1 /*
   2  * reserved comment block
   3  * DO NOT REMOVE OR ALTER!
   4  */
   5 /*
   6  * Copyright 2001-2004 The Apache Software Foundation.
   7  *
   8  * Licensed under the Apache License, Version 2.0 (the "License");
   9  * you may not use this file except in compliance with the License.
  10  * You may obtain a copy of the License at
  11  *
  12  *     http://www.apache.org/licenses/LICENSE-2.0
  13  *
  14  * Unless required by applicable law or agreed to in writing, software
  15  * distributed under the License is distributed on an "AS IS" BASIS,
  16  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  17  * See the License for the specific language governing permissions and
  18  * limitations under the License.
  19  */
  20 /*
  21  * $Id: ElementAvailableCall.java,v 1.2.4.1 2005/09/01 14:13:01 pvedula Exp $
  22  */
  23 
  24 package com.sun.org.apache.xalan.internal.xsltc.compiler;
  25 
  26 import java.util.Vector;
  27 
  28 import com.sun.org.apache.bcel.internal.generic.ConstantPoolGen;
  29 import com.sun.org.apache.bcel.internal.generic.PUSH;
  30 import com.sun.org.apache.xalan.internal.xsltc.compiler.util.ClassGenerator;
  31 import com.sun.org.apache.xalan.internal.xsltc.compiler.util.ErrorMsg;
  32 import com.sun.org.apache.xalan.internal.xsltc.compiler.util.MethodGenerator;
  33 import com.sun.org.apache.xalan.internal.xsltc.compiler.util.Type;
  34 import com.sun.org.apache.xalan.internal.xsltc.compiler.util.TypeCheckError;
  35 
  36 /**
  37  * @author Jacek Ambroziak
  38  * @author Santiago Pericas-Geertsen
  39  */
  40 final class ElementAvailableCall extends FunctionCall {
  41 
  42     public ElementAvailableCall(QName fname, Vector arguments) {
  43         super(fname, arguments);
  44     }
  45 
  46     /**
  47      * Force the argument to this function to be a literal string.
  48      */
  49     public Type typeCheck(SymbolTable stable) throws TypeCheckError {
  50         if (argument() instanceof LiteralExpr) {
  51             return _type = Type.Boolean;
  52         }
  53         ErrorMsg err = new ErrorMsg(ErrorMsg.NEED_LITERAL_ERR,
  54                                     "element-available", this);
  55         throw new TypeCheckError(err);
  56     }
  57 
  58     /**
  59      * Returns an object representing the compile-time evaluation
  60      * of an expression. We are only using this for function-available
  61      * and element-available at this time.
  62      */
  63     public Object evaluateAtCompileTime() {
  64         return getResult() ? Boolean.TRUE : Boolean.FALSE;
  65     }
  66 
  67     /**
  68      * Returns the result that this function will return
  69      */
  70     public boolean getResult() {
  71         try {
  72             final LiteralExpr arg = (LiteralExpr) argument();
  73             final String qname = arg.getValue();
  74             final int index = qname.indexOf(':');
  75             final String localName = (index > 0) ?
  76                 qname.substring(index + 1) : qname;
  77             return getParser().elementSupported(arg.getNamespace(),
  78                                                 localName);
  79         }
  80         catch (ClassCastException e) {
  81             return false;
  82         }
  83     }
  84 
  85     /**
  86      * Calls to 'element-available' are resolved at compile time since
  87      * the namespaces declared in the stylsheet are not available at run
  88      * time. Consequently, arguments to this function must be literals.
  89      */
  90     public void translate(ClassGenerator classGen, MethodGenerator methodGen) {
  91         final ConstantPoolGen cpg = classGen.getConstantPool();
  92         final boolean result = getResult();
  93         methodGen.getInstructionList().append(new PUSH(cpg, result));
  94     }
  95 }