lavu: Add av_strnstr()

This is a length limited version of strstr()
Signed-off-by: Vladimir Pantelic <vladoman@gmail.com>
Signed-off-by: Luca Barbato <lu_zero@gentoo.org>

Changelog

 Entries are sorted chronologically from oldest to youngest within each release,
 releases are sorted from youngest to oldest.
 
+version 10:
+- av_strnstr
+
+
 version 9:
 - av_basename and av_dirname
 - adobe and limelight publisher authentication in RTMP

doc/APIchanges

@@ -13,6 +13,9 @@ libavutil:     2012-10-22
 
 API changes, most recent first:
 
+2013-01-xx - xxxxxxx - lavu 52.6.0 - avstring.h
+  Add av_strnstr()
+
 2013-01-xx - xxxxxxx - lavu 52.5.0 - hmac.h
   Add AVHMAC.
 

libavutil/avstring.c

@@ -65,6 +65,20 @@ char *av_stristr(const char *s1, const char *s2)
     return NULL;
 }
 
+char *av_strnstr(const char *haystack, const char *needle, size_t hay_length)
+{
+    size_t needle_len = strlen(needle);
+    if (!needle_len)
+        return haystack;
+    while (hay_length >= needle_len) {
+        hay_length--;
+        if (!memcmp(haystack, needle, needle_len))
+            return haystack;
+        haystack++;
+    }
+    return NULL;
+}
+
 size_t av_strlcpy(char *dst, const char *src, size_t size)
 {
     size_t len = 0;

libavutil/avstring.h

@@ -66,6 +66,21 @@ int av_stristart(const char *str, const char *pfx, const char **ptr);
  */
 char *av_stristr(const char *haystack, const char *needle);
 
+/**
+ * Locate the first occurrence of the string needle in the string haystack
+ * where not more than hay_length characters are searched. A zero-length
+ * string needle is considered to match at the start of haystack.
+ *
+ * This function is a length-limited version of the standard strstr().
+ *
+ * @param haystack   string to search in
+ * @param needle     string to search for
+ * @param hay_length length of string to search in
+ * @return           pointer to the located match within haystack
+ *                   or a null pointer if no match
+ */
+char *av_strnstr(const char *haystack, const char *needle, size_t hay_length);
+
 /**
  * Copy the string src to dst, but no more than size - 1 bytes, and
  * null-terminate dst.

libavutil/version.h

@@ -37,7 +37,7 @@
  */
 
 #define LIBAVUTIL_VERSION_MAJOR 52
-#define LIBAVUTIL_VERSION_MINOR  5
+#define LIBAVUTIL_VERSION_MINOR  6
 #define LIBAVUTIL_VERSION_MICRO  0
 
 #define LIBAVUTIL_VERSION_INT   AV_VERSION_INT(LIBAVUTIL_VERSION_MAJOR, \