From 9008b155d3c8d2a32c4c8945f1174243d48d4e90 Mon Sep 17 00:00:00 2001
From: obscuren <geffobscura@gmail.com>
Date: Thu, 4 Dec 2014 10:28:02 +0100
Subject: Renamed `chain` => `core`

---
 core/state_transition.go | 198 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 198 insertions(+)
 create mode 100644 core/state_transition.go

(limited to 'core/state_transition.go')

diff --git a/core/state_transition.go b/core/state_transition.go
new file mode 100644
index 000000000..e3eea57de
--- /dev/null
+++ b/core/state_transition.go
@@ -0,0 +1,198 @@
+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.State
+	block              *types.Block
+
+	cb, rec, sen *state.StateObject
+}
+
+func NewStateTransition(coinbase *state.StateObject, tx *types.Transaction, state *state.State, 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()
+		receiver *state.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
+	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, receiver.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.State) *state.StateObject {
+	addr := tx.CreationAddress(state)
+
+	contract := state.GetOrNewStateObject(addr)
+	contract.InitCode = tx.Data
+
+	return contract
+}
-- 
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