libcruft-util/hash/murmur/common.cpp

142 lines
4.4 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 2015 Danny Robson <danny@nerdcruft.net>
*/
#include "common.hpp"
#include "../../debug.hpp"
///////////////////////////////////////////////////////////////////////////////
namespace util::hash::murmur {
template <>
uint32_t
tail<uint32_t> (const uint8_t *restrict bytes, size_t len)
{
uint32_t h = 0;
switch (len % sizeof (uint32_t)) {
case 3: h += bytes[2] << 16;
case 2: h += bytes[1] << 8;
case 1: h += bytes[0];
break;
default:
unreachable ();
}
return h;
}
}
//-----------------------------------------------------------------------------
namespace util::hash::murmur {
template <>
uint64_t
tail<uint64_t> (const uint8_t *restrict bytes, size_t len)
{
uint64_t h = 0;
switch (len % sizeof (uint64_t)) {
case 7: h += uint64_t(bytes[6]) << 48;
case 6: h += uint64_t(bytes[5]) << 40;
case 5: h += uint64_t(bytes[4]) << 32;
case 4: h += uint64_t(bytes[3]) << 24;
case 3: h += uint64_t(bytes[2]) << 16;
case 2: h += uint64_t(bytes[1]) << 8;
case 1: h += uint64_t(bytes[0]);
break;
default:
unreachable ();
}
return h;
}
}
//-----------------------------------------------------------------------------
namespace util::hash::murmur {
template <>
std::array<uint32_t,4>
tail_array<uint32_t> (const uint8_t *restrict bytes, size_t len)
{
std::array<uint32_t,4> result {0,0,0,0};
switch (len % 16) {
case 15: result[3] |= bytes[14] << 16;
case 14: result[3] |= bytes[13] << 8;
case 13: result[3] |= bytes[12] << 0;
case 12: result[2] |= bytes[11] << 24;
case 11: result[2] |= bytes[10] << 16;
case 10: result[2] |= bytes[ 9] << 8;
case 9: result[2] |= bytes[ 8] << 0;
case 8: result[1] |= bytes[ 7] << 24;
case 7: result[1] |= bytes[ 6] << 16;
case 6: result[1] |= bytes[ 5] << 8;
case 5: result[1] |= bytes[ 4] << 0;
case 4: result[0] |= bytes[ 3] << 24;
case 3: result[0] |= bytes[ 2] << 16;
case 2: result[0] |= bytes[ 1] << 8;
case 1: result[0] |= bytes[ 0] << 0;
break;
default:
unreachable ();
}
return result;
}
}
//-----------------------------------------------------------------------------
namespace util::hash::murmur {
template <>
std::array<uint64_t,2>
tail_array<uint64_t> (const uint8_t *restrict bytes, size_t len)
{
std::array<uint64_t,2> result {0, 0};
switch(len & 15)
{
case 15: result[1] |= ((uint64_t)bytes[14]) << 48;
case 14: result[1] |= ((uint64_t)bytes[13]) << 40;
case 13: result[1] |= ((uint64_t)bytes[12]) << 32;
case 12: result[1] |= ((uint64_t)bytes[11]) << 24;
case 11: result[1] |= ((uint64_t)bytes[10]) << 16;
case 10: result[1] |= ((uint64_t)bytes[ 9]) << 8;
case 9: result[1] |= ((uint64_t)bytes[ 8]) << 0;
case 8: result[0] |= ((uint64_t)bytes[ 7]) << 56;
case 7: result[0] |= ((uint64_t)bytes[ 6]) << 48;
case 6: result[0] |= ((uint64_t)bytes[ 5]) << 40;
case 5: result[0] |= ((uint64_t)bytes[ 4]) << 32;
case 4: result[0] |= ((uint64_t)bytes[ 3]) << 24;
case 3: result[0] |= ((uint64_t)bytes[ 2]) << 16;
case 2: result[0] |= ((uint64_t)bytes[ 1]) << 8;
case 1: result[0] |= ((uint64_t)bytes[ 0]) << 0;
break;
default:
unreachable ();
};
return result;
}
}