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  • Committer: Bazaar Package Importer
  • Author(s): Alessio Treglia
  • Date: 2010-11-04 11:46:25 UTC
  • mto: This revision was merged to the branch mainline in revision 8.
  • Revision ID: james.westby@ubuntu.com-20101104114625-8xfdhvhpsm51i0nu
Tags: upstream-0.8.0
Import upstream version 0.8.0

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libs/boost-lib/boost/functional/hash/detail/float_functions.hpp
 
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// Copyright 2005-2009 Daniel James.
 
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// Distributed under the Boost Software License, Version 1.0. (See accompanying
 
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// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
 
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#if !defined(BOOST_FUNCTIONAL_HASH_DETAIL_FLOAT_FUNCTIONS_HPP)
 
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#define BOOST_FUNCTIONAL_HASH_DETAIL_FLOAT_FUNCTIONS_HPP
 
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#include <boost/config.hpp>
 
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#include <boost/config/no_tr1/cmath.hpp>
 
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#if defined(_MSC_VER) && (_MSC_VER >= 1020)
 
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# pragma once
 
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#endif
 
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// The C++ standard requires that the C float functions are overloarded
 
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// for float, double and long double in the std namespace, but some of the older
 
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// library implementations don't support this. On some that don't, the C99
 
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// float functions (frexpf, frexpl, etc.) are available.
 
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//
 
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// The following tries to automatically detect which are available.
 
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namespace boost {
 
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    namespace hash_detail {
 
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        // Returned by dummy versions of the float functions.
 
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        struct not_found {
 
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            // Implicitly convertible to float and long double in order to avoid
 
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            // a compile error when the dummy float functions are used.
 
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            inline operator float() const { return 0; }
 
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            inline operator long double() const { return 0; }
 
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        };
 
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        // A type for detecting the return type of functions.
 
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        template <typename T> struct is;
 
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        template <> struct is<float> { char x[10]; };
 
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        template <> struct is<double> { char x[20]; };
 
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        template <> struct is<long double> { char x[30]; };
 
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        template <> struct is<boost::hash_detail::not_found> { char x[40]; };
 
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        // Used to convert the return type of a function to a type for sizeof.
 
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        template <typename T> is<T> float_type(T);
 
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        // call_ldexp
 
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        //
 
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        // This will get specialized for float and long double
 
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        template <typename Float> struct call_ldexp
 
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        {
 
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            typedef double float_type;
 
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            inline double operator()(double a, int b) const
 
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            {
 
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                using namespace std;
 
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                return ldexp(a, b);
 
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            }
 
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        };
 
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        // call_frexp
 
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        //
 
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        // This will get specialized for float and long double
 
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        template <typename Float> struct call_frexp
 
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        {
 
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            typedef double float_type;
 
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            inline double operator()(double a, int* b) const
 
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            {
 
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                using namespace std;
 
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                return frexp(a, b);
 
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            }
 
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        };
 
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    }
 
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}
 
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// A namespace for dummy functions to detect when the actual function we want
 
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// isn't available. ldexpl, ldexpf etc. might be added tby the macros below.
 
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//
 
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// AFAICT these have to be outside of the boost namespace, as if they're in
 
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// the boost namespace they'll always be preferable to any other function
 
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// (since the arguments are built in types, ADL can't be used).
 
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namespace boost_hash_detect_float_functions {
 
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    template <class Float> boost::hash_detail::not_found ldexp(Float, int);
 
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    template <class Float> boost::hash_detail::not_found frexp(Float, int*);    
 
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}
 
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// Macros for generating specializations of call_ldexp and call_frexp.
 
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//
 
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// check_cpp and check_c99 check if the C++ or C99 functions are available.
 
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//
 
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// Then the call_* functions select an appropriate implementation.
 
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//
 
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// I used c99_func in a few places just to get a unique name.
 
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//
 
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// Important: when using 'using namespace' at namespace level, include as
 
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// little as possible in that namespace, as Visual C++ has an odd bug which
 
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// can cause the namespace to be imported at the global level. This seems to
 
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// happen mainly when there's a template in the same namesapce.
 
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#define BOOST_HASH_CALL_FLOAT_FUNC(cpp_func, c99_func, type1, type2)    \
 
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namespace boost_hash_detect_float_functions {                           \
 
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    template <class Float>                                              \
 
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    boost::hash_detail::not_found c99_func(Float, type2);               \
 
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}                                                                       \
 
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                                                                        \
 
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namespace boost {                                                       \
 
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    namespace hash_detail {                                             \
 
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        namespace c99_func##_detect {                                   \
 
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            using namespace std;                                        \
 
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            using namespace boost_hash_detect_float_functions;          \
 
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                                                                        \
 
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            struct check {                                              \
 
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                static type1 x;                                         \
 
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                static type2 y;                                         \
 
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                BOOST_STATIC_CONSTANT(bool, cpp =                       \
 
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                    sizeof(float_type(cpp_func(x,y)))                   \
 
