New fuel management code. Only works with YASim currently. It's a benign

no-op under other FDMs.

Nasal/fuel.nas

@@ -0,0 +1,119 @@
+# Properties under /consumables/fuel/tank[n]:
+# + level-gal_us    - Current fuel load.  Can be set by user code.
+# + level-lbs       - OUTPUT ONLY property, do not try to set
+# + selected        - boolean indicating tank selection.
+# + density-ppg     - Fuel density, in lbs/gallon.
+# + capacity-gal_us - Tank capacity 
+#
+# Properties under /engines/engine[n]:
+# + fuel-consumed-lbs - Output from the FDM, zeroed by this script
+# + out-of-fuel       - boolean, set by this code.
+
+UPDATE_PERIOD = 0.3;
+
+fuelUpdate = func {
+    if(getprop("/sim/freeze/fuel")) { return registerTimer(); }
+
+    AllEngines = props.globals.getNode("engines").getChildren("engine");
+
+    # Sum the consumed fuel
+    total = 0;
+    foreach(e; AllEngines) {
+        fuel = e.getNode("fuel-consumed-lbs", 1);
+        consumed = fuel.getValue();
+        if(consumed == nil) { consumed = 0; }
+        total = total + consumed;
+        fuel.setDoubleValue(0);
+    }
+
+    # Unfortunately, FDM initialization hasn't happened when we start
+    # running.  Wait for the FDM to start running before we set any output
+    # properties.  This also prevents us from mucking with FDMs that
+    # don't support this fuel scheme.
+    if(total == 0) { return registerTimer(); }
+    if(!initialized) { initialize(); }
+
+    AllTanks = props.globals.getNode("consumables/fuel").getChildren("tank");
+
+    # Build a list of selected tanks
+    selectedTanks = [];
+    foreach(t; AllTanks) {
+        if(t.getNode("selected", 1).getBoolValue()) {
+            append(selectedTanks, t);
+        }
+    }
+
+    # Subtract fuel from tanks, set auxilliary properties.  Set out-of-fuel
+    # when any one tank is dry.
+    outOfFuel = 0;
+    if(size(selectedTanks) == 0) {
+        outOfFuel = 1;
+    } else {
+        fuelPerTank = total / size(selectedTanks);
+        foreach(t; selectedTanks) {
+            ppg = t.getNode("density-ppg").getValue();
+            lbs = t.getNode("level-gal_us").getValue() * ppg;
+            lbs = lbs - fuelPerTank;
+            if(lbs < 0) { lbs = 0; outOfFuel = 1; }
+            gals = lbs / ppg;
+            t.getNode("level-gal_us").setDoubleValue(gals);
+            t.getNode("level-lbs").setDoubleValue(lbs);
+        }
+    }
+    
+    # Total fuel properties
+    gals = lbs = cap = 0;
+    foreach(t; AllTanks) {
+        cap = cap + t.getNode("capacity-gal_us").getValue();
+        gals = gals + t.getNode("level-gal_us").getValue();
+        lbs = lbs + t.getNode("level-lbs").getValue();
+    }
+    setprop("/consumables/fuel/total-fuel-gals", gals);
+    setprop("/consumables/fuel/total-fuel-lbs", lbs);
+    setprop("/consumables/fuel/total-fuel-norm", gals/cap);
+
+    foreach(e; AllEngines) {
+        e.getNode("out-of-fuel").setBoolValue(outOfFuel);
+    }
+
+    registerTimer();
+}
+
+# Initalize: Make sure all needed properties are present and accounted
+# for, and that they have sane default values.
+initialized = 0;
+initialize = func {
+    AllEngines = props.globals.getNode("engines").getChildren("engine");
+    AllTanks = props.globals.getNode("consumables/fuel").getChildren("tank");
+
+    foreach(e; AllEngines) {
+        e.getNode("fuel-consumed-lbs", 1).setDoubleValue(0);
+        e.getNode("out-of-fuel", 1).setBoolValue(0);
+    }
+
+    foreach(t; AllTanks) {
+        initDoubleProp(t, "level-gal_us", 0);
+        initDoubleProp(t, "level-lbs", 0);
+        initDoubleProp(t, "capacity-gal_us", 1); # Not zero (div/zero issue)
+        initDoubleProp(t, "density-ppg", 6.0); # gasoline
+
+        if(t.getNode("selected") == nil) {
+            t.getNode("selected", 1).setBoolValue(1);
+        }
+    }
+    initialized = 1;
+}
+
+initDoubleProp = func {
+    node = arg[0]; prop = arg[1]; val = arg[2];
+    if(node.getNode(prop) != nil) {
+        val = num(node.getNode(prop).getValue());
+    }
+    node.getNode(prop, 1).setDoubleValue(val);
+}
+
+# Fire it up
+registerTimer = func {
+    settimer(fuelUpdate, UPDATE_PERIOD);
+}
+registerTimer();

Nasal/props.nas

@@ -29,8 +29,8 @@ Node = {
     getNode        : func { wrap(_getNode(me._g, arg)) },
 
     getBoolValue : func {
-        val = getValue();
-        if(getType() == "STRING" and val == "false") { 0 }
+        val = me.getValue();
+        if(me.getType() == "STRING" and val == "false") { 0 }
         else { val }
     }
 };