| /* Compute hash value for given string according to ELF standard. |
| Copyright (C) 2006 Red Hat, Inc. |
| This file is part of elfutils. |
| Written by Ulrich Drepper <drepper@redhat.com>, 1995. |
| |
| This file is free software; you can redistribute it and/or modify |
| it under the terms of either |
| |
| * the GNU Lesser General Public License as published by the Free |
| Software Foundation; either version 3 of the License, or (at |
| your option) any later version |
| |
| or |
| |
| * the GNU General Public License as published by the Free |
| Software Foundation; either version 2 of the License, or (at |
| your option) any later version |
| |
| or both in parallel, as here. |
| |
| elfutils is distributed in the hope that it will be useful, but |
| WITHOUT ANY WARRANTY; without even the implied warranty of |
| MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| General Public License for more details. |
| |
| You should have received copies of the GNU General Public License and |
| the GNU Lesser General Public License along with this program. If |
| not, see <http://www.gnu.org/licenses/>. */ |
| |
| #ifndef _DL_HASH_H |
| #define _DL_HASH_H 1 |
| |
| |
| /* This is the hashing function specified by the ELF ABI. In the |
| first five operations no overflow is possible so we optimized it a |
| bit. */ |
| static inline unsigned int |
| __attribute__ ((__pure__)) |
| _dl_elf_hash (const char *name) |
| { |
| const unsigned char *iname = (const unsigned char *) name; |
| unsigned int hash = (unsigned int) *iname++; |
| if (*iname != '\0') |
| { |
| hash = (hash << 4) + (unsigned int) *iname++; |
| if (*iname != '\0') |
| { |
| hash = (hash << 4) + (unsigned int) *iname++; |
| if (*iname != '\0') |
| { |
| hash = (hash << 4) + (unsigned int) *iname++; |
| if (*iname != '\0') |
| { |
| hash = (hash << 4) + (unsigned int) *iname++; |
| while (*iname != '\0') |
| { |
| unsigned int hi; |
| hash = (hash << 4) + (unsigned int) *iname++; |
| hi = hash & 0xf0000000; |
| |
| /* The algorithm specified in the ELF ABI is as |
| follows: |
| |
| if (hi != 0) |
| hash ^= hi >> 24; |
| |
| hash &= ~hi; |
| |
| But the following is equivalent and a lot |
| faster, especially on modern processors. */ |
| |
| hash ^= hi; |
| hash ^= hi >> 24; |
| } |
| } |
| } |
| } |
| } |
| return hash; |
| } |
| |
| #endif /* dl-hash.h */ |