# HG changeset patch
# User František Kučera <franta-hg@frantovo.cz>
# Date 1531608321 -7200
# Node ID 03750aff86196e3b25df1bb82a978ee13af8a388
# Parent  01dd90eeedbbb87d7ae40f439dbd8f799d511d17
writer only writes + refactoring

diff -r 01dd90eeedbb -r 03750aff8619 include/RelpipeWriterException.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/include/RelpipeWriterException.h	Sun Jul 15 00:45:21 2018 +0200
@@ -0,0 +1,26 @@
+#pragma once
+
+#include <string>
+
+using namespace std;
+
+namespace relpipe {
+namespace writer {
+
+class RelpipeWriterException {
+private:
+	wstring message;
+public:
+
+	RelpipeWriterException(wstring message) :
+	message(message) {
+	}
+
+	wstring getMessge() {
+		return message;
+	}
+
+};
+
+}
+}
\ No newline at end of file
diff -r 01dd90eeedbb -r 03750aff8619 nbproject/configurations.xml
--- a/nbproject/configurations.xml	Sat Jul 14 23:24:10 2018 +0200
+++ b/nbproject/configurations.xml	Sun Jul 15 00:45:21 2018 +0200
@@ -4,8 +4,13 @@
     <logicalFolder name="HeaderFiles"
                    displayName="Header Files"
                    projectFiles="true">
+      <itemPath>src/BooleanDataTypeWriter.h</itemPath>
       <itemPath>include/DataTypeWriter.h</itemPath>
       <itemPath>include/DataTypeWriterBase.h</itemPath>
+      <itemPath>src/DataTypeWriterCatalog.h</itemPath>
+      <itemPath>src/IntegerDataTypeWriter.h</itemPath>
+      <itemPath>include/RelpipeWriterException.h</itemPath>
+      <itemPath>src/StringDataTypeWriter.h</itemPath>
       <itemPath>src/format.h</itemPath>
       <itemPath>include/typedefs.h</itemPath>
     </logicalFolder>
@@ -45,12 +50,22 @@
       </item>
       <item path="include/DataTypeWriterBase.h" ex="false" tool="3" flavor2="0">
       </item>
+      <item path="include/RelpipeWriterException.h" ex="false" tool="3" flavor2="0">
+      </item>
       <item path="include/typedefs.h" ex="false" tool="3" flavor2="0">
       </item>
+      <item path="src/BooleanDataTypeWriter.h" ex="false" tool="3" flavor2="0">
+      </item>
       <item path="src/DataTypeWriter.cpp" ex="false" tool="1" flavor2="0">
       </item>
       <item path="src/DataTypeWriterBase.cpp" ex="false" tool="1" flavor2="0">
       </item>
+      <item path="src/DataTypeWriterCatalog.h" ex="false" tool="3" flavor2="0">
+      </item>
+      <item path="src/IntegerDataTypeWriter.h" ex="false" tool="3" flavor2="0">
+      </item>
+      <item path="src/StringDataTypeWriter.h" ex="false" tool="3" flavor2="0">
+      </item>
       <item path="src/format.h" ex="false" tool="3" flavor2="0">
       </item>
     </conf>
@@ -78,12 +93,22 @@
       </item>
       <item path="include/DataTypeWriterBase.h" ex="false" tool="3" flavor2="0">
       </item>
+      <item path="include/RelpipeWriterException.h" ex="false" tool="3" flavor2="0">
+      </item>
       <item path="include/typedefs.h" ex="false" tool="3" flavor2="0">
       </item>
+      <item path="src/BooleanDataTypeWriter.h" ex="false" tool="3" flavor2="0">
+      </item>
       <item path="src/DataTypeWriter.cpp" ex="false" tool="1" flavor2="0">
       </item>
       <item path="src/DataTypeWriterBase.cpp" ex="false" tool="1" flavor2="0">
       </item>
+      <item path="src/DataTypeWriterCatalog.h" ex="false" tool="3" flavor2="0">
+      </item>
+      <item path="src/IntegerDataTypeWriter.h" ex="false" tool="3" flavor2="0">
