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Add convenience functions to pointers

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The functions added:
- {*const T,*mut T}::{wrapping_,}byte_{offset,add,sub}
- {*const T,*mut T}::{byte_offset_from,is_aligned,is_aligned_to}
This commit is contained in:
Maybe Waffle 2022-04-04 14:36:49 +04:00
parent 3a08bd7873
commit c8c91f757a
2 changed files with 320 additions and 2 deletions
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161
library/core/src/ptr/const_ptr.rs
View File

@ -455,6 +455,25 @@ impl<T: ?Sized> *const T {
unsafe { intrinsics::offset(self, count) }
}
/// Calculates the offset from a pointer in bytes.
///
/// `count` is in units of **bytes**.
///
/// This is purely a convenience for casting to a `u8` pointer and
/// using [offset][pointer::offset] on it. See that method for documentation
/// and safety requirements.
#[must_use]
#[inline(always)]
#[unstable(feature = "pointer_byte_offsets", issue = "none")]
#[rustc_const_unstable(feature = "const_pointer_byte_offsets", issue = "none")]
pub const unsafe fn byte_offset(self, count: isize) -> Self
where
T: Sized,
{
// SAFETY: the caller must uphold the safety contract for `offset`.
unsafe { self.cast::<u8>().offset(count).cast::<T>() }
}
/// Calculates the offset from a pointer using wrapping arithmetic.
///
/// `count` is in units of T; e.g., a `count` of 3 represents a pointer
@ -517,6 +536,24 @@ impl<T: ?Sized> *const T {
unsafe { intrinsics::arith_offset(self, count) }
}
/// Calculates the offset from a pointer in bytes using wrapping arithmetic.
///
/// `count` is in units of **bytes**.
///
/// This is purely a convenience for casting to a `u8` pointer and
/// using [wrapping_offset][pointer::wrapping_offset] on it. See that method
/// for documentation.
#[must_use]
#[inline(always)]
#[unstable(feature = "pointer_byte_offsets", issue = "none")]
#[rustc_const_unstable(feature = "const_pointer_byte_offsets", issue = "none")]
pub const fn wrapping_byte_offset(self, count: isize) -> Self
where
T: Sized,
{
self.cast::<u8>().wrapping_offset(count).cast::<T>()
}
/// Calculates the distance between two pointers. The returned value is in
/// units of T: the distance in bytes divided by `mem::size_of::<T>()`.
///
@ -611,6 +648,23 @@ impl<T: ?Sized> *const T {
unsafe { intrinsics::ptr_offset_from(self, origin) }
}
/// Calculates the distance between two pointers. The returned value is in
/// units of **bytes**.
///
/// This is purely a convenience for casting to a `u8` pointer and
/// using [offset_from][pointer::offset_from] on it. See that method for
/// documentation and safety requirements.
#[inline(always)]
#[unstable(feature = "pointer_byte_offsets", issue = "none")]
#[rustc_const_unstable(feature = "const_pointer_byte_offsets", issue = "none")]
pub const unsafe fn byte_offset_from(self, origin: *const T) -> isize
where
T: Sized,
{
// SAFETY: the caller must uphold the safety contract for `offset_from`.
unsafe { self.cast::<u8>().offset_from(origin.cast::<u8>()) }
}
/// Calculates the distance between two pointers, *where it's known that
/// `self` is equal to or greater than `origin`*. The returned value is in
/// units of T: the distance in bytes is divided by `mem::size_of::<T>()`.
@ -813,6 +867,25 @@ impl<T: ?Sized> *const T {
unsafe { self.offset(count as isize) }
}
/// Calculates the offset from a pointer in bytes (convenience for `.byte_offset(count as isize)`).
///
/// `count` is in units of bytes.
///
/// This is purely a convenience for casting to a `u8` pointer and
/// using [add][pointer::add] on it. See that method for documentation
/// and safety requirements.
#[must_use]
#[inline(always)]
#[unstable(feature = "pointer_byte_offsets", issue = "none")]
#[rustc_const_unstable(feature = "const_pointer_byte_offsets", issue = "none")]
pub const unsafe fn byte_add(self, count: usize) -> Self
where
T: Sized,
{
// SAFETY: the caller must uphold the safety contract for `add`.
unsafe { self.cast::<u8>().add(count).cast::<T>() }
}
/// Calculates the offset from a pointer (convenience for
/// `.offset((count as isize).wrapping_neg())`).
