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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()
)
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, self.rec.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
}
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