erigon-pulse/core/blockchain.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 core implements the Ethereum consensus protocol.
package core

import (
	"context"
	"errors"
	"fmt"
	"io"
	"math/big"
	"sort"
	"sync"
	"sync/atomic"
	"time"

	lru "github.com/hashicorp/golang-lru"

	"github.com/ledgerwatch/turbo-geth/common"
	"github.com/ledgerwatch/turbo-geth/common/debug"
	"github.com/ledgerwatch/turbo-geth/common/mclock"
	"github.com/ledgerwatch/turbo-geth/common/prque"
	"github.com/ledgerwatch/turbo-geth/consensus"
	"github.com/ledgerwatch/turbo-geth/consensus/misc"
	"github.com/ledgerwatch/turbo-geth/core/rawdb"
	"github.com/ledgerwatch/turbo-geth/core/state"
	"github.com/ledgerwatch/turbo-geth/core/types"
	"github.com/ledgerwatch/turbo-geth/core/vm"
	"github.com/ledgerwatch/turbo-geth/ethdb"
	"github.com/ledgerwatch/turbo-geth/event"
	"github.com/ledgerwatch/turbo-geth/log"
	"github.com/ledgerwatch/turbo-geth/metrics"
	"github.com/ledgerwatch/turbo-geth/params"
	"github.com/ledgerwatch/turbo-geth/rlp"
)

var (
	headBlockGauge     = metrics.NewRegisteredGauge("chain/head/block", nil)
	headHeaderGauge    = metrics.NewRegisteredGauge("chain/head/header", nil)
	headFastBlockGauge = metrics.NewRegisteredGauge("chain/head/receipt", nil)

	accountReadTimer   = metrics.NewRegisteredTimer("chain/account/reads", nil)
	accountHashTimer   = metrics.NewRegisteredTimer("chain/account/hashes", nil)
	accountUpdateTimer = metrics.NewRegisteredTimer("chain/account/updates", nil)
	accountCommitTimer = metrics.NewRegisteredTimer("chain/account/commits", nil)

	storageReadTimer   = metrics.NewRegisteredTimer("chain/storage/reads", nil)
	storageHashTimer   = metrics.NewRegisteredTimer("chain/storage/hashes", nil)
	storageUpdateTimer = metrics.NewRegisteredTimer("chain/storage/updates", nil)
	storageCommitTimer = metrics.NewRegisteredTimer("chain/storage/commits", nil)

	blockInsertTimer     = metrics.NewRegisteredTimer("chain/inserts", nil)
	blockValidationTimer = metrics.NewRegisteredTimer("chain/validation", nil)
	blockExecutionTimer  = metrics.NewRegisteredTimer("chain/execution", nil)
	blockWriteTimer      = metrics.NewRegisteredTimer("chain/write", nil)
	blockReorgAddMeter   = metrics.NewRegisteredMeter("chain/reorg/drop", nil)
	blockReorgDropMeter  = metrics.NewRegisteredMeter("chain/reorg/add", nil)

	blockPrefetchExecuteTimer   = metrics.NewRegisteredTimer("chain/prefetch/executes", nil)
	blockPrefetchInterruptMeter = metrics.NewRegisteredMeter("chain/prefetch/interrupts", nil)

	errInsertionInterrupted = errors.New("insertion is interrupted")

	// ErrNotFound is returned when sought data isn't found.
	ErrNotFound = errors.New("data not found")
)

const (
	bodyCacheLimit      = 256
	blockCacheLimit     = 256
	receiptsCacheLimit  = 32
	txLookupCacheLimit  = 1024
	maxFutureBlocks     = 256
	maxTimeFutureBlocks = 30
	badBlockLimit       = 10
	triesInMemory       = 128

	// BlockChainVersion ensures that an incompatible database forces a resync from scratch.
	//
	// Changelog:
	//
	// - Version 4
	//   The following incompatible database changes were added:
	//   * the `BlockNumber`, `TxHash`, `TxIndex`, `BlockHash` and `Index` fields of log are deleted
	//   * the `Bloom` field of receipt is deleted
	//   * the `BlockIndex` and `TxIndex` fields of txlookup are deleted
	// - Version 5
	//  The following incompatible database changes were added:
	//    * the `TxHash`, `GasCost`, and `ContractAddress` fields are no longer stored for a receipt
	//    * the `TxHash`, `GasCost`, and `ContractAddress` fields are computed by looking up the
	//      receipts' corresponding block
	// - Version 6
	//  The following incompatible database changes were added:
	//    * Transaction lookup information stores the corresponding block number instead of block hash
	// - Version 7
	//  The following incompatible database changes were added:
	//    * Use freezer as the ancient database to maintain all ancient data
	BlockChainVersion uint64 = 7
)

// CacheConfig contains the configuration values for the trie caching/pruning
// that's resident in a blockchain.
type CacheConfig struct {
	Pruning             bool
	TrieCleanLimit      int           // Memory allowance (MB) to use for caching trie nodes in memory
	TrieCleanNoPrefetch bool          // Whether to disable heuristic state prefetching for followup blocks
	TrieDirtyLimit      int           // Memory limit (MB) at which to start flushing dirty trie nodes to disk
	TrieTimeLimit       time.Duration // Time limit after which to flush the current in-memory trie to disk

	BlocksBeforePruning uint64
	BlocksToPrune       uint64
	PruneTimeout        time.Duration
	ArchiveSyncInterval uint64
	DownloadOnly        bool
	NoHistory           bool
}

// BlockChain represents the canonical chain given a database with a genesis
// block. The Blockchain manages chain imports, reverts, chain reorganisations.
//
// Importing blocks in to the block chain happens according to the set of rules
// defined by the two stage Validator. Processing of blocks is done using the
// Processor which processes the included transaction. The validation of the state
// is done in the second part of the Validator. Failing results in aborting of
// the import.
//
// The BlockChain also helps in returning blocks from **any** chain included
// in the database as well as blocks that represents the canonical chain. It's
// important to note that GetBlock can return any block and does not need to be
// included in the canonical one where as GetBlockByNumber always represents the
// canonical chain.
type BlockChain struct {
	chainConfig *params.ChainConfig // Chain & network configuration
	cacheConfig *CacheConfig        // Cache configuration for pruning

	db     ethdb.DbWithPendingMutations // Low level persistent database to store final content in
	triegc *prque.Prque                 // Priority queue mapping block numbers to tries to gc
	gcproc time.Duration                // Accumulates canonical block processing for trie dumping

	hc            *HeaderChain
	rmLogsFeed    event.Feed
	chainFeed     event.Feed
	chainSideFeed event.Feed
	chainHeadFeed event.Feed
	logsFeed      event.Feed
	blockProcFeed event.Feed
	scope         event.SubscriptionScope
	genesisBlock  *types.Block

	chainmu sync.RWMutex // blockchain insertion lock

	currentBlock     atomic.Value // Current head of the block chain
	committedBlock   atomic.Value // Committed head of the block chain
	currentFastBlock atomic.Value // Current head of the fast-sync chain (may be above the block chain!)

	trieDbState   *state.TrieDbState
	bodyCache     *lru.Cache // Cache for the most recent block bodies
	bodyRLPCache  *lru.Cache // Cache for the most recent block bodies in RLP encoded format
	receiptsCache *lru.Cache // Cache for the most recent receipts per block
	blockCache    *lru.Cache // Cache for the most recent entire blocks
	txLookupCache *lru.Cache // Cache for the most recent transaction lookup data.
	futureBlocks  *lru.Cache // future blocks are blocks added for later processing

	quit    chan struct{} // blockchain quit channel
	running int32         // running must be called atomically
	// procInterrupt must be atomically called
	procInterrupt int32          // interrupt signaler for block processing
	wg            sync.WaitGroup // chain processing wait group for shutting down
	quitMu        sync.RWMutex

	engine     consensus.Engine
	validator  Validator  // Block and state validator interface
	prefetcher Prefetcher // Block state prefetcher interface
	processor  Processor  // Block transaction processor interface
	vmConfig   vm.Config

	badBlocks           *lru.Cache                     // Bad block cache
	shouldPreserve      func(*types.Block) bool        // Function used to determine whether should preserve the given block.
	terminateInsert     func(common.Hash, uint64) bool // Testing hook used to terminate ancient receipt chain insertion.
	highestKnownBlock   uint64
	highestKnownBlockMu sync.Mutex
	enableReceipts      bool // Whether receipts need to be written to the database
	enableTxLookupIndex bool // Whether we store tx lookup index into the database
	enablePreimages     bool // Whether we store preimages into the database
	resolveReads        bool
	pruner              Pruner
}

// NewBlockChain returns a fully initialised block chain using information
// available in the database. It initialises the default Ethereum Validator and
// Processor.
func NewBlockChain(db ethdb.Database, cacheConfig *CacheConfig, chainConfig *params.ChainConfig, engine consensus.Engine, vmConfig vm.Config, shouldPreserve func(block *types.Block) bool) (*BlockChain, error) {
	if cacheConfig == nil {
		cacheConfig = &CacheConfig{
			Pruning:             false,
			BlocksBeforePruning: 1024,
			TrieCleanLimit:      256,
			TrieDirtyLimit:      256,
			TrieTimeLimit:       5 * time.Minute,
			DownloadOnly:        false,
			NoHistory:           false,
		}
	}
	if cacheConfig.ArchiveSyncInterval == 0 {
		cacheConfig.ArchiveSyncInterval = 1024
	}

	bodyCache, _ := lru.New(bodyCacheLimit)
	bodyRLPCache, _ := lru.New(bodyCacheLimit)
	receiptsCache, _ := lru.New(receiptsCacheLimit)
	blockCache, _ := lru.New(blockCacheLimit)
	txLookupCache, _ := lru.New(txLookupCacheLimit)
	futureBlocks, _ := lru.New(maxFutureBlocks)
	badBlocks, _ := lru.New(badBlockLimit)
	cdb := db.NewBatch()

	bc := &BlockChain{
		chainConfig:         chainConfig,
		cacheConfig:         cacheConfig,
		db:                  cdb,
		triegc:              prque.New(nil),
		quit:                make(chan struct{}),
		shouldPreserve:      shouldPreserve,
		bodyCache:           bodyCache,
		bodyRLPCache:        bodyRLPCache,
		receiptsCache:       receiptsCache,
		blockCache:          blockCache,
		txLookupCache:       txLookupCache,
		futureBlocks:        futureBlocks,
		engine:              engine,
		vmConfig:            vmConfig,
		badBlocks:           badBlocks,
		enableTxLookupIndex: true,
		enableReceipts:      false,
		enablePreimages:     true,
	}
	bc.validator = NewBlockValidator(chainConfig, bc, engine)
	bc.prefetcher = newStatePrefetcher(chainConfig, bc, engine)
	bc.processor = NewStateProcessor(chainConfig, bc, engine)

	var err error
	bc.hc, err = NewHeaderChain(cdb, chainConfig, engine, bc.getProcInterrupt)
	if err != nil {
		return nil, err
	}
	bc.genesisBlock = bc.GetBlockByNumber(0)
	if bc.genesisBlock == nil {
		return nil, ErrNoGenesis
	}

	if err := bc.loadLastState(); err != nil {
		return nil, err
	}
	// The first thing the node will do is reconstruct the verification data for
	// the head block (ethash cache or clique voting snapshot). Might as well do
	// it in advance.
	bc.engine.VerifyHeader(bc, bc.CurrentHeader(), true)

