Rust Essentials - Second Edition

Using std::mem

In unsafe code, the use of the modules std::mem (which contains functions to work with memory at a low level) and std::ptr (which contains functions to work with raw pointers) is common, as we saw with std::mem::transmute.

Here are some more examples.

To swap two variables by explicitly using pointers, use std::mem::swap like this:

   // code from Chapter 10/code/swap.rs: 
use std::mem; 
 
fn main() { 
   let mut n = 0; 
   let mut m = 1;  
   mem::swap(&mut n, &mut m); 
   println!("n: {} m: {}", n, m); 
} 

This prints out the following:

n: 1 m: 0

As another example, the mem::size_of_val() function from the mem module takes a reference to a value and returns the number of bytes it occupies in memory. mem::size_ of returns the size of the given type ...