| |
| // 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; |
| } |