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| author | mark <markm@cs.wisc.edu> | 2020-06-11 21:31:49 -0500 |
|---|---|---|
| committer | mark <markm@cs.wisc.edu> | 2020-07-27 19:51:13 -0500 |
| commit | 2c31b45ae878b821975c4ebd94cc1e49f6073fd0 (patch) | |
| tree | 14f64e683e3f64dcbcfb8c2c7cb45ac7592e6e09 /src/libcore/slice/mod.rs | |
| parent | 9be8ffcb0206fc1558069a7b4766090df7877659 (diff) | |
| download | rust-2c31b45ae878b821975c4ebd94cc1e49f6073fd0.tar.gz rust-2c31b45ae878b821975c4ebd94cc1e49f6073fd0.zip | |
mv std libs to library/
Diffstat (limited to 'src/libcore/slice/mod.rs')
| -rw-r--r-- | src/libcore/slice/mod.rs | 6453 |
1 files changed, 0 insertions, 6453 deletions
diff --git a/src/libcore/slice/mod.rs b/src/libcore/slice/mod.rs deleted file mode 100644 index 9ed5a1f9622..00000000000 --- a/src/libcore/slice/mod.rs +++ /dev/null @@ -1,6453 +0,0 @@ -// 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() - } -} |