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