63 lines
1.6 KiB
C++
63 lines
1.6 KiB
C++
/*
|
|
* This Source Code Form is subject to the terms of the Mozilla Public
|
|
* License, v. 2.0. If a copy of the MPL was not distributed with this
|
|
* file, You can obtain one at http://mozilla.org/MPL/2.0/.
|
|
*
|
|
* Copyright 2010-2015 Danny Robson <danny@nerdcruft.net>
|
|
*/
|
|
|
|
#include "fnv1a.hpp"
|
|
|
|
using cruft::hash::fnv1a;
|
|
|
|
|
|
///////////////////////////////////////////////////////////////////////////////
|
|
// 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 <typename DigestT>
|
|
struct constants { };
|
|
|
|
|
|
//-----------------------------------------------------------------------------
|
|
template <>
|
|
struct constants<uint32_t> {
|
|
static constexpr uint32_t prime = 16777619u;
|
|
static constexpr uint32_t bias = 2166136261u;
|
|
};
|
|
|
|
|
|
//-----------------------------------------------------------------------------
|
|
template <>
|
|
struct constants<uint64_t> {
|
|
static constexpr uint64_t prime = 1099511628211u;
|
|
static constexpr uint64_t bias = 14695981039346656037u;
|
|
};
|
|
|
|
|
|
///////////////////////////////////////////////////////////////////////////////
|
|
template <typename DigestT>
|
|
typename fnv1a<DigestT>::digest_t
|
|
fnv1a<DigestT>::operator() (const cruft::view<const uint8_t*> data) const noexcept
|
|
{
|
|
auto result = constants<DigestT>::bias;
|
|
|
|
for (auto i: data) {
|
|
result ^= i;
|
|
result *= constants<DigestT>::prime;
|
|
}
|
|
|
|
return result;
|
|
}
|
|
|
|
|
|
template struct cruft::hash::fnv1a<uint32_t>;
|
|
template struct cruft::hash::fnv1a<uint64_t>;
|