| # 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() |