extend MQTT integration support with seen filter and variable compression

src/lib/ebus/message.cpp

@@ -115,7 +115,7 @@ Message::Message(const string& filename, const string& circuit, const string& le
       m_data(data), m_deleteData(deleteData),
       m_pollPriority(pollPriority),
       m_usedByCondition(false), m_isScanMessage(false), m_condition(condition),
-      m_lastUpdateTime(0), m_lastChangeTime(0), m_pollOrder(0), m_lastPollTime(0) {
+      m_dataHandlerState(0), m_lastUpdateTime(0), m_lastChangeTime(0), m_pollOrder(0), m_lastPollTime(0) {
   if (circuit == "scan") {
     setScanMessage();
     m_pollPriority = 0;
@@ -1025,6 +1025,14 @@ void Message::decodeJson(bool leadingSeparator, bool appendDirectionCondition, b
   *output << "\n   }";
 }
 
+bool Message::setDataHandlerState(int state) {
+  if (state == m_dataHandlerState) {
+    return false;
+  }
+  m_dataHandlerState = state;
+  return true;
+}
+
 
 ChainedMessage::ChainedMessage(const string& filename, const string& circuit, const string& level, const string& name,
     bool isWrite, const map<string, string>& attributes,

src/lib/ebus/message.h

@@ -525,6 +525,19 @@ class Message : public AttributedItem {
    */
   time_t getCreateTime() const { return m_createTime; }
 
+  /**
+   * Get the arbitrary state value for data handlers.
+   * @return the state value.
+   */
+  int getDataHandlerState() const { return m_dataHandlerState; }
+
+  /**
+   * Set the arbitrary state value for data handlers.
+   * @param state the new state value.
+   * @return true when the state was changed.
+   */
+  bool setDataHandlerState(int state);
+
   /**
    * Get the time when this message was last seen with reasonable data.
    * @return the time when this message was last seen, or 0.
@@ -660,9 +673,12 @@ class Message : public AttributedItem {
   /** the last seen @a SlaveSymbolString. */
   SlaveSymbolString m_lastSlaveData;
 
-  /** the system time when the message was created. */
+  /** the system time when the message was created or changed in poll priority. */
   time_t m_createTime;
 
+  /** an arbitrary state for data handlers. */
+  int m_dataHandlerState;
+
   /** the system time when the message was last updated, 0 for never. */
   time_t m_lastUpdateTime;