basefunction.java

java中比较著名的js引擎当属mozilla开源的rhino

/* -*- Mode: java; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
 *
 * ***** BEGIN LICENSE BLOCK *****
 * Version: MPL 1.1/GPL 2.0
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 * http://www.mozilla.org/MPL/
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is Rhino code, released
 * May 6, 1999.
 *
 * The Initial Developer of the Original Code is
 * Netscape Communications Corporation.
 * Portions created by the Initial Developer are Copyright (C) 1997-1999
 * the Initial Developer. All Rights Reserved.
 *
 * Contributor(s):
 *   Norris Boyd
 *   Igor Bukanov
 *   Roger Lawrence
 *   Mike McCabe
 *
 * Alternatively, the contents of this file may be used under the terms of
 * the GNU General Public License Version 2 or later (the "GPL"), in which
 * case the provisions of the GPL are applicable instead of those above. If
 * you wish to allow use of your version of this file only under the terms of
 * the GPL and not to allow others to use your version of this file under the
 * MPL, indicate your decision by deleting the provisions above and replacing
 * them with the notice and other provisions required by the GPL. If you do
 * not delete the provisions above, a recipient may use your version of this
 * file under either the MPL or the GPL.
 *
 * ***** END LICENSE BLOCK ***** */

package org.mozilla.javascript;

/**
 * The base class for Function objects
 * See ECMA 15.3.
 * @author Norris Boyd
 */
public class BaseFunction extends IdScriptableObject implements Function
{

    static final long serialVersionUID = 5311394446546053859L;

    private static final Object FUNCTION_TAG = new Object();

    static void init(Scriptable scope, boolean sealed)
    {
        BaseFunction obj = new BaseFunction();
        obj.isPrototypePropertyImmune = true;
        obj.exportAsJSClass(MAX_PROTOTYPE_ID, scope, sealed);
    }

    public BaseFunction()
    {
    }

    public BaseFunction(Scriptable scope, Scriptable prototype)
    {
        super(scope, prototype);
    }

    public String getClassName() {
        return "Function";
    }

    /**
     * Implements the instanceof operator for JavaScript Function objects.
     * <p>
     * <code>
     * foo = new Foo();<br>
     * foo instanceof Foo;  // true<br>
     * </code>
     *
     * @param instance The value that appeared on the LHS of the instanceof
     *              operator
     * @return true if the "prototype" property of "this" appears in
     *              value's prototype chain
     *
     */
    public boolean hasInstance(Scriptable instance)
    {
        Object protoProp = ScriptableObject.getProperty(this, "prototype");
        if (protoProp instanceof Scriptable) {
            return ScriptRuntime.jsDelegatesTo(instance, (Scriptable)protoProp);
        }
        throw ScriptRuntime.typeError1("msg.instanceof.bad.prototype",
                                       getFunctionName());
    }

// #string_id_map#

    private static final int
        Id_length       = 1,
        Id_arity        = 2,
        Id_name         = 3,
        Id_prototype    = 4,
        Id_arguments    = 5,

        MAX_INSTANCE_ID = 5;

    protected int getMaxInstanceId()
    {
        return MAX_INSTANCE_ID;
    }

    protected int findInstanceIdInfo(String s)
    {
        int id;
// #generated# Last update: 2001-05-20 00:12:12 GMT+02:00
        L0: { id = 0; String X = null; int c;
            L: switch (s.length()) {
            case 4: X="name";id=Id_name; break L;
            case 5: X="arity";id=Id_arity; break L;
            case 6: X="length";id=Id_length; break L;
            case 9: c=s.charAt(0);
                if (c=='a') { X="arguments";id=Id_arguments; }
                else if (c=='p') { X="prototype";id=Id_prototype; }
                break L;
            }
            if (X!=null && X!=s && !X.equals(s)) id = 0;
        }
// #/generated#
// #/string_id_map#

        if (id == 0) return super.findInstanceIdInfo(s);

