elf/dl-hash.h

   1 /* Compute hash alue for given string according to ELF standard.
   2    Copyright (C) 1995, 1996, 1997 Free Software Foundation, Inc.
   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
   6    modify it under the terms of the GNU Library General Public License as
   7    published by the Free Software Foundation; either version 2 of the
   8    License, or (at your option) any later version.
   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
  13    Library General Public License for more details.
  14
  15    You should have received a copy of the GNU Library General Public
  16    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  17    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  18    Boston, MA 02111-1307, USA.  */
  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
  25    first five operations now overflow is possible so we optimized it a
  26    bit.  */
  27 static inline unsigned
  28 _dl_elf_hash (const char *name)
  29 {
  30   unsigned long int hash = 0;
  31   if (*name != '\0')
  32     {
  33       hash = (hash << 4) + *name++;
  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;
  51                           if (hi != 0)
  52                             {
  53                               hash ^= hi >> 24;
  54                               /* The ELF ABI says `hash &= ~hi', but
  55                                  this is equivalent in this case and
  56                                  on some machines one insn instead of
  57                                  two.  */
  58                               hash ^= hi;
  59                             }
  60                         }
  61                     }
  62                 }
  63             }
  64         }
  65     }
  66   return hash;
  67 }
  68
  69 #endif /* dl-hash.h */