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authorRoland McGrath <roland@gnu.org>1995-02-18 01:27:10 +0000
committerRoland McGrath <roland@gnu.org>1995-02-18 01:27:10 +0000
commit28f540f45bbacd939bfd07f213bcad2bf730b1bf (patch)
tree15f07c4c43d635959c6afee96bde71fb1b3614ee /sysdeps/generic/strstr.c
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diff --git a/sysdeps/generic/strstr.c b/sysdeps/generic/strstr.c
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+/* Copyright (C) 1991, 1992 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., 675 Mass Ave,
+Cambridge, MA 02139, USA. */
+
+#include <ansidecl.h>
+#include <stddef.h>
+#include <string.h>
+
+/* Return the first ocurrence of NEEDLE in HAYSTACK. */
+char *
+DEFUN(strstr, (haystack, needle),
+ CONST char *CONST haystack AND
+ CONST char *CONST needle)
+{
+ register CONST char *CONST needle_end = strchr(needle, '\0');
+ register CONST char *CONST haystack_end = strchr(haystack, '\0');
+ register CONST size_t needle_len = needle_end - needle;
+ register CONST size_t needle_last = needle_len - 1;
+ register CONST char *begin;
+
+ if (needle_len == 0)
+ return (char *) haystack; /* ANSI 4.11.5.7, line 25. */
+ if ((size_t) (haystack_end - haystack) < needle_len)
+ return NULL;
+
+ for (begin = &haystack[needle_last]; begin < haystack_end; ++begin)
+ {
+ register CONST char *n = &needle[needle_last];
+ register CONST char *h = begin;
+
+ do
+ if (*h != *n)
+ goto loop; /* continue for loop */
+ while (--n >= needle && --h >= haystack);
+
+ return (char *) h;
+
+ loop:;
+ }
+
+ return NULL;
+}