mirror of
git://sourceware.org/git/glibc.git
synced 2024-12-27 04:41:02 +08:00
69 lines
2.3 KiB
C
69 lines
2.3 KiB
C
/* Copyright (C) 2011-2013 Free Software Foundation, Inc.
|
|
This file is part of the GNU C Library.
|
|
Contributed by Chris Metcalf <cmetcalf@tilera.com>, 2011.
|
|
|
|
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
|
|
<http://www.gnu.org/licenses/>. */
|
|
|
|
#include <string.h>
|
|
#include <stdint.h>
|
|
|
|
#undef strchr
|
|
|
|
char *
|
|
strchr (const char *s, int c)
|
|
{
|
|
int z, g;
|
|
|
|
/* Get an aligned pointer. */
|
|
const uintptr_t s_int = (uintptr_t) s;
|
|
const uint32_t *p = (const uint32_t *) (s_int & -4);
|
|
|
|
/* Create four copies of the byte for which we are looking. */
|
|
const uint32_t goal = 0x01010101 * (uint8_t) c;
|
|
|
|
/* Read the first aligned word, but force bytes before the string to
|
|
match neither zero nor goal (we make sure the high bit of each
|
|
byte is 1, and the low 7 bits are all the opposite of the goal
|
|
byte). Note that this shift count expression works because we
|
|
know shift counts are taken mod 32. */
|
|
const uint32_t before_mask = (1 << (s_int << 3)) - 1;
|
|
uint32_t v = (*p | before_mask) ^ (goal & __insn_shrib (before_mask, 1));
|
|
|
|
uint32_t zero_matches, goal_matches;
|
|
while (1)
|
|
{
|
|
/* Look for a terminating '\0'. */
|
|
zero_matches = __insn_seqb (v, 0);
|
|
|
|
/* Look for the goal byte. */
|
|
goal_matches = __insn_seqb (v, goal);
|
|
|
|
if (__builtin_expect ((zero_matches | goal_matches) != 0, 0))
|
|
break;
|
|
|
|
v = *++p;
|
|
}
|
|
|
|
z = __insn_ctz (zero_matches);
|
|
g = __insn_ctz (goal_matches);
|
|
|
|
/* If we found c before '\0' we got a match. Note that if c == '\0'
|
|
then g == z, and we correctly return the address of the '\0'
|
|
rather than NULL. */
|
|
return (g <= z) ? ((char *) p) + (g >> 3) : NULL;
|
|
}
|
|
weak_alias (strchr, index)
|
|
libc_hidden_builtin_def (strchr)
|