How to generate a unique hash for a URL?

Question

Given these two images from twitter.

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


        

Answer 1

I'm playing with thumbalizr using a modified version of their caching script, and it has a few good solutions I think. The code is on github.com/mptre/thumbalizr but the short version is that is uses md5 to build the file names, and it takes the first two characters from the filename and uses it to create a folder which is named the exact same thing. This means that it is easy to break the folders up, and fast to find the corresponding folder without a database. Kind of blew my mind with it's simplicity.

It generates file names like this http://pappmaskin.no/opensource/delicious_snapcasa/mptre-thumbalizr/cache/fc/fcc3a328e0f4c1b51bf5e13747614e7a_1280_1024_8_90_250.png

the last part, _1280_1024_8_90_250, matches the different settings that the script uses when talking to the thumbalizr api, but I guess fcc3a328e0f4c1b51bf5e13747614e7a is a straight md5 of the url, in this case for thumbalizr.com

I tried changing the config to generate images 200px wide, and that images goes in the same folder, but instead of _250.png it is called _200.png

I haven't had time to dig that much in the code, but I'm sure it could be pulled apart from the thumbalizr logic and made more generic.