// Tests that head headers and head blocks can be assigned, individually.
func TestHeadStorage(t *testing.T) {
	db, _ := ethdb.NewMemDatabase()

	blockHead := types.NewBlockWithHeader(&types.Header{Extra: []byte("test block header")})
	blockFull := types.NewBlockWithHeader(&types.Header{Extra: []byte("test block full")})

	// Check that no head entries are in a pristine database
	if entry := GetHeadHeaderHash(db); entry != (common.Hash{}) {
		t.Fatalf("Non head header entry returned: %v", entry)
	}
	if entry := GetHeadBlockHash(db); entry != (common.Hash{}) {
		t.Fatalf("Non head block entry returned: %v", entry)
	}
	// Assign separate entries for the head header and block
	if err := WriteHeadHeaderHash(db, blockHead.Hash()); err != nil {
		t.Fatalf("Failed to write head header hash: %v", err)
	}
	if err := WriteHeadBlockHash(db, blockFull.Hash()); err != nil {
		t.Fatalf("Failed to write head block hash: %v", err)
	}
	// Check that both heads are present, and different (i.e. two heads maintained)
	if entry := GetHeadHeaderHash(db); entry != blockHead.Hash() {
		t.Fatalf("Head header hash mismatch: have %v, want %v", entry, blockHead.Hash())
	}
	if entry := GetHeadBlockHash(db); entry != blockFull.Hash() {
		t.Fatalf("Head block hash mismatch: have %v, want %v", entry, blockFull.Hash())
	}
}

// createBlock assembles a new block at the given chain height.
func createBlock(i int, parent, hash common.Hash) *types.Block {
	header := &types.Header{Number: big.NewInt(int64(i))}
	block := types.NewBlockWithHeader(header)
	block.HeaderHash = hash
	block.ParentHeaderHash = parent
	return block
}

func mustConvertGenesis(testGenesis btHeader) *types.Block {
	hdr := mustConvertHeader(testGenesis)
	hdr.Number = big.NewInt(0)
	b := types.NewBlockWithHeader(hdr)
	b.Td = new(big.Int)
	return b
}

func testInvalidBlockBodyAttack(t *testing.T, protocol int) {
	// Create two peers, one feeding invalid block bodies
	targetBlocks := 4*blockCacheLimit - 15
	hashes, validBlocks := makeChain(targetBlocks, 0, genesis)

	invalidBlocks := make(map[common.Hash]*types.Block)
	for hash, block := range validBlocks {
		invalidBlocks[hash] = types.NewBlockWithHeader(block.Header())
	}

	tester := newTester()
	tester.newPeer("valid", protocol, hashes, validBlocks)
	tester.newPeer("attack", protocol, hashes, invalidBlocks)

	// Synchronise with the valid peer (will pull contents from the attacker too)
	if err := tester.sync("valid", nil); err != nil {
		t.Fatalf("failed to synchronise blocks: %v", err)
	}
	if imported := len(tester.ownBlocks); imported != len(hashes) {
		t.Fatalf("synchronised block mismatch: have %v, want %v", imported, len(hashes))
	}
	// Make sure the attacker was detected and dropped in the mean time
	if _, ok := tester.peerHashes["attack"]; ok {
		t.Fatalf("block body attacker not detected/dropped")
	}
}

// Tests that partial block contents don't get reassembled into full blocks.
func TestPartialBlockStorage(t *testing.T) {
	db, _ := ethdb.NewMemDatabase()
	block := types.NewBlockWithHeader(&types.Header{Extra: []byte("test block")})

	// Store a header and check that it's not recognized as a block
	if err := WriteHeader(db, block.Header()); err != nil {
		t.Fatalf("Failed to write header into database: %v", err)
	}
	if entry := GetBlock(db, block.Hash()); entry != nil {
		t.Fatalf("Non existent block returned: %v", entry)
	}
	DeleteHeader(db, block.Hash())

