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Match floating point hash values in 32 bit mode

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This commit is contained in:
Peter Dimov
2022-05-30 02:35:00 +03:00
parent 0eada2ae93
commit e04ca1f442
1 changed files with 80 additions and 8 deletions
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88
include/boost/container_hash/hash.hpp
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@@ -168,34 +168,54 @@ namespace boost
namespace hash_detail
{
template<class T, std::size_t Bits = sizeof(T) * CHAR_BIT, int Digits = std::numeric_limits<T>::digits> struct hash_float_impl;
template<class T,
std::size_t Bits = sizeof(T) * CHAR_BIT,
int Digits = std::numeric_limits<T>::digits,
std::size_t size_t_bits = sizeof(std::size_t) * CHAR_BIT>
struct hash_float_impl;
// float
template<class T, int Digits> struct hash_float_impl<T, 32, Digits>
template<class T, int Digits, std::size_t size_t_bits> struct hash_float_impl<T, 32, Digits, size_t_bits>
{
static std::size_t fn( T v )
{
boost::uint32_t w;
std::memcpy( &w, &v, sizeof( v ) );
return boost::hash_value( w );
return w;
}
};
// double
template<class T, int Digits> struct hash_float_impl<T, 64, Digits>
template<class T, int Digits> struct hash_float_impl<T, 64, Digits, 64>
{
static std::size_t fn( T v )
{
boost::uint64_t w;
std::memcpy( &w, &v, sizeof( v ) );
return boost::hash_value( w );
return w;
}
};
template<class T, int Digits> struct hash_float_impl<T, 64, Digits, 32>
{
static std::size_t fn( T v )
{
boost::uint32_t w[ 2 ];
std::memcpy( &w, &v, sizeof( v ) );
std::size_t seed = 0;
seed ^= static_cast<std::size_t>( w[0] ) + ( seed << 6 ) + ( seed >> 2 );
seed ^= static_cast<std::size_t>( w[1] ) + ( seed << 6 ) + ( seed >> 2 );
return seed;
}
};
// 80 bit long double in 12 bytes
template<class T> struct hash_float_impl<T, 96, 64>
template<class T> struct hash_float_impl<T, 96, 64, 64>
{
static std::size_t fn( T v )
{
@@ -211,8 +231,25 @@ namespace boost
}
};
template<class T> struct hash_float_impl<T, 96, 64, 32>
{
static std::size_t fn( T v )
{
boost::uint32_t w[ 3 ] = {};
std::memcpy( &w, &v, 80 / CHAR_BIT );
std::size_t seed = 0;
seed ^= static_cast<std::size_t>( w[0] ) + ( seed << 6 ) + ( seed >> 2 );
seed ^= static_cast<std::size_t>( w[1] ) + ( seed << 6 ) + ( seed >> 2 );
seed ^= static_cast<std::size_t>( w[2] ) + ( seed << 6 ) + ( seed >> 2 );
return seed;
}
};
// 80 bit long double in 16 bytes
template<class T> struct hash_float_impl<T, 128, 64>
template<class T> struct hash_float_impl<T, 128, 64, 64>
{
static std::size_t fn( T v )
{
@@ -228,8 +265,25 @@ namespace boost
}
};
template<class T> struct hash_float_impl<T, 128, 64, 32>
{
static std::size_t fn( T v )
{
boost::uint32_t w[ 3 ] = {};
std::memcpy( &w, &v, 80 / CHAR_BIT );
std::size_t seed = 0;
seed ^= static_cast<std::size_t>( w[0] ) + ( seed << 6 ) + ( seed >> 2 );
seed ^= static_cast<std::size_t>( w[1] ) + ( seed << 6 ) + ( seed >> 2 );
seed ^= static_cast<std::size_t>( w[2] ) + ( seed << 6 ) + ( seed >> 2 );
return seed;
}
};
// 128 bit long double
template<class T, int Digits> struct hash_float_impl<T, 128, Digits>
template<class T, int Digits> struct hash_float_impl<T, 128, Digits, 64>
{
static std::size_t fn( T v )
{
@@ -245,6 +299,24 @@ namespace boost
}
};
template<class T, int Digits> struct hash_float_impl<T, 128, Digits, 32>
{
static std::size_t fn( T v )
{
boost::uint32_t w[ 4 ];
std::memcpy( &w, &v, sizeof( v ) );
std::size_t seed = 0;
seed ^= static_cast<std::size_t>( w[0] ) + ( seed << 6 ) + ( seed >> 2 );
seed ^= static_cast<std::size_t>( w[1] ) + ( seed << 6 ) + ( seed >> 2 );
seed ^= static_cast<std::size_t>( w[2] ) + ( seed << 6 ) + ( seed >> 2 );
seed ^= static_cast<std::size_t>( w[3] ) + ( seed << 6 ) + ( seed >> 2 );
return seed;
}
};
} // namespace hash_detail
template <typename T>