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rust: import upstream alloc crate

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This is a subset of the Rust standard library `alloc` crate,
version 1.62.0, licensed under "Apache-2.0 OR MIT", from:

    https://github.com/rust-lang/rust/tree/1.62.0/library/alloc/src

The files are copied as-is, with no modifications whatsoever
(not even adding the SPDX identifiers).

For copyright details, please see:

    https://github.com/rust-lang/rust/blob/1.62.0/COPYRIGHT

The next patch modifies these files as needed for use within
the kernel. This patch split allows reviewers to double-check
the import and to clearly see the differences introduced.

Vendoring `alloc`, at least for the moment, allows us to have fallible
allocations support (i.e. the `try_*` versions of methods which return
a `Result` instead of panicking) early on. It also gives a bit more
freedom to experiment with new interfaces and to iterate quickly.

Eventually, the goal is to have everything the kernel needs in
upstream `alloc` and drop it from the kernel tree.

For a summary of work on `alloc` happening upstream, please see:

    https://github.com/Rust-for-Linux/linux/issues/408

The following script may be used to verify the contents:

    for path in $(cd rust/alloc/ && find . -type f -name '*.rs'); do
        curl --silent --show-error --location \
            https://github.com/rust-lang/rust/raw/1.62.0/library/alloc/src/$path \
            | diff --unified rust/alloc/$path - && echo $path: OK
    done

Reviewed-by: Kees Cook <keescook@chromium.org>
Co-developed-by: Alex Gaynor <alex.gaynor@gmail.com>
Signed-off-by: Alex Gaynor <alex.gaynor@gmail.com>
Co-developed-by: Wedson Almeida Filho <wedsonaf@google.com>
Signed-off-by: Wedson Almeida Filho <wedsonaf@google.com>
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
This commit is contained in:
Miguel Ojeda 2022-05-06 17:52:44 +02:00
parent 12f577216a
commit 753dece88d
13 changed files with 9037 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

438
rust/alloc/alloc.rs Normal file
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//! Memory allocation APIs
#![stable(feature = "alloc_module", since = "1.28.0")]
#[cfg(not(test))]
use core::intrinsics;
use core::intrinsics::{min_align_of_val, size_of_val};
use core::ptr::Unique;
#[cfg(not(test))]
use core::ptr::{self, NonNull};
#[stable(feature = "alloc_module", since = "1.28.0")]
#[doc(inline)]
pub use core::alloc::*;
use core::marker::Destruct;
#[cfg(test)]
mod tests;
extern "Rust" {
// These are the magic symbols to call the global allocator. rustc generates
// them to call `__rg_alloc` etc. if there is a `#[global_allocator]` attribute
// (the code expanding that attribute macro generates those functions), or to call
// the default implementations in libstd (`__rdl_alloc` etc. in `library/std/src/alloc.rs`)
// otherwise.
// The rustc fork of LLVM also special-cases these function names to be able to optimize them
// like `malloc`, `realloc`, and `free`, respectively.
#[rustc_allocator]
#[rustc_allocator_nounwind]
fn __rust_alloc(size: usize, align: usize) -> *mut u8;
#[rustc_allocator_nounwind]
fn __rust_dealloc(ptr: *mut u8, size: usize, align: usize);
#[rustc_allocator_nounwind]
fn __rust_realloc(ptr: *mut u8, old_size: usize, align: usize, new_size: usize) -> *mut u8;
#[rustc_allocator_nounwind]
fn __rust_alloc_zeroed(size: usize, align: usize) -> *mut u8;
}
/// The global memory allocator.
///
/// This type implements the [`Allocator`] trait by forwarding calls
/// to the allocator registered with the `#[global_allocator]` attribute
/// if there is one, or the `std` crate’s default.
///
/// Note: while this type is unstable, the functionality it provides can be
/// accessed through the [free functions in `alloc`](self#functions).
#[unstable(feature = "allocator_api", issue = "32838")]
#[derive(Copy, Clone, Default, Debug)]
#[cfg(not(test))]
pub struct Global;
#[cfg(test)]
pub use std::alloc::Global;
/// Allocate memory with the global allocator.
///
/// This function forwards calls to the [`GlobalAlloc::alloc`] method
/// of the allocator registered with the `#[global_allocator]` attribute
/// if there is one, or the `std` crate’s default.
///
/// This function is expected to be deprecated in favor of the `alloc` method
/// of the [`Global`] type when it and the [`Allocator`] trait become stable.
///
/// # Safety
///
/// See [`GlobalAlloc::alloc`].
///
/// # Examples
///
/// ```
/// use std::alloc::{alloc, dealloc, Layout};
///
/// unsafe {
/// let layout = Layout::new::<u16>();
/// let ptr = alloc(layout);
///
/// *(ptr as *mut u16) = 42;
/// assert_eq!(*(ptr as *mut u16), 42);
///
/// dealloc(ptr, layout);
/// }
/// ```
#[stable(feature = "global_alloc", since = "1.28.0")]
#[must_use = "losing the pointer will leak memory"]
#[inline]
pub unsafe fn alloc(layout: Layout) -> *mut u8 {
unsafe { __rust_alloc(layout.size(), layout.align()) }
}
/// Deallocate memory with the global allocator.
///
/// This function forwards calls to the [`GlobalAlloc::dealloc`] method
/// of the allocator registered with the `#[global_allocator]` attribute
/// if there is one, or the `std` crate’s default.
///
/// This function is expected to be deprecated in favor of the `dealloc` method
/// of the [`Global`] type when it and the [`Allocator`] trait become stable.
///
/// # Safety
///
/// See [`GlobalAlloc::dealloc`].
#[stable(feature = "global_alloc", since = "1.28.0")]
#[inline]
pub unsafe fn dealloc(ptr: *mut u8, layout: Layout) {
unsafe { __rust_dealloc(ptr, layout.size(), layout.align()) }
}
/// Reallocate memory with the global allocator.
///
/// This function forwards calls to the [`GlobalAlloc::realloc`] method
/// of the allocator registered with the `#[global_allocator]` attribute
/// if there is one, or the `std` crate’s default.
///
/// This function is expected to be deprecated in favor of the `realloc` method
/// of the [`Global`] type when it and the [`Allocator`] trait become stable.
///
/// # Safety
///
/// See [`GlobalAlloc::realloc`].
#[stable(feature = "global_alloc", since = "1.28.0")]
#[must_use = "losing the pointer will leak memory"]
#[inline]
pub unsafe fn realloc(ptr: *mut u8, layout: Layout, new_size: usize) -> *mut u8 {
unsafe { __rust_realloc(ptr, layout.size(), layout.align(), new_size) }
}
/// Allocate zero-initialized memory with the global allocator.
///
/// This function forwards calls to the [`GlobalAlloc::alloc_zeroed`] method
/// of the allocator registered with the `#[global_allocator]` attribute
/// if there is one, or the `std` crate’s default.
///
/// This function is expected to be deprecated in favor of the `alloc_zeroed` method
/// of the [`Global`] type when it and the [`Allocator`] trait become stable.
///
/// # Safety
///
/// See [`GlobalAlloc::alloc_zeroed`].
///
/// # Examples
///
/// ```
/// use std::alloc::{alloc_zeroed, dealloc, Layout};
///
/// unsafe {
/// let layout = Layout::new::<u16>();
/// let ptr = alloc_zeroed(layout);
///
/// assert_eq!(*(ptr as *mut u16), 0);
///
/// dealloc(ptr, layout);
/// }
/// ```
#[stable(feature = "global_alloc", since = "1.28.0")]
#[must_use = "losing the pointer will leak memory"]
#[inline]
pub unsafe fn alloc_zeroed(layout: Layout) -> *mut u8 {
unsafe { __rust_alloc_zeroed(layout.size(), layout.align()) }
}
#[cfg(not(test))]
impl Global {
#[inline]
fn alloc_impl(&self, layout: Layout, zeroed: bool) -> Result<NonNull<[u8]>, AllocError> {
match layout.size() {
0 => Ok(NonNull::slice_from_raw_parts(layout.dangling(), 0)),
// SAFETY: `layout` is non-zero in size,
size => unsafe {
let raw_ptr = if zeroed { alloc_zeroed(layout) } else { alloc(layout) };
let ptr = NonNull::new(raw_ptr).ok_or(AllocError)?;
Ok(NonNull::slice_from_raw_parts(ptr, size))
},
}
}
// SAFETY: Same as `Allocator::grow`
#[inline]
unsafe fn grow_impl(
&self,
ptr: NonNull<u8>,
old_layout: Layout,
new_layout: Layout,
zeroed: bool,
) -> Result<NonNull<[u8]>, AllocError> {
debug_assert!(
new_layout.size() >= old_layout.size(),
"`new_layout.size()` must be greater than or equal to `old_layout.size()`"
);
match old_layout.size() {
0 => self.alloc_impl(new_layout, zeroed),
// SAFETY: `new_size` is non-zero as `old_size` is greater than or equal to `new_size`
// as required by safety conditions. Other conditions must be upheld by the caller
old_size if old_layout.align() == new_layout.align() => unsafe {
let new_size = new_layout.size();
// `realloc` probably checks for `new_size >= old_layout.size()` or something similar.
intrinsics::assume(new_size >= old_layout.size());
let raw_ptr = realloc(ptr.as_ptr(), old_layout, new_size);
let ptr = NonNull::new(raw_ptr).ok_or(AllocError)?;
if zeroed {
raw_ptr.add(old_size).write_bytes(0, new_size - old_size);
}
Ok(NonNull::slice_from_raw_parts(ptr, new_size))
},
// SAFETY: because `new_layout.size()` must be greater than or equal to `old_size`,
// both the old and new memory allocation are valid for reads and writes for `old_size`
// bytes. Also, because the old allocation wasn't yet deallocated, it cannot overlap
// `new_ptr`. Thus, the call to `copy_nonoverlapping` is safe. The safety contract
// for `dealloc` must be upheld by the caller.
old_size => unsafe {
let new_ptr = self.alloc_impl(new_layout, zeroed)?;
ptr::copy_nonoverlapping(ptr.as_ptr(), new_ptr.as_mut_ptr(), old_size);
self.deallocate(ptr, old_layout);
Ok(new_ptr)
},
}
}
}
#[unstable(feature = "allocator_api", issue = "32838")]
#[cfg(not(test))]
unsafe impl Allocator for Global {
#[inline]
fn allocate(&self, layout: Layout) -> Result<NonNull<[u8]>, AllocError> {
self.alloc_impl(layout, false)
}
#[inline]
fn allocate_zeroed(&self, layout: Layout) -> Result<NonNull<[u8]>, AllocError> {
self.alloc_impl(layout, true)
}
#[inline]
unsafe fn deallocate(&self, ptr: NonNull<u8>, layout: Layout) {
if layout.size() != 0 {
// SAFETY: `layout` is non-zero in size,
// other conditions must be upheld by the caller
unsafe { dealloc(ptr.as_ptr(), layout) }
}
}
#[inline]
unsafe fn grow(
&self,
ptr: NonNull<u8>,
old_layout: Layout,
new_layout: Layout,
) -> Result<NonNull<[u8]>, AllocError> {
// SAFETY: all conditions must be upheld by the caller
unsafe { self.grow_impl(ptr, old_layout, new_layout, false) }
}
#[inline]
unsafe fn grow_zeroed(
&self,
ptr: NonNull<u8>,
old_layout: Layout,
new_layout: Layout,
) -> Result<NonNull<[u8]>, AllocError> {
// SAFETY: all conditions must be upheld by the caller
unsafe { self.grow_impl(ptr, old_layout, new_layout, true) }
}
#[inline]
unsafe fn shrink(
&self,
ptr: NonNull<u8>,
old_layout: Layout,
new_layout: Layout,
) -> Result<NonNull<[u8]>, AllocError> {
debug_assert!(
new_layout.size() <= old_layout.size(),
"`new_layout.size()` must be smaller than or equal to `old_layout.size()`"
);
match new_layout.size() {
// SAFETY: conditions must be upheld by the caller
0 => unsafe {
self.deallocate(ptr, old_layout);
Ok(NonNull::slice_from_raw_parts(new_layout.dangling(), 0))
},
// SAFETY: `new_size` is non-zero. Other conditions must be upheld by the caller
new_size if old_layout.align() == new_layout.align() => unsafe {
// `realloc` probably checks for `new_size <= old_layout.size()` or something similar.
intrinsics::assume(new_size <= old_layout.size());
let raw_ptr = realloc(ptr.as_ptr(), old_layout, new_size);
let ptr = NonNull::new(raw_ptr).ok_or(AllocError)?;
Ok(NonNull::slice_from_raw_parts(ptr, new_size))
},
// SAFETY: because `new_size` must be smaller than or equal to `old_layout.size()`,
// both the old and new memory allocation are valid for reads and writes for `new_size`
// bytes. Also, because the old allocation wasn't yet deallocated, it cannot overlap
// `new_ptr`. Thus, the call to `copy_nonoverlapping` is safe. The safety contract
// for `dealloc` must be upheld by the caller.
new_size => unsafe {
let new_ptr = self.allocate(new_layout)?;
ptr::copy_nonoverlapping(ptr.as_ptr(), new_ptr.as_mut_ptr(), new_size);
self.deallocate(ptr, old_layout);
Ok(new_ptr)
},
}
}
}
/// The allocator for unique pointers.
#[cfg(all(not(no_global_oom_handling), not(test)))]
#[lang = "exchange_malloc"]
#[inline]
unsafe fn exchange_malloc(size: usize, align: usize) -> *mut u8 {
let layout = unsafe { Layout::from_size_align_unchecked(size, align) };
match Global.allocate(layout) {
Ok(ptr) => ptr.as_mut_ptr(),
Err(_) => handle_alloc_error(layout),
}
}
#[cfg_attr(not(test), lang = "box_free")]
#[inline]
#[rustc_const_unstable(feature = "const_box", issue = "92521")]
// This signature has to be the same as `Box`, otherwise an ICE will happen.
// When an additional parameter to `Box` is added (like `A: Allocator`), this has to be added here as
// well.
// For example if `Box` is changed to `struct Box<T: ?Sized, A: Allocator>(Unique<T>, A)`,
// this function has to be changed to `fn box_free<T: ?Sized, A: Allocator>(Unique<T>, A)` as well.
pub(crate) const unsafe fn box_free<T: ?Sized, A: ~const Allocator + ~const Destruct>(
ptr: Unique<T>,
alloc: A,
) {
unsafe {
let size = size_of_val(ptr.as_ref());
let align = min_align_of_val(ptr.as_ref());
let layout = Layout::from_size_align_unchecked(size, align);
alloc.deallocate(From::from(ptr.cast()), layout)
}
}
// # Allocation error handler
#[cfg(not(no_global_oom_handling))]
extern "Rust" {
// This is the magic symbol to call the global alloc error handler. rustc generates
// it to call `__rg_oom` if there is a `#[alloc_error_handler]`, or to call the
// default implementations below (`__rdl_oom`) otherwise.
fn __rust_alloc_error_handler(size: usize, align: usize) -> !;
}
/// Abort on memory allocation error or failure.
///
/// Callers of memory allocation APIs wishing to abort computation
/// in response to an allocation error are encouraged to call this function,
/// rather than directly invoking `panic!` or similar.
///
/// The default behavior of this function is to print a message to standard error
/// and abort the process.
/// It can be replaced with [`set_alloc_error_hook`] and [`take_alloc_error_hook`].
///
/// [`set_alloc_error_hook`]: ../../std/alloc/fn.set_alloc_error_hook.html
/// [`take_alloc_error_hook`]: ../../std/alloc/fn.take_alloc_error_hook.html
#[stable(feature = "global_alloc", since = "1.28.0")]
#[rustc_const_unstable(feature = "const_alloc_error", issue = "92523")]
#[cfg(all(not(no_global_oom_handling), not(test)))]
#[cold]
pub const fn handle_alloc_error(layout: Layout) -> ! {
const fn ct_error(_: Layout) -> ! {
panic!("allocation failed");
}
fn rt_error(layout: Layout) -> ! {
unsafe {
__rust_alloc_error_handler(layout.size(), layout.align());
}
}
unsafe { core::intrinsics::const_eval_select((layout,), ct_error, rt_error) }
}
// For alloc test `std::alloc::handle_alloc_error` can be used directly.
#[cfg(all(not(no_global_oom_handling), test))]
pub use std::alloc::handle_alloc_error;
#[cfg(all(not(no_global_oom_handling), not(test)))]
#[doc(hidden)]
#[allow(unused_attributes)]
#[unstable(feature = "alloc_internals", issue = "none")]
pub mod __alloc_error_handler {
use crate::alloc::Layout;
// called via generated `__rust_alloc_error_handler`
// if there is no `#[alloc_error_handler]`
#[rustc_std_internal_symbol]
pub unsafe extern "C-unwind" fn __rdl_oom(size: usize, _align: usize) -> ! {
panic!("memory allocation of {size} bytes failed")
}
// if there is an `#[alloc_error_handler]`
#[rustc_std_internal_symbol]
pub unsafe extern "C-unwind" fn __rg_oom(size: usize, align: usize) -> ! {
let layout = unsafe { Layout::from_size_align_unchecked(size, align) };
extern "Rust" {
#[lang = "oom"]
fn oom_impl(layout: Layout) -> !;
}
unsafe { oom_impl(layout) }
}
}
/// Specialize clones into pre-allocated, uninitialized memory.
/// Used by `Box::clone` and `Rc`/`Arc::make_mut`.
pub(crate) trait WriteCloneIntoRaw: Sized {
unsafe fn write_clone_into_raw(&self, target: *mut Self);
}
impl<T: Clone> WriteCloneIntoRaw for T {
#[inline]
default unsafe fn write_clone_into_raw(&self, target: *mut Self) {
// Having allocated *first* may allow the optimizer to create
// the cloned value in-place, skipping the local and move.
unsafe { target.write(self.clone()) };
}
}
impl<T: Copy> WriteCloneIntoRaw for T {
#[inline]
unsafe fn write_clone_into_raw(&self, target: *mut Self) {
// We can always copy in-place, without ever involving a local value.
unsafe { target.copy_from_nonoverlapping(self, 1) };
}
}

