callback_i.h

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// -*- C++ -*-
// Callback_i.h,v 1.10 2002/01/29 20:20:40 okellogg Exp

// ============================================================================
//
// = LIBRARY
//     AMI_Observer
//
// = FILENAME
//     Callback_i.h
//
// = DESCRIPTION
//     Header file for the Web_Server::Callback implementation.
//
// = AUTHOR
//     Ossama Othman <[e-mail]>
//
// ============================================================================

#ifndef CALLBACK_I_H
#define CALLBACK_I_H

#include "ace/FILE_Addr.h"
#include "ace/FILE_IO.h"
#include "Push_Web_ServerS.h"

#if !defined (ACE_LACKS_PRAGMA_ONCE)
# pragma once
#endif /* ACE_LACKS_PRAGMA_ONCE */

// This is to remove "inherits via dominance" warnings from MSVC.
// MSVC is being a little too paranoid.
#if defined(_MSC_VER)
#if (_MSC_VER >= 1200)
#pragma warning(push)
#endif /* _MSC_VER >= 1200 */
#pragma warning(disable:4250)
#endif /* _MSC_VER */

// Implement the Web_Server::Callback interface.
class Callback_i :
  public virtual POA_Web_Server::Callback,
  public virtual PortableServer::RefCountServantBase
{
  // = TITLE
  //    Implement the Web_Server::Callback interface.
  //
  // = DESCRIPTION
  //    A <Callback> object implements the Observer pattern.  It
  //    simply "watches" while the Content Server pushes chunks of
  //    data to itself.  Once the Content Server pushes the last chunk
  //    of data, the <Callback> object spawns an external viewer to
  //    display the pushed data based on the data content type
  //    returned by the Iterator_Factory::register_callback() method.
  //
  //    Since the server pushes data to the <Callback> object
  //    asynchronously, and since instances of this <Callback> class
  //    are registered with the Content Server asynchronously, there
  //    is no guarantee that the metadata containing the content type
  //    will arrive before the content of the file.  As such, this
  //    class atomically sets and checks the flags that provide the
  //    current condition of the metadata and content, in case two
  //    concurrently running threads attempt to update the state
  //    contained within a given <Callback> object.

  friend class Callback_i_Friend;
  // Dummy friend class declaration to quiet down a warning.

public:
  Callback_i (int *request_count);
  // Constructor

  virtual void next_chunk (const Web_Server::Chunk_Type &chunk,
                           CORBA::Boolean last_chunk
                           ACE_ENV_ARG_DECL)
    ACE_THROW_SPEC ((CORBA::SystemException));
  // This operation returns the next <chunk> of the file starting at
  // <offset>.  If there are no more bindings, false is returned.

  void metadata (const Web_Server::Metadata_Type &metadata);
  // Set metadata associated with received data.

private:

  ~Callback_i (void);
  // Destructor must be private to ensure that this object is
  // allocated on the heap.

  int metadata_received (void);
  // Returns one if the metadata was received, and zero otherwise.

  int content_received (void);
  // Returns one if the entire content was received, and zero
  // otherwise.

  int get_viewer (char *viewer, size_t length);
  // Get the name of the viewer associated with the file being
  // retrieved.

  int spawn_viewer (void);
  // Spawn an external view to display the retrieved file.

private:

  void deactivate (ACE_ENV_SINGLE_ARG_DECL);
  // Deactivate this Callback servant.

private:

  ACE_FILE_Addr file_;
  // The Addr corresponding to the retrieved file.

  ACE_FILE_IO file_io_;
  // The object that provides all file related IO operations
  // (e.g. read, write, etc).

  Web_Server::AMI_CallbackHandler_var ami_handler_;
  // Reference to this Reply Handler's self.

  Web_Server::Metadata_Type metadata_;
  // The metadata associated with the file being retrieved from the
  // web server.

  int last_chunk_;
  // Flag that indicates entire data content has been received.

  TAO_SYNCH_MUTEX lock_;
  // Lock used to prevent race conditions when checking to see if
  // metadata or entire content has been received.

  int *request_count_;
  // Pointer to external status monitoring variable. The contents (not
  // the pointer itself) of the <pending_data> parameter will be
  // decremented when file retrieval has completed.
};

#if defined(_MSC_VER) && (_MSC_VER >= 1200)
#pragma warning(pop)
#endif /* _MSC_VER */

#endif  /* CALLBACK_I_H */