scriptruntime.java

java中比较著名的js引擎当属mozilla开源的rhino

    {
        Scriptable parent = scope.getParentScope();
        if (parent == null) {
            Object result = topScopeName(cx, scope, name);
            if (result == Scriptable.NOT_FOUND) {
                throw notFoundError(scope, name);
            }
            return result;
        }

        return nameOrFunction(cx, scope, parent, name, false);
    }

    private static Object nameOrFunction(Context cx, Scriptable scope,
                                         Scriptable parentScope, String name,
                                         boolean asFunctionCall)
    {
        Object result;
        Scriptable thisObj = scope; // It is used only if asFunctionCall==true.

        XMLObject firstXMLObject = null;
        for (;;) {
            if (scope instanceof NativeWith) {
                Scriptable withObj = scope.getPrototype();
                if (withObj instanceof XMLObject) {
                    XMLObject xmlObj = (XMLObject)withObj;
                    if (xmlObj.ecmaHas(cx, name)) {
                        // function this should be the target object of with
                        thisObj = xmlObj;
                        result = xmlObj.ecmaGet(cx, name);
                        break;
                    }
                    if (firstXMLObject == null) {
                        firstXMLObject = xmlObj;
                    }
                } else {
                    result = ScriptableObject.getProperty(withObj, name);
                    if (result != Scriptable.NOT_FOUND) {
                        // function this should be the target object of with
                        thisObj = withObj;
                        break;
                    }
                }
            } else if (scope instanceof NativeCall) {
                // NativeCall does not prototype chain and Scriptable.get
                // can be called directly.
                result = scope.get(name, scope);
                if (result != Scriptable.NOT_FOUND) {
                    if (asFunctionCall) {
                        // ECMA 262 requires that this for nested funtions
                        // should be top scope
                        thisObj = ScriptableObject.
                                      getTopLevelScope(parentScope);
                    }
                    break;
                }
            } else {
                // Can happen if Rhino embedding decided that nested
                // scopes are useful for what ever reasons.
                result = ScriptableObject.getProperty(scope, name);
                if (result != Scriptable.NOT_FOUND) {
                    thisObj = scope;
                    break;
                }
            }
            scope = parentScope;
            parentScope = parentScope.getParentScope();
            if (parentScope == null) {
                result = topScopeName(cx, scope, name);
                if (result == Scriptable.NOT_FOUND) {
                    if (firstXMLObject == null || asFunctionCall) {
                        throw notFoundError(scope, name);
                    }
                    // The name was not found, but we did find an XML
                    // object in the scope chain and we are looking for name,
                    // not function. The result should be an empty XMLList
                    // in name context.
                    result = firstXMLObject.ecmaGet(cx, name);
                }
                // For top scope thisObj for functions is always scope itself.
                thisObj = scope;
                break;
            }
        }

        if (asFunctionCall) {
            if (!(result instanceof Callable)) {
                throw notFunctionError(result, name);
            }
            storeScriptable(cx, thisObj);
        }

        return result;
    }

    private static Object topScopeName(Context cx, Scriptable scope,
                                       String name)
    {
        if (cx.useDynamicScope) {
            scope = checkDynamicScope(cx.topCallScope, scope);
        }
        return ScriptableObject.getProperty(scope, name);
    }


