Check the gsm0503_xcch_decode return value

- Discard the message when gsm0503_xcch_decode returns -1
- Add automated decrypt test

See https://groups.google.com/d/msg/gr-gsm/9nOkIdrGOck/qTZh47McCQAJ

1 files changed, 5 insertions, 1 deletions

diff --git a/lib/decoding/control_channels_decoder_impl.cc b/lib/decoding/control_channels_decoder_impl.cc
index a6abaa3..bf0d976 100644
--- a/lib/decoding/control_channels_decoder_impl.cc
+++ b/lib/decoding/control_channels_decoder_impl.cc
@@ -105,7 +105,11 @@ namespace gr {
             //convert to soft bits
             ubits2sbits(bursts_u, bursts_s, 116 * 4);
             //decode
-            gsm0503_xcch_decode(result, bursts_s, &n_errors, &n_bits_total);
+            if (-1 == gsm0503_xcch_decode(result, bursts_s, &n_errors, &n_bits_total))
+            {
+                //Possibly an encrypted message
+                return;
+            }
 
             //extract header of the first burst of the four bursts
             pmt::pmt_t first_header_plus_burst = pmt::cdr(d_bursts[0]);