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Refactor detail::hash_value_L

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This commit is contained in:
Peter Dimov
2021-03-13 04:10:41 +02:00
parent 8be0a4a5fe
commit a2dab8c7d3
1 changed files with 37 additions and 13 deletions
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50
include/boost/variant2/variant.hpp
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@ -26,6 +26,7 @@
#include <initializer_list>
#include <utility>
#include <functional> // std::hash
#include <cstdint>
//
@ -2195,28 +2196,51 @@ void swap( variant<T...> & v, variant<T...> & w )
namespace detail
{
inline std::size_t hash_value_impl_( mp11::mp_true, std::size_t index, std::size_t value )
{
boost::ulong_long_type hv = ( boost::ulong_long_type( 0xCBF29CE4 ) << 32 ) + 0x84222325;
boost::ulong_long_type const prime = ( boost::ulong_long_type( 0x00000100 ) << 32 ) + 0x000001B3;
hv ^= index;
hv *= prime;
hv ^= value;
hv *= prime;
return static_cast<std::size_t>( hv );
}
inline std::size_t hash_value_impl_( mp11::mp_false, std::size_t index, std::size_t value )
{
std::size_t hv = 0x811C9DC5;
std::size_t const prime = 0x01000193;
hv ^= index;
hv *= prime;
hv ^= value;
hv *= prime;
return hv;
}
inline std::size_t hash_value_impl( std::size_t index, std::size_t value )
{
return hash_value_impl_( mp11::mp_bool< (SIZE_MAX > UINT32_MAX) >(), index, value );
}
template<class V> struct hash_value_L
{
V const & v;
template<class I> std::size_t operator()( I ) const
{
boost::ulong_long_type hv = ( boost::ulong_long_type( 0xCBF29CE4 ) << 32 ) + 0x84222325;
boost::ulong_long_type const prime = ( boost::ulong_long_type( 0x00000100 ) << 32 ) + 0x000001B3;
// index
hv ^= I::value;
hv *= prime;
// value
auto const & t = unsafe_get<I::value>( v );
hv ^= std::hash<remove_cv_ref_t<decltype(t)>>()( t );
hv *= prime;
std::size_t index = I::value;
std::size_t value = std::hash<remove_cv_ref_t<decltype(t)>>()( t );
return static_cast<std::size_t>( hv );
return hash_value_impl( index, value );
}
};