path: root/core/state/statedb.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 provides a caching layer atop the Ethereum state trie.
package state

import (
    "fmt"
    "math/big"
    "sort"
    "sync"

    "github.com/ethereum/go-ethereum/common"
    "github.com/ethereum/go-ethereum/core/vm"
    "github.com/ethereum/go-ethereum/crypto"
    "github.com/ethereum/go-ethereum/ethdb"
    "github.com/ethereum/go-ethereum/logger"
    "github.com/ethereum/go-ethereum/logger/glog"
    "github.com/ethereum/go-ethereum/rlp"
    "github.com/ethereum/go-ethereum/trie"
    lru "github.com/hashicorp/golang-lru"
)

// The starting nonce determines the default nonce when new accounts are being
// created.
var StartingNonce uint64

// Trie cache generation limit after which to evic trie nodes from memory.
var MaxTrieCacheGen = uint16(120)

const (
    // Number of past tries to keep. This value is chosen such that
    // reasonable chain reorg depths will hit an existing trie.
    maxPastTries = 12

    // Number of codehash->size associations to keep.
    codeSizeCacheSize = 100000
)

type revision struct {
    id           int
    journalIndex int
}

// StateDBs within the ethereum protocol are used to store anything
// within the merkle trie. StateDBs take care of caching and storing
// nested states. It's the general query interface to retrieve:
// * Contracts
// * Accounts
type StateDB struct {
    db            ethdb.Database
    trie          *trie.SecureTrie
    pastTries     []*trie.SecureTrie
    codeSizeCache *lru.Cache

    // This map holds 'live' objects, which will get modified while processing a state transition.
    stateObjects      map[common.Address]*StateObject
    stateObjectsDirty map[common.Address]struct{}

    // The refund counter, also used by state transitioning.
    refund *big.Int

    thash, bhash common.Hash
    txIndex      int
    logs         map[common.Hash]vm.Logs
    logSize      uint

    // Journal of state modifications. This is the backbone of
    // Snapshot and RevertToSnapshot.
    journal        journal
    validRevisions []revision
    nextRevisionId int

    lock sync.Mutex
}

// Create a new state from a given trie
func New(root common.Hash, db ethdb.Database) (*StateDB, error) {
    tr, err := trie.NewSecure(root, db, MaxTrieCacheGen)
    if err != nil {
        return nil, err
    }
    csc, _ := lru.New(codeSizeCacheSize)
    return &StateDB{
        db:                db,
        trie:              tr,
        codeSizeCache:     csc,
        stateObjects:      make(map[common.Address]*StateObject),
        stateObjectsDirty: make(map[common.Address]struct{}),
        refund:            new(big.Int),
        logs:              make(map[common.Hash]vm.Logs),
    }, nil
}

// New creates a new statedb by reusing any journalled tries to avoid costly
// disk io.
func (self *StateDB) New(root common.Hash) (*StateDB, error) {
    self.lock.Lock()
    defer self.lock.Unlock()

    tr, err := self.openTrie(root)
    if err != nil {
        return nil, err
    }
    return &StateDB{
        db:                self.db,
        trie:              tr,
        codeSizeCache:     self.codeSizeCache,
        stateObjects:      make(map[common.Address]*StateObject),
        stateObjectsDirty: make(map[common.Address]struct{}),
        refund:            new(big.Int),
        logs:              make(map[common.Hash]vm.Logs),
    }, nil
}

