| 1 | /* |
|---|---|
| 2 | * Copyright Andrey Semashev 2016. |
| 3 | * Distributed under the Boost Software License, Version 1.0. |
| 4 | * (See accompanying file LICENSE_1_0.txt or copy at |
| 5 | * http://www.boost.org/LICENSE_1_0.txt) |
| 6 | */ |
| 7 | /*! |
| 8 | * \file murmur3.hpp |
| 9 | * \author Andrey Semashev |
| 10 | * \date 16.01.2016 |
| 11 | * |
| 12 | * \brief This header is the Boost.Log library implementation, see the library documentation |
| 13 | * at http://www.boost.org/doc/libs/release/libs/log/doc/html/index.html. |
| 14 | * |
| 15 | * This file implements MurmurHash3 hash function implementation. See https://en.wikipedia.org/wiki/MurmurHash. |
| 16 | */ |
| 17 | |
| 18 | #ifndef BOOST_LOG_MURMUR3_HPP_INCLUDED_ |
| 19 | #define BOOST_LOG_MURMUR3_HPP_INCLUDED_ |
| 20 | |
| 21 | #include <boost/log/detail/config.hpp> |
| 22 | #include <boost/cstdint.hpp> |
| 23 | #include <boost/log/detail/header.hpp> |
| 24 | |
| 25 | namespace boost { |
| 26 | |
| 27 | BOOST_LOG_OPEN_NAMESPACE |
| 28 | |
| 29 | namespace aux { |
| 30 | |
| 31 | //! 32-bit MurmurHash3 algorithm implementation (https://en.wikipedia.org/wiki/MurmurHash) |
| 32 | class murmur3_32 |
| 33 | { |
| 34 | private: |
| 35 | uint32_t m_state; |
| 36 | uint32_t m_len; |
| 37 | |
| 38 | static BOOST_CONSTEXPR_OR_CONST uint32_t c1 = 0xcc9e2d51; |
| 39 | static BOOST_CONSTEXPR_OR_CONST uint32_t c2 = 0x1b873593; |
| 40 | static BOOST_CONSTEXPR_OR_CONST uint32_t r1 = 15; |
| 41 | static BOOST_CONSTEXPR_OR_CONST uint32_t r2 = 13; |
| 42 | static BOOST_CONSTEXPR_OR_CONST uint32_t m = 5; |
| 43 | static BOOST_CONSTEXPR_OR_CONST uint32_t n = 0xe6546b64; |
| 44 | |
| 45 | public: |
| 46 | explicit BOOST_CONSTEXPR murmur3_32(uint32_t seed) BOOST_NOEXCEPT : m_state(seed), m_len(0u) |
| 47 | { |
| 48 | } |
| 49 | |
| 50 | //! Mixing stage of the 32-bit MurmurHash3 algorithm |
| 51 | void mix(uint32_t value) BOOST_NOEXCEPT |
| 52 | { |
| 53 | value *= c1; |
| 54 | value = (value << r1) | (value >> (32u - r1)); |
| 55 | value *= c2; |
| 56 | |
| 57 | uint32_t h = m_state ^ value; |
| 58 | m_state = ((h << r2) | (h >> (32u - r2))) * m + n; |
| 59 | m_len += 4u; |
| 60 | } |
| 61 | |
| 62 | //! Finalization stage of the 32-bit MurmurHash3 algorithm |
| 63 | uint32_t finalize() BOOST_NOEXCEPT |
| 64 | { |
| 65 | uint32_t h = m_state ^ m_len; |
| 66 | h ^= h >> 16u; |
| 67 | h *= 0x85ebca6bu; |
| 68 | h ^= h >> 13u; |
| 69 | h *= 0xc2b2ae35u; |
| 70 | h ^= h >> 16u; |
| 71 | m_state = h; |
| 72 | return h; |
| 73 | } |
| 74 | }; |
| 75 | |
| 76 | } // namespace aux |
| 77 | |
| 78 | BOOST_LOG_CLOSE_NAMESPACE // namespace log |
| 79 | |
| 80 | } // namespace boost |
| 81 | |
| 82 | #include <boost/log/detail/footer.hpp> |
| 83 | |
| 84 | #endif // BOOST_LOG_MURMUR3_HPP_INCLUDED_ |
| 85 |