1 /* Compute hash value for given string according to ELF standard.
2 Copyright (C) 1995-2017 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
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 Lesser General Public License for more details.
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, see
17 <http://www.gnu.org/licenses/>. */
23 /* This is the hashing function specified by the ELF ABI. In the
24 first five operations no overflow is possible so we optimized it a
27 __attribute__ ((unused
))
28 _dl_elf_hash (const char *name_arg
)
30 const unsigned char *name
= (const unsigned char *) name_arg
;
31 unsigned long int hash
= *name
;
32 if (hash
!= 0 && name
[1] != '\0')
34 hash
= (hash
<< 4) + name
[1];
37 hash
= (hash
<< 4) + name
[2];
40 hash
= (hash
<< 4) + name
[3];
43 hash
= (hash
<< 4) + name
[4];
48 hash
= (hash
<< 4) + *name
++;
49 hi
= hash
& 0xf0000000;
51 /* The algorithm specified in the ELF ABI is as
59 But the following is equivalent and a lot
60 faster, especially on modern processors. */
65 /* Second part of the modified formula. This
66 operation can be lifted outside the loop. */
75 #endif /* dl-hash.h */