Short URL or tiny URL is an URL used to represent a long URL. For example, http://tinyurl.com/45lk7x will be redirect to http://www.snippetit.com/2008/10/implement-your-own-short-url.
There are 2 main advantages of using short URL:
- Easy to remember - Instead of remember an URL with 50 or more characters, you only need to remember a few (5 or more depending on application's implementation).
- More portable - Some systems have limitation on the total character to be used. For example SMS (short message services) and Twitter. When you want to send an 50 characters' URL to a friend via SMS, you only left 90 characters for your message.
Implement your own short URL is simple as 1, 2 and 3:
- Define your own URL mapping algorithm.
- Have a database to store the mapped URL.
- Implement your URL mapping algorithm.
I'm not sure how the others create URL mapping algorithm, but at here, I will show my simple and fast's short URL implementation. The following is the specification of my implementation:
The system uses 6 characters of short code to represent an URL of any length. The valid characters for the short codes are ASCII 'a' to 'z' and '0' to '5' where each character contains 2^5 (32) states. 6 characters of short code can used to map 32^6 (1,073,741,824) URLs so it is unlikely to be used up in the near future.
First, you will need a database to store and retrieve your mapped URL. Below is the suggested database schema:
CREATE TABLE mappedURL ( shortCode char(6) not null, lognURL text not null, PRIMARY KEY shortCodeInd (shortCode), );
Second, you will need to define an algorithm to map the long URL into short code. Below is the suggested algorithm:
loop1: while true calculate md5 of the URL loop2: from 1st 4 bytes to 4th 4 bytes of md5 result cast the 4 bytes to an integer loop3: for shortCodeChar to shortCodeChar use 1st 5 bits of the integer to find the value in codeMap remove 5 bits from the integer end loop3 save shortCodeChar as shortCode if shorCode does not exist in database insert the short code and original URL into database break loop1: else retrieve the stored URL from database if original URL equals to URL stored in database break loop1: end if end if end loop2 insert '-' at the front of the URL end loop1 return shortCode
Note: codeMap contains value of valid characters from 'a' to 'z' (index 0 to 25) and '0'-'5' (index 26 to 31).
Third, you will need to create a page that receive a short code and redirect browser to the mapped URL in database:
if valid short code and exists in database redirect browser to the mapped URL else show error or redirect to an error page end if
And that's all. You can use this implementation within your own domain as well to shorten the long URL of your blog before you send it to your friend. For example:
http://domain/long-long-long-long-url.html to http://go.domain/abcdef
Please note that there will be no source code provided in this page because you can implement it in any web languages (e.g. PHP, ASP or JSP) easily.
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