package ethchain import ( "fmt" "math/big" "github.com/ethereum/eth-go/ethstate" "github.com/ethereum/eth-go/ethtrie" "github.com/ethereum/eth-go/ethutil" "github.com/ethereum/eth-go/ethvm" ) /* * 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, receiver []byte tx *Transaction gas, gasPrice *big.Int value *big.Int data []byte state *ethstate.State block *Block cb, rec, sen *ethstate.StateObject } func NewStateTransition(coinbase *ethstate.StateObject, tx *Transaction, state *ethstate.State, block *Block) *StateTransition { return &StateTransition{coinbase.Address(), tx.Recipient, tx, new(big.Int), new(big.Int).Set(tx.GasPrice), tx.Value, tx.Data, state, block, coinbase, nil, nil} } func (self *StateTransition) Coinbase() *ethstate.StateObject { if self.cb != nil { return self.cb } self.cb = self.state.GetOrNewStateObject(self.coinbase) return self.cb } func (self *StateTransition) Sender() *ethstate.StateObject { if self.sen != nil { return self.sen } self.sen = self.state.GetOrNewStateObject(self.tx.Sender()) return self.sen } func (self *StateTransition) Receiver() *ethstate.StateObject { if self.tx != nil && self.tx.CreatesContract() { return nil } if self.rec != nil { return self.rec } self.rec = self.state.GetOrNewStateObject(self.tx.Recipient) return self.rec } func (self *StateTransition) MakeStateObject(state *ethstate.State, tx *Transaction) *ethstate.StateObject { contract := MakeContract(tx, state) return contract } 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 { var err error sender := self.Sender() if sender.Balance.Cmp(self.tx.GasValue()) < 0 { return fmt.Errorf("Insufficient funds to pre-pay gas. Req %v, has %v", self.tx.GasValue(), sender.Balance) } coinbase := self.Coinbase() err = coinbase.BuyGas(self.tx.Gas, self.tx.GasPrice) if err != nil { return err } self.AddGas(self.tx.Gas) sender.SubAmount(self.tx.GasValue()) return nil } func (self *StateTransition) RefundGas() { coinbase, sender := self.Coinbase(), self.Sender() coinbase.RefundGas(self.gas, self.tx.GasPrice) // Return remaining gas remaining := new(big.Int).Mul(self.gas, self.tx.GasPrice) sender.AddAmount(remaining) } func (self *StateTransition) preCheck() (err error) { var ( tx = self.tx sender = self.Sender() ) // Make sure this transaction's nonce is correct if sender.Nonce != tx.Nonce { return NonceError(tx.Nonce, sender.Nonce) } // Pre-pay gas / Buy gas of the coinbase account if err = self.BuyGas(); err != nil { return err } return nil } func (self *StateTransition) TransitionState() (err error) { statelogger.Debugf("(~) %x\n", self.tx.Hash()) defer func() { if r := recover(); r != nil { statelogger.Infoln(r) err = fmt.Errorf("state transition err %v", r) } }() // XXX Transactions after this point are considered valid. if err = self.preCheck(); err != nil { return } var ( tx = self.tx sender = self.Sender() receiver *ethstate.StateObject ) defer self.RefundGas() // Increment the nonce for the next transaction sender.Nonce += 1 // Transaction gas if err = self.UseGas(ethvm.GasTx); err != nil { return } // Pay data gas dataPrice := big.NewInt(int64(len(self.data))) dataPrice.Mul(dataPrice, ethvm.GasData) if err = self.UseGas(dataPrice); err != nil { return } if sender.Balance.Cmp(self.value) < 0 { return fmt.Errorf("Insufficient funds to transfer value. Req %v, has %v", self.value, sender.Balance) } var snapshot *ethstate.State // If the receiver is nil it's a contract (\0*32). if tx.CreatesContract() { // Subtract the (irreversible) amount from the senders account sender.SubAmount(self.value) snapshot = self.state.Copy() // Create a new state object for the contract receiver = self.MakeStateObject(self.state, tx) self.rec = receiver if receiver == nil { return fmt.Errorf("Unable to create contract") } // Add the amount to receivers account which should conclude this transaction receiver.AddAmount(self.value) } else { receiver = self.Receiver() // Subtract the amount from the senders account sender.SubAmount(self.value) // Add the amount to receivers account which should conclude this transaction receiver.AddAmount(self.value) snapshot = self.state.Copy() } msg := self.state.Manifest().AddMessage(ðstate.Message{ To: receiver.Address(), From: sender.Address(), Input: self.tx.Data, Origin: sender.Address(), Block: self.block.Hash(), Timestamp: self.block.Time, Coinbase: self.block.Coinbase, Number: self.block.Number, Value: self.value, }) // Process the init code and create 'valid' contract if IsContractAddr(self.receiver) { // Evaluate the initialization script // and use the return value as the // script section for the state object. self.data = nil code, err := self.Eval(msg, receiver.Init(), receiver, "init") if err != nil { self.state.Set(snapshot) return fmt.Errorf("Error during init execution %v", err) } receiver.Code = code msg.Output = code } else { if len(receiver.Code) > 0 { ret, err := self.Eval(msg, receiver.Code, receiver, "code") if err != nil { self.state.Set(snapshot) return fmt.Errorf("Error during code execution %v", err) } msg.Output = ret } } return } func (self *StateTransition) transferValue(sender, receiver *ethstate.StateObject) error { if sender.Balance.Cmp(self.value) < 0 { return fmt.Errorf("Insufficient funds to transfer value. Req %v, has %v", self.value, sender.Balance) } // Subtract the amount from the senders account sender.SubAmount(self.value) // Add the amount to receivers account which should conclude this transaction receiver.AddAmount(self.value) return nil } func (self *StateTransition) Eval(msg *ethstate.Message, script []byte, context *ethstate.StateObject, typ string) (ret []byte, err error) { var ( transactor = self.Sender() state = self.state env = NewEnv(state, self.tx, self.block) callerClosure = ethvm.NewClosure(msg, transactor, context, script, self.gas, self.gasPrice) ) vm := ethvm.New(env) vm.Verbose = true vm.Fn = typ ret, _, err = callerClosure.Call(vm, self.tx.Data) if err == nil { // Execute POSTs for e := vm.Queue().Front(); e != nil; e = e.Next() { msg := e.Value.(*ethvm.Message) msg.Exec(msg.Addr(), transactor) } } return } // Converts an transaction in to a state object func MakeContract(tx *Transaction, state *ethstate.State) *ethstate.StateObject { // Create contract if there's no recipient if tx.IsContract() { addr := tx.CreationAddress() contract := state.NewStateObject(addr) contract.InitCode = tx.Data contract.State = ethstate.New(ethtrie.New(ethutil.Config.Db, "")) return contract } return nil }