Subj : Re: cc65 compression technique optimizations?
To   : Andreas Kohlbach
From : Harry Potter
Date : Wed Oct 09 2019 12:03 pm

On Wednesday, October 9, 2019 at 2:55:44 PM UTC-4, Andreas Kohlbach wrote:
> Yes, post some snippets please. I won't be able to help because I am a
> lousy 6502 assembly coder but generally interested what you have done so
> far.
> --
> Andreas
>
It is written in C using cc65.  Here are two code snippets:
-------------------------
static unsigned sslz_getcomp (int pos, register unsigned char len)
{
   register unsigned i2, j2; //register unsigned char k;
   static unsigned char k, n, o;//=0;
   static unsigned char comp, compa, bestcomp;
   bestcomp=(len<<3)+2;
   tmpcptr=&InBuffer[pos];
   i=5;
   if (len<=3) i=7;
   if (len<=2) i=7;
   j2=(len<=2?60:len<=3?600:7*1024);
   if (pos<j2) j2=pos;
   o=0;
   for (i2=1; i2<=j2; ++i2) {
      --tmpcptr;
      if (len>=4) {
         if (i2==1) {i+=3; k+=3;}
         if (i2==250) {i+=4; k+=3;}
         if (i2==1800) {i+=3; k+=3;}
      }
      j=i; n=0;
      for (e=0; e<len; ++e) {
         if (cin[e]==((unsigned char*)tmpcptr)[e]) {
            sslz_tocomp[e]=1;
            ++n;
            ++j;
         } else {
            sslz_tocomp[e]=0;
            j+=9;
         }
      }
      if (j<bestcomp && n>=2) {
         if (n>=2) o=1;
         bestcomp=j;
         //m=1;
         sslz_offs=i2-1;
         //memcpy (&sslz_best, &sslz_tocomp, sizeof(sslz_tocomp));
         __asm__ (
            "\tldx\t_buflen\n"
            "\tdex\n"
            "@aaa:\r\n"
            "\tlda\t_sslz_tocomp,x\n"
            "\tsta\t_sslz_best,x\n"
            "\tdex\n"
            "\tbpl\t@aaa\n"
            );
      }
   }
   sslz_comp=bestcomp;
   return o;
}
-------------------------
      j=0; y=&InBuffer[in+i];
      for (k=0; k<108 && j<108; /*++k*/) {
         if ((len!=2 && len!=3 && len<7) && j>=12) {j=108; break;}
         m=0;
         --y;
         if ((unsigned)y<(unsigned)&InBuffer) {k= 108; break;}
         if (cin[i]==*y) break;
         if (j>=0) {
            for (l=1;l<=j; ++l) {
               //if (InBuffer[in+i-l-1]==InBuffer[in+i-j-1]) {
               if (*y==y[l]) {
                  m=1; break;
               }
            }
         }
         if (m) {++j; continue;}
         ++j;
         ++k;
      }
xcomp:
      l2=in+i;
      if (k<108 && j<108) {
         po_offs[i]=k; //comp+=/*5-(k<4)*/(k<6?1:getnumbits(po_getnumlits(vz.InPos-buflen+i+1)));
         if (len!=2 && len!=3 && len<7) comp+=EstimDist(k, 
po_getnumlits(in+i));
         else comp+=EstimDist (k, po_getnumlits2(l2));       }
      else {
         po_offs[i]=-1;
         if ((len!=2 && len!=3 && len<7)) x=po_writelit (l2, InBuffer[l2], &l);
         else x=po_writelit1a (in+i, InBuffer[in+i], &l);
         po_nl1[i]=x; po_nl2[i]=l;
         comp+=EstimDist (x, l)+1;
      }
   }
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