idscriptableobject.java

java中比较著名的js引擎当属mozilla开源的rhino

/* -*- Mode: java; tab-width: 4; indent-tabs-mode: 1; 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):
 *   Igor Bukanov
 *
 * 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
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 * 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;

import java.io.*;

/**
Base class for native object implementation that uses IdFunctionObject to export its methods to script via <class-name>.prototype object.

Any descendant should implement at least the following methods:
    findInstanceIdInfo
    getInstanceIdName
    execIdCall
    methodArity

To define non-function properties, the descendant should override
    getInstanceIdValue
    setInstanceIdValue
to get/set property value and provide its default attributes.


To customize initializition of constructor and protype objects, descendant
may override scopeInit or fillConstructorProperties methods.

*/
public abstract class IdScriptableObject extends ScriptableObject
    implements IdFunctionCall
{
    private transient volatile PrototypeValues prototypeValues;

    private static final class PrototypeValues implements Serializable
    {
        static final long serialVersionUID = 3038645279153854371L;

        private static final int VALUE_SLOT = 0;
        private static final int NAME_SLOT = 1;
        private static final int SLOT_SPAN = 2;

        private IdScriptableObject obj;
        private Object tag;
        private int maxId;
        private volatile Object[] valueArray;
        private volatile short[] attributeArray;
        private volatile int lastFoundId = 1;

        // The following helps to avoid creation of valueArray during runtime
        // initialization for common case of "constructor" property
        int constructorId;
        private IdFunctionObject constructor;
        private short constructorAttrs;

        PrototypeValues(IdScriptableObject obj, int maxId)
        {
            if (obj == null) throw new IllegalArgumentException();
            if (maxId < 1) throw new IllegalArgumentException();
            this.obj = obj;
            this.maxId = maxId;
        }

        final int getMaxId()
        {
            return maxId;
        }

        final void initValue(int id, String name, Object value, int attributes)
        {
            if (!(1 <= id && id <= maxId))
                throw new IllegalArgumentException();
            if (name == null)
                throw new IllegalArgumentException();
            if (value == NOT_FOUND)
                throw new IllegalArgumentException();
            ScriptableObject.checkValidAttributes(attributes);
            if (obj.findPrototypeId(name) != id)
                throw new IllegalArgumentException(name);

            if (id == constructorId) {
                if (!(value instanceof IdFunctionObject)) {
                    throw new IllegalArgumentException("consructor should be initialized with IdFunctionObject");
                }
                constructor = (IdFunctionObject)value;
                constructorAttrs = (short)attributes;
                return;
            }

            initSlot(id, name, value, attributes);
        }

        private void initSlot(int id, String name, Object value,
                              int attributes)
        {
            Object[] array = valueArray;
            if (array == null)
                throw new IllegalStateException();

            if (value == null) {
                value = UniqueTag.NULL_VALUE;
            }
            int index = (id - 1) * SLOT_SPAN;
            synchronized (this) {
                Object value2 = array[index + VALUE_SLOT];
                if (value2 == null) {
                    array[index + VALUE_SLOT] = value;
                    array[index + NAME_SLOT] = name;
                    attributeArray[id - 1] = (short)attributes;
                } else {
                    if (!name.equals(array[index + NAME_SLOT]))
                         throw new IllegalStateException();
                }
            }
        }

        final IdFunctionObject createPrecachedConstructor()
        {
            if (constructorId != 0) throw new IllegalStateException();
            constructorId = obj.findPrototypeId("constructor");
            if (constructorId == 0) {
                throw new IllegalStateException(
                    "No id for constructor property");
            }
            obj.initPrototypeId(constructorId);
            if (constructor == null) {
                throw new IllegalStateException(
                    obj.getClass().getName()+".initPrototypeId() did not "
                    +"initialize id="+constructorId);
            }
            constructor.initFunction(obj.getClassName(),
                                     ScriptableObject.getTopLevelScope(obj));
            constructor.markAsConstructor(obj);
            return constructor;
        }

        final int findId(String name)
        {
            Object[] array = valueArray;
            if (array == null) {
                return obj.findPrototypeId(name);
            }
            int id = lastFoundId;
            if (name == array[(id - 1) * SLOT_SPAN + NAME_SLOT]) {
                return id;
            }
            id = obj.findPrototypeId(name);
            if (id != 0) {
                int nameSlot = (id - 1) * SLOT_SPAN + NAME_SLOT;
                // Make cache to work!
                array[nameSlot] = name;
                lastFoundId = id;
            }
            return id;
        }

