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"
	"math/rand"
	"runtime"
	"sync"
	"sync/atomic"
	"time"

	"github.com/hashicorp/golang-lru"
	"go.opencensus.io/trace"

	"github.com/gochain-io/gochain/common"
	"github.com/gochain-io/gochain/common/mclock"
	"github.com/gochain-io/gochain/common/prque"
	"github.com/gochain-io/gochain/consensus"
	"github.com/gochain-io/gochain/core/rawdb"
	"github.com/gochain-io/gochain/core/state"
	"github.com/gochain-io/gochain/core/types"
	"github.com/gochain-io/gochain/core/vm"
	"github.com/gochain-io/gochain/crypto"
	"github.com/gochain-io/gochain/ethdb"
	"github.com/gochain-io/gochain/log"
	"github.com/gochain-io/gochain/metrics"
	"github.com/gochain-io/gochain/params"
	"github.com/gochain-io/gochain/rlp"
	"github.com/gochain-io/gochain/trie"
)

var (
	blockInsertTimer     = metrics.NewRegisteredTimer("chain/inserts", nil)
	blockValidationTimer = metrics.NewRegisteredTimer("chain/validation", nil)
	blockExecutionTimer  = metrics.NewRegisteredTimer("chain/execution", nil)
	blockWriteTimer      = metrics.NewRegisteredTimer("chain/write", nil)

	ErrNoGenesis = errors.New("Genesis not found in chain")
	ErrStopping  = errors.New("stopping")
)

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

	// BlockChainVersion ensures that an incompatible database forces a resync from scratch.
	BlockChainVersion = 3
)

// CacheConfig contains the configuration values for the trie caching/pruning
// that's resident in a blockchain.
type CacheConfig struct {
	Disabled      bool          // Whether to disable trie write caching (archive node)
	TrieNodeLimit int           // Memory limit (MB) at which to flush the current in-memory trie to disk
	TrieTimeLimit time.Duration // Time limit after which to flush the current in-memory trie to disk
}

// 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     common.Database // 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    RemovedLogsFeed
	chainFeed     ChainFeed
	chainSideFeed ChainSideFeed
	chainHeadFeed ChainHeadFeed
	logsFeed      LogsFeed

	genesisBlock *types.Block

	mu      sync.RWMutex // global mutex for locking chain operations
	chainmu sync.RWMutex // blockchain insertion lock
	procmu  sync.RWMutex // block processor lock

	checkpoint       int          // checkpoint counts towards the new checkpoint
	currentBlock     atomic.Value // Current head of the block chain
	currentFastBlock atomic.Value // Current head of the fast-sync chain (may be above the block chain!)

	stateCache    state.Database // State database to reuse between imports (contains state cache)
	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
	futureBlocks  *lru.Cache     // future blocks are blocks added for later processing

	quit    chan struct{} // blockchain quit channel. Must hold write lock on wgQuitMu to close.
	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. Must hold read lock on wgQuitMu to Add.
	wgQuitMu      sync.RWMutex   // Lock to ensure wg.Add is not called after quit is closed. Write locked when closing quit, read locked when checking quit and adding to wg.

	engine     consensus.Engine
	processor  Processor // block processor interface
	validator  Validator // block and state validator interface
	vmConfig   vm.Config
	parWorkers int // Number of workers to spawn for parallel tasks.

	badBlocks *lru.Cache // Bad block cache
}

// NewBlockChain returns a fully initialised block chain using information
// available in the database. It initialises the default Ethereum Validator and
// Processor.
func NewBlockChain(ctx context.Context, db common.Database, cacheConfig *CacheConfig, chainConfig *params.ChainConfig, engine consensus.Engine, vmConfig vm.Config) (*BlockChain, error) {
	if cacheConfig == nil {
		cacheConfig = &CacheConfig{
			TrieNodeLimit: 256 * 1024 * 1024,
			TrieTimeLimit: 5 * time.Minute,
		}
	}
	bodyCache, _ := lru.New(bodyCacheLimit)
	bodyRLPCache, _ := lru.New(bodyCacheLimit)
	receiptsCache, _ := lru.New(receiptsCacheLimit)
	blockCache, _ := lru.New(blockCacheLimit)
	futureBlocks, _ := lru.New(maxFutureBlocks)
	badBlocks, _ := lru.New(badBlockLimit)

	bc := &BlockChain{
		chainConfig:   chainConfig,
		cacheConfig:   cacheConfig,
		db:            db,
		triegc:        prque.New(nil),
		stateCache:    state.NewDatabase(db),
		quit:          make(chan struct{}),
		bodyCache:     bodyCache,
		bodyRLPCache:  bodyRLPCache,
		receiptsCache: receiptsCache,
		blockCache:    blockCache,
		futureBlocks:  futureBlocks,
		engine:        engine,
		vmConfig:      vmConfig,
		parWorkers:    runtime.GOMAXPROCS(0),
		badBlocks:     badBlocks,
	}
	bc.SetValidator(NewBlockValidator(chainConfig, bc, engine))
	bc.SetProcessor(NewStateProcessor(chainConfig, bc, engine))

	var err error
	bc.hc, err = NewHeaderChain(db, 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
	}
	// 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)
				if err := bc.SetHead(header.Number.Uint64() - 1); err != nil {
					log.Error("Cannot set blockchain head", "err", err)
				}
				log.Error("Chain rewind was successful, resuming normal operation")
			}
		}
	}
	// Take ownership of this particular state
	go bc.update()
	return bc, nil
}

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

// 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.GlobalTable())
	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
	if _, err := state.New(currentBlock.Root(), bc.stateCache); err != nil {
		// Dangling block without a state associated, init from scratch
		log.Warn("Head state missing, repairing chain", "number", currentBlock.Number(), "hash", currentBlock.Hash())
		if err := bc.repair(&currentBlock); err != nil {
			return err
		}
	}
	// Everything seems to be fine, set as the head block
	bc.currentBlock.Store(currentBlock)

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

	// Restore the last known head fast block
	bc.currentFastBlock.Store(currentBlock)
	if head := rawdb.ReadHeadFastBlockHash(bc.db.GlobalTable()); head != (common.Hash{}) {
		if block := bc.GetBlockByHash(head); block != nil {
			bc.currentFastBlock.Store(block)
		}
	}

