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# -*- 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
#
# http://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.
'''Data transformation functions.
From bytes to a number, number to bytes, etc.
'''
import binascii
from rsa import common
from rsa._compat import byte, is_integer, b
def bytes2int(raw_bytes):
r"""Converts a list of bytes or an 8-bit string to an integer.
When using unicode strings, encode it to some encoding like UTF8 first.
>>> (((128 * 256) + 64) * 256) + 15
8405007
>>> bytes2int('\x80@\x0f')
8405007
"""
return int(binascii.hexlify(raw_bytes), 16)
def int2bytes(number, block_size=None):
r'''Converts a number to a string of bytes.
@param number: the number to convert
@param block_size: the number of bytes to output. If the number encoded to
bytes is less than this, the block will be zero-padded. When not given,
the returned block is not padded.
@throws OverflowError when block_size is given and the number takes up more
bytes than fit into the block.
>>> int2bytes(123456789)
'\x07[\xcd\x15'
>>> bytes2int(int2bytes(123456789))
123456789
>>> int2bytes(123456789, 6)
'\x00\x00\x07[\xcd\x15'
>>> bytes2int(int2bytes(123456789, 128))
123456789
>>> int2bytes(123456789, 3)
Traceback (most recent call last):
...
OverflowError: Needed 4 bytes for number, but block size is 3
'''
# Type checking
if not is_integer(number):
raise TypeError("You must pass an integer for 'number', not %s" %
type(number).__name__)
if number < 0:
raise ValueError('Negative numbers cannot be used: %i' % number)
# Do some bounds checking
if block_size is not None:
needed_bytes = common.byte_size(number)
if needed_bytes > block_size:
raise OverflowError('Needed %i bytes for number, but block size '
'is %i' % (needed_bytes, block_size))
# Convert the number to bytes.
raw_bytes = []
while number > 0:
raw_bytes.insert(0, byte(number & 0xFF))
number >>= 8
# Pad with zeroes to fill the block
if block_size is not None:
padding = (block_size - needed_bytes) * b('\x00')
else:
padding = b('')
return padding + b('').join(raw_bytes)
if __name__ == '__main__':
import doctest
doctest.testmod()
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