2003/07/06 13:42:15
[org.ibex.core.git] / src / org / xwt / js / CompiledFunctionImpl.java
index ae92d06..e8fa95f 100644 (file)
@@ -4,8 +4,9 @@ package org.xwt.js;
 import org.xwt.util.*;
 import java.io.*;
 
+// FIXME: could use some cleaning up
 /** a JavaScript function, compiled into bytecode */
-public class CompiledFunctionImpl extends JS.Callable implements ByteCodes, Tokens {
+class CompiledFunctionImpl extends JSCallable implements ByteCodes, Tokens {
 
     // Fields and Accessors ///////////////////////////////////////////////
 
@@ -13,13 +14,12 @@ public class CompiledFunctionImpl extends JS.Callable implements ByteCodes, Toke
     private String sourceName;
     public String getSourceName() throws JS.Exn { return sourceName; }
     
-    /** the first line of this function */
-    private int firstLine;
-    public int getFirstLine() throws JS.Exn { return firstLine; }
-       
     /** the line numbers */
     private int[] line = new int[10];
 
+    /** the first line of this script */
+    private int firstLine = -1;
+
     /** the instructions */
     private int[] op = new int[10];
 
@@ -33,52 +33,48 @@ public class CompiledFunctionImpl extends JS.Callable implements ByteCodes, Toke
     /** the scope in which this function was declared; by default this function is called in a fresh subscope of the parentScope */
     private JS.Scope parentScope;
 
-
     // Constructors ////////////////////////////////////////////////////////
 
     private CompiledFunctionImpl cloneWithNewParentScope(JS.Scope s) throws IOException {
-       CompiledFunctionImpl ret = new JS.CompiledFunction(sourceName, firstLine, null, s);
-       ret.paste(this);
-       return ret;
+        CompiledFunctionImpl ret = new JS.CompiledFunction(sourceName, firstLine, null, s);
+        ret.paste(this);
+        return ret;
     }
 
     protected CompiledFunctionImpl(String sourceName, int firstLine, Reader sourceCode, JS.Scope parentScope) throws IOException {
-       this.sourceName = sourceName;
-       this.firstLine = firstLine;
-       this.parentScope = parentScope;
-       if (sourceCode == null) return;
-       Parser p = new Parser(sourceCode, sourceName, firstLine);
-       try {
-           while(true) {
-               int s = size();
-               p.parseStatement(this, null);
-               if (s == size()) break;
-           }
-           add(-1, Tokens.RETURN);
-       } catch (Exception e) {
-           if (Log.on) Log.log(Parser.class, e);
-       }
+        this.sourceName = sourceName;
+        this.firstLine = firstLine;
+        this.parentScope = parentScope;
+        if (sourceCode == null) return;
+        Parser p = new Parser(sourceCode, sourceName, firstLine);
+        while(true) {
+            int s = size();
+            p.parseStatement(this, null);
+            if (s == size()) break;
+        }
+        add(-1, LITERAL, null); 
+        add(-1, RETURN);
     }
     
     public Object call(JS.Array args) throws JS.Exn { return call(args, new FunctionScope(sourceName, parentScope)); }
     public Object call(JS.Array args, JS.Scope scope) throws JS.Exn {
-       CompiledFunctionImpl saved = (CompiledFunctionImpl)Context.currentFunction.get(Thread.currentThread());
-       try {
-           Context.currentFunction.put(Thread.currentThread(), this);
-           Context cx = Context.getContextForThread(Thread.currentThread());
-           int size = cx.stack.size();
-           cx.stack.push(new Context.CallMarker());
-           cx.stack.push(args);
-           eval(scope);
-           Object ret = cx.stack.pop();
-           if (cx.stack.size() > size)
-               Log.log(this, "warning, stack grew by " + (cx.stack.size() - size) +
-                       " elements during call to " + Context.getCurrentSourceNameAndLine());
-           return ret;
-       } finally {
-           if (saved == null) Context.currentFunction.remove(Thread.currentThread());
-           else Context.currentFunction.put(Thread.currentThread(), saved);
-       }
+        JS.Thread cx = JS.Thread.fromJavaThread(java.lang.Thread.currentThread());
+        CompiledFunction saved = cx.currentCompiledFunction;
+        try {
+            cx.currentCompiledFunction = (CompiledFunction)this;
+            int size = cx.stack.size();
+            cx.stack.push(new CallMarker());
+            cx.stack.push(args);
+            eval(scope);
+            Object ret = cx.stack.pop();
+            // FIXME: if we catch an exception in Java, JS won't notice and the stack will be messed up
+            if (cx.stack.size() > size)
+                // this should never happen
+                throw new Error("ERROR: stack grew by " + (cx.stack.size() - size) + " elements during call");
+            return ret;
+        } finally {
+            cx.currentCompiledFunction = saved;
+        }
     }
 
