src/org/ibex/js/Interpreter.java

   1 // Copyright 2000-2005 the Contributors, as shown in the revision logs.
   2 // Licensed under the Apache Public Source License 2.0 ("the License").
   3 // You may not use this file except in compliance with the License.
   4
   5 package org.ibex.js;
   6
   7 import org.ibex.util.*;
   8 import java.util.*;
   9
  10 /** Encapsulates a single JS interpreter (ie call stack) */
  11 class Interpreter implements ByteCodes, Tokens, Pausable {
  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     final Stack stack = new Stack(); ///< the object stack
  24     int pc = 0;                   ///< the program counter
  25
  26     Interpreter(JSFunction f, boolean pauseable, JS[] args) {
  27         this.f = f;
  28         this.pausecount = pauseable ? 0 : -1;
  29         this.scope = f.parentScope;
  30         try {
  31             stack.push(new CallMarker(null));    // the "root function returned" marker -- f==null
  32             stack.push(args);
  33         } catch(JSExn e) {
  34             throw new Error("should never happen");
  35         }
  36     }
  37
  38     Interpreter(JS.Trap t, JS val, boolean pauseOnPut) {
  39         this.pausecount = -1;
  40         try {
  41             setupTrap(t,val,new TrapMarker(null,t,val,pauseOnPut));
  42         } catch(JSExn e) {
  43             throw new Error("should never happen");
  44         }
  45     }
  46
  47     private boolean get = false;
  48     // FIXME: split this stuff out into a Script instance control object
  49     //        so it's possible to make JS either single or multi threaded.
  50     /** this is the only synchronization point we need in order to be threadsafe */
  51     public synchronized Object run(Object o) throws JSExn {
  52         if (f == null) throw new AlreadyRunningException("function already finished");
  53         if (scope == null) throw new RuntimeException("scope is null");
  54
  55         Thread t = Thread.currentThread();
  56         Interpreter old = (Interpreter)threadToInterpreter.get(t);
  57         threadToInterpreter.put(t, this);
  58
  59         if (get) stack.push(o);
  60
  61         try {
  62             return run();
  63         } finally {
  64             if (old == null) threadToInterpreter.remove(t);
  65             else threadToInterpreter.put(t, old);
  66         }
  67     }
  68
  69     public void pause() throws NotPausableException {
  70         if (pausecount == -1 || f == null) throw new NotPausableException();
  71         pausecount++;
  72         switch(f.op[pc]) {
  73             case Tokens.RETURN: case ByteCodes.PUT: get = false; break;
  74             case ByteCodes.GET: case ByteCodes.CALL: get = true; break;
  75             default: throw new Error("should never happen");
  76         }
  77     }
  78
  79     static int getLine() {
  80         Interpreter c = Interpreter.current();
  81         return c == null || c.f == null || c.pc < 0 || c.pc >= c.f.size ? -1 : c.f.line[c.pc];
  82     }
  83
  84     static String getSourceName() {
  85         Interpreter c = Interpreter.current();
  86         return c == null || c.f == null ? null : c.f.sourceName;
  87     }
  88
  89     private static JSExn je(String s) { return new JSExn(getSourceName() + ":" + getLine() + " " + s); }
  90
  91     private JS run() throws JSExn {
  92
  93         // if pausecount changes after a get/put/call, we know we've been paused
  94         final int initialPauseCount = pausecount;
  95
  96         OUTER: for(;; pc++) {
  97         try {
  98             int op = f.op[pc];
  99             Object arg = f.arg[pc];
 100             if(op == FINALLY_DONE) {
 101                 FinallyData fd = (FinallyData) stack.pop();
 102                 if(fd == null) continue OUTER; // NOP
 103                 if(fd.exn != null) throw fd.exn;
 104                 op = fd.op;
 105                 arg = fd.arg;
 106             }
 107             switch(op) {
 108             case LITERAL: stack.push((JS)arg); break;
 109             case OBJECT: stack.push(new JS.Obj()); break;
 110             case ARRAY: stack.push(new JSArray(Script.toInt((JS)arg))); break;
 111             //case DECLARE: scope.declare((JS)(arg==null ? stack.peek() : arg)); if(arg != null) stack.push((JS)arg); break;
 112             case JT: if (Script.toBoolean((JS)stack.pop())) pc += Script.toInt((JS)arg) - 1; break;
 113             case JF: if (!Script.toBoolean((JS)stack.pop())) pc += Script.toInt((JS)arg) - 1; break;
 114             case JMP: pc += Script.toInt((JS)arg) - 1; break;
 115             case POP: stack.pop(); break;
 116             case SWAP: stack.swap(); break;
