以太坊源码分析(24)core-state源码分析
core/state 包主要为以太坊的state trie提供了一层缓存层(cache)
- database主要提供了trie树的抽象，提供trie树的缓存和合约代码长度的缓存。
- journal主要提供了操作日志，以及操作回滚的功能。
- state_object是account对象的抽象，提供了账户的一些功能。
- statedb主要是提供了state trie的部分功能。
## database.go
database.go 提供了一个数据库的抽象。
数据结构
// Database wraps access to tries and contract code.
type Database interface {
// Accessing tries:
// OpenTrie opens the main account trie.
// OpenStorageTrie opens the storage trie of an account.
// OpenTrie 打开了主账号的trie树
// OpenStorageTrie 打开了一个账号的storage trie
OpenTrie(root common.Hash) (Trie, error)
OpenStorageTrie(addrHash, root common.Hash) (Trie, error)
// Accessing contract code:
// 访问合约代码
ContractCode(addrHash, codeHash common.Hash) ([]byte, error)
// 访问合约的大小。 这个方法可能经常被调用。因为有缓存。
ContractCodeSize(addrHash, codeHash common.Hash) (int, error)
// CopyTrie returns an independent copy of the given trie.
// CopyTrie 返回了一个指定trie的独立的copy
CopyTrie(Trie) Trie
}
// NewDatabase creates a backing store for state. The returned database is safe for
// concurrent use and retains cached trie nodes in memory.
func NewDatabase(db ethdb.Database) Database {
csc, _ := lru.New(codeSizeCacheSize)
return &cachingDB{db: db, codeSizeCache: csc}
}
type cachingDB struct {
db ethdb.Database
mu sync.Mutex
pastTries []*trie.SecureTrie //trie树的缓存
codeSizeCache *lru.Cache //合约代码大小的缓存
}
OpenTrie，从缓存里面查找。如果找到了返回缓存的trie的copy， 否则重新构建一颗树返回。
func (db *cachingDB) OpenTrie(root common.Hash) (Trie, error) {
db.mu.Lock()
defer db.mu.Unlock()
for i := len(db.pastTries) - 1; i >= 0; i-- {
if db.pastTries[i].Hash() == root {
return cachedTrie{db.pastTries[i].Copy(), db}, nil
}
}
tr, err := trie.NewSecure(root, db.db, MaxTrieCacheGen)
if err != nil {
return nil, err
}
return cachedTrie{tr, db}, nil
}
func (db *cachingDB) OpenStorageTrie(addrHash, root common.Hash) (Trie, error) {
return trie.NewSecure(root, db.db, 0)
}
ContractCode 和 ContractCodeSize, ContractCodeSize有缓存。
func (db *cachingDB) ContractCode(addrHash, codeHash common.Hash) ([]byte, error) {
code, err := db.db.Get(codeHash[:])
if err == nil {
db.codeSizeCache.Add(codeHash, len(code))
}
return code, err
}
func (db *cachingDB) ContractCodeSize(addrHash, codeHash common.Hash) (int, error) {
if cached, ok := db.codeSizeCache.Get(codeHash); ok {
return cached.(int), nil
}
code, err := db.ContractCode(addrHash, codeHash)
if err == nil {
db.codeSizeCache.Add(codeHash, len(code))
}
return len(code), err
}
cachedTrie的结构和commit方法，commit的时候会调用pushTrie方法把之前的Trie树缓存起来。
// cachedTrie inserts its trie into a cachingDB on commit.
