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Edit File: TupleHash256.py

# ===================================================================
#
# Copyright (c) 2021, Legrandin <helderijs@gmail.com>
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions
# are met:
#
# 1. Redistributions of source code must retain the above copyright
#    notice, this list of conditions and the following disclaimer.
# 2. Redistributions in binary form must reproduce the above copyright
#    notice, this list of conditions and the following disclaimer in
#    the documentation and/or other materials provided with the
#    distribution.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
# FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
# COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
# BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
# LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
# CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
# ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
# POSSIBILITY OF SUCH DAMAGE.
# ===================================================================

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)

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