Add API for channel frame deferral.
authorMark Michelson <mmichelson@digium.com>
Thu, 3 Nov 2016 21:36:13 +0000 (16:36 -0500)
committerGeorge Joseph <gjoseph@digium.com>
Tue, 8 Nov 2016 12:37:54 +0000 (07:37 -0500)
There are several places in Asterisk that have duplicated logic
for deferring important frames until later.

This commit adds a couple of API calls to facilitate this automatically.

ast_channel_start_defer_frames(): Future reads of deferrable frames on
this channel will be deferred until later.

ast_channel_stop_defer_frames(): Any frames that have been deferred get
requeued onto the channel.

ASTERISK-26343

Change-Id: I3e1b87bc6796f222442fa6f7d1b6a4706fb33641

include/asterisk/channel.h
main/channel.c
main/channel_internal_api.c

index ff92cc8..e5f53f0 100644 (file)
@@ -967,6 +967,11 @@ enum {
         * The channel is executing a subroutine or macro
         */
        AST_FLAG_SUBROUTINE_EXEC = (1 << 27),
+       /*!
+        * The channel is currently in an operation where
+        * frames should be deferred.
+        */
+       AST_FLAG_DEFER_FRAMES = (1 << 28),
 };
 
 /*! \brief ast_bridge_config flags */
@@ -4671,4 +4676,37 @@ enum ast_channel_error {
  */
 enum ast_channel_error ast_channel_errno(void);
 
+/*!
+ * \brief Retrieve the deferred read queue.
+ */
+struct ast_readq_list *ast_channel_deferred_readq(struct ast_channel *chan);
+
+/*!
+ * \brief Start deferring deferrable frames on this channel
+ *
+ * Sometimes, a channel gets entered into a mode where a "main" application
+ * is tasked with servicing frames on the channel, but that application does
+ * not need to act on those frames. However, it would be imprudent to simply
+ * drop important frames. This function can be called so that important frames
+ * will be deferred, rather than placed in the channel frame queue as normal.
+ *
+ * \pre chan MUST be locked before calling
+ *
+ * \param chan The channel on which frames should be deferred
+ */
+void ast_channel_start_defer_frames(struct ast_channel *chan);
+
+/*!
+ * \brief Stop deferring deferrable frames on this channel
+ *
+ * When it is time to stop deferring frames on the channel, all deferred frames
+ * will be queued onto the channel's read queue so that the next servicer of
+ * the channel can handle those frames as necessary.
+ *
+ * \pre chan MUST be locked before calling
+ *
+ * \param chan The channel on which to stop deferring frames.
+ */
+void ast_channel_stop_defer_frames(struct ast_channel *chan);
+
 #endif /* _ASTERISK_CHANNEL_H */
index cdb6569..6317f6f 100644 (file)
@@ -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
index 1cb91e7..50f6c5d 100644 (file)
@@ -221,6 +221,7 @@ struct ast_channel {
        struct stasis_cp_single *topics;                /*!< Topic for all channel's events */
        struct stasis_forward *endpoint_forward;        /*!< Subscription for event forwarding to endpoint's topic */
        struct stasis_forward *endpoint_cache_forward; /*!< Subscription for cache updates to endpoint's topic */
+       struct ast_readq_list deferred_readq;
 };
 
 /*! \brief The monotonically increasing integer counter for channel uniqueids */
@@ -1681,3 +1682,8 @@ enum ast_channel_error ast_channel_internal_errno(void)
 
        return *error_code;
 }
+
+struct ast_readq_list *ast_channel_deferred_readq(struct ast_channel *chan)
+{
+       return &chan->deferred_readq;
+}