	// 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)
	log.Info("Loaded most recent local full block", "number", currentBlock.Number(), "hash", currentBlock.Hash(), "td", blockTd)
	log.Info("Loaded most recent local fast block", "number", currentFastBlock.Number(), "hash", currentFastBlock.Hash(), "td", fastTd)

	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.mu.Lock()
	defer bc.mu.Unlock()

	// Rewind the header chain, deleting all block bodies until then
	bc.hc.SetHead(head, rawdb.DeleteBody)
	currentHeader := bc.hc.CurrentHeader()

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

	currentBlock := bc.CurrentBlock()
	currentFastBlock := bc.CurrentFastBlock()

	// Rewind the block chain, ensuring we don't end up with a stateless head block
	if currentBlock != nil && currentHeader.Number.Uint64() < currentBlock.NumberU64() {
		currentBlock = bc.GetBlock(currentHeader.Hash(), currentHeader.Number.Uint64())
		bc.currentBlock.Store(currentBlock)
	}
	if currentBlock != nil {
		if _, err := state.New(currentBlock.Root(), bc.stateCache); err != nil {
			// Rewound state missing, rolled back to before pivot, reset to genesis
			currentBlock = bc.genesisBlock
			bc.currentBlock.Store(currentBlock)
		}
	}
	// Rewind the fast block in a simpleton way to the target head
	if currentFastBlock := bc.CurrentFastBlock(); currentFastBlock != nil && currentHeader.Number.Uint64() < currentFastBlock.NumberU64() {
		currentFastBlock = bc.GetBlock(currentHeader.Hash(), currentHeader.Number.Uint64())
		bc.currentFastBlock.Store(currentFastBlock)
	}
	// If either blocks reached nil, reset to the genesis state
	if currentBlock == nil {
		currentBlock = bc.genesisBlock
		bc.currentBlock.Store(currentBlock)
	}
	if currentFastBlock == nil {
		currentFastBlock = bc.genesisBlock
		bc.currentFastBlock.Store(currentFastBlock)
	}
	rawdb.WriteHeadBlockHash(bc.db.GlobalTable(), currentBlock.Hash())
	rawdb.WriteHeadFastBlockHash(bc.db.GlobalTable(), currentFastBlock.Hash())
	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 _, err := trie.NewSecure(block.Root(), bc.stateCache.TrieDB(), 0); err != nil {
		return err
	}
	// If all checks out, manually set the head block
	bc.mu.Lock()
	bc.currentBlock.Store(block)
	bc.mu.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)
}

// SetProcessor sets the processor required for making state modifications.
func (bc *BlockChain) SetProcessor(processor Processor) {
	bc.procmu.Lock()
	defer bc.procmu.Unlock()
	bc.processor = processor
}

// SetValidator sets the validator which is used to validate incoming blocks.
func (bc *BlockChain) SetValidator(validator Validator) {
	bc.procmu.Lock()
	defer bc.procmu.Unlock()
	bc.validator = validator
}

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

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

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

// StateAt returns a new mutable state based on a particular point in time.
func (bc *BlockChain) StateAt(root common.Hash) (*state.StateDB, error) {
	return state.New(root, bc.stateCache)
}

// 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.mu.Lock()
	defer bc.mu.Unlock()

	// Prepare the genesis block and reinitialise the chain
	bc.hc.WriteTd(genesis.Hash(), genesis.NumberU64(), genesis.Difficulty())
	rawdb.WriteBlock(bc.db, genesis)
	bc.genesisBlock = genesis
	bc.insert(bc.genesisBlock)
	bc.currentBlock.Store(bc.genesisBlock)
	bc.hc.SetGenesis(bc.genesisBlock.Header())
	bc.hc.SetCurrentHeader(bc.genesisBlock.Header())
	bc.currentFastBlock.Store(bc.genesisBlock)

	return nil
}

// repair tries to repair the current blockchain by rolling back the current block
// until one with associated state is found. This is needed to fix incomplete db
// writes caused either by crashes/power outages, or simply non-committed tries.
//
// This method only rolls back the current block. The current header and current
// fast block are left intact.
func (bc *BlockChain) repair(head **types.Block) error {
	for {
		// Abort if we've rewound to a head block that does have associated state
		if _, err := state.New((*head).Root(), bc.stateCache); err == nil {
			log.Info("Rewound blockchain to past state", "number", (*head).Number(), "hash", (*head).Hash())
			return nil
		}
		// Otherwise rewind one block and recheck state availability there
		(*head) = bc.GetBlock((*head).ParentHash(), (*head).NumberU64()-1)
	}
}

// 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.mu.RLock()
	defer bc.mu.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
}

// insert 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) insert(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())
	rawdb.WriteHeadBlockHash(bc.db.GlobalTable(), block.Hash())
	bc.currentBlock.Store(block)

	// If the block is better than our head or is on a different chain, force update heads
	if updateHeads {
		bc.hc.SetCurrentHeader(block.Header())

		rawdb.WriteHeadFastBlockHash(bc.db.GlobalTable(), block.Hash())
		bc.currentFastBlock.Store(block)
	}
}

// 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(hash)
	if number == nil {
		return nil
	}
	body := rawdb.ReadBody(bc.db.BodyTable(), 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(hash)
	if number == nil {
		return nil
	}
	body := rawdb.ReadBodyRLP(bc.db.BodyTable(), 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.BodyTable(), hash, number)
}

// HasState checks if state trie is fully present in the database or not.
func (bc *BlockChain) HasState(hash common.Hash) bool {
	_, err := bc.stateCache.OpenTrie(hash)
	return err == nil
}

// 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 bc.HasState(block.Root())
}

// 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(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.GlobalTable(), hash)
	if number == nil {
		return nil
	}

	receipts := rawdb.ReadReceipts(bc.db.ReceiptTable(), hash, *number)
	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(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
}

