1 /* Compute hash value for given string according to ELF standard. 2 Copyright (C) 1995-1998, 2002, 2004 Free Software Foundation, Inc. 3 Written by Ulrich Drepper <drepper (at) redhat.com>, 1995. 4 5 This program is free software; you can redistribute it and/or modify 6 it under the terms of the GNU General Public License as published by 7 the Free Software Foundation, version 2. 8 9 This program is distributed in the hope that it will be useful, 10 but WITHOUT ANY WARRANTY; without even the implied warranty of 11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 12 GNU General Public License for more details. 13 14 You should have received a copy of the GNU General Public License 15 along with this program; if not, write to the Free Software Foundation, 16 Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */ 17 18 #ifndef _DL_HASH_H 19 #define _DL_HASH_H 1 20 21 22 /* This is the hashing function specified by the ELF ABI. In the 23 first five operations no overflow is possible so we optimized it a 24 bit. */ 25 static inline unsigned int 26 __attribute__ ((__pure__)) 27 _dl_elf_hash (const char *name) 28 { 29 const unsigned char *iname = (const unsigned char *) name; 30 unsigned int hash = (unsigned int) *iname++; 31 if (*iname != '\0') 32 { 33 hash = (hash << 4) + (unsigned int) *iname++; 34 if (*iname != '\0') 35 { 36 hash = (hash << 4) + (unsigned int) *iname++; 37 if (*iname != '\0') 38 { 39 hash = (hash << 4) + (unsigned int) *iname++; 40 if (*iname != '\0') 41 { 42 hash = (hash << 4) + (unsigned int) *iname++; 43 while (*iname != '\0') 44 { 45 unsigned int hi; 46 hash = (hash << 4) + (unsigned int) *iname++; 47 hi = hash & 0xf0000000; 48 49 /* The algorithm specified in the ELF ABI is as 50 follows: 51 52 if (hi != 0) 53 hash ^= hi >> 24; 54 55 hash &= ~hi; 56 57 But the following is equivalent and a lot 58 faster, especially on modern processors. */ 59 60 hash ^= hi; 61 hash ^= hi >> 24; 62 } 63 } 64 } 65 } 66 } 67 return hash; 68 } 69 70 #endif /* dl-hash.h */ 71
