roken: add rk_memmem()

lib/roken/memmem.c

@@ -0,0 +1,72 @@
+/*
+ * Copyright (c) 1995, 1996, 1997 Kungliga Tekniska Högskolan
+ * (Royal Institute of Technology, Stockholm, Sweden).
+ * All rights reserved.
+ *
+ * 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. Neither the name of the Institute nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE 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 INSTITUTE 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 <config.h>
+#include <stdlib.h>
+#include <string.h>
+
+#ifndef HAVE_MEMMEM
+#include "roken.h"
+ROKEN_LIB_FUNCTION void * ROKEN_LIB_CALL
+memmem(const void *haystack,
+       size_t haystacklen,
+       const void *needle,
+       size_t needlelen)
+{
+  const unsigned char *hs = haystack;
+  const unsigned char *n = needle;
+  size_t hsi, ni;
+
+  if (haystacklen < needlelen || haystacklen == 0)
+      return NULL;
+  /*
+   * Imagine a haystack of length 5 and needle of length 2, then the largest
+   * index in the haystack at which we can bother looking for the needle is:
+   *
+   *    0 1 2 3 4
+   *   +---------+
+   *   |?|?|?|?|?|
+   *   +---------+
+   *          ^
+   *           \
+   *            here, at index 3, which is 5 - 2, and less than (5 - 2 + 1).
+   */
+  for (hsi = 0, ni = 0; hsi < (haystacklen - needlelen + 1); hsi++, ni = 0) {
+      while (ni < needlelen && n[ni] == hs[hsi + ni])
+          ni++;
+      if (ni == needlelen)
+          return rk_UNCONST(&hs[hsi]);
+  }
+  return NULL;
+}
+#endif