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#include <stdint.h>
29#include <stdlib.h>
30#undef get16bits
31#if (defined(__GNUC__) && defined(__i386__)) || defined(__WATCOMC__) \
32  || defined(_MSC_VER) || defined (__BORLANDC__) || defined (__TURBOC__)
33#define get16bits(d) (*((const uint16_t *) (d)))
34#endif
35
36#if !defined (get16bits)
37#define get16bits(d) ((((uint32_t)(((const uint8_t *)(d))[1])) << 8)\
38                       +(uint32_t)(((const uint8_t *)(d))[0]) )
39#endif
40
41uint32_t SuperFastHash (const char * data, int len) {
42uint32_t hash = len, tmp;
43int rem;
44
45    if (len <= 0 || data == NULL) return 0;
46
47    rem = len & 3;
48    len >>= 2;
49
50    /* Main loop */
51    for (;len > 0; len--) {
52        hash  += get16bits (data);
53        tmp    = (get16bits (data+2) << 11) ^ hash;
54        hash   = (hash << 16) ^ tmp;
55        data  += 2*sizeof (uint16_t);
56        hash  += hash >> 11;
57    }
58
59    /* Handle end cases */
60    switch (rem) {
61        case 3: hash += get16bits (data);
62                hash ^= hash << 16;
63                hash ^= ((signed char)data[sizeof (uint16_t)]) << 18;
64                hash += hash >> 11;
65                break;
66        case 2: hash += get16bits (data);
67                hash ^= hash << 11;
68                hash += hash >> 17;
69                break;
70        case 1: hash += (signed char)*data;
71                hash ^= hash << 10;
72                hash += hash >> 1;
73    }
74
75    /* Force "avalanching" of final 127 bits */
76    hash ^= hash << 3;
77    hash += hash >> 5;
78    hash ^= hash << 4;
79    hash += hash >> 17;
80    hash ^= hash << 25;
81    hash += hash >> 6;
82
83    return hash;
84}
85