 117             case DUP: stack.push(stack.peek()); break;
 118             case NEWSCOPE: {
 119                 int n = Script.toInt((JS)arg);
 120                 scope = new JSScope(scope,(n>>>16)&0xffff,(n>>>0)&0xffff);
 121                 break;
 122             }
 123             case OLDSCOPE: scope = scope.parent; break;
 124             case GLOBALSCOPE: stack.push(scope.getGlobal()); break;
 125             case SCOPEGET: stack.push(scope.get((JS)arg)); break;
 126             case SCOPEPUT: scope.put((JS)arg, (JS)stack.peek()); break;
 127             case ASSERT: if (!Script.toBoolean((JS)stack.pop())) throw je("ibex.assertion.failed"); break;
 128             case BITNOT: stack.push(Script.N(~Script.toLong((JS)stack.pop()))); break;
 129             case BANG: stack.push(Script.B(!Script.toBoolean((JS)stack.pop()))); break;
 130             case NEWFUNCTION: stack.push(((JSFunction)arg)._cloneWithNewParentScope(scope)); break;
 131             case LABEL: break;
 132
 133             case TYPEOF: {
 134                 Object o = stack.pop();
 135                 if (o == null) stack.push(null);
 136                 else if (o instanceof JSString) stack.push(Script.S("string"));
 137                 else if (o instanceof JSNumber.B) stack.push(Script.S("boolean"));
 138                 else if (o instanceof JSNumber) stack.push(Script.S("number"));
 139                 else stack.push(Script.S("object"));
 140                 break;
 141             }
 142
 143             case PUSHKEYS: {
 144                 JS o = (JS)stack.peek();
 145                 stack.push(o == null ? null : o.keys());
 146                 break;
 147             }
 148
 149             case LOOP:
 150                 stack.push(new LoopMarker(pc, (String)(pc > 0 && f.op[pc - 1] == LABEL ? f.arg[pc - 1] : null), scope));
 151                 stack.push(Script.T);
 152                 break;
 153
 154             case BREAK:
 155             case CONTINUE:
 156                 while(!stack.empty()) {
 157                     JS o = (JS)stack.pop();
 158                     if (o instanceof CallMarker) je("break or continue not within a loop");
 159                     if (o instanceof TryMarker) {
 160                         if(((TryMarker)o).finallyLoc < 0) continue; // no finally block, keep going
 161                         stack.push(new FinallyData(op, arg));
 162                         scope = ((TryMarker)o).scope;
 163                         pc = ((TryMarker)o).finallyLoc - 1;
 164                         continue OUTER;
 165                     }
 166                     if (o instanceof LoopMarker) {
 167                         if (arg == null || arg.equals(((LoopMarker)o).label)) {
 168                             int loopInstructionLocation = ((LoopMarker)o).location;
 169                             int endOfLoop = Script.toInt((JS)f.arg[loopInstructionLocation]) + loopInstructionLocation;
 170                             scope = ((LoopMarker)o).scope;
 171                             if (op == CONTINUE) { stack.push(o); stack.push(Script.F); }
 172                             pc = op == BREAK ? endOfLoop - 1 : loopInstructionLocation;
 173                             continue OUTER;
 174                         }
 175                     }
 176                 }
 177                 throw new Error("CONTINUE/BREAK invoked but couldn't find LoopMarker at " +
 178                                 getSourceName() + ":" + getLine());
 179
 180             case TRY: {
 181                 int[] jmps = (int[]) arg;
 182                 // jmps[0] is how far away the catch block is, jmps[1] is how far away the finally block is
 183                 // each can be < 0 if the specified block does not exist
 184                 stack.push(new TryMarker(jmps[0] < 0 ? -1 : pc + jmps[0], jmps[1] < 0 ? -1 : pc + jmps[1], this));
 185                 break;
 186             }
 187
 188             case RETURN: {
 189                 JS retval = (JS)stack.pop();
 190                 while(!stack.empty()) {
 191                     Object o = stack.pop();
 192                     if (o instanceof TryMarker) {
 193                         if(((TryMarker)o).finallyLoc < 0) continue;
 194                         stack.push(retval);
 195                         stack.push(new FinallyData(RETURN));
 196                         scope = ((TryMarker)o).scope;
 197                         pc = ((TryMarker)o).finallyLoc - 1;
 198                         continue OUTER;
 199                     } else if (o instanceof CallMarker) {
 200                         boolean didTrapPut = false;
 201                         if (o instanceof TrapMarker) { // handles return component of a write trap
