#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 void usage(void)
{
 fprintf(stderr,"Usage: %s pseudo-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) );
}

static int dfdr(void *data, int len)
{
 char *dp;
 int n;

 dp = data;
 while (len > 0)
  { n = read(dfd,dp,len);
    if (n <= 0) return(1);
    dp += n;
    len -= n;
  }
 return(0);
}

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

 if (ac != 2) usage();
 dfd = open(av[1],O_RDWR,0);
 if (dfd < 0)
  { fprintf(stderr,"%s: %s: %s\n",__progname,av[1],strerror(errno));
    exit(1);
  }
 while (1)
  { if (dfdr(&opc,1)) exit(0);
    switch (opc)
     { case 'o':
	   { unsigned char args[2];
	     char rbuf[4];
	     int err;
	     if (dfdr(&args[0],2))
	      { fprintf(stderr,"%s: can't read open rwflag/part\n",__progname);
		exit(1);
	      }
	     switch (args[0])
	      { case 'r':
		case 'w':
		case 'b':
		   putchar('o');
		   putchar(args[0]);
		   putchar(args[1]);
		   fflush(stdout);
		   if (fread(&rbuf[0],1,4,stdin) != 4)
		    { fprintf(stderr,"%s: can't read open reply\n",__progname);
		      exit(1);
		    }
		   err = get4(&rbuf[0]);
		   write(dfd,&err,sizeof(int));
		   break;
		default:
		   fprintf(stderr,"%s: protocol error: invalid open flag 0x%02x\n",__progname,args[0]);
		   exit(1);
		   break;
	      }
	   }
	  break;
       case 'c':
	  putchar('c');
	  fflush(stdout);
	  break;
       case 'r':
	   { unsigned int blkno;
	     char buf[516];
	     int err;
	     if (dfdr(&blkno,sizeof(unsigned int)))
	      { fprintf(stderr,"%s: can't get read sector #\n",__progname);
		exit(1);
	      }
	     set4(&buf[0],blkno);
	     putchar('r');
	     fwrite(&buf[0],1,4,stdout);
	     fflush(stdout);
	     if (fread(&buf[0],1,516,stdin) != 516)
	      { fprintf(stderr,"%s: can't read read reply\n",__progname);
		exit(1);
	      }
	     err = get4(&buf[0]);
	     write(dfd,&err,sizeof(err));
	     write(dfd,&buf[4],512);
	   }
	  break;
       case 'w':
	   { char buf[516];
	     unsigned int blkno;
	     int err;
	     if ( dfdr(&blkno,sizeof(unsigned int)) ||
		  dfdr(&buf[4],512) )
	      { fprintf(stderr,"%s: can't read write packet\n",__progname);
		exit(1);
	      }
	     set4(&buf[0],blkno);
	     putchar('w');
	     fwrite(&buf[0],1,516,stdout);
	     fflush(stdout);
	     if (fread(&buf[0],1,4,stdin) != 4)
	      { fprintf(stderr,"%s: can't read write reply\n",__progname);
		exit(1);
	      }
	     err = get4(&buf[0]);
	     write(dfd,&err,sizeof(int));
	   }
	  break;
       case 'z':
	   { int sz;
	     char resp[4];
	     putchar('z');
	     fflush(stdout);
	     if (fread(&resp[0],1,4,stdin) != 4)
	      { fprintf(stderr,"%s: can't read write reply\n",__progname);
		exit(1);
	      }
	     sz = get4(&resp[0]);
	     write(dfd,&sz,sizeof(int));
	   }
	  break;
       default:
	  fprintf(stderr,"%s: protocol error: invalid command 0x%02x\n",__progname,opc);
	  exit(1);
	  break;
     }
  }
}