	if frozen, err := bc.db.Ancients(); err == nil && frozen > 0 {
		var (
			needRewind bool
			low        uint64
		)
		// The head full block may be rolled back to a very low height due to
		// blockchain repair. If the head full block is even lower than the ancient
		// chain, truncate the ancient store.
		fullBlock := bc.CurrentBlock()
		if fullBlock != nil && fullBlock != bc.genesisBlock && fullBlock.NumberU64() < frozen-1 {
			needRewind = true
			low = fullBlock.NumberU64()
		}
		// In fast sync, it may happen that ancient data has been written to the
		// ancient store, but the LastFastBlock has not been updated, truncate the
		// extra data here.
		fastBlock := bc.CurrentFastBlock()
		if fastBlock != nil && fastBlock.NumberU64() < frozen-1 {
			needRewind = true
			if fastBlock.NumberU64() < low || low == 0 {
				low = fastBlock.NumberU64()
			}
		}
		if needRewind {
			var hashes []common.Hash
			previous := bc.CurrentHeader().Number.Uint64()
			for i := low + 1; i <= bc.CurrentHeader().Number.Uint64(); i++ {
				hashes = append(hashes, rawdb.ReadCanonicalHash(bc.db, i))
			}
			bc.Rollback(hashes)
			log.Warn("Truncate ancient chain", "from", previous, "to", low)
		}
	}
	// Check the current state of the block hashes and make sure that we do not have any of the bad blocks in our chain
	for hash := range BadHashes {
		if header := bc.GetHeaderByHash(hash); header != nil {
			// get the canonical block corresponding to the offending header's number
			headerByNumber := bc.GetHeaderByNumber(header.Number.Uint64())
			// make sure the headerByNumber (if present) is in our current canonical chain
			if headerByNumber != nil && headerByNumber.Hash() == header.Hash() {
				log.Error("Found bad hash, rewinding chain", "number", header.Number, "hash", header.ParentHash)
				bc.SetHead(header.Number.Uint64() - 1)
				log.Error("Chain rewind was successful, resuming normal operation")
			}
		}
	}
	// Take ownership of this particular state
	go bc.update()
	if cacheConfig.Pruning {
		var innerErr error
		bc.pruner, innerErr = NewBasicPruner(db, bc, bc.cacheConfig)
		if innerErr != nil {
			log.Error("Pruner init error", "err", innerErr)
			return nil, innerErr
		}

		innerErr = bc.pruner.Start()
		if innerErr != nil {
			log.Error("Pruner start error", "err", innerErr)
			return nil, innerErr
		}
	}
	return bc, nil
}

func (bc *BlockChain) SetResolveReads(rr bool) {
	bc.resolveReads = rr
}

func (bc *BlockChain) EnableReceipts(er bool) {
	bc.enableReceipts = er
}

func (bc *BlockChain) EnableTxLookupIndex(et bool) {
	bc.enableTxLookupIndex = et
}

func (bc *BlockChain) EnablePreimages(ep bool) {
	bc.enablePreimages = ep
}

func (bc *BlockChain) GetTrieDbState() (*state.TrieDbState, error) {
	if bc.trieDbState == nil && !bc.cacheConfig.DownloadOnly {
		currentBlockNr := bc.CurrentBlock().NumberU64()
		trieDbState, err := bc.GetTrieDbStateByBlock(bc.CurrentBlock().Header().Root, currentBlockNr)
		if err != nil {
			return nil, err
		}
		bc.setTrieDbState(trieDbState)
		log.Info("Creation complete.")
	}
	return bc.trieDbState, nil
}

func (bc *BlockChain) setTrieDbState(trieDbState *state.TrieDbState) {
	log.Warn("trieDbState has been changed", "isNil", trieDbState == nil, "callers", debug.Callers(20))
	bc.trieDbState = trieDbState
}

func (bc *BlockChain) GetTrieDbStateByBlock(root common.Hash, blockNr uint64) (*state.TrieDbState, error) {
	if bc.trieDbState == nil || bc.trieDbState.LastRoot() != root || bc.trieDbState.GetBlockNr() != blockNr {
		log.Info("Creating IntraBlockState from latest state", "block", blockNr, "isNIl", bc.trieDbState == nil, "callers", debug.Callers(20))
		tds := state.NewTrieDbState(root, bc.db, blockNr)
		tds.SetNoHistory(bc.NoHistory())
		tds.SetResolveReads(bc.resolveReads)
		tds.EnablePreimages(bc.enablePreimages)

		log.Info("Creation complete.")
		return tds, nil
	}
	return bc.trieDbState, nil
}

func (bc *BlockChain) getProcInterrupt() bool {
	return atomic.LoadInt32(&bc.procInterrupt) == 1
}

// GetVMConfig returns the block chain VM config.
func (bc *BlockChain) GetVMConfig() *vm.Config {
	return &bc.vmConfig
}

// empty returns an indicator whether the blockchain is empty.
// Note, it's a special case that we connect a non-empty ancient
// database with an empty node, so that we can plugin the ancient
// into node seamlessly.
func (bc *BlockChain) empty() bool {
	genesis := bc.genesisBlock.Hash()
	for _, hash := range []common.Hash{rawdb.ReadHeadBlockHash(bc.db), rawdb.ReadHeadHeaderHash(bc.db), rawdb.ReadHeadFastBlockHash(bc.db)} {
		if hash != genesis {
			return false
		}
	}
	return true
}

// loadLastState loads the last known chain state from the database. This method
// assumes that the chain manager mutex is held.
func (bc *BlockChain) loadLastState() error {
	// Restore the last known head block
	head := rawdb.ReadHeadBlockHash(bc.db)
	if head == (common.Hash{}) {
		// Corrupt or empty database, init from scratch
		log.Warn("Empty database, resetting chain")
		return bc.Reset()
	}
	// Make sure the entire head block is available
	currentBlock := bc.GetBlockByHash(head)
	if currentBlock == nil {
		// Corrupt or empty database, init from scratch
		log.Warn("Head block missing, resetting chain", "hash", head)
		return bc.Reset()
	}
	// Make sure the state associated with the block is available
	// Everything seems to be fine, set as the head block
	bc.currentBlock.Store(currentBlock)
	headBlockGauge.Update(int64(currentBlock.NumberU64()))

	// Restore the last known head header
	currentHeader := currentBlock.Header()
	if head := rawdb.ReadHeadHeaderHash(bc.db); head != (common.Hash{}) {
		if header := bc.GetHeaderByHash(head); header != nil {
			currentHeader = header
		}
	}
	bc.hc.SetCurrentHeader(bc.db, currentHeader)

	// Restore the last known head fast block
	bc.currentFastBlock.Store(currentBlock)
	headFastBlockGauge.Update(int64(currentBlock.NumberU64()))

	if head := rawdb.ReadHeadFastBlockHash(bc.db); head != (common.Hash{}) {
		if block := bc.GetBlockByHash(head); block != nil {
			bc.currentFastBlock.Store(block)
			headFastBlockGauge.Update(int64(block.NumberU64()))
		}
	}
	// Issue a status log for the user
	currentFastBlock := bc.CurrentFastBlock()

	headerTd := bc.GetTd(currentHeader.Hash(), currentHeader.Number.Uint64())
	blockTd := bc.GetTd(currentBlock.Hash(), currentBlock.NumberU64())
	fastTd := bc.GetTd(currentFastBlock.Hash(), currentFastBlock.NumberU64())

	log.Info("Loaded most recent local header", "number", currentHeader.Number, "hash", currentHeader.Hash(), "td", headerTd, "age", common.PrettyAge(time.Unix(int64(currentHeader.Time), 0)))
	log.Info("Loaded most recent local full block", "number", currentBlock.Number(), "hash", currentBlock.Hash(), "td", blockTd, "age", common.PrettyAge(time.Unix(int64(currentBlock.Time()), 0)))
	log.Info("Loaded most recent local fast block", "number", currentFastBlock.Number(), "hash", currentFastBlock.Hash(), "td", fastTd, "age", common.PrettyAge(time.Unix(int64(currentFastBlock.Time()), 0)))

	return nil
}

// SetHead rewinds the local chain to a new head. In the case of headers, everything
// above the new head will be deleted and the new one set. In the case of blocks
// though, the head may be further rewound if block bodies are missing (non-archive
// nodes after a fast sync).
func (bc *BlockChain) SetHead(head uint64) error {
	log.Warn("Rewinding blockchain", "target", head)

	bc.chainmu.Lock()
	defer bc.chainmu.Unlock()

	updateFn := func(db rawdb.DatabaseWriter, header *types.Header) {
		// Rewind the block chain, ensuring we don't end up with a stateless head block
		if currentBlock := bc.CurrentBlock(); currentBlock != nil && header.Number.Uint64() < currentBlock.NumberU64() {
			newHeadBlock := bc.GetBlock(header.Hash(), header.Number.Uint64())
			if newHeadBlock == nil {
				newHeadBlock = bc.genesisBlock
			}
			rawdb.WriteHeadBlockHash(db, newHeadBlock.Hash())

			// Degrade the chain markers if they are explicitly reverted.
			// In theory we should update all in-memory markers in the
			// last step, however the direction of SetHead is from high
			// to low, so it's safe the update in-memory markers directly.
			bc.currentBlock.Store(newHeadBlock)
			headBlockGauge.Update(int64(newHeadBlock.NumberU64()))
		}

		// Rewind the fast block in a simpleton way to the target head
		if currentFastBlock := bc.CurrentFastBlock(); currentFastBlock != nil && header.Number.Uint64() < currentFastBlock.NumberU64() {
			newHeadFastBlock := bc.GetBlock(header.Hash(), header.Number.Uint64())
			// If either blocks reached nil, reset to the genesis state
			if newHeadFastBlock == nil {
				newHeadFastBlock = bc.genesisBlock
			}
			rawdb.WriteHeadFastBlockHash(db, newHeadFastBlock.Hash())

			// Degrade the chain markers if they are explicitly reverted.
			// In theory we should update all in-memory markers in the
			// last step, however the direction of SetHead is from high
			// to low, so it's safe the update in-memory markers directly.
			bc.currentFastBlock.Store(newHeadFastBlock)
			headFastBlockGauge.Update(int64(newHeadFastBlock.NumberU64()))
		}
	}

	// Rewind the header chain, deleting all block bodies until then
	delFn := func(db rawdb.DatabaseDeleter, hash common.Hash, num uint64) {
		// Ignore the error here since light client won't hit this path
		frozen, _ := bc.db.Ancients()
		if num+1 <= frozen {
			// Truncate all relative data(header, total difficulty, body, receipt
			// and canonical hash) from ancient store.
			if err := bc.db.TruncateAncients(num + 1); err != nil {
				log.Crit("Failed to truncate ancient data", "number", num, "err", err)
			}

			// Remove the hash <-> number mapping from the active store.
			rawdb.DeleteHeaderNumber(db, hash)
		} else {
			// Remove relative body and receipts from the active store.
			// The header, total difficulty and canonical hash will be
			// removed in the hc.SetHead function.
			rawdb.DeleteBody(db, hash, num)
			rawdb.DeleteReceipts(db, hash, num)
		}
		// Todo(rjl493456442) txlookup, bloombits, etc
	}
	bc.hc.SetHead(head, updateFn, delFn)

	// Clear out any stale content from the caches
	bc.bodyCache.Purge()
	bc.bodyRLPCache.Purge()
	bc.receiptsCache.Purge()
	bc.blockCache.Purge()
	bc.txLookupCache.Purge()
	bc.futureBlocks.Purge()

	return bc.loadLastState()
}

// FastSyncCommitHead sets the current head block to the one defined by the hash
// irrelevant what the chain contents were prior.
func (bc *BlockChain) FastSyncCommitHead(hash common.Hash) error {
	// Make sure that both the block as well at its state trie exists
	block := bc.GetBlockByHash(hash)
	if block == nil {
		return fmt.Errorf("non existent block [%x…]", hash[:4])
	}
	// If all checks out, manually set the head block
	bc.chainmu.Lock()
	bc.currentBlock.Store(block)
	headBlockGauge.Update(int64(block.NumberU64()))
	bc.chainmu.Unlock()

	log.Info("Committed new head block", "number", block.Number(), "hash", hash)
	return nil
}

// GasLimit returns the gas limit of the current HEAD block.
func (bc *BlockChain) GasLimit() uint64 {
	return bc.CurrentBlock().GasLimit()
}

// CurrentBlock retrieves the current head block of the canonical chain. The
// block is retrieved from the blockchain's internal cache.
func (bc *BlockChain) CurrentBlock() *types.Block {
	return bc.currentBlock.Load().(*types.Block)
}

// CurrentFastBlock retrieves the current fast-sync head block of the canonical
// chain. The block is retrieved from the blockchain's internal cache.
func (bc *BlockChain) CurrentFastBlock() *types.Block {
	return bc.currentFastBlock.Load().(*types.Block)
}

// Validator returns the current validator.
func (bc *BlockChain) Validator() Validator {
	return bc.validator
}

