src/org/ibex/js/Interpreter.java

   1 // Copyright 2004 Adam Megacz, see the COPYING file for licensing [GPL]
   2 package org.ibex.js;
   3
   4 import org.ibex.util.*;
   5 import java.util.*;
   6
   7 /** Encapsulates a single JS interpreter (ie call stack) */
   8 class Interpreter implements ByteCodes, Tokens {
   9     // Thread-Interpreter Mapping /////////////////////////////////////////////////////////////////////////
  10
  11     static Interpreter current() { return (Interpreter)threadToInterpreter.get(Thread.currentThread()); }
  12     private static Hashtable threadToInterpreter = new Hashtable();
  13
  14
  15     // Instance members and methods //////////////////////////////////////////////////////////////////////
  16
  17     int pausecount;               ///< the number of times pause() has been invoked; -1 indicates unpauseable
  18     JSFunction f = null;          ///< the currently-executing JSFunction
  19     JSScope scope;                ///< the current top-level scope (LIFO stack via NEWSCOPE/OLDSCOPE)
  20     final Stack stack = new Stack(); ///< the object stack
  21     int pc = 0;                   ///< the program counter
  22
  23     Interpreter(JSFunction f, boolean pauseable, JSArgs args) {
  24         this.f = f;
  25         this.pausecount = pauseable ? 0 : -1;
  26         this.scope = f.parentScope;
  27         try {
  28             stack.push(new CallMarker(null));    // the "root function returned" marker -- f==null
  29             stack.push(args);
  30         } catch(JSExn e) {
  31             throw new Error("should never happen");
  32         }
  33     }
  34
  35     Interpreter(Trap t, JS val, boolean pauseOnPut) {
  36         this.pausecount = -1;
  37         try {
  38             setupTrap(t,val,new TrapMarker(null,t,val,pauseOnPut));
  39         } catch(JSExn e) {
  40             throw new Error("should never happen");
  41         }
  42     }
  43
  44     /** this is the only synchronization point we need in order to be threadsafe */
  45     synchronized JS resume() throws JSExn {
  46         if(f == null) throw new RuntimeException("function already finished");
  47         if(scope == null) throw new RuntimeException("scope is null");
  48         Thread t = Thread.currentThread();
  49         Interpreter old = (Interpreter)threadToInterpreter.get(t);
  50         threadToInterpreter.put(t, this);
  51         try {
  52             return run();
  53         } finally {
  54             if (old == null) threadToInterpreter.remove(t);
  55             else threadToInterpreter.put(t, old);
  56         }
  57     }
  58
  59     static int getLine() {
  60         Interpreter c = Interpreter.current();
  61         return c == null || c.f == null || c.pc < 0 || c.pc >= c.f.size ? -1 : c.f.line[c.pc];
  62     }
  63
  64     static String getSourceName() {
  65         Interpreter c = Interpreter.current();
  66         return c == null || c.f == null ? null : c.f.sourceName;
  67     }
  68
  69     private static JSExn je(String s) { return new JSExn(getSourceName() + ":" + getLine() + " " + s); }
  70
  71     private JS run() throws JSExn {
  72
  73         // if pausecount changes after a get/put/call, we know we've been paused
  74         final int initialPauseCount = pausecount;
  75
  76         OUTER: for(;; pc++) {
  77         try {
  78             int op = f.op[pc];
  79             Object arg = f.arg[pc];
  80             if(op == FINALLY_DONE) {
  81                 FinallyData fd = (FinallyData) stack.pop();
  82                 if(fd == null) continue OUTER; // NOP
  83                 if(fd.exn != null) throw fd.exn;
  84                 op = fd.op;
  85                 arg = fd.arg;
  86             }
  87             switch(op) {
  88             case LITERAL: stack.push((JS)arg); break;
  89             case OBJECT: stack.push(new JS.O()); break;
  90             case ARRAY: stack.push(new JSArray(JS.toInt((JS)arg))); break;
  91             //case DECLARE: scope.declare((JS)(arg==null ? stack.peek() : arg)); if(arg != null) stack.push((JS)arg); break;
  92             case JT: if (JS.toBoolean(stack.pop())) pc += JS.toInt((JS)arg) - 1; break;
  93             case JF: if (!JS.toBoolean(stack.pop())) pc += JS.toInt((JS)arg) - 1; break;
