How to generate a unique hash for a URL ?

Posted by Jacques René Mesrine on Stack Overflow See other posts from Stack Overflow or by Jacques René Mesrine
Published on 2009-10-27T08:22:02Z Indexed on 2010/03/20 16:31 UTC
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algorithm-design

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algorithm

Given these two images from twitter.

http://a3.twimg.com/profile_images/130500759/lowres_profilepic.jpg
http://a1.twimg.com/profile_images/58079916/lowres_profilepic.jpg

I want to download them to local filesystem & store them in a single directory. How shall I overcome name conflicts ?

In the example above, I cannot store them as *lowres_profilepic.jpg*. My design idea is treat the URLs as opaque strings except for the last segment. What algorithms (implemented as f) can I use to hash the prefixes into unique strings.

f( "http://a3.twimg.com/profile_images/130500759/" ) = 6tgjsdjfjdhgf
f( "http://a1.twimg.com/profile_images/58079916/" )  = iuhd87ysdfhdk

That way, I can save the files as:-

6tgjsdjfjdhgf_lowres_profilepic.jpg
iuhd87ysdfhdk_lowres_profilepic.jpg

I don't want a cryptographic algorithm as it this needs to be a performant operation.

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