// Processor returns the current processor.
func (bc *BlockChain) Processor() Processor {
	return bc.processor
}

// State returns a new mutable state based on the current HEAD block.
func (bc *BlockChain) State() (*state.IntraBlockState, *state.DbState, error) {
	return bc.StateAt(bc.CurrentBlock().NumberU64())
}

// StateAt returns a new mutable state based on a particular point in time.
func (bc *BlockChain) StateAt(blockNr uint64) (*state.IntraBlockState, *state.DbState, error) {
	dbstate := state.NewDbState(bc.db, blockNr)
	return state.New(dbstate), dbstate, nil
}

// GetAddressFromItsHash returns the preimage of a given address hash.
func (bc *BlockChain) GetAddressFromItsHash(hash common.Hash) (common.Address, error) {
	var addr common.Address

	_, dbstate, err := bc.State()
	if err != nil {
		return addr, err
	}

	key := dbstate.GetKey(hash.Bytes())
	if len(key) != common.AddressLength {
		return addr, ErrNotFound
	}

	addr.SetBytes(key)
	return addr, nil
}

// Reset purges the entire blockchain, restoring it to its genesis state.
func (bc *BlockChain) Reset() error {
	return bc.ResetWithGenesisBlock(bc.genesisBlock)
}

// ResetWithGenesisBlock purges the entire blockchain, restoring it to the
// specified genesis state.
func (bc *BlockChain) ResetWithGenesisBlock(genesis *types.Block) error {
	// Dump the entire block chain and purge the caches
	if err := bc.SetHead(0); err != nil {
		return err
	}
	bc.chainmu.Lock()
	defer bc.chainmu.Unlock()

	rawdb.WriteTd(bc.db, genesis.Hash(), genesis.NumberU64(), genesis.Difficulty())
	rawdb.WriteBlock(context.Background(), bc.db, genesis)
	bc.writeHeadBlock(genesis)

	// Last update all in-memory chain markers
	bc.genesisBlock = genesis
	bc.currentBlock.Store(bc.genesisBlock)
	headBlockGauge.Update(int64(bc.genesisBlock.NumberU64()))
	bc.hc.SetGenesis(bc.genesisBlock.Header())
	bc.hc.SetCurrentHeader(bc.db, bc.genesisBlock.Header())
	bc.currentFastBlock.Store(bc.genesisBlock)
	headFastBlockGauge.Update(int64(bc.genesisBlock.NumberU64()))
	return nil
}

// Export writes the active chain to the given writer.
func (bc *BlockChain) Export(w io.Writer) error {
	return bc.ExportN(w, uint64(0), bc.CurrentBlock().NumberU64())
}

// ExportN writes a subset of the active chain to the given writer.
func (bc *BlockChain) ExportN(w io.Writer, first uint64, last uint64) error {
	bc.chainmu.RLock()
	defer bc.chainmu.RUnlock()

	if first > last {
		return fmt.Errorf("export failed: first (%d) is greater than last (%d)", first, last)
	}
	log.Info("Exporting batch of blocks", "count", last-first+1)

	start, reported := time.Now(), time.Now()
	for nr := first; nr <= last; nr++ {
		block := bc.GetBlockByNumber(nr)
		if block == nil {
			return fmt.Errorf("export failed on #%d: not found", nr)
		}
		if err := block.EncodeRLP(w); err != nil {
			return err
		}
		if time.Since(reported) >= statsReportLimit {
			log.Info("Exporting blocks", "exported", block.NumberU64()-first, "elapsed", common.PrettyDuration(time.Since(start)))
			reported = time.Now()
		}
	}
	return nil
}

// writeHeadBlock injects a new head block into the current block chain. This method
// assumes that the block is indeed a true head. It will also reset the head
// header and the head fast sync block to this very same block if they are older
// or if they are on a different side chain.
//
// Note, this function assumes that the `mu` mutex is held!
func (bc *BlockChain) writeHeadBlock(block *types.Block) {
	// If the block is on a side chain or an unknown one, force other heads onto it too
	updateHeads := rawdb.ReadCanonicalHash(bc.db, block.NumberU64()) != block.Hash()

	// Add the block to the canonical chain number scheme and mark as the head
	rawdb.WriteCanonicalHash(bc.db, block.Hash(), block.NumberU64())
	if bc.enableTxLookupIndex && !bc.cacheConfig.DownloadOnly {
		rawdb.WriteTxLookupEntries(bc.db, block)
	}
	rawdb.WriteHeadBlockHash(bc.db, block.Hash())

	if updateHeads {
		bc.hc.SetCurrentHeader(bc.db, block.Header())
		rawdb.WriteHeadFastBlockHash(bc.db, block.Hash())
	}

	// If the block is better than our head or is on a different chain, force update heads
	if updateHeads {
		bc.currentFastBlock.Store(block)
		headFastBlockGauge.Update(int64(block.NumberU64()))
	}
	bc.currentBlock.Store(block)
	headBlockGauge.Update(int64(block.NumberU64()))
}

// Genesis retrieves the chain's genesis block.
func (bc *BlockChain) Genesis() *types.Block {
	return bc.genesisBlock
}

// GetBody retrieves a block body (transactions and uncles) from the database by
// hash, caching it if found.
func (bc *BlockChain) GetBody(hash common.Hash) *types.Body {
	// Short circuit if the body's already in the cache, retrieve otherwise
	if cached, ok := bc.bodyCache.Get(hash); ok {
		body := cached.(*types.Body)
		return body
	}
	number := bc.hc.GetBlockNumber(bc.db, hash)
	if number == nil {
		return nil
	}
	body := rawdb.ReadBody(bc.db, hash, *number)
	if body == nil {
		return nil
	}
	// Cache the found body for next time and return
	bc.bodyCache.Add(hash, body)
	return body
}

// GetBodyRLP retrieves a block body in RLP encoding from the database by hash,
// caching it if found.
func (bc *BlockChain) GetBodyRLP(hash common.Hash) rlp.RawValue {
	// Short circuit if the body's already in the cache, retrieve otherwise
	if cached, ok := bc.bodyRLPCache.Get(hash); ok {
		return cached.(rlp.RawValue)
	}
	number := bc.hc.GetBlockNumber(bc.db, hash)
	if number == nil {
		return nil
	}
	body := rawdb.ReadBodyRLP(bc.db, hash, *number)
	if len(body) == 0 {
		return nil
	}
	// Cache the found body for next time and return
	bc.bodyRLPCache.Add(hash, body)
	return body
}

// HasBlock checks if a block is fully present in the database or not.
func (bc *BlockChain) HasBlock(hash common.Hash, number uint64) bool {
	if bc.blockCache.Contains(hash) {
		return true
	}
	return rawdb.HasBody(bc.db, hash, number)
}

// HasFastBlock checks if a fast block is fully present in the database or not.
func (bc *BlockChain) HasFastBlock(hash common.Hash, number uint64) bool {
	if !bc.HasBlock(hash, number) {
		return false
	}
	if bc.receiptsCache.Contains(hash) {
		return true
	}
	return rawdb.HasReceipts(bc.db, hash, number)
}

// HasBlockAndState checks if a block and associated state trie is fully present
// in the database or not, caching it if present.
func (bc *BlockChain) HasBlockAndState(hash common.Hash, number uint64) bool {
	// Check first that the block itself is known
	block := bc.GetBlock(hash, number)
	if block == nil {
		return false
	}
	return true
}

// CachedBlocks returns the hashes of the cached blocks.
func (bc *BlockChain) CachedBlocks() []common.Hash {
	a := bc.blockCache.Keys()
	b := make([]common.Hash, len(a))
	for i := range a {
		b[i] = a[i].(common.Hash)
	}
	return b
}

// AvailableBlocks returns the hashes of easily available blocks.
func (bc *BlockChain) AvailableBlocks() []common.Hash {
	var res []common.Hash
	blockNbr := bc.CurrentBlock().NumberU64()
	for i := 0; i < blockCacheLimit; i++ {
		block := bc.GetBlockByNumber(blockNbr)
		if block == nil {
			break
		}
		res = append(res, block.Hash())

		if blockNbr == 0 {
			break
		}
		blockNbr--
	}
	return res
}

// GetBlock retrieves a block from the database by hash and number,
// caching it if found.
func (bc *BlockChain) GetBlock(hash common.Hash, number uint64) *types.Block {
	// Short circuit if the block's already in the cache, retrieve otherwise
	if block, ok := bc.blockCache.Get(hash); ok {
		return block.(*types.Block)
	}
	block := rawdb.ReadBlock(bc.db, hash, number)
	if block == nil {
		return nil
	}
	// Cache the found block for next time and return
	bc.blockCache.Add(block.Hash(), block)
	return block
}

// GetBlockByHash retrieves a block from the database by hash, caching it if found.
func (bc *BlockChain) GetBlockByHash(hash common.Hash) *types.Block {
	number := bc.hc.GetBlockNumber(bc.db, hash)
	if number == nil {
		return nil
	}
	return bc.GetBlock(hash, *number)
}

// GetBlockByNumber retrieves a block from the database by number, caching it
// (associated with its hash) if found.
func (bc *BlockChain) GetBlockByNumber(number uint64) *types.Block {
	hash := rawdb.ReadCanonicalHash(bc.db, number)
	if hash == (common.Hash{}) {
		return nil
	}
	return bc.GetBlock(hash, number)
}

// GetReceiptsByHash retrieves the receipts for all transactions in a given block.
func (bc *BlockChain) GetReceiptsByHash(hash common.Hash) types.Receipts {
	if receipts, ok := bc.receiptsCache.Get(hash); ok {
		return receipts.(types.Receipts)
	}
	number := rawdb.ReadHeaderNumber(bc.db, hash)
	if number == nil {
		return nil
	}
	receipts := rawdb.ReadReceipts(bc.db, hash, *number, bc.chainConfig)
	if receipts == nil {
		return nil
	}
	bc.receiptsCache.Add(hash, receipts)
	return receipts
}

// GetBlocksFromHash returns the block corresponding to hash and up to n-1 ancestors.
// [deprecated by eth/62]
func (bc *BlockChain) GetBlocksFromHash(hash common.Hash, n int) (blocks []*types.Block) {
	number := bc.hc.GetBlockNumber(bc.db, hash)
	if number == nil {
		return nil
	}
	for i := 0; i < n; i++ {
		block := bc.GetBlock(hash, *number)
		if block == nil {
			break
		}
		blocks = append(blocks, block)
		hash = block.ParentHash()
		*number--
	}
	return
}

// GetUnclesInChain retrieves all the uncles from a given block backwards until
// a specific distance is reached.
func (bc *BlockChain) GetUnclesInChain(block *types.Block, length int) []*types.Header {
	uncles := []*types.Header{}
	for i := 0; block != nil && i < length; i++ {
		uncles = append(uncles, block.Uncles()...)
		block = bc.GetBlock(block.ParentHash(), block.NumberU64()-1)
	}
	return uncles
}

// ByteCode retrieves the runtime byte code associated with an account.
func (bc *BlockChain) ByteCode(addr common.Address) ([]byte, error) {
	stateDB, _, err := bc.State()
	if err != nil {
		return nil, err
	}
	return stateDB.GetCode(addr), nil
}

// Stop stops the blockchain service. If any imports are currently in progress
// it will abort them using the procInterrupt.
func (bc *BlockChain) Stop() {
	if !atomic.CompareAndSwapInt32(&bc.running, 0, 1) {
		return
	}
	// Unsubscribe all subscriptions registered from blockchain
	bc.scope.Close()
	close(bc.quit)

	bc.waitJobs()

	if bc.pruner != nil {
		bc.pruner.Stop()
	}
	log.Info("Blockchain stopped")
}

func (bc *BlockChain) procFutureBlocks() {
	blocks := make([]*types.Block, 0, bc.futureBlocks.Len())
	for _, hash := range bc.futureBlocks.Keys() {
		if block, exist := bc.futureBlocks.Peek(hash); exist {
			blocks = append(blocks, block.(*types.Block))
		}
	}
	if len(blocks) > 0 {
		sort.Slice(blocks, func(i, j int) bool {
			return blocks[i].NumberU64() < blocks[j].NumberU64()
		})
		// Insert one by one as chain insertion needs contiguous ancestry between blocks
		for i := range blocks {
			_, _ = bc.InsertChain(context.Background(), blocks[i:i+1])
		}
	}
}