  94             case JMP: pc += JS.toInt((JS)arg) - 1; break;
  95             case POP: stack.pop(); break;
  96             case SWAP: stack.swap(); break;
  97             case DUP: stack.push(stack.peek()); break;
  98             case NEWSCOPE: {
  99                 int n = JS.toInt((JS)arg);
 100                 scope = new JSScope(scope,(n>>>16)&0xffff,(n>>>0)&0xffff);
 101                 break;
 102             }
 103             case OLDSCOPE: scope = scope.parent; break;
 104             case GLOBALSCOPE: stack.push(scope.getGlobal()); break;
 105             case SCOPEGET: stack.push(scope.get((JS)arg)); break;
 106             case SCOPEPUT: scope.put((JS)arg,stack.peek()); break;
 107             case ASSERT: if (!JS.toBoolean(stack.pop())) throw je("ibex.assertion.failed"); break;
 108             case BITNOT: stack.push(JS.N(~JS.toLong(stack.pop()))); break;
 109             case BANG: stack.push(JS.B(!JS.toBoolean(stack.pop()))); break;
 110             case NEWFUNCTION: stack.push(((JSFunction)arg)._cloneWithNewParentScope(scope)); break;
 111             case LABEL: break;
 112
 113             case TYPEOF: {
 114                 Object o = stack.pop();
 115                 if (o == null) stack.push(null);
 116                 else if (o instanceof JSString) stack.push(JS.S("string"));
 117                 else if (o instanceof JSNumber.B) stack.push(JS.S("boolean"));
 118                 else if (o instanceof JSNumber) stack.push(JS.S("number"));
 119                 else stack.push(JS.S("object"));
 120                 break;
 121             }
 122
 123             case PUSHKEYS: {
 124                 JS o = stack.peek();
 125                 stack.push(o == null ? null : o.keys());
 126                 break;
 127             }
 128
 129             case LOOP:
 130                 stack.push(new LoopMarker(pc, pc > 0 && f.op[pc - 1] == LABEL ? (String)f.arg[pc - 1] : (String)null, scope));
 131                 stack.push(JS.T);
 132                 break;
 133
 134             case BREAK:
 135             case CONTINUE:
 136                 while(!stack.empty()) {
 137                     JS o = stack.pop();
 138                     if (o instanceof CallMarker) je("break or continue not within a loop");
 139                     if (o instanceof TryMarker) {
 140                         if(((TryMarker)o).finallyLoc < 0) continue; // no finally block, keep going
 141                         stack.push(new FinallyData(op, arg));
 142                         scope = ((TryMarker)o).scope;
 143                         pc = ((TryMarker)o).finallyLoc - 1;
 144                         continue OUTER;
 145                     }
 146                     if (o instanceof LoopMarker) {
 147                         if (arg == null || arg.equals(((LoopMarker)o).label)) {
 148                             int loopInstructionLocation = ((LoopMarker)o).location;
 149                             int endOfLoop = JS.toInt((JS)f.arg[loopInstructionLocation]) + loopInstructionLocation;
 150                             scope = ((LoopMarker)o).scope;
 151                             if (op == CONTINUE) { stack.push(o); stack.push(JS.F); }
 152                             pc = op == BREAK ? endOfLoop - 1 : loopInstructionLocation;
 153                             continue OUTER;
 154                         }
 155                     }
 156                 }
 157                 throw new Error("CONTINUE/BREAK invoked but couldn't find LoopMarker at " +
 158                                 getSourceName() + ":" + getLine());
 159
 160             case TRY: {
 161                 int[] jmps = (int[]) arg;
 162                 // jmps[0] is how far away the catch block is, jmps[1] is how far away the finally block is
 163                 // each can be < 0 if the specified block does not exist
 164                 stack.push(new TryMarker(jmps[0] < 0 ? -1 : pc + jmps[0], jmps[1] < 0 ? -1 : pc + jmps[1], this));
 165                 break;
 166             }
 167
 168             case RETURN: {
 169                 JS retval = stack.pop();
 170                 while(!stack.empty()) {
 171                     Object o = stack.pop();
 172                     if (o instanceof TryMarker) {
