dep/ACE_wrappers/ace/Dynamic_Service_Dependency.h

   1 // -*- C++ -*-
   2
   3 //=============================================================================
   4 /**
   5  *  @file    Dynamic_Service_Dependency.h
   6  *
   7  *  $Id: Dynamic_Service_Dependency.h 80826 2008-03-04 14:51:23Z wotte $
   8  *
   9  *  @author Iliyan Jeliazkov <iliyan@ociweb.com>
  10  */
  11 //=============================================================================
  12
  13 #ifndef ACE_DYNAMIC_SERVICE_DEPENDENCY_H
  14 #define ACE_DYNAMIC_SERVICE_DEPENDENCY_H
  15
  16 #include /**/ "ace/pre.h"
  17
  18
  19 #if !defined (ACE_LACKS_PRAGMA_ONCE)
  20 # pragma once
  21 #endif /* ACE_LACKS_PRAGMA_ONCE */
  22
  23 #include "ace/Dynamic_Service_Base.h"
  24 #include "ace/Service_Object.h"
  25 #include "ace/DLL.h"
  26
  27 ACE_BEGIN_VERSIONED_NAMESPACE_DECL
  28
  29 /**
  30  * @class ACE_Dynamic_Service_Dependency
  31  *
  32  * @brief Provides a way to declare dependency on specific service,
  33  * thus helping to avoid order of initialization issues with instances
  34  * of an objects whose implementation code resides in dynamically loaded
  35  * services.
  36  *
  37  * It is disastrous to have dynamically loadable services create and give away
  38  * ownership of objects and then ending up being unloaded before all those
  39  * instances have been deleted. Normally the code for such objects classes
  40  * resides within the TEXT segment of the DLL, which implements the service.
  41  * If a service gets removed, its DLL may be unmapped from memory and then
  42  * any attempt to invoke a method on the said objects will cause SEGV.
  43  *
  44  * Such instances must contain a member of ACE_Dynamic_Service_Dependency
  45  * initialized with the service they depend on.
  46  * ACE_Dynamic_Service_Dependency's constructor and destructor are
  47  * "magical" - they work by maintaining the underlying dynamic service's
  48  * DLL reference count.
  49  */
  50 class ACE_Export ACE_Dynamic_Service_Dependency
  51 {
  52 public:
  53   ACE_Dynamic_Service_Dependency  (const ACE_Service_Gestalt *cfg,
  54                                    const ACE_TCHAR *principal);
  55   ACE_Dynamic_Service_Dependency  (const ACE_TCHAR *principal);
  56   ~ACE_Dynamic_Service_Dependency (void);
  57
  58 private:
  59   void init (const ACE_Service_Gestalt *cfg, const ACE_TCHAR *principal);
  60
  61 private:
  62   ACE_DLL tracker_;
  63 };
  64
  65 ACE_END_VERSIONED_NAMESPACE_DECL
  66
  67
  68 #include /**/ "ace/post.h"
  69
  70 #endif /* ACE_DYNAMIC_SERVICE_DEPENDENCY_H */