ceph/src/boost/libs/move/include/boost/move/traits.hpp

   1 //////////////////////////////////////////////////////////////////////////////
   2 //
   3 // (C) Copyright Ion Gaztanaga 2009-2012.
   4 // Distributed under the Boost Software License, Version 1.0.
   5 // (See accompanying file LICENSE_1_0.txt or copy at
   6 // http://www.boost.org/LICENSE_1_0.txt)
   7 //
   8 // See http://www.boost.org/libs/move for documentation.
   9 //
  10 //////////////////////////////////////////////////////////////////////////////
  11
  12 //! \file
  13
  14 #ifndef BOOST_MOVE_TRAITS_HPP
  15 #define BOOST_MOVE_TRAITS_HPP
  16
  17 #ifndef BOOST_CONFIG_HPP
  18 #  include <boost/config.hpp>
  19 #endif
  20 #
  21 #if defined(BOOST_HAS_PRAGMA_ONCE)
  22 #  pragma once
  23 #endif
  24
  25 #include <boost/move/detail/config_begin.hpp>
  26
  27 #ifndef BOOST_NO_CXX11_RVALUE_REFERENCES
  28 #include <boost/move/core.hpp>
  29 #endif
  30 #include <boost/move/detail/meta_utils.hpp>
  31 #include <boost/move/detail/type_traits.hpp>
  32
  33 namespace boost {
  34
  35 //! If this trait yields to true
  36 //! (<i>has_trivial_destructor_after_move &lt;T&gt;::value == true</i>)
  37 //! means that if T is used as argument of a move construction/assignment,
  38 //! there is no need to call T's destructor.
  39 //! This optimization tipically is used to improve containers' performance.
  40 //!
  41 //! By default this trait is true if the type has trivial destructor,
  42 //! every class should specialize this trait if it wants to improve performance
  43 //! when inserted in containers.
  44 template <class T>
  45 struct has_trivial_destructor_after_move
  46    : ::boost::move_detail::is_trivially_destructible<T>
  47 {};
  48
  49 //! By default this traits returns
  50 //! <pre>boost::is_nothrow_move_constructible<T>::value && boost::is_nothrow_move_assignable<T>::value </pre>.
  51 //! Classes with non-throwing move constructor
  52 //! and assignment can specialize this trait to obtain some performance improvements.
  53 template <class T>
  54 struct has_nothrow_move
  55 {
  56    static const bool value = boost::move_detail::is_nothrow_move_constructible<T>::value &&
  57                              boost::move_detail::is_nothrow_move_assignable<T>::value;
  58 };
  59
  60 namespace move_detail {
  61
  62 template <class T>
  63 struct is_nothrow_move_constructible_or_uncopyable
  64 {
  65    //The standard requires is_nothrow_move_constructible for move_if_noexcept
  66    //but a user (usually in C++03) might specialize has_nothrow_move which includes it
  67    static const bool value = is_nothrow_move_constructible<T>::value ||
  68                              has_nothrow_move<T>::value ||
  69                             !is_copy_constructible<T>::value;
  70 };
  71
  72 }  //move_detail {
  73 }  //namespace boost {
  74
  75 #include <boost/move/detail/config_end.hpp>
  76
  77 #endif //#ifndef BOOST_MOVE_TRAITS_HPP