poco/Foundation/include/Poco/Dynamic/VarHolder.h

//
// VarHolder.h
//
// $Id: //poco/svn/Foundation/include/Poco/VarHolder.h#3 $
//
// Library: Foundation
// Package: Dynamic
// Module:  VarHolder
//
// Definition of the VarHolder class.
//
// Copyright (c) 2007, Applied Informatics Software Engineering GmbH.
// and Contributors.
//
// Permission is hereby granted, free of charge, to any person or organization
// obtaining a copy of the software and accompanying documentation covered by
// this license (the "Software") to use, reproduce, display, distribute,
// execute, and transmit the Software, and to prepare derivative works of the
// Software, and to permit third-parties to whom the Software is furnished to
// do so, all subject to the following:
// 
// The copyright notices in the Software and this entire statement, including
// the above license grant, this restriction and the following disclaimer,
// must be included in all copies of the Software, in whole or in part, and
// all derivative works of the Software, unless such copies or derivative
// works are solely in the form of machine-executable object code generated by
// a source language processor.
// 
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
// SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
// FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
// ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.
//


#ifndef Foundation_VarHolder_INCLUDED
#define Foundation_VarHolder_INCLUDED


#include "Poco/Foundation.h"
#include "Poco/NumberFormatter.h"
#include "Poco/NumberParser.h"
#include "Poco/DateTime.h"
#include "Poco/Timestamp.h"
#include "Poco/LocalDateTime.h"
#include "Poco/DateTimeFormat.h"
#include "Poco/DateTimeFormatter.h"
#include "Poco/DateTimeParser.h"
#include "Poco/String.h"
#include "Poco/Exception.h"
#include <vector>
#include <typeinfo>
#undef min
#undef max
#include <limits>


namespace Poco {
namespace Dynamic {


class Var;


bool Foundation_API isJSONString(const Var& any);
	/// Returns true for values that should be JSON-formatted as string.

void Foundation_API appendJSONString(std::string& val, const Var& any);
	/// Converts the any to a JSON value and adds it to val


class Foundation_API VarHolder
	/// Interface for a data holder used by the Var class. 
	/// Provides methods to convert between data types.
	/// Only data types for which VarHolder specialization exists are supported.
	/// 
	/// Provided are specializations for all C++ built-in types with addition of 
	/// std::string, DateTime, LocalDateTime, Timestamp, std::vector<Var> and DynamicStruct.
	///
	/// Additional types can be supported by adding specializations. When implementing specializations,
	/// the only condition is that they reside in Poco namespace and implement the pure virtual functions
	/// clone() and type().
	///
	/// Those conversions that are not implemented shall fail back to this base
	/// class implementation. All the convert() function overloads in this class
	/// throw BadCastException.
{
public:
	virtual ~VarHolder();
		/// Destroys the VarHolder.

	virtual VarHolder* clone() const;
		/// Throws NotImplementedException. Implementation should
		/// deep-copy the VarHolder.
		
	virtual const std::type_info& type() const;
		/// Throws NotImplementedException. Implementation should
		/// return the type information for the stored content.

	virtual void convert(Int8& val) const;
		/// Throws BadCastException. Must be overriden in a type
		/// specialization in order to suport the conversion.

	virtual void convert(Int16& val) const;
		/// Throws BadCastException. Must be overriden in a type
		/// specialization in order to suport the conversion.

	virtual void convert(Int32& val) const;
		/// Throws BadCastException. Must be overriden in a type
		/// specialization in order to suport the conversion.

	virtual void convert(Int64& val) const;
		/// Throws BadCastException. Must be overriden in a type
		/// specialization in order to suport the conversion.

	virtual void convert(UInt8& val) const;
		/// Throws BadCastException. Must be overriden in a type
		/// specialization in order to suport the conversion.

	virtual void convert(UInt16& val) const;
		/// Throws BadCastException. Must be overriden in a type
		/// specialization in order to suport the conversion.

	virtual void convert(UInt32& val) const;
		/// Throws BadCastException. Must be overriden in a type
		/// specialization in order to suport the conversion.

	virtual void convert(UInt64& val) const;
		/// Throws BadCastException. Must be overriden in a type
		/// specialization in order to suport the conversion.

	virtual void convert(DateTime& val) const;
		/// Throws BadCastException. Must be overriden in a type
		/// specialization in order to suport the conversion.

	virtual void convert(LocalDateTime& val) const;
		/// Throws BadCastException. Must be overriden in a type
		/// specialization in order to suport the conversion.

	virtual void convert(Timestamp& val) const;
		/// Throws BadCastException. Must be overriden in a type
		/// specialization in order to suport the conversion.

#ifndef POCO_LONG_IS_64_BIT
	void convert(long& val) const;
		/// Calls convert(Int32).

	void convert(unsigned long& val) const;
		/// Calls convert(UInt32).
#endif
	virtual void convert(bool& val) const;
		/// Throws BadCastException. Must be overriden in a type
		/// specialization in order to suport the conversion.

	virtual void convert(float& val) const;
		/// Throws BadCastException. Must be overriden in a type
		/// specialization in order to suport the conversion.

	virtual void convert(double& val) const;
		/// Throws BadCastException. Must be overriden in a type
		/// specialization in order to suport the conversion.

	virtual void convert(char& val) const;
		/// Throws BadCastException. Must be overriden in a type
		/// specialization in order to suport the conversion.

	virtual void convert(std::string& val) const;
		/// Throws BadCastException. Must be overriden in a type
		/// specialization in order to suport the conversion.

	virtual bool isArray() const;
		/// Returns false. Must be properly overriden in a type
		/// specialization in order to suport the diagnostic.

	virtual bool isStruct() const;
		/// Returns false. Must be properly overriden in a type
		/// specialization in order to suport the diagnostic.

	virtual bool isInteger() const;
		/// Returns false. Must be properly overriden in a type
		/// specialization in order to suport the diagnostic.

	virtual bool isSigned() const;
		/// Returns false. Must be properly overriden in a type
		/// specialization in order to suport the diagnostic.

	virtual bool isNumeric() const;
		/// Returns false. Must be properly overriden in a type
		/// specialization in order to suport the diagnostic.

	virtual bool isString() const;
		/// Returns false. Must be properly overriden in a type
		/// specialization in order to suport the diagnostic.

protected:
	VarHolder();
		/// Creates the VarHolder.

