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	diff --git a/src/validation.cpp b/src/validation.cpp
	index f28df40329..8f9c79aed9 100644
	--- a/src/validation.cpp
	+++ b/src/validation.cpp
	@@ -1,5627 +1,5631 @@
	// Copyright (c) 2009-2010 Satoshi Nakamoto
	// Copyright (c) 2009-2016 The Bitcoin Core developers
	// Copyright (c) 2017-2018 The Bitcoin developers
	// Distributed under the MIT software license, see the accompanying
	// file COPYING or http://www.opensource.org/licenses/mit-license.php.

	#include <validation.h>

	#include <arith_uint256.h>
	#include <blockindexworkcomparator.h>
	#include <blockvalidity.h>
	#include <chainparams.h>
	#include <checkpoints.h>
	#include <checkqueue.h>
	#include <config.h>
	#include <consensus/activation.h>
	#include <consensus/consensus.h>
	#include <consensus/merkle.h>
	#include <consensus/tx_verify.h>
	#include <consensus/validation.h>
	#include <flatfile.h>
	#include <fs.h>
	#include <hash.h>
	#include <index/txindex.h>
	#include <init.h>
	#include <policy/fees.h>
	#include <policy/policy.h>
	#include <pow.h>
	#include <primitives/block.h>
	#include <primitives/transaction.h>
	#include <random.h>
	#include <reverse_iterator.h>
	#include <script/script.h>
	#include <script/scriptcache.h>
	#include <script/sigcache.h>
	#include <script/standard.h>
	#include <timedata.h>
	#include <tinyformat.h>
	#include <txdb.h>
	#include <txmempool.h>
	#include <ui_interface.h>
	#include <undo.h>
	#include <util.h>
	#include <utilmoneystr.h>
	#include <utilstrencodings.h>
	#include <validationinterface.h>
	#include <warnings.h>

	#include <boost/algorithm/string/replace.hpp>
	#include <boost/thread.hpp> // boost::this_thread::interruption_point() (mingw)

	#include <atomic>
	#include <future>
	#include <sstream>
	#include <thread>

	#if defined(NDEBUG)
	#error "Bitcoin cannot be compiled without assertions."
	#endif

	#define MICRO 0.000001
	#define MILLI 0.001
	class ConnectTrace;

	/**
	* CChainState stores and provides an API to update our local knowledge of the
	* current best chain and header tree.
	*
	* It generally provides access to the current block tree, as well as functions
	* to provide new data, which it will appropriately validate and incorporate in
	* its state as necessary.
	*
	* Eventually, the API here is targeted at being exposed externally as a
	* consumable libconsensus library, so any functions added must only call
	* other class member functions, pure functions in other parts of the consensus
	* library, callbacks via the validation interface, or read/write-to-disk
	* functions (eventually this will also be via callbacks).
	*/
	class CChainState {
	private:
	/**
	* The set of all CBlockIndex entries with BLOCK_VALID_TRANSACTIONS (for
	* itself and all ancestors) and as good as our current tip or better.
	* Entries may be failed, though, and pruning nodes may be missing the data
	* for the block.
	*/
	std::set<CBlockIndex *, CBlockIndexWorkComparator> setBlockIndexCandidates;

	/**
	* the ChainState CriticalSection
	* A lock that must be held when modifying this ChainState - held in
	* ActivateBestChain()
	*/
	CCriticalSection m_cs_chainstate;

	/**
	* Every received block is assigned a unique and increasing identifier, so
	* we know which one to give priority in case of a fork.
	* Blocks loaded from disk are assigned id 0, so start the counter at 1.
	*/
	std::atomic<int32_t> nBlockSequenceId{1};
	/** Decreasing counter (used by subsequent preciousblock calls). */
	int32_t nBlockReverseSequenceId = -1;
	/** chainwork for the last block that preciousblock has been applied to. */
	arith_uint256 nLastPreciousChainwork = 0;

