Excessively slow when opening a "large" file

I am working on a project for which I need to generate a cpp file.

To check if my file is right, I drag and drop it on QtCreator, but it completely froze. The file is less than 400kb.

I suspect that the issue doesn't come only from the file size, but also from the bad formatting,...

Expected behavior:

Fast loading, be able to scroll in the editor view correctly. QtCreator freeze so much that it is hard to close the file.

PS: The zip contains my first try, same file serialized with a QDataStream instead of a QTextStream