1 /* Copyright (c) 2010, Paul Hsieh
2 * All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions are met:
6 *
7 * * Redistributions of source code must retain the above copyright notice, this
8 * list of conditions and the following disclaimer.
9 * * Redistributions in binary form must reproduce the above copyright notice,
10 * this list of conditions and the following disclaimer in the documentation
11 * and/or other materials provided with the distribution.
12 * * Neither my name, Paul Hsieh, nor the names of any other contributors to the
13 * code use may not be used to endorse or promote products derived from this
14 * software without specific prior written permission.
15 *
16 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
17 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
20 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
21 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
22 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
23 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
24 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
25 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
26 * POSSIBILITY OF SUCH DAMAGE.
27 */
28
29 #include <stddef.h>
30 #include <stdint.h>
31
32 #undef get16bits
33 #if (defined(__GNUC__) && defined(__i386__)) || defined(__WATCOMC__) \
34 || defined(_MSC_VER) || defined (__BORLANDC__) || defined (__TURBOC__)
35 #define get16bits(d) (*((const uint16_t *) (d)))
36 #endif
37
38 #if !defined (get16bits)
39 #define get16bits(d) ((((uint32_t)(((const uint8_t *)(d))[1])) << 8)\
40 +(uint32_t)(((const uint8_t *)(d))[0]) )
41 #endif
42
SuperFastHash(const char * data,int len,uint32_t hash)43 uint32_t SuperFastHash (const char * data, int len, uint32_t hash) {
44 uint32_t tmp;
45 int rem;
46
47 if (len <= 0 || data == NULL) return 0;
48
49 rem = len & 3;
50 len >>= 2;
51
52 /* Main loop */
53 for (;len > 0; len--) {
54 hash += get16bits (data);
55 tmp = (get16bits (data+2) << 11) ^ hash;
56 hash = (hash << 16) ^ tmp;
57 data += 2*sizeof (uint16_t);
58 hash += hash >> 11;
59 }
60
61 /* Handle end cases */
62 switch (rem) {
63 case 3: hash += get16bits (data);
64 hash ^= hash << 16;
65 hash ^= ((signed char)data[sizeof (uint16_t)]) << 18;
66 hash += hash >> 11;
67 break;
68 case 2: hash += get16bits (data);
69 hash ^= hash << 11;
70 hash += hash >> 17;
71 break;
72 case 1: hash += (signed char)*data;
73 hash ^= hash << 10;
74 hash += hash >> 1;
75 }
76
77 /* Force "avalanching" of final 127 bits */
78 hash ^= hash << 3;
79 hash += hash >> 5;
80 hash ^= hash << 4;
81 hash += hash >> 17;
82 hash ^= hash << 25;
83 hash += hash >> 6;
84
85 return hash;
86 }
87