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abf0909b68
According to CONTRIBUTING.md: "Algorithms in this repo should not be how-to examples for existing Python packages."
67 lines
2.3 KiB
Python
67 lines
2.3 KiB
Python
def base16_encode(data: bytes) -> str:
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"""
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Encodes the given bytes into base16.
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>>> base16_encode(b'Hello World!')
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'48656C6C6F20576F726C6421'
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>>> base16_encode(b'HELLO WORLD!')
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'48454C4C4F20574F524C4421'
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>>> base16_encode(b'')
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''
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"""
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# Turn the data into a list of integers (where each integer is a byte),
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# Then turn each byte into its hexadecimal representation, make sure
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# it is uppercase, and then join everything together and return it.
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return "".join([hex(byte)[2:].zfill(2).upper() for byte in list(data)])
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def base16_decode(data: str) -> bytes:
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"""
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Decodes the given base16 encoded data into bytes.
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>>> base16_decode('48656C6C6F20576F726C6421')
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b'Hello World!'
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>>> base16_decode('48454C4C4F20574F524C4421')
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b'HELLO WORLD!'
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>>> base16_decode('')
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b''
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>>> base16_decode('486')
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Traceback (most recent call last):
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...
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ValueError: Base16 encoded data is invalid:
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Data does not have an even number of hex digits.
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>>> base16_decode('48656c6c6f20576f726c6421')
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Traceback (most recent call last):
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...
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ValueError: Base16 encoded data is invalid:
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Data is not uppercase hex or it contains invalid characters.
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>>> base16_decode('This is not base64 encoded data.')
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Traceback (most recent call last):
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...
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ValueError: Base16 encoded data is invalid:
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Data is not uppercase hex or it contains invalid characters.
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"""
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# Check data validity, following RFC3548
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# https://www.ietf.org/rfc/rfc3548.txt
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if (len(data) % 2) != 0:
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raise ValueError(
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"""Base16 encoded data is invalid:
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Data does not have an even number of hex digits."""
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)
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# Check the character set - the standard base16 alphabet
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# is uppercase according to RFC3548 section 6
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if not set(data) <= set("0123456789ABCDEF"):
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raise ValueError(
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"""Base16 encoded data is invalid:
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Data is not uppercase hex or it contains invalid characters."""
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)
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# For every two hexadecimal digits (= a byte), turn it into an integer.
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# Then, string the result together into bytes, and return it.
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return bytes(int(data[i] + data[i + 1], 16) for i in range(0, len(data), 2))
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if __name__ == "__main__":
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import doctest
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doctest.testmod()
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