createBufferSource and buffer setter on buffer source node

9 files changed, 152 insertions, 62 deletions

diff --git a/components/script/dom/audiobuffer.rs b/components/script/dom/audiobuffer.rs
index 8f0a72a440c..5d028cc3cd9 100644
--- a/components/script/dom/audiobuffer.rs
+++ b/components/script/dom/audiobuffer.rs
@@ -14,8 +14,8 @@ use dom_struct::dom_struct;
 use js::jsapi::{Heap, JSContext, JSObject, JS_StealArrayBufferContents};
 use js::rust::CustomAutoRooterGuard;
 use js::typedarray::{CreateWith, Float32Array};
+use servo_media::audio::buffer_source_node::AudioBuffer as ServoMediaAudioBuffer;
 use std::ptr::{self, NonNull};
-use std::slice;
 use std::sync::{Arc, Mutex};
 
 type JSAudioChannel = Heap<*mut JSObject>;
@@ -25,7 +25,7 @@ pub struct AudioBuffer {
     reflector_: Reflector,
     js_channels: DomRefCell<Vec<JSAudioChannel>>,
     #[ignore_malloc_size_of = "Arc"]
-    shared_channels: Arc<Mutex<Vec<Vec<f32>>>>,
+    shared_channels: Arc<Mutex<ServoMediaAudioBuffer>>,
     sample_rate: f32,
     length: u32,
     duration: f64,
@@ -53,11 +53,12 @@ impl AudioBuffer {
         AudioBuffer {
             reflector_: Reflector::new(),
             js_channels: DomRefCell::new(js_channels),
-            shared_channels: Arc::new(Mutex::new(vec![vec![0.; length as usize]; number_of_channels as usize])),
-            sample_rate: sample_rate,
-            length: length,
-            duration: length as f64 / sample_rate as f64,
-            number_of_channels: number_of_channels,
+            shared_channels: Arc::new(Mutex::new(
+                    ServoMediaAudioBuffer::new(number_of_channels as u8, length as usize))),
+                    sample_rate: sample_rate,
+                    length: length,
+                    duration: length as f64 / sample_rate as f64,
+                    number_of_channels: number_of_channels,
         }
     }
 
@@ -88,7 +89,7 @@ impl AudioBuffer {
 
             // Move the channel data from shared_channels to js_channels.
             rooted!(in (cx) let mut array = ptr::null_mut::<JSObject>());
-            let shared_channel = (*self.shared_channels.lock().unwrap()).remove(i);
+            let shared_channel = (*self.shared_channels.lock().unwrap()).buffers.remove(i);
             if unsafe {
                 Float32Array::create(cx, CreateWith::Slice(&shared_channel), array.handle_mut())
             }.is_err() {
@@ -102,7 +103,7 @@ impl AudioBuffer {
 
     /// https://webaudio.github.io/web-audio-api/#acquire-the-content
     #[allow(unsafe_code)]
-    pub fn acquire_contents(&self) -> Option<Arc<Mutex<Vec<Vec<f32>>>>> {
+    pub fn acquire_contents(&self) -> Option<Arc<Mutex<ServoMediaAudioBuffer>>> {
         let cx = self.global().get_cx();
         for (i, channel) in self.js_channels.borrow_mut().iter().enumerate() {
             // Step 1.
@@ -112,17 +113,25 @@ impl AudioBuffer {
 
             // Step 2.
             let channel_data = unsafe {
-                slice::from_raw_parts(
-                    JS_StealArrayBufferContents(cx, channel.handle()) as *mut f32,
-                    self.length as usize
-                    ).to_vec()
+                typedarray!(in(cx) let array: Float32Array = channel.get());
+                if let Ok(array) = array {
+                    // XXX TypedArrays API does not expose a way to steal the buffer's
+                    //     content.
+                    let data = array.to_vec();
+                    let _ = JS_StealArrayBufferContents(cx, channel.handle());
+                    data
+                } else {
+                    return None;
+                }
             };
 
             channel.set(ptr::null_mut());
 
