272 lines
8.1 KiB
Plaintext
272 lines
8.1 KiB
Plaintext
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// Copyright 2005-2012 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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#if !defined(BOOST_FUNCTIONAL_HASH_DETAIL_HASH_FLOAT_HEADER)
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#define BOOST_FUNCTIONAL_HASH_DETAIL_HASH_FLOAT_HEADER
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#include <boost/config.hpp>
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#if defined(BOOST_HAS_PRAGMA_ONCE)
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#pragma once
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#endif
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#include <boost/functional/hash/detail/float_functions.hpp>
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#include <boost/functional/hash/detail/limits.hpp>
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#include <boost/utility/enable_if.hpp>
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#include <boost/integer/static_log2.hpp>
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#include <boost/cstdint.hpp>
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#include <boost/assert.hpp>
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#include <boost/limits.hpp>
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#include <cstring>
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#if defined(BOOST_MSVC)
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#pragma warning(push)
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#if BOOST_MSVC >= 1400
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#pragma warning(disable:6294) // Ill-defined for-loop: initial condition does
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// not satisfy test. Loop body not executed
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#endif
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#endif
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// Can we use fpclassify?
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// STLport
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#if defined(__SGI_STL_PORT) || defined(_STLPORT_VERSION)
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#define BOOST_HASH_USE_FPCLASSIFY 0
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// GNU libstdc++ 3
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#elif defined(__GLIBCPP__) || defined(__GLIBCXX__)
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# if (defined(__USE_ISOC99) || defined(_GLIBCXX_USE_C99_MATH)) && \
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!(defined(macintosh) || defined(__APPLE__) || defined(__APPLE_CC__))
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# define BOOST_HASH_USE_FPCLASSIFY 1
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# else
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# define BOOST_HASH_USE_FPCLASSIFY 0
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# endif
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// Everything else
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#else
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# define BOOST_HASH_USE_FPCLASSIFY 0
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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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////////////////////////////////////////////////////////////////////////
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// Binary hash function
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//
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// Only used for floats with known iec559 floats, and certain values in
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// numeric_limits
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inline std::size_t hash_binary(char* ptr, std::size_t length)
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{
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std::size_t seed = 0;
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if (length >= sizeof(std::size_t)) {
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std::memcpy(&seed, ptr, sizeof(std::size_t));
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length -= sizeof(std::size_t);
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ptr += sizeof(std::size_t);
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while(length >= sizeof(std::size_t)) {
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std::size_t buffer = 0;
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std::memcpy(&buffer, ptr, sizeof(std::size_t));
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hash_float_combine(seed, buffer);
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length -= sizeof(std::size_t);
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ptr += sizeof(std::size_t);
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}
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}
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if (length > 0) {
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std::size_t buffer = 0;
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std::memcpy(&buffer, ptr, length);
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hash_float_combine(seed, buffer);
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}
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return seed;
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}
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template <typename Float, unsigned digits, unsigned max_exponent>
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struct enable_binary_hash
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{
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BOOST_STATIC_CONSTANT(bool, value =
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std::numeric_limits<Float>::is_iec559 &&
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std::numeric_limits<Float>::digits == digits &&
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std::numeric_limits<Float>::radix == 2 &&
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std::numeric_limits<Float>::max_exponent == max_exponent);
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};
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template <typename Float>
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inline std::size_t float_hash_impl(Float v,
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BOOST_DEDUCED_TYPENAME boost::enable_if_c<
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enable_binary_hash<Float, 24, 128>::value,
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std::size_t>::type)
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{
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return hash_binary((char*) &v, 4);
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}
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template <typename Float>
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inline std::size_t float_hash_impl(Float v,
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BOOST_DEDUCED_TYPENAME boost::enable_if_c<
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enable_binary_hash<Float, 53, 1024>::value,
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std::size_t>::type)
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{
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return hash_binary((char*) &v, 8);
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}
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template <typename Float>
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inline std::size_t float_hash_impl(Float v,
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BOOST_DEDUCED_TYPENAME boost::enable_if_c<
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enable_binary_hash<Float, 64, 16384>::value,
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std::size_t>::type)
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{
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return hash_binary((char*) &v, 10);
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}
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template <typename Float>
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inline std::size_t float_hash_impl(Float v,
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BOOST_DEDUCED_TYPENAME boost::enable_if_c<
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enable_binary_hash<Float, 113, 16384>::value,
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std::size_t>::type)
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{
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return hash_binary((char*) &v, 16);
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}
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////////////////////////////////////////////////////////////////////////
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// Portable hash function
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//
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// Used as a fallback when the binary hash function isn't supported.