	template <typename F, typename T>
	void convertToSmaller(const F& from, T& to) const
		/// This function is meant to convert signed numeric values from
		/// larger to smaller type. It checks the upper and lower bound and
		/// if from value is within limits of type T (i.e. check calls do not throw), 
		/// it is converted.
	{
		poco_static_assert (std::numeric_limits<F>::is_specialized);
		poco_static_assert (std::numeric_limits<T>::is_specialized);
		poco_static_assert (std::numeric_limits<F>::is_signed);
		poco_static_assert (std::numeric_limits<T>::is_signed);

		if (std::numeric_limits<F>::is_integer)
		{
			checkUpperLimit<F,T>(from); 
			checkLowerLimit<F,T>(from);
		}
		else
		{
			checkUpperLimitFloat<F,T>(from); 
			checkLowerLimitFloat<F,T>(from); 
		}
		
		to = static_cast<T>(from);
	}

	template <typename F, typename T>
	void convertToSmallerUnsigned(const F& from, T& to) const
		/// This function is meant for converting unsigned integral data types,
		/// from larger to smaller type. Since lower limit is always 0 for unigned types, 
		/// only the upper limit is checked, thus saving some cycles compared to the signed 
		/// version of the function. If the value to be converted is smaller than
		/// the maximum value for the target type, the conversion is performed.
	{
		poco_static_assert (std::numeric_limits<F>::is_specialized);
		poco_static_assert (std::numeric_limits<T>::is_specialized);
		poco_static_assert (!std::numeric_limits<F>::is_signed);
		poco_static_assert (!std::numeric_limits<T>::is_signed);

		checkUpperLimit<F,T>(from); 
		to = static_cast<T>(from);
	}

	template <typename F, typename T>
	void convertSignedToUnsigned(const F& from, T& to) const
		/// This function is meant for converting signed integral data types to
		/// unsigned data types. Negative values can not be converted and if one is 
		/// encountered, RangeException is thrown. 
		/// If upper limit is within the target data type limits, the conversion is performed.
	{
		poco_static_assert (std::numeric_limits<F>::is_specialized);
		poco_static_assert (std::numeric_limits<T>::is_specialized);
		poco_static_assert (std::numeric_limits<F>::is_signed);
		poco_static_assert (!std::numeric_limits<T>::is_signed);

		if (from < 0)
			throw RangeException("Value too small.");
		checkUpperLimit<F,T>(from); 
		to = static_cast<T>(from);
	}

	template <typename F, typename T>
	void convertSignedFloatToUnsigned(const F& from, T& to) const
		/// This function is meant for converting floating point data types to
		/// unsigned integral data types. Negative values can not be converted and if one is 
		/// encountered, RangeException is thrown. 
		/// If uper limit is within the target data type limits, the conversion is performed.
	{
		poco_static_assert (std::numeric_limits<F>::is_specialized);
		poco_static_assert (std::numeric_limits<T>::is_specialized);
		poco_static_assert (!std::numeric_limits<F>::is_integer);
		poco_static_assert (std::numeric_limits<T>::is_integer);
		poco_static_assert (!std::numeric_limits<T>::is_signed);

		if (from < 0)
			throw RangeException("Value too small.");
		checkUpperLimitFloat<F,T>(from); 
		to = static_cast<T>(from);
	}

	template <typename F, typename T>
	void convertUnsignedToSigned(const F& from, T& to) const
		/// This function is meant for converting unsigned integral data types to
		/// unsigned data types. Negative values can not be converted and if one is 
		/// encountered, RangeException is thrown. 
		/// If upper limit is within the target data type limits, the converiosn is performed.
	{
		poco_static_assert (std::numeric_limits<F>::is_specialized);
		poco_static_assert (std::numeric_limits<T>::is_specialized);
		poco_static_assert (!std::numeric_limits<F>::is_signed);
		poco_static_assert (std::numeric_limits<T>::is_signed);

		checkUpperLimit<F,T>(from); 
		to = static_cast<T>(from);
	}

private:
	template <typename F, typename T>
	void checkUpperLimit(const F& from) const
	{
		if ((sizeof(T) < sizeof(F)) &&
			(from > static_cast<F>(std::numeric_limits<T>::max())))
		{
			throw RangeException("Value too large.");
		}
		else
		if (static_cast<T>(from) > std::numeric_limits<T>::max()) 
		{
			throw RangeException("Value too large.");
		}
	}

	template <typename F, typename T>
	void checkUpperLimitFloat(const F& from) const
	{
		if (from > std::numeric_limits<T>::max())
			throw RangeException("Value too large.");
	}

	template <typename F, typename T>
	void checkLowerLimitFloat(const F& from) const
	{
		if (from < -std::numeric_limits<T>::max()) 
			throw RangeException("Value too small.");
	}

	template <typename F, typename T>
	void checkLowerLimit(const F& from) const
	{
		if (from < std::numeric_limits<T>::min()) 
			throw RangeException("Value too small.");
	}
};


//
// inlines
//

inline VarHolder* VarHolder::clone() const
{
	throw NotImplementedException("Not implemented: VarHolder::clone()");
}


inline const std::type_info& VarHolder::type() const
{
	throw NotImplementedException("Not implemented: VarHolder::type()");
}

inline void VarHolder::convert(Int8& val) const
{
	throw BadCastException("Can not convert to Int8");
}


inline void VarHolder::convert(Int16& val) const
{
	throw BadCastException("Can not convert to Int16");
}


inline void VarHolder::convert(Int32& val) const
{
	throw BadCastException("Can not convert to Int32");
}


inline void VarHolder::convert(Int64& val) const
{
	throw BadCastException("Can not convert to Int64");
}


inline void VarHolder::convert(UInt8& val) const
{
	throw BadCastException("Can not convert to UInt8");
}


inline void VarHolder::convert(UInt16& val) const
{
	throw BadCastException("Can not convert to UInt16");
}


inline void VarHolder::convert(UInt32& val) const
{
	throw BadCastException("Can not convert to UInt32");
}


inline void VarHolder::convert(UInt64& val) const
{
	throw BadCastException("Can not convert to UInt64");
}


inline void VarHolder::convert(DateTime& val) const
{
	throw BadCastException("Can not convert to DateTime");
}


inline void VarHolder::convert(LocalDateTime& val) const
{
	throw BadCastException("Can not convert to LocalDateTime");
}


inline void VarHolder::convert(Timestamp& val) const
{
	throw BadCastException("Can not convert to Timestamp");
}


#ifndef POCO_LONG_IS_64_BIT
inline void VarHolder::convert(long& val) const
{
	Int32 tmp;
	convert(tmp);
	val = tmp;
}


inline void VarHolder::convert(unsigned long& val) const
{
	UInt32 tmp;
	convert(tmp);
	val = tmp;
}
#endif


inline void VarHolder::convert(bool& val) const
{
	throw BadCastException("Can not convert to bool");
}


inline void VarHolder::convert(float& val) const
{
	throw BadCastException("Can not convert to float");
}


inline void VarHolder::convert(double& val) const
{
	throw BadCastException("Can not convert to double");
}


inline void VarHolder::convert(char& val) const
{
	throw BadCastException("Can not convert to char");
}


inline void VarHolder::convert(std::string& val) const
{
	throw BadCastException("Can not convert to std::string");
}


inline bool VarHolder::isArray() const
{
	return false;
}


inline bool VarHolder::isStruct() const
{
	return false;
}

inline bool VarHolder::isInteger() const
{
	return false;
}


inline bool VarHolder::isSigned() const
{
	return false;
}


inline bool VarHolder::isNumeric() const
{
	return false;
}


inline bool VarHolder::isString() const
{
	return false;
}


template <typename T>
class VarHolderImpl: public VarHolder
	/// Template based implementation of a VarHolder. 
	/// This class provides type storage for user-defined types
	/// that do not have VarHolderImpl specialization.
	///
	/// The actual conversion work happens in the template specializations
	/// of this class.
	///
	/// VarHolderImpl throws following exceptions:
	///		BadCastException (if the requested conversion is not implemented)
	///		RangeException (if an attempt is made to assign a numeric value outside of the target min/max limits
	///		SyntaxException (if an attempt is made to convert a string containing non-numeric characters to number)
	///
	/// In order to support efficient direct extraction of the held value,
	/// all specializations must additionally implement a public member function:
	///
	///     const T& value() const
	///
	/// returning a const reference to the actual stored value.
{
public:
	VarHolderImpl(const T& val): _val(val)
	{
	}