-            // Step 3 and part of 4 (which will complete turning shared_channels
-            // data into js_channels ArrayBuffers in restore_js_channel_data).
-            (*self.shared_channels.lock().unwrap())[i] = channel_data;
+            // Step 3.
+            (*self.shared_channels.lock().unwrap()).buffers[i] = channel_data;
+
+            // Step 4 will complete turning shared_channels
+            // data into js_channels ArrayBuffers in restore_js_channel_data.
         }
 
         self.js_channels.borrow_mut().clear();
@@ -167,16 +176,18 @@ impl AudioBufferMethods for AudioBuffer {
     }
 
     fn CopyFromChannel(&self,
-                       destination: CustomAutoRooterGuard<Float32Array>,
-                       channel_number: u32,
-                       start_in_channel: u32) -> Fallible<()> {
+                       _destination: CustomAutoRooterGuard<Float32Array>,
+                       _channel_number: u32,
+                       _start_in_channel: u32) -> Fallible<()> {
+        // XXX
         Ok(())
     }
 
     fn CopyToChannel(&self,
-                     source: CustomAutoRooterGuard<Float32Array>,
-                     channel_number: u32,
-                     start_in_channel: u32) -> Fallible<()> {
+                     _source: CustomAutoRooterGuard<Float32Array>,
+                     _channel_number: u32,
+                     _start_in_channel: u32) -> Fallible<()> {
+        // XXX
         Ok(())
     }
 }
diff --git a/components/script/dom/audiobuffersourcenode.rs b/components/script/dom/audiobuffersourcenode.rs
index 931e86ad21c..6eefe8c9ad5 100644
--- a/components/script/dom/audiobuffersourcenode.rs
+++ b/components/script/dom/audiobuffersourcenode.rs
@@ -12,10 +12,12 @@ use dom::bindings::codegen::Bindings::AudioBufferSourceNodeBinding::AudioBufferS
 use dom::bindings::codegen::Bindings::AudioParamBinding::AutomationRate;
 use dom::bindings::codegen::Bindings::AudioNodeBinding::AudioNodeOptions;
 use dom::bindings::codegen::Bindings::AudioNodeBinding::{ChannelCountMode, ChannelInterpretation};
-use dom::bindings::error::Fallible;
+use dom::bindings::codegen::Bindings::AudioScheduledSourceNodeBinding::AudioScheduledSourceNodeBinding::AudioScheduledSourceNodeMethods;
+use dom::bindings::error::{Error, Fallible};
+use dom::bindings::inheritance::Castable;
 use dom::bindings::num::Finite;
 use dom::bindings::reflector::reflect_dom_object;
-use dom::bindings::root::DomRoot;
+use dom::bindings::root::{DomRoot, MutNullableDom};
 use dom::window::Window;
 use dom_struct::dom_struct;
 use servo_media::audio::buffer_source_node::AudioBufferSourceNodeMessage;
@@ -33,8 +35,8 @@ audio_param_impl!(Detune, AudioBufferSourceNode, AudioBufferSourceNodeMessage, S
 
 #[dom_struct]
 pub struct AudioBufferSourceNode {
-    node: AudioScheduledSourceNode,
-    //    buffer: Option<DomRoot<AudioBuffer>>,
+    source_node: AudioScheduledSourceNode,
+    buffer: MutNullableDom<AudioBuffer>,
     playback_rate: DomRoot<AudioParam>,
     detune: DomRoot<AudioParam>,
     loop_enabled: Cell<bool>,
@@ -54,28 +56,29 @@ impl AudioBufferSourceNode {
         node_options.channelCount = Some(2);
         node_options.channelCountMode = Some(ChannelCountMode::Max);
         node_options.channelInterpretation = Some(ChannelInterpretation::Speakers);
-        let node = AudioScheduledSourceNode::new_inherited(
+        let source_node = AudioScheduledSourceNode::new_inherited(
             AudioNodeType::AudioBufferSourceNode(options.into()),
             context,
             &node_options,
             0 /* inputs */,
             1 /* outputs */,
             );
-        let playback_rate = PlaybackRate::new(context.audio_context_impl(), node.node_id());
+        let node_id = source_node.node().node_id();
+        let playback_rate = PlaybackRate::new(context.audio_context_impl(), node_id);
         let playback_rate = AudioParam::new(&window,
                                             Box::new(playback_rate),
                                             AutomationRate::K_rate,
                                             *options.playbackRate,
                                             f32::MIN, f32::MAX);
-        let detune = Detune::new(context.audio_context_impl(), node.node_id());
+        let detune = Detune::new(context.audio_context_impl(), node_id);
         let detune = AudioParam::new(&window,
                                      Box::new(detune),
                                      AutomationRate::K_rate,
                                      *options.detune,
                                      f32::MIN, f32::MAX);
         AudioBufferSourceNode {
-            node,
-            // buffer: options.buffer,
+            source_node,
+            buffer: Default::default(),
             playback_rate,
             detune,
             loop_enabled: Cell::new(options.loop_),
@@ -104,6 +107,31 @@ impl AudioBufferSourceNode {
 }
 
