[modbus_slave]:added support of the callback context execution (#97)

Author: ValentiWorkLearning

src/ModbusSlave.cpp

@@ -867,14 +867,14 @@ uint8_t Modbus::executeCallback(uint8_t slaveAddress, uint8_t callbackIndex, uin
         {
             if (callback)
             {
-                callback(Modbus::readFunctionCode(), address, length);
+                callback(Modbus::readFunctionCode(), address, length,_pModbusCallbackContext);
             }
         }
         else if (_slaves[i].getUnitAddress() == slaveAddress)
         {
             if (callback)
             {
-                return callback(Modbus::readFunctionCode(), address, length);
+                return callback(Modbus::readFunctionCode(), address, length,_pModbusCallbackContext);
             }
             else
             {
@@ -1028,6 +1028,14 @@ uint16_t Modbus::reportException(uint8_t exceptionCode)
     return Modbus::writeResponse();
 }
 
+
+
+void Modbus::setCallbackContext(void* pModbusCallbackContext) noexcept
+{
+    _pModbusCallbackContext = pModbusCallbackContext;
+}
+
+
 /**
  * Calculate the CRC of the passed byte array from zero up to the passed length.
  *

src/ModbusSlave.h

@@ -119,7 +119,7 @@ enum
   STATUS_GATEWAY_TARGET_DEVICE_FAILED_TO_RESPOND,
 };
 
-typedef uint8_t (*ModbusCallback)(uint8_t, uint16_t, uint16_t);
+using ModbusCallback = uint8_t (*)(uint8_t, uint16_t, uint16_t, void*);
 
 /**
  * @class ModbusSlave
@@ -169,6 +169,8 @@ class Modbus
   uint64_t getTotalBytesSent();
   uint64_t getTotalBytesReceived();
 
+  void setCallbackContext(void* pModbusCallbackContext) noexcept;
+
   // This cbVector is a pointer to cbVector of the first slave, to allow shorthand syntax:
   //     Modbus slave(SLAVE_ID, CTRL_PIN);
   //     slave.cbVector[CB_WRITE_COILS] = writeDigitalOut;
@@ -209,6 +211,8 @@ class Modbus
   uint64_t _totalBytesSent = 0;
   uint64_t _totalBytesReceived = 0;
 
+  void* _pModbusCallbackContext = nullptr;
+
   bool relevantAddress(uint8_t unitAddress);
   bool readRequest();
   bool validateRequest();