	~VarHolderImpl()
	{
	}

	const std::type_info& type() const
	{
		return typeid(T);
	}

	VarHolder* clone() const
	{
		return new VarHolderImpl(_val);
	}

	const T& value() const
	{
		return _val;
	}

private:
	VarHolderImpl();
	VarHolderImpl(const VarHolderImpl&);
	VarHolderImpl& operator = (const VarHolderImpl&);

	T _val;
};


template <>
class VarHolderImpl<Int8>: public VarHolder
{
public:
	VarHolderImpl(Int8 val): _val(val)
	{
	}

	~VarHolderImpl()
	{
	}
	
	const std::type_info& type() const
	{
		return typeid(Int8);
	}

	void convert(Int8& val) const
	{
		val = _val;
	}

	void convert(Int16& val) const
	{
		val = _val;
	}
	
	void convert(Int32& val) const
	{
		val = _val;
	}

	void convert(Int64& val) const
	{
		val = _val;
	}

	void convert(UInt8& val) const
	{
		convertSignedToUnsigned(_val, val);
	}

	void convert(UInt16& val) const
	{
		convertSignedToUnsigned(_val, val);
	}
	
	void convert(UInt32& val) const
	{
		convertSignedToUnsigned(_val, val);
	}

	void convert(UInt64& val) const
	{
		convertSignedToUnsigned(_val, val);
	}

	void convert(bool& val) const
	{
		val = (_val != 0);
	}

	void convert(float& val) const
	{
		val = static_cast<float>(_val);
	}

	void convert(double& val) const
	{
		val = static_cast<double>(_val);
	}

	void convert(char& val) const
	{
		val = static_cast<char>(_val);
	}

	void convert(std::string& val) const
	{
		val = NumberFormatter::format(_val);
	}

	VarHolder* clone() const
	{
		return new VarHolderImpl(_val);
	}
	
	const Int8& value() const
	{
		return _val;
	}

	bool isArray() const
	{
		return false;
	}

	bool isStruct() const
	{
		return false;
	}

	bool isInteger() const
	{
		return std::numeric_limits<Int8>::is_integer;
	}

	bool isSigned() const
	{
		return std::numeric_limits<Int8>::is_signed;
	}

	bool isNumeric() const
	{
		return std::numeric_limits<Int8>::is_specialized;
	}

	bool isString() const
	{
		return false;
	}

private:
	VarHolderImpl();
	VarHolderImpl(const VarHolderImpl&);
	VarHolderImpl& operator = (const VarHolderImpl&);

	Int8 _val;
};


template <>
class VarHolderImpl<Int16>: public VarHolder
{
public:
	VarHolderImpl(Int16 val): _val(val)
	{
	}

	~VarHolderImpl()
	{
	}
	
	const std::type_info& type() const
	{
		return typeid(Int16);
	}

	void convert(Int8& val) const
	{
		convertToSmaller(_val, val);
	}

	void convert(Int16& val) const
	{
		val = _val;
	}
	
	void convert(Int32& val) const
	{
		val = _val;
	}

	void convert(Int64& val) const
	{
		val = _val;
	}

	void convert(UInt8& val) const
	{
		convertSignedToUnsigned(_val, val);
	}

	void convert(UInt16& val) const
	{
		convertSignedToUnsigned(_val, val);
	}
	
	void convert(UInt32& val) const
	{
		convertSignedToUnsigned(_val, val);
	}

	void convert(UInt64& val) const
	{
		convertSignedToUnsigned(_val, val);
	}

	void convert(bool& val) const
	{
		val = (_val != 0);
	}

	void convert(float& val) const
	{
		val = static_cast<float>(_val);
	}

	void convert(double& val) const
	{
		val = static_cast<double>(_val);
	}

	void convert(char& val) const
	{
		UInt8 tmp;
		convert(tmp);
		val = static_cast<char>(tmp);
	}

	void convert(std::string& val) const
	{
		val = NumberFormatter::format(_val);
	}

	VarHolder* clone() const
	{
		return new VarHolderImpl(_val);
	}

	const Int16& value() const
	{
		return _val;
	}

	bool isArray() const
	{
		return false;
	}

	bool isStruct() const
	{
		return false;
	}

	bool isInteger() const
	{
		return std::numeric_limits<Int16>::is_integer;
	}

	bool isSigned() const
	{
		return std::numeric_limits<Int16>::is_signed;
	}

	bool isNumeric() const
	{
		return std::numeric_limits<Int16>::is_specialized;
	}

	bool isString() const
	{
		return false;
	}

private:
	VarHolderImpl();
	VarHolderImpl(const VarHolderImpl&);
	VarHolderImpl& operator = (const VarHolderImpl&);

	Int16 _val;
};


template <>
class VarHolderImpl<Int32>: public VarHolder
{
public:
	VarHolderImpl(Int32 val): _val(val)
	{
	}

	~VarHolderImpl()
	{
	}

	const std::type_info& type() const
	{
		return typeid(Int32);
	}

	void convert(Int8& val) const
	{
		convertToSmaller(_val, val);
	}

	void convert(Int16& val) const
	{
		convertToSmaller(_val, val);
	}
	
	void convert(Int32& val) const
	{
		val = _val;
	}

	void convert(Int64& val) const
	{
		val = _val;
	}

	void convert(UInt8& val) const
	{
		convertSignedToUnsigned(_val, val);
	}

	void convert(UInt16& val) const
	{
		convertSignedToUnsigned(_val, val);
	}
	
	void convert(UInt32& val) const
	{
		convertSignedToUnsigned(_val, val);
	}

	void convert(UInt64& val) const
	{
		convertSignedToUnsigned(_val, val);
	}

	void convert(bool& val) const
	{
		val = (_val != 0);
	}

	void convert(float& val) const
	{
		val = static_cast<float>(_val);
	}

	void convert(double& val) const
	{
		val = static_cast<double>(_val);
	}

	void convert(char& val) const
	{
		UInt8 tmp;
		convert(tmp);
		val = static_cast<char>(tmp);
	}

	void convert(std::string& val) const
	{
		val = NumberFormatter::format(_val);
	}

	VarHolder* clone() const
	{
		return new VarHolderImpl(_val);
	}

	const Int32& value() const
	{
		return _val;
	}

	bool isArray() const
	{
		return false;
	}

	bool isStruct() const
	{
		return false;
	}

	bool isInteger() const
	{
		return std::numeric_limits<Int32>::is_integer;
	}

	bool isSigned() const
	{
		return std::numeric_limits<Int32>::is_signed;
	}

	bool isNumeric() const
	{
		return std::numeric_limits<Int32>::is_specialized;
	}

	bool isString() const
	{
		return false;
	}

private:
	VarHolderImpl();
	VarHolderImpl(const VarHolderImpl&);
	VarHolderImpl& operator = (const VarHolderImpl&);

