Don't retry reads if we're not talking to actual hardware.

Fixes #18.

lib/fluxreader/fluxreader.h

@@ -20,6 +20,7 @@ public:
 public:
     virtual std::unique_ptr<Fluxmap> readFlux(int track, int side) = 0;
     virtual void recalibrate() {}
+    virtual bool retryable() { return false; }
 };
 
 extern void setHardwareFluxReaderRevolutions(int revolutions);

lib/fluxreader/hardwarefluxreader.cc

@@ -29,10 +29,16 @@ public:
         return usbRead(side, revolutions);
     }
 
-    void recalibrate() {
+    void recalibrate()
+    {
         usbRecalibrate();
     }
 
+    bool retryable()
+    {
+        return true;
+    }
+
 private:
     unsigned _drive;
     unsigned _revolutions;

lib/reader.cc

@@ -65,6 +65,11 @@ void Track::recalibrate()
 	_fluxReader->recalibrate();
 }
 
+bool Track::retryable()
+{
+	return _fluxReader->retryable();
+}
+
 std::vector<std::unique_ptr<Track>> readTracks()
 {
     const DataSpec& dataSpec = source.value;
@@ -172,6 +177,9 @@ void readDiskCommand(AbstractDecoder& decoder, const std::string& outputFilename
 
 			std::cout << std::endl
                       << "       ";
+
+			if (!track->retryable())
+				break;
             if (retry == 0)
                 std::cout << "giving up" << std::endl
                           << "       ";

lib/reader.h

@@ -20,6 +20,7 @@ public:
 public:
     std::unique_ptr<Fluxmap> read();
     void recalibrate();
+    bool retryable();
 
     unsigned track;
     unsigned side;