boost/unordered/detail/move.hpp
/*
Copyright 2005-2007 Adobe Systems Incorporated
Use, modification and distribution are 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).
*/
/*************************************************************************************************/
#ifndef BOOST_UNORDERED_DETAIL_MOVE_HEADER
#define BOOST_UNORDERED_DETAIL_MOVE_HEADER
#include <boost/mpl/bool.hpp>
#include <boost/mpl/and.hpp>
#include <boost/mpl/or.hpp>
#include <boost/mpl/not.hpp>
#include <boost/type_traits/is_convertible.hpp>
#include <boost/type_traits/is_same.hpp>
#include <boost/type_traits/is_class.hpp>
#include <boost/utility/enable_if.hpp>
#include <boost/unordered/detail/config.hpp>
/*************************************************************************************************/
namespace boost {
namespace unordered_detail {
/*************************************************************************************************/
namespace move_detail {
/*************************************************************************************************/
#if !defined(BOOST_UNORDERED_NO_HAS_MOVE_ASSIGN)
/*************************************************************************************************/
template <typename T>
struct class_has_move_assign {
class type {
typedef T& (T::*E)(T t);
typedef char (&no_type)[1];
typedef char (&yes_type)[2];
template <E e> struct sfinae { typedef yes_type type; };
template <class U>
static typename sfinae<&U::operator=>::type test(int);
template <class U>
static no_type test(...);
public:
enum {value = sizeof(test<T>(1)) == sizeof(yes_type)};
};
};
/*************************************************************************************************/
template<typename T>
struct has_move_assign : boost::mpl::and_<boost::is_class<T>, class_has_move_assign<T> > {};
/*************************************************************************************************/
class test_can_convert_anything { };
/*************************************************************************************************/
#endif // BOOST_UNORDERED_NO_HAS_MOVE_ASSIGN
/*************************************************************************************************/
/*
REVISIT (sparent@adobe.com): This is a work around for Boost 1.34.1 and VC++ 2008 where
boost::is_convertible<T, T> fails to compile.
*/
template <typename T, typename U>
struct is_convertible : boost::mpl::or_<
boost::is_same<T, U>,
boost::is_convertible<T, U>
> { };
/*************************************************************************************************/
} //namespace move_detail
/*************************************************************************************************/
/*!
\ingroup move_related
\brief move_from is used for move_ctors.
*/
template <typename T>
struct move_from
{
explicit move_from(T& x) : source(x) { }
T& source;
};
/*************************************************************************************************/
#if !defined(BOOST_UNORDERED_NO_HAS_MOVE_ASSIGN)
/*************************************************************************************************/
/*!
\ingroup move_related
\brief The is_movable trait can be used to identify movable types.
*/
template <typename T>
struct is_movable : boost::mpl::and_<
boost::is_convertible<move_from<T>, T>,
move_detail::has_move_assign<T>,
boost::mpl::not_<boost::is_convertible<move_detail::test_can_convert_anything, T> >
> { };
/*************************************************************************************************/
#else // BOOST_UNORDERED_NO_HAS_MOVE_ASSIGN
// On compilers which don't have adequate SFINAE support, treat most types as unmovable,
// unless the trait is specialized.
template <typename T>
struct is_movable : boost::mpl::false_ { };
#endif
/*************************************************************************************************/
#if !defined(BOOST_NO_SFINAE)
/*************************************************************************************************/
/*!
\ingroup move_related
\brief copy_sink and move_sink are used to select between overloaded operations according to
whether type T is movable and convertible to type U.
\sa move
*/
template <typename T,
typename U = T,
typename R = void*>
struct copy_sink : boost::enable_if<
boost::mpl::and_<
boost::unordered_detail::move_detail::is_convertible<T, U>,
boost::mpl::not_<is_movable<T> >
>,
R
>
{ };
/*************************************************************************************************/
/*!
\ingroup move_related
\brief move_sink and copy_sink are used to select between overloaded operations according to
whether type T is movable and convertible to type U.
\sa move
*/
template <typename T,
typename U = T,
typename R = void*>
struct move_sink : boost::enable_if<
boost::mpl::and_<
boost::unordered_detail::move_detail::is_convertible<T, U>,
is_movable<T>
>,
R
>
{ };
/*************************************************************************************************/
/*!
\ingroup move_related
\brief This version of move is selected when T is_movable . It in turn calls the move
constructor. This call, with the help of the return value optimization, will cause x to be moved
instead of copied to its destination. See adobe/test/move/main.cpp for examples.
*/
template <typename T>
T move(T& x, typename move_sink<T>::type = 0) { return T(move_from<T>(x)); }
/*************************************************************************************************/
/*!
\ingroup move_related
\brief This version of move is selected when T is not movable . The net result will be that
x gets copied.
*/
template <typename T>
T& move(T& x, typename copy_sink<T>::type = 0) { return x; }
/*************************************************************************************************/
#else // BOOST_NO_SFINAE
// On compilers without SFINAE, define copy_sink to always use the copy function.
template <typename T,
typename U = T,
typename R = void*>
struct copy_sink
{
typedef R type;
};
// Always copy the element unless this is overloaded.
template <typename T>
T& move(T& x) {
return x;
}
#endif // BOOST_NO_SFINAE
} // namespace unordered_detail
} // namespace boost
/*************************************************************************************************/
#endif
/*************************************************************************************************/
