Refactored conversion routines used in the Typesystem class and the Variant class into an own class, implemented missing conversion from string to integer/double, implemented proper JSON serialization of variants

6 files changed, 670 insertions, 182 deletions

diff --git a/src/core/common/Variant.cpp b/src/core/common/Variant.cpp
index e216aa1..b1a65ea 100644
--- a/src/core/common/Variant.cpp
+++ b/src/core/common/Variant.cpp
@@ -20,8 +20,11 @@
 
 #include <core/managed/Managed.hpp>
 
+#include "Logger.hpp"
 #include "Utils.hpp"
 #include "Variant.hpp"
+#include "VariantConverter.hpp"
+#include "VariantWriter.hpp"
 
 namespace ousia {
 
@@ -68,115 +71,124 @@ const char *Variant::getTypeName(Type type)
 
 Variant::boolType Variant::toBool() const
 {
-	switch (getType()) {
-		case Type::NULLPTR:
-			return false;
-		case Type::BOOL:
-			return asBool();
-		case Type::INT:
-			return asInt() != 0;
-		case Type::DOUBLE:
-			return asDouble() != 0.0;
-		default:
-			return true;
-	}
-	return false;
+	ExceptionLogger logger;
+	Variant res{*this};
+	VariantConverter::toBool(res, logger, VariantConverter::Mode::ALL);
+	return res.asBool();
 }
 
 Variant::intType Variant::toInt() const
 {
-	switch (getType()) {
-		case Type::NULLPTR:
-			return 0;
-		case Type::BOOL:
-			return asBool() ? 1 : 0;
-		case Type::INT:
-			return asInt();
-		case Type::DOUBLE:
-			return asDouble();
-		case Type::STRING:
-		case Type::MAGIC:
-			return 0;  // TODO: Parse string as int
-		case Type::ARRAY: {
-			// JavaScript behaviour when converting arrays to ints
-			const arrayType &a = asArray();
-			return (a.size() == 1) ? a[0].toInt() : 0;
-		}
-		default:
-			return 0;
-	}
-	return false;
+	ExceptionLogger logger;
+	Variant res{*this};
+	VariantConverter::toInt(res, logger, VariantConverter::Mode::ALL);
+	return res.asInt();
 }
 
 Variant::doubleType Variant::toDouble() const
 {
-	switch (getType()) {
-		case Type::NULLPTR:
-			return 0.0;
-		case Type::BOOL:
-			return asBool() ? 1.0 : 0.0;
-		case Type::INT:
-			return asInt();
-		case Type::DOUBLE:
-			return asDouble();
-		case Type::STRING:
-		case Type::MAGIC:
-			return 0.0;  // TODO: Parse string as double
-		case Type::ARRAY: {
-			// JavaScript behaviour when converting array to doubles
-			const arrayType &a = asArray();
-			return (a.size() == 1) ? a[0].toDouble() : 0;
-		}
-		default:
-			return 0.0;
-	}
-	return false;
+	ExceptionLogger logger;
+	Variant res{*this};
+	VariantConverter::toDouble(res, logger, VariantConverter::Mode::ALL);
+	return res.asDouble();
 }
 
