124 lines
3.2 KiB
C++
124 lines
3.2 KiB
C++
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/*
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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 2018 Danny Robson <danny@nerdcruft.net>
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*/
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#include "siphash.hpp"
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#include "../bitwise.hpp"
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#include "../debug.hpp"
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#include "../endian.hpp"
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using util::hash::siphash;
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///////////////////////////////////////////////////////////////////////////////
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static constexpr
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uint64_t INITIALISERS[4] = {
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0x736f6d6570736575,
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0x646f72616e646f6d,
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0x6c7967656e657261,
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0x7465646279746573,
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};
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///////////////////////////////////////////////////////////////////////////////
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void
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round (uint64_t v[4])
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{
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using util::rotatel;
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v[0] += v[1]; v[2] += v[3];
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v[1] = rotatel (v[1], 13); v[3] = rotatel (v[3], 16);
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v[1] ^= v[0]; v[3] ^= v[2];
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v[0] = rotatel (v[0], 32);
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v[2] += v[1]; v[0] += v[3];
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v[1] = rotatel (v[1], 17); v[3] = rotatel (v[3], 21);
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v[1] ^= v[2]; v[3] ^= v[0];
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v[2] = rotatel (v[2], 32);
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}
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///////////////////////////////////////////////////////////////////////////////
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template <typename ValueT>
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ValueT
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readle (const void *ptr)
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{
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return util::htol (*reinterpret_cast<const ValueT*> (ptr));
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}
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///////////////////////////////////////////////////////////////////////////////
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template <int C, int D>
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siphash<C,D>::siphash (std::array<uint64_t,2> _key) noexcept:
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m_key (_key)
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{ ; }
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//-----------------------------------------------------------------------------
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template <int C, int D>
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typename siphash<C,D>::digest_t
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siphash<C,D>::operator() (util::view<const uint8_t*> data) const noexcept
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{
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// init
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uint64_t state[4] = {
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m_key[0] ^ INITIALISERS[0],
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m_key[1] ^ INITIALISERS[1],
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m_key[0] ^ INITIALISERS[2],
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m_key[1] ^ INITIALISERS[3],
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};
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// update
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auto cursor = data.begin ();
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for ( ; data.end () - cursor > 8; cursor += sizeof (uint64_t)) {
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auto word = readle<uint64_t> (cursor);
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state[3] ^= word;
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for (int c = 0; c < C; ++c)
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round (state);
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state[0] ^= word;
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}
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// drain
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union {
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uint64_t d64 = 0;
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uint8_t d08[8];
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} accum;
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if (cursor != data.cend ()) {
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std::copy (cursor, data.cend (), std::begin (accum.d08));
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cursor = data.cend ();
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}
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CHECK_EQ (cursor, data.cend ());
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// append the length
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accum.d08[7] = data.size ();
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state[3] ^= accum.d64;
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for (int c = 0; c < C; ++c)
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round (state);
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state[0] ^= accum.d64;
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// finalisation
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state[2] ^= 0xff;
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for (int d = 0; d < D; ++d)
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round (state);
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return state[0] ^ state[1] ^ state[2] ^ state[3];
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}
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///////////////////////////////////////////////////////////////////////////////
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template class util::hash::siphash<2,4>;
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