Compute the 64-bit hash of the input bytes object using the chibihash64 algorithm.

chibihash64.py

def chibihash64__load64le(p, offset=0):
    """Load 8 bytes from the input bytes object as a little-endian 64-bit integer."""
    return int.from_bytes(p[offset : offset + 8], "little", signed=False)


def chibihash64(key, seed=0):
    """
    Compute the 64-bit hash of the input bytes object using the chibihash64 algorithm.

    Parameters:
        key (bytes): The input data to hash.
        seed (int): An optional seed value for the hash function.

    Returns:
        int: The 64-bit hash value.
    """
    k = key
    l = len(k)
    P1 = 0x2B7E151628AED2A5
    P2 = 0x9E3793492EEDC3F7
    P3 = 0x3243F6A8885A308D
    h = [P1, P2, P3, seed & 0xFFFFFFFFFFFFFFFF]

    pos = 0
    while l - pos >= 32:
        for i in range(4):
            lane = chibihash64__load64le(k, pos)
            h[i] ^= lane
            h[i] = (h[i] * P1) & 0xFFFFFFFFFFFFFFFF
            h[(i + 1) & 3] ^= ((lane << 40) | (lane >> 24)) & 0xFFFFFFFFFFFFFFFF
            pos += 8

    h[0] = (h[0] + ((l << 32) | (l >> 32))) & 0xFFFFFFFFFFFFFFFF
    if (l - pos) & 1:
        h[0] ^= k[pos]
        pos += 1
    h[0] = (h[0] * P2) & 0xFFFFFFFFFFFFFFFF
    h[0] ^= h[0] >> 31

    i = 1
    while l - pos >= 8:
        h[i] ^= chibihash64__load64le(k, pos)
        h[i] = (h[i] * P2) & 0xFFFFFFFFFFFFFFFF
        h[i] ^= h[i] >> 31
        pos += 8
        i += 1

    i = 0
    while l - pos > 0:
        b0 = k[pos]
        b1 = k[pos + 1] if pos + 1 < l else 0
        val = b0 | (b1 << 8)
        h[i] ^= val
        h[i] = (h[i] * P3) & 0xFFFFFFFFFFFFFFFF
        h[i] ^= h[i] >> 31
        pos += 2
        i += 1

    x = seed & 0xFFFFFFFFFFFFFFFF
    x ^= (h[0] * ((h[2] >> 32) | 1)) & 0xFFFFFFFFFFFFFFFF
    x ^= (h[1] * ((h[3] >> 32) | 1)) & 0xFFFFFFFFFFFFFFFF
    x ^= (h[2] * ((h[0] >> 32) | 1)) & 0xFFFFFFFFFFFFFFFF
    x ^= (h[3] * ((h[1] >> 32) | 1)) & 0xFFFFFFFFFFFFFFFF

    x &= 0xFFFFFFFFFFFFFFFF

    # moremur mixing function
    x ^= x >> 27
    x = (x * 0x3C79AC492BA7B653) & 0xFFFFFFFFFFFFFFFF
    x ^= x >> 33
    x = (x * 0x1C69B3F74AC4AE35) & 0xFFFFFFFFFFFFFFFF
    x ^= x >> 27

    return x & 0xFFFFFFFFFFFFFFFF


def chibihash64_hexdigest(key, seed=0):
    """
    Compute the 64-bit hash of the input bytes object and return it as a hexadecimal string.

    Parameters:
        key (bytes): The input data to hash.
        seed (int): An optional seed value for the hash function.

    Returns:
        str: The 64-bit hash value as a 16-character hexadecimal string.
    """
    hash_value = chibihash64(key, seed)
    return f"{hash_value:016x}"


if __name__ == "__main__":
    data = b"hello world"
    seed = 0
    hex_hash = chibihash64_hexdigest(data, seed)
    print(f"Hex digest: {hex_hash}")