gstreamer-app: AppSink futures adapter

An adapter for AppSink that adds futures capabilities to it in the form of a Stream.

gstreamer-app/src/app_sink.rs

@@ -303,11 +303,20 @@ impl AppSinkStream {
     }
 }
 
+#[cfg(any(feature = "v1_10"))]
+impl Drop for AppSinkStream {
+    fn drop(&mut self) {
+        self.app_sink.set_callbacks(AppSinkCallbacks::new().build());
+    }
+}
+
 #[cfg(any(feature = "v1_10"))]
 impl Stream for AppSinkStream {
     type Item = gst::Sample;
 
     fn poll_next(self: Pin<&mut Self>, context: &mut Context) -> Poll<Option<Self::Item>> {
+        let mut waker = self.waker_reference.lock().unwrap();
+
         self.app_sink
             .try_pull_sample(gst::ClockTime::from_mseconds(0))
             .map(|sample| Poll::Ready(Some(sample)))
@@ -316,24 +325,42 @@ impl Stream for AppSinkStream {
                     return Poll::Ready(None);
                 }
 
-                self.waker_reference
-                    .lock()
-                    .unwrap()
-                    .replace(context.waker().to_owned());
+                waker.replace(context.waker().to_owned());
 
                 Poll::Pending
             })
     }
 }
 
+#[cfg(any(feature = "v1_10"))]
 #[cfg(test)]
 mod tests {
     use super::*;
+    use futures_util::StreamExt;
+    use gst::prelude::*;
 
     #[test]
     fn test_app_sink_stream() {
         gst::init().unwrap();
 
-        unimplemented!()
+        let videotestsrc = gst::ElementFactory::make("videotestsrc", None).unwrap();
+        let appsink = gst::ElementFactory::make("appsink", None).unwrap();
+
+        videotestsrc.set_property("num-buffers", &5).unwrap();
+
+        let pipeline = gst::Pipeline::new(None);
+        pipeline.add(&videotestsrc).unwrap();
+        pipeline.add(&appsink).unwrap();
+
+        videotestsrc.link(&appsink).unwrap();
+
+        let app_sink_stream = appsink.dynamic_cast::<AppSink>().unwrap().stream();
+        let samples_future = app_sink_stream.collect::<Vec<gst::Sample>>();
+
+        pipeline.set_state(gst::State::Playing).unwrap();
+        let samples = futures_executor::block_on(samples_future);
+        pipeline.set_state(gst::State::Null).unwrap();
+
+        assert_eq!(samples.len(), 5);
     }
 }