Mini Shell

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# Copyright (c) 2021, Legrandin <helderijs@gmail.com>
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from . import cSHAKE256
from .TupleHash128 import TupleHash


def new(**kwargs):
    """Create a new TupleHash256 object.

    Args:
       digest_bytes (integer):
        Optional. The size of the digest, in bytes.
        Default is 64. Minimum is 8.
       digest_bits (integer):
        Optional and alternative to ``digest_bytes``.
        The size of the digest, in bits (and in steps of 8).
        Default is 512. Minimum is 64.
       custom (bytes):
        Optional.
        A customization bytestring (``S`` in SP 800-185).

    :Return: A :class:`TupleHash` object
    """

    digest_bytes = kwargs.pop("digest_bytes", None)
    digest_bits = kwargs.pop("digest_bits", None)
    if None not in (digest_bytes, digest_bits):
        raise TypeError("Only one digest parameter must be provided")
    if (None, None) == (digest_bytes, digest_bits):
        digest_bytes = 64
    if digest_bytes is not None:
        if digest_bytes < 8:
            raise ValueError("'digest_bytes' must be at least 8")
    else:
        if digest_bits < 64 or digest_bits % 8:
            raise ValueError("'digest_bytes' must be at least 64 "
                             "in steps of 8")
        digest_bytes = digest_bits // 8

    custom = kwargs.pop("custom", b'')

    if kwargs:
        raise TypeError("Unknown parameters: " + str(kwargs))

    return TupleHash(custom, cSHAKE256, digest_bytes)