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/* Copyright (C) 1992, 1993, 1994 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>
/* Search no more than N bytes of S for C. */
void *
memchr (const void *s, int c, size_t n)
{
const char *char_ptr;
const unsigned long int *longword_ptr;
unsigned long int charmask;
size_t x;
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 = s; n > 0 && ((unsigned long int) char_ptr & 7) != 0;
--n, ++char_ptr)
if (*char_ptr == c)
return (void *) char_ptr;
if (n == (size_t)0)
return NULL;
x = n;
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;
if (x < 4)
x = (size_t) 0;
else
x -= 4;
/* 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 (ge & le)
{
/* Which of the bytes was the C? */
unsigned char *cp = (unsigned char *) (longword_ptr - 1);
int i;
for (i = 0; i < 6; i++)
if (cp[i] == c)
return &cp[i];
return &cp[7];
}
if (x == (size_t)0)
break;
}
return NULL;
}
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