///
@ -877,6 +950,26 @@ impl<T: ?Sized> *const T {
unsafe { self.offset((count as isize).wrapping_neg()) }
}
/// Calculates the offset from a pointer in bytes (convenience for
/// `.byte_offset((count as isize).wrapping_neg())`).
///
/// `count` is in units of bytes.
///
/// This is purely a convenience for casting to a `u8` pointer and
/// using [sub][pointer::sub] on it. See that method for documentation
/// and safety requirements.
#[must_use]
#[inline(always)]
#[unstable(feature = "pointer_byte_offsets", issue = "none")]
#[rustc_const_unstable(feature = "const_pointer_byte_offsets", issue = "none")]
pub const unsafe fn byte_sub(self, count: usize) -> Self
where
T: Sized,
{
// SAFETY: the caller must uphold the safety contract for `sub`.
unsafe { self.cast::<u8>().sub(count).cast::<T>() }
}
/// Calculates the offset from a pointer using wrapping arithmetic.
/// (convenience for `.wrapping_offset(count as isize)`)
///
@ -939,6 +1032,24 @@ impl<T: ?Sized> *const T {
self.wrapping_offset(count as isize)
}
/// Calculates the offset from a pointer in bytes using wrapping arithmetic.
/// (convenience for `.wrapping_byte_offset(count as isize)`)
///
/// `count` is in units of bytes.
///
/// This is purely a convenience for casting to a `u8` pointer and
/// using [wrapping_add][pointer::wrapping_add] on it. See that method for documentation.
#[must_use]
#[inline(always)]
#[unstable(feature = "pointer_byte_offsets", issue = "none")]
#[rustc_const_unstable(feature = "const_pointer_byte_offsets", issue = "none")]
pub const fn wrapping_byte_add(self, count: usize) -> Self
where
T: Sized,
{
self.cast::<u8>().wrapping_add(count).cast::<T>()
}
/// Calculates the offset from a pointer using wrapping arithmetic.
/// (convenience for `.wrapping_offset((count as isize).wrapping_neg())`)
///
@ -1001,6 +1112,24 @@ impl<T: ?Sized> *const T {
self.wrapping_offset((count as isize).wrapping_neg())
}
/// Calculates the offset from a pointer in bytes using wrapping arithmetic.
/// (convenience for `.wrapping_offset((count as isize).wrapping_neg())`)
///
/// `count` is in units of bytes.
///
/// This is purely a convenience for casting to a `u8` pointer and
/// using [wrapping_sub][pointer::wrapping_sub] on it. See that method for documentation.
#[must_use]
#[inline(always)]
#[unstable(feature = "pointer_byte_offsets", issue = "none")]
#[rustc_const_unstable(feature = "const_pointer_byte_offsets", issue = "none")]
pub const fn wrapping_byte_sub(self, count: usize) -> Self
where
T: Sized,
{
self.cast::<u8>().wrapping_sub(count).cast::<T>()
}
/// Reads the value from `self` without moving it. This leaves the
/// memory in `self` unchanged.
///
@ -1154,12 +1283,42 @@ impl<T: ?Sized> *const T {
}
// SAFETY:
// It is permisseble for `align_offset` to always return `usize::MAX`,
// It is permissible for `align_offset` to always return `usize::MAX`,
// algorithm correctness can not depend on `align_offset` returning non-max values.
//
// As such the behaviour can't change after replacing `align_offset` with `usize::MAX`, only performance can.
unsafe { intrinsics::const_eval_select((self, align), ctfe_impl, rt_impl) }
}
/// Returns whether the pointer is properly aligned for `T`.
#[must_use]
#[inline]
#[unstable(feature = "pointer_is_aligned", issue = "none")]
pub fn is_aligned(self) -> bool
where
T: Sized,
{
self.addr() % core::mem::align_of::<T>() == 0
}
/// Returns whether the pointer is aligned to `align`.
///
/// # Panics
///
/// The function panics if `align` is not a power-of-two (this includes 0).
