Extensive rewrite of basyx::vab

This commit
 - Significantly improves and simplifies frame handling
 - Introduces proper exception handling in vab return frames
 - Adjusts VAB behaviour to reflect changes made in the Java SDK
 - Fixes bugs in server code
 - Fixes bugs in model provider code

Change-Id: Iada7096102c3dc6d42a4832ab488d0b4799dd15c
Signed-off-by: Thomas Psota <thomas.psota@iese.fraunhofer.de>
diff --git a/sdks/c++/basys.sdk.cc/src/vab/CMakeLists.txt b/sdks/c++/basys.sdk.cc/src/vab/CMakeLists.txt
index f3425fa..549a9e0 100644
--- a/sdks/c++/basys.sdk.cc/src/vab/CMakeLists.txt
+++ b/sdks/c++/basys.sdk.cc/src/vab/CMakeLists.txt
@@ -25,7 +25,8 @@
 target_sources(${BASYX_VAB_LIB_SUFFIX}
     PRIVATE
         ${CMAKE_CURRENT_SOURCE_DIR}/vab/backend/connector/native/BaSyxConnector.cpp
-        ${CMAKE_CURRENT_SOURCE_DIR}/vab/backend/connector/native/frame/BaSyxNativeFrameBuilder.cpp
+        ${CMAKE_CURRENT_SOURCE_DIR}/vab/backend/connector/native/frame/Frame.cpp
+        ${CMAKE_CURRENT_SOURCE_DIR}/vab/backend/connector/native/frame/EntityWrapper.cpp
         ${CMAKE_CURRENT_SOURCE_DIR}/vab/core/proxy/VABElementProxy.cpp
         ${CMAKE_CURRENT_SOURCE_DIR}/vab/core/util/VABPath.cpp
         ${CMAKE_CURRENT_SOURCE_DIR}/vab/core/VABConnectionManager.cpp
@@ -40,7 +41,8 @@
         ${BASYX_VAB_INCLUDE_DIR}/backend/connector/IBaSyxConnector.h
         ${BASYX_VAB_INCLUDE_DIR}/backend/connector/JSONProvider.h
         ${BASYX_VAB_INCLUDE_DIR}/backend/connector/native/BaSyxConnector.h
-        ${BASYX_VAB_INCLUDE_DIR}/backend/connector/native/frame/BaSyxNativeFrameBuilder.h
+        ${BASYX_VAB_INCLUDE_DIR}/backend/connector/native/frame/Frame.h
+        ${BASYX_VAB_INCLUDE_DIR}/backend/connector/native/frame/EntityWrapper.h
         ${BASYX_VAB_INCLUDE_DIR}/core/IModelProvider.h
         ${BASYX_VAB_INCLUDE_DIR}/core/proxy/IVABElementProxy.h
         ${BASYX_VAB_INCLUDE_DIR}/core/proxy/VABElementProxy.h
diff --git a/sdks/c++/basys.sdk.cc/src/vab/vab/backend/connector/native/BaSyxConnector.cpp b/sdks/c++/basys.sdk.cc/src/vab/vab/backend/connector/native/BaSyxConnector.cpp
index c5fdd01..8924014 100644
--- a/sdks/c++/basys.sdk.cc/src/vab/vab/backend/connector/native/BaSyxConnector.cpp
+++ b/sdks/c++/basys.sdk.cc/src/vab/vab/backend/connector/native/BaSyxConnector.cpp
@@ -6,7 +6,8 @@
 */
 
 #include <BaSyx/vab/backend/connector/native/BaSyxConnector.h>
-#include <BaSyx/vab/backend/connector/native/frame/BaSyxNativeFrameBuilder.h>
+#include <BaSyx/vab/backend/connector/native/frame/Frame.h>
+#include <BaSyx/vab/backend/connector/native/frame/EntityWrapper.h>
 #include <BaSyx/vab/provider/native/frame/BaSyxNativeFrameHelper.h>
 
 #include <BaSyx/shared/serialization/json.h>
@@ -22,8 +23,7 @@
 namespace native {
 
 NativeConnector::NativeConnector(std::string const& address, int port)
-	: builder{}
-	, socket{ basyx::net::tcp::Socket::Connect(address, port) }
+	: socket{ basyx::net::tcp::Socket::Connect(address, port) }
 	, log{ "NativeConnector" }
 {
 	log.trace("Connected to {}:{}", address, port);
@@ -32,7 +32,6 @@
 
