Fix PCM buffer size calculations in worker thread

After changes in the commit f79ddf4 the calculation of the PCM buffer
size was incorrect (actual PCM format size was not taken into account
in all places). This bug manifested itself in an occasional memory
corruptions resulting in writing incorrect samples to PCM device.

utils/aplay/aplay.c

@@ -316,7 +316,8 @@ static void *pcm_worker_routine(struct pcm_worker *w) {
 
 	/* Initialize the max read length to 10 ms. Later, when the PCM device
 	 * will be opened, this value will be adjusted to one period size. */
-	size_t pcm_max_read_len = pcm_1s_samples / 100;
+	size_t pcm_max_read_len_init = pcm_1s_samples / 100 * pcm_format_size;
+	size_t pcm_max_read_len = pcm_max_read_len_init;
 	size_t pcm_open_retries = 0;
 
 	/* These variables determine how and when the pause command will be send
@@ -348,7 +349,7 @@ static void *pcm_worker_routine(struct pcm_worker *w) {
 		case 0:
 			debug("Device marked as inactive: %s", w->addr);
 			pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, NULL);
-			pcm_max_read_len = pcm_1s_samples / 100;
+			pcm_max_read_len = pcm_max_read_len_init;
 			pause_counter = pause_bytes = 0;
 			ffb_rewind(&buffer);
 			if (w->pcm != NULL) {
@@ -365,8 +366,8 @@ static void *pcm_worker_routine(struct pcm_worker *w) {
 			break;
 
 		#define MIN(a,b) a < b ? a : b
-		size_t _in = MIN(pcm_max_read_len, ffb_len_in(&buffer));
-		if ((ret = read(w->ba_pcm_fd, buffer.tail, _in * pcm_format_size)) == -1) {
+		size_t _in = MIN(pcm_max_read_len, ffb_blen_in(&buffer));
+		if ((ret = read(w->ba_pcm_fd, buffer.tail, _in)) == -1) {
 			if (errno == EINTR)
 				continue;
 			error("PCM FIFO read error: %s", strerror(errno));
@@ -409,14 +410,14 @@ static void *pcm_worker_routine(struct pcm_worker *w) {
 			if (alsa_pcm_open(&w->pcm, pcm_device, pcm_format, w->ba_pcm.channels,
 						w->ba_pcm.sampling, &buffer_time, &period_time, &tmp) != 0) {
 				warn("Couldn't open PCM: %s", tmp);
-				pcm_max_read_len = buffer.size;
+				pcm_max_read_len = pcm_max_read_len_init;
 				usleep(50000);
 				free(tmp);
 				continue;
 			}
 
 			snd_pcm_get_params(w->pcm, &buffer_size, &period_size);
-			pcm_max_read_len = period_size * w->ba_pcm.channels;
+			pcm_max_read_len = period_size * w->ba_pcm.channels * pcm_format_size;
 			pcm_open_retries = 0;
 
 			if (verbose >= 2) {
@@ -440,9 +441,10 @@ static void *pcm_worker_routine(struct pcm_worker *w) {
 		w->active = true;
 		timeout = 500;
 
+		ffb_seek(&buffer, ret);
+
 		/* calculate the overall number of frames in the buffer */
-		ffb_seek(&buffer, ret / pcm_format_size);
-		snd_pcm_sframes_t frames = ffb_len_out(&buffer) / w->ba_pcm.channels;
+		snd_pcm_sframes_t frames = ffb_blen_out(&buffer) / w->ba_pcm.channels / pcm_format_size;
 
 		if ((frames = snd_pcm_writei(w->pcm, buffer.data, frames)) < 0)
 			switch (-frames) {
@@ -458,7 +460,7 @@ static void *pcm_worker_routine(struct pcm_worker *w) {
 			}
 
 		/* move leftovers to the beginning and reposition tail */
-		ffb_shift(&buffer, frames * w->ba_pcm.channels);
+		ffb_shift(&buffer, frames * w->ba_pcm.channels * pcm_format_size);
 
 	}