f32 stereo voice callback example

unsigned currentSample=0;
void user_callback(void* userdata, void* _stream, int size, SDL_bool hasInput){
  if(userdata == NULL){ exit_early: memset(_stream,0,size); return; }

  kit_acodecPCM* pcm = userdata;
  Uint64 numSamples = pcm->numSamples;
  kit_acodecPCM_F32S* src = pcm->f32s;

  if(pcm->format != AUDIO_F32) goto exit_early;
  if(pcm->channels != 2) goto exit_early;
  if(currentSample >= numSamples) goto exit_early;

  memset(_stream,0,size);
  kit_acodecPCM_F32S* dst=_stream; int len=size/(2*4);
  for(int i=0; i<len; ++i){
    dst[i] = src[currentSample];
    dst[i].l *= 0.7;
    dst[i].r *= 0.7;
    if((++currentSample)>=numSamples){ currentSample=-1; break; }
  }
}