79 lines
2.1 KiB
C++
79 lines
2.1 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 2016 Danny Robson <danny@nerdcruft.net>
|
|
*/
|
|
|
|
#if defined(__UTIL_HASH_MURMUR_MURMUR2_IPP)
|
|
#error
|
|
#endif
|
|
|
|
#define __UTIL_HASH_MURMUR_MURMUR2_IPP
|
|
|
|
|
|
///////////////////////////////////////////////////////////////////////////////
|
|
namespace util { namespace hash { namespace murmur2 { namespace detail {
|
|
template <typename T> struct constants;
|
|
|
|
template <>
|
|
struct constants<uint32_t> {
|
|
static const uint32_t m = 0x5bd1e995;
|
|
static const int32_t r = 24;
|
|
};
|
|
|
|
template <>
|
|
struct constants<uint64_t> {
|
|
static const uint64_t m = 0xc6a4a7935bd1e995;
|
|
static const int64_t r = 47;
|
|
};
|
|
} } } }
|
|
|
|
|
|
/////////////////////////////////////////////////////////////////////
|
|
constexpr uint32_t
|
|
util::hash::murmur2::mix (uint32_t h, uint32_t k)
|
|
{
|
|
constexpr uint32_t m = detail::constants<uint32_t>::m;
|
|
constexpr uint32_t r = detail::constants<uint32_t>::r;
|
|
|
|
k *= m;
|
|
k ^= k >> r;
|
|
k *= m;
|
|
|
|
h *= m;
|
|
h ^= k;
|
|
|
|
return h;
|
|
}
|
|
|
|
|
|
//-----------------------------------------------------------------------------
|
|
// 64 bit murmur2 mixing function. Note the last two lines are swapped
|
|
// compared with 32 bit murmur2_mix. It's not clear if this is deliberate
|
|
// in the canonical implementation, so we just leave it to help compatibility.
|
|
constexpr uint64_t
|
|
util::hash::murmur2::mix (uint64_t h, uint64_t k)
|
|
{
|
|
constexpr uint64_t m = detail::constants<uint64_t>::m;
|
|
constexpr uint64_t r = detail::constants<uint64_t>::r;
|
|
|
|
k *= m;
|
|
k ^= k >> r;
|
|
k *= m;
|
|
|
|
h ^= k;
|
|
h *= m;
|
|
|
|
return h;
|
|
}
|