pub const IPC_MSG_WORDS: usize = 6;
pub const MAX_IPC_BYTES: usize = 40;

pub fn pack_bytes(src: &[u8]) -> [u64; IPC_MSG_WORDS] {
    let count = src.len().min(MAX_IPC_BYTES);
    let mut msg = [0u64; IPC_MSG_WORDS];
    msg[0] = count as u64;
    (0..count).for_each(|i| {
        let word_idx = i / 8;
        let byte_idx = i % 8;
        msg[1 + word_idx] |= (src[i] as u64) << (byte_idx * 8);
    });
    msg
}

pub fn unpack_bytes(msg: &[u64; IPC_MSG_WORDS], dst: &mut [u8; MAX_IPC_BYTES]) -> usize {
    let actual = (msg[0] as usize).min(MAX_IPC_BYTES);
    (0..actual).for_each(|i| {
        let word_idx = i / 8;
        let byte_idx = i % 8;
        dst[i] = ((msg[1 + word_idx] >> (byte_idx * 8)) & 0xFF) as u8;
    });
    actual
}