 impl AudioBufferSourceNodeMethods for AudioBufferSourceNode {
+    /// https://webaudio.github.io/web-audio-api/#dom-audiobuffersourcenode-buffer
+    fn GetBuffer(&self) -> Fallible<Option<DomRoot<AudioBuffer>>> {
+        Ok(self.buffer.get())
+    }
+
+    /// https://webaudio.github.io/web-audio-api/#dom-audiobuffersourcenode-buffer
+    fn SetBuffer(&self, new_buffer: Option<&AudioBuffer>) -> Fallible<()> {
+        if new_buffer.is_some() && self.buffer.get().is_some() {
+            return Err(Error::InvalidState);
+        }
+
+        self.buffer.set(new_buffer);
+
+        if self.source_node.started() {
+            if let Some(buffer) = self.buffer.get() {
+                let buffer = buffer.acquire_contents();
+                self.source_node.node().message(
+                    AudioNodeMessage::AudioBufferSourceNode(
+                        AudioBufferSourceNodeMessage::SetBuffer(buffer)));
+            }
+        }
+
+        Ok(())
+    }
+
     fn PlaybackRate(&self) -> DomRoot<AudioParam> {
         DomRoot::from_ref(&self.playback_rate)
     }
@@ -136,8 +164,17 @@ impl AudioBufferSourceNodeMethods for AudioBufferSourceNode {
         self.loop_end.set(*loop_end)
     }
 
-    fn Start(&self, when: Finite<f64>, offset: Option<Finite<f64>>, duration: Option<Finite<f64>>) {
-        // XXX
+    fn Start(&self,
+             when: Finite<f64>,
+             _offset: Option<Finite<f64>>,
+             _duration: Option<Finite<f64>>) -> Fallible<()> {
+        if let Some(buffer) = self.buffer.get() {
+            let buffer = buffer.acquire_contents();
+            self.source_node.node().message(
+                AudioNodeMessage::AudioBufferSourceNode(
+                    AudioBufferSourceNodeMessage::SetBuffer(buffer)));
+        }
+        self.source_node.upcast::<AudioScheduledSourceNode>().Start(when)
     }
 }
 
diff --git a/components/script/dom/audioscheduledsourcenode.rs b/components/script/dom/audioscheduledsourcenode.rs
index 8c8240fdf67..da284e02910 100644
--- a/components/script/dom/audioscheduledsourcenode.rs
+++ b/components/script/dom/audioscheduledsourcenode.rs
@@ -5,14 +5,17 @@ use dom::audionode::AudioNode;
 use dom::baseaudiocontext::BaseAudioContext;
 use dom::bindings::codegen::Bindings::AudioScheduledSourceNodeBinding::AudioScheduledSourceNodeMethods;
 use dom::bindings::codegen::Bindings::AudioNodeBinding::AudioNodeOptions;
+use dom::bindings::error::{Error, Fallible};
 use dom::bindings::num::Finite;
 use dom_struct::dom_struct;
-use servo_media::audio::graph::NodeId;
 use servo_media::audio::node::{AudioNodeMessage, AudioNodeType, AudioScheduledSourceNodeMessage};
+use std::cell::Cell;
 
 #[dom_struct]
 pub struct AudioScheduledSourceNode {
     node: AudioNode,
+    started: Cell<bool>,
+    stopped: Cell<bool>,
 }
 
 impl AudioScheduledSourceNode {
@@ -24,11 +27,17 @@ impl AudioScheduledSourceNode {
         AudioScheduledSourceNode {
             node: AudioNode::new_inherited(node_type, None /* node_id */,
                                            context, options, number_of_inputs, number_of_outputs),
+                                           started: Cell::new(false),
+                                           stopped: Cell::new(false),
         }
     }
 
-    pub fn node_id(&self) -> NodeId {
-        self.node.node_id()
+    pub fn node(&self) -> &AudioNode {
+        &self.node
+    }
+
+    pub fn started(&self) -> bool {
+        self.started.get()
     }
 }
 
@@ -37,16 +46,26 @@ impl AudioScheduledSourceNodeMethods for AudioScheduledSourceNode {
     event_handler!(ended, GetOnended, SetOnended);
 
