dll/example/tutorial8/refcounting_api.hpp

// Copyright 2014 Renato Tegon Forti, Antony Polukhin.
//
// Distributed under the Boost Software License, Version 1.0.
// (See accompanying file LICENSE_1_0.txt
// or copy at http://www.boost.org/LICENSE_1_0.txt)

//[plugcpp_my_plugin_refcounting_api
#include "../tutorial_common/plugin_api.hpp"
#include <boost/filesystem/path.hpp>

class my_refcounting_api : public my_plugin_api {
public:
    // Returns path to shared object that holds a plugin.
    // Must be instantiated in plugin.
    virtual boost::filesystem::path location() const = 0;
};
//]


//[plugcpp_library_holding_deleter_api
#include <boost/dll/shared_library.hpp>
#include <boost/make_shared.hpp>
namespace detail {
    struct library_holding_deleter {
        boost::shared_ptr<boost::dll::shared_library> lib_;

        library_holding_deleter(my_refcounting_api* ptr)
            : lib_(boost::make_shared<boost::dll::shared_library>(ptr->location()))
        {}  

        void operator()(my_refcounting_api* p) const {
            delete p;
        }
    };
}
//]
//[plugcpp_library_holding_deleter_api_bind
#include <boost/shared_ptr.hpp>
inline boost::shared_ptr<my_refcounting_api> bind(my_refcounting_api* ptr) {
    return boost::shared_ptr<my_refcounting_api>(
        ptr,
        detail::library_holding_deleter(ptr)
    );
}
//]

//[plugcpp_get_plugin_refcounting
#include <boost/dll/import_function.hpp>
inline boost::shared_ptr<my_refcounting_api> get_plugin(
    boost::filesystem::path path, boost::string_ref func_name) 
{
    typedef my_refcounting_api*(func_t)();
    boost::function<func_t> f = boost::dll::import_function_alias<func_t>(
        path, 
        func_name, 
        boost::dll::load_mode::append_decorations // will be ignored for executable
    );

    // `f` goes out of scope here and will be destroyed.
    // Returned variable holds a reference to 
    // shared_library and it is safe to use it.
    return bind( f() );
}

//]