 Variant::stringType Variant::toString(bool escape) const
 {
-	switch (getType()) {
-		case Type::NULLPTR:
-			return "null";
-		case Type::BOOL:
-			return asBool() ? "true" : "false";
-		case Type::INT: {
-			std::stringstream ss;
-			ss << asInt();
-			return ss.str();
-		}
-		case Type::DOUBLE: {
-			std::stringstream ss;
-			ss << asDouble();
-			return ss.str();
-		}
-		case Type::STRING: {
-		case Type::MAGIC:
-			// TODO: Use proper serialization function
-			if (escape) {
-				std::stringstream ss;
-				ss << "\"" << asString() << "\"";
-				return ss.str();
-			} else {
-				return asString();
-			}
-		}
-		case Type::ARRAY:
-			return Utils::join(asArray(), ", ", "[", "]");
-		case Type::MAP:
-			return Utils::join(asMap(), ", ", "{", "}");
-		case Type::OBJECT: {
-			std::stringstream ss;
-			ss << "<object " << ptrVal << ">";
-			return ss.str();
-		}
-		case Type::FUNCTION: {
-			std::stringstream ss;
-			ss << "<function " << static_cast<functionType*>(ptrVal)->get() << ">";
-			return ss.str();
-		}
+	ExceptionLogger logger;
+	Variant res{*this};
+	VariantConverter::toString(res, logger, VariantConverter::Mode::ALL);
+	return res.asString();
+}
+
+/* Output stream operators */
+
+std::ostream &operator<<(std::ostream &os, const Variant &v)
+{
+	VariantWriter::writeJson(v, os, true);
+	return os;
+}
+
+/* Comparison operators */
+
+bool operator<(const Variant &lhs, const Variant &rhs)
+{
+	// If the types do not match, we can not do a meaningful comparison.
+	if (lhs.getType() != rhs.getType()) {
+		throw Variant::TypeException(lhs.getType(), rhs.getType());
+	}
+	switch (lhs.getType()) {
+		case Variant::Type::NULLPTR:
+			return false;
+		case Variant::Type::BOOL:
+			return lhs.boolVal < rhs.boolVal;
+		case Variant::Type::INT:
+			return lhs.intVal < rhs.intVal;
+		case Variant::Type::DOUBLE:
+			return lhs.doubleVal < rhs.doubleVal;
+		case Variant::Type::MAGIC:
+		case Variant::Type::STRING:
+			return lhs.asString() < rhs.asString();
+		case Variant::Type::ARRAY:
+			return lhs.asArray() < rhs.asArray();
+		case Variant::Type::MAP:
+			return lhs.asMap() < rhs.asMap();
+		case Variant::Type::OBJECT:
+			return lhs.asObject().get() < rhs.asObject().get();
+		case Variant::Type::FUNCTION:
+			return lhs.asFunction() < rhs.asFunction();
+	}
+	throw OusiaException("Internal Error! Unknown type!");
+}
+
+bool operator>(const Variant &lhs, const Variant &rhs)
+{
+	return rhs < lhs;
+}
+
+bool operator<=(const Variant &lhs, const Variant &rhs)
+{
+	return !(lhs > rhs);
+}
+
+bool operator>=(const Variant &lhs, const Variant &rhs)
+{
+	return !(lhs < rhs);
+}
+
+bool operator==(const Variant &lhs, const Variant &rhs)
+{
+	if (lhs.getType() != rhs.getType()) {
+		return false;
+	}
+	switch (lhs.getType()) {
+		case Variant::Type::NULLPTR:
+			return true;
+		case Variant::Type::BOOL:
+			return lhs.boolVal == rhs.boolVal;
+		case Variant::Type::INT:
+			return lhs.intVal == rhs.intVal;
+		case Variant::Type::DOUBLE:
+			return lhs.doubleVal == rhs.doubleVal;
+		case Variant::Type::STRING:
+		case Variant::Type::MAGIC:
+			return lhs.asString() == rhs.asString();
+		case Variant::Type::ARRAY:
+			return lhs.asArray() == rhs.asArray();
+		case Variant::Type::MAP:
+			return lhs.asMap() == rhs.asMap();
+		case Variant::Type::OBJECT:
+			return lhs.asObject() == rhs.asObject();
+		case Variant::Type::FUNCTION:
+			return lhs.asFunction() == rhs.asFunction();
 	}
-	return "";
+	throw OusiaException("Internal Error! Unknown type!");
 }
+
+bool operator!=(const Variant &lhs, const Variant &rhs)
+{
+	return !(lhs == rhs);
+}
+
 }
 
diff --git a/src/core/common/Variant.hpp b/src/core/common/Variant.hpp
index 9c061c1..254e748 100644
--- a/src/core/common/Variant.hpp
+++ b/src/core/common/Variant.hpp
@@ -864,23 +864,17 @@ public:
 	 */
 	const char *getTypeName() { return Variant::getTypeName(getType()); }
 
-	/**
-	 * Prints the Variant to the output stream.
+	/*
+	 * Output stream operator.
 	 */
-	friend std::ostream &operator<<(std::ostream &os, const Variant &v)
-	{
-		return os << v.toString(true);
-	}
 
