diff options
Diffstat (limited to 'sysdeps/generic/strstr.c')
-rw-r--r-- | sysdeps/generic/strstr.c | 123 |
1 files changed, 123 insertions, 0 deletions
diff --git a/sysdeps/generic/strstr.c b/sysdeps/generic/strstr.c new file mode 100644 index 0000000..fce1f2a --- /dev/null +++ b/sysdeps/generic/strstr.c @@ -0,0 +1,123 @@ +/* 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 */ + +#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 (phaystack, pneedle) + 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_builtin_def (strstr) |