ftmod_libpri: Incoming overlap receiving digits have to be appended to the DNIS.

Libpri doesn't do that for us, so handle things on our end.
Other parts of the previous patch seem to work fine.
Signed-off-by: Stefan Knoblich <s.knoblich@axsentis.de>

libs/freetdm/src/ftmod/ftmod_libpri/ftmod_libpri.c

@@ -34,6 +34,10 @@
 #include "private/ftdm_core.h"
 #include "ftmod_libpri.h"
 
+#ifndef MIN
+#define MIN(x,y)	(((x) < (y)) ? (x) : (y))
+#endif
+
 static void _ftdm_channel_set_state_force(ftdm_channel_t *chan, const ftdm_channel_state_t state)
 {
 	assert(chan);
@@ -882,10 +886,22 @@ static int on_info(lpwrap_pri_t *spri, lpwrap_pri_event_t event_type, pri_event
 		ftdm_log_chan(chan, FTDM_LOG_DEBUG, "-- Incoming INFORMATION indication, current called number: '%s', number complete: %s\n",
 			pevent->ring.callednum, pevent->ring.complete ? "yes" : "no");
 
+		/* append digits to dnis */
+		if (!ftdm_strlen_zero(pevent->ring.callednum)) {
+			int digits = strlen(pevent->ring.callednum);
+			int offset = strlen(caller_data->dnis.digits);
+			int len    = MIN(sizeof(caller_data->dnis.digits) - 1 - offset, digits);
+
+			if (len < digits) {
+				ftdm_log_chan(chan, FTDM_LOG_WARNING, "Length %d of digit string exceeds available space %d of DNIS, truncating!\n",
+					digits, len);
+			}
+
+			ftdm_copy_string(&caller_data->dnis.digits[offset], (char *)pevent->ring.callednum, len);
+			caller_data->dnis.digits[offset + len] = '\0';
+		}
 		if (pevent->ring.complete) {
 			ftdm_log_chan_msg(chan, FTDM_LOG_DEBUG, "Number complete indicated, moving channel to RING state\n");
-			/* copy final value */
-			ftdm_set_string(caller_data->dnis.digits, (char *)pevent->ring.callednum);
 			/* notify switch */
 			ftdm_set_state(chan, FTDM_CHANNEL_STATE_RING);
 		}