Mercurial > hg > octave-nkf > gnulib-hg
changeset 8119:f2eb2edc65c3
Rewrite c-strstr.c for maintainability.
author | Bruno Haible <bruno@clisp.org> |
---|---|
date | Sun, 11 Feb 2007 13:58:43 +0000 |
parents | bb6b331e158d |
children | 03da4921af94 |
files | ChangeLog lib/c-strstr.c |
diffstat | 2 files changed, 54 insertions(+), 100 deletions(-) [+] |
line wrap: on
line diff
--- a/ChangeLog +++ b/ChangeLog @@ -1,5 +1,7 @@ 2007-02-11 Bruno Haible <bruno@clisp.org> + * lib/c-strstr.c: Complete rewrite for maintainability. + * modules/c-strstr-tests: New file. * tests/test-c-strstr.c: New file.
--- a/lib/c-strstr.c +++ b/lib/c-strstr.c @@ -1,118 +1,70 @@ -/* Copyright (C) 1994, 1999, 2002-2003, 2005-2006 Free Software Foundation, Inc. -This file is part of the GNU C Library. +/* c-strstr.c -- substring search in C locale + Copyright (C) 2005-2007 Free Software Foundation, Inc. + Written by Bruno Haible <bruno@clisp.org>, 2005, 2007. -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. + 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. -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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */ + 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. -/* - * 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 */ + 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */ #include <config.h> /* Specification. */ #include "c-strstr.h" -#include <string.h> +#include <stddef.h> -typedef unsigned chartype; - +/* Find the first occurrence of NEEDLE in HAYSTACK. */ char * -c_strstr (const char *phaystack, const char *pneedle) +c_strstr (const char *haystack, const char *needle) { - register const unsigned char *haystack, *needle; - register chartype b, c; - - haystack = (const unsigned char *) phaystack; - needle = (const unsigned char *) pneedle; + /* Be careful not to look at the entire extent of haystack or needle + until needed. This is useful because of these two cases: + - haystack may be very long, and a match of needle found early, + - needle may be very long, and not even a short initial segment of + needle may be found in haystack. */ + if (*needle != '\0') + { + /* Speed up the following searches of needle by caching its first + character. */ + unsigned char b = (unsigned char) *needle; - b = *needle; - if (b != '\0') - { - haystack--; /* possible ANSI violation */ - do + needle++; + for (;; haystack++) { - 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 + if (*haystack == '\0') + /* No match. */ + return NULL; + if ((unsigned char) *haystack == b) + /* The first character matches. */ { - 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; + const char *rhaystack = haystack + 1; + const char *rneedle = needle; - 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; - } + for (;; rhaystack++, rneedle++) + { + if (*rneedle == '\0') + /* Found a match. */ + return (char *) haystack; + if (*rhaystack == '\0') + /* No match. */ + return NULL; + if ((unsigned char) *rhaystack != (unsigned char) *rneedle) + /* Nothing in this round. */ + break; + } + } + } } -foundneedle: - return (char *) haystack; -ret0: - return 0; + else + return (char *) haystack; }