ilo-vm/source/ilo-68k-mac.c

/* ilo for System 6 / Mac 68k
   Copyright (c) 2022, Charles Childers

   Deriving from the ilo for MS-DOS, this makes use of
   an internally segmented memory model.
   
   The 68k CPU is big endian. Since the ilo images and
   blocks are stored in little endian a fix() function
   has been written and is used to convert between the
   formats as needed.
   
   As with all ilo systems, this needs an ilo.rom and
   ilo.blocks. It's likely to crash if these are not
   present.
  
   I'm building this using Think C 5.0.2, using the ANSI
   library. It's not tested with any other compiler on
   68k.
*/

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

#define SLICES 8
#define SLICESIZE 8192

long ip, sp, rp, data[32], address[256];
long *memory[SLICES];

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

unsigned long fix(unsigned long v) {
  return (((v & 0x000000FF) << 24)|
          ((v & 0x0000FF00) << 8) |
          ((v & 0x00FF0000) >> 8) |
          ((v & 0xFF000000) >> 24));
}

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

void save_image() {
  FILE *fp;
  long i, x;
  fp = fopen("ilo.rom", "wb");
  for (i = 0; i < 65536; i++) {
    x = fix(fetch(i));
    fwrite(&x, 4, 1, fp);
  }
  fclose(fp);
}

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

void write_block() {
  FILE *f;
  long block, buffer, x, c;
  buffer = pop();
  block = pop();
  f = fopen("ilo.blocks", "r+b");
  fseek(f, 4096 * block, SEEK_SET);
  for (x = 0; x < 1024; x++) {
    c = fix(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 execute(long address) {
  long opcode, o;
  ip = address;
  while (ip < 65536) {
    opcode = fetch(ip);
    switch (opcode) {
      case 0: break;
      case 1793: ip = fetch(ip + 1) - 1; break;
      case 2049: process(1); process(8); break;
      case 67502597: push(NOS); break;
      default:
        o =  opcode        & 0xFF; if (o != 0) process(o);
        o = (opcode >> 8)  & 0xFF; if (o != 0) process(o);
        o = (opcode >> 16) & 0xFF; if (o != 0) process(o);
        o = (opcode >> 24) & 0xFF; if (o != 0) process(o);
        break;
    }
    ip++;
  }
}

void 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");
}