libcruft-util/hash.cpp

90 lines
2.3 KiB
C++

/*
* This file is part of libgim.
*
* libgim is free software: you can redistribute it and/or modify it under the
* terms of the GNU General Public License as published by the Free Software
* Foundation, either version 3 of the License, or (at your option) any later
* version.
*
* libgim is distributed in the hope that it will be useful, but WITHOUT ANY
* WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
* FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
* details.
*
* You should have received a copy of the GNU General Public License
* along with libgim. If not, see <http://www.gnu.org/licenses/>.
*
* Copyright 2010 Danny Robson <danny@nerdcruft.net>
*/
#include "hash.hpp"
uint32_t
util::wang32 (uint32_t key) {
uint32_t c2 = 0x27d4eb2d; // a prime or an odd constant
key = (key ^ 61) ^ (key >> 16);
key = key + (key << 3);
key = key ^ (key >> 4);
key = key * c2;
key = key ^ (key >> 15);
return key;
}
uint64_t
util::wang64 (uint64_t key) {
key = (~key) + (key << 21); // key = (key << 21) - key - 1;
key = key ^ (key >> 24);
key = (key + (key << 3)) + (key << 8); // key * 265
key = key ^ (key >> 14);
key = (key + (key << 2)) + (key << 4); // key * 21
key = key ^ (key >> 28);
key = key + (key << 31);
return key;
}
// 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
static const uint32_t FNV_1a_32_PRIME = 16777619U;
static const uint64_t FNV_1a_64_PRIME = 1099511628211U;
// Bias is the FNV-0 hash of "chongo <Landon Curt Noll> /\\../\\"
static const uint32_t FNV_1a_32_BIAS = 2166136261U;
static const uint64_t FNV_1a_64_BIAS = 14695981039346656037U;
uint32_t
util::fnv1a32 (const void *_data, size_t size) {
const uint8_t *data = static_cast<const uint8_t*> (_data);
uint32_t result = FNV_1a_32_BIAS;
for (size_t i = 0; i < size; ++i) {
result ^= data[i];
result *= FNV_1a_32_PRIME;
}
return result;
}
uint64_t
util::fnv1a64 (const void *_data, size_t size) {
const uint8_t *data = static_cast<const uint8_t*> (_data);
uint64_t result = FNV_1a_64_BIAS;
for (size_t i = 0; i < size; ++i) {
result ^= data[i];
result *= FNV_1a_64_PRIME;
}
return result;
}