	Int32 _val;
};


template <>
class VarHolderImpl<Int64>: public VarHolder
{
public:
	VarHolderImpl(Int64 val): _val(val)
	{
	}

	~VarHolderImpl()
	{
	}

	const std::type_info& type() const
	{
		return typeid(Int64);
	}

	void convert(Int8& val) const
	{
		convertToSmaller(_val, val);
	}

	void convert(Int16& val) const
	{
		convertToSmaller(_val, val);
	}
	
	void convert(Int32& val) const
	{
		convertToSmaller(_val, val);
	}

	void convert(Int64& val) const
	{
		val = _val;
	}

	void convert(UInt8& val) const
	{
		convertSignedToUnsigned(_val, val);
	}

	void convert(UInt16& val) const
	{
		convertSignedToUnsigned(_val, val);
	}
	
	void convert(UInt32& val) const
	{
		convertSignedToUnsigned(_val, val);
	}

	void convert(UInt64& val) const
	{
		convertSignedToUnsigned(_val, val);
	}

	void convert(bool& val) const
	{
		val = (_val != 0);
	}

	void convert(float& val) const
	{
		val = static_cast<float>(_val);
	}

	void convert(double& val) const
	{
		val = static_cast<double>(_val);
	}

	void convert(char& val) const
	{
		UInt8 tmp;
		convert(tmp);
		val = static_cast<char>(tmp);
	}

	void convert(std::string& val) const
	{
		val = NumberFormatter::format(_val);
	}

	void convert(DateTime& dt) const
	{
		dt = Timestamp(_val);
	}

	void convert(LocalDateTime& ldt) const
	{
		ldt = Timestamp(_val);
	}

	void convert(Timestamp& val) const
	{
		val = Timestamp(_val);
	}

	VarHolder* clone() const
	{
		return new VarHolderImpl(_val);
	}

	const Int64& value() const
	{
		return _val;
	}

	bool isArray() const
	{
		return false;
	}

	bool isStruct() const
	{
		return false;
	}

	bool isInteger() const
	{
		return std::numeric_limits<Int64>::is_integer;
	}

	bool isSigned() const
	{
		return std::numeric_limits<Int64>::is_signed;
	}

	bool isNumeric() const
	{
		return std::numeric_limits<Int64>::is_specialized;
	}

	bool isString() const
	{
		return false;
	}

private:
	VarHolderImpl();
	VarHolderImpl(const VarHolderImpl&);
	VarHolderImpl& operator = (const VarHolderImpl&);

	Int64 _val;
};


template <>
class VarHolderImpl<UInt8>: public VarHolder
{
public:
	VarHolderImpl(UInt8 val): _val(val)
	{
	}

	~VarHolderImpl()
	{
	}
	
	const std::type_info& type() const
	{
		return typeid(UInt8);
	}

	void convert(Int8& val) const
	{
		convertUnsignedToSigned(_val, val);
	}

	void convert(Int16& val) const
	{
		convertUnsignedToSigned(_val, val);
	}
	
	void convert(Int32& val) const
	{
		val = static_cast<Int32>(_val);
	}

	void convert(Int64& val) const
	{
		val = static_cast<Int64>(_val);
	}

	void convert(UInt8& val) const
	{
		val = _val;
	}

	void convert(UInt16& val) const
	{
		val = _val;
	}
	
	void convert(UInt32& val) const
	{
		val = _val;
	}

	void convert(UInt64& val) const
	{
		val = _val;
	}

	void convert(bool& val) const
	{
		val = (_val != 0);
	}

	void convert(float& val) const
	{
		val = static_cast<float>(_val);
	}

	void convert(double& val) const
	{
		val = static_cast<double>(_val);
	}

	void convert(char& val) const
	{
		UInt8 tmp;
		convert(tmp);
		val = static_cast<char>(tmp);
	}

	void convert(std::string& val) const
	{
		val = NumberFormatter::format(_val);
	}

	VarHolder* clone() const
	{
		return new VarHolderImpl(_val);
	}

	const UInt8& value() const
	{
		return _val;
	}

	bool isArray() const
	{
		return false;
	}

	bool isStruct() const
	{
		return false;
	}

	bool isInteger() const
	{
		return std::numeric_limits<UInt8>::is_integer;
	}

	bool isSigned() const
	{
		return std::numeric_limits<UInt8>::is_signed;
	}

	bool isNumeric() const
	{
		return std::numeric_limits<UInt8>::is_specialized;
	}

	bool isString() const
	{
		return false;
	}

private:
	VarHolderImpl();
	VarHolderImpl(const VarHolderImpl&);
	VarHolderImpl& operator = (const VarHolderImpl&);

	UInt8 _val;
};


template <>
class VarHolderImpl<UInt16>: public VarHolder
{
public:
	VarHolderImpl(UInt16 val): _val(val)
	{
	}

	~VarHolderImpl()
	{
	}

	const std::type_info& type() const
	{
		return typeid(UInt16);
	}

	void convert(Int8& val) const
	{
		convertUnsignedToSigned(_val, val);
	}

	void convert(Int16& val) const
	{
		convertUnsignedToSigned(_val, val);
	}
	
	void convert(Int32& val) const
	{
		convertUnsignedToSigned(_val, val);
	}

	void convert(Int64& val) const
	{
		val = static_cast<Int64>(_val);
	}

	void convert(UInt8& val) const
	{
		convertToSmallerUnsigned(_val, val);
	}

	void convert(UInt16& val) const
	{
		val = _val;
	}
	
	void convert(UInt32& val) const
	{
		val = _val;
	}

	void convert(UInt64& val) const
	{
		val = _val;
	}

	void convert(bool& val) const
	{
		val = (_val != 0);
	}

	void convert(float& val) const
	{
		val = static_cast<float>(_val);
	}

	void convert(double& val) const
	{
		val = static_cast<double>(_val);
	}

	void convert(char& val) const
	{
		UInt8 tmp;
		convert(tmp);
		val = static_cast<char>(tmp);
	}

	void convert(std::string& val) const
	{
		val = NumberFormatter::format(_val);
	}

	VarHolder* clone() const
	{
		return new VarHolderImpl(_val);
	}

	const UInt16& value() const
	{
		return _val;
	}

	bool isArray() const
	{
		return false;
	}

	bool isStruct() const
	{
		return false;
	}

	bool isInteger() const
	{
		return std::numeric_limits<UInt16>::is_integer;
	}

	bool isSigned() const
	{
		return std::numeric_limits<UInt16>::is_signed;
	}

	bool isNumeric() const
	{
		return std::numeric_limits<UInt16>::is_specialized;
	}

	bool isString() const
	{
		return false;
	}

private:
	VarHolderImpl();
	VarHolderImpl(const VarHolderImpl&);
	VarHolderImpl& operator = (const VarHolderImpl&);

	UInt16 _val;
};


template <>
class VarHolderImpl<UInt32>: public VarHolder
{
public:
	VarHolderImpl(UInt32 val): _val(val)
	{
	}

