Do not return garbage when a virtual sensor cannot be evaluated at a given time.

DCDBLib/include_internal/virtualsensor_internal.h

@@ -30,6 +30,19 @@
 namespace DCDB {
 namespace VirtualSensor {
 
+/**
+ * @brief Exception class for errors during Physical Sensor Evaluation
+ *
+ * Exceptions of this type are thrown whenever the the evaluation of
+ * a physical sensor is impossible due to data being out of range.
+ * What() returns a human readable error string.
+ */
+class PhysicalSensorEvaluatorException : public std::runtime_error
+{
+public:
+  PhysicalSensorEvaluatorException(const std::string& msg) : runtime_error(msg) {}
+};
+
 namespace qi = boost::spirit::qi;
 namespace ascii = boost::spirit::ascii;
 

DCDBLib/src/virtualsensor.cpp

@@ -11,6 +11,7 @@
 #include "dcdbglobals.h"
 
 #include <iostream>
+#include <sstream>
 #include <iomanip>
 #include <numeric>
 #include <cstdlib>
@@ -219,7 +220,14 @@ int64_t VSensorExpressionImpl::physicalSensorInterpolator(Connection* connection
           readingBefore.value = (int64_t)value;
       }
       else {
-          std::cerr << "Cannot find reading for sensor " << sensor.name << " prior to time " << t.getString() << "(" << t.getRaw() << ")" << std::endl;
+          std::stringstream msg;
+          msg << "Cannot find reading for sensor " << sensor.name << " prior to time " << t.getString() << "(" << t.getRaw() << ")" << std::endl;
+          cass_iterator_free(rows);
+          cass_result_free(cresult);
+          cass_statement_free(statement);
+          cass_future_free(future);
+          cass_prepared_free(prepared);
+          throw(PhysicalSensorEvaluatorException(msg.str()));
       }
       cass_iterator_free(rows);
       cass_result_free(cresult);
@@ -265,7 +273,14 @@ int64_t VSensorExpressionImpl::physicalSensorInterpolator(Connection* connection
           readingAfter.value = (int64_t)value;
       }
       else {
-          std::cerr << "Cannot find reading for sensor " << sensor.name << " following time " << t.getString() << "(" << t.getRaw() << ")" << std::endl;
+          std::stringstream msg;
+          msg << "Cannot find reading for sensor " << sensor.name << " following time " << t.getString() << "(" << t.getRaw() << ")" << std::endl;
+          cass_iterator_free(rows);
+          cass_result_free(cresult);
+          cass_statement_free(statement);
+          cass_future_free(future);
+          cass_prepared_free(prepared);
+          throw(PhysicalSensorEvaluatorException(msg.str()));
       }
       cass_iterator_free(rows);
       cass_result_free(cresult);
@@ -455,12 +470,17 @@ VSError VSensorImpl::query(std::list<SensorDataStoreReading>& result, TimeStamp&
       i <= (tzero.getRaw() + (n_end * frequency));
       i += frequency)
   {
-    int64_t eval = expression->evaluateAt(i);
-    TimeStamp t(i);
-    SensorDataStoreReading r;
-    r.timeStamp = t;
-    r.value = eval;
-    result.push_back(r);
+      try {
+          int64_t eval = expression->evaluateAt(i);
+          TimeStamp t(i);
+          SensorDataStoreReading r;
+          r.timeStamp = t;
+          r.value = eval;
+          result.push_back(r);
+      }
+      catch (PhysicalSensorEvaluatorException& e) {
+          std::cerr << e.what();
+      }
   }
 
   return VS_OK;