path: root/core/state/state_object.go

// Copyright 2014 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.

package state

import (
    "bytes"
    "fmt"
    "io"
    "math/big"
    "time"

    "github.com/ethereum/go-ethereum/common"
    "github.com/ethereum/go-ethereum/crypto"
    "github.com/ethereum/go-ethereum/metrics"
    "github.com/ethereum/go-ethereum/rlp"
)

var emptyCodeHash = crypto.Keccak256(nil)

type Code []byte

func (c Code) String() string {
    return string(c) //strings.Join(Disassemble(c), " ")
}

type Storage map[common.Hash]common.Hash

func (s Storage) String() (str string) {
    for key, value := range s {
        str += fmt.Sprintf("%X : %X\n", key, value)
    }

    return
}

func (s Storage) Copy() Storage {
    cpy := make(Storage)
    for key, value := range s {
        cpy[key] = value
    }

    return cpy
}

// stateObject represents an Ethereum account which is being modified.
//
// The usage pattern is as follows:
// First you need to obtain a state object.
// Account values can be accessed and modified through the object.
// Finally, call CommitTrie to write the modified storage trie into a database.
type stateObject struct {
    address  common.Address
    addrHash common.Hash // hash of ethereum address of the account
    data     Account
    db       *StateDB

    // DB error.
    // State objects are used by the consensus core and VM which are
    // unable to deal with database-level errors. Any error that occurs
    // during a database read is memoized here and will eventually be returned
    // by StateDB.Commit.
    dbErr error

    // Write caches.
    trie Trie // storage trie, which becomes non-nil on first access
    code Code // contract bytecode, which gets set when code is loaded

    originStorage Storage // Storage cache of original entries to dedup rewrites
    dirtyStorage  Storage // Storage entries that need to be flushed to disk
    fakeStorage   Storage // Fake storage which constructed by caller for debugging purpose.

    // Cache flags.
    // When an object is marked suicided it will be delete from the trie
    // during the "update" phase of the state transition.
    dirtyCode bool // true if the code was updated
    suicided  bool
    deleted   bool
}

// empty returns whether the account is considered empty.
func (s *stateObject) empty() bool {
    return s.data.Nonce == 0 && s.data.Balance.Sign() == 0 && bytes.Equal(s.data.CodeHash, emptyCodeHash)
}

// Account is the Ethereum consensus representation of accounts.
// These objects are stored in the main account trie.
type Account struct {
    Nonce    uint64
    Balance  *big.Int
    Root     common.Hash // merkle root of the storage trie
    CodeHash []byte
}

// newObject creates a state object.
func newObject(db *StateDB, address common.Address, data Account) *stateObject {
    if data.Balance == nil {
        data.Balance = new(big.Int)
    }
    if data.CodeHash == nil {
        data.CodeHash = emptyCodeHash
    }
    return &stateObject{
        db:            db,
        address:       address,
        addrHash:      crypto.Keccak256Hash(address[:]),
        data:          data,
        originStorage: make(Storage),
        dirtyStorage:  make(Storage),
    }
}

// EncodeRLP implements rlp.Encoder.
func (s *stateObject) EncodeRLP(w io.Writer) error {
    return rlp.Encode(w, s.data)
}

// setError remembers the first non-nil error it is called with.
func (s *stateObject) setError(err error) {
    if s.dbErr == nil {
        s.dbErr = err
    }
}

func (s *stateObject) markSuicided() {
    s.suicided = true
}

func (s *stateObject) touch() {
    s.db.journal.append(touchChange{
        account: &s.address,
    })
    if s.address == ripemd {
        // Explicitly put it in the dirty-cache, which is otherwise generated from
        // flattened journals.
        s.db.journal.dirty(s.address)
    }
}

func (s *stateObject) getTrie(db Database) Trie {
    if s.trie == nil {
        var err error
        s.trie, err = db.OpenStorageTrie(s.addrHash, s.data.Root)
        if err != nil {
            s.trie, _ = db.OpenStorageTrie(s.addrHash, common.Hash{})
            s.setError(fmt.Errorf("can't create storage trie: %v", err))
        }
    }
    return s.trie
}