// Reset clears out all emphemeral state objects from the state db, but keeps
// the underlying state trie to avoid reloading data for the next operations.
func (self *StateDB) Reset(root common.Hash) error {
    self.lock.Lock()
    defer self.lock.Unlock()

    tr, err := self.openTrie(root)
    if err != nil {
        return err
    }
    self.trie = tr
    self.stateObjects = make(map[common.Address]*StateObject)
    self.stateObjectsDirty = make(map[common.Address]struct{})
    self.thash = common.Hash{}
    self.bhash = common.Hash{}
    self.txIndex = 0
    self.logs = make(map[common.Hash]vm.Logs)
    self.logSize = 0
    self.clearJournalAndRefund()

    return nil
}

// openTrie creates a trie. It uses an existing trie if one is available
// from the journal if available.
func (self *StateDB) openTrie(root common.Hash) (*trie.SecureTrie, error) {
    for i := len(self.pastTries) - 1; i >= 0; i-- {
        if self.pastTries[i].Hash() == root {
            tr := *self.pastTries[i]
            return &tr, nil
        }
    }
    return trie.NewSecure(root, self.db, MaxTrieCacheGen)
}

func (self *StateDB) pushTrie(t *trie.SecureTrie) {
    self.lock.Lock()
    defer self.lock.Unlock()

    if len(self.pastTries) >= maxPastTries {
        copy(self.pastTries, self.pastTries[1:])
        self.pastTries[len(self.pastTries)-1] = t
    } else {
        self.pastTries = append(self.pastTries, t)
    }
}

func (self *StateDB) StartRecord(thash, bhash common.Hash, ti int) {
    self.thash = thash
    self.bhash = bhash
    self.txIndex = ti
}

func (self *StateDB) AddLog(log *vm.Log) {
    self.journal = append(self.journal, addLogChange{txhash: self.thash})

    log.TxHash = self.thash
    log.BlockHash = self.bhash
    log.TxIndex = uint(self.txIndex)
    log.Index = self.logSize
    self.logs[self.thash] = append(self.logs[self.thash], log)
    self.logSize++
}

func (self *StateDB) GetLogs(hash common.Hash) vm.Logs {
    return self.logs[hash]
}

func (self *StateDB) Logs() vm.Logs {
    var logs vm.Logs
    for _, lgs := range self.logs {
        logs = append(logs, lgs...)
    }
    return logs
}

func (self *StateDB) AddRefund(gas *big.Int) {
    self.journal = append(self.journal, refundChange{prev: new(big.Int).Set(self.refund)})
    self.refund.Add(self.refund, gas)
}

// Exist reports whether the given account address exists in the state.
// Notably this also returns true for suicided accounts.
func (self *StateDB) Exist(addr common.Address) bool {
    return self.GetStateObject(addr) != nil
}

// Empty returns whether the state object is either non-existant
// or empty according to the EIP161 specification (balance = nonce = code = 0)
func (self *StateDB) Empty(addr common.Address) bool {
    so := self.GetStateObject(addr)
    return so == nil || so.empty()
}

func (self *StateDB) GetAccount(addr common.Address) vm.Account {
    return self.GetStateObject(addr)
}

// Retrieve the balance from the given address or 0 if object not found
func (self *StateDB) GetBalance(addr common.Address) *big.Int {
    stateObject := self.GetStateObject(addr)
    if stateObject != nil {
        return stateObject.Balance()
    }
    return common.Big0
}

func (self *StateDB) GetNonce(addr common.Address) uint64 {
    stateObject := self.GetStateObject(addr)
    if stateObject != nil {
        return stateObject.Nonce()
    }

    return StartingNonce
}

func (self *StateDB) GetCode(addr common.Address) []byte {
    stateObject := self.GetStateObject(addr)
    if stateObject != nil {
        code := stateObject.Code(self.db)
        key := common.BytesToHash(stateObject.CodeHash())
        self.codeSizeCache.Add(key, len(code))
        return code
    }
    return nil
}

func (self *StateDB) GetCodeSize(addr common.Address) int {
    stateObject := self.GetStateObject(addr)
    if stateObject == nil {
        return 0
    }
    key := common.BytesToHash(stateObject.CodeHash())
    if cached, ok := self.codeSizeCache.Get(key); ok {
        return cached.(int)
    }
    size := len(stateObject.Code(self.db))
    if stateObject.dbErr == nil {
        self.codeSizeCache.Add(key, size)
    }
    return size
}

func (self *StateDB) GetCodeHash(addr common.Address) common.Hash {
    stateObject := self.GetStateObject(addr)
    if stateObject == nil {
        return common.Hash{}
    }
    return common.BytesToHash(stateObject.CodeHash())
}

func (self *StateDB) GetState(a common.Address, b common.Hash) common.Hash {
    stateObject := self.GetStateObject(a)
    if stateObject != nil {
        return stateObject.GetState(self.db, b)
    }
    return common.Hash{}
}

func (self *StateDB) HasSuicided(addr common.Address) bool {
    stateObject := self.GetStateObject(addr)
    if stateObject != nil {
        return stateObject.suicided
    }
    return false
}

