57 lines
1.6 KiB
C++
57 lines
1.6 KiB
C++
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// Copyright 2005-2009 Daniel James.
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// Distributed under the Boost Software License, Version 1.0. (See accompanying
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// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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// A non-portable hash function form non-zero floats on x86.
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//
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// Even if you're on an x86 platform, this might not work if their floating
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// point isn't set up as this expects. So this should only be used if it's
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// absolutely certain that it will work.
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#if !defined(BOOST_FUNCTIONAL_HASH_DETAIL_HASH_FLOAT_X86_HEADER)
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#define BOOST_FUNCTIONAL_HASH_DETAIL_HASH_FLOAT_X86_HEADER
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#include <boost/cstdint.hpp>
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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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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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inline std::size_t float_hash_impl(float v)
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{
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boost::uint32_t* ptr = (boost::uint32_t*)&v;
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std::size_t seed = *ptr;
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return seed;
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}
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inline std::size_t float_hash_impl(double v)
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{
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boost::uint32_t* ptr = (boost::uint32_t*)&v;
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std::size_t seed = *ptr++;
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hash_float_combine(seed, *ptr);
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return seed;
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}
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inline std::size_t float_hash_impl(long double v)
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{
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boost::uint32_t* ptr = (boost::uint32_t*)&v;
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std::size_t seed = *ptr++;
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hash_float_combine(seed, *ptr++);
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hash_float_combine(seed, *(boost::uint16_t*)ptr);
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return seed;
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}
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}
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}
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#endif
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