buf = buf_ptr = reinterpret_cast<unsigned char*>(data);
buf = reinterpret_cast<const unsigned char*>(data); buf_ptr = const_cast<unsigned char*>(buf);
	BufferDataSource(char *data, unsigned int len)	{		// data can be NULL if len is also 0		assert(data!=0 || len==0);		buf = buf_ptr = reinterpret_cast<unsigned char*>(data);		size = len;	};