/*
 * SETTERS
 */

func (self *StateDB) AddBalance(addr common.Address, amount *big.Int) {
    stateObject := self.GetOrNewStateObject(addr)
    if stateObject != nil {
        stateObject.AddBalance(amount)
    }
}

func (self *StateDB) SetBalance(addr common.Address, amount *big.Int) {
    stateObject := self.GetOrNewStateObject(addr)
    if stateObject != nil {
        stateObject.SetBalance(amount)
    }
}

func (self *StateDB) SetNonce(addr common.Address, nonce uint64) {
    stateObject := self.GetOrNewStateObject(addr)
    if stateObject != nil {
        stateObject.SetNonce(nonce)
    }
}

func (self *StateDB) SetCode(addr common.Address, code []byte) {
    stateObject := self.GetOrNewStateObject(addr)
    if stateObject != nil {
        stateObject.SetCode(crypto.Keccak256Hash(code), code)
    }
}

func (self *StateDB) SetState(addr common.Address, key common.Hash, value common.Hash) {
    stateObject := self.GetOrNewStateObject(addr)
    if stateObject != nil {
        stateObject.SetState(self.db, key, value)
    }
}

// Suicide marks the given account as suicided.
// This clears the account balance.
//
// The account's state object is still available until the state is committed,
// GetStateObject will return a non-nil account after Suicide.
func (self *StateDB) Suicide(addr common.Address) bool {
    stateObject := self.GetStateObject(addr)
    if stateObject == nil {
        return false
    }
    self.journal = append(self.journal, suicideChange{
        account:     &addr,
        prev:        stateObject.suicided,
        prevbalance: new(big.Int).Set(stateObject.Balance()),
    })
    stateObject.markSuicided()
    stateObject.data.Balance = new(big.Int)
    return true
}

//
// Setting, updating & deleting state object methods
//

// updateStateObject writes the given object to the trie.
func (self *StateDB) updateStateObject(stateObject *StateObject) {
    addr := stateObject.Address()
    data, err := rlp.EncodeToBytes(stateObject)
    if err != nil {
        panic(fmt.Errorf("can't encode object at %x: %v", addr[:], err))
    }
    self.trie.Update(addr[:], data)
}

// deleteStateObject removes the given object from the state trie.
func (self *StateDB) deleteStateObject(stateObject *StateObject) {
    stateObject.deleted = true
    addr := stateObject.Address()
    self.trie.Delete(addr[:])
}

// Retrieve a state object given my the address. Returns nil if not found.
func (self *StateDB) GetStateObject(addr common.Address) (stateObject *StateObject) {
    // Prefer 'live' objects.
    if obj := self.stateObjects[addr]; obj != nil {
        if obj.deleted {
            return nil
        }
        return obj
    }

    // Load the object from the database.
    enc := self.trie.Get(addr[:])
    if len(enc) == 0 {
        return nil
    }
    var data Account
    if err := rlp.DecodeBytes(enc, &data); err != nil {
        glog.Errorf("can't decode object at %x: %v", addr[:], err)
        return nil
    }
    // Insert into the live set.
    obj := newObject(self, addr, data, self.MarkStateObjectDirty)
    self.setStateObject(obj)
    return obj
}

func (self *StateDB) setStateObject(object *StateObject) {
    self.stateObjects[object.Address()] = object
}

