/* ALSA test program based on pcsx-r ALSA plugin. */

/***************************************************************************
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version. See also the license.txt file for *
 *   additional informations.                                              *
 *                                                                         *
 ***************************************************************************/

#define ALSA_PCM_NEW_HW_PARAMS_API
#define ALSA_PCM_NEW_SW_PARAMS_API
#include <alsa/asoundlib.h>
#include <math.h>

static snd_pcm_t *handle = NULL;
static snd_pcm_uframes_t buffer_size;

// SETUP SOUND
void
SetupSound (void)
{
  snd_pcm_hw_params_t *hwparams;
  snd_pcm_status_t *status;
  unsigned int pspeed;
  int pchannels = 2;
  int format;
  int err;

  pspeed = 44100;
  format = SND_PCM_FORMAT_S16;

  if ((err = snd_pcm_open (&handle, "default",
			   SND_PCM_STREAM_PLAYBACK, SND_PCM_NONBLOCK)) < 0)
    {
      printf ("Audio open error: %s\n", snd_strerror (err));
      return;
    }

  if ((err = snd_pcm_nonblock (handle, 0)) < 0)
    {
      printf ("Can't set blocking moded: %s\n", snd_strerror (err));
      return;
    }

  snd_pcm_hw_params_alloca (&hwparams);

  if ((err = snd_pcm_hw_params_any (handle, hwparams)) < 0)
    {
      printf ("Broken configuration for this PCM: %s\n", snd_strerror (err));
      return;
    }

  if ((err =
       snd_pcm_hw_params_set_access (handle, hwparams,
				     SND_PCM_ACCESS_RW_INTERLEAVED)) < 0)
    {
      printf ("Access type not available: %s\n", snd_strerror (err));
      return;
    }

  if ((err = snd_pcm_hw_params_set_format (handle, hwparams, format)) < 0)
    {
      printf ("Sample format not available: %s\n", snd_strerror (err));
      return;
    }

  if ((err =
       snd_pcm_hw_params_set_channels (handle, hwparams, pchannels)) < 0)
    {
      printf ("Channels count not available: %s\n", snd_strerror (err));
      return;
    }

  if ((err =
       snd_pcm_hw_params_set_rate_near (handle, hwparams, &pspeed, 0)) < 0)
    {
      printf ("Rate not available: %s\n", snd_strerror (err));
      return;
    }
  if ((err = snd_pcm_hw_params (handle, hwparams)) < 0)
    {
      printf ("Unable to install hw params: %s\n", snd_strerror (err));
      return;
    }

  snd_pcm_status_alloca (&status);
  if ((err = snd_pcm_status (handle, status)) < 0)
    {
      printf ("Unable to get status: %s\n", snd_strerror (err));
      return;
    }

  buffer_size = snd_pcm_status_get_avail (status);
  printf ("ALSA buffer size: %d\n", buffer_size);
}

// REMOVE SOUND
void
RemoveSound (void)
{
  if (handle != NULL)
    {
      snd_pcm_drop (handle);
      snd_pcm_close (handle);
      handle = NULL;
    }
}

unsigned long
SoundGetFreeBuffers (void)
{
  signed long l;

  if (handle == NULL)		// failed to open?
    return 0;
  l = snd_pcm_avail_update (handle);
  if (l < 0)
    {
      if (snd_pcm_state (handle) == SND_PCM_STATE_XRUN)
	{
          snd_pcm_prepare (handle);
	  //snd_pcm_recover (handle, -EPIPE, 0);
	  return 0;
	}
      else
	{
	  printf
	    ("some other unrelated error happened, that we don't care about\n");
	  exit (0);
	}
    }
  return l;

}

// FEED SOUND DATA
void
SoundFeedStreamData (unsigned char *pSound, long samples)
{
  if (handle == NULL)
    return;

  if (snd_pcm_state (handle) == SND_PCM_STATE_XRUN)
    {
      snd_pcm_prepare (handle);
      //snd_pcm_recover (handle, -EPIPE, 0);
    }
  snd_pcm_writei (handle, pSound, samples);
}

int
main (int argc, char *argv[])
{
  #define BUFLEN 100
  signed short data[BUFLEN];
  int i;


  for (i = 0; i < BUFLEN; i++)
    data[i] = 64.0 * 256.0 * sin ((3.14159 * 2.0 * i) / 441);

  SetupSound ();

  while (1)
    {
      if ((i = SoundGetFreeBuffers ()) > (BUFLEN/2))
	{ // buffer has enough room for another block of samples

	  SoundFeedStreamData ((unsigned char *) data, BUFLEN/2);
	}
      else
	{
	  //printf ("buffer has only %d free buffers\n", i);
	}
      usleep (5000);		// sleep 5000 microsecond
      // this loop should run 200 times per second
      // delivering up to (200*BUFLEN/2) samples per second
      // rate is 44100. buffer length is 33791
      // (200*BUFLEN/2) = 10000
      // Therefore it causes a buffer underrun approx 200 
      // times per second
    }

  RemoveSound ();
}