path: root/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 (
    crand "crypto/rand"
    "errors"
    "fmt"
    "io"
    "math"
    "math/big"
    mrand "math/rand"
    "runtime"
    "sync"
    "sync/atomic"
    "time"

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

var (
    chainlogger = logger.NewLogger("CHAIN")
    jsonlogger  = logger.NewJsonLogger()

    blockInsertTimer = metrics.NewTimer("chain/inserts")

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

const (
    headerCacheLimit    = 512
    bodyCacheLimit      = 256
    tdCacheLimit        = 1024
    blockCacheLimit     = 256
    maxFutureBlocks     = 256
    maxTimeFutureBlocks = 30
    // must be bumped when consensus algorithm is changed, this forces the upgradedb
    // command to be run (forces the blocks to be imported again using the new algorithm)
    BlockChainVersion = 3
)

// 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 {
    chainDb      ethdb.Database
    eventMux     *event.TypeMux
    genesisBlock *types.Block
    // Last known total difficulty
    mu      sync.RWMutex
    chainmu sync.RWMutex
    tsmu    sync.RWMutex
    procmu  sync.RWMutex

    checkpoint       int           // checkpoint counts towards the new checkpoint
    currentHeader    *types.Header // Current head of the header chain (may be above the block chain!)
    currentBlock     *types.Block  // Current head of the block chain
    currentFastBlock *types.Block  // Current head of the fast-sync chain (may be above the block chain!)

    headerCache  *lru.Cache // Cache for the most recent block headers
    bodyCache    *lru.Cache // Cache for the most recent block bodies
    bodyRLPCache *lru.Cache // Cache for the most recent block bodies in RLP encoded format
    tdCache      *lru.Cache // Cache for the most recent block total difficulties
    blockCache   *lru.Cache // Cache for the most recent entire blocks
    futureBlocks *lru.Cache // future blocks are blocks added for later processing

    quit    chan struct{}
    running int32 // running must be called automically
    // procInterrupt must be atomically called
    procInterrupt int32 // interrupt signaler for block processing
    wg            sync.WaitGroup

    pow       pow.PoW
    rand      *mrand.Rand
    processor Processor
    validator Validator
}

// NewBlockChain returns a fully initialised block chain using information
// available in the database. It initialiser the default Ethereum Validator and
// Processor.
func NewBlockChain(chainDb ethdb.Database, pow pow.PoW, mux *event.TypeMux) (*BlockChain, error) {
    headerCache, _ := lru.New(headerCacheLimit)
    bodyCache, _ := lru.New(bodyCacheLimit)
    bodyRLPCache, _ := lru.New(bodyCacheLimit)
    tdCache, _ := lru.New(tdCacheLimit)
    blockCache, _ := lru.New(blockCacheLimit)
    futureBlocks, _ := lru.New(maxFutureBlocks)

    bc := &BlockChain{
        chainDb:      chainDb,
        eventMux:     mux,
        quit:         make(chan struct{}),
        headerCache:  headerCache,
        bodyCache:    bodyCache,
        bodyRLPCache: bodyRLPCache,
        tdCache:      tdCache,
        blockCache:   blockCache,
        futureBlocks: futureBlocks,
        pow:          pow,
    }
    // Seed a fast but crypto originating random generator
    seed, err := crand.Int(crand.Reader, big.NewInt(math.MaxInt64))
    if err != nil {
        return nil, err
    }
    bc.rand = mrand.New(mrand.NewSource(seed.Int64()))
    bc.SetValidator(NewBlockValidator(bc, pow))
    bc.SetProcessor(NewStateProcessor(bc))

    bc.genesisBlock = bc.GetBlockByNumber(0)
    if bc.genesisBlock == nil {
        bc.genesisBlock, err = WriteDefaultGenesisBlock(chainDb)
        if err != nil {
            return nil, err
        }
        glog.V(logger.Info).Infoln("WARNING: Wrote default ethereum genesis block")
    }
    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.GetHeader(hash); header != nil {
            glog.V(logger.Error).Infof("Found bad hash, rewinding chain to block #%d [%x…]", header.Number, header.ParentHash[:4])
            bc.SetHead(header.Number.Uint64() - 1)
            glog.V(logger.Error).Infoln("Chain rewind was successful, resuming normal operation")
        }
    }
    // Take ownership of this particular state
    go bc.update()
    return bc, nil
}

// loadLastState loads the last known chain state from the database. This method
// assumes that the chain manager mutex is held.
func (self *BlockChain) loadLastState() error {
    // Restore the last known head block
    head := GetHeadBlockHash(self.chainDb)
    if head == (common.Hash{}) {
        // Corrupt or empty database, init from scratch
        self.Reset()
    } else {
        if block := self.GetBlock(head); block != nil {
            // Block found, set as the current head
            self.currentBlock = block
        } else {
            // Corrupt or empty database, init from scratch
            self.Reset()
        }
    }
    // Restore the last known head header
    self.currentHeader = self.currentBlock.Header()
    if head := GetHeadHeaderHash(self.chainDb); head != (common.Hash{}) {
        if header := self.GetHeader(head); header != nil {
            self.currentHeader = header
        }
    }
    // Restore the last known head fast block
    self.currentFastBlock = self.currentBlock
    if head := GetHeadFastBlockHash(self.chainDb); head != (common.Hash{}) {
        if block := self.GetBlock(head); block != nil {
            self.currentFastBlock = block
        }
    }
    // Issue a status log and return
    headerTd := self.GetTd(self.currentHeader.Hash())
    blockTd := self.GetTd(self.currentBlock.Hash())
    fastTd := self.GetTd(self.currentFastBlock.Hash())

