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document is_aligned{,_to}

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This commit is contained in:
Lukas Markeffsky 2022-10-22 19:15:03 +02:00
parent a906f6cb69
commit 093c02ed46
2 changed files with 268 additions and 8 deletions
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138
library/core/src/ptr/const_ptr.rs
View file

@ -1364,8 +1364,72 @@ impl<T: ?Sized> *const T {
}
/// Returns whether the pointer is properly aligned for `T`.
// #[cfg(not(bootstrap))] -- Calling this function in a const context from the bootstrap
// compiler will always return false.
///
/// # Examples
///
/// Basic usage:
/// ```
/// #![feature(pointer_is_aligned)]
/// #![feature(pointer_byte_offsets)]
///
/// let data: i32 = 42;
/// let ptr: *const i32 = &data;
///
/// assert!(ptr.is_aligned());
/// assert!(!ptr.wrapping_byte_add(1).is_aligned());
/// ```
///
/// # At compiletime
/// **Note: Alignment at compiletime is experimental and subject to change. See the
/// [tracking issue] for details.**
///
/// At compiletime, the compiler may not know where a value will end up in memory.
/// Calling this function on a pointer created from a reference at compiletime will only
/// return `true` if the pointer is guaranteed to be aligned. This means that the pointer
/// is never aligned if cast to a type with a stricter alignment than the reference's
/// underlying allocation.
///
#[cfg_attr(bootstrap, doc = "```ignore")]
#[cfg_attr(not(bootstrap), doc = "```")]
/// #![feature(pointer_is_aligned)]
/// #![feature(const_pointer_is_aligned)]
///
/// const _: () = {
/// let data: i32 = 42;
/// let ptr: *const i32 = &data;
/// assert!(ptr.is_aligned());
///
/// // At runtime either `ptr1` or `ptr2` would be aligned,
/// // but at compiletime neither is aligned.
/// let ptr1: *const i64 = ptr.cast();
/// let ptr2: *const i64 = ptr.wrapping_add(1).cast();
/// assert!(!ptr1.is_aligned());
/// assert!(!ptr2.is_aligned());
/// };
/// ```
///
/// If a pointer is created from a fixed address, this function behaves the same during
/// runtime and compiletime.
///
#[cfg_attr(bootstrap, doc = "```ignore")]
#[cfg_attr(not(bootstrap), doc = "```")]
/// #![feature(pointer_is_aligned)]
/// #![feature(const_pointer_is_aligned)]
///
/// const _: () = {
/// let ptr = 40 as *const i32;
/// assert!(ptr.is_aligned());
///
/// // For pointers with a known address, runtime and
/// // compiletime behavior are identical.
/// let ptr1: *const i64 = ptr.cast();
/// let ptr2: *const i64 = ptr.wrapping_add(1).cast();
/// assert!(ptr1.is_aligned());
/// assert!(!ptr2.is_aligned());
/// };
/// ```
///
/// [tracking issue]: https://github.com/rust-lang/rust/issues/comming-soon
#[must_use]
#[inline]
#[unstable(feature = "pointer_is_aligned", issue = "96284")]
@ -1385,8 +1449,74 @@ impl<T: ?Sized> *const T {
/// # Panics
///
/// The function panics if `align` is not a power-of-two (this includes 0).
// #[cfg(not(bootstrap))] -- Calling this function in a const context from the bootstrap
// compiler will always return false.
///
/// # Examples
///
/// Basic usage:
/// ```
/// #![feature(pointer_is_aligned)]
/// #![feature(pointer_byte_offsets)]
///
/// let data: i32 = 42;
/// let ptr: *const i32 = &data;
///
/// assert!(ptr.is_aligned_to(1));
/// assert!(ptr.is_aligned_to(2));
/// assert!(ptr.is_aligned_to(4));
///
/// assert!(ptr.wrapping_byte_add(2).is_aligned_to(2));
/// assert!(!ptr.wrapping_byte_add(2).is_aligned_to(4));
///
/// assert_ne!(ptr.is_aligned_to(8), ptr.wrapping_add(1).is_aligned_to(8));
/// ```
///
/// # At compiletime
/// **Note: Alignment at compiletime is experimental and subject to change. See the
/// [tracking issue] for details.**
///
/// At compiletime, the compiler may not know where a value will end up in memory.