// TrieNode retrieves a blob of data associated with a trie node (or code hash)
// either from ephemeral in-memory cache, or from persistent storage.
func (bc *BlockChain) TrieNode(hash common.Hash) ([]byte, error) {
	return bc.stateCache.TrieDB().Node(hash)
}

// 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.rmLogsFeed.Close()
	bc.chainFeed.Close()
	bc.chainSideFeed.Close()
	bc.chainHeadFeed.Close()
	bc.logsFeed.Close()
	bc.closeQuit()
	atomic.StoreInt32(&bc.procInterrupt, 1)

	bc.wg.Wait()

	// Ensure the state of a recent block is also stored to disk before exiting.
	// We're writing three different states to catch different restart scenarios:
	//  - HEAD:     So we don't need to reprocess any blocks in the general case
	//  - HEAD-1:   So we don't do large reorgs if our HEAD becomes an uncle
	//  - HEAD-127: So we have a hard limit on the number of blocks reexecuted
	if !bc.cacheConfig.Disabled {
		triedb := bc.stateCache.TrieDB()

		for _, offset := range []uint64{0, 1, triesInMemory - 1} {
			if number := bc.CurrentBlock().NumberU64(); number > offset {
				recent := bc.GetBlockByNumber(number - offset)

				log.Info("Writing cached state to disk", "block", recent.Number(), "hash", recent.Hash(), "root", recent.Root())
				if err := triedb.Commit(recent.Root(), true); err != nil {
					log.Error("Failed to commit recent state trie", "err", err)
				}
			}
		}
		for !bc.triegc.Empty() {
			triedb.Dereference(bc.triegc.PopItem().(common.Hash))
		}
		if size, _ := triedb.Size(); size != 0 {
			log.Error("Dangling trie nodes after full cleanup")
		}
	}
	log.Info("Blockchain manager stopped")
}

func (bc *BlockChain) procFutureBlocks(ctx context.Context) {
	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 {
		types.BlockBy(types.Number).Sort(blocks)

		// Insert one by one as chain insertion needs contiguous ancestry between blocks
		for i := range blocks {
			if n, err := bc.InsertChain(ctx, blocks[i:i+1]); err != nil {
				log.Error("Cannot insert future blocks into chain", "n", n, "err", err)
			}
		}
	}
}

// WriteStatus status of write
type WriteStatus byte

const (
	NonStatTy WriteStatus = iota
	CanonStatTy
	SideStatTy
)

func (ws WriteStatus) String() string {
	switch ws {
	case NonStatTy:
		return "NonStatTy"
	case CanonStatTy:
		return "CanonStatTy"
	case SideStatTy:
		return "SideStatTy"
	default:
		return fmt.Sprintf("unknown WriteStatus: %d", ws)
	}
}

// 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.mu.Lock()
	defer bc.mu.Unlock()

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

		currentHeader := bc.hc.CurrentHeader()
		if currentHeader.Hash() == hash {
			bc.hc.SetCurrentHeader(bc.GetHeader(currentHeader.ParentHash, currentHeader.Number.Uint64()-1))
		}
		if currentFastBlock := bc.CurrentFastBlock(); currentFastBlock.Hash() == hash {
			newFastBlock := bc.GetBlock(currentFastBlock.ParentHash(), currentFastBlock.NumberU64()-1)
			bc.currentFastBlock.Store(newFastBlock)
			rawdb.WriteHeadFastBlockHash(bc.db.GlobalTable(), newFastBlock.Hash())
		}
		if currentBlock := bc.CurrentBlock(); currentBlock.Hash() == hash {
			newBlock := bc.GetBlock(currentBlock.ParentHash(), currentBlock.NumberU64()-1)
			bc.currentBlock.Store(newBlock)
			rawdb.WriteHeadBlockHash(bc.db.GlobalTable(), newBlock.Hash())
		}
	}
}

// SetReceiptsData computes all the non-consensus fields of the receipts
func SetReceiptsData(ctx context.Context, config *params.ChainConfig, block *types.Block, receipts types.Receipts) error {
	signer := types.MakeSigner(config, block.Number())

	transactions, logIndex := block.Transactions(), uint(0)
	if len(transactions) != len(receipts) {
		return errors.New("transaction and receipt count mismatch")
	}

	for j := 0; j < len(receipts); j++ {
		// The transaction hash can be retrieved from the transaction itself
		receipts[j].TxHash = transactions[j].Hash()

		// The contract address can be derived from the transaction itself
		if transactions[j].To() == nil {
			// Deriving the signer is expensive, only do if it's actually needed
			from, _ := types.Sender(signer, transactions[j])
			receipts[j].ContractAddress = crypto.CreateAddress(from, transactions[j].Nonce())
		}
		// The used gas can be calculated based on previous receipts
		if j == 0 {
			receipts[j].GasUsed = receipts[j].CumulativeGasUsed
		} else {
			receipts[j].GasUsed = receipts[j].CumulativeGasUsed - receipts[j-1].CumulativeGasUsed
		}
		// The derived log fields can simply be set from the block and transaction
		for k := 0; k < len(receipts[j].Logs); k++ {
			receipts[j].Logs[k].BlockNumber = block.NumberU64()
			receipts[j].Logs[k].BlockHash = block.Hash()
			receipts[j].Logs[k].TxHash = receipts[j].TxHash
			receipts[j].Logs[k].TxIndex = uint(j)
			receipts[j].Logs[k].Index = logIndex
			logIndex++
		}
	}
	return nil
}

// InsertReceiptChain attempts to complete an already existing header chain with
// transaction and receipt data.
func (bc *BlockChain) InsertReceiptChain(ctx context.Context, blockChain types.Blocks, receiptChain []types.Receipts) (int, error) {
	if !bc.wgAdd() {
		return 0, ErrStopping
	}
	defer bc.wg.Done()

