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swoole_hash.h
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/*
+----------------------------------------------------------------------+
| Swoole |
+----------------------------------------------------------------------+
| This source file is subject to version 2.0 of the Apache license, |
| that is bundled with this package in the file LICENSE, and is |
| available through the world-wide-web at the following url: |
| http://www.apache.org/licenses/LICENSE-2.0.html |
| If you did not receive a copy of the Apache2.0 license and are unable|
| to obtain it through the world-wide-web, please send a note to |
| [email protected] so we can mail you a copy immediately. |
+----------------------------------------------------------------------+
| Author: Tianfeng Han <[email protected]> |
+----------------------------------------------------------------------+
*/
#ifndef SW_HASH_H_
#define SW_HASH_H_
SW_EXTERN_C_BEGIN
#include <stdint.h>
#define HASH_JEN_MIX(a, b, c) \
do { \
a -= b; \
a -= c; \
a ^= (c >> 13); \
b -= c; \
b -= a; \
b ^= (a << 8); \
c -= a; \
c -= b; \
c ^= (b >> 13); \
a -= b; \
a -= c; \
a ^= (c >> 12); \
b -= c; \
b -= a; \
b ^= (a << 16); \
c -= a; \
c -= b; \
c ^= (b >> 5); \
a -= b; \
a -= c; \
a ^= (c >> 3); \
b -= c; \
b -= a; \
b ^= (a << 10); \
c -= a; \
c -= b; \
c ^= (b >> 15); \
} while (0)
/**
* jenkins
*/
static inline uint64_t swoole_hash_jenkins(const char *key, size_t keylen) {
uint64_t hashv;
unsigned i, j, k;
hashv = 0xfeedbeef;
i = j = 0x9e3779b9;
k = (unsigned) (keylen);
while (k >= 12) {
i += (key[0] + ((unsigned) key[1] << 8) + ((unsigned) key[2] << 16) + ((unsigned) key[3] << 24));
j += (key[4] + ((unsigned) key[5] << 8) + ((unsigned) key[6] << 16) + ((unsigned) key[7] << 24));
hashv += (key[8] + ((unsigned) key[9] << 8) + ((unsigned) key[10] << 16) + ((unsigned) key[11] << 24));
HASH_JEN_MIX(i, j, hashv);
key += 12;
k -= 12;
}
hashv += keylen;
switch (k) {
case 11:
hashv += ((unsigned) key[10] << 24);
/* no break */
case 10:
hashv += ((unsigned) key[9] << 16);
/* no break */
case 9:
hashv += ((unsigned) key[8] << 8);
/* no break */
case 8:
j += ((unsigned) key[7] << 24);
/* no break */
case 7:
j += ((unsigned) key[6] << 16);
/* no break */
case 6:
j += ((unsigned) key[5] << 8);
/* no break */
case 5:
j += key[4];
/* no break */
case 4:
i += ((unsigned) key[3] << 24);
/* no break */
case 3:
i += ((unsigned) key[2] << 16);
/* no break */
case 2:
i += ((unsigned) key[1] << 8);
/* no break */
case 1:
i += key[0];
}
HASH_JEN_MIX(i, j, hashv);
return hashv;
}
/**
* MurmurHash2(Austin Appleby)
*/
static inline uint32_t swoole_hash_austin(const char *key, unsigned int keylen) {
unsigned int h, k;
h = 0 ^ keylen;
while (keylen >= 4) {
k = key[0];
k |= key[1] << 8;
k |= key[2] << 16;
k |= key[3] << 24;
k *= 0x5bd1e995;
k ^= k >> 24;
k *= 0x5bd1e995;
h *= 0x5bd1e995;
h ^= k;
key += 4;
keylen -= 4;
}
switch (keylen) {
case 3:
h ^= key[2] << 16;
/* no break */
case 2:
h ^= key[1] << 8;
/* no break */
case 1:
h ^= key[0];
h *= 0x5bd1e995;
}
h ^= h >> 13;
h *= 0x5bd1e995;
h ^= h >> 15;
return h;
}
/* {{{ DJBX33A (Daniel J. Bernstein, Times 33 with Addition)
*
* This is Daniel J. Bernstein's popular `times 33' hash function as
* posted by him years ago on comp->lang.c. It basically uses a function
* like ``hash(i) = hash(i-1) * 33 + str[i]''. This is one of the best
* known hash functions for strings. Because it is both computed very
* fast and distributes very well.
*
* The magic of number 33, i.e. why it works better than many other
* constants, prime or not, has never been adequately explained by
* anyone. So I try an explanation: if one experimentally tests all
* multipliers between 1 and 256 (as RSE did now) one detects that even
* numbers are not useable at all. The remaining 128 odd numbers
* (except for the number 1) work more or less all equally well. They
* all distribute in an acceptable way and this way fill a hash table
* with an average percent of approx. 86%.
*
* If one compares the Chi^2 values of the variants, the number 33 not
* even has the best value. But the number 33 and a few other equally
* good numbers like 17, 31, 63, 127 and 129 have nevertheless a great
* advantage to the remaining numbers in the large set of possible
* multipliers: their multiply operation can be replaced by a faster
* operation based on just one shift plus either a single addition
* or subtraction operation. And because a hash function has to both
* distribute good _and_ has to be very fast to compute, those few
* numbers should be preferred and seems to be the reason why Daniel J.
* Bernstein also preferred it.
*
* -- Ralf S. Engelschall <[email protected]>
*/
static inline uint64_t swoole_hash_php(const char *key, size_t len) {
ulong_t hash = 5381;
/* variant with the hash unrolled eight times */
for (; len >= 8; len -= 8) {
hash = ((hash << 5) + hash) + *key++;
hash = ((hash << 5) + hash) + *key++;
hash = ((hash << 5) + hash) + *key++;
hash = ((hash << 5) + hash) + *key++;
hash = ((hash << 5) + hash) + *key++;
hash = ((hash << 5) + hash) + *key++;
hash = ((hash << 5) + hash) + *key++;
hash = ((hash << 5) + hash) + *key++;
}
switch (len) {
case 7:
hash = ((hash << 5) + hash) + *key++; /* fallthrough... */
/* no break */
case 6:
hash = ((hash << 5) + hash) + *key++; /* fallthrough... */
/* no break */
case 5:
hash = ((hash << 5) + hash) + *key++; /* fallthrough... */
/* no break */
case 4:
hash = ((hash << 5) + hash) + *key++; /* fallthrough... */
/* no break */
case 3:
hash = ((hash << 5) + hash) + *key++; /* fallthrough... */
/* no break */
case 2:
hash = ((hash << 5) + hash) + *key++; /* fallthrough... */
/* no break */
case 1:
hash = ((hash << 5) + hash) + *key++;
break;
case 0:
break;
default:
break;
}
return hash;
}
#define CRC_STRING_MAXLEN 256
uint32_t swoole_crc32(const char *data, uint32_t size);
SW_EXTERN_C_END
#endif /* SW_HASH_H_ */