	~VarHolderImpl()
	{
	}

	const std::type_info& type() const
	{
		return typeid(UInt32);
	}

	void convert(Int8& val) const
	{
		convertUnsignedToSigned(_val, val);
	}

	void convert(Int16& val) const
	{
		convertUnsignedToSigned(_val, val);
	}
	
	void convert(Int32& val) const
	{
		convertUnsignedToSigned(_val, val);
	}

	void convert(Int64& val) const
	{
		convertUnsignedToSigned(_val, val);
	}

	void convert(UInt8& val) const
	{
		convertToSmallerUnsigned(_val, val);
	}

	void convert(UInt16& val) const
	{
		convertToSmallerUnsigned(_val, val);
	}
	
	void convert(UInt32& val) const
	{
		val = _val;
	}

	void convert(UInt64& val) const
	{
		val = _val;
	}

	void convert(bool& val) const
	{
		val = (_val != 0);
	}

	void convert(float& val) const
	{
		val = static_cast<float>(_val);
	}

	void convert(double& val) const
	{
		val = static_cast<double>(_val);
	}

	void convert(char& val) const
	{
		UInt8 tmp;
		convert(tmp);
		val = static_cast<char>(tmp);
	}

	void convert(std::string& val) const
	{
		val = NumberFormatter::format(_val);
	}

	VarHolder* clone() const
	{
		return new VarHolderImpl(_val);
	}

	const UInt32& value() const
	{
		return _val;
	}

	bool isArray() const
	{
		return false;
	}

	bool isStruct() const
	{
		return false;
	}

	bool isInteger() const
	{
		return std::numeric_limits<UInt32>::is_integer;
	}

	bool isSigned() const
	{
		return std::numeric_limits<UInt32>::is_signed;
	}

	bool isNumeric() const
	{
		return std::numeric_limits<UInt32>::is_specialized;
	}

	bool isString() const
	{
		return false;
	}

private:
	VarHolderImpl();
	VarHolderImpl(const VarHolderImpl&);
	VarHolderImpl& operator = (const VarHolderImpl&);

	UInt32 _val;
};


template <>
class VarHolderImpl<UInt64>: public VarHolder
{
public:
	VarHolderImpl(UInt64 val): _val(val)
	{
	}

	~VarHolderImpl()
	{
	}

	const std::type_info& type() const
	{
		return typeid(UInt64);
	}

	void convert(Int8& val) const
	{
		convertUnsignedToSigned(_val, val);
	}

	void convert(Int16& val) const
	{
		convertUnsignedToSigned(_val, val);
	}
	
	void convert(Int32& val) const
	{
		convertUnsignedToSigned(_val, val);
	}

	void convert(Int64& val) const
	{
		convertUnsignedToSigned(_val, val);
	}

	void convert(UInt8& val) const
	{
		convertToSmallerUnsigned(_val, val);
	}

	void convert(UInt16& val) const
	{
		convertToSmallerUnsigned(_val, val);
	}
	
	void convert(UInt32& val) const
	{
		convertToSmallerUnsigned(_val, val);
	}

	void convert(UInt64& val) const
	{
		val = _val;
	}

	void convert(bool& val) const
	{
		val = (_val != 0);
	}

	void convert(float& val) const
	{
		val = static_cast<float>(_val);
	}

	void convert(double& val) const
	{
		val = static_cast<double>(_val);
	}

	void convert(char& val) const
	{
		UInt8 tmp;
		convert(tmp);
		val = static_cast<char>(tmp);
	}

	void convert(std::string& val) const
	{
		val = NumberFormatter::format(_val);
	}

	void convert(DateTime& dt) const
	{
		Int64 val;
		convertUnsignedToSigned(_val, val);
		dt = Timestamp(val);
	}

	void convert(LocalDateTime& ldt) const
	{
		Int64 val;
		convertUnsignedToSigned(_val, val);
		ldt = Timestamp(val);
	}

	void convert(Timestamp& val) const
	{
		Int64 tmp;
		convertUnsignedToSigned(_val, tmp);
		val = Timestamp(tmp);
	}

	VarHolder* clone() const
	{
		return new VarHolderImpl(_val);
	}

	const UInt64& value() const
	{
		return _val;
	}

	bool isArray() const
	{
		return false;
	}

	bool isStruct() const
	{
		return false;
	}

	bool isInteger() const
	{
		return std::numeric_limits<UInt64>::is_integer;
	}

	bool isSigned() const
	{
		return std::numeric_limits<UInt64>::is_signed;
	}

	bool isNumeric() const
	{
		return std::numeric_limits<UInt64>::is_specialized;
	}

	bool isString() const
	{
		return false;
	}

private:
	VarHolderImpl();
	VarHolderImpl(const VarHolderImpl&);
	VarHolderImpl& operator = (const VarHolderImpl&);

	UInt64 _val;
};


template <>
class VarHolderImpl<bool>: public VarHolder
{
public:
	VarHolderImpl(bool val): _val(val)
	{
	}

	~VarHolderImpl()
	{
	}

	const std::type_info& type() const
	{
		return typeid(bool);
	}

	void convert(Int8& val) const
	{
		val = static_cast<Int8>(_val ? 1 : 0);
	}

	void convert(Int16& val) const
	{
		val = static_cast<Int16>(_val ? 1 : 0);
	}
	
	void convert(Int32& val) const
	{
		val = static_cast<Int32>(_val ? 1 : 0);
	}

	void convert(Int64& val) const
	{
		val = static_cast<Int64>(_val ? 1 : 0);
	}

	void convert(UInt8& val) const
	{
		val = static_cast<UInt8>(_val ? 1 : 0);
	}

	void convert(UInt16& val) const
	{
		val = static_cast<UInt16>(_val ? 1 : 0);
	}
	
	void convert(UInt32& val) const
	{
		val = static_cast<UInt32>(_val ? 1 : 0);
	}

	void convert(UInt64& val) const
	{
		val = static_cast<UInt64>(_val ? 1 : 0);
	}

	void convert(bool& val) const
	{
		val = _val;
	}

	void convert(float& val) const
	{
		val = (_val ? 1.0f : 0.0f);
	}

	void convert(double& val) const
	{
		val = (_val ? 1.0 : 0.0);
	}

	void convert(char& val) const
	{
		val = static_cast<char>(_val ? 1 : 0);
	}

	void convert(std::string& val) const
	{
		val = (_val ? "true" : "false");
	}

	VarHolder* clone() const
	{
		return new VarHolderImpl(_val);
	}

	const bool& value() const
	{
		return _val;
	}

	bool isArray() const
	{
		return false;
	}

	bool isStruct() const
	{
		return false;
	}

	bool isInteger() const
	{
		return std::numeric_limits<bool>::is_integer;
	}

	bool isSigned() const
	{
		return std::numeric_limits<bool>::is_signed;
	}

	bool isNumeric() const
	{
		return std::numeric_limits<bool>::is_specialized;
	}

	bool isString() const
	{
		return false;
	}

private:
	VarHolderImpl();
	VarHolderImpl(const VarHolderImpl&);
	VarHolderImpl& operator = (const VarHolderImpl&);

	bool _val;
};


template <>
class VarHolderImpl<float>: public VarHolder
{
public:
	VarHolderImpl(float val): _val(val)
	{
	}

