#include <SDL2/SDL.h>
#include <math.h>

#define PI 3.14159265358979323846
#define BufferSizeInSamples 2048
#define BytesPerSample 2   // 16 bit PCM
#define BufferSizeInBytes (BufferSizeInSamples * BytesPerSample)
#define SampleRate 44100   // Hz
#define Frequence 1000     // Hz
#define Volume 0.1         // 0..1
#define x (Frequence * 2000 / SampleRate)

int counter = 0;

void audioCallback(void *userdata, Uint8 *stream, int len) {
	short buffer[BufferSizeInSamples];
	int i;
	for(i = 0; i < BufferSizeInSamples; i++)
		buffer[i] = (short)(sin((float)((counter + i) % x) / x * 2 * PI) * 32767);
	SDL_MixAudio(stream, (const Uint8 *)buffer, BufferSizeInBytes, SDL_MIX_MAXVOLUME * Volume);
	counter = counter + BufferSizeInSamples;
}

int main(int argc, char* argv[]) {
	if(SDL_Init(SDL_INIT_AUDIO) < 0) {
		printf("Init() failed");
		return -1;
	}
	SDL_AudioSpec audioSpec;
	audioSpec.freq = SampleRate;
	audioSpec.format = AUDIO_S16;
	audioSpec.channels = 1;
	audioSpec.samples = BufferSizeInBytes;
	audioSpec.callback = audioCallback;
	audioSpec.userdata = NULL;
	if(SDL_OpenAudio(&audioSpec, NULL) < 0 ) {
		printf("OpenAudio() failed");
		return -1;
	}
	SDL_PauseAudio(0);
	// run program for 2 seconds
	int t = 2000;
	while(t > 0) {
		SDL_Delay(100);
		t = t - 100;
	}
}