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CatOrNot/venv/lib/python3.6/site-packages/rsa/_compat.py

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2018-12-11 00:32:28 +01:00
# -*- coding: utf-8 -*-
#
# Copyright 2011 Sybren A. Stüvel <sybren@stuvel.eu>
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# https://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""Python compatibility wrappers."""
from __future__ import absolute_import
import itertools
import sys
from struct import pack
MAX_INT = sys.maxsize
MAX_INT64 = (1 << 63) - 1
MAX_INT32 = (1 << 31) - 1
MAX_INT16 = (1 << 15) - 1
PY2 = sys.version_info[0] == 2
# Determine the word size of the processor.
if MAX_INT == MAX_INT64:
# 64-bit processor.
MACHINE_WORD_SIZE = 64
elif MAX_INT == MAX_INT32:
# 32-bit processor.
MACHINE_WORD_SIZE = 32
else:
# Else we just assume 64-bit processor keeping up with modern times.
MACHINE_WORD_SIZE = 64
if PY2:
integer_types = (int, long)
range = xrange
zip = itertools.izip
else:
integer_types = (int, )
range = range
zip = zip
def write_to_stdout(data):
"""Writes bytes to stdout
:type data: bytes
"""
if PY2:
sys.stdout.write(data)
else:
# On Py3 we must use the buffer interface to write bytes.
sys.stdout.buffer.write(data)
def is_bytes(obj):
"""
Determines whether the given value is a byte string.
:param obj:
The value to test.
:returns:
``True`` if ``value`` is a byte string; ``False`` otherwise.
"""
return isinstance(obj, bytes)
def is_integer(obj):
"""
Determines whether the given value is an integer.
:param obj:
The value to test.
:returns:
``True`` if ``value`` is an integer; ``False`` otherwise.
"""
return isinstance(obj, integer_types)
def byte(num):
"""
Converts a number between 0 and 255 (both inclusive) to a base-256 (byte)
representation.
Use it as a replacement for ``chr`` where you are expecting a byte
because this will work on all current versions of Python::
:param num:
An unsigned integer between 0 and 255 (both inclusive).
:returns:
A single byte.
"""
return pack("B", num)
def xor_bytes(b1, b2):
"""
Returns the bitwise XOR result between two bytes objects, b1 ^ b2.
Bitwise XOR operation is commutative, so order of parameters doesn't
generate different results. If parameters have different length, extra
length of the largest one is ignored.
:param b1:
First bytes object.
:param b2:
Second bytes object.
:returns:
Bytes object, result of XOR operation.
"""
if PY2:
return ''.join(byte(ord(x) ^ ord(y)) for x, y in zip(b1, b2))
return bytes(x ^ y for x, y in zip(b1, b2))
def get_word_alignment(num, force_arch=64,
_machine_word_size=MACHINE_WORD_SIZE):
"""
Returns alignment details for the given number based on the platform
Python is running on.
:param num:
Unsigned integral number.
:param force_arch:
If you don't want to use 64-bit unsigned chunks, set this to
anything other than 64. 32-bit chunks will be preferred then.
Default 64 will be used when on a 64-bit machine.
:param _machine_word_size:
(Internal) The machine word size used for alignment.
:returns:
4-tuple::
(word_bits, word_bytes,
max_uint, packing_format_type)
"""
max_uint64 = 0xffffffffffffffff
max_uint32 = 0xffffffff
max_uint16 = 0xffff
max_uint8 = 0xff
if force_arch == 64 and _machine_word_size >= 64 and num > max_uint32:
# 64-bit unsigned integer.
return 64, 8, max_uint64, "Q"
elif num > max_uint16:
# 32-bit unsigned integer
return 32, 4, max_uint32, "L"
elif num > max_uint8:
# 16-bit unsigned integer.
return 16, 2, max_uint16, "H"
else:
# 8-bit unsigned integer.
return 8, 1, max_uint8, "B"