/*
 *  This extra small demo sends silence to your speakers if all your ALSA plugins support rewinds properly.
 */

#include <asoundlib.h>

#include <stdio.h>
#include <stdlib.h>

const char* device = "hw:2";
const int channels = 2;
const snd_pcm_sframes_t period_size = 1024;
const int periods = 4;
const int rate = 48000;
const int freq = 440;


int main(int argc, char* argv[])
{
        int err;
        unsigned int c, i, s, t;
	short *wave;
	short *silence;
	unsigned int half_period = rate / 2 / freq;

        snd_pcm_t *handle;
	snd_output_t *out = NULL;

	snd_pcm_hw_params_t *params;
	snd_pcm_sw_params_t *swparams;

	snd_pcm_hw_params_alloca(&params);
	snd_pcm_sw_params_alloca(&swparams);

	t = 0;

	snd_output_stdio_attach(&out, stderr, 0);
	wave = calloc(period_size, sizeof(short) * channels);
	silence = calloc(period_size * periods, sizeof(short) * channels);

	if ((err = snd_pcm_open(&handle, device, SND_PCM_STREAM_PLAYBACK, 0)) < 0) {
		fprintf(stderr, "Playback open error: %s\n", snd_strerror(err));
		exit(EXIT_FAILURE);
	}

	err =   snd_pcm_hw_params_any(handle, params) < 0 ||
		snd_pcm_hw_params_set_rate_resample(handle, params, 1) < 0 ||
		snd_pcm_hw_params_set_access(handle, params, SND_PCM_ACCESS_RW_INTERLEAVED) < 0 ||
		snd_pcm_hw_params_set_format(handle, params, SND_PCM_FORMAT_S16) < 0 ||
		snd_pcm_hw_params_set_channels(handle, params, channels) < 0 ||
		snd_pcm_hw_params_set_rate(handle, params, rate, 0) < 0 ||
		snd_pcm_hw_params_set_period_size(handle, params, period_size, 0) < 0 ||
		snd_pcm_hw_params_set_periods(handle, params, periods, 0) < 0 ||
		snd_pcm_hw_params(handle, params) < 0;
	if (err) {
		fprintf(stderr, "Playback hwparams error: %s\n", snd_strerror(err));
		exit(EXIT_FAILURE);
	}

	err =   snd_pcm_sw_params_current(handle, swparams) < 0 ||
		snd_pcm_sw_params_set_start_threshold(handle, swparams, period_size) < 0 ||
		snd_pcm_sw_params_set_avail_min(handle, swparams, period_size) < 0 ||
		snd_pcm_sw_params(handle, swparams) < 0;
	if (err) {
		fprintf(stderr, "Playback swparams error: %s\n", snd_strerror(err));
		exit(EXIT_FAILURE);
	}

	snd_pcm_dump(handle, out);
	fprintf(stderr, "Playing silence\n");
	fflush(stderr);
	memset(silence, 0, period_size * sizeof(short) * channels);
	for (i = 0; i < periods; i++) {
		err = snd_pcm_writei(handle, silence, period_size);
		if (err != period_size) {
			fprintf(stderr, "Playback incomplete write or error: %d\n", err);
			exit(EXIT_FAILURE);
		}
	}
	fprintf(stderr, "Playing tricks\n");
	for (i = 0; i < 100; i++) {
		snd_pcm_sframes_t towrite;
		err = snd_pcm_rewindable(handle);
		if (err < period_size) {
			fprintf(stderr, "Cannot rewind, got %d\n", err);
			exit(EXIT_FAILURE);
		}
		towrite = snd_pcm_rewind(handle, period_size);
		if (towrite < period_size) {
			fprintf(stderr, "Rewind attempt failed or didn't yield as much as we want, got %d\n", err);
			exit(EXIT_FAILURE);
		}
		fprintf(stderr, "Rewind attempt forgot %d samples out of %d requested\n", (int)towrite, (int)period_size);
		err = snd_pcm_writei(handle, silence, towrite);
		if (err != towrite) {
			fprintf(stderr, "Writing silence: incomplete write or error: %d\n", err);
			exit(EXIT_FAILURE);
		}

		for (s = 0; s < period_size; s++) {
			short val = (t % (2 * half_period) >= half_period) ? 30000 : -30000;
			for (c = 0; c < channels; c++)
				wave[c + s * channels] = val;
			t++;
		}

		err = snd_pcm_writei(handle, wave, period_size);
		if (err != period_size) {
			fprintf(stderr, "Writing wave: incomplete write or error: %d\n", err);
			exit(EXIT_FAILURE);
		}
	}
	snd_pcm_drop(handle);
	snd_pcm_close(handle);

	free(wave);
	free(silence);


	return 0;
}