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//! A module for working with borrowed data.
#![stable(feature = "rust1", since = "1.0.0")]
use core::cmp::Ordering;
use core::hash::{Hash, Hasher};
use core::ops::Deref;
#[cfg(not(no_global_oom_handling))]
use core::ops::{Add, AddAssign};
#[stable(feature = "rust1", since = "1.0.0")]
pub use core::borrow::{Borrow, BorrowMut};
use crate::fmt;
#[cfg(not(no_global_oom_handling))]
use crate::string::String;
use Cow::*;
#[stable(feature = "rust1", since = "1.0.0")]
impl<'a, B: ?Sized> Borrow<B> for Cow<'a, B>
where
B: ToOwned,
<B as ToOwned>::Owned: 'a,
{
fn borrow(&self) -> &B {
&**self
}
}
/// A generalization of `Clone` to borrowed data.
///
/// Some types make it possible to go from borrowed to owned, usually by
/// implementing the `Clone` trait. But `Clone` works only for going from `&T`
/// to `T`. The `ToOwned` trait generalizes `Clone` to construct owned data
/// from any borrow of a given type.
#[cfg_attr(not(test), rustc_diagnostic_item = "ToOwned")]
#[stable(feature = "rust1", since = "1.0.0")]
pub trait ToOwned {
/// The resulting type after obtaining ownership.
#[stable(feature = "rust1", since = "1.0.0")]
type Owned: Borrow<Self>;
/// Creates owned data from borrowed data, usually by cloning.
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// let s: &str = "a";
/// let ss: String = s.to_owned();
///
/// let v: &[i32] = &[1, 2];
/// let vv: Vec<i32> = v.to_owned();
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
#[must_use = "cloning is often expensive and is not expected to have side effects"]
fn to_owned(&self) -> Self::Owned;
/// Uses borrowed data to replace owned data, usually by cloning.
///
/// This is borrow-generalized version of `Clone::clone_from`.
///
/// # Examples
///
/// Basic usage:
///
/// ```
/// # #![feature(toowned_clone_into)]
/// let mut s: String = String::new();
/// "hello".clone_into(&mut s);
///
/// let mut v: Vec<i32> = Vec::new();
/// [1, 2][..].clone_into(&mut v);
/// ```
#[unstable(feature = "toowned_clone_into", reason = "recently added", issue = "41263")]
fn clone_into(&self, target: &mut Self::Owned) {
*target = self.to_owned();
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<T> ToOwned for T
where
T: Clone,
{
type Owned = T;
fn to_owned(&self) -> T {
self.clone()
}
fn clone_into(&self, target: &mut T) {
target.clone_from(self);
}
}
/// A clone-on-write smart pointer.
///
/// The type `Cow` is a smart pointer providing clone-on-write functionality: it
/// can enclose and provide immutable access to borrowed data, and clone the
/// data lazily when mutation or ownership is required. The type is designed to
/// work with general borrowed data via the `Borrow` trait.
///
/// `Cow` implements `Deref`, which means that you can call
/// non-mutating methods directly on the data it encloses. If mutation
/// is desired, `to_mut` will obtain a mutable reference to an owned
/// value, cloning if necessary.
///
/// If you need reference-counting pointers, note that
/// [`Rc::make_mut`][crate::rc::Rc::make_mut] and
/// [`Arc::make_mut`][crate::sync::Arc::make_mut] can provide clone-on-write
/// functionality as well.
///
/// # Examples
///
/// ```
/// use std::borrow::Cow;
///
/// fn abs_all(input: &mut Cow<[i32]>) {
/// for i in 0..input.len() {
/// let v = input[i];
/// if v < 0 {
/// // Clones into a vector if not already owned.
/// input.to_mut()[i] = -v;
/// }
/// }
/// }
///
/// // No clone occurs because `input` doesn't need to be mutated.
/// let slice = [0, 1, 2];
/// let mut input = Cow::from(&slice[..]);
/// abs_all(&mut input);
///
/// // Clone occurs because `input` needs to be mutated.
/// let slice = [-1, 0, 1];
/// let mut input = Cow::from(&slice[..]);
/// abs_all(&mut input);
///
/// // No clone occurs because `input` is already owned.
/// let mut input = Cow::from(vec![-1, 0, 1]);
/// abs_all(&mut input);
/// ```
///
/// Another example showing how to keep `Cow` in a struct:
///
/// ```
/// use std::borrow::Cow;
///
/// struct Items<'a, X: 'a> where [X]: ToOwned<Owned = Vec<X>> {
/// values: Cow<'a, [X]>,
/// }
///
/// impl<'a, X: Clone + 'a> Items<'a, X> where [X]: ToOwned<Owned = Vec<X>> {
/// fn new(v: Cow<'a, [X]>) -> Self {
/// Items { values: v }
/// }
/// }
///
/// // Creates a container from borrowed values of a slice
/// let readonly = [1, 2];
/// let borrowed = Items::new((&readonly[..]).into());
/// match borrowed {
/// Items { values: Cow::Borrowed(b) } => println!("borrowed {b:?}"),
/// _ => panic!("expect borrowed value"),
/// }
///
/// let mut clone_on_write = borrowed;
/// // Mutates the data from slice into owned vec and pushes a new value on top
/// clone_on_write.values.to_mut().push(3);
/// println!("clone_on_write = {:?}", clone_on_write.values);
///
/// // The data was mutated. Let's check it out.
/// match clone_on_write {
/// Items { values: Cow::Owned(_) } => println!("clone_on_write contains owned data"),
/// _ => panic!("expect owned data"),
/// }
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
#[cfg_attr(not(test), rustc_diagnostic_item = "Cow")]
pub enum Cow<'a, B: ?Sized + 'a>
where
B: ToOwned,
{
/// Borrowed data.
#[stable(feature = "rust1", since = "1.0.0")]
Borrowed(#[stable(feature = "rust1", since = "1.0.0")] &'a B),
/// Owned data.
#[stable(feature = "rust1", since = "1.0.0")]
Owned(#[stable(feature = "rust1", since = "1.0.0")] <B as ToOwned>::Owned),
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<B: ?Sized + ToOwned> Clone for Cow<'_, B> {
fn clone(&self) -> Self {
match *self {
Borrowed(b) => Borrowed(b),
Owned(ref o) => {
let b: &B = o.borrow();
Owned(b.to_owned())
}
}
}
fn clone_from(&mut self, source: &Self) {
match (self, source) {
(&mut Owned(ref mut dest), &Owned(ref o)) => o.borrow().clone_into(dest),
(t, s) => *t = s.clone(),
}
}
}
impl<B: ?Sized + ToOwned> Cow<'_, B> {
/// Returns true if the data is borrowed, i.e. if `to_mut` would require additional work.
///
/// # Examples
///
/// ```
/// #![feature(cow_is_borrowed)]
/// use std::borrow::Cow;
///
/// let cow = Cow::Borrowed("moo");
/// assert!(cow.is_borrowed());
///
/// let bull: Cow<'_, str> = Cow::Owned("...moo?".to_string());
/// assert!(!bull.is_borrowed());
/// ```
#[unstable(feature = "cow_is_borrowed", issue = "65143")]
#[rustc_const_unstable(feature = "const_cow_is_borrowed", issue = "65143")]
pub const fn is_borrowed(&self) -> bool {
match *self {
Borrowed(_) => true,
Owned(_) => false,
}
}
/// Returns true if the data is owned, i.e. if `to_mut` would be a no-op.
///
/// # Examples
///
/// ```
/// #![feature(cow_is_borrowed)]
/// use std::borrow::Cow;
///
/// let cow: Cow<'_, str> = Cow::Owned("moo".to_string());
/// assert!(cow.is_owned());
///
/// let bull = Cow::Borrowed("...moo?");
/// assert!(!bull.is_owned());
/// ```
#[unstable(feature = "cow_is_borrowed", issue = "65143")]
#[rustc_const_unstable(feature = "const_cow_is_borrowed", issue = "65143")]
pub const fn is_owned(&self) -> bool {
!self.is_borrowed()
}
/// Acquires a mutable reference to the owned form of the data.
///
/// Clones the data if it is not already owned.
///
/// # Examples
///
/// ```
/// use std::borrow::Cow;
///
/// let mut cow = Cow::Borrowed("foo");
/// cow.to_mut().make_ascii_uppercase();
///
/// assert_eq!(
/// cow,
/// Cow::Owned(String::from("FOO")) as Cow<str>
/// );
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn to_mut(&mut self) -> &mut <B as ToOwned>::Owned {
match *self {
Borrowed(borrowed) => {
*self = Owned(borrowed.to_owned());
match *self {
Borrowed(..) => unreachable!(),
Owned(ref mut owned) => owned,
}
}
Owned(ref mut owned) => owned,
}
}
/// Extracts the owned data.
///
/// Clones the data if it is not already owned.
///
/// # Examples
///
/// Calling `into_owned` on a `Cow::Borrowed` returns a clone of the borrowed data:
///
/// ```
/// use std::borrow::Cow;
///
/// let s = "Hello world!";
/// let cow = Cow::Borrowed(s);
///
/// assert_eq!(
/// cow.into_owned(),
/// String::from(s)
/// );
/// ```
///
/// Calling `into_owned` on a `Cow::Owned` returns the owned data. The data is moved out of the
/// `Cow` without being cloned.
///
/// ```
/// use std::borrow::Cow;
///
/// let s = "Hello world!";
/// let cow: Cow<str> = Cow::Owned(String::from(s));
///
/// assert_eq!(
/// cow.into_owned(),
/// String::from(s)
/// );
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
pub fn into_owned(self) -> <B as ToOwned>::Owned {
match self {
Borrowed(borrowed) => borrowed.to_owned(),
Owned(owned) => owned,
}
}
}
#[stable(feature = "rust1", since = "1.0.0")]
#[rustc_const_unstable(feature = "const_deref", issue = "88955")]
impl<B: ?Sized + ToOwned> const Deref for Cow<'_, B>
where
B::Owned: ~const Borrow<B>,
{
type Target = B;
fn deref(&self) -> &B {
match *self {
Borrowed(borrowed) => borrowed,
Owned(ref owned) => owned.borrow(),
}
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<B: ?Sized> Eq for Cow<'_, B> where B: Eq + ToOwned {}
#[stable(feature = "rust1", since = "1.0.0")]
impl<B: ?Sized> Ord for Cow<'_, B>
where
B: Ord + ToOwned,
{
#[inline]
fn cmp(&self, other: &Self) -> Ordering {
Ord::cmp(&**self, &**other)
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<'a, 'b, B: ?Sized, C: ?Sized> PartialEq<Cow<'b, C>> for Cow<'a, B>
where
B: PartialEq<C> + ToOwned,
C: ToOwned,
{
#[inline]
fn eq(&self, other: &Cow<'b, C>) -> bool {
PartialEq::eq(&**self, &**other)
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<'a, B: ?Sized> PartialOrd for Cow<'a, B>
where
B: PartialOrd + ToOwned,
{
#[inline]
fn partial_cmp(&self, other: &Cow<'a, B>) -> Option<Ordering> {
PartialOrd::partial_cmp(&**self, &**other)
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<B: ?Sized> fmt::Debug for Cow<'_, B>
where
B: fmt::Debug + ToOwned<Owned: fmt::Debug>,
{
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
match *self {
Borrowed(ref b) => fmt::Debug::fmt(b, f),
Owned(ref o) => fmt::Debug::fmt(o, f),
}
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<B: ?Sized> fmt::Display for Cow<'_, B>
where
B: fmt::Display + ToOwned<Owned: fmt::Display>,
{
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
match *self {
Borrowed(ref b) => fmt::Display::fmt(b, f),
Owned(ref o) => fmt::Display::fmt(o, f),
}
}
}
#[stable(feature = "default", since = "1.11.0")]
impl<B: ?Sized> Default for Cow<'_, B>
where
B: ToOwned<Owned: Default>,
{
/// Creates an owned Cow<'a, B> with the default value for the contained owned value.
fn default() -> Self {
Owned(<B as ToOwned>::Owned::default())
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<B: ?Sized> Hash for Cow<'_, B>
where
B: Hash + ToOwned,
{
#[inline]
fn hash<H: Hasher>(&self, state: &mut H) {
Hash::hash(&**self, state)
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<T: ?Sized + ToOwned> AsRef<T> for Cow<'_, T> {
fn as_ref(&self) -> &T {
self
}
}
#[cfg(not(no_global_oom_handling))]
#[stable(feature = "cow_add", since = "1.14.0")]
impl<'a> Add<&'a str> for Cow<'a, str> {
type Output = Cow<'a, str>;
#[inline]
fn add(mut self, rhs: &'a str) -> Self::Output {
self += rhs;
self
}
}
#[cfg(not(no_global_oom_handling))]
#[stable(feature = "cow_add", since = "1.14.0")]
impl<'a> Add<Cow<'a, str>> for Cow<'a, str> {
type Output = Cow<'a, str>;
#[inline]
fn add(mut self, rhs: Cow<'a, str>) -> Self::Output {
self += rhs;
self
}
}
#[cfg(not(no_global_oom_handling))]
#[stable(feature = "cow_add", since = "1.14.0")]
impl<'a> AddAssign<&'a str> for Cow<'a, str> {
fn add_assign(&mut self, rhs: &'a str) {
if self.is_empty() {
*self = Cow::Borrowed(rhs)
} else if !rhs.is_empty() {
if let Cow::Borrowed(lhs) = *self {
let mut s = String::with_capacity(lhs.len() + rhs.len());
s.push_str(lhs);
*self = Cow::Owned(s);
}
self.to_mut().push_str(rhs);
}
}
}
#[cfg(not(no_global_oom_handling))]
#[stable(feature = "cow_add", since = "1.14.0")]
impl<'a> AddAssign<Cow<'a, str>> for Cow<'a, str> {
fn add_assign(&mut self, rhs: Cow<'a, str>) {
if self.is_empty() {
*self = rhs
} else if !rhs.is_empty() {
if let Cow::Borrowed(lhs) = *self {
let mut s = String::with_capacity(lhs.len() + rhs.len());
s.push_str(lhs);
*self = Cow::Owned(s);
}
self.to_mut().push_str(&rhs);
}
}
}

