path: root/core/state/database.go

// Copyright 2017 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 (
    "fmt"
    "sync"

    "github.com/dexon-foundation/dexon/common"
    "github.com/dexon-foundation/dexon/ethdb"
    "github.com/dexon-foundation/dexon/trie"
    lru "github.com/hashicorp/golang-lru"
)

// Trie cache generation limit after which to evict 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
)

// Database wraps access to tries and contract code.
type Database interface {
    // OpenTrie opens the main account trie.
    OpenTrie(root common.Hash) (Trie, error)

    // OpenStorageTrie opens the storage trie of an account.
    OpenStorageTrie(addrHash, root common.Hash) (Trie, error)

    // CopyTrie returns an independent copy of the given trie.
    CopyTrie(Trie) Trie

    // ContractCode retrieves a particular contract's code.
    ContractCode(addrHash, codeHash common.Hash) ([]byte, error)

    // ContractCodeSize retrieves a particular contracts code's size.
    ContractCodeSize(addrHash, codeHash common.Hash) (int, error)

    // TrieDB retrieves the low level trie database used for data storage.
    TrieDB() *trie.Database
}

// Trie is a Ethereum Merkle Trie.
type Trie interface {
    TryGet(key []byte) ([]byte, error)
    TryUpdate(key, value []byte) error
    TryDelete(key []byte) error
    Commit(onleaf trie.LeafCallback) (common.Hash, error)
    Hash() common.Hash
    NodeIterator(startKey []byte) trie.NodeIterator
    GetKey([]byte) []byte // TODO(fjl): remove this when SecureTrie is removed
    Prove(key []byte, fromLevel uint, proofDb ethdb.Putter) error
}

// NewDatabase creates a backing store for state. The returned database is safe for
// concurrent use and retains a few recent expanded trie nodes in memory. To keep
// more historical state in memory, use the NewDatabaseWithCache constructor.
func NewDatabase(db ethdb.Database) Database {
    return NewDatabaseWithCache(db, 0)
}

// NewDatabase creates a backing store for state. The returned database is safe for
// concurrent use and retains both a few recent expanded trie nodes in memory, as
// well as a lot of collapsed RLP trie nodes in a large memory cache.
func NewDatabaseWithCache(db ethdb.Database, cache int) Database {
    csc, _ := lru.New(codeSizeCacheSize)
    return &cachingDB{
        db:            trie.NewDatabaseWithCache(db, cache),
        codeSizeCache: csc,
    }
}

type cachingDB struct {
    db            *trie.Database
    mu            sync.Mutex
    pastTries     []*trie.SecureTrie
    codeSizeCache *lru.Cache
}

// OpenTrie opens the main account trie.
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) 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)
    }
}

// OpenStorageTrie opens the storage trie of an account.
func (db *cachingDB) OpenStorageTrie(addrHash, root common.Hash) (Trie, error) {
    return trie.NewSecure(root, db.db, 0)
}

// CopyTrie returns an independent copy of the given trie.
func (db *cachingDB) CopyTrie(t Trie) Trie {
    switch t := t.(type) {
    case cachedTrie:
        return cachedTrie{t.SecureTrie.Copy(), db}
    case *trie.SecureTrie:
        return t.Copy()
    default:
        panic(fmt.Errorf("unknown trie type %T", t))
    }
}

// ContractCode retrieves a particular contract's code.
func (db *cachingDB) ContractCode(addrHash, codeHash common.Hash) ([]byte, error) {
    code, err := db.db.Node(codeHash)
    if err == nil {
        db.codeSizeCache.Add(codeHash, len(code))
    }
    return code, err
}

// ContractCodeSize retrieves a particular contracts code's size.
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)
    return len(code), err
}

// TrieDB retrieves any intermediate trie-node caching layer.
func (db *cachingDB) TrieDB() *trie.Database {
    return db.db
}

// cachedTrie inserts its trie into a cachingDB on commit.
type cachedTrie struct {
    *trie.SecureTrie
    db *cachingDB
}

func (m cachedTrie) Commit(onleaf trie.LeafCallback) (common.Hash, error) {
    root, err := m.SecureTrie.Commit(onleaf)
    if err == nil {
        m.db.pushTrie(m.SecureTrie)
    }
    return root, err
}

func (m cachedTrie) Prove(key []byte, fromLevel uint, proofDb ethdb.Putter) error {
    return m.SecureTrie.Prove(key, fromLevel, proofDb)
}