Question

I am writing a game for iOS that uses .tmx map files. I am creating the maps in the application ‘Tiled’ and then at some point before they get to iOS, I’m parsing them with Perl.

When I save the files as straight XML, it’s a cinch for perl to parse them. However, cocos2d insists that the files be base64-encoded. The ‘Tiled’ map editor has no problem saving files with this encoding scheme, and iOS reads them just fine, but it’s presenting problems for my perl code.

For some reason, the standard MIME::Base64 decode_base64() method in perl is not cutting the mustard here- when I decode the strings, I get one or two binary characters– question marks in diamond boxes and such.

And the vague documentation for the TMX file format makes it unclear if there is some other encoding going on before or after the base64 encoding which might be causing this problems. I looked at the cpp source for the encoder, and I saw lots of references to Latin1, but I couldn’t decipher what’s going on in detail.

I noticed that when I tried doing my own tests with MIME::Base64, encoding and then decoding a test string, the encoded text looks dramatically different than that which I see coming out of the TMX files– for instance, my base64-encoded text for a short string looks like this:

aGVyZSBpcyBhIHNlbnRlbmNl

But the base64-encoded text coming from the TMX files looks like this:

9QAAAAABAAANAQAAGAEAAA==

Any suggestions on what else I might try in attempts to decode a string that looks like that?

Answer 1

I think this page might be what you’re looking for. It suggests that first you decode_base64, then (if the compression="gzip" attribute is present) use gunzip to uncompress it, and finally use unpack('V*', $data) to extract the list of 4-byte little-endian integers.