/// Calling this function on a pointer created from a reference at compiletime will only
/// return `true` if the pointer is guaranteed to be aligned. This means that the pointer
/// cannot be stricter aligned than the reference's underlying allocation.
///
#[cfg_attr(bootstrap, doc = "```ignore")]
#[cfg_attr(not(bootstrap), doc = "```")]
/// #![feature(pointer_is_aligned)]
/// #![feature(const_pointer_is_aligned)]
///
/// const _: () = {
/// let data: i32 = 42;
/// let ptr: *const i32 = &data;
///
/// assert!(ptr.is_aligned_to(1));
/// assert!(ptr.is_aligned_to(2));
/// assert!(ptr.is_aligned_to(4));
///
/// // At compiletime, we know for sure that the pointer isn't aligned to 8.
/// assert!(!ptr.is_aligned_to(8));
/// assert!(!ptr.wrapping_add(1).is_aligned_to(8));
/// };
/// ```
///
/// If a pointer is created from a fixed address, this function behaves the same during
/// runtime and compiletime.
///
#[cfg_attr(bootstrap, doc = "```ignore")]
#[cfg_attr(not(bootstrap), doc = "```")]
/// #![feature(pointer_is_aligned)]
/// #![feature(const_pointer_is_aligned)]
///
/// const _: () = {
/// let ptr = 40 as *const i32;
/// assert!(ptr.is_aligned_to(1));
/// assert!(ptr.is_aligned_to(2));
/// assert!(ptr.is_aligned_to(4));
/// assert!(ptr.is_aligned_to(8));
/// assert!(!ptr.is_aligned_to(16));
/// };
/// ```
///
/// [tracking issue]: https://github.com/rust-lang/rust/issues/comming-soon
#[must_use]
#[inline]
#[unstable(feature = "pointer_is_aligned", issue = "96284")]

138
library/core/src/ptr/mut_ptr.rs
View file

@ -1632,8 +1632,72 @@ impl<T: ?Sized> *mut T {
}
/// Returns whether the pointer is properly aligned for `T`.
// #[cfg(not(bootstrap))] -- Calling this function in a const context from the bootstrap
// compiler will always return false.
///
/// # Examples
///
/// Basic usage:
/// ```
/// #![feature(pointer_is_aligned)]
/// #![feature(pointer_byte_offsets)]
///
/// let data: i32 = 42;
/// let ptr: *const i32 = &data;
///
/// assert!(ptr.is_aligned());
/// assert!(!ptr.wrapping_byte_add(1).is_aligned());
/// ```
///
/// # At compiletime
/// **Note: Alignment at compiletime is experimental and subject to change. See the
/// [tracking issue] for details.**
///
/// At compiletime, the compiler may not know where a value will end up in memory.
/// Calling this function on a pointer created from a reference at compiletime will only
/// return `true` if the pointer is guaranteed to be aligned. This means that the pointer
/// is never aligned if cast to a type with a stricter alignment than the reference's
/// underlying allocation.
///
#[cfg_attr(bootstrap, doc = "```ignore")]
#[cfg_attr(not(bootstrap), doc = "```")]
/// #![feature(pointer_is_aligned)]
/// #![feature(const_pointer_is_aligned)]
///
/// const _: () = {
/// let data: i32 = 42;
/// let ptr: *const i32 = &data;
/// assert!(ptr.is_aligned());
///
/// // At runtime either `ptr1` or `ptr2` would be aligned,
/// // but at compiletime neither is aligned.
/// let ptr1: *const i64 = ptr.cast();
/// let ptr2: *const i64 = ptr.wrapping_add(1).cast();
/// assert!(!ptr1.is_aligned());
/// assert!(!ptr2.is_aligned());
/// };
/// ```
///
/// If a pointer is created from a fixed address, this function behaves the same during
/// runtime and compiletime.