	// Store a body and check that it's not recognized as a block
	if err := WriteBody(db, block.Hash(), &types.Body{block.Transactions(), block.Uncles()}); err != nil {
		t.Fatalf("Failed to write body into database: %v", err)
	}
	if entry := GetBlock(db, block.Hash()); entry != nil {
		t.Fatalf("Non existent block returned: %v", entry)
	}
	DeleteBody(db, block.Hash())

	// Store a header and a body separately and check reassembly
	if err := WriteHeader(db, block.Header()); err != nil {
		t.Fatalf("Failed to write header into database: %v", err)
	}
	if err := WriteBody(db, block.Hash(), &types.Body{block.Transactions(), block.Uncles()}); err != nil {
		t.Fatalf("Failed to write body into database: %v", err)
	}
	if entry := GetBlock(db, block.Hash()); entry == nil {
		t.Fatalf("Stored block not found")
	} else if entry.Hash() != block.Hash() {
		t.Fatalf("Retrieved block mismatch: have %v, want %v", entry, block)
	}
}

// verifyNoncesFromHeaders starts a concurrent header nonce verification,
// returning a quit channel to abort the operations and a results channel
// to retrieve the async verifications.
func verifyNoncesFromHeaders(checker pow.PoW, headers []*types.Header) (chan<- struct{}, <-chan nonceCheckResult) {
	items := make([]pow.Block, len(headers))
	for i, header := range headers {
		items[i] = types.NewBlockWithHeader(header)
	}
	return verifyNonces(checker, items)
}

// makeHeaderChain creates a deterministic chain of headers rooted at parent.
func makeHeaderChain(parent *types.Header, n int, db ethdb.Database, seed int) []*types.Header {
	blocks := makeBlockChain(types.NewBlockWithHeader(parent), n, db, seed)
	headers := make([]*types.Header, len(blocks))
	for i, block := range blocks {
		headers[i] = block.Header()
	}
	return headers
}

// Reserve reserves a set of headers for the given peer, skipping any previously
// failed download. Beside the next batch of needed fetches, it also returns a
// flag whether empty blocks were queued requiring processing.
func (q *queue) Reserve(p *peer, count int) (*fetchRequest, bool, error) {
	q.lock.Lock()
	defer q.lock.Unlock()

	// Short circuit if the pool has been depleted, or if the peer's already
	// downloading something (sanity check not to corrupt state)
	if q.headerQueue.Empty() {
		return nil, false, nil
	}
	if _, ok := q.pendPool[p.id]; ok {
		return nil, false, nil
	}
	// Calculate an upper limit on the bodies we might fetch (i.e. throttling)
	space := len(q.blockCache) - len(q.blockPool)
	for _, request := range q.pendPool {
		space -= len(request.Headers)
	}
	// Retrieve a batch of headers, skipping previously failed ones
	send := make([]*types.Header, 0, count)
	skip := make([]*types.Header, 0)

	process := false
	for proc := 0; proc < space && len(send) < count && !q.headerQueue.Empty(); proc++ {
		header := q.headerQueue.PopItem().(*types.Header)

		// If the header defines an empty block, deliver straight
		if header.TxHash == types.DeriveSha(types.Transactions{}) && header.UncleHash == types.CalcUncleHash([]*types.Header{}) {
			if err := q.enqueue("", types.NewBlockWithHeader(header)); err != nil {
				return nil, false, errInvalidChain
			}
			delete(q.headerPool, header.Hash())
			process, space, proc = true, space-1, proc-1
			continue
		}
		// If it's a content block, add to the body fetch request
		if p.ignored.Has(header.Hash()) {
			skip = append(skip, header)
		} else {
			send = append(send, header)
		}
	}
	// Merge all the skipped headers back
	for _, header := range skip {
		q.headerQueue.Push(header, -float32(header.Number.Uint64()))
	}
	// Assemble and return the block download request
	if len(send) == 0 {
		return nil, process, nil
	}
	request := &fetchRequest{
		Peer:    p,
		Headers: send,
		Time:    time.Now(),
	}
	q.pendPool[p.id] = request

