Implement audiounit_get_current_channel_layout

README.md

@@ -59,9 +59,9 @@ By applying the [patch][integrate-with-cubeb] to integrate within [Cubeb][cubeb]
 
 ### Interanl APIs
 
-- 🥚 : 8/75 (10.6%)
+- 🥚 : 7/75 (9.3%)
 - 🐣 : 7/75 (9.3%)
-- 🐥 : 60/75 (80%)
+- 🐥 : 61/75 (81.3%)
 
 | Interanl AudioUnit APIs                     | status |
 | ------------------------------------------- | ------ |
@@ -96,7 +96,7 @@ By applying the [patch][integrate-with-cubeb] to integrate within [Cubeb][cubeb]
 | audiounit_get_default_device_id             | 🐥      |
 | audiounit_convert_channel_layout            | 🐥      |
 | audiounit_get_preferred_channel_layout      | 🥚      |
-| audiounit_get_current_channel_layout        | 🥚      |
+| audiounit_get_current_channel_layout        | 🐥      |
 | audiounit_destroy                           | 🥚      |
 | audio_stream_desc_init                      | 🐥      |
 | audiounit_init_mixer                        | 🥚      |

src/backend/auto_release.rs

@@ -21,6 +21,10 @@ impl<T> AutoRelease<T> {
         self.ptr = ptr;
     }
 
+    pub fn as_ref(&self) -> &T {
+        unsafe { &*self.ptr }
+    }
+
     pub fn as_mut_ptr(&self) -> *mut T {
         self.ptr
     }

src/backend/mod.rs

@@ -1049,6 +1049,39 @@ fn audiounit_convert_channel_layout(layout: &AudioChannelLayout) -> ChannelLayou
     return cl;
 }
 
+fn audiounit_get_current_channel_layout(output_unit: AudioUnit) -> ChannelLayout
+{
+    let mut rv = NO_ERR;
+    let mut size: usize = 0;
+
+    rv = audio_unit_get_property_info(output_unit,
+                                      kAudioUnitProperty_AudioChannelLayout,
+                                      kAudioUnitScope_Output,
+                                      AU_OUT_BUS,
+                                      &mut size,
+                                      ptr::null_mut());
+    if rv != NO_ERR {
+        cubeb_log!("AudioUnitGetPropertyInfo/kAudioUnitProperty_AudioChannelLayout rv={}", rv);
+        // TODO: This property isn't known before macOS 10.12, attempt another method.
+        return ChannelLayout::UNDEFINED;
+    }
+    assert!(size > 0);
+
+    let layout = make_sized_audio_channel_layout(size);
+    rv = audio_unit_get_property(output_unit,
+                                 kAudioUnitProperty_AudioChannelLayout,
+                                 kAudioUnitScope_Output,
+                                 AU_OUT_BUS,
+                                 layout.as_mut_ptr(),
+                                 &mut size);
+    if rv != NO_ERR {
+        cubeb_log!("AudioUnitGetProperty/kAudioUnitProperty_AudioChannelLayout rv={}", rv);
+        return ChannelLayout::UNDEFINED;
+    }
+
+    audiounit_convert_channel_layout(layout.as_ref())
+}
+
 fn audio_stream_desc_init(ss: &mut AudioStreamBasicDescription,
                           stream_params: &StreamParams) -> Result<()>
 {

src/backend/test.rs

@@ -2213,6 +2213,45 @@ fn test_convert_channel_layout() {
     }
 }
 
+// get_current_channel_layout
+// ------------------------------------
+// TODO: Should it be prevented ? The AudioUnitElement is for output only.
+//       It should be called for the input side.
+// #[test]
+// fn test_get_current_channel_layout_input() {
+//     // Initialize the unit to the default input device.
+//     let default_input_id = audiounit_get_default_device_id(DeviceType::INPUT);
+//     if !valid_id(default_input_id) {
+//         return;
+//     }
+//     let mut unit: AudioUnit = ptr::null_mut();
+//     let device = device_info {
+//         id: default_input_id,
+//         flags: device_flags::DEV_INPUT | device_flags::DEV_SYSTEM_DEFAULT
+//     };
+
+//     assert!(audiounit_create_unit(&mut unit, &device).is_ok());
+//     assert!(!unit.is_null());
+//     assert_eq!(audiounit_get_current_channel_layout(unit), ChannelLayout::UNDEFINED);
+// }
+
+#[test]
+fn test_get_current_channel_layout_output() {
+    // Initialize the unit to default output device.
+    let default_output_id = audiounit_get_default_device_id(DeviceType::OUTPUT);
+    if !valid_id(default_output_id) {
+        return;
+    }
+    let mut unit: AudioUnit = ptr::null_mut();
+    let device = device_info {
+        id: default_output_id,
+        flags: device_flags::DEV_OUTPUT | device_flags::DEV_SYSTEM_DEFAULT
+    };
+    assert!(audiounit_create_unit(&mut unit, &device).is_ok());
+    assert!(!unit.is_null());
+    assert_ne!(audiounit_get_current_channel_layout(unit), ChannelLayout::UNDEFINED);
+}
+
 // audio_stream_desc_init
 // ------------------------------------
 #[test]

src/backend/utils.rs

@@ -189,6 +189,27 @@ pub fn audio_object_remove_property_listener(
     }
 }
 
+pub fn audio_unit_get_property_info(
+    unit: sys::AudioUnit,
+    property: sys::AudioUnitPropertyID,
+    scope: sys::AudioUnitScope,
+    element: sys::AudioUnitElement,
+    size: *mut usize,
+    writable: *mut sys::Boolean
+) -> sys::OSStatus {
+    assert!(!unit.is_null());
+    unsafe {
+        sys::AudioUnitGetPropertyInfo(
+            unit,
+            property,
+            scope,
+            element,
+            size as *mut sys::UInt32,
+            writable
+        )
+    }
+}
+
 pub fn audio_unit_get_property<T>(
     unit: sys::AudioUnit,
     property: sys::AudioUnitPropertyID,