X-Git-Url: http://erislabs.net/gitweb/?a=blobdiff_plain;f=lib%2Fmemchr.c;h=3c5ecfd0e10b1dcc32f149fe0a92d4194dedfd35;hb=a8df888bfdbd98882a6909821db496b1ef9f5b36;hp=cb8d4a22acd6e9cc3d810957c0f0c71fa8ce68ac;hpb=87e2683e04a8ef7d18ea8f515e65d8885e5a2355;p=gnulib.git diff --git a/lib/memchr.c b/lib/memchr.c index cb8d4a22a..3c5ecfd0e 100644 --- a/lib/memchr.c +++ b/lib/memchr.c @@ -1,70 +1,111 @@ -/* Copyright (C) 1991 Free Software Foundation, Inc. - Based on strlen implemention by Torbjorn Granlund (tege@sics.se), +/* Copyright (C) 1991, 1993, 1996, 1997, 1999, 2000, 2003, 2004 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. + +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. -The GNU C Library is distributed in the hope that it will be useful, +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, +Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */ +#ifdef HAVE_CONFIG_H +# include +#endif +#include +#include -/* Search no more than N bytes of S for C. */ +#if defined _LIBC +# include +#else +# define reg_char char +#endif + +#include + +#if HAVE_BP_SYM_H || defined _LIBC +# include +#else +# define BP_SYM(sym) sym +#endif + +#undef memchr +#undef __memchr -char * -memchr(s, c, n) - unsigned char * s ; - int c ; - unsigned n; +/* Search no more than N bytes of S for C. */ +void * +__memchr (void const *s, int c_in, 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; + unsigned reg_char c; + int i; - c = (unsigned char) c; + c = (unsigned char) c_in; /* 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 && (size_t) char_ptr % sizeof longword != 0; --n, ++char_ptr) if (*char_ptr == c) - return (char *) char_ptr; + return (void *) char_ptr; + + /* All these elucidatory comments refer to 4-byte longwords, + but the theory applies equally well to any size longwords. */ - longword_ptr = (unsigned long int *) char_ptr; + longword_ptr = (const 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. */ - magic_bits = 0x7efefeff; - /* Set up a longword, each of whose bytes is C. */ + /* Set MAGIC_BITS to be this pattern of 1 and 0 bits. + Set CHARMASK to be a longword, each of whose bytes is C. */ + + magic_bits = 0xfefefefe; charmask = c | (c << 8); charmask |= charmask << 16; +#if 0xffffffffU < ULONG_MAX + magic_bits |= magic_bits << 32; + charmask |= charmask << 32; + if (8 < sizeof longword) + for (i = 64; i < sizeof longword * 8; i *= 2) + { + magic_bits |= magic_bits << i; + charmask |= charmask << i; + } +#endif + magic_bits = (ULONG_MAX >> 1) & (magic_bits | 1); /* 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 +145,10 @@ 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. */ @@ -116,30 +157,45 @@ 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 (void *) cp; if (cp[1] == c) - return (char *) &cp[1]; + return (void *) &cp[1]; if (cp[2] == c) - return (char *) &cp[2]; + return (void *) &cp[2]; if (cp[3] == c) - return (char *) &cp[3]; + return (void *) &cp[3]; + if (4 < sizeof longword && cp[4] == c) + return (void *) &cp[4]; + if (5 < sizeof longword && cp[5] == c) + return (void *) &cp[5]; + if (6 < sizeof longword && cp[6] == c) + return (void *) &cp[6]; + if (7 < sizeof longword && cp[7] == c) + return (void *) &cp[7]; + if (8 < sizeof longword) + for (i = 8; i < sizeof longword; i++) + if (cp[i] == c) + return (void *) &cp[i]; } - 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 (void *) char_ptr; else ++char_ptr; } return 0; } +#ifdef weak_alias +weak_alias (__memchr, BP_SYM (memchr)) +#endif