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 #ifdef __BORLANDC__
  22 #pragma option push -Vx- -Ve-
  23 #endif
  24
  25 namespace boost {
  26
  27 template <typename T> struct alignment_of;
  28
  29 // get the alignment of some arbitrary type:
  30 namespace detail {
  31
  32 template <typename T>
  33 struct alignment_of_hack
  34 {
  35     char c;
  36     T t;
  37     alignment_of_hack();
  38 };
  39
  40
  41 template <unsigned A, unsigned S>
  42 struct alignment_logic
  43 {
  44     BOOST_STATIC_CONSTANT(std::size_t, value = A < S ? A : S);
  45 };
  46
  47
  48 template< typename T >
  49 struct alignment_of_impl
  50 {
  51     BOOST_STATIC_CONSTANT(std::size_t, value =
  52         (::boost::detail::alignment_logic<
  53             sizeof(detail::alignment_of_hack<T>) - sizeof(T),
  54             sizeof(T)
  55         >::value));
  56 };
  57
  58 } // namespace detail
  59
  60 BOOST_TT_AUX_SIZE_T_TRAIT_DEF1(alignment_of,T,::boost::detail::alignment_of_impl<T>::value)
  61
  62 // references have to be treated specially, assume
  63 // that a reference is just a special pointer:
  64 #ifndef BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
  65 template <typename T>
  66 struct alignment_of<T&>
  67     : alignment_of<T*>
  68 {
  69 };
  70 #endif
  71 #ifdef __BORLANDC__
  72 // long double gives an incorrect value of 10 (!)
  73 // unless we do this...
  74 struct long_double_wrapper{ long double ld; };
  75 template<> struct alignment_of<long double>
  76    : public alignment_of<long_double_wrapper>{};
  77 #endif
  78
  79 // void has to be treated specially:
  80 BOOST_TT_AUX_SIZE_T_TRAIT_SPEC1(alignment_of,void,0)
  81 #ifndef BOOST_NO_CV_VOID_SPECIALIZATIONS
  82 BOOST_TT_AUX_SIZE_T_TRAIT_SPEC1(alignment_of,void const,0)
  83 BOOST_TT_AUX_SIZE_T_TRAIT_SPEC1(alignment_of,void volatile,0)
  84 BOOST_TT_AUX_SIZE_T_TRAIT_SPEC1(alignment_of,void const volatile,0)
  85 #endif
  86
  87 } // namespace boost
  88
  89 #ifdef __BORLANDC__
  90 #pragma option pop
  91 #endif
  92 #ifdef BOOST_MSVC
  93 #   pragma warning(pop)
  94 #endif
  95
  96 #include "boost/type_traits/detail/size_t_trait_undef.hpp"
  97
  98 #endif // BOOST_TT_ALIGNMENT_OF_HPP_INCLUDED
  99