src/org/xwt/js/Interpreter.java

   1 // Copyright 2003 Adam Megacz, see the COPYING file for licensing [GPL]
   2 package org.xwt.js;
   3
   4 import org.xwt.util.*;
   5 import java.util.*;
   6 import java.io.*;
   7
   8 /** Encapsulates a single JS interpreter (ie call stack) */
   9 class Interpreter implements ByteCodes, Tokens {
  10
  11
  12     // Thread-Interpreter Mapping /////////////////////////////////////////////////////////////////////////
  13
  14     static Interpreter current() { return (Interpreter)threadToInterpreter.get(Thread.currentThread()); }
  15     private static Hashtable threadToInterpreter = new Hashtable();
  16
  17
  18     // Instance members and methods //////////////////////////////////////////////////////////////////////
  19
  20     int pausecount;               ///< the number of times pause() has been invoked; -1 indicates unpauseable
  21     JSFunction f = null;          ///< the currently-executing JSFunction
  22     JSScope scope;                ///< the current top-level scope (LIFO stack via NEWSCOPE/OLDSCOPE)
  23     Vec stack = new Vec();        ///< the object stack
  24     int pc = 0;                   ///< the program counter
  25
  26     Interpreter(JSFunction f, boolean pauseable, JSArray args) {
  27         stack.push(new Interpreter.CallMarker(this));    // the "root function returned" marker -- f==null
  28         this.f = f;
  29         this.pausecount = pauseable ? 0 : -1;
  30         this.scope = new JSScope(f.parentScope);
  31         stack.push(args);
  32     }
  33
  34     /** this is the only synchronization point we need in order to be threadsafe */
  35     synchronized Object resume() throws JSExn {
  36         Thread t = Thread.currentThread();
  37         Interpreter old = (Interpreter)threadToInterpreter.get(t);
  38         threadToInterpreter.put(t, this);
  39         try {
  40             return run();
  41         } finally {
  42             if (old == null) threadToInterpreter.remove(t);
  43             else threadToInterpreter.put(t, old);
  44         }
  45     }
  46
  47     private static JSExn je(String s) { return new JSExn(JS.getSourceName() + ":" + JS.getLine() + " " + s); }
  48
  49     // FIXME: double check the trap logic
  50     private Object run() throws JSExn {
  51
  52         // if pausecount changes after a get/put/call, we know we've been paused
  53         final int initialPauseCount = pausecount;
  54
  55         OUTER: for(;; pc++) {
  56         try {
  57             if (f == null) return stack.pop();
  58             int op = f.op[pc];
  59             Object arg = f.arg[pc];
  60             if(op == FINALLY_DONE) {
  61                 FinallyData fd = (FinallyData) stack.pop();
  62                 if(fd == null) continue OUTER; // NOP
  63                 if(fd.exn != null) throw fd.exn;
  64                 op = fd.op;
  65                 arg = fd.arg;
  66             }
  67             switch(op) {
  68             case LITERAL: stack.push(arg); break;
  69             case OBJECT: stack.push(new JS()); break;
  70             case ARRAY: stack.push(new JSArray(JS.toNumber(arg).intValue())); break;
  71             case DECLARE: scope.declare((String)(arg==null ? stack.peek() : arg)); if(arg != null) stack.push(arg); break;
  72             case TOPSCOPE: stack.push(scope); break;
  73             case JT: if (JS.toBoolean(stack.pop())) pc += JS.toNumber(arg).intValue() - 1; break;
  74             case JF: if (!JS.toBoolean(stack.pop())) pc += JS.toNumber(arg).intValue() - 1; break;
  75             case JMP: pc += JS.toNumber(arg).intValue() - 1; break;
  76             case POP: stack.pop(); break;
  77             case SWAP: {
  78                 int depth = (arg == null ? 1 : JS.toInt(arg));
  79                 Object save = stack.elementAt(stack.size() - 1);
  80                 for(int i=stack.size() - 1; i > stack.size() - 1 - depth; i--)
  81                     stack.setElementAt(stack.elementAt(i-1), i);
  82                 stack.setElementAt(save, stack.size() - depth - 1);
  83                 break; }
  84             case DUP: stack.push(stack.peek()); break;
  85             case NEWSCOPE: scope = new JSScope(scope); break;
  86             case OLDSCOPE: scope = scope.getParentScope(); break;
  87             case ASSERT: if (!JS.toBoolean(stack.pop())) throw je("xwt.assertion.failed" /*FEATURE: line number*/); break;
  88             case BITNOT: stack.push(JS.N(~JS.toLong(stack.pop()))); break;
  89             case BANG: stack.push(JS.B(!JS.toBoolean(stack.pop()))); break;
  90             case NEWFUNCTION: stack.push(((JSFunction)arg).cloneWithNewParentScope(scope)); break;
