src/com/sun/org/apache/xalan/internal/xsltc/compiler/AlternativePattern.java

/*
 * reserved comment block
 * DO NOT REMOVE OR ALTER!
 */
/*
 * Copyright 2001-2004 The Apache Software Foundation.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
/*
 * $Id: AlternativePattern.java,v 1.2.4.1 2005/09/01 09:18:46 pvedula Exp $
 */

package com.sun.org.apache.xalan.internal.xsltc.compiler;

import com.sun.org.apache.bcel.internal.generic.GOTO;
import com.sun.org.apache.bcel.internal.generic.InstructionHandle;
import com.sun.org.apache.bcel.internal.generic.InstructionList;
import com.sun.org.apache.xalan.internal.xsltc.compiler.util.ClassGenerator;
import com.sun.org.apache.xalan.internal.xsltc.compiler.util.MethodGenerator;
import com.sun.org.apache.xalan.internal.xsltc.compiler.util.Type;
import com.sun.org.apache.xalan.internal.xsltc.compiler.util.TypeCheckError;

/**
 * @author Jacek Ambroziak
 * @author Santiago Pericas-Geertsen
 */
final class AlternativePattern extends Pattern {
    private final Pattern _left;
    private final Pattern _right;

    /**
     * Construct an alternative pattern. The method <code>setParent</code>
     * should not be called in this case.
     */
    public AlternativePattern(Pattern left, Pattern right) {
        _left = left;
        _right = right;
    }

    public void setParser(Parser parser) {
        super.setParser(parser);
        _left.setParser(parser);
        _right.setParser(parser);
    }

    public Pattern getLeft() {
        return _left;
    }

    public Pattern getRight() {
        return _right;
    }

    /**
     * The type of an '|' is not really defined, hence null is returned.
     */
    public Type typeCheck(SymbolTable stable) throws TypeCheckError {
        _left.typeCheck(stable);
        _right.typeCheck(stable);
        return null;
    }

    public double getPriority() {
        double left = _left.getPriority();
        double right = _right.getPriority();

        if (left < right)
            return(left);
        else
            return(right);
    }

    public String toString() {
        return "alternative(" + _left + ", " + _right + ')';
    }

    public void translate(ClassGenerator classGen, MethodGenerator methodGen) {
        final InstructionList il = methodGen.getInstructionList();

        _left.translate(classGen, methodGen);
        final InstructionHandle gotot = il.append(new GOTO(null));
        il.append(methodGen.loadContextNode());
        _right.translate(classGen, methodGen);

        _left._trueList.backPatch(gotot);
        _left._falseList.backPatch(gotot.getNext());

        _trueList.append(_right._trueList.add(gotot));
        _falseList.append(_right._falseList);
    }
}