This function adds len bytes of data, pointed at buf to random entropy pool. It's advaiceable to call it from time to time, with some user supplied data (like current time after keystroke, or sth like that), to get trurly random results from yw_random_get(3) and other. Note that used hashing function (MD5) allows you to add any data (including confidential or predictable one, like output of cat /dev/zero :^), while having no visible connection with results of random fetching function. Also note, that random pool is initialized on startup with output of /dev/urandom, whenever possible, current time, and content of ~/.Yrandseed file if present. ~/.Yrandseed is updated on each startup. All random handling functions are threadsafe -- i.e. only one thread can fetch/add to pool at once, which is enforced by mutex.