pub fn write_u32_le(n: u32, slice: &mut [u8]) {
    assert!(slice.len() >= 4);
    let bytes = n.to_le_bytes();
    slice[0] = bytes[0];
    slice[1] = bytes[1];
    slice[2] = bytes[2];
    slice[3] = bytes[3];
}
Write a u32 in little endian format to the beginning of the given slice.
This panics if the slice has length less than 4.
src/bytes.rs