boost/math/special_functions/detail/fp_traits.hpp
// fp_traits.hpp
#ifndef BOOST_MATH_FP_TRAITS_HPP
#define BOOST_MATH_FP_TRAITS_HPP
// Copyright (c) 2006 Johan Rade
// 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)
/*
To support old compilers, care has been taken to avoid partial template
specialization and meta function forwarding.
With these techniques, the code could be simplified.
*/
#if defined(__vms) && defined(__DECCXX) && !__IEEE_FLOAT
// The VAX floating point formats are used (for float and double)
# define BOOST_FPCLASSIFY_VAX_FORMAT
#endif
#include <cstring>
#include <cstdint>
#include <limits>
#include <type_traits>
#include <boost/math/tools/is_standalone.hpp>
#include <boost/math/tools/assert.hpp>
// Determine endianness
#ifndef BOOST_MATH_STANDALONE
#include <boost/predef/other/endian.h>
#define BOOST_MATH_ENDIAN_BIG_BYTE BOOST_ENDIAN_BIG_BYTE
#define BOOST_MATH_ENDIAN_LITTLE_BYTE BOOST_ENDIAN_LITTLE_BYTE
#elif (__cplusplus >= 202002L || _MSVC_LANG >= 202002L)
#if __has_include(<bit>)
#include <bit>
#define BOOST_MATH_ENDIAN_BIG_BYTE (std::endian::native == std::endian::big)
#define BOOST_MATH_ENDIAN_LITTLE_BYTE (std::endian::native == std::endian::little)
#else
#error Missing <bit> header. Please disable standalone mode, and file an issue at https://github.com/boostorg/math
#endif
#elif defined(_WIN32)
#define BOOST_MATH_ENDIAN_BIG_BYTE 0
#define BOOST_MATH_ENDIAN_LITTLE_BYTE 1
#elif defined(__BYTE_ORDER__)
#define BOOST_MATH_ENDIAN_BIG_BYTE (__BYTE_ORDER__ == __ORDER_BIG_ENDIAN__)
#define BOOST_MATH_ENDIAN_LITTLE_BYTE (__BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__)
#else
#error Could not determine endian type. Please disable standalone mode, and file an issue at https://github.com/boostorg/math
#endif // Determine endianness
static_assert((BOOST_MATH_ENDIAN_BIG_BYTE || BOOST_MATH_ENDIAN_LITTLE_BYTE)
&& !(BOOST_MATH_ENDIAN_BIG_BYTE && BOOST_MATH_ENDIAN_LITTLE_BYTE),
"Inconsistent endianness detected. Please disable standalone mode, and file an issue at https://github.com/boostorg/math");
#ifdef BOOST_NO_STDC_NAMESPACE
namespace std{ using ::memcpy; }
#endif
#ifndef FP_NORMAL
#define FP_ZERO 0
#define FP_NORMAL 1
#define FP_INFINITE 2
#define FP_NAN 3
#define FP_SUBNORMAL 4
#else
#define BOOST_HAS_FPCLASSIFY
#ifndef fpclassify
# if (defined(__GLIBCPP__) || defined(__GLIBCXX__)) \
&& defined(_GLIBCXX_USE_C99_MATH) \
&& !(defined(_GLIBCXX_USE_C99_FP_MACROS_DYNAMIC) \
&& (_GLIBCXX_USE_C99_FP_MACROS_DYNAMIC != 0))
# ifdef _STLP_VENDOR_CSTD
# if _STLPORT_VERSION >= 0x520
# define BOOST_FPCLASSIFY_PREFIX ::__std_alias::
# else
# define BOOST_FPCLASSIFY_PREFIX ::_STLP_VENDOR_CSTD::
# endif
# else
# define BOOST_FPCLASSIFY_PREFIX ::std::
# endif
# else
# undef BOOST_HAS_FPCLASSIFY
# define BOOST_FPCLASSIFY_PREFIX
# endif
#elif (defined(__HP_aCC) && !defined(__hppa))
// aCC 6 appears to do "#define fpclassify fpclassify" which messes us up a bit!
