Avoid large buffer on stack, to prevent stack overflows

This affectes:
 * demodulation in libfsk
 * audio processing in libmobile

src/libfsk/fsk.c

@@ -361,6 +361,8 @@ void fsk_demod_cleanup(fsk_demod_t *fsk)
 //#define DEBUG_MODULATOR
 //#define DEBUG_FILTER
 
+#define CHUNK 1024
+
 /* Demodulates bits
  *
  * If bit is received, callback function send_bit() is called.
@@ -375,15 +377,21 @@ void fsk_demod_cleanup(fsk_demod_t *fsk)
  */
 void fsk_demod_receive(fsk_demod_t *fsk, sample_t *sample, int length)
 {
-	sample_t I[length], Q[length], frequency[length], f;
+	sample_t I[CHUNK], Q[CHUNK], frequency[CHUNK], f;
 	int i;
 	int bit;
 	double level, quality;
 
-	/* demod samples to offset around center frequency */
-	fm_demodulate_real(&fsk->demod, frequency, length, sample, I, Q);
-
 	for (i = 0; i < length; i++) {
+		/* this is called on first sample and subsequently every sample defined by CHUNK */
+		if (i % CHUNK == 0) {
+			length -= i;
+			i = 0;
+			/* demod CHUNK samples to offset around center frequency */
+			fm_demodulate_real(&fsk->demod, frequency, (length > CHUNK) ? CHUNK : length, sample, I, Q);
+			sample += CHUNK;
+		}
+
 		f = frequency[i];
 		if (f < 0)
 			bit = fsk->low_bit;

src/libmobile/main_mobile.c

@@ -617,6 +617,7 @@ void main_mobile_loop(const char *name, int *quit, void (*myhandler)(void), cons
 	sender_t *sender;
 	double last_time_call = 0, begin_time, now, sleep;
 	struct termios term, term_orig;
+	int num_chan, i;
 	int c;
 	int rc;
 
@@ -693,6 +694,15 @@ void main_mobile_loop(const char *name, int *quit, void (*myhandler)(void), cons
 	if (console_open_audio(buffer_size, dsp_interval))
 		return;
 
+	/* alloc memory for audio processing */
+	for (num_chan = 0, sender = sender_head; sender; num_chan++, sender = sender->next);
+	sample_t *samples[num_chan];
+	uint8_t *powers[num_chan];
+	for (i = 0; i < num_chan; i++) {
+		samples[i] = calloc(buffer_size, sizeof(**samples));
+		powers[i] = calloc(buffer_size, sizeof(**powers));
+	}
+
 	/* real time priority */
 	if (rt_prio > 0) {
 		struct sched_param schedp;
@@ -739,7 +749,7 @@ void main_mobile_loop(const char *name, int *quit, void (*myhandler)(void), cons
 			/* do not process audio for an audio slave, since it is done by audio master */
 			if (sender->master) /* if master is set, we are an audio slave */
 				continue;
-			process_sender_audio(sender, quit, buffer_size);
+			process_sender_audio(sender, quit, samples, powers, buffer_size);
 		}
 
 		/* process audio for call instances */
@@ -855,6 +865,11 @@ next_char:
 	signal(SIGTERM, SIG_DFL);
 	signal(SIGPIPE, SIG_DFL);
 
+	for (i = 0; i < num_chan; i++) {
+		free(samples[i]);
+		free(powers[i]);
+	}
+
 	/* reset terminal */
 	tcsetattr(0, TCSANOW, &term_orig);
 	

src/libmobile/sender.c

@@ -331,7 +331,7 @@ static void gain_samples(sample_t *samples, int length, double gain)
 }
 
 /* Handle audio streaming of one transceiver. */
-void process_sender_audio(sender_t *sender, int *quit, int buffer_size)
+void process_sender_audio(sender_t *sender, int *quit, sample_t **samples, uint8_t **power, int buffer_size)
 {
 	sender_t *inst;
 	int rc, count;
@@ -342,15 +342,9 @@ void process_sender_audio(sender_t *sender, int *quit, int buffer_size)
 
 	/* count instances for audio channel */
 	for (num_chan = 0, inst = sender; inst; num_chan++, inst = inst->slave);
-	sample_t buff[num_chan][buffer_size], *samples[num_chan];
-	uint8_t pbuff[num_chan][buffer_size], *power[num_chan];
 	enum paging_signal paging_signal[num_chan];
 	int on[num_chan];
 	double rf_level_db[num_chan];
-	for (i = 0; i < num_chan; i++) {
-		samples[i] = buff[i];
-		power[i] = pbuff[i];
-	}
 
 #ifdef DEBUG_TIME_CONSUMPTION
 	t1 = get_time();

src/libmobile/sender.h

@@ -100,7 +100,7 @@ void sender_set_fm(sender_t *sender, double max_deviation, double max_modulation
 void sender_set_am(sender_t *sender, double max_modulation, double speech_deviation, double max_display, double modulation_index);
 int sender_open_audio(int buffer_size, double interval);
 int sender_start_audio(void);
-void process_sender_audio(sender_t *sender, int *quit, int buffer_size);
+void process_sender_audio(sender_t *sender, int *quit, sample_t **samples, uint8_t **power, int buffer_size);
 void sender_send(sender_t *sender, sample_t *samples, uint8_t *power, int count);
 void sender_receive(sender_t *sender, sample_t *samples, int count, double rf_level_db);
 void sender_paging(sender_t *sender, int on);