/* Copyright (C) 2004 - 2008  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.internal.marshall;

import com.db4o.internal.*;
import com.db4o.marshall.*;


/**
 * @exclude
 */
public class ObjectHeaderContext extends AbstractReadContext implements MarshallingInfo, HandlerVersionContext{
    
    protected ObjectHeader _objectHeader;
    
	private int _aspectCount;
    
    public ObjectHeaderContext(Transaction transaction, ReadBuffer buffer, ObjectHeader objectHeader) {
        super(transaction, buffer);
        _objectHeader = objectHeader;
    }
    
    public final ObjectHeaderAttributes headerAttributes(){
        return _objectHeader._headerAttributes;
    }

    public final boolean isNull(int fieldIndex) {
        return headerAttributes().isNull(fieldIndex);
    }

    public final int handlerVersion() {
        return _objectHeader.handlerVersion();
    }
    
    public void beginSlot() {
        // do nothing
    }
    
    public ContextState saveState(){
        return new ContextState(offset());
    }
    
    public void restoreState(ContextState state){
        seek(state._offset);
    }

	public Object readFieldValue(ClassMetadata classMetadata, FieldMetadata field) {
		if(! classMetadata.seekToField(this, field)){
	        return null;
	    }
	   	return field.read(this);
	}

	public ClassMetadata classMetadata(){
	    return _objectHeader.classMetadata(); 
	}
	
	public int aspectCount() {
		return _aspectCount;
	}

	public void aspectCount(int count) {
		_aspectCount = count;
	}

}