    glog.V(logger.Info).Infof("Last header: #%d [%x…] TD=%v", self.currentHeader.Number, self.currentHeader.Hash().Bytes()[:4], headerTd)
    glog.V(logger.Info).Infof("Last block: #%d [%x…] TD=%v", self.currentBlock.Number(), self.currentBlock.Hash().Bytes()[:4], blockTd)
    glog.V(logger.Info).Infof("Fast block: #%d [%x…] TD=%v", self.currentFastBlock.Number(), self.currentFastBlock.Hash().Bytes()[:4], 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) {
    bc.mu.Lock()
    defer bc.mu.Unlock()

    // Figure out the highest known canonical headers and/or blocks
    height := uint64(0)
    if bc.currentHeader != nil {
        if hh := bc.currentHeader.Number.Uint64(); hh > height {
            height = hh
        }
    }
    if bc.currentBlock != nil {
        if bh := bc.currentBlock.NumberU64(); bh > height {
            height = bh
        }
    }
    if bc.currentFastBlock != nil {
        if fbh := bc.currentFastBlock.NumberU64(); fbh > height {
            height = fbh
        }
    }
    // Gather all the hashes that need deletion
    drop := make(map[common.Hash]struct{})

    for bc.currentHeader != nil && bc.currentHeader.Number.Uint64() > head {
        drop[bc.currentHeader.Hash()] = struct{}{}
        bc.currentHeader = bc.GetHeader(bc.currentHeader.ParentHash)
    }
    for bc.currentBlock != nil && bc.currentBlock.NumberU64() > head {
        drop[bc.currentBlock.Hash()] = struct{}{}
        bc.currentBlock = bc.GetBlock(bc.currentBlock.ParentHash())
    }
    for bc.currentFastBlock != nil && bc.currentFastBlock.NumberU64() > head {
        drop[bc.currentFastBlock.Hash()] = struct{}{}
        bc.currentFastBlock = bc.GetBlock(bc.currentFastBlock.ParentHash())
    }
    // Roll back the canonical chain numbering
    for i := height; i > head; i-- {
        DeleteCanonicalHash(bc.chainDb, i)
    }
    // Delete everything found by the above rewind
    for hash, _ := range drop {
        DeleteHeader(bc.chainDb, hash)
        DeleteBody(bc.chainDb, hash)
        DeleteTd(bc.chainDb, hash)
    }
    // Clear out any stale content from the caches
    bc.headerCache.Purge()
    bc.bodyCache.Purge()
    bc.bodyRLPCache.Purge()
    bc.blockCache.Purge()
    bc.futureBlocks.Purge()

    // Update all computed fields to the new head
    if bc.currentBlock == nil {
        bc.currentBlock = bc.genesisBlock
    }
    if bc.currentHeader == nil {
        bc.currentHeader = bc.genesisBlock.Header()
    }
    if bc.currentFastBlock == nil {
        bc.currentFastBlock = bc.genesisBlock
    }
    if err := WriteHeadBlockHash(bc.chainDb, bc.currentBlock.Hash()); err != nil {
        glog.Fatalf("failed to reset head block hash: %v", err)
    }
    if err := WriteHeadHeaderHash(bc.chainDb, bc.currentHeader.Hash()); err != nil {
        glog.Fatalf("failed to reset head header hash: %v", err)
    }
    if err := WriteHeadFastBlockHash(bc.chainDb, bc.currentFastBlock.Hash()); err != nil {
        glog.Fatalf("failed to reset head fast block hash: %v", err)
    }
    bc.loadLastState()
}

// FastSyncCommitHead sets the current head block to the one defined by the hash
// irrelevant what the chain contents were prior.
func (self *BlockChain) FastSyncCommitHead(hash common.Hash) error {
    // Make sure that both the block as well at its state trie exists
    block := self.GetBlock(hash)
    if block == nil {
        return fmt.Errorf("non existent block [%x…]", hash[:4])
    }
    if _, err := trie.NewSecure(block.Root(), self.chainDb); err != nil {
        return err
    }
    // If all checks out, manually set the head block
    self.mu.Lock()
    self.currentBlock = block
    self.mu.Unlock()

    glog.V(logger.Info).Infof("committed block #%d [%x…] as new head", block.Number(), hash[:4])
    return nil
}

