dns-example.md

DNS Example

Requirements Specification

(derived from SDD/Goals):

1. The DNS contract shall allow any user to register a name that has not already been registered to another owner. (sha256[:3] is c84d)
2. The DNS contract shall reject any request to register a name that is already registered to another user. (sha256[:3] is 35a4)
3. The DNS contract shall allow the owner of a domain to change the resolved address. (sha256[:3] is e532)
4. The DNS contract shall allow anyone to perform a lookup of a registered domain’s resolved address. (sha256[:3] is fffc)

Implementation:

{% code-tabs %} {% code-tabs-item title="DNS.sol" %}

/** @title DNS Registrar */
contract DNS {
   // Store the owner of a particular domain
   mapping(string => address) public domainOwner;

   // Store the resolution of a particular domain
   /// @imp fffc `public` provides access method for domain resolver
   mapping(string => address) public domainResolution;

   /** @title setDomainResolution Allows user to set resolution for address
     * @param _domain Domain name as ASCII string
     * @param _resolution Address domain will resolve to
     */
   function setDomainResolution(
     string _domain,
     address _resolution
   )
     public
   {
     /// @imp c84d Check if name has been previously registered
     if (domainOwner[_domain] != 0x0)
     {
        /// @imp 35a4 Reject if domain has been registered to another user
        require(domainOwner[_domain] == msg.sender);
     }
     else // domain owner is unset for this domain
     {
        /// @imp c84d Keep track of newly registered domain
        domainOwner[_domain] = msg.sender;
     }

     /// @imp c84d Allow user to set resolution for newly registered domain
     /// @imp e532 Allow user to change resolution for a domain they own
     domainResolution[_domain] = _resolution;
   }
}

{% endcode-tabs-item %} {% endcode-tabs %}