signedencoder.java

Java Communicating Agents是一个用于开发网络反应式信息agent的框架

/*
 * $Source: /home/data/cvsroot/src/jacomma/icm/io/imp/SignedEncoder.java,v $
 * $Revision: 1.6 $
 * $Date: 2000/10/28 20:09:07 $
 *
 * This file is part of the jacomma framework
 * Copyright (c) 2000 	Dimitrios Vyzovitis
 *			mailto:[e-mail]
 *			
 *
 *			
 *			
 *			
 *
 *	This library is free software; you can redistribute it and/or modify
 *	it under the terms of the GNU Library General Public License as published by
 *	the Free Software Foundation; either version 2 of the License, or
 *	(at your option) any later version.
 *
 *	This library 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 Library General Public License for more details.
 *
 *	You should have received a copy of the GNU Library General Public License
 *	along with this library; if not, write to the Free Software
 *	Foundation, Inc., 59 Temple Place, Suite 330, 
 *	Boston, MA  02111-1307  USA
 */

package jacomma.icm.io.imp;

import jacomma.icm.io.EncObject;
import jacomma.icm.io.EncObjectType;
import jacomma.icm.io.ObjectEncoder;
import jacomma.icm.io.EncObjectSignature;

/**
 * TBA
 **/
public class SignedEncoder extends EncoderTemplate {

	public SignedEncoder() {
		all_.add( EncObject.class );
	}

	public EncObject encode( Object obj, Object hint, boolean s ) {
		// hint is ignored
		EncObject val = (EncObject)obj;
		EncObject eo = null;
		CacheKey key = new CacheKey( obj );
		
		if ( (eo = (EncObject)cache_.get( key )) == null ) {
			String sig = EncObjectSignature.signatureOf( val );
			
			EncObject seo = Registry.instance
				.getEncoder( sig ).encode( sig );
			eo = (EncObject)cache_.try_put( key, new 
				EncObjectImp( EncObjectType.Signed, 
							  new EncObject[]{ seo, val } ) );
			
		}
		
		// encapsulated signed objects are signed as Any
		// However, since they do get the signature of the contained object
		// (setSignature below), wee need to explicitly check for their type
		// to avoid propagating the signature to the wrapper.
		eo.setSignature( EncObjectSignature.Any );
		// This call might look redundant here, but it can raise race conditions
		// if placed inside the cache-hit code.
				
		return s ? sign( eo ) : eo;
		
	}

}