This week's book giveaway is in the Mac OS forum. We're giving away four copies of a choice of "Take Control of Upgrading to Yosemite" or "Take Control of Automating Your Mac" and have Joe Kissell on-line! See this thread for details.
I only read the magic cookie before opening the file to find out the file is correct or not.
Checking the file corruption is beyond the scope (if your instruction didn't require you to do so) and I think you'll not get an extra point if you do the things that didn't required by the instruction.