diff options
Diffstat (limited to 'library/core/src/slice/mod.rs')
| -rw-r--r-- | library/core/src/slice/mod.rs | 6453 |
1 files changed, 6453 insertions, 0 deletions
diff --git a/library/core/src/slice/mod.rs b/library/core/src/slice/mod.rs new file mode 100644 index 00000000000..9ed5a1f9622 --- /dev/null +++ b/library/core/src/slice/mod.rs @@ -0,0 +1,6453 @@ +// ignore-tidy-filelength +// ignore-tidy-undocumented-unsafe + +//! Slice management and manipulation. +//! +//! For more details see [`std::slice`]. +//! +//! [`std::slice`]: ../../std/slice/index.html + +#![stable(feature = "rust1", since = "1.0.0")] + +// How this module is organized. +// +// The library infrastructure for slices is fairly messy. There's +// a lot of stuff defined here. Let's keep it clean. +// +// The layout of this file is thus: +// +// * Inherent methods. This is where most of the slice API resides. +// * Implementations of a few common traits with important slice ops. +// * Definitions of a bunch of iterators. +// * Free functions. +// * The `raw` and `bytes` submodules. +// * Boilerplate trait implementations. + +use crate::cmp; +use crate::cmp::Ordering::{self, Equal, Greater, Less}; +use crate::fmt; +use crate::intrinsics::{assume, exact_div, is_aligned_and_not_null, unchecked_sub}; +use crate::iter::*; +use crate::marker::{self, Copy, Send, Sized, Sync}; +use crate::mem; +use crate::ops::{self, FnMut, Range}; +use crate::option::Option; +use crate::option::Option::{None, Some}; +use crate::ptr::{self, NonNull}; +use crate::result::Result; +use crate::result::Result::{Err, Ok}; + +#[unstable( + feature = "slice_internals", + issue = "none", + reason = "exposed from core to be reused in std; use the memchr crate" +)] +/// Pure rust memchr implementation, taken from rust-memchr +pub mod memchr; + +mod rotate; +mod sort; + +// +// Extension traits +// + +#[lang = "slice"] +#[cfg(not(test))] +impl<T> [T] { + /// Returns the number of elements in the slice. + /// + /// # Examples + /// + /// ``` + /// let a = [1, 2, 3]; + /// assert_eq!(a.len(), 3); + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + #[rustc_const_stable(feature = "const_slice_len", since = "1.32.0")] + #[inline] + // SAFETY: const sound because we transmute out the length field as a usize (which it must be) + #[allow(unused_attributes)] + #[allow_internal_unstable(const_fn_union)] + pub const fn len(&self) -> usize { + unsafe { crate::ptr::Repr { rust: self }.raw.len } + } + + /// Returns `true` if the slice has a length of 0. + /// + /// # Examples + /// + /// ``` + /// let a = [1, 2, 3]; + /// assert!(!a.is_empty()); + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + #[rustc_const_stable(feature = "const_slice_is_empty", since = "1.32.0")] + #[inline] + pub const fn is_empty(&self) -> bool { + self.len() == 0 + } + + /// Returns the first element of the slice, or `None` if it is empty. + /// + /// # Examples + /// + /// ``` + /// let v = [10, 40, 30]; + /// assert_eq!(Some(&10), v.first()); + /// + /// let w: &[i32] = &[]; + /// assert_eq!(None, w.first()); + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + #[inline] + pub fn first(&self) -> Option<&T> { + if let [first, ..] = self { Some(first) } else { None } + } + + /// Returns a mutable pointer to the first element of the slice, or `None` if it is empty. + /// + /// # Examples + /// + /// ``` + /// let x = &mut [0, 1, 2]; + /// + /// if let Some(first) = x.first_mut() { + /// *first = 5; + /// } + /// assert_eq!(x, &[5, 1, 2]); + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + #[inline] + pub fn first_mut(&mut self) -> Option<&mut T> { + if let [first, ..] = self { Some(first) } else { None } + } + + /// Returns the first and all the rest of the elements of the slice, or `None` if it is empty. + /// + /// # Examples + /// + /// ``` + /// let x = &[0, 1, 2]; + /// + /// if let Some((first, elements)) = x.split_first() { + /// assert_eq!(first, &0); + /// assert_eq!(elements, &[1, 2]); + /// } + /// ``` + #[stable(feature = "slice_splits", since = "1.5.0")] + #[inline] + pub fn split_first(&self) -> Option<(&T, &[T])> { + if let [first, tail @ ..] = self { Some((first, tail)) } else { None } + } + + /// Returns the first and all the rest of the elements of the slice, or `None` if it is empty. + /// + /// # Examples + /// + /// ``` + /// let x = &mut [0, 1, 2]; + /// + /// if let Some((first, elements)) = x.split_first_mut() { + /// *first = 3; + /// elements[0] = 4; + /// elements[1] = 5; + /// } + /// assert_eq!(x, &[3, 4, 5]); + /// ``` + #[stable(feature = "slice_splits", since = "1.5.0")] + #[inline] + pub fn split_first_mut(&mut self) -> Option<(&mut T, &mut [T])> { + if let [first, tail @ ..] = self { Some((first, tail)) } else { None } + } + + /// Returns the last and all the rest of the elements of the slice, or `None` if it is empty. + /// + /// # Examples + /// + /// ``` + /// let x = &[0, 1, 2]; + /// + /// if let Some((last, elements)) = x.split_last() { + /// assert_eq!(last, &2); + /// assert_eq!(elements, &[0, 1]); + /// } + /// ``` + #[stable(feature = "slice_splits", since = "1.5.0")] + #[inline] + pub fn split_last(&self) -> Option<(&T, &[T])> { + if let [init @ .., last] = self { Some((last, init)) } else { None } + } + + /// Returns the last and all the rest of the elements of the slice, or `None` if it is empty. + /// + /// # Examples + /// + /// ``` + /// let x = &mut [0, 1, 2]; + /// + /// if let Some((last, elements)) = x.split_last_mut() { + /// *last = 3; + /// elements[0] = 4; + /// elements[1] = 5; + /// } + /// assert_eq!(x, &[4, 5, 3]); + /// ``` + #[stable(feature = "slice_splits", since = "1.5.0")] + #[inline] + pub fn split_last_mut(&mut self) -> Option<(&mut T, &mut [T])> { + if let [init @ .., last] = self { Some((last, init)) } else { None } + } + + /// Returns the last element of the slice, or `None` if it is empty. + /// + /// # Examples + /// + /// ``` + /// let v = [10, 40, 30]; + /// assert_eq!(Some(&30), v.last()); + /// + /// let w: &[i32] = &[]; + /// assert_eq!(None, w.last()); + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + #[inline] + pub fn last(&self) -> Option<&T> { + if let [.., last] = self { Some(last) } else { None } + } + + /// Returns a mutable pointer to the last item in the slice. + /// + /// # Examples + /// + /// ``` + /// let x = &mut [0, 1, 2]; + /// + /// if let Some(last) = x.last_mut() { + /// *last = 10; + /// } + /// assert_eq!(x, &[0, 1, 10]); + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + #[inline] + pub fn last_mut(&mut self) -> Option<&mut T> { + if let [.., last] = self { Some(last) } else { None } + } + + /// Returns a reference to an element or subslice depending on the type of + /// index. + /// + /// - If given a position, returns a reference to the element at that + /// position or `None` if out of bounds. + /// - If given a range, returns the subslice corresponding to that range, + /// or `None` if out of bounds. + /// + /// # Examples + /// + /// ``` + /// let v = [10, 40, 30]; + /// assert_eq!(Some(&40), v.get(1)); + /// assert_eq!(Some(&[10, 40][..]), v.get(0..2)); + /// assert_eq!(None, v.get(3)); + /// assert_eq!(None, v.get(0..4)); + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + #[inline] + pub fn get<I>(&self, index: I) -> Option<&I::Output> + where + I: SliceIndex<Self>, + { + index.get(self) + } + + /// Returns a mutable reference to an element or subslice depending on the + /// type of index (see [`get`]) or `None` if the index is out of bounds. + /// + /// [`get`]: #method.get + /// + /// # Examples + /// + /// ``` + /// let x = &mut [0, 1, 2]; + /// + /// if let Some(elem) = x.get_mut(1) { + /// *elem = 42; + /// } + /// assert_eq!(x, &[0, 42, 2]); + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + #[inline] + pub fn get_mut<I>(&mut self, index: I) -> Option<&mut I::Output> + where + I: SliceIndex<Self>, + { + index.get_mut(self) + } + + /// Returns a reference to an element or subslice, without doing bounds + /// checking. + /// + /// This is generally not recommended, use with caution! + /// Calling this method with an out-of-bounds index is *[undefined behavior]* + /// even if the resulting reference is not used. + /// For a safe alternative see [`get`]. + /// + /// [`get`]: #method.get + /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html + /// + /// # Examples + /// + /// ``` + /// let x = &[1, 2, 4]; + /// + /// unsafe { + /// assert_eq!(x.get_unchecked(1), &2); + /// } + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + #[inline] + pub unsafe fn get_unchecked<I>(&self, index: I) -> &I::Output + where + I: SliceIndex<Self>, + { + // SAFETY: the caller must uphold most of the safety requirements for `get_unchecked`; + // the slice is dereferencable because `self` is a safe reference. + // The returned pointer is safe because impls of `SliceIndex` have to guarantee that it is. + unsafe { &*index.get_unchecked(self) } + } + + /// Returns a mutable reference to an element or subslice, without doing + /// bounds checking. + /// + /// This is generally not recommended, use with caution! + /// Calling this method with an out-of-bounds index is *[undefined behavior]* + /// even if the resulting reference is not used. + /// For a safe alternative see [`get_mut`]. + /// + /// [`get_mut`]: #method.get_mut + /// [undefined behavior]: https://doc.rust-lang.org/reference/behavior-considered-undefined.html + /// + /// # Examples + /// + /// ``` + /// let x = &mut [1, 2, 4]; + /// + /// unsafe { + /// let elem = x.get_unchecked_mut(1); + /// *elem = 13; + /// } + /// assert_eq!(x, &[1, 13, 4]); + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + #[inline] + pub unsafe fn get_unchecked_mut<I>(&mut self, index: I) -> &mut I::Output + where + I: SliceIndex<Self>, + { + // SAFETY: the caller must uphold the safety requirements for `get_unchecked_mut`; + // the slice is dereferencable because `self` is a safe reference. + // The returned pointer is safe because impls of `SliceIndex` have to guarantee that it is. + unsafe { &mut *index.get_unchecked_mut(self) } + } + + /// Returns a raw pointer to the slice's buffer. + /// + /// The caller must ensure that the slice outlives the pointer this + /// function returns, or else it will end up pointing to garbage. + /// + /// The caller must also ensure that the memory the pointer (non-transitively) points to + /// is never written to (except inside an `UnsafeCell`) using this pointer or any pointer + /// derived from it. If you need to mutate the contents of the slice, use [`as_mut_ptr`]. + /// + /// Modifying the container referenced by this slice may cause its buffer + /// to be reallocated, which would also make any pointers to it invalid. + /// + /// # Examples + /// + /// ``` + /// let x = &[1, 2, 4]; + /// let x_ptr = x.as_ptr(); + /// + /// unsafe { + /// for i in 0..x.len() { + /// assert_eq!(x.get_unchecked(i), &*x_ptr.add(i)); + /// } + /// } + /// ``` + /// + /// [`as_mut_ptr`]: #method.as_mut_ptr + #[stable(feature = "rust1", since = "1.0.0")] + #[rustc_const_stable(feature = "const_slice_as_ptr", since = "1.32.0")] + #[inline] + pub const fn as_ptr(&self) -> *const T { + self as *const [T] as *const T + } + + /// Returns an unsafe mutable pointer to the slice's buffer. + /// + /// The caller must ensure that the slice outlives the pointer this + /// function returns, or else it will end up pointing to garbage. + /// + /// Modifying the container referenced by this slice may cause its buffer + /// to be reallocated, which would also make any pointers to it invalid. + /// + /// # Examples + /// + /// ``` + /// let x = &mut [1, 2, 4]; + /// let x_ptr = x.as_mut_ptr(); + /// + /// unsafe { + /// for i in 0..x.len() { + /// *x_ptr.add(i) += 2; + /// } + /// } + /// assert_eq!(x, &[3, 4, 6]); + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + #[inline] + pub fn as_mut_ptr(&mut self) -> *mut T { + self as *mut [T] as *mut T + } + + /// Returns the two raw pointers spanning the slice. + /// + /// The returned range is half-open, which means that the end pointer + /// points *one past* the last element of the slice. This way, an empty + /// slice is represented by two equal pointers, and the difference between + /// the two pointers represents the size of the slice. + /// + /// See [`as_ptr`] for warnings on using these pointers. The end pointer + /// requires extra caution, as it does not point to a valid element in the + /// slice. + /// + /// This function is useful for interacting with foreign interfaces which + /// use two pointers to refer to a range of elements in memory, as is + /// common in C++. + /// + /// It can also be useful to check if a pointer to an element refers to an + /// element of this slice: + /// + /// ``` + /// #![feature(slice_ptr_range)] + /// + /// let a = [1, 2, 3]; + /// let x = &a[1] as *const _; + /// let y = &5 as *const _; + /// + /// assert!(a.as_ptr_range().contains(&x)); + /// assert!(!a.as_ptr_range().contains(&y)); + /// ``` + /// + /// [`as_ptr`]: #method.as_ptr + #[unstable(feature = "slice_ptr_range", issue = "65807")] + #[inline] + pub fn as_ptr_range(&self) -> Range<*const T> { + // The `add` here is safe, because: + // + // - Both pointers are part of the same object, as pointing directly + // past the object also counts. + // + // - The size of the slice is never larger than isize::MAX bytes, as + // noted here: + // - https://github.com/rust-lang/unsafe-code-guidelines/issues/102#issuecomment-473340447 + // - https://doc.rust-lang.org/reference/behavior-considered-undefined.html + // - https://doc.rust-lang.org/core/slice/fn.from_raw_parts.html#safety + // (This doesn't seem normative yet, but the very same assumption is + // made in many places, including the Index implementation of slices.) + // + // - There is no wrapping around involved, as slices do not wrap past + // the end of the address space. + // + // See the documentation of pointer::add. + let start = self.as_ptr(); + let end = unsafe { start.add(self.len()) }; + start..end + } + + /// Returns the two unsafe mutable pointers spanning the slice. + /// + /// The returned range is half-open, which means that the end pointer + /// points *one past* the last element of the slice. This way, an empty + /// slice is represented by two equal pointers, and the difference between + /// the two pointers represents the size of the slice. + /// + /// See [`as_mut_ptr`] for warnings on using these pointers. The end + /// pointer requires extra caution, as it does not point to a valid element + /// in the slice. + /// + /// This function is useful for interacting with foreign interfaces which + /// use two pointers to refer to a range of elements in memory, as is + /// common in C++. + /// + /// [`as_mut_ptr`]: #method.as_mut_ptr + #[unstable(feature = "slice_ptr_range", issue = "65807")] + #[inline] + pub fn as_mut_ptr_range(&mut self) -> Range<*mut T> { + // See as_ptr_range() above for why `add` here is safe. + let start = self.as_mut_ptr(); + let end = unsafe { start.add(self.len()) }; + start..end + } + + /// Swaps two elements in the slice. + /// + /// # Arguments + /// + /// * a - The index of the first element + /// * b - The index of the second element + /// + /// # Panics + /// + /// Panics if `a` or `b` are out of bounds. + /// + /// # Examples + /// + /// ``` + /// let mut v = ["a", "b", "c", "d"]; + /// v.swap(1, 3); + /// assert!(v == ["a", "d", "c", "b"]); + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + #[inline] + pub fn swap(&mut self, a: usize, b: usize) { + unsafe { + // Can't take two mutable loans from one vector, so instead just cast + // them to their raw pointers to do the swap + let pa: *mut T = &mut self[a]; + let pb: *mut T = &mut self[b]; + ptr::swap(pa, pb); + } + } + + /// Reverses the order of elements in the slice, in place. + /// + /// # Examples + /// + /// ``` + /// let mut v = [1, 2, 3]; + /// v.reverse(); + /// assert!(v == [3, 2, 1]); + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + #[inline] + pub fn reverse(&mut self) { + let mut i: usize = 0; + let ln = self.len(); + + // For very small types, all the individual reads in the normal + // path perform poorly. We can do better, given efficient unaligned + // load/store, by loading a larger chunk and reversing a register. + + // Ideally LLVM would do this for us, as it knows better than we do + // whether unaligned reads are efficient (since that changes between + // different ARM versions, for example) and what the best chunk size + // would be. Unfortunately, as of LLVM 4.0 (2017-05) it only unrolls + // the loop, so we need to do this ourselves. (Hypothesis: reverse + // is troublesome because the sides can be aligned differently -- + // will be, when the length is odd -- so there's no way of emitting + // pre- and postludes to use fully-aligned SIMD in the middle.) + + let fast_unaligned = cfg!(any(target_arch = "x86", target_arch = "x86_64")); + + if fast_unaligned && mem::size_of::<T>() == 1 { + // Use the llvm.bswap intrinsic to reverse u8s in a usize + let chunk = mem::size_of::<usize>(); + while i + chunk - 1 < ln / 2 { + unsafe { + let pa: *mut T = self.get_unchecked_mut(i); + let pb: *mut T = self.get_unchecked_mut(ln - i - chunk); + let va = ptr::read_unaligned(pa as *mut usize); + let vb = ptr::read_unaligned(pb as *mut usize); + ptr::write_unaligned(pa as *mut usize, vb.swap_bytes()); + ptr::write_unaligned(pb as *mut usize, va.swap_bytes()); + } + i += chunk; + } + } + + if fast_unaligned && mem::size_of::<T>() == 2 { + // Use rotate-by-16 to reverse u16s in a u32 + let chunk = mem::size_of::<u32>() / 2; + while i + chunk - 1 < ln / 2 { + unsafe { + let pa: *mut T = self.get_unchecked_mut(i); + let pb: *mut T = self.get_unchecked_mut(ln - i - chunk); + let va = ptr::read_unaligned(pa as *mut u32); + let vb = ptr::read_unaligned(pb as *mut u32); + ptr::write_unaligned(pa as *mut u32, vb.rotate_left(16)); + ptr::write_unaligned(pb as *mut u32, va.rotate_left(16)); + } + i += chunk; + } + } + + while i < ln / 2 { + // Unsafe swap to avoid the bounds check in safe swap. + unsafe { + let pa: *mut T = self.get_unchecked_mut(i); + let pb: *mut T = self.get_unchecked_mut(ln - i - 1); + ptr::swap(pa, pb); + } + i += 1; + } + } + + /// Returns an iterator over the slice. + /// + /// # Examples + /// + /// ``` + /// let x = &[1, 2, 4]; + /// let mut iterator = x.iter(); + /// + /// assert_eq!(iterator.next(), Some(&1)); + /// assert_eq!(iterator.next(), Some(&2)); + /// assert_eq!(iterator.next(), Some(&4)); + /// assert_eq!(iterator.next(), None); + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + #[inline] + pub fn iter(&self) -> Iter<'_, T> { + unsafe { + let ptr = self.as_ptr(); + assume(!ptr.is_null()); + + let end = if mem::size_of::<T>() == 0 { + (ptr as *const u8).wrapping_add(self.len()) as *const T + } else { + ptr.add(self.len()) + }; + + Iter { ptr: NonNull::new_unchecked(ptr as *mut T), end, _marker: marker::PhantomData } + } + } + + /// Returns an iterator that allows modifying each value. + /// + /// # Examples + /// + /// ``` + /// let x = &mut [1, 2, 4]; + /// for elem in x.iter_mut() { + /// *elem += 2; + /// } + /// assert_eq!(x, &[3, 4, 6]); + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + #[inline] + pub fn iter_mut(&mut self) -> IterMut<'_, T> { + unsafe { + let ptr = self.as_mut_ptr(); + assume(!ptr.is_null()); + + let end = if mem::size_of::<T>() == 0 { + (ptr as *mut u8).wrapping_add(self.len()) as *mut T + } else { + ptr.add(self.len()) + }; + + IterMut { ptr: NonNull::new_unchecked(ptr), end, _marker: marker::PhantomData } + } + } + + /// Returns an iterator over all contiguous windows of length + /// `size`. The windows overlap. If the slice is shorter than + /// `size`, the iterator returns no values. + /// + /// # Panics + /// + /// Panics if `size` is 0. + /// + /// # Examples + /// + /// ``` + /// let slice = ['r', 'u', 's', 't']; + /// let mut iter = slice.windows(2); + /// assert_eq!(iter.next().unwrap(), &['r', 'u']); + /// assert_eq!(iter.next().unwrap(), &['u', 's']); + /// assert_eq!(iter.next().unwrap(), &['s', 't']); + /// assert!(iter.next().is_none()); + /// ``` + /// + /// If the slice is shorter than `size`: + /// + /// ``` + /// let slice = ['f', 'o', 'o']; + /// let mut iter = slice.windows(4); + /// assert!(iter.next().is_none()); + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + #[inline] + pub fn windows(&self, size: usize) -> Windows<'_, T> { + assert!(size != 0); + Windows { v: self, size } + } + + /// Returns an iterator over `chunk_size` elements of the slice at a time, starting at the + /// beginning of the slice. + /// + /// The chunks are slices and do not overlap. If `chunk_size` does not divide the length of the + /// slice, then the last chunk will not have length `chunk_size`. + /// + /// See [`chunks_exact`] for a variant of this iterator that returns chunks of always exactly + /// `chunk_size` elements, and [`rchunks`] for the same iterator but starting at the end of the + /// slice. + /// + /// # 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()); + /// ``` + /// + /// [`chunks_exact`]: #method.chunks_exact + /// [`rchunks`]: #method.rchunks + #[stable(feature = "rust1", since = "1.0.0")] + #[inline] + pub fn chunks(&self, chunk_size: usize) -> Chunks<'_, T> { + assert!(chunk_size != 0); + Chunks { v: self, chunk_size } + } + + /// Returns an iterator over `chunk_size` elements of the slice at a time, starting at the + /// beginning of the slice. + /// + /// 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 have length `chunk_size`. + /// + /// See [`chunks_exact_mut`] for a variant of this iterator that returns chunks of always + /// exactly `chunk_size` elements, and [`rchunks_mut`] for the same iterator but starting at + /// the end of the slice. + /// + /// # Panics + /// + /// Panics if `chunk_size` is 0. + /// + /// # Examples + /// + /// ``` + /// let v = &mut [0, 0, 0, 0, 0]; + /// let mut count = 1; + /// + /// for chunk in v.chunks_mut(2) { + /// for elem in chunk.iter_mut() { + /// *elem += count; + /// } + /// count += 1; + /// } + /// assert_eq!(v, &[1, 1, 2, 2, 3]); + /// ``` + /// + /// [`chunks_exact_mut`]: #method.chunks_exact_mut + /// [`rchunks_mut`]: #method.rchunks_mut + #[stable(feature = "rust1", since = "1.0.0")] + #[inline] + pub fn chunks_mut(&mut self, chunk_size: usize) -> ChunksMut<'_, T> { + assert!(chunk_size != 0); + ChunksMut { v: self, chunk_size } + } + + /// Returns an iterator over `chunk_size` elements of the slice at a time, starting at the + /// beginning of the slice. + /// + /// 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 and can be retrieved + /// from the `remainder` function of the iterator. + /// + /// Due to each chunk having exactly `chunk_size` elements, the compiler can often optimize the + /// resulting code better than in the case of [`chunks`]. + /// + /// See [`chunks`] for a variant of this iterator that also returns the remainder as a smaller + /// chunk, and [`rchunks_exact`] for the same iterator but starting at the end of the slice. + /// + /// # Panics + /// + /// Panics if `chunk_size` is 0. + /// + /// # Examples + /// + /// ``` + /// let slice = ['l', 'o', 'r', 'e', 'm']; + /// let mut iter = slice.chunks_exact(2); + /// 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`]: #method.chunks + /// [`rchunks_exact`]: #method.rchunks_exact + #[stable(feature = "chunks_exact", since = "1.31.0")] + #[inline] + pub fn chunks_exact(&self, chunk_size: usize) -> ChunksExact<'_, T> { + assert!