boost/boost/type_traits/alignment_of.hpp

   1
   2 // (C) Copyright John Maddock 2000.
   3 // Permission to copy, use, modify, sell and distribute this software is
   4 // granted provided this copyright notice appears in all copies. This software
   5 // is provided "as is" without express or implied warranty, and with no claim
   6 // as to its suitability for any purpose.
   7
   8 #ifndef BOOST_TT_ALIGNMENT_OF_HPP_INCLUDED
   9 #define BOOST_TT_ALIGNMENT_OF_HPP_INCLUDED
  10
  11 #include "boost/config.hpp"
  12 #include <cstddef>
  13
  14 // should be the last #include
  15 #include "boost/type_traits/detail/size_t_trait_def.hpp"
  16
  17 #ifdef BOOST_MSVC
  18 #   pragma warning(push)
  19 #   pragma warning(disable: 4121) // alignment is sensitive to packing
  20 #endif
  21
  22 namespace boost {
  23
  24 template <typename T> struct alignment_of;
  25
  26 // get the alignment of some arbitrary type:
  27 namespace detail {
  28
  29 template <typename T>
  30 struct alignment_of_hack
  31 {
  32     char c;
  33     T t;
  34     alignment_of_hack();
  35 };
  36
  37
  38 template <unsigned A, unsigned S>
  39 struct alignment_logic
  40 {
  41     BOOST_STATIC_CONSTANT(std::size_t, value = A < S ? A : S);
  42 };
  43
  44
  45 template< typename T >
  46 struct alignment_of_impl
  47 {
  48     BOOST_STATIC_CONSTANT(std::size_t, value =
  49         (::boost::detail::alignment_logic<
  50             sizeof(detail::alignment_of_hack<T>) - sizeof(T),
  51             sizeof(T)
  52         >::value));
  53 };
  54
  55 } // namespace detail
  56
  57 BOOST_TT_AUX_SIZE_T_TRAIT_DEF1(alignment_of,T,::boost::detail::alignment_of_impl<T>::value)
  58
  59 // references have to be treated specially, assume
  60 // that a reference is just a special pointer:
  61 #ifndef BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
  62 template <typename T>
  63 struct alignment_of<T&>
  64     : alignment_of<T*>
  65 {
  66 };
  67 #endif
  68
  69 // void has to be treated specially:
  70 BOOST_TT_AUX_SIZE_T_TRAIT_SPEC1(alignment_of,void,0)
  71 #ifndef BOOST_NO_CV_VOID_SPECIALIZATIONS
  72 BOOST_TT_AUX_SIZE_T_TRAIT_SPEC1(alignment_of,void const,0)
  73 BOOST_TT_AUX_SIZE_T_TRAIT_SPEC1(alignment_of,void volatile,0)
  74 BOOST_TT_AUX_SIZE_T_TRAIT_SPEC1(alignment_of,void const volatile,0)
  75 #endif
  76
  77 } // namespace boost
  78
  79 #ifdef BOOST_MSVC
  80 #   pragma warning(pop)
  81 #endif
  82
  83 #include "boost/type_traits/detail/size_t_trait_undef.hpp"
  84
  85 #endif // BOOST_TT_ALIGNMENT_OF_HPP_INCLUDED