plugeth/ethchain/state_transition.go

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package ethchain
import (
"fmt"
"math/big"
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"github.com/ethereum/eth-go/ethstate"
"github.com/ethereum/eth-go/ethtrie"
"github.com/ethereum/eth-go/ethutil"
"github.com/ethereum/eth-go/ethvm"
)
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/*
* 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 {
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coinbase, receiver []byte
tx *Transaction
gas, gasPrice *big.Int
value *big.Int
data []byte
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state *ethstate.State
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block *Block
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cb, rec, sen *ethstate.StateObject
}
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func NewStateTransition(coinbase *ethstate.StateObject, tx *Transaction, state *ethstate.State, block *Block) *StateTransition {
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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}
}
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func (self *StateTransition) Coinbase() *ethstate.StateObject {
if self.cb != nil {
return self.cb
}
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self.cb = self.state.GetOrNewStateObject(self.coinbase)
return self.cb
}
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func (self *StateTransition) Sender() *ethstate.StateObject {
if self.sen != nil {
return self.sen
}
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self.sen = self.state.GetOrNewStateObject(self.tx.Sender())
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return self.sen
}
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func (self *StateTransition) Receiver() *ethstate.StateObject {
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if self.tx != nil && self.tx.CreatesContract() {
return nil
}
if self.rec != nil {
return self.rec
}
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self.rec = self.state.GetOrNewStateObject(self.tx.Recipient)
return self.rec
}
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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
}
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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)
}
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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) {
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statelogger.Debugf("(~) %x\n", self.tx.Hash())
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/*
defer func() {
if r := recover(); r != nil {
logger.Infoln(r)
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err = fmt.Errorf("state transition err %v", r)
}
}()
*/
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// XXX Transactions after this point are considered valid.
if err = self.preCheck(); err != nil {
return
}
var (
tx = self.tx
sender = self.Sender()
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receiver *ethstate.StateObject
)
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defer self.RefundGas()
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// Increment the nonce for the next transaction
sender.Nonce += 1
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// Transaction gas
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if err = self.UseGas(ethvm.GasTx); err != nil {
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return
}
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// Pay data gas
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dataPrice := big.NewInt(int64(len(self.data)))
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dataPrice.Mul(dataPrice, ethvm.GasData)
if err = self.UseGas(dataPrice); err != nil {
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return
}
if sender.Balance.Cmp(self.value) < 0 {
return fmt.Errorf("Insufficient funds to transfer value. Req %v, has %v", self.value, sender.Balance)
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}
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var snapshot *ethstate.State
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// If the receiver is nil it's a contract (\0*32).
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if tx.CreatesContract() {
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// Subtract the (irreversible) amount from the senders account
sender.SubAmount(self.value)
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snapshot = self.state.Copy()
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// Create a new state object for the contract
receiver = self.MakeStateObject(self.state, tx)
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self.rec = receiver
if receiver == nil {
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return fmt.Errorf("Unable to create contract")
}
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// Add the amount to receivers account which should conclude this transaction
receiver.AddAmount(self.value)
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} else {
receiver = self.Receiver()
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// 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)
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snapshot = self.state.Copy()
}
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msg := self.state.Manifest().AddMessage(&ethstate.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,
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Value: self.value,
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})
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// Process the init code and create 'valid' contract
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if IsContractAddr(self.receiver) {
// Evaluate the initialization script
// and use the return value as the
// script section for the state object.
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self.data = nil
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code, err := self.Eval(msg, receiver.Init(), receiver, "init")
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if err != nil {
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self.state.Set(snapshot)
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return fmt.Errorf("Error during init execution %v", err)
}
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receiver.Code = code
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msg.Output = code
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} else {
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if len(receiver.Code) > 0 {
ret, err := self.Eval(msg, receiver.Code, receiver, "code")
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if err != nil {
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self.state.Set(snapshot)
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return fmt.Errorf("Error during code execution %v", err)
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}
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msg.Output = ret
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}
}
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return
}
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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)
}
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// 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 (
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transactor = self.Sender()
state = self.state
env = NewEnv(state, self.tx, self.block)
callerClosure = ethvm.NewClosure(msg, transactor, context, script, self.gas, self.gasPrice)
)
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vm := ethvm.New(env)
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vm.Verbose = true
vm.Fn = typ
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ret, _, err = callerClosure.Call(vm, self.tx.Data)
return
}
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// 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
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contract.State = ethstate.New(ethtrie.New(ethutil.Config.Db, ""))
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return contract
}
return nil
}