	/**
	* In order to efficiently track invalidity of headers, we keep the set of
	* blocks which we tried to connect and found to be invalid here (ie which
	* were set to BLOCK_FAILED_VALID since the last restart). We can then
	* walk this set and check if a new header is a descendant of something in
	* this set, preventing us from having to walk mapBlockIndex when we try
	* to connect a bad block and fail.
	*
	* While this is more complicated than marking everything which descends
	* from an invalid block as invalid at the time we discover it to be
	* invalid, doing so would require walking all of mapBlockIndex to find all
	* descendants. Since this case should be very rare, keeping track of all
	* BLOCK_FAILED_VALID blocks in a set should be just fine and work just as
	* well.
	*
	* Because we already walk mapBlockIndex in height-order at startup, we go
	* ahead and mark descendants of invalid blocks as FAILED_CHILD at that
	* time, instead of putting things in this set.
	*/
	std::set<CBlockIndex *> m_failed_blocks;

	public:
	CChain chainActive;
	BlockMap mapBlockIndex;
	std::multimap<CBlockIndex , CBlockIndex > mapBlocksUnlinked;
	CBlockIndex *pindexBestInvalid = nullptr;
	CBlockIndex *pindexBestParked = nullptr;

	bool LoadBlockIndex(const Config &config, CBlockTreeDB &blocktree);

	bool ActivateBestChain(
	const Config &config, CValidationState &state,
	std::shared_ptr<const CBlock> pblock = std::shared_ptr<const CBlock>());

	bool AcceptBlockHeader(const Config &config, const CBlockHeader &block,
	CValidationState &state, CBlockIndex **ppindex);
	bool AcceptBlock(const Config &config,
	const std::shared_ptr<const CBlock> &pblock,
	CValidationState &state, bool fRequested,
	const CDiskBlockPos dbp, bool fNewBlock);

	// Block (dis)connection on a given view:
	DisconnectResult DisconnectBlock(const CBlock &block,
	const CBlockIndex *pindex,
	CCoinsViewCache &view);
	bool ConnectBlock(const Config &config, const CBlock &block,
	CValidationState &state, CBlockIndex *pindex,
	CCoinsViewCache &view, bool fJustCheck = false);

	// Block disconnection on our pcoinsTip:
	bool DisconnectTip(const Config &config, CValidationState &state,
	DisconnectedBlockTransactions *disconnectpool);

	// Manual block validity manipulation:
	bool PreciousBlock(const Config &config, CValidationState &state,
	CBlockIndex *pindex);
	bool UnwindBlock(const Config &config, CValidationState &state,
	CBlockIndex *pindex, bool invalidate);
	bool ResetBlockFailureFlags(CBlockIndex *pindex);
	template <typename F>
	void UpdateFlagsForBlock(CBlockIndex pindexBase, CBlockIndex pindex, F f);
	template <typename F, typename C>
	void UpdateFlags(CBlockIndex *pindex, F f, C fchild);
	template <typename F> void UpdateFlags(CBlockIndex *pindex, F f);
	/** Remove parked status from a block and its descendants. */
	bool UnparkBlockImpl(CBlockIndex *pindex, bool fClearChildren);

	bool ReplayBlocks(const Config &config, CCoinsView *view);
	bool RewindBlockIndex(const Config &config);
	bool LoadGenesisBlock(const CChainParams &chainparams);

	void PruneBlockIndexCandidates();

	void UnloadBlockIndex();

	private:
	bool ActivateBestChainStep(const Config &config, CValidationState &state,
	CBlockIndex *pindexMostWork,
	const std::shared_ptr<const CBlock> &pblock,
	bool &fInvalidFound, ConnectTrace &connectTrace);
	bool ConnectTip(const Config &config, CValidationState &state,
	CBlockIndex *pindexNew,
	const std::shared_ptr<const CBlock> &pblock,
	ConnectTrace &connectTrace,
	DisconnectedBlockTransactions &disconnectpool);

	CBlockIndex *AddToBlockIndex(const CBlockHeader &block);
	/** Create a new block index entry for a given block hash */
	CBlockIndex *InsertBlockIndex(const uint256 &hash);
	void CheckBlockIndex(const Consensus::Params &consensusParams);

	void InvalidBlockFound(CBlockIndex *pindex, const CValidationState &state);
	CBlockIndex *FindMostWorkChain();
	bool ReceivedBlockTransactions(const CBlock &block, CValidationState &state,
	CBlockIndex *pindexNew,
	const CDiskBlockPos &pos);

	bool RollforwardBlock(const CBlockIndex *pindex, CCoinsViewCache &inputs,
	const Config &config);
	} g_chainstate;

