use std::{
    arch::arm::{vld1q_u8, vst1q_u8, vuzpq_u8},
    convert::TryInto,
};

const GROUP_BY: usize = 32;
pub const fn out_size(in_size: usize) -> usize {
    in_size / 2
}

pub fn run(buf: &mut [u8]) {
    let n_raw = buf.len();
    let mut in_cursor = 0;
    let mut out_cursor = 0;

    let mut res = [0u8; 16];

    while in_cursor + GROUP_BY <= n_raw {
        let a: &[u8; 16] = buf[in_cursor..in_cursor + 16].try_into().unwrap();
        let b: &[u8; 16] = buf[in_cursor + 16..in_cursor + 32].try_into().unwrap();

        unsafe {
            let a = vld1q_u8(a as *const u8);
            let b = vld1q_u8(b as *const u8);
            let z = vuzpq_u8(a, b);
            vst1q_u8(&mut res as *mut u8, z.0);
        }

        buf[out_cursor..out_cursor + 16].copy_from_slice(&res);
        out_cursor += 16;
        in_cursor += GROUP_BY;
    }
}