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Background:

I am using Clojure, on Java 7.0 on Ubuntu Linux 12.10, with an Ext4 file system.

Problem:

I have an arbitrary Clojure string. I would like to encode it into a valid filename.

Question:

What is the optimal way / what is a good builtin for doing this?

Note:

The encoded file name does not have to be human readable. I just need to be able to recover the original string from the filename.

EDIT:

Although if strings that are valid names gets mapped to something that is human readbale (and close to it's original value, that would be nice too.)

Thanks!

EDIT:

encode: takes arbitrary string as input; creates valid filename as output

decode: takes file name from encode, recovers original string

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  • Your question is incomplete... We don't know what "encode" means in this context. Commented Dec 8, 2012 at 6:46
  • @RobertHarvey: Thanks. Added an edit. Is it clear now? Commented Dec 8, 2012 at 6:48

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If it doesn't need to be human readable, just base64 encode it. That will remove any file name invalid characters from the string.

http://richhickey.github.com/clojure-contrib/base64-api.html

If they still don't have a decoder in native clojure, use a Java base64 decode function.

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4 Comments

That wouldn't quite work because base64 includes '/', so you would generate invalid filenames. You'd have to replace '/' by another character outside the base64 alphabet.
Then you'll need a Java function that can do base62 encoding, like this one.
lol, should I just drop down to base 16, and use the builtin functions for represeting numbers in hex? :-)
You mean encode the string as two hex digits per byte? In most file systems there is a limit on how many characters you can use in a file name, and that will double the size of your string, whereas base62 should only increase the size slightly for ordinary text.

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