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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