	// Do a sanity check that the provided chain is actually ordered and linked
	for i := 1; i < len(blockChain); i++ {
		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])
		}
	}

	var (
		stats  = struct{ processed, ignored int32 }{}
		start  = time.Now()
		bytes  = 0
		gbatch = bc.db.GlobalTable().NewBatch()
		bbatch = bc.db.BodyTable().NewBatch()
		rbatch = bc.db.ReceiptTable().NewBatch()
	)
	for i, block := range blockChain {
		receipts := receiptChain[i]
		// Short circuit insertion if shutting down or processing failed
		if atomic.LoadInt32(&bc.procInterrupt) == 1 {
			return 0, nil
		}
		// 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])
		}
		// Skip if the entire data is already known
		if bc.HasBlock(block.Hash(), block.NumberU64()) {
			stats.ignored++
			continue
		}
		// Compute all the non-consensus fields of the receipts
		if err := SetReceiptsData(ctx, bc.chainConfig, block, receipts); err != nil {
			return i, fmt.Errorf("failed to set receipts data: %v", err)
		}
		// Write all the data out into the database
		rawdb.WriteBody(bbatch, block.Hash(), block.NumberU64(), block.Body())
		rawdb.WriteReceipts(rbatch, block.Hash(), block.NumberU64(), receipts)
		rawdb.WriteTxLookupEntries(gbatch, block)
		stats.processed++

		if bbatch.ValueSize() >= ethdb.IdealBatchSize || rbatch.ValueSize() >= ethdb.IdealBatchSize {
			rawdb.Must("flush global batch", gbatch.Write)
			rawdb.Must("flush body batch", bbatch.Write)
			rawdb.Must("flush receipts batch", rbatch.Write)
			bytes += gbatch.ValueSize()
			bytes += bbatch.ValueSize()
			bytes += rbatch.ValueSize()
			gbatch.Reset()
			bbatch.Reset()
			rbatch.Reset()
		}
	}
	if gbatch.ValueSize() > 0 {
		bytes += gbatch.ValueSize()
		rawdb.Must("write global batch", gbatch.Write)
	}
	if bbatch.ValueSize() > 0 {
		bytes += bbatch.ValueSize()
		rawdb.Must("write body batch", bbatch.Write)
	}
	if rbatch.ValueSize() > 0 {
		bytes += rbatch.ValueSize()
		rawdb.Must("write receipts batch", rbatch.Write)
	}

	// Update the head fast sync block if better
	bc.mu.Lock()
	head := blockChain[len(blockChain)-1]
	if td := bc.GetTd(head.Hash(), head.NumberU64()); td != nil { // Rewind may have occurred, skip in that case
		currentFastBlock := bc.CurrentFastBlock()
		if bc.GetTd(currentFastBlock.Hash(), currentFastBlock.NumberU64()).Cmp(td) < 0 {
			rawdb.WriteHeadFastBlockHash(bc.db.GlobalTable(), head.Hash())
			bc.currentFastBlock.Store(head)
		}
	}
	bc.mu.Unlock()

	log.Info("Imported new block receipts",
		"count", stats.processed,
		"elapsed", common.PrettyDuration(time.Since(start)),
		"number", head.Number(),
		"hash", head.Hash(),
		"size", common.StorageSize(bytes),
		"ignored", stats.ignored)
	return 0, nil
}

var lastWrite uint64

// WriteBlockWithoutState writes only the block and its metadata to the database,
// but does not write any state. This is used to construct competing side forks
// up to the point where they exceed the canonical total difficulty.
func (bc *BlockChain) WriteBlockWithoutState(block *types.Block, td *big.Int) (err error) {
	if !bc.wgAdd() {
		return ErrStopping
	}
	defer bc.wg.Done()

	bc.hc.WriteTd(block.Hash(), block.NumberU64(), td)
	rawdb.WriteBlock(bc.db, block)
	return 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, state *state.StateDB) (status WriteStatus, err error) {
	ctx, span := trace.StartSpan(ctx, "BlockChain.WriteBlockWithState")
	defer span.End()

	if !bc.wgAdd() {
		return 0, ErrStopping
	}
	defer bc.wg.Done()

	// Calculate the total difficulty of the block
	ptd := bc.GetTd(block.ParentHash(), block.NumberU64()-1)
	if ptd == nil {
		return NonStatTy, consensus.ErrUnknownAncestor
	}
	// Make sure no inconsistent state is leaked during insertion
	bc.mu.Lock()
	defer bc.mu.Unlock()

	currentBlock := bc.CurrentBlock()
	currentHash := currentBlock.Hash()
	localTd := bc.GetTd(currentHash, currentBlock.NumberU64())
	externTd := new(big.Int).Add(block.Difficulty(), ptd)

	// Irrelevant of the canonical status, write the block itself to the database
	hash := block.Hash()
	bc.hc.WriteTd(hash, block.NumberU64(), externTd)
	rawdb.WriteBlock(bc.db, block)
	root, err := state.Commit(bc.chainConfig.IsEIP158(block.Number()))
	if err != nil {
		return NonStatTy, err
	}
	triedb := bc.stateCache.TrieDB()

	// If we're running an archive node, always flush
	if bc.cacheConfig.Disabled {
		if err := triedb.Commit(root, false); err != nil {
			return NonStatTy, err
		}
	} else {
		// Full but not archive node, do proper garbage collection
		triedb.Reference(root, common.Hash{}) // metadata reference to keep trie alive
		bc.triegc.Push(root, -int64(block.NumberU64()))

		if current := block.NumberU64(); current > triesInMemory {
			// If we exceeded our memory allowance, flush matured singleton nodes to disk
			var (
				nodes, imgs = triedb.Size()
				limit       = common.StorageSize(bc.cacheConfig.TrieNodeLimit) * 1024 * 1024
			)
			if nodes > limit || imgs > 4*1024*1024 {
				triedb.Cap(limit - ethdb.IdealBatchSize)
			}
			// Find the next state trie we need to commit
			header := bc.GetHeaderByNumber(current - triesInMemory)
			chosen := header.Number.Uint64()