(chunk_size != 0); + let rem = self.len() % chunk_size; + let len = self.len() - rem; + let (fst, snd) = self.split_at(len); + ChunksExact { v: fst, rem: snd, chunk_size } + } + + /// Returns an iterator over `chunk_size` elements of the slice at a time, starting at the + /// beginning of the slice. + /// + /// 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 and can be + /// retrieved from the `into_remainder` function of the iterator. + /// + /// Due to each chunk having exactly `chunk_size` elements, the compiler can often optimize the + /// resulting code better than in the case of [`chunks_mut`]. + /// + /// See [`chunks_mut`] for a variant of this iterator that also returns the remainder as a + /// smaller chunk, and [`rchunks_exact_mut`] for the same iterator but starting at the end of + /// the slice. + /// + /// # Panics + /// + /// Panics if `chunk_size` is 0. + /// + /// # Examples + /// + /// ``` + /// let v = &mut [0, 0, 0, 0, 0]; + /// let mut count = 1; + /// + /// for chunk in v.chunks_exact_mut(2) { + /// for elem in chunk.iter_mut() { + /// *elem += count; + /// } + /// count += 1; + /// } + /// assert_eq!(v, &[1, 1, 2, 2, 0]); + /// ``` + /// + /// [`chunks_mut`]: #method.chunks_mut + /// [`rchunks_exact_mut`]: #method.rchunks_exact_mut + #[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); + 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 `chunk_size` elements of the slice at a time, starting at the end + /// of the slice. + /// + /// The chunks are slices and do not overlap. If `chunk_size` does not divide the length of the + /// slice, then the last chunk will not have length `chunk_size`. + /// + /// See [`rchunks_exact`] for a variant of this iterator that returns chunks of always exactly + /// `chunk_size` elements, and [`chunks`] for the same iterator but starting at the beginning + /// of the slice. + /// + /// # Panics + /// + /// Panics if `chunk_size` is 0. + /// + /// # Examples + /// + /// ``` + /// let slice = ['l', 'o', 'r', 'e', 'm']; + /// let mut iter = slice.rchunks(2); + /// assert_eq!(iter.next().unwrap(), &['e', 'm']); + /// assert_eq!(iter.next().unwrap(), &['o', 'r']); + /// assert_eq!(iter.next().unwrap(), &['l']); + /// assert!(iter.next().is_none()); + /// ``` + /// + /// [`rchunks_exact`]: #method.rchunks_exact + /// [`chunks`]: #method.chunks + #[stable(feature = "rchunks", since = "1.31.0")] + #[inline] + pub fn rchunks(&self, chunk_size: usize) -> RChunks<'_, T> { + assert!(chunk_size != 0); + RChunks { v: self, chunk_size } + } + + /// Returns an iterator over `chunk_size` elements of the slice at a time, starting at the end + /// of the slice. + /// + /// 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 have length `chunk_size`. + /// + /// See [`rchunks_exact_mut`] for a variant of this iterator that returns chunks of always + /// exactly `chunk_size` elements, and [`chunks_mut`] for the same iterator but starting at the + /// beginning of the slice. + /// + /// # Panics + /// + /// Panics if `chunk_size` is 0. + /// + /// # Examples + /// + /// ``` + /// let v = &mut [0, 0, 0, 0, 0]; + /// let mut count = 1; + /// + /// for chunk in v.rchunks_mut(2) { + /// for elem in chunk.iter_mut() { + /// *elem += count; + /// } + /// count += 1; + /// } + /// assert_eq!(v, &[3, 2, 2, 1, 1]); + /// ``` + /// + /// [`rchunks_exact_mut`]: #method.rchunks_exact_mut + /// [`chunks_mut`]: #method.chunks_mut + #[stable(feature = "rchunks", since = "1.31.0")] + #[inline] + pub fn rchunks_mut(&mut self, chunk_size: usize) -> RChunksMut<'_, T> { + assert!(chunk_size != 0); + RChunksMut { v: self, chunk_size } + } + + /// Returns an iterator over `chunk_size` elements of the slice at a time, starting at the + /// end of the slice. + /// + /// 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 and can be retrieved + /// from the `remainder` function of the iterator. + /// + /// Due to each chunk having exactly `chunk_size` elements, the compiler can often optimize the + /// resulting code better than in the case of [`chunks`]. + /// + /// See [`rchunks`] for a variant of this iterator that also returns the remainder as a smaller + /// chunk, and [`chunks_exact`] for the same iterator but starting at the beginning of the + /// slice. + /// + /// # Panics + /// + /// Panics if `chunk_size` is 0. + /// + /// # Examples + /// + /// ``` + /// let slice = ['l', 'o', 'r', 'e', 'm']; + /// let mut iter = slice.rchunks_exact(2); + /// assert_eq!(iter.next().unwrap(), &['e', 'm']); + /// assert_eq!(iter.next().unwrap(), &['o', 'r']); + /// assert!(iter.next().is_none()); + /// assert_eq!(iter.remainder(), &['l']); + /// ``` + /// + /// [`chunks`]: #method.chunks + /// [`rchunks`]: #method.rchunks + /// [`chunks_exact`]: #method.chunks_exact + #[stable(feature = "rchunks", since = "1.31.0")] + #[inline] + pub fn rchunks_exact(&self, chunk_size: usize) -> RChunksExact<'_, T> { + assert!(chunk_size != 0); + let rem = self.len() % chunk_size; + let (fst, snd) = self.split_at(rem); + RChunksExact { v: snd, rem: fst, chunk_size } + } + + /// Returns an iterator over `chunk_size` elements of the slice at a time, starting at the end + /// of the slice. + /// + /// 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 and can be + /// retrieved from the `into_remainder` function of the iterator. + /// + /// Due to each chunk having exactly `chunk_size` elements, the compiler can often optimize the + /// resulting code better than in the case of [`chunks_mut`]. + /// + /// See [`rchunks_mut`] for a variant of this iterator that also returns the remainder as a + /// smaller chunk, and [`chunks_exact_mut`] for the same iterator but starting at the beginning + /// of the slice. + /// + /// # Panics + /// + /// Panics if `chunk_size` is 0. + /// + /// # Examples + /// + /// ``` + /// let v = &mut [0, 0, 0, 0, 0]; + /// let mut count = 1; + /// + /// for chunk in v.rchunks_exact_mut(2) { + /// for elem in chunk.iter_mut() { + /// *elem += count; + /// } + /// count += 1; + /// } + /// assert_eq!(v, &[0, 2, 2, 1, 1]); + /// ``` + /// + /// [`chunks_mut`]: #method.chunks_mut + /// [`rchunks_mut`]: #method.rchunks_mut + /// [`chunks_exact_mut`]: #method.chunks_exact_mut + #[stable(feature = "rchunks", since = "1.31.0")] + #[inline] + pub fn rchunks_exact_mut(&mut self, chunk_size: usize) -> RChunksExactMut<'_, T> { + assert!(chunk_size != 0); + let rem = self.len() % chunk_size; + let (fst, snd) = self.split_at_mut(rem); + RChunksExactMut { v: snd, rem: fst, chunk_size } + } + + /// Divides one slice into two at an index. + /// + /// The first will contain all indices from `[0, mid)` (excluding + /// the index `mid` itself) and the second will contain all + /// indices from `[mid, len)` (excluding the index `len` itself). + /// + /// # Panics + /// + /// Panics if `mid > len`. + /// + /// # Examples + /// + /// ``` + /// let v = [1, 2, 3, 4, 5, 6]; + /// + /// { + /// let (left, right) = v.split_at(0); + /// assert!(left == []); + /// assert!(right == [1, 2, 3, 4, 5, 6]); + /// } + /// + /// { + /// let (left, right) = v.split_at(2); + /// assert!(left == [1, 2]); + /// assert!(right == [3, 4, 5, 6]); + /// } + /// + /// { + /// let (left, right) = v.split_at(6); + /// assert!(left == [1, 2, 3, 4, 5, 6]); + /// assert!(right == []); + /// } + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + #[inline] + pub fn split_at(&self, mid: usize) -> (&[T], &[T]) { + (&self[..mid], &self[mid..]) + } + + /// Divides one mutable slice into two at an index. + /// + /// The first will contain all indices from `[0, mid)` (excluding + /// the index `mid` itself) and the second will contain all + /// indices from `[mid, len)` (excluding the index `len` itself). + /// + /// # Panics + /// + /// Panics if `mid > len`. + /// + /// # Examples + /// + /// ``` + /// let mut v = [1, 0, 3, 0, 5, 6]; + /// // scoped to restrict the lifetime of the borrows + /// { + /// let (left, right) = v.split_at_mut(2); + /// assert!(left == [1, 0]); + /// assert!(right == [3, 0, 5, 6]); + /// left[1] = 2; + /// right[1] = 4; + /// } + /// assert!(v == [1, 2, 3, 4, 5, 6]); + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + #[inline] + pub fn split_at_mut(&mut self, mid: usize) -> (&mut [T], &mut [T]) { + let len = self.len(); + let ptr = self.as_mut_ptr(); + + unsafe { + assert!(mid <= len); + + (from_raw_parts_mut(ptr, mid), from_raw_parts_mut(ptr.add(mid), len - mid)) + } + } + + /// Returns an iterator over subslices separated by elements that match + /// `pred`. The matched element is not contained in the subslices. + /// + /// # Examples + /// + /// ``` + /// let slice = [10, 40, 33, 20]; + /// let mut iter = slice.split(|num| num % 3 == 0); + /// + /// assert_eq!(iter.next().unwrap(), &[10, 40]); + /// assert_eq!(iter.next().unwrap(), &[20]); + /// assert!(iter.next().is_none()); + /// ``` + /// + /// If the first element is matched, an empty slice will be the first item + /// returned by the iterator. Similarly, if the last element in the slice + /// is matched, an empty slice will be the last item returned by the + /// iterator: + /// + /// ``` + /// let slice = [10, 40, 33]; + /// let mut iter = slice.split(|num| num % 3 == 0); + /// + /// assert_eq!(iter.next().unwrap(), &[10, 40]); + /// assert_eq!(iter.next().unwrap(), &[]); + /// assert!(iter.next().is_none()); + /// ``` + /// + /// If two matched elements are directly adjacent, an empty slice will be + /// present between them: + /// + /// ``` + /// let slice = [10, 6, 33, 20]; + /// let mut iter = slice.split(|num| num % 3 == 0); + /// + /// assert_eq!(iter.next().unwrap(), &[10]); + /// assert_eq!(iter.next().unwrap(), &[]); + /// assert_eq!(iter.next().unwrap(), &[20]); + /// assert!(iter.next().is_none()); + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + #[inline] + pub fn split<F>(&self, pred: F) -> Split<'_, T, F> + where + F: FnMut(&T) -> bool, + { + Split { v: self, pred, finished: false } + } + + /// Returns an iterator over mutable subslices separated by elements that + /// match `pred`. The matched element is not contained in the subslices. + /// + /// # Examples + /// + /// ``` + /// let mut v = [10, 40, 30, 20, 60, 50]; + /// + /// for group in v.split_mut(|num| *num % 3 == 0) { + /// group[0] = 1; + /// } + /// assert_eq!(v, [1, 40, 30, 1, 60, 1]); + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + #[inline] + pub fn split_mut<F>(&mut self, pred: F) -> SplitMut<'_, T, F> + where + F: FnMut(&T) -> bool, + { + SplitMut { v: self, pred, finished: false } + } + + /// Returns an iterator over subslices separated by elements that match + /// `pred`. The matched element is contained in the end of the previous + /// subslice as a terminator. + /// + /// # Examples + /// + /// ``` + /// #![feature(split_inclusive)] + /// let slice = [10, 40, 33, 20]; + /// let mut iter = slice.split_inclusive(|num| num % 3 == 0); + /// + /// assert_eq!(iter.next().unwrap(), &[10, 40, 33]); + /// assert_eq!(iter.next().unwrap(), &[20]); + /// assert!(iter.next().is_none()); + /// ``` + /// + /// If the last element of the slice is matched, + /// that element will be considered the terminator of the preceding slice. + /// That slice will be the last item returned by the iterator. + /// + /// ``` + /// #![feature(split_inclusive)] + /// let slice = [3, 10, 40, 33]; + /// let mut iter = slice.split_inclusive(|num| num % 3 == 0); + /// + /// assert_eq!(iter.next().unwrap(), &[3]); + /// assert_eq!(iter.next().unwrap(), &[10, 40, 33]); + /// assert!(iter.next().is_none()); + /// ``` + #[unstable(feature = "split_inclusive", issue = "72360")] + #[inline] + pub fn split_inclusive<F>(&self, pred: F) -> SplitInclusive<'_, T, F> + where + F: FnMut(&T) -> bool, + { + SplitInclusive { v: self, pred, finished: false } + } + + /// Returns an iterator over mutable subslices separated by elements that + /// match `pred`. The matched element is contained in the previous + /// subslice as a terminator. + /// + /// # Examples + /// + /// ``` + /// #![feature(split_inclusive)] + /// let mut v = [10, 40, 30, 20, 60, 50]; + /// + /// for group in v.split_inclusive_mut(|num| *num % 3 == 0) { + /// let terminator_idx = group.len()-1; + /// group[terminator_idx] = 1; + /// } + /// assert_eq!(v, [10, 40, 1, 20, 1, 1]); + /// ``` + #[unstable(feature = "split_inclusive", issue = "72360")] + #[inline] + pub fn split_inclusive_mut<F>(&mut self, pred: F) -> SplitInclusiveMut<'_, T, F> + where + F: FnMut(&T) -> bool, + { + SplitInclusiveMut { v: self, pred, finished: false } + } + + /// Returns an iterator over subslices separated by elements that match + /// `pred`, starting at the end of the slice and working backwards. + /// The matched element is not contained in the subslices. + /// + /// # Examples + /// + /// ``` + /// let slice = [11, 22, 33, 0, 44, 55]; + /// let mut iter = slice.rsplit(|num| *num == 0); + /// + /// assert_eq!(iter.next().unwrap(), &[44, 55]); + /// assert_eq!(iter.next().unwrap(), &[11, 22, 33]); + /// assert_eq!(iter.next(), None); + /// ``` + /// + /// As with `split()`, if the first or last element is matched, an empty + /// slice will be the first (or last) item returned by the iterator. + /// + /// ``` + /// let v = &[0, 1, 1, 2, 3, 5, 8]; + /// let mut it = v.rsplit(|n| *n % 2 == 0); + /// assert_eq!(it.next().unwrap(), &[]); + /// assert_eq!(it.next().unwrap(), &[3, 5]); + /// assert_eq!(it.next().unwrap(), &[1, 1]); + /// assert_eq!(it.next().unwrap(), &[]); + /// assert_eq!(it.next(), None); + /// ``` + #[stable(feature = "slice_rsplit", since = "1.27.0")] + #[inline] + pub fn rsplit<F>(&self, pred: F) -> RSplit<'_, T, F> + where + F: FnMut(&T) -> bool, + { + RSplit { inner: self.split(pred) } + } + + /// Returns an iterator over mutable subslices separated by elements that + /// match `pred`, starting at the end of the slice and working + /// backwards. The matched element is not contained in the subslices. + /// + /// # Examples + /// + /// ``` + /// let mut v = [100, 400, 300, 200, 600, 500]; + /// + /// let mut count = 0; + /// for group in v.rsplit_mut(|num| *num % 3 == 0) { + /// count += 1; + /// group[0] = count; + /// } + /// assert_eq!(v, [3, 400, 300, 2, 600, 1]); + /// ``` + /// + #[stable(feature = "slice_rsplit", since = "1.27.0")] + #[inline] + pub fn rsplit_mut<F>(&mut self, pred: F) -> RSplitMut<'_, T, F> + where + F: FnMut(&T) -> bool, + { + RSplitMut { inner: self.split_mut(pred) } + } + + /// Returns an iterator over subslices separated by elements that match + /// `pred`, limited to returning at most `n` items. The matched element is + /// not contained in the subslices. + /// + /// The last element returned, if any, will contain the remainder of the + /// slice. + /// + /// # Examples + /// + /// Print the slice split once by numbers divisible by 3 (i.e., `[10, 40]`, + /// `[20, 60, 50]`): + /// + /// ``` + /// let v = [10, 40, 30, 20, 60, 50]; + /// + /// for group in v.splitn(2, |num| *num % 3 == 0) { + /// println!("{:?}", group); + /// } + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + #[inline] + pub fn splitn<F>(&self, n: usize, pred: F) -> SplitN<'_, T, F> + where + F: FnMut(&T) -> bool, + { + SplitN { inner: GenericSplitN { iter: self.split(pred), count: n } } + } + + /// Returns an iterator over subslices separated by elements that match + /// `pred`, limited to returning at most `n` items. The matched element is + /// not contained in the subslices. + /// + /// The last element returned, if any, will contain the remainder of the + /// slice. + /// + /// # Examples + /// + /// ``` + /// let mut v = [10, 40, 30, 20, 60, 50]; + /// + /// for group in v.splitn_mut(2, |num| *num % 3 == 0) { + /// group[0] = 1; + /// } + /// assert_eq!(v, [1, 40, 30, 1, 60, 50]); + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + #[inline] + pub fn splitn_mut<F>(&mut self, n: usize, pred: F) -> SplitNMut<'_, T, F> + where + F: FnMut(&T) -> bool, + { + SplitNMut { inner: GenericSplitN { iter: self.split_mut(pred), count: n } } + } + + /// Returns an iterator over subslices separated by elements that match + /// `pred` limited to returning at most `n` items. This starts at the end of + /// the slice and works backwards. The matched element is not contained in + /// the subslices. + /// + /// The last element returned, if any, will contain the remainder of the + /// slice. + /// + /// # Examples + /// + /// Print the slice split once, starting from the end, by numbers divisible + /// by 3 (i.e., `[50]`, `[10, 40, 30, 20]`): + /// + /// ``` + /// let v = [10, 40, 30, 20, 60, 50]; + /// + /// for group in v.rsplitn(2, |num| *num % 3 == 0) { + /// println!("{:?}", group); + /// } + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + #[inline] + pub fn rsplitn<F>(&self, n: usize, pred: F) -> RSplitN<'_, T, F> + where + F: FnMut(&T) -> bool, + { + RSplitN { inner: GenericSplitN { iter: self.rsplit(pred), count: n } } + } + + /// Returns an iterator over subslices separated by elements that match + /// `pred` limited to returning at most `n` items. This starts at the end of + /// the slice and works backwards. The matched element is not contained in + /// the subslices. + /// + /// The last element returned, if any, will contain the remainder of the + /// slice. + /// + /// # Examples + /// + /// ``` + /// let mut s = [10, 40, 30, 20, 60, 50]; + /// + /// for group in s.rsplitn_mut(2, |num| *num % 3 == 0) { + /// group[0] = 1; + /// } + /// assert_eq!(s, [1, 40, 30, 20, 60, 1]); + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + #[inline] + pub fn rsplitn_mut<F>(&mut self, n: usize, pred: F) -> RSplitNMut<'_, T, F> + where + F: FnMut(&T) -> bool, + { + RSplitNMut { inner: GenericSplitN { iter: self.rsplit_mut(pred), count: n } } + } + + /// Returns `true` if the slice contains an element with the given value. + /// + /// # Examples + /// + /// ``` + /// let v = [10, 40, 30]; + /// assert!(v.contains(&30)); + /// assert!(!v.contains(&50)); + /// ``` + /// + /// If you do not have an `&T`, but just an `&U` such that `T: Borrow<U>` + /// (e.g. `String: Borrow<str>`), you can use `iter().any`: + /// + /// ``` + /// let v = [String::from("hello"), String::from("world")]; // slice of `String` + /// assert!(v.iter().any(|e| e == "hello")); // search with `&str` + /// assert!(!v.iter().any(|e| e == "hi")); + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + pub fn contains(&self, x: &T) -> bool + where + T: PartialEq, + { + x.slice_contains(self) + } + + /// Returns `true` if `needle` is a prefix of the slice. + /// + /// # Examples + /// + /// ``` + /// let v = [10, 40, 30]; + /// assert!(v.starts_with(&[10])); + /// assert!(v.starts_with(&[10, 40])); + /// assert!(!v.starts_with(&[50])); + /// assert!(!v.starts_with(&[10, 50])); + /// ``` + /// + /// Always returns `true` if `needle` is an empty slice: + /// + /// ``` + /// let v = &[10, 40, 30]; + /// assert!(v.starts_with(&[])); + /// let v: &[u8] = &[]; + /// assert!(v.starts_with(&[])); + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + pub fn starts_with(&self, needle: &[T]) -> bool + where + T: PartialEq, + { + let n = needle.len(); + self.len() >= n && needle == &self[..n] + } + + /// Returns `true` if `needle` is a suffix of the slice. + /// + /// # Examples + /// + /// ``` + /// let v = [10, 40, 30]; + /// assert!(v.ends_with(&[30])); + /// assert!(v.ends_with(&[40, 30])); + /// assert!(!v.ends_with(&[50])); + /// assert!(!v.ends_with(&[50, 30])); + /// ``` + /// + /// Always returns `true` if `needle` is an empty slice: + /// + /// ``` + /// let v = &[10, 40, 30]; + /// assert!(v.ends_with(&[])); + /// let v: &[u8] = &[]; + /// assert!(v.ends_with(&[])); + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + pub fn ends_with(&self, needle: &[T]) -> bool + where + T: PartialEq, + { + let (m, n) = (self.len(), needle.len()); + m >= n && needle == &self[m - n..] + } + + /// Returns a subslice with the prefix removed. + /// + /// This method returns [`None`] if slice does not start with `prefix`. + /// Also it returns the original slice if `prefix` is an empty slice. + /// + /// # Examples + /// + /// ``` + /// #![feature(slice_strip)] + /// let v = &[10, 40, 30]; + /// assert_eq!(v.strip_prefix(&[10]), Some(&[40, 30][..])); + /// assert_eq!(v.strip_prefix(&[10, 40]), Some(&[30][..])); + /// assert_eq!(v.strip_prefix(&[50]), None); + /// assert_eq!(v.strip_prefix(&[10, 50]), None); + /// ``` + #[must_use = "returns the subslice without modifying the original"] + #[unstable(feature = "slice_strip", issue = "73413")] + pub fn strip_prefix(&self, prefix: &[T]) -> Option<&[T]> + where + T: PartialEq, + { + let n = prefix.len(); + if n <= self.len() { + let (head, tail) = self.split_at(n); + if head == prefix { + return Some(tail); + } + } + None + } + + /// Returns a subslice with the suffix removed. + /// + /// This method returns [`None`] if slice does not end with `suffix`. + /// Also it returns the original slice if `suffix` is an empty slice + /// + /// # Examples + /// + /// ``` + /// #![feature(slice_strip)] + /// let v = &[10, 40, 30]; + /// assert_eq!(v.strip_suffix(&[30]), Some(&[10, 40][..])); + /// assert_eq!(v.strip_suffix(&[40, 30]), Some(&[10][..])); + /// assert_eq!(v.strip_suffix(&[50]), None); + /// assert_eq!(v.strip_suffix(&[50, 30]), None); + /// ``` + #[must_use = "returns the subslice without modifying the original"] + #[unstable(feature = "slice_strip", issue = "73413")] + pub fn strip_suffix(&self, suffix: &[T]) -> Option<&[T]> + where + T: PartialEq, + { + let (len, n) = (self.len(), suffix.len()); + if n <= len { + let (head, tail) = self.split_at(len - n); + if tail == suffix { + return Some(head); + } + } + None + } + + /// Binary searches this sorted slice for a given element. + /// + /// If the value is found then [`Result::Ok`] is returned, containing the + /// index of the matching element. If there are multiple matches, then any + /// one of the matches could be returned. If the value is not found then + /// [`Result::Err`] is returned, containing the index where a matching + /// element could be inserted while maintaining sorted order. + /// + /// # Examples + /// + /// Looks up a series of four elements. The first is found, with a + /// uniquely determined position; the second and third are not + /// found; the fourth could match any position in `[1, 4]`. + /// + /// ``` + /// let s = [0, 1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55]; + /// + /// assert_eq!(s.binary_search(&13), Ok(9)); + /// assert_eq!(s.binary_search(&4), Err(7)); + /// assert_eq!(s.binary_search(&100), Err(13)); + /// let r = s.binary_search(&1); + /// assert!(match r { Ok(1..=4) => true, _ => false, }); + /// ``` + /// + /// If you want to insert an item to a sorted vector, while maintaining + /// sort order: + /// + /// ``` + /// let mut s = vec![0, 1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55]; + /// let num = 42; + /// let idx = s.binary_search(&num).unwrap_or_else(|x| x); + /// s.insert(idx, num); + /// assert_eq!