4 #if defined(__FreeBSD__)
5 #include <sys/endian.h>
11 * Example hash function.
13 * Copyright 2009-2012 - Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
15 * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
16 * OR IMPLIED. ANY USE IS AT YOUR OWN RISK.
18 * Permission is hereby granted to use or copy this program for any
19 * purpose, provided the above notices are retained on all copies.
20 * Permission to modify the code and to distribute modified code is
21 * granted, provided the above notices are retained, and a notice that
22 * the code was modified is included with the above copyright notice.
27 * Source: http://burtleburtle.net/bob/c/lookup3.c
28 * Originally Public Domain
31 #define rot(x, k) (((x) << (k)) | ((x) >> (32 - (k))))
33 #define mix(a, b, c) \
35 a -= c; a ^= rot(c, 4); c += b; \
36 b -= a; b ^= rot(a, 6); a += c; \
37 c -= b; c ^= rot(b, 8); b += a; \
38 a -= c; a ^= rot(c, 16); c += b; \
39 b -= a; b ^= rot(a, 19); a += c; \
40 c -= b; c ^= rot(b, 4); b += a; \
43 #define final(a, b, c) \
45 c ^= b; c -= rot(b, 14); \
46 a ^= c; a -= rot(c, 11); \
47 b ^= a; b -= rot(a, 25); \
48 c ^= b; c -= rot(b, 16); \
49 a ^= c; a -= rot(c, 4); \
50 b ^= a; b -= rot(a, 14); \
51 c ^= b; c -= rot(b, 24); \
54 #if (BYTE_ORDER == LITTLE_ENDIAN)
55 #define HASH_LITTLE_ENDIAN 1
57 #define HASH_LITTLE_ENDIAN 0
62 * hashlittle() -- hash a variable-length key into a 32-bit value
63 * k : the key (the unaligned variable-length array of bytes)
64 * length : the length of the key, counting by bytes
65 * initval : can be any 4-byte value
66 * Returns a 32-bit value. Every bit of the key affects every bit of
67 * the return value. Two keys differing by one or two bits will have
68 * totally different hash values.
70 * The best hash table sizes are powers of 2. There is no need to do
71 * mod a prime (mod is sooo slow!). If you need less than 32 bits,
72 * use a bitmask. For example, if you need only 10 bits, do
73 * h = (h & hashmask(10));
74 * In which case, the hash table should have hashsize(10) elements.
76 * If you are hashing n strings (uint8_t **)k, do it like this:
77 * for (i = 0, h = 0; i < n; ++i) h = hashlittle(k[i], len[i], h);
79 * By Bob Jenkins, 2006. bob_jenkins@burtleburtle.net. You may use this
80 * code any way you wish, private, educational, or commercial. It's free.
82 * Use for hash table lookup, or anything where one collision in 2^^32 is
83 * acceptable. Do NOT use for cryptographic purposes.
86 uint32_t hashlittle(const void *key
, size_t length
, uint32_t initval
)
88 uint32_t a
, b
, c
; /* internal state */
94 /* Set up the internal state */
95 a
= b
= c
= 0xdeadbeef + ((uint32_t)length
) + initval
;
98 if (HASH_LITTLE_ENDIAN
&& ((u
.i
& 0x3) == 0)) {
99 const uint32_t *k
= (const uint32_t *) key
; /* read 32-bit chunks */
101 /*------ all but last block: aligned reads and affect 32 bits of (a,b,c) */
102 while (length
> 12) {
111 /*----------------------------- handle the last (probably partial) block */
113 * "k[2]&0xffffff" actually reads beyond the end of the string, but
114 * then masks off the part it's not allowed to read. Because the
115 * string is aligned, the masked-off tail is in the same word as the
116 * rest of the string. Every machine with memory protection I've seen
117 * does it on word boundaries, so is OK with this. But VALGRIND will
118 * still catch it and complain. The masking trick does make the hash
119 * noticeably faster for short strings (like English words).
