/* Remove nil tokens from the input stream.
Copyright (c) 2006 The Regents of the University of California.
All rights reserved.
Permission is hereby granted, without written agreement and without
license or royalty fees, to use, copy, modify, and distribute this
software and its documentation for any purpose, provided that the above
copyright notice and the following two paragraphs appear in all copies
of this software.
IN NO EVENT SHALL THE UNIVERSITY OF CALIFORNIA BE LIABLE TO ANY PARTY
FOR DIRECT, INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES
ARISING OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN IF
THE UNIVERSITY OF CALIFORNIA HAS BEEN ADVISED OF THE POSSIBILITY OF
SUCH DAMAGE.
THE UNIVERSITY OF CALIFORNIA SPECIFICALLY DISCLAIMS ANY WARRANTIES,
INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE SOFTWARE
PROVIDED HEREUNDER IS ON AN "AS IS" BASIS, AND THE UNIVERSITY OF
CALIFORNIA HAS NO OBLIGATION TO PROVIDE MAINTENANCE, SUPPORT, UPDATES,
ENHANCEMENTS, OR MODIFICATIONS.
PT_COPYRIGHT_VERSION_2
COPYRIGHTENDKEY
*/
package ptolemy.actor.lib;
import ptolemy.data.Token;
import ptolemy.kernel.CompositeEntity;
import ptolemy.kernel.util.IllegalActionException;
import ptolemy.kernel.util.NameDuplicationException;
//////////////////////////////////////////////////////////////////////////
//// RemoveNilTokens
/**
Read in tokens and silently discard any tokens that are marked as
nil. Non-nill tokens are transferred to the output.
<p>In the real world, data sources sometimes pass null values
when data sources are sparsely populated. The null values are sometimes
called missing values. The Ptolemy II expression language represents
the missing or null tokens with the string "nil".
<p>This actor should not be used in the SDF domain because
the number of tokens sent to the output depends on the input.
@see ptolemy.data.Token#isNil()
@see ptolemy.data.Token#NIL
@author Christopher Brooks
@version $Id$
@since Ptolemy II 5.2
@Pt.ProposedRating Red (cxh)
@Pt.AcceptedRating Red (cxh)
*/
public class RemoveNilTokens extends Transformer {
/** Construct an actor with the given container and name.
* @param container The container.
* @param name The name of this actor.
* @exception IllegalActionException If the actor cannot be contained
* by the proposed container.
* @exception NameDuplicationException If the container already has an
* actor with this name.
*/
public RemoveNilTokens(CompositeEntity container, String name)
throws NameDuplicationException, IllegalActionException {
super(container, name);
}
///////////////////////////////////////////////////////////////////
//// public methods ////
/** Read tokens from the input and output all non-nil (non-missing)
* tokens. If we get a nil (aka missing) token, then the token
* is read, but no output is sent. Thus, this actor cannot
* be used in the SDF domain.
* @exception IllegalActionException If there is no director.
*/
public void fire() throws IllegalActionException {
super.fire();
if (input.hasToken(0)) {
Token in = input.get(0);
if (!in.isNil()) {
output.send(0, in);
}
}
}
}