	return request, process, nil
}

// GetBlock retrieves an entire block corresponding to the hash, assembling it
// back from the stored header and body.
func GetBlock(db ethdb.Database, hash common.Hash) *types.Block {
	// Retrieve the block header and body contents
	header := GetHeader(db, hash)
	if header == nil {
		return nil
	}
	body := GetBody(db, hash)
	if body == nil {
		return nil
	}
	// Reassemble the block and return
	return types.NewBlockWithHeader(header).WithBody(body.Transactions, body.Uncles)
}

// Tests block storage and retrieval operations.
func TestBlockStorage(t *testing.T) {
	db, _ := ethdb.NewMemDatabase()

	// Create a test block to move around the database and make sure it's really new
	block := types.NewBlockWithHeader(&types.Header{
		Extra:       []byte("test block"),
		UncleHash:   types.EmptyUncleHash,
		TxHash:      types.EmptyRootHash,
		ReceiptHash: types.EmptyRootHash,
	})
	if entry := GetBlock(db, block.Hash()); entry != nil {
		t.Fatalf("Non existent block returned: %v", entry)
	}
	if entry := GetHeader(db, block.Hash()); entry != nil {
		t.Fatalf("Non existent header returned: %v", entry)
	}
	if entry := GetBody(db, block.Hash()); entry != nil {
		t.Fatalf("Non existent body returned: %v", entry)
	}
	// Write and verify the block in the database
	if err := WriteBlock(db, block); err != nil {
		t.Fatalf("Failed to write block into database: %v", err)
	}
	if entry := GetBlock(db, block.Hash()); entry == nil {
		t.Fatalf("Stored block not found")
	} else if entry.Hash() != block.Hash() {
		t.Fatalf("Retrieved block mismatch: have %v, want %v", entry, block)
	}
	if entry := GetHeader(db, block.Hash()); entry == nil {
		t.Fatalf("Stored header not found")
	} else if entry.Hash() != block.Header().Hash() {
		t.Fatalf("Retrieved header mismatch: have %v, want %v", entry, block.Header())
	}
	if entry := GetBody(db, block.Hash()); entry == nil {
		t.Fatalf("Stored body not found")
	} else if types.DeriveSha(types.Transactions(entry.Transactions)) != types.DeriveSha(block.Transactions()) || types.CalcUncleHash(entry.Uncles) != types.CalcUncleHash(block.Uncles()) {
		t.Fatalf("Retrieved body mismatch: have %v, want %v", entry, &types.Body{block.Transactions(), block.Uncles()})
	}
	// Delete the block and verify the execution
	DeleteBlock(db, block.Hash())
	if entry := GetBlock(db, block.Hash()); entry != nil {
		t.Fatalf("Deleted block returned: %v", entry)
	}
	if entry := GetHeader(db, block.Hash()); entry != nil {
		t.Fatalf("Deleted header returned: %v", entry)
	}
	if entry := GetBody(db, block.Hash()); entry != nil {
		t.Fatalf("Deleted body returned: %v", entry)
	}
}

// See YP section 4.3.4. "Block Header Validity"
// Validates a block. Returns an error if the block is invalid.
func ValidateHeader(pow pow.PoW, block *types.Header, parent *types.Block, checkPow, uncle bool) error {
	if big.NewInt(int64(len(block.Extra))).Cmp(params.MaximumExtraDataSize) == 1 {
		return fmt.Errorf("Block extra data too long (%d)", len(block.Extra))
	}

	if uncle {
		if block.Time.Cmp(common.MaxBig) == 1 {
			return BlockTSTooBigErr
		}
	} else {
		if block.Time.Cmp(big.NewInt(time.Now().Unix())) == 1 {
			return BlockFutureErr
		}
	}
	if block.Time.Cmp(parent.Time()) != 1 {
		return BlockEqualTSErr
	}