	~VarHolderImpl()
	{
	}

	const std::type_info& type() const
	{
		return typeid(float);
	}

	void convert(Int8& val) const
	{
		convertToSmaller(_val, val);
	}

	void convert(Int16& val) const
	{
		convertToSmaller(_val, val);
	}
	
	void convert(Int32& val) const
	{
		convertToSmaller(_val, val);
	}

	void convert(Int64& val) const
	{
		convertToSmaller(_val, val);
	}

	void convert(UInt8& val) const
	{
		convertSignedFloatToUnsigned(_val, val);
	}

	void convert(UInt16& val) const
	{
		convertSignedFloatToUnsigned(_val, val);
	}
	
	void convert(UInt32& val) const
	{
		convertSignedFloatToUnsigned(_val, val);
	}

	void convert(UInt64& val) const
	{
		convertSignedFloatToUnsigned(_val, val);
	}

	void convert(bool& val) const
	{
		val = !(_val <= std::numeric_limits<float>::min() && 
			_val >= -1 * std::numeric_limits<float>::min());
	}

	void convert(float& val) const
	{
		val = _val;
	}

	void convert(double& val) const
	{
		val = _val;
	}

	void convert(char& val) const
	{
		UInt8 tmp;
		convert(tmp);
		val = static_cast<char>(tmp);
	}

	void convert(std::string& val) const
	{
		val = NumberFormatter::format(_val);
	}

	VarHolder* clone() const
	{
		return new VarHolderImpl(_val);
	}

	const float& value() const
	{
		return _val;
	}

	bool isArray() const
	{
		return false;
	}

	bool isStruct() const
	{
		return false;
	}

	bool isInteger() const
	{
		return std::numeric_limits<float>::is_integer;
	}

	bool isSigned() const
	{
		return std::numeric_limits<float>::is_signed;
	}

	bool isNumeric() const
	{
		return std::numeric_limits<float>::is_specialized;
	}

	bool isString() const
	{
		return false;
	}

private:
	VarHolderImpl();
	VarHolderImpl(const VarHolderImpl&);
	VarHolderImpl& operator = (const VarHolderImpl&);

	float _val;
};


template <>
class VarHolderImpl<double>: public VarHolder
{
public:
	VarHolderImpl(double val): _val(val)
	{
	}

	~VarHolderImpl()
	{
	}

	const std::type_info& type() const
	{
		return typeid(double);
	}

	void convert(Int8& val) const
	{
		convertToSmaller(_val, val);
	}

	void convert(Int16& val) const
	{
		convertToSmaller(_val, val);
	}
	
	void convert(Int32& val) const
	{
		convertToSmaller(_val, val);
	}

	void convert(Int64& val) const
	{
		convertToSmaller(_val, val);
	}

	void convert(UInt8& val) const
	{
		convertSignedFloatToUnsigned(_val, val);
	}

	void convert(UInt16& val) const
	{
		convertSignedFloatToUnsigned(_val, val);
	}
	
	void convert(UInt32& val) const
	{
		convertSignedFloatToUnsigned(_val, val);
	}

	void convert(UInt64& val) const
	{
		convertSignedFloatToUnsigned(_val, val);
	}

	void convert(bool& val) const
	{
		val = !(_val <= std::numeric_limits<double>::min() && 
			_val >= -1 * std::numeric_limits<double>::min());
	}

	void convert(float& val) const
	{
		double fMin = -1 * std::numeric_limits<float>::max();
		double fMax = std::numeric_limits<float>::max();

		if (_val < fMin) throw RangeException("Value too small.");
		if (_val > fMax) throw RangeException("Value too large.");

		val = static_cast<float>(_val);
	}

	void convert(double& val) const
	{
		val = _val;
	}

	void convert(char& val) const
	{
		UInt8 tmp;
		convert(tmp);
		val = static_cast<char>(tmp);
	}

	void convert(std::string& val) const
	{
		val = NumberFormatter::format(_val);
	}

	VarHolder* clone() const
	{
		return new VarHolderImpl(_val);
	}

	const double& value() const
	{
		return _val;
	}

	bool isArray() const
	{
		return false;
	}

	bool isStruct() const
	{
		return false;
	}

	bool isInteger() const
	{
		return std::numeric_limits<double>::is_integer;
	}

	bool isSigned() const
	{
		return std::numeric_limits<double>::is_signed;
	}

	bool isNumeric() const
	{
		return std::numeric_limits<double>::is_specialized;
	}

	bool isString() const
	{
		return false;
	}

private:
	VarHolderImpl();
	VarHolderImpl(const VarHolderImpl&);
	VarHolderImpl& operator = (const VarHolderImpl&);

	double _val;
};


template <>
class VarHolderImpl<char>: public VarHolder
{
public:
	VarHolderImpl(char val): _val(val)
	{
	}

	~VarHolderImpl()
	{
	}

	const std::type_info& type() const
	{
		return typeid(char);
	}

	void convert(Int8& val) const
	{
		val = static_cast<Int8>(_val);
	}

	void convert(Int16& val) const
	{
		val = static_cast<UInt8>(_val);
	}
	
	void convert(Int32& val) const
	{
		val = static_cast<UInt8>(_val);
	}

	void convert(Int64& val) const
	{
		val = static_cast<UInt8>(_val);
	}

	void convert(UInt8& val) const
	{
		val = static_cast<UInt8>(_val);
	}

	void convert(UInt16& val) const
	{
		val = static_cast<UInt8>(_val);
	}
	
	void convert(UInt32& val) const
	{
		val = static_cast<UInt8>(_val);
	}

	void convert(UInt64& val) const
	{
		val = static_cast<UInt8>(_val);
	}

	void convert(bool& val) const
	{
		val = (_val != '\0');
	}

	void convert(float& val) const
	{
		val = static_cast<float>(_val);
	}

	void convert(double& val) const
	{
		val = static_cast<double>(_val);
	}

	void convert(char& val) const
	{
		val = _val;
	}

	void convert(std::string& val) const
	{
		val = std::string(1, _val);
	}

	VarHolder* clone() const
	{
		return new VarHolderImpl(_val);
	}

	const char& value() const
	{
		return _val;
	}

	bool isArray() const
	{
		return false;
	}

	bool isStruct() const
	{
		return false;
	}

	bool isInteger() const
	{
		return std::numeric_limits<char>::is_integer;
	}

	bool isSigned() const
	{
		return std::numeric_limits<char>::is_signed;
	}

	bool isNumeric() const
	{
		return std::numeric_limits<char>::is_specialized;
	}

	bool isString() const
	{
		return false;
	}

private:
	VarHolderImpl();
	VarHolderImpl(const VarHolderImpl&);
	VarHolderImpl& operator = (const VarHolderImpl&);

	char _val;
};


template <>
class VarHolderImpl<std::string>: public VarHolder
{
public:
	VarHolderImpl(const char* pVal): _val(pVal)
	{
	}

