package ethchain import ( "fmt" "github.com/ethereum/eth-go/ethutil" "math/big" ) /* * 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 []byte tx *Transaction gas *big.Int state *State block *Block cb, rec, sen *StateObject } func NewStateTransition(coinbase *StateObject, tx *Transaction, state *State, block *Block) *StateTransition { return &StateTransition{coinbase.Address(), tx, new(big.Int), state, block, coinbase, nil, nil} } func (self *StateTransition) Coinbase() *StateObject { if self.cb != nil { return self.cb } self.cb = self.state.GetAccount(self.coinbase) return self.cb } func (self *StateTransition) Sender() *StateObject { if self.sen != nil { return self.sen } self.sen = self.state.GetAccount(self.tx.Sender()) return self.sen } func (self *StateTransition) Receiver() *StateObject { if self.tx.CreatesContract() { return nil } if self.rec != nil { return self.rec } self.rec = self.state.GetAccount(self.tx.Recipient) return self.rec } func (self *StateTransition) MakeStateObject(state *State, tx *Transaction) *StateObject { contract := MakeContract(tx, state) if contract != nil { state.states[string(tx.CreationAddress())] = contract.state return contract } return nil } 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.Amount.Cmp(self.tx.GasValue()) < 0 { return fmt.Errorf("Insufficient funds to pre-pay gas. Req %v, has %v", self.tx.GasValue(), self.tx.Value) } coinbase := self.Coinbase() err = coinbase.BuyGas(self.tx.Gas, self.tx.GasPrice) if err != nil { return err } //self.state.UpdateStateObject(coinbase) self.AddGas(self.tx.Gas) sender.SubAmount(self.tx.GasValue()) return nil } func (self *StateTransition) TransitionState() (err error) { //snapshot := st.state.Snapshot() defer func() { if r := recover(); r != nil { ethutil.Config.Log.Infoln(r) err = fmt.Errorf("state transition err %v", r) } }() var ( tx = self.tx sender = self.Sender() receiver *StateObject ) // 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 } // XXX Transactions after this point are considered valid. defer func() { self.state.UpdateStateObject(sender) self.state.UpdateStateObject(receiver) }() // Increment the nonce for the next transaction sender.Nonce += 1 // Get the receiver (TODO fix this, if coinbase is the receiver we need to save/retrieve) receiver = self.Receiver() // Transaction gas if err = self.UseGas(GasTx); err != nil { return err } // Pay data gas dataPrice := big.NewInt(int64(len(tx.Data))) dataPrice.Mul(dataPrice, GasData) if err = self.UseGas(dataPrice); err != nil { return err } // If the receiver is nil it's a contract (\0*32). if receiver == nil { // Create a new state object for the contract receiver = self.MakeStateObject(self.state, tx) if receiver == nil { return fmt.Errorf("ERR. Unable to create contract with transaction %v", tx) } } // Transfer value from sender to receiver if err = self.transferValue(sender, receiver); err != nil { return err } // Process the init code and create 'valid' contract if tx.CreatesContract() { // Evaluate the initialization script // and use the return value as the // script section for the state object. //script, gas, err = sm.Eval(state, contract.Init(), contract, tx, block) code, err := self.Eval(receiver.Init(), receiver) if err != nil { return fmt.Errorf("Error during init script run %v", err) } receiver.script = code } else { if len(receiver.Script()) > 0 { _, err := self.Eval(receiver.Script(), receiver) if err != nil { return fmt.Errorf("Error during code execution %v", err) } } } // Return remaining gas remaining := new(big.Int).Mul(self.gas, tx.GasPrice) sender.AddAmount(remaining) return nil } func (self *StateTransition) transferValue(sender, receiver *StateObject) error { if sender.Amount.Cmp(self.tx.Value) < 0 { return fmt.Errorf("Insufficient funds to transfer value. Req %v, has %v", self.tx.Value, sender.Amount) } if self.tx.Value.Cmp(ethutil.Big0) > 0 { // Subtract the amount from the senders account sender.SubAmount(self.tx.Value) // Add the amount to receivers account which should conclude this transaction receiver.AddAmount(self.tx.Value) ethutil.Config.Log.Debugf("%x => %x (%v) %x\n", sender.Address()[:4], receiver.Address()[:4], self.tx.Value, self.tx.Hash()) } return nil } func (self *StateTransition) Eval(script []byte, context *StateObject) (ret []byte, err error) { var ( tx = self.tx block = self.block initiator = self.Sender() state = self.state ) closure := NewClosure(initiator, context, script, state, self.gas, tx.GasPrice) vm := NewVm(state, nil, RuntimeVars{ Origin: initiator.Address(), BlockNumber: block.BlockInfo().Number, PrevHash: block.PrevHash, Coinbase: block.Coinbase, Time: block.Time, Diff: block.Difficulty, Value: tx.Value, }) ret, _, err = closure.Call(vm, tx.Data, nil) return }