1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
|
/* jhash.h: Jenkins hash support.
*
* Copyright (C) 1996 Bob Jenkins (bob_jenkins@burtleburtle.net)
*
* http://burtleburtle.net/bob/hash/
*
* These are the credits from Bob's sources:
*
* lookup2.c, by Bob Jenkins, December 1996, Public Domain.
* hash(), hash2(), hash3, and mix() are externally useful functions.
* Routines to test the hash are included if SELF_TEST is defined.
* You can use this free for any purpose. It has no warranty.
*
* Copyright (C) 2003 David S. Miller (davem@redhat.com)
*
* I've modified Bob's hash to be useful in the Linux kernel, and
* any bugs present are surely my fault. -DaveM
*/
#include "zebra.h"
#include "jhash.h"
/* The golden ration: an arbitrary value */
#define JHASH_GOLDEN_RATIO 0x9e3779b9
/* NOTE: Arguments are modified. */
#define __jhash_mix(a, b, c) \
{ \
a -= b; \
a -= c; \
a ^= (c >> 13); \
b -= c; \
b -= a; \
b ^= (a << 8); \
c -= a; \
c -= b; \
c ^= (b >> 13); \
a -= b; \
a -= c; \
a ^= (c >> 12); \
b -= c; \
b -= a; \
b ^= (a << 16); \
c -= a; \
c -= b; \
c ^= (b >> 5); \
a -= b; \
a -= c; \
a ^= (c >> 3); \
b -= c; \
b -= a; \
b ^= (a << 10); \
c -= a; \
c -= b; \
c ^= (b >> 15); \
}
/* The most generic version, hashes an arbitrary sequence
* of bytes. No alignment or length assumptions are made about
* the input key.
*/
uint32_t jhash(const void *key, uint32_t length, uint32_t initval)
{
uint32_t a, b, c, len;
const uint8_t *k = key;
len = length;
a = b = JHASH_GOLDEN_RATIO;
c = initval;
while (len >= 12) {
a += (k[0] + ((uint32_t)k[1] << 8) + ((uint32_t)k[2] << 16)
+ ((uint32_t)k[3] << 24));
b += (k[4] + ((uint32_t)k[5] << 8) + ((uint32_t)k[6] << 16)
+ ((uint32_t)k[7] << 24));
c += (k[8] + ((uint32_t)k[9] << 8) + ((uint32_t)k[10] << 16)
+ ((uint32_t)k[11] << 24));
__jhash_mix(a, b, c);
k += 12;
len -= 12;
}
c += length;
switch (len) {
case 11:
c += ((uint32_t)k[10] << 24);
/* fallthru */
case 10:
c += ((uint32_t)k[9] << 16);
/* fallthru */
case 9:
c += ((uint32_t)k[8] << 8);
/* fallthru */
case 8:
b += ((uint32_t)k[7] << 24);
/* fallthru */
case 7:
b += ((uint32_t)k[6] << 16);
/* fallthru */
case 6:
b += ((uint32_t)k[5] << 8);
/* fallthru */
case 5:
b += k[4];
/* fallthru */
case 4:
a += ((uint32_t)k[3] << 24);
/* fallthru */
case 3:
a += ((uint32_t)k[2] << 16);
/* fallthru */
case 2:
a += ((uint32_t)k[1] << 8);
/* fallthru */
case 1:
a += k[0];
}
__jhash_mix(a, b, c);
return c;
}
/* A special optimized version that handles 1 or more of uint32_ts.
* The length parameter here is the number of uint32_ts in the key.
*/
uint32_t jhash2(const uint32_t *k, uint32_t length, uint32_t initval)
{
uint32_t a, b, c, len;
a = b = JHASH_GOLDEN_RATIO;
c = initval;
len = length;
while (len >= 3) {
a += k[0];
b += k[1];
c += k[2];
__jhash_mix(a, b, c);
k += 3;
len -= 3;
}
c += length * 4;
switch (len) {
case 2:
b += k[1];
/* fallthru */
case 1:
a += k[0];
}
__jhash_mix(a, b, c);
return c;
}
/* A special ultra-optimized versions that knows they are hashing exactly
* 3, 2 or 1 word(s).
*
* NOTE: In partilar the "c += length; __jhash_mix(a,b,c);" normally
* done at the end is not done here.
*/
uint32_t jhash_3words(uint32_t a, uint32_t b, uint32_t c, uint32_t initval)
{
a += JHASH_GOLDEN_RATIO;
b += JHASH_GOLDEN_RATIO;
c += initval;
__jhash_mix(a, b, c);
return c;
}
uint32_t jhash_2words(uint32_t a, uint32_t b, uint32_t initval)
{
return jhash_3words(a, b, 0, initval);
}
uint32_t jhash_1word(uint32_t a, uint32_t initval)
{
return jhash_3words(a, 0, 0, initval);
}
|