  91             case LABEL: break;
  92
  93             case TYPEOF: {
  94                 Object o = stack.pop();
  95                 if (o == null) stack.push(null);
  96                 else if (o instanceof JS) stack.push(((JS)o).typeName());
  97                 else if (o instanceof String) stack.push("string");
  98                 else if (o instanceof Number) stack.push("number");
  99                 else if (o instanceof Boolean) stack.push("boolean");
 100                 else stack.push("unknown");
 101                 break;
 102             }
 103
 104             case PUSHKEYS: {
 105                 Object o = stack.peek();
 106                 Enumeration e = ((JS)o).keys();
 107                 JSArray a = new JSArray();
 108                 while(e.hasMoreElements()) a.addElement(e.nextElement());
 109                 stack.push(a);
 110                 break;
 111             }
 112
 113             case LOOP:
 114                 stack.push(new LoopMarker(pc, pc > 0 && f.op[pc - 1] == LABEL ? (String)f.arg[pc - 1] : (String)null, scope));
 115                 stack.push(Boolean.TRUE);
 116                 break;
 117
 118             case BREAK:
 119             case CONTINUE:
 120                 while(stack.size() > 0) {
 121                     Object o = stack.pop();
 122                     if (o instanceof CallMarker) je("break or continue not within a loop");
 123                     if (o instanceof TryMarker) {
 124                         if(((TryMarker)o).finallyLoc < 0) continue; // no finally block, keep going
 125                         stack.push(new FinallyData(op, arg));
 126                         scope = ((TryMarker)o).scope;
 127                         pc = ((TryMarker)o).finallyLoc - 1;
 128                         continue OUTER;
 129                     }
 130                     if (o instanceof LoopMarker) {
 131                         if (arg == null || arg.equals(((LoopMarker)o).label)) {
 132                             int loopInstructionLocation = ((LoopMarker)o).location;
 133                             int endOfLoop = ((Integer)f.arg[loopInstructionLocation]).intValue() + loopInstructionLocation;
 134                             scope = ((LoopMarker)o).scope;
 135                             if (op == CONTINUE) { stack.push(o); stack.push(Boolean.FALSE); }
 136                             pc = op == BREAK ? endOfLoop - 1 : loopInstructionLocation;
 137                             continue OUTER;
 138                         }
 139                     }
 140                 }
 141                 throw new Error("CONTINUE/BREAK invoked but couldn't find LoopMarker at " +
 142                                 JS.getSourceName() + ":" + JS.getLine());
 143
 144             case TRY: {
 145                 int[] jmps = (int[]) arg;
 146                 // jmps[0] is how far away the catch block is, jmps[1] is how far away the finally block is
 147                 // each can be < 0 if the specified block does not exist
 148                 stack.push(new TryMarker(jmps[0] < 0 ? -1 : pc + jmps[0], jmps[1] < 0 ? -1 : pc + jmps[1], this));
 149                 break;
 150             }
 151
 152             case RETURN: {
 153                 Object retval = stack.pop();
 154                 while(stack.size() > 0) {
 155                     Object o = stack.pop();
 156                     if (o instanceof TryMarker) {
 157                         if(((TryMarker)o).finallyLoc < 0) continue;
 158                         stack.push(retval);
 159                         stack.push(new FinallyData(RETURN));
 160                         scope = ((TryMarker)o).scope;
 161                         pc = ((TryMarker)o).finallyLoc - 1;
 162                         continue OUTER;
 163                     } else if (o instanceof CallMarker) {
 164                         if (scope instanceof Trap.TrapScope) { // handles return component of a read trap
 165                             Trap.TrapScope ts = (Trap.TrapScope)scope;
 166                             if (retval != null) ts.cascadeHappened = true;
 167                             if (!ts.cascadeHappened) {
 168                                 ts.cascadeHappened = true;
 169                                 Trap t = ts.t.next;
 170                                 while (t != null && t.f.numFormalArgs == 0) t = t.next;
 171                                 if (t == null) {
 172                                     ((JS)ts.t.trapee).put(ts.t.name, ts.val);
 173                                     if (pausecount > initialPauseCount) { pc++; return null; }   // we were paused
