147 lines
3.5 KiB
C++
147 lines
3.5 KiB
C++
// Copyright 2021-2023 Peter Dimov
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// Distributed under the Boost Software License, Version 1.0.
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// https://www.boost.org/LICENSE_1_0.txt
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#ifndef BOOST_HASH_DETAIL_HASH_INTEGRAL_HPP
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#define BOOST_HASH_DETAIL_HASH_INTEGRAL_HPP
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#include <boost/container_hash/detail/hash_mix.hpp>
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#include <type_traits>
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#include <cstddef>
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#include <climits>
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namespace boost
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{
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namespace hash_detail
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{
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// libstdc++ doesn't provide support for __int128 in the standard traits
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template<class T> struct is_integral: public std::is_integral<T>
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{
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};
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template<class T> struct is_unsigned: public std::is_unsigned<T>
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{
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};
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template<class T> struct make_unsigned: public std::make_unsigned<T>
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{
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};
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#if defined(__SIZEOF_INT128__)
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template<> struct is_integral<__int128_t>: public std::true_type
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{
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};
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template<> struct is_integral<__uint128_t>: public std::true_type
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{
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};
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template<> struct is_unsigned<__int128_t>: public std::false_type
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{
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};
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template<> struct is_unsigned<__uint128_t>: public std::true_type
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{
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};
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template<> struct make_unsigned<__int128_t>
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{
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typedef __uint128_t type;
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};
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template<> struct make_unsigned<__uint128_t>
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{
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typedef __uint128_t type;
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};
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#endif
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template<class T,
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bool bigger_than_size_t = (sizeof(T) > sizeof(std::size_t)),
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bool is_unsigned = is_unsigned<T>::value,
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std::size_t size_t_bits = sizeof(std::size_t) * CHAR_BIT,
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std::size_t type_bits = sizeof(T) * CHAR_BIT>
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struct hash_integral_impl;
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template<class T, bool is_unsigned, std::size_t size_t_bits, std::size_t type_bits> struct hash_integral_impl<T, false, is_unsigned, size_t_bits, type_bits>
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{
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static std::size_t fn( T v )
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{
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return static_cast<std::size_t>( v );
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}
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};
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template<class T, std::size_t size_t_bits, std::size_t type_bits> struct hash_integral_impl<T, true, false, size_t_bits, type_bits>
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{
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static std::size_t fn( T v )
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{
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typedef typename make_unsigned<T>::type U;
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if( v >= 0 )
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{
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return hash_integral_impl<U>::fn( static_cast<U>( v ) );
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}
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else
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{
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return ~hash_integral_impl<U>::fn( static_cast<U>( ~static_cast<U>( v ) ) );
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}
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}
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};
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template<class T> struct hash_integral_impl<T, true, true, 32, 64>
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{
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static std::size_t fn( T v )
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{
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std::size_t seed = 0;
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seed = static_cast<std::size_t>( v >> 32 ) + hash_detail::hash_mix( seed );
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seed = static_cast<std::size_t>( v & 0xFFFFFFFF ) + hash_detail::hash_mix( seed );
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return seed;
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}
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};
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template<class T> struct hash_integral_impl<T, true, true, 32, 128>
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{
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static std::size_t fn( T v )
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{
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std::size_t seed = 0;
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seed = static_cast<std::size_t>( v >> 96 ) + hash_detail::hash_mix( seed );
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seed = static_cast<std::size_t>( v >> 64 ) + hash_detail::hash_mix( seed );
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seed = static_cast<std::size_t>( v >> 32 ) + hash_detail::hash_mix( seed );
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seed = static_cast<std::size_t>( v ) + hash_detail::hash_mix( seed );
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return seed;
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}
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};
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template<class T> struct hash_integral_impl<T, true, true, 64, 128>
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{
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static std::size_t fn( T v )
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{
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std::size_t seed = 0;
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seed = static_cast<std::size_t>( v >> 64 ) + hash_detail::hash_mix( seed );
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seed = static_cast<std::size_t>( v ) + hash_detail::hash_mix( seed );
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return seed;
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}
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};
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} // namespace hash_detail
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template <typename T>
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typename std::enable_if<hash_detail::is_integral<T>::value, std::size_t>::type
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hash_value( T v )
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{
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return hash_detail::hash_integral_impl<T>::fn( v );
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}
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} // namespace boost
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#endif // #ifndef BOOST_HASH_DETAIL_HASH_INTEGRAL_HPP
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