	VarHolderImpl(const std::string& val): _val(val)
	{
	}

	~VarHolderImpl()
	{
	}

	const std::type_info& type() const
	{
		return typeid(std::string);
	}

	void convert(Int8& val) const
	{
		int v = NumberParser::parse(_val);
		convertToSmaller(v, val);
	}

	void convert(Int16& val) const
	{
		int v = NumberParser::parse(_val);
		convertToSmaller(v, val);
	}
	
	void convert(Int32& val) const
	{
		val = NumberParser::parse(_val);
	}

	void convert(Int64& val) const
	{
		val = NumberParser::parse64(_val);
	}

	void convert(UInt8& val) const
	{
		unsigned int v = NumberParser::parseUnsigned(_val);
		convertToSmallerUnsigned(v, val);
	}

	void convert(UInt16& val) const
	{
		unsigned int v = NumberParser::parseUnsigned(_val);
		convertToSmallerUnsigned(v, val);
	}
	
	void convert(UInt32& val) const
	{
		val = NumberParser::parseUnsigned(_val);
	}

	void convert(UInt64& val) const
	{
		val = NumberParser::parseUnsigned64(_val);
	}

	void convert(bool& val) const
	{
		static const std::string VAL_FALSE("false");
		static const std::string VAL_INT_FALSE("0");

		if (_val.empty() ||
			_val == VAL_INT_FALSE ||
			(icompare(_val, VAL_FALSE) == 0))
		{
			val = false;
		}
		else val = true;
	}

	void convert(float& val) const
	{
		double v = NumberParser::parseFloat(_val);
		convertToSmaller(v, val);
	}

	void convert(double& val) const
	{
		val = NumberParser::parseFloat(_val);
	}

	void convert(char& val) const
	{
		if (_val.empty())
			val = '\0';
		else
			val = _val[0];
	}

	void convert(std::string& val) const
	{
		val = _val;
	}

	void convert(DateTime& val) const
	{
		int tzd = 0;
		if (!DateTimeParser::tryParse(DateTimeFormat::ISO8601_FORMAT, _val, val, tzd))
			throw BadCastException("string -> DateTime");
	}

	void convert(LocalDateTime& ldt) const
	{
		int tzd = 0;
		DateTime tmp;
		if (!DateTimeParser::tryParse(DateTimeFormat::ISO8601_FORMAT, _val, tmp, tzd))
			throw BadCastException("string -> LocalDateTime");

		ldt = LocalDateTime(tzd, tmp, false);
	}

	void convert(Timestamp& ts) const
	{
		int tzd = 0;
		DateTime tmp;
		if (!DateTimeParser::tryParse(DateTimeFormat::ISO8601_FORMAT, _val, tmp, tzd))
			throw BadCastException("string -> Timestamp");

		ts = tmp.timestamp();
	}

	VarHolder* clone() const
	{
		return new VarHolderImpl(_val);
	}

	const std::string& value() const
	{
		return _val;
	}

	bool isArray() const
	{
		return false;
	}

	bool isStruct() const
	{
		return false;
	}

	bool isInteger() const
	{
		return false;
	}

	bool isSigned() const
	{
		return false;
	}

	bool isNumeric() const
	{
		return false;
	}

	bool isString() const
	{
		return true;
	}

private:
	VarHolderImpl();
	VarHolderImpl(const VarHolderImpl&);
	VarHolderImpl& operator = (const VarHolderImpl&);

	std::string _val;
};


#ifndef POCO_LONG_IS_64_BIT


template <>
class VarHolderImpl<long>: public VarHolder
{
public:
	VarHolderImpl(long val): _val(val)
	{
	}

	~VarHolderImpl()
	{
	}

	const std::type_info& type() const
	{
		return typeid(long);
	}

	void convert(Int8& val) const
	{
		convertToSmaller(_val, val);
	}

	void convert(Int16& val) const
	{
		convertToSmaller(_val, val);
	}
	
	void convert(Int32& val) const
	{
		val = static_cast<Int32>(_val);
	}

	void convert(Int64& val) const
	{
		val = static_cast<Int64>(_val);
	}

	void convert(UInt8& val) const
	{
		convertSignedToUnsigned(_val, val);
	}

	void convert(UInt16& val) const
	{
		convertSignedToUnsigned(_val, val);
	}
	
	void convert(UInt32& val) const
	{
		convertSignedToUnsigned(_val, val);
	}

	void convert(UInt64& val) const
	{
		convertSignedToUnsigned(_val, val);
	}

	void convert(bool& val) const
	{
		val = (_val != 0);
	}

	void convert(float& val) const
	{
		val = static_cast<float>(_val);
	}

	void convert(double& val) const
	{
		val = static_cast<double>(_val);
	}

	void convert(char& val) const
	{
		UInt8 tmp;
		convert(tmp);
		val = static_cast<char>(tmp);
	}

	void convert(std::string& val) const
	{
		val = NumberFormatter::format(_val);
	}

	VarHolder* clone() const
	{
		return new VarHolderImpl(_val);
	}

	const long& value() const
	{
		return _val;
	}

	bool isArray() const
	{
		return false;
	}

	bool isStruct() const
	{
		return false;
	}

	bool isInteger() const
	{
		return std::numeric_limits<long>::is_integer;
	}

	bool isSigned() const
	{
		return std::numeric_limits<long>::is_signed;
	}

	bool isNumeric() const
	{
		return std::numeric_limits<long>::is_specialized;
	}

	bool isString() const
	{
		return false;
	}

private:
	VarHolderImpl();
	VarHolderImpl(const VarHolderImpl&);
	VarHolderImpl& operator = (const VarHolderImpl&);

	long _val;
};


template <>
class VarHolderImpl<unsigned long>: public VarHolder
{
public:
	VarHolderImpl(unsigned long val): _val(val)
	{
	}

	~VarHolderImpl()
	{
	}

	const std::type_info& type() const
	{
		return typeid(unsigned long);
	}

	void convert(Int8& val) const
	{
		convertUnsignedToSigned(_val, val);
	}

	void convert(Int16& val) const
	{
		convertUnsignedToSigned(_val, val);
	}
	
	void convert(Int32& val) const
	{
		convertUnsignedToSigned(_val, val);
	}

	void convert(Int64& val) const
	{
		convertUnsignedToSigned(_val, val);
	}

	void convert(UInt8& val) const
	{
		convertToSmallerUnsigned(_val, val);
	}

	void convert(UInt16& val) const
	{
		convertToSmallerUnsigned(_val, val);
	}
	
	void convert(UInt32& val) const
	{
		convertToSmallerUnsigned(_val, val);
	}

	void convert(UInt64& val) const
	{
		val = static_cast<UInt64>(_val);
	}

	void convert(bool& val) const
	{
		val = (_val != 0);
	}

	void convert(float& val) const
	{
		val = static_cast<float>(_val);
	}

	void convert(double& val) const
	{
		val = static_cast<double>(_val);
	}

	void convert(char& val) const
	{
		UInt8 tmp;
		convert(tmp);
		val = static_cast<char>(tmp);
	}

	void convert(std::string& val) const
	{
		val = NumberFormatter::format(_val);
	}

