boost/boost/type_traits/type_with_alignment.hpp

   1 //  (C) Copyright John Maddock 2000.
   2 //  Use, modification and distribution are subject to the Boost Software License,
   3 //  Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
   4 //  http://www.boost.org/LICENSE_1_0.txt).
   5 //
   6 //  See http://www.boost.org/libs/type_traits for most recent version including documentation.
   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/preprocessor/list/transform.hpp>
  16 #include <boost/preprocessor/list/append.hpp>
  17 #include <boost/type_traits/alignment_of.hpp>
  18 #include <boost/type_traits/is_pod.hpp>
  19 #include <boost/static_assert.hpp>
  20 #include <boost/config.hpp>
  21
  22 // should be the last #include
  23 #include <boost/type_traits/detail/bool_trait_def.hpp>
  24
  25 #include <cstddef>
  26
  27 #ifdef BOOST_MSVC
  28 #   pragma warning(push)
  29 #   pragma warning(disable: 4121) // alignment is sensitive to packing
  30 #endif
  31
  32 namespace boost {
  33
  34 #ifndef __BORLANDC__
  35
  36 namespace detail {
  37
  38 class alignment_dummy;
  39 typedef void (*function_ptr)();
  40 typedef int (alignment_dummy::*member_ptr);
  41 typedef int (alignment_dummy::*member_function_ptr)();
  42
  43 #ifdef BOOST_HAS_LONG_LONG
  44 #define BOOST_TT_ALIGNMENT_BASE_TYPES BOOST_PP_TUPLE_TO_LIST( \
  45         12, ( \
  46         char, short, int, long,  ::boost::long_long_type, float, double, long double \
  47         , void*, function_ptr, member_ptr, member_function_ptr))
  48 #else
  49 #define BOOST_TT_ALIGNMENT_BASE_TYPES BOOST_PP_TUPLE_TO_LIST( \
  50         11, ( \
  51         char, short, int, long, float, double, long double \
  52         , void*, function_ptr, member_ptr, member_function_ptr))
  53 #endif
  54
  55 #define BOOST_TT_HAS_ONE_T(D,Data,T) boost::detail::has_one_T< T >
  56
  57 #define BOOST_TT_ALIGNMENT_STRUCT_TYPES                         \
  58         BOOST_PP_LIST_TRANSFORM(BOOST_TT_HAS_ONE_T,             \
  59                                 X,                              \
  60                                 BOOST_TT_ALIGNMENT_BASE_TYPES)
  61
  62 #define BOOST_TT_ALIGNMENT_TYPES                                \
  63         BOOST_PP_LIST_APPEND(BOOST_TT_ALIGNMENT_BASE_TYPES,     \
  64                              BOOST_TT_ALIGNMENT_STRUCT_TYPES)
  65
  66 //
  67 // lower_alignment_helper --
  68 //
  69 // This template gets instantiated a lot, so use partial
  70 // specialization when available to reduce the compiler burden.
  71 //
  72 #ifdef BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
  73 template <bool found = true>
  74 struct lower_alignment_helper_impl
  75 {
  76     template <std::size_t, class>
  77     struct apply
  78     {
  79         typedef char type;
  80         enum { value = true };
  81     };
  82 };
  83
  84 template <>
  85 struct lower_alignment_helper_impl<false>
  86 {
  87     template <std::size_t target, class TestType>
  88     struct apply
  89       : mpl::if_c<(alignment_of<TestType>::value == target), TestType, char>
  90     {
  91         enum { value = (alignment_of<TestType>::value == target) };
  92     };
  93 };
  94
  95 template <bool found, std::size_t target, class TestType>
  96 struct lower_alignment_helper
  97   : lower_alignment_helper_impl<found>::template apply<target,TestType>
  98 {
  99 };
 100 #else
 101 template <bool found, std::size_t target, class TestType>
 102 struct lower_alignment_helper
 103 {
 104     typedef char type;
 105     enum { value = true };
 106 };
 107
 108 template <std::size_t target, class TestType>
 109 struct lower_alignment_helper<false,target,TestType>
 110 {
 111     enum { value = (alignment_of<TestType>::value == target) };
 112     typedef typename mpl::if_c<value, TestType, char>::type type;
 113 };
 114 #endif
 115
 116 #define BOOST_TT_CHOOSE_MIN_ALIGNMENT(R,P,I,T)                                  \
 117         typename lower_alignment_helper<                                        \
 118           BOOST_PP_CAT(found,I),target,T                                        \
 119         >::type BOOST_PP_CAT(t,I);                                              \
 120         enum {                                                                  \
 121             BOOST_PP_CAT(found,BOOST_PP_INC(I))                                 \
 122               = lower_alignment_helper<BOOST_PP_CAT(found,I),target,T >::value  \
 123         };
 124
 125 #define BOOST_TT_CHOOSE_T(R,P,I,T) T BOOST_PP_CAT(t,I);
 126
 127 template <typename T>
 128 struct has_one_T
 129 {
 130   T data;
 131 };
 132
 133 template <std::size_t target>
 134 union lower_alignment
 135 {
 136     enum { found0 = false };
 137
 138     BOOST_PP_LIST_FOR_EACH_I(
 139           BOOST_TT_CHOOSE_MIN_ALIGNMENT
 140         , ignored
 141         , BOOST_TT_ALIGNMENT_TYPES
 142         )
 143 };
 144
 145 union max_align
 146 {
 147     BOOST_PP_LIST_FOR_EACH_I(
 148           BOOST_TT_CHOOSE_T
 149         , ignored
 150         , BOOST_TT_ALIGNMENT_TYPES
 151         )
 152 };
 153
 154 #undef BOOST_TT_ALIGNMENT_BASE_TYPES
 155 #undef BOOST_TT_HAS_ONE_T
 156 #undef BOOST_TT_ALIGNMENT_STRUCT_TYPES
 157 #undef BOOST_TT_ALIGNMENT_TYPES
 158 #undef BOOST_TT_CHOOSE_MIN_ALIGNMENT
 159 #undef BOOST_TT_CHOOSE_T
 160
 161 template<std::size_t TAlign, std::size_t Align>
