Free Hero Mesh

static int colocation(Uint32 a,Uint32 b) {
  if(a==VOIDLINK || b==VOIDLINK) return 0;
  if((objects[a]->oflags|objects[b]->oflags)&OF_DESTROYED) return 0;
  if((objects[a]->oflags^objects[b]->oflags)&OF_BIZARRO) return 0;
  return (objects[a]->x==objects[b]->x && objects[a]->y==objects[b]->y);
}

static Uint32 pat_find_at(int xy,Uint32 m4,Uint32 m5,Uint32 m6,Uint32 m7,Uint8 cl) {
  Uint8 n=playfield[xy];
  Object*o;
  while(n!=VOIDLINK) {
    o=objects[n];
    if(!(o->oflags&(OF_DESTROYED|OF_VISUALONLY))) {
      if(o->misc4.t==TY_SOUND || o->misc4.t==TY_USOUND) Throw("Cannot convert sound to type");
      if(o->misc5.t==TY_SOUND || o->misc5.t==TY_USOUND) Throw("Cannot convert sound to type");
      if(o->misc6.t==TY_SOUND || o->misc6.t==TY_USOUND) Throw("Cannot convert sound to type");
      if(o->misc7.t==TY_SOUND || o->misc7.t==TY_USOUND) Throw("Cannot convert sound to type");
      if(o->misc4.t==TY_NUMBER && (o->misc4.u&m4)) return n;
      if(o->misc5.t==TY_NUMBER && (o->misc5.u&m5)) return n;
      if(o->misc6.t==TY_NUMBER && (o->misc6.u&m6)) return n;
      if(o->misc7.t==TY_NUMBER && (o->misc7.u&m7)) return n;
      if(classes[o->class]->collisionLayers&cl) return n;
    }
    n=o->up;
  }
  return VOIDLINK;
}

typedef struct {
  Uint16 ptr,depth;
  Uint8 x,y,dir,t;
} ChoicePoint;