#[must_use]
#[inline]
#[unstable(feature = "pointer_is_aligned", issue = "none")]
pub fn is_aligned_to(self, align: usize) -> bool
where
T: Sized,
{
if !align.is_power_of_two() {
panic!("is_aligned_to: align is not a power-of-two");
}
self.addr() % align == 0
}
}
impl<T> *const [T] {

161
library/core/src/ptr/mut_ptr.rs
View File

@ -467,6 +467,25 @@ impl<T: ?Sized> *mut T {
unsafe { intrinsics::offset(self, count) as *mut T }
}
/// Calculates the offset from a pointer in bytes.
///
/// `count` is in units of **bytes**.
///
/// This is purely a convenience for casting to a `u8` pointer and
/// using [offset][pointer::offset] on it. See that method for documentation
/// and safety requirements.
#[must_use]
#[inline(always)]
#[unstable(feature = "pointer_byte_offsets", issue = "none")]
#[rustc_const_unstable(feature = "const_pointer_byte_offsets", issue = "none")]
pub const unsafe fn byte_offset(self, count: isize) -> Self
where
T: Sized,
{
// SAFETY: the caller must uphold the safety contract for `offset`.
unsafe { self.cast::<u8>().offset(count).cast::<T>() }
}
/// Calculates the offset from a pointer using wrapping arithmetic.
/// `count` is in units of T; e.g., a `count` of 3 represents a pointer
/// offset of `3 * size_of::<T>()` bytes.
@ -528,6 +547,24 @@ impl<T: ?Sized> *mut T {
unsafe { intrinsics::arith_offset(self, count) as *mut T }
}
/// Calculates the offset from a pointer in bytes using wrapping arithmetic.
///
/// `count` is in units of **bytes**.
///
/// This is purely a convenience for casting to a `u8` pointer and
/// using [wrapping_offset][pointer::wrapping_offset] on it. See that method
/// for documentation.
#[must_use]
#[inline(always)]
#[unstable(feature = "pointer_byte_offsets", issue = "none")]
#[rustc_const_unstable(feature = "const_pointer_byte_offsets", issue = "none")]
pub const fn wrapping_byte_offset(self, count: isize) -> Self
where
T: Sized,
{
self.cast::<u8>().wrapping_offset(count).cast::<T>()
}
/// Returns `None` if the pointer is null, or else returns a unique reference to
/// the value wrapped in `Some`. If the value may be uninitialized, [`as_uninit_mut`]
/// must be used instead.
@ -787,6 +824,23 @@ impl<T: ?Sized> *mut T {
unsafe { (self as *const T).offset_from(origin) }
}
/// Calculates the distance between two pointers. The returned value is in
/// units of **bytes**.
///
/// This is purely a convenience for casting to a `u8` pointer and
/// using [offset_from][pointer::offset_from] on it. See that method for
/// documentation and safety requirements.
#[inline(always)]
#[unstable(feature = "pointer_byte_offsets", issue = "none")]
#[rustc_const_unstable(feature = "const_pointer_byte_offsets", issue = "none")]
pub const unsafe fn byte_offset_from(self, origin: *const T) -> isize
where
T: Sized,
{
// SAFETY: the caller must uphold the safety contract for `offset_from`.
unsafe { self.cast::<u8>().offset_from(origin.cast::<u8>()) }
}
/// Calculates the distance between two pointers, *where it's known that
/// `self` is equal to or greater than `origin`*. The returned value is in
/// units of T: the distance in bytes is divided by `mem::size_of::<T>()`.
@ -922,6 +976,25 @@ impl<T: ?Sized> *mut T {
unsafe { self.offset(count as isize) }
}
/// Calculates the offset from a pointer in bytes (convenience for `.byte_offset(count as isize)`).
///
/// `count` is in units of bytes.
///
/// This is purely a convenience for casting to a `u8` pointer and
/// using [add][pointer::add] on it. See that method for documentation
/// and safety requirements.
#[must_use]
#[inline(always)]
#[unstable(feature = "pointer_byte_offsets", issue = "none")]
#[rustc_const_unstable(feature = "const_pointer_byte_offsets", issue = "none")]
pub const unsafe fn byte_add(self, count: usize) -> Self
where
T: Sized,
{
// SAFETY: the caller must uphold the safety contract for `add`.
unsafe { self.cast::<u8>().add(count).cast::<T>() }
}
/// Calculates the offset from a pointer (convenience for
/// `.offset((count as isize).wrapping_neg())`).