        int attr;
        switch (id) {
          case Id_length:
          case Id_arity:
          case Id_name:
            attr = DONTENUM | READONLY | PERMANENT;
            break;
          case Id_prototype:
            attr = (isPrototypePropertyImmune)
                   ? DONTENUM | READONLY | PERMANENT
                   : DONTENUM;
            break;
          case Id_arguments:
            attr = DONTENUM | PERMANENT;
            break;
          default: throw new IllegalStateException();
        }
        return instanceIdInfo(attr, id);
    }

    protected String getInstanceIdName(int id)
    {
        switch (id) {
            case Id_length:       return "length";
            case Id_arity:        return "arity";
            case Id_name:         return "name";
            case Id_prototype:    return "prototype";
            case Id_arguments:    return "arguments";
        }
        return super.getInstanceIdName(id);
    }

    protected Object getInstanceIdValue(int id)
    {
        switch (id) {
          case Id_length:    return ScriptRuntime.wrapInt(getLength());
          case Id_arity:     return ScriptRuntime.wrapInt(getArity());
          case Id_name:      return getFunctionName();
          case Id_prototype: return getPrototypeProperty();
          case Id_arguments: return getArguments();
        }
        return super.getInstanceIdValue(id);
    }

    protected void setInstanceIdValue(int id, Object value)
    {
        if (id == Id_prototype) {
            if (!isPrototypePropertyImmune) {
                prototypeProperty = (value != null)
                                    ? value : UniqueTag.NULL_VALUE;
            }
            return;
        } else if (id == Id_arguments) {
            if (value == NOT_FOUND) {
                // This should not be called since "arguments" is PERMANENT
                Kit.codeBug();
            }
            defaultPut("arguments", value);
        }
        super.setInstanceIdValue(id, value);
    }

    protected void fillConstructorProperties(IdFunctionObject ctor)
    {
        // Fix up bootstrapping problem: getPrototype of the IdFunctionObject
        // can not return Function.prototype because Function object is not
        // yet defined.
        ctor.setPrototype(this);
        super.fillConstructorProperties(ctor);
    }

    protected void initPrototypeId(int id)
    {
        String s;
        int arity;
        switch (id) {
          case Id_constructor: arity=1; s="constructor"; break;
          case Id_toString:    arity=1; s="toString";    break;
          case Id_toSource:    arity=1; s="toSource";    break;
          case Id_apply:       arity=2; s="apply";       break;
          case Id_call:        arity=1; s="call";        break;
          default: throw new IllegalArgumentException(String.valueOf(id));
        }
        initPrototypeMethod(FUNCTION_TAG, id, s, arity);
    }

    public Object execIdCall(IdFunctionObject f, Context cx, Scriptable scope,
                             Scriptable thisObj, Object[] args)
    {
        if (!f.hasTag(FUNCTION_TAG)) {
            return super.execIdCall(f, cx, scope, thisObj, args);
        }
        int id = f.methodId();
        switch (id) {
          case Id_constructor:
            return jsConstructor(cx, scope, args);

          case Id_toString: {
            BaseFunction realf = realFunction(thisObj, f);
            int indent = ScriptRuntime.toInt32(args, 0);
            return realf.decompile(indent, 0);
          }

          case Id_toSource: {
            BaseFunction realf = realFunction(thisObj, f);
            int indent = 0;
            int flags = Decompiler.TO_SOURCE_FLAG;
            if (args.length != 0) {
                indent = ScriptRuntime.toInt32(args[0]);
                if (indent >= 0) {
                    flags = 0;
                } else {
                    indent = 0;
                }
            }
            return realf.decompile(indent, flags);
          }

          case Id_apply:
          case Id_call:
            return ScriptRuntime.applyOrCall(id == Id_apply,
                                             cx, scope, thisObj, args);
        }
        throw new IllegalArgumentException(String.valueOf(id));
    }

    private BaseFunction realFunction(Scriptable thisObj, IdFunctionObject f)
    {
        Object x = thisObj.getDefaultValue(ScriptRuntime.FunctionClass);
        if (x instanceof BaseFunction) {