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/* Copyright (C) 2004 - 2005  db4objects Inc.  http://www.db4o.com

This file is part of the db4o open source object database.

db4o is free software; you can redistribute it and/or modify it under
the terms of version 2 of the GNU General Public License as published
by the Free Software Foundation and as clarified by db4objects' GPL 
interpretation policy, available at
http://www.db4o.com/about/company/legalpolicies/gplinterpretation/
Alternatively you can write to db4objects, Inc., 1900 S Norfolk Street,
Suite 350, San Mateo, CA 94403, USA.

db4o is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
for more details.

You should have received a copy of the GNU General Public License along
with this program; if not, write to the Free Software Foundation, Inc.,
59 Temple Place - Suite 330, Boston, MA  02111-1307, USA. */
package com.db4o;

import com.db4o.ext.*;
import com.db4o.types.*;

/**
 * no reading
 * no writing
 * no updates
 * no weak references
 * navigation by ID only both sides need synchronised ClassCollections and
 * MetaInformationCaches
 * 
 */
public class YapObjectCarrier extends YapMemoryFile {
	
	YapObjectCarrier (YapStream a_callingStream, MemoryFile memoryFile) {
	    super(a_callingStream, memoryFile);
	}
	
	void initialize0b(){
		// do nothing
	}
	
	void initialize1(){
	    i_handlers = i_parent.i_handlers;
		i_classCollection = i_parent.i_classCollection;
		i_config = i_parent.i_config;
		i_references = new YapReferences(this);
		initialize2();
	}
	
	void initialize2NObjectCarrier(){
		// do nothing
	}
	
	void initializeEssentialClasses(){
	    // do nothing
	}
	
	void initialize4NObjectCarrier(){
		// do nothing
	}
	
	void initNewClassCollection(){
	    // do nothing
	}
	
    boolean canUpdate(){
        return false;
    }
    
	void configureNewFile() {
	    i_writeAt = HEADER_LENGTH;
	}
		
    public boolean close() {
        
        // TODO: An object carrier can simply be gc'd.
        // It does not need to be cleaned up.
        
        synchronized (i_lock) {
            boolean ret = close1();
            if (ret) {
				i_config = null;
            }
            return ret;
        }
    }
	
	void createTransaction() {
		i_trans = new TransactionObjectCarrier(this, null);
		i_systemTrans = i_trans;
	}
	
	long currentVersion(){
	    return 0;
	}
    
    public Db4oType db4oTypeStored(Transaction a_trans, Object a_object) {
        return null;
    }
	
    public boolean dispatchsEvents() {
        return false;
    }
	
    protected void finalize() {
        // do nothing
    }
	
	
	public final void free(int a_address, int a_length){
		// do nothing
	}
	
	public int getSlot(int a_length){
		int address = i_writeAt;
		i_writeAt += a_length;
		return address;
	}
	
	public Db4oDatabase identity() {
	    return i_parent.identity();
	}
	
	boolean maintainsIndices(){
		return false;
	}
	
	void message(String msg){
		// do nothing
	}
	
	boolean needsLockFileThread() {
	    return false;
	}
	
	public void raiseVersion(long a_minimumVersion){
	    // do nothing
	}
	
	void readThis(){
		// do nothing
	}
	
	boolean stateMessages(){
		return false; // overridden to do nothing in YapObjectCarrier
	}
	
	void write(boolean shuttingDown) {
		checkNeededUpdates();
		writeDirty();
		getTransaction().commit();
	}
	
	final void writeHeader(boolean shuttingDown) {
	    // do nothing
	}
	
    void writeBootRecord() {
        // do nothing
    }

}