// WriteStatus status of write
type WriteStatus byte

const (
	NonStatTy WriteStatus = iota
	CanonStatTy
	SideStatTy
)

// Rollback is designed to remove a chain of links from the database that aren't
// certain enough to be valid.
func (bc *BlockChain) Rollback(chain []common.Hash) {
	bc.chainmu.Lock()
	defer bc.chainmu.Unlock()

	for i := len(chain) - 1; i >= 0; i-- {
		hash := chain[i]

		// Degrade the chain markers if they are explicitly reverted.
		// In theory we should update all in-memory markers in the
		// last step, however the direction of rollback is from high
		// to low, so it's safe the update in-memory markers directly.
		currentHeader := bc.hc.CurrentHeader()
		if currentHeader.Hash() == hash {
			bc.hc.SetCurrentHeader(bc.db, bc.GetHeader(currentHeader.ParentHash, currentHeader.Number.Uint64()-1))
		}
		if currentFastBlock := bc.CurrentFastBlock(); currentFastBlock.Hash() == hash {
			newFastBlock := bc.GetBlock(currentFastBlock.ParentHash(), currentFastBlock.NumberU64()-1)
			rawdb.WriteHeadFastBlockHash(bc.db, currentFastBlock.ParentHash())
			bc.currentFastBlock.Store(newFastBlock)
			headFastBlockGauge.Update(int64(newFastBlock.NumberU64()))
		}
		if currentBlock := bc.CurrentBlock(); currentBlock.Hash() == hash {
			newBlock := bc.GetBlock(currentBlock.ParentHash(), currentBlock.NumberU64()-1)
			rawdb.WriteHeadBlockHash(bc.db, currentBlock.ParentHash())
			bc.currentBlock.Store(newBlock)
			headBlockGauge.Update(int64(newBlock.NumberU64()))
		}
	}
	if _, err := bc.db.Commit(); err != nil {
		log.Crit("Failed to rollback chain markers", "err", err)
	}
	// Truncate ancient data which exceeds the current header.
	//
	// Notably, it can happen that system crashes without truncating the ancient data
	// but the head indicator has been updated in the active store. Regarding this issue,
	// system will self recovery by truncating the extra data during the setup phase.
	//if err := bc.truncateAncient(bc.hc.CurrentHeader().Number.Uint64()); err != nil {
	//	log.Crit("Truncate ancient store failed", "err", err)
	//}
}

// truncateAncient rewinds the blockchain to the specified header and deletes all
// data in the ancient store that exceeds the specified header.
func (bc *BlockChain) truncateAncient(head uint64) error {
	frozen, err := bc.db.Ancients()
	if err != nil {
		return err
	}
	// Short circuit if there is no data to truncate in ancient store.
	if frozen <= head+1 {
		return nil
	}
	// Truncate all the data in the freezer beyond the specified head
	if err := bc.db.TruncateAncients(head + 1); err != nil {
		return err
	}
	// Clear out any stale content from the caches
	bc.hc.headerCache.Purge()
	bc.hc.tdCache.Purge()
	bc.hc.numberCache.Purge()

	// Clear out any stale content from the caches
	bc.bodyCache.Purge()
	bc.bodyRLPCache.Purge()
	bc.receiptsCache.Purge()
	bc.blockCache.Purge()
	bc.txLookupCache.Purge()
	bc.futureBlocks.Purge()

	log.Info("Rewind ancient data", "number", head)
	return nil
}

// numberHash is just a container for a number and a hash, to represent a block
type numberHash struct {
	number uint64
	hash   common.Hash
}

// InsertReceiptChain attempts to complete an already existing header chain with
// transaction and receipt data.
func (bc *BlockChain) InsertReceiptChain(blockChain types.Blocks, receiptChain []types.Receipts, ancientLimit uint64) (int, error) {
	// We don't require the chainMu here since we want to maximize the
	// concurrency of header insertion and receipt insertion.
	if err := bc.addJob(); err != nil {
		return 0, err
	}
	defer bc.doneJob()

	var (
		ancientBlocks, liveBlocks     types.Blocks
		ancientReceipts, liveReceipts []types.Receipts
	)
	// Do a sanity check that the provided chain is actually ordered and linked
	for i := 0; i < len(blockChain); i++ {
		if i != 0 {
			if blockChain[i].NumberU64() != blockChain[i-1].NumberU64()+1 || blockChain[i].ParentHash() != blockChain[i-1].Hash() {
				log.Error("Non contiguous receipt insert", "number", blockChain[i].Number(), "hash", blockChain[i].Hash(), "parent", blockChain[i].ParentHash(),
					"prevnumber", blockChain[i-1].Number(), "prevhash", blockChain[i-1].Hash())
				return 0, fmt.Errorf("non contiguous insert: item %d is #%d [%x…], item %d is #%d [%x…] (parent [%x…])", i-1, blockChain[i-1].NumberU64(),
					blockChain[i-1].Hash().Bytes()[:4], i, blockChain[i].NumberU64(), blockChain[i].Hash().Bytes()[:4], blockChain[i].ParentHash().Bytes()[:4])
			}
		}
		if blockChain[i].NumberU64() <= ancientLimit {
			ancientBlocks, ancientReceipts = append(ancientBlocks, blockChain[i]), append(ancientReceipts, receiptChain[i])
		} else {
			liveBlocks, liveReceipts = append(liveBlocks, blockChain[i]), append(liveReceipts, receiptChain[i])
		}
	}

	var (
		stats = struct{ processed, ignored int32 }{}
		start = time.Now()
		size  = 0
	)
	// updateHead updates the head fast sync block if the inserted blocks are better
	// and returns a indicator whether the inserted blocks are canonical.
	updateHead := func(head *types.Block) bool {
		bc.chainmu.Lock()

		// Rewind may have occurred, skip in that case.
		if bc.CurrentHeader().Number.Cmp(head.Number()) >= 0 {
			currentFastBlock, td := bc.CurrentFastBlock(), bc.GetTd(head.Hash(), head.NumberU64())
			if bc.GetTd(currentFastBlock.Hash(), currentFastBlock.NumberU64()).Cmp(td) < 0 {
				rawdb.WriteHeadFastBlockHash(bc.db, head.Hash())
				bc.currentFastBlock.Store(head)
				headFastBlockGauge.Update(int64(head.NumberU64()))
				bc.chainmu.Unlock()
				return true
			}
		}
		bc.chainmu.Unlock()
		return false
	}
	// writeAncient writes blockchain and corresponding receipt chain into ancient store.
	//
	// this function only accepts canonical chain data. All side chain will be reverted
	// eventually.
	/*
		writeAncient := func(blockChain types.Blocks, receiptChain []types.Receipts) (int, error) {
			var (
				previous = bc.CurrentFastBlock()
			)
			// If any error occurs before updating the head or we are inserting a side chain,
			// all the data written this time wll be rolled back.
			defer func() {
				if previous != nil {
					if err := bc.truncateAncient(previous.NumberU64()); err != nil {
						log.Crit("Truncate ancient store failed", "err", err)
					}
				}
			}()
			var deleted []*numberHash
			for i, block := range blockChain {
				// Short circuit insertion if shutting down or processing failed
				if bc.getProcInterrupt() {
					return 0, errInsertionInterrupted
				}
				// Short circuit insertion if it is required(used in testing only)
				if bc.terminateInsert != nil && bc.terminateInsert(block.Hash(), block.NumberU64()) {
					return i, errors.New("insertion is terminated for testing purpose")
				}
				// Short circuit if the owner header is unknown
				if !bc.HasHeader(block.Hash(), block.NumberU64()) {
					return i, fmt.Errorf("containing header #%d [%x…] unknown", block.Number(), block.Hash().Bytes()[:4])
				}

				// Turbo-Geth doesn't have fast sync support

				// Flush data into ancient database.
				size += rawdb.WriteAncientBlock(bc.db, block, receiptChain[i], bc.GetTd(block.Hash(), block.NumberU64()))
				if bc.enableTxLookupIndex {
					rawdb.WriteTxLookupEntries(bc.db, block)
				}

				stats.processed++
			}

			if !updateHead(blockChain[len(blockChain)-1]) {
				return 0, errors.New("side blocks can't be accepted as the ancient chain data")
			}
			previous = nil // disable rollback explicitly

			// Wipe out canonical block data.
			for _, nh := range deleted {
				rawdb.DeleteBlockWithoutNumber(bc.db, nh.hash, nh.number)
				rawdb.DeleteCanonicalHash(bc.db, nh.number)
			}
			for _, block := range blockChain {
				// Always keep genesis block in active database.
				if block.NumberU64() != 0 {
					rawdb.DeleteBlockWithoutNumber(bc.db, block.Hash(), block.NumberU64())
					rawdb.DeleteCanonicalHash(bc.db, block.NumberU64())
				}
			}

			// Wipe out side chain too.
			for _, nh := range deleted {
				for _, hash := range rawdb.ReadAllHashes(bc.db, nh.number) {
					rawdb.DeleteBlock(bc.db, hash, nh.number)
				}
			}
			for _, block := range blockChain {
				// Always keep genesis block in active database.
				if block.NumberU64() != 0 {
					for _, hash := range rawdb.ReadAllHashes(bc.db, block.NumberU64()) {
						rawdb.DeleteBlock(bc.db, hash, block.NumberU64())
					}
				}
			}
			return 0, nil
		}
	*/
	// writeLive writes blockchain and corresponding receipt chain into active store.
	writeLive := func(blockChain types.Blocks, receiptChain []types.Receipts) (int, error) {
		batch := bc.db.NewBatch()
		for i, block := range blockChain {
			// Short circuit insertion if shutting down or processing failed
			if bc.getProcInterrupt() {
				return 0, errInsertionInterrupted
			}
			// Short circuit if the owner header is unknown
			if !bc.HasHeader(block.Hash(), block.NumberU64()) {
				return i, fmt.Errorf("containing header #%d [%x…] unknown", block.Number(), block.Hash().Bytes()[:4])
			}
			if bc.HasBlock(block.Hash(), block.NumberU64()) {
				stats.ignored++
				continue
			}
			// Write all the data out into the database
			rawdb.WriteBody(context.Background(), batch, block.Hash(), block.NumberU64(), block.Body())
			rawdb.WriteReceipts(batch, block.Hash(), block.NumberU64(), receiptChain[i])
			if bc.enableTxLookupIndex {
				rawdb.WriteTxLookupEntries(batch, block)
			}

			stats.processed++
			if batch.BatchSize() >= batch.IdealBatchSize() {
				if _, err := batch.Commit(); err != nil {
					return 0, err
				}
				size += batch.BatchSize()
				batch = bc.db.NewBatch()
			}
			stats.processed++
		}
		if batch.BatchSize() > 0 {
			size += batch.BatchSize()
			if _, err := batch.Commit(); err != nil {
				return 0, err
			}
		}
		updateHead(blockChain[len(blockChain)-1])
		return 0, nil
	}

	// Write downloaded chain data and corresponding receipt chain data.
	/*
		if len(ancientBlocks) > 0 {
			if n, err := writeAncient(ancientBlocks, ancientReceipts); err != nil {
				if err == errInsertionInterrupted {
					return 0, nil
				}
				return n, err
			}
		}
	*/
	if len(liveBlocks) > 0 {
		if n, err := writeLive(liveBlocks, liveReceipts); err != nil {
			if err == errInsertionInterrupted {
				return 0, nil
			}
			return n, err
		}
	}

	head := blockChain[len(blockChain)-1]
	context := []interface{}{
		"count", stats.processed, "elapsed", common.PrettyDuration(time.Since(start)),
		"number", head.Number(), "hash", head.Hash(), "age", common.PrettyAge(time.Unix(int64(head.Time()), 0)),
		"size", common.StorageSize(size),
	}
	if stats.ignored > 0 {
		context = append(context, []interface{}{"ignored", stats.ignored}...)
	}
	log.Info("Imported new block receipts", context...)

