static char info[]=" D64 2 Zipcode   Version 1.0   Tony Ambardar (C) 1993\n";
/*
Wrote this mostly by looking through some zipcode 4-packs and playing with
Zipcode 2.0, so that I could try .D64 software from the watson archive on
my C64 at home. No guarantees.

You are free to re-use this code so long as you give credit where it's due.

(C) 1993     Tony Ambardar
*/

#include <stdio.h>
#include <errno.h>
#include <string.h>

#define DBLOCKS (683)

typedef unsigned char byte;
typedef enum { WHOLE=0, VARIABLE, NONE } repeat_t;
static char repeat_c[]=".oO";

byte image_buffer[DBLOCKS*256],max_sector[35];
static byte trk_lims[4] = {0, 8, 16, 25};

/* Per sector info */

int num_repeats;
byte repchar;
int rle_len;
struct 
{
  int startpos;
  int len;
} rep_info[64];

static char filename[255] = "0!";

FILE *imgfile,*zipfile;

main(int argc, char *argv[]) 
{
  repeat_t rep_scan();
  byte *sec_buf;
  int i,j,k,track, sector,base;
  int oddadd,evenadd,begin,length;
  int pos;
   
  repeat_t sec_type;
   
  if(argc != 2) {
    printf("%s",info);
    printf("Converts a .D64 disk image to a Zipcode 4-pack\n\n");      
    printf("Usage: %s  diskimage.d64\n",argv[0]);
    exit(0);
  }

  init_stuff(argv[1]);

  if ((pos = strcspn(argv[1], ".d64")) == 0)
    pos = strcspn(argv[1], ".D64");

  argv[1][pos] = 0;

  zipfile = NULL;
  strcat(filename,argv[1]);
  printf("%s\n", filename);
  base=0;
  oddadd=11, evenadd= -10;
  printf("\n            RLE Compression Map:\n");
  printf("O = No Compression  -->  . = Max. Compression\n");
  for(track=0; track<35; base+=max_sector[track++]+1) {
    printf("\nTrack: %2u ",track+1);
    openfiles(track,filename);
    if(track==17 || track==24) --oddadd, ++evenadd;
    i=base-evenadd;
    sector= -evenadd;
    for(k=0; k <= max_sector[track]; k++) {
      i+= k % 2 ? oddadd : evenadd;
      sec_buf = image_buffer +i*256;
      sector += k % 2 ? oddadd : evenadd;
      sec_type = rep_scan(sec_buf);
      printf("%c",repeat_c[sec_type]);

#ifdef EBUG1
      printf("\nT: %2u S: %2u Type: %c  Repchar: %3u\n",track+1,sector,
	     repeat_c[sec_type],repchar);
#endif

#ifdef EBUG2
      for(j=0;j<256;j++)
	printf("\\%3o",*(sec_buf+j));
#endif   

      if(sec_type==NONE) {
	fputc(track+1,zipfile),fputc(sector,zipfile);
	fwrite((sec_buf),1,256,zipfile);
      }
      else if(sec_type==WHOLE) {
	fputc(track+1+64,zipfile),fputc(sector,zipfile);
	fputc(*(sec_buf),zipfile);
      }
      else {			/* VARIABLE */
	fputc(track+1+128,zipfile),fputc(sector,zipfile);
	fputc(rle_len,zipfile),fputc(repchar,zipfile);
	for(j=0; j<num_repeats; j++) {
	  begin= j==0? 0 : 
	  rep_info[j-1].startpos+rep_info[j-1].len;
	  length = rep_info[j].startpos - begin;
	  fwrite((sec_buf+begin),1,length,zipfile);
	  fputc(repchar,zipfile),
	  fputc(rep_info[j].len,zipfile);
	  fputc(*(sec_buf+rep_info[j].startpos),zipfile);
	}
	begin=rep_info[j-1].startpos+rep_info[j-1].len;
	length = 256 - begin;
	fwrite((sec_buf+begin),1,length,zipfile);
      }
    }
  }
  printf("\n\nDone.\n");
  close(zipfile);
}

openfiles(int trk,char *name)
{
  int i;
  for(i=0; i<4; i++)
    if(trk_lims[i] == trk) {
      if(zipfile != NULL) fclose(zipfile);
      ++*name;
      if(!(zipfile = fopen(name,"w"))) {
	perror(name);
	exit(errno);
      }
      /*  Write headers. \041 \041 is a disk ID I think */
            
      if(i==0) fputs("\376\003\041\041",zipfile);
      else fprintf(zipfile,"%c%c",0,4);
    }
return(0);
}


init_stuff(char *name)
{
  int i;

  for(i=0; i<17; max_sector[i++]=20);
  for(i=17; i<24; max_sector[i++]=18);
  for(i=24; i<30; max_sector[i++]=17);
  for(i=30; i<35; max_sector[i++]=16);
   
  if(!(imgfile = fopen(name,"r"))) {
    perror(name);
    exit(errno);
  }
  else {
    if(fread(image_buffer,1,sizeof(image_buffer),imgfile) 
       != sizeof(image_buffer)) {
      fprintf(stderr,"D64 image could be wrong size!\n");
      exit(1);
    }
    close(imgfile);
  }
return(0);
}

repeat_t rep_scan(byte *sec_buf)
{
  int i,j,count;
  char table[256];

  rle_len=256;
  num_repeats=0;
      
  for(i=0; i<255; i++) {
    count=0;
    while(i<255 && *(sec_buf+i)==*(sec_buf+i+1)) {
      i++,count++;
    }
    if(count >= 3) {
      rep_info[num_repeats].startpos=i-count;
      rep_info[num_repeats].len=count+1;
      ++num_repeats;
    }         
  }
  if(num_repeats==0) return NONE;
  else
    if(count==255) return WHOLE;

  /*  VARIABLE  */

  rle_len += num_repeats*3;
  for(i=0; i< num_repeats; i++)
    rle_len -= rep_info[i].len;
  if(rle_len >253) return NONE;
      
  for(j=0; j<256; table[j++]=1);
  for(j=0; j<256;  table[*(sec_buf+j++)]=0);
  for(j=0; j<256 && table[j]==0; j++);
  repchar = j;
   
#ifdef EBUG1
  printf("\nRepeats: %2u RLE_len: %3u Repchar: %3u\n",i,rle_len,j);
  for(j=0;j<i;j++)
    printf("Start: %3u Length: %3u\n",rep_info[j].startpos,rep_info[j].len);
#endif   
  return VARIABLE;   
}