MEGALZ PC REINCARNATION
I. What the f*ck that all is about?
From the ancient times I was using nice MegaLZ speccy packer.
But there were two problems - first, it wasn't released publicly
(available only to mayHem members), second, it has somewhat not
perfect packing in comparison with other packers available. On
the other hand, I like MegaLZ depacker, which is 110 bytes long,
fully relocatable and just looks nice =) That's why I decided to
improve packing ratio while keeping original nice 110-byte Z80
depacker (and thus remaining original packed file format). For
the simplicity and for memory consumption & speed reasons,
packer was re-written from scratch in C in portable manner. Up
to now console MegaLZ packer was successfully built under win32,
amigaos, linux-i586 and ARM.
II. Some words about packing efficiency.
While the original Speccy MegaLZ (old MegaLZ) was quite
straightforward in selection of LZ codes, this new MegaLZ does a
nice thing: it selects the best LZ codes chain through all the
file, using smart algorithm, which is close to the Dijkstra
algorithm for searching a shortest path. As a result, packed
file sizes decrease up to 5%, which is equivalent to size
decrease about 1000 bytes on 20kB packed file. Some comparison
of packing ratio with other packers available on Speccy was also
III. How to use it.
First, take suitable executable file from "Exe" directory, and
then put it to the comfortable place you can call it from. Up
to now, there are 3 executables: for amigaos (built on SAS/C),
for win32 console (built on MSVS 6), for linux (built for i586
on gcc3.2.3 under linux redhat7.3). If for some cases
executables do not fit your needs, you have then to build from
sources your own one...
Then, invoke it with no arguments and follow tips.
If you prefer reading instructions first, you have to remember
simple pattern: "MegaLZ [options] <input filename> [<output
filename>]", where options could be -h, -g and -d. -h means
just printing some help. -g means using simple (greedy) LZ
codes selection instead of advanced (optimal). In greedy mode,
files get bigger yet their size coincide with the size given by
original Speccy MegaLZ packer. -d means doing depacking instead
of packing. If you do not specify output filename, input
filename will be used with addition of suitable extension.
IV. Depacking back.
First way to recover files from packed ones is to use -d
option. The second and the most natural way is to use Z80
depacker, which is in "Z80" directory, given as Z80 assembler
source code, easily adaptable to any particular assembler.
Detailed usage instructions are given in the source file itself.
Third way - using universal C depacker, which is the part of C
source code of overall MegaLZ packer.
V. Where is that all?
Distributive is divided in three parts: basic part contains
only executables and Z80 depacker, development part contains
complete C sources and benchmark part contains thoroughful
comparison of packing abilities with other Speccy packers.
VI. Copy right?
The original MegaLZ Speccy packer, Z80 depacker and packed file
format (C) fyrex^mhm.
Advanced C MegaLZ packer (C) lvd^mhm.
This product is supplied "as-is", without any explicit and
implicit warranties of any kind. The authors are not
responsible for any kind of problems, losses, injuries and
deceases resulting anyhow from using, not using or misusing this
The product can be spread freely as original archives provided
no changes are made to it.
04.01.2006 mayHem lvd^mhm