DJB hash function in python and some variants

djbHash.py

"""DJB hash function in python and some variants"""

MAGIC_NUMBER = 0x1505    # 5381

MASK_24 = (1 << 24) - 1  # 0xFFFFFF
MASK_32 = (1 << 32) - 1  # 0xFFFFFFFF
MASK_64 = (1 << 64) - 1  # 0xFFFFFFFFFFFFFFFF


def djb(string):
    """impl"""
    _hash = MAGIC_NUMBER
    while string:
        _hash = (_hash << 5) + _hash + ord(string[0])
        string = string[1:]
    return _hash


def djb_reversed(string):
    """DJB Hash on reversed string"""
    return djb(string[::-1])


def djb_24(string):
    """ clamp djb hash to 24 bits via Xor folding"""
    _hash = djb(string)
    return ((_hash >> 24) ^ _hash) & MASK_24


def djb_32(string):
    """ clamp djb hash to 32 bits via Xor folding"""
    _hash = djb(string)
    return ((_hash >> 32) ^ _hash) & MASK_32


def djb_64(string):
    """ clamp djb hash to 64 bits via Xor folding"""
    _hash = djb(string)
    return ((_hash >> 64) ^ _hash) & MASK_64