63 lines
1.7 KiB
C++
63 lines
1.7 KiB
C++
/*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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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 "fasthash.hpp"
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#include "../endian.hpp"
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#include "../debug.hpp"
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using util::hash::fasthash;
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///////////////////////////////////////////////////////////////////////////////
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template <>
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uint64_t
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fasthash<uint64_t>::operator() (uint64_t seed, const util::view<const uint8_t*> data) const
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{
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static const uint64_t m = 0x880355f21e6d1965;
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uint64_t result = seed ^ (data.size () * m);
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auto cursor = data.begin ();
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for (auto last = data.end () - data.size () % 8; cursor < last; cursor += 8) {
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result ^= mix (readle<uint64_t> (cursor));
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result *= m;
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}
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size_t remain = data.size () % 8;
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if (remain) {
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uint64_t accum = 0;
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for (size_t i = 0; i < remain; ++i)
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accum ^= uint64_t {cursor[i]} << i * 8;
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result ^= mix (accum);
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result *= m;
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}
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return mix (result);
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}
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//-----------------------------------------------------------------------------
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template <>
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uint32_t
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fasthash<uint32_t>::operator() (uint64_t seed, const util::view<const uint8_t*> data) const
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{
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auto h = fasthash<uint64_t> {} (seed, data);
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return (h & 0xffffffff) - (h >> 32);
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}
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