			// If we exceeded out time allowance, flush an entire trie to disk
			if bc.gcproc > bc.cacheConfig.TrieTimeLimit {
				// If we're exceeding limits but haven't reached a large enough memory gap,
				// warn the user that the system is becoming unstable.
				if chosen < lastWrite+triesInMemory && bc.gcproc >= 2*bc.cacheConfig.TrieTimeLimit {
					log.Info("State in memory for too long, committing", "time", bc.gcproc, "allowance", bc.cacheConfig.TrieTimeLimit, "optimum", float64(chosen-lastWrite)/triesInMemory)
				}
				// Flush an entire trie and restart the counters
				if err := triedb.Commit(header.Root, true); err != nil {
					log.Error("Cannot commit trie db", "err", err)
				}
				lastWrite = chosen
				bc.gcproc = 0
			}
			// Garbage collect anything below our required write retention
			for !bc.triegc.Empty() {
				root, number := bc.triegc.Pop()
				if uint64(-number) > chosen {
					bc.triegc.Push(root, number)
					break
				}
				triedb.Dereference(root.(common.Hash))
			}
		}
	}
	rawdb.WriteReceipts(bc.db.ReceiptTable(), block.Hash(), block.NumberU64(), receipts)
	local := chainHead{localTd, currentBlock.NumberU64(), currentBlock.GasUsed()}
	external := chainHead{externTd, block.NumberU64(), block.GasUsed()}
	if reorg(local, external) {
		// Reorganise the chain if the parent is not the head block
		if block.ParentHash() != currentBlock.Hash() {
			log.Info("Reorganizing block chain", "oldnum", currentBlock.NumberU64(), "newnum", block.NumberU64(), "oldtd", localTd, "newtd", externTd, "oldhash", currentHash, "newhash", hash)
			start := time.Now()
			if err := bc.reorg(ctx, currentBlock, block); err != nil {
				return NonStatTy, err
			}
			dur := time.Since(start)
			log.Info("Reorganized block chain", "dur", common.PrettyDuration(dur))
		}
		rawdb.WriteTxLookupEntries(bc.db.GlobalTable(), block)
		rawdb.WritePreimages(bc.db.GlobalTable(), block.NumberU64(), state.Preimages())
		status = CanonStatTy
	} else {
		status = SideStatTy
	}

	// Set new head.
	if status == CanonStatTy {
		bc.insert(block)
	}
	bc.futureBlocks.Remove(block.Hash())
	return status, nil
}

type chainHead struct {
	totalDifficulty *big.Int
	number          uint64
	gasUsed         uint64
}

// reorg returns true if the external chainHead should be used instead of local.
// Cases include:
//  - higher total difficulty
//  - same total difficulty and lesser number
//  - same total difficulty and number, more gas used
//  - same total difficulty, number, and gas used, random 50/50 chance
// Please refer to http://www.cs.cornell.edu/~ie53/publications/btcProcFC.pdf
func reorg(local, external chainHead) bool {
	cmp := external.totalDifficulty.Cmp(local.totalDifficulty)
	if cmp != 0 {
		return cmp > 0
	}
	log.Info("Reorg same difficulty", "diff", local.totalDifficulty, "oldnum", local.number, "newnum", external.number)
	// Split same-difficulty blocks by number, then most gas used, then randomly.
	if external.number < local.number {
		return true
	}
	if external.number == local.number {
		if external.gasUsed > local.gasUsed {
			return true
		}
		if external.gasUsed == local.gasUsed && rand.Float64() < 0.5 {
			return true
		}
	}
	return false
}

// 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 := big.NewInt(time.Now().Unix() + maxTimeFutureBlocks)
	if block.Time().Cmp(max) > 0 {
		return fmt.Errorf("future block timestamp %v > allowed %v", block.Time(), max)
	}
	bc.futureBlocks.Add(block.Hash(), block)
	return nil
}

// 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) {
	ctx, span := trace.StartSpan(ctx, "BlockChain.InsertChain", trace.WithSampler(trace.AlwaysSample()))
	defer span.End()
	span.AddAttributes(trace.Int64Attribute("len", int64(len(chain))))

	// Sanity check that we have something meaningful to import
	if len(chain) == 0 {
		return 0, nil
	}
	// Do a sanity check that the provided chain is actually ordered and linked.
	for i := 1; i < len(chain); i++ {
		if chain[i].NumberU64() != chain[i-1].NumberU64()+1 || chain[i].ParentHash() != chain[i-1].Hash() {
			// Chain broke ancestry, log a message (programming error) and skip insertion
			log.Error("Non contiguous block insert", "number", chain[i].Number(), "hash", chain[i].Hash(),
				"parent", chain[i].ParentHash(), "prevnumber", chain[i-1].Number(), "prevhash", chain[i-1].Hash())

			return 0, fmt.Errorf("non contiguous insert: item %d is #%d [%x…], item %d is #%d [%x…] (parent [%x…])", i-1, chain[i-1].NumberU64(),
				chain[i-1].Hash().Bytes()[:4], i, chain[i].NumberU64(), chain[i].Hash().Bytes()[:4], chain[i].ParentHash().Bytes()[:4])
		}
	}
	// Pre-checks passed, start the full block imports
	if !bc.wgAdd() {
		return 0, ErrStopping
	}
	bc.chainmu.Lock()
	n, events, logs, err := bc.insertChain(ctx, chain, true)
	bc.chainmu.Unlock()
	bc.wg.Done()

	bc.PostChainEvents(ctx, events, logs)
	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) (int, []interface{}, []*types.Log, error) {
	// If the chain is terminating, don't even bother starting u
	if atomic.LoadInt32(&bc.procInterrupt) == 1 {
		return 0, nil, nil, 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()}
		events        = make([]interface{}, 0, len(chain))
		lastCanon     *types.Block
		coalescedLogs []*types.Log
	)
	// Start the parallel header verifier
	headers := make([]*types.Header, len(chain))
	for i, block := range chain {
		headers[i] = block.Header()
	}
	abortHeaders, results := bc.engine.VerifyHeaders(ctx, bc, headers)
	defer close(abortHeaders)

	// Peek the error for the first block to decide the directing import logic
	it := newInsertIterator(chain, results, bc.Validator())

	block, err := it.next(ctx)
	switch {
	// First block is pruned, insert as sidechain and reorg only if TD grows enough
	case err == consensus.ErrPrunedAncestor:
		return bc.insertSidechain(ctx, it)

