procqueue: add processing state callback

In some cases it's required to wait for some queue items
to finish processing. For example, the ALSA sink writes the
audio samples to the buffer in non-blocking mode, so as soon
as all of them will be written, a program may finish execution,
causing the playback abort.

To prevent that, this change extends the library's API, allowing
each queue item to have a processing state callback that returns
a positive integer if processing is not finished yet,
and 0 otherwise.

include/osmocom/gapk/procqueue.h

@@ -40,6 +40,7 @@ struct osmo_gapk_pq_item {
 	 *  \param[in] in_len length of input data \a in
 	 *  \returns number of output bytes written to \a out; negative on error */
 	int  (*proc)(void *state, uint8_t *out, const uint8_t *in, unsigned int in_len);
+	int  (*wait)(void *state);
 	void (*exit)(void *state);
 
 	/*! \brief link to a processing queue */

src/pq_alsa.c

@@ -138,6 +138,7 @@ pq_queue_alsa_op(struct osmo_gapk_pq *pq, const char *alsa_dev, unsigned int blk
 	item->len_out = in_out_n ? blk_len : 0;
 	item->state   = state;
 	item->proc    = in_out_n ? pq_cb_alsa_input : pq_cb_alsa_output;
+	item->wait    = NULL;
 	item->exit    = pq_cb_alsa_exit;
 
 	return 0;

src/pq_codec.c

@@ -71,6 +71,7 @@ osmo_gapk_pq_queue_codec(struct osmo_gapk_pq *pq, const struct osmo_gapk_codec_d
 	}
 
 	item->exit = codec->codec_exit;
+	item->wait = NULL;
 
 	LOGPGAPK(LOGL_DEBUG, "PQ: Adding codec %s, %s format %s\n", codec->name,
 		enc_dec_n ? "encoding to" : "decoding from", fmt->name);

src/pq_file.c

@@ -83,6 +83,7 @@ pq_queue_file_op(struct osmo_gapk_pq *pq, FILE *fh, unsigned int blk_len, int in
 	item->len_out = in_out_n ? blk_len : 0;
 	item->state   = state;
 	item->proc    = in_out_n ? pq_cb_file_input : pq_cb_file_output;
+	item->wait    = NULL;
 	item->exit    = pq_cb_file_exit;
 
 	return 0;

src/pq_format.c

@@ -70,6 +70,7 @@ osmo_gapk_pq_queue_fmt_convert(struct osmo_gapk_pq *pq, const struct osmo_gapk_f
 	}
 
 	item->proc = pq_cb_fmt_convert;
+	item->wait = NULL;
 
 	return 0;
 }

src/pq_rtp.c

@@ -229,6 +229,7 @@ pq_queue_rtp_op(struct osmo_gapk_pq *pq, int udp_fd, unsigned int blk_len, int i
 	item->len_out = in_out_n ? blk_len : 0;
 	item->state   = state;
 	item->proc    = in_out_n ? pq_cb_rtp_input : pq_cb_rtp_output;
+	item->wait    = NULL;
 	item->exit    = pq_cb_rtp_exit;
 
 	return 0;