 	/**
-	 * Prints a key value pair to the output stream.
+	 * Prints the Variant to the output stream as JSON data.
+	 *
+	 * @param os is the output stream the variant should be written to.
+	 * @param v is the variant that should be written to the output stream.
 	 */
-	friend std::ostream &operator<<(std::ostream &os,
-	                                const mapType::value_type &v)
-	{
-		// TODO: Use proper serialization function
-		return os << "\"" << v.first << "\": " << v.second.toString(true);
-	}
+	friend std::ostream &operator<<(std::ostream &os, const Variant &v);
 
 	/*
 	 * Comprison operators.
@@ -895,35 +889,7 @@ public:
 	 * @param rhs is the right hand side of the comparison.
 	 * @return true if lhs is smaller than rhs.
 	 */
-	friend bool operator<(const Variant &lhs, const Variant &rhs)
-	{
-		// If the types do not match, we can not do a meaningful comparison.
-		if (lhs.getType() != rhs.getType()) {
-			throw TypeException(lhs.getType(), rhs.getType());
-		}
-		switch (lhs.getType()) {
-			case Type::NULLPTR:
-				return false;
-			case Type::BOOL:
-				return lhs.boolVal < rhs.boolVal;
-			case Type::INT:
-				return lhs.intVal < rhs.intVal;
-			case Type::DOUBLE:
-				return lhs.doubleVal < rhs.doubleVal;
-			case Type::MAGIC:
-			case Type::STRING:
-				return lhs.asString() < rhs.asString();
-			case Type::ARRAY:
-				return lhs.asArray() < rhs.asArray();
-			case Type::MAP:
-				return lhs.asMap() < rhs.asMap();
-			case Type::OBJECT:
-				return lhs.asObject().get() < rhs.asObject().get();
-			case Type::FUNCTION:
-				return lhs.asFunction() < rhs.asFunction();
-		}
-		throw OusiaException("Internal Error! Unknown type!");
-	}
+	friend bool operator<(const Variant &lhs, const Variant &rhs);
 
 	/**
 	 * Returns true if the given left hand side is larger than the right hand
@@ -934,10 +900,7 @@ public:
 	 * @param rhs is the right hand side of the comparison.
 	 * @return true if lhs is larger than rhs.
 	 */
-	friend bool operator>(const Variant &lhs, const Variant &rhs)
-	{
-		return rhs < lhs;
-	}
+	friend bool operator>(const Variant &lhs, const Variant &rhs);
 
 	/**
 	 * Returns true if the given left hand side is smaller or equal to the
@@ -948,10 +911,7 @@ public:
 	 * @param rhs is the right hand side of the comparison.
 	 * @return true if lhs is smaller than or equal to rhs.
 	 */
-	friend bool operator<=(const Variant &lhs, const Variant &rhs)
-	{
-		return !(lhs > rhs);
-	}
+	friend bool operator<=(const Variant &lhs, const Variant &rhs);
 
 	/**
 	 * Returns true if the given left hand side is larger or equal to the
@@ -962,10 +922,7 @@ public:
 	 * @param rhs is the right hand side of the comparison.
 	 * @return true if lhs is larger than or equal to rhs.
 	 */
-	friend bool operator>=(const Variant &lhs, const Variant &rhs)
-	{
-		return !(lhs < rhs);
-	}
+	friend bool operator>=(const Variant &lhs, const Variant &rhs);
 
 	/**
 	 * Returns true if the given left hand side and right hand side are equal.
@@ -976,34 +933,7 @@ public:
 	 * @param rhs is the right hand side of the comparison.
 	 * @return true if lhs equals rhs.
 	 */
-	friend bool operator==(const Variant &lhs, const Variant &rhs)
-	{
-		if (lhs.getType() != rhs.getType()) {
-			return false;
-		}
-		switch (lhs.getType()) {
-			case Type::NULLPTR:
-				return true;
-			case Type::BOOL:
-				return lhs.boolVal == rhs.boolVal;
-			case Type::INT:
-				return lhs.intVal == rhs.intVal;
-			case Type::DOUBLE:
-				return lhs.doubleVal == rhs.doubleVal;
-			case Type::STRING:
-			case Type::MAGIC:
-				return lhs.asString() == rhs.asString();
-			case Type::ARRAY:
-				return lhs.asArray() == rhs.asArray();
-			case Type::MAP:
-				return lhs.asMap() == rhs.asMap();
-			case Type::OBJECT:
-				return lhs.asObject() == rhs.asObject();
-			case Type::FUNCTION:
-				return lhs.asFunction() == rhs.asFunction();
-		}
-		throw OusiaException("Internal Error! Unknown type!");
-	}
+	friend bool operator==(const Variant &lhs, const Variant &rhs);
 