 
@@ -95,22 +91,38 @@ public class CompiledFunctionImpl extends JS.Callable implements ByteCodes, Toke
             Object[] arg2 = new Object[op.length * 2]; System.arraycopy(arg, 0, arg2, 0, arg.length); arg = arg2;
             int[] op2 = new int[op.length * 2]; System.arraycopy(op, 0, op2, 0, op.length); op = op2;
         }
-       this.line[size] = line;
+        this.line[size] = line;
         op[size] = op_;
         arg[size] = arg_;
         size++;
         return this;
     }
+    
+    public int getLine(int pc) {
+        if(pc < 0 || pc >= size) return -1;
+        return line[pc];
+    }
 
 
     // Invoking the Bytecode ///////////////////////////////////////////////////////
         
-    int pc = 0;
     void eval(JS.Scope s) {
-       final Vec t = Context.getContextForThread(Thread.currentThread()).stack;
+        final JS.Thread cx = JS.Thread.fromJavaThread(java.lang.Thread.currentThread());
+        final Vec t = cx.stack;
+        int pc;
+        int lastPC = -1;
         OUTER: for(pc=0; pc<size; pc++) {
-           String label = null;
-           switch(op[pc]) {
+            String label = null;
+            cx.pc = lastPC = pc;
+            int curOP = op[pc];
+            Object curArg = arg[pc];
+            if(curOP == FINALLY_DONE) {
+                FinallyData fd = (FinallyData) t.pop();
+                if(fd == null) continue OUTER; // NOP
+                curOP = fd.op;
+                curArg = fd.arg;
+            }
+            switch(curOP) {
             case LITERAL: t.push(arg[pc]); break;
             case OBJECT: t.push(new JS.Obj()); break;
             case ARRAY: t.push(new JS.Array(JS.toNumber(arg[pc]).intValue())); break;
@@ -122,32 +134,31 @@ public class CompiledFunctionImpl extends JS.Callable implements ByteCodes, Toke
             case POP: t.pop(); break;
             case SWAP: { Object o1 = t.pop(); Object o2 = t.pop(); t.push(o1); t.push(o2); break; }
             case DUP: t.push(t.peek()); break;
-            case NEWSCOPE: /*s = new JS.Scope(s);*/ break;
-           case OLDSCOPE: /*s = s.getParentScope();*/ break;
+            case NEWSCOPE: s = new JS.Scope(s); break;
+            case OLDSCOPE: s = s.getParentScope(); break;
             case ASSERT: if (!JS.toBoolean(t.pop())) throw je("assertion failed"); break;
             case BITNOT: t.push(new Long(~JS.toLong(t.pop()))); break;
             case BANG: t.push(new Boolean(!JS.toBoolean(t.pop()))); break;
 
