/*
 * The Apache Software License, Version 1.1
 * 
 * Copyright (c) 1999-2000 The Apache Software Foundation.  All rights
 * reserved.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer. 
 * 
 * 2. Redistributions in binary form must reproduce the above copyright
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 *    distribution.
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 * 3. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:  
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
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 * 4. The names "Xerces" and "Apache Software Foundation" must
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 * 5. Products derived from this software may not be called "Apache",
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 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 * 
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation, and was
 * originally based on software copyright (c) 1999, International
 * Business Machines, Inc., http://www.ibm.com .  For more information
 * on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 */

/*
 * $Id: DOM_DocumentFragment.hpp,v 1.6 2000/07/28 01:33:31 aruna1 Exp $
 */

#ifndef DOM_DocumentFragment_HEADER_GUARD_
#define DOM_DocumentFragment_HEADER_GUARD_

#include <util/XercesDefs.hpp>
#include <dom/DOM_Node.hpp>

class DocumentFragmentImpl;

/**
 * <code>DocumentFragment</code> is a "lightweight" or "minimal" 
 * <code>Document</code> object. 
 *
 * It is very common to want to be able to 
 * extract a portion of a document's tree or to create a new fragment of a 
 * document. Imagine implementing a user command like cut or rearranging a 
 * document by moving fragments around. It is desirable to have an object 
 * which can hold such fragments and it is quite natural to use a Node for 
 * this purpose. While it is true that a <code>Document</code> object could 
 * fulfil this role,  a <code>Document</code> object can potentially be a 
 * heavyweight  object, depending on the underlying implementation. What is 
 * really needed for this is a very lightweight object.  
 * <code>DocumentFragment</code> is such an object.
 * <p>Furthermore, various operations -- such as inserting nodes as children 
 * of another <code>Node</code> -- may take <code>DocumentFragment</code> 
 * objects as arguments;  this results in all the child nodes of the 
 * <code>DocumentFragment</code>  being moved to the child list of this node.
 * <p>The children of a <code>DocumentFragment</code> node are zero or more 
 * nodes representing the tops of any sub-trees defining the structure of the 
 * document. <code>DocumentFragment</code> nodes do not need to be 
 * well-formed XML documents (although they do need to follow the rules 
 * imposed upon well-formed XML parsed entities, which can have multiple top 
 * nodes).  For example, a <code>DocumentFragment</code> might have only one 
 * child and that child node could be a <code>Text</code> node. Such a 
 * structure model  represents neither an HTML document nor a well-formed XML 
 * document.  
 * <p>When a <code>DocumentFragment</code> is inserted into a  
 * <code>Document</code> (or indeed any other <code>Node</code> that may take 
 * children) the children of the <code>DocumentFragment</code> and not the 
 * <code>DocumentFragment</code>  itself are inserted into the 
 * <code>Node</code>. This makes the <code>DocumentFragment</code> very 
 * useful when the user wishes to create nodes that are siblings; the 
 * <code>DocumentFragment</code> acts as the parent of these nodes so that the
 *  user can use the standard methods from the <code>Node</code>  interface, 
 * such as <code>insertBefore()</code> and  <code>appendChild()</code>.  
 */

class CDOM_EXPORT DOM_DocumentFragment: public DOM_Node {

public:
    /** @name Constructors and assignment operators */
    //@{
    /**
    * Default constructor for <code>DOM_DocumentFragment</code>.  The resulting object does not
    * refer to an actual Document Fragment node; it will compare == to 0, and is similar
    * to a null object reference variable in Java.  It may subsequently be
    * assigned to refer to an actual Document Fragment node.
    * <p>
    * New document fragment nodes are created by DOM_Document::createDocumentFragment().
    *
    */

    DOM_DocumentFragment();

    /**
      * Copy constructor.  Creates a new <code>DOM_DocumentFragment</code> that refers to the
      *   same underlying node as the original.  See also DOM_Node::clone(),
      * which will copy the actual Document fragment node, rather than just creating a new
      * reference to the original node.
      *
      * @param other The object to be copied
      */
    DOM_DocumentFragment(const DOM_DocumentFragment &other);

    /**
      * Assignment operator
      *
      * @param other The object to be copied
      */
    DOM_DocumentFragment & operator = (const DOM_DocumentFragment &other);

    /**
      * Assignment operator.  This overloaded variant is provided for
      *   the sole purpose of setting a DOM_Node reference variable to
      *   zero.  Nulling out a reference variable in this way will decrement
      *   the reference count on the underlying Node object that the variable
      *   formerly referenced.  This effect is normally obtained when reference
      *   variable goes out of scope, but zeroing them can be useful for
      *   global instances, or for local instances that will remain in scope
      *   for an extended time,  when the storage belonging to the underlying
      *   node needs to be reclaimed.
      *
      * @param val.  Only a value of 0, or null, is allowed.
      */
    DOM_DocumentFragment & operator = (const DOM_NullPtr *val);

	//@}
    /** @name Destructor */
    //@{
	    
    /**
      * Destructor.  The object being destroyed is the reference
      * object, not the underlying Comment node itself.
      *
      */
    ~DOM_DocumentFragment();

	//@}

protected:
    DOM_DocumentFragment(DocumentFragmentImpl *);

    friend class DOM_Document;
    friend class RangeImpl;
};

#endif
