1 |
|
|
/* $OpenBSD: hash_func.c,v 1.1 2008/06/21 15:39:15 joris Exp $ */ |
2 |
|
|
|
3 |
|
|
/*- |
4 |
|
|
* Copyright (c) 1990, 1993 |
5 |
|
|
* The Regents of the University of California. All rights reserved. |
6 |
|
|
* |
7 |
|
|
* This code is derived from software contributed to Berkeley by |
8 |
|
|
* Margo Seltzer. |
9 |
|
|
* |
10 |
|
|
* Redistribution and use in source and binary forms, with or without |
11 |
|
|
* modification, are permitted provided that the following conditions |
12 |
|
|
* are met: |
13 |
|
|
* 1. Redistributions of source code must retain the above copyright |
14 |
|
|
* notice, this list of conditions and the following disclaimer. |
15 |
|
|
* 2. Redistributions in binary form must reproduce the above copyright |
16 |
|
|
* notice, this list of conditions and the following disclaimer in the |
17 |
|
|
* documentation and/or other materials provided with the distribution. |
18 |
|
|
* 3. Neither the name of the University nor the names of its contributors |
19 |
|
|
* may be used to endorse or promote products derived from this software |
20 |
|
|
* without specific prior written permission. |
21 |
|
|
* |
22 |
|
|
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND |
23 |
|
|
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
24 |
|
|
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
25 |
|
|
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE |
26 |
|
|
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL |
27 |
|
|
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS |
28 |
|
|
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) |
29 |
|
|
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT |
30 |
|
|
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY |
31 |
|
|
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
32 |
|
|
* SUCH DAMAGE. |
33 |
|
|
*/ |
34 |
|
|
|
35 |
|
|
#include <sys/types.h> |
36 |
|
|
#include <sys/queue.h> |
37 |
|
|
|
38 |
|
|
#include "hash.h" |
39 |
|
|
|
40 |
|
|
/* Chris Torek's hash function. */ |
41 |
|
|
u_int32_t |
42 |
|
|
hash4(const char *key, size_t len) |
43 |
|
|
{ |
44 |
|
|
u_int32_t h, loop; |
45 |
|
|
const char *k; |
46 |
|
|
|
47 |
|
|
#define HASH4 h = (h << 5) + h + *k++; |
48 |
|
|
|
49 |
|
|
h = 0; |
50 |
|
|
k = key; |
51 |
|
|
if (len > 0) { |
52 |
|
|
loop = (len + 8 - 1) >> 3; |
53 |
|
|
|
54 |
|
|
switch (len & (8 - 1)) { |
55 |
|
|
case 0: |
56 |
|
|
do { /* All fall throughs */ |
57 |
|
|
HASH4; |
58 |
|
|
case 7: |
59 |
|
|
HASH4; |
60 |
|
|
case 6: |
61 |
|
|
HASH4; |
62 |
|
|
case 5: |
63 |
|
|
HASH4; |
64 |
|
|
case 4: |
65 |
|
|
HASH4; |
66 |
|
|
case 3: |
67 |
|
|
HASH4; |
68 |
|
|
case 2: |
69 |
|
|
HASH4; |
70 |
|
|
case 1: |
71 |
|
|
HASH4; |
72 |
|
|
} while (--loop); |
73 |
|
|
} |
74 |
|
|
|
75 |
|
|
} |
76 |
|
|
return (h); |
77 |
|
|
} |