	// First block is future, shove it (and all children) to the future queue (unknown ancestor)
	case err == consensus.ErrFutureBlock || (err == consensus.ErrUnknownAncestor && bc.futureBlocks.Contains(it.first().ParentHash())):
		for block != nil && (it.index == 0 || err == consensus.ErrUnknownAncestor) {
			if err := bc.addFutureBlock(block); err != nil {
				return it.index, events, coalescedLogs, err
			}
			block, err = it.next(ctx)
		}
		stats.queued += it.processed()
		stats.ignored += it.remaining()

		// If there are any still remaining, mark as ignored
		return it.index, events, coalescedLogs, err

	// First block (and state) is known
	//   1. We did a roll-back, and should now do a re-import
	//   2. The block is stored as a sidechain, and is lying about it's stateroot, and passes a stateroot
	// 	    from the canonical chain, which has not been verified.
	case err == ErrKnownBlock:
		// Skip all known blocks that behind us
		current := bc.CurrentBlock().NumberU64()

		for block != nil && err == ErrKnownBlock && current >= block.NumberU64() {
			stats.ignored++
			block, err = it.next(ctx)
		}
		// Falls through to the block import

	// Some other error occurred, abort
	case err != nil:
		stats.ignored += len(it.chain)
		bc.reportBlock(block, nil, err)
		return it.index, events, coalescedLogs, err
	}
	// No validation errors for the first block (or chain prefix skipped)
	for ; block != nil && err == nil; block, err = it.next(ctx) {
		// If the chain is terminating, stop processing blocks
		if atomic.LoadInt32(&bc.procInterrupt) == 1 {
			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 it.index, events, coalescedLogs, ErrBlacklistedHash
		}
		// Retrieve the parent block and it's state to execute on top
		start := time.Now()

		parent := it.previous()
		if parent == nil {
			parent = bc.GetBlock(block.ParentHash(), block.NumberU64()-1)
		}
		state, err := state.New(parent.Root(), bc.stateCache)
		if err != nil {
			return it.index, events, coalescedLogs, err
		}
		// Process block using the parent state as reference point.
		t0 := time.Now()
		receipts, logs, usedGas, err := bc.processor.Process(ctx, block, state, bc.vmConfig)
		t1 := time.Now()
		if err != nil {
			bc.reportBlock(block, receipts, err)
			return it.index, events, coalescedLogs, err
		}
		// Validate the state using the default validator
		if err := bc.Validator().ValidateState(ctx, block, parent, state, receipts, usedGas); err != nil {
			bc.reportBlock(block, receipts, err)
			return it.index, events, coalescedLogs, err
		}
		t2 := time.Now()
		proctime := time.Since(start)

		// Write the block to the chain and get the status.
		status, err := bc.WriteBlockWithState(ctx, block, receipts, state)
		t3 := time.Now()
		if err != nil {
			return it.index, events, coalescedLogs, err
		}
		blockInsertTimer.UpdateSince(start)
		blockExecutionTimer.Update(t1.Sub(t0))
		blockValidationTimer.Update(t2.Sub(t1))
		blockWriteTimer.Update(t3.Sub(t2))
		switch status {
		case CanonStatTy:
			log.Debug("Inserted new block", "number", block.Number(), "hash", block.Hash(), "diff", block.Difficulty(),
				"uncles", len(block.Uncles()), "txs", len(block.Transactions()), "gas", block.GasUsed(),
				"elapsed", common.PrettyDuration(time.Since(start)),
				"root", block.Root())

			coalescedLogs = append(coalescedLogs, logs...)
			events = append(events, ChainEvent{block, block.Hash(), logs})
			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(),
				"diff", block.Difficulty(), "elapsed", common.PrettyDuration(time.Since(start)),
				"txs", len(block.Transactions()), "gas", block.GasUsed(), "uncles", len(block.Uncles()),
				"root", block.Root())
			events = append(events, ChainSideEvent{block})
		}
		blockInsertTimer.UpdateSince(start)
		stats.processed++
		stats.usedGas += usedGas

		cache, _ := bc.stateCache.TrieDB().Size()
		stats.report(chain, it.index, cache)
	}
	// Any blocks remaining here? The only ones we care about are the future ones
	if block != nil && err == consensus.ErrFutureBlock {
		if err := bc.addFutureBlock(block); err != nil {
			return it.index, events, coalescedLogs, err
		}
		block, err = it.next(ctx)

		for ; block != nil && err == consensus.ErrUnknownAncestor; block, err = it.next(ctx) {
			if err := bc.addFutureBlock(block); err != nil {
				return it.index, events, coalescedLogs, err
			}
			stats.queued++
		}
	}
	stats.ignored += it.remaining()

	// Append a single chain head event if we've progressed the chain
	if lastCanon != nil && bc.CurrentBlock().Hash() == lastCanon.Hash() {
		events = append(events, ChainHeadEvent{lastCanon})
	}
	return it.index, events, coalescedLogs, err
}

// insertSidechain is called when an import batch hits upon a pruned ancestor
// error, which happens when a sidechain with a sufficiently old fork-block is
// found.
//
// The method writes all (header-and-body-valid) blocks to disk, then tries to
// switch over to the new chain if the TD exceeded the current chain.
func (bc *BlockChain) insertSidechain(ctx context.Context, it *insertIterator) (int, []interface{}, []*types.Log, error) {
	var (
		externTd *big.Int
		current  = bc.CurrentBlock().NumberU64()
	)
	// The first sidechain block error is already verified to be ErrPrunedAncestor.
	// Since we don't import them here, we expect ErrUnknownAncestor for the remaining
	// ones. Any other errors means that the block is invalid, and should not be written
	// to disk.
	block, err := it.current(), consensus.ErrPrunedAncestor
	for ; block != nil && (err == consensus.ErrPrunedAncestor); block, err = it.next(ctx) {
		// Check the canonical state root for that number
		if number := block.NumberU64(); current >= number {
			if canonical := bc.GetBlockByNumber(number); canonical != nil && canonical.Root() == block.Root() {
				// This is most likely a shadow-state attack. When a fork is imported into the
				// database, and it eventually reaches a block height which is not pruned, we
				// just found that the state already exist! This means that the sidechain block
				// refers to a state which already exists in our canon chain.
				//
				// If left unchecked, we would now proceed importing the blocks, without actually
				// having verified the state of the previous blocks.
				log.Warn("Sidechain ghost-state attack detected", "number", block.NumberU64(), "sideroot", block.Root(), "canonroot", canonical.Root())

