Client: rewrite response decoding logic with new decoder

The commit rewrites response decoding with the new decoder.

Public structure `Data` is reworked. Now you need to call `data.decode`
with tuple format passed as template parameters - the method will return
parsed tuples in std::vector.

examples/Simple.cpp

@@ -61,17 +61,15 @@ using Net_t = LibevNetProvider<Buf_t, DefaultStream>;
 //doclabel16-1
 template <class BUFFER>
 std::vector<UserTuple>
-decodeUserTuple(BUFFER &buf, Data<BUFFER> &data)
+decodeUserTuple(Data<BUFFER> &data)
 {
+	auto tuples = data.template decode<std::tuple<uint64_t, std::string, double>>();
 	std::vector<UserTuple> results;
-	for(auto& t: data.tuples) {
+	for(auto& t: tuples) {
 		UserTuple tuple;
-		mpp::Dec dec(buf);
-		dec.SetPosition(t.begin);
-		dec.SetReader(false, UserTupleReader<BUFFER>{dec, tuple});
-		mpp::ReadResult_t res = dec.Read();
-		assert(res == mpp::READ_SUCCESS);
-		(void) res;
+		tuple.field1 = std::get<0>(t);
+		tuple.field2 = std::get<1>(t);
+		tuple.field3 = std::get<2>(t);
 		results.push_back(tuple);
 	}
 	return results;
@@ -80,10 +78,10 @@ decodeUserTuple(BUFFER &buf, Data<BUFFER> &data)
 
 template<class BUFFER>
 void
-printResponse(Connection<BUFFER, Net_t> &conn, Response<BUFFER> &response)
+printResponse(Response<BUFFER> &response)
 {
 	if (response.body.error_stack != std::nullopt) {
-		Error err = (*response.body.error_stack).error;
+		Error err = (*response.body.error_stack)[0];
 		std::cout << "RESPONSE ERROR: msg=" << err.msg <<
 			  " line=" << err.file << " file=" << err.file <<
 			  " errno=" << err.saved_errno <<
@@ -92,12 +90,11 @@ printResponse(Connection<BUFFER, Net_t> &conn, Response<BUFFER> &response)
 	}
 	if (response.body.data != std::nullopt) {
 		Data<BUFFER>& data = *response.body.data;
-		if (data.tuples.empty()) {
+		std::vector<UserTuple> tuples = decodeUserTuple(data);
+		if (tuples.empty()) {
 			std::cout << "Empty result" << std::endl;
 			return;
 		}
-		std::vector<UserTuple> tuples =
-			decodeUserTuple(conn.getInBuf(), data);
 		for (auto const& t : tuples) {
 			std::cout << t << std::endl;
 		}
@@ -204,7 +201,7 @@ main()
 	 * rely on response code storing in the header or check
 	 * Response->body.data and Response->body.error_stack members.
 	 */
-	printResponse<Buf_t>(conn, *response);
+	printResponse<Buf_t>(*response);
 	//doclabel11-2
 	/* Let's wait for both futures at once. */
 	std::vector<rid_t> futures(2);
@@ -216,7 +213,7 @@ main()
 		assert(conn.futureIsReady(futures[i]));
 		response = conn.getResponse(futures[i]);
 		assert(response != std::nullopt);
-		printResponse<Buf_t>(conn, *response);
+		printResponse<Buf_t>(*response);
 	}
 	//doclabel11-3
 	/* Let's create another connection. */

src/Client/ResponseDecoder.hpp

@@ -51,7 +51,7 @@ static constexpr size_t MP_RESPONSE_SIZE = 5;
 template<class BUFFER>
 class ResponseDecoder {
 public:
-	ResponseDecoder(BUFFER &buf) : m_Dec(buf) {};
+	ResponseDecoder(BUFFER &buf) : it(buf.begin()) {};
 	~ResponseDecoder() { };
 	ResponseDecoder() = delete;
 	ResponseDecoder(const ResponseDecoder& decoder) = delete;
@@ -64,18 +64,17 @@ class ResponseDecoder {
 private:
 	int decodeHeader(Header &header);
 	int decodeBody(Body<BUFFER> &body);
-	mpp::Dec<BUFFER> m_Dec;
+	iterator_t<BUFFER> it;
 };
 
 template<class BUFFER>
 int
 ResponseDecoder<BUFFER>::decodeResponseSize()
 {
 	int size = -1;
-	m_Dec.SetReader(false, mpp::SimpleReader<BUFFER, mpp::MP_INT, int>{size});
-	mpp::ReadResult_t res = m_Dec.Read();
+	bool ok = mpp::decode(it, size);
 	//TODO: raise more detailed error
-	if (res != mpp::READ_SUCCESS)
+	if (!ok)
 		return -1;
 	return size;
 }
@@ -84,24 +83,17 @@ template<class BUFFER>
 int
 ResponseDecoder<BUFFER>::decodeHeader(Header &header)
 {
-	m_Dec.SetReader(false, HeaderReader{m_Dec, header});
-	mpp::ReadResult_t res = m_Dec.Read();
-	if (res != mpp::READ_SUCCESS)
-		return -1;
-	return 0;
+	bool ok = mpp::decode(it, header);
+	return ok ? 0 : -1;
 }
 
 template<class BUFFER>
 int
 ResponseDecoder<BUFFER>::decodeBody(Body<BUFFER> &body)
 {
-	m_Dec.SetReader(false, BodyReader{m_Dec, body});
-	mpp::ReadResult_t res = m_Dec.Read();
-	if (res != mpp::READ_SUCCESS)
-		return -1;
-	if (body.data != std::nullopt)
-		body.data->end = m_Dec.getPosition();
-	return 0;
+
+	bool ok = mpp::decode(it, body);
+	return ok ? 0 : -1;
 }
 
 template<class BUFFER>
@@ -123,7 +115,7 @@ template<class BUFFER>
 void
 ResponseDecoder<BUFFER>::reset(iterator_t<BUFFER> &itr)
 {
-	m_Dec.SetPosition(itr);
+	it = itr;
 }
 
 static inline uint32_t