Client: rewrite response decoding logic with new decoder

The commit rewrites response decoding logic using new decoder. Field
IPROTO_ERROR_24 is not parsed anymore - it is a duplicate of the last
error message in the error stack. Also, the whole error stack is decoded
now (before the patch, only the first value was decoded).
MP_ERROR_FIELDS are still not decoded.

Public structure `Data` is reworked. Now you need to call `data.decode`
method and pass a container of arrays - every tuple will be decoded as
an array and put to the container.

Author: drewdzzz

examples/Reader.hpp

@@ -41,6 +41,9 @@ struct UserTuple {
 	uint64_t field1;
 	std::string field2;
 	double field3;
+
+	static constexpr auto mpp = std::make_tuple(
+		&UserTuple::field1, &UserTuple::field2, &UserTuple::field3);
 };
 //doclabel13-2
 
@@ -50,59 +53,3 @@ operator<<(std::ostream& strm, const UserTuple &t)
 	return strm << "Tuple: field1=" << t.field1 << " field2=" << t.field2 <<
 		       " field3=" << t.field3;
 }
-
-using Buf_t = tnt::Buffer<16 * 1024>;
-using BufIter_t = typename Buf_t::iterator;
-
-//doclabel14-1
-struct UserTupleValueReader : mpp::DefaultErrorHandler {
-	explicit UserTupleValueReader(UserTuple& t) : tuple(t) {}
-	static constexpr mpp::Family VALID_TYPES = mpp::MP_INT | mpp::MP_STR | mpp::MP_FLT;
-	template <class T>
-	void Value(BufIter_t&, mpp::compact::Family, T v)
-	{
-		if constexpr (std::is_integral_v<T>) {
-			tuple.field1 = v;
-		} else {
-			static_assert(std::is_floating_point_v<T>);
-			tuple.field3 = v;
-		}
-	}
-	void Value(BufIter_t& itr, mpp::compact::Family, mpp::StrValue v)
-	{
-		BufIter_t tmp = itr;
-		tmp += v.offset;
-		std::string &dst = tuple.field2;
-		while (v.size) {
-			dst.push_back(*tmp);
-			++tmp;
-			--v.size;
-		}
-	}
-	void WrongType(mpp::Family expected, mpp::Family got)
-	{
-		std::cout << "expected type is " << expected <<
-			     " but got " << got << std::endl;
-	}
-
-	BufIter_t* StoreEndIterator() { return nullptr; }
-	UserTuple& tuple;
-};
-//doclabel14-2
-
-//doclabel15-1
-template <class BUFFER>
-struct UserTupleReader : mpp::SimpleReaderBase<BUFFER, mpp::MP_ARR> {
-
-	UserTupleReader(mpp::Dec<BUFFER>& d, UserTuple& t) : dec(d), tuple(t) {}
-
-	void Value(const iterator_t<BUFFER>&, mpp::compact::Family, mpp::ArrValue u)
-	{
-		assert(u.size == 3);
-		(void) u;
-		dec.SetReader(false, UserTupleValueReader{tuple});
-	}
-	mpp::Dec<BUFFER>& dec;
-	UserTuple& tuple;
-};
-//doclabel15-2

examples/Simple.cpp

@@ -58,32 +58,24 @@ using Buf_t = tnt::Buffer<16 * 1024>;
 using Net_t = LibevNetProvider<Buf_t, DefaultStream>;
 //doclabel02-2
 
-//doclabel16-1
+//doclabel14-1
 template <class BUFFER>
 std::vector<UserTuple>
-decodeUserTuple(BUFFER &buf, Data<BUFFER> &data)
+decodeUserTuple(Data<BUFFER> &data)
 {
 	std::vector<UserTuple> results;
-	for(auto& t: data.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;
-		results.push_back(tuple);
-	}
+	bool ok = data.decode(results);
+	assert(ok);
 	return results;
 }
-//doclabel16-2
+//doclabel14-2
 
 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 +84,11 @@ 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 +195,7 @@ 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 +207,7 @@ 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 +51,8 @@ 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(iterator_t<BUFFER> &itr) : it(itr) {};
 	~ResponseDecoder() { };
 	ResponseDecoder() = delete;
 	ResponseDecoder(const ResponseDecoder& decoder) = delete;
@@ -62,57 +63,31 @@ class ResponseDecoder {
 	void reset(iterator_t<BUFFER> &itr);
 
 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;
 }
 
-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;
-}
-
-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;
-}
-
 template<class BUFFER>
 int
 ResponseDecoder<BUFFER>::decodeResponse(Response<BUFFER> &response)
 {
-	if (decodeHeader(response.header) != 0) {
+	/* Decode header and body separately to get more detailed error. */
+	if (!mpp::decode(it, response.header)) {
 		LOG_ERROR("Failed to decode header");
 		return -1;
 	}
-	if (decodeBody(response.body) != 0) {
+	if (!mpp::decode(it, response.body)) {
 		LOG_ERROR("Failed to decode body");
 		return -1;
 	}
@@ -123,7 +98,7 @@ template<class BUFFER>
 void
 ResponseDecoder<BUFFER>::reset(iterator_t<BUFFER> &itr)
 {
-	m_Dec.SetPosition(itr);
+	it = itr;
 }
 
 static inline uint32_t