mirror of
https://github.com/boostorg/functional.git
synced 2026-07-10 10:31:01 +02:00
Daniel James
116 lines
3.2 KiB
C++
116 lines
3.2 KiB
C++
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// (C) Copyright Daniel James 2005.
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// Use, modification and distribution are subject to the
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// Boost Software License, Version 1.0. (See accompanying file
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// LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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//
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// Based on Peter Dimov's proposal
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// http://www.open-std.org/JTC1/SC22/WG21/docs/papers/2005/n1756.pdf
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// issue 6.18.
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#if !defined(BOOST_FUNCTIONAL_DETAIL_HASH_FLOAT_HEADER)
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#define BOOST_FUNCTIONAL_DETAIL_HASH_FLOAT_HEADER
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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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#include <boost/functional/detail/float_functions.hpp>
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#include <boost/limits.hpp>
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#include <boost/assert.hpp>
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#include <errno.h>
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#if defined(BOOST_MSVC)
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# define BOOST_HASH_USE_FPCLASS
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#elif (defined(__GLIBCPP__) || defined(__GLIBCXX__)) \
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&& (defined(__USE_ISOC99) || defined(_GLIBCXX_USE_C99_MATH))
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# define BOOST_HASH_USE_FPCLASSIFY
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#endif
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namespace boost
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{
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namespace hash_detail
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{
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inline void hash_float_combine(std::size_t& seed, std::size_t value)
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{
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seed ^= value + (seed<<6) + (seed>>2);
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}
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template <class T>
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inline std::size_t float_hash_impl(T v)
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{
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int exp = 0;
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errno = 0;
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v = boost::hash_detail::call_frexp(v, &exp);
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if(errno) return 0;
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std::size_t seed = 0;
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std::size_t const length
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= (std::numeric_limits<T>::digits +
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std::numeric_limits<int>::digits - 1)
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/ std::numeric_limits<int>::digits;
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for(std::size_t i = 0; i < length; ++i)
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{
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v = boost::hash_detail::call_ldexp(v, std::numeric_limits<int>::digits);
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int const part = static_cast<int>(v);
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v -= part;
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hash_float_combine(seed, part);
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}
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hash_float_combine(seed, exp);
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return seed;
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}
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template <class T>
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inline std::size_t float_hash_value(T v)
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{
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#if defined(BOOST_HASH_USE_FPCLASSIFY)
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using namespace std;
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switch (fpclassify(v)) {
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case FP_ZERO:
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return 0;
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case FP_INFINITE:
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return (std::size_t)(v > 0 ? -1 : -2);
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case FP_NAN:
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return (std::size_t)(-3);
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case FP_NORMAL:
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case FP_SUBNORMAL:
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return float_hash_impl(v);
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default:
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BOOST_ASSERT(0);
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return 0;
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}
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#elif defined(BOOST_HASH_USE_FPCLASS)
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switch(_fpclass(v)) {
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case _FPCLASS_NZ:
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case _FPCLASS_PZ:
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return 0;
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case _FPCLASS_PINF:
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return (std::size_t)(-1);
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case _FPCLASS_NINF:
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return (std::size_t)(-2);
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case _FPCLASS_SNAN:
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case _FPCLASS_QNAN:
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return (std::size_t)(-3);
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case _FPCLASS_NN:
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case _FPCLASS_ND:
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return float_hash_impl(v);
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case _FPCLASS_PD:
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case _FPCLASS_PN:
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return float_hash_impl(v);
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default:
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BOOST_ASSERT(0);
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return 0;
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}
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#else
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return float_hash_impl(v);
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#endif
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}
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}
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}
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#endif
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