mirror of
https://gitlab.com/libvirt/libvirt.git
synced 2024-11-01 10:51:12 +00:00
adf846d3c9
Use ATTRIBUTE_FALLTHROUGH, introduced by commit
5d84f5961b, instead of comments to
indicate that the fall through is an intentional behavior.
Signed-off-by: Marc Hartmayer <mhartmay@linux.vnet.ibm.com>
Reviewed-by: Boris Fiuczynski <fiuczy@linux.vnet.ibm.com>
Reviewed-by: Bjoern Walk <bwalk@linux.vnet.ibm.com>
122 lines
2.7 KiB
C
122 lines
2.7 KiB
C
/*
|
|
* virhashcode.c: hash code generation
|
|
*
|
|
* Copyright (C) 2012 Red Hat, Inc.
|
|
*
|
|
* This library is free software; you can redistribute it and/or
|
|
* modify it under the terms of the GNU Lesser General Public
|
|
* License as published by the Free Software Foundation; either
|
|
* version 2.1 of the License, or (at your option) any later version.
|
|
*
|
|
* This library 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
|
|
* Lesser General Public License for more details.
|
|
*
|
|
* You should have received a copy of the GNU Lesser General Public
|
|
* License along with this library. If not, see
|
|
* <http://www.gnu.org/licenses/>.
|
|
*
|
|
* The hash code generation is based on the public domain MurmurHash3 from Austin Appleby:
|
|
* http://code.google.com/p/smhasher/source/browse/trunk/MurmurHash3.cpp
|
|
*
|
|
* We use only the 32 bit variant because the 2 produce different results while
|
|
* we need to produce the same result regardless of the architecture as
|
|
* clients can be both 64 or 32 bit at the same time.
|
|
*/
|
|
|
|
#include <config.h>
|
|
|
|
#include "virhashcode.h"
|
|
#include "bitrotate.h"
|
|
|
|
/* slower than original but handles platforms that do only aligned reads */
|
|
static inline uint32_t getblock(const uint8_t *p, int i)
|
|
{
|
|
uint32_t r;
|
|
size_t size = sizeof(r);
|
|
|
|
memcpy(&r, &p[i * size], size);
|
|
|
|
return r;
|
|
}
|
|
|
|
/*
|
|
* Finalization mix - force all bits of a hash block to avalanche
|
|
*/
|
|
static inline uint32_t fmix(uint32_t h)
|
|
{
|
|
h ^= h >> 16;
|
|
h *= 0x85ebca6b;
|
|
h ^= h >> 13;
|
|
h *= 0xc2b2ae35;
|
|
h ^= h >> 16;
|
|
|
|
return h;
|
|
}
|
|
|
|
|
|
uint32_t virHashCodeGen(const void *key, size_t len, uint32_t seed)
|
|
{
|
|
const uint8_t *blocks;
|
|
const uint8_t *tail;
|
|
size_t nblocks;
|
|
uint32_t h1;
|
|
uint32_t k1;
|
|
uint32_t c1;
|
|
uint32_t c2;
|
|
size_t i;
|
|
|
|
blocks = (const uint8_t *)key;
|
|
nblocks = len / 4;
|
|
h1 = seed;
|
|
c1 = 0xcc9e2d51;
|
|
c2 = 0x1b873593;
|
|
|
|
/* body */
|
|
|
|
for (i = 0; i < nblocks; i++) {
|
|
|
|
k1 = getblock(blocks, i);
|
|
|
|
k1 *= c1;
|
|
k1 = rotl32(k1, 15);
|
|
k1 *= c2;
|
|
|
|
h1 ^= k1;
|
|
h1 = rotl32(h1, 13);
|
|
h1 = h1 * 5 + 0xe6546b64;
|
|
}
|
|
|
|
/* tail */
|
|
|
|
tail = (const uint8_t *)key + nblocks * 4;
|
|
|
|
k1 = 0;
|
|
|
|
switch (len & 3) {
|
|
case 3:
|
|
k1 ^= tail[2] << 16;
|
|
ATTRIBUTE_FALLTHROUGH;
|
|
case 2:
|
|
k1 ^= tail[1] << 8;
|
|
ATTRIBUTE_FALLTHROUGH;
|
|
case 1:
|
|
k1 ^= tail[0];
|
|
k1 *= c1;
|
|
k1 = rotl32(k1, 15);
|
|
k1 *= c2;
|
|
h1 ^= k1;
|
|
ATTRIBUTE_FALLTHROUGH;
|
|
default:
|
|
break;
|
|
}
|
|
|
|
/* finalization */
|
|
|
|
h1 ^= len;
|
|
h1 = fmix(h1);
|
|
|
|
return h1;
|
|
}
|