From: Ian Leitch <port001@...>
Date: 2007-08-17T04:32:53+09:00
Subject: Re: shorten SHA1-hash

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You could use String#hash instead. For strings more than 6 characters (or
something), it'll return a negative number, so it's a little hacky, but:

file_contents.hash.to_s.tr('-', '0')

I'm not saying this is a nice approach, but it is pretty short ;)

Anyone with more knowledge of String#hash care to chime in?

Also, I doubt this is very cross platform friendly, just take a look at all
the ifdefs in the C hash implementation.

On 16/08/07, Peter Skovgaard <vebihl@gmail.com> wrote:
>
> In one of my railsapplications I have system for up/downloading files.
> Since I don't want people to browse all the files, but anyone should
> be able to link to his/her files each file has it's own unique URL -
> all pretty standard.
>
> Right now the URL just is /download/sha-sum-of-the-file (since I have
> the SHA anyway), but the length of the url is bugging me.
>
> Now - the problem: The SHA1-sum is, as usually, just represented in
> base16 which makes it 40 chars long. However, in an url we have at
> least a-zA-Z0-9 (and also some special characters) which gives us the
> opportunity to represent the SHA-sum in at least base62 which should
> make it about half the size.
>
> I know that I in this case just could store an extra little random
> string in my database and link to /download/little-string, but that's
> not the point here :) I would just like to hear you: How few
> (printable) characters can you shorten a SHA-sum down to?
> --
> Posted via http://www.ruby-forum.com/.
>
>

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