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def base16_encode(data: bytes) -> str:

"""

Encodes the given bytes into base16.

>>> base16_encode(b'Hello World!')

'48656C6C6F20576F726C6421'

>>> base16_encode(b'HELLO WORLD!')

'48454C4C4F20574F524C4421'

>>> base16_encode(b'')

"""

# Turn the data into a list of integers (where each integer is a byte),

# Then turn each byte into its hexadecimal representation, make sure

# it is uppercase, and then join everything together and return it.

return "".join([hex(byte)[2:].zfill(2).upper() for byte in list(data)])

def base16_decode(data: str) -> bytes:

"""

Decodes the given base16 encoded data into bytes.

>>> base16_decode('48656C6C6F20576F726C6421')

b'Hello World!'

>>> base16_decode('48454C4C4F20574F524C4421')

b'HELLO WORLD!'

>>> base16_decode('')

b''

>>> base16_decode('486')

Traceback (most recent call last):

...

ValueError: Base16 encoded data is invalid:

Data does not have an even number of hex digits.

>>> base16_decode('48656c6c6f20576f726c6421')

Traceback (most recent call last):

...

ValueError: Base16 encoded data is invalid:

Data is not uppercase hex or it contains invalid characters.

>>> base16_decode('This is not base64 encoded data.')

Traceback (most recent call last):

...

ValueError: Base16 encoded data is invalid:

Data is not uppercase hex or it contains invalid characters.

"""

# Check data validity, following RFC3548

# https://www.ietf.org/rfc/rfc3548.txt

if (len(data) % 2) != 0:

raise ValueError(

"""Base16 encoded data is invalid:

Data does not have an even number of hex digits."""

)

# Check the character set - the standard base16 alphabet

# is uppercase according to RFC3548 section 6

if not set(data) <= set("0123456789ABCDEF"):

raise ValueError(

"""Base16 encoded data is invalid:

Data is not uppercase hex or it contains invalid characters."""

)

# For every two hexadecimal digits (= a byte), turn it into an integer.

# Then, string the result together into bytes, and return it.

return bytes(int(data[i] + data[i + 1], 16) for i in range(0, len(data), 2))

if __name__ == "__main__":

import doctest

doctest.testmod()

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