static void SDLAudioCallBack(void* userData, uint8_t* stream, int len) {
    int16_t* currSample = (int16_t*)stream;
    uint32_t tone = 256;
    uint32_t period = 48000 / tone;
    uint32_t halfPeriod = period / 2;

    for (size_t i = 0; i < (len / sizeof(*currSample)); i+=2) {
        
        int16_t halfSample = ((i / halfPeriod) % 2) ? 1 : -1;
        
        currSample[i] = halfSample * 3000; //left channel 
        currSample[i+1] = halfSample * 3000; //right channel
    }

}

 SDL_AudioSpec desiredAudio = {};
    desiredAudio.channels = 2;
    desiredAudio.samples = 4096;
    desiredAudio.freq = SOUND_FREQ;
    desiredAudio.format = AUDIO_S16LSB;
    desiredAudio.callback = SDLAudioCallBack;

    if (SDL_OpenAudio(&desiredAudio, NULL) < 0) {
        printSDLErrorAndExit();
    }

static inline uint64_t
__rdtsc(void)
{
	uint32_t eax = 0, edx;

	__asm__ __volatile__("cpuid;"
			     "rdtsc;"
				: "+a" (eax), "=d" (edx)
				:
				: "%rcx", "%rbx", "memory");

	__asm__ __volatile__("xorl %%eax, %%eax;"
			     "cpuid;"
				:
				:
				: "%rax", "%rbx", "%rcx", "%rdx", "memory");

	return (((uint64_t)edx << 32) | eax);
}