     // https://webaudio.github.io/web-audio-api/#dom-audioscheduledsourcenode-start
-    fn Start(&self, when: Finite<f64>) {
+    fn Start(&self, when: Finite<f64>) -> Fallible<()> {
+        if self.started.get() || self.stopped.get() {
+            return Err(Error::InvalidState);
+        }
+        self.started.set(true);
         self.node.message(
             AudioNodeMessage::AudioScheduledSourceNode(AudioScheduledSourceNodeMessage::Start(*when))
             );
+        Ok(())
     }
 
     // https://webaudio.github.io/web-audio-api/#dom-audioscheduledsourcenode-stop
-    fn Stop(&self, when: Finite<f64>) {
+    fn Stop(&self, when: Finite<f64>) -> Fallible<()> {
+        if !self.started.get() {
+            return Err(Error::InvalidState);
+        }
+        self.stopped.set(true);
         self.node.message(
             AudioNodeMessage::AudioScheduledSourceNode(AudioScheduledSourceNodeMessage::Stop(*when))
             );
+        Ok(())
     }
 }
diff --git a/components/script/dom/baseaudiocontext.rs b/components/script/dom/baseaudiocontext.rs
index 401da6bc4d3..59247516659 100644
--- a/components/script/dom/baseaudiocontext.rs
+++ b/components/script/dom/baseaudiocontext.rs
@@ -3,15 +3,18 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 use dom::audiobuffer::AudioBuffer;
+use dom::audiobuffersourcenode::AudioBufferSourceNode;
 use dom::audiodestinationnode::AudioDestinationNode;
+use dom::audionode::MAX_CHANNEL_COUNT;
 use dom::bindings::cell::DomRefCell;
+use dom::bindings::codegen::Bindings::AudioBufferSourceNodeBinding::AudioBufferSourceOptions;
 use dom::bindings::codegen::Bindings::AudioNodeBinding::AudioNodeOptions;
 use dom::bindings::codegen::Bindings::AudioNodeBinding::{ChannelCountMode, ChannelInterpretation};
 use dom::bindings::codegen::Bindings::BaseAudioContextBinding::BaseAudioContextMethods;
 use dom::bindings::codegen::Bindings::BaseAudioContextBinding::AudioContextState;
 use dom::bindings::codegen::Bindings::GainNodeBinding::GainOptions;
 use dom::bindings::codegen::Bindings::OscillatorNodeBinding::OscillatorOptions;
-use dom::bindings::error::{Error, ErrorResult};
+use dom::bindings::error::{Error, ErrorResult, Fallible};
 use dom::bindings::inheritance::Castable;
 use dom::bindings::num::Finite;
 use dom::bindings::refcounted::Trusted;
@@ -207,23 +210,23 @@ impl BaseAudioContext {
 }
 
 impl BaseAudioContextMethods for BaseAudioContext {
-    // https://webaudio.github.io/web-audio-api/#dom-baseaudiocontext-samplerate
+    /// https://webaudio.github.io/web-audio-api/#dom-baseaudiocontext-samplerate
     fn SampleRate(&self) -> Finite<f32> {
         Finite::wrap(self.sample_rate)
     }
 
-    // https://webaudio.github.io/web-audio-api/#dom-baseaudiocontext-currenttime
+    /// https://webaudio.github.io/web-audio-api/#dom-baseaudiocontext-currenttime
     fn CurrentTime(&self) -> Finite<f64> {
         let current_time = self.audio_context_impl.current_time();
         Finite::wrap(current_time)
     }
 
-    // https://webaudio.github.io/web-audio-api/#dom-baseaudiocontext-state
+    /// https://webaudio.github.io/web-audio-api/#dom-baseaudiocontext-state
     fn State(&self) -> AudioContextState {
         self.state.get()
     }
 
-    // https://webaudio.github.io/web-audio-api/#dom-baseaudiocontext-resume
+    /// https://webaudio.github.io/web-audio-api/#dom-baseaudiocontext-resume
     #[allow(unrooted_must_root)]
     fn Resume(&self) -> Rc<Promise> {
         // Step 1.
@@ -255,14 +258,15 @@ impl BaseAudioContextMethods for BaseAudioContext {
         promise
     }
 
-    // https://webaudio.github.io/web-audio-api/#dom-baseaudiocontext-destination
+    /// https://webaudio.github.io/web-audio-api/#dom-baseaudiocontext-destination
     fn Destination(&self) -> DomRoot<AudioDestinationNode> {
         DomRoot::from_ref(self.destination.as_ref().unwrap())
     }
 
