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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)
// A general purpose hash function for non-zero floating point values.
#if !defined(BOOST_FUNCTIONAL_HASH_DETAIL_HASH_FLOAT_GENERIC_HEADER)
#define BOOST_FUNCTIONAL_HASH_DETAIL_HASH_FLOAT_GENERIC_HEADER
#include <cutl/details/boost/functional/hash/detail/float_functions.hpp>
#include <cutl/details/boost/integer/static_log2.hpp>
#include <cutl/details/boost/functional/hash/detail/limits.hpp>
#if defined(_MSC_VER) && (_MSC_VER >= 1020)
# pragma once
#endif
#if defined(BOOST_MSVC)
#pragma warning(push)
#if BOOST_MSVC >= 1400
#pragma warning(disable:6294) // Ill-defined for-loop: initial condition does
// not satisfy test. Loop body not executed
#endif
#endif
namespace cutl_details_boost
{
namespace hash_detail
{
inline void hash_float_combine(std::size_t& seed, std::size_t value)
{
seed ^= value + (seed<<6) + (seed>>2);
}
template <class T>
inline std::size_t float_hash_impl2(T v)
{
cutl_details_boost::hash_detail::call_frexp<T> frexp;
cutl_details_boost::hash_detail::call_ldexp<T> ldexp;
int exp = 0;
v = frexp(v, &exp);
// A postive value is easier to hash, so combine the
// sign with the exponent and use the absolute value.
if(v < 0) {
v = -v;
exp += limits<T>::max_exponent -
limits<T>::min_exponent;
}
v = ldexp(v, limits<std::size_t>::digits);
std::size_t seed = static_cast<std::size_t>(v);
v -= static_cast<T>(seed);
// ceiling(digits(T) * log2(radix(T))/ digits(size_t)) - 1;
std::size_t const length
= (limits<T>::digits *
cutl_details_boost::static_log2<limits<T>::radix>::value
+ limits<std::size_t>::digits - 1)
/ limits<std::size_t>::digits;
for(std::size_t i = 0; i != length; ++i)
{
v = ldexp(v, limits<std::size_t>::digits);
std::size_t part = static_cast<std::size_t>(v);
v -= static_cast<T>(part);
hash_float_combine(seed, part);
}
hash_float_combine(seed, exp);
return seed;
}
template <class T>
inline std::size_t float_hash_impl(T v)
{
typedef BOOST_DEDUCED_TYPENAME select_hash_type<T>::type type;
return float_hash_impl2(static_cast<type>(v));
}
}
}
#if defined(BOOST_MSVC)
#pragma warning(pop)
#endif
#endif
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