/*
* @(#)$Id: ResidualCalculator.java 1605 2003-10-20 18:21:43Z kohsuke $
*
* 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.ChoiceExp;
import com.sun.msv.grammar.ConcurExp;
import com.sun.msv.grammar.DataExp;
import com.sun.msv.grammar.ElementExp;
import com.sun.msv.grammar.Expression;
import com.sun.msv.grammar.ExpressionPool;
import com.sun.msv.grammar.ExpressionVisitorExpression;
import com.sun.msv.grammar.InterleaveExp;
import com.sun.msv.grammar.ListExp;
import com.sun.msv.grammar.MixedExp;
import com.sun.msv.grammar.OneOrMoreExp;
import com.sun.msv.grammar.OtherExp;
import com.sun.msv.grammar.ReferenceExp;
import com.sun.msv.grammar.SequenceExp;
import com.sun.msv.grammar.ValueExp;
/**
* computes regular expression derivative.
*
* this class receives a regexp and computes the right language after eating
* given token.
*
* @author <a href="mailto:kohsuke.kawaguchi@eng.sun.com">Kohsuke KAWAGUCHI</a>
*/
public class ResidualCalculator implements ExpressionVisitorExpression {
protected Token token;
protected final ExpressionPool pool;
public ResidualCalculator( ExpressionPool pool ) { this.pool=pool; }
/** compute the residual */
final Expression calcResidual( Expression exp, ElementToken token ) {
if( token.acceptedPatterns!=null && token.acceptedPatterns.length==1 ) {
// we can use optimization table
OptimizationTag ot;
if(exp.verifierTag==null)
exp.verifierTag = ot = new OptimizationTag();
else {
ot = (OptimizationTag)exp.verifierTag;
Expression residual = (Expression)ot.simpleElementTokenResidual.get(token.acceptedPatterns[0]);
if(residual!=null)
return residual; // cache hit.
}
this.token = token;
Expression residual = exp.visit(this);
// cache this residual
ot.simpleElementTokenResidual.put(token.acceptedPatterns[0],residual);
return residual;
}
// no chance of using cache.
this.token = token;
return exp.visit(this);
}
/** compute the residual */
public final Expression calcResidual( Expression exp, Token token ) {
if( token instanceof ElementToken )
return calcResidual(exp,(ElementToken)token);
this.token=token;
Expression r = exp.visit(this);
// if token is ignorable, make expression as so.
if( token.isIgnorable() )
r = pool.createChoice(r,exp);
return r;
}
public Expression onAttribute( AttributeExp exp ) {
if(token.match(exp)) return Expression.epsilon;
else return Expression.nullSet;
}
public Expression onChoice( ChoiceExp exp ) {
return pool.createChoice( exp.exp1.visit(this), exp.exp2.visit(this) );
}
public Expression onElement( ElementExp exp ) {
if(token.match(exp)) return Expression.epsilon;
else return Expression.nullSet;
}
public Expression onOneOrMore( OneOrMoreExp exp ) {
return pool.createSequence(
exp.exp.visit(this),
pool.createZeroOrMore(exp.exp) );
}
public Expression onMixed( MixedExp exp ) {
// if token can be interpreted as anyString, eat it.
if( token.matchAnyString() ) return exp;
// otherwise, it must be consumed by the children.
return pool.createMixed( exp.exp.visit(this) );
}
public Expression onEpsilon() {
return Expression.nullSet;
}
public Expression onNullSet() {
return Expression.nullSet;
}
public Expression onAnyString() {
// anyString is not reduced to epsilon.
// it remains there even after consuming StringToken.
if(token.matchAnyString()) return Expression.anyString;
else 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 onSequence( SequenceExp exp ) {
Expression r = pool.createSequence( exp.exp1.visit(this), exp.exp2 );
if( exp.exp1.isEpsilonReducible() )
return pool.createChoice( r, exp.exp2.visit(this) );
else
return r;
}
public Expression onData( DataExp exp ) {
if(token.match(exp)) return Expression.epsilon;
else return Expression.nullSet;
}
public Expression onValue( ValueExp exp ) {
if(token.match(exp)) return Expression.epsilon;
else return Expression.nullSet;
}
public Expression onList( ListExp exp ) {
if(token.match(exp)) return Expression.epsilon;
else return Expression.nullSet;
}
public Expression onConcur( ConcurExp exp ) {
return pool.createConcur(
exp.exp1.visit(this), exp.exp2.visit(this) );
}
public Expression onInterleave( InterleaveExp exp ) {
return pool.createChoice(
pool.createInterleave( exp.exp1.visit(this), exp.exp2 ),
pool.createInterleave( exp.exp1, exp.exp2.visit(this) ) );
}
}