inline std::size_t float_hash_impl(long double v)
{
boost::uint32_t* ptr = (boost::uint32_t*)&v;
std::size_t seed = *ptr++;
hash_float_combine(seed, *ptr++);
hash_float_combine(seed, *(boost::uint16_t*)ptr);
return seed;
}
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;
}
// The result of frexp is always between 0.5 and 1, so its
// top bit will always be 1. Subtract by 0.5 to remove that.
v -= T(0.5);
v = ldexp(v, 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
= (limits<T>::digits *
boost::static_log2<limits<T>::radix>::value - 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 -= part;
hash_float_combine(seed, part);
}
hash_float_combine(seed, exp);
return seed;
}
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 -= 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 -= part;
hash_float_combine(seed, part);
}
hash_float_combine(seed, exp);
return seed;
}
