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I have millions of strings that are exactly 6 characters (bytes) long. Each position in the string can be one of 37 possible characters (space, 0-9 and A-Z). I need to very quickly compress these strings into the smallest space possible and also be able to expand them back again later as quickly as possible.

The implementation I have now uses 6 bits per character and compresses the string into 36 bits. I split the string in half (3 characters each) and use a hash look up to convert each half to a series of 1s and 0s. I concatenate the bitstrings together (with 4 bits of padding) and used pack('B*', $bitstr) to get from 6 bytes to 5.

I know that I can do better. 37 ^ 6 = 2_565_726_409 while 2 ^ 32 = 4_294_967_296. If I treated the string as a base 37 number, it would easily fit into a 32 bit integer (4 bytes). What I am at a loss for is how to quickly translate 0 into '      ' and 2_565_726_409 into 'ZZZZZZ';

My environment is perl 5.8.8 with no compiler so I am limited to pure perl modules only. What's the best that you can do?

Cheers - L~R

In reply to Fast - Compact That String by Limbic~Region

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    Tanktalus has to figure out why his cb talker isn't working :(
    [choroba]: https?
    [choroba]: That was at least why my cb talker wasn't working.
    [Tanktalus]: curious, then, why the reader works :)
    [Tanktalus]: or posting the last hour of cb... well, maybe I should double check that first :)
    [Tanktalus]: yup, it's working. :)
    [choroba]: https://github. com/choroba/pm-cb/ commit/7b57f513596 7bf8a29d74f1c307de 9a76894cdcf

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