Why does mmap fail on iOS?

Question

I\'m trying to use mmap to read and play audio files on iOS. It works fine for files up to about 400MB. But when I try a 500MB file, I get a ENOMEM error.

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Answer 1

I don't have an answer for you, but I did test your code on my iPhone 5 running 6.0.1 and mmap succeeded on a 700MB ISO file. So I would start with other factors and assume mmap is working properly. Perhaps the error you're getting back is not really due to memory, or perhaps the memory on the device itself is somehow exhausted to where mmap is failing; try rebooting the device. Depending on your version of iOS, I wonder also if perhaps your seek to the end of the file might be causing mmap to try and map the entire file in; you might try cleaning that up and use stat instead to determine the file size, or close then re-open the file descriptor before mapping. These are all just ideas; if I could reproduce your error, I'd be glad to help fix it.