glibc/sysdeps/generic/strchr.c
Ulrich Drepper 6d52618b15 Update from main archive 961219
Thu Dec 19 23:28:33 1996  Ulrich Drepper  <drepper@cygnus.com>

	* resolv/resolv.h: Update from BIND 4.9.5-P1.
	* resolv/res_comp.c: Likewise.
	* resolv/res_debug.c: Likewise.
	* resolv/Banner: Update version number.

Thu Dec 19 20:58:53 1996  Ulrich Drepper  <drepper@cygnus.com>

	* elf/dlfcn.h: Add extern "C" wrapper.

	* io/utime.h: Don't define NULL since this isn't allowed in POSIX.
	* io/sys/stat.h: Declare `lstat' only if __USE_BSD ||
	__USE_XOPEN_EXTENDED.
	* locale/locale.h: Define NULL.
	* math/math.c: Don't include <errno.h> to define math errors.
	* stdlib/stdlib.h: Likewise.
	* posix/unistd.h: Don't declare environ.
	* posix/sys/utsname.h (struct utsname): Declare member domainname
	as __domainname is !__USE_GNU.
	* signal/signal.h: Declare size_t only if __USE_BSD ||
	__USE_XOPEN_EXTENDED.
	* stdio/stdio.h: Don't declare cuserid when __USE_POSIX, but
	instead when __USE_XOPEN.
	* string/string.h: Define strndup only if __USE_GNU.
	* sysdeps/unix/sysv/linux/clock.c: New file.
	* sysdeps/unix/sysv/linux/timebits.h: Define CLOCKS_PER_SEC as
	1000000 per X/Open standard.
	* features.h: Add code to recognize _POSIX_C_SOURCE value 199309.
	Define __USE_POSIX199309.
	* posix/unistd.h: Declare fdatasync only if __USE_POSIX199309.
	* time/time.c: Declare nanosleep only if __USE_POSIX199309.
	Patches by Rüdiger Helsch <rh@unifix.de>.

	* locale/locale.h: Add declaration of newlocale and freelocale.

	* new-malloc/Makefile (distibute): Add mtrace.awk.
	(dist-routines): Add mcheck and mtrace.
	(install-lib, non-lib.a): Define as libmcheck.a.
	* new-malloc/malloc.h: Add declaration of __malloc_initialized.
	* new-malloc/mcheck.c: New file.
	* new-malloc/mcheck.h: New file.
	* new-malloc/mtrace.c: New file.
	* new-malloc/mtrace.awk: New file.

	* posix/unistd.h: Correct prototype for usleep.
	* sysdeps/unix/bsd/usleep.c: De-ANSI-declfy.  Correct return type.
	* sysdeps/unix/sysv/linux/usleep.c: Real implementation based on
	nanosleep.

	* signal/signal.h: Change protoype of __sigpause to take two
	arguments.  Remove prototype for sigpause.  Add two different
	macros named sigpause selected when __USE_BSD or __USE_XOPEN
	are defined.  This is necessary since the old BSD definition
	of theis function collides with the X/Open definition.
	* sysdeps/posix/sigpause.c: Change function definition to also
	fit X/Open definition.

	* sysdeps/libm-i387/e_exp.S: Make sure stack is empty when the
	function is left.
	* sysdeps/libm-i387/e_expl.S: Likewise.
	Patch by HJ Lu.

1996-12-17  Paul Eggert  <eggert@twinsun.com>

	* many, many files: Spelling corrections.
	* catgets/catgetsinfo.h (mmapped):
	Renamed from mmaped (in struct catalog_info.status).
	* mach/err_kern.sub (err_codes_unix), string/stratcliff.c (main):
	Fix spelling in message.
	* po/libc.pot: Fix spelling in message for `zic'; this anticipates
	a fix in the tzcode distribution.

Wed Dec 18 15:48:02 1996  Ulrich Drepper  <drepper@cygnus.com>

	* time/strftime.c: Implement ^ flag to cause output be converted
	to use upper case characters.

	* time/zic.c: Update from ADO tzcode1996n.

Wed Dec 18 14:29:24 1996  Erik Naggum  <erik@naggum.no>

	* time/strftime.c (add): Don't change global `i' until all is over.
	Define NULL is not already defined.

Tue Dec 17 09:49:03 1996  Andreas Schwab  <schwab@issan.informatik.uni-dortmund.de>

	* libio/iovsprintf.c (_IO_vsprintf): Change `&sf' to `&sf._sbf._f'
	to avoid the need for a cast.
	* libio/iovsscanf.c (_IO_vsscanf): Likewise.

