[Mediawiki-api] Does wikipedia use different methods to compute the hash part of an image path?

I'm computing the url of an image by the following: (the md5 of the first char and the second two chars concat)

val md = MessageDigest.getInstance("MD5") val messageDigest = md.digest(fileName.getBytes) val md5 = (new BigInteger(1, messageDigest)).toString(16)

val hash1 = md5.substring(0, 1) val hash2 = md5.substring(0, 2)

val urlPart = hash1 + "/" + hash2 + "/" + fileName

Most of the time, the function works correctly but on a few cases, it is incorrect:

For "Stewie_Griffin.png", I get 2/26/Stewie_Griffin.png but the real one is 0/02/Stewie_Griffin.png

The source file info is here: http://en.wikipedia.org/wiki/File:Stewie_Griffin.png http://upload.wikimedia.org/wikipedia/en/0/02/Stewie_Griffin.png

Any ideas why the hashing scheme doesn't work sometimes?

I posted this question on stackoverflow but I might be able to get a better answer here.http://stackoverflow.com/questions/8389616/does-wikipedia-use-different-meth...