-/* Copyright (C) 1991 Free Software Foundation, Inc.
- Based on strlen implemention by Torbjorn Granlund (tege@sics.se),
+/* Copyright (C) 1991, 1993, 1997, 1999 Free Software Foundation, Inc.
+ Based on strlen implementation by Torbjorn Granlund (tege@sics.se),
with help from Dan Sahlin (dan@sics.se) and
commentary by Jim Blandy (jimb@ai.mit.edu);
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 General Public License
+along with this program; if not, write to the Free Software
+Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307,
+USA. */
+
+#ifdef HAVE_CONFIG_H
+# include <config.h>
+#endif
+
+#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 (_LIBC)
+# include <string.h>
+#endif
+
+#if defined (HAVE_LIMITS_H) || defined (_LIBC)
+# include <limits.h>
+#endif
-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. */
+#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 *
-memchr(s, c, n)
- unsigned char * s ;
- int c ;
- unsigned n;
+__ptr_t
+memchr (s, c, n)
+ const __ptr_t s;
+ int c;
+ size_t n;
{
- unsigned char *char_ptr;
- unsigned long int *longword_ptr;
+ 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 4-byte border. */
- for (char_ptr = s; n > 0 && ((unsigned long int) char_ptr & 3) != 0;
+ Do this until CHAR_PTR is aligned on a longword boundary. */
+ for (char_ptr = (const unsigned char *) s;
+ n > 0 && ((unsigned long int) char_ptr
+ & (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. */
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
+ 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 (longword) != 4 && sizeof (longword) != 8)
+ abort ();
+
+#if LONG_MAX <= LONG_MAX_32_BITS
magic_bits = 0x7efefeff;
+#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 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
if *any of the four* bytes in the longword in question are zero. */
- while (n >= 4)
+ while (n >= sizeof (longword))
{
/* We tentatively exit the loop if adding MAGIC_BITS to
LONGWORD fails to change any of the hole bits of LONGWORD.
/* 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. */
/* Which of the bytes was C? If none of them were, it was
a misfire; continue the search. */
- unsigned char *cp = ( unsigned char *) (longword_ptr - 1);
+ 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];
+ return (__ptr_t) &cp[3];
+#if LONG_MAX > 2147483647
+ if (cp[4] == c)
+ return (__ptr_t) &cp[4];
+ if (cp[5] == c)
+ return (__ptr_t) &cp[5];
+ if (cp[6] == c)
+ return (__ptr_t) &cp[6];
+ if (cp[7] == c)
+ return (__ptr_t) &cp[7];
+#endif
}
- n -= 4;
+ n -= sizeof (longword);
}
- char_ptr = ( unsigned char *) longword_ptr;
+ char_ptr = (const unsigned char *) longword_ptr;
while (n-- > 0)
{
if (*char_ptr == c)
- return (char *) char_ptr;
+ return (__ptr_t) char_ptr;
else
++char_ptr;
}
projects / gnulib.git / blobdiff