====================== =============== ========================================
GNU C 5.1 gcc --version
Clang/LLVM (optional) 11.0.0 clang --version
-Rust (optional) 1.62.0 rustc --version
+Rust (optional) 1.68.2 rustc --version
bindgen (optional) 0.56.0 bindgen --version
GNU make 3.82 make --version
bash 4.2 bash --version
mod tests;
extern "Rust" {
- // These are the magic symbols to call the global allocator. rustc generates
+ // 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`)
+ // the default implementations in std (`__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
+ // The rustc fork of LLVM 14 and earlier also special-cases these function names to be able to optimize them
// like `malloc`, `realloc`, and `free`, respectively.
#[rustc_allocator]
- #[rustc_allocator_nounwind]
+ #[rustc_nounwind]
fn __rust_alloc(size: usize, align: usize) -> *mut u8;
- #[rustc_allocator_nounwind]
+ #[rustc_deallocator]
+ #[rustc_nounwind]
fn __rust_dealloc(ptr: *mut u8, size: usize, align: usize);
- #[rustc_allocator_nounwind]
+ #[rustc_reallocator]
+ #[rustc_nounwind]
fn __rust_realloc(ptr: *mut u8, old_size: usize, align: usize, new_size: usize) -> *mut u8;
- #[rustc_allocator_nounwind]
+ #[rustc_allocator_zeroed]
+ #[rustc_nounwind]
fn __rust_alloc_zeroed(size: usize, align: usize) -> *mut u8;
}
/// # Examples
///
/// ```
-/// use std::alloc::{alloc, dealloc, Layout};
+/// use std::alloc::{alloc, dealloc, handle_alloc_error, Layout};
///
/// unsafe {
/// let layout = Layout::new::<u16>();
/// let ptr = alloc(layout);
+/// if ptr.is_null() {
+/// handle_alloc_error(layout);
+/// }
///
/// *(ptr as *mut u16) = 42;
/// assert_eq!(*(ptr as *mut u16), 42);
#[cfg(not(no_global_oom_handling))]
extern "Rust" {
- // This is the magic symbol to call the global alloc error handler. rustc generates
+ // 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) -> !;
#[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]`
+ // 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) };
+ pub unsafe fn __rdl_oom(size: usize, _align: usize) -> ! {
extern "Rust" {
- #[lang = "oom"]
- fn oom_impl(layout: Layout) -> !;
+ // This symbol is emitted by rustc next to __rust_alloc_error_handler.
+ // Its value depends on the -Zoom={panic,abort} compiler option.
+ static __rust_alloc_error_handler_should_panic: u8;
+ }
+
+ #[allow(unused_unsafe)]
+ if unsafe { __rust_alloc_error_handler_should_panic != 0 } {
+ panic!("memory allocation of {size} bytes failed")
+ } else {
+ core::panicking::panic_nounwind_fmt(format_args!(
+ "memory allocation of {size} bytes failed"
+ ))
}
- unsafe { oom_impl(layout) }
}
}
// SPDX-License-Identifier: Apache-2.0 OR MIT
-//! A pointer type for heap allocation.
+//! The `Box<T>` type for heap allocation.
//!
//! [`Box<T>`], casually referred to as a 'box', provides the simplest form of
//! heap allocation in Rust. Boxes provide ownership for this allocation, and
//! definition is just using `T*` can lead to undefined behavior, as
//! described in [rust-lang/unsafe-code-guidelines#198][ucg#198].
//!
+//! # Considerations for unsafe code
+//!
+//! **Warning: This section is not normative and is subject to change, possibly
+//! being relaxed in the future! It is a simplified summary of the rules
+//! currently implemented in the compiler.**
+//!
+//! The aliasing rules for `Box<T>` are the same as for `&mut T`. `Box<T>`
+//! asserts uniqueness over its content. Using raw pointers derived from a box
+//! after that box has been mutated through, moved or borrowed as `&mut T`
+//! is not allowed. For more guidance on working with box from unsafe code, see
+//! [rust-lang/unsafe-code-guidelines#326][ucg#326].
+//!
+//!
//! [ucg#198]: https://github.com/rust-lang/unsafe-code-guidelines/issues/198
+//! [ucg#326]: https://github.com/rust-lang/unsafe-code-guidelines/issues/326
//! [dereferencing]: core::ops::Deref
//! [`Box::<T>::from_raw(value)`]: Box::from_raw
//! [`Global`]: crate::alloc::Global
use core::borrow;
use core::cmp::Ordering;
use core::convert::{From, TryFrom};
+use core::error::Error;
use core::fmt;
use core::future::Future;
use core::hash::{Hash, Hasher};
#[cfg(not(no_global_oom_handling))]
use core::iter::FromIterator;
use core::iter::{FusedIterator, Iterator};
+use core::marker::Tuple;
use core::marker::{Destruct, Unpin, Unsize};
use core::mem;
use core::ops::{
#[cfg(not(no_global_oom_handling))]
use crate::str::from_boxed_utf8_unchecked;
#[cfg(not(no_global_oom_handling))]
+use crate::string::String;
+#[cfg(not(no_global_oom_handling))]
use crate::vec::Vec;
#[cfg(not(no_thin))]
#[cfg(not(no_thin))]
mod thin;
-/// A pointer type for heap allocation.
+/// A pointer type that uniquely owns a heap allocation of type `T`.
///
/// See the [module-level documentation](../../std/boxed/index.html) for more.
#[lang = "owned_box"]
/// ```
/// let five = Box::new(5);
/// ```
- #[cfg(not(no_global_oom_handling))]
+ #[cfg(all(not(no_global_oom_handling)))]
#[inline(always)]
#[stable(feature = "rust1", since = "1.0.0")]
#[must_use]
pub fn new(x: T) -> Self {
- box x
+ #[rustc_box]
+ Box::new(x)
}
/// Constructs a new box with uninitialized contents.
Self::new_zeroed_in(Global)
}
- /// Constructs a new `Pin<Box<T>>`. If `T` does not implement `Unpin`, then
+ /// Constructs a new `Pin<Box<T>>`. If `T` does not implement [`Unpin`], then
/// `x` will be pinned in memory and unable to be moved.
+ ///
+ /// Constructing and pinning of the `Box` can also be done in two steps: `Box::pin(x)`
+ /// does the same as <code>[Box::into_pin]\([Box::new]\(x))</code>. Consider using
+ /// [`into_pin`](Box::into_pin) if you already have a `Box<T>`, or if you want to
+ /// construct a (pinned) `Box` in a different way than with [`Box::new`].
#[cfg(not(no_global_oom_handling))]
#[stable(feature = "pin", since = "1.33.0")]
#[must_use]
#[inline(always)]
pub fn pin(x: T) -> Pin<Box<T>> {
- (box x).into()
+ (#[rustc_box]
+ Box::new(x))
+ .into()
}
/// Allocates memory on the heap then places `x` into it,
unsafe { Ok(Box::from_raw_in(ptr.as_ptr(), alloc)) }
}
- /// Constructs a new `Pin<Box<T, A>>`. If `T` does not implement `Unpin`, then
+ /// Constructs a new `Pin<Box<T, A>>`. If `T` does not implement [`Unpin`], then
/// `x` will be pinned in memory and unable to be moved.
+ ///
+ /// Constructing and pinning of the `Box` can also be done in two steps: `Box::pin_in(x, alloc)`
+ /// does the same as <code>[Box::into_pin]\([Box::new_in]\(x, alloc))</code>. Consider using
+ /// [`into_pin`](Box::into_pin) if you already have a `Box<T, A>`, or if you want to
+ /// construct a (pinned) `Box` in a different way than with [`Box::new_in`].
#[cfg(not(no_global_oom_handling))]
#[unstable(feature = "allocator_api", issue = "32838")]
#[rustc_const_unstable(feature = "const_box", issue = "92521")]
/// [`Layout`]: crate::Layout
#[stable(feature = "box_raw", since = "1.4.0")]
#[inline]
+ #[must_use = "call `drop(Box::from_raw(ptr))` if you intend to drop the `Box`"]
pub unsafe fn from_raw(raw: *mut T) -> Self {
unsafe { Self::from_raw_in(raw, Global) }
}
unsafe { &mut *mem::ManuallyDrop::new(b).0.as_ptr() }
}
- /// Converts a `Box<T>` into a `Pin<Box<T>>`
+ /// Converts a `Box<T>` into a `Pin<Box<T>>`. If `T` does not implement [`Unpin`], then
+ /// `*boxed` will be pinned in memory and unable to be moved.
///
/// This conversion does not allocate on the heap and happens in place.
///
/// This is also available via [`From`].
- #[unstable(feature = "box_into_pin", issue = "62370")]
+ ///
+ /// Constructing and pinning a `Box` with <code>Box::into_pin([Box::new]\(x))</code>
+ /// can also be written more concisely using <code>[Box::pin]\(x)</code>.
+ /// This `into_pin` method is useful if you already have a `Box<T>`, or you are
+ /// constructing a (pinned) `Box` in a different way than with [`Box::new`].
+ ///
+ /// # Notes
+ ///
+ /// It's not recommended that crates add an impl like `From<Box<T>> for Pin<T>`,
+ /// as it'll introduce an ambiguity when calling `Pin::from`.
+ /// A demonstration of such a poor impl is shown below.
+ ///
+ /// ```compile_fail
+ /// # use std::pin::Pin;
+ /// struct Foo; // A type defined in this crate.
+ /// impl From<Box<()>> for Pin<Foo> {
+ /// fn from(_: Box<()>) -> Pin<Foo> {
+ /// Pin::new(Foo)
+ /// }
+ /// }
+ ///
+ /// let foo = Box::new(());
+ /// let bar = Pin::from(foo);
+ /// ```
+ #[stable(feature = "box_into_pin", since = "1.63.0")]
#[rustc_const_unstable(feature = "const_box", issue = "92521")]
pub const fn into_pin(boxed: Self) -> Pin<Self>
where
A: 'static,
{
// It's not possible to move or replace the insides of a `Pin<Box<T>>`
- // when `T: !Unpin`, so it's safe to pin it directly without any
+ // when `T: !Unpin`, so it's safe to pin it directly without any
// additional requirements.
unsafe { Pin::new_unchecked(boxed) }
}
impl<T: Default> Default for Box<T> {
/// Creates a `Box<T>`, with the `Default` value for T.
fn default() -> Self {
- box T::default()
+ #[rustc_box]
+ Box::new(T::default())
}
}
where
A: 'static,
{
- /// Converts a `Box<T>` into a `Pin<Box<T>>`
+ /// Converts a `Box<T>` into a `Pin<Box<T>>`. If `T` does not implement [`Unpin`], then
+ /// `*boxed` will be pinned in memory and unable to be moved.
///
/// This conversion does not allocate on the heap and happens in place.
+ ///
+ /// This is also available via [`Box::into_pin`].
+ ///
+ /// Constructing and pinning a `Box` with <code><Pin<Box\<T>>>::from([Box::new]\(x))</code>
+ /// can also be written more concisely using <code>[Box::pin]\(x)</code>.
+ /// This `From` implementation is useful if you already have a `Box<T>`, or you are
+ /// constructing a (pinned) `Box` in a different way than with [`Box::new`].
fn from(boxed: Box<T, A>) -> Self {
Box::into_pin(boxed)
}
/// Converts a `&[T]` into a `Box<[T]>`
///
/// This conversion allocates on the heap
- /// and performs a copy of `slice`.
+ /// and performs a copy of `slice` and its contents.
///
/// # Examples
/// ```rust
/// println!("{boxed:?}");
/// ```
fn from(array: [T; N]) -> Box<[T]> {
- box array
+ #[rustc_box]
+ Box::new(array)
}
}
+/// Casts a boxed slice to a boxed array.
+///
+/// # Safety
+///
+/// `boxed_slice.len()` must be exactly `N`.
+unsafe fn boxed_slice_as_array_unchecked<T, A: Allocator, const N: usize>(
+ boxed_slice: Box<[T], A>,
+) -> Box<[T; N], A> {
+ debug_assert_eq!(boxed_slice.len(), N);
+
+ let (ptr, alloc) = Box::into_raw_with_allocator(boxed_slice);
+ // SAFETY: Pointer and allocator came from an existing box,
+ // and our safety condition requires that the length is exactly `N`
+ unsafe { Box::from_raw_in(ptr as *mut [T; N], alloc) }
+}
+
#[stable(feature = "boxed_slice_try_from", since = "1.43.0")]
impl<T, const N: usize> TryFrom<Box<[T]>> for Box<[T; N]> {
type Error = Box<[T]>;
/// `boxed_slice.len()` does not equal `N`.
fn try_from(boxed_slice: Box<[T]>) -> Result<Self, Self::Error> {
if boxed_slice.len() == N {
- Ok(unsafe { Box::from_raw(Box::into_raw(boxed_slice) as *mut [T; N]) })
+ Ok(unsafe { boxed_slice_as_array_unchecked(boxed_slice) })
} else {
Err(boxed_slice)
}
}
}
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "boxed_array_try_from_vec", since = "1.66.0")]
+impl<T, const N: usize> TryFrom<Vec<T>> for Box<[T; N]> {
+ type Error = Vec<T>;
+
+ /// Attempts to convert a `Vec<T>` into a `Box<[T; N]>`.
+ ///
+ /// Like [`Vec::into_boxed_slice`], this is in-place if `vec.capacity() == N`,
+ /// but will require a reallocation otherwise.
+ ///
+ /// # Errors
+ ///
+ /// Returns the original `Vec<T>` in the `Err` variant if
+ /// `boxed_slice.len()` does not equal `N`.
+ ///
+ /// # Examples
+ ///
+ /// This can be used with [`vec!`] to create an array on the heap:
+ ///
+ /// ```
+ /// let state: Box<[f32; 100]> = vec![1.0; 100].try_into().unwrap();
+ /// assert_eq!(state.len(), 100);
+ /// ```
+ fn try_from(vec: Vec<T>) -> Result<Self, Self::Error> {
+ if vec.len() == N {
+ let boxed_slice = vec.into_boxed_slice();
+ Ok(unsafe { boxed_slice_as_array_unchecked(boxed_slice) })
+ } else {
+ Err(vec)
+ }
+ }
+}
+
impl<A: Allocator> Box<dyn Any, A> {
/// Attempt to downcast the box to a concrete type.
