1  # -*- coding: utf-8 -*-
  2  #
  3  #  Copyright 2011 Sybren A. Stüvel <sybren@stuvel.eu>
  4  #
  5  #  Licensed under the Apache License, Version 2.0 (the "License");
  6  #  you may not use this file except in compliance with the License.
  7  #  You may obtain a copy of the License at
  8  #
  9  #      https://www.apache.org/licenses/LICENSE-2.0
 10  #
 11  #  Unless required by applicable law or agreed to in writing, software
 12  #  distributed under the License is distributed on an "AS IS" BASIS,
 13  #  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 14  #  See the License for the specific language governing permissions and
 15  #  limitations under the License.
 16  
 17  """Python compatibility wrappers."""
 18  
 19  import sys
 20  from struct import pack
 21  
 22  __version__ = "0.0.0-auto.0"
 23  __repo__ = "https://github.com/adafruit/Adafruit_CircuitPython_RSA.git"
 24  
 25  MAX_INT = sys.maxsize
 26  MAX_INT64 = (1 << 63) - 1
 27  MAX_INT32 = (1 << 31) - 1
 28  MAX_INT16 = (1 << 15) - 1
 29  
 30  # Determine the word size of the processor.
 31  if MAX_INT == MAX_INT64:
 32      # 64-bit processor.
 33      MACHINE_WORD_SIZE = 64
 34  elif MAX_INT == MAX_INT32:
 35      # 32-bit processor.
 36      MACHINE_WORD_SIZE = 32
 37  else:
 38      # Else we just assume 64-bit processor keeping up with modern times.
 39      MACHINE_WORD_SIZE = 64
 40  
 41  
 42  INTEGER_TYPES = (int,)
 43  
 44  
 45  def write_to_stdout(data):
 46      """Writes bytes to stdout
 47  
 48      :type data: bytes
 49      """
 50      # On Py3 we must use the buffer interface to write bytes.
 51      sys.stdout.buffer.write(data)
 52  
 53  
 54  def is_bytes(obj):
 55      """
 56      Determines whether the given value is a byte string.
 57  
 58      :param obj:
 59          The value to test.
 60      :returns:
 61          ``True`` if ``value`` is a byte string; ``False`` otherwise.
 62      """
 63      return isinstance(obj, bytes)
 64  
 65  
 66  def is_integer(obj):
 67      """
 68      Determines whether the given value is an integer.
 69  
 70      :param obj:
 71          The value to test.
 72      :returns:
 73          ``True`` if ``value`` is an integer; ``False`` otherwise.
 74      """
 75      return isinstance(obj, INTEGER_TYPES)
 76  
 77  
 78  def byte(num):
 79      """
 80      Converts a number between 0 and 255 (both inclusive) to a base-256 (byte)
 81      representation.
 82  
 83      Use it as a replacement for ``chr`` where you are expecting a byte
 84      because this will work on all current versions of Python::
 85  
 86      :param num:
 87          An unsigned integer between 0 and 255 (both inclusive).
 88      :returns:
 89          A single byte.
 90      """
 91      return pack("B", num)
 92  
 93  
 94  def xor_bytes(bytes_1, bytes_2):
 95      """
 96      Returns the bitwise XOR result between two bytes objects, bytes_1 ^ bytes_2.
 97  
 98      Bitwise XOR operation is commutative, so order of parameters doesn't
 99      generate different results. If parameters have different length, extra
100      length of the largest one is ignored.
101  
102      :param bytes_1:
103          First bytes object.
104      :param bytes_2:
105          Second bytes object.
106      :returns:
107          Bytes object, result of XOR operation.
108      """
109      return bytes(x ^ y for x, y in zip(bytes_1, bytes_2))
110  
111  
112  def get_word_alignment(num, force_arch=64, _machine_word_size=MACHINE_WORD_SIZE):
113      """
114      Returns alignment details for the given number based on the platform
115      Python is running on.
116  
117      :param num:
118          Unsigned integral number.
119      :param force_arch:
120          If you don't want to use 64-bit unsigned chunks, set this to
121          anything other than 64. 32-bit chunks will be preferred then.
122          Default 64 will be used when on a 64-bit machine.
123      :param _machine_word_size:
124          (Internal) The machine word size used for alignment.
125      :returns:
126          4-tuple::
127  
128              (word_bits, word_bytes,
129               max_uint, packing_format_type)
130      """
131      max_uint64 = 0xFFFFFFFFFFFFFFFF
132      max_uint32 = 0xFFFFFFFF
133      max_uint16 = 0xFFFF
134      max_uint8 = 0xFF
135  
136      if force_arch == 64 and _machine_word_size >= 64 and num > max_uint32:
137          # 64-bit unsigned integer.
138          return 64, 8, max_uint64, "Q"
139      if num > max_uint16:
140          # 32-bit unsigned integer
141          return 32, 4, max_uint32, "L"
142      if num > max_uint8:
143          # 16-bit unsigned integer.
144          return 16, 2, max_uint16, "H"
145      # 8-bit unsigned integer.
146      return 8, 1, max_uint8, "B"