TAO/examples/Content_Server/AMI_Observer/Callback_i.h

   1 // -*- C++ -*-
   2
   3 //=============================================================================
   4 /**
   5  *  @file     Callback_i.h
   6  *
   7  *   Header file for the Web_Server::Callback implementation.
   8  *
   9  *  @author  Ossama Othman <ossama@uci.edu>
  10  */
  11 //=============================================================================
  12
  13
  14 #ifndef CALLBACK_I_H
  15 #define CALLBACK_I_H
  16
  17 #include "ace/FILE_Addr.h"
  18 #include "ace/FILE_IO.h"
  19 #include "Push_Web_ServerS.h"
  20
  21 #if !defined (ACE_LACKS_PRAGMA_ONCE)
  22 # pragma once
  23 #endif /* ACE_LACKS_PRAGMA_ONCE */
  24
  25 // Implement the Web_Server::Callback interface.
  26 class Callback_i :
  27   public virtual POA_Web_Server::Callback
  28 {
  29   // = TITLE
  30   //    Implement the Web_Server::Callback interface.
  31   //
  32   // = DESCRIPTION
  33   //    A <Callback> object implements the Observer pattern.  It
  34   //    simply "watches" while the Content Server pushes chunks of
  35   //    data to itself.  Once the Content Server pushes the last chunk
  36   //    of data, the <Callback> object spawns an external viewer to
  37   //    display the pushed data based on the data content type
  38   //    returned by the Iterator_Factory::register_callback() method.
  39   //
  40   //    Since the server pushes data to the <Callback> object
  41   //    asynchronously, and since instances of this <Callback> class
  42   //    are registered with the Content Server asynchronously, there
  43   //    is no guarantee that the metadata containing the content type
  44   //    will arrive before the content of the file.  As such, this
  45   //    class atomically sets and checks the flags that provide the
  46   //    current condition of the metadata and content, in case two
  47   //    concurrently running threads attempt to update the state
  48   //    contained within a given <Callback> object.
  49
  50   /// Dummy friend class declaration to quiet down a warning.
  51   friend class Callback_i_Friend;
  52
  53 public:
  54   /// Constructor
  55   Callback_i (int *request_count);
  56
  57   /// This operation returns the next <chunk> of the file starting at
  58   /// <offset>.  If there are no more bindings, false is returned.
  59   virtual void next_chunk (const Web_Server::Chunk_Type &chunk,
  60                            CORBA::Boolean last_chunk);
  61
  62   /// Set metadata associated with received data.
  63   void metadata (const Web_Server::Metadata_Type &metadata);
  64
  65 private:
  66   /// Destructor must be private to ensure that this object is
  67   /// allocated on the heap.
  68   ~Callback_i ();
  69
  70   /// Returns one if the metadata was received, and zero otherwise.
  71   int metadata_received ();
  72
  73   /// Returns one if the entire content was received, and zero
  74   /// otherwise.
  75   int content_received ();
  76
  77   /// Get the name of the viewer associated with the file being
  78   /// retrieved.
  79   int get_viewer (char *viewer, size_t length);
  80
  81   /// Spawn an external view to display the retrieved file.
  82   int spawn_viewer ();
  83
  84 private:
  85   /// Deactivate this Callback servant.
  86   void deactivate ();
  87
  88 private:
  89   /// The Addr corresponding to the retrieved file.
  90   ACE_FILE_Addr file_;
  91
  92   /// The object that provides all file related IO operations
  93   /// (e.g. read, write, etc).
  94   ACE_FILE_IO file_io_;
  95
  96   /// Reference to this Reply Handler's self.
  97   Web_Server::AMI_CallbackHandler_var ami_handler_;
  98
  99   /// The metadata associated with the file being retrieved from the
 100   /// web server.
 101   Web_Server::Metadata_Type metadata_;
 102
 103   /// Flag that indicates entire data content has been received.
 104   int last_chunk_;
 105
 106   /// Lock used to prevent race conditions when checking to see if
 107   /// metadata or entire content has been received.
 108   TAO_SYNCH_MUTEX lock_;
 109
 110   /**
 111    * Pointer to external status monitoring variable. The contents (not
 112    * the pointer itself) of the <pending_data> parameter will be
 113    * decremented when file retrieval has completed.
 114    */
 115   int *request_count_;
 116 };
 117
 118 #endif  /* CALLBACK_I_H */