What's the best way to shorten/transform a string

I have several users and I would like to generate a referral url for each of the开发者_如何学编程m, but I don't think it would be nice to have something like

http://domain.com/myusername

I would prefer to buy myself a shorten domain and transfor that myusernameinto something smaller, but not generated using the database so it would be easy to manage and no need to have a special table for this.

kinda like Dropbox does, as my referral is: http://db.tt/jnYosez

is there a simple way to change between a string into a short string and vice versa ... or I can always use the User ID if I'm force to use numeric ... maybe converting to other number base ?

Any idea is mostly appreciated :)

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You can't do it inhouse without using a database. It's because the names are short and therefore it's likely that a name have been used before.

You need to generate a name (using randomness or an algorithm), check if it exists and then store it in the db.

Update

Here is a solution:

    public class NumberConverter
    {
        public const string HEX = "0123456789abcdef";
        public const string Bigger = "0123456789abcdefghihjklmnopqrstuvqyz";
        private int _numericBase;
        private string _base;

        public NumberConverter(string numberBase)
        {
            _base = numberBase;
            _numericBase = numberBase.Length;
        }

        public string ToString(int number)
        {
            var remainder = number % _numericBase;
            var div = number / _numericBase;
            string tmp = "";
            while (div > 0)
            {
                tmp = _base[remainder] + tmp;

                remainder = div % _numericBase;
                div = div / _numericBase;
            }
            tmp = _base[remainder] + tmp;

            return tmp;
        }

        public int ToNumber(string numberString)
        {
            int index = numberString.Length - 1;
            int value = 0;
            int power = 0;
            while (index >= 0)
            {
                char currentChar = numberString[index];
                var currentValue = _base.IndexOf(currentChar);
                value += currentValue * (int)Math.Pow(_numericBase, power);
                power++;
                --index;
            }

            return value;
        }
    }



    public static void Main()
    {
        var converter = new NumberConverter(NumberConverter.Bigger);
        int userId = 755757;
        var numberString = converter.ToString(userId); // prints g759
        var value = converter.ToNumber(numberString);
    }

You can shorten the numbers even more by adding more that are allowed in uris.

Theres probably a more efficient way to do it. Bitwise operations isn't really my area.

Update 2

Characters that are allowed in a URI but do not have a reserved purpose are called unreserved. These include uppercase and lowercase letters, decimal digits, hyphen, period, underscore, and tilde.

  unreserved  = ALPHA / DIGIT / "-" / "." / "_" / "~"

Which means that you can use those to shorten the url (unless your web server is using them for something else)

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You might want to look into bit.ly links, they provide an API.