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//! Collection types.
#![stable(feature = "rust1", since = "1.0.0")]
#[cfg(not(no_global_oom_handling))]
pub mod binary_heap;
#[cfg(not(no_global_oom_handling))]
mod btree;
#[cfg(not(no_global_oom_handling))]
pub mod linked_list;
#[cfg(not(no_global_oom_handling))]
pub mod vec_deque;
#[cfg(not(no_global_oom_handling))]
#[stable(feature = "rust1", since = "1.0.0")]
pub mod btree_map {
//! An ordered map based on a B-Tree.
#[stable(feature = "rust1", since = "1.0.0")]
pub use super::btree::map::*;
}
#[cfg(not(no_global_oom_handling))]
#[stable(feature = "rust1", since = "1.0.0")]
pub mod btree_set {
//! An ordered set based on a B-Tree.
#[stable(feature = "rust1", since = "1.0.0")]
pub use super::btree::set::*;
}
#[cfg(not(no_global_oom_handling))]
#[stable(feature = "rust1", since = "1.0.0")]
#[doc(no_inline)]
pub use binary_heap::BinaryHeap;
#[cfg(not(no_global_oom_handling))]
#[stable(feature = "rust1", since = "1.0.0")]
#[doc(no_inline)]
pub use btree_map::BTreeMap;
#[cfg(not(no_global_oom_handling))]
#[stable(feature = "rust1", since = "1.0.0")]
#[doc(no_inline)]
pub use btree_set::BTreeSet;
#[cfg(not(no_global_oom_handling))]
#[stable(feature = "rust1", since = "1.0.0")]
#[doc(no_inline)]
pub use linked_list::LinkedList;
#[cfg(not(no_global_oom_handling))]
#[stable(feature = "rust1", since = "1.0.0")]
#[doc(no_inline)]
pub use vec_deque::VecDeque;
use crate::alloc::{Layout, LayoutError};
use core::fmt::Display;
/// The error type for `try_reserve` methods.
#[derive(Clone, PartialEq, Eq, Debug)]
#[stable(feature = "try_reserve", since = "1.57.0")]
pub struct TryReserveError {
kind: TryReserveErrorKind,
}
impl TryReserveError {
/// Details about the allocation that caused the error
#[inline]
#[must_use]
#[unstable(
feature = "try_reserve_kind",
reason = "Uncertain how much info should be exposed",
issue = "48043"
)]
pub fn kind(&self) -> TryReserveErrorKind {
self.kind.clone()
}
}
/// Details of the allocation that caused a `TryReserveError`
#[derive(Clone, PartialEq, Eq, Debug)]
#[unstable(
feature = "try_reserve_kind",
reason = "Uncertain how much info should be exposed",
issue = "48043"
)]
pub enum TryReserveErrorKind {
/// Error due to the computed capacity exceeding the collection's maximum
/// (usually `isize::MAX` bytes).
CapacityOverflow,
/// The memory allocator returned an error
AllocError {
/// The layout of allocation request that failed
layout: Layout,
#[doc(hidden)]
#[unstable(
feature = "container_error_extra",
issue = "none",
reason = "\
Enable exposing the allocator’s custom error value \
if an associated type is added in the future: \
https://github.com/rust-lang/wg-allocators/issues/23"
)]
non_exhaustive: (),
},
}
#[unstable(
feature = "try_reserve_kind",
reason = "Uncertain how much info should be exposed",
issue = "48043"
)]
impl From<TryReserveErrorKind> for TryReserveError {
#[inline]
fn from(kind: TryReserveErrorKind) -> Self {
Self { kind }
}
}
#[unstable(feature = "try_reserve_kind", reason = "new API", issue = "48043")]
impl From<LayoutError> for TryReserveErrorKind {
/// Always evaluates to [`TryReserveErrorKind::CapacityOverflow`].
#[inline]
fn from(_: LayoutError) -> Self {
TryReserveErrorKind::CapacityOverflow
}
}
#[stable(feature = "try_reserve", since = "1.57.0")]
impl Display for TryReserveError {
fn fmt(
&self,
fmt: &mut core::fmt::Formatter<'_>,
) -> core::result::Result<(), core::fmt::Error> {
fmt.write_str("memory allocation failed")?;
let reason = match self.kind {
TryReserveErrorKind::CapacityOverflow => {
" because the computed capacity exceeded the collection's maximum"
}
TryReserveErrorKind::AllocError { .. } => {
" because the memory allocator returned a error"
}
};
fmt.write_str(reason)
}
}
/// An intermediate trait for specialization of `Extend`.
#[doc(hidden)]
trait SpecExtend<I: IntoIterator> {
/// Extends `self` with the contents of the given iterator.
fn spec_extend(&mut self, iter: I);
}

