boost/move/traits.hpp

0001 //////////////////////////////////////////////////////////////////////////////
0002 //
0003 // (C) Copyright Ion Gaztanaga 2009-2012.
0004 // Distributed under the Boost Software License, Version 1.0.
0005 // (See accompanying file LICENSE_1_0.txt or copy at
0006 // http://www.boost.org/LICENSE_1_0.txt)
0007 //
0008 // See http://www.boost.org/libs/move for documentation.
0009 //
0010 //////////////////////////////////////////////////////////////////////////////
0011
0012 //! \file
0013
0014 #ifndef BOOST_MOVE_TRAITS_HPP
0015 #define BOOST_MOVE_TRAITS_HPP
0016
0017 #ifndef BOOST_CONFIG_HPP
0018 #  include <boost/config.hpp>
0019 #endif
0020 #
0021 #if defined(BOOST_HAS_PRAGMA_ONCE)
0022 #  pragma once
0023 #endif
0024
0025 #include <boost/move/detail/config_begin.hpp>
0026
0027 #ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
0028 #include <boost/move/core.hpp>
0029 #endif
0030 #include <boost/move/detail/meta_utils.hpp>
0031 #include <boost/move/detail/type_traits.hpp>
0032
0033 namespace boost {
0034
0035 //! If this trait yields to true
0036 //! (<i>has_trivial_destructor_after_move &lt;T&gt;::value == true</i>)
0037 //! means that if T is used as argument of a move construction/assignment,
0038 //! there is no need to call T's destructor.
0039 //! This optimization tipically is used to improve containers' performance.
0040 //!
0041 //! By default this trait is true if the type has trivial destructor,
0042 //! every class should specialize this trait if it wants to improve performance
0043 //! when inserted in containers.
0044 template <class T>
0045 struct has_trivial_destructor_after_move
0046    : ::boost::move_detail::is_trivially_destructible<T>
0047 {};
0048
0049 //! By default this traits returns
0050 //! <pre>boost::is_nothrow_move_constructible<T>::value && boost::is_nothrow_move_assignable<T>::value </pre>.
0051 //! Classes with non-throwing move constructor
0052 //! and assignment can specialize this trait to obtain some performance improvements.
0053 template <class T>
0054 struct has_nothrow_move
0055 {
0056    static const bool value = boost::move_detail::is_nothrow_move_constructible<T>::value &&
0057                              boost::move_detail::is_nothrow_move_assignable<T>::value;
0058 };
0059
0060 namespace move_detail {
0061
0062 template <class T>
0063 struct is_nothrow_move_constructible_or_uncopyable
0064 {
0065    //The standard requires is_nothrow_move_constructible for move_if_noexcept
0066    //but a user (usually in C++03) might specialize has_nothrow_move which includes it
0067    static const bool value = is_nothrow_move_constructible<T>::value ||
0068                              has_nothrow_move<T>::value ||
0069                             !is_copy_constructible<T>::value;
0070 };
0071
0072 }  //move_detail {
0073 }  //namespace boost {
0074
0075 #include <boost/move/detail/config_end.hpp>
0076
0077 #endif //#ifndef BOOST_MOVE_TRAITS_HPP