From c347629c8d7dc30dc2dd22c37c3b712a36250cce Mon Sep 17 00:00:00 2001
From: Andrew Kelley <superjoe30@gmail.com>
Date: Mon, 3 Aug 2015 15:14:41 -0700
Subject: [PATCH] CoreAudio: obtain device buffer duration

---
 soundio/soundio.h |  4 ++--
 src/coreaudio.cpp | 36 +++++++++++++++++++++++++++++-------
 2 files changed, 31 insertions(+), 9 deletions(-)

diff --git a/soundio/soundio.h b/soundio/soundio.h
index cdfcac7..bdfe3be 100644
--- a/soundio/soundio.h
+++ b/soundio/soundio.h
@@ -353,8 +353,8 @@ struct SoundIoDevice {
 
     // Period duration in seconds. After this much time passes, write_callback
     // is called. If values are unknown, they are set to 0.0. These values are
-    // meaningless for PulseAudio. For JACK, buffer duration and period duration
-    // are the same.
+    // meaningless for PulseAudio and CoreAudio. For JACK, buffer duration and
+    // period duration are the same.
     double period_duration_min;
     double period_duration_max;
     double period_duration_current;
diff --git a/src/coreaudio.cpp b/src/coreaudio.cpp
index a31f1ef..52b4b94 100644
--- a/src/coreaudio.cpp
+++ b/src/coreaudio.cpp
@@ -112,13 +112,6 @@ static int aim_to_scope(SoundIoDeviceAim aim) {
                         clients should re-evaluate everything they need to know about the device,
                         particularly the layout and values of the controls.
 */
-/*
-    @constant       kAudioDevicePropertyBufferFrameSize
-                        A UInt32 whose value indicates the number of frames in the IO buffers.
-    @constant       kAudioDevicePropertyBufferFrameSizeRange
-                        An AudioValueRange indicating the minimum and maximum values, inclusive, for
-                        kAudioDevicePropertyBufferFrameSize.
-*/
 /*
     @constant       kAudioDevicePropertyLatency
                         A UInt32 containing the number of frames of latency in the AudioDevice. Note
@@ -577,6 +570,35 @@ static int refresh_devices(struct SoundIoPrivate *si) {
             rd.device->sample_rate_min = avr.mMinimum;
             rd.device->sample_rate_max = avr.mMaximum;
 
+            prop_address.mSelector = kAudioDevicePropertyBufferFrameSize;
+            prop_address.mScope = aim_to_scope(aim);
+            prop_address.mElement = kAudioObjectPropertyElementMaster;
+            io_size = sizeof(UInt32);
+            UInt32 buffer_frame_size;
+            if ((os_err = AudioObjectGetPropertyData(deviceID, &prop_address, 0, nullptr,
+                &io_size, &buffer_frame_size)))
+            {
+                deinit_refresh_devices(&rd);
+                return SoundIoErrorOpeningDevice;
+            }
+            double use_sample_rate = clamp(rd.device->sample_rate_min, rd.device->sample_rate_current,
+                rd.device->sample_rate_max);
+            rd.device->buffer_duration_current = buffer_frame_size / use_sample_rate;
+
+            prop_address.mSelector = kAudioDevicePropertyBufferFrameSizeRange;
+            prop_address.mScope = aim_to_scope(aim);
+            prop_address.mElement = kAudioObjectPropertyElementMaster;
+            io_size = sizeof(AudioValueRange);
+            if ((os_err = AudioObjectGetPropertyData(deviceID, &prop_address, 0, nullptr,
+                &io_size, &avr)))
+            {
+                deinit_refresh_devices(&rd);
+                return SoundIoErrorOpeningDevice;
+            }
+            rd.device->buffer_duration_min = avr.mMinimum / use_sample_rate;
+            rd.device->buffer_duration_max = avr.mMaximum / use_sample_rate;
+
+
 
             SoundIoList<SoundIoDevice *> *device_list;
             if (rd.device->aim == SoundIoDeviceAimOutput) {