	return 0, nil
}

// WriteBlockWithState writes the block and all associated state to the database.
func (bc *BlockChain) WriteBlockWithState(ctx context.Context, block *types.Block, receipts []*types.Receipt, logs []*types.Log, state *state.IntraBlockState, tds *state.TrieDbState, emitHeadEvent bool, execute bool) (status WriteStatus, err error) {
	if err = bc.addJob(); err != nil {
		return NonStatTy, err
	}
	defer bc.doneJob()

	bc.chainmu.Lock()
	defer bc.chainmu.Unlock()

	return bc.writeBlockWithState(ctx, block, receipts, logs, state, tds, emitHeadEvent, execute)
}

// writeBlockWithState writes the block and all associated state to the database,
// but is expects the chain mutex to be held.
func (bc *BlockChain) writeBlockWithState(ctx context.Context, block *types.Block, receipts []*types.Receipt, logs []*types.Log, stateDb *state.IntraBlockState, tds *state.TrieDbState, emitHeadEvent bool, execute bool) (status WriteStatus, err error) {
	// Make sure no inconsistent state is leaked during insertion
	currentBlock := bc.CurrentBlock()

	// Calculate the total difficulty of the block
	ptd := bc.GetTd(block.ParentHash(), block.NumberU64()-1)
	if ptd == nil {
		return NonStatTy, consensus.ErrUnknownAncestor
	}
	externTd := new(big.Int).Add(block.Difficulty(), ptd)

	// Irrelevant of the canonical status, write the block itself to the database
	if common.IsCanceled(ctx) {
		return NonStatTy, ctx.Err()
	}
	if execute {
		rawdb.WriteTd(bc.db, block.Hash(), block.NumberU64(), externTd)
	}
	rawdb.WriteBody(ctx, bc.db, block.Hash(), block.NumberU64(), block.Body())
	if execute {
		rawdb.WriteHeader(ctx, bc.db, block.Header())
	}

	if tds != nil {
		tds.SetBlockNr(block.NumberU64())
	}

	ctx = bc.WithContext(ctx, block.Number())
	if stateDb != nil && execute {
		blockWriter := tds.DbStateWriter()
		if err := stateDb.CommitBlock(ctx, blockWriter); err != nil {
			return NonStatTy, err
		}
		// Always write changesets
		if err := blockWriter.WriteChangeSets(); err != nil {
			return NonStatTy, err
		}
		// Optionally write history
		if !bc.NoHistory() {
			if err := blockWriter.WriteHistory(); err != nil {
				return NonStatTy, err
			}
		}
	}
	if bc.enableReceipts && !bc.cacheConfig.DownloadOnly && execute {
		rawdb.WriteReceipts(bc.db, block.Hash(), block.NumberU64(), receipts)
	}

	// If the total difficulty is higher than our known, add it to the canonical chain
	// Second clause in the if statement reduces the vulnerability to selfish mining.
	// Please refer to http://www.cs.cornell.edu/~ie53/publications/btcProcFC.pdf
	//reorg := externTd.Cmp(localTd) > 0
	//currentBlock = bc.CurrentBlock()
	//if !reorg && externTd.Cmp(localTd) == 0 {
	//	// Split same-difficulty blocks by number, then preferentially select
	//	// the block generated by the local miner as the canonical block.
	//	if block.NumberU64() < currentBlock.NumberU64() {
	//		reorg = true
	//	} else if block.NumberU64() == currentBlock.NumberU64() {
	//		var currentPreserve, blockPreserve bool
	//		if bc.shouldPreserve != nil {
	//			currentPreserve, blockPreserve = bc.shouldPreserve(currentBlock), bc.shouldPreserve(block)
	//		}
	//		reorg = !currentPreserve && (blockPreserve || mrand.Float64() < 0.5)
	//	}
	//}
	//if reorg {
	// Reorganise the chain if the parent is not the head block

	if execute && block.ParentHash() != currentBlock.Hash() {
		if err := bc.reorg(currentBlock, block); err != nil {
			return NonStatTy, err
		}
	}
	// Write the positional metadata for transaction/receipt lookups and preimages

	if stateDb != nil && bc.enablePreimages && !bc.cacheConfig.DownloadOnly && execute {
		rawdb.WritePreimages(bc.db, stateDb.Preimages())
	}

	status = CanonStatTy

	// Set new head.
	if execute {
		bc.writeHeadBlock(block)
	}
	bc.futureBlocks.Remove(block.Hash())

	if execute {
		bc.chainFeed.Send(ChainEvent{Block: block, Hash: block.Hash(), Logs: logs})
		if len(logs) > 0 {
			bc.logsFeed.Send(logs)
		}
	}
	// In theory we should fire a ChainHeadEvent when we inject
	// a canonical block, but sometimes we can insert a batch of
	// canonicial blocks. Avoid firing too much ChainHeadEvents,
	// we will fire an accumulated ChainHeadEvent and disable fire
	// event here.
	if emitHeadEvent && execute {
		bc.chainHeadFeed.Send(ChainHeadEvent{Block: block})
	}
	return status, nil
}

// addFutureBlock checks if the block is within the max allowed window to get
// accepted for future processing, and returns an error if the block is too far
// ahead and was not added.
func (bc *BlockChain) addFutureBlock(block *types.Block) error {
	max := uint64(time.Now().Unix() + maxTimeFutureBlocks)
	if block.Time() > max {
		return fmt.Errorf("future block timestamp %v > allowed %v", block.Time(), max)
	}
	bc.futureBlocks.Add(block.Hash(), block)
	return nil
}

// InsertBodyChain attempts to insert the given batch of block into the
// canonical chain, without executing those blocks
func (bc *BlockChain) InsertBodyChain(ctx context.Context, chain types.Blocks) (int, error) {
	// Sanity check that we have something meaningful to import
	if len(chain) == 0 {
		return 0, nil
	}

	// Remove already known canon-blocks
	var (
		block, prev *types.Block
	)
	// Do a sanity check that the provided chain is actually ordered and linked
	for i := 1; i < len(chain); i++ {
		block = chain[i]
		prev = chain[i-1]
		if block.NumberU64() != prev.NumberU64()+1 || block.ParentHash() != prev.Hash() {
			// Chain broke ancestry, log a message (programming error) and skip insertion
			log.Error("Non contiguous block insert", "number", block.Number(), "hash", block.Hash(),
				"parent", block.ParentHash(), "prevnumber", prev.Number(), "prevhash", prev.Hash())

			return 0, fmt.Errorf("non contiguous insert: item %d is #%d [%x…], item %d is #%d [%x…] (parent [%x…])", i-1, prev.NumberU64(),
				prev.Hash().Bytes()[:4], i, block.NumberU64(), block.Hash().Bytes()[:4], block.ParentHash().Bytes()[:4])
		}
	}
	// Only insert if the difficulty of the inserted chain is bigger than existing chain
	// Pre-checks passed, start the full block imports
	if err := bc.addJob(); err != nil {
		return 0, err
	}
	ctx = bc.WithContext(ctx, chain[0].Number())
	bc.chainmu.Lock()
	defer func() {
		bc.chainmu.Unlock()
		bc.doneJob()
	}()
	n, err := bc.insertChain(ctx, chain, false, false /* execute */)

	return n, err
}

// InsertChain attempts to insert the given batch of blocks in to the canonical
// chain or, otherwise, create a fork. If an error is returned it will return
// the index number of the failing block as well an error describing what went
// wrong.
//
// After insertion is done, all accumulated events will be fired.
func (bc *BlockChain) InsertChain(ctx context.Context, chain types.Blocks) (int, error) {
	// Sanity check that we have something meaningful to import
	if len(chain) == 0 {
		return 0, nil
	}

	bc.blockProcFeed.Send(true)
	defer bc.blockProcFeed.Send(false)

	// Remove already known canon-blocks
	var (
		block, prev *types.Block
	)
	// Do a sanity check that the provided chain is actually ordered and linked
	for i := 1; i < len(chain); i++ {
		block = chain[i]
		prev = chain[i-1]
		if block.NumberU64() != prev.NumberU64()+1 || block.ParentHash() != prev.Hash() {
			// Chain broke ancestry, log a message (programming error) and skip insertion
			log.Error("Non contiguous block insert", "number", block.Number(), "hash", block.Hash(),
				"parent", block.ParentHash(), "prevnumber", prev.Number(), "prevhash", prev.Hash())

			return 0, fmt.Errorf("non contiguous insert: item %d is #%d [%x…], item %d is #%d [%x…] (parent [%x…])", i-1, prev.NumberU64(),
				prev.Hash().Bytes()[:4], i, block.NumberU64(), block.Hash().Bytes()[:4], block.ParentHash().Bytes()[:4])
		}
	}
	// Only insert if the difficulty of the inserted chain is bigger than existing chain
	// Pre-checks passed, start the full block imports
	if err := bc.addJob(); err != nil {
		return 0, err
	}
	ctx = bc.WithContext(ctx, chain[0].Number())
	bc.chainmu.Lock()
	defer func() {
		bc.chainmu.Unlock()
		bc.doneJob()
	}()
	n, err := bc.insertChain(ctx, chain, true, true /* execute */)

	return n, err
}

// insertChain is the internal implementation of InsertChain, which assumes that
// 1) chains are contiguous, and 2) The chain mutex is held.
//
// This method is split out so that import batches that require re-injecting
// historical blocks can do so without releasing the lock, which could lead to
// racey behaviour. If a sidechain import is in progress, and the historic state
// is imported, but then new canon-head is added before the actual sidechain
// completes, then the historic state could be pruned again
func (bc *BlockChain) insertChain(ctx context.Context, chain types.Blocks, verifySeals bool, execute bool) (int, error) {
	log.Info("Inserting chain",
		"start", chain[0].NumberU64(), "end", chain[len(chain)-1].NumberU64(),
		"current", bc.CurrentBlock().Number().Uint64(), "currentHeader", bc.CurrentHeader().Number.Uint64())

	// If the chain is terminating, don't even bother starting u
	if bc.getProcInterrupt() {
		return 0, nil
	}
	// Start a parallel signature recovery (signer will fluke on fork transition, minimal perf loss)
	senderCacher.recoverFromBlocks(types.MakeSigner(bc.chainConfig, chain[0].Number()), chain)

	// A queued approach to delivering events. This is generally
	// faster than direct delivery and requires much less mutex
	// acquiring.
	var (
		stats     = insertStats{startTime: mclock.Now()}
		lastCanon *types.Block
	)
	// Fire a single chain head event if we've progressed the chain
	if execute {
		defer func() {
			if lastCanon != nil && bc.CurrentBlock().Hash() == lastCanon.Hash() {
				bc.chainHeadFeed.Send(ChainHeadEvent{lastCanon})
			}
		}()
	}
	// Start the parallel header verifier
	headers := make([]*types.Header, len(chain))
	seals := make([]bool, len(chain))

	for i, block := range chain {
		headers[i] = block.Header()
		seals[i] = verifySeals
	}
	var abort chan<- struct{}
	var results <-chan error
	if execute {
		abort, results = bc.engine.VerifyHeaders(bc, headers, seals)
		defer close(abort)
	}

	externTd := big.NewInt(0)
	if len(chain) > 0 && chain[0].NumberU64() > 0 {
		d := bc.GetTd(chain[0].ParentHash(), chain[0].NumberU64()-1)
		if d != nil {
			externTd = externTd.Set(d)
		}
	}

	localTd := bc.GetTd(bc.CurrentBlock().Hash(), bc.CurrentBlock().NumberU64())

	var verifyFrom int
	for verifyFrom = 0; verifyFrom < len(chain) && localTd.Cmp(externTd) >= 0; verifyFrom++ {
		header := chain[verifyFrom].Header()
		if execute {
			err := <-results
			if err != nil {
				bc.reportBlock(chain[verifyFrom], nil, err)
				return 0, err
			}
		}
		externTd = externTd.Add(externTd, header.Difficulty)
	}

	if execute && localTd.Cmp(externTd) >= 0 {
		log.Warn("Ignoring the chain segment because of insufficient difficulty",
			"external", externTd,
			"local", localTd,
			"insertingNumber", chain[0].NumberU64(),
			"currentNumber", bc.CurrentBlock().Number().Uint64(),
		)

