rust-lang/rust
1
0
Fork 0
Code Issues Pull Requests Actions 1 Packages Projects Releases Wiki Activity

Auto merge of #75021 - cuviper:array_chunks_mut, r=scottmcm

Browse Source 
Add `slice::array_chunks_mut`

This follows `array_chunks` from #74373 with a mutable version, `array_chunks_mut`. The implementation is identical apart from mutability. The new tests are adaptations of the `chunks_exact_mut` tests, plus an inference test like the one for `array_chunks`.

I reused the unstable feature `array_chunks` and tracking issue #74985, but I can separate that if desired.

r? `@withoutboats`
cc `@lcnr`
This commit is contained in:
bors
2020-09-12 03:59:46 +00:00
parent 94a7ea271f 86b9f710d0
commit 8b6838b6e1
3 changed files with 242 additions and 5 deletions
Download Patch File Download Diff File Expand all files Collapse all files

152
library/core/src/slice/mod.rs
View File

@@ -996,9 +996,9 @@ impl<T> [T] {
/// Returns an iterator over `N` elements of the slice at a time, starting at the
/// beginning of the slice.
///
/// The chunks are slices and do not overlap. If `N` does not divide the length of the
/// slice, then the last up to `N-1` elements will be omitted and can be retrieved
/// from the `remainder` function of the iterator.
/// The chunks are array references and do not overlap. If `N` does not divide the
/// length of the slice, then the last up to `N-1` elements will be omitted and can be
/// retrieved from the `remainder` function of the iterator.
///
/// This method is the const generic equivalent of [`chunks_exact`].
///
@@ -1032,6 +1032,49 @@ impl<T> [T] {
ArrayChunks { iter: array_slice.iter(), rem: snd }
}
/// Returns an iterator over `N` elements of the slice at a time, starting at the
/// beginning of the slice.
///
/// The chunks are mutable array references and do not overlap. If `N` does not divide
/// the length of the slice, then the last up to `N-1` elements will be omitted and
/// can be retrieved from the `into_remainder` function of the iterator.
///
/// This method is the const generic equivalent of [`chunks_exact_mut`].
///
/// # Panics
///
/// Panics if `N` is 0. This check will most probably get changed to a compile time
/// error before this method gets stabilized.
///
/// # Examples
///
/// ```
/// #![feature(array_chunks)]
/// let v = &mut [0, 0, 0, 0, 0];
/// let mut count = 1;
///
/// for chunk in v.array_chunks_mut() {
/// *chunk = [count; 2];
/// count += 1;
/// }
/// assert_eq!(v, &[1, 1, 2, 2, 0]);
/// ```
///
/// [`chunks_exact_mut`]: #method.chunks_exact_mut
#[unstable(feature = "array_chunks", issue = "74985")]
#[inline]
pub fn array_chunks_mut<const N: usize>(&mut self) -> ArrayChunksMut<'_, T, N> {
assert_ne!(N, 0);
let len = self.len() / N;
let (fst, snd) = self.split_at_mut(len * N);
// SAFETY: We cast a slice of `len * N` elements into
// a slice of `len` many `N` elements chunks.
unsafe {
let array_slice: &mut [[T; N]] = from_raw_parts_mut(fst.as_mut_ptr().cast(), len);
ArrayChunksMut { iter: array_slice.iter_mut(), rem: snd }
}
}
/// Returns an iterator over `chunk_size` elements of the slice at a time, starting at the end
/// of the slice.
///
@@ -5826,7 +5869,7 @@ unsafe impl<'a, T> TrustedRandomAccess for ChunksExactMut<'a, T> {
/// time), starting at the beginning of the slice.
///
/// When the slice len is not evenly divided by the chunk size, the last
/// up to `chunk_size-1` elements will be omitted but can be retrieved from
/// up to `N-1` elements will be omitted but can be retrieved from
/// the [`remainder`] function from the iterator.
