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Roland McGrath 1992-11-25 19:02:14 +00:00
parent 98f5cde0d5
commit fd725b9471
1 changed files with 85 additions and 0 deletions
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sysdeps/alpha/strchr.c Normal file
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/* 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;
}
}
}