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//! # The Rust core allocation and collections library
//!
//! This library provides smart pointers and collections for managing
//! heap-allocated values.
//!
//! This library, like libcore, normally doesn’t need to be used directly
//! since its contents are re-exported in the [`std` crate](../std/index.html).
//! Crates that use the `#![no_std]` attribute however will typically
//! not depend on `std`, so they’d use this crate instead.
//!
//! ## Boxed values
//!
//! The [`Box`] type is a smart pointer type. There can only be one owner of a
//! [`Box`], and the owner can decide to mutate the contents, which live on the
//! heap.
//!
//! This type can be sent among threads efficiently as the size of a `Box` value
//! is the same as that of a pointer. Tree-like data structures are often built
//! with boxes because each node often has only one owner, the parent.
//!
//! ## Reference counted pointers
//!
//! The [`Rc`] type is a non-threadsafe reference-counted pointer type intended
//! for sharing memory within a thread. An [`Rc`] pointer wraps a type, `T`, and
//! only allows access to `&T`, a shared reference.
//!
//! This type is useful when inherited mutability (such as using [`Box`]) is too
//! constraining for an application, and is often paired with the [`Cell`] or
//! [`RefCell`] types in order to allow mutation.
//!
//! ## Atomically reference counted pointers
//!
//! The [`Arc`] type is the threadsafe equivalent of the [`Rc`] type. It
//! provides all the same functionality of [`Rc`], except it requires that the
//! contained type `T` is shareable. Additionally, [`Arc<T>`][`Arc`] is itself
//! sendable while [`Rc<T>`][`Rc`] is not.
//!
//! This type allows for shared access to the contained data, and is often
//! paired with synchronization primitives such as mutexes to allow mutation of
//! shared resources.
//!
//! ## Collections
//!
//! Implementations of the most common general purpose data structures are
//! defined in this library. They are re-exported through the
//! [standard collections library](../std/collections/index.html).
//!
//! ## Heap interfaces
//!
//! The [`alloc`](alloc/index.html) module defines the low-level interface to the
//! default global allocator. It is not compatible with the libc allocator API.
//!
//! [`Arc`]: sync
//! [`Box`]: boxed
//! [`Cell`]: core::cell
//! [`Rc`]: rc
//! [`RefCell`]: core::cell
// To run liballoc tests without x.py without ending up with two copies of liballoc, Miri needs to be
// able to "empty" this crate. See <https://github.com/rust-lang/miri-test-libstd/issues/4>.
// rustc itself never sets the feature, so this line has no affect there.
#![cfg(any(not(feature = "miri-test-libstd"), test, doctest))]
#![allow(unused_attributes)]
#![stable(feature = "alloc", since = "1.36.0")]
#![doc(
html_playground_url = "https://play.rust-lang.org/",
issue_tracker_base_url = "https://github.com/rust-lang/rust/issues/",
test(no_crate_inject, attr(allow(unused_variables), deny(warnings)))
)]
#![doc(cfg_hide(
not(test),
not(any(test, bootstrap)),
any(not(feature = "miri-test-libstd"), test, doctest),
no_global_oom_handling,
not(no_global_oom_handling),
target_has_atomic = "ptr"
))]
#![no_std]
#![needs_allocator]
//
// Lints:
#![deny(unsafe_op_in_unsafe_fn)]
#![warn(deprecated_in_future)]
#![warn(missing_debug_implementations)]
#![warn(missing_docs)]
#![allow(explicit_outlives_requirements)]
//
// Library features:
#![cfg_attr(not(no_global_oom_handling), feature(alloc_c_string))]
#![feature(alloc_layout_extra)]
#![feature(allocator_api)]
#![feature(array_chunks)]
#![feature(array_methods)]
#![feature(array_windows)]
#![feature(assert_matches)]
#![feature(async_iterator)]
#![feature(coerce_unsized)]
#![cfg_attr(not(no_global_oom_handling), feature(const_alloc_error))]
#![feature(const_box)]
#![cfg_attr(not(no_global_oom_handling), feature(const_btree_new))]
#![feature(const_cow_is_borrowed)]
#![feature(const_convert)]
#![feature(const_size_of_val)]
#![feature(const_align_of_val)]
#![feature(const_ptr_read)]
#![feature(const_maybe_uninit_write)]
#![feature(const_maybe_uninit_as_mut_ptr)]
#![feature(const_refs_to_cell)]
#![feature(core_c_str)]
#![feature(core_intrinsics)]
#![feature(core_ffi_c)]
#![feature(const_eval_select)]
#![feature(const_pin)]
#![feature(cstr_from_bytes_until_nul)]
#![feature(dispatch_from_dyn)]
#![feature(exact_size_is_empty)]
#![feature(extend_one)]
#![feature(fmt_internals)]
#![feature(fn_traits)]
#![feature(hasher_prefixfree_extras)]
#![feature(inplace_iteration)]
#![feature(iter_advance_by)]
#![feature(layout_for_ptr)]
#![feature(maybe_uninit_slice)]
#![cfg_attr(test, feature(new_uninit))]
#![feature(nonnull_slice_from_raw_parts)]
#![feature(pattern)]
#![feature(ptr_internals)]
#![feature(ptr_metadata)]
#![feature(ptr_sub_ptr)]
#![feature(receiver_trait)]
#![feature(set_ptr_value)]
#![feature(slice_group_by)]
#![feature(slice_ptr_get)]
#![feature(slice_ptr_len)]
#![feature(slice_range)]
#![feature(str_internals)]
#![feature(strict_provenance)]
#![feature(trusted_len)]
#![feature(trusted_random_access)]
#![feature(try_trait_v2)]
#![feature(unchecked_math)]
#![feature(unicode_internals)]
#![feature(unsize)]
//
// Language features:
#![feature(allocator_internals)]
#![feature(allow_internal_unstable)]
#![feature(associated_type_bounds)]
#![feature(box_syntax)]
#![feature(cfg_sanitize)]
#![feature(const_deref)]
#![feature(const_mut_refs)]
#![feature(const_ptr_write)]
#![feature(const_precise_live_drops)]
#![feature(const_trait_impl)]
#![feature(const_try)]
#![feature(dropck_eyepatch)]
#![feature(exclusive_range_pattern)]
#![feature(fundamental)]
#![cfg_attr(not(test), feature(generator_trait))]
#![feature(hashmap_internals)]
#![feature(lang_items)]
#![feature(let_else)]
#![feature(min_specialization)]
#![feature(negative_impls)]
#![feature(never_type)]
#![feature(nll)] // Not necessary, but here to test the `nll` feature.
#![feature(rustc_allow_const_fn_unstable)]
#![feature(rustc_attrs)]
#![feature(slice_internals)]
#![feature(staged_api)]
#![cfg_attr(test, feature(test))]
#![feature(unboxed_closures)]
#![feature(unsized_fn_params)]
#![feature(c_unwind)]
//
// Rustdoc features:
#![feature(doc_cfg)]
#![feature(doc_cfg_hide)]
// Technically, this is a bug in rustdoc: rustdoc sees the documentation on `#[lang = slice_alloc]`
// blocks is for `&[T]`, which also has documentation using this feature in `core`, and gets mad
// that the feature-gate isn't enabled. Ideally, it wouldn't check for the feature gate for docs
// from other crates, but since this can only appear for lang items, it doesn't seem worth fixing.
#![feature(intra_doc_pointers)]
// Allow testing this library
#[cfg(test)]
#[macro_use]
extern crate std;
#[cfg(test)]
extern crate test;
// Module with internal macros used by other modules (needs to be included before other modules).
#[macro_use]
mod macros;
mod raw_vec;
// Heaps provided for low-level allocation strategies
pub mod alloc;
// Primitive types using the heaps above
// Need to conditionally define the mod from `boxed.rs` to avoid
// duplicating the lang-items when building in test cfg; but also need
// to allow code to have `use boxed::Box;` declarations.
#[cfg(not(test))]
pub mod boxed;
#[cfg(test)]
mod boxed {
pub use std::boxed::Box;
}
pub mod borrow;
pub mod collections;
#[cfg(not(no_global_oom_handling))]
pub mod ffi;
pub mod fmt;
pub mod rc;
pub mod slice;
pub mod str;
pub mod string;
#[cfg(target_has_atomic = "ptr")]
pub mod sync;
#[cfg(all(not(no_global_oom_handling), target_has_atomic = "ptr"))]
pub mod task;
#[cfg(test)]
mod tests;
pub mod vec;
#[doc(hidden)]
#[unstable(feature = "liballoc_internals", issue = "none", reason = "implementation detail")]
pub mod __export {
pub use core::format_args;
}