             case TYPEOF: {
-               Object o = t.pop();
-               if (o == null) t.push(null);
-               else if (o instanceof org.xwt.Box) t.push("Box");
-               else if (o instanceof JS) t.push("Object");
-               else if (o instanceof String) t.push("String");
-               else if (o instanceof Number) t.push("Number");
-               else if (o.getClass().getName().startsWith("org.xwt.js.")) t.push(o.getClass().getName().substring(11));
-               else t.push("unknown");
-               break;
-           }
+                Object o = t.pop();
+                if (o == null) t.push(null);
+                else if (o instanceof JS) t.push(((JS)o).typeName());
+                else if (o instanceof String) t.push("string");
+                else if (o instanceof Number) t.push("number");
+                else if (o instanceof Boolean) t.push("boolean");
+                else t.push("unknown");
+                break;
+            }
 
             case NEWFUNCTION: {
-               try {
-                   t.push(((CompiledFunctionImpl)arg[pc]).cloneWithNewParentScope(s));
-               } catch (IOException e) {
-                   throw new Error("this should never happen");
-               }
-               break;
-           }
+                try {
+                    t.push(((CompiledFunctionImpl)arg[pc]).cloneWithNewParentScope(s));
+                } catch (IOException e) {
+                    throw new Error("this should never happen");
+                }
+                break;
+            }
 
             case PUSHKEYS: {
                 Object o = t.peek();
@@ -161,55 +172,74 @@ public class CompiledFunctionImpl extends JS.Callable implements ByteCodes, Toke
 
             case LABEL: break;
             case LOOP: {
-               t.push(s);
-               t.push(new Context.LoopMarker(pc, pc > 0 && op[pc - 1] == LABEL ? (String)arg[pc - 1] : (String)null));
-               t.push(Boolean.TRUE);
-               break;
-           }
+                t.push(new LoopMarker(pc, pc > 0 && op[pc - 1] == LABEL ? (String)arg[pc - 1] : (String)null,s));
+                t.push(Boolean.TRUE);
+                break;
+            }
 
             case BREAK:
-           case CONTINUE:
-               while(t.size() > 0) {
-                   Object o = t.pop();
-                   if (o instanceof Context.CallMarker) ee("break or continue not within a loop");
-                   if (o != null && o instanceof Context.LoopMarker) {
-                       if (arg[pc] == null || arg[pc].equals(((Context.LoopMarker)o).label)) {
-                           int loopInstructionLocation = ((Context.LoopMarker)o).location;
-                           int endOfLoop = ((Integer)arg[loopInstructionLocation]).intValue() + loopInstructionLocation;
-                           s = (JS.Scope)t.pop();
-                           if (op[pc] == CONTINUE) { t.push(s); t.push(o); t.push(Boolean.FALSE); }
-                           pc = op[pc] == BREAK ? endOfLoop - 1 : loopInstructionLocation;
-                           continue OUTER;
-                       }
-                   }
-               }
-               throw new Error("CONTINUE/BREAK invoked but couldn't find a LoopMarker at " + sourceName + ":" + line);
+            case CONTINUE:
+                while(t.size() > 0) {
+                    Object o = t.pop();
+                    if (o instanceof CallMarker) ee("break or continue not within a loop");
+                    if (o instanceof TryMarker) {
+                        if(((TryMarker)o).finallyLoc < 0) continue; // no finally block, keep going
+                        t.push(new FinallyData(curOP, curArg));
+                        s = ((TryMarker)o).scope;
+                        pc = ((TryMarker)o).finallyLoc - 1;
+                        continue OUTER;
+                    }
+                    if (o instanceof LoopMarker) {
+                        if (curArg == null || curArg.equals(((LoopMarker)o).label)) {
+                            int loopInstructionLocation = ((LoopMarker)o).location;
+                            int endOfLoop = ((Integer)arg[loopInstructionLocation]).intValue() + loopInstructionLocation;
+                            s = ((LoopMarker)o).scope;
+                            if (curOP == CONTINUE) { t.push(o); t.push(Boolean.FALSE); }
+                            pc = curOP == BREAK ? endOfLoop - 1 : loopInstructionLocation;
+                            continue OUTER;
+                        }
+                    }
+                }
+                throw new Error("CONTINUE/BREAK invoked but couldn't find a LoopMarker at " + sourceName + ":" + getLine(pc));
 