				// If someone legitimately side-mines blocks, they would still be imported as usual. However,
				// we cannot risk writing unverified blocks to disk when they obviously target the pruning
				// mechanism.
				return it.index, nil, nil, errors.New("sidechain ghost-state attack")
			}
		}
		if externTd == nil {
			externTd = bc.GetTd(block.ParentHash(), block.NumberU64()-1)
		}
		externTd = new(big.Int).Add(externTd, block.Difficulty())

		if !bc.HasBlock(block.Hash(), block.NumberU64()) {
			start := time.Now()
			if err := bc.WriteBlockWithoutState(block, externTd); err != nil {
				return it.index, nil, nil, err
			}
			log.Debug("Inserted sidechain 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())
		}
	}
	// At this point, we've written all sidechain blocks to database. Loop ended
	// either on some other error or all were processed. If there was some other
	// error, we can ignore the rest of those blocks.
	//
	// If the externTd was larger than our local TD, we now need to reimport the previous
	// blocks to regenerate the required state
	localTd := bc.GetTd(bc.CurrentBlock().Hash(), current)
	if localTd.Cmp(externTd) > 0 {
		log.Info("Sidechain written to disk", "start", it.first().NumberU64(), "end", it.previous().NumberU64(), "sidetd", externTd, "localtd", localTd)
		return it.index, nil, nil, err
	}
	// Gather all the sidechain hashes (full blocks may be memory heavy)
	var (
		hashes  []common.Hash
		numbers []uint64
	)
	parent := bc.GetHeader(it.previous().Hash(), it.previous().NumberU64())
	for parent != nil && !bc.HasState(parent.Root) {
		hashes = append(hashes, parent.Hash())
		numbers = append(numbers, parent.Number.Uint64())

		parent = bc.GetHeader(parent.ParentHash, parent.Number.Uint64()-1)
	}
	if parent == nil {
		return it.index, nil, nil, errors.New("missing parent")
	}
	// Import all the pruned blocks to make the state available
	var (
		blocks []*types.Block
		memory common.StorageSize
	)
	for i := len(hashes) - 1; i >= 0; i-- {
		// Append the next block to our batch
		block := bc.GetBlock(hashes[i], numbers[i])

		blocks = append(blocks, block)
		memory += block.Size()

		// If memory use grew too large, import and continue. Sadly we need to discard
		// all raised events and logs from notifications since we're too heavy on the
		// memory here.
		if len(blocks) >= 2048 || memory > 64*1024*1024 {
			log.Info("Importing heavy sidechain segment", "blocks", len(blocks), "start", blocks[0].NumberU64(), "end", block.NumberU64())
			if _, _, _, err := bc.insertChain(ctx, blocks, false); err != nil {
				return 0, nil, nil, err
			}
			blocks, memory = blocks[:0], 0

			// If the chain is terminating, stop processing blocks
			if atomic.LoadInt32(&bc.procInterrupt) == 1 {
				log.Debug("Premature abort during blocks processing")
				return 0, nil, nil, nil
			}
		}
	}
	if len(blocks) > 0 {
		log.Info("Importing sidechain segment", "start", blocks[0].NumberU64(), "end", blocks[len(blocks)-1].NumberU64())
		return bc.insertChain(ctx, blocks, false)
	}
	return 0, nil, nil, nil
}

// reorgs 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(ctx context.Context, oldBlock, newBlock *types.Block) error {
	ctx, span := trace.StartSpan(ctx, "BlockChain.reorg")
	defer span.End()

	var (
		newChain    types.Blocks
		oldChain    types.Blocks
		commonBlock *types.Block
		deletedTxs  types.Transactions
		deletedLogs []*types.Log
		// collectLogs collects the logs that were generated during the
		// processing of the block that corresponds with the given hash.
		// These logs are later announced as deleted.
		collectLogs = func(hash common.Hash) {
			// Coalesce logs and set 'Removed'.
			number := bc.hc.GetBlockNumber(hash)
			if number == nil {
				return
			}
			receipts := rawdb.ReadReceipts(bc.db.ReceiptTable(), hash, *number)
			for _, receipt := range receipts {
				for _, log := range receipt.Logs {
					del := *log
					del.Removed = true
					deletedLogs = append(deletedLogs, &del)
				}
			}
		}
	)

	// first reduce whoever is higher bound
	if oldBlock.NumberU64() > newBlock.NumberU64() {
		// reduce old chain
		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())
		}
	} else {
		// reduce new chain and append new chain blocks for inserting later on
		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")
	}

	for {
		if oldBlock.Hash() == newBlock.Hash() {
			commonBlock = oldBlock
			break
		}

		oldChain = append(oldChain, oldBlock)
		newChain = append(newChain, newBlock)
		deletedTxs = append(deletedTxs, oldBlock.Transactions()...)
		collectLogs(oldBlock.Hash())