# define BOOST_FPCLASSIFY_PREFIX ::
#else
# define BOOST_FPCLASSIFY_PREFIX
#endif
#ifdef __MINGW32__
# undef BOOST_HAS_FPCLASSIFY
#endif
#endif
//------------------------------------------------------------------------------
namespace boost {
namespace math {
namespace detail {
//------------------------------------------------------------------------------
/*
The following classes are used to tag the different methods that are used
for floating point classification
*/
struct native_tag {};
template <bool has_limits>
struct generic_tag {};
struct ieee_tag {};
struct ieee_copy_all_bits_tag : public ieee_tag {};
struct ieee_copy_leading_bits_tag : public ieee_tag {};
#ifdef BOOST_NO_LIMITS_COMPILE_TIME_CONSTANTS
//
// These helper functions are used only when numeric_limits<>
// members are not compile time constants:
//
inline bool is_generic_tag_false(const generic_tag<false>*)
{
return true;
}
inline bool is_generic_tag_false(const void*)
{
return false;
}
#endif
//------------------------------------------------------------------------------
/*
Most processors support three different floating point precisions:
single precision (32 bits), double precision (64 bits)
and extended double precision (80 - 128 bits, depending on the processor)
Note that the C++ type long double can be implemented
both as double precision and extended double precision.
*/
struct unknown_precision{};
struct single_precision {};
struct double_precision {};
struct extended_double_precision {};
// native_tag version --------------------------------------------------------------
template<class T> struct fp_traits_native
{
typedef native_tag method;
};
// generic_tag version -------------------------------------------------------------
template<class T, class U> struct fp_traits_non_native
{
#ifndef BOOST_NO_LIMITS_COMPILE_TIME_CONSTANTS
typedef generic_tag<std::numeric_limits<T>::is_specialized> method;
#else
typedef generic_tag<false> method;
#endif
};
// ieee_tag versions ---------------------------------------------------------------
/*
These specializations of fp_traits_non_native contain information needed
to "parse" the binary representation of a floating point number.
Typedef members:
bits -- the target type when copying the leading bytes of a floating
point number. It is a typedef for uint32_t or uint64_t.
method -- tells us whether all bytes are copied or not.
It is a typedef for ieee_copy_all_bits_tag or ieee_copy_leading_bits_tag.
Static data members:
sign, exponent, flag, significand -- bit masks that give the meaning of the
bits in the leading bytes.
Static function members:
get_bits(), set_bits() -- provide access to the leading bytes.
*/
// ieee_tag version, float (32 bits) -----------------------------------------------
#ifndef BOOST_FPCLASSIFY_VAX_FORMAT
template<> struct fp_traits_non_native<float, single_precision>
{
typedef ieee_copy_all_bits_tag method;
static constexpr uint32_t sign = 0x80000000u;
static constexpr uint32_t exponent = 0x7f800000;
static constexpr uint32_t flag = 0x00000000;
static constexpr uint32_t significand = 0x007fffff;
typedef uint32_t bits;
static void get_bits(float x, uint32_t& a) { std::memcpy(&a, &x, 4); }
static void set_bits(float& x, uint32_t a) { std::memcpy(&x, &a, 4); }
};
// ieee_tag version, double (64 bits) ----------------------------------------------
#if defined(BOOST_NO_INT64_T) || defined(BOOST_NO_INCLASS_MEMBER_INITIALIZATION) \
|| defined(BOOST_BORLANDC) || defined(__CODEGEAR__)
template<> struct fp_traits_non_native<double, double_precision>
{
typedef ieee_copy_leading_bits_tag method;
static constexpr uint32_t sign = 0x80000000u;
static constexpr uint32_t exponent = 0x7ff00000;
static constexpr uint32_t flag = 0;
static constexpr uint32_t significand = 0x000fffff;
typedef uint32_t bits;
static void get_bits(double x, uint32_t& a)
{
std::memcpy(&a, reinterpret_cast<const unsigned char*>(&x) + offset_, 4);
}
static void set_bits(double& x, uint32_t a)
{
std::memcpy(reinterpret_cast<unsigned char*>(&x) + offset_, &a, 4);
}
private:
static constexpr int offset_ = BOOST_MATH_ENDIAN_BIG_BYTE ? 0 : 4;
};
//..............................................................................
#else
template<> struct fp_traits_non_native<double, double_precision>
{
typedef ieee_copy_all_bits_tag method;
static constexpr uint64_t sign = static_cast<uint64_t>(0x80000000u) << 32;
static constexpr uint64_t exponent = static_cast<uint64_t>(0x7ff00000) << 32;
static constexpr uint64_t flag = 0;
static constexpr uint64_t significand
= (static_cast<uint64_t>(0x000fffff) << 32) + static_cast<uint64_t>(0xffffffffu);
typedef uint64_t bits;
static void get_bits(double x, uint64_t& a) { std::memcpy(&a, &x, 8); }
static void set_bits(double& x, uint64_t a) { std::memcpy(&x, &a, 8); }
};
#endif
#endif // #ifndef BOOST_FPCLASSIFY_VAX_FORMAT
// long double (64 bits) -------------------------------------------------------
#if defined(BOOST_NO_INT64_T) || defined(BOOST_NO_INCLASS_MEMBER_INITIALIZATION)\
|| defined(BOOST_BORLANDC) || defined(__CODEGEAR__)
template<> struct fp_traits_non_native<long double, double_precision>
{
typedef ieee_copy_leading_bits_tag method;
static constexpr uint32_t sign = 0x80000000u;
static constexpr uint32_t exponent = 0x7ff00000;
static constexpr uint32_t flag = 0;
static constexpr uint32_t significand = 0x000fffff;
typedef uint32_t bits;
static void get_bits(long double x, uint32_t& a)
{
std::memcpy(&a, reinterpret_cast<const unsigned char*>(&x) + offset_, 4);
}
static void set_bits(long double& x, uint32_t a)
{
std::memcpy(reinterpret_cast<unsigned char*>(&x) + offset_, &a, 4);
}
private:
static constexpr int offset_ = BOOST_MATH_ENDIAN_BIG_BYTE ? 0 : 4;
};
//..............................................................................
