Is there a library for generating ods / xlsx documents?

I need to edit the xlsx / ods files.

I thought this was the library for this as the task seems to be relatively common. I have checked the current answers on SO, but I could not find a suitable solution.

My requirements:

• Support docx
  
  orodf
  
  
• Open source
• C ++ / C
• Cross-platform (Linux / Windows)

I don't need to make documents, edit them (read data and apply some transformations).

Also, I understand that the above documents are just s zip

archives xml

, I am looking for some library that provides some high level API.