basefunction.java

java中比较著名的js引擎当属mozilla开源的rhino

            return (BaseFunction)x;
        }
        throw ScriptRuntime.typeError1("msg.incompat.call",
                                       f.getFunctionName());
    }

    /**
     * Make value as DontEnum, DontDelete, ReadOnly
     * prototype property of this Function object
     */
    public void setImmunePrototypeProperty(Object value)
    {
        if (isPrototypePropertyImmune) {
            throw new IllegalStateException();
        }
        prototypeProperty = (value != null) ? value : UniqueTag.NULL_VALUE;
        isPrototypePropertyImmune = true;
    }

    protected Scriptable getClassPrototype()
    {
        Object protoVal = getPrototypeProperty();
        if (protoVal instanceof Scriptable) {
            return (Scriptable) protoVal;
        }
        return getClassPrototype(this, "Object");
    }

    /**
     * Should be overridden.
     */
    public Object call(Context cx, Scriptable scope, Scriptable thisObj,
                       Object[] args)
    {
        return Undefined.instance;
    }

    public Scriptable construct(Context cx, Scriptable scope, Object[] args)
    {
        Scriptable result = createObject(cx, scope);
        if (result != null) {
            Object val = call(cx, scope, result, args);
            if (val instanceof Scriptable) {
                result = (Scriptable)val;
            }
        } else {
            Object val = call(cx, scope, null, args);
            if (!(val instanceof Scriptable)) {
                // It is program error not to return Scriptable from
                // the call method if createObject returns null.
                throw new IllegalStateException(
                    "Bad implementaion of call as constructor, name="
                    +getFunctionName()+" in "+getClass().getName());
            }
            result = (Scriptable)val;
            if (result.getPrototype() == null) {
                result.setPrototype(getClassPrototype());
            }
            if (result.getParentScope() == null) {
                Scriptable parent = getParentScope();
                if (result != parent) {
                    result.setParentScope(parent);
                }
            }
        }
        return result;
    }

    /**
     * Creates new script object.
     * The default implementation of {@link #construct} uses the method to
     * to get the value for <tt>thisObj</tt> argument when invoking
     * {@link #call}.
     * The methos is allowed to return <tt>null</tt> to indicate that
     * {@link #call} will create a new object itself. In this case
     * {@link #construct} will set scope and prototype on the result
     * {@link #call} unless they are already set.
     */
    public Scriptable createObject(Context cx, Scriptable scope)
    {
        Scriptable newInstance = new NativeObject();
        newInstance.setPrototype(getClassPrototype());
        newInstance.setParentScope(getParentScope());
        return newInstance;
    }

    /**
     * Decompile the source information associated with this js
     * function/script back into a string.
     *
     * @param indent How much to indent the decompiled result.
     *
     * @param flags Flags specifying format of decompilation output.
     */
    String decompile(int indent, int flags)
    {
        StringBuffer sb = new StringBuffer();
        boolean justbody = (0 != (flags & Decompiler.ONLY_BODY_FLAG));
        if (!justbody) {
            sb.append("function ");
            sb.append(getFunctionName());
            sb.append("() {\n\t");
        }
        sb.append("[native code, arity=");
        sb.append(getArity());
        sb.append("]\n");
        if (!justbody) {
            sb.append("}\n");
        }
        return sb.toString();
    }

    public int getArity() { return 0; }

    public int getLength() { return 0; }

    public String getFunctionName()
    {
        return "";
    }

    final Object getPrototypeProperty() {
        Object result = prototypeProperty;
        if (result == null) {
            synchronized (this) {
                result = prototypeProperty;
                if (result == null) {
                    setupDefaultPrototype();
                    result = prototypeProperty;
                }
            }
        }
        else if (result == UniqueTag.NULL_VALUE) { result = null; }
        return result;
    }