 
 NativeConnector::~NativeConnector() {
-	this->socket.Close();
 }
 
 
@@ -42,65 +41,69 @@
 	log.trace("basysGet() called:");
 	log.trace("    path: {}", path);
 
-	auto entityWrapper = basysGetRaw(path);
-	auto value = basyx::serialization::json::deserialize(entityWrapper["entity"]);
+	auto value = basysProcess(Frame::Builder::Get(path));
 	return value;
 }
 
-nlohmann::json NativeConnector::basysGetRaw(std::string const& path) {
-	size_t size = builder.buildGetFrame(path, buffer.data() + BASYX_FRAMESIZE_SIZE);
-	sendData(buffer.data(), size);
-	size = receiveData(buffer.data());
-	if (buffer[4] != 0) { // Error happened
-		return ""_json; // TODO: Error handling
-	}
-	std::string data = StringTools::fromArray(buffer.data() + BASYX_FRAMESIZE_SIZE + 1);
-	return nlohmann::json::parse(data);
-}
+basyx::object NativeConnector::basysProcess(const Frame & frame)
+{
+	this->sendFrame(frame);
 
-void NativeConnector::basysSet(std::string const& path, const basyx::object & newValue)
+	auto response_frame = this->recvFrame();
+	if (response_frame.getFlag() != 0x00) {
+		return basyx::object::make_error(basyx::object::error::MalformedRequest, "invalid frame received");
+	};
+
+	auto entityWrapper = nlohmann::json::parse(response_frame.getFirstValue());
+
+	auto value = basyx::vab::EntityWrapper::from_json(entityWrapper);
+	return value;
+};
+
+basyx::object NativeConnector::basysSet(std::string const& path, const basyx::object & newValue)
 {
 	log.trace("basysSet() called:");
 	log.trace("    path: {}", path);
 
-	size_t size = builder.buildSetFrame(path, newValue, buffer.data() + BASYX_FRAMESIZE_SIZE);
-	sendData(buffer.data(), size);
-	size = receiveData(buffer.data());
+	auto return_code = basysProcess(Frame::Builder::Set(path, newValue));
+	return return_code;
 }
 
-void NativeConnector::basysCreate(std::string const& path, const basyx::object & val)
+basyx::object NativeConnector::basysCreate(std::string const& path, const basyx::object & val)
 {
-	size_t size = builder.buildCreateFrame(path, val, buffer.data() + BASYX_FRAMESIZE_SIZE);
-	sendData(buffer.data(), size);
-	size = receiveData(buffer.data());
+	log.trace("basysCreate() called:");
+	log.trace("    path: {}", path);
+
+	auto return_code = basysProcess(Frame::Builder::Create(path, val));
+	return return_code;
 }
 
 basyx::object NativeConnector::basysInvoke(std::string const& path, const basyx::object & param)
 {
-	size_t size = builder.buildInvokeFrame(path, param, buffer.data() + BASYX_FRAMESIZE_SIZE);
-	sendData(buffer.data(), size);
-	size = receiveData(buffer.data());
-	return decode(buffer.data() + 5);
+	log.trace("basysInvoke() called:");
+	log.trace("    path: {}", path);
+
+	auto return_code = basysProcess(Frame::Builder::Invoke(path, param));
+	return return_code;
 }
 
-void NativeConnector::basysDelete(std::string const& path)
+basyx::object NativeConnector::basysDelete(std::string const& path)
 {
-	size_t size = builder.buildDeleteFrame(path, buffer.data() + BASYX_FRAMESIZE_SIZE);
-	sendData(buffer.data(), size);
-	size = receiveData(buffer.data());
+	log.trace("basysDelete() called:");
+	log.trace("    path: {}", path);
+
+	auto return_code = basysProcess(Frame::Builder::Delete(path));
+	return return_code;
 }
 
-void NativeConnector::basysDelete(std::string const& path, const basyx::object & obj) {
-	size_t size = builder.buildDeleteFrame(path, obj, buffer.data() + BASYX_FRAMESIZE_SIZE);
-	sendData(buffer.data(), size);
-	size = receiveData(buffer.data());
-}
+basyx::object NativeConnector::basysDelete(std::string const& path, const basyx::object & obj) 
+{
+	log.trace("basysDelete() called:");
+	log.trace("    path: {}", path);
 