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#![unstable(feature = "raw_vec_internals", reason = "unstable const warnings", issue = "none")]
use core::alloc::LayoutError;
use core::cmp;
use core::intrinsics;
use core::mem::{self, ManuallyDrop, MaybeUninit};
use core::ops::Drop;
use core::ptr::{self, NonNull, Unique};
use core::slice;
#[cfg(not(no_global_oom_handling))]
use crate::alloc::handle_alloc_error;
use crate::alloc::{Allocator, Global, Layout};
use crate::boxed::Box;
use crate::collections::TryReserveError;
use crate::collections::TryReserveErrorKind::*;
#[cfg(test)]
mod tests;
#[cfg(not(no_global_oom_handling))]
enum AllocInit {
/// The contents of the new memory are uninitialized.
Uninitialized,
/// The new memory is guaranteed to be zeroed.
Zeroed,
}
/// A low-level utility for more ergonomically allocating, reallocating, and deallocating
/// a buffer of memory on the heap without having to worry about all the corner cases
/// involved. This type is excellent for building your own data structures like Vec and VecDeque.
/// In particular:
///
/// * Produces `Unique::dangling()` on zero-sized types.
/// * Produces `Unique::dangling()` on zero-length allocations.
/// * Avoids freeing `Unique::dangling()`.
/// * Catches all overflows in capacity computations (promotes them to "capacity overflow" panics).
/// * Guards against 32-bit systems allocating more than isize::MAX bytes.
/// * Guards against overflowing your length.
/// * Calls `handle_alloc_error` for fallible allocations.
/// * Contains a `ptr::Unique` and thus endows the user with all related benefits.
/// * Uses the excess returned from the allocator to use the largest available capacity.
///
/// This type does not in anyway inspect the memory that it manages. When dropped it *will*
/// free its memory, but it *won't* try to drop its contents. It is up to the user of `RawVec`
/// to handle the actual things *stored* inside of a `RawVec`.
///
/// Note that the excess of a zero-sized types is always infinite, so `capacity()` always returns
/// `usize::MAX`. This means that you need to be careful when round-tripping this type with a
/// `Box<[T]>`, since `capacity()` won't yield the length.
#[allow(missing_debug_implementations)]
pub(crate) struct RawVec<T, A: Allocator = Global> {
ptr: Unique<T>,
cap: usize,
alloc: A,
}
impl<T> RawVec<T, Global> {
/// HACK(Centril): This exists because stable `const fn` can only call stable `const fn`, so
/// they cannot call `Self::new()`.
///
/// If you change `RawVec<T>::new` or dependencies, please take care to not introduce anything
/// that would truly const-call something unstable.
pub const NEW: Self = Self::new();
/// Creates the biggest possible `RawVec` (on the system heap)
/// without allocating. If `T` has positive size, then this makes a
/// `RawVec` with capacity `0`. If `T` is zero-sized, then it makes a
/// `RawVec` with capacity `usize::MAX`. Useful for implementing
/// delayed allocation.
#[must_use]
pub const fn new() -> Self {
Self::new_in(Global)
}
/// Creates a `RawVec` (on the system heap) with exactly the
/// capacity and alignment requirements for a `[T; capacity]`. This is
/// equivalent to calling `RawVec::new` when `capacity` is `0` or `T` is
/// zero-sized. Note that if `T` is zero-sized this means you will
/// *not* get a `RawVec` with the requested capacity.
///
/// # Panics
///
/// Panics if the requested capacity exceeds `isize::MAX` bytes.
///
/// # Aborts
///
/// Aborts on OOM.
#[cfg(not(any(no_global_oom_handling, test)))]
#[must_use]
#[inline]
pub fn with_capacity(capacity: usize) -> Self {
Self::with_capacity_in(capacity, Global)
}
/// Like `with_capacity`, but guarantees the buffer is zeroed.
#[cfg(not(any(no_global_oom_handling, test)))]
#[must_use]
#[inline]
pub fn with_capacity_zeroed(capacity: usize) -> Self {
Self::with_capacity_zeroed_in(capacity, Global)
}
}
impl<T, A: Allocator> RawVec<T, A> {
// Tiny Vecs are dumb. Skip to:
// - 8 if the element size is 1, because any heap allocators is likely
// to round up a request of less than 8 bytes to at least 8 bytes.
// - 4 if elements are moderate-sized (<= 1 KiB).
// - 1 otherwise, to avoid wasting too much space for very short Vecs.
pub(crate) const MIN_NON_ZERO_CAP: usize = if mem::size_of::<T>() == 1 {
8
} else if mem::size_of::<T>() <= 1024 {
4
} else {
1
};
/// Like `new`, but parameterized over the choice of allocator for
/// the returned `RawVec`.
pub const fn new_in(alloc: A) -> Self {
// `cap: 0` means "unallocated". zero-sized types are ignored.
Self { ptr: Unique::dangling(), cap: 0, alloc }
}
/// Like `with_capacity`, but parameterized over the choice of
/// allocator for the returned `RawVec`.
#[cfg(not(no_global_oom_handling))]
#[inline]
pub fn with_capacity_in(capacity: usize, alloc: A) -> Self {
Self::allocate_in(capacity, AllocInit::Uninitialized, alloc)
}
/// Like `with_capacity_zeroed`, but parameterized over the choice
/// of allocator for the returned `RawVec`.
#[cfg(not(no_global_oom_handling))]
#[inline]
pub fn with_capacity_zeroed_in(capacity: usize, alloc: A) -> Self {
Self::allocate_in(capacity, AllocInit::Zeroed, alloc)
}
/// Converts the entire buffer into `Box<[MaybeUninit<T>]>` with the specified `len`.
///
/// Note that this will correctly reconstitute any `cap` changes
/// that may have been performed. (See description of type for details.)
///
/// # Safety
///
/// * `len` must be greater than or equal to the most recently requested capacity, and
/// * `len` must be less than or equal to `self.capacity()`.
///
/// Note, that the requested capacity and `self.capacity()` could differ, as
/// an allocator could overallocate and return a greater memory block than requested.
pub unsafe fn into_box(self, len: usize) -> Box<[MaybeUninit<T>], A> {
// Sanity-check one half of the safety requirement (we cannot check the other half).
debug_assert!(
len <= self.capacity(),
"`len` must be smaller than or equal to `self.capacity()`"
);
let me = ManuallyDrop::new(self);
unsafe {
let slice = slice::from_raw_parts_mut(me.ptr() as *mut MaybeUninit<T>, len);
Box::from_raw_in(slice, ptr::read(&me.alloc))
}
}
#[cfg(not(no_global_oom_handling))]
fn allocate_in(capacity: usize, init: AllocInit, alloc: A) -> Self {
// Don't allocate here because `Drop` will not deallocate when `capacity` is 0.
if mem::size_of::<T>() == 0 || capacity == 0 {
Self::new_in(alloc)
} else {
// We avoid `unwrap_or_else` here because it bloats the amount of
// LLVM IR generated.
let layout = match Layout::array::<T>(capacity) {
Ok(layout) => layout,
Err(_) => capacity_overflow(),
};
match alloc_guard(layout.size()) {
Ok(_) => {}
Err(_) => capacity_overflow(),
}
let result = match init {
AllocInit::Uninitialized => alloc.allocate(layout),
AllocInit::Zeroed => alloc.allocate_zeroed(layout),
};
let ptr = match result {
Ok(ptr) => ptr,
Err(_) => handle_alloc_error(layout),
};
// Allocators currently return a `NonNull<[u8]>` whose length
// matches the size requested. If that ever changes, the capacity
// here should change to `ptr.len() / mem::size_of::<T>()`.
Self {
ptr: unsafe { Unique::new_unchecked(ptr.cast().as_ptr()) },
cap: capacity,
alloc,
}
}
}
/// Reconstitutes a `RawVec` from a pointer, capacity, and allocator.
///
/// # Safety
///
/// The `ptr` must be allocated (via the given allocator `alloc`), and with the given
/// `capacity`.
/// The `capacity` cannot exceed `isize::MAX` for sized types. (only a concern on 32-bit
/// systems). ZST vectors may have a capacity up to `usize::MAX`.
/// If the `ptr` and `capacity` come from a `RawVec` created via `alloc`, then this is
/// guaranteed.
#[inline]
pub unsafe fn from_raw_parts_in(ptr: *mut T, capacity: usize, alloc: A) -> Self {
Self { ptr: unsafe { Unique::new_unchecked(ptr) }, cap: capacity, alloc }
}
/// Gets a raw pointer to the start of the allocation. Note that this is
/// `Unique::dangling()` if `capacity == 0` or `T` is zero-sized. In the former case, you must
/// be careful.
#[inline]
pub fn ptr(&self) -> *mut T {
self.ptr.as_ptr()
}
/// Gets the capacity of the allocation.
///
/// This will always be `usize::MAX` if `T` is zero-sized.
#[inline(always)]
pub fn capacity(&self) -> usize {
if mem::size_of::<T>() == 0 { usize::MAX } else { self.cap }
}
/// Returns a shared reference to the allocator backing this `RawVec`.
pub fn allocator(&self) -> &A {
&self.alloc
}
fn current_memory(&self) -> Option<(NonNull<u8>, Layout)> {
if mem::size_of::<T>() == 0 || self.cap == 0 {
None
} else {
// We have an allocated chunk of memory, so we can bypass runtime
// checks to get our current layout.
unsafe {
let layout = Layout::array::<T>(self.cap).unwrap_unchecked();
Some((self.ptr.cast().into(), layout))
}
}
}
/// Ensures that the buffer contains at least enough space to hold `len +
/// additional` elements. If it doesn't already have enough capacity, will
/// reallocate enough space plus comfortable slack space to get amortized
/// *O*(1) behavior. Will limit this behavior if it would needlessly cause
/// itself to panic.
///
/// If `len` exceeds `self.capacity()`, this may fail to actually allocate
/// the requested space. This is not really unsafe, but the unsafe
/// code *you* write that relies on the behavior of this function may break.
///
/// This is ideal for implementing a bulk-push operation like `extend`.
///
/// # Panics
///
/// Panics if the new capacity exceeds `isize::MAX` bytes.
///
/// # Aborts
///
/// Aborts on OOM.
#[cfg(not(no_global_oom_handling))]
#[inline]
pub fn reserve(&mut self, len: usize, additional: usize) {
// Callers expect this function to be very cheap when there is already sufficient capacity.
// Therefore, we move all the resizing and error-handling logic from grow_amortized and
// handle_reserve behind a call, while making sure that this function is likely to be
// inlined as just a comparison and a call if the comparison fails.
#[cold]
fn do_reserve_and_handle<T, A: Allocator>(
slf: &mut RawVec<T, A>,
len: usize,
additional: usize,
) {
handle_reserve(slf.grow_amortized(len, additional));
}
if self.needs_to_grow(len, additional) {
do_reserve_and_handle(self, len, additional);
}
}
/// A specialized version of `reserve()` used only by the hot and
/// oft-instantiated `Vec::push()`, which does its own capacity check.
#[cfg(not(no_global_oom_handling))]
#[inline(never)]
pub fn reserve_for_push(&mut self, len: usize) {
handle_reserve(self.grow_amortized(len, 1));
}
/// The same as `reserve`, but returns on errors instead of panicking or aborting.
pub fn try_reserve(&mut self, len: usize, additional: usize) -> Result<(), TryReserveError> {
if self.needs_to_grow(len, additional) {
self.grow_amortized(len, additional)
} else {
Ok(())
}
}
/// Ensures that the buffer contains at least enough space to hold `len +
/// additional` elements. If it doesn't already, will reallocate the
/// minimum possible amount of memory necessary. Generally this will be
/// exactly the amount of memory necessary, but in principle the allocator
/// is free to give back more than we asked for.
///
/// If `len` exceeds `self.capacity()`, this may fail to actually allocate
/// the requested space. This is not really unsafe, but the unsafe code
/// *you* write that relies on the behavior of this function may break.
///
/// # Panics
///
/// Panics if the new capacity exceeds `isize::MAX` bytes.
///
/// # Aborts
///
/// Aborts on OOM.
#[cfg(not(no_global_oom_handling))]
pub fn reserve_exact(&mut self, len: usize, additional: usize) {
handle_reserve(self.try_reserve_exact(len, additional));
}
/// The same as `reserve_exact`, but returns on errors instead of panicking or aborting.
pub fn try_reserve_exact(
&mut self,
len: usize,
additional: usize,
) -> Result<(), TryReserveError> {
if self.needs_to_grow(len, additional) { self.grow_exact(len, additional) } else { Ok(()) }
}
/// Shrinks the buffer down to the specified capacity. If the given amount
/// is 0, actually completely deallocates.
///
/// # Panics
///
/// Panics if the given amount is *larger* than the current capacity.
///
/// # Aborts
///
/// Aborts on OOM.
#[cfg(not(no_global_oom_handling))]
pub fn shrink_to_fit(&mut self, cap: usize) {
handle_reserve(self.shrink(cap));
}
}
impl<T, A: Allocator> RawVec<T, A> {
/// Returns if the buffer needs to grow to fulfill the needed extra capacity.
/// Mainly used to make inlining reserve-calls possible without inlining `grow`.
fn needs_to_grow(&self, len: usize, additional: usize) -> bool {
additional > self.capacity().wrapping_sub(len)
}
fn set_ptr_and_cap(&mut self, ptr: NonNull<[u8]>, cap: usize) {
// Allocators currently return a `NonNull<[u8]>` whose length matches
// the size requested. If that ever changes, the capacity here should
// change to `ptr.len() / mem::size_of::<T>()`.
self.ptr = unsafe { Unique::new_unchecked(ptr.cast().as_ptr()) };
self.cap = cap;
}
// This method is usually instantiated many times. So we want it to be as
// small as possible, to improve compile times. But we also want as much of
// its contents to be statically computable as possible, to make the
// generated code run faster. Therefore, this method is carefully written
// so that all of the code that depends on `T` is within it, while as much
// of the code that doesn't depend on `T` as possible is in functions that
// are non-generic over `T`.
fn grow_amortized(&mut self, len: usize, additional: usize) -> Result<(), TryReserveError> {
// This is ensured by the calling contexts.
debug_assert!(additional > 0);
if mem::size_of::<T>() == 0 {
// Since we return a capacity of `usize::MAX` when `elem_size` is
// 0, getting to here necessarily means the `RawVec` is overfull.
return Err(CapacityOverflow.into());
}
// Nothing we can really do about these checks, sadly.
let required_cap = len.checked_add(additional).ok_or(CapacityOverflow)?;
// This guarantees exponential growth. The doubling cannot overflow
// because `cap <= isize::MAX` and the type of `cap` is `usize`.
let cap = cmp::max(self.cap * 2, required_cap);
let cap = cmp::max(Self::MIN_NON_ZERO_CAP, cap);
let new_layout = Layout::array::<T>(cap);
// `finish_grow` is non-generic over `T`.
let ptr = finish_grow(new_layout, self.current_memory(), &mut self.alloc)?;
self.set_ptr_and_cap(ptr, cap);
Ok(())
}
// The constraints on this method are much the same as those on
// `grow_amortized`, but this method is usually instantiated less often so
// it's less critical.
fn grow_exact(&mut self, len: usize, additional: usize) -> Result<(), TryReserveError> {
if mem::size_of::<T>() == 0 {
// Since we return a capacity of `usize::MAX` when the type size is
// 0, getting to here necessarily means the `RawVec` is overfull.
return Err(CapacityOverflow.into());
}
let cap = len.checked_add(additional).ok_or(CapacityOverflow)?;
let new_layout = Layout::array::<T>(cap);
// `finish_grow` is non-generic over `T`.
let ptr = finish_grow(new_layout, self.current_memory(), &mut self.alloc)?;
self.set_ptr_and_cap(ptr, cap);
Ok(())
}
fn shrink(&mut self, cap: usize) -> Result<(), TryReserveError> {
assert!(cap <= self.capacity(), "Tried to shrink to a larger capacity");
let (ptr, layout) = if let Some(mem) = self.current_memory() { mem } else { return Ok(()) };
let ptr = unsafe {
// `Layout::array` cannot overflow here because it would have
// overflowed earlier when capacity was larger.
let new_layout = Layout::array::<T>(cap).unwrap_unchecked();
self.alloc
.shrink(ptr, layout, new_layout)
.map_err(|_| AllocError { layout: new_layout, non_exhaustive: () })?
};
self.set_ptr_and_cap(ptr, cap);
Ok(())
}
}
// This function is outside `RawVec` to minimize compile times. See the comment
// above `RawVec::grow_amortized` for details. (The `A` parameter isn't
// significant, because the number of different `A` types seen in practice is
// much smaller than the number of `T` types.)
#[inline(never)]
fn finish_grow<A>(
new_layout: Result<Layout, LayoutError>,
current_memory: Option<(NonNull<u8>, Layout)>,
alloc: &mut A,
) -> Result<NonNull<[u8]>, TryReserveError>
where
A: Allocator,
{
// Check for the error here to minimize the size of `RawVec::grow_*`.
let new_layout = new_layout.map_err(|_| CapacityOverflow)?;
alloc_guard(new_layout.size())?;
let memory = if let Some((ptr, old_layout)) = current_memory {
debug_assert_eq!(old_layout.align(), new_layout.align());
unsafe {
// The allocator checks for alignment equality
intrinsics::assume(old_layout.align() == new_layout.align());
alloc.grow(ptr, old_layout, new_layout)
}
} else {
alloc.allocate(new_layout)
};
memory.map_err(|_| AllocError { layout: new_layout, non_exhaustive: () }.into())
}
unsafe impl<#[may_dangle] T, A: Allocator> Drop for RawVec<T, A> {
/// Frees the memory owned by the `RawVec` *without* trying to drop its contents.
fn drop(&mut self) {
if let Some((ptr, layout)) = self.current_memory() {
unsafe { self.alloc.deallocate(ptr, layout) }
}
}
}
// Central function for reserve error handling.
#[cfg(not(no_global_oom_handling))]
#[inline]
fn handle_reserve(result: Result<(), TryReserveError>) {
match result.map_err(|e| e.kind()) {
Err(CapacityOverflow) => capacity_overflow(),
Err(AllocError { layout, .. }) => handle_alloc_error(layout),
Ok(()) => { /* yay */ }
}
}
// We need to guarantee the following:
// * We don't ever allocate `> isize::MAX` byte-size objects.
// * We don't overflow `usize::MAX` and actually allocate too little.
//
// On 64-bit we just need to check for overflow since trying to allocate
// `> isize::MAX` bytes will surely fail. On 32-bit and 16-bit we need to add
// an extra guard for this in case we're running on a platform which can use
// all 4GB in user-space, e.g., PAE or x32.
#[inline]
fn alloc_guard(alloc_size: usize) -> Result<(), TryReserveError> {
if usize::BITS < 64 && alloc_size > isize::MAX as usize {
Err(CapacityOverflow.into())
} else {
Ok(())
}
}
// One central function responsible for reporting capacity overflows. This'll
// ensure that the code generation related to these panics is minimal as there's
// only one location which panics rather than a bunch throughout the module.
#[cfg(not(no_global_oom_handling))]
fn capacity_overflow() -> ! {
panic!("capacity overflow");
}

