// 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) | |
// A non-portable hash function form non-zero floats on x86. | |
// | |
// Even if you're on an x86 platform, this might not work if their floating | |
// point isn't set up as this expects. So this should only be used if it's | |
// absolutely certain that it will work. | |
#if !defined(BOOST_FUNCTIONAL_HASH_DETAIL_HASH_FLOAT_X86_HEADER) | |
#define BOOST_FUNCTIONAL_HASH_DETAIL_HASH_FLOAT_X86_HEADER | |
#include <boost/cstdint.hpp> | |
#if defined(_MSC_VER) && (_MSC_VER >= 1020) | |
# pragma once | |
#endif | |
namespace boost | |
{ | |
namespace hash_detail | |
{ | |
inline void hash_float_combine(std::size_t& seed, std::size_t value) | |
{ | |
seed ^= value + (seed<<6) + (seed>>2); | |
} | |
inline std::size_t float_hash_impl(float v) | |
{ | |
boost::uint32_t* ptr = (boost::uint32_t*)&v; | |
std::size_t seed = *ptr; | |
return seed; | |
} | |
inline std::size_t float_hash_impl(double v) | |
{ | |
boost::uint32_t* ptr = (boost::uint32_t*)&v; | |
std::size_t seed = *ptr++; | |
hash_float_combine(seed, *ptr); | |
return seed; | |
} | |
inline std::size_t float_hash_impl(long double v) | |
{ | |
boost::uint32_t* ptr = (boost::uint32_t*)&v; | |
std::size_t seed = *ptr++; | |
hash_float_combine(seed, *ptr++); | |
hash_float_combine(seed, *(boost::uint16_t*)ptr); | |
return seed; | |
} | |
} | |
} | |
#endif |