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1 | /* Copyright (c) 1997, 1998, 1999, 2004 Free Software Foundation, Inc. |
2 | This file is part of the GNU C Library. | |
3 | Contributed by Thorsten Kukuk <kukuk@suse.de>, 1997. | |
4 | ||
5 | The GNU C Library is free software; you can redistribute it and/or | |
6 | modify it under the terms of the GNU Lesser General Public | |
7 | License as published by the Free Software Foundation; either | |
8 | version 2.1 of the License, or (at your option) any later version. | |
9 | ||
10 | The GNU C Library is distributed in the hope that it will be useful, | |
11 | but WITHOUT ANY WARRANTY; without even the implied warranty of | |
12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
13 | Lesser General Public License for more details. | |
14 | ||
15 | You should have received a copy of the GNU Lesser General Public | |
16 | License along with the GNU C Library; if not, write to the Free | |
17 | Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA | |
18 | 02111-1307 USA. */ | |
19 | ||
20 | #include <rpcsvc/nis.h> | |
21 | ||
22 | /* This is from libc/db/hash/hash_func.c, hash3 is static there */ | |
23 | /* | |
24 | * This is INCREDIBLY ugly, but fast. We break the string up into 8 byte | |
25 | * units. On the first time through the loop we get the "leftover bytes" | |
26 | * (strlen % 8). On every other iteration, we perform 8 HASHC's so we handle | |
27 | * all 8 bytes. Essentially, this saves us 7 cmp & branch instructions. If | |
28 | * this routine is heavily used enough, it's worth the ugly coding. | |
29 | * | |
30 | * OZ's original sdbm hash | |
31 | */ | |
32 | uint32_t | |
33 | __nis_hash (const void *keyarg, register size_t len) | |
34 | { | |
35 | register const u_char *key; | |
36 | register size_t loop; | |
37 | register uint32_t h; | |
38 | ||
39 | #define HASHC h = *key++ + 65599 * h | |
40 | ||
41 | h = 0; | |
42 | key = keyarg; | |
43 | if (len > 0) | |
44 | { | |
45 | loop = (len + 8 - 1) >> 3; | |
46 | switch (len & (8 - 1)) | |
47 | { | |
48 | case 0: | |
49 | do { | |
50 | HASHC; | |
51 | /* FALLTHROUGH */ | |
52 | case 7: | |
53 | HASHC; | |
54 | /* FALLTHROUGH */ | |
55 | case 6: | |
56 | HASHC; | |
57 | /* FALLTHROUGH */ | |
58 | case 5: | |
59 | HASHC; | |
60 | /* FALLTHROUGH */ | |
61 | case 4: | |
62 | HASHC; | |
63 | /* FALLTHROUGH */ | |
64 | case 3: | |
65 | HASHC; | |
66 | /* FALLTHROUGH */ | |
67 | case 2: | |
68 | HASHC; | |
69 | /* FALLTHROUGH */ | |
70 | case 1: | |
71 | HASHC; | |
72 | } while (--loop); | |
73 | } | |
74 | } | |
75 | return h; | |
76 | } |