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;
  
  import org.apache.xml.utils.QName;
  import org.apache.xpath.objects.XObject;
  
  /**
   * This class holds an instance of an argument on
   * the stack. The value of the argument can be either an
   * XObject or a String containing an expression.
   * @xsl.usage internal
   */
  public class Arg
  {
  
    /** Field m_qname: The name of this argument, expressed as a QName
     * (Qualified Name) object.
     * @see getQName
     * @see setQName
     *  */
    private QName m_qname;
  
    /**
     * Get the qualified name for this argument.
     *
     * @return QName object containing the qualified name
     */
    public final QName getQName()
    {
      return m_qname;
    }
  
    /**
     * Set the qualified name for this argument.
     *
     * @param name QName object representing the new Qualified Name.
     */
    public final void setQName(QName name)
    {
      m_qname = name;
    }
  
    /** Field m_val: Stored XObject value of this argument
     * @see #getVal()
     * @see #setVal()
     */
    private XObject m_val;
  
    /**
     * Get the value for this argument.
     *
     * @return the argument's stored XObject value.
     * @see #setVal(XObject)
     */
    public final XObject getVal()
    {
      return m_val;
    }
  
    /**
     * Set the value of this argument.
     *
     * @param val an XObject representing the arguments's value.
     * @see #getVal()
     */
    public final void setVal(XObject val)
    {
      m_val = val;
    }
    
    /**
     * Have the object release it's resources.
     * Call only when the variable or argument is going out of scope.
     */
    public void detach()
    {
      if(null != m_val)
      {
        m_val.allowDetachToRelease(true);
        m_val.detach();
      }
    }
  
  
    /** Field m_expression: Stored expression value of this argument.
     * @see #setExpression
     * @see #getExpression
     * */
    private String m_expression;
  
    /**
     * Get the value expression for this argument.
     *
     * @return String containing the expression previously stored into this
     * argument
     * @see #setExpression
     */
    public String getExpression()
    {
      return m_expression;
    }
  
    /**
     * Set the value expression for this argument.
     *
     * @param expr String containing the expression to be stored as this
     * argument's value.
     * @see #getExpression
     */
    public void setExpression(String expr)
    {
      m_expression = expr;
    }
  
    /** 
     * True if this variable was added with an xsl:with-param or
     * is added via setParameter.
     */
    private boolean m_isFromWithParam;
  
    /**
     * Tell if this variable is a parameter passed with a with-param or as 
     * a top-level parameter.
     */
     public boolean isFromWithParam()
     {
      return m_isFromWithParam;
     }
  
    /** 
     * True if this variable is currently visible.  To be visible,
     * a variable needs to come either from xsl:variable or be 
     * a "received" parameter, ie one for which an xsl:param has
     * been encountered.
     * Set at the time the object is constructed and updated as needed.
     */
    private boolean m_isVisible;
  
    /**
     * Tell if this variable is currently visible.
     */
     public boolean isVisible()
     {
      return m_isVisible;
     }
     
    /**
     * Update visibility status of this variable.
     */
     public void setIsVisible(boolean b)
     {
      m_isVisible = b;
     }
  
    /**
     * Construct a dummy parameter argument, with no QName and no
     * value (either expression string or value XObject). isVisible
     * defaults to true.
     */
    public Arg()
    {
  
      m_qname = new QName("");
      ;  // so that string compares can be done.
      m_val = null;
      m_expression = null;
      m_isVisible = true;
      m_isFromWithParam = false;
    }
  
    /**
     * Construct a parameter argument that contains an expression.
     *
     * @param qname Name of the argument, expressed as a QName object.
     * @param expression String to be stored as this argument's value expression.
     * @param isFromWithParam True if this is a parameter variable.
     */
    public Arg(QName qname, String expression, boolean isFromWithParam)
    {
  
      m_qname = qname;
      m_val = null;
      m_expression = expression;
      m_isFromWithParam = isFromWithParam;
      m_isVisible = !isFromWithParam;
    }
  
    /**
     * Construct a parameter argument which has an XObject value.
     * isVisible defaults to true.
     *
     * @param qname Name of the argument, expressed as a QName object.
     * @param val Value of the argument, expressed as an XObject
     */
    public Arg(QName qname, XObject val)
    {
  
      m_qname = qname;
      m_val = val;
      m_isVisible = true;
      m_isFromWithParam = false;
      m_expression = null;
    }
    
    /**
     * Equality function specialized for the variable name.  If the argument 
     * is not a qname, it will deligate to the super class.
     * 
     * @param   obj   the reference object with which to compare.
     * @return  <code>true</code> if this object is the same as the obj
     *          argument; <code>false</code> otherwise.
     */
    public boolean equals(Object obj) 
    {
      if(obj instanceof QName)
      {
        return m_qname.equals(obj);
      }
      else
        return super.equals(obj);
    }
  
    /**
     * Construct a parameter argument.
     *
     * @param qname Name of the argument, expressed as a QName object.
     * @param val Value of the argument, expressed as an XObject
     * @param isFromWithParam True if this is a parameter variable.
     */
    public Arg(QName qname, XObject val, boolean isFromWithParam)
    {
  
      m_qname = qname;
      m_val = val;
      m_isFromWithParam = isFromWithParam;
      m_isVisible = !isFromWithParam;
      m_expression = null;
    }
  }
  