 	/**
 	 * Returns true if the given left hand side are equal. Uses the comparison
@@ -1014,10 +944,7 @@ public:
 	 * @param rhs is the right hand side of the comparison.
 	 * @return true if lhs is not equal to rhs.
 	 */
-	friend bool operator!=(const Variant &lhs, const Variant &rhs)
-	{
-		return !(lhs == rhs);
-	}
+	friend bool operator!=(const Variant &lhs, const Variant &rhs);
 };
 }
 
diff --git a/src/core/common/VariantConverter.cpp b/src/core/common/VariantConverter.cpp
new file mode 100644
index 0000000..f9d465e
--- /dev/null
+++ b/src/core/common/VariantConverter.cpp
@@ -0,0 +1,255 @@
+/*
+    Ousía
+    Copyright (C) 2014, 2015  Benjamin Paaßen, Andreas Stöckel
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include <string>
+#include <sstream>
+
+#include "Logger.hpp"
+#include "Number.hpp"
+#include "Rtti.hpp"
+#include "Variant.hpp"
+#include "VariantConverter.hpp"
+#include "VariantWriter.hpp"
+
+namespace ousia {
+
+static std::string msgUnexpectedType(Variant::Type actualType,
+                                     Variant::Type requestedType)
+{
+	return std::string("Cannot convert ") + Variant::getTypeName(actualType) +
+	       std::string(" to ") + Variant::getTypeName(requestedType);
+}
+
+bool VariantConverter::toBool(Variant &var, Logger &logger, Mode mode)
+{
+	// Perform safe conversions
+	const Variant::Type type = var.getType();
+	switch (type) {
+		case Variant::Type::BOOL:
+			// No conversion needed if "var" already is a boolean
+			return true;
+		default:
+			break;
+	}
+
+	// Perform potentially dangerous conversions in the "ALL" mode
+	if (mode == Mode::ALL) {
+		switch (var.getType()) {
+			case Variant::Type::NULLPTR:
+				var = false;
+				return true;
+			case Variant::Type::INT:
+				var = var.asInt() != 0;
+				return true;
+			case Variant::Type::DOUBLE:
+				var = var.asDouble() != 0.0;
+				return true;
+			default:
+				var = true;
+				return true;
+		}
+	}
+
+	// No conversion possible, assign default value and log error
+	logger.error(msgUnexpectedType(var.getType(), Variant::Type::BOOL));
+	var = false;
+	return false;
+}
+
+bool VariantConverter::toInt(Variant &var, Logger &logger, Mode mode)
+{
+	// Perform safe conversions
+	const Variant::Type type = var.getType();
+	switch (type) {
+		case Variant::Type::INT:
+			// No conversion needed if "var" already is an integer
+			return true;
+		default:
+			break;
+	}
+
+	// Perform all potentially dangerous conversions in the "ALL" mode
+	if (mode == Mode::ALL) {
+		switch (type) {
+			case Variant::Type::NULLPTR:
+				var = 0;
+				return true;
+			case Variant::Type::BOOL:
+				var = var.asBool() ? 1 : 0;
+				return true;
+			case Variant::Type::DOUBLE:
+				var = (Variant::intType)var.asDouble();
+				return true;
+			case Variant::Type::STRING:
+			case Variant::Type::MAGIC: {
+				Number n;
+				n.parse(var.asString(), logger);
+				if (n.isInt()) {
+					var = (Variant::intType)n.intValue();
+				} else {
+					var = (Variant::doubleType)n.doubleValue();
+				}
+				return true;
+			}
+			case Variant::Type::ARRAY: {
+				try {
+					// JavaScript behaviour when converting arrays to doubles
+					const Variant::arrayType &a = var.asArray();
+					var = (a.size() == 1) ? a[0].toInt() : 0.0;
+					return true;
+				}
+				catch (LoggableException ex) {
+					logger.log(ex);
+				}
+			}
+			default:
+				break;
+		}
+	}
+
+	// No conversion possible, assign default value and log error
+	logger.error(msgUnexpectedType(var.getType(), Variant::Type::INT));
