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.xpath.functions;
  
  import org.apache.xalan.res.XSLMessages;
  import org.apache.xml.dtm.DTM;
  import org.apache.xml.utils.XMLString;
  import org.apache.xpath.XPathContext;
  import org.apache.xpath.objects.XString;
  import org.apache.xpath.res.XPATHErrorResources;
  
  /**
   * Base class for functions that accept one argument that can be defaulted if
   * not specified.
   * @xsl.usage advanced
   */
  public class FunctionDef1Arg extends FunctionOneArg
  {
      static final long serialVersionUID = 2325189412814149264L;
  
    /**
     * Execute the first argument expression that is expected to return a
     * nodeset.  If the argument is null, then return the current context node.
     *
     * @param xctxt Runtime XPath context.
     *
     * @return The first node of the executed nodeset, or the current context
     *         node if the first argument is null.
     *
     * @throws javax.xml.transform.TransformerException if an error occurs while
     *                                   executing the argument expression.
     */
    protected int getArg0AsNode(XPathContext xctxt)
            throws javax.xml.transform.TransformerException
    {
  
      return (null == m_arg0)
             ? xctxt.getCurrentNode() : m_arg0.asNode(xctxt);
    }
    
    /**
     * Tell if the expression is a nodeset expression.
     * @return true if the expression can be represented as a nodeset.
     */
    public boolean Arg0IsNodesetExpr()
    {
      return (null == m_arg0) ? true : m_arg0.isNodesetExpr();
    }
  
    /**
     * Execute the first argument expression that is expected to return a
     * string.  If the argument is null, then get the string value from the
     * current context node.
     *
     * @param xctxt Runtime XPath context.
     *
     * @return The string value of the first argument, or the string value of the
     *         current context node if the first argument is null.
     *
     * @throws javax.xml.transform.TransformerException if an error occurs while
     *                                   executing the argument expression.
     */
    protected XMLString getArg0AsString(XPathContext xctxt)
            throws javax.xml.transform.TransformerException
    {
      if(null == m_arg0)
      {
        int currentNode = xctxt.getCurrentNode();
        if(DTM.NULL == currentNode)
          return XString.EMPTYSTRING;
        else
        {
          DTM dtm = xctxt.getDTM(currentNode);
          return dtm.getStringValue(currentNode);
        }
        
      }
      else
        return m_arg0.execute(xctxt).xstr();   
    }
  
    /**
     * Execute the first argument expression that is expected to return a
     * number.  If the argument is null, then get the number value from the
     * current context node.
     *
     * @param xctxt Runtime XPath context.
     *
     * @return The number value of the first argument, or the number value of the
     *         current context node if the first argument is null.
     *
     * @throws javax.xml.transform.TransformerException if an error occurs while
     *                                   executing the argument expression.
     */
    protected double getArg0AsNumber(XPathContext xctxt)
            throws javax.xml.transform.TransformerException
    {
  
      if(null == m_arg0)
      {
        int currentNode = xctxt.getCurrentNode();
        if(DTM.NULL == currentNode)
          return 0;
        else
        {
          DTM dtm = xctxt.getDTM(currentNode);
          XMLString str = dtm.getStringValue(currentNode);
          return str.toDouble();
        }
        
      }
      else
        return m_arg0.execute(xctxt).num();
    }
  
    /**
     * Check that the number of arguments passed to this function is correct.
     *
     * @param argNum The number of arguments that is being passed to the function.
     *
     * @throws WrongNumberArgsException if the number of arguments is not 0 or 1.
     */
    public void checkNumberArgs(int argNum) throws WrongNumberArgsException
    {
      if (argNum > 1)
        reportWrongNumberArgs();
    }
  
    /**
     * Constructs and throws a WrongNumberArgException with the appropriate
     * message for this function object.
     *
     * @throws WrongNumberArgsException
     */
    protected void reportWrongNumberArgs() throws WrongNumberArgsException {
        throw new WrongNumberArgsException(XSLMessages.createXPATHMessage(XPATHErrorResources.ER_ZERO_OR_ONE, null)); //"0 or 1");
    }
  
    /**
     * Tell if this expression or it's subexpressions can traverse outside
     * the current subtree.
     *
     * @return true if traversal outside the context node's subtree can occur.
     */
    public boolean canTraverseOutsideSubtree()
    {
      return (null == m_arg0) ? false : super.canTraverseOutsideSubtree();
    }
  }
  