 202                             TrapMarker tm = (TrapMarker) o;
 203                             boolean cascade = tm.t.isWriteTrap() && !tm.cascadeHappened && !Script.toBoolean(retval);
 204                             if(cascade) {
 205                                 JS.Trap t = tm.t.nextWrite();
 206                                 if(t == null && tm.t.target() instanceof JS.Clone) {
 207                                     t = ((JS.Clone)tm.t.target()).clonee.getTrap(tm.t.key());
 208                                     if(t != null && !t.isWriteTrap()) t = t.nextWrite();
 209                                 }
 210                                 if(t != null) {
 211                                     tm.t = t; // we reuse the old trap marker
 212                                     setupTrap(t, tm.val, tm);
 213                                     pc--; // we increment it on the next iter
 214                                     continue OUTER;
 215                                 } else {
 216                                     didTrapPut = true;
 217                                     if(!tm.pauseOnPut) tm.t.target().put(tm.t.key(), tm.val);
 218                                 }
 219                             }
 220                         }
 221                         CallMarker cm = (CallMarker) o;
 222                         scope = cm.scope;
 223                         pc = cm.pc - 1;
 224                         f = cm.f;
 225                         if (didTrapPut) {
 226                             if (((TrapMarker)cm).pauseOnPut) { pc++; return ((TrapMarker)cm).val; }
 227                             if (pausecount > initialPauseCount) { pc++; return null; }   // we were paused
 228                         } else {
 229                             stack.push(retval);
 230                         }
 231                         if (f == null) return retval;
 232                         continue OUTER;
 233                     }
 234                 }
 235                 throw new Error("error: RETURN invoked but couldn't find a CallMarker!");
 236             }
 237
 238             case CASCADE: {
 239                 boolean write = Script.toBoolean((JS)arg);
 240                 JS val = write ? (JS)stack.pop() : null;
 241                 CallMarker o = stack.findCall();
 242                 if(!(o instanceof TrapMarker)) throw new JSExn("tried to CASCADE while not in a trap");
 243                 TrapMarker tm = (TrapMarker) o;
 244                 JS key = tm.t.key();
 245                 JS target = tm.t.target();
 246                 if(tm.t.isWriteTrap() != write) throw new JSExn("tried to do a " + (write?"write":"read") + " cascade in a " + (write?"read":"write") + " trap");
 247                 JS.Trap t = write ? tm.t.nextWrite() : tm.t.nextRead();
 248                 // FIXME: Doesn't handle multiple levels of clone's (probably can just make this a while loop)
 249                 if(t == null && target instanceof JS.Clone) {
 250                     target = ((JS.Clone)target).clonee;
 251                     t = target.getTrap(key);
 252                     if(t != null) t = write ? t.write() : t.read();
 253                 }
 254                 if(write) {
 255                     tm.cascadeHappened = true;
 256                     stack.push(val);
 257                 }
 258                 if(t != null) {
 259                     setupTrap(t,val,new TrapMarker(this,t,val,tm.pauseOnPut));
 260                     pc--; // we increment later
 261                 } else {
 262                     if(write) {
 263                         if (tm.pauseOnPut) { pc++; return val; }
 264                         target.put(key,val);
 265                     } else {
 266                         JS ret = target.get(key);
 267                         if (ret != null && ret instanceof JS.Method) ret = new Stub(target, key);
 268                         stack.push(ret);
 269                     }
 270                     if (pausecount > initialPauseCount) { pc++; return null; }   // we were paused
 271                 }
 272                 break;
 273             }
 274
 275             case PUT: {
 276                 JS val = (JS)stack.pop();
 277                 JS key = (JS)stack.pop();
 278                 JS target = (JS)stack.peek();
 279                 if (target == null) throw je("tried to put " + Script.str(val) + " to the " + Script.str(key) + " property on the null value");
 280                 if (key == null) throw je("tried to assign \"" + Script.str(val) + "\" to the null key");
 281
 282                 JS.Trap t = target.getTrap(key);
 283                 if(t != null) t = t.write();