 174                                 } else {
 175                                     stack.push(o);
 176                                     JSArray args = new JSArray();
 177                                     args.addElement(ts.val);
 178                                     stack.push(args);
 179                                     f = t.f;
 180                                     scope = new Trap.TrapScope(f.parentScope, t, ts.val);
 181                                     pc = -1;
 182                                     continue OUTER;
 183                                 }
 184                             }
 185                         }
 186                         scope = ((CallMarker)o).scope;
 187                         pc = ((CallMarker)o).pc - 1;
 188                         f = (JSFunction)((CallMarker)o).f;
 189                         stack.push(retval);
 190                         continue OUTER;
 191                     }
 192                 }
 193                 throw new Error("error: RETURN invoked but couldn't find a CallMarker!");
 194             }
 195
 196             case PUT: {
 197                 Object val = stack.pop();
 198                 Object key = stack.pop();
 199                 Object target = stack.peek();
 200                 if (target == null)
 201                     throw je("tried to put a value to the " + key + " property on the null value");
 202                 if (!(target instanceof JS))
 203                     throw je("tried to put a value to the " + key + " property on a " + target.getClass().getName());
 204                 if (key == null)
 205                     throw je("tried to assign \"" + (val==null?"(null)":val.toString()) + "\" to the null key");
 206
 207                 Trap t = null;
 208                 if (target instanceof Trap.TrapScope && key.equals("cascade")) {
 209                     Trap.TrapScope ts = (Trap.TrapScope)target;
 210                     t = ts.t.next;
 211                     ts.cascadeHappened = true;
 212                     while (t != null && t.f.numFormalArgs == 0) t = t.next;
 213                     if (t == null) { target = ts.t.trapee; key = ts.t.name; }
 214
 215                 } else if (target instanceof Trap.TrapScope && key.equals(((Trap.TrapScope)target).t.name)) {
 216                     throw je("tried to put to " + key + " inside a trap it owns; use cascade instead");
 217
 218                 } else if (target instanceof JS) {
 219                     if (target instanceof JSScope) {
 220                         JSScope p = (JSScope)target; // search the scope-path for the trap
 221                         t = p.getTrap(key);
 222                         while (t == null && p.getParentScope() != null) { p = p.getParentScope(); t = p.getTrap(key); }
 223                     } else {
 224                         t = ((JS)target).getTrap(key);
 225                     }
 226
 227                     while (t != null && t.f.numFormalArgs == 0) t = t.next; // find the first write trap
 228                     if (t != null) {
 229                         stack.push(new CallMarker(this));
 230                         JSArray args = new JSArray();
 231                         args.addElement(val);
 232                         stack.push(args);
 233                     }
 234                 }
 235                 if (t != null) {
 236                     f = t.f;
 237                     scope = new Trap.TrapScope(f.parentScope, t, val);
 238                     pc = -1;
 239                     break;
 240                 }
 241                 ((JS)target).put(key, val);
 242                 if (pausecount > initialPauseCount) { pc++; return null; }   // we were paused
 243                 stack.push(val);
 244                 break;
 245             }
 246
 247             case GET:
 248             case GET_PRESERVE: {
 249                 Object o, v;
 250                 if (op == GET) {
 251                     v = arg == null ? stack.pop() : arg;
 252                     o = stack.pop();
 253                 } else {
 254                     v = stack.pop();
 255                     o = stack.peek();
 256                     stack.push(v);
 257                 }
 258                 Object ret = null;
 259                 if (v == null) throw je("tried to get the null key from " + o);
 260                 if (o == null) throw je("tried to get property \"" + v + "\" from the null object");
 261                 if (o instanceof String || o instanceof Number || o instanceof Boolean) {
 262                     ret = getFromPrimitive(o,v);
 263                     stack.push(ret);
 264                     break;
