"""Common codec utility tests."""
import struct

from go1_pro_sdk.utils.common import gen_crc


def _gen_crc_bitwise(data: bytes) -> bytes:
    crc = 0xFFFFFFFF
    for (word,) in struct.iter_unpack("<I", data):
        for bit in range(32):
            x = (crc >> 31) & 1
            crc <<= 1
            crc &= 0xFFFFFFFF
            if x ^ (1 & (word >> (31 - bit))):
                crc ^= 0x04c11db7
    return struct.pack("<I", crc)


def test_gen_crc_matches_reference_bitwise():
    samples = [
        b"",
        bytes(4),
        bytes(range(64)),
        b"\xfe\xef\xff\x00" + bytes(range(252)) * 2,
    ]
    for sample in samples:
        assert gen_crc(sample) == _gen_crc_bitwise(sample)