///
impl<I: FusedIterator + ?Sized, A: Allocator> FusedIterator for Box<I, A> {}
#[stable(feature = "boxed_closure_impls", since = "1.35.0")]
-impl<Args, F: FnOnce<Args> + ?Sized, A: Allocator> FnOnce<Args> for Box<F, A> {
+impl<Args
: Tuple, F: FnOnce<Args> + ?Sized, A: Allocator> FnOnce<Args> for Box<F, A> {
type Output = <F as FnOnce<Args>>::Output;
extern "rust-call" fn call_once(self, args: Args) -> Self::Output {
}
#[stable(feature = "boxed_closure_impls", since = "1.35.0")]
-impl<Args, F: FnMut<Args> + ?Sized, A: Allocator> FnMut<Args> for Box<F, A> {
+impl<Args
: Tuple, F: FnMut<Args> + ?Sized, A: Allocator> FnMut<Args> for Box<F, A> {
extern "rust-call" fn call_mut(&mut self, args: Args) -> Self::Output {
<F as FnMut<Args>>::call_mut(self, args)
}
}
#[stable(feature = "boxed_closure_impls", since = "1.35.0")]
-impl<Args, F: Fn<Args> + ?Sized, A: Allocator> Fn<Args> for Box<F, A> {
+impl<Args
: Tuple, F: Fn<Args> + ?Sized, A: Allocator> Fn<Args> for Box<F, A> {
extern "rust-call" fn call(&self, args: Args) -> Self::Output {
<F as Fn<Args>>::call(self, args)
}
}
-#[unstable(feature = "coerce_unsized", issue = "27732")]
+#[unstable(feature = "coerce_unsized", issue = "18598")]
impl<T: ?Sized + Unsize<U>, U: ?Sized, A: Allocator> CoerceUnsized<Box<U, A>> for Box<T, A> {}
#[unstable(feature = "dispatch_from_dyn", issue = "none")]
* could have a method to project a Pin<T> from it.
*/
#[stable(feature = "pin", since = "1.33.0")]
-#[rustc_const_unstable(feature = "const_box", issue = "92521")]
-impl<T: ?Sized, A: Allocator> const Unpin for Box<T, A> where A: 'static {}
+impl<T: ?Sized, A: Allocator> Unpin for Box<T, A> where A: 'static {}
#[unstable(feature = "generator_trait", issue = "43122")]
impl<G: ?Sized + Generator<R> + Unpin, R, A: Allocator> Generator<R> for Box<G, A>
(**self).size_hint()
}
}
+
+impl dyn Error {
+ #[inline]
+ #[stable(feature = "error_downcast", since = "1.3.0")]
+ #[rustc_allow_incoherent_impl]
+ /// Attempts to downcast the box to a concrete type.
+ pub fn downcast<T: Error + 'static>(self: Box<Self>) -> Result<Box<T>, Box<dyn Error>> {
+ if self.is::<T>() {
+ unsafe {
+ let raw: *mut dyn Error = Box::into_raw(self);
+ Ok(Box::from_raw(raw as *mut T))
+ }
+ } else {
+ Err(self)
+ }
+ }
+}
+
+impl dyn Error + Send {
+ #[inline]
+ #[stable(feature = "error_downcast", since = "1.3.0")]
+ #[rustc_allow_incoherent_impl]
+ /// Attempts to downcast the box to a concrete type.
+ pub fn downcast<T: Error + 'static>(self: Box<Self>) -> Result<Box<T>, Box<dyn Error + Send>> {
+ let err: Box<dyn Error> = self;
+ <dyn Error>::downcast(err).map_err(|s| unsafe {
+ // Reapply the `Send` marker.
+ mem::transmute::<Box<dyn Error>, Box<dyn Error + Send>>(s)
+ })
+ }
+}
+
+impl dyn Error + Send + Sync {
+ #[inline]
+ #[stable(feature = "error_downcast", since = "1.3.0")]
+ #[rustc_allow_incoherent_impl]
+ /// Attempts to downcast the box to a concrete type.
+ pub fn downcast<T: Error + 'static>(self: Box<Self>) -> Result<Box<T>, Box<Self>> {
+ let err: Box<dyn Error> = self;
+ <dyn Error>::downcast(err).map_err(|s| unsafe {
+ // Reapply the `Send + Sync` marker.
+ mem::transmute::<Box<dyn Error>, Box<dyn Error + Send + Sync>>(s)
+ })
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<'a, E: Error + 'a> From<E> for Box<dyn Error + 'a> {
+ /// Converts a type of [`Error`] into a box of dyn [`Error`].
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::error::Error;
+ /// use std::fmt;
+ /// use std::mem;
+ ///
+ /// #[derive(Debug)]
+ /// struct AnError;
+ ///
+ /// impl fmt::Display for AnError {
+ /// fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ /// write!(f, "An error")
+ /// }
+ /// }
+ ///
+ /// impl Error for AnError {}
+ ///
+ /// let an_error = AnError;
+ /// assert!(0 == mem::size_of_val(&an_error));
+ /// let a_boxed_error = Box::<dyn Error>::from(an_error);
+ /// assert!(mem::size_of::<Box<dyn Error>>() == mem::size_of_val(&a_boxed_error))
+ /// ```
+ fn from(err: E) -> Box<dyn Error + 'a> {
+ Box::new(err)
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<'a, E: Error + Send + Sync + 'a> From<E> for Box<dyn Error + Send + Sync + 'a> {
+ /// Converts a type of [`Error`] + [`Send`] + [`Sync`] into a box of
+ /// dyn [`Error`] + [`Send`] + [`Sync`].
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::error::Error;
+ /// use std::fmt;
+ /// use std::mem;
+ ///
+ /// #[derive(Debug)]
+ /// struct AnError;
+ ///
+ /// impl fmt::Display for AnError {
+ /// fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ /// write!(f, "An error")
+ /// }
+ /// }
+ ///
+ /// impl Error for AnError {}
+ ///
+ /// unsafe impl Send for AnError {}
+ ///
+ /// unsafe impl Sync for AnError {}
+ ///
+ /// let an_error = AnError;
+ /// assert!(0 == mem::size_of_val(&an_error));
+ /// let a_boxed_error = Box::<dyn Error + Send + Sync>::from(an_error);
+ /// assert!(
+ /// mem::size_of::<Box<dyn Error + Send + Sync>>() == mem::size_of_val(&a_boxed_error))
+ /// ```
+ fn from(err: E) -> Box<dyn Error + Send + Sync + 'a> {
+ Box::new(err)
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "rust1", since = "1.0.0")]
+impl From<String> for Box<dyn Error + Send + Sync> {
+ /// Converts a [`String`] into a box of dyn [`Error`] + [`Send`] + [`Sync`].
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::error::Error;
+ /// use std::mem;
+ ///
+ /// let a_string_error = "a string error".to_string();
+ /// let a_boxed_error = Box::<dyn Error + Send + Sync>::from(a_string_error);
+ /// assert!(
+ /// mem::size_of::<Box<dyn Error + Send + Sync>>() == mem::size_of_val(&a_boxed_error))
+ /// ```
+ #[inline]
+ fn from(err: String) -> Box<dyn Error + Send + Sync> {
+ struct StringError(String);
+
+ impl Error for StringError {
+ #[allow(deprecated)]
+ fn description(&self) -> &str {
+ &self.0
+ }
+ }
+
+ impl fmt::Display for StringError {
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ fmt::Display::fmt(&self.0, f)
+ }
+ }
+
+ // Purposefully skip printing "StringError(..)"
+ impl fmt::Debug for StringError {
+ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+ fmt::Debug::fmt(&self.0, f)
+ }
+ }
+
+ Box::new(StringError(err))
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "string_box_error", since = "1.6.0")]
+impl From<String> for Box<dyn Error> {
+ /// Converts a [`String`] into a box of dyn [`Error`].
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::error::Error;
+ /// use std::mem;
+ ///
+ /// let a_string_error = "a string error".to_string();
+ /// let a_boxed_error = Box::<dyn Error>::from(a_string_error);
+ /// assert!(mem::size_of::<Box<dyn Error>>() == mem::size_of_val(&a_boxed_error))
+ /// ```
+ fn from(str_err: String) -> Box<dyn Error> {
+ let err1: Box<dyn Error + Send + Sync> = From::from(str_err);
+ let err2: Box<dyn Error> = err1;
+ err2
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<'a> From<&str> for Box<dyn Error + Send + Sync + 'a> {
+ /// Converts a [`str`] into a box of dyn [`Error`] + [`Send`] + [`Sync`].
+ ///
+ /// [`str`]: prim@str
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::error::Error;
+ /// use std::mem;
+ ///
+ /// let a_str_error = "a str error";
+ /// let a_boxed_error = Box::<dyn Error + Send + Sync>::from(a_str_error);
+ /// assert!(
+ /// mem::size_of::<Box<dyn Error + Send + Sync>>() == mem::size_of_val(&a_boxed_error))
+ /// ```
+ #[inline]
+ fn from(err: &str) -> Box<dyn Error + Send + Sync + 'a> {
+ From::from(String::from(err))
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "string_box_error", since = "1.6.0")]
+impl From<&str> for Box<dyn Error> {
+ /// Converts a [`str`] into a box of dyn [`Error`].
+ ///
+ /// [`str`]: prim@str
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::error::Error;
+ /// use std::mem;
+ ///
+ /// let a_str_error = "a str error";
+ /// let a_boxed_error = Box::<dyn Error>::from(a_str_error);
+ /// assert!(mem::size_of::<Box<dyn Error>>() == mem::size_of_val(&a_boxed_error))
+ /// ```
+ fn from(err: &str) -> Box<dyn Error> {
+ From::from(String::from(err))
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "cow_box_error", since = "1.22.0")]
+impl<'a, 'b> From<Cow<'b, str>> for Box<dyn Error + Send + Sync + 'a> {
+ /// Converts a [`Cow`] into a box of dyn [`Error`] + [`Send`] + [`Sync`].
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::error::Error;
+ /// use std::mem;
+ /// use std::borrow::Cow;
+ ///
+ /// let a_cow_str_error = Cow::from("a str error");
+ /// let a_boxed_error = Box::<dyn Error + Send + Sync>::from(a_cow_str_error);
+ /// assert!(
+ /// mem::size_of::<Box<dyn Error + Send + Sync>>() == mem::size_of_val(&a_boxed_error))
+ /// ```
+ fn from(err: Cow<'b, str>) -> Box<dyn Error + Send + Sync + 'a> {
+ From::from(String::from(err))
+ }
+}
+
+#[cfg(not(no_global_oom_handling))]
+#[stable(feature = "cow_box_error", since = "1.22.0")]
+impl<'a> From<Cow<'a, str>> for Box<dyn Error> {
+ /// Converts a [`Cow`] into a box of dyn [`Error`].
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// use std::error::Error;
+ /// use std::mem;
+ /// use std::borrow::Cow;
+ ///
+ /// let a_cow_str_error = Cow::from("a str error");
+ /// let a_boxed_error = Box::<dyn Error>::from(a_cow_str_error);
+ /// assert!(mem::size_of::<Box<dyn Error>>() == mem::size_of_val(&a_boxed_error))
+ /// ```
+ fn from(err: Cow<'a, str>) -> Box<dyn Error> {
+ From::from(String::from(err))
+ }
+}
+
+#[stable(feature = "box_error", since = "1.8.0")]
+impl<T: core::error::Error> core::error::Error for Box<T> {
+ #[allow(deprecated, deprecated_in_future)]
+ fn description(&self) -> &str {
+ core::error::Error::description(&**self)
+ }
+
+ #[allow(deprecated)]
+ fn cause(&self) -> Option<&dyn core::error::Error> {
+ core::error::Error::cause(&**self)
+ }
+
+ fn source(&self) -> Option<&(dyn core::error::Error + 'static)> {
+ core::error::Error::source(&**self)
+ }
+}
" because the computed capacity exceeded the collection's maximum"
}
TryReserveErrorKind::AllocError { .. } => {
- " because the memory allocator returned a error"
+ " because the memory allocator returned an error"
}
};
fmt.write_str(reason)
/// Extends `self` with the contents of the given iterator.
fn spec_extend(&mut self, iter: I);
}
+
+#[stable(feature = "try_reserve", since = "1.57.0")]
+impl core::error::Error for TryReserveError {}
//! This library provides smart pointers and collections for managing
//! heap-allocated values.
//!
-//! This library, like libcore, normally doesn’t need to be used directly
+//! This library, like core, 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.
