#include <alsa/asoundlib.h>

 #include <math.h>

 #include <inttypes.h>

 int main(int argc, char **argv)

 {

     long loops;

     snd_pcm_t *handle;

     snd_pcm_hw_params_t *params;

     snd_pcm_uframes_t frames;

     unsigned int val;

     int rc;

     int size;

     int dir;

     char *buffer;

     /* Open PCM device for playback. */

     rc = snd_pcm_open(&handle, "default", SND_PCM_STREAM_PLAYBACK, );

     if (rc < ) {

         fprintf(stderr, "unable to open pcm device: %s\n", snd_strerror(rc));

         exit();

     }

     /* Allocate a hardware parameters object. */

     snd_pcm_hw_params_alloca(&params);

     /* Fill it in with default values. */

     snd_pcm_hw_params_any(handle, params);

     /* Interleaved mode */

     snd_pcm_hw_params_set_access(handle, params, SND_PCM_ACCESS_RW_INTERLEAVED);

     /* Signed 16-bit format */

     snd_pcm_hw_params_set_format(handle, params, SND_PCM_FORMAT_S16);

     /* Two channels (stereo) */

     snd_pcm_hw_params_set_channels(handle, params, );

     /* 16000 samples/second sampling rate */

     val = ;

     snd_pcm_hw_params_set_rate_near(handle, params, &val, &dir);

     /* Set period size to 32 frames. */

     frames = ;

     snd_pcm_hw_params_set_period_size_near(handle, params, &frames, &dir);

     /* Write the parameters to the driver */

     rc = snd_pcm_hw_params(handle, params);

     if (rc < ) {

         fprintf(stderr, "unable to set hw parameters: %s\n", snd_strerror(rc));

         exit();

     }

     /* Use a buffer large enough to hold one period */

     snd_pcm_hw_params_get_period_size(params, &frames, &dir);

     size = frames *  * ; /* 2 bytes/sample, 2 channels */

     buffer = (char *) malloc(size);

     if(buffer == NULL) {

         fprintf(stderr, "Not enough Memory!\n");

         exit();

     }

     /* We want to loop for 15 seconds */

     snd_pcm_hw_params_get_period_time(params, &val, &dir);

     /* 15 seconds in microseconds divided by period time */

     loops =  / val;

     for (size_t i = ; i < size; i += ) {

         // Generate a 500Hz tone

         *((int16_t *)(buffer + i)) = (uint16_t)(16384.0*sin(i*2.0*M_PI/size));

         *((int16_t *)(buffer + i + )) = (uint16_t)(16384.0*sin(i*2.0*M_PI/size));

         // Generate a 2kHz tone

         *((int16_t *)(buffer + i)) += (uint16_t)(16384.0*sin(i*8.0*M_PI/size));

         *((int16_t *)(buffer + i + )) += (uint16_t)(16384.0*sin(i*8.0*M_PI/size));

     }

     while (loops > ) {

         loops--;

         //rc = read(0, buffer, size);

         //if (rc == 0) {

         //    fprintf(stderr, "end of file on input\n");

         //    break;

         //} else if (rc != size) {

         //    fprintf(stderr, "short read: read %d bytes\n", rc);

         //}

         rc = snd_pcm_writei(handle, buffer, frames);

         if (rc == -EPIPE) {

             /* EPIPE means underrun */

             fprintf(stderr, "underrun occurred\n");

             snd_pcm_prepare(handle);

         } else if (rc < ) {

             fprintf(stderr,"error from writei: %s\n", snd_strerror(rc));

         } else if (rc != (int)frames) {

             fprintf(stderr,"short write, write %d frames\n", rc);

         }

     }

     snd_pcm_drop(handle);

     snd_pcm_drain(handle);

     snd_pcm_close(handle);

     free(buffer);

     return ;

 }