+      </item>
+      <item path="src/StringDataTypeWriter.h" ex="false" tool="3" flavor2="0">
+      </item>
       <item path="src/format.h" ex="false" tool="3" flavor2="0">
       </item>
     </conf>
diff -r 01dd90eeedbb -r 03750aff8619 src/BooleanDataType.h
--- a/src/BooleanDataType.h	Sat Jul 14 23:24:10 2018 +0200
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,45 +0,0 @@
-#pragma once
-
-#include <string>
-#include <iostream>
-
-#include "DataType.h"
-#include "RelpipeException.h"
-
-using namespace std;
-
-namespace rp_prototype {
-
-class BooleanDataType : public DataType<bool> {
-private:
-	const wstring TRUE = L"true";
-	const wstring FALSE = L"false";
-public:
-
-	BooleanDataType() : DataType<bool>(DATA_TYPE_ID_BOOLEAN, DATA_TYPE_CODE_BOOLEAN) {
-	}
-
-	bool readValue(istream &input) override {
-		auto value = input.get(); // TODO: check failbit
-		if (value == 0) return false;
-		else if (value == 1) return true;
-		else throw RelpipeException(L"Unable to convert the octet to boolean", EXIT_CODE_DATA_ERROR);
-	}
-
-	void writeValue(ostream &output, const bool &value) override {
-		output.put(value ? 1 : 0);
-	}
-
-	bool toValue(const wstring &stringValue) override {
-		if (stringValue == TRUE) return true;
-		else if (stringValue == FALSE) return false;
-		else throw RelpipeException(L"Unable to convert the string to boolean", EXIT_CODE_DATA_ERROR);
-	}
-
-	wstring toString(const bool &value) override {
-		return value ? TRUE : FALSE;
-	}
-
-};
-
-}
\ No newline at end of file
diff -r 01dd90eeedbb -r 03750aff8619 src/BooleanDataTypeWriter.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/BooleanDataTypeWriter.h	Sun Jul 15 00:45:21 2018 +0200
@@ -0,0 +1,35 @@
+#pragma once
+
+#include <string>
+#include <iostream>
+
+#include "../include/DataTypeWriter.h"
+#include "../include/RelpipeWriterException.h"
+#include "format.h"
+
+namespace relpipe {
+namespace writer {
+
+class BooleanDataTypeWriter : public DataTypeWriter<boolean_t> {
+private:
+	const string_t TRUE = L"true";
+	const string_t FALSE = L"false";
+public:
+
+	BooleanDataTypeWriter() : DataTypeWriter<boolean_t>(DATA_TYPE_ID_BOOLEAN, DATA_TYPE_CODE_BOOLEAN) {
+	}
+
+	void writeValue(std::ostream &output, const boolean_t &value) override {
+		output.put(value ? 1 : 0);
+	}
+
+	bool toValue(const string_t &stringValue) override {
+		if (stringValue == TRUE) return true;
+		else if (stringValue == FALSE) return false;
+		else throw RelpipeWriterException(L"Unable to convert the string to boolean");
+	}
+
+};
+
+}
+}
\ No newline at end of file
diff -r 01dd90eeedbb -r 03750aff8619 src/DataTypeCatalog.h
--- a/src/DataTypeCatalog.h	Sat Jul 14 23:24:10 2018 +0200
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,47 +0,0 @@
-#pragma once
-
-#include <string>
-#include <iostream>
-#include <vector>
-
-#include "common.h"
-#include "DataType.h"
-#include "BooleanDataType.h"
-#include "IntegerDataType.h"
-#include "StringDataType.h"
-
-using namespace std;
-
-namespace rp_prototype {
-
-class DataTypeCatalog {
-private:
-	BooleanDataType booleanType;
-	IntegerDataType integerType;
-	StringDataType stringType;
-	vector<DataTypeBase*> types = {&booleanType, &integerType, &stringType};
-public:
-
-	integer_t toTypeId(const wstring typeCode) {
-		for (DataTypeBase* dataType : types) if (dataType->supports(typeCode)) return dataType->getTypeId();
