Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Jump to bottom

Simplify some pointer method implementations #103701

Merged
merged 2 commits into from
Nov 19, 2022
Merged

Simplify some pointer method implementations #103701

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
6c54745
Make `pointer::with_metadata_of` const (+simplify implementation)
WaffleLapkin Oct 28, 2022
d3b5192
Simplify implementation of various pointer methods
WaffleLapkin Oct 28, 2022
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
1 change: 1 addition & 0 deletions library/core/src/lib.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -154,6 +154,7 @@
#![feature(maybe_uninit_uninit_array)]
#![feature(ptr_alignment_type)]
#![feature(ptr_metadata)]
#![feature(set_ptr_value)]
#![feature(slice_ptr_get)]
#![feature(slice_split_at_unchecked)]
#![feature(str_internals)]
Expand Down
29 changes: 10 additions & 19 deletions library/core/src/ptr/const_ptr.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -79,19 +79,14 @@ impl<T: ?Sized> *const T {
/// }
/// ```
#[unstable(feature = "set_ptr_value", issue = "75091")]
#[rustc_const_unstable(feature = "set_ptr_value", issue = "75091")]
#[must_use = "returns a new pointer rather than modifying its argument"]
#[inline]
pub fn with_metadata_of<U>(self, mut val: *const U) -> *const U
pub const fn with_metadata_of<U>(self, meta: *const U) -> *const U
where
U: ?Sized,
{
let target = &mut val as *mut *const U as *mut *const u8;
// SAFETY: In case of a thin pointer, this operations is identical
// to a simple assignment. In case of a fat pointer, with the current
// fat pointer layout implementation, the first field of such a
// pointer is always the data pointer, which is likewise assigned.
unsafe { *target = self as *const u8 };
val
from_raw_parts::<U>(self as *const (), metadata(meta))
}

/// Changes constness without changing the type.
Expand Down Expand Up @@ -478,8 +473,7 @@ impl<T: ?Sized> *const T {
#[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
pub const unsafe fn byte_offset(self, count: isize) -> Self {
// SAFETY: the caller must uphold the safety contract for `offset`.
let this = unsafe { self.cast::<u8>().offset(count).cast::<()>() };
from_raw_parts::<T>(this, metadata(self))
unsafe { self.cast::<u8>().offset(count).with_metadata_of(self) }
}

/// Calculates the offset from a pointer using wrapping arithmetic.
Expand Down Expand Up @@ -559,7 +553,7 @@ impl<T: ?Sized> *const T {
#[unstable(feature = "pointer_byte_offsets", issue = "96283")]
#[rustc_const_unstable(feature = "const_pointer_byte_offsets", issue = "96283")]
pub const fn wrapping_byte_offset(self, count: isize) -> Self {
from_raw_parts::<T>(self.cast::<u8>().wrapping_offset(count).cast::<()>(), metadata(self))
self.cast::<u8>().wrapping_offset(count).with_metadata_of(self)
}

/// Masks out bits of the pointer according to a mask.
Expand All @@ -572,8 +566,7 @@ impl<T: ?Sized> *const T {
#[must_use = "returns a new pointer rather than modifying its argument"]
#[inline(always)]
pub fn mask(self, mask: usize) -> *const T {
let this = intrinsics::ptr_mask(self.cast::<()>(), mask);
from_raw_parts::<T>(this, metadata(self))
intrinsics::ptr_mask(self.cast::<()>(), mask).with_metadata_of(self)
}

/// Calculates the distance between two pointers. The returned value is in
Expand Down Expand Up @@ -911,8 +904,7 @@ impl<T: ?Sized> *const T {
#[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
pub const unsafe fn byte_add(self, count: usize) -> Self {
// SAFETY: the caller must uphold the safety contract for `add`.
let this = unsafe { self.cast::<u8>().add(count).cast::<()>() };
from_raw_parts::<T>(this, metadata(self))
unsafe { self.cast::<u8>().add(count).with_metadata_of(self) }
}

/// Calculates the offset from a pointer (convenience for
Expand Down Expand Up @@ -998,8 +990,7 @@ impl<T: ?Sized> *const T {
#[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
pub const unsafe fn byte_sub(self, count: usize) -> Self {
// SAFETY: the caller must uphold the safety contract for `sub`.
let this = unsafe { self.cast::<u8>().sub(count).cast::<()>() };
from_raw_parts::<T>(this, metadata(self))
unsafe { self.cast::<u8>().sub(count).with_metadata_of(self) }
}

/// Calculates the offset from a pointer using wrapping arithmetic.
Expand Down Expand Up @@ -1079,7 +1070,7 @@ impl<T: ?Sized> *const T {
#[unstable(feature = "pointer_byte_offsets", issue = "96283")]
#[rustc_const_unstable(feature = "const_pointer_byte_offsets", issue = "96283")]
pub const fn wrapping_byte_add(self, count: usize) -> Self {
from_raw_parts::<T>(self.cast::<u8>().wrapping_add(count).cast::<()>(), metadata(self))
self.cast::<u8>().wrapping_add(count).with_metadata_of(self)
}

/// Calculates the offset from a pointer using wrapping arithmetic.
Expand Down Expand Up @@ -1159,7 +1150,7 @@ impl<T: ?Sized> *const T {
#[unstable(feature = "pointer_byte_offsets", issue = "96283")]
#[rustc_const_unstable(feature = "const_pointer_byte_offsets", issue = "96283")]
pub const fn wrapping_byte_sub(self, count: usize) -> Self {
from_raw_parts::<T>(self.cast::<u8>().wrapping_sub(count).cast::<()>(), metadata(self))
self.cast::<u8>().wrapping_sub(count).with_metadata_of(self)
}