//! [`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(
any(not(feature = "miri-test-libstd"), test, doctest),
no_global_oom_handling,
not(no_global_oom_handling),
+ not(no_rc),
+ not(no_sync),
target_has_atomic = "ptr"
))]
#![no_std]
#![needs_allocator]
+// To run alloc tests without x.py without ending up with two copies of alloc, 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))]
//
// Lints:
#![deny(unsafe_op_in_unsafe_fn)]
+#![deny(fuzzy_provenance_casts)]
#![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_into_iter_constructors)]
#![feature(array_methods)]
#![feature(array_windows)]
#![feature(assert_matches)]
#![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))]
+#![cfg_attr(not(no_global_oom_handling), feature(const_btree_len))]
#![cfg_attr(not(no_borrow), 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_zeroed)]
#![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(core_panic)]
#![feature(const_eval_select)]
#![feature(const_pin)]
+#![feature(const_waker)]
#![feature(cstr_from_bytes_until_nul)]
#![feature(dispatch_from_dyn)]
+#![feature(error_generic_member_access)]
+#![feature(error_in_core)]
#![feature(exact_size_is_empty)]
#![feature(extend_one)]
#![feature(fmt_internals)]
#![feature(fn_traits)]
#![feature(hasher_prefixfree_extras)]
+#![feature(inline_const)]
#![feature(inplace_iteration)]
+#![cfg_attr(test, feature(is_sorted))]
#![feature(iter_advance_by)]
+#![feature(iter_next_chunk)]
+#![feature(iter_repeat_n)]
#![feature(layout_for_ptr)]
#![feature(maybe_uninit_slice)]
+#![feature(maybe_uninit_uninit_array)]
+#![feature(maybe_uninit_uninit_array_transpose)]
#![cfg_attr(test, feature(new_uninit))]
#![feature(nonnull_slice_from_raw_parts)]
#![feature(pattern)]
+#![feature(pointer_byte_offsets)]
+#![feature(provide_any)]
#![feature(ptr_internals)]
#![feature(ptr_metadata)]
#![feature(ptr_sub_ptr)]
#![feature(receiver_trait)]
+#![feature(saturating_int_impl)]
#![feature(set_ptr_value)]
+#![feature(sized_type_properties)]
+#![feature(slice_from_ptr_range)]
#![feature(slice_group_by)]
#![feature(slice_ptr_get)]
#![feature(slice_ptr_len)]
#![feature(trusted_len)]
#![feature(trusted_random_access)]
#![feature(try_trait_v2)]
+#![feature(tuple_trait)]
#![feature(unchecked_math)]
#![feature(unicode_internals)]
#![feature(unsize)]
+#![feature(utf8_chunks)]
+#![feature(std_internals)]
//
// 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)]
#![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(pointer_is_aligned)]
#![feature(slice_internals)]
#![feature(staged_api)]
+#![feature(stmt_expr_attributes)]
#![cfg_attr(test, feature(test))]
#![feature(unboxed_closures)]
#![feature(unsized_fn_params)]
#![feature(c_unwind)]
+#![feature(with_negative_coherence)]
+#![cfg_attr(test, feature(panic_update_hook))]
//
// Rustdoc features:
#![feature(doc_cfg)]
extern crate std;
#[cfg(test)]
extern crate test;
+#[cfg(test)]
+mod testing;
// Module with internal macros used by other modules (needs to be included before other modules).
#[cfg(not(no_macros))]
#[cfg(not(no_borrow))]
pub mod borrow;
pub mod collections;
-#[cfg(not(no_global_oom_handling))]
+#[cfg(all(not(no_rc), not(no_sync), not(no_global_oom_handling)))]
pub mod ffi;
#[cfg(not(no_fmt))]
pub mod fmt;
pub mod str;
#[cfg(not(no_string))]
pub mod string;
-#[cfg(not(no_sync))]
-#[cfg(target_has_atomic = "ptr")]
+#[cfg(all(not(no_rc), not(no_sync), target_has_atomic = "ptr"))]
pub mod sync;
-#[cfg(all(not(no_global_oom_handling), target_has_atomic = "ptr"))]
+#[cfg(all(not(no_global_oom_handling), not(no_rc), not(no_sync), target_has_atomic = "ptr"))]
pub mod task;
#[cfg(test)]
mod tests;
pub mod __export {
pub use core::format_args;
}
+
+#[cfg(test)]
+#[allow(dead_code)] // Not used in all configurations
+pub(crate) mod test_helpers {
+ /// Copied from `std::test_helpers::test_rng`, since these tests rely on the
+ /// seed not being the same for every RNG invocation too.
+ pub(crate) fn test_rng() -> rand_xorshift::XorShiftRng {
+ use std::hash::{BuildHasher, Hash, Hasher};
+ let mut hasher = std::collections::hash_map::RandomState::new().build_hasher();
+ std::panic::Location::caller().hash(&mut hasher);
+ let hc64 = hasher.finish();
+ let seed_vec =
+ hc64.to_le_bytes().into_iter().chain(0u8..8).collect::<crate::vec::Vec<u8>>();
+ let seed: [u8; 16] = seed_vec.as_slice().try_into().unwrap();
+ rand::SeedableRng::from_seed(seed)
+ }
+}
use core::alloc::LayoutError;
use core::cmp;
use core::intrinsics;
-use core::mem::{self, ManuallyDrop, MaybeUninit};
+use core::mem::{self, ManuallyDrop, MaybeUninit, SizedTypeProperties};
use core::ops::Drop;
use core::ptr::{self, NonNull, Unique};
use core::slice;
#[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 {
+ if T::IS_ZST || capacity == 0 {
Self::new_in(alloc)
} else {
// We avoid `unwrap_or_else` here because it bloats the amount of
fn try_allocate_in(capacity: usize, init: AllocInit, alloc: A) -> Result<Self, TryReserveError> {
// Don't allocate here because `Drop` will not deallocate when `capacity` is 0.
- if mem::size_of::<T>() == 0 || capacity == 0 {
+ if T::IS_ZST || capacity == 0 {
return Ok(Self::new_in(alloc));
}
/// 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 }
+ if T::IS_ZST { usize::MAX } else { self.cap }
}
/// Returns a shared reference to the allocator backing this `RawVec`.
}
fn current_memory(&self) -> Option<(NonNull<u8>, Layout)> {
- if mem::size_of::<T>() == 0 || self.cap == 0 {
+ if T::IS_ZST || self.cap == 0 {
None
} else {
// We have an allocated chunk of memory, so we can bypass runtime
// This is ensured by the calling contexts.
debug_assert!(additional > 0);
- if mem::size_of::<T>() == 0 {
+ if T::IS_ZST {
// 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());
// `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 {
+ if T::IS_ZST {
// 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());
Ok(())
}
- #[allow(dead_code)]
+ #[cfg(not(no_global_oom_handling))]
fn shrink(&mut self, cap: usize) -> Result<(), TryReserveError> {
assert!(cap <= self.capacity(), "Tried to shrink to a larger capacity");
// SPDX-License-Identifier: Apache-2.0 OR MIT
-//! A dynamically-sized view into a contiguous sequence, `[T]`.
+//! Utilities for the slice primitive type.
//!
//! *[See also the slice primitive type](slice).*
//!
-//! Slices are a view into a block of memory represented as a pointer and a
-//! length.
+//! Most of the structs in this module are iterator types which can only be created
+//! using a certain function. For example, `slice.iter()` yields an [`Iter`].
//!
-//! ```
-//! // slicing a Vec
-//! let vec = vec![1, 2, 3];
-//! let int_slice = &vec[..];
-//! // coercing an array to a slice
-//! let str_slice: &[&str] = &["one", "two", "three"];
-//! ```
-//!
-//! Slices are either mutable or shared. The shared slice type is `&[T]`,
-//! while the mutable slice type is `&mut [T]`, where `T` represents the element
-//! type. For example, you can mutate the block of memory that a mutable slice
-//! points to:
-//!
-//! ```
-//! let x = &mut [1, 2, 3];
-//! x[1] = 7;
-//! assert_eq!(x, &[1, 7, 3]);
-//! ```
-//!
-//! Here are some of the things this module contains:
-//!
-//! ## Structs
-//!
-//! There are several structs that are useful for slices, such as [`Iter`], which
-//! represents iteration over a slice.
-//!
-//! ## Trait Implementations
-//!
-//! There are several implementations of common traits for slices. Some examples
-//! include:
-//!
-//! * [`Clone`]
-//! * [`Eq`], [`Ord`] - for slices whose element type are [`Eq`] or [`Ord`].
-//! * [`Hash`] - for slices whose element type is [`Hash`].
-//!
-//! ## Iteration
-//!
-//! The slices implement `IntoIterator`. The iterator yields references to the
-//! slice elements.
-//!
-//! ```
-//! let numbers = &[0, 1, 2];
-//! for n in numbers {
-//! println!("{n} is a number!");
-//! }
-//! ```
-//!
-//! The mutable slice yields mutable references to the elements:
-//!
-//! ```
-//! let mut scores = [7, 8, 9];
-//! for score in &mut scores[..] {
-//! *score += 1;
-//! }
-//! ```
-//!
-//! This iterator yields mutable references to the slice's elements, so while
-//! the element type of the slice is `i32`, the element type of the iterator is
-//! `&mut i32`.
-//!
-//! * [`.iter`] and [`.iter_mut`] are the explicit methods to return the default
-//! iterators.
-//! * Further methods that return iterators are [`.split`], [`.splitn`],
-//! [`.chunks`], [`.windows`] and more.
-//!
-//! [`Hash`]: core::hash::Hash
-//! [`.iter`]: slice::iter
-//! [`.iter_mut`]: slice::iter_mut
-//! [`.split`]: slice::split
-//! [`.splitn`]: slice::splitn
-//! [`.chunks`]: slice::chunks
-//! [`.windows`]: slice::windows
+//! A few functions are provided to create a slice from a value reference
+//! or from a raw pointer.
#![stable(feature = "rust1", since = "1.0.0")]
// Many of the usings in this module are only used in the test configuration.
// It's cleaner to just turn off the unused_imports warning than to fix them.
#[cfg(not(no_global_oom_handling))]
use core::cmp::Ordering::{self, Less};
#[cfg(not(no_global_oom_handling))]
-use core::mem;
-#[cfg(not(no_global_oom_handling))]
-use core::mem::size_of;
+use core::mem::{self, SizedTypeProperties};
#[cfg(not(no_global_oom_handling))]
use core::ptr;
+#[cfg(not(no_global_oom_handling))]
+use core::slice::sort;
use crate::alloc::Allocator;
#[cfg(not(no_global_oom_handling))]
-use crate::alloc::Global;
+use crate::alloc::{self, Global};
#[cfg(not(no_global_oom_handling))]
use crate::borrow::ToOwned;
use crate::boxed::Box;
use crate::vec::Vec;
+#[cfg(test)]
+mod tests;
+
#[unstable(feature = "slice_range", issue = "76393")]
pub use core::slice::range;
#[unstable(feature = "array_chunks", issue = "74985")]
pub use core::slice::SliceIndex;
#[stable(feature = "from_ref", since = "1.28.0")]
pub use core::slice::{from_mut, from_ref};
+#[unstable(feature = "slice_from_ptr_range", issue = "89792")]
+pub use core::slice::{from_mut_ptr_range, from_ptr_range};
#[stable(feature = "rust1", since = "1.0.0")]
pub use core::slice::{from_raw_parts, from_raw_parts_mut};
#[stable(feature = "rust1", since = "1.0.0")]
where
T: Ord,
{
- merge_sort(self, |a, b| a.lt(b));
+ stable_sort(self, T::lt);
}
/// Sorts the slice with a comparator function.
where
F: FnMut(&T, &T) -> Ordering,
{
- merge_sort(self, |a, b| compare(a, b) == Less);
+ stable_sort(self, |a, b| compare(a, b) == Less);
}
/// Sorts the slice with a key extraction function.
F: FnMut(&T) -> K,
K: Ord,
{
- merge_sort(self, |a, b| f(a).lt(&f(b)));
+ stable_sort(self, |a, b| f(a).lt(&f(b)));
}
/// Sorts the slice with a key extraction function.
hack::into_vec(self)
}
- /// Creates a vector by repeating a slice `n` times.
+ /// Creates a vector by copying a slice `n` times.
///
/// # Panics
///
///
/// ```error
/// error[E0207]: the type parameter `T` is not constrained by the impl trait, self type, or predica
-/// --> src/liballoc/slice.rs:608:6
+/// --> library/alloc/src/slice.rs:608:6
/// |
/// 608 | impl<T: Clone, V: Borrow<[T]>> Concat for [V] {
/// | ^ unconstrained type parameter
////////////////////////////////////////////////////////////////////////////////
#[stable(feature = "rust1", since = "1.0.0")]
-impl<T> Borrow<[T]> for Vec<T> {
+impl<T, A: Allocator> Borrow<[T]> for Vec<T, A> {
fn borrow(&self) -> &[T] {
&self[..]
}
}
#[stable(feature = "rust1", since = "1.0.0")]
-impl<T> BorrowMut<[T]> for Vec<T> {
+impl<T, A: Allocator> BorrowMut<[T]> for Vec<T, A> {
fn borrow_mut(&mut self) -> &mut [T] {
&mut self[..]
}
// Sorting
////////////////////////////////////////////////////////////////////////////////
-/// Inserts `v[0]` into pre-sorted sequence `v[1..]` so that whole `v[..]` becomes sorted.
-///
-/// This is the integral subroutine of insertion sort.
+#[inline]
#[cfg(not(no_global_oom_handling))]
-fn insert_head<T, F>(v: &mut [T], is_less: &mut F)
+fn stable_sort<T, F>(v: &mut [T], mut is_less: F)
where
F: FnMut(&T, &T) -> bool,
{
- if v.len() >= 2 && is_less(&v[1], &v[0]) {
- unsafe {
- // There are three ways to implement insertion here:
- //
- // 1. Swap adjacent elements until the first one gets to its final destination.
- // However, this way we copy data around more than is necessary. If elements are big
- // structures (costly to copy), this method will be slow.
- //
- // 2. Iterate until the right place for the first element is found. Then shift the
- // elements succeeding it to make room for it and finally place it into the
- // remaining hole. This is a good method.
- //
- // 3. Copy the first element into a temporary variable. Iterate until the right place
- // for it is found. As we go along, copy every traversed element into the slot
- // preceding it. Finally, copy data from the temporary variable into the remaining
- // hole. This method is very good. Benchmarks demonstrated slightly better
- // performance than with the 2nd method.
- //
- // All methods were benchmarked, and the 3rd showed best results. So we chose that one.
- let tmp = mem::ManuallyDrop::new(ptr::read(&v[0]));
-
- // Intermediate state of the insertion process is always tracked by `hole`, which
- // serves two purposes:
- // 1. Protects integrity of `v` from panics in `is_less`.
- // 2. Fills the remaining hole in `v` in the end.
- //
- // Panic safety:
- //
- // If `is_less` panics at any point during the process, `hole` will get dropped and
- // fill the hole in `v` with `tmp`, thus ensuring that `v` still holds every object it
- // initially held exactly once.
