diff --git a/library/alloc/src/lib.rs b/library/alloc/src/lib.rs index 6350e38554647..097db30d634cc 100644 --- a/library/alloc/src/lib.rs +++ b/library/alloc/src/lib.rs @@ -75,6 +75,7 @@ #![cfg_attr(not(test), feature(generator_trait))] #![cfg_attr(test, feature(test))] #![feature(allocator_api)] +#![feature(array_chunks)] #![feature(allow_internal_unstable)] #![feature(arbitrary_self_types)] #![feature(box_patterns)] diff --git a/library/alloc/src/slice.rs b/library/alloc/src/slice.rs index 3d51115fe01d3..b791c775548cd 100644 --- a/library/alloc/src/slice.rs +++ b/library/alloc/src/slice.rs @@ -95,6 +95,8 @@ use crate::borrow::ToOwned; use crate::boxed::Box; use crate::vec::Vec; +#[unstable(feature = "array_chunks", issue = "74985")] +pub use core::slice::ArrayChunks; #[stable(feature = "slice_get_slice", since = "1.28.0")] pub use core::slice::SliceIndex; #[stable(feature = "from_ref", since = "1.28.0")] diff --git a/library/core/src/slice/mod.rs b/library/core/src/slice/mod.rs index 9ed5a1f962215..93608a1ce4864 100644 --- a/library/core/src/slice/mod.rs +++ b/library/core/src/slice/mod.rs @@ -680,7 +680,7 @@ impl [T] { #[stable(feature = "rust1", since = "1.0.0")] #[inline] pub fn windows(&self, size: usize) -> Windows<'_, T> { - assert!(size != 0); + assert_ne!(size, 0); Windows { v: self, size } } @@ -714,7 +714,7 @@ impl [T] { #[stable(feature = "rust1", since = "1.0.0")] #[inline] pub fn chunks(&self, chunk_size: usize) -> Chunks<'_, T> { - assert!(chunk_size != 0); + assert_ne!(chunk_size, 0); Chunks { v: self, chunk_size } } @@ -752,7 +752,7 @@ impl [T] { #[stable(feature = "rust1", since = "1.0.0")] #[inline] pub fn chunks_mut(&mut self, chunk_size: usize) -> ChunksMut<'_, T> { - assert!(chunk_size != 0); + assert_ne!(chunk_size, 0); ChunksMut { v: self, chunk_size } } @@ -789,7 +789,7 @@ impl [T] { #[stable(feature = "chunks_exact", since = "1.31.0")] #[inline] pub fn chunks_exact(&self, chunk_size: usize) -> ChunksExact<'_, T> { - assert!(chunk_size != 0); + assert_ne!(chunk_size, 0); let rem = self.len() % chunk_size; let len = self.len() - rem; let (fst, snd) = self.split_at(len); @@ -834,13 +834,52 @@ impl [T] { #[stable(feature = "chunks_exact", since = "1.31.0")] #[inline] pub fn chunks_exact_mut(&mut self, chunk_size: usize) -> ChunksExactMut<'_, T> { - assert!(chunk_size != 0); + assert_ne!(chunk_size, 0); let rem = self.len() % chunk_size; let len = self.len() - rem; let (fst, snd) = self.split_at_mut(len); ChunksExactMut { v: fst, rem: snd, chunk_size } } + /// 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. + /// + /// This method is the const generic equivalent of [`chunks_exact`]. + /// + /// # 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 slice = ['l', 'o', 'r', 'e', 'm']; + /// let mut iter = slice.array_chunks(); + /// assert_eq!(iter.next().unwrap(), &['l', 'o']); + /// assert_eq!(iter.next().unwrap(), &['r', 'e']); + /// assert!(iter.next().is_none()); + /// assert_eq!(iter.remainder(), &['m']); + /// ``` + /// + /// [`chunks_exact`]: #method.chunks_exact + #[unstable(feature = "array_chunks", issue = "74985")] + #[inline] + pub fn array_chunks(&self) -> ArrayChunks<'_, T, N> { + assert_ne!