    /**
     * Returns the object in the scope chain that has a given property.
     *
     * The order of evaluation of an assignment expression involves
     * evaluating the lhs to a reference, evaluating the rhs, and then
     * modifying the reference with the rhs value. This method is used
     * to 'bind' the given name to an object containing that property
     * so that the side effects of evaluating the rhs do not affect
     * which property is modified.
     * Typically used in conjunction with setName.
     *
     * See ECMA 10.1.4
     */
    public static Scriptable bind(Context cx, Scriptable scope, String id)
    {
        Scriptable firstXMLObject = null;
        Scriptable parent = scope.getParentScope();
        childScopesChecks: if (parent != null) {
            // Check for possibly nested "with" scopes first
            while (scope instanceof NativeWith) {
                Scriptable withObj = scope.getPrototype();
                if (withObj instanceof XMLObject) {
                    XMLObject xmlObject = (XMLObject)withObj;
                    if (xmlObject.ecmaHas(cx, id)) {
                        return xmlObject;
                    }
                    if (firstXMLObject == null) {
                        firstXMLObject = xmlObject;
                    }
                } else {
                    if (ScriptableObject.hasProperty(withObj, id)) {
                        return withObj;
                    }
                }
                scope = parent;
                parent = parent.getParentScope();
                if (parent == null) {
                    break childScopesChecks;
                }
            }
            for (;;) {
                if (ScriptableObject.hasProperty(scope, id)) {
                    return scope;
                }
                scope = parent;
                parent = parent.getParentScope();
                if (parent == null) {
                    break childScopesChecks;
                }
            }
        }
        // scope here is top scope
        if (cx.useDynamicScope) {
            scope = checkDynamicScope(cx.topCallScope, scope);
        }
        if (ScriptableObject.hasProperty(scope, id)) {
            return scope;
        }
        // Nothing was found, but since XML objects always bind
        // return one if found
        return firstXMLObject;
    }

    public static Object setName(Scriptable bound, Object value,
                                 Context cx, Scriptable scope, String id)
    {
        if (bound != null) {
            if (bound instanceof XMLObject) {
                XMLObject xmlObject = (XMLObject)bound;
                xmlObject.ecmaPut(cx, id, value);
            } else {
                ScriptableObject.putProperty(bound, id, value);
            }
        } else {
            // "newname = 7;", where 'newname' has not yet
            // been defined, creates a new property in the
            // top scope unless strict mode is specified.
            if (cx.hasFeature(Context.FEATURE_STRICT_VARS)) {
                throw Context.reportRuntimeError1("msg.assn.create.strict", id);
            }
            // Find the top scope by walking up the scope chain.
            bound = ScriptableObject.getTopLevelScope(scope);
            if (cx.useDynamicScope) {
                bound = checkDynamicScope(cx.topCallScope, bound);
            }
            bound.put(id, bound, value);
        }
        return value;
    }

    /**
     * This is the enumeration needed by the for..in statement.
     *
     * See ECMA 12.6.3.
     *
     * IdEnumeration maintains a ObjToIntMap to make sure a given
     * id is enumerated only once across multiple objects in a
     * prototype chain.
     *
     * XXX - ECMA delete doesn't hide properties in the prototype,
     * but js/ref does. This means that the js/ref for..in can
     * avoid maintaining a hash table and instead perform lookups
     * to see if a given property has already been enumerated.
     *
     */
    private static class IdEnumeration
    {
        Scriptable obj;
        Object[] ids;
        int index;
        ObjToIntMap used;
        String currentId;
        boolean enumValues;
    }

    public static Object enumInit(Object value, Context cx, boolean enumValues)
    {
        IdEnumeration x = new IdEnumeration();
        x.obj = toObjectOrNull(cx, value);
        if (x.obj != null) {
            // null or undefined do not cause errors but rather lead to empty
            // "for in" loop
            x.enumValues = enumValues;
            // enumInit should read all initial ids before returning
            // or "for (a.i in a)" would wrongly enumerate i in a as well
            enumChangeObject(x);
        }
        return x;
    }

    public static Boolean enumNext(Object enumObj)
    {
        // OPT this could be more efficient
        boolean result;
        IdEnumeration x = (IdEnumeration)enumObj;
        for (;;) {
            if (x.obj == null) {
                result = false;
                break;
            }
            if (x.index == x.ids.length) {
                x.obj = x.obj.getPrototype();
                enumChangeObject(x);
                continue;
            }
            Object id = x.ids[x.index++];
            if (x.used != null && x.used.has(id)) {
                continue;
            }
            if (id instanceof String) {
                String strId = (String)id;
                if (!x.obj.has(strId, x.obj))
                    continue;   // must have been deleted
                x.currentId = strId;
            } else {
                int intId = ((Number)id).intValue();
                if (!x.obj.has(intId, x.obj))
                    continue;   // must have been deleted
                x.currentId = String.valueOf(intId);
            }
            result = true;
            break;
        }
        return wrapBoolean(result);
    }

