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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, refs := range self.state.Refunds() {
for _, ref := range refs {
coinbaseSub.Add(self.gas, ref)
refund := ethutil.BigMin(uhalf, ref)
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)
}
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