1 | /* Copyright (c) 1997-2022 Free Software Foundation, Inc. |
2 | This file is part of the GNU C Library. |
3 | |
4 | The GNU C Library is free software; you can redistribute it and/or |
5 | modify it under the terms of the GNU Lesser General Public |
6 | License as published by the Free Software Foundation; either |
7 | version 2.1 of the License, or (at your option) any later version. |
8 | |
9 | The GNU C Library is distributed in the hope that it will be useful, |
10 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
11 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
12 | Lesser General Public License for more details. |
13 | |
14 | You should have received a copy of the GNU Lesser General Public |
15 | License along with the GNU C Library; if not, see |
16 | <https://www.gnu.org/licenses/>. */ |
17 | |
18 | #include <nss.h> |
19 | |
20 | /* This is from libc/db/hash/hash_func.c, hash3 is static there */ |
21 | /* |
22 | * This is INCREDIBLY ugly, but fast. We break the string up into 8 byte |
23 | * units. On the first time through the loop we get the "leftover bytes" |
24 | * (strlen % 8). On every other iteration, we perform 8 HASHC's so we handle |
25 | * all 8 bytes. Essentially, this saves us 7 cmp & branch instructions. If |
26 | * this routine is heavily used enough, it's worth the ugly coding. |
27 | * |
28 | * OZ's original sdbm hash |
29 | */ |
30 | uint32_t |
31 | __nss_hash (const void *keyarg, size_t len) |
32 | { |
33 | const unsigned char *key; |
34 | size_t loop; |
35 | uint32_t h; |
36 | |
37 | #define HASHC h = *key++ + 65599 * h |
38 | |
39 | h = 0; |
40 | key = keyarg; |
41 | if (len > 0) |
42 | { |
43 | loop = (len + 8 - 1) >> 3; |
44 | switch (len & (8 - 1)) |
45 | { |
46 | case 0: |
47 | do |
48 | { |
49 | HASHC; |
50 | /* FALLTHROUGH */ |
51 | case 7: |
52 | HASHC; |
53 | /* FALLTHROUGH */ |
54 | case 6: |
55 | HASHC; |
56 | /* FALLTHROUGH */ |
57 | case 5: |
58 | HASHC; |
59 | /* FALLTHROUGH */ |
60 | case 4: |
61 | HASHC; |
62 | /* FALLTHROUGH */ |
63 | case 3: |
64 | HASHC; |
65 | /* FALLTHROUGH */ |
66 | case 2: |
67 | HASHC; |
68 | /* FALLTHROUGH */ |
69 | case 1: |
70 | HASHC; |
71 | } |
72 | while (--loop); |
73 | } |
74 | } |
75 | return h; |
76 | } |
77 | |
78 | libc_hidden_def (__nss_hash) |
79 | |