-/* Copyright (C) 1994, 1999 Free Software Foundation, Inc.
-This file is part of the GNU C Library.
+/* Copyright (C) 1991-1994, 1996-1998, 2000, 2004, 2007-2014 Free Software
+ Foundation, Inc.
+ This file is part of the GNU C Library.
-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 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 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.
-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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
+ You should have received a copy of the GNU General Public License along
+ with this program; if not, see <http://www.gnu.org/licenses/>. */
-/*
- * 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 */
+/* This particular implementation was written by Eric Blake, 2008. */
-#if HAVE_CONFIG_H
+#ifndef _LIBC
# include <config.h>
#endif
-#if defined _LIBC || defined HAVE_STRING_H
-# include <string.h>
-#endif
-#include <sys/types.h>
+/* Specification of strstr. */
+#include <string.h>
+
+#include <stdbool.h>
-typedef unsigned chartype;
+#ifndef _LIBC
+# define __builtin_expect(expr, val) (expr)
+#endif
-#undef strstr
+#define RETURN_TYPE char *
+#define AVAILABLE(h, h_l, j, n_l) \
+ (!memchr ((h) + (h_l), '\0', (j) + (n_l) - (h_l)) \
+ && ((h_l) = (j) + (n_l)))
+#include "str-two-way.h"
+/* Return the first occurrence of NEEDLE in HAYSTACK. Return HAYSTACK
+ if NEEDLE is empty, otherwise NULL if NEEDLE is not found in
+ HAYSTACK. */
char *
-strstr (const char *phaystack, const char *pneedle)
+strstr (const char *haystack_start, const char *needle_start)
{
- 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;
+ const char *haystack = haystack_start;
+ const char *needle = needle_start;
+ size_t needle_len; /* Length of NEEDLE. */
+ size_t haystack_len; /* Known minimum length of HAYSTACK. */
+ bool ok = true; /* True if NEEDLE is prefix of HAYSTACK. */
+
+ /* Determine length of NEEDLE, and in the process, make sure
+ HAYSTACK is at least as long (no point processing all of a long
+ NEEDLE if HAYSTACK is too short). */
+ while (*haystack && *needle)
+ ok &= *haystack++ == *needle++;
+ if (*needle)
+ return NULL;
+ if (ok)
+ return (char *) haystack_start;
+
+ /* Reduce the size of haystack using strchr, since it has a smaller
+ linear coefficient than the Two-Way algorithm. */
+ needle_len = needle - needle_start;
+ haystack = strchr (haystack_start + 1, *needle_start);
+ if (!haystack || __builtin_expect (needle_len == 1, 0))
+ return (char *) haystack;
+ needle -= needle_len;
+ haystack_len = (haystack > haystack_start + needle_len ? 1
+ : needle_len + haystack_start - haystack);
+
+ /* Perform the search. Abstract memory is considered to be an array
+ of 'unsigned char' values, not an array of 'char' values. See
+ ISO C 99 section 6.2.6.1. */
+ if (needle_len < LONG_NEEDLE_THRESHOLD)
+ return two_way_short_needle ((const unsigned char *) haystack,
+ haystack_len,
+ (const unsigned char *) needle, needle_len);
+ return two_way_long_needle ((const unsigned char *) haystack, haystack_len,
+ (const unsigned char *) needle, needle_len);
}
+
+#undef LONG_NEEDLE_THRESHOLD
projects / gnulib.git / blobdiff