Mercurial > touhou-doc
diff 06/pbg3.xhtml @ 1:b1bec4b5ccf3
Add anm and pbg3 file formats, and improve the std one.
| author | Emmanuel Gil Peyrot <linkmauve@linkmauve.fr> |
|---|---|
| date | Tue, 02 Aug 2011 14:18:01 +0200 |
| parents | |
| children | 2925b0e246c6 |
line wrap: on
line diff
new file mode 100644 --- /dev/null +++ b/06/pbg3.xhtml @@ -0,0 +1,61 @@ +<?xml version="1.0" encoding="utf-8"?> +<?xml-stylesheet type="text/css" href="../style.css"?> +<!DOCTYPE html> +<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en"> + <head> + <title>PBG3 format</title> + </head> + <body> + <h1>PBG3 format</h1> + <p>The PBG3 format is an archive format used by EoSD.</p> + + <p>It is a bitstream composed of a header, a file table, and LZSS-compressed files.</p> + + + <h2>Reading integers</h2> + <p>Integers in PBG3 files are never signed, they are not byte-aligned, and have a variable size.<br/> + Their size is given by two bits: 00 means the number is stored in one byte, 10 means it is stored in three bytes.</p> + + <p>Ex:</p> +<pre> + 0x0012 is stored as: 0000010010 + 0x0112 is stored as: 010000000100010010 +</pre> + + + <h2>Reading strings</h2> + <p>Strings are stored as standard NULL-terminated sequences of bytes.<br/> + The only catch is they are not byte-aligned.</p> + + + <h2>Header</h2> + <p>The header is composed of three fields:</p> + <ul> + <li>magic (string): "PBG3"</li> + <li>number of entries (integer)</li> + <li>offset of the file table (integer)</li> + </ul> + + <p>The size of the header is thus comprised between 52 bits and 100 bits.</p> + + + <h2>File table</h2> + <p>The file table starts at a byte boundary, but as the rest of the file, isn't byte-aligned.<br/> + It consists of a sequence of entries.<br/> + Each entry is composed of five fields:</p> + <ul> + <li>unknown1 (int) #TODO</li> + <li>unknown2 (int) #TODO</li> + <li>checksum (int): simple checksum of compressed data</li> + <li>size (int): size of uncompressed data</li> + <li>name (string): name of the file</li> + </ul> + + <p>The checksum is a mere sum of the compressed data.<br/> + Files are compressed using the LZSS algorithm, with a dictionary size of 8192 bytes and a minimum matching length of 4 bytes.<br/> + The size of the offset component of (offset, length) tuples is 13 bits, whereas the size of the length component is 4 bits.<br/> + A file ends with a (0, 0) tuple, that is, 18 zero bits.</p> + + <p>Uncompressing a LZSS-compressed file is quite easy, see lzss.py.</p> + </body> +</html>