-		throw RelpipeException(L"Unsupported data type: " + typeCode, EXIT_CODE_DATA_ERROR);
-	}
-
-	wstring toTypeCode(const integer_t typeId) {
-		for (DataTypeBase* dataType : types) if (dataType->supports(typeId)) return dataType->getTypeCode();
-		throw RelpipeException(L"Unsupported data type: " + typeId, EXIT_CODE_DATA_ERROR);
-	}
-
-	void writeString(ostream &output, const wstring &stringValue, const integer_t typeId) {
-		for (DataTypeBase* dataType : types) if (dataType->supports(typeId)) return dataType->writeString(output, stringValue);
-		throw RelpipeException(L"Unsupported data type: " + typeId, EXIT_CODE_DATA_ERROR);
-	}
-
-	wstring readString(istream &input, const integer_t typeId) {
-		for (DataTypeBase* dataType : types) if (dataType->supports(typeId)) return dataType->readString(input);
-		throw RelpipeException(L"Unsupported data type: " + typeId, EXIT_CODE_DATA_ERROR);
-	}
-
-};
-
-}
\ No newline at end of file
diff -r 01dd90eeedbb -r 03750aff8619 src/DataTypeWriterCatalog.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/DataTypeWriterCatalog.h	Sun Jul 15 00:45:21 2018 +0200
@@ -0,0 +1,42 @@
+#pragma once
+
+#include <string>
+#include <iostream>
+#include <vector>
+
+#include "../include/typedefs.h"
+#include "../include/DataTypeWriterBase.h"
+#include "BooleanDataTypeWriter.h"
+#include "IntegerDataTypeWriter.h"
+#include "StringDataTypeWriter.h"
+
+namespace relpipe {
+namespace writer {
+
+class DataTypeCatalog {
+private:
+	BooleanDataTypeWriter booleanWriter;
+	IntegerDataTypeWriter integerWriter;
+	StringDataTypeWriter stringWriter;
+	vector<DataTypeWriterBase*> writers = {&booleanWriter, &integerWriter, &stringWriter};
+public:
+
+	integer_t toTypeId(const string_t typeCode) {
+		for (DataTypeWriterBase* writer : writers) if (writer->supports(typeCode)) return writer->getTypeId();
+		throw RelpipeWriterException(L"Unsupported data type: " + typeCode);
+	}
+
+	string_t toTypeCode(const integer_t typeId) {
+		for (DataTypeWriterBase* writer : writers) if (writer->supports(typeId)) return writer->getTypeCode();
+		throw RelpipeWriterException(L"Unsupported data type: " + typeId);
+	}
+
+	void writeString(std::ostream &output, const string_t &stringValue, const integer_t typeId) {
+		for (DataTypeWriterBase* writer : writers) if (writer->supports(typeId)) return writer->writeString(output, stringValue);
+		throw RelpipeWriterException(L"Unsupported data type: " + typeId);
+	}
+
+};
+
+}
+}
\ No newline at end of file
diff -r 01dd90eeedbb -r 03750aff8619 src/IntegerDataType.h
--- a/src/IntegerDataType.h	Sat Jul 14 23:24:10 2018 +0200
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,131 +0,0 @@
-#pragma once
-
-#include <string>
-#include <iostream>
-#include <cassert>
-#include <limits>
-
-#include "common.h"
-#include "DataType.h"
-#include "RelpipeException.h"
-
-using namespace std;
-
-namespace rp_prototype {
-
-/**
- * The prototype does not have various integer and other numeric data types,
- * it just works with one type of integer.
- * But this integer has variable length -- smaller values occupy only one byte, bigger ones, more bytes 1,2,4,8 + first byte (contains length signalization).
- * In the real implementation of relational pipes, there will be DataTypes for particular numeric types.
- * 
- * TODO: support also big endian architectures.
