1
2 #include <linux/ceph/types.h>
3 #include <linux/module.h>
4
5 /*
6 * Robert Jenkin's hash function.
7 * https://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
23 unsigned int ceph_str_hash_rjenkins(const char *str, unsigned int 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) {
51 case 11:
52 c = c + ((__u32)k[10] << 24);
53 fallthrough;
54 case 10:
55 c = c + ((__u32)k[9] << 16);
56 fallthrough;
57 case 9:
58 c = c + ((__u32)k[8] << 8);
59 /* the first byte of c is reserved for the length */
60 fallthrough;
61 case 8:
62 b = b + ((__u32)k[7] << 24);
63 fallthrough;
64 case 7:
65 b = b + ((__u32)k[6] << 16);
66 fallthrough;
67 case 6:
68 b = b + ((__u32)k[5] << 8);
69 fallthrough;
70 case 5:
71 b = b + k[4];
72 fallthrough;
73 case 4:
74 a = a + ((__u32)k[3] << 24);
75 fallthrough;
76 case 3:
77 a = a + ((__u32)k[2] << 16);
78 fallthrough;
79 case 2:
80 a = a + ((__u32)k[1] << 8);
81 fallthrough;
82 case 1:
83 a = a + k[0];
84 /* case 0: nothing left to add */
85 }
86 mix(a, b, c);
87
88 return c;
89 }
90
91 /*
92 * linux dcache hash
93 */
94 unsigned int ceph_str_hash_linux(const char *str, unsigned int length)
95 {
96 unsigned long hash = 0;
97 unsigned char c;
98
99 while (length--) {
100 c = *str++;
101 hash = (hash + (c << 4) + (c >> 4)) * 11;
102 }
103 return hash;
104 }
105
106
107 unsigned int ceph_str_hash(int type, const char *s, unsigned int len)
108 {
109 switch (type) {
110 case CEPH_STR_HASH_LINUX:
111 return ceph_str_hash_linux(s, len);
112 case CEPH_STR_HASH_RJENKINS:
113 return ceph_str_hash_rjenkins(s, len);
114 default:
115 return -1;
116 }
117 }
118 EXPORT_SYMBOL(ceph_str_hash);
119
120 const char *ceph_str_hash_name(int type)
121 {
122 switch (type) {
123 case CEPH_STR_HASH_LINUX:
124 return "linux";
125 case CEPH_STR_HASH_RJENKINS:
126 return "rjenkins";
127 default:
128 return "unknown";
129 }
130 }
131 EXPORT_SYMBOL(ceph_str_hash_name);
132
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