-/* return: negative on errors, zero if not everything was sent, one otherwise */
-static int send_queued_chunks(struct sender_client *sc,
+/**
+ * Try to empty the chunk queue for this fd.
+ *
+ * \param fd The file descriptor.
+ * \param cq The list of queued chunks.
+ * \param max_bytes_per_write Do not send more than this in one go.
+ *
+ * \return Negative on errors, zero if not everything was sent, one otherwise.
+ */
+int send_queued_chunks(int fd, struct chunk_queue *cq,