/* 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. 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. 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( const char *phaystack, const char *pneedle) { register const unsigned char *haystack, *needle; register chartype b, c; haystack = (const unsigned char *) phaystack; needle = (const unsigned char *) pneedle; b = *needle; if (b != '\0') { haystack--; /* possible ANSI violation */ do { c = *++haystack; if (c == '\0') goto ret0; } while (c != b); c = *++needle; if (c == '\0') goto foundneedle; ++needle; goto jin; for (;;) { register chartype a; register const unsigned char *rhaystack, *rneedle; 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; 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; }