             case TRY: {
-               t.push(new Context.TryMarker(pc + ((Integer)arg[pc]).intValue(), s));
-               break;
-           }
+                int[] jmps = (int[]) arg[pc];
+                // jmps[0] is how far away the catch block is, jmps[1] is how far away the finally block is
+                // each can be < 0 if the specified block does not exist
+                t.push(new TryMarker(jmps[0] < 0 ? -1 : pc + jmps[0], jmps[1] < 0 ? -1 : pc + jmps[1],s));
+                break;
+            }
 
             case RETURN: {
-               Object retval = t.pop();
-               while(t.size() > 0) {
-                   Object o = t.pop();
-                   if (o != null && o instanceof Context.CallMarker) {
-                       t.push(retval);
-                       return;
-                   }
-               }
-               throw new Error("error: RETURN invoked but couldn't find a CallMarker!");
-           }
+                Object retval = t.pop();
+                while(t.size() > 0) {
+                    Object o = t.pop();
+                    if (o instanceof TryMarker) {
+                        if(((TryMarker)o).finallyLoc < 0) continue;
+                        t.push(retval); 
+                        t.push(new FinallyData(RETURN));
+                        s = ((TryMarker)o).scope;
+                        pc = ((TryMarker)o).finallyLoc - 1;
+                        continue OUTER;
+                    }
+                    if (o instanceof CallMarker) {
+                        t.push(retval);
+                        return;
+                    }
+                }
+                throw new Error("error: RETURN invoked but couldn't find a CallMarker!");
+            }
 
             case PUT: {
                 Object val = t.pop();
                 Object key = t.pop();
-               Object target = t.peek();
+                Object target = t.peek();
                 if (target == null)
-                   throw je("tried to put a value to the " + key + " property on the null value");
+                    throw je("tried to put a value to the " + key + " property on the null value");
                 if (!(target instanceof JS))
-                   throw je("tried to put a value to the " + key + " property on a " + target.getClass().getName());
+                    throw je("tried to put a value to the " + key + " property on a " + target.getClass().getName());
+                if (key == null)
+                    throw je("tried to assign \"" + (val==null?"(null)":val.toString()) + "\" to the null key");
                 ((JS)target).put(key, val);
                 t.push(val);
                 break;
@@ -217,59 +247,94 @@ public class CompiledFunctionImpl extends JS.Callable implements ByteCodes, Toke
 