// Retrieve a state object or create a new state object if nil
func (self *StateDB) GetOrNewStateObject(addr common.Address) *StateObject {
    stateObject := self.GetStateObject(addr)
    if stateObject == nil || stateObject.deleted {
        stateObject, _ = self.createObject(addr)
    }
    return stateObject
}

// MarkStateObjectDirty adds the specified object to the dirty map to avoid costly
// state object cache iteration to find a handful of modified ones.
func (self *StateDB) MarkStateObjectDirty(addr common.Address) {
    self.stateObjectsDirty[addr] = struct{}{}
}

// createObject creates a new state object. If there is an existing account with
// the given address, it is overwritten and returned as the second return value.
func (self *StateDB) createObject(addr common.Address) (newobj, prev *StateObject) {
    prev = self.GetStateObject(addr)
    newobj = newObject(self, addr, Account{}, self.MarkStateObjectDirty)
    newobj.setNonce(StartingNonce) // sets the object to dirty
    if prev == nil {
        if glog.V(logger.Core) {
            glog.Infof("(+) %x\n", addr)
        }
        self.journal = append(self.journal, createObjectChange{account: &addr})
    } else {
        self.journal = append(self.journal, resetObjectChange{prev: prev})
    }
    self.setStateObject(newobj)
    return newobj, prev
}

// CreateAccount explicitly creates a state object. If a state object with the address
// already exists the balance is carried over to the new account.
//
// CreateAccount is called during the EVM CREATE operation. The situation might arise that
// a contract does the following:
//
//   1. sends funds to sha(account ++ (nonce + 1))
//   2. tx_create(sha(account ++ nonce)) (note that this gets the address of 1)
//
// Carrying over the balance ensures that Ether doesn't disappear.
func (self *StateDB) CreateAccount(addr common.Address) vm.Account {
    new, prev := self.createObject(addr)
    if prev != nil {
        new.setBalance(prev.data.Balance)
    }
    return new
}

// Copy creates a deep, independent copy of the state.
// Snapshots of the copied state cannot be applied to the copy.
func (self *StateDB) Copy() *StateDB {
    self.lock.Lock()
    defer self.lock.Unlock()

    // Copy all the basic fields, initialize the memory ones
    state := &StateDB{
        db:                self.db,
        trie:              self.trie,
        pastTries:         self.pastTries,
        codeSizeCache:     self.codeSizeCache,
        stateObjects:      make(map[common.Address]*StateObject, len(self.stateObjectsDirty)),
        stateObjectsDirty: make(map[common.Address]struct{}, len(self.stateObjectsDirty)),
        refund:            new(big.Int).Set(self.refund),
        logs:              make(map[common.Hash]vm.Logs, len(self.logs)),
        logSize:           self.logSize,
    }
    // Copy the dirty states and logs
    for addr, _ := range self.stateObjectsDirty {
        state.stateObjects[addr] = self.stateObjects[addr].deepCopy(state, state.MarkStateObjectDirty)
        state.stateObjectsDirty[addr] = struct{}{}
    }
    for hash, logs := range self.logs {
        state.logs[hash] = make(vm.Logs, len(logs))
        copy(state.logs[hash], logs)
    }
    return state
}

// Snapshot returns an identifier for the current revision of the state.
func (self *StateDB) Snapshot() int {
    id := self.nextRevisionId
    self.nextRevisionId++
    self.validRevisions = append(self.validRevisions, revision{id, len(self.journal)})
    return id
}

// RevertToSnapshot reverts all state changes made since the given revision.
func (self *StateDB) RevertToSnapshot(revid int) {
    // Find the snapshot in the stack of valid snapshots.
    idx := sort.Search(len(self.validRevisions), func(i int) bool {
        return self.validRevisions[i].id >= revid
    })
    if idx == len(self.validRevisions) || self.validRevisions[idx].id != revid {
        panic(fmt.Errorf("revision id %v cannot be reverted", revid))
    }
    snapshot := self.validRevisions[idx].journalIndex

    // Replay the journal to undo changes.
    for i := len(self.journal) - 1; i >= snapshot; i-- {
        self.journal[i].undo(self)
    }
    self.journal = self.journal[:snapshot]

