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git.proxmox.com Git - mirror_ubuntu-eoan-kernel.git/blob - include/linux/jhash.h
4 /* jhash.h: Jenkins hash support.
6 * Copyright (C) 2006. Bob Jenkins (bob_jenkins@burtleburtle.net)
8 * http://burtleburtle.net/bob/hash/
10 * These are the credits from Bob's sources:
12 * lookup3.c, by Bob Jenkins, May 2006, Public Domain.
14 * These are functions for producing 32-bit hashes for hash table lookup.
15 * hashword(), hashlittle(), hashlittle2(), hashbig(), mix(), and final()
16 * are externally useful functions. Routines to test the hash are included
17 * if SELF_TEST is defined. You can use this free for any purpose. It's in
18 * the public domain. It has no warranty.
20 * Copyright (C) 2009-2010 Jozsef Kadlecsik (kadlec@blackhole.kfki.hu)
22 * I've modified Bob's hash to be useful in the Linux kernel, and
23 * any bugs present are my fault.
26 #include <linux/bitops.h>
27 #include <linux/unaligned/packed_struct.h>
29 /* Best hash sizes are of power of two */
30 #define jhash_size(n) ((u32)1<<(n))
31 /* Mask the hash value, i.e (value & jhash_mask(n)) instead of (value % n) */
32 #define jhash_mask(n) (jhash_size(n)-1)
34 /* __jhash_mix -- mix 3 32-bit values reversibly. */
35 #define __jhash_mix(a, b, c) \
37 a -= c; a ^= rol32(c, 4); c += b; \
38 b -= a; b ^= rol32(a, 6); a += c; \
39 c -= b; c ^= rol32(b, 8); b += a; \
40 a -= c; a ^= rol32(c, 16); c += b; \
41 b -= a; b ^= rol32(a, 19); a += c; \
42 c -= b; c ^= rol32(b, 4); b += a; \
45 /* __jhash_final - final mixing of 3 32-bit values (a,b,c) into c */
46 #define __jhash_final(a, b, c) \
48 c ^= b; c -= rol32(b, 14); \
49 a ^= c; a -= rol32(c, 11); \
50 b ^= a; b -= rol32(a, 25); \
51 c ^= b; c -= rol32(b, 16); \
52 a ^= c; a -= rol32(c, 4); \
53 b ^= a; b -= rol32(a, 14); \
54 c ^= b; c -= rol32(b, 24); \
57 /* An arbitrary initial parameter */
58 #define JHASH_INITVAL 0xdeadbeef
60 /* jhash - hash an arbitrary key
61 * @k: sequence of bytes as key
62 * @length: the length of the key
63 * @initval: the previous hash, or an arbitray value
65 * The generic version, hashes an arbitrary sequence of bytes.
66 * No alignment or length assumptions are made about the input key.
68 * Returns the hash value of the key. The result depends on endianness.
70 static inline u32
jhash(const void *key
, u32 length
, u32 initval
)
75 /* Set up the internal state */
76 a
= b
= c
= JHASH_INITVAL
+ length
+ initval
;
78 /* All but the last block: affect some 32 bits of (a,b,c) */
80 a
+= __get_unaligned_cpu32(k
);
81 b
+= __get_unaligned_cpu32(k
+ 4);
82 c
+= __get_unaligned_cpu32(k
+ 8);
87 /* Last block: affect all 32 bits of (c) */
89 case 12: c
+= (u32
)k
[11]<<24; /* fall through */
90 case 11: c
+= (u32
)k
[10]<<16; /* fall through */
91 case 10: c
+= (u32
)k
[9]<<8; /* fall through */
92 case 9: c
+= k
[8]; /* fall through */
93 case 8: b
+= (u32
)k
[7]<<24; /* fall through */
94 case 7: b
+= (u32
)k
[6]<<16; /* fall through */
95 case 6: b
+= (u32
)k
[5]<<8; /* fall through */
96 case 5: b
+= k
[4]; /* fall through */
97 case 4: a
+= (u32
)k
[3]<<24; /* fall through */
98 case 3: a
+= (u32
)k
[2]<<16; /* fall through */
99 case 2: a
+= (u32
)k
[1]<<8; /* fall through */
101 __jhash_final(a
, b
, c
);
102 case 0: /* Nothing left to add */
109 /* jhash2 - hash an array of u32's
110 * @k: the key which must be an array of u32's
111 * @length: the number of u32's in the key
112 * @initval: the previous hash, or an arbitray value
114 * Returns the hash value of the key.
116 static inline u32
jhash2(const u32
*k
, u32 length
, u32 initval
)
120 /* Set up the internal state */
121 a
= b
= c
= JHASH_INITVAL
+ (length
<<2) + initval
;
123 /* Handle most of the key */
128 __jhash_mix(a
, b
, c
);
133 /* Handle the last 3 u32's */
135 case 3: c
+= k
[2]; /* fall through */
136 case 2: b
+= k
[1]; /* fall through */
138 __jhash_final(a
, b
, c
);
139 case 0: /* Nothing left to add */
147 /* __jhash_nwords - hash exactly 3, 2 or 1 word(s) */
148 static inline u32
__jhash_nwords(u32 a
, u32 b
, u32 c
, u32 initval
)
154 __jhash_final(a
, b
, c
);
159 static inline u32
jhash_3words(u32 a
, u32 b
, u32 c
, u32 initval
)
161 return __jhash_nwords(a
, b
, c
, initval
+ JHASH_INITVAL
+ (3 << 2));
164 static inline u32
jhash_2words(u32 a
, u32 b
, u32 initval
)
166 return __jhash_nwords(a
, b
, 0, initval
+ JHASH_INITVAL
+ (2 << 2));
169 static inline u32
jhash_1word(u32 a
, u32 initval
)
171 return __jhash_nwords(a
, 0, 0, initval
+ JHASH_INITVAL
+ (1 << 2));
174 #endif /* _LINUX_JHASH_H */