// GasLimit returns the gas limit of the current HEAD block.
func (self *BlockChain) GasLimit() *big.Int {
    self.mu.RLock()
    defer self.mu.RUnlock()

    return self.currentBlock.GasLimit()
}

// LastBlockHash return the hash of the HEAD block.
func (self *BlockChain) LastBlockHash() common.Hash {
    self.mu.RLock()
    defer self.mu.RUnlock()

    return self.currentBlock.Hash()
}

// CurrentHeader retrieves the current head header of the canonical chain. The
// header is retrieved from the blockchain's internal cache.
func (self *BlockChain) CurrentHeader() *types.Header {
    self.mu.RLock()
    defer self.mu.RUnlock()

    return self.currentHeader
}

// CurrentBlock retrieves the current head block of the canonical chain. The
// block is retrieved from the blockchain's internal cache.
func (self *BlockChain) CurrentBlock() *types.Block {
    self.mu.RLock()
    defer self.mu.RUnlock()

    return self.currentBlock
}

// CurrentFastBlock retrieves the current fast-sync head block of the canonical
// chain. The block is retrieved from the blockchain's internal cache.
func (self *BlockChain) CurrentFastBlock() *types.Block {
    self.mu.RLock()
    defer self.mu.RUnlock()

    return self.currentFastBlock
}

// Status returns status information about the current chain such as the HEAD Td,
// the HEAD hash and the hash of the genesis block.
func (self *BlockChain) Status() (td *big.Int, currentBlock common.Hash, genesisBlock common.Hash) {
    self.mu.RLock()
    defer self.mu.RUnlock()

    return self.GetTd(self.currentBlock.Hash()), self.currentBlock.Hash(), self.genesisBlock.Hash()
}

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

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

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

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

// AuxValidator returns the auxiliary validator (Proof of work atm)
func (self *BlockChain) AuxValidator() pow.PoW { return self.pow }

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

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

// ResetWithGenesisBlock purges the entire blockchain, restoring it to the
// specified genesis state.
func (bc *BlockChain) ResetWithGenesisBlock(genesis *types.Block) {
    // Dump the entire block chain and purge the caches
    bc.SetHead(0)

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

    // Prepare the genesis block and reinitialise the chain
    if err := WriteTd(bc.chainDb, genesis.Hash(), genesis.Difficulty()); err != nil {
        glog.Fatalf("failed to write genesis block TD: %v", err)
    }
    if err := WriteBlock(bc.chainDb, genesis); err != nil {
        glog.Fatalf("failed to write genesis block: %v", err)
    }
    bc.genesisBlock = genesis
    bc.insert(bc.genesisBlock)
    bc.currentBlock = bc.genesisBlock
    bc.currentHeader = bc.genesisBlock.Header()
    bc.currentFastBlock = bc.genesisBlock
}

// Export writes the active chain to the given writer.
func (self *BlockChain) Export(w io.Writer) error {
    if err := self.ExportN(w, uint64(0), self.currentBlock.NumberU64()); err != nil {
        return err
    }
    return nil
}

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

    if first > last {
        return fmt.Errorf("export failed: first (%d) is greater than last (%d)", first, last)
    }

    glog.V(logger.Info).Infof("exporting %d blocks...\n", last-first+1)

    for nr := first; nr <= last; nr++ {
        block := self.GetBlockByNumber(nr)
        if block == nil {
            return fmt.Errorf("export failed on #%d: not found", nr)
        }

        if err := block.EncodeRLP(w); err != nil {
            return err
        }
    }

    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 := GetCanonicalHash(bc.chainDb, block.NumberU64()) != block.Hash()

    // Add the block to the canonical chain number scheme and mark as the head
    if err := WriteCanonicalHash(bc.chainDb, block.Hash(), block.NumberU64()); err != nil {
        glog.Fatalf("failed to insert block number: %v", err)
    }
    if err := WriteHeadBlockHash(bc.chainDb, block.Hash()); err != nil {
        glog.Fatalf("failed to insert head block hash: %v", err)
    }
    bc.currentBlock = block

    // If the block is better than out head or is on a different chain, force update heads
    if updateHeads {
        if err := WriteHeadHeaderHash(bc.chainDb, block.Hash()); err != nil {
            glog.Fatalf("failed to insert head header hash: %v", err)
        }
        bc.currentHeader = block.Header()

        if err := WriteHeadFastBlockHash(bc.chainDb, block.Hash()); err != nil {
            glog.Fatalf("failed to insert head fast block hash: %v", err)
        }
        bc.currentFastBlock = block
    }
}

// Accessors
func (bc *BlockChain) Genesis() *types.Block {
    return bc.genesisBlock
}

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

// GetHeader retrieves a block header from the database by hash, caching it if
// found.
func (self *BlockChain) GetHeader(hash common.Hash) *types.Header {
    // Short circuit if the header's already in the cache, retrieve otherwise
    if header, ok := self.headerCache.Get(hash); ok {
        return header.(*types.Header)
    }
    header := GetHeader(self.chainDb, hash)
    if header == nil {
        return nil
    }
    // Cache the found header for next time and return
    self.headerCache.Add(header.Hash(), header)
    return header
}

// GetHeaderByNumber retrieves a block header from the database by number,
// caching it (associated with its hash) if found.
func (self *BlockChain) GetHeaderByNumber(number uint64) *types.Header {
    hash := GetCanonicalHash(self.chainDb, number)
    if hash == (common.Hash{}) {
        return nil
    }
    return self.GetHeader(hash)
}