124 case 12: c
+=k
[2]; b
+=k
[1]; a
+=k
[0]; break;
125 case 11: c
+=k
[2]&0xffffff; b
+=k
[1]; a
+=k
[0]; break;
126 case 10: c
+=k
[2]&0xffff; b
+=k
[1]; a
+=k
[0]; break;
127 case 9 : c
+=k
[2]&0xff; b
+=k
[1]; a
+=k
[0]; break;
128 case 8 : b
+=k
[1]; a
+=k
[0]; break;
129 case 7 : b
+=k
[1]&0xffffff; a
+=k
[0]; break;
130 case 6 : b
+=k
[1]&0xffff; a
+=k
[0]; break;
131 case 5 : b
+=k
[1]&0xff; a
+=k
[0]; break;
132 case 4 : a
+=k
[0]; break;
133 case 3 : a
+=k
[0]&0xffffff; break;
134 case 2 : a
+=k
[0]&0xffff; break;
135 case 1 : a
+=k
[0]&0xff; break;
136 case 0 : return c
; /* zero length strings require no mixing */
139 #else /* make valgrind happy */
143 k8
= (const uint8_t *) k
;
145 case 12: c
+=k
[2]; b
+=k
[1]; a
+=k
[0]; break;
146 case 11: c
+=((uint32_t) k8
[10])<<16; /* fall through */
147 case 10: c
+=((uint32_t) k8
[9])<<8; /* fall through */
148 case 9 : c
+=k8
[8]; /* fall through */
149 case 8 : b
+=k
[1]; a
+=k
[0]; break;
150 case 7 : b
+=((uint32_t) k8
[6])<<16; /* fall through */
151 case 6 : b
+=((uint32_t) k8
[5])<<8; /* fall through */
152 case 5 : b
+=k8
[4]; /* fall through */
153 case 4 : a
+=k
[0]; break;
154 case 3 : a
+=((uint32_t) k8
[2])<<16; /* fall through */
155 case 2 : a
+=((uint32_t) k8
[1])<<8; /* fall through */
156 case 1 : a
+=k8
[0]; break;
160 #endif /* !valgrind */
162 } else if (HASH_LITTLE_ENDIAN
&& ((u
.i
& 0x1) == 0)) {
163 const uint16_t *k
= (const uint16_t *) key
; /* read 16-bit chunks */
166 /*--------------- all but last block: aligned reads and different mixing */
169 a
+= k
[0] + (((uint32_t) k
[1])<<16);
170 b
+= k
[2] + (((uint32_t) k
[3])<<16);
171 c
+= k
[4] + (((uint32_t) k
[5])<<16);
177 /*----------------------------- handle the last (probably partial) block */
178 k8
= (const uint8_t *) k
;
181 case 12: c
+=k
[4]+(((uint32_t) k
[5])<<16);
182 b
+=k
[2]+(((uint32_t) k
[3])<<16);
183 a
+=k
[0]+(((uint32_t) k
[1])<<16);
185 case 11: c
+=((uint32_t) k8
[10])<<16; /* fall through */
187 b
+=k
[2]+(((uint32_t) k
[3])<<16);
188 a
+=k
[0]+(((uint32_t) k
[1])<<16);
190 case 9 : c
+=k8
[8]; /* fall through */
191 case 8 : b
+=k
[2]+(((uint32_t) k
[3])<<16);
192 a
+=k
[0]+(((uint32_t) k
[1])<<16);
194 case 7 : b
+=((uint32_t) k8
[6])<<16; /* fall through */
196 a
+=k
[0]+(((uint32_t) k
[1])<<16);
198 case 5 : b
+=k8
[4]; /* fall through */
199 case 4 : a
+=k
[0]+(((uint32_t) k
[1])<<16);
201 case 3 : a
+=((uint32_t) k8
[2])<<16; /* fall through */
206 case 0 : return c
; /* zero length requires no mixing */
209 } else { /* need to read the key one byte at a time */
210 const uint8_t *k
= (const uint8_t *)key
;
212 /*--------------- all but the last block: affect some 32 bits of (a, b, c) */
213 while (length
> 12) {
215 a
+= ((uint32_t) k
[1])<<8;
216 a
+= ((uint32_t) k
[2])<<16;
217 a
+= ((uint32_t) k
[3])<<24;
219 b
+= ((uint32_t) k
[5])<<8;
220 b
+= ((uint32_t) k
[6])<<16;
221 b
+= ((uint32_t) k
[7])<<24;
223 c
+= ((uint32_t) k
[9])<<8;
224 c
+= ((uint32_t) k
[10])<<16;
225 c
+= ((uint32_t) k
[11])<<24;
231 /*-------------------------------- last block: affect all 32 bits of (c) */
232 switch (length
) { /* all the case statements fall through */
233 case 12: c
+=((uint32_t) k
[11])<<24; /* fall through */
234 case 11: c
+=((uint32_t) k
[10])<<16; /* fall through */
235 case 10: c
+=((uint32_t) k
[9])<<8; /* fall through */
236 case 9 : c
+=k
[8]; /* fall through */
237 case 8 : b
+=((uint32_t) k
[7])<<24; /* fall through */
238 case 7 : b
+=((uint32_t) k
[6])<<16; /* fall through */
239 case 6 : b
+=((uint32_t) k
[5])<<8; /* fall through */
240 case 5 : b
+=k
[4]; /* fall through */
241 case 4 : a
+=((uint32_t) k
[3])<<24; /* fall through */
242 case 3 : a
+=((uint32_t) k
[2])<<16; /* fall through */
243 case 2 : a
+=((uint32_t) k
[1])<<8; /* fall through */
255 uint32_t jhash(const void *key
, size_t length
, uint32_t seed
)
257 return hashlittle(key
, length
, seed
);
260 #endif /* _JHASH_H */
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