1da0c48c4Sopenharmony_ci/* Compute hash value for given string according to ELF standard. 2da0c48c4Sopenharmony_ci Copyright (C) 1995-2015 Free Software Foundation, Inc. 3da0c48c4Sopenharmony_ci This file is part of the GNU C Library. 4da0c48c4Sopenharmony_ci 5da0c48c4Sopenharmony_ci The GNU C Library is free software; you can redistribute it and/or 6da0c48c4Sopenharmony_ci modify it under the terms of the GNU Lesser General Public 7da0c48c4Sopenharmony_ci License as published by the Free Software Foundation; either 8da0c48c4Sopenharmony_ci version 2.1 of the License, or (at your option) any later version. 9da0c48c4Sopenharmony_ci 10da0c48c4Sopenharmony_ci The GNU C Library is distributed in the hope that it will be useful, 11da0c48c4Sopenharmony_ci but WITHOUT ANY WARRANTY; without even the implied warranty of 12da0c48c4Sopenharmony_ci MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 13da0c48c4Sopenharmony_ci Lesser General Public License for more details. 14da0c48c4Sopenharmony_ci 15da0c48c4Sopenharmony_ci You should have received a copy of the GNU Lesser General Public 16da0c48c4Sopenharmony_ci License along with the GNU C Library; if not, see 17da0c48c4Sopenharmony_ci <http://www.gnu.org/licenses/>. */ 18da0c48c4Sopenharmony_ci 19da0c48c4Sopenharmony_ci#ifndef _DL_HASH_H 20da0c48c4Sopenharmony_ci#define _DL_HASH_H 1 21da0c48c4Sopenharmony_ci 22da0c48c4Sopenharmony_ci 23da0c48c4Sopenharmony_ci/* This is the hashing function specified by the ELF ABI. In the 24da0c48c4Sopenharmony_ci first five operations no overflow is possible so we optimized it a 25da0c48c4Sopenharmony_ci bit. */ 26da0c48c4Sopenharmony_cistatic unsigned int 27da0c48c4Sopenharmony_ci__attribute__ ((unused)) 28da0c48c4Sopenharmony_ci_dl_elf_hash (const char *name_arg) 29da0c48c4Sopenharmony_ci{ 30da0c48c4Sopenharmony_ci const unsigned char *name = (const unsigned char *) name_arg; 31da0c48c4Sopenharmony_ci unsigned long int hash = *name; 32da0c48c4Sopenharmony_ci if (hash != 0 && name[1] != '\0') 33da0c48c4Sopenharmony_ci { 34da0c48c4Sopenharmony_ci hash = (hash << 4) + name[1]; 35da0c48c4Sopenharmony_ci if (name[2] != '\0') 36da0c48c4Sopenharmony_ci { 37da0c48c4Sopenharmony_ci hash = (hash << 4) + name[2]; 38da0c48c4Sopenharmony_ci if (name[3] != '\0') 39da0c48c4Sopenharmony_ci { 40da0c48c4Sopenharmony_ci hash = (hash << 4) + name[3]; 41da0c48c4Sopenharmony_ci if (name[4] != '\0') 42da0c48c4Sopenharmony_ci { 43da0c48c4Sopenharmony_ci hash = (hash << 4) + name[4]; 44da0c48c4Sopenharmony_ci name += 5; 45da0c48c4Sopenharmony_ci while (*name != '\0') 46da0c48c4Sopenharmony_ci { 47da0c48c4Sopenharmony_ci unsigned long int hi; 48da0c48c4Sopenharmony_ci hash = (hash << 4) + *name++; 49da0c48c4Sopenharmony_ci hi = hash & 0xf0000000; 50da0c48c4Sopenharmony_ci 51da0c48c4Sopenharmony_ci /* The algorithm specified in the ELF ABI is as 52da0c48c4Sopenharmony_ci follows: 53da0c48c4Sopenharmony_ci 54da0c48c4Sopenharmony_ci if (hi != 0) 55da0c48c4Sopenharmony_ci hash ^= hi >> 24; 56da0c48c4Sopenharmony_ci 57da0c48c4Sopenharmony_ci hash &= ~hi; 58da0c48c4Sopenharmony_ci 59da0c48c4Sopenharmony_ci But the following is equivalent and a lot 60da0c48c4Sopenharmony_ci faster, especially on modern processors. */ 61da0c48c4Sopenharmony_ci 62da0c48c4Sopenharmony_ci hash ^= hi >> 24; 63da0c48c4Sopenharmony_ci } 64da0c48c4Sopenharmony_ci 65da0c48c4Sopenharmony_ci /* Second part of the modified formula. This 66da0c48c4Sopenharmony_ci operation can be lifted outside the loop. */ 67da0c48c4Sopenharmony_ci hash &= 0x0fffffff; 68da0c48c4Sopenharmony_ci } 69da0c48c4Sopenharmony_ci } 70da0c48c4Sopenharmony_ci } 71da0c48c4Sopenharmony_ci } 72da0c48c4Sopenharmony_ci return hash; 73da0c48c4Sopenharmony_ci} 74da0c48c4Sopenharmony_ci 75da0c48c4Sopenharmony_ci#endif /* dl-hash.h */ 76