objectdbimpl.java

来自「SRI international 发布的OAA框架软件」· Java 代码 · 共 131 行

/* $Id: ObjectDBImpl.java,v 1.3 2003/09/30 01:44:44 giuli Exp $*/
/**************************************************************************
 * Copyright 2001, 2002 SRI International. All rights reserved.
 *
 * The material contained in this file is confidential and proprietary to SRI
 * International and may not be reproduced, published, or disclosed to others
 * without authorization from SRI International.
 *
 * DISCLAIMER OF WARRANTIES
 *
 * SRI International MAKES NO REPRESENTATIONS OR WARRANTIES ABOUT THE
 * SUITABILITY OF THE SOFTWARE, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT
 * LIMITED TO THE IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
 * PARTICULAR PURPOSE, OR NON-INFRINGEMENT. SRI International SHALL NOT BE
 * LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE AS A RESULT OF USING, MODIFYING
 * OR DISTRIBUTING THIS SOFTWARE
 **************************************************************************/
package com.sri.sedc.javanetbridge;

import java.util.List;
import java.util.ArrayList;

/**
 * Default implementation of ObjectDB.
 */
class ObjectDBImpl implements ObjectDB {
    // Note: Maps cannot be used here, because they rely on equals and hashCode.
    // Also, indexOf is not used in the lists for the same reason. Object references
    // in this database are stored per object, and an id is not valid for more than
    // one object.
    private List objects = new ArrayList(100);
    private List ids = new ArrayList(100);
    private List refCounts = new ArrayList(100);
    private volatile int objIdCounter = 0;

    public ObjectDBImpl() {
    }

    public synchronized int addObjRef(Object obj) {
        int indx = getObjIndx(obj);
        int id = -1;
        if (indx == -1) {
            // Add the object
            objIdCounter++;
            objects.add(obj);
            ids.add(new Integer(id = objIdCounter));
            refCounts.add(new Integer(1));
        } else {
            int refCount = ((Integer)refCounts.get(indx)).intValue();
            refCounts.set(indx, new Integer(refCount + 1));
            id = ((Integer)ids.get(indx)).intValue();
        }
        return id;
    }

    public synchronized void clear() {
        objects.clear();
        ids.clear();
        refCounts.clear();
        objIdCounter = 0;
    }

    public synchronized List getObjects() {
        List ret = new ArrayList(objects.size());
        ret.addAll(objects);
        return ret;
    }

    public synchronized int releaseObjRef(Object obj) {
        return releaseObjRefImpl(getObjIndx(obj));
    }

    private int releaseObjRefImpl(int indx) {
        if (indx >= 0) {
            int refCount = ((Integer)refCounts.get(indx)).intValue();
            if (refCount == 1) {
                // delete the object
                objects.remove(indx);
                ids.remove(indx);
                refCounts.remove(indx);
                return 0;
            } else {
                // decrement the reference count
                refCount--;
                refCounts.set(indx, new Integer(refCount));
                return refCount;
            }
        }

        return -1;
    }

    public synchronized int releaseObjRef(int id) {
        return releaseObjRefImpl(getObjIndx(id));
    }

    public synchronized Object getObjFromId(int id) throws ObjectNotFoundException {
        int indx = getObjIndx(id);
        if (indx == -1) {
            throw new ObjectNotFoundException("ObjectDB: No object entry exists for id " + id);
        }
        return objects.get(indx);
    }

    public synchronized int getIdFromObj(Object obj) throws ObjectNotFoundException {
        int indx = getObjIndx(obj);
        if (indx == -1) {
            throw new ObjectNotFoundException("ObjectDB:getIdFromObj: No object entry exists");
        }
        return ((Integer)ids.get(indx)).intValue();
    }

    private int getObjIndx(Object obj) {
        for (int i = 0; i < objects.size(); i++) {
            if (obj == objects.get(i)) {
                return i;
            }
        }
        return -1;
    }

    private int getObjIndx(int id) {
        for (int i = 0; i < ids.size(); i++) {
            if (id == ((Integer)ids.get(i)).intValue()) {
                return i;
            }
        }
        return -1;
    }
}