#define MAXCHOICE 80
static Uint32 v_pattern(Uint16*code,int ptr,Uint32 obj,char all) {
  Uint8 x=objects[obj]->x;
  Uint8 y=objects[obj]->y;
  Uint8 d=objects[obj]->dir;
  Uint32 n=VOIDLINK;
  Uint32 m;
  Uint16 g;
  Value v;
  static ChoicePoint cp[MAXCHOICE];
  Uint8 cpi=0;
  cp->depth=vstackptr;
  again: switch(code[ptr++]) {
    case 0 ... 7:
      n=VOIDLINK;
      x+=x_delta[code[ptr-1]];
      y+=y_delta[code[ptr-1]];
      if(x<1 || x>pfwidth || y<1 || y>pfheight) goto fail;
      break;
    case 8 ... 15:
      n=VOIDLINK;
      x+=x_delta[(code[ptr-1]+objects[obj]->dir)&7];
      y+=y_delta[(code[ptr-1]+objects[obj]->dir)&7];
      if(x<1 || x>pfwidth || y<1 || y>pfheight) goto fail;
      break;
    case 0x0200 ... 0x02FF:
      g=code[ptr-1]&255;
      goto message;
    case 0x1000 ... 0x10FF:
      g=code[ptr-1]&255;
      if(g<0x20) n=pat_find_at(x+y*64-65,1UL<<(g&31),0,0,0,0);
      else if(g<0x40) n=pat_find_at(x+y*64-65,0,1UL<<(g&31),0,0,0);
      else if(g<0x60) n=pat_find_at(x+y*64-65,0,0,1UL<<(g&31),0,0);
      else if(g<0x80) n=pat_find_at(x+y*64-65,0,0,0,1UL<<(g&31),0);
      else n=pat_find_at(x+y*64-65,0,0,0,0,1U<<(g&7));
      if(n==VOIDLINK) goto fail;
      break;
    case 0x4000 ... 0x7FFF:
      n=obj_class_at(code[ptr-1]&0x3FFF,x,y);
      if(n==VOIDLINK) goto fail;
      break;
    case 0xC000 ... 0xFFFF:
      g=(code[ptr-1]&0x3FFF)+256;
    message:
      m=playfield[x+y*64-65];
      while(m!=VOIDLINK) {
        v=send_message(obj,m,g,NVALUE(d),OVALUE(n),NVALUE(0));
        if(v.t==TY_NUMBER) {
          if(v.u==1) goto fail;
          else if(v.u==2) break;
          else if(v.u) Throw("Invalid return value from message in pattern matching");
        } else if(v.t>TY_MAXTYPE) {
          n=v_object(v);
          x=objects[n]->x;
          y=objects[n]->y;
        } else {
          Throw("Type mismatch");
        }
        m=objects[m]->up;
      }
      break;
    case OP_ADD:
      if(vstackptr>=VSTACKSIZE-1) Throw("Stack overflow");
      m=(n==VOIDLINK?obj_bottom_at(x,y):n);
      Push(OVALUE(m));
      break;
    case OP_AGAIN:
      if(cp[cpi].ptr!=ptr+1) {
        if(cpi>=MAXCHOICE-1) Throw("Choice overflow");
        cpi++;
        cp[cpi].ptr=ptr+1;
      }
      cp[cpi].x=x;
      cp[cpi].y=y;
      cp[cpi].dir=d;
      cp[cpi].depth=vstackptr;
      ptr=code[ptr]+2;
      break;
    case OP_BEGIN:
      ptr++;
      break;
    case OP_CLIMB:
      if(playfield[x+y*64-65]==VOIDLINK || height_at(x,y)>objects[obj]->climb) goto fail;
      break;
    case OP_CLIMB_C:
      g=code[ptr++];
      if(playfield[x+y*64-65]==VOIDLINK || height_at(x,y)>g) goto fail;
      break;
    case OP_CUT:
      if(cpi) cpi--;
      break;
    case OP_DIR:
      d=objects[obj]->dir;
      break;
    case OP_DIR_C:
      if(n==VOIDLINK) Throw("No object specified in pattern");
      d=objects[n]->dir;
      break;
    case OP_DIR_E:
      changed=1;
      objects[obj]->dir=d;
      break;
    case OP_DIR_EC:
      if(n==VOIDLINK) Throw("No object specified in pattern");
      changed=1;
      objects[n]->dir=d;
      break;
    case OP_EIGHT:
      if(cpi>=MAXCHOICE-8) Throw("Choice overflow");
      d=0;
      cpi+=7;
      cp[cpi].x=x;
      cp[cpi].y=y;
      cp[cpi].depth=vstackptr;
      cp[cpi].ptr=ptr;
      cp[cpi-1]=cp[cpi-2]=cp[cpi-3]=cp[cpi-4]=cp[cpi-5]=cp[cpi-6]=cp[cpi];
      cp[cpi].dir=1;
      cp[cpi-1].dir=2;
      cp[cpi-2].dir=3;
      cp[cpi-3].dir=4;
      cp[cpi-4].dir=5;
      cp[cpi-5].dir=6;
      cp[cpi-6].dir=7;
      break;
    case OP_ELSE:
      ptr--;
      while(code[ptr]==OP_ELSE) ptr=code[ptr+2];
      break;
    case OP_FOUR:
      if(cpi>=MAXCHOICE-4) Throw("Choice overflow");
      d=0;
      cpi+=3;
      cp[cpi].x=x;
      cp[cpi].y=y;
      cp[cpi].depth=vstackptr;
      cp[cpi].ptr=ptr;
      cp[cpi-1]=cp[cpi-2]=cp[cpi];
      cp[cpi].dir=2;
      cp[cpi-1].dir=4;
      cp[cpi-2].dir=6;
      break;
    case OP_HEIGHT:
      if(playfield[x+y*64-65]==VOIDLINK || height_at(x,y)<=objects[obj]->climb) goto fail;
      break;
    case OP_HEIGHT_C:
      g=code[ptr++];
      if(playfield[x+y*64-65]==VOIDLINK || height_at(x,y)<=g) goto fail;
      break;
    case OP_IF:
      if(cpi>=MAXCHOICE-1) Throw("Pattern stack overflow");
      cpi++;
      cp[cpi].x=x;
      cp[cpi].y=y;
      cp[cpi].dir=d;
      cp[cpi].depth=vstackptr;
      cp[cpi].ptr=code[ptr++];
      break;
    case OP_LOC:
      if(vstackptr>=VSTACKSIZE-2) Throw("Stack overflow");
      Push(NVALUE(x));
      Push(NVALUE(y));
      break;
    case OP_MARK:
      if(vstackptr>=VSTACKSIZE-1) Throw("Stack overflow");
      Push(UVALUE(0,TY_MARK));
      break;
    case OP_MUL:
      cp[cpi].x=x;
      cp[cpi].y=y;
      cp[cpi].dir=d;
      break;
    case OP_OBJABOVE:
      if(n==VOIDLINK) Throw("No object specified in pattern");
      n=obj_above(n);
      break;
    case OP_OBJBELOW:
      if(n==VOIDLINK) Throw("No object specified in pattern");
      n=obj_below(n);
      break;
    case OP_OBJBOTTOMAT:
      n=obj_bottom_at(x,y);
      break;
    case OP_OBJTOPAT:
      n=obj_top_at(x,y);
      break;
    case OP_RET:
      return n==VOIDLINK?obj_bottom_at(x,y):n;
    case OP_SUB:
      if(vstackptr>=VSTACKSIZE-1) Throw("Stack overflow");
      Push(NVALUE(0));
      break;
    case OP_THEN:
      // This opcode does nothing
      break;
    case OP_TRACE:
      if(main_options['t']) {
        printf("ptr=%d cpi=%d x=%d y=%d dir=%d obj=%lu ",ptr,cpi,x,y,d,(long)n);
        printf("[ptr=%d x=%d y=%d dir=%d]\n",cp[cpi].ptr,cp[cpi].x,cp[cpi].y,cp[cpi].dir);
      }
      break;
    default: Throw("Unimplemented opcode in pattern");
  }
  goto again;
  fail:
  if(vstackptr<cp->depth) Throw("Stack underflow in pattern matching");
  vstackptr=cp[cpi].depth;
  if(!cpi) return VOIDLINK;
  x=cp[cpi].x;
  y=cp[cpi].y;
  d=cp[cpi].dir;
  ptr=cp[cpi].ptr;
  n=VOIDLINK;
  cpi--;
  goto again;
}

