Add a very experimental C++ interface

Author: Jacajack

.github/workflows/v3.0-ci.yml

@@ -52,6 +52,15 @@ jobs:
       - name: Build AVR slave example
         run: make -C examples/avrslave
 
+  cpp-build:
+    name: "C++ build test"
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2
+      - name: Compile
+        run: make -C test/cpp
+
   examples-build:
     name: "Build examples"
     runs-on: ubuntu-latest
@@ -66,6 +75,12 @@ jobs:
       run: make -C examples/integration
     - name: Build user-defined functions example
       run: make -C examples/userfun
+    - name: Run user-defined functions example
+      run: ./examples/userfun/userfun
+    - name: Build C++ example
+      run: make -C examples/cpp
+    - name: Run C++ example
+      run: ./examples/cpp/cppdemo
 
   main-test:
     name: "Tests"

examples/cpp/.gitignore

@@ -0,0 +1 @@
+cppdemo

examples/cpp/cppdemo.cpp

@@ -0,0 +1,90 @@
+#include <iostream>
+#include <iomanip>
+#define LIGHTMODBUS_FULL
+#define LIGHTMODBUS_IMPL
+#include <lightmodbus/lightmodbus.hpp>
+
+ModbusError regCallback(
+	const ModbusSlave *slave,
+	const ModbusRegisterCallbackArgs *args,
+	ModbusRegisterCallbackResult *result)
+{
+	switch (args->query)
+	{
+		// No write access
+		case MODBUS_REGQ_W_CHECK:
+			result->exceptionCode = MODBUS_EXCEP_SLAVE_FAILURE;
+			break;
+
+		// Read access to everything
+		case MODBUS_REGQ_R_CHECK:
+			result->exceptionCode = MODBUS_EXCEP_NONE;
+			break;
+
+		// Return 7 when reading
+		case MODBUS_REGQ_R:
+			result->value = 7;
+			break;
+		
+		// Ignore write requests (should not happen)
+		case MODBUS_REGQ_W:
+			throw std::runtime_error{"this should never happen"};
+			break;
+	}
+
+	// Always return MODBUS_OK
+	return MODBUS_OK;
+}
+
+ModbusError dataCallback(const ModbusMaster *master, const ModbusDataCallbackArgs *args)
+{
+	// I'm sorry, C++ people... I'm too tired right now to use std::cout
+	std::printf(
+		"Received data:\n"
+		"\t from: %d\n"
+		"\t  fun: %d\n"
+		"\t type: %s\n"
+		"\t   id: %d\n"
+		"\tvalue: %d\n",
+		args->address,
+		args->function,
+		modbusDataTypeStr(args->type),
+		args->index,
+		args->value
+	);
+
+	// Always return MODBUS_OK
+	return MODBUS_OK;
+}
+
+int main()
+{
+	llm::Slave slave(regCallback);
+	llm::Master master(dataCallback);
+
+	try
+	{
+		// Look how neat it looks
+		master.buildRequest01RTU(4, 15, 3);
+		slave.parseRequestRTU(4, master.getRequest(), master.getRequestLength());
+		master.parseResponseRTU(
+			master.getRequest(),
+			master.getRequestLength(),
+			slave.getResponse(),
+			slave.getResponseLength());
+	}
+	catch (const llm::GeneralError &e)
+	{
+		std::cerr << "General error (serious): " << e.what() << std::endl;
+	}
+	catch (const llm::RequestError &e)
+	{
+		std::cerr << "Request error: " << e.what() << std::endl;
+	}
+	catch (const llm::ResponseError &e)
+	{
+		std::cerr << "Response error: " << e.what() << std::endl;
+	}
+
+	return 0;
+}

examples/cpp/makefile

@@ -0,0 +1,2 @@
+all:
+	g++ -o cppdemo cppdemo.cpp -Wall -I../../include