 173                         if(((TryMarker)o).finallyLoc < 0) continue;
 174                         stack.push(retval);
 175                         stack.push(new FinallyData(RETURN));
 176                         scope = ((TryMarker)o).scope;
 177                         pc = ((TryMarker)o).finallyLoc - 1;
 178                         continue OUTER;
 179                     } else if (o instanceof CallMarker) {
 180                         boolean didTrapPut = false;
 181                         if (o instanceof TrapMarker) { // handles return component of a write trap
 182                             TrapMarker tm = (TrapMarker) o;
 183                             boolean cascade = tm.t.isWriteTrap() && !tm.cascadeHappened && !JS.toBoolean(retval);
 184                             if(cascade) {
 185                                 Trap t = tm.t.nextWriteTrap();
 186                                 if(t == null && tm.t.target instanceof JS.Clone) {
 187                                     t = ((JS.Clone)tm.t.target).clonee.getTrap(tm.t.key);
 188                                     if(t != null) t = t.writeTrap();
 189                                 }
 190                                 if(t != null) {
 191                                     tm.t = t; // we reuse the old trap marker
 192                                     setupTrap(t,tm.val,tm);
 193                                     pc--; // we increment it on the next iter
 194                                     continue OUTER;
 195                                 } else {
 196                                     didTrapPut = true;
 197                                     if(!tm.pauseOnPut) tm.t.target.put(tm.t.key,tm.val);
 198                                 }
 199                             }
 200                         }
 201                         CallMarker cm = (CallMarker) o;
 202                         scope = cm.scope;
 203                         pc = cm.pc - 1;
 204                         f = cm.f;
 205                         if (didTrapPut) {
 206                             if (((TrapMarker)cm).pauseOnPut) { pc++; return ((TrapMarker)cm).val; }
 207                             if (pausecount > initialPauseCount) { pc++; return null; }   // we were paused
 208                         } else {
 209                             stack.push(retval);
 210                         }
 211                         if (f == null) return retval;
 212                         continue OUTER;
 213                     }
 214                 }
 215                 throw new Error("error: RETURN invoked but couldn't find a CallMarker!");
 216             }
 217
 218             case CASCADE: {
 219                 boolean write = JS.toBoolean((JS)arg);
 220                 JS val = write ? stack.pop() : null;
 221                 CallMarker o = stack.findCall();
 222                 if(!(o instanceof TrapMarker)) throw new JSExn("tried to CASCADE while not in a trap");
 223                 TrapMarker tm = (TrapMarker) o;
 224                 JS key = tm.t.key;
 225                 JS target = tm.t.target;
 226                 if(tm.t.isWriteTrap() != write) throw new JSExn("tried to do a " + (write?"write":"read") + " cascade in a " + (write?"read":"write") + " trap");
 227                 Trap t = write ? tm.t.nextWriteTrap() : tm.t.nextReadTrap();
 228                 // FIXME: Doesn't handle multiple levels of clone's (probably can just make this a while loop)
 229                 if(t == null && target instanceof JS.Clone) {
 230                     target = ((JS.Clone)target).clonee;
 231                     t = target.getTrap(key);
 232                     if(t != null) t = write ? t.writeTrap() : t.readTrap();
 233                 }
 234                 if(write) {
 235                     tm.cascadeHappened = true;
 236                     stack.push(val);
 237                 }
 238                 if(t != null) {
 239                     setupTrap(t,val,new TrapMarker(this,t,val,tm.pauseOnPut));
 240                     pc--; // we increment later
 241                 } else {
 242                     if(write) {
 243                         if (tm.pauseOnPut) { pc++; return val; }
 244                         target.put(key,val);