    // Remove invalidated snapshots from the stack.
    self.validRevisions = self.validRevisions[:idx]
}

// GetRefund returns the current value of the refund counter.
// The return value must not be modified by the caller and will become
// invalid at the next call to AddRefund.
func (self *StateDB) GetRefund() *big.Int {
    return self.refund
}

// IntermediateRoot computes the current root hash of the state trie.
// It is called in between transactions to get the root hash that
// goes into transaction receipts.
func (s *StateDB) IntermediateRoot(deleteEmptyObjects bool) common.Hash {
    for addr, _ := range s.stateObjectsDirty {
        stateObject := s.stateObjects[addr]
        if stateObject.suicided || (deleteEmptyObjects && stateObject.empty()) {
            s.deleteStateObject(stateObject)
        } else {
            stateObject.updateRoot(s.db)
            s.updateStateObject(stateObject)
        }
    }
    // Invalidate journal because reverting across transactions is not allowed.
    s.clearJournalAndRefund()
    return s.trie.Hash()
}

// DeleteSuicides flags the suicided objects for deletion so that it
// won't be referenced again when called / queried up on.
//
// DeleteSuicides should not be used for consensus related updates
// under any circumstances.
func (s *StateDB) DeleteSuicides() {
    // Reset refund so that any used-gas calculations can use this method.
    s.clearJournalAndRefund()

    for addr, _ := range s.stateObjectsDirty {
        stateObject := s.stateObjects[addr]

        // If the object has been removed by a suicide
        // flag the object as deleted.
        if stateObject.suicided {
            stateObject.deleted = true
        }
        delete(s.stateObjectsDirty, addr)
    }
}

// Commit commits all state changes to the database.
func (s *StateDB) Commit(deleteEmptyObjects bool) (root common.Hash, err error) {
    root, batch := s.CommitBatch(deleteEmptyObjects)
    return root, batch.Write()
}

// CommitBatch commits all state changes to a write batch but does not
// execute the batch. It is used to validate state changes against
// the root hash stored in a block.
func (s *StateDB) CommitBatch(deleteEmptyObjects bool) (root common.Hash, batch ethdb.Batch) {
    batch = s.db.NewBatch()
    root, _ = s.commit(batch, deleteEmptyObjects)

    glog.V(logger.Debug).Infof("Trie cache stats: %d misses, %d unloads", trie.CacheMisses(), trie.CacheUnloads())
    return root, batch
}

func (s *StateDB) clearJournalAndRefund() {
    s.journal = nil
    s.validRevisions = s.validRevisions[:0]
    s.refund = new(big.Int)
}

func (s *StateDB) commit(dbw trie.DatabaseWriter, deleteEmptyObjects bool) (root common.Hash, err error) {
    defer s.clearJournalAndRefund()

    // Commit objects to the trie.
    for addr, stateObject := range s.stateObjects {
        _, isDirty := s.stateObjectsDirty[addr]
        switch {
        case stateObject.suicided || (isDirty && deleteEmptyObjects && stateObject.empty()):
            // If the object has been removed, don't bother syncing it
            // and just mark it for deletion in the trie.
            s.deleteStateObject(stateObject)
        case isDirty:
            // Write any contract code associated with the state object
            if stateObject.code != nil && stateObject.dirtyCode {
                if err := dbw.Put(stateObject.CodeHash(), stateObject.code); err != nil {
                    return common.Hash{}, err
                }
                stateObject.dirtyCode = false
            }
            // Write any storage changes in the state object to its storage trie.
            if err := stateObject.CommitTrie(s.db, dbw); err != nil {
                return common.Hash{}, err
            }
            // Update the object in the main account trie.
            s.updateStateObject(stateObject)
        }
        delete(s.stateObjectsDirty, addr)
    }
    // Write trie changes.
    root, err = s.trie.CommitTo(dbw)
    if err == nil {
        s.pushTrie(s.trie)
    }
    return root, err
}