type cachedTrie struct {
*trie.SecureTrie
db *cachingDB
}
func (m cachedTrie) CommitTo(dbw trie.DatabaseWriter) (common.Hash, error) {
root, err := m.SecureTrie.CommitTo(dbw)
if err == nil {
m.db.pushTrie(m.SecureTrie)
}
return root, err
}
func (db *cachingDB) pushTrie(t *trie.SecureTrie) {
db.mu.Lock()
defer db.mu.Unlock()
if len(db.pastTries) >= maxPastTries {
copy(db.pastTries, db.pastTries[1:])
db.pastTries[len(db.pastTries)-1] = t
} else {
db.pastTries = append(db.pastTries, t)
}
}
## journal.go
journal代表了操作日志， 并针对各种操作的日志提供了对应的回滚功能。 可以基于这个日志来做一些事务类型的操作。
类型定义，定义了journalEntry这个接口，提供了undo的功能。 journal 就是journalEntry的列表。
type journalEntry interface {
undo(*StateDB)
}
type journal []journalEntry
各种不同的日志类型以及undo方法。
createObjectChange struct { //创建对象的日志。 undo方法就是从StateDB中删除创建的对象。
account *common.Address
}
func (ch createObjectChange) undo(s *StateDB) {
delete(s.stateObjects, *ch.account)
delete(s.stateObjectsDirty, *ch.account)
}
// 对于stateObject的修改， undo方法就是把值改为原来的对象。
resetObjectChange struct {
prev *stateObject
}
func (ch resetObjectChange) undo(s *StateDB) {
s.setStateObject(ch.prev)
}
// 自杀的更改。自杀应该是删除账号，但是如果没有commit的化，对象还没有从stateDB删除。
suicideChange struct {
account *common.Address
prev bool // whether account had already suicided
prevbalance *big.Int
}
func (ch suicideChange) undo(s *StateDB) {
obj := s.getStateObject(*ch.account)
if obj != nil {
obj.suicided = ch.prev
obj.setBalance(ch.prevbalance)
}
}
// Changes to individual accounts.
balanceChange struct {
account *common.Address
prev *big.Int
}
nonceChange struct {
account *common.Address
prev uint64
}
storageChange struct {
account *common.Address
key, prevalue common.Hash
}
codeChange struct {
account *common.Address
prevcode, prevhash []byte
}
func (ch balanceChange) undo(s *StateDB) {
s.getStateObject(*ch.account).setBalance(ch.prev)
}
func (ch nonceChange) undo(s *StateDB) {
s.getStateObject(*ch.account).setNonce(ch.prev)
}
func (ch codeChange) undo(s *StateDB) {
s.getStateObject(*ch.account).setCode(common.BytesToHash(ch.prevhash), ch.prevcode)
}
func (ch storageChange) undo(s *StateDB) {
s.getStateObject(*ch.account).setState(ch.key, ch.prevalue)
}
// 我理解是DAO事件的退款处理
refundChange struct {
prev *big.Int
}
func (ch refundChange) undo(s *StateDB) {
s.refund = ch.prev
}
// 增加了日志的修改
addLogChange struct {
txhash common.Hash
}
func (ch addLogChange) undo(s *StateDB) {
logs := s.logs[ch.txhash]
if len(logs) == 1 {
delete(s.logs, ch.txhash)
} else {
s.logs[ch.txhash] = logs[:len(logs)-1]
}
s.logSize--
}
// 这个是增加 VM看到的 SHA3的 原始byte[], 增加SHA3 hash -> byte[] 的对应关系
addPreimageChange struct {
hash common.Hash
}
func (ch addPreimageChange) undo(s *StateDB) {
delete(s.preimages, ch.hash)
}
touchChange struct {
account *common.Address
prev bool
prevDirty bool
}
var ripemd = common.HexToAddress("0000000000000000000000000000000000000003")
func (ch touchChange) undo(s *StateDB) {
if !ch.prev && *ch.account != ripemd {
s.getStateObject(*ch.account).touched = ch.prev
if !ch.prevDirty {
delete(s.stateObjectsDirty, *ch.account)
}
}
}
## state_object.go
stateObject表示正在修改的以太坊帐户。
数据结构
type Storage map[common.Hash]common.Hash
// stateObject represents an Ethereum account which is being modified.
// stateObject表示正在修改的以太坊帐户。
// 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.
