code: /*
   * Licensed to the Apache Software Foundation (ASF) under one
   * or more contributor license agreements. See the NOTICE file
   * distributed with this work for additional information
   * regarding copyright ownership. The ASF licenses this file
   * to you 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.
   */
  /*
   * $Id$
   */
  
  package org.apache.xalan.xsltc.compiler;
  
  import org.apache.bcel.generic.InstructionHandle;
  import org.apache.bcel.generic.InstructionList;
  import org.apache.xalan.xsltc.compiler.util.BooleanType;
  import org.apache.xalan.xsltc.compiler.util.ClassGenerator;
  import org.apache.xalan.xsltc.compiler.util.ErrorMsg;
  import org.apache.xalan.xsltc.compiler.util.MethodGenerator;
  import org.apache.xalan.xsltc.compiler.util.Type;
  import org.apache.xalan.xsltc.compiler.util.TypeCheckError;
  import org.apache.xalan.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());
      }
  }
  