MEDIUM: h2: start to implement the frames processing loop

The rcv_buf() callback now calls h2_process_demux() after an recv() call
leaving some data in the buffer, and the snd_buf() callback calls
h2_process_mux() to try to process pending data from streams.

src/mux_h2.c

@@ -576,6 +576,19 @@ static struct h2s *h2c_stream_new(struct h2c *h2c, int id)
 	return h2s;
 }
 
+/* process Rx frames to be demultiplexed */
+static void h2_process_demux(struct h2c *h2c)
+{
+}
+
+/* process Tx frames from streams to be multiplexed. Returns > 0 if it reached
+ * the end.
+ */
+static int h2_process_mux(struct h2c *h2c)
+{
+	return 1;
+}
+
 
 /*********************************************************/
 /* functions below are I/O callbacks from the connection */
@@ -619,7 +632,7 @@ static void h2_recv(struct connection *conn)
 	if (buf->i == buf->size)
 		h2c->flags |= H2_CF_DEM_DFULL;
 
-	/* FIXME: should we try to process streams here instead of doing it in ->wake ? */
+	h2_process_demux(h2c);
 
 	/* after streams have been processed, we should have made some room */
 	if (buf->i != buf->size)
@@ -631,8 +644,7 @@ static void h2_recv(struct connection *conn)
 static void h2_send(struct connection *conn)
 {
 	struct h2c *h2c = conn->mux_ctx;
-
+	int done;
-	/* FIXME: should we try to process pending streams here instead of doing it in ->wake ? */
 
 	if (conn->flags & CO_FL_ERROR)
 		return;
@@ -642,29 +654,50 @@ static void h2_send(struct connection *conn)
 		return;
 	}
 
+	/* This loop is quite simple : it tries to fill as much as it can from
+	 * pending streams into the existing buffer until it's reportedly full
+	 * or the end of send requests is reached. Then it tries to send this
+	 * buffer's contents out, marks it not full if at least one byte could
+	 * be sent, and tries again.
+	 *
+	 * The snd_buf() function normally takes a "flags" argument which may
+	 * be made of a combination of CO_SFL_MSG_MORE to indicate that more
+	 * data immediately comes and CO_SFL_STREAMER to indicate that the
+	 * connection is streaming lots of data (used to increase TLS record
+	 * size at the expense of latency). The former can be sent any time
+	 * there's a buffer full flag, as it indicates at least one stream
+	 * attempted to send and failed so there are pending data. An
+	 * alternative would be to set it as long as there's an active stream
+	 * but that would be problematic for ACKs until we have an absolute
+	 * guarantee that all waiters have at least one byte to send. The
+	 * latter should possibly not be set for now.
+	 */
+
+	done = 0;
+	while (!done) {
+		unsigned int flags = 0;
+
+		/* fill as much as we can into the current buffer */
+		while (((h2c->flags & (H2_CF_MUX_MFULL|H2_CF_MUX_MALLOC)) == 0) && !done)
+			done = h2_process_mux(h2c);
+
+		if (conn->flags & CO_FL_ERROR)
+			break;
+
+		if (h2c->flags & (H2_CF_MUX_MFULL | H2_CF_DEM_MBUSY | H2_CF_DEM_MROOM))
+			flags |= CO_SFL_MSG_MORE;
+
+		if (conn->xprt->snd_buf(conn, h2c->mbuf, flags) <= 0)
+			break;
+
+		/* wrote at least one byte, the buffer is not full anymore */
+		h2c->flags &= ~(H2_CF_MUX_MFULL | H2_CF_DEM_MROOM);
+	}
+
 	if (conn->flags & CO_FL_SOCK_WR_SH) {
 		/* output closed, nothing to send, clear the buffer to release it */
 		h2c->mbuf->o = 0;
 	}
-
-	/* pending response data, we need to try to send or subscribe to
-	 * writes. The snd_buf() function takes a "flags" argument which
-	 * may be made of a combination of CO_SFL_MSG_MORE to indicate
-	 * that more data immediately comes and CO_SFL_STREAMER to
-	 * indicate that the connection is streaming lots of data (used
-	 * to increase TLS record size at the expense of latency). The
-	 * former could be sent any time there's a buffer full flag, as
-	 * it indicates at least one stream attempted to send and failed
-	 * so there are pending data. And alternative would be to set it
-	 * as long as there's an active stream but that would be
-	 * problematic for ACKs. The latter should possibly not be set
-	 * for now.
-	 */
-	if (conn->xprt->snd_buf(conn, h2c->mbuf, 0) > 0)
-		h2c->flags &= ~(H2_CF_MUX_MFULL | H2_CF_DEM_MROOM);
-
-	if (conn->flags & CO_FL_ERROR)
-		return;
 }
 
 /* call the wake up function of all streams attached to the connection */