Fast hash of NSData?
Fast hash of NSData?
- Subject: Fast hash of NSData?
- From: Graham Cox <email@hidden>
- Date: Fri, 29 Nov 2013 20:58:19 +0100
Another general question.
Does anyone have a quick-and-dirty (but functional) way to hash NSData? I’m currently using SHA-1 but it’s quite slow. All I need is a way to determine whether one block of data is identical to another or not - but every bit counts. It doesn’t need to be of crypto-standard, but SHA-1 was convenient. Note that this can’t be the same as simply seeing whether one object is the same as another - I really do need to know if two different objects hold the same data bytes, and to derive a short, unique value that can be used as a key.
I’ve previously written my own quick-and-dirty hash that was basically a weighted sum of the bytes, modulo some number, but it turned out to have collisions more often than I expected, so SHA-1 was then used to fix that problem. Now it’s causing quite a noticeable performance hit in some cases.
—Graham
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