All InDesign Versions--determining version before opening

Question

At one point I scan a variable number of documents for information.  This involves opening the document, going through it, and closing the document.
If I open a CS3 document in CS5, no problem.  But if I open a CS5 document in CS3, InDesign crashes.
I know that I can open each document using STDIO and read the 31st byte (I believe it's that one) to determine a version, but is there any better way?  Please remember that this needs to work on both platforms, so reading the Mac type isn't a good solution.
TIA!
John

Answer 1

JADarnell wrote:
Good morning Sir/Madam:
First of all, thanks for the contribution.  Though I may respectfully disagree with you, I still greatly appreciate the fact that you went out of your way to contribute to this discussion.
I'm a Sir
How come you think you disagree? There is nothing strange about some value in the header being designated as "the official version number". Adobe likes to keep this information well under wraps in the SDK, but perhaps there is a reason for that. In any case, the variable names I used come from a document on XMP:
http://wwwimages.adobe.com/www.adobe.com/content/dam/Adobe/en/devnet/xmp/pdfs/XMPSpecifica tionPart3.pdf
-- see page 38 for their (somewhat abbreviated) structure of INDD files headers. The long word starting at position 29 (where the first byte is number 0) is not specified in there but has been confirmed as the actual version number.
In this header you also find the Object Stream Endianness specification, and (from memory) you need that to successfully parse files older than CS3.
Originally, the endianness of long words in InDesign files depended on the platform they were created with, but Adobe decided somewhere along the line it would be smarter to just make the endianness a part of the "official" specs. To read older files you still need the code, though. It's very well possible your Mac/Win files are just not old enough. My personal code for this works with INDD files for as long back as I care to look -- *at least* back to InDesign 2.0 (and then only because I cannot find older files).
Then again, I admit all of the above is my personal conjecture. If you still want to disagree, you're free to examine the files yourself and devise something that works better.