///
/// This struct is created by the [`array_chunks`] method on [slices].
@@ -5843,7 +5886,7 @@ pub struct ArrayChunks<'a, T: 'a, const N: usize> {
impl<'a, T, const N: usize> ArrayChunks<'a, T, N> {
/// Returns the remainder of the original slice that is not going to be
/// returned by the iterator. The returned slice has at most `chunk_size-1`
/// returned by the iterator. The returned slice has at most `N-1`
/// elements.
#[unstable(feature = "array_chunks", issue = "74985")]
pub fn remainder(&self) -> &'a [T] {
@@ -5929,6 +5972,105 @@ unsafe impl<'a, T, const N: usize> TrustedRandomAccess for ArrayChunks<'a, T, N>
}
}
/// An iterator over a slice in (non-overlapping) mutable chunks (`N` elements
/// at a time), starting at the beginning of the slice.
///
/// When the slice len is not evenly divided by the chunk size, the last
/// up to `N-1` elements will be omitted but can be retrieved from
/// the [`into_remainder`] function from the iterator.
///
/// This struct is created by the [`array_chunks_mut`] method on [slices].
///
/// [`array_chunks_mut`]: ../../std/primitive.slice.html#method.array_chunks_mut
/// [`into_remainder`]: ../../std/slice/struct.ArrayChunksMut.html#method.into_remainder
/// [slices]: ../../std/primitive.slice.html
#[derive(Debug)]
#[unstable(feature = "array_chunks", issue = "74985")]
pub struct ArrayChunksMut<'a, T: 'a, const N: usize> {
iter: IterMut<'a, [T; N]>,
rem: &'a mut [T],
}
impl<'a, T, const N: usize> ArrayChunksMut<'a, T, N> {
/// Returns the remainder of the original slice that is not going to be
/// returned by the iterator. The returned slice has at most `N-1`
/// elements.
#[unstable(feature = "array_chunks", issue = "74985")]
pub fn into_remainder(self) -> &'a mut [T] {
self.rem
}
}
#[unstable(feature = "array_chunks", issue = "74985")]
impl<'a, T, const N: usize> Iterator for ArrayChunksMut<'a, T, N> {
type Item = &'a mut [T; N];
#[inline]
fn next(&mut self) -> Option<&'a mut [T; N]> {
self.iter.next()
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
self.iter.size_hint()
}
#[inline]
fn count(self) -> usize {
self.iter.count()
}
#[inline]
fn nth(&mut self, n: usize) -> Option<Self::Item> {
self.iter.nth(n)
}
#[inline]
fn last(self) -> Option<Self::Item> {
self.iter.last()
}
unsafe fn get_unchecked(&mut self, i: usize) -> &'a mut [T; N] {
// SAFETY: The safety guarantees of `get_unchecked` are transferred to
// the caller.
unsafe { self.iter.get_unchecked(i) }
}
}
#[unstable(feature = "array_chunks", issue = "74985")]
impl<'a, T, const N: usize> DoubleEndedIterator for ArrayChunksMut<'a, T, N> {
#[inline]
fn next_back(&mut self) -> Option<&'a mut [T; N]> {
self.iter.next_back()
}
#[inline]
fn nth_back(&mut self, n: usize) -> Option<Self::Item> {
self.iter.nth_back(n)
}
}
#[unstable(feature = "array_chunks", issue = "74985")]
impl<T, const N: usize> ExactSizeIterator for ArrayChunksMut<'_, T, N> {
fn is_empty(&self) -> bool {
self.iter.is_empty()
}
}
#[unstable(feature = "trusted_len", issue = "37572")]
unsafe impl<T, const N: usize> TrustedLen for ArrayChunksMut<'_, T, N> {}
#[unstable(feature = "array_chunks", issue = "74985")]
impl<T, const N: usize> FusedIterator for ArrayChunksMut<'_, T, N> {}
#[doc(hidden)]
#[unstable(feature = "array_chunks", issue = "74985")]
unsafe impl<'a, T, const N: usize> TrustedRandomAccess for ArrayChunksMut<'a, T, N> {
fn may_have_side_effect() -> bool {
false
}
}
/// An iterator over a slice in (non-overlapping) chunks (`chunk_size` elements at a
/// time), starting at the end of the slice.
///