How to write ASCII and BINARY data to the same file at the same time

I work with VTK data type for my outputs. As my data gets bigger and bigger, writing to ASCII takes a considerable amount of time and what I have done so far.

I need to change this in binary format, but the problem is that there are some headers in the file (see http://www.vtk.org/VTK/img/file-formats.pdf ) that need to be written in ASCII even for binary files.

Now I don’t have enough experience with binary formats, and my first attempt was to open two streams through

ofstream asciiWriter(file_name.c_str());
ofstream binWriter(file_name.c_str(), ios::app | ios::binary);

The problem is that the result seems disorganized asciiWriterand binWriternot displayed in the correct order, so I cannot process my file in ParaView. I tried using asciiWriter.flush()and binWriter.flush()when I finished writing the header / data, but that also does not help.

What should I do?

PS: I do not want to use the VTK package itself ... it is HUGE and adds to my code dependency!