#else
template<> struct fp_traits_non_native<long double, double_precision>
{
typedef ieee_copy_all_bits_tag method;
static const uint64_t sign = static_cast<uint64_t>(0x80000000u) << 32;
static const uint64_t exponent = static_cast<uint64_t>(0x7ff00000) << 32;
static const uint64_t flag = 0;
static const uint64_t significand
= (static_cast<uint64_t>(0x000fffff) << 32) + static_cast<uint64_t>(0xffffffffu);
typedef uint64_t bits;
static void get_bits(long double x, uint64_t& a) { std::memcpy(&a, &x, 8); }
static void set_bits(long double& x, uint64_t a) { std::memcpy(&x, &a, 8); }
};
#endif
// long double (>64 bits), x86 and x64 -----------------------------------------
#if defined(__i386) || defined(__i386__) || defined(_M_IX86) \
|| defined(__amd64) || defined(__amd64__) || defined(_M_AMD64) \
|| defined(__x86_64) || defined(__x86_64__) || defined(_M_X64)
// Intel extended double precision format (80 bits)
template<>
struct fp_traits_non_native<long double, extended_double_precision>
{
typedef ieee_copy_leading_bits_tag method;
static constexpr uint32_t sign = 0x80000000u;
static constexpr uint32_t exponent = 0x7fff0000;
static constexpr uint32_t flag = 0x00008000;
static constexpr uint32_t significand = 0x00007fff;
typedef uint32_t bits;
static void get_bits(long double x, uint32_t& a)
{
std::memcpy(&a, reinterpret_cast<const unsigned char*>(&x) + 6, 4);
}
static void set_bits(long double& x, uint32_t a)
{
std::memcpy(reinterpret_cast<unsigned char*>(&x) + 6, &a, 4);
}
};
// long double (>64 bits), Itanium ---------------------------------------------
#elif defined(__ia64) || defined(__ia64__) || defined(_M_IA64)
// The floating point format is unknown at compile time
// No template specialization is provided.
// The generic_tag definition is used.
// The Itanium supports both
// the Intel extended double precision format (80 bits) and
// the IEEE extended double precision format with 15 exponent bits (128 bits).
#elif defined(__GNUC__) && (LDBL_MANT_DIG == 106)
//
// Define nothing here and fall though to generic_tag:
// We have GCC's "double double" in effect, and any attempt
// to handle it via bit-fiddling is pretty much doomed to fail...
//
// long double (>64 bits), PowerPC ---------------------------------------------
#elif defined(__powerpc) || defined(__powerpc__) || defined(__POWERPC__) \
|| defined(__ppc) || defined(__ppc__) || defined(__PPC__)
// PowerPC extended double precision format (128 bits)
template<>
struct fp_traits_non_native<long double, extended_double_precision>
{
typedef ieee_copy_leading_bits_tag method;
static constexpr uint32_t sign = 0x80000000u;
static constexpr uint32_t exponent = 0x7ff00000;
static constexpr uint32_t flag = 0x00000000;
static constexpr uint32_t significand = 0x000fffff;
typedef uint32_t bits;
static void get_bits(long double x, uint32_t& a)
{
std::memcpy(&a, reinterpret_cast<const unsigned char*>(&x) + offset_, 4);
}
static void set_bits(long double& x, uint32_t a)
{
std::memcpy(reinterpret_cast<unsigned char*>(&x) + offset_, &a, 4);
}
private:
static constexpr int offset_ = BOOST_MATH_ENDIAN_BIG_BYTE ? 0 : 12;
};
// long double (>64 bits), Motorola 68K ----------------------------------------
#elif defined(__m68k) || defined(__m68k__) \
|| defined(__mc68000) || defined(__mc68000__) \
// Motorola extended double precision format (96 bits)
// It is the same format as the Intel extended double precision format,
// except that 1) it is big-endian, 2) the 3rd and 4th byte are padding, and
// 3) the flag bit is not set for infinity
template<>
struct fp_traits_non_native<long double, extended_double_precision>
{
typedef ieee_copy_leading_bits_tag method;
static constexpr uint32_t sign = 0x80000000u;
static constexpr uint32_t exponent = 0x7fff0000;
static constexpr uint32_t flag = 0x00008000;
static constexpr uint32_t significand = 0x00007fff;
// copy 1st, 2nd, 5th and 6th byte. 3rd and 4th byte are padding.
