/* * This Source Code Form is subject to the terms of the Mozilla Public * License, v. 2.0. If a copy of the MPL was not distributed with this * file, You can obtain one at http://mozilla.org/MPL/2.0/. * * Copyright 2015 Danny Robson <danny@nerdcruft.net> */ #ifndef __UTIL_HASH_MURMUR_MURMUR2_HPP #define __UTIL_HASH_MURMUR_MURMUR2_HPP #include "../../view.hpp" #include <cstddef> #include <cstdint> // Austin Appleby's MumurHash2, and MurmurHash64A. The exhaustive list of // variants is deliberately not provided. You can damn well align your data or // fix the algorithm. namespace cruft::hash { namespace detail::murmur2 { template <typename T> struct constants; template <> struct constants<uint32_t> { static const uint32_t m = 0x5bd1e995; static const int32_t r = 24; }; template <> struct constants<uint64_t> { static const uint64_t m = 0xc6a4a7935bd1e995; static const int64_t r = 47; }; } template <typename DigestT> class murmur2 { public: using digest_t = DigestT; using seed_t = DigestT; murmur2 (seed_t _seed): m_seed (_seed) { ; } static constexpr uint32_t mix (uint32_t h, uint32_t k) { constexpr uint32_t m = detail::murmur2::constants<uint32_t>::m; constexpr uint32_t r = detail::murmur2::constants<uint32_t>::r; k *= m; k ^= k >> r; k *= m; h *= m; h ^= k; return h; } static constexpr uint64_t mix (uint64_t h, uint64_t k) { constexpr uint64_t m = detail::murmur2::constants<uint64_t>::m; constexpr uint64_t r = detail::murmur2::constants<uint64_t>::r; k *= m; k ^= k >> r; k *= m; h ^= k; h *= m; return h; } digest_t operator() (cruft::view<const uint8_t*> data) const noexcept; private: seed_t m_seed; }; } #endif