diff options
Diffstat (limited to 'boost/container_hash/detail/hash_float.hpp')
| -rw-r--r-- | boost/container_hash/detail/hash_float.hpp | 271 |
1 files changed, 271 insertions, 0 deletions
diff --git a/boost/container_hash/detail/hash_float.hpp b/boost/container_hash/detail/hash_float.hpp new file mode 100644 index 0000000000..f763428508 --- /dev/null +++ b/boost/container_hash/detail/hash_float.hpp @@ -0,0 +1,271 @@ + +// 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 + +#include <boost/config.hpp> +#if defined(BOOST_HAS_PRAGMA_ONCE) +#pragma once +#endif + +#include <boost/container_hash/detail/float_functions.hpp> +#include <boost/container_hash/detail/limits.hpp> +#include <boost/core/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)) { + std::memcpy(&seed, ptr, sizeof(std::size_t)); + 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, static_cast<std::size_t>(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__) && !defined(__clang__) + 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 |