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Filename : SHAKE128.py
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# ===================================================================
#
# Copyright (c) 2015, Legrandin <helderijs@gmail.com>
# All rights reserved.
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# 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.
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#    the documentation and/or other materials provided with the
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from Crypto.Util.py3compat import bord

from Crypto.Util._raw_api import (load_pycryptodome_raw_lib,
                                  VoidPointer, SmartPointer,
                                  create_string_buffer,
                                  get_raw_buffer, c_size_t,
                                  c_uint8_ptr, c_ubyte)

from Crypto.Hash.keccak import _raw_keccak_lib

class SHAKE128_XOF(object):
    """A SHAKE128 hash object.
    Do not instantiate directly.
    Use the :func:`new` function.

    :ivar oid: ASN.1 Object ID
    :vartype oid: string
    """

    # ASN.1 Object ID
    oid = "2.16.840.1.101.3.4.2.11"

    def __init__(self, data=None):
        state = VoidPointer()
        result = _raw_keccak_lib.keccak_init(state.address_of(),
                                             c_size_t(32),
                                             c_ubyte(24))
        if result:
            raise ValueError("Error %d while instantiating SHAKE128"
                             % result)
        self._state = SmartPointer(state.get(),
                                   _raw_keccak_lib.keccak_destroy)
        self._is_squeezing = False
        self._padding = 0x1F
        if data:
            self.update(data)

    def update(self, data):
        """Continue hashing of a message by consuming the next chunk of data.

        Args:
            data (byte string/byte array/memoryview): The next chunk of the message being hashed.
        """

        if self._is_squeezing:
            raise TypeError("You cannot call 'update' after the first 'read'")

        result = _raw_keccak_lib.keccak_absorb(self._state.get(),
                                               c_uint8_ptr(data),
                                               c_size_t(len(data)))
        if result:
            raise ValueError("Error %d while updating SHAKE128 state"
                             % result)
        return self

    def read(self, length):
        """
        Compute the next piece of XOF output.

        .. note::
            You cannot use :meth:`update` anymore after the first call to
            :meth:`read`.

        Args:
            length (integer): the amount of bytes this method must return

        :return: the next piece of XOF output (of the given length)
        :rtype: byte string
        """

        self._is_squeezing = True
        bfr = create_string_buffer(length)
        result = _raw_keccak_lib.keccak_squeeze(self._state.get(),
                                                bfr,
                                                c_size_t(length),
                                                c_ubyte(self._padding))
        if result:
            raise ValueError("Error %d while extracting from SHAKE128"
                             % result)

        return get_raw_buffer(bfr)

    def new(self, data=None):
        return type(self)(data=data)


def new(data=None):
    """Return a fresh instance of a SHAKE128 object.

    Args:
       data (bytes/bytearray/memoryview):
        The very first chunk of the message to hash.
        It is equivalent to an early call to :meth:`update`.
        Optional.

    :Return: A :class:`SHAKE128_XOF` object
    """

    return SHAKE128_XOF(data=data)