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 Hu Chunming
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/*
* Copyright Andrey Semashev 2016.
* 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)
*/
/*!
* \file murmur3.hpp
* \author Andrey Semashev
* \date 16.01.2016
*
* \brief This header is the Boost.Log library implementation, see the library documentation
* at http://www.boost.org/doc/libs/release/libs/log/doc/html/index.html.
*
* This file implements MurmurHash3 hash function implementation. See https://en.wikipedia.org/wiki/MurmurHash.
*/
#ifndef BOOST_LOG_MURMUR3_HPP_INCLUDED_
#define BOOST_LOG_MURMUR3_HPP_INCLUDED_
#include <boost/log/detail/config.hpp>
#include <boost/cstdint.hpp>
#include <boost/log/detail/header.hpp>
namespace boost {
BOOST_LOG_OPEN_NAMESPACE
namespace aux {
//! 32-bit MurmurHash3 algorithm implementation (https://en.wikipedia.org/wiki/MurmurHash)
class murmur3_32
{
private:
uint32_t m_state;
uint32_t m_len;
static BOOST_CONSTEXPR_OR_CONST uint32_t c1 = 0xcc9e2d51;
static BOOST_CONSTEXPR_OR_CONST uint32_t c2 = 0x1b873593;
static BOOST_CONSTEXPR_OR_CONST uint32_t r1 = 15;
static BOOST_CONSTEXPR_OR_CONST uint32_t r2 = 13;
static BOOST_CONSTEXPR_OR_CONST uint32_t m = 5;
static BOOST_CONSTEXPR_OR_CONST uint32_t n = 0xe6546b64;
public:
explicit BOOST_CONSTEXPR murmur3_32(uint32_t seed) BOOST_NOEXCEPT : m_state(seed), m_len(0u)
{
}
//! Mixing stage of the 32-bit MurmurHash3 algorithm
void mix(uint32_t value) BOOST_NOEXCEPT
{
value *= c1;
value = (value << r1) | (value >> (32u - r1));
value *= c2;
uint32_t h = m_state ^ value;
m_state = ((h << r2) | (h >> (32u - r2))) * m + n;
m_len += 4u;
}
//! Finalization stage of the 32-bit MurmurHash3 algorithm
uint32_t finalize() BOOST_NOEXCEPT
{
uint32_t h = m_state ^ m_len;
h ^= h >> 16u;
h *= 0x85ebca6bu;
h ^= h >> 13u;
h *= 0xc2b2ae35u;
h ^= h >> 16u;
m_state = h;
return h;
}
};
} // namespace aux
BOOST_LOG_CLOSE_NAMESPACE // namespace log
} // namespace boost
#include <boost/log/detail/footer.hpp>
#endif // BOOST_LOG_MURMUR3_HPP_INCLUDED_
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