text: /* Copyright (c) 2016, 2017, Oracle and/or its affiliates. All rights reserved.
  
  This program is free software; you can redistribute it and/or modify
  it under the terms of the GNU General Public License, version 2.0,
  as published by the Free Software Foundation.
  
  This program is also distributed with certain software (including
  but not limited to OpenSSL) that is licensed under separate terms,
  as designated in a particular file or component or in included license
  documentation.  The authors of MySQL hereby grant you an additional
  permission to link the program and your derivative works with the
  separately licensed software that they have included with MySQL.
  
  This program is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License, version 2.0, for more details.
  
  You should have received a copy of the GNU General Public License
  along with this program; if not, write to the Free Software
  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA */
  
  #ifndef MYSQL_SERVICE_PLUGIN_REGISTRY_INCLUDED
  /**
    @file
    Declaration of the registry plugin service
  */
  
  #include <mysql/components/services/registry.h>
  
  /**
    @ingroup group_ext_plugin_services
    A bridge service allowing plugins to work with the registry.
  
    This allows traditional MySQL plugins to interact with the service
    registry.
    All this plugins service does is to return a reference to the
    registry service.
    Using that the plugins can access the rest of the registry and
    dynamic loaders services, as well as other services present in the
    registry.
    Note that the plugins must release the service references they
    acquire otherwise resources will be leaked and normal unload order
    may be affected.
  */
  extern "C" struct plugin_registry_service_st {
    /**
      Acquire a pointer to the registry service
  
      The reference must be released by calling
      plugin_registry_service_st::mysql_plugin_registry_release_func()
      See @ref mysql_plugin_registry_acquire() for more details.
  
      Once you receive the registry pointer you can use it to aquire
      references to other services your plugin might be interested in.
  
      @note
      This is to be considered an "expensive" operation because it
      requires access to the global structures of the
      @ref PAGE_COMPONENTS_REGISTRY. Avoid using it in situations
      where fast and scalable execution is requred.
      Since the registry service is very unlikely to change often
      holding on to the reference to it for extended time periods
      is a safe bet.
  
      @note
      Achieveing scalability through preserving references does not
      come for free.
      These are some of the effects on code that caches active
      references:
      - components implementing services to which active references
      are held cannot be unloaded.
      - code keeping an active refernece to e.g. a default service
      implementation will not switch to a possible new default
      service implementation installed by a component loaded in
      the meanwhile, as taking the updated default service implementation
      would only happen at the time of aquiring a new reference.
  
      @return the registry pointer
  
      See also: @ref PAGE_COMPONENTS, @ref PAGE_COMPONENTS_REGISTRY,
      @ref mysql_plugin_registry_acquire(), @ref mysql_plugin_registry_release()
    */
    SERVICE_TYPE(registry) * (*mysql_plugin_registry_acquire_func)();
    /**
      Release a pointer to the registry service
  
      Releases the reference to the registry service, as returned by
      @ref mysql_plugin_registry_acquire().
      After this call the reigstry_ptr is undefined and
      should not be used anymore.
      See @ref mysql_plugin_registry_release() for more details.
  
      @warning
      Before releasing the reference to the registry service please
      make sure you have released all the other service references
      that you explicitly or implicitly acquired. These can't be
      released without a valid reference to the registry service.
  
      @note
      This is also to be considered an "expensive" operation.
      See @ref plugin_registry_service_st::mysql_plugin_registry_acquire_func
      for more details on pros and cons of re-acquiring references vs caching
      and reusing them.
  
      @param registry_ptr   the registry pointer
      @return execution status
      @retval 0 success
      @retval non-zero failure
  
      See also @ref PAGE_COMPONENTS, @ref PAGE_COMPONENTS_REGISTRY,
      @ref mysql_plugin_registry_release(), @ref mysql_plugin_registry_acquire()
    */
    int (*mysql_plugin_registry_release_func)(SERVICE_TYPE(registry) *
                                              registry_ptr);
  } * plugin_registry_service;
  
  #ifdef MYSQL_DYNAMIC_PLUGIN
  #define mysql_plugin_registry_acquire() \
    plugin_registry_service->mysql_plugin_registry_acquire_func()
  #define mysql_plugin_registry_release(r) \
    plugin_registry_service->mysql_plugin_registry_release_func(r)
  #else
  SERVICE_TYPE(registry) * mysql_plugin_registry_acquire();
  int mysql_plugin_registry_release(SERVICE_TYPE(registry) *);
  #endif
  
  #define MYSQL_SERVICE_PLUGIN_REGISTRY_INCLUDED
  #endif /* MYSQL_SERVICE_PLUGIN_REGISTRY_INCLUDED */
  