Thanks again for your feedback. I thought that you were talking about a different inlining 
As far as I know c or c++ is able to inline code, but that is not what I am looking for.
It seems that my approach is somewhat procedure coded so I do not have multi tasking coded at present.
I read the file
I parse the file (into an object)
The lines of this object are then inlined.
If it is a linetype 1 then I read the reference file from disk (see above.....)
But I think this reading is not the time consuming factor, as is does not really read from the disk (content is still in memory). I guess.
So it must be something wrong with my objects.
As far as I know c or c++ is able to inline code, but that is not what I am looking for.It seems that my approach is somewhat procedure coded so I do not have multi tasking coded at present.
I read the file
I parse the file (into an object)
The lines of this object are then inlined.
If it is a linetype 1 then I read the reference file from disk (see above.....)
But I think this reading is not the time consuming factor, as is does not really read from the disk (content is still in memory). I guess.
So it must be something wrong with my objects.