#include <stdio.h>
#include <fcntl.h>
#include <errno.h>
#include <stdlib.h>
#include <unistd.h>
#include <strings.h>

extern const char *__progname;

static int dfd;
static int ro;

static void usage(void)
{
 fprintf(stderr,"Usage: %s raw-disk-device\n",__progname);
 exit(1);
}

static void set4(void *dp, unsigned int v)
{
 ((unsigned char *)dp)[0] = (v >> 24) & 0xff;
 ((unsigned char *)dp)[1] = (v >> 16) & 0xff;
 ((unsigned char *)dp)[2] = (v >>  8) & 0xff;
 ((unsigned char *)dp)[3] =  v        & 0xff;
}

static unsigned int get4(void *dp)
{
 return( (((unsigned char *)dp)[0] * 0x01000000) +
	 (((unsigned char *)dp)[1] * 0x00010000) +
	 (((unsigned char *)dp)[2] * 0x00000100) +
	 (((unsigned char *)dp)[3] * 0x00000001) );
}

int main(int, char **);
int main(int ac, char **av)
{
 int opc;

 if (ac != 2) usage();
 ro = 0;
 dfd = open(av[1],O_RDWR,0);
 if (dfd < 0)
  { ro = 1;
    dfd = open(av[1],O_RDONLY,0);
    if (dfd < 0)
     { fprintf(stderr,"%s: %s: %s\n",__progname,av[1],strerror(errno));
       exit(1);
     }
  }
 while (1)
  { opc = getchar();
    if (opc == EOF) exit(0);
    switch (opc)
     { case 'o':
	   { int rwflag;
	     int part;
	     char rbuf[4];
	     rwflag = getchar();
	     if (rwflag == EOF)
	      { fprintf(stderr,"%s: EOF reading open rwflag\n",__progname);
		exit(1);
	      }
	     part = getchar();
	     if (part == EOF)
	      { fprintf(stderr,"%s: EOF reading open partition\n",__progname);
		exit(1);
	      }
	     switch (rwflag)
	      { case 'r':
		   set4(&rbuf[0],0);
		   break;
		case 'w': case 'b':
		   set4(&rbuf[0],ro?EROFS:0);
		   break;
		default:
		   fprintf(stderr,"%s: protocol error: invalid open flag 0x%02x\n",__progname,rwflag);
		   exit(1);
		   break;
	      }
	     write(1,&rbuf[0],4);
	   }
	  break;
       case 'c':
	  break;
       case 'r':
	   { unsigned int blkno;
	     char rbuf[516];
	     int n;
	     if (fread(&rbuf[0],1,4,stdin) != 4)
	      { fprintf(stderr,"%s: can't get read sector #\n",__progname);
		exit(1);
	      }
	     blkno = get4(&rbuf[0]);
	     n = pread(dfd,&rbuf[4],512,blkno*(off_t)512);
	     if (n < 0)
	      { set4(&rbuf[0],errno);
	      }
	     else if (n != 512)
	      { set4(&rbuf[0],EIO);
	      }
	     else
	      { set4(&rbuf[0],0);
	      }
	     write(1,&rbuf[0],516);
	   }
	  break;
       case 'w':
	   { char wbuf[516];
	     unsigned int blkno;
	     char rbuf[4];
	     int n;
	     if (fread(&wbuf[0],1,516,stdin) != 516)
	      { fprintf(stderr,"%s: can't get write packet\n",__progname);
		exit(1);
	      }
	     blkno = get4(&wbuf[0]);
	     n = pwrite(dfd,&wbuf[4],512,blkno*(off_t)512);
	     if (n < 0)
	      { set4(&rbuf[0],errno);
	      }
	     else if (n != 512)
	      { set4(&rbuf[0],EIO);
	      }
	     else
	      { set4(&rbuf[0],0);
	      }
	     write(1,&rbuf[0],4);
	   }
	  break;
       case 'z':
	   { unsigned int l;
	     unsigned int h;
	     unsigned int m;
	     char resp[4];
	     static int ok(unsigned int b)
	      { char junk[512];
		return(pread(dfd,&junk[0],512,b*(off_t)512)==512);
	      }
	     l = 0;
	     h = 1;
	     while (ok(l))
	      { l = h;
		h <<= 1;
	      }
	     while (h-l > 1)
	      { m = (h + l) >> 1;
		if (ok(m)) l = m; else h = m;
	      }
	     set4(&resp[0],h);
	     write(1,&resp[0],4);
	   }
	  break;
       default:
	  fprintf(stderr,"%s: protocol error: invalid command 0x%02x\n",__progname,opc);
	  exit(1);
	  break;
     }
  }
}