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 namespace detail{
 193
 194 template <std::size_t Align>
 195 class type_with_alignment_imp
 196 {
 197     typedef ::boost::detail::lower_alignment<Align> t1;
 198     typedef typename mpl::if_c<
 199           ::boost::detail::is_aligned< ::boost::alignment_of<t1>::value,Align >::value
 200         , t1
 201         , ::boost::detail::max_align
 202         >::type align_t;
 203
 204     BOOST_STATIC_CONSTANT(std::size_t, found = alignment_of<align_t>::value);
 205
 206     BOOST_STATIC_ASSERT(found >= Align);
 207     BOOST_STATIC_ASSERT(found % Align == 0);
 208
 209  public:
 210     typedef align_t type;
 211 };
 212
 213 }
 214
 215 template <std::size_t Align>
 216 class type_with_alignment
 217   : public ::boost::detail::type_with_alignment_imp<Align>
 218 {
 219 };
 220
 221 #if defined(__GNUC__)
 222 namespace align {
 223 struct __attribute__((__aligned__(2))) a2 {};
 224 struct __attribute__((__aligned__(4))) a4 {};
 225 struct __attribute__((__aligned__(8))) a8 {};
 226 struct __attribute__((__aligned__(16))) a16 {};
 227 struct __attribute__((__aligned__(32))) a32 {};
 228 }
 229
 230 template<> class type_with_alignment<1>  { public: typedef char type; };
 231 template<> class type_with_alignment<2>  { public: typedef align::a2 type; };
 232 template<> class type_with_alignment<4>  { public: typedef align::a4 type; };
 233 template<> class type_with_alignment<8>  { public: typedef align::a8 type; };
 234 template<> class type_with_alignment<16> { public: typedef align::a16 type; };
 235 template<> class type_with_alignment<32> { public: typedef align::a32 type; };
 236
 237 namespace detail {
 238 BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC1(is_pod,::boost::align::a2,true)
 239 BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC1(is_pod,::boost::align::a4,true)
 240 BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC1(is_pod,::boost::align::a8,true)
 241 BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC1(is_pod,::boost::align::a16,true)
 242 BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC1(is_pod,::boost::align::a32,true)
 243 }
 244 #endif
 245 #if (defined(BOOST_MSVC) || (defined(BOOST_INTEL) && defined(_MSC_VER))) && _MSC_VER >= 1300
 246 //
 247 // MSVC supports types which have alignments greater than the normal
 248 // maximum: these are used for example in the types __m64 and __m128
 249 // to provide types with alignment requirements which match the SSE
 250 // registers.  Therefore we extend type_with_alignment<> to support
 251 // such types, however, we have to be careful to use a builtin type
 252 // whenever possible otherwise we break previously working code:
 253 // see http://article.gmane.org/gmane.comp.lib.boost.devel/173011
 254 // for an example and test case.  Thus types like a8 below will
 255 // be used *only* if the existing implementation can't provide a type
 256 // with suitable alignment.  This does mean however, that type_with_alignment<>
 257 // may return a type which cannot be passed through a function call
 258 // by value (and neither can any type containing such a type like
 259 // Boost.Optional).  However, this only happens when we have no choice
 260 // in the matter because no other "ordinary" type is available.
