Fix TIST transmission over ZMQ output

The last ETI frame in each ZMQ message was truncated, which
inadvertedly zeroed the its TIST field.

2 files changed, 13 insertions, 2 deletions

diff --git a/src/dabOutput/dabOutput.h b/src/dabOutput/dabOutput.h
index 72a15d4..6048d51 100644
--- a/src/dabOutput/dabOutput.h
+++ b/src/dabOutput/dabOutput.h
@@ -278,9 +278,15 @@ struct zmq_dab_message_t
     }
     uint32_t version;
     int16_t buflen[NUM_FRAMES_PER_ZMQ_MESSAGE];
+    /* The head stops here. Use the macro below to calculate
+     * the head size.
+     */
+
     uint8_t  buf[NUM_FRAMES_PER_ZMQ_MESSAGE*6144];
 };
 
+#define ZMQ_DAB_MESSAGE_HEAD_LENGTH (4 + NUM_FRAMES_PER_ZMQ_MESSAGE*2)
+
 // -------------- ZeroMQ message queue ------------------
 class DabOutputZMQ : public DabOutput
 {
diff --git a/src/dabOutput/dabOutputZMQ.cpp b/src/dabOutput/dabOutputZMQ.cpp
index ac26403..6a9d669 100644
--- a/src/dabOutput/dabOutputZMQ.cpp
+++ b/src/dabOutput/dabOutputZMQ.cpp
@@ -70,6 +70,7 @@ int DabOutputZMQ::Write(void* buffer, int size)
 {
     int offset = 0;
 
+    // Increment the offset by the accumulated frame offsets
     for (int i = 0; i < zmq_message_ix; i++) {
         offset += zmq_message.buflen[i];
     }
@@ -77,12 +78,17 @@ int DabOutputZMQ::Write(void* buffer, int size)
     if (offset + size > NUM_FRAMES_PER_ZMQ_MESSAGE*6144) {
         throw std::runtime_error("FAULT: invalid ETI frame size!");
     }
+
+    // Append the new frame to our message
     memcpy(zmq_message.buf + offset, buffer, size);
     zmq_message.buflen[zmq_message_ix] = size;
     zmq_message_ix++;
 
+    // As soon as we have NUM_FRAMES_PER_ZMQ_MESSAGE frames, we transmit
     if (zmq_message_ix == NUM_FRAMES_PER_ZMQ_MESSAGE) {
-        int full_length = 0;
+
+        // Size of the header:
+        int full_length = ZMQ_DAB_MESSAGE_HEAD_LENGTH;
 
         for (int i = 0; i < NUM_FRAMES_PER_ZMQ_MESSAGE; i++) {
             full_length += zmq_message.buflen[i];
@@ -93,7 +99,6 @@ int DabOutputZMQ::Write(void* buffer, int size)
         const int flags = 0;
         zmq_send(zmq_pub_sock_,
                 (uint8_t*)&zmq_message,
-                NUM_FRAMES_PER_ZMQ_MESSAGE * sizeof(*zmq_message.buflen) +
                 full_length, flags);
 
         for (int i = 0; i < NUM_FRAMES_PER_ZMQ_MESSAGE; i++) {