/*
* @(#)$Id: AttributePruner.java 1566 2003-06-09 20:37:49Z kk122374 $
*
* Copyright 2001 Sun Microsystems, Inc. All Rights Reserved.
*
* This software is the proprietary information of Sun Microsystems, Inc.
* Use is subject to license terms.
*
*/
package com.sun.msv.verifier.regexp;
import com.sun.msv.grammar.AttributeExp;
import com.sun.msv.grammar.ElementExp;
import com.sun.msv.grammar.Expression;
import com.sun.msv.grammar.ExpressionCloner;
import com.sun.msv.grammar.ExpressionPool;
import com.sun.msv.grammar.OtherExp;
import com.sun.msv.grammar.ReferenceExp;
/**
* Creates an expression whose AttributeExp is completely replaced by nullSet.
*
* This step is used to remove all unconsumed AttributeExp from the expression.
*
* @author <a href="mailto:kohsuke.kawaguchi@eng.sun.com">Kohsuke KAWAGUCHI</a>
*/
public class AttributePruner extends ExpressionCloner
{
public AttributePruner( ExpressionPool pool ) { super(pool); }
public Expression onAttribute( AttributeExp exp ) { return Expression.nullSet; }
public Expression onRef( ReferenceExp exp ) { return exp.exp.visit(this); }
public Expression onOther( OtherExp exp ) { return exp.exp.visit(this); }
public Expression onElement( ElementExp exp ) { return exp; }
public final Expression prune( Expression exp ) {
// check the cache first.
OptimizationTag ot = (OptimizationTag)exp.verifierTag;
if(ot==null) exp.verifierTag = ot = new OptimizationTag();
else
if( ot.attributePrunedExpression!=null )
return ot.attributePrunedExpression;
// cache miss. compute it.
Expression r = exp.visit(this);
ot.attributePrunedExpression = r; // cache this result
return r;
}
}