -> Result<[T; N], array::IntoIter<T, N>>; +} + +impl<'a, const N: usize, I, T: 'a> SpecNextChunk<'a, N, T> for I +where + I: Iterator<Item = &'a T>, + T: Copy, +{ + default fn spec_next_chunk(&mut self) -> Result<[T; N], array::IntoIter<T, N>> { + array::iter_next_chunk(&mut self.map(|e| *e)) + } +} + +impl<'a, const N: usize, T: 'a> SpecNextChunk<'a, N, T> for crate::slice::Iter<'a, T> +where + T: Copy, +{ + fn spec_next_chunk(&mut self) -> Result<[T; N], array::IntoIter<T, N>> { + let mut raw_array = MaybeUninit::uninit_array(); + + let len = self.len(); + + if T::IS_ZST { + if len < N { + let _ = self.advance_by(len); + // SAFETY: ZSTs can be conjured ex nihilo; only the amount has to be correct + return Err(unsafe { array::IntoIter::new_unchecked(raw_array, 0..len) }); + } + + let _ = self.advance_by(N); + // SAFETY: ditto + return Ok(unsafe { MaybeUninit::array_assume_init(raw_array) }); + } + + if len < N { + // SAFETY: `len` indicates that this many elements are available and we just checked that + // it fits into the array. + unsafe { + ptr::copy_nonoverlapping( + self.as_ref().as_ptr(), + raw_array.as_mut_ptr() as *mut T, + len, + ); + let _ = self.advance_by(len); + return Err(array::IntoIter::new_unchecked(raw_array, 0..len)); + } + } + + // SAFETY: `len` is larger than the array size. Copy a fixed amount here to fully initialize + // the array. + unsafe { + ptr::copy_nonoverlapping(self.as_ref().as_ptr(), raw_array.as_mut_ptr() as *mut T, N); + let _ = self.advance_by(N); + Ok(MaybeUninit::array_assume_init(raw_array)) + } + } +} |