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template <class T>
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inline std::size_t float_hash_impl2(T v)
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{
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boost::hash_detail::call_frexp<T> frexp;
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boost::hash_detail::call_ldexp<T> ldexp;
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int exp = 0;
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v = frexp(v, &exp);
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// A postive value is easier to hash, so combine the
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// sign with the exponent and use the absolute value.
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if(v < 0) {
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v = -v;
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exp += limits<T>::max_exponent -
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limits<T>::min_exponent;
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}
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v = ldexp(v, limits<std::size_t>::digits);
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std::size_t seed = static_cast<std::size_t>(v);
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v -= static_cast<T>(seed);
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// ceiling(digits(T) * log2(radix(T))/ digits(size_t)) - 1;
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std::size_t const length
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= (limits<T>::digits *
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boost::static_log2<limits<T>::radix>::value
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+ limits<std::size_t>::digits - 1)
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/ limits<std::size_t>::digits;
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for(std::size_t i = 0; i != length; ++i)
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{
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v = ldexp(v, limits<std::size_t>::digits);
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std::size_t part = static_cast<std::size_t>(v);
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v -= static_cast<T>(part);
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hash_float_combine(seed, part);
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}
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hash_float_combine(seed, static_cast<std::size_t>(exp));
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return seed;
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}
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#if !defined(BOOST_HASH_DETAIL_TEST_WITHOUT_GENERIC)
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template <class T>
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inline std::size_t float_hash_impl(T v, ...)
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{
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typedef BOOST_DEDUCED_TYPENAME select_hash_type<T>::type type;
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return float_hash_impl2(static_cast<type>(v));
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}
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#endif
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}
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}
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#if BOOST_HASH_USE_FPCLASSIFY
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#include <boost/config/no_tr1/cmath.hpp>
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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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template <class T>
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inline std::size_t float_hash_value(T v)
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{
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#if defined(fpclassify)
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switch (fpclassify(v))
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#elif BOOST_HASH_CONFORMANT_FLOATS
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switch (std::fpclassify(v))
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#else
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using namespace std;
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switch (fpclassify(v))
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#endif
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{
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case FP_ZERO:
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return 0;
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case FP_INFINITE:
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return (std::size_t)(v > 0 ? -1 : -2);
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case FP_NAN:
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return (std::size_t)(-3);
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case FP_NORMAL:
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case FP_SUBNORMAL:
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return float_hash_impl(v, 0);
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default:
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BOOST_ASSERT(0);
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return 0;
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}
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}
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}
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}
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#else // !BOOST_HASH_USE_FPCLASSIFY
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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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template <class T>
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inline bool is_zero(T v)
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{
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#if !defined(__GNUC__)
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return v == 0;
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#else
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// GCC's '-Wfloat-equal' will complain about comparing
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// v to 0, but because it disables warnings for system
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// headers it won't complain if you use std::equal_to to
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// compare with 0. Resulting in this silliness:
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return std::equal_to<T>()(v, 0);
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#endif
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}
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template <class T>
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inline std::size_t float_hash_value(T v)
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{
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return boost::hash_detail::is_zero(v) ? 0 : float_hash_impl(v, 0);
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}
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}
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}
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#endif // BOOST_HASH_USE_FPCLASSIFY
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#undef BOOST_HASH_USE_FPCLASSIFY
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#if defined(BOOST_MSVC)
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#pragma warning(pop)
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#endif
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#endif
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