105 lines
2.8 KiB
C++
105 lines
2.8 KiB
C++
/*
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* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/.
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* limitations under the License.
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*
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* Copyright 2015 Danny Robson <danny@nerdcruft.net>
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*/
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#include "murmur2.hpp"
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#include "common.hpp"
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#include "../../debug/panic.hpp"
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using cruft::hash::murmur2;
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///////////////////////////////////////////////////////////////////////////////
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static uint32_t
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hash_32 (const void *restrict key,
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size_t len,
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uint32_t seed)
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{
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// setup
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constexpr auto m = cruft::hash::detail::murmur2::constants<uint32_t>::m;
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uint32_t h = seed ^ (len & 0xffffffff);
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// body
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auto cursor = reinterpret_cast<const uint32_t*> (key);
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auto last = cursor + len / sizeof (uint32_t);
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for (; cursor < last; ++cursor)
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h = cruft::hash::murmur2<uint32_t>::mix (h, *cursor);
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// tail
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if (len % sizeof (uint32_t)) {
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h ^= cruft::hash::murmur::tail<uint32_t> (reinterpret_cast<const uint8_t*> (cursor), len);
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h *= m;
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}
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// finalise
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h ^= h >> 13;
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h *= m;
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h ^= h >> 15;
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return h;
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}
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//-----------------------------------------------------------------------------
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static uint64_t
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hash_64 (const void *restrict key,
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size_t len,
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uint64_t seed)
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{
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// setup
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constexpr auto m = cruft::hash::detail::murmur2::constants<uint64_t>::m;
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constexpr auto r = cruft::hash::detail::murmur2::constants<uint64_t>::r;
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uint64_t h = seed ^ (len * m);
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// body
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auto cursor = reinterpret_cast<const uint64_t*> (key);
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auto last = cursor + len / sizeof (uint64_t);
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for (; cursor < last; ++cursor)
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h = cruft::hash::murmur2<uint64_t>::mix (h, *cursor);
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// tail
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if (len % sizeof (uint64_t)) {
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h ^= cruft::hash::murmur::tail<uint64_t> (reinterpret_cast<const uint8_t*> (cursor), len);
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h *= m;
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}
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// finalise
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h ^= h >> r;
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h *= m;
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h ^= h >> r;
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return h;
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}
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///////////////////////////////////////////////////////////////////////////////
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template <typename DigestT>
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typename murmur2<DigestT>::digest_t
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murmur2<DigestT>::operator() (cruft::view<const uint8_t*> data) const noexcept
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{
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static_assert (std::is_same_v<DigestT,uint32_t> || std::is_same_v<DigestT,uint64_t>);
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if constexpr (std::is_same_v<DigestT,uint32_t>) {
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return hash_32 (data.data (), data.size (), m_seed);
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}
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if constexpr (std::is_same_v<DigestT,uint64_t>) {
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return hash_64 (data.data (), data.size (), m_seed);
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}
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unreachable ();
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}
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///////////////////////////////////////////////////////////////////////////////
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template class cruft::hash::murmur2<uint32_t>;
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template class cruft::hash::murmur2<uint64_t>;
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