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                        == sizeof(is<type1>));                          \
 
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                BOOST_STATIC_CONSTANT(bool, c99 =                       \
 
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                    sizeof(float_type(c99_func(x,y)))                   \
 
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                        == sizeof(is<type1>));                          \
 
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            };                                                          \
 
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        }                                                               \
 
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                                                                        \
 
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        template <bool x>                                               \
 
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        struct call_c99_##c99_func :                                    \
 
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            boost::hash_detail::call_##cpp_func<double> {};             \
 
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                                                                        \
 
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        template <>                                                     \
 
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        struct call_c99_##c99_func<true> {                              \
 
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            typedef type1 float_type;                                   \
 
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                                                                        \
 
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            template <typename T>                                       \
 
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            inline type1 operator()(type1 a, T b)  const                \
 
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            {                                                           \
 
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                using namespace std;                                    \
 
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                return c99_func(a, b);                                  \
 
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            }                                                           \
 
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        };                                                              \
 
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                                                                        \
 
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        template <bool x>                                               \
 
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        struct call_cpp_##c99_func :                                    \
 
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            call_c99_##c99_func<                                        \
 
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                ::boost::hash_detail::c99_func##_detect::check::c99     \
 
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            > {};                                                       \
 
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                                                                        \
 
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        template <>                                                     \
 
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        struct call_cpp_##c99_func<true> {                              \
 
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            typedef type1 float_type;                                   \
 
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                                                                        \
 
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            template <typename T>                                       \
 
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            inline type1 operator()(type1 a, T b)  const                \
 
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            {                                                           \
 
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                using namespace std;                                    \
 
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                return cpp_func(a, b);                                  \
 
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            }                                                           \
 
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        };                                                              \
 
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                                                                        \
 
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        template <>                                                     \
 
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        struct call_##cpp_func<type1> :                                 \
 
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            call_cpp_##c99_func<                                        \
 
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                ::boost::hash_detail::c99_func##_detect::check::cpp     \
 
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            > {};                                                       \
 
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    }                                                                   \
 
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}
 
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#define BOOST_HASH_CALL_FLOAT_MACRO(cpp_func, c99_func, type1, type2)   \
 
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namespace boost {                                                       \
 
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    namespace hash_detail {                                             \
 
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                                                                        \
 
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        template <>                                                     \
 
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        struct call_##cpp_func<type1> {                                 \
 
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            typedef type1 float_type;                                   \
 
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            inline type1 operator()(type1 x, type2 y) const {           \
 
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                return c99_func(x, y);                                  \
 
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            }                                                           \
 
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        };                                                              \
 
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    }                                                                   \
 
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}
 
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#if defined(ldexpf)
 
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BOOST_HASH_CALL_FLOAT_MACRO(ldexp, ldexpf, float, int)
 
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#else
 
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BOOST_HASH_CALL_FLOAT_FUNC(ldexp, ldexpf, float, int)
 
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#endif
 
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#if defined(ldexpl)
 
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BOOST_HASH_CALL_FLOAT_MACRO(ldexp, ldexpl, long double, int)
 
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#else
 
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BOOST_HASH_CALL_FLOAT_FUNC(ldexp, ldexpl, long double, int)
 
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#endif
 
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#if defined(frexpf)
 
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BOOST_HASH_CALL_FLOAT_MACRO(frexp, frexpf, float, int*)
 
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#else
 
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BOOST_HASH_CALL_FLOAT_FUNC(frexp, frexpf, float, int*)
 
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#endif
 
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#if defined(frexpl)
 
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BOOST_HASH_CALL_FLOAT_MACRO(frexp, frexpl, long double, int*)
 
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#else
 
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BOOST_HASH_CALL_FLOAT_FUNC(frexp, frexpl, long double, int*)
 
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#endif
 
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209
#undef BOOST_HASH_CALL_FLOAT_MACRO
 
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#undef BOOST_HASH_CALL_FLOAT_FUNC
 
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212
 
 
213
namespace boost
 
214
{
 
215
    namespace hash_detail
 
216
    {
 
217
        template <typename Float1, typename Float2>
 
218
        struct select_hash_type_impl {
 
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            typedef double type;
 
220
        };
 
221
 
 
222
        template <>
 
223
        struct select_hash_type_impl<float, float> {
 
224
            typedef float type;
 
225
        };
 
226
 
 
227
        template <>
 
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        struct select_hash_type_impl<long double, long double> {
 
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            typedef long double type;
 
230
        };
 
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232
 
 
233
        // select_hash_type
 
234
        //
 
235
        // If there is support for a particular floating point type, use that
 
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        // otherwise use double (there's always support for double).
 
237
             
 
238
        template <typename Float>
 
239
        struct select_hash_type : select_hash_type_impl<
 
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                BOOST_DEDUCED_TYPENAME call_ldexp<Float>::float_type,
 
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                BOOST_DEDUCED_TYPENAME call_frexp<Float>::float_type
 
242
            > {};            
 
243
    }
 
244
}
 
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#endif