Add basic-tutorial-6 from the GStreamer tutorials

https://cgit.freedesktop.org/gstreamer/gst-docs/tree/examples/tutorials/basic-tutorial-6.c

Fixes https://github.com/sdroege/gstreamer-rs/pull/43

tutorials/src/bin/basic-tutorial-6.rs

@@ -0,0 +1,164 @@
+extern crate gstreamer as gst;
+use gst::prelude::*;
+use gst::MessageView;
+
+
+fn print_caps(caps: gst::Caps, prefix: &str) {
+    if caps.is_any() {
+        println!("{}ANY", prefix);
+        return;
+    }
+
+    if caps.is_empty() {
+        println!("{}EMPTY", prefix);
+        return;
+    }
+
+    for structure in caps.iter() {
+        println!("{}{}", prefix, structure.get_name());
+        for (field, value) in structure.iter() {
+            println!("{}  {}:{:?}", prefix, field, value);
+        }
+    }
+}
+
+// Prints information about a Pad Template, including its Capabilitites
+fn print_pad_template_information(factory: &gst::ElementFactory) {
+    let long_name = factory
+        .get_metadata("long-name")
+        .expect("Failed to get long-name of element factory.");
+    println!("Pad Template for {}:", long_name);
+
+    if factory.get_num_pad_templates() == 0u32 {
+        println!("  None");
+        return;
+    }
+
+    for pad_template in factory.get_static_pad_templates() {
+        if pad_template.direction() == gst::PadDirection::Src {
+            println!("  SRC template: '{}'", pad_template.name_template());
+        } else if pad_template.direction() == gst::PadDirection::Sink {
+            println!("  SINK template: '{}'", pad_template.name_template());
+        } else {
+            println!("  UNKNOWN!!! template: '{}'", pad_template.name_template());
+        }
+
+        if pad_template.presence() == gst::PadPresence::Always {
+            println!("  Availability: Always");
+        } else if pad_template.presence() == gst::PadPresence::Sometimes {
+            println!("  Availability: Sometimes");
+        } else if pad_template.presence() == gst::PadPresence::Request {
+            println!("  Availability: On request");
+        } else {
+            println!("  Availability: UNKNOWN!!!");
+        }
+
+        let caps = pad_template.get_caps();
+        println!("  Capabilities:");
+        print_caps(caps, "    ");
+    }
+}
+
+fn print_pad_capabilities(element: &gst::Element, pad_name: &str) {
+    let pad = element
+        .get_static_pad(pad_name)
+        .expect("Could not retrieve pad");
+
+    println!("Caps for the {} pad:", pad_name);
+    match pad.get_current_caps() {
+        Some(caps) => {
+            print_caps(caps, "      ");
+        }
+        None => {
+            let caps = pad.query_caps(None).expect("Failed to query caps on pad");
+            print_caps(caps, "      ");
+        }
+    }
+}
+
+fn main() {
+    // Initialize GStreamer
+    gst::init().unwrap();
+
+    // Create the element factories
+    let source_factory =
+        gst::ElementFactory::find("audiotestsrc").expect("Failed to create audiotestsrc factory.");
+    let sink_factory = gst::ElementFactory::find("autoaudiosink")
+        .expect("Failed to create autoaudiosink factory.");
+
+    // Print information about the pad templates of these factories
+    print_pad_template_information(&source_factory);
+    print_pad_template_information(&sink_factory);
+
+    // Ask the factories to instantiate actual elements
+    let source = source_factory
+        .create("source")
+        .expect("Failed to create source element");
+    let sink = sink_factory
+        .create("sink")
+        .expect("Failed to create sink element");
+
+    // Create the empty pipeline
+    let pipeline = gst::Pipeline::new("test-pipeline");
+
+    pipeline.add_many(&[&source, &sink]).unwrap();
+    source.link(&sink).expect("Elements could not be linked.");
+
+    // Print initial negotiated caps (in NULL state)
+    println!("In NULL state:");
+    print_pad_capabilities(&sink, "sink");
+
+    // Start playing
+    let ret = pipeline.set_state(gst::State::Playing);
+    if ret == gst::StateChangeReturn::Failure {
+        eprintln!(
+            "Unable to set the pipeline to the playing state (check the bus for error messages)."
+        )
+    }
+
+    // Wait until error, EOS or State Change
+    let bus = pipeline.get_bus().unwrap();
+
+    loop {
+        let msg = bus.timed_pop(gst::CLOCK_TIME_NONE);
+
+        match msg {
+            Some(msg) => {
+                match msg.view() {
+                    MessageView::Error(err) => {
+                        println!(
+                            "Error received from element {}: {} ({:?})",
+                            msg.get_src().get_path_string(),
+                            err.get_error(),
+                            err.get_debug()
+                        );
+                        break;
+                    }
+                    MessageView::Eos(..) => {
+                        println!("End-Of-Stream reached.");
+                        break;
+                    }
+                    MessageView::StateChanged(state) =>
+                        // We are only interested in state-changed messages from the pipeline
+                        if msg.get_src() == pipeline {
+                            let new_state = state.get_current();
+                            let old_state = state.get_old();
+
+                            println!(
+                                "Pipeline state changed from {:?} to {:?}",
+                                old_state,
+                                new_state
+                            );
+                            print_pad_capabilities(&sink, "sink");
+                        },
+                    _ => (),
+                }
+            }
+            None => (),
+        }
+    }
+
+    // Shutdown pipeline
+    let ret = pipeline.set_state(gst::State::Null);
+    assert_ne!(ret, gst::StateChangeReturn::Failure);
+}