string2wstring.h

/* string2wstring.h */
#pragma once 

#include <string> 
#include <vector> 
#include <locale> 
#include <functional> 
#include <iostream> 

// Put this class in your personal toolbox... 
template<class E,
class T = std::char_traits<E>,
class A = std::allocator<E> >

class Widen : public std::unary_function<
	const std::string&,std::basic_string<E,T,A> >
{
	std::locale loc_;
	const std::ctype<E>* pCType_;

	// No copy-constructor, no assignment operator... 
	Widen( const Widen& );
	Widen& operator= ( const Widen& );

public:
	// Constructor... 
	Widen( const std::locale& loc = std::locale() ) : loc_( loc )
	{
#if defined(_MSC_VER) && (_MSC_VER < 1300) // VC++ 6.0... 
		using namespace std;
		pCType_ = &_USE( loc,ctype<E> );
#else 
		pCType_ = &std::use_facet<std::ctype<E> >( loc );
#endif 
	}

	// Conversion... 
	std::basic_string<E,T,A> operator() ( const std::string& str ) const
	{
		typename std::basic_string<E,T,A>::size_type srcLen =
			str.length();
		const char* pSrcBeg = str.c_str();
		std::vector<E> tmp( srcLen );

		pCType_->widen( pSrcBeg,pSrcBeg + srcLen,&tmp[ 0 ] );
		return std::basic_string<E,T,A>( &tmp[ 0 ],srcLen );
	}
};

/*
// How to use it... 
int main()
{
	Widen<wchar_t> to_wstring;
	std::string s = "my test string";
	std::wstring w = to_wstring( s );
	std::wcout << w << L"\n";
}
*/