How to add a custom validator ?

gistfile1.php

/*@var $this myCustomInputFilter extends InputFilter*/

 /* Cnpj */
        $this->add([
            'type' => 'Zend\InputFilter\InputFilter',
            'vCnpj' => [
                'name' => 'vCnpj',
                'required' => true,
                            ],
        ]);