// GetState retrieves a value from the account storage trie.
func (s *stateObject) GetState(db Database, key common.Hash) common.Hash {
    // If the fake storage is set, only lookup the state here(in the debugging mode)
    if s.fakeStorage != nil {
        return s.fakeStorage[key]
    }
    // If we have a dirty value for this state entry, return it
    value, dirty := s.dirtyStorage[key]
    if dirty {
        return value
    }
    // Otherwise return the entry's original value
    return s.GetCommittedState(db, key)
}

// GetCommittedState retrieves a value from the committed account storage trie.
func (s *stateObject) GetCommittedState(db Database, key common.Hash) common.Hash {
    // If the fake storage is set, only lookup the state here(in the debugging mode)
    if s.fakeStorage != nil {
        return s.fakeStorage[key]
    }
    // If we have the original value cached, return that
    value, cached := s.originStorage[key]
    if cached {
        return value
    }
    // Track the amount of time wasted on reading the storage trie
    if metrics.EnabledExpensive {
        defer func(start time.Time) { s.db.StorageReads += time.Since(start) }(time.Now())
    }
    // Otherwise load the value from the database
    enc, err := s.getTrie(db).TryGet(key[:])
    if err != nil {
        s.setError(err)
        return common.Hash{}
    }
    if len(enc) > 0 {
        _, content, _, err := rlp.Split(enc)
        if err != nil {
            s.setError(err)
        }
        value.SetBytes(content)
    }
    s.originStorage[key] = value
    return value
}

// SetState updates a value in account storage.
func (s *stateObject) SetState(db Database, key, value common.Hash) {
    // If the fake storage is set, put the temporary state update here.
    if s.fakeStorage != nil {
        s.fakeStorage[key] = value
        return
    }
    // If the new value is the same as old, don't set
    prev := s.GetState(db, key)
    if prev == value {
        return
    }
    // New value is different, update and journal the change
    s.db.journal.append(storageChange{
        account:  &s.address,
        key:      key,
        prevalue: prev,
    })
    s.setState(key, value)
}

// SetStorage replaces the entire state storage with the given one.
//
// After this function is called, all original state will be ignored and state
// lookup only happens in the fake state storage.
//
// Note this function should only be used for debugging purpose.
func (s *stateObject) SetStorage(storage map[common.Hash]common.Hash) {
    // Allocate fake storage if it's nil.
    if s.fakeStorage == nil {
        s.fakeStorage = make(Storage)
    }
    for key, value := range storage {
        s.fakeStorage[key] = value
    }
    // Don't bother journal since this function should only be used for
    // debugging and the `fake` storage won't be committed to database.
}

func (s *stateObject) setState(key, value common.Hash) {
    s.dirtyStorage[key] = value
}

// updateTrie writes cached storage modifications into the object's storage trie.
func (s *stateObject) updateTrie(db Database) Trie {
    // Track the amount of time wasted on updating the storge trie
    if metrics.EnabledExpensive {
        defer func(start time.Time) { s.db.StorageUpdates += time.Since(start) }(time.Now())
    }
    // Update all the dirty slots in the trie
    tr := s.getTrie(db)
    for key, value := range s.dirtyStorage {
        delete(s.dirtyStorage, key)

        // Skip noop changes, persist actual changes
        if value == s.originStorage[key] {
            continue
        }
        s.originStorage[key] = value

        if (value == common.Hash{}) {
            s.setError(tr.TryDelete(key[:]))
            continue
        }
        // Encoding []byte cannot fail, ok to ignore the error.
        v, _ := rlp.EncodeToBytes(common.TrimLeftZeroes(value[:]))
        s.setError(tr.TryUpdate(key[:], v))
    }
    return tr
}

// UpdateRoot sets the trie root to the current root hash of
func (s *stateObject) updateRoot(db Database) {
    s.updateTrie(db)

    // Track the amount of time wasted on hashing the storge trie
    if metrics.EnabledExpensive {
        defer func(start time.Time) { s.db.StorageHashes += time.Since(start) }(time.Now())
    }
    s.data.Root = s.trie.Hash()
}