(s, [0, 1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 42, 55]); + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + pub fn binary_search(&self, x: &T) -> Result<usize, usize> + where + T: Ord, + { + self.binary_search_by(|p| p.cmp(x)) + } + + /// Binary searches this sorted slice with a comparator function. + /// + /// The comparator function should implement an order consistent + /// with the sort order of the underlying slice, returning an + /// order code that indicates whether its argument is `Less`, + /// `Equal` or `Greater` the desired target. + /// + /// If the value is found then [`Result::Ok`] is returned, containing the + /// index of the matching element. If there are multiple matches, then any + /// one of the matches could be returned. If the value is not found then + /// [`Result::Err`] is returned, containing the index where a matching + /// element could be inserted while maintaining sorted order. + /// + /// # Examples + /// + /// Looks up a series of four elements. The first is found, with a + /// uniquely determined position; the second and third are not + /// found; the fourth could match any position in `[1, 4]`. + /// + /// ``` + /// let s = [0, 1, 1, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55]; + /// + /// let seek = 13; + /// assert_eq!(s.binary_search_by(|probe| probe.cmp(&seek)), Ok(9)); + /// let seek = 4; + /// assert_eq!(s.binary_search_by(|probe| probe.cmp(&seek)), Err(7)); + /// let seek = 100; + /// assert_eq!(s.binary_search_by(|probe| probe.cmp(&seek)), Err(13)); + /// let seek = 1; + /// let r = s.binary_search_by(|probe| probe.cmp(&seek)); + /// assert!(match r { Ok(1..=4) => true, _ => false, }); + /// ``` + #[stable(feature = "rust1", since = "1.0.0")] + #[inline] + pub fn binary_search_by<'a, F>(&'a self, mut f: F) -> Result<usize, usize> + where + F: FnMut(&'a T) -> Ordering, + { + let s = self; + let mut size = s.len(); + if size == 0 { + return Err(0); + } + let mut base = 0usize; + while size > 1 { + let half = size / 2; + let mid = base + half; + // mid is always in [0, size), that means mid is >= 0 and < size. + // mid >= 0: by definition + // mid < size: mid = size / 2 + size / 4 + size / 8 ... + let cmp = f(unsafe { s.get_unchecked(mid) }); + base = if cmp == Greater { base } else { mid }; + size -= half; + } + // base is always in [0, size) because base <= mid. + let cmp = f(unsafe { s.get_unchecked(base) }); + if cmp == Equal { Ok(base) } else { Err(base + (cmp == Less) as usize) } + } + + /// Binary searches this sorted slice with a key extraction function. + /// + /// Assumes that the slice is sorted by the key, for instance with + /// [`sort_by_key`] using the same key extraction function. + /// + /// If the value is found then [`Result::Ok`] is returned, containing the + /// index of the matching element. If there are multiple matches, then any + /// one of the matches could be returned. If the value is not found then + /// [`Result::Err`] is returned, containing the index where a matching + /// element could be inserted while maintaining sorted order. + /// + /// [`sort_by_key`]: #method.sort_by_key + /// + /// # Examples + /// + /// Looks up a series of four elements in a slice of pairs sorted by + /// their second elements. The first is found, with a uniquely + /// determined position; the second and third are not found; the + /// fourth could match any position in `[1, 4]`. + /// + /// ``` + /// let s = [(0, 0), (2, 1), (4, 1), (5, 1), (3, 1), + /// (1, 2), (2, 3), (4, 5), (5, 8), (3, 13), + /// (1, 21), (2, 34), (4, 55)]; + /// + /// assert_eq!(s.binary_search_by_key(&13, |&(a,b)| b), Ok(9)); + /// assert_eq!(s.binary_search_by_key(&4, |&(a,b)| b), Err(7)); + /// assert_eq!(s.binary_search_by_key(&100, |&(a,b)| b), Err(13)); + /// let r = s.binary_search_by_key(&1, |&(a,b)| b); + /// assert!(match r { Ok(1..=4) => true, _ => false, }); + /// ``` + #[stable(feature = "slice_binary_search_by_key", since = "1.10.0")] + #[inline] + pub fn binary_search_by_key<'a, B, F>(&'a self, b: &B, mut f: F) -> Result<usize, usize> + where + F: FnMut(&'a T) -> B, + B: Ord, + { + self.binary_search_by(|k| f(k).cmp(b)) + } + + /// Sorts the slice, but may not preserve the order of equal elements. + /// + /// This sort is unstable (i.e., may reorder equal elements), in-place + /// (i.e., does not allocate), and *O*(*n* \* log(*n*)) worst-case. + /// + /// # Current implementation + /// + /// The current algorithm is based on [pattern-defeating quicksort][pdqsort] by Orson Peters, + /// which combines the fast average case of randomized quicksort with the fast worst case of + /// heapsort, while achieving linear time on slices with certain patterns. It uses some + /// randomization to avoid degenerate cases, but with a fixed seed to always provide + /// deterministic behavior. + /// + /// It is typically faster than stable sorting, except in a few special cases, e.g., when the + /// slice consists of several concatenated sorted sequences. + /// + /// # Examples + /// + /// ``` + /// let mut v = [-5, 4, 1, -3, 2]; + /// + /// v.sort_unstable(); + /// assert!(v == [-5, -3, 1, 2, 4]); + /// ``` + /// + /// [pdqsort]: https://github.com/orlp/pdqsort + #[stable(feature = "sort_unstable", since = "1.20.0")] + #[inline] + pub fn sort_unstable(&mut self) + where + T: Ord, + { + sort::quicksort(self, |a, b| a.lt(b)); + } + + /// Sorts the slice with a comparator function, but may not preserve the order of equal + /// elements. + /// + /// This sort is unstable (i.e., may reorder equal elements), in-place + /// (i.e., does not allocate), and *O*(*n* \* log(*n*)) worst-case. + /// + /// The comparator function must define a total ordering for the elements in the slice. If + /// the ordering is not total, the order of the elements is unspecified. An order is a + /// total order if it is (for all a, b and c): + /// + /// * total and antisymmetric: exactly one of a < b, a == b or a > b is true; and + /// * transitive, a < b and b < c implies a < c. The same must hold for both == and >. + /// + /// For example, while [`f64`] doesn't implement [`Ord`] because `NaN != NaN`, we can use + /// `partial_cmp` as our sort function when we know the slice doesn't contain a `NaN`. + /// + /// ``` + /// let mut floats = [5f64, 4.0, 1.0, 3.0, 2.0]; + /// floats.sort_unstable_by(|a, b| a.partial_cmp(b).unwrap()); + /// assert_eq!(floats, [1.0, 2.0, 3.0, 4.0, 5.0]); + /// ``` + /// + /// # Current implementation + /// + /// The current algorithm is based on [pattern-defeating quicksort][pdqsort] by Orson Peters, + /// which combines the fast average case of randomized quicksort with the fast worst case of + /// heapsort, while achieving linear time on slices with certain patterns. It uses some + /// randomization to avoid degenerate cases, but with a fixed seed to always provide + /// deterministic behavior. + /// + /// It is typically faster than stable sorting, except in a few special cases, e.g., when the + /// slice consists of several concatenated sorted sequences. + /// + /// # Examples + /// + /// ``` + /// let mut v = [5, 4, 1, 3, 2]; + /// v.sort_unstable_by(|a, b| a.cmp(b)); + /// assert!(v == [1, 2, 3, 4, 5]); + /// + /// // reverse sorting + /// v.sort_unstable_by(|a, b| b.cmp(a)); + /// assert!(v == [5, 4, 3, 2, 1]); + /// ``` + /// + /// [pdqsort]: https://github.com/orlp/pdqsort + #[stable(feature = "sort_unstable", since = "1.20.0")] + #[inline] + pub fn sort_unstable_by<F>(&mut self, mut compare: F) + where + F: FnMut(&T, &T) -> Ordering, + { + sort::quicksort(self, |a, b| compare(a, b) == Ordering::Less); + } + + /// Sorts the slice with a key extraction function, but may not preserve the order of equal + /// elements. + /// + /// This sort is unstable (i.e., may reorder equal elements), in-place + /// (i.e., does not allocate), and *O*(m \* *n* \* log(*n*)) worst-case, where the key function is + /// *O*(*m*). + /// + /// # Current implementation + /// + /// The current algorithm is based on [pattern-defeating quicksort][pdqsort] by Orson Peters, + /// which combines the fast average case of randomized quicksort with the fast worst case of + /// heapsort, while achieving linear time on slices with certain patterns. It uses some + /// randomization to avoid degenerate cases, but with a fixed seed to always provide + /// deterministic behavior. + /// + /// Due to its key calling strategy, [`sort_unstable_by_key`](#method.sort_unstable_by_key) + /// is likely to be slower than [`sort_by_cached_key`](#method.sort_by_cached_key) in + /// cases where the key function is expensive. + /// + /// # Examples + /// + /// ``` + /// let mut v = [-5i32, 4, 1, -3, 2]; + /// + /// v.sort_unstable_by_key(|k| k.abs()); + /// assert!(v == [1, 2, -3, 4, -5]); + /// ``` + /// + /// [pdqsort]: https://github.com/orlp/pdqsort + #[stable(feature = "sort_unstable", since = "1.20.0")] + #[inline] + pub fn sort_unstable_by_key<K, F>(&mut self, mut f: F) + where + F: FnMut(&T) -> K, + K: Ord, + { + sort::quicksort(self, |a, b| f(a).lt(&f(b))); + } + + /// Reorder the slice such that the element at `index` is at its final sorted position. + /// + /// This reordering has the additional property that any value at position `i < index` will be + /// less than or equal to any value at a position `j > index`. Additionally, this reordering is + /// unstable (i.e. any number of equal elements may end up at position `index`), in-place + /// (i.e. does not allocate), and *O*(*n*) worst-case. This function is also/ known as "kth + /// element" in other libraries. It returns a triplet of the following values: all elements less + /// than the one at the given index, the value at the given index, and all elements greater than + /// the one at the given index. + /// + /// # Current implementation + /// + /// The current algorithm is based on the quickselect portion of the same quicksort algorithm + /// used for [`sort_unstable`]. + /// + /// [`sort_unstable`]: #method.sort_unstable + /// + /// # Panics + /// + /// Panics when `index >= len()`, meaning it always panics on empty slices. + /// + /// # Examples + /// + /// ``` + /// #![feature(slice_partition_at_index)] + /// + /// let mut v = [-5i32, 4, 1, -3, 2]; + /// + /// // Find the median + /// v.partition_at_index(2); + /// + /// // We are only guaranteed the slice will be one of the following, based on the way we sort + /// // about the specified index. + /// assert!(v == [-3, -5, 1, 2, 4] || + /// v == [-5, -3, 1, 2, 4] || + /// v == [-3, -5, 1, 4, 2] || + /// v == [-5, -3, 1, 4, 2]); + /// ``` + #[unstable(feature = "slice_partition_at_index", issue = "55300")] + #[inline] + pub fn partition_at_index(&mut self, index: usize) -> (&mut [T], &mut T, &mut [T]) + where + T: Ord, + { + let mut f = |a: &T, b: &T| a.lt(b); + sort::partition_at_index(self, index, &mut f) + } + + /// Reorder the slice with a comparator function such that the element at `index` is at its + /// final sorted position. + /// + /// This reordering has the additional property that any value at position `i < index` will be + /// less than or equal to any value at a position `j > index` using the comparator function. + /// Additionally, this reordering is unstable (i.e. any number of equal elements may end up at + /// position `index`), in-place (i.e. does not allocate), and *O*(*n*) worst-case. This function + /// is also known as "kth element" in other libraries. It returns a triplet of the following + /// values: all elements less than the one at the given index, the value at the given index, + /// and all elements greater than the one at the given index, using the provided comparator + /// function. + /// + /// # Current implementation + /// + /// The current algorithm is based on the quickselect portion of the same quicksort algorithm + /// used for [`sort_unstable`]. + /// + /// [`sort_unstable`]: #method.sort_unstable + /// + /// # Panics + /// + /// Panics when `index >= len()`, meaning it always panics on empty slices. + /// + /// # Examples + /// + /// ``` + /// #![feature(slice_partition_at_index)] + /// + /// let mut v = [-5i32, 4, 1, -3, 2]; + /// + /// // Find the median as if the slice were sorted in descending order. + /// v.partition_at_index_by(2, |a, b| b.cmp(a)); + /// + /// // We are only guaranteed the slice will be one of the following, based on the way we sort + /// // about the specified index. + /// assert!(v == [2, 4, 1, -5, -3] || + /// v == [2, 4, 1, -3, -5] || + /// v == [4, 2, 1, -5, -3] || + /// v == [4, 2, 1, -3, -5]); + /// ``` + #[unstable(feature = "slice_partition_at_index", issue = "55300")] + #[inline] + pub fn partition_at_index_by<F>( + &mut self, + index: usize, + mut compare: F, + ) -> (&mut [T], &mut T, &mut [T]) + where + F: FnMut(&T, &T) -> Ordering, + { + let mut f = |a: &T, b: &T| compare(a, b) == Less; + sort::partition_at_index(self, index, &mut f) + } + + /// Reorder the slice with a key extraction function such that the element at `index` is at its + /// final sorted position. + /// + /// This reordering has the additional property that any value at position `i < index` will be + /// less than or equal to any value at a position `j > index` using the key extraction function. + /// Additionally, this reordering is unstable (i.e. any number of equal elements may end up at + /// position `index`), in-place (i.e. does not allocate), and *O*(*n*) worst-case. This function + /// is also known as "kth element" in other libraries. It returns a triplet of the following + /// values: all elements less than the one at the given index, the value at the given index, and + /// all elements greater than the one at the given index, using the provided key extraction + /// function. + /// + /// # Current implementation + /// + /// The current algorithm is based on the quickselect portion of the same quicksort algorithm + /// used for [`sort_unstable`]. + /// + /// [`sort_unstable`]: #method.sort_unstable + /// + /// # Panics + /// + /// Panics when `index >= len()`, meaning it always panics on empty slices. + /// + /// # Examples + /// + /// ``` + /// #![feature(slice_partition_at_index)] + /// + /// let mut v = [-5i32, 4, 1, -3, 2]; + /// + /// // Return the median as if the array were sorted according to absolute value. + /// v.partition_at_index_by_key(2, |a| a.abs()); + /// + /// // We are only guaranteed the slice will be one of the following, based on the way we sort + /// // about the specified index. + /// assert!(v == [1, 2, -3, 4, -5] || + /// v == [1, 2, -3, -5, 4] || + /// v == [2, 1, -3, 4, -5] || + /// v == [2, 1, -3, -5, 4]); + /// ``` + #[unstable(feature = "slice_partition_at_index", issue = "55300")] + #[inline] + pub fn partition_at_index_by_key<K, F>( + &mut self, + index: usize, + mut f: F, + ) -> (&mut [T], &mut T, &mut [T]) + where + F: FnMut(&T) -> K, + K: Ord, + { + let mut g = |a: &T, b: &T| f(a).lt(&f(b)); + sort::partition_at_index(self, index, &mut g) + } + + /// Moves all consecutive repeated elements to the end of the slice according to the + /// [`PartialEq`] trait implementation. + /// + /// Returns two slices. The first contains no consecutive repeated elements. + /// The second contains all the duplicates in no specified order. + /// + /// If the slice is sorted, the first returned slice contains no duplicates. + /// + /// # Examples + /// + /// ``` + /// #![feature(slice_partition_dedup)] + /// + /// let mut slice = [1, 2, 2, 3, 3, 2, 1, 1]; + /// + /// let (dedup, duplicates) = slice.partition_dedup(); + /// + /// assert_eq!(dedup, [1, 2, 3, 2, 1]); + /// assert_eq!(duplicates, [2, 3, 1]); + /// ``` + #[unstable(feature = "slice_partition_dedup", issue = "54279")] + #[inline] + pub fn partition_dedup(&mut self) -> (&mut [T], &mut [T]) + where + T: PartialEq, + { + self.partition_dedup_by(|a, b| a == b) + } + + /// Moves all but the first of consecutive elements to the end of the slice satisfying + /// a given equality relation. + /// + /// Returns two slices. The first contains no consecutive repeated elements. + /// The second contains all the duplicates in no specified order. + /// + /// The `same_bucket` function is passed references to two elements from the slice and + /// must determine if the elements compare equal. The elements are passed in opposite order + /// from their order in the slice, so if `same_bucket(a, b)` returns `true`, `a` is moved + /// at the end of the slice. + /// + /// If the slice is sorted, the first returned slice contains no duplicates. + /// + /// # Examples + /// + /// ``` + /// #![feature(slice_partition_dedup)] + /// + /// let mut slice = ["foo", "Foo", "BAZ", "Bar", "bar", "baz", "BAZ"]; + /// + /// let (dedup, duplicates) = slice.partition_dedup_by(|a, b| a.eq_ignore_ascii_case(b)); + /// + /// assert_eq!(dedup, ["foo", "BAZ", "Bar", "baz"]); + /// assert_eq!(duplicates, ["bar", "Foo", "BAZ"]); + /// ``` + #[unstable(feature = "slice_partition_dedup", issue = "54279")] + #[inline] + pub fn partition_dedup_by<F>(&mut self, mut same_bucket: F) -> (&mut [T], &mut [T]) + where + F: FnMut(&mut T, &mut T) -> bool, + { + // Although we have a mutable reference to `self`, we cannot make + // *arbitrary* changes. The `same_bucket` calls could panic, so we + // must ensure that the slice is in a valid state at all times. + // + // The way that we handle this is by using swaps; we iterate + // over all the elements, swapping as we go so that at the end + // the elements we wish to keep are in the front, and those we + // wish to reject are at the back. We can then split the slice. + // This operation is still `O(n)`. + // + // Example: We start in this state, where `r` represents "next + // read" and `w` represents "next_write`. + // + // r + // +---+---+---+---+---+---+ + // | 0 | 1 | 1 | 2 | 3 | 3 | + // +---+---+---+---+---+---+ + // w + // + // Comparing self[r] against self[w-1], this is not a duplicate, so + // we swap self[r] and self[w] (no effect as r==w) and then increment both + // r and w, leaving us with: + // + // r + // +---+---+---+---+---+---+ + // | 0 | 1 | 1 | 2 | 3 | 3 | + // +---+---+---+---+---+---+ + // w + // + // Comparing self[r] against self[w-1], this value is a duplicate, + // so we increment `r` but leave everything else unchanged: + // + // r + // +---+---+---+---+---+---+ + // | 0 | 1 | 1 | 2 | 3 | 3 | + // +---+---+---+---+---+---+ + // w + // + // Comparing self[r] against self[w-1], this is not a duplicate, + // so swap self[r] and self[w] and advance r and w: + // + // r + // +---+---+---+---+---+---+ + // | 0 | 1 | 2 | 1 | 3 | 3 | + // +---+---+---+---+---+---+ + // w + // + // Not a duplicate, repeat: + // + // r + // +---+---+---+---+---+---+ + // | 0 | 1 | 2 | 3 | 1 | 3 | + // +---+---+---+---+---+---+ + // w + // + // Duplicate, advance r. End of slice. Split at w. + + let len = self.len(); + if len <= 1 { + return (self, &mut []); + } + + let ptr = self.as_mut_ptr(); + let mut next_read: usize = 1; + let mut next_write: usize = 1; + + unsafe { + // Avoid bounds checks by using raw pointers. + while next_read < len { + let ptr_read = ptr.add(next_read); + let prev_ptr_write = ptr.add(next_write - 1); + if !same_bucket(&mut *ptr_read, &mut *prev_ptr_write) { + if next_read != next_write { + let ptr_write = prev_ptr_write.offset(1); + mem::swap(&mut *ptr_read, &mut *ptr_write); + } + next_write += 1; + } + next_read += 1; + } + } + + self.split_at_mut(next_write) + } + + /// Moves all but the first of consecutive elements to the end of the slice that resolve + /// to the same key. + /// + /// Returns two slices. The first contains no consecutive repeated elements. + /// The second contains all the duplicates in no specified order. + /// + /// If the slice is sorted, the first returned slice contains no duplicates. + /// + /// # Examples + /// + /// ``` + /// #![feature(slice_partition_dedup)] + /// + /// let mut slice = [10, 20, 21, 30, 30, 20, 11, 13]; + /// + /// let (dedup, duplicates) = slice.partition_dedup_by_key(|i| *i / 10); + /// + /// assert_eq!(dedup, [10, 20, 30, 20, 11]); + /// assert_eq!(duplicates, [21, 30, 13]); + /// ``` + #[unstable(feature = "slice_partition_dedup", issue = "54279")] + #[inline] + pub fn partition_dedup_by_key<K, F>(&mut self, mut key: F) -> (&mut [T], &mut [T]) + where + F: FnMut(&mut T) -> K, + K: PartialEq, + { + self.partition_dedup_by(|a, b| key(a) == key(b)) + } + + /// Rotates the slice in-place such that the first `mid` elements of the + /// slice move to the end while the last `self.len() - mid` elements move to + /// the front. After calling `rotate_left`, the element previously at index + /// `mid` will become the first element in the slice. + /// + /// # Panics + /// + /// This function will panic if `mid` is greater than the length of the + /// slice. Note that `mid == self.len()` does _not_ panic and is a no-op + /// rotation. + /// + /// # Complexity + /// + /// Takes linear (in `self.len()`) time. + /// + /// # Examples + /// + /// ``` + /// let mut a = ['a', 'b', 'c', 'd', 'e', 'f']; + /// a.rotate_left(2); + /// assert_eq!(a, ['c', 'd', 'e', 'f', 'a', 'b']); + /// ``` + /// + /// Rotating a subslice: + /// + /// ``` + /// let mut a = ['a', 'b', 'c', 'd', 'e', 'f']; + /// a[1..5].rotate_left(1); + /// assert_eq!(a, ['a', 'c', 'd', 'e', 'b', 'f']); + /// ``` + #[stable(feature = "slice_rotate", since = "1.26.0")] + pub fn rotate_left(&mut self, mid: usize) { + assert!(mid <= self.len()); + let k = self.len() - mid; + + unsafe { + let p = self.as_mut_ptr(); + rotate::ptr_rotate(mid, p.add(mid), k); + } + } + + /// Rotates the slice in-place such that the first `self.len() - k` + /// elements of the slice move to the end while the last `k` elements move + /// to the front. After calling `rotate_right`, the element previously at + /// index `self.len() - k` will become the first element in the slice. + /// + /// # Panics + /// + /// This function will panic if `k` is greater than the length of the + /// slice. Note that `k == self.len()` does _not_ panic and is a no-op + /// rotation. + /// + /// # Complexity + /// + /// Takes linear (in `self.len()`) time. + /// + /// # Examples + /// + /// ``` + /// let mut a = ['a', 'b', 'c', 'd', 'e', 'f']; + /// a.rotate_right(2); + /// assert_eq!(a, ['e', 'f', 'a', 'b', 'c', 'd']); + /// ``` + /// + /// Rotate a subslice: + /// + /// ``` + /// let mut a = ['a', 'b', 'c', 'd', 'e', 'f']; + /// a[1..5].rotate_right(1); + /// assert_eq!(a, ['a', 'e', 'b', 'c', 'd', 'f']); + /// ``` + #[stable(feature = "slice_rotate", since = "1.26.0")] + pub fn rotate_right(&mut self, k: usize) { + assert!(k <= self.len()); + let mid = self.len() - k; + + unsafe { + let p = self.as_mut_ptr(); + rotate::ptr_rotate(mid, p.add(mid), k); + } + } + + /// Fills `self` with elements by cloning `value`. + /// + /// # Examples + /// + /// ``` + /// #![feature(slice_fill)] + /// + /// let mut buf = vec![0; 10]; + /// buf.fill(1); + /// assert_eq!