/// Reads the value from `self` without moving it. This leaves the
Expand Down
36 changes: 10 additions & 26 deletions library/core/src/ptr/mut_ptr.rs
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -78,23 +78,14 @@ impl<T: ?Sized> *mut T {
/// }
/// ```
#[unstable(feature = "set_ptr_value", issue = "75091")]
#[rustc_const_unstable(feature = "set_ptr_value", issue = "75091")]
#[must_use = "returns a new pointer rather than modifying its argument"]
#[inline]
pub fn with_metadata_of<U>(self, val: *const U) -> *mut U
pub const fn with_metadata_of<U>(self, meta: *const U) -> *mut U
where
U: ?Sized,
{
// Prepare in the type system that we will replace the pointer value with a mutable
// pointer, taking the mutable provenance from the `self` pointer.
let mut val = val as *mut U;
// Pointer to the pointer value within the value.
let target = &mut val as *mut *mut U as *mut *mut u8;
// SAFETY: In case of a thin pointer, this operations is identical
// to a simple assignment. In case of a fat pointer, with the current
// fat pointer layout implementation, the first field of such a
// pointer is always the data pointer, which is likewise assigned.
unsafe { *target = self as *mut u8 };
val
from_raw_parts_mut::<U>(self as *mut (), metadata(meta))
}

/// Changes constness without changing the type.
Expand Down Expand Up @@ -496,8 +487,7 @@ impl<T: ?Sized> *mut T {
#[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
pub const unsafe fn byte_offset(self, count: isize) -> Self {
// SAFETY: the caller must uphold the safety contract for `offset`.
let this = unsafe { self.cast::<u8>().offset(count).cast::<()>() };
from_raw_parts_mut::<T>(this, metadata(self))
unsafe { self.cast::<u8>().offset(count).with_metadata_of(self) }
}

/// Calculates the offset from a pointer using wrapping arithmetic.
Expand Down Expand Up @@ -576,10 +566,7 @@ impl<T: ?Sized> *mut T {
#[unstable(feature = "pointer_byte_offsets", issue = "96283")]
#[rustc_const_unstable(feature = "const_pointer_byte_offsets", issue = "96283")]
pub const fn wrapping_byte_offset(self, count: isize) -> Self {
from_raw_parts_mut::<T>(
self.cast::<u8>().wrapping_offset(count).cast::<()>(),
metadata(self),
)
self.cast::<u8>().wrapping_offset(count).with_metadata_of(self)
}

/// Masks out bits of the pointer according to a mask.
Expand All @@ -592,8 +579,7 @@ impl<T: ?Sized> *mut T {
#[must_use = "returns a new pointer rather than modifying its argument"]
#[inline(always)]
pub fn mask(self, mask: usize) -> *mut T {
let this = intrinsics::ptr_mask(self.cast::<()>(), mask) as *mut ();
from_raw_parts_mut::<T>(this, metadata(self))
intrinsics::ptr_mask(self.cast::<()>(), mask).cast_mut().with_metadata_of(self)
}

/// Returns `None` if the pointer is null, or else returns a unique reference to
Expand Down Expand Up @@ -1020,8 +1006,7 @@ impl<T: ?Sized> *mut T {
#[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
pub const unsafe fn byte_add(self, count: usize) -> Self {
// SAFETY: the caller must uphold the safety contract for `add`.
let this = unsafe { self.cast::<u8>().add(count).cast::<()>() };
from_raw_parts_mut::<T>(this, metadata(self))
unsafe { self.cast::<u8>().add(count).with_metadata_of(self) }
}

/// Calculates the offset from a pointer (convenience for
Expand Down Expand Up @@ -1107,8 +1092,7 @@ impl<T: ?Sized> *mut T {
#[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
pub const unsafe fn byte_sub(self, count: usize) -> Self {
// SAFETY: the caller must uphold the safety contract for `sub`.
let this = unsafe { self.cast::<u8>().sub(count).cast::<()>() };
from_raw_parts_mut::<T>(this, metadata(self))
unsafe { self.cast::<u8>().sub(count).with_metadata_of(self) }
}

/// Calculates the offset from a pointer using wrapping arithmetic.
Expand Down Expand Up @@ -1188,7 +1172,7 @@ impl<T: ?Sized> *mut T {
#[unstable(feature = "pointer_byte_offsets", issue = "96283")]
#[rustc_const_unstable(feature = "const_pointer_byte_offsets", issue = "96283")]
pub const fn wrapping_byte_add(self, count: usize) -> Self {
from_raw_parts_mut::<T>(self.cast::<u8>().wrapping_add(count).cast::<()>(), metadata(self))
self.cast::<u8>().wrapping_add(count).with_metadata_of(self)
}

/// Calculates the offset from a pointer using wrapping arithmetic.
Expand Down Expand Up @@ -1268,7 +1252,7 @@ impl<T: ?Sized> *mut T {
#[unstable(feature = "pointer_byte_offsets", issue = "96283")]
#[rustc_const_unstable(feature = "const_pointer_byte_offsets", issue = "96283")]
pub const fn wrapping_byte_sub(self, count: usize) -> Self {
from_raw_parts_mut::<T>(self.cast::<u8>().wrapping_sub(count).cast::<()>(), metadata(self))
self.cast::<u8>().wrapping_sub(count).with_metadata_of(self)
}

/// Reads the value from `self` without moving it. This leaves the
Expand Down