extend MQTT integration support

src/lib/ebus/data.h

@@ -209,6 +209,12 @@ class DataField : public AttributedItem {
    */
   virtual bool isSet() const { return false; }
 
+  /**
+   * Return whether this is a @a ValueListDataField.
+   * @return true if this is a @a DataFieldSet.
+   */
+  virtual bool isList() const { return false; }
+
   /**
    * Factory method for creating new instances.
    * @param isWriteMessage whether the field is part of a write message (default false).
@@ -534,6 +540,9 @@ class ValueListDataField : public SingleDataField {
   // @copydoc
   const ValueListDataField* clone() const override;
 
+  // @copydoc
+  bool isList() const override { return true; }
+
   // @copydoc
   result_t derive(const string& name, PartType partType, int divisor,
       const map<unsigned int, string>& values, map<string, string>* attributes,

src/lib/ebus/datatype.cpp

@@ -674,6 +674,16 @@ result_t NumberDataType::derive(int divisor, size_t bitCount, const NumberDataTy
   return RESULT_OK;
 }
 
+result_t NumberDataType::getMinMax(bool getMax, const OutputFormat outputFormat, ostream* output) const {
+  size_t length;
+  if (m_bitCount<8) {
+    length = 1;
+  } else {
+    length = m_bitCount/8;
+  }
+  return readFromRawValue(length, getMax ? m_maxValue : m_minValue, outputFormat, output);
+}
+
 result_t NumberDataType::readRawValue(size_t offset, size_t length, const SymbolString& input,
                                       unsigned int* value) const {
   size_t start = 0, count = length;
@@ -725,12 +735,17 @@ result_t NumberDataType::readRawValue(size_t offset, size_t length, const Symbol
 result_t NumberDataType::readSymbols(size_t offset, size_t length, const SymbolString& input,
                                      OutputFormat outputFormat, ostream* output) const {
   unsigned int value = 0;
-  int signedValue;
 
   result_t result = readRawValue(offset, length, input, &value);
   if (result != RESULT_OK) {
     return result;
   }
+  return readFromRawValue(length, value, outputFormat, output);
+}
+
+result_t NumberDataType::readFromRawValue(size_t length, unsigned int value,
+                                          OutputFormat outputFormat, ostream* output) const {
+  int signedValue;
   *output << setw(0) << dec;  // initialize output
 
   if (!hasFlag(REQ) && value == m_replacement) {

src/lib/ebus/datatype.h

@@ -493,6 +493,15 @@ class NumberDataType : public DataType {
    */
   unsigned int getMaxValue() const { return m_maxValue; }
 
+  /**
+   * Get the minimum or maximum value.
+   * @param getMax true for the maximum, false for the minimum.
+   * @param outputFormat the @a OutputFormat options to use.
+   * @param output the ostream to append the formatted value to.
+   * @return @a RESULT_OK on success, or an error code.
+   */
+  result_t getMinMax(bool getMax, const OutputFormat outputFormat, ostream* output) const;
+
   /**
    * @return the divisor (negative for reciprocal).
    */
@@ -516,6 +525,16 @@ class NumberDataType : public DataType {
   result_t readSymbols(size_t offset, size_t length, const SymbolString& input,
       const OutputFormat outputFormat, ostream* output) const override;
 
+  /**
+   * Internal method for interpreting a numeric raw value.
+   * @param value the numeric raw value.
+   * @param outputFormat the @a OutputFormat options to use.
+   * @param output the ostream to append the formatted value to.
+   * @return @a RESULT_OK on success, or an error code.
+   */
+  result_t readFromRawValue(size_t length, unsigned int value,
+                            OutputFormat outputFormat, ostream* output) const;
+
   /**
    * Internal method for writing the numeric raw value to a @a SymbolString.
    * @param value the numeric raw value to write.