 245                     } else {
 246                         JS ret = target.get(key);
 247                         if (ret == JS.METHOD) ret = new Stub(target, key);
 248                         stack.push(ret);
 249                     }
 250                     if (pausecount > initialPauseCount) { pc++; return null; }   // we were paused
 251                 }
 252                 break;
 253             }
 254
 255             case PUT: {
 256                 JS val = stack.pop();
 257                 JS key = stack.pop();
 258                 JS target = stack.peek();
 259                 if (target == null) throw je("tried to put " + JS.debugToString(val) + " to the " + JS.debugToString(key) + " property on the null value");
 260                 if (key == null) throw je("tried to assign \"" + JS.debugToString(val) + "\" to the null key");
 261
 262                 Trap t = target.getTrap(key);
 263                 if(t != null) t = t.writeTrap();
 264
 265                 if(t == null && target instanceof JS.Clone) {
 266                     target = ((JS.Clone)target).clonee;
 267                     t = target.getTrap(key);
 268                     if(t != null) t = t.writeTrap();
 269                 }
 270
 271                 stack.push(val);
 272
 273                 if(t != null) {
 274                     setupTrap(t,val,new TrapMarker(this,t,val));
 275                     pc--; // we increment later
 276                 } else {
 277                     target.put(key,val);
 278                     if (pausecount > initialPauseCount) { pc++; return null; }   // we were paused
 279                 }
 280                 break;
 281             }
 282
 283             case GET:
 284             case GET_PRESERVE: {
 285                 JS target, key;
 286                 if (op == GET) {
 287                     key = arg == null ? stack.pop() : (JS)arg;
 288                     target = stack.pop();
 289                 } else {
 290                     key = stack.pop();
 291                     target = stack.peek();
 292                     stack.push(key);
 293                 }
 294                 JS ret = null;
 295                 if (key == null) throw je("tried to get the null key from " + JS.debugToString(target));
 296                 if (target == null) throw je("tried to get property \"" + JS.debugToString(key) + "\" from the null object");
 297
 298                 Trap t = target.getTrap(key);
 299                 if(t != null) t = t.readTrap();
 300
 301                 if(t == null && target instanceof JS.Clone) {
 302                     target = ((JS.Clone)target).clonee;
 303                     t = target.getTrap(key);
 304                     if(t != null) t = t.readTrap();
 305                 }
 306
 307                 if(t != null) {
 308                     setupTrap(t,null,new TrapMarker(this,t,null));
 309                     pc--; // we increment later
 310                 } else {
 311                     ret = target.get(key);
 312                     if (pausecount > initialPauseCount) { pc++; return null; }   // we were paused
 313                     if (ret == JS.METHOD) ret = new Stub(target, key);
 314                     stack.push(ret);
 315                 }
 316                 break;
 317             }
 318
 319             case CALL: case CALLMETHOD: {
 320                 int numArgs = JS.toInt((JS)arg);
 321
 322                 JS[] rest = numArgs > 3 ? new JS[numArgs - 3] : null;
 323                 for(int i=numArgs - 1; i>2; i--) rest[i-3] = stack.pop();
 324                 JS a2 = numArgs <= 2 ? null : stack.pop();
 325                 JS a1 = numArgs <= 1 ? null : stack.pop();
 326                 JS a0 = numArgs <= 0 ? null : stack.pop();
 327
 328                 JS method = null;
 329                 JS ret = null;
 330                 JS object = stack.pop();
 331
 332                 if (op == CALLMETHOD) {
 333                     if (object == JS.METHOD) {
 334                         method = stack.pop();
 335                         object = stack.pop();
 336                     } else if (object == null) {
 337                         method = stack.pop();
 338                         object = stack.pop();