(N, 0); + let len = self.len() / N; + let (fst, snd) = self.split_at(len * N); + // SAFETY: We cast a slice of `len * N` elements into + // a slice of `len` many `N` elements chunks. + let array_slice: &[[T; N]] = unsafe { from_raw_parts(fst.as_ptr().cast(), len) }; + ArrayChunks { iter: array_slice.iter(), rem: snd } + } + /// Returns an iterator over `chunk_size` elements of the slice at a time, starting at the end /// of the slice. /// @@ -5432,6 +5471,110 @@ unsafe impl<'a, T> TrustedRandomAccess for ChunksExactMut<'a, T> { } } +/// An iterator over a slice in (non-overlapping) 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 `chunk_size-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]. +/// +/// [`array_chunks`]: ../../std/primitive.slice.html#method.array_chunks +/// [`remainder`]: ../../std/slice/struct.ArrayChunks.html#method.remainder +/// [slices]: ../../std/primitive.slice.html +#[derive(Debug)] +#[unstable(feature = "array_chunks", issue = "74985")] +pub struct ArrayChunks<'a, T: 'a, const N: usize> { + iter: Iter<'a, [T; N]>, + rem: &'a [T], +} + +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` + /// elements. + #[unstable(feature = "array_chunks", issue = "74985")] + pub fn remainder(&self) -> &'a [T] { + self.rem + } +} + +// FIXME(#26925) Remove in favor of `#[derive(Clone)]` +#[unstable(feature = "array_chunks", issue = "74985")] +impl Clone for ArrayChunks<'_, T, N> { + fn clone(&self) -> Self { + ArrayChunks { iter: self.iter.clone(), rem: self.rem } + } +} + +#[unstable(feature = "array_chunks", issue = "74985")] +impl<'a, T, const N: usize> Iterator for ArrayChunks<'a, T, N> { + type Item = &'a [T; N]; + + #[inline] + fn next(&mut self) -> Option<&'a [T; N]> { + self.iter.next() + } + + #[inline] + fn size_hint(&self) -> (usize, Option) { + self.iter.size_hint() + } + + #[inline] + fn count(self) -> usize { + self.iter.count() + } + + #[inline] + fn nth(&mut self, n: usize) -> Option { + self.iter.nth(n) + } + + #[inline] + fn last(self) -> Option { + self.iter.last() + } +} + +#[unstable(feature = "array_chunks", issue = "74985")] +impl<'a, T, const N: usize> DoubleEndedIterator for ArrayChunks<'a, T, N> { + #[inline] + fn next_back(&mut self) -> Option<&'a [T; N]> { + self.iter.next_back() + } + + #[inline] + fn nth_back(&mut self, n: usize) -> Option { + self.iter.nth_back(n) + } +} + +#[unstable(feature = "array_chunks", issue = "74985")] +impl ExactSizeIterator for ArrayChunks<'_, T, N> { + fn is_empty(&self) -> bool { + self.iter.is_empty() + } +} + +#[unstable(feature = "trusted_len", issue = "37572")] +unsafe impl TrustedLen for ArrayChunks<'_, T, N> {} + +#[unstable(feature = "array_chunks", issue = "74985")] +impl FusedIterator for ArrayChunks<'_, T, N> {} + +#[doc(hidden)] +#[unstable(feature = "array_chunks", issue = "74985")] +unsafe impl<'a, T, const N: usize> TrustedRandomAccess for ArrayChunks<'a, T, N> { + unsafe fn get_unchecked(&mut self, i: usize) -> &'a [T; N] { + unsafe { self.iter.get_unchecked(i) } + } + 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. /// diff --git a/library/core/tests/lib.rs b/library/core/tests/lib.rs index 47ed6db6c677b..6b28a815f033a 100644 --- a/library/core/tests/lib.rs +++ b/library/core/tests/lib.rs @@ -1,4 +1,5 @@ #![feature(alloc_layout_extra)] +#![feature(array_chunks)] #![feature(bool_to_option)] #![feature(bound_cloned)] #![feature(box_syntax)] diff --git a/library/core/tests/slice.rs b/library/core/tests/slice.rs index 8e240832c13b8..27cc7fce1daa3 100644 --- a/library/core/tests/slice.rs +++ b/library/core/tests/slice.rs @@ -473,6 +473,97 @@ fn test_chunks_exact_mut_zip() { assert_eq!(v1, [13, 14, 19, 20, 4]); } +#[test] +fn test_array_chunks_infer() { + let v: &[i32] = &[0, 1, 2, 3, 4, -4]; + let c = v.array_chunks(); + for &[a, b, c] in c { + assert_eq!(a + b + c, 3); + } + + let v2: &[i32] = &[0, 1, 2, 3, 4, 5, 6]; + let total = v2.array_chunks().map(|&[a, b]| a * b).sum::(); + assert_eq!(total, 2 * 3 + 4 * 5); +} + +#[test] +fn test_array_chunks_count() { + let v: &[i32] = &[0, 1, 2, 3, 4, 5]; + let c = v.array_chunks::<3>(); + assert_eq!(c.count(), 2); + + let v2: &[i32] = &[0, 1, 2, 3, 4]; + let c2 = v2.array_chunks::<2>(); + assert_eq!(c2.count(), 2); + + let v3: &[i32] = &[]; + let c3 = v3.array_chunks::<2>(); + assert_eq!(c3.count(), 0); +} + +#[test] +fn test_array_chunks_nth() { + let v: &[i32] = &[0, 1, 2, 3, 4, 5]; + let mut c = v.array_chunks::<2>(); + assert_eq!(c.nth(1).unwrap(), &[2, 3]); + assert_eq!(c.next().unwrap(), &[4, 5]); + + let v2: &[i32] = &[0, 1, 2, 3, 4, 5, 6]; + let mut c2 = v2.array_chunks::<3>(); + assert_eq!(c2.nth(1).unwrap(), &[3, 4, 5]); + assert_eq!(c2.next(), None); +} + +#[test] +fn test_array_chunks_nth_back() { + let v: &[i32] = &[0, 1, 2, 3, 4, 5]; + let mut c = v.array_chunks::<2>(); + assert_eq!(c.nth_back(1).unwrap(), &[2, 3]); + assert_eq!(c.next().unwrap(), &[0, 1]); + assert_eq!(c.next(), None); + + let v2: &[i32] = &[0, 1, 2, 3, 4]; + let mut c2 = v2.array_chunks::<3>(); + assert_eq!(c2.nth_back(0).unwrap(), &[0, 1, 2]); + assert_eq!(c2.next(), None); + assert_eq!(c2.next_back(), None); + + let v3: &[i32] = &[0, 1, 2, 3, 4]; + let mut c3 = v3.array_chunks::<10>(); + assert_eq!(c3.nth_back(0), None); +} + +#[test] +fn test_array_chunks_last() { + let v: &[i32] = &[0, 1, 2, 3, 4, 5]; + let c = v.array_chunks::<2>(); + assert_eq!(c.last().unwrap(), &[4, 5]); + + let v2: &[i32] = &[0, 1, 2, 3, 4]; + let c2 = v2.array_chunks::<2>(); + assert_eq!(c2.last().unwrap(), &[2, 3]); +} + +#[test] +fn test_array_chunks_remainder() { + let v: &[i32] = &[0, 1, 2, 3, 4]; + let c = v.array_chunks::<2>(); + assert_eq!(c.remainder(), &[4]); +} + +#[test] +fn test_array_chunks_zip() { + let v1: &[i32] = &[0, 1, 2, 3, 4]; + let v2: &[i32] = &[6, 7, 8, 9, 10]; + + let res = v1 + .array_chunks::<2>() + .zip(v2.array_chunks::<2>()) + .map(|(a, b)| a.iter().sum::() + b.iter().sum::()) + .collect::>(); + assert_eq!(res, vec![14, 22]); +} + #[test] fn test_rchunks_count() { let v: &[i32] = &[0, 1, 2, 3, 4, 5];