vm.c

/* blokvm -- a darkf implementation of blockeduser's terrible vm
   copyright (c) 2012 darkf */

#include <stdio.h>
#include <stdlib.h>

/* 3 * 255^2 */
#define BITMAP_SIZE 195075
#define JMP fseek(fp, PC, SEEK_SET);

typedef unsigned char uchar;

char filename[] = "fib.BPF";
char bitmap1[BITMAP_SIZE], bitmap2[BITMAP_SIZE];
int mem[256];
long PC = 0;

int main()
{
	FILE *fp;
	long flen, code_offset;
	uchar op;

	/* open file */
	fp = fopen(filename, "rb");
	if(!fp) {
		printf("failed to open file %s\n", filename);
		return 1;
	}

	/* get filesize */
	fseek(fp, 0, SEEK_END);
	flen = ftell(fp);
	fseek(fp, 0, SEEK_SET);

	/* read bitmaps */
	fread(bitmap1, BITMAP_SIZE, 1, fp);
	fread(bitmap2, BITMAP_SIZE, 1, fp);

	code_offset = ftell(fp);
	printf("offset = %d\n", code_offset);
    //PC = ftell(fp);

    while(!feof(fp)) {
		PC = ftell(fp) - 1;
		fread(&op, sizeof(op), 1, fp); /* read op */
		//printf("op: %d | PC=%d\n", op, PC);
		switch(op)
		{
		  case 10: /* Do */
			{
			  /*uchar addr, oper, type, data;*/
		      uchar args[4];
			  int data;
			  fread(args, 1, 4, fp);
			  switch(args[2] /* type */)
			  {
			    case 1: data = args[3]; break; /* immediate value */
				case 2: data = mem[args[3]]; break; /* memory dereference */
			  }

			  switch(args[1] /* operation */)
			  {
			    case 10: mem[args[0]]  = data; break; /* assignment */
				case 20: mem[args[0]] += data; break; /* + */
				case 30: mem[args[0]] -= data; break; /* - */
				case 40: mem[args[0]] *= data; break; /* * */
				case 50: mem[args[0]] /= data; break; /* / */
			  }

		      break;
			}
		  case 12: /* PtrTo */
		  {
			uchar addr;
			fread(&addr, sizeof(uchar), 1, fp);
			//printf("ptrto: addr=%d PC=%d\n", addr, PC);
			mem[addr] = PC+3;
		    break;
		  }
		  case 13: /* PtrFrom */
		  {
			uchar addr;
			fread(&addr, sizeof(uchar), 1, fp);
			//printf("ptrfrom: addr=%d mem=%d\n", addr, mem[addr]);
			PC = mem[addr];
			JMP
			break;
		  }
		  case 31: /* bPtrTo */
		  {
			uchar args[3];
			fread(args, 3, 1, fp);
			if(mem[args[0]] < 1)
			{
				if(args[1] == 10) PC += mem[args[2]]; /* jump forward */
				else if(args[1] == 20) PC -= mem[args[2]]; /* jump backward */
				JMP
			}
			break;
		  }
		  case 35: /* zPtrTo */
		  {
			uchar args[3];
			fread(args, 3, 1, fp);
			if(mem[args[0]] > args[1])
			{
				PC += mem[args[2]];
				JMP
			}
			break;
		  }
		  case 14: /* BoolDie */
		  {
			uchar addr;
			fread(&addr, 1, 1, fp);
			printf("booldie: %d\n", mem[addr]);
			if(mem[addr] < 0)
				exit(1);
			break;
		  }

		  case 20: /* Draw */
			break;
		  case 21: /* vDraw */
			break;
		  case 30: /* OutputDraw */
			break;

		  case 25: /* mx */
			break;
		  case 26: /* my */
			break;
		  case 50: /* cmx */
			break;
		  case 51: /* cmy */
			break;
		  
		  case 15: /* Wait */
			break;
		  case 11: /* Echo */
		  {
			uchar addr;
			fread(&addr, 1, 1, fp);
			printf("echo: %d\n", mem[addr]);
			break;
		  }
		  case 255: /* End */
		    printf("end\n");
			break;
		  default: /* bad opcode */
		    printf("bad opcode: %d | PC=%d\n", op, PC);
			break;
		}
	}

	fclose(fp);
	return 0;
}