boost/functional/hash/detail/float_functions.hpp

   1
   2 // Copyright 2005-2009 Daniel James.
   3 // Distributed under the Boost Software License, Version 1.0. (See accompanying
   4 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
   5
   6 #if !defined(BOOST_FUNCTIONAL_HASH_DETAIL_FLOAT_FUNCTIONS_HPP)
   7 #define BOOST_FUNCTIONAL_HASH_DETAIL_FLOAT_FUNCTIONS_HPP
   8
   9 #include <boost/config.hpp>
  10 #if defined(BOOST_HAS_PRAGMA_ONCE)
  11 #pragma once
  12 #endif
  13
  14 #include <boost/config/no_tr1/cmath.hpp>
  15
  16 // Set BOOST_HASH_CONFORMANT_FLOATS to 1 for libraries known to have
  17 // sufficiently good floating point support to not require any
  18 // workarounds.
  19 //
  20 // When set to 0, the library tries to automatically
  21 // use the best available implementation. This normally works well, but
  22 // breaks when ambiguities are created by odd namespacing of the functions.
  23 //
  24 // Note that if this is set to 0, the library should still take full
  25 // advantage of the platform's floating point support.
  26
  27 #if defined(__SGI_STL_PORT) || defined(_STLPORT_VERSION)
  28 #   define BOOST_HASH_CONFORMANT_FLOATS 0
  29 #elif defined(__LIBCOMO__)
  30 #   define BOOST_HASH_CONFORMANT_FLOATS 0
  31 #elif defined(__STD_RWCOMPILER_H__) || defined(_RWSTD_VER)
  32 // Rogue Wave library:
  33 #   define BOOST_HASH_CONFORMANT_FLOATS 0
  34 #elif defined(_LIBCPP_VERSION)
  35 // libc++
  36 #   define BOOST_HASH_CONFORMANT_FLOATS 1
  37 #elif defined(__GLIBCPP__) || defined(__GLIBCXX__)
  38 // GNU libstdc++ 3
  39 #   if defined(__GNUC__) && __GNUC__ >= 4
  40 #       define BOOST_HASH_CONFORMANT_FLOATS 1
  41 #   else
  42 #       define BOOST_HASH_CONFORMANT_FLOATS 0
  43 #   endif
  44 #elif defined(__STL_CONFIG_H)
  45 // generic SGI STL
  46 #   define BOOST_HASH_CONFORMANT_FLOATS 0
  47 #elif defined(__MSL_CPP__)
  48 // MSL standard lib:
  49 #   define BOOST_HASH_CONFORMANT_FLOATS 0
  50 #elif defined(__IBMCPP__)
  51 // VACPP std lib (probably conformant for much earlier version).
  52 #   if __IBMCPP__ >= 1210
  53 #       define BOOST_HASH_CONFORMANT_FLOATS 1
  54 #   else
  55 #       define BOOST_HASH_CONFORMANT_FLOATS 0
  56 #   endif
  57 #elif defined(MSIPL_COMPILE_H)
  58 // Modena C++ standard library
  59 #   define BOOST_HASH_CONFORMANT_FLOATS 0
  60 #elif (defined(_YVALS) && !defined(__IBMCPP__)) || defined(_CPPLIB_VER)
  61 // Dinkumware Library (this has to appear after any possible replacement libraries):
  62 #   if _CPPLIB_VER >= 405
  63 #       define BOOST_HASH_CONFORMANT_FLOATS 1
  64 #   else
  65 #       define BOOST_HASH_CONFORMANT_FLOATS 0
  66 #   endif
  67 #else
  68 #   define BOOST_HASH_CONFORMANT_FLOATS 0
  69 #endif
  70
  71 #if BOOST_HASH_CONFORMANT_FLOATS
  72
  73 // The standard library is known to be compliant, so don't use the
  74 // configuration mechanism.
  75
  76 namespace boost {
  77     namespace hash_detail {
  78         template <typename Float>
  79         struct call_ldexp {
  80             typedef Float float_type;
  81             inline Float operator()(Float x, int y) const {
  82                 return std::ldexp(x, y);
  83             }
  84         };
  85
  86         template <typename Float>
  87         struct call_frexp {
  88             typedef Float float_type;
  89             inline Float operator()(Float x, int* y) const {
  90                 return std::frexp(x, y);
  91             }
  92         };
  93
  94         template <typename Float>
  95         struct select_hash_type
  96         {
  97             typedef Float type;
  98         };
  99     }
 100 }
 101
 102 #else // BOOST_HASH_CONFORMANT_FLOATS == 0
 103
 104 // The C++ standard requires that the C float functions are overloarded
 105 // for float, double and long double in the std namespace, but some of the older
 106 // library implementations don't support this. On some that don't, the C99
 107 // float functions (frexpf, frexpl, etc.) are available.
