# Now decode little endian with "0" padding, which are leading zeros. Thus, the result will be QUJD REVG Rw (without spaces). But for the third, it will add a double in the output in order to complete the 4 needed characters. # First decode the base64, adding the required "=" padding.ĭecoded = base64.b64decode(chars + b"="*b64_pad_len) Base64 deals with the first block (producing 4 characters) and the second (as they are complete). # Do the reverse of the url_safe conversion above.Ĭhars = chars.replace(b"-", b"/").replace(b".", b"+") This no longer conforms to base64, but looks betterĮncoded = base64.b64encode(packed).split(b"=")Įncoded = encoded.replace(b"/", b"-").replace(b"+", b".") Other familiar tools to you that are also in coreutils. Set to True to convert "/" to "-" and "+" to base64: This is a program that is in the coreutils (or GNU Core Utilities) package that comes pre-packaged with your Mac or Linux OS. :param url_safe: base64 may contain "/" and "+", which do not play well def int_to_chars(number, url_safe = True):Ĭonvert an integer to base64. Whenever the number of bytes in your input can't be divided by 3, padding is required according to the standard. 4 base64 characters can encode 4624 bits, which equals 3 bytes. Note the flag url_safe which makes the solution non-base64 compliant, but works better with URLs. Base64 encoding maps the input bytes (8 bit) to a 6 bit representation. Then convert to base64, removing the unnecessary = sign. We first encode the integer into a byte array using little endian, and automatically remove any extra leading zeros. Here is the manual page for base64: herong. This is particularly helpful for encoding database keys. If you are using a Linux system, you can use the built-in command base64 to perform Base64 encoding and decoding. The function below converts an unsigned 64 bit integer into base64 representation, and back again. > final_number1 = int.from_bytes(decoded, byteorder="big")įor more details on bitwise operations, check : Output of crc32b in PHP is not equal to Python answer). > final_number0 = sum((item * 256 ** idx for idx, item in enumerate(reversed(decoded)))) > encoded, code() # Don't let yourself tricked by the variable and method names resemblance > encoded = base64.b64encode(number_bytes) > number_bytes = number.to_bytes((number.bit_length() + 7) // 8, byteorder="big") # Here's where the magic happens Things being done manually (this could also be applied to the "forward" process).to_bytes( length, byteorder, *, signed=False)( endianness is important, and in this case it's big):įor the backwards process, reversed steps are required. One elegant way would be using : struct - Interpret bytes as packed binary data, but given the fact that Python numbers are not fixed size, some additional computation would be required (for example, the number is 5 bytes long).Īpparently, the online converter, applied the base64 encoding on the number's memory representation, which can be obtained via : int.
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