+	var = 0;
+	return false;
+}
+
+bool VariantConverter::toDouble(Variant &var, Logger &logger, Mode mode)
+{
+	// Perform safe conversions
+	const Variant::Type type = var.getType();
+	switch (type) {
+		case Variant::Type::DOUBLE:
+			// No conversion needed if "var" already is a double
+			return true;
+		case Variant::Type::INT:
+			// Converting integers to doubles is safe
+			var = (Variant::doubleType)var.asInt();
+			return true;
+		default:
+			break;
+	}
+
+	// Perform all potentially dangerous conversions in the "ALL" mode
+	if (mode == Mode::ALL) {
+		switch (type) {
+			case Variant::Type::NULLPTR:
+				var = 0.0;
+				return true;
+			case Variant::Type::BOOL:
+				var = var.asBool() ? 1.0 : 0.0;
+				return true;
+			case Variant::Type::STRING:
+			case Variant::Type::MAGIC: {
+				Number n;
+				n.parse(var.asString(), logger);
+				var = (Variant::doubleType)n.doubleValue();
+				return true;
+			}
+			case Variant::Type::ARRAY: {
+				try {
+					// JavaScript behaviour when converting arrays to doubles
+					const Variant::arrayType &a = var.asArray();
+					var = (a.size() == 1) ? a[0].toDouble() : 0.0;
+					return true;
+				}
+				catch (LoggableException ex) {
+					logger.log(ex);
+				}
+			}
+			default:
+				break;
+		}
+	}
+
+	// No conversion possible, assign default value and log error
+	logger.error(msgUnexpectedType(var.getType(), Variant::Type::DOUBLE));
+	var = 0.0;
+	return false;
+}
+
+bool VariantConverter::toString(Variant &var, Logger &logger, Mode mode)
+{
+	// Perform safe conversions (all these operations are considered "lossless")
+	const Variant::Type type = var.getType();
+	switch (type) {
+		case Variant::Type::NULLPTR:
+			var = "null";
+			return true;
+		case Variant::Type::BOOL:
+			var = var.asBool() ? "true" : "false";
+			return true;
+		case Variant::Type::INT: {
+			std::stringstream ss;
+			ss << var.asInt();
+			var = ss.str().c_str();
+			return true;
+		}
+		case Variant::Type::DOUBLE: {
+			std::stringstream ss;
+			ss << var.asDouble();
+			var = ss.str().c_str();
+			return true;
+		}
+		case Variant::Type::MAGIC:
+		case Variant::Type::STRING:
+			// No conversion needed if "var" already is a string (or a magic
+			// string value)
+			return true;
+		default:
+			break;
+	}
+
+	// Perform lossy conversions
+	if (mode == Mode::ALL) {
+		switch (type) {
+			case Variant::Type::ARRAY:
+			case Variant::Type::MAP: {
+				std::stringstream ss;
+				VariantWriter::writeJson(var, ss, false);
+				var = ss.str().c_str();
+				return true;
+			}
+			case Variant::Type::OBJECT: {
+				// Print object address and type
+				Variant::objectType obj = var.asObject();
+				std::stringstream ss;
+				ss << "<object " << obj.get() << " (" << obj->type().name << ")"
+				   << ">";
+				var = ss.str().c_str();
+				return true;
+			}
+			case Variant::Type::FUNCTION: {
+				// Print function pointer address
+				Variant::functionType obj = var.asFunction();
+				std::stringstream ss;
+				ss << "<function " << obj.get() << ">";
+				var = ss.str().c_str();
+				return true;
+			}
+			default:
+				break;
+		}
+	}
+
+	// No conversion possible, assign default value and log error
+	logger.error(msgUnexpectedType(var.getType(), Variant::Type::STRING));
+	var = "";
+	return false;
+}
+}
+
diff --git a/src/core/common/VariantConverter.hpp b/src/core/common/VariantConverter.hpp
new file mode 100644
index 0000000..b683083
--- /dev/null
+++ b/src/core/common/VariantConverter.hpp
@@ -0,0 +1,72 @@
+/*
+    Ousía
