ceph/src/boost/libs/dll/example/tutorial8/refcounting_api.hpp

   1 // Copyright 2014 Renato Tegon Forti, Antony Polukhin.
   2 // Copyright 2015-2019 Antony Polukhin.
   3 //
   4 // Distributed under the Boost Software License, Version 1.0.
   5 // (See accompanying file LICENSE_1_0.txt
   6 // or copy at http://www.boost.org/LICENSE_1_0.txt)
   7
   8 //[plugcpp_my_plugin_refcounting_api
   9 #include "../tutorial_common/my_plugin_api.hpp"
  10 #include <boost/dll/config.hpp>
  11
  12 class my_refcounting_api: public my_plugin_api {
  13 public:
  14     // Returns path to shared object that holds a plugin.
  15     // Must be instantiated in plugin.
  16     virtual boost::dll::fs::path location() const = 0;
  17 };
  18 //]
  19
  20
  21 //[plugcpp_library_holding_deleter_api_bind
  22 #include <boost/shared_ptr.hpp>
  23 #include <boost/make_shared.hpp>
  24 #include <boost/dll/shared_library.hpp>
  25
  26 struct library_holding_deleter {
  27     boost::shared_ptr<boost::dll::shared_library> lib_;
  28
  29     void operator()(my_refcounting_api* p) const {
  30         delete p;
  31     }
  32 };
  33
  34 inline boost::shared_ptr<my_refcounting_api> bind(my_refcounting_api* plugin) {
  35     // getting location of the shared library that holds the plugin
  36     boost::dll::fs::path location = plugin->location();
  37
  38     // `make_shared` is an efficient way to create a shared pointer
  39     boost::shared_ptr<boost::dll::shared_library> lib
  40         = boost::make_shared<boost::dll::shared_library>(location);
  41
  42     library_holding_deleter deleter;
  43     deleter.lib_ = lib;
  44
  45     return boost::shared_ptr<my_refcounting_api>(
  46         plugin, deleter
  47     );
  48 }
  49 //]
  50
  51 //[plugcpp_get_plugin_refcounting
  52 #include <boost/dll/import.hpp>
  53 #include <boost/function.hpp>
  54 inline boost::shared_ptr<my_refcounting_api> get_plugin(
  55     boost::dll::fs::path path, const char* func_name)
  56 {
  57     typedef my_refcounting_api*(func_t)();
  58     boost::function<func_t> creator = boost::dll::import_alias<func_t>(
  59         path,
  60         func_name,
  61         boost::dll::load_mode::append_decorations   // will be ignored for executable
  62     );
  63
  64     // `plugin` does not hold a reference to shared library. If `creator` will go out of scope,
  65     // then `plugin` can not be used.
  66     my_refcounting_api* plugin = creator();
  67
  68     // Returned variable holds a reference to
  69     // shared_library and it is safe to use it.
  70     return bind( plugin );
  71
  72     // `creator` goes out of scope here and will be destroyed.
  73 }
  74
  75 //]
  76
  77