	* sunrpc/rpc/xdr.h: Add prototype for xdr_free.
1996-12-20 01:39:50 +00:00

184 lines
5.9 KiB
C

/* Copyright (C) 1991, 1993, 1994, 1995, 1996 Free Software Foundation, Inc.
Based on strlen implementation by Torbjorn Granlund (tege@sics.se),
with help from Dan Sahlin (dan@sics.se) and
bug fix and commentary by Jim Blandy (jimb@ai.mit.edu);
adaptation to strchr suggested by Dick Karpinski (dick@cca.ucsf.edu),
and implemented by Roland McGrath (roland@ai.mit.edu).
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., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA. */
#include <ansidecl.h>
#include <string.h>
/* Find the first occurrence of C in S. */
char *
DEFUN(strchr, (s, c), CONST char *s AND int c)
{
CONST unsigned char *char_ptr;
CONST unsigned long int *longword_ptr;
unsigned long int longword, magic_bits, charmask;
c = (unsigned char) c;
/* Handle the first few characters by reading one character at a time.
Do this until CHAR_PTR is aligned on a longword boundary. */
for (char_ptr = s; ((unsigned long int) char_ptr
& (sizeof (longword) - 1)) != 0;
++char_ptr)
if (*char_ptr == c)
return (PTR) char_ptr;
else if (*char_ptr == '\0')
return NULL;
/* All these elucidatory comments refer to 4-byte longwords,
but the theory applies equally well to 8-byte longwords. */
longword_ptr = (unsigned long int *) char_ptr;
/* Bits 31, 24, 16, and 8 of this number are zero. Call these bits
the "holes." Note that there is a hole just to the left of
each byte, with an extra at the end:
bits: 01111110 11111110 11111110 11111111
bytes: AAAAAAAA BBBBBBBB CCCCCCCC DDDDDDDD
The 1-bits make sure that carries propagate to the next 0-bit.
The 0-bits provide holes for carries to fall into. */
switch (sizeof (longword))
{
case 4: magic_bits = 0x7efefeffL; break;
case 8: magic_bits = (0x7efefefeL << 32) | 0xfefefeffL; break;
default:
abort ();
}
/* Set up a longword, each of whose bytes is C. */
charmask = c | (c << 8);
charmask |= charmask << 16;
if (sizeof (longword) > 4)
charmask |= charmask << 32;
if (sizeof (longword) > 8)
abort ();
/* Instead of the traditional loop which tests each character,
we will test a longword at a time. The tricky part is testing
if *any of the four* bytes in the longword in question are zero. */
for (;;)
{
/* We tentatively exit the loop if adding MAGIC_BITS to
LONGWORD fails to change any of the hole bits of LONGWORD.
1) Is this safe? Will it catch all the zero bytes?
Suppose there is a byte with all zeros. Any carry bits
propagating from its left will fall into the hole at its
least significant bit and stop. Since there will be no
carry from its most significant bit, the LSB of the
byte to the left will be unchanged, and the zero will be
detected.
2) Is this worthwhile? Will it ignore everything except
zero bytes? Suppose every byte of LONGWORD has a bit set
somewhere. There will be a carry into bit 8. If bit 8
is set, this will carry into bit 16. If bit 8 is clear,
one of bits 9-15 must be set, so there will be a carry
into bit 16. Similarly, there will be a carry into bit
24. If one of bits 24-30 is set, there will be a carry
into bit 31, so all of the hole bits will be changed.
The one misfire occurs when bits 24-30 are clear and bit
31 is set; in this case, the hole at bit 31 is not
changed. If we had access to the processor carry flag,
we could close this loophole by putting the fourth hole
at bit 32!
So it ignores everything except 128's, when they're aligned
properly.
3) But wait! Aren't we looking for C as well as zero?
Good point. So what we do is XOR LONGWORD with a longword,
each of whose bytes is C. This turns each byte that is C
into a zero. */
longword = *longword_ptr++;
/* Add MAGIC_BITS to LONGWORD. */
if ((((longword + magic_bits)
/* Set those bits that were unchanged by the addition. */
^ ~longword)
/* Look at only the hole bits. If any of the hole bits
are unchanged, most likely one of the bytes was a
zero. */
& ~magic_bits) != 0 ||
/* That caught zeroes. Now test for C. */
((((longword ^ charmask) + magic_bits) ^ ~(longword ^ charmask))
& ~magic_bits) != 0)
{
/* Which of the bytes was C or zero?
If none of them were, it was a misfire; continue the search. */
CONST unsigned char *cp = (CONST unsigned char *) (longword_ptr - 1);
if (*cp == c)
return (char *) cp;
else if (*cp == '\0')
return NULL;
if (*++cp == c)
return (char *) cp;
else if (*cp == '\0')
return NULL;
if (*++cp == c)
return (char *) cp;
else if (*cp == '\0')
return NULL;
if (*++cp == c)
return (char *) cp;
else if (*cp == '\0')
return NULL;
if (sizeof (longword) > 4)
{
if (*++cp == c)
return (char *) cp;
else if (*cp == '\0')
return NULL;
if (*++cp == c)
return (char *) cp;
else if (*cp == '\0')
return NULL;
if (*++cp == c)
return (char *) cp;
else if (*cp == '\0')
return NULL;
if (*++cp == c)
return (char *) cp;
else if (*cp == '\0')
return NULL;
}
}
}
return NULL;
}
#ifdef weak_alias
#undef index
weak_alias (strchr, index)
#endif