             case GET:
             case GET_PRESERVE: {
-               Object o, v;
-               if (op[pc] == GET) {
-                   v = t.pop();
-                   o = t.pop();
-               } else {
-                   v = t.pop();
-                   o = t.peek();
-                   t.push(v);
-               }
-               Object ret = null;
-               if (o == null) throw je("tried to get property \"" + v + "\" from the null value");
-               if (v == null) throw je("tried to get the null key from " + v);
-               if (o instanceof String) {
-                   ret = getFromString((String)o, v);
-               } else if (o instanceof Boolean) {
-                   throw je("Not Implemented: properties on Boolean objects");
-               } else if (o instanceof Number) {
-                   Log.log(this, "Not Implemented: properties on Number objects");
-               } else if (o instanceof JS) {
-                   ret = ((JS)o).get(v);
-               }
+                Object o, v;
+                if (op[pc] == GET) {
+                    v = t.pop();
+                    o = t.pop();
+                } else {
+                    v = t.pop();
+                    o = t.peek();
+                    t.push(v);
+                }
+                Object ret = null;
+                if (o == null) throw je("tried to get property \"" + v + "\" from the null value");
+                if (v == null) throw je("tried to get the null key from " + o);
+                if (o instanceof String || o instanceof Number || o instanceof Boolean)
+                    ret = Internal.getFromPrimitive(o,v);
+                else if (o instanceof JS)
+                    ret = ((JS)o).get(v);
+                else 
+                    throw je("tried to get property " + v + " from a " + o.getClass().getName());
                 t.push(ret);
                 break;
             }
-                    
-            case CALL: {
+            
+            case CALLMETHOD:
+            case CALL:
+            {
                 JS.Array arguments = new JS.Array();
                 int numArgs = JS.toNumber(arg[pc]).intValue();
                 arguments.setSize(numArgs);
                 for(int j=numArgs - 1; j >= 0; j--) arguments.setElementAt(t.pop(), j);
-                JS.Callable f = (JS.Callable)t.pop();
-                if (f == null) throw je("attempted to call null");
-               try {
-                   t.push(f.call(arguments));
-                   break;
-               } catch (JS.Exn e) {
-                   t.push(e);
-               }
+                Object o = t.pop();
+                if(o == null) throw je("attempted to call null");
+                try {
+                    Object ret;
+                    if(op[pc] == CALLMETHOD) {
+                        Object method = o;
+                        o = t.pop();
+                        if(o instanceof String || o instanceof Number || o instanceof Boolean)
+                            ret = Internal.callMethodOnPrimitive(o,method,arguments);
+                        else if(o instanceof JS)
+                            ret = ((JS)o).callMethod(method,arguments,false);
+                        else
+                            throw new JS.Exn("Tried to call a method on an object that isn't a JS object");
+                    } else {                   
+                        ret = ((JS.Callable)o).call(arguments);
+                    }
+                    t.push(ret);
+                    break;
+                } catch (JS.Exn e) {
+                    t.push(e);
+                }
             }
             // fall through if exception was thrown
-           case THROW: {
-               Object exn = t.pop();
-               while(t.size() > 0) {
-                   Object o = t.pop();
-                   if (o instanceof Context.TryMarker) {
-                       t.push(exn);
-                       pc = ((Context.TryMarker)o).location - 1;
-                       s = ((Context.TryMarker)o).scope;
-                       continue OUTER;
-                   }
-               }
-               throw new JS.Exn(exn);
-           }
+            case THROW: {
+                Object exn = t.pop();
+                while(t.size() > 0) {
+                    Object o = t.pop();
+                    if (o instanceof CatchMarker || o instanceof TryMarker) {
+                        boolean inCatch = o instanceof CatchMarker;
+                        if(inCatch) {
+                            o = t.pop();
+                            if(((TryMarker)o).finallyLoc < 0) continue; // no finally block, keep going
+                        }
+                        if(!inCatch && ((TryMarker)o).catchLoc >= 0) {
+                            // run the catch block, this will implicitly run the finally block, if it exists
+                            t.push(o);
+                            t.push(catchMarker);
+                            t.push((exn instanceof JS.Exn) ? ((JS.Exn)exn).getObject() : exn);
+                            s = ((TryMarker)o).scope;
+                            pc = ((TryMarker)o).catchLoc - 1;
+                            continue OUTER;
+                        } else {
+                            t.push(exn);
+                            t.push(new FinallyData(THROW));
+                            s = ((TryMarker)o).scope;
+                            pc = ((TryMarker)o).finallyLoc - 1;
+                            continue OUTER;
+                        }
+                    }
+                    // no handler found within this func
+                    if(o instanceof CallMarker) {
+                        if(exn instanceof JS.Exn)
+                            throw (JS.Exn)exn;
+                        else
+                            throw new JS.Exn(exn);
+                    }
+                }
+                throw new Error("error: THROW invoked but couldn't find a Try or Call Marker!");
+            }
 
             case INC: case DEC: {
                 boolean isPrefix = JS.toBoolean(arg[pc]);
@@ -316,26 +381,27 @@ public class CompiledFunctionImpl extends JS.Callable implements ByteCodes, Toke
                 case URSH: t.push(new Long(JS.toLong(left) >>> JS.toLong(right))); break;
                         
