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- /* Compute hash value for given string according to ELF standard.
- Copyright (C) 1995-2019 Free Software Foundation, Inc.
- This file is part of the GNU C Library.
- The GNU C Library is free software; you can redistribute it and/or
- modify it under the terms of the GNU Lesser General Public
- License as published by the Free Software Foundation; either
- version 2.1 of the License, or (at your option) any later version.
- The GNU C Library 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
- Lesser General Public License for more details.
- You should have received a copy of the GNU Lesser General Public
- License along with the GNU C Library; 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 unsigned int
- __attribute__ ((unused))
- _dl_elf_hash (const char *name_arg)
- {
- const unsigned char *name = (const unsigned char *) name_arg;
- unsigned long int hash = *name;
- if (hash != 0 && name[1] != '\0')
- {
- hash = (hash << 4) + name[1];
- if (name[2] != '\0')
- {
- hash = (hash << 4) + name[2];
- if (name[3] != '\0')
- {
- hash = (hash << 4) + name[3];
- if (name[4] != '\0')
- {
- hash = (hash << 4) + name[4];
- name += 5;
- while (*name != '\0')
- {
- unsigned long int hi;
- hash = (hash << 4) + *name++;
- 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 >> 24;
- }
- /* Second part of the modified formula. This
- operation can be lifted outside the loop. */
- hash &= 0x0fffffff;
- }
- }
- }
- }
- return hash;
- }
- #endif /* dl-hash.h */
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