使用模式如下：
首先你需要获得一个state_object。
帐户值可以通过对象访问和修改。
最后，调用CommitTrie将修改后的存储trie写入数据库。
type stateObject struct {
address common.Address
addrHash common.Hash // hash of ethereum address of the account 以太坊账号地址的hash值
data Account // 这个是实际的以太坊账号的信息
db *StateDB //状态数据库
// 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.
//
数据库错误。
stateObject会被共识算法的核心和VM使用，在这些代码内部无法处理数据库级别的错误。
在数据库读取期间发生的任何错误都会在这里被存储，最终将由StateDB.Commit返回。
dbErr error
// Write caches. 写缓存
trie Trie // storage trie, which becomes non-nil on first access 用户的存储trie ，在第一次访问的时候变得非空
code Code // contract bytecode, which gets set when code is loaded 合约代码，当代码被加载的时候被设置
cachedStorage Storage // Storage entry cache to avoid duplicate reads 用户存储对象的缓存，用来避免重复读
dirtyStorage Storage // Storage entries that need to be flushed to disk 需要刷入磁盘的用户存储对象
// Cache flags. Cache 标志
// When an object is marked suicided it will be delete from the trie
// during the "update" phase of the state transition.
// 当一个对象被标记为自杀时，它将在状态转换的“更新”阶段期间从树中删除。
dirtyCode bool // true if the code was updated 如果代码被更新，会设置为true
suicided bool
touched bool
deleted bool
onDirty func(addr common.Address) // Callback method to mark a state object newly dirty 第一次被设置为drity的时候会被调用。
}
// Account is the Ethereum consensus representation of accounts.
// These objects are stored in the main account trie.
// 帐户是以太坊共识表示的帐户。 这些对象存储在main account trie。
type Account struct {
Nonce uint64
Balance *big.Int
Root common.Hash // merkle root of the storage trie
CodeHash []byte
}
构造函数
// newObject creates a state object.
func newObject(db *StateDB, address common.Address, data Account, onDirty func(addr common.Address)) *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,
cachedStorage: make(Storage),
dirtyStorage: make(Storage),
onDirty: onDirty,
}
}
RLP的编码方式，只会编码 Account对象。
// EncodeRLP implements rlp.Encoder.
func (c *stateObject) EncodeRLP(w io.Writer) error {
return rlp.Encode(w, c.data)
}
一些状态改变的函数。
func (self *stateObject) markSuicided() {
self.suicided = true
if self.onDirty != nil {
self.onDirty(self.Address())
self.onDirty = nil
}
}
func (c *stateObject) touch() {
c.db.journal = append(c.db.journal, touchChange{
account: &c.address,
prev: c.touched,
prevDirty: c.onDirty == nil,
})
if c.onDirty != nil {
c.onDirty(c.Address())
c.onDirty = nil
}
c.touched = true
}
Storage的处理
// getTrie返回账户的Storage Trie
func (c *stateObject) getTrie(db Database) Trie {
if c.trie == nil {
var err error
c.trie, err = db.OpenStorageTrie(c.addrHash, c.data.Root)
if err != nil {
c.trie, _ = db.OpenStorageTrie(c.addrHash, common.Hash{})
c.setError(fmt.Errorf("can't create storage trie: %v", err))
}
}
return c.trie
}
// GetState returns a value in account storage.
// GetState 返回account storage 的一个值，这个值的类型是Hash类型。
// 说明account storage里面只能存储hash值？
// 如果缓存里面存在就从缓存里查找，否则从数据库里面查询。然后存储到缓存里面。
func (self *stateObject) GetState(db Database, key common.Hash) common.Hash {
value, exists := self.cachedStorage[key]
if exists {
return value
}
// Load from DB in case it is missing.
enc, err := self.getTrie(db).TryGet(key[:])
if err != nil {
self.setError(err)
return common.Hash{}
}
if len(enc) > 0 {
_, content, _, err := rlp.Split(enc)
if err != nil {
self.setError(err)
}
value.SetBytes(content)
}
if (value != common.Hash{}) {
self.cachedStorage[key] = value
}
return value
}
// SetState updates a value in account storage.
