ceph/src/boost/libs/type_traits/include/boost/type_traits/is_empty.hpp

   1
   2 // (C) Copyright Steve Cleary, Beman Dawes, Howard Hinnant & John Maddock 2000.
   3 //  Use, modification and distribution are subject to the Boost Software License,
   4 //  Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
   5 //  http://www.boost.org/LICENSE_1_0.txt).
   6 //
   7 //  See http://www.boost.org/libs/type_traits for most recent version including documentation.
   8
   9 #ifndef BOOST_TT_IS_EMPTY_HPP_INCLUDED
  10 #define BOOST_TT_IS_EMPTY_HPP_INCLUDED
  11
  12 #include <boost/type_traits/is_convertible.hpp>
  13 #include <boost/type_traits/detail/config.hpp>
  14 #include <boost/type_traits/intrinsics.hpp>
  15
  16 #include <boost/type_traits/remove_cv.hpp>
  17 #include <boost/type_traits/is_class.hpp>
  18 #include <boost/type_traits/add_reference.hpp>
  19
  20 #ifndef BOOST_INTERNAL_IS_EMPTY
  21 #define BOOST_INTERNAL_IS_EMPTY(T) false
  22 #else
  23 #define BOOST_INTERNAL_IS_EMPTY(T) BOOST_IS_EMPTY(T)
  24 #endif
  25
  26 namespace boost {
  27
  28 namespace detail {
  29
  30
  31 #ifdef BOOST_MSVC
  32 #pragma warning(push)
  33 #pragma warning(disable:4624) // destructor could not be generated
  34 #endif
  35
  36 template <typename T>
  37 struct empty_helper_t1 : public T
  38 {
  39     empty_helper_t1();  // hh compiler bug workaround
  40     int i[256];
  41 private:
  42    // suppress compiler warnings:
  43    empty_helper_t1(const empty_helper_t1&);
  44    empty_helper_t1& operator=(const empty_helper_t1&);
  45 };
  46
  47 #ifdef BOOST_MSVC
  48 #pragma warning(pop)
  49 #endif
  50
  51 struct empty_helper_t2 { int i[256]; };
  52
  53 #if !BOOST_WORKAROUND(__BORLANDC__, < 0x600)
  54
  55 template <typename T, bool is_a_class = false>
  56 struct empty_helper
  57 {
  58     BOOST_STATIC_CONSTANT(bool, value = false);
  59 };
  60
  61 template <typename T>
  62 struct empty_helper<T, true>
  63 {
  64     BOOST_STATIC_CONSTANT(
  65         bool, value = (sizeof(empty_helper_t1<T>) == sizeof(empty_helper_t2))
  66         );
  67 };
  68
  69 template <typename T>
  70 struct is_empty_impl
  71 {
  72     typedef typename remove_cv<T>::type cvt;
  73     BOOST_STATIC_CONSTANT(
  74         bool,
  75         value = ( ::boost::detail::empty_helper<cvt,::boost::is_class<T>::value>::value || BOOST_INTERNAL_IS_EMPTY(cvt)));
  76 };
  77
  78 #else // __BORLANDC__
  79
  80 template <typename T, bool is_a_class, bool convertible_to_int>
  81 struct empty_helper
  82 {
  83     BOOST_STATIC_CONSTANT(bool, value = false);
  84 };
  85
  86 template <typename T>
  87 struct empty_helper<T, true, false>
  88 {
  89     BOOST_STATIC_CONSTANT(bool, value = (
  90         sizeof(empty_helper_t1<T>) == sizeof(empty_helper_t2)
  91         ));
  92 };
  93
  94 template <typename T>
  95 struct is_empty_impl
  96 {
  97    typedef typename remove_cv<T>::type cvt;
  98    typedef typename add_reference<T>::type r_type;
  99
 100    BOOST_STATIC_CONSTANT(
 101        bool, value = (
 102               ::boost::detail::empty_helper<
 103                   cvt
 104                 , ::boost::is_class<T>::value
 105                 , ::boost::is_convertible< r_type,int>::value
 106               >::value || BOOST_INTERNAL_IS_EMPTY(cvt));
 107 };
 108
 109 #endif // __BORLANDC__
 110
 111 } // namespace detail
 112
 113 template <class T> struct is_empty : integral_constant<bool, ::boost::detail::is_empty_impl<T>::value> {};
 114
 115 } // namespace boost
 116
 117 #undef BOOST_INTERNAL_IS_EMPTY
 118
 119 #endif // BOOST_TT_IS_EMPTY_HPP_INCLUDED
 120