blob: e7a2d7adedea0ddc56e62475a11c83dcb9408063 [file] [log] [blame]
// 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 the safety requirements for `get_unchecked`.
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`.
unsafe { 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 {
self.iter().all(|b| b.is_ascii())
}
/// 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();
}
}
}
#[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