 284
 285                 if(t == null && target instanceof JS.Clone) {
 286                     target = ((JS.Clone)target).clonee;
 287                     t = target.getTrap(key);
 288                     if(t != null) t = t.nextWrite();
 289                 }
 290
 291                 stack.push(val);
 292
 293                 if(t != null) {
 294                     setupTrap(t,val,new TrapMarker(this,t,val));
 295                     pc--; // we increment later
 296                 } else {
 297                     target.put(key,val);
 298                     if (pausecount > initialPauseCount) { pc++; return null; }   // we were paused
 299                 }
 300                 break;
 301             }
 302
 303             case GET:
 304             case GET_PRESERVE: {
 305                 JS target, key;
 306                 if (op == GET) {
 307                     key = arg == null ? (JS)stack.pop() : (JS)arg;
 308                     target = (JS)stack.pop();
 309                 } else {
 310                     key = (JS)stack.pop();
 311                     target = (JS)stack.peek();
 312                     stack.push(key);
 313                 }
 314                 JS ret = null;
 315                 if (key == null) throw je("tried to get the null key from " + Script.str(target));
 316                 if (target == null) throw je("tried to get property \"" + Script.str(key) + "\" from the null object");
 317
 318                 JS.Trap t = target.getTrap(key);
 319                 if(t != null) t = t.read();
 320
 321                 if(t == null && target instanceof JS.Clone) {
 322                     target = ((JS.Clone)target).clonee;
 323                     t = target.getTrap(key);
 324                     if(t != null) t = t.nextRead();
 325                 }
 326
 327                 if(t != null) {
 328                     setupTrap(t,null,new TrapMarker(this,t,null));
 329                     pc--; // we increment later
 330                 } else {
 331                     ret = target.get(key);
 332                     if (pausecount > initialPauseCount) { pc++; return null; }   // we were paused
 333
 334                     if (ret != null && ret instanceof JS.Method) ret = new Stub(target, key);
 335                     stack.push(ret);
 336                 }
 337                 break;
 338             }
 339
 340             case CALL: case CALLMETHOD: {
 341                 // FIXME: can a lot of simple cases in Parser be
 342                 // reduced so creating a new JS[] is not necessary?
 343                 JS[] jsargs;
 344                 if (arg instanceof JSNumber.I) {
 345                     jsargs = new JS[((JSNumber.I)arg).toInt()];
 346                     for (int i=0; i < jsargs.length; i++) jsargs[i] = (JS)stack.pop();
 347                 } else jsargs = (JS[])arg;
 348
 349                 JS method = null;
 350                 JS ret = null;
 351                 JS object = (JS)stack.pop();
 352
 353                 if (op == CALLMETHOD) {
 354                     if (object == null) {
 355                         method = (JS)stack.pop();
 356                         object = (JS)stack.pop();
 357                         throw new JSExn("function '"+Script.str(method)+"' not found in " + object.getClass().getName());
 358                     } else if (object instanceof JS.Method) {
 359                         method = (JS)stack.pop();
 360                         object = (JS)stack.pop();
 361                     } else {
 362                         stack.pop();
 363                         stack.pop();
 364                     }
 365                 }
 366
 367                 if (object instanceof JSFunction) {
 368                     stack.push(new CallMarker(this));
 369                     stack.push(jsargs);
 370                     f = (JSFunction)object;
 371                     scope = f.parentScope;
 372                     pc = -1;
 373                     break;
 374                 } else {
 375                     JS c = (JS)object;
 376                     ret = method == null ? c.call(jsargs) : c.call(method, jsargs);
 377                 }
 378
 379                 if (pausecount > initialPauseCount) { pc++; return null; }
 380                 stack.push(ret);
 381                 break;
 382             }
 383
 384             case THROW:
 385                 throw new JSExn((JS)stack.pop(), this);
 386
 387                 /* FIXME GRAMMAR
 388             case MAKE_GRAMMAR: {
 389                 final Grammar r = (Grammar)arg;
 390                 final JSScope final_scope = scope;
 391                 Grammar r2 = new Grammar() {
