bufferevent_read
size_t bufferevent_read(struct bufferevent *bufev, void *data, size_t size);
read = bufferevent_read(bufev, s->sbuf + s->sbuf_valid,
read = bufferevent_read(bufev, s->cbuf + s->cbuf_valid,
len = bufferevent_read(bev, buf, clt->clt_fcgi.toread);