                 case LT: case LE: case GT: case GE: {
-                   if (left == null) left = new Integer(0);
-                   if (right == null) right = new Integer(0);
-                   int result = 0;
-                   if (left instanceof String || right instanceof String) {
-                       result = left.toString().compareTo(right.toString());
-                   } else {
-                       result = (int)java.lang.Math.ceil(JS.toDouble(left) - JS.toDouble(right));
-                   }
-                   t.push(new Boolean((op[pc] == LT && result < 0) || (op[pc] == LE && result <= 0) ||
-                                      (op[pc] == GT && result > 0) || (op[pc] == GE && result >= 0)));
-                   break;
-               }
+                    if (left == null) left = new Integer(0);
+                    if (right == null) right = new Integer(0);
+                    int result = 0;
+                    if (left instanceof String || right instanceof String) {
+                        result = left.toString().compareTo(right.toString());
+                    } else {
+                        result = (int)java.lang.Math.ceil(JS.toDouble(left) - JS.toDouble(right));
+                    }
+                    t.push(new Boolean((op[pc] == LT && result < 0) || (op[pc] == LE && result <= 0) ||
+                                       (op[pc] == GT && result > 0) || (op[pc] == GE && result >= 0)));
+                    break;
+                }
                     
                 case EQ:
-               case NE: {
+                case NE: {
                     Object l = left;
                     Object r = right;
                     boolean ret;
                     if (l == null) { Object tmp = r; r = l; l = tmp; }
                     if (l == null && r == null) ret = true;
+                    else if (r == null) ret = false; // l != null, so its false
                     else if (l instanceof Boolean) ret = new Boolean(JS.toBoolean(r)).equals(l);
                     else if (l instanceof Number) ret = JS.toNumber(r).doubleValue() == JS.toNumber(l).doubleValue();
                     else if (l instanceof String) ret = r != null && l.equals(r.toString());
@@ -346,65 +412,89 @@ public class CompiledFunctionImpl extends JS.Callable implements ByteCodes, Toke
                 default: throw new Error("unknown opcode " + op[pc]);
                 } }
             }
-       }
-    }
-
-
-    // Helpers for Number, String, and Boolean ////////////////////////////////////////
-
-    private Object getFromString(final String o, final Object v) {
-       if (v.equals("length")) return new Integer(((String)o).length());
-       else if (v.equals("substring")) return new JS.Callable() {
-               public Object call(JS.Array args) {
-                   if (args.length() == 1) return ((String)o).substring(JS.toNumber(args.elementAt(0)).intValue());
-                   else if (args.length() == 2) return ((String)o).substring(JS.toNumber(args.elementAt(0)).intValue(),
-                                                                             JS.toNumber(args.elementAt(1)).intValue());
-                   else throw je("String.substring() can only take one or two arguments");
-               }
-           };
-       else if (v.equals("toLowerCase")) return new JS.Callable() {
-               public Object call(JS.Array args) {
-                   return ((String)o).toLowerCase();
-               } };
-       else if (v.equals("toUpperCase")) return new JS.Callable() {
-               public Object call(JS.Array args) {
-                   return ((String)o).toString().toUpperCase();
-               } };
-       else if (v.equals("charAt")) return new JS.Callable() {
-               public Object call(JS.Array args) {
-                   return ((String)o).charAt(JS.toNumber(args.elementAt(0)).intValue()) + "";
-               } };
-       else if (v.equals("lastIndexOf")) return new JS.Callable() {
-               public Object call(JS.Array args) {
-                   if (args.length() != 1) return null;
-                   return new Integer(((String)o).lastIndexOf(args.elementAt(0).toString()));
-               } };
-       else if (v.equals("indexOf")) return new JS.Callable() {
-               public Object call(JS.Array args) {
-                   if (args.length() != 1) return null;
-                   return new Integer(((String)o).indexOf(args.elementAt(0).toString()));
-               } };
-       throw je("Not Implemented: propery " + v + " on String objects");
+        }
+        // this should never happen, we will ALWAYS have a RETURN at the end of the func
+        throw new Error("Just fell out of CompiledFunction::eval() loop. Last PC was " + lastPC);
     }
 