 108 //
 109 // The following tries to automatically detect which are available.
 110
 111 namespace boost {
 112     namespace hash_detail {
 113
 114         // Returned by dummy versions of the float functions.
 115
 116         struct not_found {
 117             // Implicitly convertible to float and long double in order to avoid
 118             // a compile error when the dummy float functions are used.
 119
 120             inline operator float() const { return 0; }
 121             inline operator long double() const { return 0; }
 122         };
 123
 124         // A type for detecting the return type of functions.
 125
 126         template <typename T> struct is;
 127         template <> struct is<float> { char x[10]; };
 128         template <> struct is<double> { char x[20]; };
 129         template <> struct is<long double> { char x[30]; };
 130         template <> struct is<boost::hash_detail::not_found> { char x[40]; };
 131
 132         // Used to convert the return type of a function to a type for sizeof.
 133
 134         template <typename T> is<T> float_type(T);
 135
 136         // call_ldexp
 137         //
 138         // This will get specialized for float and long double
 139
 140         template <typename Float> struct call_ldexp
 141         {
 142             typedef double float_type;
 143
 144             inline double operator()(double a, int b) const
 145             {
 146                 using namespace std;
 147                 return ldexp(a, b);
 148             }
 149         };
 150
 151         // call_frexp
 152         //
 153         // This will get specialized for float and long double
 154
 155         template <typename Float> struct call_frexp
 156         {
 157             typedef double float_type;
 158
 159             inline double operator()(double a, int* b) const
 160             {
 161                 using namespace std;
 162                 return frexp(a, b);
 163             }
 164         };
 165     }
 166 }
 167
 168 // A namespace for dummy functions to detect when the actual function we want
 169 // isn't available. ldexpl, ldexpf etc. might be added tby the macros below.
 170 //
 171 // AFAICT these have to be outside of the boost namespace, as if they're in
 172 // the boost namespace they'll always be preferable to any other function
 173 // (since the arguments are built in types, ADL can't be used).
 174
 175 namespace boost_hash_detect_float_functions {
 176     template <class Float> boost::hash_detail::not_found ldexp(Float, int);
 177     template <class Float> boost::hash_detail::not_found frexp(Float, int*);
 178 }
 179
 180 // Macros for generating specializations of call_ldexp and call_frexp.
 181 //
 182 // check_cpp and check_c99 check if the C++ or C99 functions are available.
 183 //
 184 // Then the call_* functions select an appropriate implementation.
 185 //
 186 // I used c99_func in a few places just to get a unique name.
 187 //
 188 // Important: when using 'using namespace' at namespace level, include as
 189 // little as possible in that namespace, as Visual C++ has an odd bug which
 190 // can cause the namespace to be imported at the global level. This seems to
 191 // happen mainly when there's a template in the same namesapce.
