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package com.sun.msv.reader.trex;
import com.sun.msv.grammar.Expression;
import com.sun.msv.grammar.ReferenceExp;
import com.sun.msv.reader.ExpressionOwner;
import com.sun.msv.reader.GrammarReader;
import com.sun.msv.reader.SimpleState;
import com.sun.msv.reader.State;
import com.sun.msv.util.StartTagInfo;
/**
* parses <define> declaration.
*
* @author <a href="mailto:kohsuke.kawaguchi@eng.sun.com">Kohsuke KAWAGUCHI</a>
*/
public abstract class DefineState extends SimpleState implements ExpressionOwner {
/**
* expression object that is being created.
* See {@link #castPattern} and {@link #annealPattern} methods
* for how will a pattern be created.
*/
protected Expression exp = null; // or Expression.epsilon if <define /> is allowed.
/**
* Container to which the expression will be assigned.
*/
private ReferenceExp ref;
/**
* Obtains a {@link ReferenceExp} that represents the target
* pattern block.
*
* @return null
* If there was an error in the input, this method may
* return null.
*/
public final ReferenceExp getRef() {
return ref;
}
/** receives a Pattern object that is contained in this element. */
public final void onEndChild( Expression child ) {
if( exp==null ) { // first one.
exp = child;
} else {
exp = reader.pool.createSequence(exp,child);
}
}
protected void startSelf() {
super.startSelf();
ref = getReference();
}
protected void endSelf() {
if( exp==null ) {
reader.reportError( GrammarReader.ERR_MISSING_CHILD_EXPRESSION );
exp = Expression.nullSet;
// recover by assuming some pattern.
}
if(ref==null) return; // error. abort.
final TREXBaseReader reader = (TREXBaseReader)this.reader;
final String combine = startTag.getCollapsedAttribute("combine");
exp = callInterceptExpression(exp);
// combine two patterns
Expression newexp = doCombine( ref, exp, combine );
if( newexp==null )
reader.reportError( TREXBaseReader.ERR_BAD_COMBINE, combine );
// recover by ignoring this definition
else
ref.exp = newexp;
reader.setDeclaredLocationOf(ref);
((ExpressionOwner)parentState).onEndChild(ref);
}
protected State createChildState( StartTagInfo tag ) {
return reader.createExpressionChildState(this,tag);
}
/**
*
* @return null in case of error.
*/
protected ReferenceExp getReference() {
final String name = startTag.getCollapsedAttribute("name");
if(name==null) {
// name attribute is required.
reader.reportError( TREXBaseReader.ERR_MISSING_ATTRIBUTE,
"ref","name");
return null;
}
final TREXBaseReader reader = (TREXBaseReader)this.reader;
return reader.grammar.namedPatterns.getOrCreate(name);
}
/**
* combines two expressions into one as specified by the combine parameter,
* and returns a new expression.
*
* If the combine parameter is invalid, then return null.
*/
protected abstract Expression doCombine( ReferenceExp baseExp, Expression newExp, String combine );
}