- * TODO: throw exception if a value was stored in bigger type than needed (while reading – there should be only one supported way how to encode a single value)
- * 
- * Example of encoded values:
- * -------------------------------------------------------------------------------------------------
- * $ for n in 0 1 10 250 251 252 65535 65536 4294967295 4294967296 18446744073709551615; do printf '%20s = ' $n; dist/Debug/GNU-Linux/rp-prototype write integer $n | hd | head -n 1; done
- *                    0 = 00000000  00                                                |.|
- *                    1 = 00000000  01                                                |.|
- *                   10 = 00000000  0a                                                |.|
- *                  250 = 00000000  fa                                                |.|
- *                  251 = 00000000  fb fb                                             |..|
- *                  252 = 00000000  fb fc                                             |..|
- *                65535 = 00000000  fc ff ff                                          |...|
- *                65536 = 00000000  fd 00 00 01 00                                    |.....|
- *           4294967295 = 00000000  fd ff ff ff ff                                    |.....|
- *           4294967296 = 00000000  fe 00 00 00 00 01 00 00  00                       |.........|
- * 18446744073709551615 = 00000000  fe ff ff ff ff ff ff ff  ff                       |.........|
- * -------------------------------------------------------------------------------------------------
- * 
- * Example of decoded values:
- * -------------------------------------------------------------------------------------------------
- * $ for n in 0 1 10 250 251 252 65535 65536 4294967295 4294967296 18446744073709551615; do dist/Debug/GNU-Linux/rp-prototype write integer $n | dist/Debug/GNU-Linux/rp-prototype read integer; done;
- * 0
- * 1
- * 10
- * 250
- * 251
- * 252
- * 65535
- * 65536
- * 4294967295
- * 4294967296
- * 18446744073709551615
- * -------------------------------------------------------------------------------------------------
- * 
- * Note: similar format as original idea: https://en.wikipedia.org/wiki/X.690#Length_octets
- * 
- */
-class IntegerDataType : public DataType<integer_t> {
-private:
-	static const uint8_t INTEGER_TYPE_UINT8 = 251;
-	static const uint8_t INTEGER_TYPE_UINT16 = 252;
-	static const uint8_t INTEGER_TYPE_UINT32 = 253;
-	static const uint8_t INTEGER_TYPE_UINT64 = 254;
-	static const uint8_t INTEGER_TYPE_RESERVED = 255;
-
-	template<typename T> integer_t read(istream &input) {
-		T value = 0;
-		input.read(reinterpret_cast<char *> (&value), sizeof (value));
-		return value;
-	}
-
-	template<typename T> void write(ostream &output, const integer_t &value) {
-		assert(sizeof (T) <= sizeof (value));
-		output.write(reinterpret_cast<const char *> (&value), sizeof (T));
-	}
-
-	template<typename T> void write(ostream &output, const uint8_t type, const integer_t &value) {
-		write<uint8_t>(output, type);
-		write<T>(output, value);
-	}
-
-	template<typename T> bool fits(const integer_t &value) {
-		return value <= numeric_limits<T>::max();
-	}
-
-public:
-
-	IntegerDataType() : DataType<integer_t>(DATA_TYPE_ID_INTEGER, DATA_TYPE_CODE_INTEGER) {
-	}
-
-	integer_t readValue(istream &input) override {
-		uint8_t first;
-		input.read(reinterpret_cast<char *> (&first), sizeof (first));
-		if (input.good()) {
-
-			if (first < INTEGER_TYPE_UINT8) return first;
-			else if (first == INTEGER_TYPE_UINT8) return read<uint8_t>(input);
-			else if (first == INTEGER_TYPE_UINT16) return read<uint16_t>(input);
-			else if (first == INTEGER_TYPE_UINT32) return read<uint32_t>(input);
-			else if (first == INTEGER_TYPE_UINT64) return read<uint64_t>(input);
-			else throw RelpipeException(L"Error while parsing integer type: unsupported type", EXIT_CODE_DATA_ERROR);
-		} else {
-			throw RelpipeException(L"Error while reading integer from the stream.", EXIT_CODE_DATA_ERROR);
-		}
-	}
-
-	void writeValue(ostream &output, const integer_t &value) override {
-		// output << value; // by zapsalo číslo jako ASII text
-
-		if (value < INTEGER_TYPE_UINT8) write<uint8_t>(output, value);
-		else if (fits<uint8_t>(value)) write<uint8_t>(output, INTEGER_TYPE_UINT8, value);
-		else if (fits<uint16_t>(value)) write<uint16_t>(output, INTEGER_TYPE_UINT16, value);
-		else if (fits<uint32_t>(value)) write<uint32_t>(output, INTEGER_TYPE_UINT32, value);
-		else if (fits<uint64_t>(value)) write<uint64_t>(output, INTEGER_TYPE_UINT64, value);
-		else throw RelpipeException(L"Error while writing integer type: value too long", EXIT_CODE_DATA_ERROR);
-	}
-
-	integer_t toValue(const wstring &stringValue) override {
-		// throws „terminate called after throwing an instance of 'std::invalid_argument'“ SIGABRT, core dumped on invalid number
-		return stoul(stringValue);
-	}
-
-	wstring toString(const integer_t &value) override {
-		return to_wstring(value);
-	}
-
-};
-
-}
\ No newline at end of file
diff -r 01dd90eeedbb -r 03750aff8619 src/IntegerDataTypeWriter.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/IntegerDataTypeWriter.h	Sun Jul 15 00:45:21 2018 +0200
@@ -0,0 +1,104 @@
+#pragma once
+
+#include <string>
+#include <iostream>
+#include <cassert>
+#include <limits>
+
+#include "../include/DataTypeWriter.h"
+#include "format.h"
+
+namespace relpipe {
+namespace writer {
+
+/**
+ * The prototype does not have various integer and other numeric data types,
+ * it just works with one type of integer.
