1 files changed, 276 insertions, 0 deletions
diff --git a/ethchain/state_transition.go b/ethchain/state_transition.go
new file mode 100644
index 000000000..1274915d5
--- /dev/null
+++ b/ethchain/state_transition.go
@@ -0,0 +1,276 @@
+package ethchain
+
+import (
+	"fmt"
+	"math/big"
+
+	"github.com/ethereum/go-ethereum/ethstate"
+	"github.com/ethereum/go-ethereum/ethtrie"
+	"github.com/ethereum/go-ethereum/ethutil"
+	"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                 *Transaction
+	gas, gasPrice      *big.Int
+	value              *big.Int
+	data               []byte
+	state              *ethstate.State
+	block              *Block
+
+	cb, rec, sen *ethstate.StateObject
+}
+
+func NewStateTransition(coinbase *ethstate.StateObject, tx *Transaction, state *ethstate.State, block *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() *ethstate.StateObject {
+	if self.cb != nil {
+		return self.cb
+	}
+
+	self.cb = self.state.GetOrNewStateObject(self.coinbase)
+	return self.cb
+}
+func (self *StateTransition) Sender() *ethstate.StateObject {
+	if self.sen != nil {
+		return self.sen
+	}
+
+	self.sen = self.state.GetOrNewStateObject(self.tx.Sender())
+
+	return self.sen
+}
+func (self *StateTransition) Receiver() *ethstate.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())
+
+	defer func() {
+		if r := recover(); r != nil {
+			statelogger.Infoln(r)
+			err = fmt.Errorf("state transition err %v", r)
+		}
+	}()
+
+	// XXX Transactions after this point are considered valid.
+	if err = self.preCheck(); err != nil {
+		return
+	}
+
+	var (
+		tx       = self.tx
+		sender   = self.Sender()
+		receiver *ethstate.StateObject
+	)
+
+	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
+	dataPrice := big.NewInt(int64(len(self.data)))
+	dataPrice.Mul(dataPrice, vm.GasData)
+	if err = self.UseGas(dataPrice); err != nil {
+		return
+	}
+
+	if sender.Balance().Cmp(self.value) < 0 {
+		return fmt.Errorf("Insufficient funds to transfer value. Req %v, has %v", self.value, sender.Balance)
+	}
+
+	var snapshot *ethstate.State
+	// If the receiver is nil it's a contract (\0*32).
+	if tx.CreatesContract() {
+		// Subtract the (irreversible) amount from the senders account
+		sender.SubAmount(self.value)
+
+		snapshot = self.state.Copy()
+
+		// Create a new state object for the contract
+		receiver := MakeContract(tx, self.state)
+		self.rec = receiver
+		if receiver == nil {
+			return fmt.Errorf("Unable to create contract")
+		}
+
+		// Add the amount to receivers account which should conclude this transaction
+		receiver.AddAmount(self.value)
+	} else {
+		receiver = self.Receiver()
+
+		// 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)
+
+		snapshot = self.state.Copy()
+	}
+
+	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,
+		Value: self.value,
+	})
+
+	// Process the init code and create 'valid' contract
+	if IsContractAddr(self.receiver) {
+		// Evaluate the initialization script
+		// and use the return value as the
+		// script section for the state object.
+		self.data = nil
+
+		code, err := self.Eval(msg, receiver.Init(), receiver)
+		if err != nil {
+			self.state.Set(snapshot)
+
+			return fmt.Errorf("Error during init execution %v", err)
+		}
+
+		receiver.Code = code
+		msg.Output = code
+	} else {
+		if len(receiver.Code) > 0 {
+			ret, err := self.Eval(msg, receiver.Code, receiver)
+			if err != nil {
+				self.state.Set(snapshot)
+
+				return fmt.Errorf("Error during code execution %v", err)
+			}
+
+			msg.Output = ret
+		}
+	}
+
+	return
+}
+
+func (self *StateTransition) Eval(msg *ethstate.Message, script []byte, context *ethstate.StateObject) (ret []byte, err error) {
+	var (
+		transactor    = self.Sender()
+		state         = self.state
+		env           = NewEnv(state, self.tx, self.block)
+		callerClosure = vm.NewClosure(msg, transactor, context, script, self.gas, self.gasPrice)
+	)
+
+	//vm := vm.New(env, vm.Type(ethutil.Config.VmType))
+	evm := vm.New(env, vm.DebugVmTy)
+
+	ret, _, err = callerClosure.Call(evm, self.tx.Data)
+
+	return
+}
+
+// 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(state)
+
+		contract := state.GetOrNewStateObject(addr)
+		contract.InitCode = tx.Data
+		contract.State = ethstate.New(ethtrie.New(ethutil.Config.Db, ""))
+
+		return contract
+	}
+
+	return nil
+}