mirror of
https://gitlab.com/kicad/code/kicad.git
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80abdee90d
Probably doesn't add much directly, but it documents and enforces the implied contract that the hash is fixed, and could be used for, say, compile time hash tables.
57 lines
1.9 KiB
C++
57 lines
1.9 KiB
C++
/*
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* This program source code file is part of KiCad, a free EDA CAD application.
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*
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* Copyright (C) 2022 KiCad Developers, see CHANGELOG.TXT for contributors.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 3
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* of the License, or (at your option) any later version.
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*
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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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*
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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, you may find one here:
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* http://www.gnu.org/licenses/gpl-3.0.html
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* or you may search the http://www.gnu.org website for the version 3 license,
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* or you may write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA
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*/
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#pragma once
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#include <functional>
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/**
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* This is a dummy function to take the final case of hash_combine below
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* @param seed
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*/
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static inline constexpr void hash_combine( std::size_t& seed )
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{
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}
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/**
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* Combine multiple hashes utilizing previous hash result.
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*
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* @tparam T A hashable type
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* @param seed A seed value input and output for the result.
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* @param val A hashable object of type T
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*/
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template <typename T, typename... Types>
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static inline constexpr void hash_combine( std::size_t& seed, const T& val, const Types&... args )
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{
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seed ^= std::hash<T>()( val ) + 0x9e3779b9 + ( seed << 6 ) + ( seed >> 2 );
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hash_combine( seed, args... );
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}
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template <typename... Types>
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static inline constexpr std::size_t hash_val( const Types&... args )
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{
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std::size_t seed = 0xa82de1c0;
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hash_combine( seed, args... );
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return seed;
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}
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