-// TODO: Error handling
-/**
-	* Builds a send frame and sends it to server
-	* @param msg a frame constructed with the BaSyxNativeFrameBuilder
-	*/
+	auto return_code = basysProcess(Frame::Builder::Delete(path, obj));
+	return return_code;
+}
 
 void NativeConnector::sendData(char* msg, size_t size) 
 {
@@ -110,10 +113,6 @@
 
 	CoderTools::setInt32(msg, 0, size);
 	size += BASYX_FRAMESIZE_SIZE;
-#ifdef PRINT_FRAME
-	log.debug("Sending:");
-	vab::provider::native::frame::BaSyxNativeFrameHelper::printFrame(msg, size);
-#endif
 
 	log.debug("Sending {} bytes.", size);
 	int sent_bytes = this->socket.Send(basyx::net::make_buffer(msg, size));
@@ -125,7 +124,8 @@
 }
 
 // TODO: Error handling
-size_t NativeConnector::receiveData(char* data) {
+size_t NativeConnector::receiveData(char* data) 
+{
 	log.trace("receiveData() called");
 	log.trace("    data: 0x{0:x}", (std::size_t)data);
 
@@ -135,10 +135,6 @@
 	log.debug("Received {} bytes.", recv_bytes);
 
 	if (recv_bytes > 0) {
-#ifdef PRINT_FRAME
-		log.debug("Received:");
-		vab::provider::native::frame::BaSyxNativeFrameHelper::printFrame(data, recv_bytes);
-#endif
 		return recv_bytes;
 	}
 	else {
@@ -147,10 +143,23 @@
 	}
 }
 
-basyx::object NativeConnector::decode(char* buffer)
+void NativeConnector::sendFrame(const Frame & frame)
 {
-	std::string data = StringTools::fromArray(buffer);
-	return basyx::serialization::json::deserialize(data).Get<basyx::object::object_map_t&>()["entity"];
+	Frame::write_to_buffer(
+		basyx::net::make_buffer(
+			buffer.data() + BASYX_FRAMESIZE_SIZE, default_buffer_length - BASYX_FRAMESIZE_SIZE), 
+		frame);
+
+	sendData(buffer.data(), frame.size());
+};
+
+Frame NativeConnector::recvFrame()
+{
+	this->receiveData(buffer.data());
+	auto size = *reinterpret_cast<uint32_t*>(buffer.data());
+	auto frame = Frame::read_from_buffer(basyx::net::make_buffer(this->buffer.data() + BASYX_FRAMESIZE_SIZE, size));
+
+	return frame;
 };
 
