/***************************************************************
   crc's _ _
        (_) | ___
        | | |/ _ \  a tiny virtual computer
        | | | (_) | 64kw RAM, 32-bit, Dual Stack, MISC
        |_|_|\___/  ilo.c (c) charles childers
 **************************************************************/

/* This implementation uses memory separated into multiple
   banks. This makes it easier to run on systems with less
   RAM. */

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

#define SLICES 8
#define SLICESIZE 8192

long ip, sp, rp, data[33], address[257];
long *memory[SLICES];

#define TOS  data[sp]
#define NOS  data[sp-1]
#define TORS address[rp]

long pop() {
  sp--;
  return data[sp + 1];
}

void push(long value) {
  sp++;
  data[sp] = value;
}

void store(long a, long v) {
  long slice = a / SLICESIZE;
  long actual = a - (slice * SLICESIZE);
  memory[slice][actual] = v;
}

long fetch(long a) {
  long slice = a / SLICESIZE;
  long actual = a - (slice * SLICESIZE);
  return memory[slice][actual];
}

void prepare_vm() {
  for (ip = 0; ip < 32;  ip++) data[ip] = 0;
  for (ip = 0; ip < 128; ip++) address[ip] = 0;
  ip = sp = rp = 0;
}

void load_image() {
  FILE *fp;
  long x, y;
  fp = fopen("ilo.rom", "rb");
  for (y = 0; y < 65536; y++) {
    x = 0;
    fread(&x, 4, 1, fp);
    store(y, x);
  }
  fclose(fp);
  prepare_vm();
}

void save_image() {
  FILE *fp;
  long i;
  fp = fopen("ilo.rom", "wb");
  for (i = 0; i < SLICES; i++)
    fwrite(&memory[i], sizeof(long), SLICESIZE, fp);
  fclose(fp);
}

void read_block() {
  FILE *f;
  long block, buffer, x, c;
  buffer = pop();
  block = pop();
  f = fopen("ilo.blo", "r+b");
  fseek(f, 4096 * block, SEEK_SET);
  for (x = 0; x < 1024; x++) {
    c = 0;
    fread(&c, 4, 1, f);
    store(buffer + x, c);
  }
  fclose(f);
}

void write_block() {
  FILE *f;
  long block, buffer, x, c;
  buffer = pop();
  block = pop();
  f = fopen("ilo.blo", "r+b");
  fseek(f, 4096 * block, SEEK_SET);
  for (x = 0; x < 1024; x++) {
    c = fetch(buffer + x);
    fwrite(&c, 4, 1, f);
  }
  fclose(f);
}

void process(long o) {
  long a, b, target, flag;
  long src, dest, len;
  switch (o) {
    case 0: break;
    case 1: ip++; push(fetch(ip)); break;
    case 2: push(TOS); break;
    case 3: data[sp] = 0; sp--; break;
    case 4: a = TOS; TOS = NOS; NOS = a; break;
    case 5: rp++; TORS = pop(); break;
    case 6: push(TORS); rp--; break;
    case 7: ip = pop() - 1; break;
    case 8: rp++; TORS = ip; ip = pop() - 1; break;
    case 9: target = pop(); flag = pop();
            if (flag != 0) { rp++; TORS = ip; ip = target - 1; }
            break;
    case 10: target = pop(); flag = pop();
             if (flag != 0) ip = target - 1; break;
    case 11: ip = TORS; rp--; break;
    case 12: NOS = (NOS == TOS) ? -1 : 0; sp--; break;
    case 13: NOS = (NOS != TOS) ? -1 : 0; sp--; break;
    case 14: NOS = (NOS < TOS) ? -1 : 0; sp--; break;
    case 15: NOS = (NOS > TOS) ? -1 : 0; sp--; break;
    case 16: TOS = fetch(TOS); break;
    case 17: store(TOS, NOS); sp--; sp--; break;
    case 18: NOS += TOS; sp--; break;
    case 19: NOS -= TOS; sp--; break;
    case 20: NOS *= TOS; sp--; break;
    case 21: a = TOS; b = NOS; TOS = b / a; NOS = b % a; break;
    case 22: NOS = TOS & NOS; sp--; break;
    case 23: NOS = TOS | NOS; sp--; break;
    case 24: NOS = TOS ^ NOS; sp--; break;
    case 25: NOS = NOS << TOS; sp--; break;
    case 26: NOS = NOS >> TOS; sp--; break;
    case 27: len = pop(); dest = pop();
             src = pop(); flag = -1;
             while (len) {
               if (fetch(dest) != fetch(src)) flag = 0;
               len -= 1; src += 1; dest += 1;
             }; push(flag); break;
    case 28: len = pop(); dest = pop();
             src = pop();
             while (len) {
               store(dest, fetch(src));
               len -= 1; src += 1; dest += 1;
             }; break;
    case 29: switch (pop()) {
               case 0: putc(pop(), stdout);  break;
               case 1: push(getc(stdin)); break;
               case 2: read_block(); break;
               case 3: write_block(); break;
               case 4: save_image(); break;
               case 5: load_image(); ip = -1; break;
               case 6: ip = 65536; break;
               case 7: push(sp); push(rp); break;
               default:  break;
             } break;
    default: break;
  }
}

void process_opcode_bundle(long opcode) {
  process(opcode & 0xFF);
  process((opcode >> 8) & 0xFF);
  process((opcode >> 16) & 0xFF);
  process((opcode >> 24) & 0xFF);
}

void execute(long address) {
  ip = address;
  while (ip < 65536) {
    process_opcode_bundle(fetch(ip));
    ip++;
  }
}

int main(long argc, char **argv) {
  long i;
  for (i = 0; i < SLICES; i++)
    memory[i] = malloc(SLICESIZE * sizeof(long));
  load_image();
  execute(0);
  for (i = 0; i < SLICES; i++)
    free(memory[i]);
  for (i = 1; sp >= i; i++) printf(" %d", data[i]);
  printf("\n");
}