File: utils.py

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import binascii


def _consistent_hash(value, ring_size):
    """
    Maps the value to a node value between 0 and 4095
    using CRC, then down to one of the ring nodes.
    """
    if ring_size == 1:
        # Avoid the overhead of hashing and modulo when it is unnecessary.
        return 0

    if isinstance(value, str):
        value = value.encode("utf8")
    bigval = binascii.crc32(value) & 0xFFF
    ring_divisor = 4096 / float(ring_size)
    return int(bigval / ring_divisor)