// 往 account storeage 里面设置一个值 key value 的类型都是Hash类型。
func (self *stateObject) SetState(db Database, key, value common.Hash) {
self.db.journal = append(self.db.journal, storageChange{
account: &self.address,
key: key,
prevalue: self.GetState(db, key),
})
self.setState(key, value)
}
func (self *stateObject) setState(key, value common.Hash) {
self.cachedStorage[key] = value
self.dirtyStorage[key] = value
if self.onDirty != nil {
self.onDirty(self.Address())
self.onDirty = nil
}
}
提交 Commit
// CommitTrie the storage trie of the object to dwb.
// This updates the trie root.
// 步骤，首先打开，然后修改，然后提交或者回滚
func (self *stateObject) CommitTrie(db Database, dbw trie.DatabaseWriter) error {
self.updateTrie(db) // updateTrie把修改过的缓存写入Trie树
if self.dbErr != nil {
return self.dbErr
}
root, err := self.trie.CommitTo(dbw)
if err == nil {
self.data.Root = root
}
return err
}
// updateTrie writes cached storage modifications into the object's storage trie.
func (self *stateObject) updateTrie(db Database) Trie {
tr := self.getTrie(db)
for key, value := range self.dirtyStorage {
delete(self.dirtyStorage, key)
if (value == common.Hash{}) {
self.setError(tr.TryDelete(key[:]))
continue
}
// Encoding []byte cannot fail, ok to ignore the error.
v, _ := rlp.EncodeToBytes(bytes.TrimLeft(value[:], "\x00"))
self.setError(tr.TryUpdate(key[:], v))
}
return tr
}
// UpdateRoot sets the trie root to the current root hash of
// 把账号的root设置为当前的trie树的跟。
func (self *stateObject) updateRoot(db Database) {
self.updateTrie(db)
self.data.Root = self.trie.Hash()
}
额外的一些功能 ，deepCopy提供了state_object的深拷贝。
func (self *stateObject) deepCopy(db *StateDB, onDirty func(addr common.Address)) *stateObject {
stateObject := newObject(db, self.address, self.data, onDirty)
if self.trie != nil {
stateObject.trie = db.db.CopyTrie(self.trie)
}
stateObject.code = self.code
stateObject.dirtyStorage = self.dirtyStorage.Copy()
stateObject.cachedStorage = self.dirtyStorage.Copy()
stateObject.suicided = self.suicided
stateObject.dirtyCode = self.dirtyCode
stateObject.deleted = self.deleted
return stateObject
}
## statedb.go
stateDB用来存储以太坊中关于merkle trie的所有内容。 StateDB负责缓存和存储嵌套状态。 这是检索合约和账户的一般查询界面：
数据结构
type StateDB struct {
db Database // 后端的数据库
trie Trie // trie树 main account trie
// This map holds 'live' objects, which will get modified while processing a state transition.
// 下面的Map用来存储当前活动的对象，这些对象在状态转换的时候会被修改。
// stateObjects 用来缓存对象
// stateObjectsDirty用来缓存被修改过的对象。
stateObjects map[common.Address]*stateObject
stateObjectsDirty map[common.Address]struct{}
// 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
// The refund counter, also used by state transitioning.
// refund计数器。 暂时还不清楚功能。
refund *big.Int
thash, bhash common.Hash //当前的transaction hash 和block hash
txIndex int // 当前的交易的index
logs map[common.Hash][]*types.Log // 日志 key是交易的hash值
logSize uint
preimages map[common.Hash][]byte // EVM计算的 SHA3->byte[]的映射关系
// Journal of state modifications. This is the backbone of
// Snapshot and RevertToSnapshot.