	expd := CalcDifficulty(block.Time.Uint64(), parent.Time().Uint64(), parent.Number(), parent.Difficulty())
	if expd.Cmp(block.Difficulty) != 0 {
		return fmt.Errorf("Difficulty check failed for block %v, %v", block.Difficulty, expd)
	}

	var a, b *big.Int
	a = parent.GasLimit()
	a = a.Sub(a, block.GasLimit)
	a.Abs(a)
	b = parent.GasLimit()
	b = b.Div(b, params.GasLimitBoundDivisor)
	if !(a.Cmp(b) < 0) || (block.GasLimit.Cmp(params.MinGasLimit) == -1) {
		return fmt.Errorf("GasLimit check failed for block %v (%v > %v)", block.GasLimit, a, b)
	}

	num := parent.Number()
	num.Sub(block.Number, num)
	if num.Cmp(big.NewInt(1)) != 0 {
		return BlockNumberErr
	}

	if checkPow {
		// Verify the nonce of the block. Return an error if it's not valid
		if !pow.Verify(types.NewBlockWithHeader(block)) {
			return ValidationError("Block's nonce is invalid (= %x)", block.Nonce)
		}
	}

	return nil
}

func makeChainWithDiff(genesis *types.Block, d []int, seed byte) []*types.Block {
	var chain []*types.Block
	for i, difficulty := range d {
		header := &types.Header{Number: big.NewInt(int64(i + 1)), Difficulty: big.NewInt(int64(difficulty))}
		block := types.NewBlockWithHeader(header)
		copy(block.HeaderHash[:2], []byte{byte(i + 1), seed})
		if i == 0 {
			block.ParentHeaderHash = genesis.Hash()
		} else {
			copy(block.ParentHeaderHash[:2], []byte{byte(i), seed})
		}

		chain = append(chain, block)
	}
	return chain
}

// Validates a header. Returns an error if the header is invalid.
//
// See YP section 4.3.4. "Block Header Validity"
func ValidateHeader(config *ChainConfig, pow pow.PoW, header *types.Header, parent *types.Header, checkPow, uncle bool) error {
	if big.NewInt(int64(len(header.Extra))).Cmp(params.MaximumExtraDataSize) == 1 {
		return fmt.Errorf("Header extra data too long (%d)", len(header.Extra))
	}

	if uncle {
		if header.Time.Cmp(common.MaxBig) == 1 {
			return BlockTSTooBigErr
		}
	} else {
		if header.Time.Cmp(big.NewInt(time.Now().Unix())) == 1 {
			return BlockFutureErr
		}
	}
	if header.Time.Cmp(parent.Time) != 1 {
		return BlockEqualTSErr
	}

	expd := CalcDifficulty(config, header.Time.Uint64(), parent.Time.Uint64(), parent.Number, parent.Difficulty)
	if expd.Cmp(header.Difficulty) != 0 {
		return fmt.Errorf("Difficulty check failed for header %v, %v", header.Difficulty, expd)
	}

	a := new(big.Int).Set(parent.GasLimit)
	a = a.Sub(a, header.GasLimit)
	a.Abs(a)
	b := new(big.Int).Set(parent.GasLimit)
	b = b.Div(b, params.GasLimitBoundDivisor)
	if !(a.Cmp(b) < 0) || (header.GasLimit.Cmp(params.MinGasLimit) == -1) {
		return fmt.Errorf("GasLimit check failed for header %v (%v > %v)", header.GasLimit, a, b)
	}

	num := new(big.Int).Set(parent.Number)
	num.Sub(header.Number, num)
	if num.Cmp(big.NewInt(1)) != 0 {
		return BlockNumberErr
	}

	if checkPow {
		// Verify the nonce of the header. Return an error if it's not valid
		if !pow.Verify(types.NewBlockWithHeader(header)) {
			return &BlockNonceErr{header.Number, header.Hash(), header.Nonce.Uint64()}
		}
	}
	// If all checks passed, validate the extra-data field for hard forks
	return ValidateDAOHeaderExtraData(config, header)
}