 392                         public int match(String s, int start, Map v, JSScope scope) throws JSExn {
 393                             return r.match(s, start, v, final_scope);
 394                         }
 395                         public int matchAndWrite(String s, int start, Map v, JSScope scope, String key) throws JSExn {
 396                             return r.matchAndWrite(s, start, v, final_scope, key);
 397                         }
 398                         public Object call(Object a0, Object a1, Object a2, Object[] rest, int nargs) throws JSExn {
 399                             Map v = new Map();
 400                             r.matchAndWrite((String)a0, 0, v, final_scope, "foo");
 401                             return v.get("foo");
 402                         }
 403                     };
 404                 Object obj = stack.pop();
 405                 if (obj != null && obj instanceof Grammar) r2 = new Grammar.Alternative((Grammar)obj, r2);
 406                 stack.push(r2);
 407                 break;
 408             }
 409                 */
 410             case ADD_TRAP: case DEL_TRAP: {
 411                 JS val = (JS)stack.pop();
 412                 JS key = (JS)stack.pop();
 413                 JS js = (JS)stack.peek();
 414                 // A trap addition/removal
 415                 if(!(val instanceof JSFunction)) throw new JSExn("tried to add/remove a non-function trap"); // FIXME
 416                 if(op == ADD_TRAP) js.addTrap(key, val);
 417                 else js.delTrap(key, val);
 418                 break;
 419             }
 420
 421             case ADD: {
 422                 int count = ((JSNumber)arg).toInt();
 423                 if(count < 2) throw new Error("this should never happen");
 424                 if(count == 2) {
 425                     // common case
 426                     JS right = (JS)stack.pop();
 427                     JS left = (JS)stack.pop();
 428                     JS ret;
 429                     if(left instanceof JSString || right instanceof JSString)
 430                         ret = Script.S(Script.toString(left).concat(Script.toString(right)));
 431                     else if(left instanceof JSNumber.D || right instanceof JSNumber.D)
 432                         ret = Script.N(Script.toDouble(left) + Script.toDouble(right));
 433                     else {
 434                         long l = Script.toLong(left) + Script.toLong(right);
 435                         if(l < Integer.MIN_VALUE || l > Integer.MAX_VALUE) ret = Script.N(l);
 436                         ret = Script.N((int)l);
 437                     }
 438                     stack.push(ret);
 439                 } else {
 440                     JS[] args = new JS[count];
 441                     while(--count >= 0) args[count] = (JS)stack.pop();
 442                     if(args[0] instanceof JSString) {
 443                         StringBuffer sb = new StringBuffer(64);
 444                         for(int i=0;i<args.length;i++) sb.append(Script.toString(args[i]));
 445                         stack.push(Script.S(sb.toString()));
 446                     } else {
 447                         int numStrings = 0;
 448                         for(int i=0;i<args.length;i++) if(args[i] instanceof JSString) numStrings++;
 449                         if(numStrings == 0) {
 450                             double d = 0.0;
 451                             for(int i=0;i<args.length;i++) d += Script.toDouble(args[i]);
 452                             stack.push(Script.N(d));
 453                         } else {
 454                             int i=0;
 455                             StringBuffer sb = new StringBuffer(64);
 456                             if(!(args[0] instanceof JSString || args[1] instanceof JSString)) {
 457                                 double d=0.0;
 458                                 do {
 459                                     d += Script.toDouble(args[i++]);
 460                                 } while(!(args[i] instanceof JSString));
 461                                 sb.append(Script.toString(Script.N(d)));
 462                             }
 463                             while(i < args.length) sb.append(Script.toString(args[i++]));
 464                             stack.push(Script.S(sb.toString()));
 465                         }
 466                     }
 467                 }
 468                 break;
 469             }
 470
 471             default: {
 472                 JS right = (JS)stack.pop();
 473                 JS left = (JS)stack.pop();
 474                 switch(op) {
 475
 476                 case BITOR: stack.push(Script.N(Script.toLong(left) | Script.toLong(right))); break;