 339                         throw new JSExn("function '"+JS.debugToString(method)+"' not found in " + object.getClass().getName());
 340                     } else {
 341                         stack.pop();
 342                         stack.pop();
 343                     }
 344                 }
 345
 346                 if (object instanceof JSFunction) {
 347                     stack.push(new CallMarker(this));
 348                     stack.push(new JSArgs(a0,a1,a2,rest,numArgs,object));
 349                     f = (JSFunction)object;
 350                     scope = f.parentScope;
 351                     pc = -1;
 352                     break;
 353                 } else {
 354                     JS c = (JS)object;
 355                     ret = method == null ? c.call(a0, a1, a2, rest, numArgs) : c.callMethod(method, a0, a1, a2, rest, numArgs);
 356                 }
 357
 358                 if (pausecount > initialPauseCount) { pc++; return null; }
 359                 stack.push(ret);
 360                 break;
 361             }
 362
 363             case THROW:
 364                 throw new JSExn(stack.pop(), this);
 365
 366                 /* FIXME GRAMMAR
 367             case MAKE_GRAMMAR: {
 368                 final Grammar r = (Grammar)arg;
 369                 final JSScope final_scope = scope;
 370                 Grammar r2 = new Grammar() {
 371                         public int match(String s, int start, Hash v, JSScope scope) throws JSExn {
 372                             return r.match(s, start, v, final_scope);
 373                         }
 374                         public int matchAndWrite(String s, int start, Hash v, JSScope scope, String key) throws JSExn {
 375                             return r.matchAndWrite(s, start, v, final_scope, key);
 376                         }
 377                         public Object call(Object a0, Object a1, Object a2, Object[] rest, int nargs) throws JSExn {
 378                             Hash v = new Hash();
 379                             r.matchAndWrite((String)a0, 0, v, final_scope, "foo");
 380                             return v.get("foo");
 381                         }
 382                     };
 383                 Object obj = stack.pop();
 384                 if (obj != null && obj instanceof Grammar) r2 = new Grammar.Alternative((Grammar)obj, r2);
 385                 stack.push(r2);
 386                 break;
 387             }
 388                 */
 389             case ADD_TRAP: case DEL_TRAP: {
 390                 JS val = stack.pop();
 391                 JS key = stack.pop();
 392                 JS js = stack.peek();
 393                 // A trap addition/removal
 394                 if(!(val instanceof JSFunction)) throw new JSExn("tried to add/remove a non-function trap");
 395                 if(op == ADD_TRAP) js.addTrap(key, (JSFunction)val);
 396                 else js.delTrap(key, (JSFunction)val);
 397                 break;
 398             }
 399
 400             case ADD: {
 401                 int count = ((JSNumber)arg).toInt();
 402                 if(count < 2) throw new Error("this should never happen");
 403                 if(count == 2) {
 404                     // common case
 405                     JS right = stack.pop();
 406                     JS left = stack.pop();
 407                     JS ret;
 408                     if(left instanceof JSString || right instanceof JSString)
 409                         ret = JS.S(JS.toString(left).concat(JS.toString(right)));
 410                     else if(left instanceof JSNumber.D || right instanceof JSNumber.D)
 411                         ret = JS.N(JS.toDouble(left) + JS.toDouble(right));
 412                     else {
 413                         long l = JS.toLong(left) + JS.toLong(right);
 414                         if(l < Integer.MIN_VALUE || l > Integer.MAX_VALUE) ret = JS.N(l);
 415                         ret = JS.N((int)l);
 416                     }
 417                     stack.push(ret);
 418                 } else {
 419                     JS[] args = new JS[count];
 420                     while(--count >= 0) args[count] = stack.pop();
 421                     if(args[0] instanceof JSString) {