 265                 } else if (o instanceof JS) {
 266                     Trap t = null;
 267                     if (o instanceof Trap.TrapScope && v.equals("cascade")) {
 268                         t = ((Trap.TrapScope)o).t.next;
 269                         while (t != null && t.f.numFormalArgs != 0) t = t.next;
 270                         if (t == null) { v = ((Trap.TrapScope)o).t.name; o = ((Trap.TrapScope)o).t.trapee; }
 271
 272                     } else if (o instanceof JS) {
 273                         if (o instanceof JSScope) {
 274                             JSScope p = (JSScope)o; // search the scope-path for the trap
 275                             t = p.getTrap(v);
 276                             while (t == null && p.getParentScope() != null) { p = p.getParentScope(); t = p.getTrap(v); }
 277                         } else {
 278                             t = ((JS)o).getTrap(v);
 279                         }
 280
 281                         while (t != null && t.f.numFormalArgs != 0) t = t.next; // get first read trap
 282                         if (t != null) {
 283                             stack.push(new CallMarker(this));
 284                             JSArray args = new JSArray();
 285                             stack.push(args);
 286                         }
 287                     }
 288                     if (t != null) {
 289                         f = t.f;
 290                         scope = new Trap.TrapScope(f.parentScope, t, null);
 291                         ((Trap.TrapScope)scope).cascadeHappened = true;
 292                         pc = -1;
 293                         break;
 294                     }
 295                     ret = ((JS)o).get(v);
 296                     if (ret == JS.METHOD) ret = new Stub((JS)o, v);
 297                     if (pausecount > initialPauseCount) { pc++; return null; }   // we were paused
 298                     stack.push(ret);
 299                     break;
 300                 }
 301                 throw je("tried to get property " + v + " from a " + o.getClass().getName());
 302             }
 303
 304             case CALL: case CALLMETHOD: {
 305                 int numArgs = JS.toInt(arg);
 306                 Object method = null;
 307                 Object ret = null;
 308                 Object object = stack.pop();
 309
 310                 if (op == CALLMETHOD) {
 311                     if (object == JS.METHOD) {
 312                         method = stack.pop();
 313                         object = stack.pop();
 314                     } else if (object == null) {
 315                         Object name = stack.pop();
 316                         stack.pop();
 317                         throw new JSExn("function '"+name+"' not found");
 318                     } else {
 319                         stack.pop();
 320                         stack.pop();
 321                     }
 322                 }
 323                 Object[] rest = numArgs > 3 ? new Object[numArgs - 3] : null;
 324                 for(int i=numArgs - 1; i>2; i--) rest[i-3] = stack.pop();
 325                 Object a2 = numArgs <= 2 ? null : stack.pop();
 326                 Object a1 = numArgs <= 1 ? null : stack.pop();
 327                 Object a0 = numArgs <= 0 ? null : stack.pop();
 328
 329                 if (object instanceof String || object instanceof Number || object instanceof Boolean) {
 330                     ret = callMethodOnPrimitive(object, method, a0, a1, a2, null, numArgs);
 331
 332                 } else if (object instanceof JSFunction) {
 333                     // FIXME: use something similar to call0/call1/call2 here
 334                     JSArray arguments = new JSArray();
 335                     for(int i=0; i<numArgs; i++) arguments.addElement(i==0?a0:i==1?a1:i==2?a2:rest[i-3]);
 336                     stack.push(new CallMarker(this));
 337                     stack.push(arguments);
 338                     f = (JSFunction)object;
 339                     scope = new JSScope(f.parentScope);
 340                     pc = -1;
 341                     break;
 342
 343                 } else if (object instanceof JS) {
 344                     JS c = (JS)object;
 345                     ret = method == null ? c.call(a0, a1, a2, rest, numArgs) : c.callMethod(method, a0, a1, a2, rest, numArgs);
 346
 347                 } else {
 348                     throw new JSExn("can't call a " + object + " @" + pc + "\n" + f.dump());
 349
 350                 }
 351                 if (pausecount > initialPauseCount) { pc++; return null; }
 352                 stack.push(ret);
 353                 break;
