This patch creates a couple of tests around how autoeject works.
[m6w6/libmemcached] / libhashkit / murmur.cc
1 /*
2 "Murmur" hash provided by Austin, tanjent@gmail.com
3 http://murmurhash.googlepages.com/
4
5 Note - This code makes a few assumptions about how your machine behaves -
6
7 1. We can read a 4-byte value from any address without crashing
8 2. sizeof(int) == 4
9
10 And it has a few limitations -
11 1. It will not work incrementally.
12 2. It will not produce the same results on little-endian and big-endian
13 machines.
14
15 Updated to murmur2 hash - BP
16 */
17
18 #include <libhashkit/common.h>
19
20 uint32_t hashkit_murmur(const char *key, size_t length, void *context)
21 {
22 /*
23 'm' and 'r' are mixing constants generated offline. They're not
24 really 'magic', they just happen to work well.
25 */
26
27 const unsigned int m= 0x5bd1e995;
28 const uint32_t seed= (0xdeadbeef * (uint32_t)length);
29 const int r= 24;
30
31
32 // Initialize the hash to a 'random' value
33
34 uint32_t h= seed ^ (uint32_t)length;
35
36 // Mix 4 bytes at a time into the hash
37
38 const unsigned char * data= (const unsigned char *)key;
39 (void)context;
40
41 while(length >= 4)
42 {
43 unsigned int k = *(unsigned int *)data;
44
45 k *= m;
46 k ^= k >> r;
47 k *= m;
48
49 h *= m;
50 h ^= k;
51
52 data += 4;
53 length -= 4;
54 }
55
56 // Handle the last few bytes of the input array
57
58 switch(length)
59 {
60 case 3: h ^= ((uint32_t)data[2]) << 16;
61 case 2: h ^= ((uint32_t)data[1]) << 8;
62 case 1: h ^= data[0];
63 h *= m;
64 default: break;
65 };
66
67 /*
68 Do a few final mixes of the hash to ensure the last few bytes are
69 well-incorporated.
70 */
71
72 h ^= h >> 13;
73 h *= m;
74 h ^= h >> 15;
75
76 return h;
77 }