diff --git a/src/liballoc/lib.rs b/src/liballoc/lib.rs index 3cc3ea467966b..d8ce28695ab6f 100644 --- a/src/liballoc/lib.rs +++ b/src/liballoc/lib.rs @@ -124,6 +124,7 @@ #![feature(unsize)] #![feature(allocator_internals)] #![feature(on_unimplemented)] +#![feature(exact_chunks)] #![cfg_attr(not(test), feature(fused, fn_traits, placement_new_protocol, swap_with_slice, i128))] #![cfg_attr(test, feature(test, box_heap))] diff --git a/src/liballoc/slice.rs b/src/liballoc/slice.rs index fa73197885be7..bae366736379c 100644 --- a/src/liballoc/slice.rs +++ b/src/liballoc/slice.rs @@ -123,6 +123,8 @@ pub use core::slice::{from_raw_parts, from_raw_parts_mut}; pub use core::slice::{from_ref, from_ref_mut}; #[unstable(feature = "slice_get_slice", issue = "35729")] pub use core::slice::SliceIndex; +#[unstable(feature = "exact_chunks", issue = "47115")] +pub use core::slice::{ExactChunks, ExactChunksMut}; //////////////////////////////////////////////////////////////////////////////// // Basic slice extension methods @@ -631,6 +633,31 @@ impl [T] { core_slice::SliceExt::chunks(self, chunk_size) } + /// Returns an iterator over `chunk_size` elements of the slice at a + /// time. The chunks are slices and do not overlap. If `chunk_size` does + /// not divide the length of the slice, then the last up to `chunk_size-1` + /// elements will be omitted. + /// + /// # Panics + /// + /// Panics if `chunk_size` is 0. + /// + /// # Examples + /// + /// ``` + /// let slice = ['l', 'o', 'r', 'e', 'm']; + /// let mut iter = slice.chunks(2); + /// assert_eq!(iter.next().unwrap(), &['l', 'o']); + /// assert_eq!(iter.next().unwrap(), &['r', 'e']); + /// assert_eq!(iter.next().unwrap(), &['m']); + /// assert!(iter.next().is_none()); + /// ``` + #[unstable(feature = "exact_chunks", issue = "47115")] + #[inline] + pub fn exact_chunks(&self, chunk_size: usize) -> ExactChunks { + core_slice::SliceExt::exact_chunks(self, chunk_size) + } + /// Returns an iterator over `chunk_size` elements of the slice at a time. /// The chunks are mutable slices, and do not overlap. If `chunk_size` does /// not divide the length of the slice, then the last chunk will not @@ -660,6 +687,35 @@ impl [T] { core_slice::SliceExt::chunks_mut(self, chunk_size) } + /// Returns an iterator over `chunk_size` elements of the slice at a time. + /// The chunks are mutable slices, and do not overlap. If `chunk_size` does + /// not divide the length of the slice, then the last up to `chunk_size-1` + /// elements will be omitted. + /// + /// # Panics + /// + /// Panics if `chunk_size` is 0. + /// + /// # Examples + /// + /// ``` + /// let v = &mut [0, 0, 0, 0, 0]; + /// let mut count = 1; + /// + /// for chunk in v.exact_chunks_mut(2) { + /// for elem in chunk.iter_mut() { + /// *elem += count; + /// } + /// count += 1; + /// } + /// assert_eq!(v, &[1, 1, 2, 2, 3]); + /// ``` + #[unstable(feature = "exact_chunks", issue = "47115")] + #[inline] + pub fn exact_chunks_mut(&mut self, chunk_size: usize) -> ExactChunksMut { + core_slice::SliceExt::exact_chunks_mut(self, chunk_size) + } + /// Divides one slice into two at an index. /// /// The first will contain all indices from `[0, mid)` (excluding diff --git a/src/libcore/slice/mod.rs b/src/libcore/slice/mod.rs index 72036d6d3a248..5791b1d6e79c6 100644 --- a/src/libcore/slice/mod.rs +++ b/src/libcore/slice/mod.rs @@ -104,6 +104,9 @@ pub trait SliceExt { #[stable(feature = "core", since = "1.6.0")] fn chunks(&self, size: usize) -> Chunks; + #[unstable(feature = "exact_chunks", issue = "47115")] + fn exact_chunks(&self, size: usize) -> ExactChunks; + #[stable(feature = "core", since = "1.6.0")] fn get(&self, index: I) -> Option<&I::Output> where I: SliceIndex; @@ -181,6 +184,9 @@ pub trait SliceExt { #[stable(feature = "core", since = "1.6.0")] fn chunks_mut(&mut self, chunk_size: usize) -> ChunksMut; + #[unstable(feature = "exact_chunks", issue = "47115")] + fn exact_chunks_mut(&mut self, size: usize) -> ExactChunksMut; + #[stable(feature = "core", since = "1.6.0")] fn swap(&mut self, a: usize, b: usize); @@ -353,6 +359,14 @@ impl SliceExt for [T] { Chunks { v: self, chunk_size: chunk_size } } + #[inline] + fn exact_chunks(&self, chunk_size: usize) -> ExactChunks { + assert!(chunk_size != 0); + let rem = self.len() % chunk_size; + let len = self.len() - rem; + ExactChunks { v: &self[..len], chunk_size: chunk_size} + } + #[inline] fn get(&self, index: I) -> Option<&I::Output> where I: SliceIndex<[T]> @@ -536,6 +550,14 @@ impl SliceExt for [T] { ChunksMut { v: self, chunk_size: chunk_size } } + #[inline] + fn exact_chunks_mut(&mut self, chunk_size: usize) -> ExactChunksMut { + assert!(chunk_size != 0); + let rem = self.len() % chunk_size; + let len = self.len() - rem; + ExactChunksMut { v: &mut self[..len], chunk_size: chunk_size} + } + #[inline] fn swap(&mut self, a: usize, b: usize) { unsafe { @@ -2365,6 +2387,214 @@ unsafe impl<'a, T> TrustedRandomAccess for ChunksMut<'a, T> { fn may_have_side_effect() -> bool { false } } +/// An iterator over a slice in (non-overlapping) chunks (`chunk_size` elements at a +/// time). +/// +/// When the slice len is not evenly divided by the chunk size, the last +/// up to `chunk_size-1` elements will be omitted. +/// +/// This struct is created by the [`exact_chunks`] method on [slices]. +/// +/// [`exact_chunks`]: ../../std/primitive.slice.html#method.exact_chunks +/// [slices]: ../../std/primitive.slice.html +#[derive(Debug)] +#[unstable(feature = "exact_chunks", issue = "47115")] +pub struct ExactChunks<'a, T:'a> { + v: &'a [T], + chunk_size: usize +} + +// FIXME(#26925) Remove in favor of `#[derive(Clone)]` +#[unstable(feature = "exact_chunks", issue = "47115")] +impl<'a, T> Clone for ExactChunks<'a, T> { + fn clone(&self) -> ExactChunks<'a, T> { + ExactChunks { + v: self.v, + chunk_size: self.chunk_size, + } + } +} + +#[unstable(feature = "exact_chunks", issue = "47115")] +impl<'a, T> Iterator for ExactChunks<'a, T> { + type Item = &'a [T]; + + #[inline] + fn next(&mut self) -> Option<&'a [T]> { + if self.v.len() < self.chunk_size { + None + } else { + let (fst, snd) = self.v.split_at(self.chunk_size); + self.v = snd; + Some(fst) + } + } + + #[inline] + fn size_hint(&self) -> (usize, Option) { + let n = self.v.len() / self.chunk_size; + (n, Some(n)) + } + + #[inline] + fn count(self) -> usize { + self.len() + } + + #[inline] + fn nth(&mut self, n: usize) -> Option { + let (start, overflow) = n.overflowing_mul(self.chunk_size); + if start >= self.v.len() || overflow { + self.v = &[]; + None + } else { + let end = match start.checked_add(self.chunk_size) { + Some(sum) => cmp::min(self.v.len(), sum), + None => self.v.len(), + }; + + if end - start != self.chunk_size { + self.v = &[]; + None + } else { + let nth = &self.v[start..end]; + self.v = &self.v[end..]; + Some(nth) + } + } + } + + #[inline] + fn last(self) -> Option { + if self.v.len() < self.chunk_size { + None + } else { + let start = self.v.len() - self.chunk_size; + Some(&self.v[start..]) + } + } +} + +#[unstable(feature = "exact_chunks", issue = "47115")] +impl<'a, T> DoubleEndedIterator for ExactChunks<'a, T> { + #[inline] + fn next_back(&mut self) -> Option<&'a [T]> { + if self.v.len() < self.chunk_size { + None + } else { + let (fst, snd) = self.v.split_at(self.v.len() - self.chunk_size); + self.v = fst; + Some(snd) + } + } +} + +#[unstable(feature = "exact_chunks", issue = "47115")] +impl<'a, T> ExactSizeIterator for ExactChunks<'a, T> {} + +#[unstable(feature = "fused", issue = "35602")] +impl<'a, T> FusedIterator for ExactChunks<'a, T> {} + +/// An iterator over a slice in (non-overlapping) mutable chunks (`chunk_size` +/// elements at a time). When the slice len is not evenly divided by the chunk +/// size, the last up to `chunk_size-1` elements will be omitted. +/// +/// This struct is created by the [`exact_chunks_mut`] method on [slices]. +/// +/// [`exact_chunks_mut`]: ../../std/primitive.slice.html#method.exact_chunks_mut +/// [slices]: ../../std/primitive.slice.html +#[derive(Debug)] +#[unstable(feature = "exact_chunks", issue = "47115")] +pub struct ExactChunksMut<'a, T:'a> { + v: &'a mut [T], + chunk_size: usize +} + +#[unstable(feature = "exact_chunks", issue = "47115")] +impl<'a, T> Iterator for ExactChunksMut<'a, T> { + type Item = &'a mut [T]; + + #[inline] + fn next(&mut self) -> Option<&'a mut [T]> { + if self.v.len() < self.chunk_size { + None + } else { + let tmp = mem::replace(&mut self.v, &mut []); + let (head, tail) = tmp.split_at_mut(self.chunk_size); + self.v = tail; + Some(head) + } + } + + #[inline] + fn size_hint(&self) -> (usize, Option) { + let n = self.v.len() / self.chunk_size; + (n, Some(n)) + } + + #[inline] + fn count(self) -> usize { + self.len() + } + + #[inline] + fn nth(&mut self, n: usize) -> Option<&'a mut [T]> { + let (start, overflow) = n.overflowing_mul(self.chunk_size); + if start >= self.v.len() || overflow { + self.v = &mut []; + None + } else { + let end = match start.checked_add(self.chunk_size) { + Some(sum) => cmp::min(self.v.len(), sum), + None => self.v.len(), + }; + + if end - start != self.chunk_size { + self.v = &mut []; + None + } else { + let tmp = mem::replace(&mut self.v, &mut []); + let (head, tail) = tmp.split_at_mut(end); + let (_, nth) = head.split_at_mut(start); + self.v = tail; + Some(nth) + } + } + } + + #[inline] + fn last(self) -> Option { + if self.v.len() < self.chunk_size { + None + } else { + let start = (self.v.len() - self.chunk_size) / self.chunk_size * self.chunk_size; + Some(&mut self.v[start..]) + } + } +} + +#[unstable(feature = "exact_chunks", issue = "47115")] +impl<'a, T> DoubleEndedIterator for ExactChunksMut<'a, T> { + #[inline] + fn next_back(&mut self) -> Option<&'a mut [T]> { + if self.v.len() < self.chunk_size { + None + } else { + let tmp = mem::replace(&mut self.v, &mut []); + let tmp_len = tmp.len(); + let (head, tail) = tmp.split_at_mut(tmp_len - self.chunk_size); + self.v = head; + Some(tail) + } + } +} + +#[unstable(feature = "exact_chunks", issue = "47115")] +impl<'a, T> ExactSizeIterator for ExactChunksMut<'a, T> {} + +#[unstable(feature = "fused", issue = "35602")] +impl<'a, T> FusedIterator for ExactChunksMut<'a, T> {} + // // Free functions //