AP_Stats: make singleton and add flighttime accessor

libraries/AP_Stats/AP_Stats.cpp

@@ -42,11 +42,20 @@ const AP_Param::GroupInfo AP_Stats::var_info[] = {
     AP_GROUPEND
 };
 
+AP_Stats *AP_Stats::_singleton;
+
+// constructor
+AP_Stats::AP_Stats(void)
+{
+    _singleton = this;
+}
+
 void AP_Stats::copy_variables_from_parameters()
 {
     flttime = params.flttime;
     runtime = params.runtime;
     reset = params.reset;
+    flttime_boot = flttime;
 }
 
 void AP_Stats::init()
@@ -121,3 +130,17 @@ void AP_Stats::set_flying(const bool is_flying)
         _flying_ms = 0;
     }
 }
+
+/*
+  get time in flight since boot
+ */
+uint32_t AP_Stats::get_flight_time_s(void)
+{
+    update_flighttime();
+    return flttime - flttime_boot;
+}
+
+AP_Stats *AP::stats(void)
+{
+    return AP_Stats::get_singleton();
+}

libraries/AP_Stats/AP_Stats.h

@@ -9,14 +9,17 @@
 class AP_Stats
 {
 public:
-
+    // constructor
+    AP_Stats();
+    
     // these variables are periodically written into the actual
     // parameters.  If you add a variable here, make sure to update
     // init() to set initial values from the parameters!
     uint32_t flttime; // seconds in flight (or driving)
     uint32_t runtime; // total wallclock time spent running ArduPilot (seconds)
     uint32_t reset; // last time parameters were reset
-
+    uint32_t flttime_boot; // seconds in flight (or driving), at boot
+    
     void init();
 
     // copy state into underlying parameters:
@@ -28,10 +31,25 @@ public:
 
     void set_flying(bool b);
 
+    // accessor for is_flying
+    bool get_is_flying(void) {
+        return _flying_ms != 0;
+    }
+
+    // accessor for flighttime. Returns 0 if not flying, otherwise
+    // total time flying since boot in seconds
+    uint32_t get_flight_time_s(void);
+    
+    // get singleton
+    static AP_Stats *get_singleton(void) {
+        return _singleton;
+    }
+    
     static const struct AP_Param::GroupInfo var_info[];
 
 private:
-
+    static AP_Stats *_singleton;
+    
     struct {
         AP_Int16 bootcount;
         AP_Int32 flttime;
@@ -51,3 +69,7 @@ private:
     void update_runtime();
 
 };
+
+namespace AP {
+    AP_Stats *stats();
+};