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✏️ Editing: TupleHash128.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
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#
# 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
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# ===================================================================

from Crypto.Util.py3compat import bord, is_bytes, tobytes

from . import cSHAKE128
from .cSHAKE128 import _encode_str, _right_encode

class TupleHash(object):
    """A Tuple hash object.
    Do not instantiate directly.
    Use the :func:`new` function.
    """

def __init__(self, custom, cshake, digest_size):

self.digest_size = digest_size

self._cshake = cshake._new(b'', custom, b'TupleHash')
        self._digest = None

def update(self, data):
        """Authenticate the next byte string in the tuple.

Args:
            data (bytes/bytearray/memoryview): The next byte string.
        """

if self._digest is not None:
            raise TypeError("You cannot call 'update' after 'digest' or 'hexdigest'")

if not is_bytes(data):
            raise TypeError("You can only call 'update' on bytes")

self._cshake.update(_encode_str(tobytes(data)))

return self

def digest(self):
        """Return the **binary** (non-printable) digest of the tuple of byte strings.

:return: The hash digest. Binary form.
        :rtype: byte string
        """

if self._digest is None:
            self._cshake.update(_right_encode(self.digest_size * 8))
            self._digest = self._cshake.read(self.digest_size)

return self._digest

def hexdigest(self):
        """Return the **printable** digest of the tuple of byte strings.

:return: The hash digest. Hexadecimal encoded.
        :rtype: string
        """

return "".join(["%02x" % bord(x) for x in tuple(self.digest())])

def new(self, **kwargs):
        """Return a new instance of a TupleHash object.
        See :func:`new`.
        """

if "digest_bytes" not in kwargs and "digest_bits" not in kwargs:
            kwargs["digest_bytes"] = self.digest_size

return new(**kwargs)

def new(**kwargs):
    """Create a new TupleHash128 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, cSHAKE128, digest_bytes)

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