///
@ -986,6 +1059,26 @@ impl<T: ?Sized> *mut T {
unsafe { self.offset((count as isize).wrapping_neg()) }
}
/// Calculates the offset from a pointer in bytes (convenience for
/// `.byte_offset((count as isize).wrapping_neg())`).
///
/// `count` is in units of bytes.
///
/// This is purely a convenience for casting to a `u8` pointer and
/// using [sub][pointer::sub] on it. See that method for documentation
/// and safety requirements.
#[must_use]
#[inline(always)]
#[unstable(feature = "pointer_byte_offsets", issue = "none")]
#[rustc_const_unstable(feature = "const_pointer_byte_offsets", issue = "none")]
pub const unsafe fn byte_sub(self, count: usize) -> Self
where
T: Sized,
{
// SAFETY: the caller must uphold the safety contract for `sub`.
unsafe { self.cast::<u8>().sub(count).cast::<T>() }
}
/// Calculates the offset from a pointer using wrapping arithmetic.
/// (convenience for `.wrapping_offset(count as isize)`)
///
@ -1048,6 +1141,24 @@ impl<T: ?Sized> *mut T {
self.wrapping_offset(count as isize)
}
/// Calculates the offset from a pointer in bytes using wrapping arithmetic.
/// (convenience for `.wrapping_byte_offset(count as isize)`)
///
/// `count` is in units of bytes.
///
/// This is purely a convenience for casting to a `u8` pointer and
/// using [wrapping_add][pointer::wrapping_add] on it. See that method for documentation.
#[must_use]
#[inline(always)]
#[unstable(feature = "pointer_byte_offsets", issue = "none")]
#[rustc_const_unstable(feature = "const_pointer_byte_offsets", issue = "none")]
pub const fn wrapping_byte_add(self, count: usize) -> Self
where
T: Sized,
{
self.cast::<u8>().wrapping_add(count).cast::<T>()
}
/// Calculates the offset from a pointer using wrapping arithmetic.
/// (convenience for `.wrapping_offset((count as isize).wrapping_neg())`)
///
@ -1110,6 +1221,24 @@ impl<T: ?Sized> *mut T {
self.wrapping_offset((count as isize).wrapping_neg())
}
/// Calculates the offset from a pointer in bytes using wrapping arithmetic.
/// (convenience for `.wrapping_offset((count as isize).wrapping_neg())`)
///
/// `count` is in units of bytes.
///
/// This is purely a convenience for casting to a `u8` pointer and
/// using [wrapping_sub][pointer::wrapping_sub] on it. See that method for documentation.
#[must_use]
#[inline(always)]
#[unstable(feature = "pointer_byte_offsets", issue = "none")]
#[rustc_const_unstable(feature = "const_pointer_byte_offsets", issue = "none")]
pub const fn wrapping_byte_sub(self, count: usize) -> Self
where
T: Sized,
{
self.cast::<u8>().wrapping_sub(count).cast::<T>()
}
/// Reads the value from `self` without moving it. This leaves the
/// memory in `self` unchanged.
///
@ -1420,12 +1549,42 @@ impl<T: ?Sized> *mut T {
}
// SAFETY:
// It is permisseble for `align_offset` to always return `usize::MAX`,
// It is permissible for `align_offset` to always return `usize::MAX`,
// algorithm correctness can not depend on `align_offset` returning non-max values.
//
// As such the behaviour can't change after replacing `align_offset` with `usize::MAX`, only performance can.
unsafe { intrinsics::const_eval_select((self, align), ctfe_impl, rt_impl) }
}
/// Returns whether the pointer is properly aligned for `T`.
#[must_use]
#[inline]
#[unstable(feature = "pointer_is_aligned", issue = "none")]
pub fn is_aligned(self) -> bool
where
T: Sized,
{
self.addr() % core::mem::align_of::<T>() == 0
}
/// Returns whether the pointer is aligned to `align`.
///
/// # Panics
///
/// The function panics if `align` is not a power-of-two (this includes 0).
#[must_use]
#[inline]
#[unstable(feature = "pointer_is_aligned", issue = "none")]
pub fn is_aligned_to(self, align: usize) -> bool
where
T: Sized,
{
if !align.is_power_of_two() {
panic!("is_aligned_to: align is not a power-of-two");
}
self.addr() % align == 0
}
}
impl<T> *mut [T] {