Temporarily transmute [u8] to [u16]

Question

I have a [u8; 16384] and a u16. How would I \"temporarily transmute\" the array so I can set the two u8s at once, the first to the lea

Answer 1

slice::align_to and slice::align_to_mut are stable as of Rust 1.30. These functions handle the alignment concerns that sellibitze brings up.

The big- and little- endian problems are still yours to worry about. You may be able to use methods like u16::to_le to help with that. I don't have access to a big-endian computer to test with, however.

fn example(blob: &mut [u8; 16], value: u16) {
   // I copied this example from Stack Overflow without providing 
   // rationale why my specific case is safe.
   let (head, body, tail) = unsafe { blob.align_to_mut::() };

   // This example simply does not handle the case where the input data
   // is misaligned such that there are bytes that cannot be correctly
   // reinterpreted as u16.
   assert!(head.is_empty());
   assert!(tail.is_empty());

   body[0] = value
}

fn main() {
   let mut data = [0; 16];
   example(&mut data, 500);
   println!("{:?}", data);
}