User Tools

Site Tools


Full source and example code is in here:

A variant of literal/copy compression (LZMPiE) that uses an extra common dictionary (hence LZMPiED) calculated from multiple input files, to reduce overall compressed data size.

The build for this tool is also a good demonstration on how to unit test 6502 code along with java code.

Command line parameters:

  <dictionary size in bytes (decimal)> <output file name> <start offset in files (skip start bytes) (decimal)> [input files]

Example usage:

  java -jar target\DictionaryCompression-1.0-SNAPSHOT-jar-with-dependencies.jar 1024 target/compressed 2 TestData/Mule.prg TestData/MeanStreak.prg TestData/Lobster.prg TestData/Dinosaur_Disco.prg "TestData/Turrican remixed.prg" TestData/Nintendo.prg TestData/WizballGuitar.prg

Which equals 11,745 bytes

Compare this with the result of using LZMPi to compress each file individually:

  ..\bin\LZMPi.exe -c TestData/Mule.prg target/compressed_Mule.prg.cmp2
  ..\bin\LZMPi.exe -c TestData/MeanStreak.prg target/compressed_MeanStreak.prg.cmp2
  ..\bin\LZMPi.exe -c TestData/Lobster.prg target/compressed_Lobster.prg.cmp2
  ..\bin\LZMPi.exe -c TestData/Dinosaur_Disco.prg target/compressed_Dinosaur_Disco.prg.cmp2
  ..\bin\LZMPi.exe -c "TestData/Turrican remixed.prg" "target/compressed_Turrican remixed.prg.cmp2"
  ..\bin\LZMPi.exe -c TestData/Nintendo.prg target/compressed_Nintendo.prg.cmp2
  ..\bin\LZMPi.exe -c TestData/WizballGuitar.prg target/compressed_WizballGuitar.prg.cmp2
  dir target\*.cmp2

Which equals 13,088 bytes

The dictionary compression is 1,343 bytes smaller.


To assemble the demo, first run the command line about in “Example usage” to produce the compressed output files.

6502 asm source to decompression is in: asm\DictionaryDecompression.a

Demo source (ACME format) is in: asm\Demo.a

It can be assembled using: BuildIt.bat

Assembled demo prg file is in: target\Demo.prg

The dictionary is at $c000 so if you're using a memory viewer it shows when it is read. The compressed data is much lower in memory at around $a50. The decompression address is $8000

base/dictionary_compression.txt · Last modified: 2022-08-14 12:10 by martin_piper