 }
diff --git a/sdks/c++/basys.sdk.cc/src/vab/vab/backend/connector/native/frame/BaSyxNativeFrameBuilder.cpp b/sdks/c++/basys.sdk.cc/src/vab/vab/backend/connector/native/frame/BaSyxNativeFrameBuilder.cpp
deleted file mode 100644
index 34987eb..0000000
--- a/sdks/c++/basys.sdk.cc/src/vab/vab/backend/connector/native/frame/BaSyxNativeFrameBuilder.cpp
+++ /dev/null
@@ -1,91 +0,0 @@
-/*
- * BaSyxNativeFrameBuilder.cpp
- *
- *  Created on: 14.08.2018
- *      Author: schnicke
- */
-
-#include <BaSyx/vab/backend/connector/native/frame/BaSyxNativeFrameBuilder.h>
-
-#include <BaSyx/shared/serialization/json.h>
-
-#include <BaSyx/util/tools/StringTools.h>
-
-namespace basyx {
-namespace vab {
-namespace connector {
-namespace native {
-namespace frame {
-
-	
-BaSyxNativeFrameBuilder::BaSyxNativeFrameBuilder() { };
-
-size_t BaSyxNativeFrameBuilder::buildGetFrame(std::string const& path, char * buffer)
-{
-	return encodeCommandAndPath(BaSyxCommand::Get, path, buffer);
-}
-
-size_t BaSyxNativeFrameBuilder::buildSetFrame(std::string const& path, const basyx::object & newVal, char * buffer)
-{
-	size_t size = encodeCommandAndPath(BaSyxCommand::Set, path, buffer);
-	size += encodeValue(newVal, buffer + size);
-	return size;
-}
-
-size_t BaSyxNativeFrameBuilder::buildCreateFrame(std::string const& path, const basyx::object & newVal, char * buffer)
-{
-	size_t size = encodeCommandAndPath(BaSyxCommand::Create, path, buffer);
-	size += encodeValue(newVal, buffer + size);
-	return size;
-}
-
-size_t BaSyxNativeFrameBuilder::buildDeleteFrame(std::string const& path, char * buffer)
-{
-	return encodeCommandAndPath(BaSyxCommand::Delete, path, buffer);
-}
-
-size_t BaSyxNativeFrameBuilder::buildDeleteFrame(std::string const& path, const basyx::object & deleteVal, char * buffer)
-{
-	size_t size = encodeCommandAndPath(BaSyxCommand::Delete, path, buffer);
-	size += encodeValue(deleteVal, buffer + size);
-	return size;
-}
-
-size_t BaSyxNativeFrameBuilder::buildInvokeFrame(std::string const& path, const basyx::object & param, char * buffer)
-{
-	size_t size = encodeCommandAndPath(BaSyxCommand::Invoke, path, buffer);
-	size += encodeValue(param, buffer + size);
-	return size;
-}
-
-size_t BaSyxNativeFrameBuilder::buildInvokeFrame(std::string const& path, const basyx::object::object_list_t & params, char * buffer)
-{
-	size_t size = encodeCommandAndPath(BaSyxCommand::Invoke, path, buffer);
-	size += encodeValue(params, buffer + size);
-	return size;
-}
-
-size_t BaSyxNativeFrameBuilder::encodeCommand(BaSyxCommand command, char* buffer)
-{
-	buffer[0] = static_cast<uint8_t>(command);
-	return 1;
-}
-
-std::size_t BaSyxNativeFrameBuilder::encodeValue(const basyx::object & value, char * buffer)
-{
-	std::string dumped = basyx::serialization::json::serialize(value).dump(4);
-	return StringTools::toArray(dumped, buffer);
-}
-
-size_t BaSyxNativeFrameBuilder::encodeCommandAndPath(BaSyxCommand command, std::string const& path, char* buffer)
-{
-	size_t size = encodeCommand(command, buffer);
-	size += StringTools::toArray(path, buffer + size);
-	return size;
-}
-
-}
-}
-}
-}
-}
diff --git a/sdks/c++/basys.sdk.cc/src/vab/vab/backend/connector/native/frame/EntityWrapper.cpp b/sdks/c++/basys.sdk.cc/src/vab/vab/backend/connector/native/frame/EntityWrapper.cpp
new file mode 100644
index 0000000..37c2989
--- /dev/null
+++ b/sdks/c++/basys.sdk.cc/src/vab/vab/backend/connector/native/frame/EntityWrapper.cpp
@@ -0,0 +1,112 @@
+#include <BaSyx/vab/backend/connector/native/frame/EntityWrapper.h>
+
+using basyx::vab::EntityWrapper;
+
+
+namespace {
+	std::string prepareErrorCode(basyx::object::error errorCode)
+	{
+		std::string error;
+		switch (errorCode)
+		{
+		case basyx::object::error::PropertyNotFound:
+			error = "ResourceNotFoundException";
+			break;
+		case basyx::object::error::ObjectAlreadyExists:
+			error = "ResourceAlreadyExistsException";
+			break;
+		case basyx::object::error::MalformedRequest:
+			error = "MalformedRequestException";
+			break;
+		default:
+			error = "ProviderException";
+			break;
+		};
+		return error;
+	};
+
+	std::string prepareErrorMessage(basyx::object::error errorCode, const std::string & message)
+	{
+		return prepareErrorCode(errorCode) + ": " + message;
+	};
+}
+
+basyx::object build_exception(const std::string & type, const std::string & message)
+{
+	basyx::object::error error = basyx::object::error::ProviderException;
+
+	if (type == "ResourceNotFoundException")
+	{
+		error = basyx::object::error::PropertyNotFound;
+	}
+	else if (type == "ResourceAlreadyExistsException")
+	{
+		error = basyx::object::error::ObjectAlreadyExists;
+	}
+	else if (type == "MalformedRequestException")
+	{
+		error = basyx::object::error::MalformedRequest;
+	}
+	else if (type == "ProviderException")
+	{
+		error = basyx::object::error::ProviderException;
+	};
+
+	return basyx::object::make_error(error, message);
+};
+
+basyx::json_t EntityWrapper::build_from_error(basyx::object::error error, const std::string & message)
+{
+	json_t msg;
+	msg["messageType"] = 6;
+	msg["text"] = prepareErrorMessage(error, message);
+	msg["code"] = nullptr;
+
+	basyx::json_t j_obj;
+	j_obj["success"] = false;
+	j_obj["isException"] = true;
+	j_obj["messages"] = json_t::array({ msg });
+	j_obj["entityType"] = prepareErrorCode(error);
+	return j_obj;
+};
+
+basyx::json_t EntityWrapper::build_from_object(const basyx::object & object)
+{
+	basyx::json_t j_obj;
+	if (object.IsError())
+	{
