#include <stdio.h>

struct dir0 {
  unsigned short dfirstblk;
  unsigned short dflastblk;
  unsigned short dfkind;
  char length;
  char dvid[7];
  unsigned short deovblk;
  unsigned short dnumfiles;
  unsigned short dloadtime;
  unsigned short dlastboot;
  unsigned short padding;
};
struct dirn {
  unsigned short dfirstblk;
  unsigned short dflastblk;
  unsigned short dfkind;
  char length;
  char dtid[15];
  unsigned short dlastbyte;
  unsigned short daccess;
};

unsigned short swap(unsigned short x) {
  union u {
    unsigned short x;
    unsigned char c[2];
  } u;
  unsigned char s;
  u.x = x;
  s = u.c[0];
  u.c[0] = u.c[1];
  u.c[1] = s;
  return u.x;
}


int main(int argc, char* argv[])
{
  char name[17];
  char cbuf[512];
  char buf[512*4];
  FILE* in,*out;
  int i,n,k;
  int b,e,l;
  struct dir0* dir0;
  struct dirn* dirn;

  if (argc != 2) {
    fprintf(stderr,"Usage: %s diskimage.bin\n",argv[0]);
    exit (1);
  }

  if ((in=fopen(argv[1],"rb"))==NULL) {
    fprintf(stderr,"Can't read %s\n",argv[1]);
    exit(2);
  }

  /* read boot block (two sectors) */
  printf("Extract boot record\n");
  fread(buf,2,512,in);
  out = fopen("bootrec.bin","wb");
  fwrite(buf,2,512,out);
  fclose(out);

  /* read directory records */
  fread(buf,4,512,in);
  dir0 = (struct dir0*)buf;
  dirn = (struct dirn*)(buf+26);
  printf("Directory:\n");
  printf("  firstblock=%d\n",swap(dir0->dfirstblk));
  printf("  lastblock=%d\n",swap(dir0->dflastblk));
  printf("  volumeid=");
  for (i=0; i<dir0->length; i++) printf("%c",dir0->dvid[i]);
  putchar('\n');
  printf("  lastblock=%d\n",swap(dir0->deovblk));
  printf("  numfiles=%d\n",swap(dir0->dnumfiles));

  for (n=0; n<swap(dir0->dnumfiles); n++) {
    if (dirn[n].dfkind) {
      printf("\nFile=");
      for (i=0; i<dirn[n].length; i++) printf("%c",dirn[n].dtid[i]);
      putchar('\n');
      b = swap(dirn[n].dfirstblk);
      e = swap(dirn[n].dflastblk);
      l = swap(dirn[n].dlastbyte);
      printf("  firstblock=%d\n",b);
      printf("  lastblock=%d\n",e);
      printf("  filetype=0x%04x\n",swap(dirn[n].dfkind));
      printf("  lastbyte=%d\n",l);
      memset(name,0,17);
      strncpy(name,dirn[n].dtid,dirn[n].length);
      out = fopen(name,"wb");
      fseek(in,b*512,0);
      for (k=0; k<(e-b)-1; k++) {
	fread(cbuf,1,512,in);
	fwrite(cbuf,1,512,out);
      }
      fread(cbuf,1,l,in);
      fwrite(cbuf,1,l,out);
      fclose(out);
    }	
  }
}