version_type.hpp

来自「Boost provides free peer-reviewed portab」· HPP 代码 · 共 90 行

//////////////////////////////////////////////////////////////////////////////
//
// (C) Copyright Ion Gaztanaga 2005-2008. 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)
//
// See http://www.boost.org/libs/interprocess for documentation.
//
//////////////////////////////////////////////////////////////////////////////
//
//       This code comes from N1953 document by Howard E. Hinnant
//
//////////////////////////////////////////////////////////////////////////////


#ifndef BOOST_INTERPROCESS_DETAIL_VERSION_TYPE_HPP
#define BOOST_INTERPROCESS_DETAIL_VERSION_TYPE_HPP

#include <boost/interprocess/detail/mpl.hpp>
#include <boost/interprocess/detail/type_traits.hpp>


namespace boost{
namespace interprocess{
namespace detail{

//using namespace boost;

template <class T, unsigned V>
struct version_type
    : public detail::integral_constant<unsigned, V>
{
    typedef T type;

    version_type(const version_type<T, 0>&);
};

namespace impl{

template <class T, 
          bool = detail::is_convertible<version_type<T, 0>, typename T::version>::value>
struct extract_version
{
   static const unsigned value = 1;
};

template <class T>
struct extract_version<T, true>
{
   static const unsigned value = T::version::value;
};

template <class T>
struct has_version
{
   private:
   struct two {char _[2];};
   template <class U> static two test(...);
   template <class U> static char test(const typename U::version*);
   public:
   static const bool value = sizeof(test<T>(0)) == 1;
   void dummy(){}
};

template <class T, bool = has_version<T>::value>
struct version
{
   static const unsigned value = 1;
};

template <class T>
struct version<T, true>
{
   static const unsigned value = extract_version<T>::value;
};

}  //namespace impl

template <class T>
struct version
   : public detail::integral_constant<unsigned, impl::version<T>::value>
{
};

}  //namespace detail{
}  //namespace interprocess{
}  //namespace boost{

#endif   //#define BOOST_INTERPROCESS_DETAIL_VERSION_TYPE_HPP