+		return build_from_error(object.getError(), object.getErrorMessage());
+	}
+	else
+	{
+		j_obj["success"] = true;
+//		j_obj["isException"] = false;
+		j_obj["entityType"] = "entity";
+		j_obj["entity"] = basyx::serialization::json::serialize(object);
+	}
+	return j_obj;
+};
+
+
+basyx::object EntityWrapper::from_json(const basyx::json_t & json)
+{
+	bool success = json["success"];
+	// everyhing okay, deserialize entity
+	if (success)
+	{
+		if (json.contains("entity"))
+			return basyx::serialization::json::deserialize(json["entity"]);
+		else
+			return basyx::object::make_null();
+	}
+	// something went wrong, check for exception
+	else if (json.contains("isException") && json.contains("messages"))
+	{
+		return build_exception(json["entityType"], json["messages"][0]["text"]);
+	}
+	// error and no exception; create one
+	else
+	{
+		return basyx::object::make_error(basyx::object::error::MalformedRequest);
+	};
+};
\ No newline at end of file
diff --git a/sdks/c++/basys.sdk.cc/src/vab/vab/backend/connector/native/frame/Frame.cpp b/sdks/c++/basys.sdk.cc/src/vab/vab/backend/connector/native/frame/Frame.cpp
new file mode 100644
index 0000000..9d7a649
--- /dev/null
+++ b/sdks/c++/basys.sdk.cc/src/vab/vab/backend/connector/native/frame/Frame.cpp
@@ -0,0 +1,166 @@
+#include <BaSyx/vab/backend/connector/native/frame/Frame.h>
+
+#include <BaSyx/util/tools/StringTools.h>
+
+using namespace basyx::vab::connector::native;
+
+Frame::Frame()
+	: flag(0xFF)
+	, value_1()
+	, value_2()
+{
+};
+
+Frame::Frame(uint8_t flag, const std::string & value_1) 
+	: flag(flag)
+	, value_1(value_1)
+	, value_2()
+{
+};
+
+Frame::Frame(uint8_t flag, const std::string & value_1, const std::string & value_2)
+	: flag(flag)
+	, value_1(value_1)
+	, value_2(value_2)
+{
+};
+
+uint8_t Frame::getFlag() const
+{
+	return this->flag;
+};
+
+void Frame::setFlag(uint8_t flag)
+{
+	this->flag = flag;
+};
+
+void Frame::setFlag(BaSyxCommand flag)
+{
+	this->flag = static_cast<decltype(this->flag)>(flag);
+};
+
+const std::string & Frame::getFirstValue() const
+{
+	return this->value_1;
+};
+
+void Frame::setFirstValue(const std::string & value)
+{
+	this->value_1 = value;
+};
+
+const std::string & Frame::getSecondValue() const
+{
+	return this->value_2;
+};
+
+void Frame::setSecondValue(const std::string & value)
+{
+	this->value_2 = value;
+};
+
+bool Frame::write_to_buffer(const basyx::net::Buffer & buffer, const Frame & frame)
+{
+	// bail out if buffer to small
+	if (frame.size() > buffer.size())
+		return false;
+
+	std::size_t pos = 0;
+	char * data = reinterpret_cast<char*>(buffer.data());
+
+	// write command field
+	data[pos] = static_cast<uint8_t>(frame.getFlag());
+	pos += 1;
+	
+	// write first value field
+	pos += StringTools::toArray(frame.getFirstValue(), &data[pos]);
+
+	// write second value field
+	if (!frame.getSecondValue().empty())
+	{
+		pos += StringTools::toArray(frame.getSecondValue(), &data[pos]);
+	};
+
+	return true;
+};
+
+Frame Frame::read_from_buffer(const basyx::net::Buffer & buffer)
+{
+	Frame frame;
+
+	std::size_t pos = 0;
+	char * data = reinterpret_cast<char*>(buffer.data());
+	
+	uint8_t flag = static_cast<uint8_t>(data[pos]);
+	frame.setFlag(flag);
+	pos += 1;
+
+	frame.setFirstValue(StringTools::fromArray(&data[pos]));
+	pos += frame.getFirstValue().size() + sizeof(uint32_t);
+
+	if (pos < buffer.size())
+	{
+		frame.setSecondValue(StringTools::fromArray(&data[pos]));
+		pos += frame.getSecondValue().size() + sizeof(uint32_t);
+	};
+
+	return frame;
+};
+
+std::size_t Frame::size() const
+{
+	std::size_t size = 1; // size of flag field
+	size += sizeof(uint32_t) + this->getFirstValue().size(); // size of first value + length
+
+	if(!this->getSecondValue().empty())
+		size += sizeof(uint32_t) + this->getSecondValue().size(); // size of second value + length
+
+	return size;
+};
+
+Frame Frame::Builder::Get(const std::string & path)
+{
+	return Frame{ static_cast<uint8_t>(BaSyxCommand::Get), path };
+};
+
+Frame Frame::Builder::Set(const std::string & path, const basyx::object & value)
+{
+	return Frame{
+		static_cast<uint8_t>(BaSyxCommand::Set),
+		path,
+		basyx::serialization::json::serialize(value).dump(4)
+	};
+};
+
+Frame Frame::Builder::Create(const std::string & path, const basyx::object & value)
+{
+	return Frame{
+		static_cast<uint8_t>(BaSyxCommand::Create),
+		path,
+		basyx::serialization::json::serialize(value).dump(4)
+	};
+};
+
+Frame Frame::Builder::Delete(const std::string & path)
+{
+	return Frame{ static_cast<uint8_t>(BaSyxCommand::Delete), path };
+}; 
+
+Frame Frame::Builder::Delete(const std::string & path, const basyx::object & value)
+{
+	return Frame{
+		static_cast<uint8_t>(BaSyxCommand::Delete),
+		path,
+		basyx::serialization::json::serialize(value).dump(4)
+	};
+};
+
+Frame Frame::Builder::Invoke(const std::string & path, const basyx::object & value)
+{
+	return Frame{
+		static_cast<uint8_t>(BaSyxCommand::Invoke),
+		path,
+		basyx::serialization::json::serialize(value).dump(4)
+	};
+};
\ No newline at end of file
diff --git a/sdks/c++/basys.sdk.cc/src/vab/vab/provider/VABModelProvider.cpp b/sdks/c++/basys.sdk.cc/src/vab/vab/provider/VABModelProvider.cpp
index b63c498..10b2a67 100644
--- a/sdks/c++/basys.sdk.cc/src/vab/vab/provider/VABModelProvider.cpp
+++ b/sdks/c++/basys.sdk.cc/src/vab/vab/provider/VABModelProvider.cpp
@@ -87,11 +87,12 @@
 	// Only write values, that already exist
 	auto thisElement = parentElement.getProperty(propertyName);
 