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

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

// GetTd retrieves a block's total difficulty in the canonical chain from the
// database by hash, caching it if found.
func (self *BlockChain) GetTd(hash common.Hash) *big.Int {
    // Short circuit if the td's already in the cache, retrieve otherwise
    if cached, ok := self.tdCache.Get(hash); ok {
        return cached.(*big.Int)
    }
    td := GetTd(self.chainDb, hash)
    if td == nil {
        return nil
    }
    // Cache the found body for next time and return
    self.tdCache.Add(hash, td)
    return td
}

// HasBlock checks if a block is fully present in the database or not, caching
// it if present.
func (bc *BlockChain) HasBlock(hash common.Hash) bool {
    return bc.GetBlock(hash) != 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) bool {
    // Check first that the block itself is known
    block := bc.GetBlock(hash)
    if block == nil {
        return false
    }
    // Ensure the associated state is also present
    _, err := state.New(block.Root(), bc.chainDb)
    return err == nil
}

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

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

// GetBlockHashesFromHash retrieves a number of block hashes starting at a given
// hash, fetching towards the genesis block.
func (self *BlockChain) GetBlockHashesFromHash(hash common.Hash, max uint64) []common.Hash {
    // Get the origin header from which to fetch
    header := self.GetHeader(hash)
    if header == nil {
        return nil
    }
    // Iterate the headers until enough is collected or the genesis reached
    chain := make([]common.Hash, 0, max)
    for i := uint64(0); i < max; i++ {
        if header = self.GetHeader(header.ParentHash); header == nil {
            break
        }
        chain = append(chain, header.Hash())
        if header.Number.Cmp(common.Big0) == 0 {
            break
        }
    }
    return chain
}

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

// GetUnclesInChain retrieves all the uncles from a given block backwards until
// a specific distance is reached.
func (self *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 = self.GetBlock(block.ParentHash())
    }
    return uncles
}

// 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
    }
    close(bc.quit)
    atomic.StoreInt32(&bc.procInterrupt, 1)

    bc.wg.Wait()

    glog.V(logger.Info).Infoln("Chain manager stopped")
}

func (self *BlockChain) procFutureBlocks() {
    blocks := make([]*types.Block, self.futureBlocks.Len())
    for i, hash := range self.futureBlocks.Keys() {
        block, _ := self.futureBlocks.Get(hash)
        blocks[i] = block.(*types.Block)
    }
    if len(blocks) > 0 {
        types.BlockBy(types.Number).Sort(blocks)
        self.InsertChain(blocks)
    }
}

type writeStatus byte

const (
    NonStatTy writeStatus = iota
    CanonStatTy
    SplitStatTy
    SideStatTy
)

// 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 (self *BlockChain) writeHeader(header *types.Header) error {
    self.wg.Add(1)
    defer self.wg.Done()

    // Calculate the total difficulty of the header
    ptd := self.GetTd(header.ParentHash)
    if ptd == nil {
        return ParentError(header.ParentHash)
    }

    localTd := self.GetTd(self.currentHeader.Hash())
    externTd := new(big.Int).Add(header.Difficulty, ptd)

    // Make sure no inconsistent state is leaked during insertion
    self.mu.Lock()
    defer self.mu.Unlock()

    // 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
    if externTd.Cmp(localTd) > 0 || (externTd.Cmp(localTd) == 0 && mrand.Float64() < 0.5) {
        // Delete any canonical number assignments above the new head
        for i := header.Number.Uint64() + 1; GetCanonicalHash(self.chainDb, i) != (common.Hash{}); i++ {
            DeleteCanonicalHash(self.chainDb, i)
        }
        // Overwrite any stale canonical number assignments
        head := self.GetHeader(header.ParentHash)
        for GetCanonicalHash(self.chainDb, head.Number.Uint64()) != head.Hash() {
            WriteCanonicalHash(self.chainDb, head.Hash(), head.Number.Uint64())
            head = self.GetHeader(head.ParentHash)
        }
        // Extend the canonical chain with the new header
        if err := WriteCanonicalHash(self.chainDb, header.Hash(), header.Number.Uint64()); err != nil {
            glog.Fatalf("failed to insert header number: %v", err)
        }
        if err := WriteHeadHeaderHash(self.chainDb, header.Hash()); err != nil {
            glog.Fatalf("failed to insert head header hash: %v", err)
        }
        self.currentHeader = types.CopyHeader(header)
    }
    // Irrelevant of the canonical status, write the header itself to the database
    if err := WriteTd(self.chainDb, header.Hash(), externTd); err != nil {
        glog.Fatalf("failed to write header total difficulty: %v", err)
    }
    if err := WriteHeader(self.chainDb, header); err != nil {
        glog.Fatalf("filed to write header contents: %v", err)
    }
    return nil
}

// 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 verfy nonces, as well as
// because nonces can be verified sparsely, not needing to check each.
func (self *BlockChain) InsertHeaderChain(chain []*types.Header, checkFreq int) (int, error) {
    self.wg.Add(1)
    defer self.wg.Done()

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

    // Collect some import statistics to report on
    stats := struct{ processed, ignored int }{}
    start := time.Now()

