73 lines
2.1 KiB
Python
73 lines
2.1 KiB
Python
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# Copyright 2011 Sybren A. Stüvel <sybren@stuvel.eu>
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# https://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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"""Data transformation functions.
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From bytes to a number, number to bytes, etc.
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"""
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import math
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def bytes2int(raw_bytes: bytes) -> int:
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r"""Converts a list of bytes or an 8-bit string to an integer.
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When using unicode strings, encode it to some encoding like UTF8 first.
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>>> (((128 * 256) + 64) * 256) + 15
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8405007
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>>> bytes2int(b'\x80@\x0f')
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8405007
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"""
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return int.from_bytes(raw_bytes, 'big', signed=False)
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def int2bytes(number: int, fill_size: int = 0) -> bytes:
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"""
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Convert an unsigned integer to bytes (big-endian)::
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Does not preserve leading zeros if you don't specify a fill size.
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:param number:
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Integer value
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:param fill_size:
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If the optional fill size is given the length of the resulting
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byte string is expected to be the fill size and will be padded
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with prefix zero bytes to satisfy that length.
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:returns:
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Raw bytes (base-256 representation).
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:raises:
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``OverflowError`` when fill_size is given and the number takes up more
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bytes than fit into the block. This requires the ``overflow``
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argument to this function to be set to ``False`` otherwise, no
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error will be raised.
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"""
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if number < 0:
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raise ValueError("Number must be an unsigned integer: %d" % number)
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bytes_required = max(1, math.ceil(number.bit_length() / 8))
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if fill_size > 0:
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return number.to_bytes(fill_size, 'big')
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return number.to_bytes(bytes_required, 'big')
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if __name__ == '__main__':
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import doctest
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doctest.testmod()
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