move.hpp

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//////////////////////////////////////////////////////////////////////////////
//
// (C) Copyright Ion Gaztanaga 2006. 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.
//
//////////////////////////////////////////////////////////////////////////////

#ifndef BOOST_INTERPROCESS_MOVE_HPP
#define BOOST_INTERPROCESS_MOVE_HPP

#if (defined _MSC_VER) && (_MSC_VER >= 1200)
#  pragma once
#endif

#include <boost/interprocess/detail/config_begin.hpp>
#include <boost/interprocess/detail/workaround.hpp>
#include <boost/interprocess/interprocess_fwd.hpp>
#include <boost/interprocess/detail/mpl.hpp>

//!\file
//!Describes a function and a type to emulate move semantics.

namespace boost {
namespace interprocess {

//!Trait class to detect if a type is
//!movable
template <class T>
struct is_movable
{
   enum {  value = false };
};

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

#ifndef BOOST_INTERPROCESS_RVALUE_REFERENCE

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

namespace boost {
namespace interprocess {
namespace detail {

//!An object that represents a
//!moved object.
template<class T>
struct moved_object
{  
   moved_object(const T &obj)
      :  m_obj(const_cast<T *>(&obj))
   {}

   T &get() const
   {  return *m_obj;  }

   private:
   T *m_obj; 
};

// Metafunction that, given movable T, provides move_source<T>, else T&.
template <typename T>
struct move_type
{
   public: // metafunction result
   typedef typename if_<is_movable<T>, moved_object<T>, T&>::type type;
};

template <typename T> 
class move_return
{
   typedef moved_object<T> moved_type;
   private:
   mutable T m_moved;


   public:
   typedef T type;

   move_return(const T& returned)
      : m_moved(moved_object<T>(returned))
   {}

   move_return(const move_return& operand)
      : m_moved(const_cast<move_return&>(operand))
   {}

   operator moved_type() const
   {  return moved_type(m_moved);  }
};

template <typename T>
struct return_type
{
   public: // metafunction result

   typedef typename if_<is_movable<T>, move_return<T>, T>::type type;
};

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

namespace boost {
namespace interprocess {

namespace detail{

//!A function that converts an object to a moved object so that 
//!it can match a function taking a detail::moved_object object.
template<class Object>
typename detail::move_type<Object>::type move_impl(const Object &object)
{  
   typedef typename detail::move_type<Object>::type type;
   return type(object);   
}

template <class T>
inline const T& forward_impl(const T &t)
{  return t;   }

template <class T>
inline T& forward_impl(T &t)
{  return t;   }

template <class T>
inline detail::moved_object<T> forward_impl(detail::moved_object<T> &t)
{  return t;   }

}  //namespace detail {

//!A function that converts an object to a moved object so that 
//!it can match a function taking a detail::moved_object object.
template<class Object>
typename detail::move_type<Object>::type move(const Object &object)
{     return detail::move_impl(object);  }

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

#else //#ifdef BOOST_INTERPROCESS_RVALUE_REFERENCE

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

namespace boost {
namespace interprocess {

namespace detail {

template <class T>
inline typename detail::remove_reference<T>::type&& move_impl(T&& t)
{  return t;   }

template <class T>
inline T&& forward_impl(typename detail::identity<T>::type&& t)
{  return t;   }

}  //namespace detail {

template <class T>
inline typename detail::remove_reference<T>::type&& move(T&& t)
{  return t;   }

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

#endif   //#ifdef BOOST_INTERPROCESS_RVALUE_REFERENCE

#include <boost/interprocess/detail/config_end.hpp>

#endif   //#ifndef BOOST_INTERPROCESS_MOVE_HPP