    // Generate the list of headers that should be POW verified
    verify := make([]bool, len(chain))
    for i := 0; i < len(verify)/checkFreq; i++ {
        index := i*checkFreq + self.rand.Intn(checkFreq)
        if index >= len(verify) {
            index = len(verify) - 1
        }
        verify[index] = true
    }
    verify[len(verify)-1] = true // Last should always be verified to avoid junk

    // Create the header verification task queue and worker functions
    tasks := make(chan int, len(chain))
    for i := 0; i < len(chain); i++ {
        tasks <- i
    }
    close(tasks)

    errs, failed := make([]error, len(tasks)), int32(0)
    process := func(worker int) {
        for index := range tasks {
            header, hash := chain[index], chain[index].Hash()

            // Short circuit insertion if shutting down or processing failed
            if atomic.LoadInt32(&self.procInterrupt) == 1 {
                return
            }
            if atomic.LoadInt32(&failed) > 0 {
                return
            }
            // Short circuit if the header is bad or already known
            if BadHashes[hash] {
                errs[index] = BadHashError(hash)
                atomic.AddInt32(&failed, 1)
                return
            }
            if self.HasHeader(hash) {
                continue
            }
            // Verify that the header honors the chain parameters
            checkPow := verify[index]

            var err error
            if index == 0 {
                err = self.Validator().ValidateHeader(header, self.GetHeader(header.ParentHash), checkPow)
            } else {
                err = self.Validator().ValidateHeader(header, chain[index-1], checkPow)
            }
            if err != nil {
                errs[index] = err
                atomic.AddInt32(&failed, 1)
                return
            }
        }
    }
    // Start as many worker threads as goroutines allowed
    pending := new(sync.WaitGroup)
    for i := 0; i < runtime.GOMAXPROCS(0); i++ {
        pending.Add(1)
        go func(id int) {
            defer pending.Done()
            process(id)
        }(i)
    }
    pending.Wait()

    // If anything failed, report
    if failed > 0 {
        for i, err := range errs {
            if err != nil {
                return i, err
            }
        }
    }
    // All headers passed verification, import them into the database
    for i, header := range chain {
        // Short circuit insertion if shutting down
        if atomic.LoadInt32(&self.procInterrupt) == 1 {
            glog.V(logger.Debug).Infoln("premature abort during header chain processing")
            break
        }
        hash := header.Hash()

        // If the header's already known, skip it, otherwise store
        if self.HasHeader(hash) {
            stats.ignored++
            continue
        }
        if err := self.writeHeader(header); err != nil {
            return i, err
        }
        stats.processed++
    }
    // Report some public statistics so the user has a clue what's going on
    first, last := chain[0], chain[len(chain)-1]
    glog.V(logger.Info).Infof("imported %d header(s) (%d ignored) in %v. #%v [%x… / %x…]", stats.processed, stats.ignored,
        time.Since(start), last.Number, first.Hash().Bytes()[:4], last.Hash().Bytes()[:4])

    return 0, nil
}

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

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

        if self.currentHeader.Hash() == hash {
            self.currentHeader = self.GetHeader(self.currentHeader.ParentHash)
            WriteHeadHeaderHash(self.chainDb, self.currentHeader.Hash())
        }
        if self.currentFastBlock.Hash() == hash {
            self.currentFastBlock = self.GetBlock(self.currentFastBlock.ParentHash())
            WriteHeadFastBlockHash(self.chainDb, self.currentFastBlock.Hash())
        }
        if self.currentBlock.Hash() == hash {
            self.currentBlock = self.GetBlock(self.currentBlock.ParentHash())
            WriteHeadBlockHash(self.chainDb, self.currentBlock.Hash())
        }
    }
}

// InsertReceiptChain attempts to complete an already existing header chain with
// transaction and receipt data.
func (self *BlockChain) InsertReceiptChain(blockChain types.Blocks, receiptChain []types.Receipts) (int, error) {
    self.wg.Add(1)
    defer self.wg.Done()

    // Collect some import statistics to report on
    stats := struct{ processed, ignored int32 }{}
    start := time.Now()

    // Create the block importing task queue and worker functions
    tasks := make(chan int, len(blockChain))
    for i := 0; i < len(blockChain) && i < len(receiptChain); i++ {
        tasks <- i
    }
    close(tasks)

    errs, failed := make([]error, len(tasks)), int32(0)
    process := func(worker int) {
        for index := range tasks {
            block, receipts := blockChain[index], receiptChain[index]

