make it work (1s, 440Hz tone)

Makefile

@@ -1,6 +1,6 @@
 all: example
 
-example:
+example: *.h *.cc
 	clang++ -std=c++11 -stdlib=libc++ -Wl,-framework,CoreAudio -Wl,-framework,AudioUnit coreaudio_example.cc coreaudio_example_main.cc -o example
 
 clean:

coreaudio_example.cc

@@ -53,7 +53,7 @@ static struct CoreAudioFormatDescriptionMap format_map[] = {
     {FMT_S16_BE, 16, sizeof (int16_t), kAudioFormatFlagIsSignedInteger | kAudioFormatFlagIsBigEndian},
     {FMT_S32_LE, 32, sizeof (int32_t), kAudioFormatFlagIsSignedInteger},
     {FMT_S32_BE, 32, sizeof (int32_t), kAudioFormatFlagIsSignedInteger | kAudioFormatFlagIsBigEndian},
-    {FMT_FLOAT,  32, sizeof (float),   kAudioFormatFlagIsFloat},
+    {FMT_FLOAT,  32, sizeof (float),   kAudioFormatFlagsNativeFloatPacked | kAudioFormatFlagIsNonInterleaved},
 };
 
 /*
@@ -118,7 +118,7 @@ This gives you an output unit you can send data to using a callback. Now we
 should actually set up the unit for playback...
 */
 
-bool open_audio (int format, int rate, int chan, AURenderCallbackStruct * callback)
+bool open_audio (enum format_type format, int rate, int chan, AURenderCallbackStruct * callback)
 {
     struct CoreAudioFormatDescriptionMap * m = nullptr;
 

coreaudio_example_main.cc

@@ -1 +1,58 @@
-int main() { return 0; }
+#include "coreaudio_example.h"
+
+static double gtheta = 0;
+
+OSStatus tone(void *inRef, AudioUnitRenderActionFlags *ioActionFlags, const AudioTimeStamp *inTimeStamp, UInt32 inBusNumber, UInt32 inNumberFrames, AudioBufferList *ioData) {
+    // Fixed amplitude is good enough for our purposes
+    const double amplitude = 0.25;
+
+    // Get the tone parameters out of the static var
+    // could be stored in inRef
+    double theta = gtheta;
+    double theta_increment = 2.0 * M_PI * 440 / 44100;
+
+    // This is a mono tone generator so we only need the first buffer
+    const int channel = 0;
+    Float32 *buffer = (Float32 *)ioData->mBuffers[channel].mData;
+
+    // Generate the samples
+    for (UInt32 frame = 0; frame < inNumberFrames; frame++) 
+    {
+        buffer[frame] = sin(theta) * amplitude;
+
+        theta += theta_increment;
+        if (theta > 2.0 * M_PI)
+        {
+            theta -= 2.0 * M_PI;
+        }
+    }
+
+    printf("%f\n", theta);
+    gtheta = theta;
+
+    return noErr;
+}
+
+int main() {
+    coreaudio_example::init();
+
+    AURenderCallbackStruct callback;
+    callback.inputProc = tone;
+    callback.inputProcRefCon = nullptr; // could pass a struct to store state like theta
+
+    bool ok = coreaudio_example::open_audio(coreaudio_example::FMT_FLOAT, 44100, 1, &callback);
+    if (!ok) {
+        coreaudio_example::cleanup();
+        fprintf(stderr, "failed to open\n");
+        return 1;
+    }
+
+    coreaudio_example::set_volume(100);
+
+    // sleep 1s, rendering via callback happens in another thread
+    usleep(1000000);
+
+    coreaudio_example::close_audio();
+    coreaudio_example::cleanup();
+    return 0;
+}