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mentions provenance, changes argument type, adds must_use attr

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oliver-giersch 2020-08-11 16:14:34 +02:00
parent 441fd22557
commit 19c9674966
2 changed files with 26 additions and 8 deletions
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17
library/core/src/ptr/const_ptr.rs
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@ -662,6 +662,11 @@ impl<T: ?Sized> *const T {
/// will only affect the pointer part, whereas for (thin) pointers to
/// sized types, this has the same effect as a simple assignment.
///
/// The resulting pointer will have provenance of `val`, i.e., for a fat
/// pointer, this operation is semantically the same as creating a new
/// fat pointer with the data pointer value of `val` but the metadata of
/// `self`.
///
/// # Examples
///
/// This function is primarily useful for allowing byte-wise pointer
@ -673,13 +678,17 @@ impl<T: ?Sized> *const T {
/// let arr: [i32; 3] = [1, 2, 3];
/// let mut ptr = &arr[0] as *const dyn Debug;
/// let thin = ptr as *const u8;
/// ptr = ptr.set_ptr_value(unsafe { thin.add(8).cast() });
/// assert_eq!(unsafe { *(ptr as *const i32) }, 3);
/// unsafe {
/// ptr = ptr.set_ptr_value(thin.add(8));
/// # assert_eq!(*(ptr as *const i32), 3);
/// println!("{:?}", &*ptr); // will print "3"
/// }
/// ```
#[unstable(feature = "set_ptr_value", issue = "75091")]
#[must_use = "returns a new pointer rather than modifying its argument"]
#[inline]
pub fn set_ptr_value(mut self, val: *const ()) -> Self {
let thin = &mut self as *mut *const T as *mut *const ();
pub fn set_ptr_value(mut self, val: *const u8) -> Self {
let thin = &mut self as *mut *const T 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

17
library/core/src/ptr/mut_ptr.rs
View file

@ -718,6 +718,11 @@ impl<T: ?Sized> *mut T {
/// will only affect the pointer part, whereas for (thin) pointers to
/// sized types, this has the same effect as a simple assignment.
///
/// The resulting pointer will have provenance of `val`, i.e., for a fat
/// pointer, this operation is semantically the same as creating a new
/// fat pointer with the data pointer value of `val` but the metadata of
/// `self`.
///
/// # Examples
///
/// This function is primarily useful for allowing byte-wise pointer
@ -729,13 +734,17 @@ impl<T: ?Sized> *mut T {
/// let mut arr: [i32; 3] = [1, 2, 3];
/// let mut ptr = &mut arr[0] as *mut dyn Debug;
/// let thin = ptr as *mut u8;
/// ptr = ptr.set_ptr_value(unsafe { thin.add(8).cast() });
/// assert_eq!(unsafe { *(ptr as *mut i32) }, 3);
/// unsafe {
/// ptr = ptr.set_ptr_value(thin.add(8));
/// # assert_eq!(*(ptr as *mut i32), 3);
/// println!("{:?}", &*ptr); // will print "3"
/// }
/// ```
#[unstable(feature = "set_ptr_value", issue = "75091")]
#[must_use = "returns a new pointer rather than modifying its argument"]
#[inline]
pub fn set_ptr_value(mut self, val: *mut ()) -> Self {
let thin = &mut self as *mut *mut T as *mut *mut ();
pub fn set_ptr_value(mut self, val: *mut u8) -> Self {
let thin = &mut self as *mut *mut T 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