            // Short circuit insertion if shutting down or processing failed
            if atomic.LoadInt32(&self.procInterrupt) == 1 {
                return
            }
            if atomic.LoadInt32(&failed) > 0 {
                return
            }
            // Short circuit if the owner header is unknown
            if !self.HasHeader(block.Hash()) {
                errs[index] = fmt.Errorf("containing header #%d [%x…] unknown", block.Number(), block.Hash().Bytes()[:4])
                atomic.AddInt32(&failed, 1)
                return
            }
            // Skip if the entire data is already known
            if self.HasBlock(block.Hash()) {
                atomic.AddInt32(&stats.ignored, 1)
                continue
            }
            // Compute all the non-consensus fields of the receipts
            transactions, logIndex := block.Transactions(), uint(0)
            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 MessageCreatesContract(transactions[j]) {
                    from, _ := transactions[j].From()
                    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 = new(big.Int).Set(receipts[j].CumulativeGasUsed)
                } else {
                    receipts[j].GasUsed = new(big.Int).Sub(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++
                }
            }
            // Write all the data out into the database
            if err := WriteBody(self.chainDb, block.Hash(), &types.Body{block.Transactions(), block.Uncles()}); err != nil {
                errs[index] = fmt.Errorf("failed to write block body: %v", err)
                atomic.AddInt32(&failed, 1)
                glog.Fatal(errs[index])
                return
            }
            if err := WriteBlockReceipts(self.chainDb, block.Hash(), receipts); err != nil {
                errs[index] = fmt.Errorf("failed to write block receipts: %v", err)
                atomic.AddInt32(&failed, 1)
                glog.Fatal(errs[index])
                return
            }
            if err := WriteMipmapBloom(self.chainDb, block.NumberU64(), receipts); err != nil {
                errs[index] = fmt.Errorf("failed to write log blooms: %v", err)
                atomic.AddInt32(&failed, 1)
                glog.Fatal(errs[index])
                return
            }
            if err := WriteTransactions(self.chainDb, block); err != nil {
                errs[index] = fmt.Errorf("failed to write individual transactions: %v", err)
                atomic.AddInt32(&failed, 1)
                glog.Fatal(errs[index])
                return
            }
            if err := WriteReceipts(self.chainDb, receipts); err != nil {
                errs[index] = fmt.Errorf("failed to write individual receipts: %v", err)
                atomic.AddInt32(&failed, 1)
                glog.Fatal(errs[index])
                return
            }
            atomic.AddInt32(&stats.processed, 1)
        }
    }
    // Start as many worker threads as goroutines allowed
    pending := new(sync.WaitGroup)
    for i := 0; i < runtime.GOMAXPROCS(0); i++ {
        pending.Add(1)
        go func(id int) {
            defer pending.Done()
            process(id)
        }(i)
    }
    pending.Wait()

    // If anything failed, report
    if failed > 0 {
        for i, err := range errs {
            if err != nil {
                return i, err
            }
        }
    }
    if atomic.LoadInt32(&self.procInterrupt) == 1 {
        glog.V(logger.Debug).Infoln("premature abort during receipt chain processing")
        return 0, nil
    }
    // Update the head fast sync block if better
    self.mu.Lock()
    head := blockChain[len(errs)-1]
    if self.GetTd(self.currentFastBlock.Hash()).Cmp(self.GetTd(head.Hash())) < 0 {
        if err := WriteHeadFastBlockHash(self.chainDb, head.Hash()); err != nil {
            glog.Fatalf("failed to update head fast block hash: %v", err)
        }
        self.currentFastBlock = head
    }
    self.mu.Unlock()

    // Report some public statistics so the user has a clue what's going on
    first, last := blockChain[0], blockChain[len(blockChain)-1]
    glog.V(logger.Info).Infof("imported %d receipt(s) (%d ignored) in %v. #%d [%x… / %x…]", stats.processed, stats.ignored,
        time.Since(start), last.Number(), first.Hash().Bytes()[:4], last.Hash().Bytes()[:4])

    return 0, nil
}

// WriteBlock writes the block to the chain.
func (self *BlockChain) WriteBlock(block *types.Block) (status writeStatus, err error) {
    self.wg.Add(1)
    defer self.wg.Done()

    // Calculate the total difficulty of the block
    ptd := self.GetTd(block.ParentHash())
    if ptd == nil {
        return NonStatTy, ParentError(block.ParentHash())
    }

    localTd := self.GetTd(self.currentBlock.Hash())
    externTd := new(big.Int).Add(block.Difficulty(), ptd)

    // Make sure no inconsistent state is leaked during insertion
    self.mu.Lock()
    defer self.mu.Unlock()

    // 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
    if externTd.Cmp(localTd) > 0 || (externTd.Cmp(localTd) == 0 && mrand.Float64() < 0.5) {
        // Reorganize the chain if the parent is not the head block
        if block.ParentHash() != self.currentBlock.Hash() {
            if err := self.reorg(self.currentBlock, block); err != nil {
                return NonStatTy, err
            }
        }
        // Insert the block as the new head of the chain
        self.insert(block)
        status = CanonStatTy
    } else {
        status = SideStatTy
    }
    // Irrelevant of the canonical status, write the block itself to the database
    if err := WriteTd(self.chainDb, block.Hash(), externTd); err != nil {
        glog.Fatalf("failed to write block total difficulty: %v", err)
    }
    if err := WriteBlock(self.chainDb, block); err != nil {
        glog.Fatalf("filed to write block contents: %v", err)
    }
    self.futureBlocks.Remove(block.Hash())

    return
}

// InsertChain will attempt to insert the given chain in to the canonical chain or, otherwise, create a fork. It an error is returned
// it will return the index number of the failing block as well an error describing what went wrong (for possible errors see core/errors.go).
func (self *BlockChain) InsertChain(chain types.Blocks) (int, error) {
    self.wg.Add(1)
    defer self.wg.Done()

    self.chainmu.Lock()
    defer self.chainmu.Unlock()

