/* VM6Fh C front-end */

#include <string.h>

// for debugging
void mark1() { printf("here1\n"); }
void mark2() { printf("here2\n"); }
void mark3() { printf("here3\n"); }
void mark4() { printf("here4\n"); }
void mark5() { printf("Fetch-Decode-Execute Loop ...\n"); }

void printvmstate(unsigned char *vmcode, unsigned int *vmstack, 
                  unsigned int *vmdata, unsigned int vpc,
		  unsigned int vsp)
{ int i;
  printf("Current state of VM6Fh (all values in hex):\n");
  printf("CODE:\n");
  for(i=0;i<128;i++) printf("%4x ",*(vmcode+i));
  printf("\n\nSTACK: (bottom-up)\n");
  for(i=31;i>=0;i--) printf("%4x ",*(vmstack+i));
  printf("\n\nDATA\n");
  for(i=0;i<32;i++) printf("%4x ",*(vmdata+i));
  printf("\n---------------------------\n");
  printf("vpc = %8x,  vsp = %8x\n",vpc,vsp);
}

// convert insruction to binary
unsigned char assemble(const char * A)
{   unsigned char operand = 0;
    unsigned char opcode = 0; 
    char B[8];  // buffer
    sscanf(A,"%s",B);
    if (!strcmp(B,"add"))  opcode = 0;
    if (!strcmp(B,"sub"))  opcode = 1;
    if (!strcmp(B,"nand")) opcode = 2;
    if (!strcmp(B,"push")) 
      { opcode = 3;
        sscanf(A,"%s %s",B,B);
	operand = (unsigned char) atoi(B);
      }
    if (!strcmp(B,"pop")) 
      { opcode = 4;
        sscanf(A,"%s %s",B,B);
	operand = (unsigned char) atoi(B);
      }
    if (!strcmp(B,"jz")) 
      { opcode = 6;
        sscanf(A,"%s %s",B,B);
	operand = (unsigned char) atoi(B);
      }
    if (!strcmp(B,"pushc"))
      { opcode = 5;
        sscanf(A,"%s %s",B,B);
	operand = (unsigned char) atoi(B);
      }
    if (!strcmp(B,"ja"))
      { opcode = 7;
//        sscanf(A,"%s %s",B,B);
//	  operand = (unsigned char) atoi(B);
      }
    opcode = opcode * 32;     // shift left 5 bits
    return (operand | opcode);
} // assemble


void load(unsigned char * addr, unsigned char inst)
{ 
    *addr = inst;
}


// each program will be passed start of vmcode, where instructions will be
// stored
void useprog1(unsigned char * m)
{
    load(m++,assemble("pushc 3"));
    load(m++,assemble("pushc 5"));
    load(m++,assemble("pushc 7"));
    load(m++,assemble("add"));
    load(m++,assemble("pop 1"));
    load(m++,assemble("pop 2"));
    load(m++,assemble("pop 3"));
}

void useprog2(unsigned char * m)
{
    // this program computes sum of i from 1 to 10
    *m++ = assemble("pushc 10");    
    *m++ = assemble("pop 0");    // store counter to mem
    *m++ = assemble("pushc 0");  // identity for +
    *m++ = assemble("push 0");   // load counter from memory
    *m++ = assemble("add");      
    *m++ = assemble("pushc 1");
    *m++ = assemble("push 0");
    *m++ = assemble("sub");      // subtract one from counter
    *m++ = assemble("jz 4");
    *m++ = assemble("pop 0");    // store counter back to ram
    *m++ = assemble("pushc 3");
    *m++ = assemble("ja");
    *m++ = assemble("pop 4");
    *m++ = assemble("pop 4");
    *m++ = assemble("pop 4");    // will cause exception, ends program
}

void useprog3(unsigned char *m)
{
    // implements or as a function of nand
    *m++ = assemble("pushc 0");    
    *m++ = assemble("pushc 0");    
    *m++ = assemble("nand");
    *m++ = assemble("pushc 1");    
    *m++ = assemble("pushc 1");    
    *m++ = assemble("nand");
    *m++ = assemble("nand");
    *m++ = assemble("pop 0");
    *m++ = assemble("pop 1");
    *m++ = assemble("pop 2");
}


/* other utilities  0 - ignore*/

void p2addr(unsigned char* a, unsigned char * b)
{ printf("%d and %d\n",a,b); }