Create a string as printf do

Format.h

#ifndef FORMAT_H_
#define FORMAT_H_

#include <string>
#include <cstdarg>
#include <cstdio>

class Format: public std::string {
public:
	inline Format(const char* format, ...) {
		va_list args;
		va_start(args, format);
		size_t const bufferSize = ::vsnprintf(0, 0, format, args) + 1;
		this->resize(bufferSize);
		va_end(args);
		va_start(args, format);
		::vsnprintf(&((*this)[0]), bufferSize, format, args);
		va_end(args);
	}
};

#endif /*FORMAT_H_*/