 192
 193 #define BOOST_HASH_CALL_FLOAT_FUNC(cpp_func, c99_func, type1, type2)    \
 194 namespace boost_hash_detect_float_functions {                           \
 195     template <class Float>                                              \
 196     boost::hash_detail::not_found c99_func(Float, type2);               \
 197 }                                                                       \
 198                                                                         \
 199 namespace boost {                                                       \
 200     namespace hash_detail {                                             \
 201         namespace c99_func##_detect {                                   \
 202             using namespace std;                                        \
 203             using namespace boost_hash_detect_float_functions;          \
 204                                                                         \
 205             struct check {                                              \
 206                 static type1 x;                                         \
 207                 static type2 y;                                         \
 208                 BOOST_STATIC_CONSTANT(bool, cpp =                       \
 209                     sizeof(float_type(cpp_func(x,y)))                   \
 210                         == sizeof(is<type1>));                          \
 211                 BOOST_STATIC_CONSTANT(bool, c99 =                       \
 212                     sizeof(float_type(c99_func(x,y)))                   \
 213                         == sizeof(is<type1>));                          \
 214             };                                                          \
 215         }                                                               \
 216                                                                         \
 217         template <bool x>                                               \
 218         struct call_c99_##c99_func :                                    \
 219             boost::hash_detail::call_##cpp_func<double> {};             \
 220                                                                         \
 221         template <>                                                     \
 222         struct call_c99_##c99_func<true> {                              \
 223             typedef type1 float_type;                                   \
 224                                                                         \
 225             template <typename T>                                       \
 226             inline type1 operator()(type1 a, T b)  const                \
 227             {                                                           \
 228                 using namespace std;                                    \
 229                 return c99_func(a, b);                                  \
 230             }                                                           \
 231         };                                                              \
 232                                                                         \
 233         template <bool x>                                               \
 234         struct call_cpp_##c99_func :                                    \
 235             call_c99_##c99_func<                                        \
 236                 ::boost::hash_detail::c99_func##_detect::check::c99     \
 237             > {};                                                       \
 238                                                                         \
 239         template <>                                                     \
 240         struct call_cpp_##c99_func<true> {                              \
 241             typedef type1 float_type;                                   \
 242                                                                         \
 243             template <typename T>                                       \
 244             inline type1 operator()(type1 a, T b)  const                \
 245             {                                                           \
 246                 using namespace std;                                    \
 247                 return cpp_func(a, b);                                  \
 248             }                                                           \
 249         };                                                              \
 250                                                                         \
 251         template <>                                                     \
 252         struct call_##cpp_func<type1> :                                 \
 253             call_cpp_##c99_func<                                        \
 254                 ::boost::hash_detail::c99_func##_detect::check::cpp     \
 255             > {};                                                       \
 256     }                                                                   \
 257 }
 258
 259 #define BOOST_HASH_CALL_FLOAT_MACRO(cpp_func, c99_func, type1, type2)   \
 260 namespace boost {                                                       \
 261     namespace hash_detail {                                             \
 262                                                                         \
 263         template <>                                                     \
 264         struct call_##cpp_func<type1> {                                 \
 265             typedef type1 float_type;                                   \
 266             inline type1 operator()(type1 x, type2 y) const {           \
 267                 return c99_func(x, y);                                  \
 268             }                                                           \
 269         };                                                              \
 270     }                                                                   \
 271 }
 272
 273 #if defined(ldexpf)
 274 BOOST_HASH_CALL_FLOAT_MACRO(ldexp, ldexpf, float, int)
 275 #else
 276 BOOST_HASH_CALL_FLOAT_FUNC(ldexp, ldexpf, float, int)
 277 #endif
 278
 279 #if defined(ldexpl)
 280 BOOST_HASH_CALL_FLOAT_MACRO(ldexp, ldexpl, long double, int)
 281 #else
 282 BOOST_HASH_CALL_FLOAT_FUNC(ldexp, ldexpl, long double, int)
 283 #endif
 284
 285 #if defined(frexpf)
 286 BOOST_HASH_CALL_FLOAT_MACRO(frexp, frexpf, float, int*)
 287 #else
 288 BOOST_HASH_CALL_FLOAT_FUNC(frexp, frexpf, float, int*)
 289 #endif
 290
 291 #if defined(frexpl)
 292 BOOST_HASH_CALL_FLOAT_MACRO(frexp, frexpl, long double, int*)
 293 #else
 294 BOOST_HASH_CALL_FLOAT_FUNC(frexp, frexpl, long double, int*)
 295 #endif
 296
 297 #undef BOOST_HASH_CALL_FLOAT_MACRO
 298 #undef BOOST_HASH_CALL_FLOAT_FUNC
 299
 300
 301 namespace boost
 302 {
 303     namespace hash_detail
 304     {
 305         template <typename Float1, typename Float2>
 306         struct select_hash_type_impl {
 307             typedef double type;
 308         };
 309
 310         template <>
 311         struct select_hash_type_impl<float, float> {
 312             typedef float type;
 313         };
 314
 315         template <>
 316         struct select_hash_type_impl<long double, long double> {
 317             typedef long double type;
 318         };
 319
 320
 321         // select_hash_type
 322         //
 323         // If there is support for a particular floating point type, use that
 324         // otherwise use double (there's always support for double).
 325
 326         template <typename Float>
 327         struct select_hash_type : select_hash_type_impl<
 328                 BOOST_DEDUCED_TYPENAME call_ldexp<Float>::float_type,
 329                 BOOST_DEDUCED_TYPENAME call_frexp<Float>::float_type
 330             > {};
 331     }
 332 }
 333
 334 #endif // BOOST_HASH_CONFORMANT_FLOATS
 335
 336 #endif