text: //
  // EntityResolver.h
  //
  // $Id$
  //
  // Library: XML
  // Package: SAX
  // Module:  SAX
  //
  // SAX EntityResolver Interface.
  //
  // Copyright (c) 2004-2006, Applied Informatics Software Engineering GmbH.
  // and Contributors.
  //
  // Permission is hereby granted, free of charge, to any person or organization
  // obtaining a copy of the software and accompanying documentation covered by
  // this license (the "Software") to use, reproduce, display, distribute,
  // execute, and transmit the Software, and to prepare derivative works of the
  // Software, and to permit third-parties to whom the Software is furnished to
  // do so, all subject to the following:
  // 
  // The copyright notices in the Software and this entire statement, including
  // the above license grant, this restriction and the following disclaimer,
  // must be included in all copies of the Software, in whole or in part, and
  // all derivative works of the Software, unless such copies or derivative
  // works are solely in the form of machine-executable object code generated by
  // a source language processor.
  // 
  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  // FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
  // SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
  // FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
  // ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
  // DEALINGS IN THE SOFTWARE.
  //
  
  
  #ifndef SAX_EntityResolver_INCLUDED
  #define SAX_EntityResolver_INCLUDED
  
  
  #include "Poco/XML/XML.h"
  #include "Poco/XML/XMLString.h"
  
  
  namespace Poco {
  namespace XML {
  
  
  class InputSource;
  
  
  class XML_API EntityResolver
  	/// If a SAX application needs to implement customized handling for external entities, 
  	/// it must implement this interface and register an instance with the SAX driver using 
  	/// the setEntityResolver method.
  	/// 
  	/// The XML reader will then allow the application to intercept any external entities 
  	/// (including the external DTD subset and external parameter entities, if any) before 
  	/// including them.
  	/// 
  	/// Many SAX applications will not need to implement this interface, but it will be 
  	/// especially useful for applications that build XML documents from databases or other 
  	/// specialised input sources, or for applications that use URI types other than URLs.
  	///
  	/// The application can also use this interface to redirect system identifiers to local 
  	/// URIs or to look up replacements in a catalog (possibly by using the public identifier).
  {
  public:
  	virtual InputSource* resolveEntity(const XMLString* publicId, const XMLString& systemId) = 0;
  		/// Allow the application to resolve external entities.
  		/// 
  		/// The parser will call this method before opening any external entity except the 
  		/// top-level document entity. Such entities include the external DTD subset and 
  		/// external parameter entities referenced within the DTD (in either case, only 
  		/// if the parser reads external parameter entities), and external general entities 
  		/// referenced within the document element (if the parser reads external general entities). 
  		/// The application may request that the parser locate the entity itself, that it use an 
  		/// alternative URI, or that it use data provided by the application (as a character or 
  		/// byte input stream).
  		/// 
  		/// Application writers can use this method to redirect external system identifiers to 
  		/// secure and/or local URIs, to look up public identifiers in a catalogue, or to read an 
  		/// entity from a database or other input source (including, for example, a dialog box). 
  		/// Neither XML nor SAX specifies a preferred policy for using public or system IDs to resolve 
  		/// resources. However, SAX specifies how to interpret any InputSource returned by this method, 
  		/// and that if none is returned, then the system ID will be dereferenced as a URL.
  		/// 
  		/// If the system identifier is a URL, the SAX parser must resolve it fully before reporting it to 
  		/// the application.
  		/// 
  		/// Note that publicId maybe null, therefore we pass a pointer rather than a reference.
  
  	virtual void releaseInputSource(InputSource* pSource) = 0;
  		/// This is a non-standard extension to SAX!
  		/// Called by the parser when the input source returned by ResolveEntity is
  		/// no longer needed. Should free any resources used by the input source.
  
  protected:
  	virtual ~EntityResolver();
  };
  
  
  } } // namespace Poco::XML
  
  
  #endif // SAX_EntityResolver_INCLUDED
  