I am trying to provide a callback function that can be invoked when an audio processor has completed. I initially went down the route of doing:

  let complete = false;
  const callbackPtr = module.addFunction(() => {
    complete = true;
  }, 'v');
  
  ...

  const ptr = module._malloc(lpc.length);
  const copy = new Uint8Array(module.HEAPU8.buffer, ptr, lpc.length);
  copy.set(lpc);
  speak(ptr, lpc.length, callbackPtr);
  module._free(ptr);

However, I was getting table index is out of bounds despite having -sALLOW_MEMORY_GROWTH=1 -sALLOW_TABLE_GROWTH=1 options… And then I realized, this is happening because the function pointer is getting executed in the audio thread and does not exist there…

So, then I thought perhaps I need to do this with postMessage, so I was going to try to do:

EM_BOOL AudioCallback(int numInputs, const AudioSampleFrame *inputs,
                      int numOutputs, AudioSampleFrame *outputs,
                      int numParams, const AudioParamFrame *params,
                      void *userData) {


  SampleStreamable *sampleStreamable = static_cast<SampleStreamable *>(userData);
  int frames = 128;

  for (int i = 0; i < numOutputs; i++) {
    sampleStreamable->process(outputs[i].data, frames*outputs[i].numberOfChannels);
  }

  EM_ASM({
    if ($0) {
      postMessage('audio-processing-complete');
    }
  }, sampleStreamable->isComplete)

  return EM_TRUE;
}

However, that results in postMessage is not defined.

How can I properly execute a callback on the main thread?