Macro mut_array_refs

macro_rules! mut_array_refs {
    ( $arr:expr, $( $pre:expr ),* ; .. ;  $( $post:expr ),* ) => { ... };
    ( $arr:expr, $( $len:expr ),* ) => { ... };
}

You can use mut_array_refs to generate a series of mutable array references to an input mutable array reference. The idea is if you want to break an array into a series of contiguous and non-overlapping mutable array references. Like array_refs!, mut_array_refs! is a bit funny in that it insists on slicing up the entire array. This is intentional, as I find it handy to make me ensure that my sub-arrays add up to the entire array. This macro will never panic, since the sizes are all checked at compile time.

Note that unlike array_mut_ref!, mut_array_refs requires that the first argument be a mutable array reference. The following arguments are the lengths of each subarray you wish a reference to. The total of these arguments must equal the size of the array itself. Also note that this macro allows you to take out multiple mutable references to a single object, which is both weird and powerful.

#[macro_use]
extern crate arrayref;

fn write_u16(bytes: &mut [u8; 2], num: u16) {
     bytes[0] = num as u8;
     bytes[1] = (num >> 8) as u8;
}
fn write_u32(bytes: &mut [u8; 4], num: u32) {
     bytes[0] = num as u8;
     bytes[1] = (num >> 8) as u8; // this is buggy to save space...
}
// ...
let mut data = [0,1,2,3,4,0,6,7];
let (a,b,c) = mut_array_refs![&mut data,2,2,4];
// let's write out some nice prime numbers!
write_u16(a, 37);
write_u16(b, 73);
write_u32(c, 137); // approximate inverse of the fine structure constant!