 354             }
 355
 356             case THROW:
 357                 throw new JSExn(stack.pop());
 358
 359             case MAKE_GRAMMAR: {
 360                 final Grammar r = (Grammar)arg;
 361                 final JSScope final_scope = scope;
 362                 Grammar r2 = new Grammar() {
 363                         public int match(String s, int start, Hash v, JSScope scope) throws JSExn {
 364                             return r.match(s, start, v, final_scope);
 365                         }
 366                         public int matchAndWrite(String s, int start, Hash v, JSScope scope, String key) throws JSExn {
 367                             return r.matchAndWrite(s, start, v, final_scope, key);
 368                         }
 369                         public Object call(Object a0, Object a1, Object a2, Object[] rest, int nargs) throws JSExn {
 370                             Hash v = new Hash();
 371                             r.matchAndWrite((String)a0, 0, v, final_scope, "foo");
 372                             return v.get("foo");
 373                         }
 374                     };
 375                 Object obj = stack.pop();
 376                 if (obj != null && obj instanceof Grammar) r2 = new Grammar.Alternative((Grammar)obj, r2);
 377                 stack.push(r2);
 378                 break;
 379             }
 380
 381             case ASSIGN_SUB: case ASSIGN_ADD: {
 382                 Object val = stack.pop();
 383                 Object key = stack.pop();
 384                 Object obj = stack.peek();
 385                 if (val instanceof JSFunction && obj instanceof JS) {
 386                     // A trap addition/removal
 387                     JS js = obj instanceof JSScope ? ((JSScope)obj).top() : (JS) obj;
 388                     if(op == ASSIGN_ADD) js.addTrap(key, (JSFunction)val);
 389                     else js.delTrap(key, (JSFunction)val);
 390                     pc += ((Integer)arg).intValue() - 1;
 391                 } else {
 392                     // The following setup is VERY important. The generated bytecode depends on the stack
 393                     // being setup like this (top to bottom) KEY, OBJ, VAL, KEY, OBJ
 394                     stack.push(key);
 395                     stack.push(val);
 396                     stack.push(obj);
 397                     stack.push(key);
 398                 }
 399                 break;
 400             }
 401
 402             case ADD: {
 403                 int count = ((Number)arg).intValue();
 404                 if(count < 2) throw new Error("this should never happen");
 405                 if(count == 2) {
 406                     // common case
 407                     Object right = stack.pop();
 408                     Object left = stack.pop();
 409                     if(left instanceof String || right instanceof String)
 410                         stack.push(JS.toString(left).concat(JS.toString(right)));
 411                     else stack.push(JS.N(JS.toDouble(left) + JS.toDouble(right)));
 412                 } else {
 413                     Object[] args = new Object[count];
 414                     while(--count >= 0) args[count] = stack.pop();
 415                     if(args[0] instanceof String) {
 416                         StringBuffer sb = new StringBuffer(64);
 417                         for(int i=0;i<args.length;i++) sb.append(JS.toString(args[i]));
 418                         stack.push(sb.toString());
 419                     } else {
 420                         int numStrings = 0;
 421                         for(int i=0;i<args.length;i++) if(args[i] instanceof String) numStrings++;
 422                         if(numStrings == 0) {
 423                             double d = 0.0;
 424                             for(int i=0;i<args.length;i++) d += JS.toDouble(args[i]);
 425                             stack.push(JS.N(d));
 426                         } else {
 427                             int i=0;
 428                             StringBuffer sb = new StringBuffer(64);
 429                             if(!(args[0] instanceof String || args[1] instanceof String)) {
 430                                 double d=0.0;
 431                                 do {
 432                                     d += JS.toDouble(args[i++]);
 433                                 } while(!(args[i] instanceof String));
 434                                 sb.append(JS.toString(JS.N(d)));
 435                             }
 436                             while(i < args.length) sb.append(JS.toString(args[i++]));
 437                             stack.push(sb.toString());