 477                 case BITXOR: stack.push(Script.N(Script.toLong(left) ^ Script.toLong(right))); break;
 478                 case BITAND: stack.push(Script.N(Script.toLong(left) & Script.toLong(right))); break;
 479
 480                 case SUB: stack.push(Script.N(Script.toDouble(left) - Script.toDouble(right))); break;
 481                 case MUL: stack.push(Script.N(Script.toDouble(left) * Script.toDouble(right))); break;
 482                 case DIV: stack.push(Script.N(Script.toDouble(left) / Script.toDouble(right))); break;
 483                 case MOD: stack.push(Script.N(Script.toDouble(left) % Script.toDouble(right))); break;
 484
 485                 case LSH: stack.push(Script.N(Script.toLong(left) << Script.toLong(right))); break;
 486                 case RSH: stack.push(Script.N(Script.toLong(left) >> Script.toLong(right))); break;
 487                 case URSH: stack.push(Script.N(Script.toLong(left) >>> Script.toLong(right))); break;
 488
 489                 //#repeat </<=/>/>= LT/LE/GT/GE
 490                 case LT: {
 491                     if(left instanceof JSString && right instanceof JSString)
 492                         stack.push(Script.B(Script.toString(left).compareTo(Script.toString(right)) < 0));
 493                     else
 494                         stack.push(Script.B(Script.toDouble(left) < Script.toDouble(right)));
 495                 }
 496                 //#end
 497
 498                 case EQ:
 499                 case NE: {
 500                     boolean ret;
 501                     if(left == null && right == null) ret = true;
 502                     else if(left == null || right == null) ret = false;
 503                     else ret = left.equals(right);
 504                     stack.push(Script.B(op == EQ ? ret : !ret)); break;
 505                 }
 506
 507                 default: throw new Error("unknown opcode " + op);
 508                 } }
 509             }
 510
 511         } catch(JSExn e) {
 512             catchException(e);
 513             pc--; // it'll get incremented on the next iteration
 514         } // end try/catch
 515         } // end for
 516     }
 517
 518     /** tries to find a handler withing the call chain for this exception
 519         if a handler is found the interpreter is setup to call the exception handler
 520         if a handler is not found the exception is thrown
 521     */
 522     void catchException(JSExn e) throws JSExn {
 523         while(!stack.empty()) {
 524             Object o = stack.pop();
 525             if (o instanceof CatchMarker || o instanceof TryMarker) {
 526                 boolean inCatch = o instanceof CatchMarker;
 527                 if(inCatch) {
 528                     o = (JS)stack.pop();
 529                     if(((TryMarker)o).finallyLoc < 0) continue; // no finally block, keep going
 530                 }
 531                 if(!inCatch && ((TryMarker)o).catchLoc >= 0) {
 532                     // run the catch block, this will implicitly run the finally block, if it exists
 533                     stack.push(o);
 534                     stack.push(catchMarker);
 535                     stack.push(e.getObject());
 536                     f = ((TryMarker)o).f;
 537                     scope = ((TryMarker)o).scope;
 538                     pc = ((TryMarker)o).catchLoc;
 539                     return;
 540                 } else {
 541                     stack.push(new FinallyData(e));
 542                     f = ((TryMarker)o).f;
 543                     scope = ((TryMarker)o).scope;
 544                     pc = ((TryMarker)o).finallyLoc;
 545                     return;
 546                 }
 547             }
 548         }
 549         throw e;
 550     }
 551
 552     void setupTrap(JS.Trap t, JS val, CallMarker cm) throws JSExn {
 553         stack.push(cm);
 554         stack.push(new TrapArgs(t, val));
 555         f = (JSFunction)t.function(); // FIXME
 556         scope = f.parentScope;
 557         pc = 0;
 558     }
 559
 560
 561     // Markers //////////////////////////////////////////////////////////////////////
 562
 563     static class Marker {}
 564
 565     static class CallMarker extends Marker {
 566         final int pc;
 567         final JSScope scope;
 568         final JSFunction f;
 569         public CallMarker(Interpreter cx) {
 570             pc = cx == null ? -1 : cx.pc + 1;
 571             scope = cx == null ? null : cx.scope;
 572             f = cx == null ? null : cx.f;
 573         }
 574     }
 575
 576     static class TrapMarker extends CallMarker {
 577         JS.Trap t;
 578         JS val;
 579         boolean cascadeHappened;