 422                         StringBuffer sb = new StringBuffer(64);
 423                         for(int i=0;i<args.length;i++) sb.append(JS.toString(args[i]));
 424                         stack.push(JS.S(sb.toString()));
 425                     } else {
 426                         int numStrings = 0;
 427                         for(int i=0;i<args.length;i++) if(args[i] instanceof JSString) numStrings++;
 428                         if(numStrings == 0) {
 429                             double d = 0.0;
 430                             for(int i=0;i<args.length;i++) d += JS.toDouble(args[i]);
 431                             stack.push(JS.N(d));
 432                         } else {
 433                             int i=0;
 434                             StringBuffer sb = new StringBuffer(64);
 435                             if(!(args[0] instanceof JSString || args[1] instanceof JSString)) {
 436                                 double d=0.0;
 437                                 do {
 438                                     d += JS.toDouble(args[i++]);
 439                                 } while(!(args[i] instanceof JSString));
 440                                 sb.append(JS.toString(JS.N(d)));
 441                             }
 442                             while(i < args.length) sb.append(JS.toString(args[i++]));
 443                             stack.push(JS.S(sb.toString()));
 444                         }
 445                     }
 446                 }
 447                 break;
 448             }
 449
 450             default: {
 451                 JS right = stack.pop();
 452                 JS left = stack.pop();
 453                 switch(op) {
 454
 455                 case BITOR: stack.push(JS.N(JS.toLong(left) | JS.toLong(right))); break;
 456                 case BITXOR: stack.push(JS.N(JS.toLong(left) ^ JS.toLong(right))); break;
 457                 case BITAND: stack.push(JS.N(JS.toLong(left) & JS.toLong(right))); break;
 458
 459                 case SUB: stack.push(JS.N(JS.toDouble(left) - JS.toDouble(right))); break;
 460                 case MUL: stack.push(JS.N(JS.toDouble(left) * JS.toDouble(right))); break;
 461                 case DIV: stack.push(JS.N(JS.toDouble(left) / JS.toDouble(right))); break;
 462                 case MOD: stack.push(JS.N(JS.toDouble(left) % JS.toDouble(right))); break;
 463
 464                 case LSH: stack.push(JS.N(JS.toLong(left) << JS.toLong(right))); break;
 465                 case RSH: stack.push(JS.N(JS.toLong(left) >> JS.toLong(right))); break;
 466                 case URSH: stack.push(JS.N(JS.toLong(left) >>> JS.toLong(right))); break;
 467
 468                 //#repeat </<=/>/>= LT/LE/GT/GE
 469                 case LT: {
 470                     if(left instanceof JSString && right instanceof JSString)
 471                         stack.push(JS.B(JS.toString(left).compareTo(JS.toString(right)) < 0));
 472                     else
 473                         stack.push(JS.B(JS.toDouble(left) < JS.toDouble(right)));
 474                 }
 475                 //#end
 476
 477                 case EQ:
 478                 case NE: {
 479                     boolean ret;
 480                     if(left == null && right == null) ret = true;
 481                     else if(left == null || right == null) ret = false;
 482                     else ret = left.jsequals(right);
 483                     stack.push(JS.B(op == EQ ? ret : !ret)); break;
 484                 }
 485
 486                 default: throw new Error("unknown opcode " + op);
 487                 } }
 488             }
 489
 490         } catch(JSExn e) {
 491             catchException(e);
 492             pc--; // it'll get incremented on the next iteration
 493         } // end try/catch
 494         } // end for
 495     }
 496
 497     /** tries to find a handler withing the call chain for this exception
 498         if a handler is found the interpreter is setup to call the exception handler
 499         if a handler is not found the exception is thrown
 500     */
 501     void catchException(JSExn e) throws JSExn {
 502         while(!stack.empty()) {
 503             JS o = stack.pop();
 504             if (o instanceof CatchMarker || o instanceof TryMarker) {
