libelf/dl-hash.h

/* Compute hash value for given string according to ELF standard.
   Copyright (C) 1995-1998, 2002, 2004 Free Software Foundation, Inc.
   Written by Ulrich Drepper <drepper@redhat.com>, 1995.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation, version 2.

   This program 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 a copy of the GNU General Public License
   along with this program; if not, write to the Free Software Foundation,
   Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */

#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 */