Method TransitionDb

core/state_transition.go:187–232

TransitionDb will transition the state by applying the current message and returning the result including the the used gas. It returns an error if it failed. An error indicates a consensus issue.

()

// returning the result including the the used gas. It returns an error if it
// failed. An error indicates a consensus issue.
func (st *StateTransition) TransitionDb() (ret []byte, usedGas uint64, failed bool, err error) {
	if err = st.preCheck(); err != nil {
		return
	}

	msg := st.msg
	sender := vm.AccountRef(msg.From())
	contractCreation := msg.To() == nil

	// Pay intrinsic gas
	gas, err := IntrinsicGas(st.data, contractCreation)
	if err != nil {
		return nil, 0, false, err
	}
	if err = st.useGas(gas); err != nil {
		return nil, 0, false, err
	}

	var (
		evm = st.evm
		// vm errors do not effect consensus and are therefor
		// not assigned to err, except for insufficient balance
		// error.
		vmerr error
	)
	if contractCreation {
		ret, _, st.gas, vmerr = evm.Create(sender, st.data, st.gas, st.value)
	} else {
		// Increment the nonce for the next transaction
		st.state.SetNonce(msg.From(), st.state.GetNonce(sender.Address())+1)
		ret, st.gas, vmerr = evm.Call(sender, st.to(), st.data, st.gas, st.value)
	}
	if vmerr != nil {
		log.Debug("VM returned with error", "err", vmerr)
		// The only possible consensus-error would be if there wasn't
		// sufficient balance to make the transfer happen. The first
		// balance transfer may never fail.
		if vmerr == vm.ErrInsufficientBalance {
			return nil, 0, false, vmerr
		}
	}
	st.refundGas()
	st.state.AddBalance(st.evm.Coinbase, new(big.Int).Mul(new(big.Int).SetUint64(st.gasUsed()), st.gasPrice))

	return ret, st.gasUsed(), vmerr != nil, err
}

func (st *StateTransition) refundGas() {
	// Apply refund counter, capped to half of the used gas.