| |
| // 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 |