urcu-ht: add correct hash, implement delete_all
[urcu.git] / urcu / jhash.h
1 #ifndef _KCOMPAT_JHASH_H
2 #define _KCOMPAT_JHASH_H
3
4 /* jhash.h: Jenkins hash support.
5 *
6 * Copyright (C) 1996 Bob Jenkins (bob_jenkins@burtleburtle.net)
7 *
8 * http://burtleburtle.net/bob/hash/
9 *
10 * These are the credits from Bob's sources:
11 *
12 * lookup2.c, by Bob Jenkins, December 1996, Public Domain.
13 * hash(), hash2(), hash3, and mix() are externally useful functions.
14 * Routines to test the hash are included if SELF_TEST is defined.
15 * You can use this free for any purpose. It has no warranty.
16 *
17 * Copyright (C) 2003 David S. Miller (davem@redhat.com)
18 *
19 * I've modified Bob's hash to be useful in the Linux kernel, and
20 * any bugs present are surely my fault. -DaveM
21 */
22
23 #include <stdint.h>
24
25 typedef uint32_t u32;
26
27 /* NOTE: Arguments are modified. */
28 #define __jhash_mix(a, b, c) \
29 { \
30 a -= b; a -= c; a ^= (c>>13); \
31 b -= c; b -= a; b ^= (a<<8); \
32 c -= a; c -= b; c ^= (b>>13); \
33 a -= b; a -= c; a ^= (c>>12); \
34 b -= c; b -= a; b ^= (a<<16); \
35 c -= a; c -= b; c ^= (b>>5); \
36 a -= b; a -= c; a ^= (c>>3); \
37 b -= c; b -= a; b ^= (a<<10); \
38 c -= a; c -= b; c ^= (b>>15); \
39 }
40
41 /* The golden ration: an arbitrary value */
42 #define JHASH_GOLDEN_RATIO 0x9e3779b9
43
44 /* The most generic version, hashes an arbitrary sequence
45 * of bytes. No alignment or length assumptions are made about
46 * the input key.
47 */
48 static inline u32 jhash(const void *key, u32 length, u32 initval)
49 {
50 u32 a, b, c, len;
51 const u8 *k = key;
52
53 len = length;
54 a = b = JHASH_GOLDEN_RATIO;
55 c = initval;
56
57 while (len >= 12) {
58 a += (k[0] +((u32)k[1]<<8) +((u32)k[2]<<16) +((u32)k[3]<<24));
59 b += (k[4] +((u32)k[5]<<8) +((u32)k[6]<<16) +((u32)k[7]<<24));
60 c += (k[8] +((u32)k[9]<<8) +((u32)k[10]<<16)+((u32)k[11]<<24));
61
62 __jhash_mix(a,b,c);
63
64 k += 12;
65 len -= 12;
66 }
67
68 c += length;
69 switch (len) {
70 case 11: c += ((u32)k[10]<<24);
71 case 10: c += ((u32)k[9]<<16);
72 case 9 : c += ((u32)k[8]<<8);
73 case 8 : b += ((u32)k[7]<<24);
74 case 7 : b += ((u32)k[6]<<16);
75 case 6 : b += ((u32)k[5]<<8);
76 case 5 : b += k[4];
77 case 4 : a += ((u32)k[3]<<24);
78 case 3 : a += ((u32)k[2]<<16);
79 case 2 : a += ((u32)k[1]<<8);
80 case 1 : a += k[0];
81 };
82
83 __jhash_mix(a,b,c);
84
85 return c;
86 }
87
88 #endif /* _KCOMPAT_JHASH_H */
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