blame: source/code/Libs/include/cereal/details/static_object.hpp

/*! \file static_object.hpp

    \brief Internal polymorphism static object support

    \ingroup Internal */

/*

  Copyright (c) 2014, Randolph Voorhies, Shane Grant

  All rights reserved.

  Redistribution and use in source and binary forms, with or without

  modification, are permitted provided that the following conditions are met:

      * Redistributions of source code must retain the above copyright

        notice, this list of conditions and the following disclaimer.

      * Redistributions in binary form must reproduce the above copyright

        notice, this list of conditions and the following disclaimer in the

        documentation and/or other materials provided with the distribution.

      * Neither the name of cereal nor the

        names of its contributors may be used to endorse or promote products

        derived from this software without specific prior written permission.

  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND

  ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED

  WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE

  DISCLAIMED. IN NO EVENT SHALL RANDOLPH VOORHIES OR SHANE GRANT BE LIABLE FOR ANY

  DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES

  (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;

  LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND

  ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT

  (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS

  SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

*/

#ifndef CEREAL_DETAILS_STATIC_OBJECT_HPP_

#define CEREAL_DETAILS_STATIC_OBJECT_HPP_

#include "cereal/macros.hpp"

#if CEREAL_THREAD_SAFE

#include <mutex>

#endif

//! Prevent link optimization from removing non-referenced static objects

/*! Especially for polymorphic support, we create static objects which

    may not ever be explicitly referenced.  Most linkers will detect this

    and remove the code causing various unpleasant runtime errors.  These

    macros, adopted from Boost (see force_include.hpp) prevent this

    (C) Copyright 2002 Robert Ramey - http://www.rrsd.com .

    Use, modification and distribution is subject to 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) */

#ifdef _MSC_VER

#   define CEREAL_DLL_EXPORT __declspec(dllexport)

#   define CEREAL_USED

#else // clang or gcc

#   define CEREAL_DLL_EXPORT

#   define CEREAL_USED __attribute__ ((__used__))

#endif

namespace cereal

{

  namespace detail

  {

    //! A static, pre-execution object

    /*! This class will create a single copy (singleton) of some

        type and ensures that merely referencing this type will

        cause it to be instantiated and initialized pre-execution.

        For example, this is used heavily in the polymorphic pointer

        serialization mechanisms to bind various archive types with

        different polymorphic classes */

    template <class T>

    class CEREAL_DLL_EXPORT StaticObject

    {

      private:

        //! Forces instantiation at pre-execution time

        static void instantiate( T const & ) {}

        static T & create()

        {

          static T t;

          instantiate(instance);

          return t;

        }

        StaticObject( StaticObject const & /*other*/ ) {}

      public:

        static T & getInstance()

        {

          return create();

        }

        //! A class that acts like std::lock_guard

        class LockGuard

        {

          #if CEREAL_THREAD_SAFE

          public:

            LockGuard(std::mutex & m) : lock(m) {}

          private:

            std::unique_lock<std::mutex> lock;

          #else

          public:

            ~LockGuard() CEREAL_NOEXCEPT {} // prevents variable not used

          #endif

        };

        //! Attempts to lock this static object for the current scope

        /*! @note This function is a no-op if cereal is not compiled with

                  thread safety enabled (CEREAL_THREAD_SAFE = 1).

            This function returns an object that holds a lock for

            this StaticObject that will release its lock upon destruction. This

            call will block until the lock is available. */

        static LockGuard lock()

        {

          #if CEREAL_THREAD_SAFE

          static std::mutex instanceMutex;

          return LockGuard{instanceMutex};

          #else

          return LockGuard{};

          #endif

        }

      private:

        static T & instance;

    };

    template <class T> T & StaticObject<T>::instance = StaticObject<T>::create();

  } // namespace detail

} // namespace cereal

#endif // CEREAL_DETAILS_STATIC_OBJECT_HPP_