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85f72e9c2a
1998-12-25 Ulrich Drepper <drepper@cygnus.com> * elf/dl-hash.h: Move to... * sysdeps/generic/dl-hash.h: ...here. Correct parameter type (must be unsigned char). Remove conditional from inner loop and rearrange binary operations (12-22% performance increase). * sysdeps/i386/i686/dl-hash.h: New file. Yet 10% faster than optimized generic version.
75 lines
2.0 KiB
C
75 lines
2.0 KiB
C
/* Compute hash alue for given string according to ELF standard.
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Copyright (C) 1995, 1996, 1997, 1998 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Library General Public License as
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published by the Free Software Foundation; either version 2 of the
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License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Library General Public License for more details.
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You should have received a copy of the GNU Library General Public
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License along with the GNU C Library; see the file COPYING.LIB. If not,
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write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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Boston, MA 02111-1307, USA. */
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#ifndef _DL_HASH_H
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#define _DL_HASH_H 1
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/* This is the hashing function specified by the ELF ABI. In the
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first five operations no overflow is possible so we optimized it a
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bit. */
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static inline unsigned int
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_dl_elf_hash (const unsigned char *name)
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{
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unsigned long int hash = 0;
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if (*name != '\0')
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{
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hash = *name++;
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if (*name != '\0')
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{
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hash = (hash << 4) + *name++;
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if (*name != '\0')
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{
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hash = (hash << 4) + *name++;
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if (*name != '\0')
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{
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hash = (hash << 4) + *name++;
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if (*name != '\0')
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{
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hash = (hash << 4) + *name++;
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while (*name != '\0')
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{
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unsigned long int hi;
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hash = (hash << 4) + *name++;
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hi = hash & 0xf0000000;
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/* The algorithm specified in the ELF ABI is as
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follows:
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if (hi != 0)
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hash ^= hi >> 24;
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hash &= ~hi;
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But the following is equivalent and a lot
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faster, especially on modern processors. */
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hash ^= hi;
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hash ^= hi >> 24;
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}
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}
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}
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}
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}
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}
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return hash;
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}
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#endif /* dl-hash.h */
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