package core import ( "fmt" "math/big" "github.com/ethereum/go-ethereum/core/types" "github.com/ethereum/go-ethereum/crypto" "github.com/ethereum/go-ethereum/ethutil" "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 msg Message gas, gasPrice *big.Int initialGas *big.Int value *big.Int data []byte state *state.StateDB block *types.Block cb, rec, sen *state.StateObject Env vm.Environment } type Message interface { Hash() []byte From() []byte To() []byte GasPrice() *big.Int Gas() *big.Int Value() *big.Int Nonce() uint64 Data() []byte } func AddressFromMessage(msg Message) []byte { // Generate a new address return crypto.Sha3(ethutil.NewValue([]interface{}{msg.From(), msg.Nonce()}).Encode())[12:] } func MessageCreatesContract(msg Message) bool { return len(msg.To()) == 0 } func MessageGasValue(msg Message) *big.Int { return new(big.Int).Mul(msg.Gas(), msg.GasPrice()) } func NewStateTransition(coinbase *state.StateObject, msg Message, state *state.StateDB, block *types.Block) *StateTransition { return &StateTransition{coinbase.Address(), msg.To(), msg, new(big.Int), new(big.Int).Set(msg.GasPrice()), new(big.Int), msg.Value(), msg.Data(), state, block, coinbase, nil, nil, nil} } func (self *StateTransition) VmEnv() vm.Environment { if self.Env == nil { self.Env = NewEnv(self.state, self.msg, self.block) } return self.Env } func (self *StateTransition) Coinbase() *state.StateObject { return self.state.GetOrNewStateObject(self.coinbase) } func (self *StateTransition) From() *state.StateObject { return self.state.GetOrNewStateObject(self.msg.From()) } func (self *StateTransition) To() *state.StateObject { if self.msg != nil && MessageCreatesContract(self.msg) { return nil } return self.state.GetOrNewStateObject(self.msg.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 { var err error sender := self.From() if sender.Balance().Cmp(MessageGasValue(self.msg)) < 0 { return fmt.Errorf("Insufficient funds to pre-pay gas. Req %v, has %v", MessageGasValue(self.msg), sender.Balance()) } coinbase := self.Coinbase() err = coinbase.BuyGas(self.msg.Gas(), self.msg.GasPrice()) if err != nil { return err } self.AddGas(self.msg.Gas()) self.initialGas.Set(self.msg.Gas()) sender.SubAmount(MessageGasValue(self.msg)) return nil } func (self *StateTransition) preCheck() (err error) { var ( msg = self.msg sender = self.From() ) // 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 { return err } return nil } func (self *StateTransition) TransitionState() (ret []byte, err error) { statelogger.Debugf("(~) %x\n", self.msg.Hash()) // XXX Transactions after this point are considered valid. if err = self.preCheck(); err != nil { return } var ( msg = self.msg sender = self.From() ) 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 } vmenv := self.VmEnv() var ref vm.ClosureRef if MessageCreatesContract(msg) { self.rec = MakeContract(msg, self.state) ret, err, ref = vmenv.Create(sender, self.rec.Address(), self.msg.Data(), self.gas, self.gasPrice, self.value) ref.SetCode(ret) } else { ret, err = vmenv.Call(self.From(), self.To().Address(), self.msg.Data(), self.gas, self.gasPrice, self.value) } if err != nil { statelogger.Debugln(err) } return } // Converts an transaction in to a state object func MakeContract(msg Message, state *state.StateDB) *state.StateObject { addr := AddressFromMessage(msg) contract := state.GetOrNewStateObject(addr) contract.InitCode = msg.Data() return contract } func (self *StateTransition) RefundGas() { coinbaseSub := new(big.Int).Set(self.gas) uhalf := new(big.Int).Div(self.GasUsed(), ethutil.Big2) for addr, ref := range self.state.Refunds() { refund := ethutil.BigMin(uhalf, ref) coinbaseSub.Add(self.gas, refund) self.state.AddBalance([]byte(addr), refund.Mul(refund, self.msg.GasPrice())) } coinbase, sender := self.Coinbase(), self.From() coinbase.RefundGas(coinbaseSub, self.msg.GasPrice()) // Return remaining gas remaining := new(big.Int).Mul(self.gas, self.msg.GasPrice()) sender.AddAmount(remaining) } func (self *StateTransition) GasUsed() *big.Int { return new(big.Int).Sub(self.initialGas, self.gas) }