Base36 Encode a String?

Question

I've been looking online, but can't find a solution to this. In Python, Ruby, or Java, how can I base 36 encode the following string: nOrG9Eh0uyeilM8Nnu5pTywj3935kW+5=

I want to encode that string and then decode it back in Base36. I just want to know if it's even possible. — Bradford, May 18 '11 at 18:57
To all the people sharing code to encode a number, thanks, but I'm trying to encode a string. Please excuse me if that's not possible. I see libraries that can base 64 encode a string, though. — Bradford, May 18 '11 at 19:00
@SLaks Encryption also includes algorithms that are hopelessly naive ;) — gshauger, May 18 '11 at 19:10

score 9 · Accepted Answer · answered May 18 '11 at 19:32

9

Ruby

To base 36:

s.unpack('H*')[0].to_i(16).to_s 36

From base 36:

[s36.to_i(36).to_s(16)].pack 'H*'

answered May 18 '11 at 19:32

DigitalRoss

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Very nice, DigitalRoss. Thanks. – Bradford May 19 '11 at 14:00

score 1 · Answer 2 · answered Apr 20 '12 at 11:23

I have just done this:

  static String encodeRootId(final String value) {
    try {
      final BigInteger bigInteger = new BigInteger(value.getBytes("UTF-8"));
      final String encoded = bigInteger.toString(Character.MAX_RADIX);

      //must encode the sign as well
      if (bigInteger.signum() < 0) {
        return 'n' + encoded.substring(1);
      } else {
        return 'p' + encoded;
      }
    } catch (UnsupportedEncodingException e) {
      throw new RuntimeException("impossible");
    }
  }

the trick to convert the string bytes[] to a big int brought the disadvantage of having to manually encode the possible -, admittedly not pretty but a quick solution.

also, in my use case i dont have to decode and performance is not a concern.

score 0 · Answer 3 · answered May 18 '11 at 18:58

0

Looks like wikipedia has an article on how to do it in python: http://en.wikipedia.org/wiki/Base_36

answered May 18 '11 at 18:58

Kaj

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score -1 · Answer 4 · edited May 23 '17 at 12:24

-1

This could be seen as a duplicate as another question... Python base 36 encoding.

Basically, there is this example on wikipedia:

def base36encode(number, alphabet='0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ'):
    """Convert positive integer to a base36 string."""
    if not isinstance(number, (int, long)):
        raise TypeError('number must be an integer')

    # Special case for zero
    if number == 0:
        return alphabet[0]

    base36 = ''

    sign = ''
    if number < 0:
        sign = '-'
        number = - number

    while number != 0:
        number, i = divmod(number, len(alphabet))
        base36 = alphabet[i] + base36

    return sign + base36

def base36decode(number):
    return int(number, 36)

print base36encode(1412823931503067241)
print base36decode('AQF8AA0006EH')

Wikipedia page: http://en.wikipedia.org/wiki/Base_36

edited May 23 '17 at 12:24

Community

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answered May 18 '11 at 18:58

Joseph Redfern

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This answers the question of how to base 36 encode a numeric value, but not a string. – Bradford May 18 '11 at 19:09
base36 is about encoding NUMBERS *only* – May 18 '11 at 19:30
1

@Bradford: Just convert your string to a number and encode it. Reverse the steps for decoding. For example if you're using 8-bit characters, consider each character code to be a Base 256 digit. – martineau May 18 '11 at 19:55
1

@Bradford: Here's a quick way to convert a string of 8-bit characters into a number: `reduce(lambda a,d: a*256 + ord(d), astring, 0)`. – martineau May 18 '11 at 20:02
Wow. Thanks a lot martineau. That's actually the answer I was looking for. It was easy to reverse with divmod too. – Bradford May 19 '11 at 01:55

Base36 Encode a String?

4 Answers4

Ruby

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