forked from boostorg/unordered
4e4f99d51f
And clean of the FNV-1 example & documentation a little. Merged revisions 47085,47132,47143-47146 via svnmerge from https://svn.boost.org/svn/boost/trunk ........ r47085 | danieljames | 2008-07-04 23:57:20 +0100 (Fri, 04 Jul 2008) | 4 lines Require explicit conversion from allocators. (Not what it says in the draft standard, but I think that might be a defect). ........ r47132 | danieljames | 2008-07-06 13:41:09 +0100 (Sun, 06 Jul 2008) | 2 lines 'Bias' should be 'basis'. ........ r47143 | danieljames | 2008-07-06 22:06:52 +0100 (Sun, 06 Jul 2008) | 1 line Clean up the FNV-1 comments. ........ r47144 | danieljames | 2008-07-06 22:07:31 +0100 (Sun, 06 Jul 2008) | 1 line I've only got one hash function for release, so no need for its own directory. ........ r47145 | danieljames | 2008-07-06 22:08:11 +0100 (Sun, 06 Jul 2008) | 1 line Remove the hash_functions directory (for now). ........ r47146 | danieljames | 2008-07-06 22:29:47 +0100 (Sun, 06 Jul 2008) | 1 line Update the docs for the new location of FNV-1. ........ [SVN r47150]
67 lines
2.0 KiB
C++
67 lines
2.0 KiB
C++
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// Copyright 2008 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 = 275519064689413815358837431229664493455u;
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// For 256 bit machines:
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// const std::size_t fnv_prime = 374144419156711147060143317175368453031918731002211u;
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// const std::size_t fnv_offset_basis = 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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