+    Copyright (C) 2014, 2015  Benjamin Paaßen, Andreas Stöckel
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef _OUSIA_VARIANT_CONVERTER_HPP_
+#define _OUSIA_VARIANT_CONVERTER_HPP_
+
+namespace ousia {
+
+// Forward declaration
+class Variant;
+class Logger;
+
+/**
+ * The VariantConverter class is used to convert a variant to a certain
+ * prespecified type. The functions ensure that the variant has the requested
+ * type, even if the conversion fails.
+ */
+class VariantConverter {
+
+public:
+	/**
+	 * Enumeration used to define the mode of conversion -- either only safe
+	 * conversions (without any data loss) are performed, or all possible
+	 * conversions are tried (with possible data loss).
+	 */
+	enum class Mode {
+		SAFE, ALL
+	};
+
+	/**
+	 * Makes sure the given variant is a boolean. If the "mode" parameter is
+	 * set to Mode::SAFE, only booleans can be converted to booleans. For all
+	 * other types the conversion fails. If "mode" is set to Mode::ALL, nullptr
+	 * values and zero numeric values are treated as "false", all other values
+	 * are treated as "true".
+	 *
+	 * @param var is instance of the Variant class that should be converted to
+	 * the requested type.
+	 * @param logger is a reference to the logger instance into which messages
+	 * should be logged.
+	 * @param mode is the conversion mode. See method description for the exact
+	 * effect.
+	 */
+	static bool toBool(Variant &var, Logger &logger, Mode mode = Mode::SAFE);
+
+	static bool toInt(Variant &var, Logger &logger, Mode mode = Mode::SAFE);
+
+	static bool toDouble(Variant &var, Logger &logger, Mode mode = Mode::SAFE);
+
+	static bool toString(Variant &var, Logger &logger, Mode mode = Mode::SAFE);
+
+};
+
+}
+
+#endif /* _OUSIA_VARIANT_CONVERTER_HPP_ */
+
diff --git a/src/core/common/VariantWriter.cpp b/src/core/common/VariantWriter.cpp
new file mode 100644
index 0000000..39dfc3b
--- /dev/null
+++ b/src/core/common/VariantWriter.cpp
@@ -0,0 +1,165 @@
+/*
+    Ousía
+    Copyright (C) 2014, 2015  Benjamin Paaßen, Andreas Stöckel
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "Variant.hpp"
+#include "VariantWriter.hpp"
+
+namespace ousia {
+
+/**
+ * Helper function used to write a JSON string, including quotation marks.
+ *
+ * @param str is the string that should be serialized.
+ * @param stream is the stream to which the JSON string should be written.
+ */
+static void writeJsonString(const std::string str, std::ostream &stream)
+{
+	stream << "\"";
+	for (char c : str) {
+		switch (c) {
+			case '\b':
+				stream << "\\b";
+				break;
+			case '\f':
+				stream << "\\f";
+				break;
+			case '\n':
+				stream << "\\n";
+				break;
+			case '\r':
+				stream << "\\r";
+				break;
+			case '\t':
+				stream << "\\t";
+				break;
+			case '\v':
+				stream << "\\v";
+				break;
+			case '\\':
+				stream << "\\";
+				break;
+			case '"':
+				stream << "\\\"";
+				break;
+			default:
+				stream << c;
+				break;
+		}
+	}
+	stream << "\"";
+}
+
+/**
+ * Helper function used to write the indentation, but only if the pretty mode
+ * is enabled.
+ *
+ * @param stream is the stream the result should be written to.
+ * @param pretty if false, no indentation is written.
+ */
+static void writeIndentation(std::ostream &stream, bool pretty, int level)
+{
+	if (pretty) {
+		for (int i = 0; i < level; i++) {
+			stream << "\t";
+		}
+	}
+}
+
+/**
+ * Helper function used to write a linebreak, but only if the pretty mode is
+ * enabled.
+ *
+ * @param stream is the stream the result should be written to.