- let mut hole = InsertionHole { src: &*tmp, dest: &mut v[1] };
- ptr::copy_nonoverlapping(&v[1], &mut v[0], 1);
-
- for i in 2..v.len() {
- if !is_less(&v[i], &*tmp) {
- break;
- }
- ptr::copy_nonoverlapping(&v[i], &mut v[i - 1], 1);
- hole.dest = &mut v[i];
- }
- // `hole` gets dropped and thus copies `tmp` into the remaining hole in `v`.
- }
- }
-
- // When dropped, copies from `src` into `dest`.
- struct InsertionHole<T> {
- src: *const T,
- dest: *mut T,
- }
-
- impl<T> Drop for InsertionHole<T> {
- fn drop(&mut self) {
- unsafe {
- ptr::copy_nonoverlapping(self.src, self.dest, 1);
- }
- }
+ if T::IS_ZST {
+ // Sorting has no meaningful behavior on zero-sized types. Do nothing.
+ return;
}
-}
-
-/// Merges non-decreasing runs `v[..mid]` and `v[mid..]` using `buf` as temporary storage, and
-/// stores the result into `v[..]`.
-///
-/// # Safety
-///
-/// The two slices must be non-empty and `mid` must be in bounds. Buffer `buf` must be long enough
-/// to hold a copy of the shorter slice. Also, `T` must not be a zero-sized type.
-#[cfg(not(no_global_oom_handling))]
-unsafe fn merge<T, F>(v: &mut [T], mid: usize, buf: *mut T, is_less: &mut F)
-where
- F: FnMut(&T, &T) -> bool,
-{
- let len = v.len();
- let v = v.as_mut_ptr();
- let (v_mid, v_end) = unsafe { (v.add(mid), v.add(len)) };
- // The merge process first copies the shorter run into `buf`. Then it traces the newly copied
- // run and the longer run forwards (or backwards), comparing their next unconsumed elements and
- // copying the lesser (or greater) one into `v`.
- //
- // As soon as the shorter run is fully consumed, the process is done. If the longer run gets
- // consumed first, then we must copy whatever is left of the shorter run into the remaining
- // hole in `v`.
- //
- // Intermediate state of the process is always tracked by `hole`, which serves two purposes:
- // 1. Protects integrity of `v` from panics in `is_less`.
- // 2. Fills the remaining hole in `v` if the longer run gets consumed first.
- //
- // Panic safety:
- //
- // If `is_less` panics at any point during the process, `hole` will get dropped and fill the
- // hole in `v` with the unconsumed range in `buf`, thus ensuring that `v` still holds every
- // object it initially held exactly once.
- let mut hole;
+ let elem_alloc_fn = |len: usize| -> *mut T {
+ // SAFETY: Creating the layout is safe as long as merge_sort never calls this with len >
+ // v.len(). Alloc in general will only be used as 'shadow-region' to store temporary swap
+ // elements.
+ unsafe { alloc::alloc(alloc::Layout::array::<T>(len).unwrap_unchecked()) as *mut T }
+ };
- if mid <= len - mid {
- // The left run is shorter.
+ let elem_dealloc_fn = |buf_ptr: *mut T, len: usize| {
+ // SAFETY: Creating the layout is safe as long as merge_sort never calls this with len >
+ // v.len(). The caller must ensure that buf_ptr was created by elem_alloc_fn with the same
+ // len.
unsafe {
- ptr::copy_nonoverlapping(v, buf, mid);
- hole = MergeHole { start: buf, end: buf.add(mid), dest: v };
+ alloc::dealloc(buf_ptr as *mut u8, alloc::Layout::array::<T>(len).unwrap_unchecked());
}
+ };
- // Initially, these pointers point to the beginnings of their arrays.
- let left = &mut hole.start;
- let mut right = v_mid;
- let out = &mut hole.dest;
-
- while *left < hole.end && right < v_end {
- // Consume the lesser side.
- // If equal, prefer the left run to maintain stability.
- unsafe {
- let to_copy = if is_less(&*right, &**left) {
- get_and_increment(&mut right)
- } else {
- get_and_increment(left)
- };
- ptr::copy_nonoverlapping(to_copy, get_and_increment(out), 1);
- }
- }
- } else {
- // The right run is shorter.
+ let run_alloc_fn = |len: usize| -> *mut sort::TimSortRun {
+ // SAFETY: Creating the layout is safe as long as merge_sort never calls this with an
+ // obscene length or 0.
unsafe {
- ptr::copy_nonoverlapping(v_mid, buf, len - mid);
- hole = MergeHole { start: buf, end: buf.add(len - mid), dest: v_mid };
+ alloc::alloc(alloc::Layout::array::<sort::TimSortRun>(len).unwrap_unchecked())
+ as *mut sort::TimSortRun
}
+ };
- // Initially, these pointers point past the ends of their arrays.
- let left = &mut hole.dest;
- let right = &mut hole.end;
- let mut out = v_end;
-
- while v < *left && buf < *right {
- // Consume the greater side.
- // If equal, prefer the right run to maintain stability.
- unsafe {
- let to_copy = if is_less(&*right.offset(-1), &*left.offset(-1)) {
- decrement_and_get(left)
- } else {
- decrement_and_get(right)
- };
- ptr::copy_nonoverlapping(to_copy, decrement_and_get(&mut out), 1);
- }
- }
- }
- // Finally, `hole` gets dropped. If the shorter run was not fully consumed, whatever remains of
- // it will now be copied into the hole in `v`.
-
- unsafe fn get_and_increment<T>(ptr: &mut *mut T) -> *mut T {
- let old = *ptr;
- *ptr = unsafe { ptr.offset(1) };
- old
- }
-
- unsafe fn decrement_and_get<T>(ptr: &mut *mut T) -> *mut T {
- *ptr = unsafe { ptr.offset(-1) };
- *ptr
- }
-
- // When dropped, copies the range `start..end` into `dest..`.
- struct MergeHole<T> {
- start: *mut T,
- end: *mut T,
- dest: *mut T,
- }
-
- impl<T> Drop for MergeHole<T> {
- fn drop(&mut self) {
- // `T` is not a zero-sized type, and these are pointers into a slice's elements.
- unsafe {
- let len = self.end.sub_ptr(self.start);
- ptr::copy_nonoverlapping(self.start, self.dest, len);
- }
- }
- }
-}
-
-/// This merge sort borrows some (but not all) ideas from TimSort, which is described in detail
-/// [here](https://github.com/python/cpython/blob/main/Objects/listsort.txt).
-///
-/// The algorithm identifies strictly descending and non-descending subsequences, which are called
-/// natural runs. There is a stack of pending runs yet to be merged. Each newly found run is pushed
-/// onto the stack, and then some pairs of adjacent runs are merged until these two invariants are
-/// satisfied:
-///
-/// 1. for every `i` in `1..runs.len()`: `runs[i - 1].len > runs[i].len`
-/// 2. for every `i` in `2..runs.len()`: `runs[i - 2].len > runs[i - 1].len + runs[i].len`
-///
-/// The invariants ensure that the total running time is *O*(*n* \* log(*n*)) worst-case.
-#[cfg(not(no_global_oom_handling))]
-fn merge_sort<T, F>(v: &mut [T], mut is_less: F)
-where
- F: FnMut(&T, &T) -> bool,
-{
- // Slices of up to this length get sorted using insertion sort.
- const MAX_INSERTION: usize = 20;
- // Very short runs are extended using insertion sort to span at least this many elements.
- const MIN_RUN: usize = 10;
-
- // Sorting has no meaningful behavior on zero-sized types.
- if size_of::<T>() == 0 {
- return;
- }
-
- let len = v.len();
-
- // Short arrays get sorted in-place via insertion sort to avoid allocations.
- if len <= MAX_INSERTION {
- if len >= 2 {
- for i in (0..len - 1).rev() {
- insert_head(&mut v[i..], &mut is_less);
- }
- }
- return;
- }
-
- // Allocate a buffer to use as scratch memory. We keep the length 0 so we can keep in it
- // shallow copies of the contents of `v` without risking the dtors running on copies if
- // `is_less` panics. When merging two sorted runs, this buffer holds a copy of the shorter run,
- // which will always have length at most `len / 2`.
- let mut buf = Vec::with_capacity(len / 2);
-
- // In order to identify natural runs in `v`, we traverse it backwards. That might seem like a
- // strange decision, but consider the fact that merges more often go in the opposite direction
- // (forwards). According to benchmarks, merging forwards is slightly faster than merging
- // backwards. To conclude, identifying runs by traversing backwards improves performance.
- let mut runs = vec![];
- let mut end = len;
- while end > 0 {
- // Find the next natural run, and reverse it if it's strictly descending.
- let mut start = end - 1;
- if start > 0 {
- start -= 1;
- unsafe {
- if is_less(v.get_unchecked(start + 1), v.get_unchecked(start)) {
- while start > 0 && is_less(v.get_unchecked(start), v.get_unchecked(start - 1)) {
- start -= 1;
- }
- v[start..end].reverse();
- } else {
- while start > 0 && !is_less(v.get_unchecked(start), v.get_unchecked(start - 1))
- {
- start -= 1;
- }
- }
- }
- }
-
- // Insert some more elements into the run if it's too short. Insertion sort is faster than
- // merge sort on short sequences, so this significantly improves performance.
- while start > 0 && end - start < MIN_RUN {
- start -= 1;
- insert_head(&mut v[start..end], &mut is_less);
- }
-
- // Push this run onto the stack.
- runs.push(Run { start, len: end - start });
- end = start;
-
- // Merge some pairs of adjacent runs to satisfy the invariants.
- while let Some(r) = collapse(&runs) {
- let left = runs[r + 1];
- let right = runs[r];
- unsafe {
- merge(
- &mut v[left.start..right.start + right.len],
- left.len,
- buf.as_mut_ptr(),
- &mut is_less,
- );
- }
- runs[r] = Run { start: left.start, len: left.len + right.len };
- runs.remove(r + 1);
- }
- }
-
- // Finally, exactly one run must remain in the stack.
- debug_assert!(runs.len() == 1 && runs[0].start == 0 && runs[0].len == len);
-
- // Examines the stack of runs and identifies the next pair of runs to merge. More specifically,
- // if `Some(r)` is returned, that means `runs[r]` and `runs[r + 1]` must be merged next. If the
- // algorithm should continue building a new run instead, `None` is returned.
- //
- // TimSort is infamous for its buggy implementations, as described here:
- // http://envisage-project.eu/timsort-specification-and-verification/
- //
- // The gist of the story is: we must enforce the invariants on the top four runs on the stack.
- // Enforcing them on just top three is not sufficient to ensure that the invariants will still
- // hold for *all* runs in the stack.
- //
- // This function correctly checks invariants for the top four runs. Additionally, if the top
- // run starts at index 0, it will always demand a merge operation until the stack is fully
- // collapsed, in order to complete the sort.
- #[inline]
- fn collapse(runs: &[Run]) -> Option<usize> {
- let n = runs.len();
- if n >= 2
- && (runs[n - 1].start == 0
- || runs[n - 2].len <= runs[n - 1].len
- || (n >= 3 && runs[n - 3].len <= runs[n - 2].len + runs[n - 1].len)
- || (n >= 4 && runs[n - 4].len <= runs[n - 3].len + runs[n - 2].len))
- {
- if n >= 3 && runs[n - 3].len < runs[n - 1].len { Some(n - 3) } else { Some(n - 2) }
- } else {
- None
+ let run_dealloc_fn = |buf_ptr: *mut sort::TimSortRun, len: usize| {
+ // SAFETY: The caller must ensure that buf_ptr was created by elem_alloc_fn with the same
+ // len.
+ unsafe {
+ alloc::dealloc(
+ buf_ptr as *mut u8,
+ alloc::Layout::array::<sort::TimSortRun>(len).unwrap_unchecked(),
+ );
}
- }
+ };
- #[derive(Clone, Copy)]
- struct Run {
- start: usize,
- len: usize,
- }
+ sort::merge_sort(v, &mut is_less, elem_alloc_fn, elem_dealloc_fn, run_alloc_fn, run_dealloc_fn);
}
use crate::alloc::{Allocator, Global};
use core::fmt;
use core::iter::{FusedIterator, TrustedLen};
-use core::mem;
+use core::mem::{self, ManuallyDrop, SizedTypeProperties};
use core::ptr::{self, NonNull};
use core::slice::{self};
pub fn allocator(&self) -> &A {
unsafe { self.vec.as_ref().allocator() }
}
+
+ /// Keep unyielded elements in the source `Vec`.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// #![feature(drain_keep_rest)]
+ ///
+ /// let mut vec = vec!['a', 'b', 'c'];
+ /// let mut drain = vec.drain(..);
+ ///
+ /// assert_eq!(drain.next().unwrap(), 'a');
+ ///
+ /// // This call keeps 'b' and 'c' in the vec.
+ /// drain.keep_rest();
+ ///
+ /// // If we wouldn't call `keep_rest()`,
+ /// // `vec` would be empty.
+ /// assert_eq!(vec, ['b', 'c']);
+ /// ```
+ #[unstable(feature = "drain_keep_rest", issue = "101122")]
+ pub fn keep_rest(self) {
+ // At this moment layout looks like this:
+ //
+ // [head] [yielded by next] [unyielded] [yielded by next_back] [tail]
+ // ^-- start \_________/-- unyielded_len \____/-- self.tail_len
+ // ^-- unyielded_ptr ^-- tail
+ //
+ // Normally `Drop` impl would drop [unyielded] and then move [tail] to the `start`.
+ // Here we want to
+ // 1. Move [unyielded] to `start`
+ // 2. Move [tail] to a new start at `start + len(unyielded)`
+ // 3. Update length of the original vec to `len(head) + len(unyielded) + len(tail)`
+ // a. In case of ZST, this is the only thing we want to do
+ // 4. Do *not* drop self, as everything is put in a consistent state already, there is nothing to do
+ let mut this = ManuallyDrop::new(self);
+
+ unsafe {
+ let source_vec = this.vec.as_mut();
+
+ let start = source_vec.len();
+ let tail = this.tail_start;
+
+ let unyielded_len = this.iter.len();
+ let unyielded_ptr = this.iter.as_slice().as_ptr();
+
+ // ZSTs have no identity, so we don't need to move them around.