// Here is where the execution of a Free Hero Mesh bytecode subroutine is executed.
#define NoIgnore() do{ changed=1; }while(0)
#define GetVariableOf(a,b) (i=v_object(Pop()),i==VOIDLINK?NVALUE(0):b(objects[i]->a))
#define GetVariableOrAttributeOf(a,b) (t2=Pop(),t2.t==TY_CLASS?NVALUE(classes[t2.u]->a):(i=v_object(t2),i==VOIDLINK?NVALUE(0):b(objects[i]->a)))
#define Numeric(a) do{ if((a).t!=TY_NUMBER) Throw("Type mismatch"); }while(0)
#define DivideBy(a) do{ Numeric(a); if(!(a).u) Throw("Division by zero"); }while(0)

    case OP_OBJCLASSAT: StackReq(3,1); t3=Pop(); t2=Pop(); t1=Pop(); Push(v_obj_class_at(t1,t2,t3)); break;
    case OP_OBJDIR: StackReq(1,1); t2=Pop(); Numeric(t2); i=obj_dir(obj,t2.u); Push(OVALUE(i)); break;
    case OP_OBJDIR_C: StackReq(2,1); t2=Pop(); Numeric(t2); i=obj_dir(v_object(Pop()),t2.u); Push(OVALUE(i)); break;
    case OP_OBJLAYERAT: StackReq(3,1); t3=Pop(); Numeric(t3); t2=Pop(); Numeric(t2); t1=Pop(); Numeric(t1); i=obj_layer_at(t1.u,t2.u,t3.u); Push(OVALUE(i)); break;
    case OP_OBJMOVINGTO: StackReq(2,0); t2=Pop(); Numeric(t2); t1=Pop(); Numeric(t1); v_obj_moving_to(t1.u,t2.u); break;
    case OP_OBJTOPAT: StackReq(2,1); t2=Pop(); Numeric(t2); t1=Pop(); Numeric(t1); i=obj_top_at(t1.u,t2.u); Push(OVALUE(i)); break;
    case OP_OVER: StackReq(2,3); t2=Pop(); t1=Pop(); Push(t1); Push(t2); Push(t1); break;
    case OP_PATTERN: StackReq(0,1); i=code[ptr++]; j=v_pattern(code,ptr,obj,0); ptr=i; Push(OVALUE(j)); break;
    case OP_PATTERN_C: StackReq(1,1); i=code[ptr++]; j=v_object(Pop()); if(j!=VOIDLINK) j=v_pattern(code,ptr,j,0); ptr=i; Push(OVALUE(j)); break;
    case OP_PICK: StackReq(0,1); t1=Pop(); Numeric(t1); if(t1.u>=vstackptr) Throw("Stack index out of range"); t1=vstack[vstackptr-t1.u-1]; Push(t1); break;
    case OP_PLAYER: StackReq(0,1); if(classes[o->class]->cflags&CF_PLAYER) Push(NVALUE(1)); else Push(NVALUE(0)); break;
    case OP_PLAYER_C: StackReq(1,1); GetClassFlagOf(CF_PLAYER); break;
    case OP_PLUSMOVE: StackReq(1,1); t1=Pop(); Numeric(t1); i=defer_move(obj,t1.u,1); Push(NVALUE(i)); break;
    case OP_PLUSMOVE_C: StackReq(2,1); t1=Pop(); Numeric(t1); i=v_object(Pop()); i=defer_move(i,t1.u,1); Push(NVALUE(i)); break;
    case OP_PLUSMOVE_D: StackReq(1,0); t1=Pop(); Numeric(t1); defer_move(obj,t1.u,1); break;
    case OP_PLUSMOVE_CD: StackReq(2,1); t1=Pop(); Numeric(t1); i=v_object(Pop()); defer_move(i,t1.u,1); break;