(buf, vec![1; 10]); + /// ``` + #[unstable(feature = "slice_fill", issue = "70758")] + pub fn fill(&mut self, value: T) + where + T: Clone, + { + if let Some((last, elems)) = self.split_last_mut() { + for el in elems { + el.clone_from(&value); + } + + *last = value + } + } + + /// Copies the elements from `src` into `self`. + /// + /// The length of `src` must be the same as `self`. + /// + /// If `T` implements `Copy`, it can be more performant to use + /// [`copy_from_slice`]. + /// + /// # Panics + /// + /// This function will panic if the two slices have different lengths. + /// + /// # Examples + /// + /// Cloning two elements from a slice into another: + /// + /// ``` + /// let src = [1, 2, 3, 4]; + /// let mut dst = [0, 0]; + /// + /// // Because the slices have to be the same length, + /// // we slice the source slice from four elements + /// // to two. It will panic if we don't do this. + /// dst.clone_from_slice(&src[2..]); + /// + /// assert_eq!(src, [1, 2, 3, 4]); + /// assert_eq!(dst, [3, 4]); + /// ``` + /// + /// Rust enforces that there can only be one mutable reference with no + /// immutable references to a particular piece of data in a particular + /// scope. Because of this, attempting to use `clone_from_slice` on a + /// single slice will result in a compile failure: + /// + /// ```compile_fail + /// let mut slice = [1, 2, 3, 4, 5]; + /// + /// slice[..2].clone_from_slice(&slice[3..]); // compile fail! + /// ``` + /// + /// To work around this, we can use [`split_at_mut`] to create two distinct + /// sub-slices from a slice: + /// + /// ``` + /// let mut slice = [1, 2, 3, 4, 5]; + /// + /// { + /// let (left, right) = slice.split_at_mut(2); + /// left.clone_from_slice(&right[1..]); + /// } + /// + /// assert_eq!(slice, [4, 5, 3, 4, 5]); + /// ``` + /// + /// [`copy_from_slice`]: #method.copy_from_slice + /// [`split_at_mut`]: #method.split_at_mut + #[stable(feature = "clone_from_slice", since = "1.7.0")] + pub fn clone_from_slice(&mut self, src: &[T]) + where + T: Clone, + { + assert!(self.len() == src.len(), "destination and source slices have different lengths"); + // NOTE: We need to explicitly slice them to the same length + // for bounds checking to be elided, and the optimizer will + // generate memcpy for simple cases (for example T = u8). + let len = self.len(); + let src = &src[..len]; + for i in 0..len { + self[i].clone_from(&src[i]); + } + } + + /// Copies all elements from `src` into `self`, using a memcpy. + /// + /// The length of `src` must be the same as `self`. + /// + /// If `T` does not implement `Copy`, use [`clone_from_slice`]. + /// + /// # Panics + /// + /// This function will panic if the two slices have different lengths. + /// + /// # Examples + /// + /// Copying two elements from a slice into another: + /// + /// ``` + /// let src = [1, 2, 3, 4]; + /// let mut dst = [0, 0]; + /// + /// // Because the slices have to be the same length, + /// // we slice the source slice from four elements + /// // to two. It will panic if we don't do this. + /// dst.copy_from_slice(&src[2..]); + /// + /// assert_eq!(src, [1, 2, 3, 4]); + /// assert_eq!(dst, [3, 4]); + /// ``` + /// + /// Rust enforces that there can only be one mutable reference with no + /// immutable references to a particular piece of data in a particular + /// scope. Because of this, attempting to use `copy_from_slice` on a + /// single slice will result in a compile failure: + /// + /// ```compile_fail + /// let mut slice = [1, 2, 3, 4, 5]; + /// + /// slice[..2].copy_from_slice(&slice[3..]); // compile fail! + /// ``` + /// + /// To work around this, we can use [`split_at_mut`] to create two distinct + /// sub-slices from a slice: + /// + /// ``` + /// let mut slice = [1, 2, 3, 4, 5]; + /// + /// { + /// let (left, right) = slice.split_at_mut(2); + /// left.copy_from_slice(&right[1..]); + /// } + /// + /// assert_eq!(slice, [4, 5, 3, 4, 5]); + /// ``` + /// + /// [`clone_from_slice`]: #method.clone_from_slice + /// [`split_at_mut`]: #method.split_at_mut + #[stable(feature = "copy_from_slice", since = "1.9.0")] + pub fn copy_from_slice(&mut self, src: &[T]) + where + T: Copy, + { + assert_eq!(self.len(), src.len(), "destination and source slices have different lengths"); + unsafe { + ptr::copy_nonoverlapping(src.as_ptr(), self.as_mut_ptr(), self.len()); + } + } + + /// Copies elements from one part of the slice to another part of itself, + /// using a memmove. + /// + /// `src` is the range within `self` to copy from. `dest` is the starting + /// index of the range within `self` to copy to, which will have the same + /// length as `src`. The two ranges may overlap. The ends of the two ranges + /// must be less than or equal to `self.len()`. + /// + /// # Panics + /// + /// This function will panic if either range exceeds the end of the slice, + /// or if the end of `src` is before the start. + /// + /// # Examples + /// + /// Copying four bytes within a slice: + /// + /// ``` + /// let mut bytes = *b"Hello, World!"; + /// + /// bytes.copy_within(1..5, 8); + /// + /// assert_eq!(&bytes, b"Hello, Wello!"); + /// ``` + #[stable(feature = "copy_within", since = "1.37.0")] + #[track_caller] + pub fn copy_within<R: ops::RangeBounds<usize>>(&mut self, src: R, dest: usize) + where + T: Copy, + { + let src_start = match src.start_bound() { + ops::Bound::Included(&n) => n, + ops::Bound::Excluded(&n) => { + n.checked_add(1).unwrap_or_else(|| slice_index_overflow_fail()) + } + ops::Bound::Unbounded => 0, + }; + let src_end = match src.end_bound() { + ops::Bound::Included(&n) => { + n.checked_add(1).unwrap_or_else(|| slice_index_overflow_fail()) + } + ops::Bound::Excluded(&n) => n, + ops::Bound::Unbounded => self.len(), + }; + assert!(src_start <= src_end, "src end is before src start"); + assert!(src_end <= self.len(), "src is out of bounds"); + let count = src_end - src_start; + assert!(dest <= self.len() - count, "dest is out of bounds"); + unsafe { + ptr::copy(self.as_ptr().add(src_start), self.as_mut_ptr().add(dest), count); + } + } + + /// Swaps all elements in `self` with those in `other`. + /// + /// The length of `other` must be the same as `self`. + /// + /// # Panics + /// + /// This function will panic if the two slices have different lengths. + /// + /// # Example + /// + /// Swapping two elements across slices: + /// + /// ``` + /// let mut slice1 = [0, 0]; + /// let mut slice2 = [1, 2, 3, 4]; + /// + /// slice1.swap_with_slice(&mut slice2[2..]); + /// + /// assert_eq!(slice1, [3, 4]); + /// assert_eq!(slice2, [1, 2, 0, 0]); + /// ``` + /// + /// Rust enforces that there can only be one mutable reference to a + /// particular piece of data in a particular scope. Because of this, + /// attempting to use `swap_with_slice` on a single slice will result in + /// a compile failure: + /// + /// ```compile_fail + /// let mut slice = [1, 2, 3, 4, 5]; + /// slice[..2].swap_with_slice(&mut slice[3..]); // compile fail! + /// ``` + /// + /// To work around this, we can use [`split_at_mut`] to create two distinct + /// mutable sub-slices from a slice: + /// + /// ``` + /// let mut slice = [1, 2, 3, 4, 5]; + /// + /// { + /// let (left, right) = slice.split_at_mut(2); + /// left.swap_with_slice(&mut right[1..]); + /// } + /// + /// assert_eq!(slice, [4, 5, 3, 1, 2]); + /// ``` + /// + /// [`split_at_mut`]: #method.split_at_mut + #[stable(feature = "swap_with_slice", since = "1.27.0")] + pub fn swap_with_slice(&mut self, other: &mut [T]) { + assert!(self.len() == other.len(), "destination and source slices have different lengths"); + unsafe { + ptr::swap_nonoverlapping(self.as_mut_ptr(), other.as_mut_ptr(), self.len()); + } + } + + /// Function to calculate lengths of the middle and trailing slice for `align_to{,_mut}`. + fn align_to_offsets<U>(&self) -> (usize, usize) { + // What we gonna do about `rest` is figure out what multiple of `U`s we can put in a + // lowest number of `T`s. And how many `T`s we need for each such "multiple". + // + // Consider for example T=u8 U=u16. Then we can put 1 U in 2 Ts. Simple. Now, consider + // for example a case where size_of::<T> = 16, size_of::<U> = 24. We can put 2 Us in + // place of every 3 Ts in the `rest` slice. A bit more complicated. + // + // Formula to calculate this is: + // + // Us = lcm(size_of::<T>, size_of::<U>) / size_of::<U> + // Ts = lcm(size_of::<T>, size_of::<U>) / size_of::<T> + // + // Expanded and simplified: + // + // Us = size_of::<T> / gcd(size_of::<T>, size_of::<U>) + // Ts = size_of::<U> / gcd(size_of::<T>, size_of::<U>) + // + // Luckily since all this is constant-evaluated... performance here matters not! + #[inline] + fn gcd(a: usize, b: usize) -> usize { + use crate::intrinsics; + // iterative stein’s algorithm + // We should still make this `const fn` (and revert to recursive algorithm if we do) + // because relying on llvm to consteval all this is… well, it makes me uncomfortable. + let (ctz_a, mut ctz_b) = unsafe { + if a == 0 { + return b; + } + if b == 0 { + return a; + } + (intrinsics::cttz_nonzero(a), intrinsics::cttz_nonzero(b)) + }; + let k = ctz_a.min(ctz_b); + let mut a = a >> ctz_a; + let mut b = b; + loop { + // remove all factors of 2 from b + b >>= ctz_b; + if a > b { + mem::swap(&mut a, &mut b); + } + b = b - a; + unsafe { + if b == 0 { + break; + } + ctz_b = intrinsics::cttz_nonzero(b); + } + } + a << k + } + let gcd: usize = gcd(mem::size_of::<T>(), mem::size_of::<U>()); + let ts: usize = mem::size_of::<U>() / gcd; + let us: usize = mem::size_of::<T>() / gcd; + + // Armed with this knowledge, we can find how many `U`s we can fit! + let us_len = self.len() / ts * us; + // And how many `T`s will be in the trailing slice! + let ts_len = self.len() % ts; + (us_len, ts_len) + } + + /// Transmute the slice to a slice of another type, ensuring alignment of the types is + /// maintained. + /// + /// This method splits the slice into three distinct slices: prefix, correctly aligned middle + /// slice of a new type, and the suffix slice. The method may make the middle slice the greatest + /// length possible for a given type and input slice, but only your algorithm's performance + /// should depend on that, not its correctness. It is permissible for all of the input data to + /// be returned as the prefix or suffix slice. + /// + /// This method has no purpose when either input element `T` or output element `U` are + /// zero-sized and will return the original slice without splitting anything. + /// + /// # Safety + /// + /// This method is essentially a `transmute` with respect to the elements in the returned + /// middle slice, so all the usual caveats pertaining to `transmute::<T, U>` also apply here. + /// + /// # Examples + /// + /// Basic usage: + /// + /// ``` + /// unsafe { + /// let bytes: [u8; 7] = [1, 2, 3, 4, 5, 6, 7]; + /// let (prefix, shorts, suffix) = bytes.align_to::<u16>(); + /// // less_efficient_algorithm_for_bytes(prefix); + /// // more_efficient_algorithm_for_aligned_shorts(shorts); + /// // less_efficient_algorithm_for_bytes(suffix); + /// } + /// ``` + #[stable(feature = "slice_align_to", since = "1.30.0")] + pub unsafe fn align_to<U>(&self) -> (&[T], &[U], &[T]) { + // Note that most of this function will be constant-evaluated, + if mem::size_of::<U>() == 0 || mem::size_of::<T>() == 0 { + // handle ZSTs specially, which is – don't handle them at all. + return (self, &[], &[]); + } + + // First, find at what point do we split between the first and 2nd slice. Easy with + // ptr.align_offset. + let ptr = self.as_ptr(); + let offset = unsafe { crate::ptr::align_offset(ptr, mem::align_of::<U>()) }; + if offset > self.len() { + (self, &[], &[]) + } else { + let (left, rest) = self.split_at(offset); + let (us_len, ts_len) = rest.align_to_offsets::<U>(); + // SAFETY: now `rest` is definitely aligned, so `from_raw_parts` below is okay, + // since the caller guarantees that we can transmute `T` to `U` safely. + unsafe { + ( + left, + from_raw_parts(rest.as_ptr() as *const U, us_len), + from_raw_parts(rest.as_ptr().add(rest.len() - ts_len), ts_len), + ) + } + } + } + + /// Transmute the slice to a slice of another type, ensuring alignment of the types is + /// maintained. + /// + /// This method splits the slice into three distinct slices: prefix, correctly aligned middle + /// slice of a new type, and the suffix slice. The method may make the middle slice the greatest + /// length possible for a given type and input slice, but only your algorithm's performance + /// should depend on that, not its correctness. It is permissible for all of the input data to + /// be returned as the prefix or suffix slice. + /// + /// This method has no purpose when either input element `T` or output element `U` are + /// zero-sized and will return the original slice without splitting anything. + /// + /// # Safety + /// + /// This method is essentially a `transmute` with respect to the elements in the returned + /// middle slice, so all the usual caveats pertaining to `transmute::<T, U>` also apply here. + /// + /// # Examples + /// + /// Basic usage: + /// + /// ``` + /// unsafe { + /// let mut bytes: [u8; 7] = [1, 2, 3, 4, 5, 6, 7]; + /// let (prefix, shorts, suffix) = bytes.align_to_mut::<u16>(); + /// // less_efficient_algorithm_for_bytes(prefix); + /// // more_efficient_algorithm_for_aligned_shorts(shorts); + /// // less_efficient_algorithm_for_bytes(suffix); + /// } + /// ``` + #[stable(feature = "slice_align_to", since = "1.30.0")] + pub unsafe fn align_to_mut<U>(&mut self) -> (&mut [T], &mut [U], &mut [T]) { + // Note that most of this function will be constant-evaluated, + if mem::size_of::<U>() == 0 || mem::size_of::<T>() == 0 { + // handle ZSTs specially, which is – don't handle them at all. + return (self, &mut [], &mut []); + } + + // First, find at what point do we split between the first and 2nd slice. Easy with + // ptr.align_offset. + let ptr = self.as_ptr(); + let offset = unsafe { crate::ptr::align_offset(ptr, mem::align_of::<U>()) }; + if offset > self.len() { + (self, &mut [], &mut []) + } else { + let (left, rest) = self.split_at_mut(offset); + let (us_len, ts_len) = rest.align_to_offsets::<U>(); + let rest_len = rest.len(); + let mut_ptr = rest.as_mut_ptr(); + // We can't use `rest` again after this, that would invalidate its alias `mut_ptr`! + // SAFETY: see comments for `align_to`. + unsafe { + ( + left, + from_raw_parts_mut(mut_ptr as *mut U, us_len), + from_raw_parts_mut(mut_ptr.add(rest_len - ts_len), ts_len), + ) + } + } + } + + /// Checks if the elements of this slice are sorted. + /// + /// That is, for each element `a` and its following element `b`, `a <= b` must hold. If the + /// slice yields exactly zero or one element, `true` is returned. + /// + /// Note that if `Self::Item` is only `PartialOrd`, but not `Ord`, the above definition + /// implies that this function returns `false` if any two consecutive items are not + /// comparable. + /// + /// # Examples + /// + /// ``` + /// #![feature(is_sorted)] + /// let empty: [i32; 0] = []; + /// + /// assert!([1, 2, 2, 9].is_sorted()); + /// assert!(![1, 3, 2, 4].is_sorted()); + /// assert!([0].is_sorted()); + /// assert!(empty.is_sorted()); + /// assert!(![0.0, 1.0, f32::NAN].is_sorted()); + /// ``` + #[inline] + #[unstable(feature = "is_sorted", reason = "new API", issue = "53485")] + pub fn is_sorted(&self) -> bool + where + T: PartialOrd, + { + self.is_sorted_by(|a, b| a.partial_cmp(b)) + } + + /// Checks if the elements of this slice are sorted using the given comparator function. + /// + /// Instead of using `PartialOrd::partial_cmp`, this function uses the given `compare` + /// function to determine the ordering of two elements. Apart from that, it's equivalent to + /// [`is_sorted`]; see its documentation for more information. + /// + /// [`is_sorted`]: #method.is_sorted + #[unstable(feature = "is_sorted", reason = "new API", issue = "53485")] + pub fn is_sorted_by<F>(&self, mut compare: F) -> bool + where + F: FnMut(&T, &T) -> Option<Ordering>, + { + self.iter().is_sorted_by(|a, b| compare(*a, *b)) + } + + /// Checks if the elements of this slice are sorted using the given key extraction function. + /// + /// Instead of comparing the slice's elements directly, this function compares the keys of the + /// elements, as determined by `f`. Apart from that, it's equivalent to [`is_sorted`]; see its + /// documentation for more information. + /// + /// [`is_sorted`]: #method.is_sorted + /// + /// # Examples + /// + /// ``` + /// #![feature(is_sorted)] + /// + /// assert!(["c", "bb", "aaa"].is_sorted_by_key(|s| s.len())); + /// assert!(![-2i32, -1, 0, 3].is_sorted_by_key(|n| n.abs())); + /// ``` + #[inline] + #[unstable(feature = "is_sorted", reason = "new API", issue = "53485")] + pub fn is_sorted_by_key<F, K>(&self, f: F) -> bool + where + F: FnMut(&T) -> K, + K: PartialOrd, + { + self.iter().is_sorted_by_key(f) + } + + /// Returns the index of the partition point according to the given predicate + /// (the index of the first element of the second partition). + /// + /// The slice is assumed to be partitioned according to the given predicate. + /// This means that all elements for which the predicate returns true are at the start of the slice + /// and all elements for which the predicate returns false are at the end. + /// For example, [7, 15, 3, 5, 4, 12, 6] is a partitioned under the predicate x % 2 != 0 + /// (all odd numbers are at the start, all even at the end). + /// + /// If this slice is not partitioned, the returned result is unspecified and meaningless, + /// as this method performs a kind of binary search. + /// + /// # Examples + /// + /// ``` + /// #![feature(partition_point)] + /// + /// let v = [1, 2, 3, 3, 5, 6, 7]; + /// let i = v.partition_point(|&x| x < 5); + /// + /// assert_eq!(i, 4); + /// assert!(v[..i].iter().all(|&x| x < 5)); + /// assert!(v[i..].iter().all(|&x| !(x < 5))); + /// ``` + #[unstable(feature = "partition_point", reason = "new API", issue = "73831")] + pub fn partition_point<P>(&self, mut pred: P) -> usize + where + P: FnMut(&T) -> bool, + { + let mut left = 0; + let mut right = self.len(); + + while left != right { + let mid = left + (right - left) / 2; + // SAFETY: + // When left < right, left <= mid < right. + // Therefore left always increases and right always decreases, + // and eigher of them is selected. + // In both cases left <= right is satisfied. + // Therefore if left < right in a step, + // left <= right is satisfied in the next step. + // Therefore as long as left != right, 0 <= left < right <= len is satisfied + // and if this case 0 <= mid < len is satisfied too. + let value = unsafe { self.get_unchecked(mid) }; + if pred(value) { + left = mid + 1; + } else { + right = mid; + } + } + + left + } +} + +#[lang = "slice_u8"] +#[cfg(not(test))] +impl [u8] { + /// Checks if all bytes in this slice are within the ASCII range. + #[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")] + #[inline] + pub fn is_ascii(&self) -> bool { + is_ascii(self) + } + + /// Checks that two slices are an ASCII case-insensitive match. + /// + /// Same as `to_ascii_lowercase(a) == to_ascii_lowercase(b)`, + /// but without allocating and copying temporaries. + #[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")] + #[inline] + pub fn eq_ignore_ascii_case(&self, other: &[u8]) -> bool { + self.len() == other.len() && self.iter().zip(other).all(|(a, b)| a.eq_ignore_ascii_case(b)) + } + + /// Converts this slice to its ASCII upper case equivalent in-place. + /// + /// ASCII letters 'a' to 'z' are mapped to 'A' to 'Z', + /// but non-ASCII letters are unchanged. + /// + /// To return a new uppercased value without modifying the existing one, use + /// [`to_ascii_uppercase`]. + /// + /// [`to_ascii_uppercase`]: #method.to_ascii_uppercase + #[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")] + #[inline] + pub fn make_ascii_uppercase(&mut self) { + for byte in self { + byte.make_ascii_uppercase(); + } + } + + /// Converts this slice to its ASCII lower case equivalent in-place. + /// + /// ASCII letters 'A' to 'Z' are mapped to 'a' to 'z', + /// but non-ASCII letters are unchanged. + /// + /// To return a new lowercased value without modifying the existing one, use + /// [`to_ascii_lowercase`]. + /// + /// [`to_ascii_lowercase`]: #method.to_ascii_lowercase + #[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")] + #[inline] + pub fn make_ascii_lowercase(&mut self) { + for byte in self { + byte.make_ascii_lowercase(); + } + } +} + +/// Returns `true` if any byte in the word `v` is nonascii (>= 128). Snarfed +/// from `../str/mod.rs`, which does something similar for utf8 validation. +#[inline] +fn contains_nonascii(v: usize) -> bool { + const NONASCII_MASK: usize = 0x80808080_80808080u64 as usize; + (NONASCII_MASK & v) != 0 +} + +/// Optimized ASCII test that will use usize-at-a-time operations instead of +/// byte-at-a-time operations (when possible). +/// +/// The algorithm we use here is pretty simple. If `s` is too short, we just +/// check each byte and be done with it. Otherwise: +/// +/// - Read the first word with an unaligned load. +/// - Align the pointer, read subsequent words until end with aligned loads. +/// - If there's a tail, the last `usize` from `s` with an unaligned load. +/// +/// If any of these loads produces something for which `contains_nonascii` +/// (above) returns true, then we know the answer is false. +#[inline] +fn is_ascii(s: &[u8]) -> bool { + const USIZE_SIZE: usize = mem::size_of::<usize>(); + + let len = s.len(); + let align_offset = s.as_ptr().align_offset(USIZE_SIZE); + + // If we wouldn't gain anything from the word-at-a-time implementation, fall + // back to a scalar loop. + // + // We also do this for architectures where `size_of::<usize>()` isn't + // sufficient alignment for `usize`, because it's a weird edge case. + if len < USIZE_SIZE || len < align_offset || USIZE_SIZE < mem::align_of::<usize>() { + return s.iter().all(|b| b.is_ascii()); + } + + // We always read the first word unaligned, which means `align_offset` is + // 0, we'd read the same value again for the aligned read. + let offset_to_aligned = if align_offset == 0 { USIZE_SIZE } else { align_offset }; + + let start = s.as_ptr(); + // SAFETY: We verify `len < USIZE_SIZE` above. + let first_word = unsafe { (start as *const usize).read_unaligned() }; + + if contains_nonascii(first_word) { + return false; + } + // We checked this above, somewhat implicitly. Note that `offset_to_aligned` + // is either `align_offset` or `USIZE_SIZE`, both of are explicitly checked + // above. + debug_assert!(offset_to_aligned <= len); + + // word_ptr is the (properly aligned) usize ptr we use to read the middle chunk of the slice. + let mut word_ptr = unsafe { start.add(offset_to_aligned) as *const usize }; + + // `byte_pos` is the byte index of `word_ptr`, used for loop end checks. + let mut byte_pos = offset_to_aligned; + + // Paranoia check about alignment, since we're about to do a bunch of + // unaligned loads. In practice this should be impossible barring a bug in + // `align_offset` though. + debug_assert_eq!((word_ptr as usize) % mem::align_of::<usize>(), 0); + + while byte_pos <= len - USIZE_SIZE { + debug_assert!( + // Sanity check that the read is in bounds + (word_ptr as usize + USIZE_SIZE) <= (start.wrapping_add(len) as usize) && + // And that our assumptions about `byte_pos` hold. + (word_ptr as usize) - (start as usize) == byte_pos + ); + + // Safety: We know `word_ptr` is properly aligned (because of + // `align_offset`), and we know that we have enough bytes between `word_ptr` and the end + let word = unsafe { word_ptr.read() }; + if contains_nonascii(word) { + return false; + } + + byte_pos += USIZE_SIZE; + // SAFETY: We know that `byte_pos <= len - USIZE_SIZE`, which means that + // after this `add`, `word_ptr` will be at most one-past-the-end. + word_ptr = unsafe { word_ptr.add(1) }; + } + + // If we have anything left over, it should be at-most 1 usize worth of bytes, + // which we check with a read_unaligned. + if byte_pos == len { + return true; + } + + // Sanity check to ensure there really is only one `usize` left. This should + // be guaranteed by our loop condition. + debug_assert!