71 lines
1.9 KiB
C++
71 lines
1.9 KiB
C++
/* Hash function characterization.
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*
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* Copyright 2022-2024 Joaquin M Lopez Munoz.
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* Distributed under the Boost Software License, Version 1.0.
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* (See accompanying file LICENSE_1_0.txt or copy at
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* http://www.boost.org/LICENSE_1_0.txt)
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*
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* See https://www.boost.org/libs/unordered for library home page.
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*/
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#ifndef BOOST_UNORDERED_HASH_TRAITS_HPP
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#define BOOST_UNORDERED_HASH_TRAITS_HPP
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#include <boost/unordered/detail/type_traits.hpp>
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namespace boost{
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namespace unordered{
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namespace detail{
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template<typename Hash,typename=void>
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struct hash_is_avalanching_impl:std::false_type{};
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template<typename IsAvalanching>
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struct avalanching_value
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{
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static constexpr bool value=IsAvalanching::value;
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};
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/* may be explicitly marked as BOOST_DEPRECATED in the future */
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template<> struct avalanching_value<void>
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{
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static constexpr bool value=true;
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};
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template<typename Hash>
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struct hash_is_avalanching_impl<
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Hash,
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boost::unordered::detail::void_t<typename Hash::is_avalanching>
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>:std::integral_constant<
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bool,
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avalanching_value<typename Hash::is_avalanching>::value
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>{};
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template<typename Hash>
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struct hash_is_avalanching_impl<
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Hash,
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typename std::enable_if<((void)Hash::is_avalanching,true)>::type
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>{}; /* Hash::is_avalanching is not a type: compile error downstream */
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} /* namespace detail */
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/* Each trait can be partially specialized by users for concrete hash functions
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* when actual characterization differs from default.
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*/
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/* hash_is_avalanching<Hash>::value is:
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* - false if Hash::is_avalanching is not present.
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* - Hash::is_avalanching::value if this is present and constexpr-convertible
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* to a bool.
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* - true if Hash::is_avalanching is void (deprecated).
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* - ill-formed otherwise.
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*/
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template<typename Hash>
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struct hash_is_avalanching: detail::hash_is_avalanching_impl<Hash>::type{};
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} /* namespace unordered */
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} /* namespace boost */
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#endif
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