70 lines
2.1 KiB
C++
70 lines
2.1 KiB
C++
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// Copyright 2008-2009 Daniel James.
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// Distributed under the Boost Software License, Version 1.0. (See accompanying
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// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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// This code is also released into the public domain.
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// Algorithm from: http://www.isthe.com/chongo/tech/comp/fnv/
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#include <string>
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namespace hash
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{
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template <std::size_t FnvPrime, std::size_t OffsetBasis>
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struct basic_fnv_1
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{
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std::size_t operator()(std::string const& text) const
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{
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std::size_t hash = OffsetBasis;
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for(std::string::const_iterator it = text.begin(), end = text.end();
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it != end; ++it)
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{
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hash *= FnvPrime;
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hash ^= *it;
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}
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return hash;
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}
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};
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template <std::size_t FnvPrime, std::size_t OffsetBasis>
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struct basic_fnv_1a
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{
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std::size_t operator()(std::string const& text) const
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{
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std::size_t hash = OffsetBasis;
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for(std::string::const_iterator it = text.begin(), end = text.end();
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it != end; ++it)
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{
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hash ^= *it;
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hash *= FnvPrime;
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}
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return hash;
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}
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};
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// For 32 bit machines:
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const std::size_t fnv_prime = 16777619u;
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const std::size_t fnv_offset_basis = 2166136261u;
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// For 64 bit machines:
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// const std::size_t fnv_prime = 1099511628211u;
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// const std::size_t fnv_offset_basis = 14695981039346656037u;
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// For 128 bit machines:
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// const std::size_t fnv_prime = 309485009821345068724781401u;
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// const std::size_t fnv_offset_basis =
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// 275519064689413815358837431229664493455u;
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// For 256 bit machines:
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// const std::size_t fnv_prime =
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// 374144419156711147060143317175368453031918731002211u;
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// const std::size_t fnv_offset_basis =
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// 100029257958052580907070968620625704837092796014241193945225284501741471925557u;
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typedef basic_fnv_1<fnv_prime, fnv_offset_basis> fnv_1;
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typedef basic_fnv_1a<fnv_prime, fnv_offset_basis> fnv_1a;
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}
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