libcruft-util/hash/siphash.cpp

116 lines
3.0 KiB
C++

/*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
* Copyright 2018 Danny Robson <danny@nerdcruft.net>
*/
#include "siphash.hpp"
#include "../bitwise.hpp"
#include "../debug.hpp"
#include "../endian.hpp"
using util::hash::siphash;
///////////////////////////////////////////////////////////////////////////////
static constexpr
uint64_t INITIALISERS[4] = {
0x736f6d6570736575,
0x646f72616e646f6d,
0x6c7967656e657261,
0x7465646279746573,
};
///////////////////////////////////////////////////////////////////////////////
static void
round (uint64_t v[4])
{
using util::rotatel;
v[0] += v[1]; v[2] += v[3];
v[1] = rotatel (v[1], 13); v[3] = rotatel (v[3], 16);
v[1] ^= v[0]; v[3] ^= v[2];
v[0] = rotatel (v[0], 32);
v[2] += v[1]; v[0] += v[3];
v[1] = rotatel (v[1], 17); v[3] = rotatel (v[3], 21);
v[1] ^= v[2]; v[3] ^= v[0];
v[2] = rotatel (v[2], 32);
}
///////////////////////////////////////////////////////////////////////////////
template <int C, int D>
siphash<C,D>::siphash (std::array<uint64_t,2> _key) noexcept:
m_key (_key)
{ ; }
//-----------------------------------------------------------------------------
template <int C, int D>
typename siphash<C,D>::digest_t
siphash<C,D>::operator() (util::view<const uint8_t*> data) const noexcept
{
// init
uint64_t state[4] = {
m_key[0] ^ INITIALISERS[0],
m_key[1] ^ INITIALISERS[1],
m_key[0] ^ INITIALISERS[2],
m_key[1] ^ INITIALISERS[3],
};
// update
auto cursor = data.begin ();
for ( ; data.end () - cursor > 8; cursor += sizeof (uint64_t)) {
auto word = readle<uint64_t> (cursor);
state[3] ^= word;
for (int c = 0; c < C; ++c)
round (state);
state[0] ^= word;
}
// drain
union {
uint64_t d64 = 0;
uint8_t d08[8];
} accum;
if (cursor != data.cend ()) {
std::copy (cursor, data.cend (), std::begin (accum.d08));
cursor = data.cend ();
}
CHECK_EQ (cursor, data.cend ());
// append the length
accum.d08[7] = data.size ();
state[3] ^= accum.d64;
for (int c = 0; c < C; ++c)
round (state);
state[0] ^= accum.d64;
// finalisation
state[2] ^= 0xff;
for (int d = 0; d < D; ++d)
round (state);
return state[0] ^ state[1] ^ state[2] ^ state[3];
}
///////////////////////////////////////////////////////////////////////////////
template class util::hash::siphash<2,4>;