Function std::ptr::replace

pub unsafe fn replace<T>(dest: *mut T, src: T) -> T

Replaces the value at dest with src, returning the old value, without dropping either.

This function is semantically equivalent to mem::replace except that it operates on raw pointers instead of references. When references are available, mem::replace should be preferred.

Safety

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

• dest must point to valid, initialized memory.

• dest must be properly aligned.

Examples

use std::ptr;

let mut rust = vec!['b', 'u', 's', 't'];

// `mem::replace` would have the same effect without requiring the unsafe
// block.
let b = unsafe {
    ptr::replace(&mut rust[0], 'r')
};

assert_eq!(b, 'b');
assert_eq!(rust, &['r', 'u', 's', 't']);