+ let needs_move = mem::size_of::<T>() != 0;
+
+ if needs_move {
+ let start_ptr = source_vec.as_mut_ptr().add(start);
+
+ // memmove back unyielded elements
+ if unyielded_ptr != start_ptr {
+ let src = unyielded_ptr;
+ let dst = start_ptr;
+
+ ptr::copy(src, dst, unyielded_len);
+ }
+
+ // memmove back untouched tail
+ if tail != (start + unyielded_len) {
+ let src = source_vec.as_ptr().add(tail);
+ let dst = start_ptr.add(unyielded_len);
+ ptr::copy(src, dst, this.tail_len);
+ }
+ }
+
+ source_vec.set_len(start + unyielded_len + this.tail_len);
+ }
+ }
}
#[stable(feature = "vec_drain_as_slice", since = "1.46.0")]
let mut vec = self.vec;
- if mem::size_of::<T>() == 0 {
+ if T::IS_ZST {
// 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 {
}
// 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
+ // it also gets touched by vec::Splice which may turn it into a dangling pointer
+ // which would make it and the vec pointer point to different allocations which would
+ // lead to invalid pointer arithmetic below.
let drop_ptr = iter.as_slice().as_ptr();
unsafe {
// SPDX-License-Identifier: Apache-2.0 OR MIT
use crate::alloc::{Allocator, Global};
-use core::ptr::{self};
-use core::slice::{self};
+use core::mem::{self, ManuallyDrop};
+use core::ptr;
+use core::slice;
use super::Vec;
pub fn allocator(&self) -> &A {
self.vec.allocator()
}
+
+ /// Keep unyielded elements in the source `Vec`.
+ ///
+ /// # Examples
+ ///
+ /// ```
+ /// #![feature(drain_filter)]
+ /// #![feature(drain_keep_rest)]
+ ///
+ /// let mut vec = vec!['a', 'b', 'c'];
+ /// let mut drain = vec.drain_filter(|_| true);
+ ///
+ /// assert_eq!(drain.next().unwrap(), 'a');
+ ///
+ /// // This call keeps 'b' and 'c' in the vec.
+ /// drain.keep_rest();
+ ///
+ /// // If we wouldn't call `keep_rest()`,
+ /// // `vec` would be empty.
+ /// assert_eq!(vec, ['b', 'c']);
+ /// ```
+ #[unstable(feature = "drain_keep_rest", issue = "101122")]
+ pub fn keep_rest(self) {
+ // At this moment layout looks like this:
+ //
+ // _____________________/-- old_len
+ // / \
+ // [kept] [yielded] [tail]
+ // \_______/ ^-- idx
+ // \-- del
+ //
+ // Normally `Drop` impl would drop [tail] (via .for_each(drop), ie still calling `pred`)
+ //
+ // 1. Move [tail] after [kept]
+ // 2. Update length of the original vec to `old_len - del`
+ // a. In case of ZST, this is the only thing we want to do
+ // 3. Do *not* drop self, as everything is put in a consistent state already, there is nothing to do
+ let mut this = ManuallyDrop::new(self);
+
+ unsafe {
+ // ZSTs have no identity, so we don't need to move them around.
+ let needs_move = mem::size_of::<T>() != 0;
+
+ if needs_move && this.idx < this.old_len && this.del > 0 {
+ let ptr = this.vec.as_mut_ptr();
+ let src = ptr.add(this.idx);
+ let dst = src.sub(this.del);
+ let tail_len = this.old_len - this.idx;
+ src.copy_to(dst, tail_len);
+ }
+
+ let new_len = this.old_len - this.del;
+ this.vec.set_len(new_len);
+ }
+ }
}
#[unstable(feature = "drain_filter", reason = "recently added", issue = "43244")]
#[cfg(not(no_global_oom_handling))]
use super::AsVecIntoIter;
use crate::alloc::{Allocator, Global};
+#[cfg(not(no_global_oom_handling))]
+use crate::collections::VecDeque;
use crate::raw_vec::RawVec;
+use core::array;
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::mem::{self, ManuallyDrop, MaybeUninit, SizedTypeProperties};
#[cfg(not(no_global_oom_handling))]
use core::ops::Deref;
use core::ptr::{self, NonNull};
// 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,
+ pub(super) end: *const T, // If T is a ZST, this is actually ptr+len. This encoding is picked so that
+ // ptr == end is a quick test for the Iterator being empty, that works
+ // for both ZST and non-ZST.
}
#[stable(feature = "vec_intoiter_debug", since = "1.13.0")]
}
/// Drops remaining elements and relinquishes the backing allocation.
+ /// This method guarantees it won't panic before relinquishing
+ /// the backing allocation.
///
/// This is roughly equivalent to the following, but more efficient
///
/// ```
/// # let mut into_iter = Vec::<u8>::with_capacity(10).into_iter();
+ /// let mut into_iter = std::mem::replace(&mut into_iter, Vec::new().into_iter());
/// (&mut into_iter).for_each(core::mem::drop);
- /// unsafe { core::ptr::write(&mut into_iter, Vec::new().into_iter()); }
+ /// std::mem::forget(into_iter);
/// ```
///
/// This method is used by in-place iteration, refer to the vec::in_place_collect
self.ptr = self.buf.as_ptr();
self.end = self.buf.as_ptr();
+ // Dropping the remaining elements can panic, so this needs to be
+ // done only after updating the other fields.
unsafe {
ptr::drop_in_place(remaining);
}
}
/// Forgets to Drop the remaining elements while still allowing the backing allocation to be freed.
- #[allow(dead_code)]
pub(crate) fn forget_remaining_elements(&mut self) {
- self.ptr = self.end;
+ // For th ZST case, it is crucial that we mutate `end` here, not `ptr`.
+ // `ptr` must stay aligned, while `end` may be unaligned.
+ self.end = self.ptr;
+ }
+
+ #[cfg(not(no_global_oom_handling))]
+ #[inline]
+ pub(crate) fn into_vecdeque(self) -> VecDeque<T, A> {
+ // Keep our `Drop` impl from dropping the elements and the allocator
+ let mut this = ManuallyDrop::new(self);
+
+ // SAFETY: This allocation originally came from a `Vec`, so it passes
+ // all those checks. We have `this.buf` ≤ `this.ptr` ≤ `this.end`,
+ // so the `sub_ptr`s below cannot wrap, and will produce a well-formed
+ // range. `end` ≤ `buf + cap`, so the range will be in-bounds.
+ // Taking `alloc` is ok because nothing else is going to look at it,
+ // since our `Drop` impl isn't going to run so there's no more code.
+ unsafe {
+ let buf = this.buf.as_ptr();
+ let initialized = if T::IS_ZST {
+ // All the pointers are the same for ZSTs, so it's fine to
+ // say that they're all at the beginning of the "allocation".
+ 0..this.len()
+ } else {
+ this.ptr.sub_ptr(buf)..this.end.sub_ptr(buf)
+ };
+ let cap = this.cap;
+ let alloc = ManuallyDrop::take(&mut this.alloc);
+ VecDeque::from_contiguous_raw_parts_in(buf, initialized, cap, alloc)
+ }
}
}
#[inline]
fn next(&mut self) -> Option<T> {
- if self.ptr as *const _ == self.end {
+ if self.ptr == 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 };
+ } else if T::IS_ZST {
+ // `ptr` has to stay where it is to remain aligned, so we reduce the length by 1 by
+ // reducing the `end`.
+ self.end = self.end.wrapping_byte_sub(1);
// Make up a value of this ZST.
Some(unsafe { mem::zeroed() })
} else {
let old = self.ptr;
- self.ptr = unsafe { self.ptr.offset(1) };
+ self.ptr = unsafe { self.ptr.add(1) };
Some(unsafe { ptr::read(old) })
}
#[inline]
fn size_hint(&self) -> (usize, Option<usize>) {
- let exact = if mem::size_of::<T>() == 0 {
+ let exact = if T::IS_ZST {
self.end.addr().wrapping_sub(self.ptr.addr())
} else {
unsafe { self.end.sub_ptr(self.ptr) }
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 }
+ if T::IS_ZST {
+ // See `next` for why we sub `end` here.
+ self.end = self.end.wrapping_byte_sub(step_size);
} else {
// SAFETY: the min() above ensures that step_size is in bounds
self.ptr = unsafe { self.ptr.add(step_size) };
self.len()
}
+ #[inline]
+ fn next_chunk<const N: usize>(&mut self) -> Result<[T; N], core::array::IntoIter<T, N>> {
+ let mut raw_ary = MaybeUninit::uninit_array();
+
+ let len = self.len();
+
+ if T::IS_ZST {
+ if len < N {
+ self.forget_remaining_elements();
+ // Safety: ZSTs can be conjured ex nihilo, only the amount has to be correct
+ return Err(unsafe { array::IntoIter::new_unchecked(raw_ary, 0..len) });
+ }
+
+ self.end = self.end.wrapping_byte_sub(N);
+ // Safety: ditto
+ return Ok(unsafe { raw_ary.transpose().assume_init() });
+ }
+
+ if len < N {
+ // Safety: `len` indicates that this many elements are available and we just checked that
+ // it fits into the array.
+ unsafe {
+ ptr::copy_nonoverlapping(self.ptr, raw_ary.as_mut_ptr() as *mut T, len);
+ self.forget_remaining_elements();
+ return Err(array::IntoIter::new_unchecked(raw_ary, 0..len));
+ }
+ }
+
+ // Safety: `len` is larger than the array size. Copy a fixed amount here to fully initialize
+ // the array.
+ return unsafe {
+ ptr::copy_nonoverlapping(self.ptr, raw_ary.as_mut_ptr() as *mut T, N);
+ self.ptr = self.ptr.add(N);
+ Ok(raw_ary.transpose().assume_init())
+ };
+ }
+
unsafe fn __iterator_get_unchecked(&mut self, i: usize) -> Self::Item
where
Self: TrustedRandomAccessNoCoerce,
// 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)) }
+ if T::IS_ZST { mem::zeroed() } else { ptr::read(self.ptr.add(i)) }
}
}
}
fn next_back(&mut self) -> Option<T> {
if self.end == self.ptr {
None
- } else if mem::size_of::<T>() == 0 {
+ } else if T::IS_ZST {
// See above for why 'ptr.offset' isn't used
- self.end = unsafe { arith_offset(self.end as *const i8, -1) as *mut T };
+ self.end = self.end.wrapping_byte_sub(1);
// Make up a value of this ZST.
Some(unsafe { mem::zeroed() })
} else {
- self.end = unsafe { self.end.offset(-1) };
+ self.end = unsafe { self.end.sub(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 {
+ if T::IS_ZST {
// 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
- }
+ self.end = self.end.wrapping_byte_sub(step_size);
} else {
// SAFETY: same as for advance_by()
- self.end = unsafe { self.end.offset(step_size.wrapping_neg() as isize) };
+ self.end = unsafe { self.end.sub(step_size) };
}
let to_drop = ptr::slice_from_raw_parts_mut(self.end as *mut T, step_size);
// SAFETY: same as for advance_by()
// SPDX-License-Identifier: Apache-2.0 OR MIT
+use core::num::{Saturating, Wrapping};
+
use crate::boxed::Box;
#[rustc_specialization_trait]
pub(super) unsafe trait IsZero {
- /// Whether this value's representation is all zeros
+ /// Whether this value's representation is all zeros,
+ /// or can be represented with all zeroes.
fn is_zero(&self) -> bool;
}
};
}
+impl_is_zero!(i8, |x| x == 0); // It is needed to impl for arrays and tuples of i8.
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!(u8, |x| x == 0); // It is needed to impl for arrays and tuples of u8.
impl_is_zero!(u16, |x| x == 0);
impl_is_zero!(u32, |x| x == 0);
impl_is_zero!(u64, |x| x == 0);
#[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
+ // it's worth doing if the array is really long. The threshold here
+ // is largely arbitrary, but was picked because as of 2022-07-01 LLVM
+ // fails to const-fold the check in `vec![[1; 32]; n]`
+ // See https://github.com/rust-lang/rust/pull/97581#issuecomment-1166628022
// Feel free to tweak if you have better evidence.
- N <= 32 && self.iter().all(IsZero::is_zero)
+ N <= 16 && self.iter().all(IsZero::is_zero)
+ }
+}
+
+// This is recursive macro.
+macro_rules! impl_for_tuples {
+ // Stopper
+ () => {
+ // No use for implementing for empty tuple because it is ZST.
+ };
+ ($first_arg:ident $(,$rest:ident)*) => {
+ unsafe impl <$first_arg: IsZero, $($rest: IsZero,)*> IsZero for ($first_arg, $($rest,)*){
+ #[inline]
+ fn is_zero(&self) -> bool{
+ // Destructure tuple to N references
+ // Rust allows to hide generic params by local variable names.
+ #[allow(non_snake_case)]
+ let ($first_arg, $($rest,)*) = self;
+
+ $first_arg.is_zero()
+ $( && $rest.is_zero() )*
+ }
+ }
+
+ impl_for_tuples!($($rest),*);
}
}
+impl_for_tuples!(A, B, C, D, E, F, G, H);
+
// `Option<&T>` and `Option<Box<T>>` are guaranteed to represent `None` as null.
