Function shuffle_into 

pub fn shuffle_into(typesize: usize, src: &[u8], dst: &mut [u8])

Like shuffle, but allows the caller to control allocation for the output.

Examples

const IN: [u8; 8] = [0x00, 0x01, 0x00, 0x02, 0x00, 0x03, 0x00, 0x04];
let mut out = [0u8; 8];
shuffle_into(2, &IN, &mut out);
assert_eq!(out, [0x00, 0x00, 0x00, 0x00, 0x01, 0x02, 0x03, 0x04]);