    private void setupDefaultPrototype()
    {
        NativeObject obj = new NativeObject();
        final int attr = ScriptableObject.DONTENUM;
        obj.defineProperty("constructor", this, attr);
        // put the prototype property into the object now, then in the
        // wacky case of a user defining a function Object(), we don't
        // get an infinite loop trying to find the prototype.
        prototypeProperty = obj;
        Scriptable proto = getObjectPrototype(this);
        if (proto != obj) {
            // not the one we just made, it must remain grounded
            obj.setPrototype(proto);
        }
    }

    private Object getArguments()
    {
      // <Function name>.arguments is deprecated, so we use a slow
      // way of getting it that doesn't add to the invocation cost.
      // TODO: add warning, error based on version
      Object value = defaultGet("arguments");
      if (value != NOT_FOUND) {
          // Should after changing <Function name>.arguments its
          // activation still be available during Function call?
          // This code assumes it should not:
          // defaultGet("arguments") != NOT_FOUND
          // means assigned arguments
          return value;
      }
      Context cx = Context.getContext();
      NativeCall activation = ScriptRuntime.findFunctionActivation(cx, this);
      return (activation == null)
             ? null
             : activation.get("arguments", activation);
    }

    private static Object jsConstructor(Context cx, Scriptable scope,
                                        Object[] args)
    {
        int arglen = args.length;
        StringBuffer sourceBuf = new StringBuffer();

        sourceBuf.append("function ");
        /* version != 1.2 Function constructor behavior -
         * print 'anonymous' as the function name if the
         * version (under which the function was compiled) is
         * less than 1.2... or if it's greater than 1.2, because
         * we need to be closer to ECMA.
         */
        if (cx.getLanguageVersion() != Context.VERSION_1_2) {
            sourceBuf.append("anonymous");
        }
        sourceBuf.append('(');

        // Append arguments as coma separated strings
        for (int i = 0; i < arglen - 1; i++) {
            if (i > 0) {
                sourceBuf.append(',');
            }
            sourceBuf.append(ScriptRuntime.toString(args[i]));
        }
        sourceBuf.append(") {");
        if (arglen != 0) {
            // append function body
            String funBody = ScriptRuntime.toString(args[arglen - 1]);
            sourceBuf.append(funBody);
        }
        sourceBuf.append('}');
        String source = sourceBuf.toString();

        int[] linep = new int[1];
        String filename = Context.getSourcePositionFromStack(linep);
        if (filename == null) {
            filename = "<eval'ed string>";
            linep[0] = 1;
        }

        String sourceURI = ScriptRuntime.
            makeUrlForGeneratedScript(false, filename, linep[0]);

        Scriptable global = ScriptableObject.getTopLevelScope(scope);

        ErrorReporter reporter;
        reporter = DefaultErrorReporter.forEval(cx.getErrorReporter());

        // Compile with explicit interpreter instance to force interpreter
        // mode.
        return cx.compileFunction(global, source, new Interpreter(), reporter,
                                  sourceURI, 1, null);
    }

    protected int findPrototypeId(String s)
    {
        int id;
// #string_id_map#
// #generated# Last update: 2004-03-17 13:23:22 CET
        L0: { id = 0; String X = null; int c;
            L: switch (s.length()) {
            case 4: X="call";id=Id_call; break L;
            case 5: X="apply";id=Id_apply; break L;
            case 8: c=s.charAt(3);
                if (c=='o') { X="toSource";id=Id_toSource; }
                else if (c=='t') { X="toString";id=Id_toString; }
                break L;
            case 11: X="constructor";id=Id_constructor; break L;
            }
            if (X!=null && X!=s && !X.equals(s)) id = 0;
        }
// #/generated#
        return id;
    }

    private static final int
        Id_constructor    = 1,
        Id_toString       = 2,
        Id_toSource       = 3,
        Id_apply          = 4,
        Id_call           = 5,

        MAX_PROTOTYPE_ID  = 5;

// #/string_id_map#

    private Object prototypeProperty;
    private boolean isPrototypePropertyImmune;
}