-	if (!parentElement.IsNull() && !thisElement.IsNull()) {
+	if (!parentElement.IsNull()/* && !thisElement.IsNull()*/) {
 		parentElement.insertKey(propertyName, newValue, true);
+		return basyx::object::error::None;
 	}
 
-	return basyx::object::error::None;
+	return basyx::object::error::PropertyNotFound;
 };
 
 basyx::object::error VABModelProvider::createValue(const std::string& path, const basyx::object newValue)
@@ -163,10 +164,11 @@
 		if (!childElement.IsNull()) {
 			//handler.DeleteValue(childElement, deletedValue);
 			childElement.remove(deletedValue);
+			return basyx::object::error::None;
 		}
 	}
 
-	return basyx::object::error::None;
+	return basyx::object::error::PropertyNotFound;
 };
 
 basyx::object::error VABModelProvider::deleteValue(const std::string& path)
@@ -200,14 +202,14 @@
 		log.error("Function not found!");
 		log.trace("Returning basyx::object::null");
 
-		return basyx::object{ nullptr };
+		return basyx::object::make_error(basyx::object::error::PropertyNotFound, "method not found");
 	}
 
 	if (!element.IsInvokable()) {
 		log.error("Found object is not invokable!");
 		log.trace("Returning basyx::object::null");
 
