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