Decode aircraft category, export in aircraft.json.

Closes #2.

dump1090.h

@@ -157,6 +157,7 @@
 #define MODES_ACFLAGS_NSEWSPD_VALID  (1<<14) // Aircraft EW and NS Speed is known
 #define MODES_ACFLAGS_LATLON_REL_OK  (1<<15) // Indicates it's OK to do a relative CPR
 #define MODES_ACFLAGS_REL_CPR_USED   (1<<16) // Lat/lon derived from relative CPR
+#define MODES_ACFLAGS_CATEGORY_VALID (1<<17) // Aircraft category is known
 
 #define MODES_ACFLAGS_LLEITHER_VALID (MODES_ACFLAGS_LLEVEN_VALID | MODES_ACFLAGS_LLODD_VALID)
 #define MODES_ACFLAGS_LLBOTH_VALID   (MODES_ACFLAGS_LLEVEN_VALID | MODES_ACFLAGS_LLODD_VALID)
@@ -385,6 +386,7 @@ struct modesMessage {
     int    ns_velocity;         // N/S velocity.
     int    vert_rate;           // Vertical rate.
     int    velocity;            // Reported by aircraft, or computed from from EW and NS velocity
+    unsigned category;          // A0 - D7 encoded as a single hex byte
 
     // DF 18
     int    cf;                  // Control Field

mode_s.c

@@ -753,6 +753,9 @@ static void decodeExtendedSquitter(struct modesMessage *mm)
             mm->flight[8] = '\0';
         }
 
+        mm->category = ((0x0E - metype) << 4) | mesub;
+        mm->bFlags |= MODES_ACFLAGS_CATEGORY_VALID;
+
         break;
     }
 
@@ -973,8 +976,8 @@ static void displayExtendedSquitter(struct modesMessage *mm) {
 
     // Decode the extended squitter message
     if (mm->metype >= 1 && mm->metype <= 4) { // Aircraft identification
-        printf("    Aircraft Type  : %c%d\n", ('A' + 4 - mm->metype), mm->mesub);
-        printf("    Identification : %s\n", mm->flight);
+        printf("    Aircraft Type  : %02X\n", mm->category);
+        printf("    Identification : %s\n", (mm->bFlags & MODES_ACFLAGS_CALLSIGN_VALID) ? mm->flight : "invalid");
     } else if (mm->metype == 19) { // Airborne Velocity
         if (mm->mesub == 1 || mm->mesub == 2) {
             printf("    EW status         : %s\n", (mm->bFlags & MODES_ACFLAGS_EWSPEED_VALID)  ? "Valid" : "Unavailable");

net_io.c

@@ -787,6 +787,8 @@ char *generateAircraftJson(const char *url_path, int *len) {
             p += snprintf(p, end-p, ",\"track\":%d", a->track);
         if (a->bFlags & MODES_ACFLAGS_SPEED_VALID)
             p += snprintf(p, end-p, ",\"speed\":%d", a->speed);
+        if (a->bFlags & MODES_ACFLAGS_CATEGORY_VALID)
+            p += snprintf(p, end-p, ",\"category\":\"%02X\"", a->category);
 
         p += snprintf(p, end-p, ",\"messages\":%ld,\"seen\":%.1f,\"rssi\":%.1f}",
                       a->messages, (now - a->seen)/1000.0,

track.c

@@ -495,6 +495,11 @@ struct aircraft *trackUpdateFromMessage(struct modesMessage *mm)
         a->vert_rate = mm->vert_rate;
     }
 
+    // If a (new) category has been received, copy it to the aircraft structure
+    if (mm->bFlags & MODES_ACFLAGS_CATEGORY_VALID) {
+        a->category = mm->category;
+    }
+
     // Update the aircrafts a->bFlags to reflect the newly received mm->bFlags;
     a->bFlags |= mm->bFlags;
 

track.h

@@ -95,6 +95,8 @@ struct aircraft {
     double        lat, lon;       // Coordinated obtained from CPR encoded data
     unsigned      pos_nuc;        // NUCp of last computed position
 
+    unsigned      category;       // Aircraft category A0 - D7 encoded as a single hex byte
+
     int           bFlags;         // Flags related to valid fields in this structure
     struct aircraft *next;        // Next aircraft in our linked list