+ * But this integer has variable length -- smaller values occupy only one byte, bigger ones, more bytes 1,2,4,8 + first byte (contains length signalization).
+ * In the real implementation of relational pipes, there will be DataTypes for particular numeric types.
+ * 
+ * TODO: support also big endian architectures.
+ * TODO: throw exception if a value was stored in bigger type than needed (while reading – there should be only one supported way how to encode a single value)
+ * 
+ * Example of encoded values:
+ * -------------------------------------------------------------------------------------------------
+ * $ for n in 0 1 10 250 251 252 65535 65536 4294967295 4294967296 18446744073709551615; do printf '%20s = ' $n; dist/Debug/GNU-Linux/rp-prototype write integer $n | hd | head -n 1; done
+ *                    0 = 00000000  00                                                |.|
+ *                    1 = 00000000  01                                                |.|
+ *                   10 = 00000000  0a                                                |.|
+ *                  250 = 00000000  fa                                                |.|
+ *                  251 = 00000000  fb fb                                             |..|
+ *                  252 = 00000000  fb fc                                             |..|
+ *                65535 = 00000000  fc ff ff                                          |...|
+ *                65536 = 00000000  fd 00 00 01 00                                    |.....|
+ *           4294967295 = 00000000  fd ff ff ff ff                                    |.....|
+ *           4294967296 = 00000000  fe 00 00 00 00 01 00 00  00                       |.........|
+ * 18446744073709551615 = 00000000  fe ff ff ff ff ff ff ff  ff                       |.........|
+ * -------------------------------------------------------------------------------------------------
+ * 
+ * Example of decoded values:
+ * -------------------------------------------------------------------------------------------------
+ * $ for n in 0 1 10 250 251 252 65535 65536 4294967295 4294967296 18446744073709551615; do dist/Debug/GNU-Linux/rp-prototype write integer $n | dist/Debug/GNU-Linux/rp-prototype read integer; done;
+ * 0
+ * 1
+ * 10
+ * 250
+ * 251
+ * 252
+ * 65535
+ * 65536
+ * 4294967295
+ * 4294967296
+ * 18446744073709551615
+ * -------------------------------------------------------------------------------------------------
+ * 
+ * Note: similar format as original idea: https://en.wikipedia.org/wiki/X.690#Length_octets
+ * 
+ */
+class IntegerDataTypeWriter : public DataTypeWriter<integer_t> {
+private:
+	static const uint8_t INTEGER_TYPE_UINT8 = 251;
+	static const uint8_t INTEGER_TYPE_UINT16 = 252;
+	static const uint8_t INTEGER_TYPE_UINT32 = 253;
+	static const uint8_t INTEGER_TYPE_UINT64 = 254;
+	static const uint8_t INTEGER_TYPE_RESERVED = 255;
+
+	template<typename T> void write(std::ostream &output, const integer_t &value) {
+		assert(sizeof (T) <= sizeof (value));
+		output.write(reinterpret_cast<const char *> (&value), sizeof (T));
+	}
+
+	template<typename T> void write(std::ostream &output, const uint8_t type, const integer_t &value) {
+		write<uint8_t>(output, type);
+		write<T>(output, value);
+	}
+
+	template<typename T> bool fits(const integer_t &value) {
+		return value <= numeric_limits<T>::max();
+	}
+
+public:
+
+	IntegerDataTypeWriter() : DataTypeWriter<integer_t>(DATA_TYPE_ID_INTEGER, DATA_TYPE_CODE_INTEGER) {
+	}
+
+	void writeValue(std::ostream &output, const integer_t &value) override {
+		// output << value; // by zapsalo číslo jako ASII text
+
+		if (value < INTEGER_TYPE_UINT8) write<uint8_t>(output, value);
+		else if (fits<uint8_t>(value)) write<uint8_t>(output, INTEGER_TYPE_UINT8, value);
