// -*- coding: utf-8 -*-

use crate::messages::MsgCrc;
use anyhow as ah;
use crc_all::CrcAlgo;

static CRC32: CrcAlgo<u32> = CrcAlgo::<u32>::new(0x4C11DB7, 32, 0, 0, true);

pub fn crc32(buf: &[u8]) -> u32 {
    let mut crc = 0;
    CRC32.init_crc(&mut crc);
    CRC32.update_crc(&mut crc, buf)
}

pub fn check_crc32(buf: &[u8]) -> ah::Result<()> {
    let begin = buf.len() - MsgCrc::LEN;
    let end = begin + MsgCrc::LEN;
    let Ok(rx_crc) = MsgCrc::unpack(&buf[begin..end]) else {
        return Err(ah::format_err!("Failed to unpack crc."));
    };
    let end = buf.len() - MsgCrc::LEN;
    let calc_crc = crc32(&buf[0..end]);
    if rx_crc.get_crc() != calc_crc {
        return Err(ah::format_err!(
            "CRC checksum mismatch (rx={:X}, calc={:X}.",
            rx_crc.get_crc(),
            calc_crc
        ));
    }
    Ok(())
}

// vim: ts=4 sw=4 expandtab