[444] | 1 | /* Compute hash value for given string according to ELF standard. |
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| 2 | Copyright (C) 1995, 1996, 1997, 1998 Free Software Foundation, Inc. |
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| 3 | This file is part of the GNU C Library. |
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| 4 | |
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| 5 | The GNU C Library is free software; you can redistribute it and/or |
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| 6 | modify it under the terms of the GNU Lesser General Public |
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| 7 | License as published by the Free Software Foundation; either |
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| 8 | version 2.1 of the License, or (at your option) any later version. |
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| 9 | |
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| 10 | The GNU C Library is distributed in the hope that it will be useful, |
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| 11 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
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| 12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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| 13 | Lesser General Public License for more details. |
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| 14 | |
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| 15 | You should have received a copy of the GNU Lesser General Public |
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| 16 | License along with the GNU C Library; if not, write to the Free |
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| 17 | Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA |
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| 18 | 02111-1307 USA. */ |
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| 19 | |
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| 20 | #ifndef _DL_HASH_H |
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| 21 | #define _DL_HASH_H 1 |
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| 22 | |
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| 23 | |
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| 24 | /* This is the hashing function specified by the ELF ABI. In the |
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| 25 | first five operations no overflow is possible so we optimized it a |
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| 26 | bit. */ |
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| 27 | static inline unsigned int |
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| 28 | _dl_elf_hash (const unsigned char *name) |
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| 29 | { |
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| 30 | unsigned long int hash = 0; |
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| 31 | if (*name != '\0') |
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| 32 | { |
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| 33 | hash = *name++; |
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| 34 | if (*name != '\0') |
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| 35 | { |
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| 36 | hash = (hash << 4) + *name++; |
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| 37 | if (*name != '\0') |
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| 38 | { |
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| 39 | hash = (hash << 4) + *name++; |
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| 40 | if (*name != '\0') |
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| 41 | { |
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| 42 | hash = (hash << 4) + *name++; |
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| 43 | if (*name != '\0') |
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| 44 | { |
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| 45 | hash = (hash << 4) + *name++; |
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| 46 | while (*name != '\0') |
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| 47 | { |
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| 48 | unsigned long int hi; |
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| 49 | hash = (hash << 4) + *name++; |
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| 50 | hi = hash & 0xf0000000; |
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| 51 | |
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| 52 | /* The algorithm specified in the ELF ABI is as |
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| 53 | follows: |
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| 54 | |
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| 55 | if (hi != 0) |
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| 56 | hash ^= hi >> 24; |
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| 57 | |
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| 58 | hash &= ~hi; |
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| 59 | |
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| 60 | But the following is equivalent and a lot |
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| 61 | faster, especially on modern processors. */ |
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| 62 | |
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| 63 | hash ^= hi; |
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| 64 | hash ^= hi >> 24; |
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| 65 | } |
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| 66 | } |
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| 67 | } |
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| 68 | } |
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| 69 | } |
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| 70 | } |
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| 71 | return hash; |
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| 72 | } |
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| 73 | |
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| 74 | #endif /* dl-hash.h */ |
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