On Thu, 2 Oct 2008, George Pollard wrote:
Hello all,
I'm currently working on a (toy) ID3 [1] tag reader, which made me think of a library which might be quite useful.
The structure of an ID3 tag goes something like this:
Header: - total size of tag - other header info A series of frames, each with: - total size of frame - other header info - frame data
Since the ID3 tag as a whole has size information, I need to pass that into the frame-reading functions to ensure that I never read past the end of the total header. This exact same requirement is present within the frame-reading function itself; it must read the frame data without reading past the end of the frame.
I've done exactly this for a MIDI file parser. It uses a State monad transformer which handles the number of remaining bytes in the chunk. http://darcs.haskell.org/midi/src/Sound/MIDI/Parser/Restricted.hs