 438                         }
 439                     }
 440                 }
 441                 break;
 442             }
 443
 444             default: {
 445                 Object right = stack.pop();
 446                 Object left = stack.pop();
 447                 switch(op) {
 448
 449                 case BITOR: stack.push(JS.N(JS.toLong(left) | JS.toLong(right))); break;
 450                 case BITXOR: stack.push(JS.N(JS.toLong(left) ^ JS.toLong(right))); break;
 451                 case BITAND: stack.push(JS.N(JS.toLong(left) & JS.toLong(right))); break;
 452
 453                 case SUB: stack.push(JS.N(JS.toDouble(left) - JS.toDouble(right))); break;
 454                 case MUL: stack.push(JS.N(JS.toDouble(left) * JS.toDouble(right))); break;
 455                 case DIV: stack.push(JS.N(JS.toDouble(left) / JS.toDouble(right))); break;
 456                 case MOD: stack.push(JS.N(JS.toDouble(left) % JS.toDouble(right))); break;
 457
 458                 case LSH: stack.push(JS.N(JS.toLong(left) << JS.toLong(right))); break;
 459                 case RSH: stack.push(JS.N(JS.toLong(left) >> JS.toLong(right))); break;
 460                 case URSH: stack.push(JS.N(JS.toLong(left) >>> JS.toLong(right))); break;
 461
 462                 case LT: case LE: case GT: case GE: {
 463                     if (left == null) left = JS.N(0);
 464                     if (right == null) right = JS.N(0);
 465                     int result = 0;
 466                     if (left instanceof String || right instanceof String) {
 467                         result = left.toString().compareTo(right.toString());
 468                     } else {
 469                         result = (int)java.lang.Math.ceil(JS.toDouble(left) - JS.toDouble(right));
 470                     }
 471                     stack.push(JS.B((op == LT && result < 0) || (op == LE && result <= 0) ||
 472                                (op == GT && result > 0) || (op == GE && result >= 0)));
 473                     break;
 474                 }
 475
 476                 case EQ:
 477                 case NE: {
 478                     Object l = left;
 479                     Object r = right;
 480                     boolean ret;
 481                     if (l == null) { Object tmp = r; r = l; l = tmp; }
 482                     if (l == null && r == null) ret = true;
 483                     else if (r == null) ret = false; // l != null, so its false
 484                     else if (l instanceof Boolean) ret = JS.B(JS.toBoolean(r)).equals(l);
 485                     else if (l instanceof Number) ret = JS.toNumber(r).doubleValue() == JS.toNumber(l).doubleValue();
 486                     else if (l instanceof String) ret = r != null && l.equals(r.toString());
 487                     else ret = l.equals(r);
 488                     stack.push(JS.B(op == EQ ? ret : !ret)); break;
 489                 }
 490
 491                 default: throw new Error("unknown opcode " + op);
 492                 } }
 493             }
 494
 495         } catch(JSExn e) {
 496             if(f.op[pc] != FINALLY_DONE) e.addBacktrace(f.sourceName,f.line[pc]);
 497             while(stack.size() > 0) {
 498                 Object o = stack.pop();
 499                 if (o instanceof CatchMarker || o instanceof TryMarker) {
 500                     boolean inCatch = o instanceof CatchMarker;
 501                     if(inCatch) {
 502                         o = stack.pop();
 503                         if(((TryMarker)o).finallyLoc < 0) continue; // no finally block, keep going
 504                     }
 505                     if(!inCatch && ((TryMarker)o).catchLoc >= 0) {
 506                         // run the catch block, this will implicitly run the finally block, if it exists
 507                         stack.push(o);
 508                         stack.push(catchMarker);
 509                         stack.push(e.getObject());
 510                         f = ((TryMarker)o).f;
 511                         scope = ((TryMarker)o).scope;
 512                         pc = ((TryMarker)o).catchLoc - 1;
 513                         continue OUTER;
 514                     } else {
 515                         stack.push(new FinallyData(e));
 516                         f = ((TryMarker)o).f;
 517                         scope = ((TryMarker)o).scope;
 518                         pc = ((TryMarker)o).finallyLoc - 1;
 519                         continue OUTER;
 520                     }
 521                 } else if(o instanceof CallMarker) {
 522                     CallMarker cm = (CallMarker) o;
 523                     if(cm.f == null)