-    // https://webaudio.github.io/web-audio-api/#dom-baseaudiocontext-onstatechange
+    /// https://webaudio.github.io/web-audio-api/#dom-baseaudiocontext-onstatechange
     event_handler!(statechange, GetOnstatechange, SetOnstatechange);
 
+    /// https://webaudio.github.io/web-audio-api/#dom-baseaudiocontext-createoscillator
     #[allow(unsafe_code)]
     fn CreateOscillator(&self) -> DomRoot<OscillatorNode> {
         let global = self.global();
@@ -271,6 +275,7 @@ impl BaseAudioContextMethods for BaseAudioContext {
         OscillatorNode::new(&window, &self, &options)
     }
 
+    /// https://webaudio.github.io/web-audio-api/#dom-baseaudiocontext-creategain
     #[allow(unsafe_code)]
     fn CreateGain(&self) -> DomRoot<GainNode> {
         let global = self.global();
@@ -279,12 +284,27 @@ impl BaseAudioContextMethods for BaseAudioContext {
         GainNode::new(&window, &self, &options)
     }
 
+    /// https://webaudio.github.io/web-audio-api/#dom-baseaudiocontext-createbuffer
     fn CreateBuffer(&self,
                     number_of_channels: u32,
                     length: u32,
-                    sample_rate: Finite<f32>) -> DomRoot<AudioBuffer> {
+                    sample_rate: Finite<f32>) -> Fallible<DomRoot<AudioBuffer>> {
+        if number_of_channels <= 0 ||
+           number_of_channels > MAX_CHANNEL_COUNT ||
+           length <= 0 ||
+           *sample_rate <= 0. {
+            return Err(Error::NotSupported);
+        }
+        let global = self.global();
+        Ok(AudioBuffer::new(&global.as_window(), number_of_channels, length, *sample_rate))
+    }
+
+    #[allow(unsafe_code)]
+    fn CreateBufferSource(&self) -> DomRoot<AudioBufferSourceNode> {
         let global = self.global();
-        AudioBuffer::new(&global.as_window(), number_of_channels, length, *sample_rate)
+        // XXX Can we do this implementing Default?
+        let options = unsafe { AudioBufferSourceOptions::empty(global.get_cx()) };
+        AudioBufferSourceNode::new(&global.as_window(), &self, &options)
     }
 }
 
diff --git a/components/script/dom/bindings/trace.rs b/components/script/dom/bindings/trace.rs
index b84651c8c8a..7a9d4d7358f 100644
--- a/components/script/dom/bindings/trace.rs
+++ b/components/script/dom/bindings/trace.rs
@@ -80,6 +80,7 @@ use offscreen_gl_context::GLLimits;
 use parking_lot::RwLock;
 use profile_traits::mem::ProfilerChan as MemProfilerChan;
 use profile_traits::time::ProfilerChan as TimeProfilerChan;
+use servo_media::audio::buffer_source_node::AudioBuffer;
 use servo_media::audio::context::AudioContext;
 use servo_media::audio::graph::NodeId;
 use script_layout_interface::OpaqueStyleAndLayoutData;
@@ -432,6 +433,7 @@ unsafe_no_jsmanaged_fields!(InteractiveWindow);
 unsafe_no_jsmanaged_fields!(CanvasId);
 unsafe_no_jsmanaged_fields!(SourceSet);
 unsafe_no_jsmanaged_fields!(AudioGraph);
+unsafe_no_jsmanaged_fields!(AudioBuffer);
 unsafe_no_jsmanaged_fields!(AudioContext);
 unsafe_no_jsmanaged_fields!(NodeId);
 
diff --git a/components/script/dom/oscillatornode.rs b/components/script/dom/oscillatornode.rs
index 7a771916834..71580e20e17 100644
--- a/components/script/dom/oscillatornode.rs
+++ b/components/script/dom/oscillatornode.rs
@@ -30,7 +30,7 @@ audio_param_impl!(Detune, OscillatorNode, OscillatorNodeMessage, SetDetune);
 
