boost/boost/type_traits/type_with_alignment.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
   5 // software is provided "as is" without express or implied warranty,
   6 // and with no claim as to its suitability for any purpose.
   7
   8 #ifndef BOOST_TT_TYPE_WITH_ALIGNMENT_INCLUDED
   9 #define BOOST_TT_TYPE_WITH_ALIGNMENT_INCLUDED
  10
  11 #include "boost/mpl/if.hpp"
  12 #include "boost/preprocessor/list/for_each_i.hpp"
  13 #include "boost/preprocessor/tuple/to_list.hpp"
  14 #include "boost/preprocessor/cat.hpp"
  15 #include "boost/type_traits/alignment_of.hpp"
  16 #include "boost/static_assert.hpp"
  17 #include "boost/config.hpp"
  18
  19 #include <cstddef>
  20
  21 #ifdef BOOST_MSVC
  22 #   pragma warning(push)
  23 #   pragma warning(disable: 4121) // alignment is sensitive to packing
  24 #endif
  25
  26 namespace boost {
  27
  28 namespace detail {
  29
  30 class alignment_dummy;
  31 typedef void (*function_ptr)();
  32 typedef int (alignment_dummy::*member_ptr);
  33 typedef int (alignment_dummy::*member_function_ptr)();
  34
  35 #define BOOST_TT_ALIGNMENT_TYPES BOOST_PP_TUPLE_TO_LIST( \
  36         11, ( \
  37         char, short, int, long, float, double, long double \
  38         , void*, function_ptr, member_ptr, member_function_ptr))
  39
  40 #define BOOST_TT_CHOOSE_MIN_ALIGNMENT(R,P,I,T) \
  41         typename mpl::if_c< \
  42            alignment_of<T>::value <= target, T, char>::type BOOST_PP_CAT(t,I);
  43
  44 #define BOOST_TT_CHOOSE_T(R,P,I,T) T BOOST_PP_CAT(t,I);
  45
  46 template <std::size_t target>
  47 union lower_alignment
  48 {
  49     BOOST_PP_LIST_FOR_EACH_I(
  50           BOOST_TT_CHOOSE_MIN_ALIGNMENT
  51         , ignored
  52         , BOOST_TT_ALIGNMENT_TYPES
  53         )
  54 };
  55
  56 union max_align
  57 {
  58     BOOST_PP_LIST_FOR_EACH_I(
  59           BOOST_TT_CHOOSE_T
  60         , ignored
  61         , BOOST_TT_ALIGNMENT_TYPES
  62         )
  63 };
  64
  65 #undef BOOST_TT_ALIGNMENT_TYPES
  66 #undef BOOST_TT_CHOOSE_MIN_ALIGNMENT
  67 #undef BOOST_TT_CHOOSE_T
  68
  69 template<int TAlign, int Align>
  70 struct is_aligned
  71 {
  72     BOOST_STATIC_CONSTANT(bool,
  73         value = (TAlign >= Align) & (TAlign % Align == 0)
  74         );
  75 };
  76
  77 } // namespace detail
  78
  79 // This alignment method originally due to Brian Parker, implemented by David
  80 // Abrahams, and then ported here by Doug Gregor.
  81 template <int Align>
  82 class type_with_alignment
  83 {
  84     typedef detail::lower_alignment<Align> t1;
  85     typedef typename mpl::if_c<
  86           ::boost::detail::is_aligned< ::boost::alignment_of<t1>::value,Align >::value
  87         , t1
  88         , detail::max_align
  89         >::type align_t;
  90
  91     BOOST_STATIC_CONSTANT(std::size_t, found = alignment_of<align_t>::value);
  92
  93     BOOST_STATIC_ASSERT(found >= Align);
  94     BOOST_STATIC_ASSERT(found % Align == 0);
  95
  96  public:
  97     typedef align_t type;
  98 };
  99
 100 } // namespace boost
 101
 102 #ifdef BOOST_MSVC
 103 #   pragma warning(pop)
 104 #endif
 105
 106 #endif // BOOST_TT_TYPE_WITH_ALIGNMENT_INCLUDED