-		return basyx::object{ nullptr };
+		return basyx::object::make_error(basyx::object::error::ProviderException, "method not invokable");
 	};
 
 	log.trace("Function found. Invoking...");
diff --git a/sdks/c++/basys.sdk.cc/src/vab/vab/provider/native/frame/BaSyxNativeFrameProcessor.cpp b/sdks/c++/basys.sdk.cc/src/vab/vab/provider/native/frame/BaSyxNativeFrameProcessor.cpp
index 805dda6..9667497 100644
--- a/sdks/c++/basys.sdk.cc/src/vab/vab/provider/native/frame/BaSyxNativeFrameProcessor.cpp
+++ b/sdks/c++/basys.sdk.cc/src/vab/vab/provider/native/frame/BaSyxNativeFrameProcessor.cpp
@@ -13,159 +13,96 @@
 #include <BaSyx/util/tools/StringTools.h>
 
 #include <BaSyx/shared/types.h>
- 
+
 namespace basyx {
 namespace vab {
 namespace provider {
 namespace native {
 namespace frame {
 
+using connector::native::Frame;
+
+
 BaSyxNativeFrameProcessor::BaSyxNativeFrameProcessor(vab::core::IModelProvider* providerBackend) 
 	: jsonProvider{ providerBackend}
 {
 }
 
-BaSyxNativeFrameProcessor::~BaSyxNativeFrameProcessor() 
+Frame BaSyxNativeFrameProcessor::processInputFrame(const Frame & frame)
 {
-}
+	auto command = static_cast<BaSyxCommand>(frame.getFlag());
 
-void BaSyxNativeFrameProcessor::processInputFrame(char const* rxFrame, std::size_t rxSize, char* txFrame, std::size_t* txSize) 
-{
-	std::size_t offset;
-	auto command = vab::provider::native::frame::BaSyxNativeFrameHelper::getCommand(rxFrame, &offset);
-	rxFrame += offset;
-	switch (command) {
+	switch (command) 
+	{
 	case BaSyxCommand::Get:
-		processGet(rxFrame, txFrame, txSize);
-		break;
+		return processGet(frame);
 	case BaSyxCommand::Set:
-		processSet(rxFrame, txFrame, txSize);
-		break;
+		return processSet(frame);
 	case BaSyxCommand::Create:
-		processCreate(rxFrame, txFrame, txSize);
-		break;
+		return processCreate(frame);
 	case BaSyxCommand::Delete:
-		processDelete(rxFrame, rxSize - offset, txFrame, txSize);
-		break;
+		return processDelete(frame);
 	case BaSyxCommand::Invoke:
-		processInvoke(rxFrame, txFrame, txSize);
-		break;
-
-	}
-}
-
-void BaSyxNativeFrameProcessor::processGet(char const* rxFrame, char* txFrame, std::size_t* txSize) 
-{
-	// Try to get the requested value
-	// TODO: Error Handling?
-
-	std::string path = BaSyxNativeFrameHelper::getString(rxFrame, 0);
-	// Advance txFrame by 5 because of the following setup of txFrame:
-	// 1 byte result field
-	// 4 byte string size
-	// N byte return value
-	std::string getResult = jsonProvider.processBaSysGet(path);
-	*txSize += getResult.size();
-	memcpy(txFrame + 5, getResult.c_str(), getResult.size());
-
-	// Set return string size
-	CoderTools::setInt32(txFrame + 1, 0, *txSize);
-	*txSize += BASYX_STRINGSIZE_SIZE;
-	
-	// Set result field to 0 to indicate success
-	txFrame[0] = 0;
-	*txSize += 1;
-}
-
-void BaSyxNativeFrameProcessor::processSet(char const* rxFrame, char* txFrame, std::size_t* txSize) 
-{
-	std::string path = BaSyxNativeFrameHelper::getString(rxFrame, 0);
-
-	// TODO: Error Handling?
-	std::string serializedValue = BaSyxNativeFrameHelper::getString(rxFrame, 1);
-	std::string getResult = jsonProvider.processBaSysSet(path, serializedValue);
-	memcpy(txFrame + 5, getResult.c_str(), getResult.size());
-
-	// Set return string size
-	CoderTools::setInt32(txFrame + 1, 0, *txSize);
-	*txSize += BASYX_STRINGSIZE_SIZE;
-	
-        // Set result field to 0 to indicate success
-	txFrame[0] = 0;
-	*txSize += 1;
-}
-
-void BaSyxNativeFrameProcessor::processCreate(char const* rxFrame, char* txFrame, std::size_t* txSize)
-{
-	std::string path = BaSyxNativeFrameHelper::getString(rxFrame, 0);
-
-	// TODO: Error Handling?
-	std::string serializedValue = BaSyxNativeFrameHelper::getString(rxFrame, 1);
-
-	std::string getResult =	jsonProvider.processBaSysCreate(path, serializedValue);
-	memcpy(txFrame + 5, getResult.c_str(), getResult.size());
-
-	// Set return string size
-	CoderTools::setInt32(txFrame + 1, 0, *txSize);
-	*txSize += BASYX_STRINGSIZE_SIZE;
-	
-        // Set result field to 0 to indicate success
-	txFrame[0] = 0;
-	*txSize += 1;
-}
-
-void BaSyxNativeFrameProcessor::processDelete(char const* rxFrame, std::size_t rxSize, char* txFrame, std::size_t* txSize) 
-{
-	std::string path = BaSyxNativeFrameHelper::getString(rxFrame, 0);
-
-        std::string result;
-
-	// Check if there is a serialized json after the path to distinguish between map/collection delete and simple delete
-	if (path.size() + BASYX_STRINGSIZE_SIZE < rxSize) {
-		std::string serializedValue = BaSyxNativeFrameHelper::getString(rxFrame,
-				1);
-            result = jsonProvider.processBaSysDelete(path, serializedValue);
-	} else {
-	    result = jsonProvider.processBaSysDelete(path);
+		return processInvoke(frame);
 	}
 
