Validate input as username

I've written this as a module, I apologize for that but I don't know how to write .patch files :(

/**
 * This module adds the "valid username" validation method
 * 
 * @author Joakim Hedlund <joakim.hedlund@klarna.com>
 */

/**
 * Implementation of hook_webform_validation_validators().
 *
 * @return array Validators, in the validator key => options array form.
 */
function webform_validation_uservalidator_webform_validation_validators(){
    $validationMethods = array();
    
    $validationMethods['username'] = array(
	'name' => "Usernames",
	'component_types' => array(
	    'textfield',
	),
	'description' => t('Verifies that the user-entered value is a valid username.'),
    );
    
    return $validationMethods;
}

/**
 * Implementation of hook_webform_validation_validate().
 */
function webform_validation_uservalidator_webform_validation_validate($validator_name, $items, $components, $rule) {
    if ($items) {
	switch ($validator_name) {
	    case 'username':
		foreach ($items as $key => $val) {
		    //load user
		    //if uid 0 or status 0 throw error
		    if ($val) {
			if (!db_result(db_query("SELECT COUNT(*) FROM {users} WHERE name = '%s' AND status = 1", $val))) {
			    // User doesn't exist
			    $errors[$key] = t('%item does not contain an active username.', array('%item' => $components[$key]['name']));
			}
		    }
		}
		return $errors;
		break;
	}
    }
}