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
}