// CommitTrie the storage trie of the object to db.
// This updates the trie root.
func (s *stateObject) CommitTrie(db Database) error {
    s.updateTrie(db)
    if s.dbErr != nil {
        return s.dbErr
    }
    // Track the amount of time wasted on committing the storge trie
    if metrics.EnabledExpensive {
        defer func(start time.Time) { s.db.StorageCommits += time.Since(start) }(time.Now())
    }
    root, err := s.trie.Commit(nil)
    if err == nil {
        s.data.Root = root
    }
    return err
}

// AddBalance removes amount from c's balance.
// It is used to add funds to the destination account of a transfer.
func (s *stateObject) AddBalance(amount *big.Int) {
    // EIP158: We must check emptiness for the objects such that the account
    // clearing (0,0,0 objects) can take effect.
    if amount.Sign() == 0 {
        if s.empty() {
            s.touch()
        }

        return
    }
    s.SetBalance(new(big.Int).Add(s.Balance(), amount))
}

// SubBalance removes amount from c's balance.
// It is used to remove funds from the origin account of a transfer.
func (s *stateObject) SubBalance(amount *big.Int) {
    if amount.Sign() == 0 {
        return
    }
    s.SetBalance(new(big.Int).Sub(s.Balance(), amount))
}

func (s *stateObject) SetBalance(amount *big.Int) {
    s.db.journal.append(balanceChange{
        account: &s.address,
        prev:    new(big.Int).Set(s.data.Balance),
    })
    s.setBalance(amount)
}

func (s *stateObject) setBalance(amount *big.Int) {
    s.data.Balance = amount
}

// Return the gas back to the origin. Used by the Virtual machine or Closures
func (s *stateObject) ReturnGas(gas *big.Int) {}

func (s *stateObject) deepCopy(db *StateDB) *stateObject {
    stateObject := newObject(db, s.address, s.data)
    if s.trie != nil {
        stateObject.trie = db.db.CopyTrie(s.trie)
    }
    stateObject.code = s.code
    stateObject.dirtyStorage = s.dirtyStorage.Copy()
    stateObject.originStorage = s.originStorage.Copy()
    stateObject.suicided = s.suicided
    stateObject.dirtyCode = s.dirtyCode
    stateObject.deleted = s.deleted
    return stateObject
}

//
// Attribute accessors
//

// Returns the address of the contract/account
func (s *stateObject) Address() common.Address {
    return s.address
}

// Code returns the contract code associated with this object, if any.
func (s *stateObject) Code(db Database) []byte {
    if s.code != nil {
        return s.code
    }
    if bytes.Equal(s.CodeHash(), emptyCodeHash) {
        return nil
    }
    code, err := db.ContractCode(s.addrHash, common.BytesToHash(s.CodeHash()))
    if err != nil {
        s.setError(fmt.Errorf("can't load code hash %x: %v", s.CodeHash(), err))
    }
    s.code = code
    return code
}

func (s *stateObject) SetCode(codeHash common.Hash, code []byte) {
    prevcode := s.Code(s.db.db)
    s.db.journal.append(codeChange{
        account:  &s.address,
        prevhash: s.CodeHash(),
        prevcode: prevcode,
    })
    s.setCode(codeHash, code)
}

func (s *stateObject) setCode(codeHash common.Hash, code []byte) {
    s.code = code
    s.data.CodeHash = codeHash[:]
    s.dirtyCode = true
}

func (s *stateObject) SetNonce(nonce uint64) {
    s.db.journal.append(nonceChange{
        account: &s.address,
        prev:    s.data.Nonce,
    })
    s.setNonce(nonce)
}

func (s *stateObject) setNonce(nonce uint64) {
    s.data.Nonce = nonce
}

func (s *stateObject) CodeHash() []byte {
    return s.data.CodeHash
}

func (s *stateObject) Balance() *big.Int {
    return s.data.Balance
}

func (s *stateObject) Nonce() uint64 {
    return s.data.Nonce
}

// Never called, but must be present to allow stateObject to be used
// as a vm.Account interface that also satisfies the vm.ContractRef
// interface. Interfaces are awesome.
func (s *stateObject) Value() *big.Int {
    panic("Value on stateObject should never be called")
}