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
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) {
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 */
94unsigned 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
107unsigned 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}
118EXPORT_SYMBOL(ceph_str_hash);
119
120const 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}
131EXPORT_SYMBOL(ceph_str_hash_name);
132