func makeChainWithDiff(genesis *types.Block, d []int, seed byte) []*types.Block {
	var chain []*types.Block
	for i, difficulty := range d {
		header := &types.Header{
			Coinbase:   common.Address{seed},
			Number:     big.NewInt(int64(i + 1)),
			Difficulty: big.NewInt(int64(difficulty)),
		}
		if i == 0 {
			header.ParentHash = genesis.Hash()
		} else {
			header.ParentHash = chain[i-1].Hash()
		}
		block := types.NewBlockWithHeader(header)
		chain = append(chain, block)
	}
	return chain
}

// Validates the current block. Returns an error if the block was invalid,
// an uncle or anything that isn't on the current block chain.
// Validation validates easy over difficult (dagger takes longer time = difficult)
func (sm *BlockProcessor) ValidateHeader(block, parent *types.Header) error {
	if big.NewInt(int64(len(block.Extra))).Cmp(params.MaximumExtraDataSize) == 1 {
		return fmt.Errorf("Block extra data too long (%d)", len(block.Extra))
	}

	expd := CalcDifficulty(block, parent)
	if expd.Cmp(block.Difficulty) != 0 {
		return fmt.Errorf("Difficulty check failed for block %v, %v", block.Difficulty, expd)
	}

	// block.gasLimit - parent.gasLimit <= parent.gasLimit / GasLimitBoundDivisor
	a := new(big.Int).Sub(block.GasLimit, parent.GasLimit)
	a.Abs(a)
	b := new(big.Int).Div(parent.GasLimit, params.GasLimitBoundDivisor)
	if !(a.Cmp(b) < 0) || (block.GasLimit.Cmp(params.MinGasLimit) == -1) {
		return fmt.Errorf("GasLimit check failed for block %v (%v > %v)", block.GasLimit, a, b)
	}

	// Allow future blocks up to 10 seconds
	if int64(block.Time) > time.Now().Unix()+4 {
		return BlockFutureErr
	}

	if new(big.Int).Sub(block.Number, parent.Number).Cmp(big.NewInt(1)) != 0 {
		return BlockNumberErr
	}

	if block.Time <= parent.Time {
		return BlockEqualTSErr //ValidationError("Block timestamp equal or less than previous block (%v - %v)", block.Time, parent.Time)
	}

	// Verify the nonce of the block. Return an error if it's not valid
	if !sm.Pow.Verify(types.NewBlockWithHeader(block)) {
		return ValidationError("Block's nonce is invalid (= %x)", block.Nonce)
	}

	return nil
}

//.........这里部分代码省略.........
			// to other parts of the system.
			var task *headerFilterTask
			select {
			case task = <-filter:
			case <-f.quit:
				return
			}
			headerFilterInMeter.Mark(int64(len(task.headers)))

			// Split the batch of headers into unknown ones (to return to the caller),
			// known incomplete ones (requiring body retrievals) and completed blocks.
			unknown, incomplete, complete := []*types.Header{}, []*announce{}, []*types.Block{}
			for _, header := range task.headers {
				hash := header.Hash()

				// Filter fetcher-requested headers from other synchronisation algorithms
				if announce := f.fetching[hash]; announce != nil && f.fetched[hash] == nil && f.completing[hash] == nil && f.queued[hash] == nil {
					// If the delivered header does not match the promised number, drop the announcer
					if header.Number.Uint64() != announce.number {
						glog.V(logger.Detail).Infof("[eth/62] Peer %s: invalid block number for [%x…]: announced %d, provided %d", announce.origin, header.Hash().Bytes()[:4], announce.number, header.Number.Uint64())
						f.dropPeer(announce.origin)
						f.forgetHash(hash)
						continue
					}
					// Only keep if not imported by other means
					if f.getBlock(hash) == nil {
						announce.header = header
						announce.time = task.time

