bsd memmem

src/memmem.c

@@ -1,67 +1,62 @@
-#ifndef _GNU_SOURCE
-
-/* Copyright (C) 1991,92,93,94,96,97,98,2000,2004,2007 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 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., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
-
-/*
-#ifndef _LIBC
-# include <config.h>
-#endif
-*/
-
-#include <stddef.h>
-#include <string.h>
-
-#ifndef _LIBC
-# define __builtin_expect(expr, val)   (expr)
-#endif
-
-#undef memmem
-
-/* Return the first occurrence of NEEDLE in HAYSTACK.  */
-void *
-memmem (haystack, haystack_len, needle, needle_len)
-     const void *haystack;
-     size_t haystack_len;
-     const void *needle;
-     size_t needle_len;
-{
-  const char *begin;
-  const char *const last_possible
-    = (const char *) haystack + haystack_len - needle_len;
-
-  if (needle_len == 0)
-    /* The first occurrence of the empty string is deemed to occur at
-       the beginning of the string.  */
-    return (void *) haystack;
-
-  /* Sanity check, otherwise the loop might search through the whole
-     memory.  */
-  if (__builtin_expect (haystack_len < needle_len, 0))
-    return NULL;
-
-  for (begin = (const char *) haystack; begin <= last_possible; ++begin)
-    if (begin[0] == ((const char *) needle)[0] &&
-	!memcmp ((const void *) &begin[1],
-		 (const void *) ((const char *) needle + 1),
-		 needle_len - 1))
-      return (void *) begin;
-
-  return NULL;
-}
-
-#endif
+/*-
+ * Copyright (c) 2005 Pascal Gloor <pascal.gloor@spale.com>
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. The name of the author may not be used to endorse or promote
+ *    products derived from this software without specific prior written
+ *    permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <string.h>
+
+/*
+ * Find the first occurrence of the byte string s in byte string l.
+ */
+
+void *
+memmem(const void *l, size_t l_len, const void *s, size_t s_len)
+{
+	register char *cur, *last;
+	const char *cl = (const char *)l;
+	const char *cs = (const char *)s;
+
+	/* we need something to compare */
+	if (l_len == 0 || s_len == 0)
+		return NULL;
+
+	/* "s" must be smaller or equal to "l" */
+	if (l_len < s_len)
+		return NULL;
+
+	/* special case where s_len == 1 */
+	if (s_len == 1)
+		return memchr(l, (int)*cs, l_len);
+
+	/* the last position where its possible to find "s" in "l" */
+	last = (char *)cl + l_len - s_len;
+
+	for (cur = (char *)cl; cur <= last; cur++)
+		if (cur[0] == cs[0] && memcmp(cur, cs, s_len) == 0)
+			return cur;
+
+	return NULL;
+}