Pure python murmer3 32 bit

murmur3_word_hash.py

CONST_START = 0x0
CONST1 = 0xCC9E2D51
CONST2 = 0x1B873593

def hash_word(text: str):
    """
    32bit murmur3 hash.
    Written by Patrick Shechet
    Based on pymmh3 by Fredrik Kihlander and Swapnil Gusani: https://github.com/wc-duck/pymmh3/blob/master/pymmh3.py
    
    """

    key = bytearray(text.encode())

    length = len(key)
    nblocks = int(length / 4)
    h1 = CONST_START

    # for each fourByteChunk of key
    for four_byte_chunk in range(0, nblocks * 4, 4):
        k1 = (
            key[four_byte_chunk + 3] << 24
            | key[four_byte_chunk + 2] << 16
            | key[four_byte_chunk + 1] << 8
            | key[four_byte_chunk + 0]
        )

        k1 = (CONST1 * k1) & 0xFFFFFFFF
        k1 = (k1 << 15 | k1 >> 17) & 0xFFFFFFFF
        k1 = (CONST2 * k1) & 0xFFFFFFFF

        h1 ^= k1
        h1 = (h1 << 13 | h1 >> 19) & 0xFFFFFFFF
        h1 = (h1 * 5 + 0xE6546B64) & 0xFFFFFFFF

    tail_index = nblocks * 4
    k1 = 0
    tail_size = length & 3

    if tail_size >= 3:
        k1 ^= key[tail_index + 2] << 16
    if tail_size >= 2:
        k1 ^= key[tail_index + 1] << 8
    if tail_size >= 1:
        k1 ^= key[tail_index + 0]

    if tail_size > 0:
        k1 = (k1 * CONST1) & 0xFFFFFFFF
        k1 = (k1 << 15 | k1 >> 17) & 0xFFFFFFFF
        k1 = (k1 * CONST2) & 0xFFFFFFFF
        h1 ^= k1

    unsigned_val = h1 ^ length
    unsigned_val ^= unsigned_val >> 16
    unsigned_val = (unsigned_val * 0x85EBCA6B) & 0xFFFFFFFF
    unsigned_val ^= unsigned_val >> 13
    unsigned_val = (unsigned_val * 0xC2B2AE35) & 0xFFFFFFFF
    unsigned_val ^= unsigned_val >> 16

    if unsigned_val & 0x80000000 == 0:
        return unsigned_val
    else:
        return -((unsigned_val ^ 0xFFFFFFFF) + 1)