 #[dom_struct]
 pub struct OscillatorNode {
-    node: AudioScheduledSourceNode,
+    source_node: AudioScheduledSourceNode,
     oscillator_type: OscillatorType,
     frequency: DomRoot<AudioParam>,
     detune: DomRoot<AudioParam>,
@@ -48,26 +48,27 @@ impl OscillatorNode {
         node_options.channelCount = Some(2);
         node_options.channelCountMode = Some(ChannelCountMode::Max);
         node_options.channelInterpretation = Some(ChannelInterpretation::Speakers);
-        let node = AudioScheduledSourceNode::new_inherited(
+        let source_node = AudioScheduledSourceNode::new_inherited(
             AudioNodeType::OscillatorNode(oscillator_options.into()),
             context,
             &node_options,
             0, /* inputs */
             1, /* outputs */
             );
-        let frequency = Frequency::new(context.audio_context_impl(), node.node_id());
+        let node_id = source_node.node().node_id();
+        let frequency = Frequency::new(context.audio_context_impl(), node_id);
         let frequency = AudioParam::new(window,
                                         Box::new(frequency),
                                         AutomationRate::A_rate,
                                         440., f32::MIN, f32::MAX);
-        let detune = Detune::new(context.audio_context_impl(), node.node_id());
+        let detune = Detune::new(context.audio_context_impl(), node_id);
         let detune = AudioParam::new(window,
                                      Box::new(detune),
                                      AutomationRate::A_rate,
                                      0., -440. / 2., 440. / 2.);
 
         OscillatorNode {
-            node,
+            source_node,
             oscillator_type: oscillator_options.type_,
             frequency,
             detune,
diff --git a/components/script/dom/webidls/AudioBufferSourceNode.webidl b/components/script/dom/webidls/AudioBufferSourceNode.webidl
index 45358fbaad8..a91a6afc393 100644
--- a/components/script/dom/webidls/AudioBufferSourceNode.webidl
+++ b/components/script/dom/webidls/AudioBufferSourceNode.webidl
@@ -18,13 +18,13 @@ dictionary AudioBufferSourceOptions {
 [Exposed=Window,
  Constructor (BaseAudioContext context, optional AudioBufferSourceOptions options)]
 interface AudioBufferSourceNode : AudioScheduledSourceNode {
-  // attribute AudioBuffer? buffer;
+  [Throws] attribute AudioBuffer? buffer;
   readonly attribute AudioParam playbackRate;
   readonly attribute AudioParam detune;
   attribute boolean loop;
   attribute double loopStart;
   attribute double loopEnd;
-  void start(optional double when = 0,
-             optional double offset,
-             optional double duration);
+  [Throws] void start(optional double when = 0,
+                      optional double offset,
+                      optional double duration);
 };
diff --git a/components/script/dom/webidls/AudioScheduledSourceNode.webidl b/components/script/dom/webidls/AudioScheduledSourceNode.webidl
index 8e058b129cc..a1ca3fc8a8c 100644
--- a/components/script/dom/webidls/AudioScheduledSourceNode.webidl
+++ b/components/script/dom/webidls/AudioScheduledSourceNode.webidl
@@ -9,6 +9,6 @@
 [Exposed=Window]
 interface AudioScheduledSourceNode : AudioNode {
   attribute EventHandler onended;
-  void start(optional double when = 0);
-  void stop(optional double when = 0);
+  [Throws] void start(optional double when = 0);
+  [Throws] void stop(optional double when = 0);
 };
diff --git a/components/script/dom/webidls/BaseAudioContext.webidl b/components/script/dom/webidls/BaseAudioContext.webidl
index 92564b29a5f..9147ca5ed58 100644
--- a/components/script/dom/webidls/BaseAudioContext.webidl
+++ b/components/script/dom/webidls/BaseAudioContext.webidl
@@ -24,13 +24,13 @@ interface BaseAudioContext : EventTarget {
   readonly attribute AudioContextState  state;
   Promise<void> resume();
   attribute EventHandler onstatechange;
-  AudioBuffer createBuffer(unsigned long numberOfChannels,
-                           unsigned long length,
-                           float sampleRate);
+  [Throws] AudioBuffer createBuffer(unsigned long numberOfChannels,
+                                    unsigned long length,
+                                    float sampleRate);
   // Promise<AudioBuffer> decodeAudioData(ArrayBuffer audioData,
   //                                      optional DecodeSuccessCallback successCallback,
   //                                      optional DecodeErrorCallback errorCallback);
-  // AudioBufferSourceNode createBufferSource();
+  AudioBufferSourceNode createBufferSource();
   // ConstantSourceNode createConstantSource();
   // ScriptProcessorNode createScriptProcessor(optional unsigned long bufferSize = 0,
   //                                           optional unsigned long numberOfInputChannels = 2,