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Diffstat (limited to 'libelf/dl-hash.h')
| -rw-r--r-- | libelf/dl-hash.h | 102 |
1 files changed, 102 insertions, 0 deletions
diff --git a/libelf/dl-hash.h b/libelf/dl-hash.h new file mode 100644 index 0000000..fd59394 --- /dev/null +++ b/libelf/dl-hash.h @@ -0,0 +1,102 @@ +/* Compute hash value for given string according to ELF standard. + Copyright (C) 2006 Red Hat, Inc. + This file is part of Red Hat elfutils. + Written by Ulrich Drepper <drepper@redhat.com>, 1995. + + Red Hat elfutils 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 of the License. + + Red Hat elfutils 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 Red Hat elfutils; if not, write to the Free Software Foundation, + Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301 USA. + + In addition, as a special exception, Red Hat, Inc. gives You the + additional right to link the code of Red Hat elfutils with code licensed + under an Open Source Initiative certified open source license + (http://www.opensource.org/licenses/index.php) and to distribute linked + combinations including the two. Non-GPL Code permitted under this + exception must only link to the code of Red Hat elfutils through those + well defined interfaces identified in the file named EXCEPTION found in + the source code files (the "Approved Interfaces"). The files of Non-GPL + Code may instantiate templates or use macros or inline functions from + the Approved Interfaces without causing the resulting work to be covered + by the GNU General Public License. Only Red Hat, Inc. may make changes + or additions to the list of Approved Interfaces. Red Hat's grant of + this exception is conditioned upon your not adding any new exceptions. + If you wish to add a new Approved Interface or exception, please contact + Red Hat. You must obey the GNU General Public License in all respects + for all of the Red Hat elfutils code and other code used in conjunction + with Red Hat elfutils except the Non-GPL Code covered by this exception. + If you modify this file, you may extend this exception to your version + of the file, but you are not obligated to do so. If you do not wish to + provide this exception without modification, you must delete this + exception statement from your version and license this file solely under + the GPL without exception. + + Red Hat elfutils is an included package of the Open Invention Network. + An included package of the Open Invention Network is a package for which + Open Invention Network licensees cross-license their patents. No patent + license is granted, either expressly or impliedly, by designation as an + included package. Should you wish to participate in the Open Invention + Network licensing program, please visit www.openinventionnetwork.com + <http://www.openinventionnetwork.com>. */ + +#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 */ |