1
2#include <linux/ceph/types.h>
3#include <linux/module.h>
4
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 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) {            /* 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 int ceph_str_hash_linux(const char *str, unsigned int length)
85{
86	unsigned long hash = 0;
87	unsigned char c;
88
89	while (length--) {
90		c = *str++;
91		hash = (hash + (c << 4) + (c >> 4)) * 11;
92	}
93	return hash;
94}
95
96
97unsigned int ceph_str_hash(int type, const char *s, unsigned int 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}
108EXPORT_SYMBOL(ceph_str_hash);
109
110const char *ceph_str_hash_name(int type)
111{
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}
121EXPORT_SYMBOL(ceph_str_hash_name);
122