// For fat pointers, the bytes that would be the pointer metadata in the `Some`
// variant are padding in the `None` variant, so ignoring them and
NonZeroUsize,
NonZeroIsize,
);
+
+macro_rules! impl_is_zero_option_of_num {
+ ($($t:ty,)+) => {$(
+ unsafe impl IsZero for Option<$t> {
+ #[inline]
+ fn is_zero(&self) -> bool {
+ const {
+ let none: Self = unsafe { core::mem::MaybeUninit::zeroed().assume_init() };
+ assert!(none.is_none());
+ }
+ self.is_none()
+ }
+ }
+ )+};
+}
+
+impl_is_zero_option_of_num!(u8, u16, u32, u64, u128, i8, i16, i32, i64, i128, usize, isize,);
+
+unsafe impl<T: IsZero> IsZero for Wrapping<T> {
+ #[inline]
+ fn is_zero(&self) -> bool {
+ self.0.is_zero()
+ }
+}
+
+unsafe impl<T: IsZero> IsZero for Saturating<T> {
+ #[inline]
+ fn is_zero(&self) -> bool {
+ self.0.is_zero()
+ }
+}
+
+macro_rules! impl_for_optional_bool {
+ ($($t:ty,)+) => {$(
+ unsafe impl IsZero for $t {
+ #[inline]
+ fn is_zero(&self) -> bool {
+ // SAFETY: This is *not* a stable layout guarantee, but
+ // inside `core` we're allowed to rely on the current rustc
+ // behaviour that options of bools will be one byte with
+ // no padding, so long as they're nested less than 254 deep.
+ let raw: u8 = unsafe { core::mem::transmute(*self) };
+ raw == 0
+ }
+ }
+ )+};
+}
+impl_for_optional_bool! {
+ Option<bool>,
+ Option<Option<bool>>,
+ Option<Option<Option<bool>>>,
+ // Could go further, but not worth the metadata overhead
+}
use core::convert::TryFrom;
use core::fmt;
use core::hash::{Hash, Hasher};
-use core::intrinsics::{arith_offset, assume};
+use core::intrinsics::assume;
use core::iter;
#[cfg(not(no_global_oom_handling))]
use core::iter::FromIterator;
use core::marker::PhantomData;
-use core::mem::{self, ManuallyDrop, MaybeUninit};
+use core::mem::{self, ManuallyDrop, MaybeUninit, SizedTypeProperties};
use core::ops::{self, Index, IndexMut, Range, RangeBounds};
use core::ptr::{self, NonNull};
use core::slice::{self, SliceIndex};
#[cfg(not(no_borrow))]
use crate::borrow::{Cow, ToOwned};
use crate::boxed::Box;
-use crate::collections::TryReserveError;
+use crate::collections::{TryReserveError, TryReserveErrorKind};
use crate::raw_vec::RawVec;
#[unstable(feature = "drain_filter", reason = "recently added", issue = "43244")]
mod set_len_on_drop;
#[cfg(not(no_global_oom_handling))]
-use self::in_place_drop::InPlaceDrop;
+use self::in_place_drop::{InPlaceDrop, InPlaceDstBufDrop};
#[cfg(not(no_global_oom_handling))]
mod in_place_drop;
/// vec[0] = 7;
/// assert_eq!(vec[0], 7);
///
-/// vec.extend([1, 2, 3].iter().copied());
+/// vec.extend([1, 2, 3]);
///
/// for x in &vec {
/// println!("{x}");
Vec { buf: RawVec::NEW, len: 0 }
}
- /// Constructs a new, empty `Vec<T>` with the specified capacity.
+ /// Constructs a new, empty `Vec<T>` with at least the specified capacity.
///
- /// The vector will be able to hold exactly `capacity` elements without
- /// reallocating. If `capacity` is 0, the vector will not allocate.
+ /// The vector will be able to hold at least `capacity` elements without
+ /// reallocating. This method is allowed to allocate for more elements than
+ /// `capacity`. If `capacity` is 0, the vector will not allocate.
///
/// It is important to note that although the returned vector has the
- /// *capacity* specified, the vector will have a zero *length*. For an
- /// explanation of the difference between length and capacity, see
+ /// minimum *capacity* specified, the vector will have a zero *length*. For
+ /// an explanation of the difference between length and capacity, see
/// *[Capacity and reallocation]*.
///
+ /// If it is important to know the exact allocated capacity of a `Vec`,
+ /// always use the [`capacity`] method after construction.
+ ///
+ /// For `Vec<T>` where `T` is a zero-sized type, there will be no allocation
+ /// and the capacity will always be `usize::MAX`.
+ ///
/// [Capacity and reallocation]: #capacity-and-reallocation
+ /// [`capacity`]: Vec::capacity
///
/// # Panics
///
///
/// // The vector contains no items, even though it has capacity for more
/// assert_eq!(vec.len(), 0);
- /// assert_eq!(vec.capacity(), 10);
+ /// assert!(vec.capacity() >= 10);
///
/// // These are all done without reallocating...
/// for i in 0..10 {
/// vec.push(i);
/// }
/// assert_eq!(vec.len(), 10);
- /// assert_eq!(vec.capacity(), 10);
+ /// assert!(vec.capacity() >= 10);
///
/// // ...but this may make the vector reallocate
/// vec.push(11);
/// assert_eq!(vec.len(), 11);
/// assert!(vec.capacity() >= 11);
+ ///
+ /// // A vector of a zero-sized type will always over-allocate, since no
+ /// // allocation is necessary
+ /// let vec_units = Vec::<()>::with_capacity(10);
+ /// assert_eq!(vec_units.capacity(), usize::MAX);
/// ```
#[cfg(not(no_global_oom_handling))]
#[inline]
Self::with_capacity_in(capacity, Global)
}
- /// Tries to construct a new, empty `Vec<T>` with the specified capacity.
+ /// Tries to construct a new, empty `Vec<T>` with at least the specified capacity.
///
- /// The vector will be able to hold exactly `capacity` elements without
- /// reallocating. If `capacity` is 0, the vector will not allocate.
+ /// The vector will be able to hold at least `capacity` elements without
+ /// reallocating. This method is allowed to allocate for more elements than
+ /// `capacity`. If `capacity` is 0, the vector will not allocate.
///
/// It is important to note that although the returned vector has the
- /// *capacity* specified, the vector will have a zero *length*. For an
- /// explanation of the difference between length and capacity, see
+ /// minimum *capacity* specified, the vector will have a zero *length*. For
+ /// an explanation of the difference between length and capacity, see
/// *[Capacity and reallocation]*.
///
+ /// If it is important to know the exact allocated capacity of a `Vec`,
+ /// always use the [`capacity`] method after construction.
+ ///
+ /// For `Vec<T>` where `T` is a zero-sized type, there will be no allocation
+ /// and the capacity will always be `usize::MAX`.
+ ///
/// [Capacity and reallocation]: #capacity-and-reallocation
+ /// [`capacity`]: Vec::capacity
///
/// # Examples
///
///
/// // The vector contains no items, even though it has capacity for more
/// assert_eq!(vec.len(), 0);
- /// assert_eq!(vec.capacity(), 10);
+ /// assert!(vec.capacity() >= 10);
///
/// // These are all done without reallocating...
/// for i in 0..10 {
/// vec.push(i);
/// }
/// assert_eq!(vec.len(), 10);
- /// assert_eq!(vec.capacity(), 10);
+ /// assert!(vec.capacity() >= 10);
///
/// // ...but this may make the vector reallocate
/// vec.push(11);
///
/// let mut result = Vec::try_with_capacity(usize::MAX);
/// assert!(result.is_err());
+ ///
+ /// // A vector of a zero-sized type will always over-allocate, since no
+ /// // allocation is necessary
+ /// let vec_units = Vec::<()>::try_with_capacity(10).unwrap();
+ /// assert_eq!(vec_units.capacity(), usize::MAX);
/// ```
#[inline]
#[stable(feature = "kernel", since = "1.0.0")]
Self::try_with_capacity_in(capacity, Global)
}
- /// Creates a `Vec<T>` directly from the raw components of another vector.
+ /// Creates a `Vec<T>` directly from a pointer, a capacity, and a length.
///
/// # Safety
///
/// This is highly unsafe, due to the number of invariants that aren't
/// checked:
///
- /// * `ptr` needs to have been previously allocated via [`String`]/`Vec<T>`
- /// (at least, it's highly likely to be incorrect if it wasn't).
+ /// * `ptr` must have been allocated using the global allocator, such as via
+ /// the [`alloc::alloc`] function.
/// * `T` needs to have the same alignment as what `ptr` was allocated with.
/// (`T` having a less strict alignment is not sufficient, the alignment really
/// needs to be equal to satisfy the [`dealloc`] requirement that memory must be
/// to be the same size as the pointer was allocated with. (Because similar to
/// alignment, [`dealloc`] must be called with the same layout `size`.)
/// * `length` needs to be less than or equal to `capacity`.
+ /// * The first `length` values must be properly initialized values of type `T`.
+ /// * `capacity` needs to be the capacity that the pointer was allocated with.
+ /// * The allocated size in bytes must be no larger than `isize::MAX`.
+ /// See the safety documentation of [`pointer::offset`].
+ ///
+ /// These requirements are always upheld by any `ptr` that has been allocated
+ /// via `Vec<T>`. Other allocation sources are allowed if the invariants are
+ /// upheld.
///
/// Violating these may cause problems like corrupting the allocator's
/// internal data structures. For example it is normally **not** safe
/// function.
///
/// [`String`]: crate::string::String
+ /// [`alloc::alloc`]: crate::alloc::alloc
/// [`dealloc`]: crate::alloc::GlobalAlloc::dealloc
///
/// # Examples
///
/// unsafe {
/// // Overwrite memory with 4, 5, 6
- /// for i in 0..len as isize {
- /// ptr::write(p.offset(i), 4 + i);
+ /// for i in 0..len {
+ /// ptr::write(p.add(i), 4 + i);
/// }
///
/// // Put everything back together into a Vec
/// assert_eq!(rebuilt, [4, 5, 6]);
/// }
/// ```
+ ///
+ /// Using memory that was allocated elsewhere:
+ ///
+ /// ```rust
+ /// #![feature(allocator_api)]
+ ///
+ /// use std::alloc::{AllocError, Allocator, Global, Layout};
+ ///
+ /// fn main() {
+ /// let layout = Layout::array::<u32>(16).expect("overflow cannot happen");
+ ///
+ /// let vec = unsafe {
+ /// let mem = match Global.allocate(layout) {
+ /// Ok(mem) => mem.cast::<u32>().as_ptr(),
+ /// Err(AllocError) => return,
+ /// };
+ ///
+ /// mem.write(1_000_000);
+ ///
+ /// Vec::from_raw_parts_in(mem, 1, 16, Global)
+ /// };
+ ///
+ /// assert_eq!(vec, &[1_000_000]);
+ /// assert_eq!(vec.capacity(), 16);
+ /// }
+ /// ```
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
pub unsafe fn from_raw_parts(ptr: *mut T, length: usize, capacity: usize) -> Self {
Vec { buf: RawVec::new_in(alloc), len: 0 }
}
- /// Constructs a new, empty `Vec<T, A>` with the specified capacity with the provided
- /// allocator.
+ /// Constructs a new, empty `Vec<T, A>` with at least the specified capacity
+ /// with the provided allocator.
///
- /// The vector will be able to hold exactly `capacity` elements without
- /// reallocating. If `capacity` is 0, the vector will not allocate.
+ /// The vector will be able to hold at least `capacity` elements without
+ /// reallocating. This method is allowed to allocate for more elements than
+ /// `capacity`. If `capacity` is 0, the vector will not allocate.
///
/// It is important to note that although the returned vector has the
- /// *capacity* specified, the vector will have a zero *length*. For an
- /// explanation of the difference between length and capacity, see
+ /// minimum *capacity* specified, the vector will have a zero *length*. For
+ /// an explanation of the difference between length and capacity, see
/// *[Capacity and reallocation]*.
///
+ /// If it is important to know the exact allocated capacity of a `Vec`,
+ /// always use the [`capacity`] method after construction.
+ ///
+ /// For `Vec<T, A>` where `T` is a zero-sized type, there will be no allocation
+ /// and the capacity will always be `usize::MAX`.
+ ///
/// [Capacity and reallocation]: #capacity-and-reallocation
+ /// [`capacity`]: Vec::capacity
///
/// # Panics
///
/// vec.push(11);
/// assert_eq!(vec.len(), 11);
/// assert!(vec.capacity() >= 11);
+ ///
+ /// // A vector of a zero-sized type will always over-allocate, since no
+ /// // allocation is necessary
+ /// let vec_units = Vec::<(), System>::with_capacity_in(10, System);
+ /// assert_eq!(vec_units.capacity(), usize::MAX);
/// ```
#[cfg(not(no_global_oom_handling))]
#[inline]
Vec { buf: RawVec::with_capacity_in(capacity, alloc), len: 0 }
}
- /// Tries to construct a new, empty `Vec<T, A>` with the specified capacity
+ /// Tries to construct a new, empty `Vec<T, A>` with at least the specified capacity
/// with the provided allocator.
///
- /// The vector will be able to hold exactly `capacity` elements without
- /// reallocating. If `capacity` is 0, the vector will not allocate.
+ /// The vector will be able to hold at least `capacity` elements without
+ /// reallocating. This method is allowed to allocate for more elements than
+ /// `capacity`. If `capacity` is 0, the vector will not allocate.
///
/// It is important to note that although the returned vector has the
- /// *capacity* specified, the vector will have a zero *length*. For an
- /// explanation of the difference between length and capacity, see
+ /// minimum *capacity* specified, the vector will have a zero *length*. For
+ /// an explanation of the difference between length and capacity, see
/// *[Capacity and reallocation]*.
///
+ /// If it is important to know the exact allocated capacity of a `Vec`,
+ /// always use the [`capacity`] method after construction.
+ ///
+ /// For `Vec<T, A>` where `T` is a zero-sized type, there will be no allocation
+ /// and the capacity will always be `usize::MAX`.
