path: root/ethchain/state.go

package ethchain

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

// States within the ethereum protocol are used to store anything
// within the merkle trie. States take care of caching and storing
// nested states. It's the general query interface to retrieve:
// * Contracts
// * Accounts
type State struct {
    // The trie for this structure
    trie *ethutil.Trie
    // Nested states
    states map[string]*State
}

// Create a new state from a given trie
func NewState(trie *ethutil.Trie) *State {
    return &State{trie: trie, states: make(map[string]*State)}
}

// Resets the trie and all siblings
func (s *State) Reset() {
    s.trie.Undo()

    // Reset all nested states
    for _, state := range s.states {
        state.Reset()
    }
}

// Syncs the trie and all siblings
func (s *State) Sync() {
    s.trie.Sync()

    // Sync all nested states
    for _, state := range s.states {
        state.Sync()
    }
}

// Purges the current trie.
func (s *State) Purge() int {
    return s.trie.NewIterator().Purge()
}

func (s *State) GetContract(addr []byte) *Contract {
    data := s.trie.Get(string(addr))
    if data == "" {
        return nil
    }

    // Whet get contract is called the retrieved value might
    // be an account. The StateManager uses this to check
    // to see if the address a tx was sent to is a contract
    // or an account
    value := ethutil.NewValueFromBytes([]byte(data))
    if value.Len() == 2 {
        return nil
    }

    // build contract
    contract := &Contract{}
    contract.RlpDecode([]byte(data))

    // Check if there's a cached state for this contract
    cachedState := s.states[string(addr)]
    if cachedState != nil {
        contract.state = cachedState
    } else {
        // If it isn't cached, cache the state
        s.states[string(addr)] = contract.state
    }

    return contract
}

func (s *State) UpdateContract(addr []byte, contract *Contract) {
    s.trie.Update(string(addr), string(contract.RlpEncode()))
}

func Compile(code []string) (script []string) {
    script = make([]string, len(code))
    for i, val := range code {
        instr, _ := ethutil.CompileInstr(val)

        script[i] = string(instr)
    }

    return
}

func (s *State) GetAccount(addr []byte) (account *Account) {
    data := s.trie.Get(string(addr))
    if data == "" {
        account = NewAccount(big.NewInt(0))
    } else {
        account = NewAccountFromData([]byte(data))
    }

    return
}

func (s *State) UpdateAccount(addr []byte, account *Account) {
    s.trie.Update(string(addr), string(account.RlpEncode()))
}

func (s *State) Cmp(other *State) bool {
    return s.trie.Cmp(other.trie)
}

type ObjType byte

const (
    NilTy ObjType = iota
    AccountTy
    ContractTy

    UnknownTy
)

// Returns the object stored at key and the type stored at key
// Returns nil if nothing is stored
func (s *State) Get(key []byte) (*ethutil.Value, ObjType) {
    // Fetch data from the trie
    data := s.trie.Get(string(key))
    // Returns the nil type, indicating nothing could be retrieved.
    // Anything using this function should check for this ret val
    if data == "" {
        return nil, NilTy
    }

    var typ ObjType
    val := ethutil.NewValueFromBytes([]byte(data))
    // Check the length of the retrieved value.
    // Len 2 = Account
    // Len 3 = Contract
    // Other = invalid for now. If other types emerge, add them here
    if val.Len() == 2 {
        typ = AccountTy
    } else if val.Len() == 3 {
        typ = ContractTy
    } else {
        typ = UnknownTy
    }

    return val, typ
}