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Sage Weil1654dd02009-11-06 21:55:25 -08001
Yehuda Sadeh3d14c5d2010-04-06 15:14:15 -07002#include <linux/ceph/types.h>
Sage Weil6c0f3af2010-11-16 11:14:34 -08003#include <linux/module.h>
Sage Weil1654dd02009-11-06 21:55:25 -08004
5/*
6 * Robert Jenkin's hash function.
7 * http://burtleburtle.net/bob/hash/evahash.html
8 * This is in the public domain.
9 */
10#define mix(a, b, c) \
11 do { \
12 a = a - b; a = a - c; a = a ^ (c >> 13); \
13 b = b - c; b = b - a; b = b ^ (a << 8); \
14 c = c - a; c = c - b; c = c ^ (b >> 13); \
15 a = a - b; a = a - c; a = a ^ (c >> 12); \
16 b = b - c; b = b - a; b = b ^ (a << 16); \
17 c = c - a; c = c - b; c = c ^ (b >> 5); \
18 a = a - b; a = a - c; a = a ^ (c >> 3); \
19 b = b - c; b = b - a; b = b ^ (a << 10); \
20 c = c - a; c = c - b; c = c ^ (b >> 15); \
21 } while (0)
22
23unsigned ceph_str_hash_rjenkins(const char *str, unsigned length)
24{
25 const unsigned char *k = (const unsigned char *)str;
26 __u32 a, b, c; /* the internal state */
27 __u32 len; /* how many key bytes still need mixing */
28
29 /* Set up the internal state */
30 len = length;
31 a = 0x9e3779b9; /* the golden ratio; an arbitrary value */
32 b = a;
33 c = 0; /* variable initialization of internal state */
34
35 /* handle most of the key */
36 while (len >= 12) {
37 a = a + (k[0] + ((__u32)k[1] << 8) + ((__u32)k[2] << 16) +
38 ((__u32)k[3] << 24));
39 b = b + (k[4] + ((__u32)k[5] << 8) + ((__u32)k[6] << 16) +
40 ((__u32)k[7] << 24));
41 c = c + (k[8] + ((__u32)k[9] << 8) + ((__u32)k[10] << 16) +
42 ((__u32)k[11] << 24));
43 mix(a, b, c);
44 k = k + 12;
45 len = len - 12;
46 }
47
48 /* handle the last 11 bytes */
49 c = c + length;
50 switch (len) { /* all the case statements fall through */
51 case 11:
52 c = c + ((__u32)k[10] << 24);
53 case 10:
54 c = c + ((__u32)k[9] << 16);
55 case 9:
56 c = c + ((__u32)k[8] << 8);
57 /* the first byte of c is reserved for the length */
58 case 8:
59 b = b + ((__u32)k[7] << 24);
60 case 7:
61 b = b + ((__u32)k[6] << 16);
62 case 6:
63 b = b + ((__u32)k[5] << 8);
64 case 5:
65 b = b + k[4];
66 case 4:
67 a = a + ((__u32)k[3] << 24);
68 case 3:
69 a = a + ((__u32)k[2] << 16);
70 case 2:
71 a = a + ((__u32)k[1] << 8);
72 case 1:
73 a = a + k[0];
74 /* case 0: nothing left to add */
75 }
76 mix(a, b, c);
77
78 return c;
79}
80
81/*
82 * linux dcache hash
83 */
84unsigned ceph_str_hash_linux(const char *str, unsigned length)
85{
Sage Weil50b885b2009-12-01 14:12:07 -080086 unsigned long hash = 0;
Sage Weil1654dd02009-11-06 21:55:25 -080087 unsigned char c;
88
Sage Weil50b885b2009-12-01 14:12:07 -080089 while (length--) {
Sage Weil1654dd02009-11-06 21:55:25 -080090 c = *str++;
91 hash = (hash + (c << 4) + (c >> 4)) * 11;
92 }
Sage Weil50b885b2009-12-01 14:12:07 -080093 return hash;
Sage Weil1654dd02009-11-06 21:55:25 -080094}
95
96
97unsigned ceph_str_hash(int type, const char *s, unsigned len)
98{
99 switch (type) {
100 case CEPH_STR_HASH_LINUX:
101 return ceph_str_hash_linux(s, len);
102 case CEPH_STR_HASH_RJENKINS:
103 return ceph_str_hash_rjenkins(s, len);
104 default:
105 return -1;
106 }
107}
Sage Weil6c0f3af2010-11-16 11:14:34 -0800108EXPORT_SYMBOL(ceph_str_hash);
Sage Weil1654dd02009-11-06 21:55:25 -0800109
Sage Weil50b885b2009-12-01 14:12:07 -0800110const char *ceph_str_hash_name(int type)
Sage Weil1654dd02009-11-06 21:55:25 -0800111{
112 switch (type) {
113 case CEPH_STR_HASH_LINUX:
114 return "linux";
115 case CEPH_STR_HASH_RJENKINS:
116 return "rjenkins";
117 default:
118 return "unknown";
119 }
120}
Sage Weil6c0f3af2010-11-16 11:14:34 -0800121EXPORT_SYMBOL(ceph_str_hash_name);