Revert "Revert "Add API for channel frame deferral.""

This reverts commit fa749866c17f91860d3e9f89742eab3e6f03ecbc.

Change-Id: Idcd1b88fa0766b1326dcc87d8905dbc314c71bd7

1 files changed, 45 insertions, 0 deletions

diff --git a/main/channel.c b/main/channel.c
index cdb6569c3..6317f6f20 100644
--- a/main/channel.c
+++ b/main/channel.c
@@ -1062,6 +1062,25 @@ struct ast_channel *__ast_dummy_channel_alloc(const char *file, int line, const
 	return tmp;
 }
 
+void ast_channel_start_defer_frames(struct ast_channel *chan)
+{
+	ast_set_flag(ast_channel_flags(chan), AST_FLAG_DEFER_FRAMES);
+}
+
+void ast_channel_stop_defer_frames(struct ast_channel *chan)
+{
+	ast_clear_flag(ast_channel_flags(chan), AST_FLAG_DEFER_FRAMES);
+
+	/* Move the deferred frames onto the channel read queue, ahead of other queued frames */
+	ast_queue_frame_head(chan, AST_LIST_FIRST(ast_channel_deferred_readq(chan)));
+	/* ast_frfree will mosey down the list and free them all */
+	if (!AST_LIST_EMPTY(ast_channel_deferred_readq(chan))) {
+		ast_frfree(AST_LIST_FIRST(ast_channel_deferred_readq(chan)));
+	}
+	/* Reset the list to be empty */
+	AST_LIST_HEAD_INIT_NOLOCK(ast_channel_deferred_readq(chan));
+}
+
 static int __ast_queue_frame(struct ast_channel *chan, struct ast_frame *fin, int head, struct ast_frame *after)
 {
 	struct ast_frame *f;
@@ -3883,6 +3902,32 @@ static struct ast_frame *__ast_read(struct ast_channel *chan, int dropaudio)
 	if (!AST_LIST_EMPTY(ast_channel_readq(chan))) {
 		int skip_dtmf = should_skip_dtmf(chan);
 
+		if (ast_test_flag(ast_channel_flags(chan), AST_FLAG_DEFER_FRAMES)) {
+			AST_LIST_TRAVERSE_SAFE_BEGIN(ast_channel_readq(chan), f, frame_list) {
+				if (ast_is_deferrable_frame(f)) {
+					if (f->frametype == AST_FRAME_CONTROL && f->subclass.integer == AST_CONTROL_HANGUP) {
+						struct ast_frame *dup;
+
+						/* Hangup is a special case. We want to defer the frame, but we also do not
+						 * want to remove it from the frame queue. So rather than just moving the frame
+						 * over, we duplicate it and move the copy to the deferred readq.
+						 *
+						 * The reason for this? This way, whoever calls ast_read() will get a NULL return
+						 * immediately and can tell the channel has hung up and do what it needs to. Also,
+						 * when frame deferral finishes, then whoever calls ast_read() next will also get
+						 * the hangup.
+						 */
+						dup = ast_frdup(f);
+						AST_LIST_INSERT_TAIL(ast_channel_deferred_readq(chan), dup, frame_list);
+					} else {
+						AST_LIST_INSERT_TAIL(ast_channel_deferred_readq(chan), f, frame_list);
+						AST_LIST_REMOVE_CURRENT(frame_list);
+					}
+				}
+			}
+			AST_LIST_TRAVERSE_SAFE_END;
+		}
+
 		AST_LIST_TRAVERSE_SAFE_BEGIN(ast_channel_readq(chan), f, frame_list) {
 			/* We have to be picky about which frame we pull off of the readq because
 			 * there are cases where we want to leave DTMF frames on the queue until