Re: Fast hash of NSData?
Re: Fast hash of NSData?
- Subject: Re: Fast hash of NSData?
- From: Scott Ribe <email@hidden>
- Date: Mon, 02 Dec 2013 08:16:06 -0700
On Dec 2, 2013, at 7:57 AM, Marcel Weiher <email@hidden> wrote:
> Then you can twiddle the hash to get you a good compromise of speed vs. collisions.
You want to optimize the hash further? Only hash the first 1MB. Except for odd cases, like two multi-image TIFFs sharing the exact same first n images (maybe the second one was created by appending to the first), that will still very rarely yield collisions--then compare collisions for identity.
One note: we're all saying that identity checks will be rare, so the amortized cost is very low. Well. That's true if the user is actually adding different files. The amortized cost is not so low if you have users who keep adding the same files over & over ;-)
--
Scott Ribe
email@hidden
http://www.elevated-dev.com/
(303) 722-0567 voice
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