View and Edit the .ppt file using objective C

I need to view and edit the .ppt file in iOS preferably using objective-C. Is there any library or sdk for this. I would appreciate any response on how to approach this. One approach may be to parse the .ppt file and display the data on iOS devices and then edit and again save the data as xml. Is there any sdk to parse the .ppt file. I would appreciate any approach to do this task.

Edit:

There are so many 3rd party applications like which can edit the ppt file. My question is what approach they took to do that?