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 java.util.Vector;
  
  import org.apache.bcel.generic.ConstantPoolGen;
  import org.apache.bcel.generic.PUSH;
  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;
  
  /**
   * @author Jacek Ambroziak
   * @author Santiago Pericas-Geertsen
   */
  final class ElementAvailableCall extends FunctionCall {
  
      public ElementAvailableCall(QName fname, Vector arguments) {
  	super(fname, arguments);
      }
  
      /**
       * Force the argument to this function to be a literal string.
       */
      public Type typeCheck(SymbolTable stable) throws TypeCheckError {
  	if (argument() instanceof LiteralExpr) {
  	    return _type = Type.Boolean;
  	}
  	ErrorMsg err = new ErrorMsg(ErrorMsg.NEED_LITERAL_ERR,
  				    "element-available", this);
  	throw new TypeCheckError(err);
      }
  
      /**
       * Returns an object representing the compile-time evaluation 
       * of an expression. We are only using this for function-available
       * and element-available at this time.
       */
      public Object evaluateAtCompileTime() {
  	return getResult() ? Boolean.TRUE : Boolean.FALSE;
      }
  
      /**
       * Returns the result that this function will return
       */
      public boolean getResult() {
  	try {
  	    final LiteralExpr arg = (LiteralExpr) argument();
  	    final String qname = arg.getValue();
  	    final int index = qname.indexOf(':');
  	    final String localName = (index > 0) ? 
  		qname.substring(index + 1) : qname;
  	    return getParser().elementSupported(arg.getNamespace(), 
  					        localName);
  	}
  	catch (ClassCastException e) {
  	    return false;
  	}
      }
  
      /**
       * Calls to 'element-available' are resolved at compile time since 
       * the namespaces declared in the stylsheet are not available at run
       * time. Consequently, arguments to this function must be literals.
       */
      public void translate(ClassGenerator classGen, MethodGenerator methodGen) {
  	final ConstantPoolGen cpg = classGen.getConstantPool();
  	final boolean result = getResult();
  	methodGen.getInstructionList().append(new PUSH(cpg, result));
      }
  }
  