Description of Daikatana .pak format

daikatana-pak.txt

// Daikatana .pak format. It's similar to Quake/Quake2 format, but supports compressed files as well.
// I think that only the following file types are compressed: .tga .bmp .wal .pcx .bsp
// I wouldn't rely on this list when unpacking, but when packing, only compress those.

// the structs are based on pakextract.c from https://github.com/yquake2/pakextract
// all ints are 32bit Little Endian.

struct pak_header
{
	char signature[4]; // {'P','A','C','K'}, like in Quake/Quake2
	int dir_offset;    // offset of the files directory within the pak file
	int dir_length;    // length of all directory entries in bytes (=> we have dir_length/72 directory entries)
		// 72 because sizeof(directory_entry) == 72 in Daikatana (in contrast to Quake where it's 64)
};

struct directory_entry
{
	char file_name[56];
	int file_pos;       // offset of entry's data within whole file
	int file_length;    // in case of is_compressed: size after decompression (else size in pak)
	// the following two are new in Daikatana:
	int compressed_length; // size of compressed data in the pak
	int is_compressed;     // 0: uncompressed, else compressed
};


Pseudocode to uncompress compressed data:
	while not done:
		read a byte (unsigned char) _x_.
		// x is never written to output, only used to determine what to do
		if      x < 64:
			x+1 bytes of uncompressed data follow (just read+write them as they are)
		else if x < 128:
			// run-length encoded zeros
			write (x - 62) zero-bytes to output
		else if x < 192:
			// run-length encoded data
			read one byte, write it (x-126) times to output
		else if x < 254:
			// this references previously uncompressed data
			read one byte to get _offset_
			read (x-190) bytes from the already uncompressed and written output data,
				starting at (offset+2) bytes before the current write position
				(and add them to output, of course)
		else if x == 255:
			you're done decompressing (used as terminator)
			// but I'd also abort once compressed_length bytes are read, to be sure