1 /* Compute hash value for given string according to ELF standard. 2 Copyright (C) 2006 Red Hat, Inc. 3 This file is part of Red Hat elfutils. 4 Written by Ulrich Drepper <drepper (at) redhat.com>, 1995. 5 6 Red Hat elfutils is free software; you can redistribute it and/or modify 7 it under the terms of the GNU General Public License as published by the 8 Free Software Foundation; version 2 of the License. 9 10 Red Hat elfutils is distributed in the hope that it will be useful, but 11 WITHOUT ANY WARRANTY; without even the implied warranty of 12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 13 General Public License for more details. 14 15 You should have received a copy of the GNU General Public License along 16 with Red Hat elfutils; if not, write to the Free Software Foundation, 17 Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301 USA. 18 19 In addition, as a special exception, Red Hat, Inc. gives You the 20 additional right to link the code of Red Hat elfutils with code licensed 21 under an Open Source Initiative certified open source license 22 (http://www.opensource.org/licenses/index.php) and to distribute linked 23 combinations including the two. Non-GPL Code permitted under this 24 exception must only link to the code of Red Hat elfutils through those 25 well defined interfaces identified in the file named EXCEPTION found in 26 the source code files (the "Approved Interfaces"). The files of Non-GPL 27 Code may instantiate templates or use macros or inline functions from 28 the Approved Interfaces without causing the resulting work to be covered 29 by the GNU General Public License. Only Red Hat, Inc. may make changes 30 or additions to the list of Approved Interfaces. Red Hat's grant of 31 this exception is conditioned upon your not adding any new exceptions. 32 If you wish to add a new Approved Interface or exception, please contact 33 Red Hat. You must obey the GNU General Public License in all respects 34 for all of the Red Hat elfutils code and other code used in conjunction 35 with Red Hat elfutils except the Non-GPL Code covered by this exception. 36 If you modify this file, you may extend this exception to your version 37 of the file, but you are not obligated to do so. If you do not wish to 38 provide this exception without modification, you must delete this 39 exception statement from your version and license this file solely under 40 the GPL without exception. 41 42 Red Hat elfutils is an included package of the Open Invention Network. 43 An included package of the Open Invention Network is a package for which 44 Open Invention Network licensees cross-license their patents. No patent 45 license is granted, either expressly or impliedly, by designation as an 46 included package. Should you wish to participate in the Open Invention 47 Network licensing program, please visit www.openinventionnetwork.com 48 <http://www.openinventionnetwork.com>. */ 49 50 #ifndef _DL_HASH_H 51 #define _DL_HASH_H 1 52 53 54 /* This is the hashing function specified by the ELF ABI. In the 55 first five operations no overflow is possible so we optimized it a 56 bit. */ 57 static inline unsigned int 58 __attribute__ ((__pure__)) 59 _dl_elf_hash (const char *name) 60 { 61 const unsigned char *iname = (const unsigned char *) name; 62 unsigned int hash = (unsigned int) *iname++; 63 if (*iname != '\0') 64 { 65 hash = (hash << 4) + (unsigned int) *iname++; 66 if (*iname != '\0') 67 { 68 hash = (hash << 4) + (unsigned int) *iname++; 69 if (*iname != '\0') 70 { 71 hash = (hash << 4) + (unsigned int) *iname++; 72 if (*iname != '\0') 73 { 74 hash = (hash << 4) + (unsigned int) *iname++; 75 while (*iname != '\0') 76 { 77 unsigned int hi; 78 hash = (hash << 4) + (unsigned int) *iname++; 79 hi = hash & 0xf0000000; 80 81 /* The algorithm specified in the ELF ABI is as 82 follows: 83 84 if (hi != 0) 85 hash ^= hi >> 24; 86 87 hash &= ~hi; 88 89 But the following is equivalent and a lot 90 faster, especially on modern processors. */ 91 92 hash ^= hi; 93 hash ^= hi >> 24; 94 } 95 } 96 } 97 } 98 } 99 return hash; 100 } 101 102 #endif /* dl-hash.h */ 103