						// If the block is empty (header only), short circuit into the final import queue
						if header.TxHash == types.DeriveSha(types.Transactions{}) && header.UncleHash == types.CalcUncleHash([]*types.Header{}) {
							glog.V(logger.Detail).Infof("[eth/62] Peer %s: block #%d [%x…] empty, skipping body retrieval", announce.origin, header.Number.Uint64(), header.Hash().Bytes()[:4])

							block := types.NewBlockWithHeader(header)
							block.ReceivedAt = task.time

							complete = append(complete, block)
							f.completing[hash] = announce
							continue
						}
						// Otherwise add to the list of blocks needing completion
						incomplete = append(incomplete, announce)
					} else {
						glog.V(logger.Detail).Infof("[eth/62] Peer %s: block #%d [%x…] already imported, discarding header", announce.origin, header.Number.Uint64(), header.Hash().Bytes()[:4])
						f.forgetHash(hash)
					}
				} else {
					// Fetcher doesn't know about it, add to the return list
					unknown = append(unknown, header)
				}
			}
			headerFilterOutMeter.Mark(int64(len(unknown)))
			select {
			case filter <- &headerFilterTask{headers: unknown, time: task.time}:
			case <-f.quit:
				return
			}
			// Schedule the retrieved headers for body completion
			for _, announce := range incomplete {
				hash := announce.header.Hash()
				if _, ok := f.completing[hash]; ok {
					continue
				}
				f.fetched[hash] = append(f.fetched[hash], announce)
				if len(f.fetched) == 1 {
					f.rescheduleComplete(completeTimer)

func mustConvertGenesis(testGenesis btHeader) *types.Block {
	hdr := mustConvertHeader(testGenesis)
	hdr.Number = big.NewInt(0)

	return types.NewBlockWithHeader(hdr)
}

// Deliver injects a block body retrieval response into the download queue.
func (q *queue) Deliver(id string, txLists [][]*types.Transaction, uncleLists [][]*types.Header) error {
	q.lock.Lock()
	defer q.lock.Unlock()

	// Short circuit if the block bodies were never requested
	request := q.pendPool[id]
	if request == nil {
		return errNoFetchesPending
	}
	bodyReqTimer.UpdateSince(request.Time)
	delete(q.pendPool, id)

	// If no block bodies were retrieved, mark them as unavailable for the origin peer
	if len(txLists) == 0 || len(uncleLists) == 0 {
		for hash, _ := range request.Headers {
			request.Peer.ignored.Add(hash)
		}
	}
	// Assemble each of the block bodies with their headers and queue for processing
	errs := make([]error, 0)
	for i, header := range request.Headers {
		// Short circuit block assembly if no more bodies are found
		if i >= len(txLists) || i >= len(uncleLists) {
			break
		}
		// Reconstruct the next block if contents match up
		if types.DeriveSha(types.Transactions(txLists[i])) != header.TxHash || types.CalcUncleHash(uncleLists[i]) != header.UncleHash {
			errs = []error{errInvalidBody}
			break
		}
		block := types.NewBlockWithHeader(header).WithBody(txLists[i], uncleLists[i])

		// Queue the block up for processing
		if err := q.enqueue(id, block); err != nil {
			errs = []error{err}
			break
		}
		request.Headers[i] = nil
		delete(q.headerPool, header.Hash())
	}
	// Return all failed or missing fetches to the queue
	for _, header := range request.Headers {
		if header != nil {
			q.headerQueue.Push(header, -float32(header.Number.Uint64()))
		}
	}
	// If none of the blocks were good, it's a stale delivery
	switch {
	case len(errs) == 0:
		return nil

	case len(errs) == 1 && errs[0] == errInvalidBody:
		return errInvalidBody

	case len(errs) == 1 && errs[0] == errInvalidChain:
		return errInvalidChain

	case len(errs) == len(request.Headers):
		return errStaleDelivery

	default:
		return fmt.Errorf("multiple failures: %v", errs)
	}
}