Want to create dynamic subdomain in codeigniter?

[eluser]Unknown[/eluser]
In my site i want to add an functionality for user to use their username with domain.

Like in codeigniter right now i want to give the user to use their own url to login in site and do other stuff.

For eg:

Code:

i Want www.username.mysite.com/login

or

Code:

www.username.mysite.com/category

so here the user can login with their credential and add the category. so i have two controller in my site with login and category.

So how to do this with the routes Or .htaccess.