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/* Compute hash value for given string according to ELF standard.
Copyright (C) 1995-2020 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library 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
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#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 unsigned int
__attribute__ ((unused))
_dl_elf_hash (const char *name_arg)
{
const unsigned char *name = (const unsigned char *) name_arg;
unsigned long int hash = *name;
if (hash != 0 && name[1] != '\0')
{
hash = (hash << 4) + name[1];
if (name[2] != '\0')
{
hash = (hash << 4) + name[2];
if (name[3] != '\0')
{
hash = (hash << 4) + name[3];
if (name[4] != '\0')
{
hash = (hash << 4) + name[4];
name += 5;
while (*name != '\0')
{
unsigned long int hi;
hash = (hash << 4) + *name++;
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 >> 24;
}
/* Second part of the modified formula. This
operation can be lifted outside the loop. */
hash &= 0x0fffffff;
}
}
}
}
return hash;
}
#endif /* dl-hash.h */
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