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path: root/ethchain/state_transition.go
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package ethchain

import (
    "fmt"
    "github.com/ethereum/eth-go/ethutil"
    "math/big"
)

type StateTransition struct {
    coinbase []byte
    tx       *Transaction
    gas      *big.Int
    state    *State
    block    *Block

    cb, rec, sen *StateObject
}

func NewStateTransition(coinbase []byte, tx *Transaction, state *State, block *Block) *StateTransition {
    return &StateTransition{coinbase, tx, new(big.Int), state, block, nil, nil, nil}
}

func (self *StateTransition) Coinbase() *StateObject {
    if self.cb != nil {
        return self.cb
    }

    self.cb = self.state.GetAccount(self.coinbase)
    return self.cb
}
func (self *StateTransition) Sender() *StateObject {
    if self.sen != nil {
        return self.sen
    }

    self.sen = self.state.GetAccount(self.tx.Sender())
    return self.sen
}
func (self *StateTransition) Receiver() *StateObject {
    if self.tx.CreatesContract() {
        return nil
    }

    if self.rec != nil {
        return self.rec
    }

    self.rec = self.state.GetAccount(self.tx.Recipient)
    return self.rec
}

func (self *StateTransition) MakeStateObject(state *State, tx *Transaction) *StateObject {
    contract := MakeContract(tx, state)
    if contract != nil {
        state.states[string(tx.CreationAddress())] = contract.state

        return contract
    }

    return nil
}

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.Amount.Cmp(self.tx.GasValue()) < 0 {
        return fmt.Errorf("Insufficient funds to pre-pay gas. Req %v, has %v", self.tx.GasValue(), self.tx.Value)
    }

    coinbase := self.Coinbase()
    err = coinbase.BuyGas(self.tx.Gas, self.tx.GasPrice)
    if err != nil {
        return err
    }
    self.state.UpdateStateObject(coinbase)

    self.AddGas(self.tx.Gas)
    sender.SubAmount(self.tx.GasValue())

    return nil
}

func (self *StateTransition) TransitionState() (err error) {
    //snapshot := st.state.Snapshot()

    defer func() {
        if r := recover(); r != nil {
            ethutil.Config.Log.Infoln(r)
            err = fmt.Errorf("%v", r)
        }
    }()

    var (
        tx       = self.tx
        sender   = self.Sender()
        receiver *StateObject
    )

    if sender.Nonce != tx.Nonce {
        return NonceError(tx.Nonce, sender.Nonce)
    }

    sender.Nonce += 1
    defer func() {
        // Notify all subscribers
        //self.Ethereum.Reactor().Post("newTx:post", tx)
    }()

    if err = self.BuyGas(); err != nil {
        return err
    }

    receiver = self.Receiver()

    if err = self.UseGas(GasTx); err != nil {
        return err
    }

    dataPrice := big.NewInt(int64(len(tx.Data)))
    dataPrice.Mul(dataPrice, GasData)
    if err = self.UseGas(dataPrice); err != nil {
        return err
    }

    if receiver == nil { // Contract
        receiver = self.MakeStateObject(self.state, tx)
        if receiver == nil {
            return fmt.Errorf("ERR. Unable to create contract with transaction %v", tx)
        }
    }

    if err = self.transferValue(sender, receiver); err != nil {
        return err
    }

    if tx.CreatesContract() {
        fmt.Println(Disassemble(receiver.Init()))
        // Evaluate the initialization script
        // and use the return value as the
        // script section for the state object.
        //script, gas, err = sm.Eval(state, contract.Init(), contract, tx, block)
        code, err := self.Eval(receiver.Init(), receiver)
        if err != nil {
            return fmt.Errorf("Error during init script run %v", err)
        }

        receiver.script = code
    }

    self.state.UpdateStateObject(sender)
    self.state.UpdateStateObject(receiver)

    return nil
}

func (self *StateTransition) transferValue(sender, receiver *StateObject) error {
    if sender.Amount.Cmp(self.tx.Value) < 0 {
        return fmt.Errorf("Insufficient funds to transfer value. Req %v, has %v", self.tx.Value, sender.Amount)
    }

    // Subtract the amount from the senders account
    sender.SubAmount(self.tx.Value)
    // Add the amount to receivers account which should conclude this transaction
    receiver.AddAmount(self.tx.Value)

    ethutil.Config.Log.Debugf("%x => %x (%v) %x\n", sender.Address()[:4], receiver.Address()[:4], self.tx.Value, self.tx.Hash())

    return nil
}

func (self *StateTransition) Eval(script []byte, context *StateObject) (ret []byte, err error) {
    var (
        tx        = self.tx
        block     = self.block
        initiator = self.Sender()
        state     = self.state
    )

    closure := NewClosure(initiator, context, script, state, self.gas, tx.GasPrice)
    vm := NewVm(state, nil, RuntimeVars{
        Origin:      initiator.Address(),
        BlockNumber: block.BlockInfo().Number,
        PrevHash:    block.PrevHash,
        Coinbase:    block.Coinbase,
        Time:        block.Time,
        Diff:        block.Difficulty,
        Value:       tx.Value,
    })
    ret, _, err = closure.Call(vm, tx.Data, nil)

    return
}