    // A queued approach to delivering events. This is generally
    // faster than direct delivery and requires much less mutex
    // acquiring.
    var (
        stats         struct{ queued, processed, ignored int }
        events        = make([]interface{}, 0, len(chain))
        coalescedLogs vm.Logs
        tstart        = time.Now()

        nonceChecked = make([]bool, len(chain))
    )

    // Start the parallel nonce verifier.
    nonceAbort, nonceResults := verifyNoncesFromBlocks(self.pow, chain)
    defer close(nonceAbort)

    txcount := 0
    for i, block := range chain {
        if atomic.LoadInt32(&self.procInterrupt) == 1 {
            glog.V(logger.Debug).Infoln("Premature abort during block chain processing")
            break
        }

        bstart := time.Now()
        // Wait for block i's nonce to be verified before processing
        // its state transition.
        for !nonceChecked[i] {
            r := <-nonceResults
            nonceChecked[r.index] = true
            if !r.valid {
                block := chain[r.index]
                return r.index, &BlockNonceErr{Hash: block.Hash(), Number: block.Number(), Nonce: block.Nonce()}
            }
        }

        if BadHashes[block.Hash()] {
            err := BadHashError(block.Hash())
            reportBlock(block, err)
            return i, err
        }
        // Stage 1 validation of the block using the chain's validator
        // interface.
        err := self.Validator().ValidateBlock(block)
        if err != nil {
            if IsKnownBlockErr(err) {
                stats.ignored++
                continue
            }

            if err == BlockFutureErr {
                // 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().Cmp(max) == 1 {
                    return i, fmt.Errorf("%v: BlockFutureErr, %v > %v", BlockFutureErr, block.Time(), max)
                }

                self.futureBlocks.Add(block.Hash(), block)
                stats.queued++
                continue
            }

            if IsParentErr(err) && self.futureBlocks.Contains(block.ParentHash()) {
                self.futureBlocks.Add(block.Hash(), block)
                stats.queued++
                continue
            }

            reportBlock(block, err)

            return i, err
        }

        // Create a new statedb using the parent block and report an
        // error if it fails.
        statedb, err := state.New(self.GetBlock(block.ParentHash()).Root(), self.chainDb)
        if err != nil {
            reportBlock(block, err)
            return i, err
        }
        // Process block using the parent state as reference point.
        receipts, logs, usedGas, err := self.processor.Process(block, statedb)
        if err != nil {
            reportBlock(block, err)
            return i, err
        }
        // Validate the state using the default validator
        err = self.Validator().ValidateState(block, self.GetBlock(block.ParentHash()), statedb, receipts, usedGas)
        if err != nil {
            reportBlock(block, err)
            return i, err
        }
        // Write state changes to database
        _, err = statedb.Commit()
        if err != nil {
            return i, err
        }

        // coalesce logs for later processing
        coalescedLogs = append(coalescedLogs, logs...)

        if err := WriteBlockReceipts(self.chainDb, block.Hash(), receipts); err != nil {
            return i, err
        }

        txcount += len(block.Transactions())
        // write the block to the chain and get the status
        status, err := self.WriteBlock(block)
        if err != nil {
            return i, err
        }

        switch status {
        case CanonStatTy:
            if glog.V(logger.Debug) {
                glog.Infof("[%v] inserted block #%d (%d TXs %v G %d UNCs) (%x...). Took %v\n", time.Now().UnixNano(), block.Number(), len(block.Transactions()), block.GasUsed(), len(block.Uncles()), block.Hash().Bytes()[0:4], time.Since(bstart))
            }
            events = append(events, ChainEvent{block, block.Hash(), logs})

            // This puts transactions in a extra db for rpc
            if err := WriteTransactions(self.chainDb, block); err != nil {
                return i, err
            }
            // store the receipts
            if err := WriteReceipts(self.chainDb, receipts); err != nil {
                return i, err
            }
            // Write map map bloom filters
            if err := WriteMipmapBloom(self.chainDb, block.NumberU64(), receipts); err != nil {
                return i, err
            }
        case SideStatTy:
            if glog.V(logger.Detail) {
                glog.Infof("inserted forked block #%d (TD=%v) (%d TXs %d UNCs) (%x...). Took %v\n", block.Number(), block.Difficulty(), len(block.Transactions()), len(block.Uncles()), block.Hash().Bytes()[0:4], time.Since(bstart))
            }
            events = append(events, ChainSideEvent{block, logs})

        case SplitStatTy:
            events = append(events, ChainSplitEvent{block, logs})
        }
        stats.processed++
    }

    if (stats.queued > 0 || stats.processed > 0 || stats.ignored > 0) && bool(glog.V(logger.Info)) {
        tend := time.Since(tstart)
        start, end := chain[0], chain[len(chain)-1]
        glog.Infof("imported %d block(s) (%d queued %d ignored) including %d txs in %v. #%v [%x / %x]\n", stats.processed, stats.queued, stats.ignored, txcount, tend, end.Number(), start.Hash().Bytes()[:4], end.Hash().Bytes()[:4])
    }
    go self.postChainEvents(events, coalescedLogs)

    return 0, 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 (self *BlockChain) reorg(oldBlock, newBlock *types.Block) error {
    var (
        newChain    types.Blocks
        commonBlock *types.Block
        oldStart    = oldBlock
        newStart    = newBlock
        deletedTxs  types.Transactions
        deletedLogs vm.Logs
        // 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(h common.Hash) {
            // Coalesce logs
            receipts := GetBlockReceipts(self.chainDb, h)
            for _, receipt := range receipts {
                deletedLogs = append(deletedLogs, receipt.Logs...)
            }
        }
    )