+ * @param pretty if false, no linebreak is written.
+ */
+static void writeLinebreak(std::ostream &stream, bool pretty)
+{
+	if (pretty) {
+		stream << "\n";
+	}
+}
+
+/**
+ * Helper function used to serialize JSON with indentation.
+ *
+ * @param var is the variant that should be serialized.
+ * @param stream is the stream the result should be written to.
+ * @param pretty if true, the resulting value is properly indented.
+ * @param level is the current indentation level.
+ */
+static void writeJsonInternal(const Variant &var, std::ostream &stream,
+                              bool pretty, int level)
+{
+	switch (var.getType()) {
+		case Variant::Type::NULLPTR:
+		case Variant::Type::BOOL:
+		case Variant::Type::INT:
+		case Variant::Type::DOUBLE:
+		case Variant::Type::FUNCTION:
+		case Variant::Type::OBJECT:
+			stream << var.toString();
+			return;
+		case Variant::Type::STRING:
+		case Variant::Type::MAGIC:
+			writeJsonString(var.toString(), stream);
+			return;
+		case Variant::Type::ARRAY: {
+			stream << "[";
+			writeLinebreak(stream, pretty);
+			const Variant::arrayType &arr = var.asArray();
+			for (size_t i = 0; i < arr.size(); i++) {
+				writeIndentation(stream, pretty, level + 1);
+				writeJsonInternal(arr[i], stream, pretty, level + 1);
+				if (i + 1 != arr.size()) {
+					stream << ",";
+				}
+				writeLinebreak(stream, pretty);
+			}
+			writeIndentation(stream, pretty, level);
+			stream << "]";
+			return;
+		}
+		case Variant::Type::MAP: {
+			writeIndentation(stream, pretty, level);
+			stream << "{";
+			writeLinebreak(stream, pretty);
+			const Variant::mapType &map = var.asMap();
+			for (auto it = map.cbegin(); it != map.cend();) {
+				writeIndentation(stream, pretty, level + 1);
+				writeJsonString(it->first, stream);
+				stream << (pretty ? ": " : ":");
+				writeJsonInternal(it->second, stream, pretty, level + 1);
+				if ((++it) != map.cend()) {
+					stream << ",";
+				}
+				writeLinebreak(stream, pretty);
+			}
+			writeIndentation(stream, pretty, level);
+			stream << "}";
+			return;
+		}
+	}
+}
+
+void VariantWriter::writeJson(const Variant &var, std::ostream &stream,
+                              bool pretty)
+{
+	writeJsonInternal(var, stream, pretty, 0);
+}
+}
+
diff --git a/src/core/common/VariantWriter.hpp b/src/core/common/VariantWriter.hpp
new file mode 100644
index 0000000..211da34
--- /dev/null
+++ b/src/core/common/VariantWriter.hpp
@@ -0,0 +1,57 @@
+/*
+    Ousía
+    Copyright (C) 2014, 2015  Benjamin Paaßen, Andreas Stöckel
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+/**
+ * @file VariantWriter.hpp
+ *
+ * Contains the VariantWriter class which provides serialization functions for
+ * Variant types.
+ *
+ * @author Andreas Stöckel (astoecke@techfak.uni-bielefeld.de)
+ */
+
+#ifndef _OUSIA_VARIANT_WRITER_HPP_
+#define _OUSIA_VARIANT_WRITER_HPP_
+
+#include <ostream>
+
+namespace ousia {
+
+// Forward declaration
+class Variant;
+
+/**
+ * Class which provides serialization functions for writing variants to an
+ * output stream in various formats.
+ */
+class VariantWriter {
+public:
+	/**
+	 * Dumps the Variant as JSON data.
+	 *
+	 * @param var is the variant that should be serialized.
+	 * @param stream is the stream the result should be written to.
+	 * @param pretty if true, the resulting value is properly indented.
+	 */
+	static void writeJson(const Variant &var, std::ostream &stream,
+	                      bool pretty = true);
+};
+}
+
+#endif /* _OUSIA_VARIANT_WRITER_HPP_ */
+