X-Git-Url: http://erislabs.net/gitweb/?a=blobdiff_plain;f=lib%2Fmemchr.c;h=eacb5c935fe32fa3ea209e2916d69fc4db17dd5d;hb=cbb86267fda18ba3e409e16cf9c460cbbed1846c;hp=44a9dc5e077d7d064b833ea27b38e71a5b203b16;hpb=398d529018aa39aee3f654e5c7094426e6664c05;p=gnulib.git diff --git a/lib/memchr.c b/lib/memchr.c index 44a9dc5e0..eacb5c935 100644 --- a/lib/memchr.c +++ b/lib/memchr.c @@ -1,61 +1,79 @@ -/* Copyright (C) 1991, 1993 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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, +USA. */ #ifdef HAVE_CONFIG_H -#include +# include #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. */ +#include + +#include + +#if defined _LIBC +# include +#else +# define reg_char char #endif -/* Search no more than N bytes of S for C. */ +#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) { 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 longword boundary. */ - for (char_ptr = s; n > 0 && ((unsigned long int) char_ptr - & (sizeof (longword) - 1)) != 0; + 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 8-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 @@ -66,26 +84,29 @@ memchr (s, c, n) 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 - magic_bits = 0x7efefeff; -#endif /* SIZEOF_LONG == 8 */ - /* 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 (SIZEOF_LONG == 8) +#if 0xffffffffU < ULONG_MAX + magic_bits |= magic_bits << 32; charmask |= charmask << 32; -#endif /* SIZEOF_LONG == 8 */ - if (sizeof (longword) > 8) - abort (); - + 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 >= sizeof (longword)) + 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. @@ -126,10 +147,10 @@ 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) @@ -140,26 +161,28 @@ memchr (s, c, n) 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]; -#if (SIZEOF_LONG == 8) - if (cp[4] == c) - return (char *) &cp[4]; - if (cp[5] == c) - return (char *) &cp[5]; - if (cp[6] == c) - return (char *) &cp[6]; - if (cp[7] == c) - return (char *) &cp[7]; -#endif /* SIZEOF_LONG == 8 */ + 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 -= sizeof (longword); + n -= sizeof longword; } char_ptr = (const unsigned char *) longword_ptr; @@ -167,10 +190,13 @@ memchr (s, c, n) 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