Allegro packfile
From Just Solve the File Format Problem
Allegro is a game programming library. The PACKFILE format is a zip-file format containing the game's assets in a way which allegro can read (normally: bitmaps, run-length-encoded sprites, mod music files from libdumb).
The magic for this file format is slh! (compressed) or slh. (uncompressed).
The allegro library is open source and comes with utility libraries for editing PACKFILEs.
Version 5 of Allegro replaces PACKFILE with standard zip utilities.
