82 lines
2.4 KiB
C++
82 lines
2.4 KiB
C++
/**
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This file is a part of rexy's general purpose library
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Copyright (C) 2020-2022 rexy712
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#ifndef REXY_HASH_HPP
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#define REXY_HASH_HPP
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#include <climits> //CHAR_BIT
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#include <cstddef> //size_t
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#include "rexy.hpp"
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#include "allocator.hpp"
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namespace rexy{
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template<class Char, REXY_ALLOCATOR_CONCEPT Alloc>
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class basic_string;
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template<class Char>
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class basic_string_view;
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namespace cx{
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template<std::size_t N, class Char>
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class string;
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}
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template<class T>
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struct hash{
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constexpr std::size_t operator()(const T& t, std::size_t salt = 0)const noexcept{
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constexpr std::size_t bytes = sizeof(std::size_t);
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std::size_t val = static_cast<std::size_t>(t);
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std::size_t hash = 5381 + salt; //magic hash number
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for(std::size_t i = 0;i < bytes;++i){
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unsigned char c = static_cast<unsigned char>(val >> (i * CHAR_BIT));
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hash = ((hash << 5) + hash) ^ c;
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}
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return hash;
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}
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};
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namespace detail{
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//jenkins one at a time hash
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template<class Str>
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struct string_hash{
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constexpr std::size_t operator()(const Str& s, std::size_t salt = 0)const noexcept{
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std::size_t hash = salt;
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for(std::size_t i = 0;i < s.length();++i){
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hash += s[i];
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hash += (hash << 10);
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hash += (hash >> 6);
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}
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hash += (hash << 3);
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hash ^= (hash << 11);
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hash += (hash << 15);
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return hash;
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}
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};
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}
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template<class Char, REXY_ALLOCATOR_CONCEPT Alloc>
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struct hash<rexy::basic_string<Char,Alloc>> : public detail::string_hash<rexy::basic_string<Char,Alloc>>{};
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template<class Char>
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struct hash<rexy::basic_string_view<Char>> : public detail::string_hash<rexy::basic_string_view<Char>>{};
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template<std::size_t N, class Char>
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struct hash<rexy::cx::string<N,Char>> : public detail::string_hash<rexy::cx::string<N,Char>>{};
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}
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#endif
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