 261 //
 262 namespace align {
 263 struct __declspec(align(8)) a8 {
 264    char m[8];
 265    typedef a8 type;
 266 };
 267 struct __declspec(align(16)) a16 {
 268    char m[16];
 269    typedef a16 type;
 270 };
 271 struct __declspec(align(32)) a32 {
 272    char m[32];
 273    typedef a32 type;
 274 };
 275 struct __declspec(align(64)) a64
 276 {
 277    char m[64];
 278    typedef a64 type;
 279 };
 280 struct __declspec(align(128)) a128 {
 281    char m[128];
 282    typedef a128 type;
 283 };
 284 }
 285
 286 template<> class type_with_alignment<8>
 287 {
 288    typedef mpl::if_c<
 289       ::boost::alignment_of<detail::max_align>::value < 8,
 290       align::a8,
 291       detail::type_with_alignment_imp<8> >::type t1;
 292 public:
 293    typedef t1::type type;
 294 };
 295 template<> class type_with_alignment<16>
 296 {
 297    typedef mpl::if_c<
 298       ::boost::alignment_of<detail::max_align>::value < 16,
 299       align::a16,
 300       detail::type_with_alignment_imp<16> >::type t1;
 301 public:
 302    typedef t1::type type;
 303 };
 304 template<> class type_with_alignment<32>
 305 {
 306    typedef mpl::if_c<
 307       ::boost::alignment_of<detail::max_align>::value < 32,
 308       align::a32,
 309       detail::type_with_alignment_imp<32> >::type t1;
 310 public:
 311    typedef t1::type type;
 312 };
 313 template<> class type_with_alignment<64> {
 314    typedef mpl::if_c<
 315       ::boost::alignment_of<detail::max_align>::value < 64,
 316       align::a64,
 317       detail::type_with_alignment_imp<64> >::type t1;
 318 public:
 319    typedef t1::type type;
 320 };
 321 template<> class type_with_alignment<128> {
 322    typedef mpl::if_c<
 323       ::boost::alignment_of<detail::max_align>::value < 128,
 324       align::a128,
 325       detail::type_with_alignment_imp<128> >::type t1;
 326 public:
 327    typedef t1::type type;
 328 };
 329
 330 namespace detail {
 331 BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC1(is_pod,::boost::align::a8,true)
 332 BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC1(is_pod,::boost::align::a16,true)
 333 BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC1(is_pod,::boost::align::a32,true)
 334 BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC1(is_pod,::boost::align::a64,true)
 335 BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC1(is_pod,::boost::align::a128,true)
 336 }
 337 #endif
 338
 339 #else
 340
 341 //
 342 // Borland specific version, we have this for two reasons:
 343 // 1) The version above doesn't always compile (with the new test cases for example)
 344 // 2) Because of Borlands #pragma option we can create types with alignments that are
 345 //    greater that the largest aligned builtin type.
 346
 347 namespace align{
 348 #pragma option push -a16
 349 struct a2{ short s; };
 350 struct a4{ int s; };
 351 struct a8{ double s; };
 352 struct a16{ long double s; };
 353 #pragma option pop
 354 }
 355
 356 namespace detail {
 357
 358 typedef ::boost::align::a16 max_align;
 359
 360 //#if ! BOOST_WORKAROUND(__CODEGEARC__, BOOST_TESTED_AT(0x610))
 361 BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC1(is_pod,::boost::align::a2,true)
 362 BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC1(is_pod,::boost::align::a4,true)
 363 BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC1(is_pod,::boost::align::a8,true)
 364 BOOST_TT_AUX_BOOL_TRAIT_IMPL_SPEC1(is_pod,::boost::align::a16,true)
 365 //#endif
 366 }
 367
 368 template <std::size_t N> struct type_with_alignment
 369 {
 370    // We should never get to here, but if we do use the maximally
 371    // aligned type:
 372    // BOOST_STATIC_ASSERT(0);
 373    typedef align::a16 type;
 374 };
 375 template <> struct type_with_alignment<1>{ typedef char type; };
 376 template <> struct type_with_alignment<2>{ typedef align::a2 type; };
 377 template <> struct type_with_alignment<4>{ typedef align::a4 type; };
 378 template <> struct type_with_alignment<8>{ typedef align::a8 type; };
 379 template <> struct type_with_alignment<16>{ typedef align::a16 type; };
 380
 381 #endif
 382
 383 } // namespace boost
 384
 385 #ifdef BOOST_MSVC
 386 #   pragma warning(pop)
 387 #endif
 388
 389 #include <boost/type_traits/detail/bool_trait_undef.hpp>
 390
 391 #endif // BOOST_TT_TYPE_WITH_ALIGNMENT_INCLUDED
 392
 393