SensorType: return invalid data when converting invalid sensor types

These are known sensor types, that have no valid assigned value. Hence cannot be converted. Use an invalid float value. For int there is not invalid int value. In dsm-api, the sensor value is limited to 8-bit, hence using INT_MIN since that exceeds that value. #14861

Signed-off-by: Andreas Fenkart andreas.fenkart@dev.digitalstrom.org

src/model/modelconst.cpp

@@ -24,7 +24,8 @@
 
 #include "modelconst.h"
 
-#include <math.h>
+#include <climits>
+#include <cmath>
 #include <ds/string.h>
 
 #include "base.h"
@@ -71,8 +72,9 @@ namespace dss {
     case SensorType::Reserved2:
     case SensorType::NotUsed:
     case SensorType::UnknownType:
-      return static_cast<double>(_sensorValue);
+      return std::nan(sensorTypeName(_sensorType).c_str());
     }
+    // by default, just forward the value. Needed when assembling events
     return static_cast<double>(_sensorValue);
   } // sensorValueToDouble
 
@@ -152,7 +154,7 @@ namespace dss {
     case SensorType::Reserved2:
     case SensorType::NotUsed:
     case SensorType::UnknownType:
-      return static_cast<int>(_sensorValue + 0.5);
+      return INT_MIN;
     }
     return static_cast<int>(_sensorValue + 0.5);
   } // doubleToSensorValue

tests/sensorconversiontest.cpp

@@ -22,6 +22,7 @@
 #define BOOST_TEST_DYN_LINK
 
 #include <boost/test/unit_test.hpp>
+#include <cmath>
 
 #include <digitalSTROM/dsuid.h>
 
@@ -52,4 +53,12 @@ BOOST_AUTO_TEST_CASE(testSensorTypeToString)
   BOOST_CHECK_EQUAL(s.str(), "Active Power");
 }
 
+BOOST_AUTO_TEST_CASE(testSensorValueToDouble)
+{
+  BOOST_CHECK(std::isnan(sensorValueToDouble(SensorType::Reserved1, 7)));
+  BOOST_CHECK(std::isnan(sensorValueToDouble(SensorType::Reserved2, 11)));
+  BOOST_CHECK(std::isnan(sensorValueToDouble(SensorType::NotUsed, 13)));
+  BOOST_CHECK(std::isnan(sensorValueToDouble(SensorType::UnknownType, 17)));
+}
+
 BOOST_AUTO_TEST_SUITE_END()

[Michael Tross]

What is the reason to return INT_MIN instead of the original value? is this some kind of error handling? I don't see benefit of this change. We lose the value in log files at least.