/* Return the offset of one string within another. Copyright (C) 1994,1996,1997,2000,2001,2003 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 Lesser General Public License as published by the Free Software Foundation; either version 2.1 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 Lesser General Public License for more details. You should have received a copy of the GNU Lesser General Public License along with the GNU C Library; 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 */ #include <string.h> typedef unsigned chartype; char *strstr (const char *phaystack, const char *pneedle) { const unsigned char *haystack, *needle; chartype b; const unsigned char *rneedle; haystack = (const unsigned char *) phaystack; if ((b = *(needle = (const unsigned char *) pneedle))) { chartype c; haystack--; /* possible ANSI violation */ { chartype a; do if (!(a = *++haystack)) goto ret0; while (a != b); } if (!(c = *++needle)) goto foundneedle; ++needle; goto jin; for (;;) { { chartype a; if (0) jin:{ if ((a = *++haystack) == c) goto crest; } else a = *++haystack; do { for (; a != b; a = *++haystack) { if (!a) goto ret0; if ((a = *++haystack) == b) break; if (!a) goto ret0; } } while ((a = *++haystack) != c); } crest: { chartype a; { const unsigned char *rhaystack; if (*(rhaystack = haystack-- + 1) == (a = *(rneedle = needle))) do { if (!a) goto foundneedle; if (*++rhaystack != (a = *++needle)) break; if (!a) goto foundneedle; } while (*++rhaystack == (a = *++needle)); needle = rneedle; /* took the register-poor aproach */ } if (!a) break; } } } foundneedle: return (char *) haystack; ret0: return 0; } libc_hidden_def(strstr)