X-Git-Url: http://erislabs.net/gitweb/?a=blobdiff_plain;f=lib%2Fmemchr.c;h=4448248946d3811c603b11548073a344cd315c5a;hb=60d00c0cbda79b3c1715e38456a02656f6e6e707;hp=cb8d4a22acd6e9cc3d810957c0f0c71fa8ce68ac;hpb=87e2683e04a8ef7d18ea8f515e65d8885e5a2355;p=gnulib.git diff --git a/lib/memchr.c b/lib/memchr.c index cb8d4a22a..444824894 100644 --- a/lib/memchr.c +++ b/lib/memchr.c @@ -1,70 +1,114 @@ -/* Copyright (C) 1991 Free Software Foundation, Inc. +/* Copyright (C) 1991, 1993 Free Software Foundation, Inc. Based on strlen implemention 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 +#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 +#endif + +#if defined (HAVE_LIMITS_H) || defined (_LIBC) +# include +#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 /* 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. @@ -104,10 +148,10 @@ memchr(s, c, n) /* 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. */ @@ -116,27 +160,37 @@ memchr(s, c, n) /* 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; }