scriptableobject.java

這是一個javascript 的 interpreter是了解 web browser的好材料

/* -*- 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
 *   Bob Jervis
 *   Roger Lawrence
 *   Steve Weiss
 *
 * 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 ***** */

// API class

package org.mozilla.javascript;

import java.lang.reflect.*;
import java.util.Hashtable;
import java.io.*;
import org.mozilla.javascript.debug.DebuggableObject;

/**
 * This is the default implementation of the Scriptable interface. This
 * class provides convenient default behavior that makes it easier to
 * define host objects.
 * <p>
 * Various properties and methods of JavaScript objects can be conveniently
 * defined using methods of ScriptableObject.
 * <p>
 * Classes extending ScriptableObject must define the getClassName method.
 *
 * @see org.mozilla.javascript.Scriptable
 * @author Norris Boyd
 */

public abstract class ScriptableObject implements Scriptable, Serializable,
                                                  DebuggableObject,
                                                  ConstProperties
{

    /**
     * The empty property attribute.
     *
     * Used by getAttributes() and setAttributes().
     *
     * @see org.mozilla.javascript.ScriptableObject#getAttributes(String)
     * @see org.mozilla.javascript.ScriptableObject#setAttributes(String, int)
     */
    public static final int EMPTY =     0x00;

    /**
     * Property attribute indicating assignment to this property is ignored.
     *
     * @see org.mozilla.javascript.ScriptableObject
     *      #put(String, Scriptable, Object)
     * @see org.mozilla.javascript.ScriptableObject#getAttributes(String)
     * @see org.mozilla.javascript.ScriptableObject#setAttributes(String, int)
     */
    public static final int READONLY =  0x01;

    /**
     * Property attribute indicating property is not enumerated.
     *
     * Only enumerated properties will be returned by getIds().
     *
     * @see org.mozilla.javascript.ScriptableObject#getIds()
     * @see org.mozilla.javascript.ScriptableObject#getAttributes(String)
     * @see org.mozilla.javascript.ScriptableObject#setAttributes(String, int)
     */
    public static final int DONTENUM =  0x02;

    /**
     * Property attribute indicating property cannot be deleted.
     *
     * @see org.mozilla.javascript.ScriptableObject#delete(String)
     * @see org.mozilla.javascript.ScriptableObject#getAttributes(String)
     * @see org.mozilla.javascript.ScriptableObject#setAttributes(String, int)
     */
    public static final int PERMANENT = 0x04;

    /**
     * Property attribute indicating that this is a const property that has not
     * been assigned yet.  The first 'const' assignment to the property will
     * clear this bit.
     */
    public static final int UNINITIALIZED_CONST = 0x08;

    public static final int CONST = PERMANENT|READONLY|UNINITIALIZED_CONST;
    /**
     * The prototype of this object.
     */
    private Scriptable prototypeObject;

    /**
     * The parent scope of this object.
     */
    private Scriptable parentScopeObject;

    private static final Slot REMOVED = new Slot(null, 0, READONLY);

    static {
        REMOVED.wasDeleted = 1;
    }

    private transient Slot[] slots;
    // If count >= 0, it gives number of keys or if count < 0,
    // it indicates sealed object where ~count gives number of keys
    private int count;

    // cache; may be removed for smaller memory footprint
    private transient Slot lastAccess = REMOVED;

    // associated values are not serialized
    private transient volatile Hashtable associatedValues;

    private static final int SLOT_QUERY = 1;
    private static final int SLOT_MODIFY = 2;
    private static final int SLOT_REMOVE = 3;
    private static final int SLOT_MODIFY_GETTER_SETTER = 4;
    private static final int SLOT_MODIFY_CONST = 5;

    private static class Slot implements Serializable
    {
        static final long serialVersionUID = -3539051633409902634L;

        String name; // This can change due to caching
        int indexOrHash;
        private volatile short attributes;
        transient volatile byte wasDeleted;
        volatile Object value;
        transient volatile Slot next;

