package core import ( "fmt" "math/big" "github.com/ethereum/go-ethereum/common" "github.com/ethereum/go-ethereum/core/state" "github.com/ethereum/go-ethereum/core/vm" "github.com/ethereum/go-ethereum/crypto" "github.com/ethereum/go-ethereum/logger" "github.com/ethereum/go-ethereum/logger/glog" "github.com/ethereum/go-ethereum/params" ) /* * The State transitioning model * * A state transition is a change made when a transaction is applied to the current world state * The state transitioning model does all all the necessary work to work out a valid new state root. * 1) Nonce handling * 2) Pre pay / buy gas of the coinbase (miner) * 3) Create a new state object if the recipient is \0*32 * 4) Value transfer * == If contract creation == * 4a) Attempt to run transaction data * 4b) If valid, use result as code for the new state object * == end == * 5) Run Script section * 6) Derive new state root */ type StateTransition struct { coinbase common.Address msg Message gas, gasPrice *big.Int initialGas *big.Int value *big.Int data []byte state *state.StateDB cb, rec, sen *state.StateObject env vm.Environment } // Message represents a message sent to a contract. type Message interface { From() (common.Address, error) To() *common.Address GasPrice() *big.Int Gas() *big.Int Value() *big.Int Nonce() uint64 Data() []byte } func AddressFromMessage(msg Message) common.Address { from, _ := msg.From() return crypto.CreateAddress(from, msg.Nonce()) } func MessageCreatesContract(msg Message) bool { return msg.To() == nil } // IntrinsicGas computes the 'intrisic gas' for a message // with the given data. func IntrinsicGas(data []byte) *big.Int { igas := new(big.Int).Set(params.TxGas) if len(data) > 0 { var nz int64 for _, byt := range data { if byt != 0 { nz++ } } m := big.NewInt(nz) m.Mul(m, params.TxDataNonZeroGas) igas.Add(igas, m) m.SetInt64(int64(len(data)) - nz) m.Mul(m, params.TxDataZeroGas) igas.Add(igas, m) } return igas } func ApplyMessage(env vm.Environment, msg Message, coinbase *state.StateObject) ([]byte, *big.Int, error) { return NewStateTransition(env, msg, coinbase).transitionState() } func NewStateTransition(env vm.Environment, msg Message, coinbase *state.StateObject) *StateTransition { return &StateTransition{ coinbase: coinbase.Address(), env: env, msg: msg, gas: new(big.Int), gasPrice: msg.GasPrice(), initialGas: new(big.Int), value: msg.Value(), data: msg.Data(), state: env.State(), cb: coinbase, } } func (self *StateTransition) Coinbase() *state.StateObject { return self.state.GetOrNewStateObject(self.coinbase) } func (self *StateTransition) From() (*state.StateObject, error) { f, err := self.msg.From() if err != nil { return nil, err } return self.state.GetOrNewStateObject(f), nil } func (self *StateTransition) To() *state.StateObject { if self.msg == nil { return nil } to := self.msg.To() if to == nil { return nil // contract creation } return self.state.GetOrNewStateObject(*to) } func (self *StateTransition) UseGas(amount *big.Int) error { if self.gas.Cmp(amount) < 0 { return OutOfGasError() } self.gas.Sub(self.gas, amount) return nil } func (self *StateTransition) AddGas(amount *big.Int) { self.gas.Add(self.gas, amount) } func (self *StateTransition) BuyGas() error { mgas := self.msg.Gas() mgval := new(big.Int).Mul(mgas, self.gasPrice) sender, err := self.From() if err != nil { return err } if sender.Balance().Cmp(mgval) < 0 { return fmt.Errorf("insufficient ETH for gas (%x). Req %v, has %v", sender.Address().Bytes()[:4], mgval, sender.Balance()) } if err = self.Coinbase().SubGas(mgas, self.gasPrice); err != nil { return err } self.AddGas(mgas) self.initialGas.Set(mgas) sender.SubBalance(mgval) return nil } func (self *StateTransition) preCheck() (err error) { msg := self.msg sender, err := self.From() if err != nil { return err } // Make sure this transaction's nonce is correct if sender.Nonce() != msg.Nonce() { return NonceError(msg.Nonce(), sender.Nonce()) } // Pre-pay gas / Buy gas of the coinbase account if err = self.BuyGas(); err != nil { if state.IsGasLimitErr(err) { return err } return InvalidTxError(err) } return nil } func (self *StateTransition) transitionState() (ret []byte, usedGas *big.Int, err error) { if err = self.preCheck(); err != nil { return } msg := self.msg sender, _ := self.From() // err checked in preCheck // Pay intrinsic gas if err = self.UseGas(IntrinsicGas(self.data)); err != nil { return nil, nil, InvalidTxError(err) } vmenv := self.env var ref vm.ContextRef if MessageCreatesContract(msg) { ret, err, ref = vmenv.Create(sender, self.data, self.gas, self.gasPrice, self.value) if err == nil { dataGas := big.NewInt(int64(len(ret))) dataGas.Mul(dataGas, params.CreateDataGas) if err := self.UseGas(dataGas); err == nil { ref.SetCode(ret) } else { ret = nil // does not affect consensus but useful for StateTests validations glog.V(logger.Core).Infoln("Insufficient gas for creating code. Require", dataGas, "and have", self.gas) } } } else { // Increment the nonce for the next transaction self.state.SetNonce(sender.Address(), sender.Nonce()+1) ret, err = vmenv.Call(sender, self.To().Address(), self.data, self.gas, self.gasPrice, self.value) } if err != nil && IsValueTransferErr(err) { return nil, nil, InvalidTxError(err) } if vm.Debug { vm.StdErrFormat(vmenv.StructLogs()) } self.refundGas() self.state.AddBalance(self.coinbase, new(big.Int).Mul(self.gasUsed(), self.gasPrice)) return ret, self.gasUsed(), err } func (self *StateTransition) refundGas() { coinbase := self.Coinbase() sender, _ := self.From() // err already checked // Return remaining gas remaining := new(big.Int).Mul(self.gas, self.gasPrice) sender.AddBalance(remaining) uhalf := remaining.Div(self.gasUsed(), common.Big2) refund := common.BigMin(uhalf, self.state.Refunds()) self.gas.Add(self.gas, refund) self.state.AddBalance(sender.Address(), refund.Mul(refund, self.gasPrice)) coinbase.AddGas(self.gas, self.gasPrice) } func (self *StateTransition) gasUsed() *big.Int { return new(big.Int).Sub(self.initialGas, self.gas) }