    // first reduce whoever is higher bound
    if oldBlock.NumberU64() > newBlock.NumberU64() {
        // reduce old chain
        for oldBlock = oldBlock; oldBlock != nil && oldBlock.NumberU64() != newBlock.NumberU64(); oldBlock = self.GetBlock(oldBlock.ParentHash()) {
            deletedTxs = append(deletedTxs, oldBlock.Transactions()...)

            collectLogs(oldBlock.Hash())
        }
    } else {
        // reduce new chain and append new chain blocks for inserting later on
        for newBlock = newBlock; newBlock != nil && newBlock.NumberU64() != oldBlock.NumberU64(); newBlock = self.GetBlock(newBlock.ParentHash()) {
            newChain = append(newChain, newBlock)
        }
    }
    if oldBlock == nil {
        return fmt.Errorf("Invalid old chain")
    }
    if newBlock == nil {
        return fmt.Errorf("Invalid new chain")
    }

    numSplit := newBlock.Number()
    for {
        if oldBlock.Hash() == newBlock.Hash() {
            commonBlock = oldBlock
            break
        }
        newChain = append(newChain, newBlock)
        deletedTxs = append(deletedTxs, oldBlock.Transactions()...)
        collectLogs(oldBlock.Hash())

        oldBlock, newBlock = self.GetBlock(oldBlock.ParentHash()), self.GetBlock(newBlock.ParentHash())
        if oldBlock == nil {
            return fmt.Errorf("Invalid old chain")
        }
        if newBlock == nil {
            return fmt.Errorf("Invalid new chain")
        }
    }

    if glog.V(logger.Debug) {
        commonHash := commonBlock.Hash()
        glog.Infof("Chain split detected @ %x. Reorganising chain from #%v %x to %x", commonHash[:4], numSplit, oldStart.Hash().Bytes()[:4], newStart.Hash().Bytes()[:4])
    }

    var addedTxs types.Transactions
    // insert blocks. Order does not matter. Last block will be written in ImportChain itself which creates the new head properly
    for _, block := range newChain {
        // insert the block in the canonical way, re-writing history
        self.insert(block)
        // write canonical receipts and transactions
        if err := WriteTransactions(self.chainDb, block); err != nil {
            return err
        }
        receipts := GetBlockReceipts(self.chainDb, block.Hash())
        // write receipts
        if err := WriteReceipts(self.chainDb, receipts); err != nil {
            return err
        }
        // Write map map bloom filters
        if err := WriteMipmapBloom(self.chainDb, block.NumberU64(), receipts); err != nil {
            return err
        }
        addedTxs = append(addedTxs, block.Transactions()...)
    }

    // calculate the difference between deleted and added transactions
    diff := types.TxDifference(deletedTxs, addedTxs)
    // 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 {
        DeleteReceipt(self.chainDb, tx.Hash())
        DeleteTransaction(self.chainDb, tx.Hash())
    }
    // Must be posted in a goroutine because of the transaction pool trying
    // to acquire the chain manager lock
    if len(diff) > 0 {
        go self.eventMux.Post(RemovedTransactionEvent{diff})
    }
    if len(deletedLogs) > 0 {
        go self.eventMux.Post(RemovedLogsEvent{deletedLogs})
    }

    return nil
}

// postChainEvents iterates over the events generated by a chain insertion and
// posts them into the event mux.
func (self *BlockChain) postChainEvents(events []interface{}, logs vm.Logs) {
    // post event logs for further processing
    self.eventMux.Post(logs)
    for _, event := range events {
        if event, ok := event.(ChainEvent); ok {
            // We need some control over the mining operation. Acquiring locks and waiting for the miner to create new block takes too long
            // and in most cases isn't even necessary.
            if self.LastBlockHash() == event.Hash {
                self.eventMux.Post(ChainHeadEvent{event.Block})
            }
        }
        // Fire the insertion events individually too
        self.eventMux.Post(event)
    }
}

func (self *BlockChain) update() {
    futureTimer := time.Tick(5 * time.Second)
    for {
        select {
        case <-futureTimer:
            self.procFutureBlocks()
        case <-self.quit:
            return
        }
    }
}

// reportBlock reports the given block and error using the canonical block
// reporting tool. Reporting the block to the service is handled in a separate
// goroutine.
func reportBlock(block *types.Block, err error) {
    if glog.V(logger.Error) {
        glog.Errorf("Bad block #%v (%s)\n", block.Number(), block.Hash().Hex())
        glog.Errorf("    %v", err)
    }
    go ReportBlock(block, err)
}