        Slot(String name, int indexOrHash, int attributes)
        {
            this.name = name;
            this.indexOrHash = indexOrHash;
            this.attributes = (short)attributes;
        }

        private void readObject(ObjectInputStream in)
            throws IOException, ClassNotFoundException
        {
            in.defaultReadObject();
            if (name != null) {
                indexOrHash = name.hashCode();
            }
        }

        final int getAttributes()
        {
            return attributes;
        }

        final synchronized void setAttributes(int value)
        {
            checkValidAttributes(value);
            attributes = (short)value;
        }

        final void checkNotReadonly()
        {
            if ((attributes & READONLY) != 0) {
                String str = (name != null ? name
                              : Integer.toString(indexOrHash));
                throw Context.reportRuntimeError1("msg.modify.readonly", str);
            }
        }

    }

    private static final class GetterSlot extends Slot
    {
        static final long serialVersionUID = -4900574849788797588L;

        Object getter;
        Object setter;

        GetterSlot(String name, int indexOrHash, int attributes)
        {
            super(name, indexOrHash, attributes);
        }
    }

    static void checkValidAttributes(int attributes)
    {
        final int mask = READONLY | DONTENUM | PERMANENT | UNINITIALIZED_CONST;
        if ((attributes & ~mask) != 0) {
            throw new IllegalArgumentException(String.valueOf(attributes));
        }
    }

    public ScriptableObject()
    {
    }

    public ScriptableObject(Scriptable scope, Scriptable prototype)
    {
        if (scope == null)
            throw new IllegalArgumentException();

        parentScopeObject = scope;
        prototypeObject = prototype;
    }

    /**
     * Return the name of the class.
     *
     * This is typically the same name as the constructor.
     * Classes extending ScriptableObject must implement this abstract
     * method.
     */
    public abstract String getClassName();

    /**
     * Returns true if the named property is defined.
     *
     * @param name the name of the property
     * @param start the object in which the lookup began
     * @return true if and only if the property was found in the object
     */
    public boolean has(String name, Scriptable start)
    {
        return null != getSlot(name, 0, SLOT_QUERY);
    }

    /**
     * Returns true if the property index is defined.
     *
     * @param index the numeric index for the property
     * @param start the object in which the lookup began
     * @return true if and only if the property was found in the object
     */
    public boolean has(int index, Scriptable start)
    {
        return null != getSlot(null, index, SLOT_QUERY);
    }

    /**
     * Returns the value of the named property or NOT_FOUND.
     *
     * If the property was created using defineProperty, the
     * appropriate getter method is called.
     *
     * @param name the name of the property
     * @param start the object in which the lookup began
     * @return the value of the property (may be null), or NOT_FOUND
     */
    public Object get(String name, Scriptable start)
    {
        return getImpl(name, 0, start);
    }

    /**
     * Returns the value of the indexed property or NOT_FOUND.
     *
     * @param index the numeric index for the property
     * @param start the object in which the lookup began
     * @return the value of the property (may be null), or NOT_FOUND
     */
    public Object get(int index, Scriptable start)
    {
        return getImpl(null, index, start);
    }

    /**
     * Sets the value of the named property, creating it if need be.
     *
     * If the property was created using defineProperty, the
     * appropriate setter method is called. <p>
     *
     * If the property's attributes include READONLY, no action is
     * taken.
     * This method will actually set the property in the start
     * object.
     *
     * @param name the name of the property
     * @param start the object whose property is being set
     * @param value value to set the property to
     */
    public void put(String name, Scriptable start, Object value)
    {
        if (putImpl(name, 0, start, value, EMPTY))
            return;

        if (start == this) throw Kit.codeBug();
        start.put(name, start, value);
    }

    /**
     * Sets the value of the indexed property, creating it if need be.
     *
     * @param index the numeric index for the property
     * @param start the object whose property is being set
     * @param value value to set the property to
     */
    public void put(int index, Scriptable start, Object value)
    {
        if (putImpl(null, index, start, value, EMPTY))
            return;

        if (start == this) throw Kit.codeBug();
        start.put(index, start, value);
    }

    /**
     * Removes a named property from the object.
     *
     * If the property is not found, or it has the PERMANENT attribute,
     * no action is taken.
     *
     * @param name the name of the property
     */
    public void delete(String name)
    {
        checkNotSealed(name, 0);
        accessSlot(name, 0, SLOT_REMOVE);
    }