		oldBlock, newBlock = bc.GetBlock(oldBlock.ParentHash(), oldBlock.NumberU64()-1), bc.GetBlock(newBlock.ParentHash(), newBlock.NumberU64()-1)
		if oldBlock == nil {
			return fmt.Errorf("Invalid old chain")
		}
		if newBlock == nil {
			return fmt.Errorf("Invalid new chain")
		}
	}
	// Ensure the user sees large reorgs
	if len(oldChain) > 0 && len(newChain) > 0 {
		logFn := log.Debug
		if len(oldChain) > 63 {
			logFn = log.Warn
		}
		logFn("Chain split detected", "number", commonBlock.Number(), "hash", commonBlock.Hash(),
			"drop", len(oldChain), "dropfrom", oldChain[0].Hash(), "add", len(newChain), "addfrom", newChain[0].Hash())
	} else {
		log.Error("Impossible reorg, please file an issue", "oldnum", oldBlock.Number(), "oldhash", oldBlock.Hash(), "newnum", newBlock.Number(), "newhash", newBlock.Hash())
	}
	// Insert the new chain, taking care of the proper incremental order
	addedTxs := make(map[common.Hash]struct{})
	batch := bc.db.GlobalTable().NewBatch()
	for i := len(newChain) - 1; i >= 0; i-- {
		// insert the block in the canonical way, re-writing history
		bc.insert(newChain[i])
		// write lookup entries for hash based transaction/receipt searches
		rawdb.WriteTxLookupEntries(batch, newChain[i])
		for _, tx := range newChain[i].Transactions() {
			addedTxs[tx.Hash()] = struct{}{}
		}
	}
	// calculate the difference between deleted and added transactions
	var diff types.Transactions
	for _, tx := range deletedTxs {
		if _, ok := addedTxs[tx.Hash()]; !ok {
			diff = append(diff, tx)
		}
	}
	// When transactions get deleted from the database that means the
	// receipts that were created in the fork must also be deleted
	for _, tx := range diff {
		rawdb.DeleteTxLookupEntry(batch, tx.Hash())
	}
	rawdb.Must("batch delete tx lookup entries", batch.Write)
	if len(deletedLogs) > 0 {
		bc.rmLogsFeed.Send(RemovedLogsEvent{deletedLogs})
	}
	if len(oldChain) > 0 {
		for _, block := range oldChain {
			bc.chainSideFeed.Send(ChainSideEvent{Block: block})
		}
	}

	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(ctx context.Context, events []interface{}, logs []*types.Log) {
	ctx, span := trace.StartSpan(ctx, "BlockChain.PostChainEvents")
	defer span.End()

	// 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:
			ctx, span := trace.StartSpan(context.Background(), "BlockChain.update-futureTimer")
			bc.procFutureBlocks(ctx)
			span.End()
		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.Header().Hash(), block.Header())
}

// 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 _, receipt := range receipts {
		receiptString += fmt.Sprintf("\t%v\n", receipt)
	}
	log.Error(fmt.Sprintf(`
########## BAD BLOCK #########
Chain config: %v

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

Error: %v
##############################
`, bc.chainConfig, block.Number(), block.Hash(), receiptString, 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(ctx context.Context, chain []*types.Header, checkFreq int) (int, error) {
	start := time.Now()
	if i, err := bc.hc.ValidateHeaderChain(ctx, 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 !bc.wgAdd() {
		return 0, ErrStopping
	}
	defer bc.wg.Done()

	whFunc := func(header *types.Header) error {
		bc.mu.Lock()
		defer bc.mu.Unlock()

		_, err := bc.hc.WriteHeader(header)
		return err
	}

	return bc.hc.InsertHeaderChain(chain, whFunc, start)
}

// writeHeader writes a header into the local chain, given that its parent is
// already known. If the total difficulty of the newly inserted header becomes
// greater than the current known TD, the canonical chain is re-routed.
//
// Note: This method is not concurrent-safe with inserting blocks simultaneously
// into the chain, as side effects caused by reorganisations cannot be emulated
// without the real blocks. Hence, writing headers directly should only be done
// in two scenarios: pure-header mode of operation (light clients), or properly
// separated header/block phases (non-archive clients).
func (bc *BlockChain) writeHeader(header *types.Header) error {
	if !bc.wgAdd() {
		return ErrStopping
	}
	defer bc.wg.Done()

	bc.mu.Lock()
	defer bc.mu.Unlock()

	_, err := bc.hc.WriteHeader(header)
	return 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(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)
}

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

	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 blockchain's chain 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, name string) {
	bc.rmLogsFeed.Subscribe(ch, name)
}

func (bc *BlockChain) UnsubscribeRemovedLogsEvent(ch chan<- RemovedLogsEvent) {
	bc.rmLogsFeed.Unsubscribe(ch)
}

// SubscribeChainEvent registers a subscription of ChainEvent.
func (bc *BlockChain) SubscribeChainEvent(ch chan<- ChainEvent, name string) {
	bc.chainFeed.Subscribe(ch, name)
}

// SubscribeChainEvent registers a subscription of ChainEvent.
func (bc *BlockChain) UnsubscribeChainEvent(ch chan<- ChainEvent) {
	bc.chainFeed.Unsubscribe(ch)
}

// SubscribeChainHeadEvent registers a subscription of ChainHeadEvent.
func (bc *BlockChain) SubscribeChainHeadEvent(ch chan<- ChainHeadEvent, name string) {
	bc.chainHeadFeed.Subscribe(ch, name)
}

// SubscribeChainHeadEvent registers a subscription of ChainHeadEvent.
func (bc *BlockChain) UnsubscribeChainHeadEvent(ch chan<- ChainHeadEvent) {
	bc.chainHeadFeed.Unsubscribe(ch)
}

// SubscribeChainSideEvent registers a subscription of ChainSideEvent.
func (bc *BlockChain) SubscribeChainSideEvent(ch chan<- ChainSideEvent, name string) {
	bc.chainSideFeed.Subscribe(ch, name)
}

func (bc *BlockChain) UnsubscribeChainSideEvent(ch chan<- ChainSideEvent) {
	bc.chainSideFeed.Unsubscribe(ch)
}

// SubscribeLogsEvent registers a subscription of []*types.Log.
func (bc *BlockChain) SubscribeLogsEvent(ch chan<- []*types.Log, name string) {
	bc.logsFeed.Subscribe(ch, name)
}

func (bc *BlockChain) UnsubscribeLogsEvent(ch chan<- []*types.Log) {
	bc.logsFeed.Unsubscribe(ch)
}

// wgAdd adds 1 to wg while holding the read lock, unless the quit channel has been closed.
// Returns true if added, or false if stopped.
func (bc *BlockChain) wgAdd() bool {
	bc.wgQuitMu.RLock()
	defer bc.wgQuitMu.RUnlock()
	select {
	case <-bc.quit:
		return false
	default:
	}
	bc.wg.Add(1)
	return true
}

// closeQuit closes the quit channel while holding the write lock.
func (bc *BlockChain) closeQuit() {
	bc.wgQuitMu.Lock()
	defer bc.wgQuitMu.Unlock()
	close(bc.quit)
}