    public static Object enumId(Object enumObj, Context cx)
    {
        IdEnumeration x = (IdEnumeration)enumObj;
        if (!x.enumValues) return x.currentId;

        Object result;

        String s = toStringIdOrIndex(cx, x.currentId);
        if (s == null) {
            int index = lastIndexResult(cx);
            result = x.obj.get(index, x.obj);
        } else {
            result = x.obj.get(s, x.obj);
        }

        return result;
    }

    private static void enumChangeObject(IdEnumeration x)
    {
        Object[] ids = null;
        while (x.obj != null) {
            ids = x.obj.getIds();
            if (ids.length != 0) {
                break;
            }
            x.obj = x.obj.getPrototype();
        }
        if (x.obj != null && x.ids != null) {
            Object[] previous = x.ids;
            int L = previous.length;
            if (x.used == null) {
                x.used = new ObjToIntMap(L);
            }
            for (int i = 0; i != L; ++i) {
                x.used.intern(previous[i]);
            }
        }
        x.ids = ids;
        x.index = 0;
    }

    /**
     * Prepare for calling name(...): return function corresponding to
     * name and make current top scope available
     * as ScriptRuntime.lastStoredScriptable() for consumption as thisObj.
     * The caller must call ScriptRuntime.lastStoredScriptable() immediately
     * after calling this method.
     */
    public static Callable getNameFunctionAndThis(String name,
                                                  Context cx,
                                                  Scriptable scope)
    {
        Scriptable parent = scope.getParentScope();
        if (parent == null) {
            Object result = topScopeName(cx, scope, name);
            if (!(result instanceof Callable)) {
                if (result == Scriptable.NOT_FOUND) {
                    throw notFoundError(scope, name);
                } else {
                    throw notFunctionError(result, name);
                }
            }
            // Top scope is not NativeWith or NativeCall => thisObj == scope
            Scriptable thisObj = scope;
            storeScriptable(cx, thisObj);
            return (Callable)result;
        }

        // name will call storeScriptable(cx, thisObj);
        return (Callable)nameOrFunction(cx, scope, parent, name, true);
    }

    /**
     * Prepare for calling obj[id](...): return function corresponding to
     * obj[id] and make obj properly converted to Scriptable available
     * as ScriptRuntime.lastStoredScriptable() for consumption as thisObj.
     * The caller must call ScriptRuntime.lastStoredScriptable() immediately
     * after calling this method.
     */
    public static Callable getElemFunctionAndThis(Object obj,
                                                  Object elem,
                                                  Context cx)
    {
        String s = toStringIdOrIndex(cx, elem);
        if (s != null) {
            return getPropFunctionAndThis(obj, s, cx);
        }
        int index = lastIndexResult(cx);

        Scriptable thisObj = toObjectOrNull(cx, obj);
        if (thisObj == null) {
            throw undefCallError(obj, String.valueOf(index));
        }

        Object value;
        for (;;) {
            // Ignore XML lookup as requred by ECMA 357, 11.2.2.1
            value = ScriptableObject.getProperty(thisObj, index);
            if (value != Scriptable.NOT_FOUND) {
                break;
            }
            if (!(thisObj instanceof XMLObject)) {
                break;
            }
            XMLObject xmlObject = (XMLObject)thisObj;
            Scriptable extra = xmlObject.getExtraMethodSource(cx);
            if (extra == null) {
                break;
            }
            thisObj = extra;
        }
        if (!(value instanceof Callable)) {
            throw notFunctionError(value, elem);
        }

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