from_ptr_range in std::slice - Rust (original) (raw)

Function from_ptr_range

Source

pub const unsafe fn from_ptr_range<'a, T>(range: Range<*const T>) -> &'a [T]

🔬This is a nightly-only experimental API. (slice_from_ptr_range #89792)

Expand description

Forms a slice from a pointer range.

This function is useful for interacting with foreign interfaces which use two pointers to refer to a range of elements in memory, as is common in C++.

§Safety

Behavior is undefined if any of the following conditions are violated:

• The start pointer of the range must be a non-null, valid and properly aligned pointer to the first element of a slice.
• The end pointer must be a valid and properly aligned pointer to _one past_the last element, such that the offset from the end to the start pointer is the length of the slice.
• The entire memory range of this slice must be contained within a single allocated object! Slices can never span across multiple allocated objects.
• The range must contain N consecutive properly initialized values of type T.
• The memory referenced by the returned slice must not be mutated for the duration of lifetime 'a, except inside an UnsafeCell.
• The total length of the range must be no larger than isize::MAX, and adding that size to start must not “wrap around” the address space. See the safety documentation of pointer::offset.

Note that a range created from slice::as_ptr_range fulfills these requirements.

§Panics

This function panics if T is a Zero-Sized Type (“ZST”).

§Caveat

The lifetime for the returned slice is inferred from its usage. To prevent accidental misuse, it’s suggested to tie the lifetime to whichever source lifetime is safe in the context, such as by providing a helper function taking the lifetime of a host value for the slice, or by explicit annotation.

§Examples

#![feature(slice_from_ptr_range)]

use core::slice;

let x = [1, 2, 3];
let range = x.as_ptr_range();

unsafe {
    assert_eq!(slice::from_ptr_range(range), &x);
}