 524                         e.addBacktrace("<java>",0); // This might not even be worth mentioning
 525                     else
 526                         e.addBacktrace(cm.f.sourceName,cm.f.line[cm.pc-1]);
 527                 }
 528             }
 529             throw e;
 530         } // end try/catch
 531         } // end for
 532     }
 533
 534
 535
 536     // Markers //////////////////////////////////////////////////////////////////////
 537
 538     public static class CallMarker {
 539         int pc;
 540         JSScope scope;
 541         JSFunction f;
 542         public CallMarker(Interpreter cx) { pc = cx.pc + 1; scope = cx.scope; f = cx.f; }
 543     }
 544
 545     public static class CatchMarker { public CatchMarker() { } }
 546     private static CatchMarker catchMarker = new CatchMarker();
 547
 548     public static class LoopMarker {
 549         public int location;
 550         public String label;
 551         public JSScope scope;
 552         public LoopMarker(int location, String label, JSScope scope) {
 553             this.location = location;
 554             this.label = label;
 555             this.scope = scope;
 556         }
 557     }
 558     public static class TryMarker {
 559         public int catchLoc;
 560         public int finallyLoc;
 561         public JSScope scope;
 562         public JSFunction f;
 563         public TryMarker(int catchLoc, int finallyLoc, Interpreter cx) {
 564             this.catchLoc = catchLoc;
 565             this.finallyLoc = finallyLoc;
 566             this.scope = cx.scope;
 567             this.f = cx.f;
 568         }
 569     }
 570     public static class FinallyData {
 571         public int op;
 572         public Object arg;
 573         public JSExn exn;
 574         public FinallyData(int op) { this(op,null); }
 575         public FinallyData(int op, Object arg) { this.op = op; this.arg = arg; }
 576         public FinallyData(JSExn exn) { this.exn = exn; } // Just throw this exn
 577     }
 578
 579
 580     // Operations on Primitives //////////////////////////////////////////////////////////////////////
 581
 582     static Object callMethodOnPrimitive(Object o, Object method, Object arg0, Object arg1, Object arg2, Object[] rest, int alength) throws JSExn {
 583         if (method == null || !(method instanceof String) || "".equals(method))
 584             throw new JSExn("attempt to call a non-existant method on a primitive");
 585
 586         if (o instanceof Number) {
 587             //#switch(method)
 588             case "toFixed": throw new JSExn("toFixed() not implemented");
 589             case "toExponential": throw new JSExn("toExponential() not implemented");
 590             case "toPrecision": throw new JSExn("toPrecision() not implemented");
 591             case "toString": {
 592                 int radix = alength >= 1 ? JS.toInt(arg0) : 10;
 593                 return Long.toString(((Number)o).longValue(),radix);
 594             }
 595             //#end
 596         } else if (o instanceof Boolean) {
 597             // No methods for Booleans
 598             throw new JSExn("attempt to call a method on a Boolean");
 599         }
 600
 601         String s = JS.toString(o);
 602         int slength = s.length();
 603         //#switch(method)
 604         case "substring": {
 605             int a = alength >= 1 ? JS.toInt(arg0) : 0;
 606             int b = alength >= 2 ? JS.toInt(arg1) : slength;
 607             if (a > slength) a = slength;
 608             if (b > slength) b = slength;
 609             if (a < 0) a = 0;
 610             if (b < 0) b = 0;
 611             if (a > b) { int tmp = a; a = b; b = tmp; }
 612             return s.substring(a,b);
 613         }
 614         case "substr": {
 615             int start = alength >= 1 ? JS.toInt(arg0) : 0;
 616             int len = alength >= 2 ? JS.toInt(arg1) : Integer.MAX_VALUE;
 617             if (start < 0) start = slength + start;
 618             if (start < 0) start = 0;
 619             if (len < 0) len = 0;
 620             if (len > slength - start) len = slength - start;
 621             if (len <= 0) return "";
 622             return s.substring(start,start+len);
 623         }
 624         case "charAt": {
 625             int p = alength >= 1 ? JS.toInt(arg0) : 0;
 626             if (p < 0 || p >= slength) return "";
 627             return s.substring(p,p+1);
 628         }
 629         case "charCodeAt": {
 630             int p = alength >= 1 ? JS.toInt(arg0) : 0;
 631             if (p < 0 || p >= slength) return JS.N(Double.NaN);
 632             return JS.N(s.charAt(p));
 633         }
 634         case "concat": {
