PublicArchive/gnu-coreutils
2
0
Fork 0
mirror of git://git.sv.gnu.org/coreutils synced 2026-06-03 22:34:50 -04:00
Code Issues Packages Projects Releases Wiki Activity

Update from glibc.

Browse Source
This commit is contained in:
Jim Meyering
1995-03-12 15:26:09 +00:00
parent 1423198343
commit e677aefec1
1 changed files with 67 additions and 46 deletions
Download Patch File Download Diff File Expand all files Collapse all files
lib/memchr.c
+67 -46
View File
@@ -5,38 +5,58 @@
adaptation to memchr 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.
NOTE: The canonical source of this file is maintained with the GNU C Library.
Bugs can be reported to bug-glibc@prep.ai.mit.edu.
The GNU C Library is distributed in the hope that it will be useful,
This program is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by the
Free Software Foundation; either version 2, or (at your option) any
later version.
This program 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.
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU 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. */
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. */
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
#if (SIZEOF_LONG != 4 && SIZEOF_LONG != 8)
error This function works only on systems for which sizeof(long) is 4 or 8.
/* The previous line would begin with `#error,' but some compilers can't
handle that even when the condition is false. */
#undef __ptr_t
#if defined (__cplusplus) || (defined (__STDC__) && __STDC__)
# define __ptr_t void *
#else /* Not C++ or ANSI C. */
# define __ptr_t char *
#endif /* C++ or ANSI C. */
#if defined (HAVE_STRING_H) || defined (_LIBC)
# include <string.h>
#endif
#if defined (HAVE_LIMIT_H) || defined (_LIBC)
# include <limit.h>
#endif
#define LONG_MAX_32_BITS 2147483647
#ifndef LONG_MAX
#define LONG_MAX LONG_MAX_32_BITS
#endif
#include <sys/types.h>
/* Search no more than N bytes of S for C. */
char *
__ptr_t
memchr (s, c, n)
unsigned char *s;
const __ptr_t s;
int c;
unsigned n;
size_t n;
{
const unsigned char *char_ptr;
const unsigned long int *longword_ptr;
@@ -50,7 +70,7 @@ memchr (s, c, n)
& (sizeof (longword) - 1)) != 0;
--n, ++char_ptr)
if (*char_ptr == c)
return (char *) char_ptr;
return (__ptr_t) char_ptr;
/* All these elucidatory comments refer to 4-byte longwords,
but the theory applies equally well to 8-byte longwords. */
@@ -60,27 +80,28 @@ memchr (s, c, n)
/* 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
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. */
#if (SIZEOF_LONG == 8)
magic_bits = ((unsigned long int) 0x7efefefe << 32) | 0xfefefeff;
#else
if (sizeof (longword) != 4 && sizeof (longword) != 8)
abort ();
#if LONG_MAX <= LONG_MAX_32_BITS
magic_bits = 0x7efefeff;
#endif /* SIZEOF_LONG == 8 */
#else
magic_bits = ((unsigned long int) 0x7efefefe << 32) | 0xfefefeff;
#endif
/* Set up a longword, each of whose bytes is C. */
charmask = c | (c << 8);
charmask |= charmask << 16;
#if (SIZEOF_LONG == 8)
charmask |= charmask << 32;
#endif /* SIZEOF_LONG == 8 */
if (sizeof (longword) > 8)
abort ();
#if LONG_MAX > LONG_MAX_32_BITS
charmask |= charmask << 32;
#endif
/* Instead of the traditional loop which tests each character,
we will test a longword at a time. The tricky part is testing
@@ -125,11 +146,11 @@ memchr (s, c, n)
/* Add MAGIC_BITS to LONGWORD. */
if ((((longword + magic_bits)
/* Set those bits that were unchanged by the addition. */
/* Set those bits that were unchanged by the addition. */
^ ~longword)
/* Look at only the hole bits. If any of the hole bits
/* 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)
@@ -140,23 +161,23 @@ memchr (s, c, n)
const unsigned char *cp = (const unsigned char *) (longword_ptr - 1);
if (cp[0] == c)
return (char *) cp;
return (__ptr_t) cp;
if (cp[1] == c)
return (char *) &cp[1];
return (__ptr_t) &cp[1];
if (cp[2] == c)
return (char *) &cp[2];
return (__ptr_t) &cp[2];
if (cp[3] == c)
return (char *) &cp[3];
#if (SIZEOF_LONG == 8)
return (__ptr_t) &cp[3];
#if LONG_MAX > 2147483647
if (cp[4] == c)
return (char *) &cp[4];
return (__ptr_t) &cp[4];
if (cp[5] == c)
return (char *) &cp[5];
return (__ptr_t) &cp[5];
if (cp[6] == c)
return (char *) &cp[6];
return (__ptr_t) &cp[6];
if (cp[7] == c)
return (char *) &cp[7];
#endif /* SIZEOF_LONG == 8 */
return (__ptr_t) &cp[7];
#endif
}
n -= sizeof (longword);
@@ -167,7 +188,7 @@ memchr (s, c, n)
while (n-- > 0)
{
if (*char_ptr == c)
return (char *) char_ptr;
return (__ptr_t) char_ptr;
else
++char_ptr;
}