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This question strikes me as almost silly, but I just want to sanity check myself. For a variety of reasons, I'm welding together a bunch of files into a single megafile before packing this as a resource in my iOS app. I'm then using NSFileHandle to open the file, seek to the right place, and read out just the bytes I want.

Is there any performance difference between doing it this way and reading loose files? Or, supposing I could choose to use just one monolithic megafile, versus, say, 10 medium-sized (but still joined) files, is there any performance difference between "opening" the large versus a smaller file?

Since I know exactly where to seek to, and I'm reading just the bytes I want, I don't see how there could be a difference. But, hey -- Stranger things have proved to be. Thanks in advance!

Brian Rak
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1 Answers1

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There could be a difference if it was an extremely large number of files. Every open file uses up resources in memory (file handles, and the like), and on some storage devices, a file will take up an entire block even if it doesn't fill it. That can lead to wasted space in extreme cases. But in practice, it probably won't be a problem. To know for sure, you can profile your code and see if it's faster one way vs. the other, and see what sort of space it takes up on a typical device.

user1118321
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  • Thanks for the reply. So these all sound like arguments in favor of using joined as opposed to loose files. The only other issue I can think of is that if you had multiple threads needing access to the monolithic resource file at the same time, perhaps there could be conflicts over who is the owner of that file handle. In my case, all access to it will occur serially. Just to be clear though, there is certainly no memory difference between creating a file handle to a 1MB file versus a 50MB file, right? – Brian Rak Nov 02 '12 at 16:55
  • None that I'm aware of. The size of the file doesn't affect the size of the file handle in memory, as far as I know. But 50 1MB files would need 50 file handles in memory if you wanted to access them all at the same time. – user1118321 Nov 02 '12 at 17:49