Finding custom lzss on arcade game .dat file

[finalscream]

Aluigi from zenhax told me to post here, so apologizes if this is in the wrong section. I have a .dat file from an arcade game that has some form of custom lzss compression on it, and I'm not sure what it is. Trying anything standard results in a semi correct file. The thread below at zenhax has a bit more info, and I attached 2 compressed & 2 uncompressed files. I'm kinda desperate here, so any help would be greatly appreciated. I also have a .dll that I believe handles decompression, but it also handles a bunch of other game logic (and I'd rather refrain from posting it publicly heh)

https://zenhax.com/viewtopic.php?f=9&p=23990#p23990

[Shelwien]

#include <stdio.h>

#include <stdlib.h>



typedef unsigned char byte;

typedef unsigned int  uint;



uint get2( FILE* f ) {

  uint c1 = getc(f);  

  uint c2 = getc(f);

  return (c1<<8)|(c2);

}



enum{ winsize=1<<12 };

byte window[winsize];



int main( void ) {



  uint c,d,i,l;



  FILE* f = fopen( "File1Compressed.dat", "rb" ); if( f==0 ) return 1;

  FILE* g = fopen( "File1Compressed.unp", "wb" ); if( g==0 ) return 1;



  for( i=0; i<winsize; i++ ) window[i]=0;



  getc(f); // skip first byte



  for(i=0;;) {



    c = getc(f); if( c==-1 ) break;



    printf( "%02X ; mask\n", c );



    for( c+=0x100; c!=1; c>>=1 ) {

      if( c&1 ) {

        d = getc(f); if( d==-1 ) break;

        printf( "  %02X ; literal\n", d );

        window[(i++)%winsize] = d;

        putc( d, g );

      } else {

        d = get2(f); if( int(d)<0 ) break;

        if( d==0 ) break; // real EOF

        printf( "  %04X ; match: dist=%i len=%i\n", d, d/16, d%16+3 );



        l = d%16+3; d=d/16+0;

        for(; l--; i++ ) {

          putc( window[i%winsize] = window[(i+winsize-d)%winsize], g );

        }

      }

    }

 

  }



}

[finalscream]

Just tested it and it works, you are amazing. Do you have a BTC address I could throw a few bucks at? I've been trying at this for weeks and got absolutely nowhere.

[Shelwien]

As a bonus, this is how I parsed it (click to zoom). Unfortunately that dll didn't help - there is some lz77 inside, but I didn't find this.
However, ida won't work with structuring of more complicated formats (bitcode etc) :(