Yeah, the fids are all 32-bits in the playlist *0 files. You know how many there are by simply looking at the "length" tag in the *1 files, or just the Linux filesize in bytes.

The two files named playlists and tags are special: I don't remember what playlists is actually for, but tags gives the layout (field order) for each record in the database file -- it lists the tags that are actually known/used.

The database file then just has a record for each tune/playlist, with the variable-length fields in the order as given by tags, using NULLs (I think..) as field terminators.

Oh wait, I just looked at the database file, and it appears that each field within each record has two bytes in front: the first byte is the binary index of that field into lines in the tags file, and the second byte is the bytecount for the ASCII data that follows. So if "artist" is the fourth line in tags, then the artist data in the database for "Bare Naked Ladies" would have 0x03 0x11 immediately in front of the band's name, on each record within database that pertains to that band.

Cheers