-	memcpy(txFrame + 5, result.c_str(), result.size());
-
-	// Set return string size
-	CoderTools::setInt32(txFrame + 1, 0, *txSize);
-	*txSize += BASYX_STRINGSIZE_SIZE;
-
-	// Set result field to 0 to indicate success
-	txFrame[0] = 0;
-	*txSize += 1;
+	return Frame{};
 }
 
-void BaSyxNativeFrameProcessor::processInvoke(char const* rxFrame, char* txFrame, std::size_t* txSize)
+Frame BaSyxNativeFrameProcessor::processGet(const Frame & frame)
 {
-	std::string path = BaSyxNativeFrameHelper::getString(rxFrame, 0);
+	auto path = frame.getFirstValue();
+	auto getResult = jsonProvider.processBaSysGet(path);
 
-	// TODO: Error Handling?
-	std::string serializedValue = BaSyxNativeFrameHelper::getString(rxFrame, 1);
-
-	// Advance txFrame by 5 because of the following setup of txFrame:
-	// 1 byte result field
-	// 4 byte string size
-	// N byte return value
-	auto result = jsonProvider.processBaSysInvoke(path, serializedValue, txFrame + 5,
-			txSize);
-
-	*txSize = result.size();
-	memcpy(txFrame + 5, result.c_str(), result.size());
-
-	// Set return value size
-	CoderTools::setInt32(txFrame + 1, 0, *txSize);
-	*txSize += BASYX_STRINGSIZE_SIZE;
-
-	// Set result field to 0 to indicate success
-	txFrame[0] = 0;
-	*txSize += 1;
+	return Frame{ 0x00, getResult };
 }
 
+Frame BaSyxNativeFrameProcessor::processSet(const Frame & frame)
+{
+	auto path = frame.getFirstValue();
+	auto value = frame.getSecondValue();
+
+	auto result = jsonProvider.processBaSysSet(path, value);
+
+	return Frame{ 0x00, result };
+};
+
+Frame BaSyxNativeFrameProcessor::processCreate(const Frame & frame)
+{
+	auto path = frame.getFirstValue();
+	auto value = frame.getSecondValue();
+
+	auto result = jsonProvider.processBaSysCreate(path, value);
+
+	return Frame{ 0x00, result };
+};
+
+Frame BaSyxNativeFrameProcessor::processDelete(const Frame & frame)
+{
+	auto path = frame.getFirstValue();
+	auto value = frame.getSecondValue();
+
+	// if no value specified, simple delete
+	if (value.empty())
+	{
+		auto result = jsonProvider.processBaSysDelete(path);
+		return Frame{ 0x00, result };
+	};
+
+	auto result = jsonProvider.processBaSysDelete(path, value);
+	return Frame{ 0x00, result };
+};
+
+Frame BaSyxNativeFrameProcessor::processInvoke(const Frame & frame)
+{
+	auto path = frame.getFirstValue();
+	auto value = frame.getSecondValue();
+
+	auto result = jsonProvider.processBaSysInvoke(path, value);
+
+	return Frame{ 0x00, result };
+};
+
 
 }
 }