+ ///
/// [Capacity and reallocation]: #capacity-and-reallocation
+ /// [`capacity`]: Vec::capacity
///
/// # Examples
///
///
/// let mut result = Vec::try_with_capacity_in(usize::MAX, System);
/// assert!(result.is_err());
+ ///
+ /// // A vector of a zero-sized type will always over-allocate, since no
+ /// // allocation is necessary
+ /// let vec_units = Vec::<(), System>::try_with_capacity_in(10, System).unwrap();
+ /// assert_eq!(vec_units.capacity(), usize::MAX);
/// ```
#[inline]
#[stable(feature = "kernel", since = "1.0.0")]
Ok(Vec { buf: RawVec::try_with_capacity_in(capacity, alloc)?, len: 0 })
}
- /// Creates a `Vec<T, A>` directly from the raw components of another vector.
+ /// Creates a `Vec<T, A>` directly from a pointer, a capacity, a length,
+ /// and an allocator.
///
/// # Safety
///
/// This is highly unsafe, due to the number of invariants that aren't
/// checked:
///
- /// * `ptr` needs to have been previously allocated via [`String`]/`Vec<T>`
- /// (at least, it's highly likely to be incorrect if it wasn't).
- /// * `T` needs to have the same size and alignment as what `ptr` was allocated with.
+ /// * `ptr` must be [*currently allocated*] via the given allocator `alloc`.
+ /// * `T` needs to have the same alignment as what `ptr` was allocated with.
/// (`T` having a less strict alignment is not sufficient, the alignment really
/// needs to be equal to satisfy the [`dealloc`] requirement that memory must be
/// allocated and deallocated with the same layout.)
+ /// * The size of `T` times the `capacity` (ie. the allocated size in bytes) needs
+ /// to be the same size as the pointer was allocated with. (Because similar to
+ /// alignment, [`dealloc`] must be called with the same layout `size`.)
/// * `length` needs to be less than or equal to `capacity`.
- /// * `capacity` needs to be the capacity that the pointer was allocated with.
+ /// * The first `length` values must be properly initialized values of type `T`.
+ /// * `capacity` needs to [*fit*] the layout size that the pointer was allocated with.
+ /// * The allocated size in bytes must be no larger than `isize::MAX`.
+ /// See the safety documentation of [`pointer::offset`].
+ ///
+ /// These requirements are always upheld by any `ptr` that has been allocated
+ /// via `Vec<T, A>`. Other allocation sources are allowed if the invariants are
+ /// upheld.
///
/// Violating these may cause problems like corrupting the allocator's
/// internal data structures. For example it is **not** safe
///
/// [`String`]: crate::string::String
/// [`dealloc`]: crate::alloc::GlobalAlloc::dealloc
+ /// [*currently allocated*]: crate::alloc::Allocator#currently-allocated-memory
+ /// [*fit*]: crate::alloc::Allocator#memory-fitting
///
/// # Examples
///
///
/// unsafe {
/// // Overwrite memory with 4, 5, 6
- /// for i in 0..len as isize {
- /// ptr::write(p.offset(i), 4 + i);
+ /// for i in 0..len {
+ /// ptr::write(p.add(i), 4 + i);
/// }
///
/// // Put everything back together into a Vec
/// assert_eq!(rebuilt, [4, 5, 6]);
/// }
/// ```
+ ///
+ /// Using memory that was allocated elsewhere:
+ ///
+ /// ```rust
+ /// use std::alloc::{alloc, Layout};
+ ///
+ /// fn main() {
+ /// let layout = Layout::array::<u32>(16).expect("overflow cannot happen");
+ /// let vec = unsafe {
+ /// let mem = alloc(layout).cast::<u32>();
+ /// if mem.is_null() {
+ /// return;
+ /// }
+ ///
+ /// mem.write(1_000_000);
+ ///
+ /// Vec::from_raw_parts(mem, 1, 16)
+ /// };
+ ///
+ /// assert_eq!(vec, &[1_000_000]);
+ /// assert_eq!(vec.capacity(), 16);
+ /// }
+ /// ```
#[inline]
#[unstable(feature = "allocator_api", issue = "32838")]
pub unsafe fn from_raw_parts_in(ptr: *mut T, length: usize, capacity: usize, alloc: A) -> Self {
(ptr, len, capacity, alloc)
}
- /// Returns the number of elements the vector can hold without
+ /// Returns the total number of elements the vector can hold without
/// reallocating.
///
/// # Examples
///
/// ```
- /// let vec: Vec<i32> = Vec::with_capacity(10);
+ /// let mut vec: Vec<i32> = Vec::with_capacity(10);
+ /// vec.push(42);
/// assert_eq!(vec.capacity(), 10);
/// ```
#[inline]
}
/// Reserves capacity for at least `additional` more elements to be inserted
- /// in the given `Vec<T>`. The collection may reserve more space to avoid
- /// frequent reallocations. After calling `reserve`, capacity will be
- /// greater than or equal to `self.len() + additional`. Does nothing if
- /// capacity is already sufficient.
+ /// in the given `Vec<T>`. The collection may reserve more space to
+ /// speculatively avoid frequent reallocations. After calling `reserve`,
+ /// capacity will be greater than or equal to `self.len() + additional`.
+ /// Does nothing if capacity is already sufficient.
///
/// # Panics
///
self.buf.reserve(self.len, additional);
}
- /// Reserves the minimum capacity for exactly `additional` more elements to
- /// be inserted in the given `Vec<T>`. After calling `reserve_exact`,
- /// capacity will be greater than or equal to `self.len() + additional`.
- /// Does nothing if the capacity is already sufficient.
+ /// Reserves the minimum capacity for at least `additional` more elements to
+ /// be inserted in the given `Vec<T>`. Unlike [`reserve`], this will not
+ /// deliberately over-allocate to speculatively avoid frequent allocations.
+ /// After calling `reserve_exact`, capacity will be greater than or equal to
+ /// `self.len() + additional`. Does nothing if the capacity is already
+ /// sufficient.
///
/// Note that the allocator may give the collection more space than it
/// requests. Therefore, capacity can not be relied upon to be precisely
}
/// Tries to reserve capacity for at least `additional` more elements to be inserted
- /// in the given `Vec<T>`. The collection may reserve more space to avoid
+ /// in the given `Vec<T>`. The collection may reserve more space to speculatively avoid
/// frequent reallocations. After calling `try_reserve`, capacity will be
- /// greater than or equal to `self.len() + additional`. Does nothing if
- /// capacity is already sufficient.
+ /// greater than or equal to `self.len() + additional` if it returns
+ /// `Ok(())`. Does nothing if capacity is already sufficient. This method
+ /// preserves the contents even if an error occurs.
///
/// # Errors
///
self.buf.try_reserve(self.len, additional)
}
- /// Tries to reserve the minimum capacity for exactly `additional`
- /// elements to be inserted in the given `Vec<T>`. After calling
- /// `try_reserve_exact`, capacity will be greater than or equal to
- /// `self.len() + additional` if it returns `Ok(())`.
+ /// Tries to reserve the minimum capacity for at least `additional`
+ /// elements to be inserted in the given `Vec<T>`. Unlike [`try_reserve`],
+ /// this will not deliberately over-allocate to speculatively avoid frequent
+ /// allocations. After calling `try_reserve_exact`, capacity will be greater
+ /// than or equal to `self.len() + additional` if it returns `Ok(())`.
/// Does nothing if the capacity is already sufficient.
///
/// Note that the allocator may give the collection more space than it
/// Converts the vector into [`Box<[T]>`][owned slice].
///
- /// Note that this will drop any excess capacity.
+ /// If the vector has excess capacity, its items will be moved into a
+ /// newly-allocated buffer with exactly the right capacity.
///
/// [owned slice]: Box
///
self
}
- /// Returns a raw pointer to the vector's buffer.
+ /// Returns a raw pointer to the vector's buffer, or a dangling raw pointer
+ /// valid for zero sized reads if the vector didn't allocate.
///
/// The caller must ensure that the vector outlives the pointer this
/// function returns, or else it will end up pointing to garbage.
ptr
}
- /// Returns an unsafe mutable pointer to the vector's buffer.
+ /// Returns an unsafe mutable pointer to the vector's buffer, or a dangling
+ /// raw pointer valid for zero sized reads if the vector didn't allocate.
///
/// The caller must ensure that the vector outlives the pointer this
/// function returns, or else it will end up pointing to garbage.
}
let len = self.len();
- if index > len {
- assert_failed(index, len);
- }
// space for the new element
if len == self.buf.capacity() {
// The spot to put the new value
{
let p = self.as_mut_ptr().add(index);
- // Shift everything over to make space. (Duplicating the
- // `index`th element into two consecutive places.)
- ptr::copy(p, p.offset(1), len - index);
+ if index < len {
+ // Shift everything over to make space. (Duplicating the
+ // `index`th element into two consecutive places.)
+ ptr::copy(p, p.add(1), len - index);
+ } else if index == len {
+ // No elements need shifting.
+ } else {
+ assert_failed(index, len);
+ }
// Write it in, overwriting the first copy of the `index`th
// element.
ptr::write(p, element);
ret = ptr::read(ptr);
// Shift everything down to fill in that spot.
- ptr::copy(ptr.offset(1), ptr, len - index - 1);
+ ptr::copy(ptr.add(1), ptr, len - index - 1);
}
self.set_len(len - 1);
ret
///
/// ```
/// let mut vec = vec![1, 2, 3, 4];
- /// vec.retain_mut(|x| if *x > 3 {
- /// false
- /// } else {
+ /// vec.retain_mut(|x| if *x <= 3 {
/// *x += 1;
/// true
+ /// } else {
+ /// false
/// });
/// assert_eq!(vec, [2, 3, 4]);
/// ```
Ok(())
}
+ /// Appends an element if there is sufficient spare capacity, otherwise an error is returned
+ /// with the element.
+ ///
+ /// Unlike [`push`] this method will not reallocate when there's insufficient capacity.
+ /// The caller should use [`reserve`] or [`try_reserve`] to ensure that there is enough capacity.
+ ///
+ /// [`push`]: Vec::push
+ /// [`reserve`]: Vec::reserve
+ /// [`try_reserve`]: Vec::try_reserve
+ ///
+ /// # Examples
+ ///
+ /// A manual, panic-free alternative to [`FromIterator`]:
+ ///
+ /// ```
+ /// #![feature(vec_push_within_capacity)]
+ ///
+ /// use std::collections::TryReserveError;
+ /// fn from_iter_fallible<T>(iter: impl Iterator<Item=T>) -> Result<Vec<T>, TryReserveError> {
+ /// let mut vec = Vec::new();
+ /// for value in iter {
+ /// if let Err(value) = vec.push_within_capacity(value) {
+ /// vec.try_reserve(1)?;
+ /// // this cannot fail, the previous line either returned or added at least 1 free slot
+ /// let _ = vec.push_within_capacity(value);
+ /// }
+ /// }
+ /// Ok(vec)
+ /// }
+ /// assert_eq!(from_iter_fallible(0..100), Ok(Vec::from_iter(0..100)));
+ /// ```
+ #[inline]
+ #[unstable(feature = "vec_push_within_capacity", issue = "100486")]
+ pub fn push_within_capacity(&mut self, value: T) -> Result<(), T> {
+ if self.len == self.buf.capacity() {
+ return Err(value);
+ }
+ unsafe {
+ let end = self.as_mut_ptr().add(self.len);
+ ptr::write(end, value);
+ self.len += 1;
+ }
+ Ok(())
+ }
+
/// Removes the last element from a vector and returns it, or [`None`] if it
/// is empty.
///
///
/// # Panics
///
- /// Panics if the number of elements in the vector overflows a `usize`.
+ /// Panics if the new capacity exceeds `isize::MAX` bytes.
///
/// # Examples
///
unsafe {
// set self.vec length's to start, to be safe in case Drain is leaked
self.set_len(start);
- // Use the borrow in the IterMut to indicate borrowing behavior of the
- // whole Drain iterator (like &mut T).
- let range_slice = slice::from_raw_parts_mut(self.as_mut_ptr().add(start), end - start);
+ let range_slice = slice::from_raw_parts(self.as_ptr().add(start), end - start);
Drain {
tail_start: end,
tail_len: len - end,
{
let len = self.len();
if new_len > len {
- self.extend_with(new_len - len, ExtendFunc(f));
+ self.extend_trusted(iter::repeat_with(f).take(new_len - len));
} else {
self.truncate(new_len);
}
/// static_ref[0] += 1;
/// assert_eq!(static_ref, &[2, 2, 3]);
/// ```
- #[cfg(not(no_global_oom_handling))]
#[stable(feature = "vec_leak", since = "1.47.0")]
#[inline]
pub fn leak<'a>(self) -> &'a mut [T]
self.reserve(range.len());
// SAFETY:
- // - `slice::range` guarantees that the given range is valid for indexing self
+ // - `slice::range` guarantees that the given range is valid for indexing self
unsafe {
self.spec_extend_from_within(range);
}
#[unstable(feature = "slice_flatten", issue = "95629")]
pub fn into_flattened(self) -> Vec<T, A> {
let (ptr, len, cap, alloc) = self.into_raw_parts_with_alloc();
- let (new_len, new_cap) = if mem::size_of::<T>() == 0 {
+ let (new_len, new_cap) = if T::IS_ZST {
(len.checked_mul(N).expect("vec len overflow"), usize::MAX)
} else {
// SAFETY:
}
}
-struct ExtendFunc<F>(F);
-impl<T, F: FnMut() -> T> ExtendWith<T> for ExtendFunc<F> {
- fn next(&mut self) -> T {
- (self.0)()
- }
- fn last(mut self) -> T {
- (self.0)()
- }
-}
-
impl<T, A: Allocator> Vec<T, A> {
#[cfg(not(no_global_oom_handling))]
/// Extend the vector by `n` values, using the given generator.
