73 lines
2.1 KiB
Python
73 lines
2.1 KiB
Python
|
# 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.
|
||
|
|
|
||
|
|
"""Data transformation functions.
|
||
|
|
|
||
|
|
From bytes to a number, number to bytes, etc.
|
||
|
|
"""
|
||
|
|
|
||
|
|
import math
|
||
|
|
|
||
|
|
|
||
|
|
def bytes2int(raw_bytes: bytes) -> int:
|
||
|
|
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(b'\x80@\x0f')
|
||
|
|
8405007
|
||
|
|
|
||
|
|
"""
|
||
|
|
return int.from_bytes(raw_bytes, "big", signed=False)
|
||
|
|
|
||
|
|
|
||
|
|
def int2bytes(number: int, fill_size: int = 0) -> bytes:
|
||
|
|
"""
|
||
|
|
Convert an unsigned integer to bytes (big-endian)::
|
||
|
|
|
||
|
|
Does not preserve leading zeros if you don't specify a fill size.
|
||
|
|
|
||
|
|
:param number:
|
||
|
|
Integer value
|
||
|
|
:param fill_size:
|
||
|
|
If the optional fill size is given the length of the resulting
|
||
|
|
byte string is expected to be the fill size and will be padded
|
||
|
|
with prefix zero bytes to satisfy that length.
|
||
|
|
:returns:
|
||
|
|
Raw bytes (base-256 representation).
|
||
|
|
:raises:
|
||
|
|
``OverflowError`` when fill_size is given and the number takes up more
|
||
|
|
bytes than fit into the block. This requires the ``overflow``
|
||
|
|
argument to this function to be set to ``False`` otherwise, no
|
||
|
|
error will be raised.
|
||
|
|
"""
|
||
|
|
|
||
|
|
if number < 0:
|
||
|
|
raise ValueError("Number must be an unsigned integer: %d" % number)
|
||
|
|
|
||
|
|
bytes_required = max(1, math.ceil(number.bit_length() / 8))
|
||
|
|
|
||
|
|
if fill_size > 0:
|
||
|
|
return number.to_bytes(fill_size, "big")
|
||
|
|
|
||
|
|
return number.to_bytes(bytes_required, "big")
|
||
|
|
|
||
|
|
|
||
|
|
if __name__ == "__main__":
|
||
|
|
import doctest
|
||
|
|
|
||
|
|
doctest.testmod()
|