		// But we still write the blocks to the database because others might build on top of them
		td := bc.GetTd(chain[0].ParentHash(), chain[0].NumberU64()-1)
		for _, block := range chain {
			log.Warn("Saving", "block", block.NumberU64(), "hash", block.Hash())
			td = new(big.Int).Add(block.Difficulty(), td)
			rawdb.WriteBlock(ctx, bc.db, block)
			rawdb.WriteTd(bc.db, block.Hash(), block.NumberU64(), td)
		}
		return 0, nil
	}
	var offset int
	var parent *types.Block
	var parentNumber = chain[0].NumberU64() - 1
	// Find correct insertion point for this chain

	preBlocks := []*types.Block{}
	parentHash := chain[0].ParentHash()
	parent = bc.GetBlock(parentHash, parentNumber)
	if parent == nil {
		log.Error("chain segment could not be inserted, missing parent", "hash", parentHash)
		return 0, fmt.Errorf("chain segment could not be inserted, missing parent %x", parentHash)
	}

	canonicalHash := rawdb.ReadCanonicalHash(bc.db, parentNumber)
	for canonicalHash != parentHash {
		log.Warn("Chain segment's parent not on canonical hash, adding to pre-blocks", "block", parentNumber, "hash", parentHash)
		preBlocks = append(preBlocks, parent)
		parentNumber--
		parentHash = parent.ParentHash()
		parent = bc.GetBlock(parentHash, parentNumber)
		if parent == nil {
			log.Error("chain segment could not be inserted, missing parent", "hash", parentHash)
			return 0, fmt.Errorf("chain segment could not be inserted, missing parent %x", parentHash)
		}
		canonicalHash = rawdb.ReadCanonicalHash(bc.db, parentNumber)
	}

	for left, right := 0, len(preBlocks)-1; left < right; left, right = left+1, right-1 {
		preBlocks[left], preBlocks[right] = preBlocks[right], preBlocks[left]
	}

	offset = len(preBlocks)
	if offset > 0 {
		chain = append(preBlocks, chain...)
	}

	var k int
	var committedK int
	// Iterate over the blocks and insert when the verifier permits
	for i, block := range chain {
		start := time.Now()
		if i >= offset {
			k = i - offset
		} else {
			k = 0
		}

		// If the chain is terminating, stop processing blocks
		if bc.getProcInterrupt() {
			log.Debug("Premature abort during blocks processing")
			break
		}

		// If the header is a banned one, straight out abort
		if BadHashes[block.Hash()] {
			bc.reportBlock(block, nil, ErrBlacklistedHash)
			return k, ErrBlacklistedHash
		}

		// Wait for the block's verification to complete
		var err error
		if i >= offset && k >= verifyFrom && execute {
			err = <-results
		}
		if err == nil {
			ctx, _ = params.GetNoHistoryByBlock(ctx, block.Number())
			err = bc.Validator().ValidateBody(ctx, block)
		}

		switch {
		case err == ErrKnownBlock:
			// Block and state both already known. However if the current block is below
			// this number we did a rollback and we should reimport it nonetheless.
			if bc.CurrentBlock().NumberU64() >= block.NumberU64() {
				//fmt.Printf("Skipped known block %d\n", block.NumberU64())
				stats.ignored++
				continue
			}

		case err == consensus.ErrFutureBlock:
			// Allow up to MaxFuture second in the future blocks. If this limit is exceeded
			// the chain is discarded and processed at a later time if given.
			max := big.NewInt(time.Now().Unix() + maxTimeFutureBlocks)
			if block.Time() > max.Uint64() {
				return k, fmt.Errorf("future block: %v > %v", block.Time(), max)
			}
			bc.futureBlocks.Add(block.Hash(), block)
			stats.queued++
			continue

		case err == consensus.ErrUnknownAncestor && bc.futureBlocks.Contains(block.ParentHash()):
			bc.futureBlocks.Add(block.Hash(), block)
			stats.queued++
			continue

		case err == consensus.ErrPrunedAncestor:
			// Block competing with the canonical chain, store in the db, but don't process
			// until the competitor TD goes above the canonical TD
			panic(err)

		case err != nil:
			bc.reportBlock(block, nil, err)
			return k, err
		}
		// Create a new statedb using the parent block and report an
		// error if it fails.
		if i > 0 {
			parent = chain[i-1]
		}
		readBlockNr := parentNumber
		var root common.Hash
		if bc.trieDbState == nil && !bc.cacheConfig.DownloadOnly && execute {
			if _, err = bc.GetTrieDbState(); err != nil {
				return k, err
			}
		}

		if !bc.cacheConfig.DownloadOnly && execute {
			root = bc.trieDbState.LastRoot()
		}

		var parentRoot common.Hash
		if parent != nil {
			parentRoot = parent.Root()
		}

		if parent != nil && root != parentRoot && !bc.cacheConfig.DownloadOnly && execute {
			log.Info("Rewinding from", "block", bc.CurrentBlock().NumberU64(), "to block", readBlockNr,
				"root", root.String(), "parentRoot", parentRoot.String())

			if _, err = bc.db.Commit(); err != nil {
				log.Error("Could not commit chainDb before rewinding", "error", err)
				if bc.committedBlock.Load() != nil {
					bc.currentBlock.Store(bc.committedBlock.Load())
				}
				bc.db.Rollback()
				bc.setTrieDbState(nil)
				return k, err
			}
			bc.committedBlock.Store(bc.currentBlock.Load())

			if err = bc.trieDbState.UnwindTo(readBlockNr); err != nil {
				bc.db.Rollback()
				log.Error("Could not rewind", "error", err)
				bc.setTrieDbState(nil)
				return k, err
			}

			root := bc.trieDbState.LastRoot()
			if root != parentRoot {
				log.Error("Incorrect rewinding", "root", fmt.Sprintf("%x", root), "expected", fmt.Sprintf("%x", parentRoot))
				bc.db.Rollback()
				bc.setTrieDbState(nil)
				return k, fmt.Errorf("incorrect rewinding: wrong root %x, expected %x", root, parentRoot)
			}
			currentBlock := bc.CurrentBlock()
			if err = bc.reorg(currentBlock, parent); err != nil {
				bc.db.Rollback()
				bc.setTrieDbState(nil)
				return k, err
			}

			if _, err = bc.db.Commit(); err != nil {
				log.Error("Could not commit chainDb after rewinding", "error", err)
				bc.db.Rollback()
				bc.setTrieDbState(nil)
				if bc.committedBlock.Load() != nil {
					bc.currentBlock.Store(bc.committedBlock.Load())
				}
				return k, err
			}
			committedK = k
			bc.committedBlock.Store(bc.currentBlock.Load())
		}

		var stateDB *state.IntraBlockState
		var receipts types.Receipts
		var usedGas uint64
		var logs []*types.Log
		if !bc.cacheConfig.DownloadOnly && execute {
			stateDB = state.New(bc.trieDbState)
			// Process block using the parent state as reference point.
			receipts, logs, usedGas, root, err = bc.processor.PreProcess(block, stateDB, bc.trieDbState, bc.vmConfig)
			reuseTrieDbState := true
			if err != nil {
				bc.rollbackBadBlock(block, receipts, err, reuseTrieDbState)
				return k, err
			}

			err = bc.Validator().ValidateGasAndRoot(block, root, usedGas, bc.trieDbState)
			if err != nil {
				bc.rollbackBadBlock(block, receipts, err, reuseTrieDbState)
				return k, err
			}

			reuseTrieDbState = false
			err = bc.processor.PostProcess(block, bc.trieDbState, receipts)
			if err != nil {
				bc.rollbackBadBlock(block, receipts, err, reuseTrieDbState)
				return k, err
			}

			err = bc.Validator().ValidateReceipts(block, receipts)
			if err != nil {
				bc.rollbackBadBlock(block, receipts, err, reuseTrieDbState)
				return k, err
			}
		}
		proctime := time.Since(start)

		// Write the block to the chain and get the status.
		status, err := bc.writeBlockWithState(ctx, block, receipts, logs, stateDB, bc.trieDbState, false, execute)
		if err != nil {
			bc.db.Rollback()
			bc.setTrieDbState(nil)
			if bc.committedBlock.Load() != nil {
				bc.currentBlock.Store(bc.committedBlock.Load())
			}
			return k, err
		}

		switch status {
		case CanonStatTy:
			log.Debug("Inserted new block", "number", block.Number(), "hash", block.Hash(),
				"uncles", len(block.Uncles()), "txs", len(block.Transactions()), "gas", block.GasUsed(),
				"elapsed", common.PrettyDuration(time.Since(start)),
				"root", block.Root())

			lastCanon = block

			// Only count canonical blocks for GC processing time
			bc.gcproc += proctime

		case SideStatTy:
			log.Debug("Inserted forked block", "number", block.Number(), "hash", block.Hash(),
				"diff", block.Difficulty(), "elapsed", common.PrettyDuration(time.Since(start)),
				"txs", len(block.Transactions()), "gas", block.GasUsed(), "uncles", len(block.Uncles()),
				"root", block.Root())

		default:
			// This in theory is impossible, but lets be nice to our future selves and leave
			// a log, instead of trying to track down blocks imports that don't emit logs.
			log.Warn("Inserted block with unknown status", "number", block.Number(), "hash", block.Hash(),
				"diff", block.Difficulty(), "elapsed", common.PrettyDuration(time.Since(start)),
				"txs", len(block.Transactions()), "gas", block.GasUsed(), "uncles", len(block.Uncles()),
				"root", block.Root())
		}
		stats.processed++
		stats.usedGas += usedGas
		toCommit := stats.needToCommit(chain, bc.db, i)
		stats.report(chain, i, bc.db, toCommit)
		if toCommit {
			var written uint64
			if written, err = bc.db.Commit(); err != nil {
				log.Error("Could not commit chainDb", "error", err)
				bc.db.Rollback()
				bc.setTrieDbState(nil)
				if bc.committedBlock.Load() != nil {
					bc.currentBlock.Store(bc.committedBlock.Load())
				}
				return k, err
			}
			bc.committedBlock.Store(bc.currentBlock.Load())
			committedK = k
			if bc.trieDbState != nil {
				bc.trieDbState.EvictTries(false)
			}
			log.Info("Database", "size", bc.db.DiskSize(), "written", written)
		}
	}

	return committedK + 1, nil
}

// statsReportLimit is the time limit during import and export after which we
// always print out progress. This avoids the user wondering what's going on.
const statsReportLimit = 8 * time.Second
const commitLimit = 60 * time.Second

func (st *insertStats) needToCommit(chain []*types.Block, db ethdb.DbWithPendingMutations, index int) bool {
	var (
		now     = mclock.Now()
		elapsed = time.Duration(now) - time.Duration(st.startTime)
	)
	if index == len(chain)-1 || elapsed >= commitLimit || db.BatchSize() >= db.IdealBatchSize() {
		return true
	}
	return false
}

// report prints statistics if some number of blocks have been processed
// or more than a few seconds have passed since the last message.
func (st *insertStats) report(chain []*types.Block, index int, batch ethdb.DbWithPendingMutations, toCommit bool) {
	// Fetch the timings for the batch
	var (
		now     = mclock.Now()
		elapsed = time.Duration(now) - time.Duration(st.startTime)
	)
	// If we're at the last block of the batch or report period reached, log
	if index == len(chain)-1 || elapsed >= statsReportLimit || toCommit {
		// Count the number of transactions in this segment
		var txs int
		for _, block := range chain[st.lastIndex : index+1] {
			txs += len(block.Transactions())
		}
		end := chain[index]
		context := []interface{}{
			"blocks", st.processed, "txs", txs, "mgas", float64(st.usedGas) / 1000000,
			"elapsed", common.PrettyDuration(elapsed), "mgasps", float64(st.usedGas) * 1000 / float64(elapsed),
			"number", end.Number(), "hash", end.Hash(), "batch", batch.BatchSize(),
		}
		if timestamp := time.Unix(int64(end.Time()), 0); time.Since(timestamp) > time.Minute {
			context = append(context, []interface{}{"age", common.PrettyAge(timestamp)}...)
		}
		if st.queued > 0 {
			context = append(context, []interface{}{"queued", st.queued}...)
		}
		if st.ignored > 0 {
			context = append(context, []interface{}{"ignored", st.ignored}...)
		}
		log.Info("Imported new chain segment", context...)
		*st = insertStats{startTime: now, lastIndex: index + 1}
	}
}

