76 lines
2.0 KiB
C++
76 lines
2.0 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 2010-2015 Danny Robson <danny@nerdcruft.net>
|
|
*/
|
|
|
|
#include "fnv1a.hpp"
|
|
|
|
|
|
///////////////////////////////////////////////////////////////////////////////
|
|
// Prime is,
|
|
// 32: 2^ 24 + 2^8 + 0x93
|
|
// 64: 2^ 40 + 2^8 + 0xb3
|
|
// 128: 2^ 88 + 2^8 + 0x3B
|
|
// 256: 2^168 + 2^8 + 0x63
|
|
// 512: 2^344 + 2^8 + 0x57
|
|
// 1024: 2^680 + 2^8 + 0x8D
|
|
//
|
|
// Bias is the FNV-0 hash of "chongo <Landon Curt Noll> /\\../\\"
|
|
|
|
template <size_t B>
|
|
struct constants { };
|
|
|
|
template <> struct constants<32> {
|
|
static constexpr uint32_t PRIME = 16777619u;
|
|
static constexpr uint32_t BIAS = 2166136261u;
|
|
};
|
|
|
|
template <> struct constants<64> {
|
|
static constexpr uint64_t PRIME = 1099511628211u;
|
|
static constexpr uint64_t BIAS = 14695981039346656037u;
|
|
};
|
|
|
|
|
|
//-----------------------------------------------------------------------------
|
|
template <typename T>
|
|
T
|
|
fnv1a (const void *restrict _data, size_t len)
|
|
{
|
|
auto *data = static_cast<const uint8_t *restrict> (_data);
|
|
T result = constants<sizeof(T)*8>::BIAS;
|
|
|
|
for (size_t i = 0; i < len; ++i) {
|
|
result ^= data[i];
|
|
result *= constants<sizeof(T)*8>::PRIME;
|
|
}
|
|
|
|
return result;
|
|
}
|
|
|
|
|
|
///////////////////////////////////////////////////////////////////////////////
|
|
uint32_t
|
|
util::hash::fnv1a32 (const void *data, size_t len)
|
|
{
|
|
return fnv1a<uint32_t> (data, len);
|
|
}
|
|
|
|
|
|
//-----------------------------------------------------------------------------
|
|
uint64_t
|
|
util::hash::fnv1a64 (const void *data, size_t len)
|
|
{
|
|
return fnv1a<uint64_t> (data, len);
|
|
}
|