booleanexpr.java

java1.6众多例子参考

/*
 * 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: BooleanExpr.java,v 1.2.4.1 2005/09/01 11:44:57 pvedula Exp $
 */

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

import com.sun.org.apache.bcel.internal.generic.ConstantPoolGen;
import com.sun.org.apache.bcel.internal.generic.GOTO;
import com.sun.org.apache.bcel.internal.generic.InstructionList;
import com.sun.org.apache.bcel.internal.generic.PUSH;
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;

/**
 * This class implements inlined calls to the XSLT standard functions 
 * true() and false().
 * @author Jacek Ambroziak
 * @author Santiago Pericas-Geertsen
 */
final class BooleanExpr extends Expression {
    private boolean _value;

    public BooleanExpr(boolean value) {
	_value = value;
    }

    public Type typeCheck(SymbolTable stable) throws TypeCheckError {
	_type = Type.Boolean;
	return _type;
    }

    public String toString() {
	return _value ? "true()" : "false()";
    }

    public boolean getValue() {
	return _value;
    }

    public boolean contextDependent() {
	return false;
    }

    public void translate(ClassGenerator classGen, MethodGenerator methodGen) {
	ConstantPoolGen cpg = classGen.getConstantPool();
	InstructionList il = methodGen.getInstructionList();
	il.append(new PUSH(cpg, _value));
    }

    public void translateDesynthesized(ClassGenerator classGen,
				       MethodGenerator methodGen) {
	final InstructionList il = methodGen.getInstructionList();
	if (_value) {
	    il.append(NOP);	// true list falls through
	}
	else {
	    _falseList.add(il.append(new GOTO(null)));
	}
    }
}