mirror of
https://sourceware.org/git/glibc.git
synced 2024-12-21 10:20:06 +00:00
86 lines
2.6 KiB
C
86 lines
2.6 KiB
C
/* Copyright (C) 1992 Free Software Foundation, Inc.
|
|
|
|
The GNU C Library is free software; you can redistribute it and/or
|
|
modify it under the terms of the GNU Library General Public License as
|
|
published by the Free Software Foundation; either version 2 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
|
|
Library General Public License for more details.
|
|
|
|
You should have received a copy of the GNU Library General Public
|
|
License along with the GNU C Library; see the file COPYING.LIB. If
|
|
not, write to the Free Software Foundation, Inc., 675 Mass Ave,
|
|
Cambridge, MA 02139, USA. */
|
|
|
|
#include <string.h>
|
|
|
|
/* Return the length of the null-terminated string STR. Scan for
|
|
the null terminator quickly by testing eight bytes at a time. */
|
|
|
|
char *
|
|
strchr (const char *str, int c)
|
|
{
|
|
const char *char_ptr;
|
|
const unsigned long int *longword_ptr;
|
|
unsigned long int charmask;
|
|
|
|
c = (unsigned char) c;
|
|
|
|
/* Handle the first few characters by reading one character at a time.
|
|
Do this until STR is aligned on a 8-byte border. */
|
|
for (char_ptr = str; ((unsigned long int) char_ptr & 7) != 0; ++char_ptr)
|
|
if (*char_ptr == '\0')
|
|
return NULL;
|
|
else if (*char_ptr == c)
|
|
return char_ptr;
|
|
|
|
longword_ptr = (unsigned long int *) char_ptr;
|
|
|
|
/* Set up a longword, each of whose bytes is C. */
|
|
charmask = c | (c << 8);
|
|
charmask |= charmask << 16;
|
|
charmask |= charmask << 32;
|
|
|
|
for (;;)
|
|
{
|
|
const unsigned long int longword = *longword_ptr++;
|
|
int ge, le, zero;
|
|
|
|
/* Set bits in ZERO if bytes in LONGWORD are zero. */
|
|
asm ("cmpbge $31, %1, %0" : "=r" (zero) : "r" (longword));
|
|
|
|
/* Set bits in GE if bytes in CHARMASK are >= bytes in LONGWORD. */
|
|
asm ("cmpbge %1, %2, %0" : "=r" (ge) : "r" (charmask), "r" (longword));
|
|
|
|
/* Set bits in LE if bytes in CHARMASK are <= bytes in LONGWORD. */
|
|
asm ("cmpbge %2, %1, %0" : "=r" (le) : "r" (charmask), "r" (longword));
|
|
|
|
/* Bytes that are both <= and >= are == to C. */
|
|
if (zero || (ge & le))
|
|
{
|
|
/* Which of the bytes was the C? */
|
|
|
|
const char *cp = (const char *) (longword_ptr - 1);
|
|
|
|
if (cp[0] == c)
|
|
return cp;
|
|
if (cp[0] == 0)
|
|
return NULL;
|
|
if (cp[1] == c)
|
|
return &cp[1];
|
|
if (cp[1] == 0)
|
|
return NULL;
|
|
if (cp[2] == c)
|
|
return &cp[2];
|
|
if (cp[2] == 0)
|
|
return NULL;
|
|
if (cp[3] == c)
|
|
return &cp[3];
|
|
return NULL;
|
|
}
|
|
}
|
|
}
|