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Diffstat (limited to 'contrib/patch/memchr.c')
| -rw-r--r-- | contrib/patch/memchr.c | 199 |
1 files changed, 0 insertions, 199 deletions
diff --git a/contrib/patch/memchr.c b/contrib/patch/memchr.c deleted file mode 100644 index c75217f..0000000 --- a/contrib/patch/memchr.c +++ /dev/null @@ -1,199 +0,0 @@ -/* Copyright (C) 1991, 1993, 1996 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). - -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. - -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 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 - -#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. */ - -__ptr_t -memchr (s, c, n) - const __ptr_t s; - int c; - size_t n; -{ - 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 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 (__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 - - 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 >= sizeof (longword)) - { - /* We tentatively exit the loop if adding MAGIC_BITS to - LONGWORD fails to change any of the hole bits of LONGWORD. - - 1) Is this safe? Will it catch all the zero bytes? - Suppose there is a byte with all zeros. Any carry bits - propagating from its left will fall into the hole at its - least significant bit and stop. Since there will be no - carry from its most significant bit, the LSB of the - byte to the left will be unchanged, and the zero will be - detected. - - 2) Is this worthwhile? Will it ignore everything except - zero bytes? Suppose every byte of LONGWORD has a bit set - somewhere. There will be a carry into bit 8. If bit 8 - is set, this will carry into bit 16. If bit 8 is clear, - one of bits 9-15 must be set, so there will be a carry - into bit 16. Similarly, there will be a carry into bit - 24. If one of bits 24-30 is set, there will be a carry - into bit 31, so all of the hole bits will be changed. - - The one misfire occurs when bits 24-30 are clear and bit - 31 is set; in this case, the hole at bit 31 is not - changed. If we had access to the processor carry flag, - we could close this loophole by putting the fourth hole - at bit 32! - - So it ignores everything except 128's, when they're aligned - properly. - - 3) But wait! Aren't we looking for C, not zero? - Good point. So what we do is XOR LONGWORD with a longword, - each of whose bytes is C. This turns each byte that is C - into a zero. */ - - longword = *longword_ptr++ ^ charmask; - - /* 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. */ - & ~magic_bits) != 0) - { - /* Which of the bytes was C? If none of them were, it was - a misfire; continue the search. */ - - const unsigned char *cp = (const unsigned char *) (longword_ptr - 1); - - if (cp[0] == c) - return (__ptr_t) cp; - if (cp[1] == c) - return (__ptr_t) &cp[1]; - if (cp[2] == c) - return (__ptr_t) &cp[2]; - if (cp[3] == c) - 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 -= sizeof (longword); - } - - char_ptr = (const unsigned char *) longword_ptr; - - while (n-- > 0) - { - if (*char_ptr == c) - return (__ptr_t) char_ptr; - else - ++char_ptr; - } - - return 0; -} |