// reorg takes two blocks, an old chain and a new chain and will reconstruct the
// blocks and inserts them to be part of the new canonical chain and accumulates
// potential missing transactions and post an event about them.
func (bc *BlockChain) reorg(oldBlock, newBlock *types.Block) error {
	var (
		newChain    types.Blocks
		oldChain    types.Blocks
		commonBlock *types.Block

		deletedTxs types.Transactions
		addedTxs   types.Transactions

		deletedLogs [][]*types.Log
		rebirthLogs [][]*types.Log

		// collectLogs collects the logs that were generated or removed during
		// the processing of the block that corresponds with the given hash.
		// These logs are later announced as deleted or reborn
		collectLogs = func(hash common.Hash, removed bool) {
			// Coalesce logs and set 'Removed'.
			number := bc.hc.GetBlockNumber(bc.db, hash)
			if number == nil {
				return
			}
			receipts := rawdb.ReadReceipts(bc.db, hash, *number, bc.chainConfig)

			var logs []*types.Log
			for _, receipt := range receipts {
				for _, log := range receipt.Logs {
					l := *log
					if removed {
						l.Removed = true
					} else {
					}
					logs = append(logs, &l)
				}
			}
			if len(logs) > 0 {
				if removed {
					deletedLogs = append(deletedLogs, logs)
				} else {
					rebirthLogs = append(rebirthLogs, logs)
				}
			}
		}
		// mergeLogs returns a merged log slice with specified sort order.
		mergeLogs = func(logs [][]*types.Log, reverse bool) []*types.Log {
			var ret []*types.Log
			if reverse {
				for i := len(logs) - 1; i >= 0; i-- {
					ret = append(ret, logs[i]...)
				}
			} else {
				for i := 0; i < len(logs); i++ {
					ret = append(ret, logs[i]...)
				}
			}
			return ret
		}
	)

	// Reduce the longer chain to the same number as the shorter one
	// first reduce whoever is higher bound
	if oldBlock.NumberU64() > newBlock.NumberU64() {
		// Old chain is longer, gather all transactions and logs as deleted ones
		for ; oldBlock != nil && oldBlock.NumberU64() != newBlock.NumberU64(); oldBlock = bc.GetBlock(oldBlock.ParentHash(), oldBlock.NumberU64()-1) {
			oldChain = append(oldChain, oldBlock)
			deletedTxs = append(deletedTxs, oldBlock.Transactions()...)
			collectLogs(oldBlock.Hash(), true)
		}
	} else {
		// New chain is longer, stash all blocks away for subsequent insertion
		for ; newBlock != nil && newBlock.NumberU64() != oldBlock.NumberU64(); newBlock = bc.GetBlock(newBlock.ParentHash(), newBlock.NumberU64()-1) {
			newChain = append(newChain, newBlock)
		}
	}
	if oldBlock == nil {
		return fmt.Errorf("invalid old chain")
	}
	if newBlock == nil {
		return fmt.Errorf("invalid new chain")
	}
	// Both sides of the reorg are at the same number, reduce both until the common
	// ancestor is found
	for {
		// If the common ancestor was found, bail out
		if oldBlock.Hash() == newBlock.Hash() {
			commonBlock = oldBlock
			break
		}
		// Remove an old block as well as stash away a new block
		oldChain = append(oldChain, oldBlock)
		deletedTxs = append(deletedTxs, oldBlock.Transactions()...)
		collectLogs(oldBlock.Hash(), true)

		newChain = append(newChain, newBlock)

		// Step back with both chains
		oldBlock = bc.GetBlock(oldBlock.ParentHash(), oldBlock.NumberU64()-1)
		if oldBlock == nil {
			return fmt.Errorf("invalid old chain")
		}
		newBlock = bc.GetBlock(newBlock.ParentHash(), newBlock.NumberU64()-1)
		if newBlock == nil {
			return fmt.Errorf("invalid new chain")
		}
	}
	// Ensure the user sees large reorgs
	if len(oldChain) > 0 && len(newChain) > 0 {
		logFn := log.Info
		msg := "Chain reorg detected"
		if len(oldChain) > 63 {
			msg = "Large chain reorg detected"
			logFn = log.Warn
		}
		logFn(msg, "number", commonBlock.Number(), "hash", commonBlock.Hash(),
			"drop", len(oldChain), "dropfrom", oldChain[0].Hash(), "add", len(newChain), "addfrom", newChain[0].Hash())
		blockReorgAddMeter.Mark(int64(len(newChain)))
		blockReorgDropMeter.Mark(int64(len(oldChain)))
	} else {
		log.Error("Impossible reorg, please file an issue", "oldnum", oldBlock.Number(), "oldhash", oldBlock.Hash(), "newnum", newBlock.Number(), "newhash", newBlock.Hash())
	}
	// Delete the old chain
	for _, oldBlock := range oldChain {
		rawdb.DeleteCanonicalHash(bc.db, oldBlock.NumberU64())
	}
	bc.writeHeadBlock(commonBlock)
	// Insert the new chain, taking care of the proper incremental order
	for i := len(newChain) - 1; i >= 0; i-- {
		// insert the block in the canonical way, re-writing history
		bc.writeHeadBlock(newChain[i])

		// Collect reborn logs due to chain reorg
		collectLogs(newChain[i].Hash(), false)

		// Write lookup entries for hash based transaction/receipt searches
		if bc.enableTxLookupIndex {
			rawdb.WriteTxLookupEntries(bc.db, newChain[i])
		}
		addedTxs = append(addedTxs, newChain[i].Transactions()...)
	}
	// When transactions get deleted from the database, the receipts that were
	// created in the fork must also be deleted
	for _, tx := range types.TxDifference(deletedTxs, addedTxs) {
		rawdb.DeleteTxLookupEntry(bc.db, tx.Hash())
	}
	// Delete any canonical number assignments above the new head
	number := bc.CurrentBlock().NumberU64()
	for i := number + 1; ; i++ {
		hash := rawdb.ReadCanonicalHash(bc.db, i)
		if hash == (common.Hash{}) {
			break
		}
		rawdb.DeleteCanonicalHash(bc.db, i)
	}

	if _, err := bc.db.Commit(); err != nil {
		return err
	}
	// If any logs need to be fired, do it now. In theory we could avoid creating
	// this goroutine if there are no events to fire, but realistcally that only
	// ever happens if we're reorging empty blocks, which will only happen on idle
	// networks where performance is not an issue either way.
	if len(deletedLogs) > 0 {
		bc.rmLogsFeed.Send(RemovedLogsEvent{mergeLogs(deletedLogs, true)})
	}
	if len(rebirthLogs) > 0 {
		bc.logsFeed.Send(mergeLogs(rebirthLogs, false))
	}
	if len(oldChain) > 0 {
		for i := len(oldChain) - 1; i >= 0; i-- {
			bc.chainSideFeed.Send(ChainSideEvent{Block: oldChain[i]})
		}
	}
	return nil
}

// PostChainEvents iterates over the events generated by a chain insertion and
// posts them into the event feed.
// TODO: Should not expose PostChainEvents. The chain events should be posted in WriteBlock.
func (bc *BlockChain) PostChainEvents(events []interface{}, logs []*types.Log) {
	// post event logs for further processing
	if logs != nil {
		bc.logsFeed.Send(logs)
	}
	for _, event := range events {
		switch ev := event.(type) {
		case ChainEvent:
			bc.chainFeed.Send(ev)

		case ChainHeadEvent:
			bc.chainHeadFeed.Send(ev)

		case ChainSideEvent:
			bc.chainSideFeed.Send(ev)
		}
	}
}

func (bc *BlockChain) update() {
	futureTimer := time.NewTicker(5 * time.Second)
	defer futureTimer.Stop()
	for {
		select {
		case <-futureTimer.C:
			bc.procFutureBlocks()
		case <-bc.quit:
			return
		}
	}
}

// BadBlocks returns a list of the last 'bad blocks' that the client has seen on the network
func (bc *BlockChain) BadBlocks() []*types.Block {
	blocks := make([]*types.Block, 0, bc.badBlocks.Len())
	for _, hash := range bc.badBlocks.Keys() {
		if blk, exist := bc.badBlocks.Peek(hash); exist {
			block := blk.(*types.Block)
			blocks = append(blocks, block)
		}
	}
	return blocks
}

// addBadBlock adds a bad block to the bad-block LRU cache
func (bc *BlockChain) addBadBlock(block *types.Block) {
	bc.badBlocks.Add(block.Hash(), block)
}

// reportBlock logs a bad block error.
func (bc *BlockChain) reportBlock(block *types.Block, receipts types.Receipts, err error) {
	bc.addBadBlock(block)

	var receiptString string
	for i, receipt := range receipts {
		receiptString += fmt.Sprintf("\t %d: cumulative: %v gas: %v contract: %v status: %v tx: %v logs: %v bloom: %x state: %x\n",
			i, receipt.CumulativeGasUsed, receipt.GasUsed, receipt.ContractAddress.Hex(),
			receipt.Status, receipt.TxHash.Hex(), receipt.Logs, receipt.Bloom, receipt.PostState)
	}
	log.Error(fmt.Sprintf(`
########## BAD BLOCK #########
Chain config: %v

Number: %v
Hash: 0x%x
%v

Error: %v
Callers: %v
##############################
`, bc.chainConfig, block.Number(), block.Hash(), receiptString, err, debug.Callers(20)))
}

func (bc *BlockChain) rollbackBadBlock(block *types.Block, receipts types.Receipts, err error, reuseTrieDbState bool) {
	bc.db.Rollback()
	if reuseTrieDbState {
		bc.setTrieDbState(bc.trieDbState.WithNewBuffer())
	} else {
		bc.setTrieDbState(nil)
	}
	bc.reportBlock(block, receipts, err)
	if bc.committedBlock.Load() != nil {
		bc.currentBlock.Store(bc.committedBlock.Load())
	}
}

func (bc *BlockChain) insertHeaderChainStaged(chain []*types.Header) (int, int, int, bool, uint64, error) {
	// The function below will insert headers, and track the lowest block
	// number that have replace the canonical chain. This number will be
	// used to trigger invalidation of further sync stages
	var newCanonical bool
	var lowestCanonicalNumber uint64
	whFunc := func(header *types.Header) error {
		status, err := bc.hc.WriteHeader(context.Background(), header)
		if err != nil {
			return err
		}
		if status == CanonStatTy {
			number := header.Number.Uint64()
			if !newCanonical || number < lowestCanonicalNumber {
				lowestCanonicalNumber = number
				newCanonical = true
			}
		}
		return nil
	}
	// Collect some import statistics to report on
	stats := struct{ processed, ignored int }{}
	// All headers passed verification, import them into the database
	for i, header := range chain {
		// Short circuit insertion if shutting down
		if bc.hc.procInterrupt() {
			log.Debug("Premature abort during headers import")
			return i, stats.processed, stats.ignored, newCanonical, lowestCanonicalNumber, errors.New("aborted")
		}
		// If the header's already known, skip it, otherwise store
		hash := header.Hash()
		if bc.hc.HasHeader(hash, header.Number.Uint64()) {
			externTd := bc.hc.GetTd(bc.hc.chainDb, hash, header.Number.Uint64())
			localTd := bc.hc.GetTd(bc.hc.chainDb, bc.hc.currentHeaderHash, bc.hc.CurrentHeader().Number.Uint64())
			if externTd == nil || externTd.Cmp(localTd) <= 0 {
				stats.ignored++
				continue
			}
		}
		if err := whFunc(header); err != nil {
			return i, stats.processed, stats.ignored, newCanonical, lowestCanonicalNumber, err
		}
		stats.processed++
	}
	// Everything processed without errors
	return len(chain), stats.processed, stats.ignored, newCanonical, lowestCanonicalNumber, nil
}

// InsertHeaderChainStaged attempts to add the chunk of headers to the headerchain
// It return the following values
// 1. (type int) number of items in the input chain that have been successfully processed and committed
// 2. (type bool) whether the insertion of this chunk has changed the canonical chain
// 3. (type uint64) the lowest block number that has been displaced from the canonical chain (this is to be used to invalidate further sync stages)
// 4. (type error) error happed during processing
func (bc *BlockChain) InsertHeaderChainStaged(chain []*types.Header, checkFreq int) (int, bool, uint64, error) {
	start := time.Now()
	if i, err := bc.hc.ValidateHeaderChain(chain, checkFreq); err != nil {
		return i, false, 0, err
	}