 505                 boolean inCatch = o instanceof CatchMarker;
 506                 if(inCatch) {
 507                     o = stack.pop();
 508                     if(((TryMarker)o).finallyLoc < 0) continue; // no finally block, keep going
 509                 }
 510                 if(!inCatch && ((TryMarker)o).catchLoc >= 0) {
 511                     // run the catch block, this will implicitly run the finally block, if it exists
 512                     stack.push(o);
 513                     stack.push(catchMarker);
 514                     stack.push(e.getObject());
 515                     f = ((TryMarker)o).f;
 516                     scope = ((TryMarker)o).scope;
 517                     pc = ((TryMarker)o).catchLoc;
 518                     return;
 519                 } else {
 520                     stack.push(new FinallyData(e));
 521                     f = ((TryMarker)o).f;
 522                     scope = ((TryMarker)o).scope;
 523                     pc = ((TryMarker)o).finallyLoc;
 524                     return;
 525                 }
 526             }
 527         }
 528         throw e;
 529     }
 530
 531     void setupTrap(Trap t, JS val, CallMarker cm) throws JSExn {
 532         stack.push(cm);
 533         stack.push(new TrapArgs(t,val));
 534         f = t.f;
 535         scope = f.parentScope;
 536         pc = 0;
 537     }
 538
 539
 540     // Markers //////////////////////////////////////////////////////////////////////
 541
 542     static class Marker extends JS {
 543         public JS get(JS key) throws JSExn { throw new Error("this should not be accessible from a script"); }
 544         public void put(JS key, JS val) throws JSExn { throw new Error("this should not be accessible from a script"); }
 545         public String coerceToString() { throw new Error("this should not be accessible from a script"); }
 546         public JS call(JS a0, JS a1, JS a2, JS[] rest, int nargs) throws JSExn { throw new Error("this should not be accessible from a script"); }
 547     }
 548
 549     static class CallMarker extends Marker {
 550         final int pc;
 551         final JSScope scope;
 552         final JSFunction f;
 553         public CallMarker(Interpreter cx) {
 554             pc = cx == null ? -1 : cx.pc + 1;
 555             scope = cx == null ? null : cx.scope;
 556             f = cx == null ? null : cx.f;
 557         }
 558     }
 559
 560     static class TrapMarker extends CallMarker {
 561         Trap t;
 562         JS val;
 563         boolean cascadeHappened;
 564         final boolean pauseOnPut;
 565         public TrapMarker(Interpreter cx, Trap t, JS val) { this(cx,t,val,false); }
 566         public TrapMarker(Interpreter cx, Trap t, JS val, boolean pauseOnPut) {
 567             super(cx);
 568             this.t = t;
 569             this.val = val;
 570             this.pauseOnPut = pauseOnPut;
 571         }
 572     }
 573
 574     static class CatchMarker extends Marker { }
 575     private static CatchMarker catchMarker = new CatchMarker();
 576
 577     static class LoopMarker extends Marker {
 578         final public int location;
 579         final public String label;
 580         final public JSScope scope;
 581         public LoopMarker(int location, String label, JSScope scope) {
 582             this.location = location;
 583             this.label = label;
 584             this.scope = scope;
 585         }
 586     }
 587     static class TryMarker extends Marker {
 588         final public int catchLoc;
 589         final public int finallyLoc;
 590         final public JSScope scope;
 591         final public JSFunction f;
 592         public TryMarker(int catchLoc, int finallyLoc, Interpreter cx) {
 593             this.catchLoc = catchLoc;
 594             this.finallyLoc = finallyLoc;
 595             this.scope = cx.scope;
 596             this.f = cx.f;
 597         }
 598     }
 599     static class FinallyData extends Marker {
 600         final public int op;
 601         final public Object arg;
 602         final public JSExn exn;
 603         public FinallyData(int op) { this(op,null); }
 604         public FinallyData(int op, Object arg) { this.op = op; this.arg = arg; this.exn = null; }
