Ethernet Square Code solution of Meitu

read the consensus to use dpos, but I don"t quite understand, what is the meaning of choosing the Packer code? The code is as follows, students who know or understand, please guide. Source code location:

https://github.com/meitu/go-e...

func (ec *EpochContext) lookupValidator(now int64) (validator common.Address, err error) {
    validator = common.Address{}
    offset := now % epochInterval  //  
    if offset%blockInterval != 0 {
        return common.Address{}, ErrInvalidMintBlockTime
    }
    offset /= blockInterval

    validators, err := ec.DposContext.GetValidators()
    if err != nil {
        return common.Address{}, err
    }
    validatorSize := len(validators)
    if validatorSize == 0 {
        return common.Address{}, errors.New("failed to lookup validator")
    }
    offset %= int64(validatorSize)
    return validators[offset], nil
}