pulse-server: calculate missing bytes differently

Based on patch from Barnabás Pőcze <pobrn@protonmail.com>

Instead of trying to keep track of the missing bytes ourselves, use the
simple tlength - avail - requested formula to request more bytes from
the client.

Fixes #1981

src/modules/module-protocol-pulse/pulse-server.c

@@ -434,7 +434,6 @@ static uint32_t fix_playback_buffer_attr(struct stream *s, struct buffer_attr *a
 		attr->prebuf = max_prebuf;
 	attr->prebuf -= attr->prebuf % frame_size;
 
-	s->missing = attr->tlength;
 	attr->fragsize = 0;
 
 	pw_log_info("[%s] maxlength:%u tlength:%u minreq:%u/%u prebuf:%u latency:%u %u",
@@ -1098,7 +1097,6 @@ struct process_data {
 	uint32_t write_inc;
 	uint32_t underrun_for;
 	uint32_t playing_for;
-	uint32_t missing;
 	uint32_t minreq;
 	uint32_t quantum;
 	unsigned int underrun:1;
@@ -1142,8 +1140,6 @@ do_process_done(struct spa_loop *loop,
 			else
 				stream_send_started(stream);
 		}
-		stream->missing += pd->missing;
-		stream->missing = SPA_MIN(stream->missing, (int64_t)stream->attr.tlength);
 		stream->playing_for += pd->playing_for;
 		if (stream->underrun_for != (uint64_t)-1)
 			stream->underrun_for += pd->underrun_for;
@@ -1254,7 +1250,6 @@ static void stream_process(void *data)
 				pd.underrun = true;
 			}
 			if ((stream->attr.prebuf == 0 || do_flush) && !stream->corked) {
-				pd.missing = size;
 				pd.playing_for = size;
 				if (avail > 0) {
 					spa_ringbuffer_read_data(&stream->ring,
@@ -1293,7 +1288,6 @@ static void stream_process(void *data)
 			spa_ringbuffer_read_update(&stream->ring, index);
 
 			pd.playing_for = size;
-			pd.missing = size;
 			pd.underrun = false;
 		}
 		buf->datas[0].chunk->offset = 0;

src/modules/module-protocol-pulse/server.c

@@ -167,7 +167,6 @@ static int handle_memblock(struct client *client, struct message *msg)
 	index += diff;
 	filled += diff;
 	stream->write_index += diff;
-	stream->missing -= diff;
 
 	if (filled < 0) {
 		/* underrun, reported on reader side */
@@ -188,13 +187,7 @@ static int handle_memblock(struct client *client, struct message *msg)
 	spa_ringbuffer_write_update(&stream->ring, index);
 	stream->requested -= SPA_MIN(msg->length, stream->requested);
 
-	if (diff < 0) {
+	stream_send_request(stream);
-		/* when we seek backwards, ask for the additional missing data
-		 * immediately so that we don't underrun in the next process */
-		pw_log_info("client %p [%s]: backwards seek of: %" PRIi64,
-			    client, client->name, diff);
-		stream_send_request(stream);
-	}
 
 finish:
 	message_free(impl, msg, false, false);

src/modules/module-protocol-pulse/stream.c

@@ -136,9 +136,6 @@ void stream_flush(struct stream *stream)
 		stream->ring.writeindex = stream->ring.readindex;
 		stream->write_index = stream->read_index;
 
-		stream->missing = stream->attr.tlength -
-			SPA_MIN(stream->requested, stream->attr.tlength);
-
 		if (stream->attr.prebuf > 0)
 			stream->in_prebuf = true;
 
@@ -153,13 +150,8 @@ void stream_flush(struct stream *stream)
 	}
 }
 
-static bool stream_prebuf_active(struct stream *stream)
+static bool stream_prebuf_active(struct stream *stream, int32_t avail)
 {
-	uint32_t index;
-	int32_t avail;
-
-	avail = spa_ringbuffer_get_write_index(&stream->ring, &index);
-
 	if (stream->in_prebuf) {
 		if (avail >= (int32_t) stream->attr.prebuf)
 			stream->in_prebuf = false;
@@ -172,17 +164,21 @@ static bool stream_prebuf_active(struct stream *stream)
 
 uint32_t stream_pop_missing(struct stream *stream)
 {
-	uint32_t missing;
+	int64_t missing, avail;
 
-	if (stream->missing <= 0)
+	avail = stream->write_index - stream->read_index;
+
+	missing = stream->attr.tlength;
+	missing -= stream->requested;
+	missing -= avail;
+
+	if (missing <= 0)
 		return 0;
 
-	if (stream->missing < stream->attr.minreq && !stream_prebuf_active(stream))
+	if (missing < stream->attr.minreq && !stream_prebuf_active(stream, avail))
 		return 0;
 
-	missing = stream->missing;
 	stream->requested += missing;
-	stream->missing = 0;
 
 	return missing;
 }
@@ -314,7 +310,6 @@ int stream_update_minreq(struct stream *stream, uint32_t minreq)
 	if (new_tlength <= old_tlength)
 		return 0;
 
-	stream->missing += new_tlength - old_tlength;
 	stream->attr.tlength = new_tlength;
 
 	if (client->version >= 15) {

src/modules/module-protocol-pulse/stream.h

@@ -83,7 +83,6 @@ struct stream {
 	int64_t delay;
 
 	uint32_t last_quantum;
-	int64_t missing;
 	int64_t requested;
 
 	struct sample_spec ss;