+		else if (fits<uint16_t>(value)) write<uint16_t>(output, INTEGER_TYPE_UINT16, value);
+		else if (fits<uint32_t>(value)) write<uint32_t>(output, INTEGER_TYPE_UINT32, value);
+		else if (fits<uint64_t>(value)) write<uint64_t>(output, INTEGER_TYPE_UINT64, value);
+		else throw RelpipeWriterException(L"Error while writing integer type: value too long");
+	}
+
+	integer_t toValue(const string_t &stringValue) override {
+		// throws „terminate called after throwing an instance of 'std::invalid_argument'“ SIGABRT, core dumped on invalid number
+		return stoul(stringValue);
+	}
+
+};
+
+}
+}
\ No newline at end of file
diff -r 01dd90eeedbb -r 03750aff8619 src/StringDataType.h
--- a/src/StringDataType.h	Sat Jul 14 23:24:10 2018 +0200
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,61 +0,0 @@
-#pragma once
-
-#include <string>
-#include <sstream>
-#include <iostream>
-#include <vector>
-#include <locale>
-#include <codecvt>
-
-#include "DataType.h"
-#include "RelpipeException.h"
-#include "IntegerDataType.h"
-
-using namespace std;
-
-namespace rp_prototype {
-
-/**
- * The prototype does not recognize any encoding,
- * it just works with c++ strings in encoding default to given platform. 
- * In the real implementation of relational pipes, there will be DataTypes for particular encodings.
- */
-class StringDataType : public DataType<wstring> {
-private:
-	IntegerDataType integerType;
-	wstring_convert<codecvt_utf8<wchar_t>> convertor; // TODO: support also other encodings.
-public:
-
-	StringDataType() : DataType<wstring>(DATA_TYPE_ID_STRING, DATA_TYPE_CODE_STRING) {
-	}
-
-	wstring readValue(istream &input) override {
-		integer_t length = integerType.readValue(input);
-		// TODO: check maximum length of single field
-		// if (length > 4000) throw RelpipeException("data too long", EXIT_CODE_DATA_ERROR);
-		vector<char> buf(length);
-		input.read(buf.data(), length);
-		if (input.good()) {
-			return convertor.from_bytes(string(buf.data(), length));
-		} else {
-			throw RelpipeException(L"Error while reading string from the stream.", EXIT_CODE_DATA_ERROR);
-		}
-	}
-
-	void writeValue(ostream &output, const wstring &value) override {
-		string s = convertor.to_bytes(value);
-		integerType.writeValue(output, s.length());
-		output << s.c_str();
-	}
-
-	wstring toValue(const wstring &stringValue) override {
-		return stringValue;
-	}
-
-	wstring toString(const wstring &value) override {
-		return value;
-	}
-
-};
-
-}
\ No newline at end of file
diff -r 01dd90eeedbb -r 03750aff8619 src/StringDataTypeWriter.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/StringDataTypeWriter.h	Sun Jul 15 00:45:21 2018 +0200
@@ -0,0 +1,43 @@
+#pragma once
+
+#include <string>
+#include <sstream>
+#include <iostream>
+#include <vector>
+#include <locale>
+#include <codecvt>
+
+#include "../include/DataTypeWriter.h"
+#include "format.h"
+
+namespace relpipe {
+namespace writer {
+
+/**
+ * The prototype does not recognize any encoding,
+ * it just works with c++ strings in encoding default to given platform. 
+ * In the real implementation of relational pipes, there will be DataTypes for particular encodings.
+ */
+class StringDataTypeWriter : public DataTypeWriter<string_t> {
+private:
+	IntegerDataTypeWriter integerType;
+	std::wstring_convert<std::codecvt_utf8<wchar_t>> convertor; // TODO: support also other encodings.
+public:
+
+	StringDataTypeWriter() : DataTypeWriter<string_t>(DATA_TYPE_ID_STRING, DATA_TYPE_CODE_STRING) {
+	}
+
+	void writeValue(std::ostream &output, const string_t &value) override {
+		std::string s = convertor.to_bytes(value);
+		integerType.writeValue(output, s.length());
+		output << s.c_str();
+	}
+
+	wstring toValue(const string_t &stringValue) override {
+		return stringValue;
+	}
+
+};
+
+}
+}
\ No newline at end of file