// Write all elements except the last one
for _ in 1..n {
ptr::write(ptr, value.next());
- ptr = ptr.offset(1);
+ ptr = ptr.add(1);
// Increment the length in every step in case next() panics
local_len.increment_len(1);
}
// Write all elements except the last one
for _ in 1..n {
ptr::write(ptr, value.next());
- ptr = ptr.offset(1);
+ ptr = ptr.add(1);
// Increment the length in every step in case next() panics
local_len.increment_len(1);
}
let (this, spare, len) = unsafe { self.split_at_spare_mut_with_len() };
// SAFETY:
- // - caller guaratees that src is a valid index
+ // - caller guarantees that src is a valid index
let to_clone = unsafe { this.get_unchecked(src) };
iter::zip(to_clone, spare)
let (init, spare) = self.split_at_spare_mut();
// SAFETY:
- // - caller guaratees that `src` is a valid index
+ // - caller guarantees that `src` is a valid index
let source = unsafe { init.get_unchecked(src) };
// SAFETY:
// - Both pointers are created from unique slice references (`&mut [_]`)
// so they are valid and do not overlap.
- // - Elements are :Copy so it's OK to to copy them, without doing
+ // - Elements are :Copy so it's OK to copy them, without doing
// anything with the original values
// - `count` is equal to the len of `source`, so source is valid for
// `count` reads
impl<T, A: Allocator> ops::Deref for Vec<T, A> {
type Target = [T];
+ #[inline]
fn deref(&self) -> &[T] {
unsafe { slice::from_raw_parts(self.as_ptr(), self.len) }
}
#[stable(feature = "rust1", since = "1.0.0")]
impl<T, A: Allocator> ops::DerefMut for Vec<T, A> {
+ #[inline]
fn deref_mut(&mut self) -> &mut [T] {
unsafe { slice::from_raw_parts_mut(self.as_mut_ptr(), self.len) }
}
// HACK(japaric): with cfg(test) the inherent `[T]::to_vec` method, which is
// required for this method definition, is not available. Instead use the
- // `slice::to_vec` function which is only available with cfg(test)
+ // `slice::to_vec` function which is only available with cfg(test)
// NB see the slice::hack module in slice.rs for more information
#[cfg(test)]
fn clone(&self) -> Self {
///
/// ```
/// let v = vec!["a".to_string(), "b".to_string()];
- /// for s in v.into_iter() {
- /// // s has type String, not &String
- /// println!("{s}");
- /// }
+ /// let mut v_iter = v.into_iter();
+ ///
+ /// let first_element: Option<String> = v_iter.next();
+ ///
+ /// assert_eq!(first_element, Some("a".to_string()));
+ /// assert_eq!(v_iter.next(), Some("b".to_string()));
+ /// assert_eq!(v_iter.next(), None);
/// ```
#[inline]
- fn into_iter(self) -> IntoIter<T, A> {
+ fn into_iter(self) -> Self::IntoIter {
unsafe {
let mut me = ManuallyDrop::new(self);
let alloc = ManuallyDrop::new(ptr::read(me.allocator()));
let begin = me.as_mut_ptr();
- let end = if mem::size_of::<T>() == 0 {
- arith_offset(begin as *const i8, me.len() as isize) as *const T
+ let end = if T::IS_ZST {
+ begin.wrapping_byte_add(me.len())
} else {
begin.add(me.len()) as *const T
};
type Item = &'a T;
type IntoIter = slice::Iter<'a, T>;
- fn into_iter(self) -> slice::Iter<'a, T> {
+ fn into_iter(self) -> Self::IntoIter {
self.iter()
}
}
type Item = &'a mut T;
type IntoIter = slice::IterMut<'a, T>;
- fn into_iter(self) -> slice::IterMut<'a, T> {
+ fn into_iter(self) -> Self::IntoIter {
self.iter_mut()
}
}
Ok(())
}
+ // specific extend for `TrustedLen` iterators, called both by the specializations
+ // and internal places where resolving specialization makes compilation slower
+ #[cfg(not(no_global_oom_handling))]
+ fn extend_trusted(&mut self, iterator: impl iter::TrustedLen<Item = T>) {
+ let (low, high) = iterator.size_hint();
+ if let Some(additional) = high {
+ debug_assert_eq!(
+ low,
+ additional,
+ "TrustedLen iterator's size hint is not exact: {:?}",
+ (low, high)
+ );
+ self.reserve(additional);
+ unsafe {
+ let ptr = self.as_mut_ptr();
+ let mut local_len = SetLenOnDrop::new(&mut self.len);
+ iterator.for_each(move |element| {
+ ptr::write(ptr.add(local_len.current_len()), element);
+ // Since the loop executes user code which can panic we have to update
+ // the length every step to correctly drop what we've written.
+ // NB can't overflow since we would have had to alloc the address space
+ local_len.increment_len(1);
+ });
+ }
+ } else {
+ // Per TrustedLen contract a `None` upper bound means that the iterator length
+ // truly exceeds usize::MAX, which would eventually lead to a capacity overflow anyway.
+ // Since the other branch already panics eagerly (via `reserve()`) we do the same here.
+ // This avoids additional codegen for a fallback code path which would eventually
+ // panic anyway.
+ panic!("capacity overflow");
+ }
+ }
+
+ // specific extend for `TrustedLen` iterators, called both by the specializations
+ // and internal places where resolving specialization makes compilation slower
+ fn try_extend_trusted(&mut self, iterator: impl iter::TrustedLen<Item = T>) -> Result<(), TryReserveError> {
+ let (low, high) = iterator.size_hint();
+ if let Some(additional) = high {
+ debug_assert_eq!(
+ low,
+ additional,
+ "TrustedLen iterator's size hint is not exact: {:?}",
+ (low, high)
+ );
+ self.try_reserve(additional)?;
+ unsafe {
+ let ptr = self.as_mut_ptr();
+ let mut local_len = SetLenOnDrop::new(&mut self.len);
+ iterator.for_each(move |element| {
+ ptr::write(ptr.add(local_len.current_len()), element);
+ // Since the loop executes user code which can panic we have to update
+ // the length every step to correctly drop what we've written.
+ // NB can't overflow since we would have had to alloc the address space
+ local_len.increment_len(1);
+ });
+ }
+ Ok(())
+ } else {
+ Err(TryReserveErrorKind::CapacityOverflow.into())
+ }
+ }
+
/// Creates a splicing iterator that replaces the specified range in the vector
/// with the given `replace_with` iterator and yields the removed items.
/// `replace_with` does not need to be the same length as `range`.
#[rustc_const_unstable(feature = "const_default_impls", issue = "87864")]
impl<T> const Default for Vec<T> {
/// Creates an empty `Vec<T>`.
+ ///
+ /// The vector will not allocate until elements are pushed onto it.
fn default() -> Vec<T> {
Vec::new()
}
/// ```
#[cfg(not(test))]
fn from(s: [T; N]) -> Vec<T> {
- <[T]>::into_vec(box s)
+ <[T]>::into_vec(
+ #[rustc_box]
+ Box::new(s),
+ )
}
#[cfg(test)]
fn from(s: [T; N]) -> Vec<T> {
- crate::slice::into_vec(box s)
+ crate::slice::into_vec(Box::new(s))
}
}
}
}
-// note: test pulls in libstd, which causes errors here
+// note: test pulls in std, which causes errors here
#[cfg(not(test))]
#[stable(feature = "vec_from_box", since = "1.18.0")]
impl<T, A: Allocator> From<Box<[T], A>> for Vec<T, A> {
}
}
-// note: test pulls in libstd, which causes errors here
+// note: test pulls in std, which causes errors here
#[cfg(not(no_global_oom_handling))]
#[cfg(not(test))]
#[stable(feature = "box_from_vec", since = "1.20.0")]
/// ```
/// assert_eq!(Box::from(vec![1, 2, 3]), vec![1, 2, 3].into_boxed_slice());
/// ```
+ ///
+ /// Any excess capacity is removed:
+ /// ```
+ /// let mut vec = Vec::with_capacity(10);
+ /// vec.extend([1, 2, 3]);
+ ///
+ /// assert_eq!(Box::from(vec), vec![1, 2, 3].into_boxed_slice());
+ /// ```
fn from(v: Vec<T, A>) -> Self {
v.into_boxed_slice()
}
pub(super) fn increment_len(&mut self, increment: usize) {
self.local_len += increment;
}
+
+ #[inline]
+ pub(super) fn current_len(&self) -> usize {
+ self.local_len
+ }
}
impl Drop for SetLenOnDrop<'_> {
// SPDX-License-Identifier: Apache-2.0 OR MIT
use crate::alloc::Allocator;
-use crate::collections::{TryReserveError, TryReserveErrorKind};
+use crate::collections::TryReserveError;
use core::iter::TrustedLen;
-use core::ptr::{self};
use core::slice::{self};
-use super::{IntoIter, SetLenOnDrop, Vec};
+use super::{IntoIter, Vec};
// Specialization trait used for Vec::extend
#[cfg(not(no_global_oom_handling))]
I: TrustedLen<Item = T>,
{
default fn spec_extend(&mut self, iterator: I) {
- // This is the case for a TrustedLen iterator.
- let (low, high) = iterator.size_hint();
- if let Some(additional) = high {
- debug_assert_eq!(
- low,
- additional,
- "TrustedLen iterator's size hint is not exact: {:?}",
- (low, high)
- );
- self.reserve(additional);
- unsafe {
- let mut ptr = self.as_mut_ptr().add(self.len());
- let mut local_len = SetLenOnDrop::new(&mut self.len);
- iterator.for_each(move |element| {
- ptr::write(ptr, element);
- ptr = ptr.offset(1);
- // Since the loop executes user code which can panic we have to bump the pointer
- // after each step.
- // NB can't overflow since we would have had to alloc the address space
- local_len.increment_len(1);
- });
- }
- } else {
- // Per TrustedLen contract a `None` upper bound means that the iterator length
- // truly exceeds usize::MAX, which would eventually lead to a capacity overflow anyway.
- // Since the other branch already panics eagerly (via `reserve()`) we do the same here.
- // This avoids additional codegen for a fallback code path which would eventually
- // panic anyway.
- panic!("capacity overflow");
- }
+ self.extend_trusted(iterator)
}
}
I: TrustedLen<Item = T>,
{
default fn try_spec_extend(&mut self, iterator: I) -> Result<(), TryReserveError> {
- // This is the case for a TrustedLen iterator.
- let (low, high) = iterator.size_hint();
- if let Some(additional) = high {
- debug_assert_eq!(
- low,
- additional,
- "TrustedLen iterator's size hint is not exact: {:?}",
- (low, high)
- );
- self.try_reserve(additional)?;
- unsafe {
- let mut ptr = self.as_mut_ptr().add(self.len());
- let mut local_len = SetLenOnDrop::new(&mut self.len);
- iterator.for_each(move |element| {
- ptr::write(ptr, element);
- ptr = ptr.offset(1);
- // Since the loop executes user code which can panic we have to bump the pointer
- // after each step.
- // NB can't overflow since we would have had to alloc the address space
- local_len.increment_len(1);
- });
- }
- Ok(())
- } else {
- Err(TryReserveErrorKind::CapacityOverflow.into())
- }
+ self.try_extend_trusted(iterator)
}
}
//! using this crate.
#![no_std]
-#![feature(core_ffi_c)]
// See <https://github.com/rust-lang/rust-bindgen/issues/1651>.
#![cfg_attr(test, allow(deref_nullptr))]
#![cfg_attr(test, allow(unaligned_references))]
/// assert!(n > 1); // Run-time check
/// }
/// ```
+///
+/// [`static_assert!`]: crate::static_assert!
#[macro_export]
macro_rules! build_assert {
($cond:expr $(,)?) => {{
//! [`Opaque`]: kernel::types::Opaque
//! [`Opaque::ffi_init`]: kernel::types::Opaque::ffi_init
//! [`pin_data`]: ::macros::pin_data
+//! [`pin_init!`]: crate::pin_init!
use crate::{
error::{self, Error},
/// A normal `let` binding with optional type annotation. The expression is expected to implement
/// [`PinInit`]/[`Init`] with the error type [`Infallible`]. If you want to use a different error
/// type, then use [`stack_try_pin_init!`].
+///
+/// [`stack_try_pin_init!`]: crate::stack_try_pin_init!
#[macro_export]
macro_rules! stack_pin_init {
(let $var:ident $(: $t:ty)? = $val:expr) => {
///
/// This initializer is for initializing data in-place that might later be moved. If you want to
/// pin-initialize, use [`pin_init!`].
+///
+/// [`try_init!`]: crate::try_init!
// For a detailed example of how this macro works, see the module documentation of the hidden
// module `__internal` inside of `init/__internal.rs`.
#[macro_export]
#![no_std]
#![feature(allocator_api)]
#![feature(coerce_unsized)]
-#![feature(core_ffi_c)]
#![feature(dispatch_from_dyn)]
-#![feature(explicit_generic_args_with_impl_trait)]
-#![feature(generic_associated_types)]
#![feature(new_uninit)]
-#![feature(pin_macro)]
#![feature(receiver_trait)]
#![feature(unsize)]
/// [`std::dbg`]: https://doc.rust-lang.org/std/macro.dbg.html
/// [`eprintln`]: https://doc.rust-lang.org/std/macro.eprintln.html
/// [`printk`]: https://www.kernel.org/doc/html/latest/core-api/printk-basics.html
+/// [`pr_info`]: crate::pr_info!
+/// [`pr_debug`]: crate::pr_debug!
#[macro_export]
macro_rules! dbg {
// NOTE: We cannot use `concat!` to make a static string as a format argument
//! userspace APIs.
#![no_std]
-#![feature(core_ffi_c)]
// See <https://github.com/rust-lang/rust-bindgen/issues/1651>.
#![cfg_attr(test, allow(deref_nullptr))]
#![cfg_attr(test, allow(unaligned_references))]
# Compile Rust sources (.rs)
# ---------------------------------------------------------------------------
-rust_allowed_features := core_ffi_c,explicit_generic_args_with_impl_trait,new_uninit,pin_macro
+rust_allowed_features := new_uninit
rust_common_cmd = \
RUST_MODFILE=$(modfile) $(RUSTC_OR_CLIPPY) $(rust_flags) \
fi
;;
rustc)
- echo 1.62.0
+ echo 1.68.2
;;
bindgen)
echo 0.56.0
projects / users / hch / configfs.git / commitdiff