        final boolean has(int id)
        {
            Object[] array = valueArray;
            if (array == null) {
                // Not yet initialized, assume all exists
                return true;
            }
            int valueSlot = (id  - 1) * SLOT_SPAN + VALUE_SLOT;
            Object value = array[valueSlot];
            if (value == null) {
                // The particular entry has not been yet initialized
                return true;
            }
            return value != NOT_FOUND;
        }

        final Object get(int id)
        {
            Object value = ensureId(id);
            if (value == UniqueTag.NULL_VALUE) {
                value = null;
            }
            return value;
        }

        final void set(int id, Scriptable start, Object value)
        {
            if (value == NOT_FOUND) throw new IllegalArgumentException();
            ensureId(id);
            int attr = attributeArray[id - 1];
            if ((attr & READONLY) == 0) {
                if (start == obj) {
                    if (value == null) {
                        value = UniqueTag.NULL_VALUE;
                    }
                    int valueSlot = (id  - 1) * SLOT_SPAN + VALUE_SLOT;
                    synchronized (this) {
                        valueArray[valueSlot] = value;
                    }
                }
                else {
                    int nameSlot = (id  - 1) * SLOT_SPAN + NAME_SLOT;
                    String name = (String)valueArray[nameSlot];
                    start.put(name, start, value);
                }
            }
        }

        final void delete(int id)
        {
            ensureId(id);
            int attr = attributeArray[id - 1];
            if ((attr & PERMANENT) == 0) {
                int valueSlot = (id  - 1) * SLOT_SPAN + VALUE_SLOT;
                synchronized (this) {
                    valueArray[valueSlot] = NOT_FOUND;
                    attributeArray[id - 1] = EMPTY;
                }
            }
        }

        final int getAttributes(int id)
        {
            ensureId(id);
            return attributeArray[id - 1];
        }

        final void setAttributes(int id, int attributes)
        {
            ScriptableObject.checkValidAttributes(attributes);
            ensureId(id);
            synchronized (this) {
                attributeArray[id - 1] = (short)attributes;
            }
        }

        final Object[] getNames(boolean getAll, Object[] extraEntries)
        {
            Object[] names = null;
            int count = 0;
            for (int id = 1; id <= maxId; ++id) {
                Object value = ensureId(id);
                if (getAll || (attributeArray[id - 1] & DONTENUM) == 0) {
                    if (value != NOT_FOUND) {
                        int nameSlot = (id  - 1) * SLOT_SPAN + NAME_SLOT;
                        String name = (String)valueArray[nameSlot];
                        if (names == null) {
                            names = new Object[maxId];
                        }
                        names[count++] = name;
                    }
                }
            }
            if (count == 0) {
                return extraEntries;
            } else if (extraEntries == null || extraEntries.length == 0) {
                if (count != names.length) {
                    Object[] tmp = new Object[count];
                    System.arraycopy(names, 0, tmp, 0, count);
                    names = tmp;
                }
                return names;
            } else {
                int extra = extraEntries.length;
                Object[] tmp = new Object[extra + count];
                System.arraycopy(extraEntries, 0, tmp, 0, extra);
                System.arraycopy(names, 0, tmp, extra, count);
                return tmp;
            }
        }

        private Object ensureId(int id)
        {
            Object[] array = valueArray;
            if (array == null) {
                synchronized (this) {
                    array = valueArray;
                    if (array == null) {
                        array = new Object[maxId * SLOT_SPAN];
                        valueArray = array;
                        attributeArray = new short[maxId];
                    }
                }
            }
            int valueSlot = (id  - 1) * SLOT_SPAN + VALUE_SLOT;
            Object value = array[valueSlot];
            if (value == null) {
                if (id == constructorId) {
                    initSlot(constructorId, "constructor",
                             constructor, constructorAttrs);
                    constructor = null; // no need to refer it any longer
                } else {
                    obj.initPrototypeId(id);
                }
                value = array[valueSlot];
                if (value == null) {
                    throw new IllegalStateException(
                        obj.getClass().getName()+".initPrototypeId(int id) "
                        +"did not initialize id="+id);
                }
            }
            return value;
        }
    }

    public IdScriptableObject()
    {
    }

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

    protected final Object defaultGet(String name)
    {
        return super.get(name, this);
    }

    protected final void defaultPut(String name, Object value)
    {
        super.put(name, this, value);
    }

    public boolean has(String name, Scriptable start)
    {
        int info = findInstanceIdInfo(name);
        if (info != 0) {
            int attr = (info >>> 16);
            if ((attr & PERMANENT) != 0) {
                return true;
            }
            int id = (info & 0xFFFF);
            return NOT_FOUND != getInstanceIdValue(id);
        }
        if (prototypeValues != null) {
            int id = prototypeValues.findId(name);
            if (id != 0) {
                return prototypeValues.has(id);
            }