 605         public FinallyData(JSExn exn) { this.exn = exn; this.op = -1; this.arg = null; } // Just throw this exn
 606     }
 607
 608     static class TrapArgs extends JS {
 609         private Trap t;
 610         private JS val;
 611         public TrapArgs(Trap t, JS val) { this.t = t; this.val = val; }
 612         public JS get(JS key) throws JSExn {
 613             if(JS.isInt(key) && JS.toInt(key) == 0) return val;
 614             //#jswitch(key)
 615             case "trapee": return t.target;
 616             case "callee": return t.f;
 617             case "trapname": return t.key;
 618             case "length": return t.isWriteTrap() ? ONE : ZERO;
 619             //#end
 620             return super.get(key);
 621         }
 622     }
 623
 624     static class JSArgs extends JS {
 625         private final JS a0;
 626         private final JS a1;
 627         private final JS a2;
 628         private final JS[] rest;
 629         private final int nargs;
 630         private final JS callee;
 631
 632         public JSArgs(JS callee) { this(null,null,null,null,0,callee); }
 633         public JSArgs(JS a0, JS callee) { this(a0,null,null,null,1,callee); }
 634         public JSArgs(JS a0, JS a1, JS a2, JS[] rest, int nargs, JS callee) {
 635             this.a0 = a0; this.a1 = a1; this.a2 = a2;
 636             this.rest = rest; this.nargs = nargs;
 637             this.callee = callee;
 638         }
 639
 640         public JS get(JS key) throws JSExn {
 641             if(JS.isInt(key)) {
 642                 int n = JS.toInt(key);
 643                 switch(n) {
 644                     case 0: return a0;
 645                     case 1: return a1;
 646                     case 2: return a2;
 647                     default: return n>= 0 && n < nargs ? rest[n-3] : null;
 648                 }
 649             }
 650             //#jswitch(key)
 651             case "callee": return callee;
 652             case "length": return JS.N(nargs);
 653             //#end
 654             return super.get(key);
 655         }
 656     }
 657
 658     static class Stub extends JS {
 659         private JS method;
 660         JS obj;
 661         public Stub(JS obj, JS method) { this.obj = obj; this.method = method; }
 662         public JS call(JS a0, JS a1, JS a2, JS[] rest, int nargs) throws JSExn {
 663             return ((JS)obj).callMethod(method, a0, a1, a2, rest, nargs);
 664         }
 665     }
 666
 667     static class Stack {
 668         private static final int MAX_STACK_SIZE = 512;
 669         private JS[] stack = new JS[64];
 670         private int sp = 0;
 671
 672         boolean empty() { return sp == 0; }
 673         void push(JS o) throws JSExn { if(sp == stack.length) grow(); stack[sp++] = o; }
 674         JS peek() { if(sp == 0) throw new RuntimeException("Stack underflow"); return stack[sp-1]; }
 675         final JS pop() { if(sp == 0) throw new RuntimeException("Stack underflow"); return stack[--sp]; }
 676         void swap() throws JSExn {
 677             if(sp < 2) throw new JSExn("stack overflow");
 678             JS tmp = stack[sp-2];
 679             stack[sp-2] = stack[sp-1];
 680             stack[sp-1] = tmp;
 681         }
 682         CallMarker findCall() {
 683             for(int i=sp-1;i>=0;i--) if(stack[i] instanceof CallMarker) return (CallMarker) stack[i];
 684             return null;
 685         }
 686         void grow() throws JSExn {
 687             if(stack.length >= MAX_STACK_SIZE) throw new JSExn("Stack overflow");
 688             JS[] stack2 = new JS[stack.length * 2];
 689             System.arraycopy(stack,0,stack2,0,stack.length);
 690         }
 691
 692         void backtrace(JSExn e) {
 693             for(int i=sp-1;i>=0;i--) {
 694                 if (stack[i] instanceof CallMarker) {
 695                     CallMarker cm = (CallMarker)stack[i];
 696                     if(cm.f == null) break;
 697                     String s = cm.f.sourceName + ":" + cm.f.line[cm.pc-1];
 698                     if(cm instanceof Interpreter.TrapMarker)
 699                         s += " (trap on " + JS.debugToString(((Interpreter.TrapMarker)cm).t.key) + ")";
 700                     e.addBacktrace(s);
 701                 }
 702             }
 703         }
 704     }
 705 }