projects / thirdparty / glibc.git / blame
| Commit | Line | Data |
|---|---|---|
| 118bad87 | 1 | /* Compute hash value for given string according to ELF standard. |
| 85f72e9c | 2 | Copyright (C) 1995, 1996, 1997, 1998 Free Software Foundation, Inc. |
| 1fb05e3d UD |
3 | This file is part of the GNU C Library. |
| 4 | ||
| 5 | The GNU C Library is free software; you can redistribute it and/or | |
| 41bdb6e2 AJ |
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. | |
| 1fb05e3d UD |
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 | |
| 41bdb6e2 | 13 | Lesser General Public License for more details. |
| 1fb05e3d | 14 | |
| 41bdb6e2 AJ |
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. */ | |
| 1fb05e3d UD |
19 | |
| 20 | #ifndef _DL_HASH_H | |
| 21 | #define _DL_HASH_H 1 | |
| 22 | ||
| 23 | ||
| 24 | /* This is the hashing function specified by the ELF ABI. In the | |
| 85f72e9c | 25 | first five operations no overflow is possible so we optimized it a |
| 1fb05e3d | 26 | bit. */ |
| 85f72e9c UD |
27 | static inline unsigned int |
| 28 | _dl_elf_hash (const unsigned char *name) | |
| 1fb05e3d UD |
29 | { |
| 30 | unsigned long int hash = 0; | |
| 31 | if (*name != '\0') | |
| 32 | { | |
| 85f72e9c | 33 | hash = *name++; |
| 1fb05e3d UD |
34 | if (*name != '\0') |
| 35 | { | |
| 36 | hash = (hash << 4) + *name++; | |
| 37 | if (*name != '\0') | |
| 38 | { | |
| 39 | hash = (hash << 4) + *name++; | |
| 40 | if (*name != '\0') | |
| 41 | { | |
| 42 | hash = (hash << 4) + *name++; | |
| 43 | if (*name != '\0') | |
| 44 | { | |
| 45 | hash = (hash << 4) + *name++; | |
| 46 | while (*name != '\0') | |
| 47 | { | |
| 48 | unsigned long int hi; | |
| 49 | hash = (hash << 4) + *name++; | |
| 50 | hi = hash & 0xf0000000; | |
| 85f72e9c UD |
51 | |
| 52 | /* The algorithm specified in the ELF ABI is as | |
| 53 | follows: | |
| 54 | ||
| 55 | if (hi != 0) | |
| 56 | hash ^= hi >> 24; | |
| 57 | ||
| 58 | hash &= ~hi; | |
| 59 | ||
| 60 | But the following is equivalent and a lot | |
| 61 | faster, especially on modern processors. */ | |
| 62 | ||
| 63 | hash ^= hi; | |
| 64 | hash ^= hi >> 24; | |
| 1fb05e3d UD |
65 | } |
| 66 | } | |
| 67 | } | |
| 68 | } | |
| 69 | } | |
| 70 | } | |
| 71 | return hash; | |
| 72 | } | |
| 73 | ||
| 74 | #endif /* dl-hash.h */ |