	// Make sure only one thread manipulates the chain at once
	bc.chainmu.Lock()
	defer bc.chainmu.Unlock()

	if err := bc.addJob(); err != nil {
		return 0, false, 0, err
	}
	defer bc.doneJob()

	n, processed, ignored, newCanonical, lowestCanonicalNumber, err := bc.insertHeaderChainStaged(chain)

	// Report some public statistics so the user has a clue what's going on
	last := chain[len(chain)-1]

	context := []interface{}{
		"count", processed, "elapsed", common.PrettyDuration(time.Since(start)),
		"number", last.Number, "hash", last.Hash(),
	}
	if timestamp := time.Unix(int64(last.Time), 0); time.Since(timestamp) > time.Minute {
		context = append(context, []interface{}{"age", common.PrettyAge(timestamp)}...)
	}
	if ignored > 0 {
		context = append(context, []interface{}{"ignored", ignored}...)
	}
	log.Info("Imported new block headers", context...)

	var written uint64
	var err1 error
	if written, err1 = bc.db.Commit(); err1 != nil {
		log.Error("Could not commit chainDb", "error", err1)
		return 0, false, 0, err1
	}
	log.Info("Database", "size", bc.db.DiskSize(), "written", written)
	return n, newCanonical, lowestCanonicalNumber, err
}

// InsertHeaderChain attempts to insert the given header chain in to the local
// chain, possibly creating a reorg. If an error is returned, it will return the
// index number of the failing header as well an error describing what went wrong.
//
// The verify parameter can be used to fine tune whether nonce verification
// should be done or not. The reason behind the optional check is because some
// of the header retrieval mechanisms already need to verify nonces, as well as
// because nonces can be verified sparsely, not needing to check each.
func (bc *BlockChain) InsertHeaderChain(chain []*types.Header, checkFreq int) (int, error) {
	start := time.Now()
	if i, err := bc.hc.ValidateHeaderChain(chain, checkFreq); err != nil {
		return i, err
	}

	// Make sure only one thread manipulates the chain at once
	bc.chainmu.Lock()
	defer bc.chainmu.Unlock()

	if err := bc.addJob(); err != nil {
		return 0, err
	}
	defer bc.doneJob()

	whFunc := func(header *types.Header) error {
		_, err := bc.hc.WriteHeader(context.Background(), header)
		return err
	}
	n, err := bc.hc.InsertHeaderChain(chain, whFunc, start)
	var written uint64
	var err1 error
	if written, err1 = bc.db.Commit(); err1 != nil {
		log.Error("Could not commit chainDb", "error", err1)
		return 0, err1
	}
	log.Info("Database", "size", bc.db.DiskSize(), "written", written)
	return n, err
}

// CurrentHeader retrieves the current head header of the canonical chain. The
// header is retrieved from the HeaderChain's internal cache.
func (bc *BlockChain) CurrentHeader() *types.Header {
	return bc.hc.CurrentHeader()
}

// GetTd retrieves a block's total difficulty in the canonical chain from the
// database by hash and number, caching it if found.
func (bc *BlockChain) GetTd(hash common.Hash, number uint64) *big.Int {
	return bc.hc.GetTd(bc.db, hash, number)
}

// GetTdByHash retrieves a block's total difficulty in the canonical chain from the
// database by hash, caching it if found.
func (bc *BlockChain) GetTdByHash(hash common.Hash) *big.Int {
	return bc.hc.GetTdByHash(hash)
}

// GetHeader retrieves a block header from the database by hash and number,
// caching it if found.
func (bc *BlockChain) GetHeader(hash common.Hash, number uint64) *types.Header {
	return bc.hc.GetHeader(hash, number)
}

// GetHeaderByHash retrieves a block header from the database by hash, caching it if
// found.
func (bc *BlockChain) GetHeaderByHash(hash common.Hash) *types.Header {
	return bc.hc.GetHeaderByHash(hash)
}

// HasHeader checks if a block header is present in the database or not, caching
// it if present.
func (bc *BlockChain) HasHeader(hash common.Hash, number uint64) bool {
	return bc.hc.HasHeader(hash, number)
}

// GetCanonicalHash returns the canonical hash for a given block number
func (bc *BlockChain) GetCanonicalHash(number uint64) common.Hash {
	return bc.hc.GetCanonicalHash(number)
}

// GetBlockHashesFromHash retrieves a number of block hashes starting at a given
// hash, fetching towards the genesis block.
func (bc *BlockChain) GetBlockHashesFromHash(hash common.Hash, max uint64) []common.Hash {
	return bc.hc.GetBlockHashesFromHash(hash, max)
}

// GetAncestor retrieves the Nth ancestor of a given block. It assumes that either the given block or
// a close ancestor of it is canonical. maxNonCanonical points to a downwards counter limiting the
// number of blocks to be individually checked before we reach the canonical chain.
//
// Note: ancestor == 0 returns the same block, 1 returns its parent and so on.
func (bc *BlockChain) GetAncestor(hash common.Hash, number, ancestor uint64, maxNonCanonical *uint64) (common.Hash, uint64) {
	return bc.hc.GetAncestor(hash, number, ancestor, maxNonCanonical)
}

// GetHeaderByNumber retrieves a block header from the database by number,
// caching it (associated with its hash) if found.
func (bc *BlockChain) GetHeaderByNumber(number uint64) *types.Header {
	return bc.hc.GetHeaderByNumber(number)
}

// Config retrieves the chain's fork configuration.
func (bc *BlockChain) Config() *params.ChainConfig { return bc.chainConfig }

// Engine retrieves the blockchain's consensus engine.
func (bc *BlockChain) Engine() consensus.Engine { return bc.engine }

// SubscribeRemovedLogsEvent registers a subscription of RemovedLogsEvent.
func (bc *BlockChain) SubscribeRemovedLogsEvent(ch chan<- RemovedLogsEvent) event.Subscription {
	return bc.scope.Track(bc.rmLogsFeed.Subscribe(ch))
}

// SubscribeChainEvent registers a subscription of ChainEvent.
func (bc *BlockChain) SubscribeChainEvent(ch chan<- ChainEvent) event.Subscription {
	return bc.scope.Track(bc.chainFeed.Subscribe(ch))
}

// SubscribeChainHeadEvent registers a subscription of ChainHeadEvent.
func (bc *BlockChain) SubscribeChainHeadEvent(ch chan<- ChainHeadEvent) event.Subscription {
	return bc.scope.Track(bc.chainHeadFeed.Subscribe(ch))
}

// SubscribeChainSideEvent registers a subscription of ChainSideEvent.
func (bc *BlockChain) SubscribeChainSideEvent(ch chan<- ChainSideEvent) event.Subscription {
	return bc.scope.Track(bc.chainSideFeed.Subscribe(ch))
}

// SubscribeLogsEvent registers a subscription of []*types.Log.
func (bc *BlockChain) SubscribeLogsEvent(ch chan<- []*types.Log) event.Subscription {
	return bc.scope.Track(bc.logsFeed.Subscribe(ch))
}

// SubscribeBlockProcessingEvent registers a subscription of bool where true means
// block processing has started while false means it has stopped.
func (bc *BlockChain) SubscribeBlockProcessingEvent(ch chan<- bool) event.Subscription {
	return bc.scope.Track(bc.blockProcFeed.Subscribe(ch))
}

func (bc *BlockChain) ChainDb() ethdb.Database {
	return bc.db
}

func (bc *BlockChain) NoHistory() bool {
	return bc.cacheConfig.NoHistory
}

func (bc *BlockChain) IsNoHistory(currentBlock *big.Int) bool {
	if currentBlock == nil {
		return bc.cacheConfig.NoHistory
	}

	if !bc.cacheConfig.NoHistory {
		return false
	}

	var isArchiveInterval bool
	currentBlockNumber := bc.CurrentBlock().Number().Uint64()
	highestKnownBlock := bc.GetHeightKnownBlock()
	if highestKnownBlock > currentBlockNumber {
		isArchiveInterval = (currentBlock.Uint64() - highestKnownBlock) <= bc.cacheConfig.ArchiveSyncInterval
	} else {
		isArchiveInterval = (currentBlock.Uint64() - currentBlockNumber) <= bc.cacheConfig.ArchiveSyncInterval
	}

	return bc.cacheConfig.NoHistory || isArchiveInterval
}

func (bc *BlockChain) NotifyHeightKnownBlock(h uint64) {
	bc.highestKnownBlockMu.Lock()
	if bc.highestKnownBlock < h {
		bc.highestKnownBlock = h
	}
	bc.highestKnownBlockMu.Unlock()
}

func (bc *BlockChain) GetHeightKnownBlock() uint64 {
	bc.highestKnownBlockMu.Lock()
	defer bc.highestKnownBlockMu.Unlock()
	return bc.highestKnownBlock
}

func (bc *BlockChain) WithContext(ctx context.Context, blockNum *big.Int) context.Context {
	ctx = bc.Config().WithEIPsFlags(ctx, blockNum)
	ctx = params.WithNoHistory(ctx, bc.NoHistory(), bc.IsNoHistory)
	return ctx
}

type Pruner interface {
	Start() error
	Stop()
}

// addJob should be called only for public methods
func (bc *BlockChain) addJob() error {
	bc.quitMu.RLock()
	defer bc.quitMu.RUnlock()
	if bc.getProcInterrupt() {
		return errors.New("blockchain is stopped")
	}
	bc.wg.Add(1)

	return nil
}

func (bc *BlockChain) doneJob() {
	bc.wg.Done()
}

func (bc *BlockChain) waitJobs() {
	bc.quitMu.Lock()
	atomic.StoreInt32(&bc.procInterrupt, 1)
	bc.wg.Wait()
	bc.quitMu.Unlock()
}

// ExecuteBlockEuphemerally runs a block from provided stateReader and
// writes the result to the provided stateWriter
func ExecuteBlockEuphemerally(
	chainConfig *params.ChainConfig,
	vmConfig *vm.Config,
	chainContext ChainContext,
	engine consensus.Engine,
	block *types.Block,
	stateReader state.StateReader,
	stateWriter state.WriterWithChangeSets,
) error {
	ibs := state.New(stateReader)
	header := block.Header()
	var receipts types.Receipts
	usedGas := new(uint64)
	gp := new(GasPool).AddGas(block.GasLimit())

	if chainConfig.DAOForkSupport && chainConfig.DAOForkBlock != nil && chainConfig.DAOForkBlock.Cmp(block.Number()) == 0 {
		misc.ApplyDAOHardFork(ibs)
	}
	noop := state.NewNoopWriter()
	for i, tx := range block.Transactions() {
		ibs.Prepare(tx.Hash(), block.Hash(), i)
		receipt, err := ApplyTransaction(chainConfig, chainContext, nil, gp, ibs, noop, header, tx, usedGas, *vmConfig)
		if err != nil {
			return fmt.Errorf("tx %x failed: %v", tx.Hash(), err)
		}
		receipts = append(receipts, receipt)
	}

	if chainConfig.IsByzantium(header.Number) {
		receiptSha := types.DeriveSha(receipts)
		if receiptSha != block.Header().ReceiptHash {
			return fmt.Errorf("mismatched receipt headers for block %d", block.NumberU64())
		}
	}

	// Finalize the block, applying any consensus engine specific extras (e.g. block rewards)
	if _, err := engine.FinalizeAndAssemble(chainConfig, header, ibs, block.Transactions(), block.Uncles(), receipts); err != nil {
		return fmt.Errorf("finalize of block %d failed: %v", block.NumberU64(), err)
	}

	ctx := chainConfig.WithEIPsFlags(context.Background(), header.Number)
	if err := ibs.CommitBlock(ctx, stateWriter); err != nil {
		return fmt.Errorf("commiting block %d failed: %v", block.NumberU64(), err)
	}

	if err := stateWriter.WriteChangeSets(); err != nil {
		return fmt.Errorf("writing changesets for block %d failed: %v", block.NumberU64(), err)
	}

	return nil
}