#include "SDL/SDL.h"
#include "math.h"

#define BUFFER_SIZE 1024    // Longitud del buffer, en samples
#define SAMPLING_RATE 44100

// Este comentario esta extraido de SDL_audio.h, porque me ha molado
/* This function is called when the audio device needs more data.
 * 'stream' is a pointer to the audio data buffer
 * 'len' is the length of that buffer in bytes.
 * Once the callback returns, the buffer will no longer be valid.
 * Stereo samples are stored in a LRLRLR ordering.
 */

void play_sen(void *userdata, Uint8 *stream, int len)
{
    int i;
    int num_samples = len / 2;
    static int pos = 0;
    float buffer[num_samples];

    Sint16 *dst_buf = (Sint16*) stream;
    for (i=0; i<num_samples ; ++i)
        buffer[i] = sin(2.0*M_PI*440.0f*(i+pos)/(float)SAMPLING_RATE);

    // Clipping y conversion a Sint16
    for (i=0; i<num_samples; ++i)
    {
        float v = buffer[i];
        if (v > 1.0f)
            v = 1.0f;
        else if (v< -1.0f)
            v = -1.0f;

        dst_buf[i] = (Sint16)(32767.0f*v);
    }
    pos += num_samples;
}

void play_whitenoise(void *userdata, Uint8 *stream, int len)
{
    int i;
    int num_samples = len / 2;
    Sint16 *buf = (Sint16*) stream;
    for (i = 0; i<num_samples ; ++i)
        buf[i] = rand()%65535-32768;
}

int main(int argc, char **argv)
{
    SDL_AudioSpec desired;
    desired.freq     = SAMPLING_RATE;// Frecuencia de muestreo
    desired.format   = AUDIO_S16SYS; // Formato de las muestras
    desired.channels = 1;            // Numero de canales
    desired.samples  = BUFFER_SIZE;  // Tamaño del buffer en samples
                                     // (potencia de 2)
    desired.callback = play_sen;     // Callback
    desired.userdata = NULL;         // Puntero a datos

    SDL_Init(SDL_INIT_AUDIO);
    SDL_OpenAudio(&desired, NULL);
    SDL_PauseAudio(0);
    getchar();
    SDL_PauseAudio(1);
    SDL_CloseAudio();
    SDL_Quit();
}