added prepareSlave for answering requests

src/lib/ebus/message.cpp

@@ -244,7 +244,6 @@ result_t Message::prepareMaster(const unsigned char srcAddress, SymbolString& ma
 		return RESULT_ERR_INVALID_ARG; // prepare not possible
 
 	SymbolString master;
-	master.clear();
 	result_t result = master.push_back(srcAddress, false, false);
 	if (result != RESULT_OK)
 		return result;
@@ -273,6 +272,24 @@ result_t Message::prepareMaster(const unsigned char srcAddress, SymbolString& ma
 	return result;
 }
 
+result_t Message::prepareSlave(SymbolString& slaveData)
+{
+	if (m_isPassive == false || m_isSet == true)
+			return RESULT_ERR_INVALID_ARG; // prepare not possible
+
+	SymbolString slave;
+	unsigned char addData = m_data->getLength(pt_slaveData);
+	result_t result = slave.push_back(addData, false, false);
+	if (result != RESULT_OK)
+		return result;
+	istringstream input;
+	result = m_data->write(input, pt_slaveData, slave, 0);
+	if (result != RESULT_OK)
+		return result;
+	slaveData = SymbolString(slave, true);
+	return result;
+}
+
 result_t Message::decode(const PartType partType, SymbolString& data,
 		ostringstream& output, bool leadingSeparator, char separator)
 {

src/lib/ebus/message.h

@@ -126,8 +126,9 @@ public:
 	 * @return the polling priority, or 0 for no polling at all.
 	 */
 	unsigned char getPollPriority() const { return m_pollPriority; }
+
 	/**
-	 * @brief Prepare master @a SymbolString for sending to the bus.
+	 * @brief Prepare the master @a SymbolString for sending a query or command to the bus.
 	 * @param masterData the master data @a SymbolString for writing symbols to.
 	 * @param input the @a istringstream to parse the formatted value(s) from.
 	 * @param separator the separator character between multiple fields.
@@ -135,6 +136,14 @@ public:
 	 */
 	result_t prepareMaster(const unsigned char srcAddress, SymbolString& masterData,
 			istringstream& input, char separator=';');
+
+	/**
+	 * @brief Prepare the slave @a SymbolString for sending an answer to the bus.
+	 * @param slaveData the slave data @a SymbolString for writing symbols to.
+	 * @return @a RESULT_OK on success, or an error code.
+	 */
+	result_t prepareSlave(SymbolString& masterData);
+
 	/**
 	 * @brief Decode a received message.
 	 * @param partType the @a PartType of the data.