// 状态修改日志。 这是Snapshot和RevertToSnapshot的支柱。
journal journal
validRevisions []revision
nextRevisionId int
lock sync.Mutex
}
构造函数
// 一般的用法 statedb, _ := state.New(common.Hash{}, state.NewDatabase(db))
// Create a new state from a given trie
func New(root common.Hash, db Database) (*StateDB, error) {
tr, err := db.OpenTrie(root)
if err != nil {
return nil, err
}
return &StateDB{
db: db,
trie: tr,
stateObjects: make(map[common.Address]*stateObject),
stateObjectsDirty: make(map[common.Address]struct{}),
refund: new(big.Int),
logs: make(map[common.Hash][]*types.Log),
preimages: make(map[common.Hash][]byte),
}, nil
}
### 对于Log的处理
state提供了Log的处理，这比较意外，因为Log实际上是存储在区块链中的，并没有存储在state trie中, state提供Log的处理， 使用了基于下面的几个函数。 奇怪的是暂时没看到如何删除logs里面的信息，如果不删除的话，应该会越积累越多。 TODO logs 删除
Prepare函数，在交易执行开始被执行。
AddLog函数，在交易执行过程中被VM执行。添加日志。同时把日志和交易关联起来，添加部分交易的信息。
GetLogs函数，交易完成取走。
// Prepare sets the current transaction hash and index and block hash which is
// used when the EVM emits new state logs.
func (self *StateDB) Prepare(thash, bhash common.Hash, ti int) {
self.thash = thash
self.bhash = bhash
self.txIndex = ti
}
func (self *StateDB) AddLog(log *types.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) []*types.Log {
return self.logs[hash]
}
func (self *StateDB) Logs() []*types.Log {
var logs []*types.Log
for _, lgs := range self.logs {
logs = append(logs, lgs...)
}
return logs
}
### stateObject处理
getStateObject,首先从缓存里面获取，如果没有就从trie树里面获取，并加载到缓存。
// 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, err := self.trie.TryGet(addr[:])
if len(enc) == 0 {
self.setError(err)
return nil
}
var data Account
if err := rlp.DecodeBytes(enc, &data); err != nil {
log.Error("Failed to decode state object", "addr", addr, "err", err)
return nil
}
// Insert into the live set.
obj := newObject(self, addr, data, self.MarkStateObjectDirty)
self.setStateObject(obj)
return obj
}
MarkStateObjectDirty， 设置一个stateObject为Dirty。 直接往stateObjectDirty对应的地址插入一个空结构体。
// 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{}{}
}
### 快照和回滚功能
Snapshot可以创建一个快照， 然后通过 RevertToSnapshot可以回滚到哪个状态，这个功能是通过journal来做到的。 每一步的修改都会往journal里面添加一个undo日志。 如果需要回滚只需要执行undo日志就行了。
// 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]
}
### 获取中间状态的 root hash值
IntermediateRoot 用来计算当前的state trie的root的hash值。这个方法会在交易执行的过程中被调用。会被存入 transaction receipt
Finalise方法会调用update方法把存放在cache层的修改写入到trie数据库里面。 但是这个时候还没有写入底层的数据库。 还没有调用commit，数据还在内存里面，还没有落地成文件。
// Finalise finalises the state by removing the self destructed objects
// and clears the journal as well as the refunds.
func (s *StateDB) Finalise(deleteEmptyObjects bool) {
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()
}
// 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 {
s.Finalise(deleteEmptyObjects)
return s.trie.Hash()
}
### commit方法
CommitTo用来提交更改。
// CommitTo writes the state to the given database.
func (s *StateDB) CommitTo(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)
log.Debug("Trie cache stats after commit", "misses", trie.CacheMisses(), "unloads", trie.CacheUnloads())
return root, err
}
### 总结
state包提供了用户和合约的状态管理的功能。 管理了状态和合约的各种状态转换。 cache， trie， 数据库。 日志和回滚功能。