1 files changed, 238 insertions, 0 deletions
diff --git a/core/state_transition.go b/core/state_transition.go
new file mode 100644
index 000000000..7b7026c29
--- /dev/null
+++ b/core/state_transition.go
@@ -0,0 +1,238 @@
+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 ETH for gas (%x). Req %v, has %v", sender.Address()[:4], 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) {
+		contract := MakeContract(msg, self.state)
+		ret, err, ref = vmenv.Create(sender, contract.Address(), self.msg.Data(), self.gas, self.gasPrice, self.value)
+		if err == nil {
+			dataGas := big.NewInt(int64(len(ret)))
+			dataGas.Mul(dataGas, vm.GasCreateByte)
+			if err = self.UseGas(dataGas); err == nil {
+				//self.state.SetCode(ref.Address(), ret)
+				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 {
+		self.UseGas(self.gas)
+	}
+
+	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() {
+	coinbase, sender := self.Coinbase(), self.From()
+	// Return remaining gas
+	remaining := new(big.Int).Mul(self.gas, self.msg.GasPrice())
+	sender.AddAmount(remaining)
+
+	uhalf := new(big.Int).Div(self.GasUsed(), ethutil.Big2)
+	for addr, ref := range self.state.Refunds() {
+		refund := ethutil.BigMin(uhalf, ref)
+		self.gas.Add(self.gas, refund)
+		self.state.AddBalance([]byte(addr), refund.Mul(refund, self.msg.GasPrice()))
+	}
+
+	coinbase.RefundGas(self.gas, self.msg.GasPrice())
+}
+
+func (self *StateTransition) GasUsed() *big.Int {
+	return new(big.Int).Sub(self.initialGas, self.gas)
+}