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use crate::alloc::{Allocator, Global};
use core::fmt;
use core::iter::{FusedIterator, TrustedLen};
use core::mem;
use core::ptr::{self, NonNull};
use core::slice::{self};
use super::Vec;
/// A draining iterator for `Vec<T>`.
///
/// This `struct` is created by [`Vec::drain`].
/// See its documentation for more.
///
/// # Example
///
/// ```
/// let mut v = vec![0, 1, 2];
/// let iter: std::vec::Drain<_> = v.drain(..);
/// ```
#[stable(feature = "drain", since = "1.6.0")]
pub struct Drain<
'a,
T: 'a,
#[unstable(feature = "allocator_api", issue = "32838")] A: Allocator + 'a = Global,
> {
/// Index of tail to preserve
pub(super) tail_start: usize,
/// Length of tail
pub(super) tail_len: usize,
/// Current remaining range to remove
pub(super) iter: slice::Iter<'a, T>,
pub(super) vec: NonNull<Vec<T, A>>,
}
#[stable(feature = "collection_debug", since = "1.17.0")]
impl<T: fmt::Debug, A: Allocator> fmt::Debug for Drain<'_, T, A> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_tuple("Drain").field(&self.iter.as_slice()).finish()
}
}
impl<'a, T, A: Allocator> Drain<'a, T, A> {
/// Returns the remaining items of this iterator as a slice.
///
/// # Examples
///
/// ```
/// let mut vec = vec!['a', 'b', 'c'];
/// let mut drain = vec.drain(..);
/// assert_eq!(drain.as_slice(), &['a', 'b', 'c']);
/// let _ = drain.next().unwrap();
/// assert_eq!(drain.as_slice(), &['b', 'c']);
/// ```
#[must_use]
#[stable(feature = "vec_drain_as_slice", since = "1.46.0")]
pub fn as_slice(&self) -> &[T] {
self.iter.as_slice()
}
/// Returns a reference to the underlying allocator.
#[unstable(feature = "allocator_api", issue = "32838")]
#[must_use]
#[inline]
pub fn allocator(&self) -> &A {
unsafe { self.vec.as_ref().allocator() }
}
}
#[stable(feature = "vec_drain_as_slice", since = "1.46.0")]
impl<'a, T, A: Allocator> AsRef<[T]> for Drain<'a, T, A> {
fn as_ref(&self) -> &[T] {
self.as_slice()
}
}
#[stable(feature = "drain", since = "1.6.0")]
unsafe impl<T: Sync, A: Sync + Allocator> Sync for Drain<'_, T, A> {}
#[stable(feature = "drain", since = "1.6.0")]
unsafe impl<T: Send, A: Send + Allocator> Send for Drain<'_, T, A> {}
#[stable(feature = "drain", since = "1.6.0")]
impl<T, A: Allocator> Iterator for Drain<'_, T, A> {
type Item = T;
#[inline]
fn next(&mut self) -> Option<T> {
self.iter.next().map(|elt| unsafe { ptr::read(elt as *const _) })
}
fn size_hint(&self) -> (usize, Option<usize>) {
self.iter.size_hint()
}
}
#[stable(feature = "drain", since = "1.6.0")]
impl<T, A: Allocator> DoubleEndedIterator for Drain<'_, T, A> {
#[inline]
fn next_back(&mut self) -> Option<T> {
self.iter.next_back().map(|elt| unsafe { ptr::read(elt as *const _) })
}
}
#[stable(feature = "drain", since = "1.6.0")]
impl<T, A: Allocator> Drop for Drain<'_, T, A> {
fn drop(&mut self) {
/// Moves back the un-`Drain`ed elements to restore the original `Vec`.
struct DropGuard<'r, 'a, T, A: Allocator>(&'r mut Drain<'a, T, A>);
impl<'r, 'a, T, A: Allocator> Drop for DropGuard<'r, 'a, T, A> {
fn drop(&mut self) {
if self.0.tail_len > 0 {
unsafe {
let source_vec = self.0.vec.as_mut();
// memmove back untouched tail, update to new length
let start = source_vec.len();
let tail = self.0.tail_start;
if tail != start {
let src = source_vec.as_ptr().add(tail);
let dst = source_vec.as_mut_ptr().add(start);
ptr::copy(src, dst, self.0.tail_len);
}
source_vec.set_len(start + self.0.tail_len);
}
}
}
}
let iter = mem::replace(&mut self.iter, (&mut []).iter());
let drop_len = iter.len();
let mut vec = self.vec;
if mem::size_of::<T>() == 0 {
// ZSTs have no identity, so we don't need to move them around, we only need to drop the correct amount.
// this can be achieved by manipulating the Vec length instead of moving values out from `iter`.
unsafe {
let vec = vec.as_mut();
let old_len = vec.len();
vec.set_len(old_len + drop_len + self.tail_len);
vec.truncate(old_len + self.tail_len);
}
return;
}
// ensure elements are moved back into their appropriate places, even when drop_in_place panics
let _guard = DropGuard(self);
if drop_len == 0 {
return;
}
// as_slice() must only be called when iter.len() is > 0 because
// vec::Splice modifies vec::Drain fields and may grow the vec which would invalidate
// the iterator's internal pointers. Creating a reference to deallocated memory
// is invalid even when it is zero-length
let drop_ptr = iter.as_slice().as_ptr();
unsafe {
// drop_ptr comes from a slice::Iter which only gives us a &[T] but for drop_in_place
// a pointer with mutable provenance is necessary. Therefore we must reconstruct
// it from the original vec but also avoid creating a &mut to the front since that could
// invalidate raw pointers to it which some unsafe code might rely on.
let vec_ptr = vec.as_mut().as_mut_ptr();
let drop_offset = drop_ptr.sub_ptr(vec_ptr);
let to_drop = ptr::slice_from_raw_parts_mut(vec_ptr.add(drop_offset), drop_len);
ptr::drop_in_place(to_drop);
}
}
}
#[stable(feature = "drain", since = "1.6.0")]
impl<T, A: Allocator> ExactSizeIterator for Drain<'_, T, A> {
fn is_empty(&self) -> bool {
self.iter.is_empty()
}
}
#[unstable(feature = "trusted_len", issue = "37572")]
unsafe impl<T, A: Allocator> TrustedLen for Drain<'_, T, A> {}
#[stable(feature = "fused", since = "1.26.0")]
impl<T, A: Allocator> FusedIterator for Drain<'_, T, A> {}

