PPMC


TABLE OF CONTENTS
-Description
-Compiling
-Files included in this release
-Timing
-Author
-Disclaimer


DESCRIPTION
This is the source code of an implementation of ppmc.
The data structures used are hash tables instead of a context trie.

A file is compressed and decompressed like that:
ppmc inputfile compressedfile
unppmc compressedfile outputfile

I don't recommend to use this for compressing vital information, because it
hasn't been fully tested, and moreover, the machine where the decompressor is
being run, must have at least as much memory as the encoder had. I recommend
to use this compressor only for researching pourposes.

For further information read ac_ppmc.html also included in the package, for
the latest version visit http://www.ross.net/arturocampos


COMPILING
The source code is in the C programming language, and was successfully
compiled with Djgpp version 2.02, a project was made which included the
following files for the encoder (call this project ppmc):
ppmc.c
ppmcdata.c
ppmcmain.c
range.c

And for the decoder (call this project unppmc)
ppmc.c
ppmcdata.c
range.c
unppmc.c

Then you just have to hit F9 and wait. I tried to do makefiles, however there
was something wrong and it didn't worked. If someone has any idea about it, or
how to compile this source for other compilers, please let me know it, so in
the next release I can include makefiles.


FILES INCLUDED IN THIS RELEASE
In the zip file ac_ppmc_html.zip you should find:

readme.txt   -> The file you're reading now.
ac_ppmc.html -> article which explains ppmc and the data structures used
ppmc.c       -> This is the main file which includes all the routines used
                by both the encoder and decoder's model.
range.c      -> The encoder and decoder's routines.
ppmcmain.c   -> The main routine for the compressor
unppmc.c     -> The main routine for the decompressor
ppmcdata.c   -> Global data structures. (used mainly by ppmc.c)
ppmc.h       -> Declarations of routines
ppmcdata.h   -> Declarations of global data and structures
range.h      -> Declarations of the routines for the range encoder and decoder
ppmc.exe     -> A compiled version of the compressor
unppmc.exe   -> A compiled version of the decompressor 

All this files are the implementation of ppmc order-4 using lazy exclusions.
In the /exclusion directory you can find the same files (unless readme) but
for ppmc order-4 using full exclusion.
I thought there was no need to include the files for ppmc-o3h, because they
are nothing else than ppmc with lazy exclusions, using only order-2 (and
lowers) but instead of using the hash key for order-2 it uses the one for
order-3. (you also have to take care about o3_byte, of course)

The executables were compiled with Djgpp 2.95 using only the switch -O6.


TIMING
The standard function to get the
time "time()", has a maximum precision of seconds. This is not enough for
testing the speed of a compressor. Due to this timing was not included in
this release.
If you are interested on compiling it with Djgpp, my original version used the
following code:

 struct time ppmc_time, ppmc_time2;
 double _time2, _time;

 // Get current time
 gettime(&ppmc_time);

 //Compress file


 // Print bpb and kbyps
 gettime(&ppmc_time2);
 printf("%s at %f bpb in ",argv[1],((float)filesize(file_output)/(float)size_file_input)*(float)8);
 _time=((ppmc_time.ti_min)*60)+(ppmc_time.ti_sec)+(((double)ppmc_time.ti_hund)/100);
 _time2=((ppmc_time2.ti_min)*60)+(ppmc_time2.ti_sec)+(((double)ppmc_time2.ti_hund)/100);
 if((_time2-_time)!=0)
   printf("%f kbytes/seconds.", ((float)size_file_input/(float)1024)/(_time2-_time));


AUTHOR
This code was made by Arturo San Emeterio Campos, you can find his home page
at: http://www.ross.net/arturocampos
And his email is: arturo-campos@mixmail.com


DISCLAIMER
Copyright (c) Arturo San Emeterio Campos 1999. All rights reserved. Permission
is granted to make verbatim copies of this files for private use only. There
is ABSOLUTELY NO WARRANTY. Use it at your OWN RISK.


                              Arturo San Emeterio Campos, Barcelona 04-Jan-2000