(byte_pos < len && len - byte_pos < USIZE_SIZE); + + // SAFETY: This relies on `len >= USIZE_SIZE`, which we check at the start. + let last_word = unsafe { (start.add(len - USIZE_SIZE) as *const usize).read_unaligned() }; + + !contains_nonascii(last_word) +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl<T, I> ops::Index<I> for [T] +where + I: SliceIndex<[T]>, +{ + type Output = I::Output; + + #[inline] + fn index(&self, index: I) -> &I::Output { + index.index(self) + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl<T, I> ops::IndexMut<I> for [T] +where + I: SliceIndex<[T]>, +{ + #[inline] + fn index_mut(&mut self, index: I) -> &mut I::Output { + index.index_mut(self) + } +} + +#[inline(never)] +#[cold] +#[track_caller] +fn slice_start_index_len_fail(index: usize, len: usize) -> ! { + panic!("range start index {} out of range for slice of length {}", index, len); +} + +#[inline(never)] +#[cold] +#[track_caller] +fn slice_end_index_len_fail(index: usize, len: usize) -> ! { + panic!("range end index {} out of range for slice of length {}", index, len); +} + +#[inline(never)] +#[cold] +#[track_caller] +fn slice_index_order_fail(index: usize, end: usize) -> ! { + panic!("slice index starts at {} but ends at {}", index, end); +} + +#[inline(never)] +#[cold] +#[track_caller] +fn slice_index_overflow_fail() -> ! { + panic!("attempted to index slice up to maximum usize"); +} + +mod private_slice_index { + use super::ops; + #[stable(feature = "slice_get_slice", since = "1.28.0")] + pub trait Sealed {} + + #[stable(feature = "slice_get_slice", since = "1.28.0")] + impl Sealed for usize {} + #[stable(feature = "slice_get_slice", since = "1.28.0")] + impl Sealed for ops::Range<usize> {} + #[stable(feature = "slice_get_slice", since = "1.28.0")] + impl Sealed for ops::RangeTo<usize> {} + #[stable(feature = "slice_get_slice", since = "1.28.0")] + impl Sealed for ops::RangeFrom<usize> {} + #[stable(feature = "slice_get_slice", since = "1.28.0")] + impl Sealed for ops::RangeFull {} + #[stable(feature = "slice_get_slice", since = "1.28.0")] + impl Sealed for ops::RangeInclusive<usize> {} + #[stable(feature = "slice_get_slice", since = "1.28.0")] + impl Sealed for ops::RangeToInclusive<usize> {} +} + +/// A helper trait used for indexing operations. +/// +/// Implementations of this trait have to promise that if the argument +/// to `get_(mut_)unchecked` is a safe reference, then so is the result. +#[stable(feature = "slice_get_slice", since = "1.28.0")] +#[rustc_on_unimplemented( + on(T = "str", label = "string indices are ranges of `usize`",), + on( + all(any(T = "str", T = "&str", T = "std::string::String"), _Self = "{integer}"), + note = "you can use `.chars().nth()` or `.bytes().nth()` +see chapter in The Book <https://doc.rust-lang.org/book/ch08-02-strings.html#indexing-into-strings>" + ), + message = "the type `{T}` cannot be indexed by `{Self}`", + label = "slice indices are of type `usize` or ranges of `usize`" +)] +pub unsafe trait SliceIndex<T: ?Sized>: private_slice_index::Sealed { + /// The output type returned by methods. + #[stable(feature = "slice_get_slice", since = "1.28.0")] + type Output: ?Sized; + + /// Returns a shared reference to the output at this location, if in + /// bounds. + #[unstable(feature = "slice_index_methods", issue = "none")] + fn get(self, slice: &T) -> Option<&Self::Output>; + + /// Returns a mutable reference to the output at this location, if in + /// bounds. + #[unstable(feature = "slice_index_methods", issue = "none")] + fn get_mut(self, slice: &mut T) -> Option<&mut Self::Output>; + + /// Returns a shared reference to the output at this location, without + /// performing any bounds checking. + /// Calling this method with an out-of-bounds index or a dangling `slice` pointer + /// is *[undefined behavior]* even if the resulting reference is not used. + /// + /// [undefined behavior]: ../../reference/behavior-considered-undefined.html + #[unstable(feature = "slice_index_methods", issue = "none")] + unsafe fn get_unchecked(self, slice: *const T) -> *const Self::Output; + + /// Returns a mutable reference to the output at this location, without + /// performing any bounds checking. + /// Calling this method with an out-of-bounds index or a dangling `slice` pointer + /// is *[undefined behavior]* even if the resulting reference is not used. + /// + /// [undefined behavior]: ../../reference/behavior-considered-undefined.html + #[unstable(feature = "slice_index_methods", issue = "none")] + unsafe fn get_unchecked_mut(self, slice: *mut T) -> *mut Self::Output; + + /// Returns a shared reference to the output at this location, panicking + /// if out of bounds. + #[unstable(feature = "slice_index_methods", issue = "none")] + #[track_caller] + fn index(self, slice: &T) -> &Self::Output; + + /// Returns a mutable reference to the output at this location, panicking + /// if out of bounds. + #[unstable(feature = "slice_index_methods", issue = "none")] + #[track_caller] + fn index_mut(self, slice: &mut T) -> &mut Self::Output; +} + +#[stable(feature = "slice_get_slice_impls", since = "1.15.0")] +unsafe impl<T> SliceIndex<[T]> for usize { + type Output = T; + + #[inline] + fn get(self, slice: &[T]) -> Option<&T> { + if self < slice.len() { unsafe { Some(&*self.get_unchecked(slice)) } } else { None } + } + + #[inline] + fn get_mut(self, slice: &mut [T]) -> Option<&mut T> { + if self < slice.len() { unsafe { Some(&mut *self.get_unchecked_mut(slice)) } } else { None } + } + + #[inline] + unsafe fn get_unchecked(self, slice: *const [T]) -> *const T { + // SAFETY: the caller guarantees that `slice` is not dangling, so it + // cannot be longer than `isize::MAX`. They also guarantee that + // `self` is in bounds of `slice` so `self` cannot overflow an `isize`, + // so the call to `add` is safe. + unsafe { slice.as_ptr().add(self) } + } + + #[inline] + unsafe fn get_unchecked_mut(self, slice: *mut [T]) -> *mut T { + // SAFETY: see comments for `get_unchecked` above. + unsafe { slice.as_mut_ptr().add(self) } + } + + #[inline] + fn index(self, slice: &[T]) -> &T { + // N.B., use intrinsic indexing + &(*slice)[self] + } + + #[inline] + fn index_mut(self, slice: &mut [T]) -> &mut T { + // N.B., use intrinsic indexing + &mut (*slice)[self] + } +} + +#[stable(feature = "slice_get_slice_impls", since = "1.15.0")] +unsafe impl<T> SliceIndex<[T]> for ops::Range<usize> { + type Output = [T]; + + #[inline] + fn get(self, slice: &[T]) -> Option<&[T]> { + if self.start > self.end || self.end > slice.len() { + None + } else { + unsafe { Some(&*self.get_unchecked(slice)) } + } + } + + #[inline] + fn get_mut(self, slice: &mut [T]) -> Option<&mut [T]> { + if self.start > self.end || self.end > slice.len() { + None + } else { + unsafe { Some(&mut *self.get_unchecked_mut(slice)) } + } + } + + #[inline] + unsafe fn get_unchecked(self, slice: *const [T]) -> *const [T] { + // SAFETY: the caller guarantees that `slice` is not dangling, so it + // cannot be longer than `isize::MAX`. They also guarantee that + // `self` is in bounds of `slice` so `self` cannot overflow an `isize`, + // so the call to `add` is safe. + unsafe { ptr::slice_from_raw_parts(slice.as_ptr().add(self.start), self.end - self.start) } + } + + #[inline] + unsafe fn get_unchecked_mut(self, slice: *mut [T]) -> *mut [T] { + // SAFETY: see comments for `get_unchecked` above. + unsafe { + ptr::slice_from_raw_parts_mut(slice.as_mut_ptr().add(self.start), self.end - self.start) + } + } + + #[inline] + fn index(self, slice: &[T]) -> &[T] { + if self.start > self.end { + slice_index_order_fail(self.start, self.end); + } else if self.end > slice.len() { + slice_end_index_len_fail(self.end, slice.len()); + } + unsafe { &*self.get_unchecked(slice) } + } + + #[inline] + fn index_mut(self, slice: &mut [T]) -> &mut [T] { + if self.start > self.end { + slice_index_order_fail(self.start, self.end); + } else if self.end > slice.len() { + slice_end_index_len_fail(self.end, slice.len()); + } + unsafe { &mut *self.get_unchecked_mut(slice) } + } +} + +#[stable(feature = "slice_get_slice_impls", since = "1.15.0")] +unsafe impl<T> SliceIndex<[T]> for ops::RangeTo<usize> { + type Output = [T]; + + #[inline] + fn get(self, slice: &[T]) -> Option<&[T]> { + (0..self.end).get(slice) + } + + #[inline] + fn get_mut(self, slice: &mut [T]) -> Option<&mut [T]> { + (0..self.end).get_mut(slice) + } + + #[inline] + unsafe fn get_unchecked(self, slice: *const [T]) -> *const [T] { + // SAFETY: the caller has to uphold the safety contract for `get_unchecked`. + unsafe { (0..self.end).get_unchecked(slice) } + } + + #[inline] + unsafe fn get_unchecked_mut(self, slice: *mut [T]) -> *mut [T] { + // SAFETY: the caller has to uphold the safety contract for `get_unchecked_mut`. + unsafe { (0..self.end).get_unchecked_mut(slice) } + } + + #[inline] + fn index(self, slice: &[T]) -> &[T] { + (0..self.end).index(slice) + } + + #[inline] + fn index_mut(self, slice: &mut [T]) -> &mut [T] { + (0..self.end).index_mut(slice) + } +} + +#[stable(feature = "slice_get_slice_impls", since = "1.15.0")] +unsafe impl<T> SliceIndex<[T]> for ops::RangeFrom<usize> { + type Output = [T]; + + #[inline] + fn get(self, slice: &[T]) -> Option<&[T]> { + (self.start..slice.len()).get(slice) + } + + #[inline] + fn get_mut(self, slice: &mut [T]) -> Option<&mut [T]> { + (self.start..slice.len()).get_mut(slice) + } + + #[inline] + unsafe fn get_unchecked(self, slice: *const [T]) -> *const [T] { + // SAFETY: the caller has to uphold the safety contract for `get_unchecked`. + unsafe { (self.start..slice.len()).get_unchecked(slice) } + } + + #[inline] + unsafe fn get_unchecked_mut(self, slice: *mut [T]) -> *mut [T] { + // SAFETY: the caller has to uphold the safety contract for `get_unchecked_mut`. + unsafe { (self.start..slice.len()).get_unchecked_mut(slice) } + } + + #[inline] + fn index(self, slice: &[T]) -> &[T] { + if self.start > slice.len() { + slice_start_index_len_fail(self.start, slice.len()); + } + unsafe { &*self.get_unchecked(slice) } + } + + #[inline] + fn index_mut(self, slice: &mut [T]) -> &mut [T] { + if self.start > slice.len() { + slice_start_index_len_fail(self.start, slice.len()); + } + unsafe { &mut *self.get_unchecked_mut(slice) } + } +} + +#[stable(feature = "slice_get_slice_impls", since = "1.15.0")] +unsafe impl<T> SliceIndex<[T]> for ops::RangeFull { + type Output = [T]; + + #[inline] + fn get(self, slice: &[T]) -> Option<&[T]> { + Some(slice) + } + + #[inline] + fn get_mut(self, slice: &mut [T]) -> Option<&mut [T]> { + Some(slice) + } + + #[inline] + unsafe fn get_unchecked(self, slice: *const [T]) -> *const [T] { + slice + } + + #[inline] + unsafe fn get_unchecked_mut(self, slice: *mut [T]) -> *mut [T] { + slice + } + + #[inline] + fn index(self, slice: &[T]) -> &[T] { + slice + } + + #[inline] + fn index_mut(self, slice: &mut [T]) -> &mut [T] { + slice + } +} + +#[stable(feature = "inclusive_range", since = "1.26.0")] +unsafe impl<T> SliceIndex<[T]> for ops::RangeInclusive<usize> { + type Output = [T]; + + #[inline] + fn get(self, slice: &[T]) -> Option<&[T]> { + if *self.end() == usize::MAX { None } else { (*self.start()..self.end() + 1).get(slice) } + } + + #[inline] + fn get_mut(self, slice: &mut [T]) -> Option<&mut [T]> { + if *self.end() == usize::MAX { + None + } else { + (*self.start()..self.end() + 1).get_mut(slice) + } + } + + #[inline] + unsafe fn get_unchecked(self, slice: *const [T]) -> *const [T] { + // SAFETY: the caller has to uphold the safety contract for `get_unchecked`. + unsafe { (*self.start()..self.end() + 1).get_unchecked(slice) } + } + + #[inline] + unsafe fn get_unchecked_mut(self, slice: *mut [T]) -> *mut [T] { + // SAFETY: the caller has to uphold the safety contract for `get_unchecked_mut`. + unsafe { (*self.start()..self.end() + 1).get_unchecked_mut(slice) } + } + + #[inline] + fn index(self, slice: &[T]) -> &[T] { + if *self.end() == usize::MAX { + slice_index_overflow_fail(); + } + (*self.start()..self.end() + 1).index(slice) + } + + #[inline] + fn index_mut(self, slice: &mut [T]) -> &mut [T] { + if *self.end() == usize::MAX { + slice_index_overflow_fail(); + } + (*self.start()..self.end() + 1).index_mut(slice) + } +} + +#[stable(feature = "inclusive_range", since = "1.26.0")] +unsafe impl<T> SliceIndex<[T]> for ops::RangeToInclusive<usize> { + type Output = [T]; + + #[inline] + fn get(self, slice: &[T]) -> Option<&[T]> { + (0..=self.end).get(slice) + } + + #[inline] + fn get_mut(self, slice: &mut [T]) -> Option<&mut [T]> { + (0..=self.end).get_mut(slice) + } + + #[inline] + unsafe fn get_unchecked(self, slice: *const [T]) -> *const [T] { + // SAFETY: the caller has to uphold the safety contract for `get_unchecked`. + unsafe { (0..=self.end).get_unchecked(slice) } + } + + #[inline] + unsafe fn get_unchecked_mut(self, slice: *mut [T]) -> *mut [T] { + // SAFETY: the caller has to uphold the safety contract for `get_unchecked_mut`. + unsafe { (0..=self.end).get_unchecked_mut(slice) } + } + + #[inline] + fn index(self, slice: &[T]) -> &[T] { + (0..=self.end).index(slice) + } + + #[inline] + fn index_mut(self, slice: &mut [T]) -> &mut [T] { + (0..=self.end).index_mut(slice) + } +} + +//////////////////////////////////////////////////////////////////////////////// +// Common traits +//////////////////////////////////////////////////////////////////////////////// + +#[stable(feature = "rust1", since = "1.0.0")] +impl<T> Default for &[T] { + /// Creates an empty slice. + fn default() -> Self { + &[] + } +} + +#[stable(feature = "mut_slice_default", since = "1.5.0")] +impl<T> Default for &mut [T] { + /// Creates a mutable empty slice. + fn default() -> Self { + &mut [] + } +} + +// +// Iterators +// + +#[stable(feature = "rust1", since = "1.0.0")] +impl<'a, T> IntoIterator for &'a [T] { + type Item = &'a T; + type IntoIter = Iter<'a, T>; + + fn into_iter(self) -> Iter<'a, T> { + self.iter() + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl<'a, T> IntoIterator for &'a mut [T] { + type Item = &'a mut T; + type IntoIter = IterMut<'a, T>; + + fn into_iter(self) -> IterMut<'a, T> { + self.iter_mut() + } +} + +// Macro helper functions +#[inline(always)] +fn size_from_ptr<T>(_: *const T) -> usize { + mem::size_of::<T>() +} + +// Inlining is_empty and len makes a huge performance difference +macro_rules! is_empty { + // The way we encode the length of a ZST iterator, this works both for ZST + // and non-ZST. + ($self: ident) => { + $self.ptr.as_ptr() as *const T == $self.end + }; +} + +// To get rid of some bounds checks (see `position`), we compute the length in a somewhat +// unexpected way. (Tested by `codegen/slice-position-bounds-check`.) +macro_rules! len { + ($self: ident) => {{ + #![allow(unused_unsafe)] // we're sometimes used within an unsafe block + + let start = $self.ptr; + let size = size_from_ptr(start.as_ptr()); + if size == 0 { + // This _cannot_ use `unchecked_sub` because we depend on wrapping + // to represent the length of long ZST slice iterators. + ($self.end as usize).wrapping_sub(start.as_ptr() as usize) + } else { + // We know that `start <= end`, so can do better than `offset_from`, + // which needs to deal in signed. By setting appropriate flags here + // we can tell LLVM this, which helps it remove bounds checks. + // SAFETY: By the type invariant, `start <= end` + let diff = unsafe { unchecked_sub($self.end as usize, start.as_ptr() as usize) }; + // By also telling LLVM that the pointers are apart by an exact + // multiple of the type size, it can optimize `len() == 0` down to + // `start == end` instead of `(end - start) < size`. + // SAFETY: By the type invariant, the pointers are aligned so the + // distance between them must be a multiple of pointee size + unsafe { exact_div(diff, size) } + } + }}; +} + +// The shared definition of the `Iter` and `IterMut` iterators +macro_rules! iterator { + ( + struct $name:ident -> $ptr:ty, + $elem:ty, + $raw_mut:tt, + {$( $mut_:tt )*}, + {$($extra:tt)*} + ) => { + // Returns the first element and moves the start of the iterator forwards by 1. + // Greatly improves performance compared to an inlined function. The iterator + // must not be empty. + macro_rules! next_unchecked { + ($self: ident) => {& $( $mut_ )* *$self.post_inc_start(1)} + } + + // Returns the last element and moves the end of the iterator backwards by 1. + // Greatly improves performance compared to an inlined function. The iterator + // must not be empty. + macro_rules! next_back_unchecked { + ($self: ident) => {& $( $mut_ )* *$self.pre_dec_end(1)} + } + + // Shrinks the iterator when T is a ZST, by moving the end of the iterator + // backwards by `n`. `n` must not exceed `self.len()`. + macro_rules! zst_shrink { + ($self: ident, $n: ident) => { + $self.end = ($self.end as * $raw_mut u8).wrapping_offset(-$n) as * $raw_mut T; + } + } + + impl<'a, T> $name<'a, T> { + // Helper function for creating a slice from the iterator. + #[inline(always)] + fn make_slice(&self) -> &'a [T] { + unsafe { from_raw_parts(self.ptr.as_ptr(), len!(self)) } + } + + // Helper function for moving the start of the iterator forwards by `offset` elements, + // returning the old start. + // Unsafe because the offset must not exceed `self.len()`. + #[inline(always)] + unsafe fn post_inc_start(&mut self, offset: isize) -> * $raw_mut T { + if mem::size_of::<T>() == 0 { + zst_shrink!(self, offset); + self.ptr.as_ptr() + } else { + let old = self.ptr.as_ptr(); + // SAFETY: the caller guarantees that `offset` doesn't exceed `self.len()`, + // so this new pointer is inside `self` and thus guaranteed to be non-null. + self.ptr = unsafe { NonNull::new_unchecked(self.ptr.as_ptr().offset(offset)) }; + old + } + } + + // Helper function for moving the end of the iterator backwards by `offset` elements, + // returning the new end. + // Unsafe because the offset must not exceed `self.len()`. + #[inline(always)] + unsafe fn pre_dec_end(&mut self, offset: isize) -> * $raw_mut T { + if mem::size_of::<T>() == 0 { + zst_shrink!(self, offset); + self.ptr.as_ptr() + } else { + // SAFETY: the caller guarantees that `offset` doesn't exceed `self.len()`, + // which is guaranteed to not overflow an `isize`. Also, the resulting pointer + // is in bounds of `slice`, which fulfills the other requirements for `offset`. + self.end = unsafe { self.end.offset(-offset) }; + self.end + } + } + } + + #[stable(feature = "rust1", since = "1.0.0")] + impl<T> ExactSizeIterator for $name<'_, T> { + #[inline(always)] + fn len(&self) -> usize { + len!(self) + } + + #[inline(always)] + fn is_empty(&self) -> bool { + is_empty!(self) + } + } + + #[stable(feature = "rust1", since = "1.0.0")] + impl<'a, T> Iterator for $name<'a, T> { + type Item = $elem; + + #[inline] + fn next(&mut self) -> Option<$elem> { + // could be implemented with slices, but this avoids bounds checks + unsafe { + assume(!self.ptr.as_ptr().is_null()); + if mem::size_of::<T>() != 0 { + assume(!self.end.is_null()); + } + if is_empty!(self) { + None + } else { + Some(next_unchecked!(self)) + } + } + } + + #[inline] + fn size_hint(&self) -> (usize, Option<usize>) { + let exact = len!(self); + (exact, Some(exact)) + } + + #[inline] + fn count(self) -> usize { + len!(self) + } + + #[inline] + fn nth(&mut self, n: usize) -> Option<$elem> { + if n >= len!(self) { + // This iterator is now empty. + if mem::size_of::<T>() == 0 { + // We have to do it this way as `ptr` may never be 0, but `end` + // could be (due to wrapping). + self.end = self.ptr.as_ptr(); + } else { + unsafe { + // End can't be 0 if T isn't ZST because ptr isn't 0 and end >= ptr + self.ptr = NonNull::new_unchecked(self.end as *mut T); + } + } + return None; + } + // We are in bounds. `post_inc_start` does the right thing even for ZSTs. + unsafe { + self.post_inc_start(n as isize); + Some(next_unchecked!(self)) + } + } + + #[inline] + fn last(mut self) -> Option<$elem> { + self.next_back() + } + + // We override the default implementation, which uses `try_fold`, + // because this simple implementation generates less LLVM IR and is + // faster to compile. + #[inline] + fn for_each<F>(mut self, mut f: F) + where + Self: Sized, + F: FnMut(Self::Item), + { + while let Some(x) = self.next() { + f(x); + } + } + + // We override the default implementation, which uses `try_fold`, + // because this simple implementation generates less LLVM IR and is + // faster to compile. + #[inline] + fn all<F>(&mut self, mut f: F) -> bool + where + Self: Sized, + F: FnMut(Self::Item) -> bool, + { + while let Some(x) = self.next() { + if !f(x) { + return false; + } + } + true + } + + // We override the default implementation, which uses `try_fold`, + // because this simple implementation generates less LLVM IR and is + // faster to compile. + #[inline] + fn any<F>(&mut self, mut f: F) -> bool + where + Self: Sized, + F: FnMut(Self::Item) -> bool, + { + while let Some(x) = self.next() { + if f(x) { + return true; + } + } + false + } + + // We override the default implementation, which uses `try_fold`, + // because this simple implementation generates less LLVM IR and is + // faster to compile. + #[inline] + fn find<P>(&mut self, mut predicate: P) -> Option<Self::Item> + where + Self: Sized, + P: FnMut(&Self::Item) -> bool, + { + while let Some(x) = self.next() { + if predicate(&x) { + return Some(x); + } + } + None + } + + // We override the default implementation, which uses `try_fold`, + // because this simple implementation generates less LLVM IR and is + // faster to compile. + #[inline] + fn find_map<B, F>(&mut self, mut f: F) -> Option<B> + where + Self: Sized, + F: FnMut(Self::Item) -> Option<B>, + { + while let Some(x) = self.next() { + if let Some(y) = f(x) { + return Some(y); + } + } + None + } + + // We override the default implementation, which uses `try_fold`, + // because this simple implementation generates less LLVM IR and is + // faster to compile. Also, the `assume` avoids a bounds check. + #[inline] + #[rustc_inherit_overflow_checks] + fn position<P>(&mut self, mut predicate: P) -> Option<usize> where + Self: Sized, + P: FnMut(Self::Item) -> bool, + { + let n = len!(self); + let mut i = 0; + while let Some(x) = self.next() { + if predicate(x) { + unsafe { assume(i < n) }; + return Some(i); + } + i += 1; + } + None + } + + // We override the default implementation, which uses `try_fold`, + // because this simple implementation generates less LLVM IR and is + // faster to compile. Also, the `assume` avoids a bounds check. + #[inline] + fn rposition<P>(&mut self, mut predicate: P) -> Option<usize> where + P: FnMut(Self::Item) -> bool, + Self: Sized + ExactSizeIterator + DoubleEndedIterator + { + let n = len!