///
#[cfg_attr(bootstrap, doc = "```ignore")]
#[cfg_attr(not(bootstrap), doc = "```")]
/// #![feature(pointer_is_aligned)]
/// #![feature(const_pointer_is_aligned)]
///
/// const _: () = {
/// let ptr = 40 as *const i32;
/// assert!(ptr.is_aligned());
///
/// // For pointers with a known address, runtime and
/// // compiletime behavior are identical.
/// let ptr1: *const i64 = ptr.cast();
/// let ptr2: *const i64 = ptr.wrapping_add(1).cast();
/// assert!(ptr1.is_aligned());
/// assert!(!ptr2.is_aligned());
/// };
/// ```
///
/// [tracking issue]: https://github.com/rust-lang/rust/issues/comming-soon
#[must_use]
#[inline]
#[unstable(feature = "pointer_is_aligned", issue = "96284")]
@ -1653,8 +1717,74 @@ impl<T: ?Sized> *mut T {
/// # Panics
///
/// The function panics if `align` is not a power-of-two (this includes 0).
// #[cfg(not(bootstrap))] -- Calling this function in a const context from the bootstrap
// compiler will always return false.
///
/// # Examples
///
/// Basic usage:
/// ```
/// #![feature(pointer_is_aligned)]
/// #![feature(pointer_byte_offsets)]
///
/// let data: i32 = 42;
/// let ptr: *const i32 = &data;
///
/// assert!(ptr.is_aligned_to(1));
/// assert!(ptr.is_aligned_to(2));
/// assert!(ptr.is_aligned_to(4));
///
/// assert!(ptr.wrapping_byte_add(2).is_aligned_to(2));
/// assert!(!ptr.wrapping_byte_add(2).is_aligned_to(4));
///
/// assert_ne!(ptr.is_aligned_to(8), ptr.wrapping_add(1).is_aligned_to(8));
/// ```
///
/// # At compiletime
/// **Note: Alignment at compiletime is experimental and subject to change. See the
/// [tracking issue] for details.**
///
/// At compiletime, the compiler may not know where a value will end up in memory.
/// Calling this function on a pointer created from a reference at compiletime will only
/// return `true` if the pointer is guaranteed to be aligned. This means that the pointer
/// cannot be stricter aligned than the reference's underlying allocation.
///
#[cfg_attr(bootstrap, doc = "```ignore")]
#[cfg_attr(not(bootstrap), doc = "```")]
/// #![feature(pointer_is_aligned)]
/// #![feature(const_pointer_is_aligned)]
///
/// const _: () = {
/// let data: i32 = 42;
/// let ptr: *const i32 = &data;
///
/// assert!(ptr.is_aligned_to(1));
/// assert!(ptr.is_aligned_to(2));
/// assert!(ptr.is_aligned_to(4));
///
/// // At compiletime, we know for sure that the pointer isn't aligned to 8.
/// assert!(!ptr.is_aligned_to(8));
/// assert!(!ptr.wrapping_add(1).is_aligned_to(8));
/// };
/// ```
///
/// If a pointer is created from a fixed address, this function behaves the same during
/// runtime and compiletime.
///
#[cfg_attr(bootstrap, doc = "```ignore")]
#[cfg_attr(not(bootstrap), doc = "```")]
/// #![feature(pointer_is_aligned)]
/// #![feature(const_pointer_is_aligned)]
///
/// const _: () = {
/// let ptr = 40 as *const i32;
/// assert!(ptr.is_aligned_to(1));
/// assert!(ptr.is_aligned_to(2));
/// assert!(ptr.is_aligned_to(4));
/// assert!(ptr.is_aligned_to(8));
/// assert!(!ptr.is_aligned_to(16));
/// };
/// ```
///
/// [tracking issue]: https://github.com/rust-lang/rust/issues/comming-soon
#[must_use]
#[inline]
#[unstable(feature = "pointer_is_aligned", issue = "96284")]