+    // Debugging //////////////////////////////////////////////////////////////////////
+
+    public String toString() {
+        StringBuffer sb = new StringBuffer(1024);
+        sb.append("\n" + sourceName + ": " + firstLine + "\n");
+        for (int i=0; i < size; i++) {
+            sb.append(i);
+            sb.append(": ");
+            if (op[i] < 0)
+                sb.append(bytecodeToString[-op[i]]);
+            else
+                sb.append(codeToString[op[i]]);
+            sb.append(" ");
+            sb.append(arg[i] == null ? "(no arg)" : arg[i]);
+            if((op[i] == JF || op[i] == JT || op[i] == JMP) && arg[i] != null && arg[i] instanceof Number) {
+                sb.append(" jump to ").append(i+((Number) arg[i]).intValue());
+            } else  if(op[i] == TRY) {
+                int[] jmps = (int[]) arg[i];
+                sb.append(" catch: ").append(jmps[0] < 0 ? "No catch block" : ""+(i+jmps[0]));
+                sb.append(" finally: ").append(jmps[1] < 0 ? "No finally block" : ""+(i+jmps[1]));
+            }
+            sb.append("\n");
+        }
+        return sb.toString();
+    } 
 
     // Exception Stuff ////////////////////////////////////////////////////////////////
 
     static class EvaluatorException extends RuntimeException { public EvaluatorException(String s) { super(s); } }
-    EvaluatorException ee(String s) { throw new EvaluatorException(sourceName + ":" + line[pc] + " " + s); }
-    JS.Exn je(String s) { throw new JS.Exn(sourceName + ":" + line[pc] + " " + s); }
+    EvaluatorException ee(String s) { throw new EvaluatorException(sourceName + ":" + JS.Thread.currentJSThread().getLine() + " " + s); }
+    JS.Exn je(String s) { throw new JS.Exn(sourceName + ":" + JS.Thread.currentJSThread().getLine() + " " + s); }
 
 
     // FunctionScope /////////////////////////////////////////////////////////////////
 
     private class FunctionScope extends JS.Scope {
-       String sourceName;
-       public FunctionScope(String sourceName, Scope parentScope) { super(parentScope); this.sourceName = sourceName; }
-       public String getSourceName() { return sourceName; }
-       public Object get(Object key) throws JS.Exn {
-           if (key.equals("trapee")) return org.xwt.Trap.currentTrapee();
-           else if (key.equals("cascade")) return org.xwt.Trap.cascadeFunction;
-           return super.get(key);
-       }
+        String sourceName;
+        public FunctionScope(String sourceName, Scope parentScope) { super(parentScope); this.sourceName = sourceName; }
+        public String getSourceName() { return sourceName; }
     }
+
+
+    // Markers //////////////////////////////////////////////////////////////////////
+
+    public static class CallMarker { public CallMarker() { } }
+    
+    public static class CatchMarker { public CatchMarker() { } }
+    private static CatchMarker catchMarker = new CatchMarker();
+    
+    public static class LoopMarker {
+        public int location;
+        public String label;
+        public JS.Scope scope;
+        public LoopMarker(int location, String label, JS.Scope scope) {
+            this.location = location;
+            this.label = label;
+            this.scope = scope;
+        }
+    }
+    public static class TryMarker {
+        public int catchLoc;
+        public int finallyLoc;
+        public JS.Scope scope;
+        public TryMarker(int catchLoc, int finallyLoc, JS.Scope scope) {
+            this.catchLoc = catchLoc;
+            this.finallyLoc = finallyLoc;
+            this.scope = scope;
+        }
+    }
+    public static class FinallyData {
+        public int op;
+        public Object arg;
+        public FinallyData(int op, Object arg) { this.op = op; this.arg = arg; }
+        public FinallyData(int op) { this(op,null); }
+    }
+}
+
+/** this class exists solely to work around a GCJ bug */
+abstract class JSCallable extends JS.Callable {
+        public abstract Object call(JS.Array args) throws JS.Exn;
 }