(self); + let mut i = n; + while let Some(x) = self.next_back() { + i -= 1; + if predicate(x) { + unsafe { assume(i < n) }; + return Some(i); + } + } + None + } + + $($extra)* + } + + #[stable(feature = "rust1", since = "1.0.0")] + impl<'a, T> DoubleEndedIterator for $name<'a, T> { + #[inline] + fn next_back(&mut self) -> Option<$elem> { + // could be implemented with slices, but this avoids bounds checks + unsafe { + assume(!self.ptr.as_ptr().is_null()); + if mem::size_of::<T>() != 0 { + assume(!self.end.is_null()); + } + if is_empty!(self) { + None + } else { + Some(next_back_unchecked!(self)) + } + } + } + + #[inline] + fn nth_back(&mut self, n: usize) -> Option<$elem> { + if n >= len!(self) { + // This iterator is now empty. + self.end = self.ptr.as_ptr(); + return None; + } + // We are in bounds. `pre_dec_end` does the right thing even for ZSTs. + unsafe { + self.pre_dec_end(n as isize); + Some(next_back_unchecked!(self)) + } + } + } + + #[stable(feature = "fused", since = "1.26.0")] + impl<T> FusedIterator for $name<'_, T> {} + + #[unstable(feature = "trusted_len", issue = "37572")] + unsafe impl<T> TrustedLen for $name<'_, T> {} + } +} + +/// Immutable slice iterator +/// +/// This struct is created by the [`iter`] method on [slices]. +/// +/// # Examples +/// +/// Basic usage: +/// +/// ``` +/// // First, we declare a type which has `iter` method to get the `Iter` struct (&[usize here]): +/// let slice = &[1, 2, 3]; +/// +/// // Then, we iterate over it: +/// for element in slice.iter() { +/// println!("{}", element); +/// } +/// ``` +/// +/// [`iter`]: ../../std/primitive.slice.html#method.iter +/// [slices]: ../../std/primitive.slice.html +#[stable(feature = "rust1", since = "1.0.0")] +pub struct Iter<'a, T: 'a> { + ptr: NonNull<T>, + end: *const T, // If T is a ZST, this is actually ptr+len. This encoding is picked so that + // ptr == end is a quick test for the Iterator being empty, that works + // for both ZST and non-ZST. + _marker: marker::PhantomData<&'a T>, +} + +#[stable(feature = "core_impl_debug", since = "1.9.0")] +impl<T: fmt::Debug> fmt::Debug for Iter<'_, T> { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + f.debug_tuple("Iter").field(&self.as_slice()).finish() + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +unsafe impl<T: Sync> Sync for Iter<'_, T> {} +#[stable(feature = "rust1", since = "1.0.0")] +unsafe impl<T: Sync> Send for Iter<'_, T> {} + +impl<'a, T> Iter<'a, T> { + /// Views the underlying data as a subslice of the original data. + /// + /// This has the same lifetime as the original slice, and so the + /// iterator can continue to be used while this exists. + /// + /// # Examples + /// + /// Basic usage: + /// + /// ``` + /// // First, we declare a type which has the `iter` method to get the `Iter` + /// // struct (&[usize here]): + /// let slice = &[1, 2, 3]; + /// + /// // Then, we get the iterator: + /// let mut iter = slice.iter(); + /// // So if we print what `as_slice` method returns here, we have "[1, 2, 3]": + /// println!("{:?}", iter.as_slice()); + /// + /// // Next, we move to the second element of the slice: + /// iter.next(); + /// // Now `as_slice` returns "[2, 3]": + /// println!("{:?}", iter.as_slice()); + /// ``` + #[stable(feature = "iter_to_slice", since = "1.4.0")] + pub fn as_slice(&self) -> &'a [T] { + self.make_slice() + } +} + +iterator! {struct Iter -> *const T, &'a T, const, {/* no mut */}, { + fn is_sorted_by<F>(self, mut compare: F) -> bool + where + Self: Sized, + F: FnMut(&Self::Item, &Self::Item) -> Option<Ordering>, + { + self.as_slice().windows(2).all(|w| { + compare(&&w[0], &&w[1]).map(|o| o != Ordering::Greater).unwrap_or(false) + }) + } +}} + +#[stable(feature = "rust1", since = "1.0.0")] +impl<T> Clone for Iter<'_, T> { + fn clone(&self) -> Self { + Iter { ptr: self.ptr, end: self.end, _marker: self._marker } + } +} + +#[stable(feature = "slice_iter_as_ref", since = "1.13.0")] +impl<T> AsRef<[T]> for Iter<'_, T> { + fn as_ref(&self) -> &[T] { + self.as_slice() + } +} + +/// Mutable slice iterator. +/// +/// This struct is created by the [`iter_mut`] method on [slices]. +/// +/// # Examples +/// +/// Basic usage: +/// +/// ``` +/// // First, we declare a type which has `iter_mut` method to get the `IterMut` +/// // struct (&[usize here]): +/// let mut slice = &mut [1, 2, 3]; +/// +/// // Then, we iterate over it and increment each element value: +/// for element in slice.iter_mut() { +/// *element += 1; +/// } +/// +/// // We now have "[2, 3, 4]": +/// println!("{:?}", slice); +/// ``` +/// +/// [`iter_mut`]: ../../std/primitive.slice.html#method.iter_mut +/// [slices]: ../../std/primitive.slice.html +#[stable(feature = "rust1", since = "1.0.0")] +pub struct IterMut<'a, T: 'a> { + ptr: NonNull<T>, + end: *mut T, // If T is a ZST, this is actually ptr+len. This encoding is picked so that + // ptr == end is a quick test for the Iterator being empty, that works + // for both ZST and non-ZST. + _marker: marker::PhantomData<&'a mut T>, +} + +#[stable(feature = "core_impl_debug", since = "1.9.0")] +impl<T: fmt::Debug> fmt::Debug for IterMut<'_, T> { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + f.debug_tuple("IterMut").field(&self.make_slice()).finish() + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +unsafe impl<T: Sync> Sync for IterMut<'_, T> {} +#[stable(feature = "rust1", since = "1.0.0")] +unsafe impl<T: Send> Send for IterMut<'_, T> {} + +impl<'a, T> IterMut<'a, T> { + /// Views the underlying data as a subslice of the original data. + /// + /// To avoid creating `&mut` references that alias, this is forced + /// to consume the iterator. + /// + /// # Examples + /// + /// Basic usage: + /// + /// ``` + /// // First, we declare a type which has `iter_mut` method to get the `IterMut` + /// // struct (&[usize here]): + /// let mut slice = &mut [1, 2, 3]; + /// + /// { + /// // Then, we get the iterator: + /// let mut iter = slice.iter_mut(); + /// // We move to next element: + /// iter.next(); + /// // So if we print what `into_slice` method returns here, we have "[2, 3]": + /// println!("{:?}", iter.into_slice()); + /// } + /// + /// // Now let's modify a value of the slice: + /// { + /// // First we get back the iterator: + /// let mut iter = slice.iter_mut(); + /// // We change the value of the first element of the slice returned by the `next` method: + /// *iter.next().unwrap() += 1; + /// } + /// // Now slice is "[2, 2, 3]": + /// println!("{:?}", slice); + /// ``` + #[stable(feature = "iter_to_slice", since = "1.4.0")] + pub fn into_slice(self) -> &'a mut [T] { + unsafe { from_raw_parts_mut(self.ptr.as_ptr(), len!(self)) } + } + + /// Views the underlying data as a subslice of the original data. + /// + /// To avoid creating `&mut [T]` references that alias, the returned slice + /// borrows its lifetime from the iterator the method is applied on. + /// + /// # Examples + /// + /// Basic usage: + /// + /// ``` + /// # #![feature(slice_iter_mut_as_slice)] + /// let mut slice: &mut [usize] = &mut [1, 2, 3]; + /// + /// // First, we get the iterator: + /// let mut iter = slice.iter_mut(); + /// // So if we check what the `as_slice` method returns here, we have "[1, 2, 3]": + /// assert_eq!(iter.as_slice(), &[1, 2, 3]); + /// + /// // Next, we move to the second element of the slice: + /// iter.next(); + /// // Now `as_slice` returns "[2, 3]": + /// assert_eq!(iter.as_slice(), &[2, 3]); + /// ``` + #[unstable(feature = "slice_iter_mut_as_slice", reason = "recently added", issue = "58957")] + pub fn as_slice(&self) -> &[T] { + self.make_slice() + } +} + +iterator! {struct IterMut -> *mut T, &'a mut T, mut, {mut}, {}} + +/// An internal abstraction over the splitting iterators, so that +/// splitn, splitn_mut etc can be implemented once. +#[doc(hidden)] +trait SplitIter: DoubleEndedIterator { + /// Marks the underlying iterator as complete, extracting the remaining + /// portion of the slice. + fn finish(&mut self) -> Option<Self::Item>; +} + +/// An iterator over subslices separated by elements that match a predicate +/// function. +/// +/// This struct is created by the [`split`] method on [slices]. +/// +/// [`split`]: ../../std/primitive.slice.html#method.split +/// [slices]: ../../std/primitive.slice.html +#[stable(feature = "rust1", since = "1.0.0")] +pub struct Split<'a, T: 'a, P> +where + P: FnMut(&T) -> bool, +{ + v: &'a [T], + pred: P, + finished: bool, +} + +#[stable(feature = "core_impl_debug", since = "1.9.0")] +impl<T: fmt::Debug, P> fmt::Debug for Split<'_, T, P> +where + P: FnMut(&T) -> bool, +{ + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + f.debug_struct("Split").field("v", &self.v).field("finished", &self.finished).finish() + } +} + +// FIXME(#26925) Remove in favor of `#[derive(Clone)]` +#[stable(feature = "rust1", since = "1.0.0")] +impl<T, P> Clone for Split<'_, T, P> +where + P: Clone + FnMut(&T) -> bool, +{ + fn clone(&self) -> Self { + Split { v: self.v, pred: self.pred.clone(), finished: self.finished } + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl<'a, T, P> Iterator for Split<'a, T, P> +where + P: FnMut(&T) -> bool, +{ + type Item = &'a [T]; + + #[inline] + fn next(&mut self) -> Option<&'a [T]> { + if self.finished { + return None; + } + + match self.v.iter().position(|x| (self.pred)(x)) { + None => self.finish(), + Some(idx) => { + let ret = Some(&self.v[..idx]); + self.v = &self.v[idx + 1..]; + ret + } + } + } + + #[inline] + fn size_hint(&self) -> (usize, Option<usize>) { + if self.finished { (0, Some(0)) } else { (1, Some(self.v.len() + 1)) } + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl<'a, T, P> DoubleEndedIterator for Split<'a, T, P> +where + P: FnMut(&T) -> bool, +{ + #[inline] + fn next_back(&mut self) -> Option<&'a [T]> { + if self.finished { + return None; + } + + match self.v.iter().rposition(|x| (self.pred)(x)) { + None => self.finish(), + Some(idx) => { + let ret = Some(&self.v[idx + 1..]); + self.v = &self.v[..idx]; + ret + } + } + } +} + +impl<'a, T, P> SplitIter for Split<'a, T, P> +where + P: FnMut(&T) -> bool, +{ + #[inline] + fn finish(&mut self) -> Option<&'a [T]> { + if self.finished { + None + } else { + self.finished = true; + Some(self.v) + } + } +} + +#[stable(feature = "fused", since = "1.26.0")] +impl<T, P> FusedIterator for Split<'_, T, P> where P: FnMut(&T) -> bool {} + +/// An iterator over subslices separated by elements that match a predicate +/// function. Unlike `Split`, it contains the matched part as a terminator +/// of the subslice. +/// +/// This struct is created by the [`split_inclusive`] method on [slices]. +/// +/// [`split_inclusive`]: ../../std/primitive.slice.html#method.split_inclusive +/// [slices]: ../../std/primitive.slice.html +#[unstable(feature = "split_inclusive", issue = "72360")] +pub struct SplitInclusive<'a, T: 'a, P> +where + P: FnMut(&T) -> bool, +{ + v: &'a [T], + pred: P, + finished: bool, +} + +#[unstable(feature = "split_inclusive", issue = "72360")] +impl<T: fmt::Debug, P> fmt::Debug for SplitInclusive<'_, T, P> +where + P: FnMut(&T) -> bool, +{ + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + f.debug_struct("SplitInclusive") + .field("v", &self.v) + .field("finished", &self.finished) + .finish() + } +} + +// FIXME(#26925) Remove in favor of `#[derive(Clone)]` +#[unstable(feature = "split_inclusive", issue = "72360")] +impl<T, P> Clone for SplitInclusive<'_, T, P> +where + P: Clone + FnMut(&T) -> bool, +{ + fn clone(&self) -> Self { + SplitInclusive { v: self.v, pred: self.pred.clone(), finished: self.finished } + } +} + +#[unstable(feature = "split_inclusive", issue = "72360")] +impl<'a, T, P> Iterator for SplitInclusive<'a, T, P> +where + P: FnMut(&T) -> bool, +{ + type Item = &'a [T]; + + #[inline] + fn next(&mut self) -> Option<&'a [T]> { + if self.finished { + return None; + } + + let idx = + self.v.iter().position(|x| (self.pred)(x)).map(|idx| idx + 1).unwrap_or(self.v.len()); + if idx == self.v.len() { + self.finished = true; + } + let ret = Some(&self.v[..idx]); + self.v = &self.v[idx..]; + ret + } + + #[inline] + fn size_hint(&self) -> (usize, Option<usize>) { + if self.finished { (0, Some(0)) } else { (1, Some(self.v.len() + 1)) } + } +} + +#[unstable(feature = "split_inclusive", issue = "72360")] +impl<'a, T, P> DoubleEndedIterator for SplitInclusive<'a, T, P> +where + P: FnMut(&T) -> bool, +{ + #[inline] + fn next_back(&mut self) -> Option<&'a [T]> { + if self.finished { + return None; + } + + // The last index of self.v is already checked and found to match + // by the last iteration, so we start searching a new match + // one index to the left. + let remainder = if self.v.is_empty() { &[] } else { &self.v[..(self.v.len() - 1)] }; + let idx = remainder.iter().rposition(|x| (self.pred)(x)).map(|idx| idx + 1).unwrap_or(0); + if idx == 0 { + self.finished = true; + } + let ret = Some(&self.v[idx..]); + self.v = &self.v[..idx]; + ret + } +} + +#[unstable(feature = "split_inclusive", issue = "72360")] +impl<T, P> FusedIterator for SplitInclusive<'_, T, P> where P: FnMut(&T) -> bool {} + +/// An iterator over the mutable subslices of the vector which are separated +/// by elements that match `pred`. +/// +/// This struct is created by the [`split_mut`] method on [slices]. +/// +/// [`split_mut`]: ../../std/primitive.slice.html#method.split_mut +/// [slices]: ../../std/primitive.slice.html +#[stable(feature = "rust1", since = "1.0.0")] +pub struct SplitMut<'a, T: 'a, P> +where + P: FnMut(&T) -> bool, +{ + v: &'a mut [T], + pred: P, + finished: bool, +} + +#[stable(feature = "core_impl_debug", since = "1.9.0")] +impl<T: fmt::Debug, P> fmt::Debug for SplitMut<'_, T, P> +where + P: FnMut(&T) -> bool, +{ + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + f.debug_struct("SplitMut").field("v", &self.v).field("finished", &self.finished).finish() + } +} + +impl<'a, T, P> SplitIter for SplitMut<'a, T, P> +where + P: FnMut(&T) -> bool, +{ + #[inline] + fn finish(&mut self) -> Option<&'a mut [T]> { + if self.finished { + None + } else { + self.finished = true; + Some(mem::replace(&mut self.v, &mut [])) + } + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl<'a, T, P> Iterator for SplitMut<'a, T, P> +where + P: FnMut(&T) -> bool, +{ + type Item = &'a mut [T]; + + #[inline] + fn next(&mut self) -> Option<&'a mut [T]> { + if self.finished { + return None; + } + + let idx_opt = { + // work around borrowck limitations + let pred = &mut self.pred; + self.v.iter().position(|x| (*pred)(x)) + }; + match idx_opt { + None => self.finish(), + Some(idx) => { + let tmp = mem::replace(&mut self.v, &mut []); + let (head, tail) = tmp.split_at_mut(idx); + self.v = &mut tail[1..]; + Some(head) + } + } + } + + #[inline] + fn size_hint(&self) -> (usize, Option<usize>) { + if self.finished { + (0, Some(0)) + } else { + // if the predicate doesn't match anything, we yield one slice + // if it matches every element, we yield len+1 empty slices. + (1, Some(self.v.len() + 1)) + } + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl<'a, T, P> DoubleEndedIterator for SplitMut<'a, T, P> +where + P: FnMut(&T) -> bool, +{ + #[inline] + fn next_back(&mut self) -> Option<&'a mut [T]> { + if self.finished { + return None; + } + + let idx_opt = { + // work around borrowck limitations + let pred = &mut self.pred; + self.v.iter().rposition(|x| (*pred)(x)) + }; + match idx_opt { + None => self.finish(), + Some(idx) => { + let tmp = mem::replace(&mut self.v, &mut []); + let (head, tail) = tmp.split_at_mut(idx); + self.v = head; + Some(&mut tail[1..]) + } + } + } +} + +#[stable(feature = "fused", since = "1.26.0")] +impl<T, P> FusedIterator for SplitMut<'_, T, P> where P: FnMut(&T) -> bool {} + +/// An iterator over the mutable subslices of the vector which are separated +/// by elements that match `pred`. Unlike `SplitMut`, it contains the matched +/// parts in the ends of the subslices. +/// +/// This struct is created by the [`split_inclusive_mut`] method on [slices]. +/// +/// [`split_inclusive_mut`]: ../../std/primitive.slice.html#method.split_inclusive_mut +/// [slices]: ../../std/primitive.slice.html +#[unstable(feature = "split_inclusive", issue = "72360")] +pub struct SplitInclusiveMut<'a, T: 'a, P> +where + P: FnMut(&T) -> bool, +{ + v: &'a mut [T], + pred: P, + finished: bool, +} + +#[unstable(feature = "split_inclusive", issue = "72360")] +impl<T: fmt::Debug, P> fmt::Debug for SplitInclusiveMut<'_, T, P> +where + P: FnMut(&T) -> bool, +{ + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + f.debug_struct("SplitInclusiveMut") + .field("v", &self.v) + .field("finished", &self.finished) + .finish() + } +} + +#[unstable(feature = "split_inclusive", issue = "72360")] +impl<'a, T, P> Iterator for SplitInclusiveMut<'a, T, P> +where + P: FnMut(&T) -> bool, +{ + type Item = &'a mut [T]; + + #[inline] + fn next(&mut self) -> Option<&'a mut [T]> { + if self.finished { + return None; + } + + let idx_opt = { + // work around borrowck limitations + let pred = &mut self.pred; + self.v.iter().position(|x| (*pred)(x)) + }; + let idx = idx_opt.map(|idx| idx + 1).unwrap_or(self.v.len()); + if idx == self.v.len() { + self.finished = true; + } + let tmp = mem::replace(&mut self.v, &mut []); + let (head, tail) = tmp.split_at_mut(idx); + self.v = tail; + Some(head) + } + + #[inline] + fn size_hint(&self) -> (usize, Option<usize>) { + if self.finished { + (0, Some(0)) + } else { + // if the predicate doesn't match anything, we yield one slice + // if it matches every element, we yield len+1 empty slices. + (1, Some(self.v.len() + 1)) + } + } +} + +#[unstable(feature = "split_inclusive", issue = "72360")] +impl<'a, T, P> DoubleEndedIterator for SplitInclusiveMut<'a, T, P> +where + P: FnMut(&T) -> bool, +{ + #[inline] + fn next_back(&mut self) -> Option<&'a mut [T]> { + if self.finished { + return None; + } + + let idx_opt = if self.v.is_empty() { + None + } else { + // work around borrowck limitations + let pred = &mut self.pred; + + // The last index of self.v is already checked and found to match + // by the last iteration, so we start searching a new match + // one index to the left. + let remainder = &self.v[..(self.v.len() - 1)]; + remainder.iter().rposition(|x| (*pred)(x)) + }; + let idx = idx_opt.map(|idx| idx + 1).unwrap_or(0); + if idx == 0 { + self.finished = true; + } + let tmp = mem::replace(&mut self.v, &mut []); + let (head, tail) = tmp.split_at_mut(idx); + self.v = head; + Some(tail) + } +} + +#[unstable(feature = "split_inclusive", issue = "72360")] +impl<T, P> FusedIterator for SplitInclusiveMut<'_, T, P> where P: FnMut(&T) -> bool {} + +/// An iterator over subslices separated by elements that match a predicate +/// function, starting from the end of the slice. +/// +/// This struct is created by the [`rsplit`] method on [slices]. +/// +/// [`rsplit`]: ../../std/primitive.slice.html#method.rsplit +/// [slices]: ../../std/primitive.slice.html +#[stable(feature = "slice_rsplit", since = "1.27.0")] +#[derive(Clone)] // Is this correct, or does it incorrectly require `T: Clone`? +pub struct RSplit<'a, T: 'a, P> +where + P: FnMut(&T) -> bool, +{ + inner: Split<'a, T, P>, +} + +#[stable(feature = "slice_rsplit", since = "1.27.0")] +impl<T: fmt::Debug, P> fmt::Debug for RSplit<'_, T, P> +where + P: FnMut(&T) -> bool, +{ + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + f.debug_struct("RSplit") + .field("v", &self.inner.v) + .field("finished", &self.inner.finished) + .finish() + } +} + +#[stable(feature = "slice_rsplit", since = "1.27.0")] +impl<'a, T, P> Iterator for RSplit<'a, T, P> +where + P: FnMut(&T) -> bool, +{ + type Item = &'a [T]; + + #[inline] + fn next(&mut self) -> Option<&'a [T]> { + self.inner.next_back() + } + + #[inline] + fn size_hint(&self) -> (usize, Option<usize>) { + self.inner.size_hint() + } +} + +#[stable(feature = "slice_rsplit", since = "1.27.0")] +impl<'a, T, P> DoubleEndedIterator for RSplit<'a, T, P> +where + P: FnMut(&T) -> bool, +{ + #[inline] + fn next_back(&mut self) -> Option<&'a [T]> { + self.inner.next() + } +} + +#[stable(feature = "slice_rsplit", since = "1.27.0")] +impl<'a, T, P> SplitIter for RSplit<'a, T, P> +where + P: FnMut(&T) -> bool, +{ + #[inline] + fn finish(&mut self) -> Option<&'a [T]> { + self.inner.finish() + } +} + +#[stable(feature = "slice_rsplit", since = "1.27.0")] +impl<T, P> FusedIterator for RSplit<'_, T, P> where P: FnMut(&T) -> bool {} + +/// An iterator over the subslices of the vector which are separated +/// by elements that match `pred`, starting from the end of the slice. +/// +/// This struct is created by the [`rsplit_mut`] method on [slices]. +/// +/// [`rsplit_mut`]: ../../std/primitive.slice.html#method.rsplit_mut +/// [slices]: ../../std/primitive.slice.html +#[stable(feature = "slice_rsplit", since = "1.27.0")] +pub struct RSplitMut<'a, T: 'a, P> +where + P: FnMut(&T) -> bool, +{ + inner: SplitMut<'a, T, P>, +} + +#[stable(feature = "slice_rsplit", since = "1.27.0")] +impl<T: fmt::Debug, P> fmt::Debug for RSplitMut<'_, T, P> +where + P: FnMut(&T) -> bool, +{ + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + f.debug_struct("RSplitMut") + .field("v", &self.inner.v) + .field("finished", &self.inner.finished) + .finish() + } +} + +#[stable(feature = "slice_rsplit", since = "1.27.0")] +impl<'a, T, P> SplitIter for RSplitMut<'a, T, P> +where + P: FnMut(&T) -> bool, +{ + #[inline] + fn finish(&mut self) -> Option<&'a mut [T]> { + self.inner.finish() + } +} + +#[stable(feature = "slice_rsplit", since = "1.27.0")] +impl<'a, T, P> Iterator for RSplitMut<'a, T, P> +where + P: FnMut(&T) -> bool, +{ + type Item = &'a mut [T]; + + #[inline] + fn next(&mut self) -> Option<&'a mut [T]> { + self.inner.next_back() + } + + #[inline] + fn size_hint(&self) -> (usize, Option<usize>) { + self.inner.size_hint() + } +} + +#[stable(feature = "slice_rsplit", since = "1.27.0")] +impl<'a, T, P> DoubleEndedIterator for RSplitMut<'a, T, P> +where + P: FnMut(&T) -> bool, +{ + #[inline] + fn next_back(&mut self) -> Option<&'a mut [T]> { + self.inner.next() + } +} + +#[stable(feature = "slice_rsplit", since = "1.27.0")] +impl<T, P> FusedIterator for RSplitMut<'_, T, P> where P: FnMut(&T) -> bool {} + +/// An private iterator over subslices separated by elements that +/// match a predicate function, splitting at most a fixed number of +/// times. +#[derive(Debug)] +struct GenericSplitN<I> { + iter: I, + count: usize, +} + +impl<T, I: SplitIter<Item = T>> Iterator for GenericSplitN<I> { + type Item = T; + + #[inline] + fn next(&mut self) -> Option<T> { + match self.count { + 0 => None, + 1 => { + self.count -= 1; + self.iter.finish() + } + _ => { + self.count -= 1; + self.iter.next() + } + } + } + + #[inline] + fn size_hint(&self) -> (usize, Option<usize>) { + let (lower, upper_opt) = self.iter.size_hint(); + (lower, upper_opt.map(|upper| cmp::min(self.count, upper))) + } +} + +/// An iterator over subslices separated by elements that match a predicate +/// function, limited to a given number of splits. +/// +/// This struct is created by the [`splitn`] method on [slices]. +/// +/// [`splitn`]: ../../std/primitive.slice.html#method.splitn +/// [slices]: ../../std/primitive.slice.html +#[stable(feature = "rust1", since = "1.0.0")] +pub struct SplitN<'a, T: 'a, P> +where + P: FnMut(&T) -> bool, +{ + inner: GenericSplitN<Split<'a, T, P>>, +} + +#[stable(feature = "core_impl_debug", since = "1.9.0")] +impl<T: fmt::Debug, P> fmt::Debug for SplitN<'_, T, P> +where + P: FnMut(&T) -> bool, +{ + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + f.debug_struct("SplitN").field("inner", &self.inner).finish() + } +} + +/// An iterator over subslices separated by elements that match a +/// predicate function, limited to a given number of splits, starting +/// from the end of the slice. +/// +/// This struct is created by the [`rsplitn`] method on [slices]. +/// +/// [`rsplitn`]: ../../std/primitive.slice.html#method.rsplitn +/// [slices]: ../../std/primitive.slice.html +#[stable(feature = "rust1", since = "1.0.0")] +pub struct RSplitN<'a, T: 'a, P> +where + P: FnMut(&T) -> bool, +{ + inner: GenericSplitN<RSplit<'a, T, P>>, +} + +#[stable(feature = "core_impl_debug", since = "1.9.0")] +impl<T: fmt::Debug, P> fmt::Debug for RSplitN<'_, T, P> +where + P: FnMut(&T) -> bool, +{ + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + f.debug_struct("RSplitN").field("inner", &self.inner).finish() + } +} + +/// An iterator over subslices separated by elements that match a predicate +/// function, limited to a given number of splits. +/// +/// This struct is created by the [`splitn_mut`] method on [slices]. +/// +/// [`splitn_mut`]: ../../std/primitive.slice.html#method.splitn_mut +/// [slices]: ../../std/primitive.slice.html +#[stable(feature = "rust1", since = "1.0.0")] +pub struct SplitNMut<'a, T: 'a, P> +where + P: FnMut(&T) -> bool, +{ + inner: GenericSplitN<SplitMut<'a, T, P>>, +} + +#[stable(feature = "core_impl_debug", since = "1.9.0")] +impl<T: fmt::Debug, P> fmt::Debug for SplitNMut<'_, T, P> +where + P: FnMut(&T) -> bool, +{ + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + f.debug_struct("SplitNMut").field("inner", &self.inner).finish() + } +} + +/// An iterator over subslices separated by elements that match a +/// predicate function, limited to a given number of splits, starting +/// from the end of the slice. +/// +/// This struct is created by the [`rsplitn_mut`] method on [slices]. +/// +/// [`rsplitn_mut`]: ../../std/primitive.slice.html#method.rsplitn_mut +/// [slices]: ../../std/primitive.slice.html +#[stable(feature = "rust1", since = "1.0.0")] +pub struct RSplitNMut<'a, T: 'a, P> +where + P: FnMut(&T) -> bool, +{ + inner: GenericSplitN<RSplitMut<'a, T, P>>, +} + +#[stable(feature = "core_impl_debug", since = "1.9.0")] +impl<T: fmt::Debug, P> fmt::Debug for RSplitNMut<'_, T, P> +where + P: FnMut(&T) -> bool, +{ + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + f.debug_struct("RSplitNMut").field("inner", &self.inner).finish() + } +} + +macro_rules! forward_iterator { + ($name:ident: $elem:ident, $iter_of:ty) => { + #[stable(feature = "rust1", since = "1.0.0")] + impl<'a, $elem, P> Iterator for $name<'a, $elem, P> + where + P: FnMut(&T) -> bool, + { + type Item = $iter_of; + + #[inline] + fn next(&mut self) -> Option<$iter_of> { + self.inner.next() + } + + #[inline] + fn size_hint(&self) -> (usize, Option<usize>) { + self.inner.size_hint() + } + } + + #[stable(feature = "fused", since = "1.26.0")] + impl<'a, $elem, P> FusedIterator for $name<'a, $elem, P> where P: FnMut(&T) -> bool {} + }; +} + +forward_iterator! { SplitN: T, &'a [T] } +forward_iterator! { RSplitN: T, &'a [T] } +forward_iterator! { SplitNMut: T, &'a mut [T] } +forward_iterator! { RSplitNMut: T, &'a mut [T] } + +/// An iterator over overlapping subslices of length `size`. +/// +/// This struct is created by the [`windows`] method on [slices]. +/// +/// [`windows`]: ../../std/primitive.slice.html#method.windows +/// [slices]: ../../std/primitive.slice.html +#[derive(Debug)] +#[stable(feature = "rust1", since = "1.0.0")] +pub struct Windows<'a, T: 'a> { + v: &'a [T], + size: usize, +} + +// FIXME(#26925) Remove in favor of `#[derive(Clone)]` +#[stable(feature = "rust1", since = "1.0.0")] +impl<T> Clone for Windows<'_, T> { + fn clone(&self) -> Self { + Windows { v: self.v, size: self.size } + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl<'a, T> Iterator for Windows<'a, T> { + type Item = &'a [T]; + + #[inline] + fn next(&mut self) -> Option<&'a [T]> { + if self.size > self.v.len() { + None + } else { + let ret = Some(&self.v[..self.size]); + self.v = &self.v[1..]; + ret + } + } + + #[inline] + fn size_hint(&self) -> (usize, Option<usize>) { + if self.size > self.v.len() { + (0, Some(0)) + } else { + let size = self.v.len() - self.size + 1; + (size, Some(size)) + } + } + + #[inline] + fn count(self) -> usize { + self.len() + } + + #[inline] + fn nth(&mut self, n: usize) -> Option<Self::Item> { + let (end, overflow) = self.size.overflowing_add(n); + if end > self.v.len() || overflow { + self.v = &[]; + None + } else { + let nth = &self.v[n..end]; + self.v = &self.v[n + 1..]; + Some(nth) + } + } + + #[inline] + fn last(self) -> Option<Self::Item> { + if self.size > self.v.len() { + None + } else { + let start = self.v.len() - self.size; + Some(&self.v[start..]) + } + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl<'a, T> DoubleEndedIterator for Windows<'a, T> { + #[inline] + fn next_back(&mut self) -> Option<&'a [T]> { + if self.size > self.v.len() { + None + } else { + let ret = Some(&self.v[self.v.len() - self.size..]); + self.v = &self.v[..self.v.len() - 1]; + ret + } + } + + #[inline] + fn nth_back(&mut self, n: usize) -> Option<Self::Item> { + let (end, overflow) = self.v.len().overflowing_sub(n); + if end < self.size || overflow { + self.v = &[]; + None + } else { + let ret = &self.v[end - self.size..end]; + self.v = &self.v[..end - 1]; + Some(ret) + } + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl<T> ExactSizeIterator for Windows<'_, T> {} + +#[unstable(feature = "trusted_len", issue = "37572")] +unsafe impl<T> TrustedLen for Windows<'_, T> {} + +#[stable(feature = "fused", since = "1.26.0")] +impl<T> FusedIterator for Windows<'_, T> {} + +#[doc(hidden)] +unsafe impl<'a, T> TrustedRandomAccess for Windows<'a, T> { + unsafe fn get_unchecked(&mut self, i: usize) -> &'a [T] { + // SAFETY: since the caller guarantees that `i` is in bounds, + // which means that `i` cannot overflow an `isize`, and the + // slice created by `from_raw_parts` is a subslice of `self.v` + // thus is guaranteed to be valid for the lifetime `'a` of `self.v`. + unsafe { from_raw_parts(self.v.as_ptr().add(i), self.size) } + } + 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 beginning of the slice. +/// +/// When the slice len is not evenly divided by the chunk size, the last slice +/// of the iteration will be the remainder. +/// +/// This struct is created by the [`chunks`] method on [slices]. +/// +/// [`chunks`]: ../../std/primitive.slice.html#method.chunks +/// [slices]: ../../std/primitive.slice.html +#[derive(Debug)] +#[stable(feature = "rust1", since = "1.0.0")] +pub struct Chunks<'a, T: 'a> { + v: &'a [T], + chunk_size: usize, +} + +// FIXME(#26925) Remove in favor of `#[derive(Clone)]` +#[stable(feature = "rust1", since = "1.0.0")] +impl<T> Clone for Chunks<'_, T> { + fn clone(&self) -> Self { + Chunks { v: self.v, chunk_size: self.chunk_size } + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl<'a, T> Iterator for Chunks<'a, T> { + type Item = &'a [T]; + + #[inline] + fn next(&mut self) -> Option<&'a [T]> { + if self.v.is_empty() { + None + } else { + let chunksz = cmp::min(self.v.len(), self.chunk_size); + let (fst, snd) = self.v.split_at(chunksz); + self.v = snd; + Some(fst) + } + } + + #[inline] + fn size_hint(&self) -> (usize, Option<usize>) { + if self.v.is_empty() { + (0, Some(0)) + } else { + let n = self.v.len() / self.chunk_size; + let rem = self.v.len() % self.chunk_size; + let n = if rem > 0 { n + 1 } else { n }; + (n, Some(n)) + } + } + + #[inline] + fn count(self) -> usize { + self.len() + } + + #[inline] + fn nth(&mut self, n: usize) -> Option<Self::Item> { + 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(), + }; + let nth = &self.v[start..end]; + self.v = &self.v[end..]; + Some(nth) + } + } + + #[inline] + fn last(self) -> Option<Self::Item> { + if self.v.is_empty() { + None + } else { + let start = (self.v.len() - 1) / self.chunk_size * self.chunk_size; + Some(&self.v[start..]) + } + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl<'a, T> DoubleEndedIterator for Chunks<'a, T> { + #[inline] + fn next_back(&mut self) -> Option<&'a [T]> { + if self.v.is_empty() { + None + } else { + let remainder = self.v.len() % self.chunk_size; + let chunksz = if remainder != 0 { remainder } else { self.chunk_size }; + let (fst, snd) = self.v.split_at(self.v.len() - chunksz); + self.v = fst; + Some(snd) + } + } + + #[inline] + fn nth_back(&mut self, n: usize) -> Option<Self::Item> { + let len = self.len(); + if n >= len { + self.v = &[]; + None + } else { + let start = (len - 1 - n) * self.chunk_size; + let end = match start.checked_add(self.chunk_size) { + Some(res) => cmp::min(res, self.v.len()), + None => self.v.len(), + }; + let nth_back = &self.v[start..end]; + self.v = &self.v[..start]; + Some(nth_back) + } + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl<T> ExactSizeIterator for Chunks<'_, T> {} + +#[unstable(feature = "trusted_len", issue = "37572")] +unsafe impl<T> TrustedLen for Chunks<'_, T> {} + +#[stable(feature = "fused", since = "1.26.0")] +impl<T> FusedIterator for Chunks<'_, T> {} + +#[doc(hidden)] +unsafe impl<'a, T> TrustedRandomAccess for Chunks<'a, T> { + unsafe fn get_unchecked(&mut self, i: usize) -> &'a [T] { + let start = i * self.chunk_size; + let end = match start.checked_add(self.chunk_size) { + None => self.v.len(), + Some(end) => cmp::min(end, self.v.len()), + }; + // SAFETY: the caller guarantees that `i` is in bounds, + // which means that `start` must be in bounds of the + // underlying `self.v` slice, and we made sure that `end` + // is also in bounds of `self.v`. Thus, `start` cannot overflow + // an `isize`, and the slice constructed by `from_raw_parts` + // is a subslice of `self.v` which is guaranteed to be valid + // for the lifetime `'a` of `self.v`. + unsafe { from_raw_parts(self.v.as_ptr().add(start), end - start) } + } + fn may_have_side_effect() -> bool { + false + } +} + +/// An iterator over a slice in (non-overlapping) mutable chunks (`chunk_size` +/// 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 slice +/// of the iteration will be the remainder. +/// +/// This struct is created by the [`chunks_mut`] method on [slices]. +/// +/// [`chunks_mut`]: ../../std/primitive.slice.html#method.chunks_mut +/// [slices]: ../../std/primitive.slice.html +#[derive(Debug)] +#[stable(feature = "rust1", since = "1.0.0")] +pub struct ChunksMut<'a, T: 'a> { + v: &'a mut [T], + chunk_size: usize, +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl<'a, T> Iterator for ChunksMut<'a, T> { + type Item = &'a mut [T]; + + #[inline] + fn next(&mut self) -> Option<&'a mut [T]> { + if self.v.is_empty() { + None + } else { + let sz = cmp::min(self.v.len(), self.chunk_size); + let tmp = mem::replace(&mut self.v, &mut []); + let (head, tail) = tmp.split_at_mut(sz); + self.v = tail; + Some(head) + } + } + + #[inline] + fn size_hint(&self) -> (usize, Option<usize>) { + if self.v.is_empty() { + (0, Some(0)) + } else { + let n = self.v.len() / self.chunk_size; + let rem = self.v.len() % self.chunk_size; + let n = if rem > 0 { n + 1 } else { n }; + (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(), + }; + 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<Self::Item> { + if self.v.is_empty() { + None + } else { + let start = (self.v.len() - 1) / self.chunk_size * self.chunk_size; + Some(&mut self.v[start..]) + } + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl<'a, T> DoubleEndedIterator for ChunksMut<'a, T> { + #[inline] + fn next_back(&mut self) -> Option<&'a mut [T]> { + if self.v.is_empty() { + None + } else { + let remainder = self.v.len() % self.chunk_size; + let sz = if remainder != 0 { remainder } else { self.chunk_size }; + let tmp = mem::replace(&mut self.v, &mut []); + let tmp_len = tmp.len(); + let (head, tail) = tmp.split_at_mut(tmp_len - sz); + self.v = head; + Some(tail) + } + } + + #[inline] + fn nth_back(&mut self, n: usize) -> Option<Self::Item> { + let len = self.len(); + if n >= len { + self.v = &mut []; + None + } else { + let start = (len - 1 - n) * self.chunk_size; + let end = match start.checked_add(self.chunk_size) { + Some(res) => cmp::min(res, self.v.len()), + None => self.v.len(), + }; + let (temp, _tail) = mem::replace(&mut self.v, &mut []).split_at_mut(end); + let (head, nth_back) = temp.split_at_mut(start); + self.v = head; + Some(nth_back) + } + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl<T> ExactSizeIterator for ChunksMut<'_, T> {} + +#[unstable(feature = "trusted_len", issue = "37572")] +unsafe impl<T> TrustedLen for ChunksMut<'_, T> {} + +#[stable(feature = "fused", since = "1.26.0")] +impl<T> FusedIterator for ChunksMut<'_, T> {} + +#[doc(hidden)] +unsafe impl<'a, T> TrustedRandomAccess for ChunksMut<'a, T> { + unsafe fn get_unchecked(&mut self, i: usize) -> &'a mut [T] { + let start = i * self.chunk_size; + let end = match start.checked_add(self.chunk_size) { + None => self.v.len(), + Some(end) => cmp::min(end, self.v.len()), + }; + // SAFETY: see comments for `Chunks::get_unchecked`. + unsafe { from_raw_parts_mut(self.v.as_mut_ptr().add(start), end - start) } + } + 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 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 [`chunks_exact`] method on [slices]. +/// +/// [`chunks_exact`]: ../../std/primitive.slice.html#method.chunks_exact +/// [`remainder`]: ../../std/slice/struct.ChunksExact.html#method.remainder +/// [slices]: ../../std/primitive.slice.html +#[derive(Debug)] +#[stable(feature = "chunks_exact", since = "1.31.0")] +pub struct ChunksExact<'a, T: 'a> { + v: &'a [T], + rem: &'a [T], + chunk_size: usize, +} + +impl<'a, T> ChunksExact<'a, T> { + /// 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. + #[stable(feature = "chunks_exact", since = "1.31.0")] + pub fn remainder(&self) -> &'a [T] { + self.rem + } +} + +// FIXME(#26925) Remove in favor of `#[derive(Clone)]` +#[stable(feature = "chunks_exact", since = "1.31.0")] +impl<T> Clone for ChunksExact<'_, T> { + fn clone(&self) -> Self { + ChunksExact { v: self.v, rem: self.rem, chunk_size: self.chunk_size } + } +} + +#[stable(feature = "chunks_exact", since = "1.31.0")] +impl<'a, T> Iterator for ChunksExact<'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<usize>) { + 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<Self::Item> { + let (start, overflow) = n.overflowing_mul(self.chunk_size); + if start >= self.v.len() || overflow { + self.v = &[]; + None + } else { + let (_, snd) = self.v.split_at(start); + self.v = snd; + self.next() + } + } + + #[inline] + fn last(mut self) -> Option<Self::Item> { + self.next_back() + } +} + +#[stable(feature = "chunks_exact", since = "1.31.0")] +impl<'a, T> DoubleEndedIterator for ChunksExact<'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) + } + } + + #[inline] + fn nth_back(&mut self, n: usize) -> Option<Self::Item> { + let len = self.len(); + if n >= len { + self.v = &[]; + None + } else { + let start = (len - 1 - n) * self.chunk_size; + let end = start + self.chunk_size; + let nth_back = &self.v[start..end]; + self.v = &self.v[..start]; + Some(nth_back) + } + } +} + +#[stable(feature = "chunks_exact", since = "1.31.0")] +impl<T> ExactSizeIterator for ChunksExact<'_, T> { + fn is_empty(&self) -> bool { + self.v.is_empty() + } +} + +#[unstable(feature = "trusted_len", issue = "37572")] +unsafe impl<T> TrustedLen for ChunksExact<'_, T> {} + +#[stable(feature = "chunks_exact", since = "1.31.0")] +impl<T> FusedIterator for ChunksExact<'_, T> {} + +#[doc(hidden)] +#[stable(feature = "chunks_exact", since = "1.31.0")] +unsafe impl<'a, T> TrustedRandomAccess for ChunksExact<'a, T> { + unsafe fn get_unchecked(&mut self, i: usize) -> &'a [T] { + let start = i * self.chunk_size; + // SAFETY: mostly identical to `Chunks::get_unchecked`. + unsafe { from_raw_parts(self.v.as_ptr().add(start), self.chunk_size) } + } + fn may_have_side_effect() -> bool { + false + } +} + +/// An iterator over a slice in (non-overlapping) mutable chunks (`chunk_size` +/// 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 +/// [`into_remainder`] function from the iterator. +/// +/// This struct is created by the [`chunks_exact_mut`] method on [slices]. +/// +/// [`chunks_exact_mut`]: ../../std/primitive.slice.html#method.chunks_exact_mut +/// [`into_remainder`]: ../../std/slice/struct.ChunksExactMut.html#method.into_remainder +/// [slices]: ../../std/primitive.slice.html +#[derive(Debug)] +#[stable(feature = "chunks_exact", since = "1.31.0")] +pub struct ChunksExactMut<'a, T: 'a> { + v: &'a mut [T], + rem: &'a mut [T], + chunk_size: usize, +} + +impl<'a, T> ChunksExactMut<'a, T> { + /// 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. + #[stable(feature = "chunks_exact", since = "1.31.0")] + pub fn into_remainder(self) -> &'a mut [T] { + self.rem + } +} + +#[stable(feature = "chunks_exact", since = "1.31.0")] +impl<'a, T> Iterator for ChunksExactMut<'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<usize>) { + 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 tmp = mem::replace(&mut self.v, &mut []); + let (_, snd) = tmp.split_at_mut(start); + self.v = snd; + self.next() + } + } + + #[inline] + fn last(mut self) -> Option<Self::Item> { + self.next_back() + } +} + +#[stable(feature = "chunks_exact", since = "1.31.0")] +impl<'a, T> DoubleEndedIterator for ChunksExactMut<'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) + } + } + + #[inline] + fn nth_back(&mut self, n: usize) -> Option<Self::Item> { + let len = self.len(); + if n >= len { + self.v = &mut []; + None + } else { + let start = (len - 1 - n) * self.chunk_size; + let end = start + self.chunk_size; + let (temp, _tail) = mem::replace(&mut self.v, &mut []).split_at_mut(end); + let (head, nth_back) = temp.split_at_mut(start); + self.v = head; + Some(nth_back) + } + } +} + +#[stable(feature = "chunks_exact", since = "1.31.0")] +impl<T> ExactSizeIterator for ChunksExactMut<'_, T> { + fn is_empty(&self) -> bool { + self.v.is_empty() + } +} + +#[unstable(feature = "trusted_len", issue = "37572")] +unsafe impl<T> TrustedLen for ChunksExactMut<'_, T> {} + +#[stable(feature = "chunks_exact", since = "1.31.0")] +impl<T> FusedIterator for ChunksExactMut<'_, T> {} + +#[doc(hidden)] +#[stable(feature = "chunks_exact", since = "1.31.0")] +unsafe impl<'a, T> TrustedRandomAccess for ChunksExactMut<'a, T> { + unsafe fn get_unchecked(&mut self, i: usize) -> &'a mut [T] { + let start = i * self.chunk_size; + // SAFETY: see comments for `ChunksExactMut::get_unchecked`. + unsafe { from_raw_parts_mut(self.v.as_mut_ptr().add(start), self.chunk_size) } + } + 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. +/// +/// When the slice len is not evenly divided by the chunk size, the last slice +/// of the iteration will be the remainder. +/// +/// This struct is created by the [`rchunks`] method on [slices]. +/// +/// [`rchunks`]: ../../std/primitive.slice.html#method.rchunks +/// [slices]: ../../std/primitive.slice.html +#[derive(Debug)] +#[stable(feature = "rchunks", since = "1.31.0")] +pub struct RChunks<'a, T: 'a> { + v: &'a [T], + chunk_size: usize, +} + +// FIXME(#26925) Remove in favor of `#[derive(Clone)]` +#[stable(feature = "rchunks", since = "1.31.0")] +impl<T> Clone for RChunks<'_, T> { + fn clone(&self) -> Self { + RChunks { v: self.v, chunk_size: self.chunk_size } + } +} + +#[stable(feature = "rchunks", since = "1.31.0")] +impl<'a, T> Iterator for RChunks<'a, T> { + type Item = &'a [T]; + + #[inline] + fn next(&mut self) -> Option<&'a [T]> { + if self.v.is_empty() { + None + } else { + let chunksz = cmp::min(self.v.len(), self.chunk_size); + let (fst, snd) = self.v.split_at(self.v.len() - chunksz); + self.v = fst; + Some(snd) + } + } + + #[inline] + fn size_hint(&self) -> (usize, Option<usize>) { + if self.v.is_empty() { + (0, Some(0)) + } else { + let n = self.v.len() / self.chunk_size; + let rem = self.v.len() % self.chunk_size; + let n = if rem > 0 { n + 1 } else { n }; + (n, Some(n)) + } + } + + #[inline] + fn count(self) -> usize { + self.len() + } + + #[inline] + fn nth(&mut self, n: usize) -> Option<Self::Item> { + let (end, overflow) = n.overflowing_mul(self.chunk_size); + if end >= self.v.len() || overflow { + self.v = &[]; + None + } else { + // Can't underflow because of the check above + let end = self.v.len() - end; + let start = match end.checked_sub(self.chunk_size) { + Some(sum) => sum, + None => 0, + }; + let nth = &self.v[start..end]; + self.v = &self.v[0..start]; + Some(nth) + } + } + + #[inline] + fn last(self) -> Option<Self::Item> { + if self.v.is_empty() { + None + } else { + let rem = self.v.len() % self.chunk_size; + let end = if rem == 0 { self.chunk_size } else { rem }; + Some(&self.v[0..end]) + } + } +} + +#[stable(feature = "rchunks", since = "1.31.0")] +impl<'a, T> DoubleEndedIterator for RChunks<'a, T> { + #[inline] + fn next_back(&mut self) -> Option<&'a [T]> { + if self.v.is_empty() { + None + } else { + let remainder = self.v.len() % self.chunk_size; + let chunksz = if remainder != 0 { remainder } else { self.chunk_size }; + let (fst, snd) = self.v.split_at(chunksz); + self.v = snd; + Some(fst) + } + } + + #[inline] + fn nth_back(&mut self, n: usize) -> Option<Self::Item> { + let len = self.len(); + if n >= len { + self.v = &[]; + None + } else { + // can't underflow because `n < len` + let offset_from_end = (len - 1 - n) * self.chunk_size; + let end = self.v.len() - offset_from_end; + let start = end.saturating_sub(self.chunk_size); + let nth_back = &self.v[start..end]; + self.v = &self.v[end..]; + Some(nth_back) + } + } +} + +#[stable(feature = "rchunks", since = "1.31.0")] +impl<T> ExactSizeIterator for RChunks<'_, T> {} + +#[unstable(feature = "trusted_len", issue = "37572")] +unsafe impl<T> TrustedLen for RChunks<'_, T> {} + +#[stable(feature = "rchunks", since = "1.31.0")] +impl<T> FusedIterator for RChunks<'_, T> {} + +#[doc(hidden)] +#[stable(feature = "rchunks", since = "1.31.0")] +unsafe impl<'a, T> TrustedRandomAccess for RChunks<'a, T> { + unsafe fn get_unchecked(&mut self, i: usize) -> &'a [T] { + let end = self.v.len() - i * self.chunk_size; + let start = match end.checked_sub(self.chunk_size) { + None => 0, + Some(start) => start, + }; + // SAFETY: mostly identical to `Chunks::get_unchecked`. + unsafe { from_raw_parts(self.v.as_ptr().add(start), end - start) } + } + fn may_have_side_effect() -> bool { + false + } +} + +/// An iterator over a slice in (non-overlapping) mutable chunks (`chunk_size` +/// elements at a time), starting at the end of the slice. +/// +/// When the slice len is not evenly divided by the chunk size, the last slice +/// of the iteration will be the remainder. +/// +/// This struct is created by the [`rchunks_mut`] method on [slices]. +/// +/// [`rchunks_mut`]: ../../std/primitive.slice.html#method.rchunks_mut +/// [slices]: ../../std/primitive.slice.html +#[derive(Debug)] +#[stable(feature = "rchunks", since = "1.31.0")] +pub struct RChunksMut<'a, T: 'a> { + v: &'a mut [T], + chunk_size: usize, +} + +#[stable(feature = "rchunks", since = "1.31.0")] +impl<'a, T> Iterator for RChunksMut<'a, T> { + type Item = &'a mut [T]; + + #[inline] + fn next(&mut self) -> Option<&'a mut [T]> { + if self.v.is_empty() { + None + } else { + let sz = cmp::min(self.v.len(), self.chunk_size); + let tmp = mem::replace(&mut self.v, &mut []); + let tmp_len = tmp.len(); + let (head, tail) = tmp.split_at_mut(tmp_len - sz); + self.v = head; + Some(tail) + } + } + + #[inline] + fn size_hint(&self) -> (usize, Option<usize>) { + if self.v.is_empty() { + (0, Some(0)) + } else { + let n = self.v.len() / self.chunk_size; + let rem = self.v.len() % self.chunk_size; + let n = if rem > 0 { n + 1 } else { n }; + (n, Some(n)) + } + } + + #[inline] + fn count(self) -> usize { + self.len() + } + + #[inline] + fn nth(&mut self, n: usize) -> Option<&'a mut [T]> { + let (end, overflow) = n.overflowing_mul(self.chunk_size); + if end >= self.v.len() || overflow { + self.v = &mut []; + None + } else { + // Can't underflow because of the check above + let end = self.v.len() - end; + let start = match end.checked_sub(self.chunk_size) { + Some(sum) => sum, + None => 0, + }; + let tmp = mem::replace(&mut self.v, &mut []); + let (head, tail) = tmp.split_at_mut(start); + let (nth, _) = tail.split_at_mut(end - start); + self.v = head; + Some(nth) + } + } + + #[inline] + fn last(self) -> Option<Self::Item> { + if self.v.is_empty() { + None + } else { + let rem = self.v.len() % self.chunk_size; + let end = if rem == 0 { self.chunk_size } else { rem }; + Some(&mut self.v[0..end]) + } + } +} + +#[stable(feature = "rchunks", since = "1.31.0")] +impl<'a, T> DoubleEndedIterator for RChunksMut<'a, T> { + #[inline] + fn next_back(&mut self) -> Option<&'a mut [T]> { + if self.v.is_empty() { + None + } else { + let remainder = self.v.len() % self.chunk_size; + let sz = if remainder != 0 { remainder } else { self.chunk_size }; + let tmp = mem::replace(&mut self.v, &mut []); + let (head, tail) = tmp.split_at_mut(sz); + self.v = tail; + Some(head) + } + } + + #[inline] + fn nth_back(&mut self, n: usize) -> Option<Self::Item> { + let len = self.len(); + if n >= len { + self.v = &mut []; + None + } else { + // can't underflow because `n < len` + let offset_from_end = (len - 1 - n) * self.chunk_size; + let end = self.v.len() - offset_from_end; + let start = end.saturating_sub(self.chunk_size); + let (tmp, tail) = mem::replace(&mut self.v, &mut []).split_at_mut(end); + let (_, nth_back) = tmp.split_at_mut(start); + self.v = tail; + Some(nth_back) + } + } +} + +#[stable(feature = "rchunks", since = "1.31.0")] +impl<T> ExactSizeIterator for RChunksMut<'_, T> {} + +#[unstable(feature = "trusted_len", issue = "37572")] +unsafe impl<T> TrustedLen for RChunksMut<'_, T> {} + +#[stable(feature = "rchunks", since = "1.31.0")] +impl<T> FusedIterator for RChunksMut<'_, T> {} + +#[doc(hidden)] +#[stable(feature = "rchunks", since = "1.31.0")] +unsafe impl<'a, T> TrustedRandomAccess for RChunksMut<'a, T> { + unsafe fn get_unchecked(&mut self, i: usize) -> &'a mut [T] { + let end = self.v.len() - i * self.chunk_size; + let start = match end.checked_sub(self.chunk_size) { + None => 0, + Some(start) => start, + }; + // SAFETY: see comments for `RChunks::get_unchecked`. + unsafe { from_raw_parts_mut(self.v.as_mut_ptr().add(start), end - start) } + } + 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. +/// +/// 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 [`rchunks_exact`] method on [slices]. +/// +/// [`rchunks_exact`]: ../../std/primitive.slice.html#method.rchunks_exact +/// [`remainder`]: ../../std/slice/struct.ChunksExact.html#method.remainder +/// [slices]: ../../std/primitive.slice.html +#[derive(Debug)] +#[stable(feature = "rchunks", since = "1.31.0")] +pub struct RChunksExact<'a, T: 'a> { + v: &'a [T], + rem: &'a [T], + chunk_size: usize, +} + +impl<'a, T> RChunksExact<'a, T> { + /// 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. + #[stable(feature = "rchunks", since = "1.31.0")] + pub fn remainder(&self) -> &'a [T] { + self.rem + } +} + +// FIXME(#26925) Remove in favor of `#[derive(Clone)]` +#[stable(feature = "rchunks", since = "1.31.0")] +impl<'a, T> Clone for RChunksExact<'a, T> { + fn clone(&self) -> RChunksExact<'a, T> { + RChunksExact { v: self.v, rem: self.rem, chunk_size: self.chunk_size } + } +} + +#[stable(feature = "rchunks", since = "1.31.0")] +impl<'a, T> Iterator for RChunksExact<'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.v.len() - self.chunk_size); + self.v = fst; + Some(snd) + } + } + + #[inline] + fn size_hint(&self) -> (usize, Option<usize>) { + 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<Self::Item> { + let (end, overflow) = n.overflowing_mul(self.chunk_size); + if end >= self.v.len() || overflow { + self.v = &[]; + None + } else { + let (fst, _) = self.v.split_at(self.v.len() - end); + self.v = fst; + self.next() + } + } + + #[inline] + fn last(mut self) -> Option<Self::Item> { + self.next_back() + } +} + +#[stable(feature = "rchunks", since = "1.31.0")] +impl<'a, T> DoubleEndedIterator for RChunksExact<'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.chunk_size); + self.v = snd; + Some(fst) + } + } + + #[inline] + fn nth_back(&mut self, n: usize) -> Option<Self::Item> { + let len = self.len(); + if n >= len { + self.v = &[]; + None + } else { + // now that we know that `n` corresponds to a chunk, + // none of these operations can underflow/overflow + let offset = (len - n) * self.chunk_size; + let start = self.v.len() - offset; + let end = start + self.chunk_size; + let nth_back = &self.v[start..end]; + self.v = &self.v[end..]; + Some(nth_back) + } + } +} + +#[stable(feature = "rchunks", since = "1.31.0")] +impl<'a, T> ExactSizeIterator for RChunksExact<'a, T> { + fn is_empty(&self) -> bool { + self.v.is_empty() + } +} + +#[unstable(feature = "trusted_len", issue = "37572")] +unsafe impl<T> TrustedLen for RChunksExact<'_, T> {} + +#[stable(feature = "rchunks", since = "1.31.0")] +impl<T> FusedIterator for RChunksExact<'_, T> {} + +#[doc(hidden)] +#[stable(feature = "rchunks", since = "1.31.0")] +unsafe impl<'a, T> TrustedRandomAccess for RChunksExact<'a, T> { + unsafe fn get_unchecked(&mut self, i: usize) -> &'a [T] { + let end = self.v.len() - i * self.chunk_size; + let start = end - self.chunk_size; + // SAFETY: mostmy identical to `Chunks::get_unchecked`. + unsafe { from_raw_parts(self.v.as_ptr().add(start), self.chunk_size) } + } + fn may_have_side_effect() -> bool { + false + } +} + +/// An iterator over a slice in (non-overlapping) mutable chunks (`chunk_size` +/// elements at a time), starting at the end 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 +/// [`into_remainder`] function from the iterator. +/// +/// This struct is created by the [`rchunks_exact_mut`] method on [slices]. +/// +/// [`rchunks_exact_mut`]: ../../std/primitive.slice.html#method.rchunks_exact_mut +/// [`into_remainder`]: ../../std/slice/struct.ChunksExactMut.html#method.into_remainder +/// [slices]: ../../std/primitive.slice.html +#[derive(Debug)] +#[stable(feature = "rchunks", since = "1.31.0")] +pub struct RChunksExactMut<'a, T: 'a> { + v: &'a mut [T], + rem: &'a mut [T], + chunk_size: usize, +} + +impl<'a, T> RChunksExactMut<'a, T> { + /// 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. + #[stable(feature = "rchunks", since = "1.31.0")] + pub fn into_remainder(self) -> &'a mut [T] { + self.rem + } +} + +#[stable(feature = "rchunks", since = "1.31.0")] +impl<'a, T> Iterator for RChunksExactMut<'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 tmp_len = tmp.len(); + let (head, tail) = tmp.split_at_mut(tmp_len - self.chunk_size); + self.v = head; + Some(tail) + } + } + + #[inline] + fn size_hint(&self) -> (usize, Option<usize>) { + 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 (end, overflow) = n.overflowing_mul(self.chunk_size); + if end >= self.v.len() || overflow { + self.v = &mut []; + None + } else { + let tmp = mem::replace(&mut self.v, &mut []); + let tmp_len = tmp.len(); + let (fst, _) = tmp.split_at_mut(tmp_len - end); + self.v = fst; + self.next() + } + } + + #[inline] + fn last(mut self) -> Option<Self::Item> { + self.next_back() + } +} + +#[stable(feature = "rchunks", since = "1.31.0")] +impl<'a, T> DoubleEndedIterator for RChunksExactMut<'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 (head, tail) = tmp.split_at_mut(self.chunk_size); + self.v = tail; + Some(head) + } + } + + #[inline] + fn nth_back(&mut self, n: usize) -> Option<Self::Item> { + let len = self.len(); + if n >= len { + self.v = &mut []; + None + } else { + // now that we know that `n` corresponds to a chunk, + // none of these operations can underflow/overflow + let offset = (len - n) * self.chunk_size; + let start = self.v.len() - offset; + let end = start + self.chunk_size; + let (tmp, tail) = mem::replace(&mut self.v, &mut []).split_at_mut(end); + let (_, nth_back) = tmp.split_at_mut(start); + self.v = tail; + Some(nth_back) + } + } +} + +#[stable(feature = "rchunks", since = "1.31.0")] +impl<T> ExactSizeIterator for RChunksExactMut<'_, T> { + fn is_empty(&self) -> bool { + self.v.is_empty() + } +} + +#[unstable(feature = "trusted_len", issue = "37572")] +unsafe impl<T> TrustedLen for RChunksExactMut<'_, T> {} + +#[stable(feature = "rchunks", since = "1.31.0")] +impl<T> FusedIterator for RChunksExactMut<'_, T> {} + +#[doc(hidden)] +#[stable(feature = "rchunks", since = "1.31.0")] +unsafe impl<'a, T> TrustedRandomAccess for RChunksExactMut<'a, T> { + unsafe fn get_unchecked(&mut self, i: usize) -> &'a mut [T] { + let end = self.v.len() - i * self.chunk_size; + let start = end - self.chunk_size; + // SAFETY: see comments for `RChunksExact::get_unchecked`. + unsafe { from_raw_parts_mut(self.v.as_mut_ptr().add(start), self.chunk_size) } + } + fn may_have_side_effect() -> bool { + false + } +} + +// +// Free functions +// + +/// Forms a slice from a pointer and a length. +/// +/// The `len` argument is the number of **elements**, not the number of bytes. +/// +/// # Safety +/// +/// Behavior is undefined if any of the following conditions are violated: +/// +/// * `data` must be [valid] for reads for `len * mem::size_of::<T>()` many bytes, +/// and it must be properly aligned. This means in particular: +/// +/// * The entire memory range of this slice must be contained within a single allocated object! +/// Slices can never span across multiple allocated objects. See [below](#incorrect-usage) +/// for an example incorrectly not taking this into account. +/// * `data` must be non-null and aligned even for zero-length slices. One +/// reason for this is that enum layout optimizations may rely on references +/// (including slices of any length) being aligned and non-null to distinguish +/// them from other data. You can obtain a pointer that is usable as `data` +/// for zero-length slices using [`NonNull::dangling()`]. +/// +/// * The memory referenced by the returned slice must not be mutated for the duration +/// of lifetime `'a`, except inside an `UnsafeCell`. +/// +/// * The total size `len * mem::size_of::<T>()` of the slice must be no larger than `isize::MAX`. +/// See the safety documentation of [`pointer::offset`]. +/// +/// # Caveat +/// +/// The lifetime for the returned slice is inferred from its usage. To +/// prevent accidental misuse, it's suggested to tie the lifetime to whichever +/// source lifetime is safe in the context, such as by providing a helper +/// function taking the lifetime of a host value for the slice, or by explicit +/// annotation. +/// +/// # Examples +/// +/// ``` +/// use std::slice; +/// +/// // manifest a slice for a single element +/// let x = 42; +/// let ptr = &x as *const _; +/// let slice = unsafe { slice::from_raw_parts(ptr, 1) }; +/// assert_eq!(slice[0], 42); +/// ``` +/// +/// ### Incorrect usage +/// +/// The following `join_slices` function is **unsound** ⚠️ +/// +/// ```rust,no_run +/// use std::slice; +/// +/// fn join_slices<'a, T>(fst: &'a [T], snd: &'a [T]) -> &'a [T] { +/// let fst_end = fst.as_ptr().wrapping_add(fst.len()); +/// let snd_start = snd.as_ptr(); +/// assert_eq!(fst_end, snd_start, "Slices must be contiguous!"); +/// unsafe { +/// // The assertion above ensures `fst` and `snd` are contiguous, but they might +/// // still be contained within _different allocated objects_, in which case +/// // creating this slice is undefined behavior. +/// slice::from_raw_parts(fst.as_ptr(), fst.len() + snd.len()) +/// } +/// } +/// +/// fn main() { +/// // `a` and `b` are different allocated objects... +/// let a = 42; +/// let b = 27; +/// // ... which may nevertheless be laid out contiguously in memory: | a | b | +/// let _ = join_slices(slice::from_ref(&a), slice::from_ref(&b)); // UB +/// } +/// ``` +/// +/// [valid]: ../../std/ptr/index.html#safety +/// [`NonNull::dangling()`]: ../../std/ptr/struct.NonNull.html#method.dangling +/// [`pointer::offset`]: ../../std/primitive.pointer.html#method.offset +#[inline] +#[stable(feature = "rust1", since = "1.0.0")] +pub unsafe fn from_raw_parts<'a, T>(data: *const T, len: usize) -> &'a [T] { + debug_assert!(is_aligned_and_not_null(data), "attempt to create unaligned or null slice"); + debug_assert!( + mem::size_of::<T>().saturating_mul(len) <= isize::MAX as usize, + "attempt to create slice covering at least half the address space" + ); + // SAFETY: the caller must uphold the safety contract for `from_raw_parts`. + unsafe { &*ptr::slice_from_raw_parts(data, len) } +} + +/// Performs the same functionality as [`from_raw_parts`], except that a +/// mutable slice is returned. +/// +/// # Safety +/// +/// Behavior is undefined if any of the following conditions are violated: +/// +/// * `data` must be [valid] for boths reads and writes for `len * mem::size_of::<T>()` many bytes, +/// and it must be properly aligned. This means in particular: +/// +/// * The entire memory range of this slice must be contained within a single allocated object! +/// Slices can never span across multiple allocated objects. +/// * `data` must be non-null and aligned even for zero-length slices. One +/// reason for this is that enum layout optimizations may rely on references +/// (including slices of any length) being aligned and non-null to distinguish +/// them from other data. You can obtain a pointer that is usable as `data` +/// for zero-length slices using [`NonNull::dangling()`]. +/// +/// * The memory referenced by the returned slice must not be accessed through any other pointer +/// (not derived from the return value) for the duration of lifetime `'a`. +/// Both read and write accesses are forbidden. +/// +/// * The total size `len * mem::size_of::<T>()` of the slice must be no larger than `isize::MAX`. +/// See the safety documentation of [`pointer::offset`]. +/// +/// [valid]: ../../std/ptr/index.html#safety +/// [`NonNull::dangling()`]: ../../std/ptr/struct.NonNull.html#method.dangling +/// [`pointer::offset`]: ../../std/primitive.pointer.html#method.offset +/// [`from_raw_parts`]: ../../std/slice/fn.from_raw_parts.html +#[inline] +#[stable(feature = "rust1", since = "1.0.0")] +pub unsafe fn from_raw_parts_mut<'a, T>(data: *mut T, len: usize) -> &'a mut [T] { + debug_assert!(is_aligned_and_not_null(data), "attempt to create unaligned or null slice"); + debug_assert!( + mem::size_of::<T>().saturating_mul(len) <= isize::MAX as usize, + "attempt to create slice covering at least half the address space" + ); + // SAFETY: the caller must uphold the safety contract for `from_raw_parts_mut`. + unsafe { &mut *ptr::slice_from_raw_parts_mut(data, len) } +} + +/// Converts a reference to T into a slice of length 1 (without copying). +#[stable(feature = "from_ref", since = "1.28.0")] +pub fn from_ref<T>(s: &T) -> &[T] { + unsafe { from_raw_parts(s, 1) } +} + +/// Converts a reference to T into a slice of length 1 (without copying). +#[stable(feature = "from_ref", since = "1.28.0")] +pub fn from_mut<T>(s: &mut T) -> &mut [T] { + unsafe { from_raw_parts_mut(s, 1) } +} + +// This function is public only because there is no other way to unit test heapsort. +#[unstable(feature = "sort_internals", reason = "internal to sort module", issue = "none")] +#[doc(hidden)] +pub fn heapsort<T, F>(v: &mut [T], mut is_less: F) +where + F: FnMut(&T, &T) -> bool, +{ + sort::heapsort(v, &mut is_less); +} + +// +// Comparison traits +// + +extern "C" { + /// Calls implementation provided memcmp. + /// + /// Interprets the data as u8. + /// + /// Returns 0 for equal, < 0 for less than and > 0 for greater + /// than. + // FIXME(#32610): Return type should be c_int + fn memcmp(s1: *const u8, s2: *const u8, n: usize) -> i32; +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl<A, B> PartialEq<[B]> for [A] +where + A: PartialEq<B>, +{ + fn eq(&self, other: &[B]) -> bool { + SlicePartialEq::equal(self, other) + } + + fn ne(&self, other: &[B]) -> bool { + SlicePartialEq::not_equal(self, other) + } +} + +#[stable(feature = "rust1", since = "1.0.0")] +impl<T: Eq> Eq for [T] {} + +/// Implements comparison of vectors lexicographically. +#[stable(feature = "rust1", since = "1.0.0")] +impl<T: Ord> Ord for [T] { + fn cmp(&self, other: &[T]) -> Ordering { + SliceOrd::compare(self, other) + } +} + +/// Implements comparison of vectors lexicographically. +#[stable(feature = "rust1", since = "1.0.0")] +impl<T: PartialOrd> PartialOrd for [T] { + fn partial_cmp(&self, other: &[T]) -> Option<Ordering> { + SlicePartialOrd::partial_compare(self, other) + } +} + +#[doc(hidden)] +// intermediate trait for specialization of slice's PartialEq +trait SlicePartialEq<B> { + fn equal(&self, other: &[B]) -> bool; + + fn not_equal(&self, other: &[B]) -> bool { + !self.equal(other) + } +} + +// Generic slice equality +impl<A, B> SlicePartialEq<B> for [A] +where + A: PartialEq<B>, +{ + default fn equal(&self, other: &[B]) -> bool { + if self.len() != other.len() { + return false; + } + + self.iter().zip(other.iter()).all(|(x, y)| x == y) + } +} + +// Use an equal-pointer optimization when types are `Eq` +impl<A> SlicePartialEq<A> for [A] +where + A: PartialEq<A> + Eq, +{ + default fn equal(&self, other: &[A]) -> bool { + if self.len() != other.len() { + return false; + } + + // While performance would suffer if `guaranteed_eq` just returned `false` + // for all arguments, correctness and return value of this function are not affected. + if self.as_ptr().guaranteed_eq(other.as_ptr()) { + return true; + } + + self.iter().zip(other.iter()).all(|(x, y)| x == y) + } +} + +// Use memcmp for bytewise equality when the types allow +impl<A> SlicePartialEq<A> for [A] +where + A: PartialEq<A> + BytewiseEquality, +{ + fn equal(&self, other: &[A]) -> bool { + if self.len() != other.len() { + return false; + } + + // While performance would suffer if `guaranteed_eq` just returned `false` + // for all arguments, correctness and return value of this function are not affected. + if self.as_ptr().guaranteed_eq(other.as_ptr()) { + return true; + } + unsafe { + let size = mem::size_of_val(self); + memcmp(self.as_ptr() as *const u8, other.as_ptr() as *const u8, size) == 0 + } + } +} + +#[doc(hidden)] +// intermediate trait for specialization of slice's PartialOrd +trait SlicePartialOrd: Sized { + fn partial_compare(left: &[Self], right: &[Self]) -> Option<Ordering>; +} + +impl<A: PartialOrd> SlicePartialOrd for A { + default fn partial_compare(left: &[A], right: &[A]) -> Option<Ordering> { + let l = cmp::min(left.len(), right.len()); + + // Slice to the loop iteration range to enable bound check + // elimination in the compiler + let lhs = &left[..l]; + let rhs = &right[..l]; + + for i in 0..l { + match lhs[i].partial_cmp(&rhs[i]) { + Some(Ordering::Equal) => (), + non_eq => return non_eq, + } + } + + left.len().partial_cmp(&right.len()) + } +} + +// This is the impl that we would like to have. Unfortunately it's not sound. +// See `partial_ord_slice.rs`. +/* +impl<A> SlicePartialOrd for A +where + A: Ord, +{ + default fn partial_compare(left: &[A], right: &[A]) -> Option<Ordering> { + Some(SliceOrd::compare(left, right)) + } +} +*/ + +impl<A: AlwaysApplicableOrd> SlicePartialOrd for A { + fn partial_compare(left: &[A], right: &[A]) -> Option<Ordering> { + Some(SliceOrd::compare(left, right)) + } +} + +trait AlwaysApplicableOrd: SliceOrd + Ord {} + +macro_rules! always_applicable_ord { + ($([$($p:tt)*] $t:ty,)*) => { + $(impl<$($p)*> AlwaysApplicableOrd for $t {})* + } +} + +always_applicable_ord! { + [] u8, [] u16, [] u32, [] u64, [] u128, [] usize, + [] i8, [] i16, [] i32, [] i64, [] i128, [] isize, + [] bool, [] char, + [T: ?Sized] *const T, [T: ?Sized] *mut T, + [T: AlwaysApplicableOrd] &T, + [T: AlwaysApplicableOrd] &mut T, + [T: AlwaysApplicableOrd] Option<T>, +} + +#[doc(hidden)] +// intermediate trait for specialization of slice's Ord +trait SliceOrd: Sized { + fn compare(left: &[Self], right: &[Self]) -> Ordering; +} + +impl<A: Ord> SliceOrd for A { + default fn compare(left: &[Self], right: &[Self]) -> Ordering { + let l = cmp::min(left.len(), right.len()); + + // Slice to the loop iteration range to enable bound check + // elimination in the compiler + let lhs = &left[..l]; + let rhs = &right[..l]; + + for i in 0..l { + match lhs[i].cmp(&rhs[i]) { + Ordering::Equal => (), + non_eq => return non_eq, + } + } + + left.len().cmp(&right.len()) + } +} + +// memcmp compares a sequence of unsigned bytes lexicographically. +// this matches the order we want for [u8], but no others (not even [i8]). +impl SliceOrd for u8 { + #[inline] + fn compare(left: &[Self], right: &[Self]) -> Ordering { + let order = + unsafe { memcmp(left.as_ptr(), right.as_ptr(), cmp::min(left.len(), right.len())) }; + if order == 0 { + left.len().cmp(&right.len()) + } else if order < 0 { + Less + } else { + Greater + } + } +} + +#[doc(hidden)] +/// Trait implemented for types that can be compared for equality using +/// their bytewise representation +trait BytewiseEquality: Eq + Copy {} + +macro_rules! impl_marker_for { + ($traitname:ident, $($ty:ty)*) => { + $( + impl $traitname for $ty { } + )* + } +} + +impl_marker_for!(BytewiseEquality, + u8 i8 u16 i16 u32 i32 u64 i64 u128 i128 usize isize char bool); + +#[doc(hidden)] +unsafe impl<'a, T> TrustedRandomAccess for Iter<'a, T> { + unsafe fn get_unchecked(&mut self, i: usize) -> &'a T { + // SAFETY: the caller must guarantee that `i` is in bounds + // of the underlying slice, so `i` cannot overflow an `isize`, + // and the returned references is guaranteed to refer to an element + // of the slice and thus guaranteed to be valid. + unsafe { &*self.ptr.as_ptr().add(i) } + } + fn may_have_side_effect() -> bool { + false + } +} + +#[doc(hidden)] +unsafe impl<'a, T> TrustedRandomAccess for IterMut<'a, T> { + unsafe fn get_unchecked(&mut self, i: usize) -> &'a mut T { + // SAFETY: see comments for `Iter::get_unchecked`. + unsafe { &mut *self.ptr.as_ptr().add(i) } + } + fn may_have_side_effect() -> bool { + false + } +} + +trait SliceContains: Sized { + fn slice_contains(&self, x: &[Self]) -> bool; +} + +impl<T> SliceContains for T +where + T: PartialEq, +{ + default fn slice_contains(&self, x: &[Self]) -> bool { + x.iter().any(|y| *y == *self) + } +} + +impl SliceContains for u8 { + fn slice_contains(&self, x: &[Self]) -> bool { + memchr::memchr(*self, x).is_some() + } +} + +impl SliceContains for i8 { + fn slice_contains(&self, x: &[Self]) -> bool { + let byte = *self as u8; + let bytes: &[u8] = unsafe { from_raw_parts(x.as_ptr() as *const u8, x.len()) }; + memchr::memchr(byte, bytes).is_some() + } +} |