Add support for RFC 4662 resource list subscriptions.

This commit adds the ability for a user to configure
a resource list in pjsip.conf. Subscribing to this
list simultaneously subscribes the subscriber to all
resources listed. This has the potential to reduce
the amount of SIP traffic when loads of subscribers
on a system attempt to subscribe to each others' states.



git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@420384 65c4cc65-6c06-0410-ace0-fbb531ad65f3

include/asterisk/strings.h

@@ -1196,4 +1196,20 @@ int ast_str_container_add(struct ao2_container *str_container, const char *add);
  */
 void ast_str_container_remove(struct ao2_container *str_container, const char *remove);
 
+/*!
+ * \brief Create a pseudo-random string of a fixed length.
+ *
+ * This function is useful for generating a string whose randomness
+ * does not need to be across all time and space, does not need to
+ * be cryptographically secure, and needs to fit in a limited space.
+ *
+ * This function will write a null byte at the final position
+ * in the buffer (buf[size - 1]). So if you pass in a size of
+ * 10, then this will generate a random 9-character string.
+ *
+ * \param buf Buffer to write random string into.
+ * \param size The size of the buffer.
+ * \return A pointer to buf
+ */
+char *ast_generate_random_string(char *buf, size_t size);
 #endif /* _ASTERISK_STRINGS_H */