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use crate::alloc::{Allocator, Global};
use core::ptr::{self};
use core::slice::{self};
use super::Vec;
/// An iterator which uses a closure to determine if an element should be removed.
///
/// This struct is created by [`Vec::drain_filter`].
/// See its documentation for more.
///
/// # Example
///
/// ```
/// #![feature(drain_filter)]
///
/// let mut v = vec![0, 1, 2];
/// let iter: std::vec::DrainFilter<_, _> = v.drain_filter(|x| *x % 2 == 0);
/// ```
#[unstable(feature = "drain_filter", reason = "recently added", issue = "43244")]
#[derive(Debug)]
pub struct DrainFilter<
'a,
T,
F,
#[unstable(feature = "allocator_api", issue = "32838")] A: Allocator = Global,
> where
F: FnMut(&mut T) -> bool,
{
pub(super) vec: &'a mut Vec<T, A>,
/// The index of the item that will be inspected by the next call to `next`.
pub(super) idx: usize,
/// The number of items that have been drained (removed) thus far.
pub(super) del: usize,
/// The original length of `vec` prior to draining.
pub(super) old_len: usize,
/// The filter test predicate.
pub(super) pred: F,
/// A flag that indicates a panic has occurred in the filter test predicate.
/// This is used as a hint in the drop implementation to prevent consumption
/// of the remainder of the `DrainFilter`. Any unprocessed items will be
/// backshifted in the `vec`, but no further items will be dropped or
/// tested by the filter predicate.
pub(super) panic_flag: bool,
}
impl<T, F, A: Allocator> DrainFilter<'_, T, F, A>
where
F: FnMut(&mut T) -> bool,
{
/// Returns a reference to the underlying allocator.
#[unstable(feature = "allocator_api", issue = "32838")]
#[inline]
pub fn allocator(&self) -> &A {
self.vec.allocator()
}
}
#[unstable(feature = "drain_filter", reason = "recently added", issue = "43244")]
impl<T, F, A: Allocator> Iterator for DrainFilter<'_, T, F, A>
where
F: FnMut(&mut T) -> bool,
{
type Item = T;
fn next(&mut self) -> Option<T> {
unsafe {
while self.idx < self.old_len {
let i = self.idx;
let v = slice::from_raw_parts_mut(self.vec.as_mut_ptr(), self.old_len);
self.panic_flag = true;
let drained = (self.pred)(&mut v[i]);
self.panic_flag = false;
// Update the index *after* the predicate is called. If the index
// is updated prior and the predicate panics, the element at this
// index would be leaked.
self.idx += 1;
if drained {
self.del += 1;
return Some(ptr::read(&v[i]));
} else if self.del > 0 {
let del = self.del;
let src: *const T = &v[i];
let dst: *mut T = &mut v[i - del];
ptr::copy_nonoverlapping(src, dst, 1);
}
}
None
}
}
fn size_hint(&self) -> (usize, Option<usize>) {
(0, Some(self.old_len - self.idx))
}
}
#[unstable(feature = "drain_filter", reason = "recently added", issue = "43244")]
impl<T, F, A: Allocator> Drop for DrainFilter<'_, T, F, A>
where
F: FnMut(&mut T) -> bool,
{
fn drop(&mut self) {
struct BackshiftOnDrop<'a, 'b, T, F, A: Allocator>
where
F: FnMut(&mut T) -> bool,
{
drain: &'b mut DrainFilter<'a, T, F, A>,
}
impl<'a, 'b, T, F, A: Allocator> Drop for BackshiftOnDrop<'a, 'b, T, F, A>
where
F: FnMut(&mut T) -> bool,
{
fn drop(&mut self) {
unsafe {
if self.drain.idx < self.drain.old_len && self.drain.del > 0 {
// This is a pretty messed up state, and there isn't really an
// obviously right thing to do. We don't want to keep trying
// to execute `pred`, so we just backshift all the unprocessed
// elements and tell the vec that they still exist. The backshift
// is required to prevent a double-drop of the last successfully
// drained item prior to a panic in the predicate.
let ptr = self.drain.vec.as_mut_ptr();
let src = ptr.add(self.drain.idx);
let dst = src.sub(self.drain.del);
let tail_len = self.drain.old_len - self.drain.idx;
src.copy_to(dst, tail_len);
}
self.drain.vec.set_len(self.drain.old_len - self.drain.del);
}
}
}
let backshift = BackshiftOnDrop { drain: self };
// Attempt to consume any remaining elements if the filter predicate
// has not yet panicked. We'll backshift any remaining elements
// whether we've already panicked or if the consumption here panics.
if !backshift.drain.panic_flag {
backshift.drain.for_each(drop);
}
}
}

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#[cfg(not(no_global_oom_handling))]
use super::AsVecIntoIter;
use crate::alloc::{Allocator, Global};
use crate::raw_vec::RawVec;
use core::fmt;
use core::intrinsics::arith_offset;
use core::iter::{
FusedIterator, InPlaceIterable, SourceIter, TrustedLen, TrustedRandomAccessNoCoerce,
};
use core::marker::PhantomData;
use core::mem::{self, ManuallyDrop};
use core::ops::Deref;
use core::ptr::{self, NonNull};
use core::slice::{self};
/// An iterator that moves out of a vector.
///
/// This `struct` is created by the `into_iter` method on [`Vec`](super::Vec)
/// (provided by the [`IntoIterator`] trait).
///
/// # Example
///
/// ```
/// let v = vec![0, 1, 2];
/// let iter: std::vec::IntoIter<_> = v.into_iter();
/// ```
#[stable(feature = "rust1", since = "1.0.0")]
#[rustc_insignificant_dtor]
pub struct IntoIter<
T,
#[unstable(feature = "allocator_api", issue = "32838")] A: Allocator = Global,
> {
pub(super) buf: NonNull<T>,
pub(super) phantom: PhantomData<T>,
pub(super) cap: usize,
// the drop impl reconstructs a RawVec from buf, cap and alloc
// to avoid dropping the allocator twice we need to wrap it into ManuallyDrop
pub(super) alloc: ManuallyDrop<A>,
pub(super) ptr: *const T,
pub(super) end: *const T,
}
#[stable(feature = "vec_intoiter_debug", since = "1.13.0")]
impl<T: fmt::Debug, A: Allocator> fmt::Debug for IntoIter<T, A> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
f.debug_tuple("IntoIter").field(&self.as_slice()).finish()
}
}
impl<T, A: Allocator> IntoIter<T, A> {
/// Returns the remaining items of this iterator as a slice.
///
/// # Examples
///
/// ```
/// let vec = vec!['a', 'b', 'c'];
/// let mut into_iter = vec.into_iter();
/// assert_eq!(into_iter.as_slice(), &['a', 'b', 'c']);
/// let _ = into_iter.next().unwrap();
/// assert_eq!(into_iter.as_slice(), &['b', 'c']);
/// ```
#[stable(feature = "vec_into_iter_as_slice", since = "1.15.0")]
pub fn as_slice(&self) -> &[T] {
unsafe { slice::from_raw_parts(self.ptr, self.len()) }
}
/// Returns the remaining items of this iterator as a mutable slice.
///
/// # Examples
///
/// ```
/// let vec = vec!['a', 'b', 'c'];
/// let mut into_iter = vec.into_iter();
/// assert_eq!(into_iter.as_slice(), &['a', 'b', 'c']);
/// into_iter.as_mut_slice()[2] = 'z';
/// assert_eq!(into_iter.next().unwrap(), 'a');
/// assert_eq!(into_iter.next().unwrap(), 'b');
/// assert_eq!(into_iter.next().unwrap(), 'z');
/// ```
#[stable(feature = "vec_into_iter_as_slice", since = "1.15.0")]
pub fn as_mut_slice(&mut self) -> &mut [T] {
unsafe { &mut *self.as_raw_mut_slice() }
}
/// Returns a reference to the underlying allocator.
#[unstable(feature = "allocator_api", issue = "32838")]
#[inline]
pub fn allocator(&self) -> &A {
&self.alloc
}
fn as_raw_mut_slice(&mut self) -> *mut [T] {
ptr::slice_from_raw_parts_mut(self.ptr as *mut T, self.len())
}
/// Drops remaining elements and relinquishes the backing allocation.
///
/// This is roughly equivalent to the following, but more efficient
///
/// ```
/// # let mut into_iter = Vec::<u8>::with_capacity(10).into_iter();
/// (&mut into_iter).for_each(core::mem::drop);
/// unsafe { core::ptr::write(&mut into_iter, Vec::new().into_iter()); }
/// ```
///
/// This method is used by in-place iteration, refer to the vec::in_place_collect
/// documentation for an overview.
#[cfg(not(no_global_oom_handling))]
pub(super) fn forget_allocation_drop_remaining(&mut self) {
let remaining = self.as_raw_mut_slice();
// overwrite the individual fields instead of creating a new
// struct and then overwriting &mut self.
// this creates less assembly
self.cap = 0;
self.buf = unsafe { NonNull::new_unchecked(RawVec::NEW.ptr()) };
self.ptr = self.buf.as_ptr();
self.end = self.buf.as_ptr();
unsafe {
ptr::drop_in_place(remaining);
}
}
/// Forgets to Drop the remaining elements while still allowing the backing allocation to be freed.
pub(crate) fn forget_remaining_elements(&mut self) {
self.ptr = self.end;
}
}
#[stable(feature = "vec_intoiter_as_ref", since = "1.46.0")]
impl<T, A: Allocator> AsRef<[T]> for IntoIter<T, A> {
fn as_ref(&self) -> &[T] {
self.as_slice()
}
}
#[stable(feature = "rust1", since = "1.0.0")]
unsafe impl<T: Send, A: Allocator + Send> Send for IntoIter<T, A> {}
#[stable(feature = "rust1", since = "1.0.0")]
unsafe impl<T: Sync, A: Allocator + Sync> Sync for IntoIter<T, A> {}
#[stable(feature = "rust1", since = "1.0.0")]
impl<T, A: Allocator> Iterator for IntoIter<T, A> {
type Item = T;
#[inline]
fn next(&mut self) -> Option<T> {
if self.ptr as *const _ == self.end {
None
} else if mem::size_of::<T>() == 0 {
// purposefully don't use 'ptr.offset' because for
// vectors with 0-size elements this would return the
// same pointer.
self.ptr = unsafe { arith_offset(self.ptr as *const i8, 1) as *mut T };
// Make up a value of this ZST.
Some(unsafe { mem::zeroed() })
} else {
let old = self.ptr;
self.ptr = unsafe { self.ptr.offset(1) };
Some(unsafe { ptr::read(old) })
}
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
let exact = if mem::size_of::<T>() == 0 {
self.end.addr().wrapping_sub(self.ptr.addr())
} else {
unsafe { self.end.sub_ptr(self.ptr) }
};
(exact, Some(exact))
}
#[inline]
fn advance_by(&mut self, n: usize) -> Result<(), usize> {
let step_size = self.len().min(n);
let to_drop = ptr::slice_from_raw_parts_mut(self.ptr as *mut T, step_size);
if mem::size_of::<T>() == 0 {
// SAFETY: due to unchecked casts of unsigned amounts to signed offsets the wraparound
// effectively results in unsigned pointers representing positions 0..usize::MAX,
// which is valid for ZSTs.
self.ptr = unsafe { arith_offset(self.ptr as *const i8, step_size as isize) as *mut T }
} else {
// SAFETY: the min() above ensures that step_size is in bounds
self.ptr = unsafe { self.ptr.add(step_size) };
}
// SAFETY: the min() above ensures that step_size is in bounds
unsafe {
ptr::drop_in_place(to_drop);
}
if step_size < n {
return Err(step_size);
}
Ok(())
}
#[inline]
fn count(self) -> usize {
self.len()
}
unsafe fn __iterator_get_unchecked(&mut self, i: usize) -> Self::Item
where
Self: TrustedRandomAccessNoCoerce,
{
// SAFETY: the caller must guarantee that `i` is in bounds of the
// `Vec<T>`, so `i` cannot overflow an `isize`, and the `self.ptr.add(i)`
// is guaranteed to pointer to an element of the `Vec<T>` and
// thus guaranteed to be valid to dereference.
//
// Also note the implementation of `Self: TrustedRandomAccess` requires
// that `T: Copy` so reading elements from the buffer doesn't invalidate
// them for `Drop`.
unsafe {
if mem::size_of::<T>() == 0 { mem::zeroed() } else { ptr::read(self.ptr.add(i)) }
}
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<T, A: Allocator> DoubleEndedIterator for IntoIter<T, A> {
#[inline]
fn next_back(&mut self) -> Option<T> {
if self.end == self.ptr {
None
} else if mem::size_of::<T>() == 0 {
// See above for why 'ptr.offset' isn't used
self.end = unsafe { arith_offset(self.end as *const i8, -1) as *mut T };
// Make up a value of this ZST.
Some(unsafe { mem::zeroed() })
} else {
self.end = unsafe { self.end.offset(-1) };
Some(unsafe { ptr::read(self.end) })
}
}
#[inline]
fn advance_back_by(&mut self, n: usize) -> Result<(), usize> {
let step_size = self.len().min(n);
if mem::size_of::<T>() == 0 {
// SAFETY: same as for advance_by()
self.end = unsafe {
arith_offset(self.end as *const i8, step_size.wrapping_neg() as isize) as *mut T
}
} else {
// SAFETY: same as for advance_by()
self.end = unsafe { self.end.offset(step_size.wrapping_neg() as isize) };
}
let to_drop = ptr::slice_from_raw_parts_mut(self.end as *mut T, step_size);
// SAFETY: same as for advance_by()
unsafe {
ptr::drop_in_place(to_drop);
}
if step_size < n {
return Err(step_size);
}
Ok(())
}
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<T, A: Allocator> ExactSizeIterator for IntoIter<T, A> {
fn is_empty(&self) -> bool {
self.ptr == self.end
}
}
#[stable(feature = "fused", since = "1.26.0")]
impl<T, A: Allocator> FusedIterator for IntoIter<T, A> {}
#[unstable(feature = "trusted_len", issue = "37572")]
unsafe impl<T, A: Allocator> TrustedLen for IntoIter<T, A> {}
#[doc(hidden)]
#[unstable(issue = "none", feature = "std_internals")]
#[rustc_unsafe_specialization_marker]
pub trait NonDrop {}
// T: Copy as approximation for !Drop since get_unchecked does not advance self.ptr
// and thus we can't implement drop-handling
#[unstable(issue = "none", feature = "std_internals")]
impl<T: Copy> NonDrop for T {}
#[doc(hidden)]
#[unstable(issue = "none", feature = "std_internals")]
// TrustedRandomAccess (without NoCoerce) must not be implemented because
// subtypes/supertypes of `T` might not be `NonDrop`
unsafe impl<T, A: Allocator> TrustedRandomAccessNoCoerce for IntoIter<T, A>
where
T: NonDrop,
{
const MAY_HAVE_SIDE_EFFECT: bool = false;
}
#[cfg(not(no_global_oom_handling))]
#[stable(feature = "vec_into_iter_clone", since = "1.8.0")]
impl<T: Clone, A: Allocator + Clone> Clone for IntoIter<T, A> {
#[cfg(not(test))]
fn clone(&self) -> Self {
self.as_slice().to_vec_in(self.alloc.deref().clone()).into_iter()
}
#[cfg(test)]
fn clone(&self) -> Self {
crate::slice::to_vec(self.as_slice(), self.alloc.deref().clone()).into_iter()
}
}
#[stable(feature = "rust1", since = "1.0.0")]
unsafe impl<#[may_dangle] T, A: Allocator> Drop for IntoIter<T, A> {
fn drop(&mut self) {
struct DropGuard<'a, T, A: Allocator>(&'a mut IntoIter<T, A>);
impl<T, A: Allocator> Drop for DropGuard<'_, T, A> {
fn drop(&mut self) {
unsafe {
// `IntoIter::alloc` is not used anymore after this and will be dropped by RawVec
let alloc = ManuallyDrop::take(&mut self.0.alloc);
// RawVec handles deallocation
let _ = RawVec::from_raw_parts_in(self.0.buf.as_ptr(), self.0.cap, alloc);
}
}
}
let guard = DropGuard(self);
// destroy the remaining elements
unsafe {
ptr::drop_in_place(guard.0.as_raw_mut_slice());
}
// now `guard` will be dropped and do the rest
}
}
// In addition to the SAFETY invariants of the following three unsafe traits
// also refer to the vec::in_place_collect module documentation to get an overview
#[unstable(issue = "none", feature = "inplace_iteration")]
#[doc(hidden)]
unsafe impl<T, A: Allocator> InPlaceIterable for IntoIter<T, A> {}
#[unstable(issue = "none", feature = "inplace_iteration")]
#[doc(hidden)]
unsafe impl<T, A: Allocator> SourceIter for IntoIter<T, A> {
type Source = Self;
#[inline]
unsafe fn as_inner(&mut self) -> &mut Self::Source {
self
}
}
#[cfg(not(no_global_oom_handling))]
unsafe impl<T> AsVecIntoIter for IntoIter<T> {
type Item = T;
fn as_into_iter(&mut self) -> &mut IntoIter<Self::Item> {
self
}
}

