if.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: If.java,v 1.2.4.1 2005/09/01 15:39:47 pvedula Exp $
 */

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

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.BooleanType;
import com.sun.org.apache.xalan.internal.xsltc.compiler.util.ClassGenerator;
import com.sun.org.apache.xalan.internal.xsltc.compiler.util.ErrorMsg;
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;
import com.sun.org.apache.xalan.internal.xsltc.compiler.util.Util;

/**
 * @author Jacek Ambroziak
 * @author Santiago Pericas-Geertsen
 * @author Morten Jorgensen
 */
final class If extends Instruction {

    private Expression _test;
    private boolean    _ignore = false;

    /**
     * Display the contents of this element
     */
    public void display(int indent) {
	indent(indent);
	Util.println("If");
	indent(indent + IndentIncrement);
	System.out.print("test ");
	Util.println(_test.toString());
	displayContents(indent + IndentIncrement);
    }

    /**
     * Parse the "test" expression and contents of this element.
     */
    public void parseContents(Parser parser) {
	// Parse the "test" expression
	_test = parser.parseExpression(this, "test", null);

        // Make sure required attribute(s) have been set
        if (_test.isDummy()) {
	    reportError(this, parser, ErrorMsg.REQUIRED_ATTR_ERR, "test");
	    return;
        }

	// Ignore xsl:if when test is false (function-available() and
	// element-available())
	Object result = _test.evaluateAtCompileTime();
	if (result != null && result instanceof Boolean) {
	    _ignore = !((Boolean) result).booleanValue();
	}

	parseChildren(parser);
    }

    /**
     * Type-check the "test" expression and contents of this element.
     * The contents will be ignored if we know the test will always fail.
     */
    public Type typeCheck(SymbolTable stable) throws TypeCheckError {
	// Type-check the "test" expression
	if (_test.typeCheck(stable) instanceof BooleanType == false) {
	    _test = new CastExpr(_test, Type.Boolean);
	}
	// Type check the element contents
	if (!_ignore) {
	    typeCheckContents(stable);
	}
	return Type.Void;
    }

    /**
     * Translate the "test" expression and contents of this element.
     * The contents will be ignored if we know the test will always fail.
     */
    public void translate(ClassGenerator classGen, MethodGenerator methodGen) {
	final InstructionList il = methodGen.getInstructionList();
	_test.translateDesynthesized(classGen, methodGen);
	// remember end of condition
	final InstructionHandle truec = il.getEnd();
	if (!_ignore) {
	    translateContents(classGen, methodGen);
	}
	_test.backPatchFalseList(il.append(NOP));
	_test.backPatchTrueList(truec.getNext());
    }
}