Untitled

	class basic_decoder	{	protected:		std::istream* is;	public:		basic_decoder(std::istream* _is) : is(_is) {}		std::istream* istream()		{			return is;		}		virtual boost::int_fast32_t decode() = 0;		virtual bool prevg() = 0;		virtual bool nextg() = 0;	};		// Basic Multi-Byte-Unit Decoder	template<class unit_type, int byte_order>	class basic_mbu_decoder : public basic_decoder	{	public:		basic_mbu_decoder(std::istream* _is) : basic_decoder(_is) {}		unit_type get_unit()		{			unit_type tmp;			for(int i=0; i < sizeof(unit_type); ++i)			{				if(byte_order == BOOST_BYTE_ORDER)					((boost::uint8_t*)&tmp)[i] = is->get();				else // If the source is a different endian than the system,					((boost::uint8_t*)&tmp)[sizeof(unit_type)-i-1] = is->get(); // fill tmp backwards.			}			return tmp;		}	};	// UTF-16 Decoder	template<int byte_order>	class utf16_decoder : public basic_mbu_decoder<boost::uint16_t, byte_order>	{	public:		utf16_decoder(std::istream* _is) : basic_mbu_decoder<boost::uint16_t, byte_order>(_is) {}		// Read until one whole character is decoded.		boost::int_fast32_t decode()		{			int pk = is->peek();			if(pk == EOF)				return EOF;			boost::uint16_t ch = get_unit();			if( istream().good() && (ch >= 0xD800 && ch <= 0xDBFF) ) // If ch is the first unit in a surrogate pair...			{				boost::uint16_t ch2 = get_unit(); // Get the following unit.				if( istream().good() && (ch2 >= 0xDC00 && ch2 <= 0xDFFF) ) // If the following unit appropriately completes the surrogate pair...				{					ch = (boost::uint16_t)((ch - (boost::uint16_t)0xD800) << 10) + (ch2 - (boost::uint16_t)0xDC00) + 0x0010000; // Magic				}				else				{					throw "Unpaired surrogate.";				}			}			return ch;		}		bool nextg() // Move get-pointer forward one full character.		{			return decode() == EOF;			/*			boost::uint16_t ch = get_unit();			if( istream().good() && (ch >= 0xD800 && ch <= 0xDBFF) )			{				boost::uint16_t ch2 = get_unit();				if( istream().good() && (ch2 < 0xDC00 || ch2 > 0xDFFF) )				{					throw "Unpaired surrogate.";				}			}*/		}		bool prevg() // Move get-pointer back on full character.		{			is->seekg(std::ios::cur, -2); // Previous unit.			boost::uint16_t ch = get_unit();			if(ch < 0xDC00 || ch > 0xDFFF) // If this is the second unit in a surrogate pair...			{				// Go back another unit to the first part of the surrogate pair.				is->seekg(std::ios::cur, -2); 				boost::uint16_t ch = get_unit();			}			return true;		}	};	typedef utf16_decoder<1234> utf16le_decoder; // Little endian UTF-16 Decoder	typedef utf16_decoder<4321> utf16be_decoder; // Big endian UTF-16 Decoder