typedef uint32_t bits;
static void get_bits(long double x, uint32_t& a)
{
std::memcpy(&a, &x, 2);
std::memcpy(reinterpret_cast<unsigned char*>(&a) + 2,
reinterpret_cast<const unsigned char*>(&x) + 4, 2);
}
static void set_bits(long double& x, uint32_t a)
{
std::memcpy(&x, &a, 2);
std::memcpy(reinterpret_cast<unsigned char*>(&x) + 4,
reinterpret_cast<const unsigned char*>(&a) + 2, 2);
}
};
// long double (>64 bits), All other processors --------------------------------
#else
// IEEE extended double precision format with 15 exponent bits (128 bits)
template<>
struct fp_traits_non_native<long double, extended_double_precision>
{
typedef ieee_copy_leading_bits_tag method;
static constexpr uint32_t sign = 0x80000000u;
static constexpr uint32_t exponent = 0x7fff0000;
static constexpr uint32_t flag = 0x00000000;
static constexpr uint32_t significand = 0x0000ffff;
typedef uint32_t bits;
static void get_bits(long double x, uint32_t& a)
{
std::memcpy(&a, reinterpret_cast<const unsigned char*>(&x) + offset_, 4);
}
static void set_bits(long double& x, uint32_t a)
{
std::memcpy(reinterpret_cast<unsigned char*>(&x) + offset_, &a, 4);
}
private:
static constexpr int offset_ = BOOST_MATH_ENDIAN_BIG_BYTE ? 0 : 12;
};
#endif
//------------------------------------------------------------------------------
// size_to_precision is a type switch for converting a C++ floating point type
// to the corresponding precision type.
template<size_t n, bool fp> struct size_to_precision
{
typedef unknown_precision type;
};
template<> struct size_to_precision<4, true>
{
typedef single_precision type;
};
template<> struct size_to_precision<8, true>
{
typedef double_precision type;
};
template<> struct size_to_precision<10, true>
{
typedef extended_double_precision type;
};
template<> struct size_to_precision<12, true>
{
typedef extended_double_precision type;
};
template<> struct size_to_precision<16, true>
{
typedef extended_double_precision type;
};
//------------------------------------------------------------------------------
//
// Figure out whether to use native classification functions based on
// whether T is a built in floating point type or not:
//
template <class T>
struct select_native
{
typedef typename size_to_precision<sizeof(T), ::std::is_floating_point<T>::value>::type precision;
typedef fp_traits_non_native<T, precision> type;
};
template<>
struct select_native<float>
{
typedef fp_traits_native<float> type;
};
template<>
struct select_native<double>
{
typedef fp_traits_native<double> type;
};
template<>
struct select_native<long double>
{
typedef fp_traits_native<long double> type;
};
//------------------------------------------------------------------------------
// fp_traits is a type switch that selects the right fp_traits_non_native
#if (defined(BOOST_MATH_USE_C99) && !(defined(__GNUC__) && (__GNUC__ < 4))) \
&& !defined(__hpux) \
&& !defined(__DECCXX)\
&& !defined(__osf__) \
&& !defined(__SGI_STL_PORT) && !defined(_STLPORT_VERSION)\
&& !defined(__FAST_MATH__)\
&& !defined(BOOST_MATH_DISABLE_STD_FPCLASSIFY)\
&& !defined(__INTEL_COMPILER)\
&& !defined(sun)\
&& !defined(__VXWORKS__)
# define BOOST_MATH_USE_STD_FPCLASSIFY
#endif
template<class T> struct fp_traits
{
typedef typename size_to_precision<sizeof(T), ::std::is_floating_point<T>::value>::type precision;
#if defined(BOOST_MATH_USE_STD_FPCLASSIFY) && !defined(BOOST_MATH_DISABLE_STD_FPCLASSIFY)
typedef typename select_native<T>::type type;
#else
typedef fp_traits_non_native<T, precision> type;
#endif
typedef fp_traits_non_native<T, precision> sign_change_type;
};
//------------------------------------------------------------------------------
} // namespace detail
} // namespace math
} // namespace boost
#endif