 635             StringBuffer sb = new StringBuffer(slength*2).append(s);
 636             for(int i=0;i<alength;i++) sb.append(i==0?arg0:i==1?arg1:i==2?arg2:rest[i-3]);
 637             return sb.toString();
 638         }
 639         case "indexOf": {
 640             String search = alength >= 1 ? arg0.toString() : "null";
 641             int start = alength >= 2 ? JS.toInt(arg1) : 0;
 642             // Java's indexOf handles an out of bounds start index, it'll return -1
 643             return JS.N(s.indexOf(search,start));
 644         }
 645         case "lastIndexOf": {
 646             String search = alength >= 1 ? arg0.toString() : "null";
 647             int start = alength >= 2 ? JS.toInt(arg1) : 0;
 648             // Java's indexOf handles an out of bounds start index, it'll return -1
 649             return JS.N(s.lastIndexOf(search,start));
 650         }
 651         case "match": return JSRegexp.stringMatch(s,arg0);
 652         case "replace": return JSRegexp.stringReplace(s,arg0,arg1);
 653         case "search": return JSRegexp.stringSearch(s,arg0);
 654         case "split": return JSRegexp.stringSplit(s,arg0,arg1,alength);
 655         case "toLowerCase": return s.toLowerCase();
 656         case "toUpperCase": return s.toUpperCase();
 657         case "toString": return s;
 658         case "slice": {
 659             int a = alength >= 1 ? JS.toInt(arg0) : 0;
 660             int b = alength >= 2 ? JS.toInt(arg1) : slength;
 661             if (a < 0) a = slength + a;
 662             if (b < 0) b = slength + b;
 663             if (a < 0) a = 0;
 664             if (b < 0) b = 0;
 665             if (a > slength) a = slength;
 666             if (b > slength) b = slength;
 667             if (a > b) return "";
 668             return s.substring(a,b);
 669         }
 670         //#end
 671         throw new JSExn("Attempted to call non-existent method: " + method);
 672     }
 673
 674     static Object getFromPrimitive(Object o, Object key) throws JSExn {
 675         boolean returnJS = false;
 676         if (o instanceof Boolean) {
 677             throw new JSExn("cannot call methods on Booleans");
 678         } else if (o instanceof Number) {
 679             if (key.equals("toPrecision") || key.equals("toExponential") || key.equals("toFixed"))
 680                 returnJS = true;
 681         }
 682         if (!returnJS) {
 683             // the string stuff applies to everything
 684             String s = o.toString();
 685
 686             // this is sort of ugly, but this list should never change
 687             // These should provide a complete (enough) implementation of the ECMA-262 String object
 688
 689             //#switch(key)
 690             case "length": return JS.N(s.length());
 691             case "substring": returnJS = true; break;
 692             case "charAt": returnJS = true; break;
 693             case "charCodeAt": returnJS = true; break;
 694             case "concat": returnJS = true; break;
 695             case "indexOf": returnJS = true; break;
 696             case "lastIndexOf": returnJS = true; break;
 697             case "match": returnJS = true; break;
 698             case "replace": returnJS = true; break;
 699             case "seatch": returnJS = true; break;
 700             case "slice": returnJS = true; break;
 701             case "split": returnJS = true; break;
 702             case "toLowerCase": returnJS = true; break;
 703             case "toUpperCase": returnJS = true; break;
 704             case "toString": returnJS = true; break;
 705             case "substr": returnJS = true; break;
 706            //#end
 707         }
 708         if (returnJS) {
 709             final Object target = o;
 710             final String method = key.toString();
 711             return new JS() {
 712                     public Object call(Object a0, Object a1, Object a2, Object[] rest, int nargs) throws JSExn {
 713                         if (nargs > 2) throw new JSExn("cannot call that method with that many arguments");
 714                         return callMethodOnPrimitive(target, method, a0, a1, a2, rest, nargs);
 715                     }
 716             };
 717         }
 718         return null;
 719     }
 720
 721     private static class Stub extends JS {
 722         private Object method;
 723         JS obj;
 724         public Stub(JS obj, Object method) { this.obj = obj; this.method = method; }
 725         public Object call(Object a0, Object a1, Object a2, Object[] rest, int nargs) throws JSExn {
 726             return ((JS)obj).callMethod(method, a0, a1, a2, rest, nargs);
 727         }
 728     }
 729 }