Macro gen_align

macro_rules! gen_align {
    (($i:expr, $idx:expr), $val:expr) => { ... };
    ($i:expr, $val:expr) => { ... };
}

gen_align!(I, u8) => I -> Result<I,E> Align the output buffer to the next multiple of specified value.

Does not modify the output buffer, but increments the output index.