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use crate::boxed::Box;
#[rustc_specialization_trait]
pub(super) unsafe trait IsZero {
/// Whether this value's representation is all zeros
fn is_zero(&self) -> bool;
}
macro_rules! impl_is_zero {
($t:ty, $is_zero:expr) => {
unsafe impl IsZero for $t {
#[inline]
fn is_zero(&self) -> bool {
$is_zero(*self)
}
}
};
}
impl_is_zero!(i16, |x| x == 0);
impl_is_zero!(i32, |x| x == 0);
impl_is_zero!(i64, |x| x == 0);
impl_is_zero!(i128, |x| x == 0);
impl_is_zero!(isize, |x| x == 0);
impl_is_zero!(u16, |x| x == 0);
impl_is_zero!(u32, |x| x == 0);
impl_is_zero!(u64, |x| x == 0);
impl_is_zero!(u128, |x| x == 0);
impl_is_zero!(usize, |x| x == 0);
impl_is_zero!(bool, |x| x == false);
impl_is_zero!(char, |x| x == '\0');
impl_is_zero!(f32, |x: f32| x.to_bits() == 0);
impl_is_zero!(f64, |x: f64| x.to_bits() == 0);
unsafe impl<T> IsZero for *const T {
#[inline]
fn is_zero(&self) -> bool {
(*self).is_null()
}
}
unsafe impl<T> IsZero for *mut T {
#[inline]
fn is_zero(&self) -> bool {
(*self).is_null()
}
}
unsafe impl<T: IsZero, const N: usize> IsZero for [T; N] {
#[inline]
fn is_zero(&self) -> bool {
// Because this is generated as a runtime check, it's not obvious that
// it's worth doing if the array is really long. The threshold here
// is largely arbitrary, but was picked because as of 2022-05-01 LLVM
// can const-fold the check in `vec![[0; 32]; n]` but not in
// `vec![[0; 64]; n]`: https://godbolt.org/z/WTzjzfs5b
// Feel free to tweak if you have better evidence.
N <= 32 && self.iter().all(IsZero::is_zero)
}
}
// `Option<&T>` and `Option<Box<T>>` are guaranteed to represent `None` as null.
// For fat pointers, the bytes that would be the pointer metadata in the `Some`
// variant are padding in the `None` variant, so ignoring them and
// zero-initializing instead is ok.
// `Option<&mut T>` never implements `Clone`, so there's no need for an impl of
// `SpecFromElem`.
unsafe impl<T: ?Sized> IsZero for Option<&T> {
#[inline]
fn is_zero(&self) -> bool {
self.is_none()
}
}
unsafe impl<T: ?Sized> IsZero for Option<Box<T>> {
#[inline]
fn is_zero(&self) -> bool {
self.is_none()
}
}
// `Option<num::NonZeroU32>` and similar have a representation guarantee that
// they're the same size as the corresponding `u32` type, as well as a guarantee
// that transmuting between `NonZeroU32` and `Option<num::NonZeroU32>` works.
// While the documentation officially makes it UB to transmute from `None`,
// we're the standard library so we can make extra inferences, and we know that
// the only niche available to represent `None` is the one that's all zeros.
macro_rules! impl_is_zero_option_of_nonzero {
($($t:ident,)+) => {$(
unsafe impl IsZero for Option<core::num::$t> {
#[inline]
fn is_zero(&self) -> bool {
self.is_none()
}
}
)+};
}
impl_is_zero_option_of_nonzero!(
NonZeroU8,
NonZeroU16,
NonZeroU32,
NonZeroU64,
NonZeroU128,
NonZeroI8,
NonZeroI16,
NonZeroI32,
NonZeroI64,
NonZeroI128,
NonZeroUsize,
NonZeroIsize,
);

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use crate::alloc::Allocator;
#[cfg(not(no_global_oom_handling))]
use crate::borrow::Cow;
use super::Vec;
macro_rules! __impl_slice_eq1 {
([$($vars:tt)*] $lhs:ty, $rhs:ty $(where $ty:ty: $bound:ident)?, #[$stability:meta]) => {
#[$stability]
impl<T, U, $($vars)*> PartialEq<$rhs> for $lhs
where
T: PartialEq<U>,
$($ty: $bound)?
{
#[inline]
fn eq(&self, other: &$rhs) -> bool { self[..] == other[..] }
#[inline]
fn ne(&self, other: &$rhs) -> bool { self[..] != other[..] }
}
}
}
__impl_slice_eq1! { [A1: Allocator, A2: Allocator] Vec<T, A1>, Vec<U, A2>, #[stable(feature = "rust1", since = "1.0.0")] }
__impl_slice_eq1! { [A: Allocator] Vec<T, A>, &[U], #[stable(feature = "rust1", since = "1.0.0")] }
__impl_slice_eq1! { [A: Allocator] Vec<T, A>, &mut [U], #[stable(feature = "rust1", since = "1.0.0")] }
__impl_slice_eq1! { [A: Allocator] &[T], Vec<U, A>, #[stable(feature = "partialeq_vec_for_ref_slice", since = "1.46.0")] }
__impl_slice_eq1! { [A: Allocator] &mut [T], Vec<U, A>, #[stable(feature = "partialeq_vec_for_ref_slice", since = "1.46.0")] }
__impl_slice_eq1! { [A: Allocator] Vec<T, A>, [U], #[stable(feature = "partialeq_vec_for_slice", since = "1.48.0")] }
__impl_slice_eq1! { [A: Allocator] [T], Vec<U, A>, #[stable(feature = "partialeq_vec_for_slice", since = "1.48.0")] }
#[cfg(not(no_global_oom_handling))]
__impl_slice_eq1! { [A: Allocator] Cow<'_, [T]>, Vec<U, A> where T: Clone, #[stable(feature = "rust1", since = "1.0.0")] }
#[cfg(not(no_global_oom_handling))]
__impl_slice_eq1! { [] Cow<'_, [T]>, &[U] where T: Clone, #[stable(feature = "rust1", since = "1.0.0")] }
#[cfg(not(no_global_oom_handling))]
__impl_slice_eq1! { [] Cow<'_, [T]>, &mut [U] where T: Clone, #[stable(feature = "rust1", since = "1.0.0")] }
__impl_slice_eq1! { [A: Allocator, const N: usize] Vec<T, A>, [U; N], #[stable(feature = "rust1", since = "1.0.0")] }
__impl_slice_eq1! { [A: Allocator, const N: usize] Vec<T, A>, &[U; N], #[stable(feature = "rust1", since = "1.0.0")] }
// NOTE: some less important impls are omitted to reduce code bloat
// FIXME(Centril): Reconsider this?
//__impl_slice_eq1! { [const N: usize] Vec<A>, &mut [B; N], }
//__impl_slice_eq1! { [const N: usize] [A; N], Vec<B>, }
//__impl_slice_eq1! { [const N: usize] &[A; N], Vec<B>, }
//__impl_slice_eq1! { [const N: usize] &mut [A; N], Vec<B>, }
//__impl_slice_eq1! { [const N: usize] Cow<'a, [A]>, [B; N], }
//__impl_slice_eq1! { [const N: usize] Cow<'a, [A]>, &[B; N], }
//__impl_slice_eq1! { [const N: usize] Cow<'a, [A]>, &mut [B; N], }