boost/functional/hash/detail/hash_float.hpp
// Copyright 2005-2012 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) #if !defined(BOOST_FUNCTIONAL_HASH_DETAIL_HASH_FLOAT_HEADER) #define BOOST_FUNCTIONAL_HASH_DETAIL_HASH_FLOAT_HEADER #if defined(_MSC_VER) && (_MSC_VER >= 1020) # pragma once #endif #include <boost/config.hpp> #include <boost/functional/hash/detail/float_functions.hpp> #include <boost/functional/hash/detail/limits.hpp> #include <boost/utility/enable_if.hpp> #include <boost/integer/static_log2.hpp> #include <boost/cstdint.hpp> #include <boost/assert.hpp> #include <boost/limits.hpp> #include <cstring> #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 // Can we use fpclassify? // STLport #if defined(__SGI_STL_PORT) || defined(_STLPORT_VERSION) #define BOOST_HASH_USE_FPCLASSIFY 0 // GNU libstdc++ 3 #elif defined(__GLIBCPP__) || defined(__GLIBCXX__) # if (defined(__USE_ISOC99) || defined(_GLIBCXX_USE_C99_MATH)) && \ !(defined(macintosh) || defined(__APPLE__) || defined(__APPLE_CC__)) # define BOOST_HASH_USE_FPCLASSIFY 1 # else # define BOOST_HASH_USE_FPCLASSIFY 0 # endif // Everything else #else # define BOOST_HASH_USE_FPCLASSIFY 0 #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); } //////////////////////////////////////////////////////////////////////// // Binary hash function // // Only used for floats with known iec559 floats, and certain values in // numeric_limits inline std::size_t hash_binary(char* ptr, std::size_t length) { std::size_t seed = 0; if (length >= sizeof(std::size_t)) { seed = *(std::size_t*) ptr; length -= sizeof(std::size_t); ptr += sizeof(std::size_t); while(length >= sizeof(std::size_t)) { std::size_t buffer = 0; std::memcpy(&buffer, ptr, sizeof(std::size_t)); hash_float_combine(seed, buffer); length -= sizeof(std::size_t); ptr += sizeof(std::size_t); } } if (length > 0) { std::size_t buffer = 0; std::memcpy(&buffer, ptr, length); hash_float_combine(seed, buffer); } return seed; } template <typename Float, unsigned digits, unsigned max_exponent> struct enable_binary_hash { BOOST_STATIC_CONSTANT(bool, value = std::numeric_limits<Float>::is_iec559 && std::numeric_limits<Float>::digits == digits && std::numeric_limits<Float>::radix == 2 && std::numeric_limits<Float>::max_exponent == max_exponent); }; template <typename Float> inline std::size_t float_hash_impl(Float v, BOOST_DEDUCED_TYPENAME boost::enable_if_c< enable_binary_hash<Float, 24, 128>::value, std::size_t>::type) { return hash_binary((char*) &v, 4); } template <typename Float> inline std::size_t float_hash_impl(Float v, BOOST_DEDUCED_TYPENAME boost::enable_if_c< enable_binary_hash<Float, 53, 1024>::value, std::size_t>::type) { return hash_binary((char*) &v, 8); } template <typename Float> inline std::size_t float_hash_impl(Float v, BOOST_DEDUCED_TYPENAME boost::enable_if_c< enable_binary_hash<Float, 64, 16384>::value, std::size_t>::type) { return hash_binary((char*) &v, 10); } template <typename Float> inline std::size_t float_hash_impl(Float v, BOOST_DEDUCED_TYPENAME boost::enable_if_c< enable_binary_hash<Float, 113, 16384>::value, std::size_t>::type) { return hash_binary((char*) &v, 16); } //////////////////////////////////////////////////////////////////////// // Portable hash function // // Used as a fallback when the binary hash function isn't supported. template <class T> inline std::size_t float_hash_impl2(T v) { boost::hash_detail::call_frexp<T> frexp; 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 * 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; } #if !defined(BOOST_HASH_DETAIL_TEST_WITHOUT_GENERIC) 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)); } #endif } } #if BOOST_HASH_USE_FPCLASSIFY #include <boost/config/no_tr1/cmath.hpp> namespace boost { namespace hash_detail { template <class T> inline std::size_t float_hash_value(T v) { #if defined(fpclassify) switch (fpclassify(v)) #elif BOOST_HASH_CONFORMANT_FLOATS switch (std::fpclassify(v)) #else using namespace std; switch (fpclassify(v)) #endif { case FP_ZERO: return 0; case FP_INFINITE: return (std::size_t)(v > 0 ? -1 : -2); case FP_NAN: return (std::size_t)(-3); case FP_NORMAL: case FP_SUBNORMAL: return float_hash_impl(v, 0); default: BOOST_ASSERT(0); return 0; } } } } #else // !BOOST_HASH_USE_FPCLASSIFY namespace boost { namespace hash_detail { template <class T> inline bool is_zero(T v) { #if !defined(__GNUC__) return v == 0; #else // GCC's '-Wfloat-equal' will complain about comparing // v to 0, but because it disables warnings for system // headers it won't complain if you use std::equal_to to // compare with 0. Resulting in this silliness: return std::equal_to<T>()(v, 0); #endif } template <class T> inline std::size_t float_hash_value(T v) { return boost::hash_detail::is_zero(v) ? 0 : float_hash_impl(v, 0); } } } #endif // BOOST_HASH_USE_FPCLASSIFY #undef BOOST_HASH_USE_FPCLASSIFY #if defined(BOOST_MSVC) #pragma warning(pop) #endif #endif