skcblitz/alsasnd.h

#define SND_MSGUNDER

typedef struct {
	snd_pcm_t *handle;
	void *buffer;
	int *conv;
	uint samplerate;
	uint blocksize;
	uint channels;
	uint width;
	uint smppos;
	uint devbufsize;
#ifdef SND_MSGUNDER
	uint underruns;
	uint lastunder;
	uint pushed;
	uint pad;
#else
	uint pad[4];
#endif
} aud_handle;

void aud_prepare(aud_handle *dev) {
	if(dev->handle == NULL) {
		return;
	}
	memset(dev->buffer, 0, dev->blocksize * dev->width * dev->channels);
	dev->smppos = 0;
	int rc = 0;
	uint tries = 0;
  	while(rc != dev->blocksize) {
		if(tries++ >= 256) {
			snd_logw(STR_AUD_PREPERR);
			return;
		}
		rc = snd_pcm_writei(dev->handle, dev->buffer, dev->blocksize);
		if(rc == -EAGAIN || (rc >= 0 && (uint)rc < dev->blocksize)) {
			snd_pcm_wait(dev->handle, 100);
		} 
		else if(rc == -EPIPE) {
			snd_pcm_prepare(dev->handle);
		}
	}
	snd_pcm_nonblock(dev->handle, 1);
	for(int z = 0; z < 16; z++) {
	 	rc = snd_pcm_writei(dev->handle, dev->buffer, dev->blocksize);
		if(rc == -EAGAIN || (rc >= 0 && (uint)rc < dev->blocksize)) {
			snd_pcm_wait(dev->handle, 100);
		} 
		else if(rc == -EPIPE) {
			snd_pcm_prepare(dev->handle);
		}
	}
	snd_pcm_nonblock(dev->handle, 0);
}

void aud_write(aud_handle *dev, void *data, uint samples) {
	int rc;
	uint blocksize = dev->blocksize;
  	while(samples > 0) {
		blocksize = samples < blocksize ? samples : blocksize;
		if(dev->handle) {
			rc = snd_pcm_writei(dev->handle, data, blocksize);
		}
		data += blocksize * dev->channels;
		samples -= blocksize;
		if(dev->handle) {
			if(rc == -EAGAIN || (rc >= 0 && (uint)rc < blocksize)) {
				snd_pcm_wait(dev->handle, 100);
			} 
			else if(rc == -EPIPE) {
#ifdef SND_MSGUNDER
				if(dev->underruns == 0) {
					dev->lastunder = dev->pushed;
				}
				dev->underruns += 1;
#endif
				snd_pcm_prepare(dev->handle);
			}
			else if(rc < 0) {
			  	snd_loge(STR_AUD_WRITERR, snd_strerror(rc), rc);
			}
#ifdef SND_MSGUNDER
			else {
			    dev->pushed += 1;
			}
			if((dev->underruns > 0) && ((dev->pushed - dev->lastunder) >= (dev->samplerate / dev->blocksize))) {
				snd_logw(STR_AUD_UNDERR, dev->underruns);
				dev->underruns = 0;
			}
#endif
		}
	}
}