 580         final boolean pauseOnPut;
 581         public TrapMarker(Interpreter cx, JS.Trap t, JS val) { this(cx,t,val,false); }
 582         public TrapMarker(Interpreter cx, JS.Trap t, JS val, boolean pauseOnPut) {
 583             super(cx);
 584             this.t = t;
 585             this.val = val;
 586             this.pauseOnPut = pauseOnPut;
 587         }
 588     }
 589
 590     static class CatchMarker extends Marker { }
 591     private static final CatchMarker catchMarker = new CatchMarker();
 592
 593     static class LoopMarker extends Marker {
 594         final public int location;
 595         final public String label;
 596         final public JSScope scope;
 597         public LoopMarker(int location, String label, JSScope scope) {
 598             this.location = location;
 599             this.label = label;
 600             this.scope = scope;
 601         }
 602     }
 603     static class TryMarker extends Marker {
 604         final public int catchLoc;
 605         final public int finallyLoc;
 606         final public JSScope scope;
 607         final public JSFunction f;
 608         public TryMarker(int catchLoc, int finallyLoc, Interpreter cx) {
 609             this.catchLoc = catchLoc;
 610             this.finallyLoc = finallyLoc;
 611             this.scope = cx.scope;
 612             this.f = cx.f;
 613         }
 614     }
 615     static class FinallyData extends Marker {
 616         final public int op;
 617         final public Object arg;
 618         final public JSExn exn;
 619         public FinallyData(int op) { this(op,null); }
 620         public FinallyData(int op, Object arg) { this.op = op; this.arg = arg; this.exn = null; }
 621         public FinallyData(JSExn exn) { this.exn = exn; this.op = -1; this.arg = null; } // Just throw this exn
 622     }
 623
 624     static class TrapArgs extends JS.Immutable {
 625         private Trap t;
 626         private JS val;
 627         public TrapArgs(Trap t, JS val) { this.t = t; this.val = val; }
 628         public JS get(JS key) throws JSExn {
 629             if(Script.isInt(key) && Script.toInt(key) == 0) return val;
 630             //#switch(Script.str(key))
 631             case "trapee": return t.target();
 632             case "callee": return t.function();
 633             case "trapname": return t.key();
 634             case "length": return t.isWriteTrap() ? Script.ONE : Script.ZERO;
 635             //#end
 636             return super.get(key);
 637         }
 638     }
 639
 640     static class Stub extends JS.Immutable {
 641         private JS method;
 642         JS obj;
 643         public Stub(JS obj, JS method) { this.obj = obj; this.method = method; }
 644         public JS call(JS[] args) throws JSExn { return obj.call(method, args); }
 645     }
 646
 647     static final class Stack {
 648         private static final int MAX_STACK_SIZE = 512;
 649         private Object[] stack = new Object[8];
 650         private int sp = 0;
 651
 652         boolean empty() { return sp == 0; }
 653         void push(Object o) throws JSExn { if(sp == stack.length) grow(); stack[sp++] = o; }
 654         Object peek() { if(sp == 0) throw new RuntimeException("stack underflow"); return stack[sp-1]; }
 655         final Object pop() { if(sp == 0) throw new RuntimeException("stack underflow"); return stack[--sp]; }
 656         void swap() throws JSExn {
 657             if(sp < 2) throw new JSExn("stack overflow");
 658             Object tmp = stack[sp-2];
 659             stack[sp-2] = stack[sp-1];
 660             stack[sp-1] = tmp;
 661         }
 662         CallMarker findCall() {
 663             for(int i=sp-1;i>=0;i--) if(stack[i] instanceof CallMarker) return (CallMarker) stack[i];
 664             return null;
 665         }
 666         void grow() throws JSExn {
 667             if(stack.length >= MAX_STACK_SIZE) throw new JSExn("stack overflow");
 668             Object[] stack2 = new Object[stack.length * 2];
 669             System.arraycopy(stack,0,stack2,0,stack.length);
 670             stack = stack2;
 671         }
 672
 673         void backtrace(JSExn e) {
 674             for(int i=sp-1;i>=0;i--) {
 675                 if (stack[i] instanceof CallMarker) {
 676                     CallMarker cm = (CallMarker)stack[i];
 677                     if(cm.f == null) break;
 678                     String s = cm.f.sourceName + ":" + cm.f.line[cm.pc-1];
 679                     if(cm instanceof Interpreter.TrapMarker)
 680                         s += " (trap on " + Script.str(((Interpreter.TrapMarker)cm).t.key()) + ")";
 681                     e.addBacktrace(s);
 682                 }
 683             }
 684         }
 685     }
 686 }