package core import ( "fmt" "math/big" "github.com/ethereum/go-ethereum/core/types" "github.com/ethereum/go-ethereum/state" "github.com/ethereum/go-ethereum/vm" ) /* * 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 *types.Transaction gas, gasPrice *big.Int value *big.Int data []byte state *state.StateDB block *types.Block cb, rec, sen *state.StateObject } func NewStateTransition(coinbase *state.StateObject, tx *types.Transaction, state *state.StateDB, block *types.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() *state.StateObject { if self.cb != nil { return self.cb } self.cb = self.state.GetOrNewStateObject(self.coinbase) return self.cb } func (self *StateTransition) Sender() *state.StateObject { if self.sen != nil { return self.sen } self.sen = self.state.GetOrNewStateObject(self.tx.Sender()) return self.sen } func (self *StateTransition) Receiver() *state.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) 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()) // XXX Transactions after this point are considered valid. if err = self.preCheck(); err != nil { return } var ( tx = self.tx sender = self.Sender() receiver *state.StateObject ) defer self.RefundGas() // Increment the nonce for the next transaction sender.Nonce += 1 // Transaction gas if err = self.UseGas(vm.GasTx); err != nil { return } // Pay data gas var dgas int64 for _, byt := range self.data { if byt != 0 { dgas += vm.GasData.Int64() } else { dgas += 1 // This is 1/5. If GasData changes this fails } } if err = self.UseGas(big.NewInt(dgas)); err != nil { return } var ret []byte vmenv := NewEnv(self.state, self.tx, self.block) var ref vm.ClosureRef if tx.CreatesContract() { self.rec = MakeContract(tx, self.state) ret, err, ref = vmenv.Create(sender, receiver.Address(), self.tx.Data, self.gas, self.gasPrice, self.value) ref.SetCode(ret) } else { ret, err = vmenv.Call(self.Sender(), self.Receiver().Address(), self.tx.Data, self.gas, self.gasPrice, self.value) } if err != nil { statelogger.Debugln(err) } return } // Converts an transaction in to a state object func MakeContract(tx *types.Transaction, state *state.StateDB) *state.StateObject { addr := tx.CreationAddress(state) contract := state.GetOrNewStateObject(addr) contract.InitCode = tx.Data return contract }