uint aud_open_dev(aud_handle *dev, const char *devname, uint samplerate, byte channels, byte width, uint frames, uint bufsize) {
	dev->channels = (uint)channels;
	dev->samplerate = samplerate;
	dev->width = (uint)width;
	dev->smppos = 0;
#ifdef SND_MSGUNDER
	dev->underruns = 0;
	dev->lastunder = 0;
	dev->pushed = 0;
#endif
	dev->handle = NULL;
	dev->buffer = NULL;
	dev->conv = NULL;
	int rc;
	int subdir = 0;
  	snd_pcm_hw_params_t *params = NULL;
	rc = snd_pcm_open(&dev->handle, devname, SND_PCM_STREAM_PLAYBACK, 0);
	if(rc < 0) {
		snd_loge(STR_AUD_OPNERR, devname, snd_strerror(rc), rc);
		return 0;
	}
	snd_pcm_hw_params_alloca(&params);
	snd_pcm_hw_params_any(dev->handle, params);
	snd_pcm_hw_params_set_access(dev->handle, params, SND_PCM_ACCESS_RW_INTERLEAVED);
	if(snd_pcm_hw_params_set_format(dev->handle, params, (dev->width == 4) ? SND_PCM_FORMAT_S32_LE : SND_PCM_FORMAT_S16_LE) != 0) {
		dev->width = (width == 4) ? 2 : 4;
		if(snd_pcm_hw_params_set_format(dev->handle, params, (dev->width == 4) ? SND_PCM_FORMAT_S32_LE : SND_PCM_FORMAT_S16_LE) != 0) {
			snd_loge(STR_AUD_FMTERR, devname);
			snd_pcm_close(dev->handle);
			return 0;
		}
		else {
			snd_logw(STR_AUD_FMTCH, devname, width * 8, dev->width * 8);
		}
	}
	snd_pcm_hw_params_set_channels(dev->handle, params, dev->channels);
  	snd_pcm_hw_params_set_rate_near(dev->handle, params, &dev->samplerate, &subdir);
	snd_pcm_uframes_t framesize = frames;
  	snd_pcm_hw_params_set_period_size_near(dev->handle, params, &framesize, &subdir);
	snd_pcm_uframes_t buffersize = bufsize;
	if(bufsize > 0) {
		snd_pcm_hw_params_set_buffer_size_near(dev->handle, params, &buffersize);
	}
	rc = snd_pcm_hw_params(dev->handle, params);
  	if(rc < 0) {
    	snd_loge(STR_AUD_HWERR, devname, snd_strerror(rc), rc);
		snd_pcm_close(dev->handle);
    	return 0;
  	}
  	snd_pcm_hw_params_get_period_size(params, &framesize, &subdir);
	snd_pcm_hw_params_get_buffer_size(params, &buffersize);
	snd_pcm_sw_params_t *swparams;
	snd_pcm_sw_params_alloca(&swparams);
	snd_pcm_sw_params_current(dev->handle, swparams);
	// snd_pcm_sw_params_set_avail_min(dev->handle, swparams, framesize);
	// snd_pcm_sw_params_set_start_threshold(dev->handle, swparams, 0);
	// snd_pcm_sw_params_set_stop_threshold(dev->handle, swparams, buffersize);
	rc = snd_pcm_sw_params(dev->handle, swparams);
	if(rc < 0) {
    	snd_loge(STR_AUD_SWERR, devname, snd_strerror(rc), rc);
		snd_pcm_close(dev->handle);
    	return 0;
	}

	dev->blocksize = framesize;
	dev->devbufsize = buffersize;
  	dev->buffer = malloc(dev->blocksize * dev->width * dev->channels);
	if(dev->width == 4)
		dev->conv = malloc(sizeof(int) * dev->channels);
	snd_pcm_wait(dev->handle, -1);
	aud_prepare(dev);
	return dev->samplerate;
}

void aud_push_raw(aud_handle *dev, void *data) {
	memcpy(&((byte*)(dev->buffer))[dev->smppos*dev->channels*dev->width], data, dev->width * dev->channels);
	dev->smppos++;
	if(dev->smppos == dev->blocksize) {
		aud_write(dev, dev->buffer, dev->blocksize);
		dev->smppos = 0;
	}
}

void aud_push(aud_handle *dev, short *data) {
	if(dev->width == 4) {
		for(int h = 0; h < dev->channels; h++) {
			dev->conv[h] = ((int)data[h]) << 16;
		}
		aud_push_raw(dev, dev->conv);
	}
	else {
		aud_push_raw(dev, data);
	}
}

void aud_flush(aud_handle *dev) {
	if(dev->smppos != 0) {
		aud_write(dev, dev->buffer, dev->smppos);
		dev->smppos = 0;
	}
}

void aud_close(aud_handle *dev) {
	if(dev->handle) {
		snd_pcm_drain(dev->handle);
		snd_pcm_close(dev->handle);
	}
  	free(dev->buffer);
	if(dev->conv)
		free(dev->conv);
}