diff options
Diffstat (limited to 'libc/string/strstr.c')
| -rw-r--r-- | libc/string/strstr.c | 155 |
1 files changed, 113 insertions, 42 deletions
diff --git a/libc/string/strstr.c b/libc/string/strstr.c index 3c853ac52..03d6c8e5f 100644 --- a/libc/string/strstr.c +++ b/libc/string/strstr.c @@ -1,54 +1,125 @@ -/* Copyright (C) 1995,1996 Robert de Bath <rdebath@cix.compulink.co.uk> - * This file is part of the Linux-8086 C library and is distributed - * under the GNU Library General Public License. - */ +/* Return the offset of one string within another. + Copyright (C) 1994, 1996, 1997 Free Software Foundation, Inc. + This file is part of the GNU C Library. -#include <string.h> + 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. -#if 1 -/* We've now got a nice fast strchr and memcmp use them */ + The GNU C Library 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. + + 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., 59 Temple Place - Suite 330, + Boston, MA 02111-1307, USA. */ + +/* + * My personal strstr() implementation that beats most other algorithms. + * Until someone tells me otherwise, I assume that this is the + * fastest implementation of strstr() in C. + * I deliberately chose not to comment it. You should have at least + * as much fun trying to understand it, as I had to write it :-). + * + * Stephen R. van den Berg, berg@pool.informatik.rwth-aachen.de */ + +#if HAVE_CONFIG_H +# include <config.h> +#endif + +#if defined _LIBC || defined HAVE_STRING_H +# include <string.h> +#endif + +typedef unsigned chartype; + +#undef strstr char * -strstr(s1, s2) -char *s1; char *s2; +strstr (phaystack, pneedle) + const char *phaystack; + const char *pneedle; { - register int l = strlen(s2); - register char * p = s1; - - if( l==0 ) return p; - - while ((p = strchr(p, *s2))) - { - if( memcmp(p, s2, l) == 0 ) - return p; - p++; - } - return (char *) 0; -} + register const unsigned char *haystack, *needle; + register chartype b, c; -#else -/* This is a nice simple self contained strstr, - now go and work out why the GNU one is faster :-) */ + haystack = (const unsigned char *) phaystack; + needle = (const unsigned char *) pneedle; -char *strstr(str1, str2) -char *str1, *str2; -{ - register char *Sptr, *Tptr; - int len = strlen(str1) -strlen(str2) + 1; + b = *needle; + if (b != '\0') + { + haystack--; /* possible ANSI violation */ + do + { + c = *++haystack; + if (c == '\0') + goto ret0; + } + while (c != b); - if (*str2) - for (; len > 0; len--, str1++){ - if (*str1 != *str2) - continue; + c = *++needle; + if (c == '\0') + goto foundneedle; + ++needle; + goto jin; - for (Sptr = str1, Tptr = str2; *Tptr != '\0'; Sptr++, Tptr++) - if (*Sptr != *Tptr) - break; + for (;;) + { + register chartype a; + register const unsigned char *rhaystack, *rneedle; - if (*Tptr == '\0') - return (char*) str1; - } + do + { + a = *++haystack; + if (a == '\0') + goto ret0; + if (a == b) + break; + a = *++haystack; + if (a == '\0') + goto ret0; +shloop: } + while (a != b); + +jin: a = *++haystack; + if (a == '\0') + goto ret0; + + if (a != c) + goto shloop; - return (char*)0; + rhaystack = haystack-- + 1; + rneedle = needle; + a = *rneedle; + + if (*rhaystack == a) + do + { + if (a == '\0') + goto foundneedle; + ++rhaystack; + a = *++needle; + if (*rhaystack != a) + break; + if (a == '\0') + goto foundneedle; + ++rhaystack; + a = *++needle; + } + while (*rhaystack == a); + + needle = rneedle; /* took the register-poor approach */ + + if (a == '\0') + break; + } + } +foundneedle: + return (char*) haystack; +ret0: + return 0; } -#endif |