Re: NSNotFound
Re: NSNotFound
- Subject: Re: NSNotFound
- From: Uli Kusterer <email@hidden>
- Date: Tue, 18 Jan 2011 05:58:06 +0100
On 17.01.2011, at 19:50, Quincey Morris wrote:
> In a slightly larger, conceptual sense, this means that unless you want to obsess over the specifics of *every* frameworks parameter *every* time you use one, the *practical*, everyday-use range of NSUInteger is 0 .. NSIntegerMax, not 0 .. NSUIntegerMax. In 32-bit, that's a 2 Gig item limit, not 4 Gigs.
Which is good to know if you want to use NSNotFound in your own classes, but largely irrelevant if it is an index into a collection of objects, like NSArray. Because in that case, just storing the pointers to these items in an array (which takes 4 bytes in 32-bit, 8 in 64-bit) already restricts the number of items to a value below NSIntegerMax.
After all, you'd already run out of address space around NSIntegerMax / 2 (NSUIntegerMax / sizeof(id), i.e. NSUIntegerMax / 4). And since you need memory for system libraries, and for the NSArray and stored object(s) itself (it could be an array containing the same object over and over, though), plus a stack and general memory management overhead, you'll lose a few bytes more.
Considering Apple's frameworks change size with each system release, I don't think there is a way to reliably calculate an upper limit. If your application is likely to even vaguely get near the ballpark of NSIntegerMax / 2, you should probably look into implementing a virtual memory-like mechanism that swaps in/out objects from disk as needed.
-- Uli Kusterer
Sole Janitor
http://www.the-void-software.com
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