All files are released under GPLv3+, project started at 21 March 2012 by Peter
"Lekensteyn" (contact lekensteyn@gmail.com http://lekensteyn.nl/). I realize
that an existing project also uses the name "PFS" (image/picture software I
believe?), therefore the program is named "pfstool" ;)

Made for handling files for the Siemens SX551 router
(https://forum.openwrt.org/viewtopic.php?id=33600)
Note: apart from the filesystem on the beginning of the file, there also seems
to be a second part after a bunch of ff ff ff ... . Using lzma to decompress
the binary file only extracts the PFS image on the beginning of the file, the
second part is ignored.

some notes below

le = little endian

lzma format from
http://svn.python.org/projects/external/xz-5.0.3/doc/lzma-file-format.txt:
00 - 01 1	properties
01 - 04 4	dictionary size
05 - 0D 8	uncompressed size (le) <-- that we are interested in

offset  length	description
00 - 07 8	"PFS/0.9" (nil)
08 - 0B	4	0 bytes (00 00 00 00)
0C - 0D 2	???
0E - 0F	2	n number of files (little endian)

10 - **	*	file information for n files (72 / 0x48) bytes,
		length 48 times n (le)
ZZ - EE *	data starting at 0x10+48n

begin - end len_hex len_dec	description
00 - 48 48 (72)	file info
00 - 3B 3C (60)	filename
3C - 3F (4)	a timestamp? (le)
40 - 43 (4)	file offset relative to ZZ (le)
44 - 47 (4)	le file size (le)

file types:

file offset: if it points to the end of the file (beyond the last byte), dynamic
content is served (observed: all cgi-bin/...exe files have this field set in
such a way) (size = 0 as well)

make
# pfstool has option -t, -x, -v and -C similar to tar. It defaults to -t
./pfstool xv -C dest/ ...bin