	VarHolder* clone() const
	{
		return new VarHolderImpl(_val);
	}

	const unsigned long& value() const
	{
		return _val;
	}

	bool isArray() const
	{
		return false;
	}

	bool isStruct() const
	{
		return false;
	}

	bool isInteger() const
	{
		return std::numeric_limits<unsigned long>::is_integer;
	}

	bool isSigned() const
	{
		return std::numeric_limits<unsigned long>::is_signed;
	}

	bool isNumeric() const
	{
		return std::numeric_limits<unsigned long>::is_specialized;
	}

	bool isString() const
	{
		return false;
	}

private:
	VarHolderImpl();
	VarHolderImpl(const VarHolderImpl&);
	VarHolderImpl& operator = (const VarHolderImpl&);

	unsigned long _val;
};


#endif // 64bit


template <typename T>
class VarHolderImpl<std::vector<T> >: public VarHolder
{
public:
	VarHolderImpl(const std::vector<T>& val): _val(val)
	{
	}

	~VarHolderImpl()
	{
	}
	
	const std::type_info& type() const
	{
		return typeid(std::vector<T>);
	}

	void convert(std::string& val) const
	{
		// Serialize in JSON format: note: although this is a vector<T>, the code only 
		// supports vector<Var>. Total specialization is not possible
		// because of the cyclic dependency between Var and VarHolder

		// JSON format definition: [ n times: elem ',' ], no ',' for last elem
		val.append("[ ");
		typename std::vector<T>::const_iterator it = _val.begin();
		typename std::vector<T>::const_iterator itEnd = _val.end();
		if (!_val.empty())
		{
			appendJSONString(val, *it);
			++it;
		}
		for (; it != itEnd; ++it)
		{
			
			val.append(", ");
			appendJSONString(val, *it);
		}
		val.append(" ]");
	}

	VarHolder* clone() const
	{
		return new VarHolderImpl(_val);
	}
	
	const std::vector<T>& value() const
	{
		return _val;
	}

	bool isArray() const
	{
		return true;
	}

	bool isStruct() const
	{
		return false;
	}

	bool isInteger() const
	{
		return false;
	}

	bool isSigned() const
	{
		return false;
	}

	bool isNumeric() const
	{
		return false;
	}

	bool isString() const
	{
		return false;
	}

	T& operator[](typename std::vector<T>::size_type n)
	{
		return _val.operator[](n);
	}

	const T& operator[](typename std::vector<T>::size_type n) const
	{
		return _val.operator[](n);
	}

private:
	VarHolderImpl();
	VarHolderImpl(const VarHolderImpl&);
	VarHolderImpl& operator = (const VarHolderImpl&);

	std::vector<T> _val;
};


template <>
class VarHolderImpl<DateTime>: public VarHolder
{
public:
	VarHolderImpl(const DateTime& val): _val(val)
	{
	}

	~VarHolderImpl()
	{
	}
	
	const std::type_info& type() const
	{
		return typeid(DateTime);
	}

	void convert(Int8& val) const
	{
		throw BadCastException();
	}

	void convert(Int16& val) const
	{
		throw BadCastException();
	}
	
	void convert(Int32& val) const
	{
		throw BadCastException();
	}

	void convert(Int64& val) const
	{
		val = _val.timestamp().epochMicroseconds();
	}

	void convert(UInt64& val) const
	{
		val = _val.timestamp().epochMicroseconds();
	}

	void convert(std::string& val) const
	{
		val = DateTimeFormatter::format(_val, Poco::DateTimeFormat::ISO8601_FORMAT);
	}

	void convert(DateTime& val) const
	{
		val = _val;
	}

	void convert(LocalDateTime& ldt) const
	{
		ldt = _val.timestamp();
	}

	void convert(Timestamp& ts) const
	{
		ts = _val.timestamp();
	}

	VarHolder* clone() const
	{
		return new VarHolderImpl(_val);
	}
	
	const DateTime& value() const
	{
		return _val;
	}

	bool isArray() const
	{
		return false;
	}

	bool isStruct() const
	{
		return false;
	}

	bool isInteger() const
	{
		return false;
	}

	bool isSigned() const
	{
		return false;
	}

	bool isNumeric() const
	{
		return false;
	}

	bool isString() const
	{
		return false;
	}

private:
	VarHolderImpl();
	VarHolderImpl(const VarHolderImpl&);
	VarHolderImpl& operator = (const VarHolderImpl&);

	DateTime _val;
};


template <>
class VarHolderImpl<LocalDateTime>: public VarHolder
{
public:
	VarHolderImpl(const LocalDateTime& val): _val(val)
	{
	}

	~VarHolderImpl()
	{
	}
	
	const std::type_info& type() const
	{
		return typeid(LocalDateTime);
	}

	void convert(Int64& val) const
	{
		val = _val.timestamp().epochMicroseconds();
	}

	void convert(UInt64& val) const
	{
		val = _val.timestamp().epochMicroseconds();
	}

	void convert(std::string& val) const
	{
		val = DateTimeFormatter::format(_val, Poco::DateTimeFormat::ISO8601_FORMAT);
	}

	void convert(DateTime& val) const
	{
		val = _val.timestamp();
	}

	void convert(LocalDateTime& ldt) const
	{
		ldt = _val;
	}

	void convert(Timestamp& ts) const
	{
		ts = _val.timestamp();
	}

	VarHolder* clone() const
	{
		return new VarHolderImpl(_val);
	}
	
	const LocalDateTime& value() const
	{
		return _val;
	}

	bool isArray() const
	{
		return false;
	}

	bool isStruct() const
	{
		return false;
	}

	bool isInteger() const
	{
		return false;
	}

	bool isSigned() const
	{
		return false;
	}

	bool isNumeric() const
	{
		return false;
	}

	bool isString() const
	{
		return false;
	}

private:
	VarHolderImpl();
	VarHolderImpl(const VarHolderImpl&);
	VarHolderImpl& operator = (const VarHolderImpl&);

	LocalDateTime _val;
};


template <>
class VarHolderImpl<Timestamp>: public VarHolder
{
public:
	VarHolderImpl(const Timestamp& val): _val(val)
	{
	}

	~VarHolderImpl()
	{
	}
	
	const std::type_info& type() const
	{
		return typeid(Timestamp);
	}

	void convert(Int64& val) const
	{
		val = _val.epochMicroseconds();
	}

	void convert(UInt64& val) const
	{
		val = _val.epochMicroseconds();
	}

	void convert(std::string& val) const
	{
		val = DateTimeFormatter::format(_val, Poco::DateTimeFormat::ISO8601_FORMAT);
	}

	void convert(DateTime& val) const
	{
		val = _val;
	}

	void convert(LocalDateTime& ldt) const
	{
		ldt = _val;
	}

	void convert(Timestamp& ts) const
	{
		ts = _val;
	}

	VarHolder* clone() const
	{
		return new VarHolderImpl(_val);
	}
	
	const Timestamp& value() const
	{
		return _val;
	}

	bool isArray() const
	{
		return false;
	}

	bool isStruct() const
	{
		return false;
	}

	bool isInteger() const
	{
		return false;
	}

	bool isSigned() const
	{
		return false;
	}

	bool isNumeric() const
	{
		return false;
	}

	bool isString() const
	{
		return false;
	}

private:
	VarHolderImpl();
	VarHolderImpl(const VarHolderImpl&);
	VarHolderImpl& operator = (const VarHolderImpl&);

	Timestamp _val;
};


} } // namespace Poco::Dynamic


#endif // Foundation_VarHolder_INCLUDED