diff options
Diffstat (limited to 'lib/memchr.c')
| -rw-r--r-- | lib/memchr.c | 111 |
1 files changed, 66 insertions, 45 deletions
diff --git a/lib/memchr.c b/lib/memchr.c index 44a9dc5e07..57f99735f3 100644 --- a/lib/memchr.c +++ b/lib/memchr.c @@ -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) +#if LONG_MAX > LONG_MAX_32_BITS charmask |= charmask << 32; -#endif /* SIZEOF_LONG == 8 */ - if (sizeof (longword) > 8) - abort (); - +#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; } |