 162 struct is_aligned
 163 {
 164     BOOST_STATIC_CONSTANT(bool,
 165         value = (TAlign >= Align) & (TAlign % Align == 0)
 166         );
 167 };
 168
 169 #ifdef BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
 170 BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC1(is_pod,::boost::detail::max_align,true)
 171 BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC1(is_pod,::boost::detail::lower_alignment<1> ,true)
 172 BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC1(is_pod,::boost::detail::lower_alignment<2> ,true)
 173 BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC1(is_pod,::boost::detail::lower_alignment<4> ,true)
 174 BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC1(is_pod,::boost::detail::lower_alignment<8> ,true)
 175 BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC1(is_pod,::boost::detail::lower_alignment<10> ,true)
 176 BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC1(is_pod,::boost::detail::lower_alignment<16> ,true)
 177 BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC1(is_pod,::boost::detail::lower_alignment<32> ,true)
 178 #endif
 179
 180 } // namespace detail
 181
 182 #ifndef BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
 183 template<std::size_t Align>
 184 struct is_pod< ::boost::detail::lower_alignment<Align> >
 185 {
 186         BOOST_STATIC_CONSTANT(std::size_t, value = true);
 187 };
 188 #endif
 189
 190 // This alignment method originally due to Brian Parker, implemented by David
 191 // Abrahams, and then ported here by Doug Gregor.
 192 template <std::size_t Align>
 193 class type_with_alignment
 194 {
 195     typedef ::boost::detail::lower_alignment<Align> t1;
 196     typedef typename mpl::if_c<
 197           ::boost::detail::is_aligned< ::boost::alignment_of<t1>::value,Align >::value
 198         , t1
 199         , ::boost::detail::max_align
 200         >::type align_t;
 201
 202     BOOST_STATIC_CONSTANT(std::size_t, found = alignment_of<align_t>::value);
 203
 204     BOOST_STATIC_ASSERT(found >= Align);
 205     BOOST_STATIC_ASSERT(found % Align == 0);
 206
 207  public:
 208     typedef align_t type;
 209 };
 210
 211 #if defined(__GNUC__)
 212 namespace align {
 213 struct __attribute__((__aligned__(2))) a2 {};
 214 struct __attribute__((__aligned__(4))) a4 {};
 215 struct __attribute__((__aligned__(8))) a8 {};
 216 struct __attribute__((__aligned__(16))) a16 {};
 217 struct __attribute__((__aligned__(32))) a32 {};
 218 }
 219
 220 template<> class type_with_alignment<1>  { public: typedef char type; };
 221 template<> class type_with_alignment<2>  { public: typedef align::a2 type; };
 222 template<> class type_with_alignment<4>  { public: typedef align::a4 type; };
 223 template<> class type_with_alignment<8>  { public: typedef align::a8 type; };
 224 template<> class type_with_alignment<16> { public: typedef align::a16 type; };
 225 template<> class type_with_alignment<32> { public: typedef align::a32 type; };
 226
 227 namespace detail {
 228 BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC1(is_pod,::boost::align::a2,true)
 229 BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC1(is_pod,::boost::align::a4,true)
 230 BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC1(is_pod,::boost::align::a8,true)
 231 BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC1(is_pod,::boost::align::a16,true)
 232 BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC1(is_pod,::boost::align::a32,true)
 233 }
 234 #endif
 235
 236 #else
 237
 238 //
 239 // Borland specific version, we have this for two reasons:
 240 // 1) The version above doesn't always compile (with the new test cases for example)
 241 // 2) Because of Borlands #pragma option we can create types with alignments that are
 242 //    greater that the largest aligned builtin type.
 243
 244 namespace align{
 245 #pragma option push -a16
 246 struct a2{ short s; };
 247 struct a4{ int s; };
 248 struct a8{ double s; };
 249 struct a16{ long double s; };
 250 #pragma option pop
 251 }
 252
 253 namespace detail {
 254
 255 typedef ::boost::align::a16 max_align;
 256
 257 BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC1(is_pod,::boost::align::a2,true)
 258 BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC1(is_pod,::boost::align::a4,true)
 259 BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC1(is_pod,::boost::align::a8,true)
 260 BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC1(is_pod,::boost::align::a16,true)
 261 }
 262
 263 template <std::size_t N> struct type_with_alignment
 264 {
 265    // We should never get to here, but if we do use the maximally
 266    // aligned type:
 267    // BOOST_STATIC_ASSERT(0);
 268    typedef align::a16 type;
 269 };
 270 template <> struct type_with_alignment<1>{ typedef char type; };
 271 template <> struct type_with_alignment<2>{ typedef align::a2 type; };
 272 template <> struct type_with_alignment<4>{ typedef align::a4 type; };
 273 template <> struct type_with_alignment<8>{ typedef align::a8 type; };
 274 template <> struct type_with_alignment<16>{ typedef align::a16 type; };
 275
 276 #endif
 277
 278 } // namespace boost
 279
 280 #ifdef BOOST_MSVC
 281 #   pragma warning(pop)
 282 #endif
 283
 284 #include <boost/type_traits/detail/bool_trait_undef.hpp>
 285
 286 #endif // BOOST_TT_TYPE_WITH_ALIGNMENT_INCLUDED
 287
 288