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Attempting to work round the dodgy std::numeric_limits<long double> on

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some BSDs.


[SVN r35345]
This commit is contained in:
Daniel James
2006-09-26 20:35:58 +00:00
parent eb5ef5e134
commit 26473491c4
2 changed files with 98 additions and 47 deletions
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61
include/boost/functional/detail/hash_float.hpp
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@@ -35,10 +35,61 @@
# endif
#endif
// On FreeBSD and OpenBSD, numeric_limits is not reliable for long doubles, but
// the macros defined in <float.h> are. I don't know if this is also be the case for
// other BSDs, but using the macros if they're available seems like the best
// choice.
#if defined(__FreeBSD__) || defined(__NetBSD__) && \
defined(__OpenBSD__) || defined(__DragonFly__)
#include <float.h>
#endif
namespace boost
{
namespace hash_detail
{
template <class T>
struct float_limits : std::numeric_limits<T> {};
#if defined(__FreeBSD__) || defined(__NetBSD__) && \
defined(__OpenBSD__) || defined(__DragonFly__)
template <>
struct float_limits<long double>
: std::numeric_limits<long double>
{
#if defined(LDBL_EPSILON)
static long double epsilon() {
return LDBL_EPSILON;
}
#endif
#if defined(LDBL_MANT_DIG)
BOOST_STATIC_CONSTANT(int, digits = LDBL_MANT_DIG);
#endif
#if defined(LDBL_MAX)
static long double (max)() {
return LDBL_MAX;
}
#endif
#if defined(LDBL_MIN)
static long double (min)() {
return LDBL_MIN;
}
#endif
#if defined(LDBL_MAX_EXP)
BOOST_STATIC_CONSTANT(int, max_exponent = LDBL_MAX_EXP);
#endif
#if defined(LDBL_MIN_EXP)
BOOST_STATIC_CONSTANT(int, min_exponent = LDBL_MIN_EXP);
#endif
};
#endif // __FreeBSD__/__NetBSD__/__OpenBSD__/__DragonFly__
inline void hash_float_combine(std::size_t& seed, std::size_t value)
{
seed ^= value + (seed<<6) + (seed>>2);
@@ -63,19 +114,19 @@ namespace boost
//BOOST_ASSERT(0 <= v && v < 0.5);
v = boost::hash_detail::call_ldexp(v,
std::numeric_limits<std::size_t>::digits + 1);
float_limits<std::size_t>::digits + 1);
std::size_t seed = static_cast<std::size_t>(v);
v -= seed;
// ceiling(digits(T) * log2(radix(T))/ digits(size_t)) - 1;
std::size_t const length
= (std::numeric_limits<T>::digits *
boost::static_log2<std::numeric_limits<T>::radix>::value - 1)
/ std::numeric_limits<std::size_t>::digits;
= (float_limits<T>::digits *
boost::static_log2<float_limits<T>::radix>::value - 1)
/ float_limits<std::size_t>::digits;
for(std::size_t i = 0; i < length; ++i)
{
v = boost::hash_detail::call_ldexp(v, std::numeric_limits<std::size_t>::digits);
v = boost::hash_detail::call_ldexp(v, float_limits<std::size_t>::digits);
std::size_t part = static_cast<std::size_t>(v);
v -= part;
hash_float_combine(seed, part);