	/**
	* Global state
	*/
	CCriticalSection cs_main;

	BlockMap &mapBlockIndex = g_chainstate.mapBlockIndex;
	CChain &chainActive = g_chainstate.chainActive;
	CBlockIndex *pindexBestHeader = nullptr;
	Mutex g_best_block_mutex;
	std::condition_variable g_best_block_cv;
	uint256 g_best_block;
	int nScriptCheckThreads = 0;
	std::atomic_bool fImporting(false);
	std::atomic_bool fReindex(false);
	bool fHavePruned = false;
	bool fPruneMode = false;
	bool fIsBareMultisigStd = DEFAULT_PERMIT_BAREMULTISIG;
	bool fRequireStandard = true;
	bool fCheckBlockIndex = false;
	bool fCheckpointsEnabled = DEFAULT_CHECKPOINTS_ENABLED;
	size_t nCoinCacheUsage = 5000 * 300;
	uint64_t nPruneTarget = 0;
	int64_t nMaxTipAge = DEFAULT_MAX_TIP_AGE;

	uint256 hashAssumeValid;
	arith_uint256 nMinimumChainWork;

	CFeeRate minRelayTxFee = CFeeRate(DEFAULT_MIN_RELAY_TX_FEE_PER_KB);
	Amount maxTxFee = DEFAULT_TRANSACTION_MAXFEE;

	CTxMemPool g_mempool;
	std::atomic_bool g_is_mempool_loaded{false};

	/** Constant stuff for coinbase transactions we create: */
	CScript COINBASE_FLAGS;

	const std::string strMessageMagic = "Bitcoin Signed Message:\n";

	// Internal stuff
	namespace {
	CBlockIndex *&pindexBestInvalid = g_chainstate.pindexBestInvalid;
	CBlockIndex *&pindexBestParked = g_chainstate.pindexBestParked;

	/**
	* The best finalized block.
	* This block cannot be reorged in any way, shape or form.
	*/
	CBlockIndex const *pindexFinalized;

	/**
	* All pairs A->B, where A (or one of its ancestors) misses transactions, but B
	* has transactions. Pruned nodes may have entries where B is missing data.
	*/
	std::multimap<CBlockIndex , CBlockIndex > &mapBlocksUnlinked =
	g_chainstate.mapBlocksUnlinked;

	CCriticalSection cs_LastBlockFile;
	std::vector<CBlockFileInfo> vinfoBlockFile;
	int nLastBlockFile = 0;
	/**
	* Global flag to indicate we should check to see if there are block/undo files
	* that should be deleted. Set on startup or if we allocate more file space when
	* we're in prune mode.
	*/
	bool fCheckForPruning = false;

	/** Dirty block index entries. */
	std::set<const CBlockIndex *> setDirtyBlockIndex;

	/** Dirty block file entries. */
	std::set<int> setDirtyFileInfo;
	} // namespace

	CBlockIndex *FindForkInGlobalIndex(const CChain &chain,
	const CBlockLocator &locator) {
	AssertLockHeld(cs_main);

	// Find the first block the caller has in the main chain
	for (const uint256 &hash : locator.vHave) {
	CBlockIndex *pindex = LookupBlockIndex(hash);
	if (pindex) {
	if (chain.Contains(pindex)) {
	return pindex;
	}
	if (pindex->GetAncestor(chain.Height()) == chain.Tip()) {
	return chain.Tip();
	}
	}
	}
	return chain.Genesis();
	}

	std::unique_ptr<CCoinsViewDB> pcoinsdbview;
	std::unique_ptr<CCoinsViewCache> pcoinsTip;
	std::unique_ptr<CBlockTreeDB> pblocktree;

	enum class FlushStateMode { NONE, IF_NEEDED, PERIODIC, ALWAYS };

	// See definition for documentation
	static bool FlushStateToDisk(const CChainParams &chainParams,
	CValidationState &state, FlushStateMode mode,
	int nManualPruneHeight = 0);
	static void FindFilesToPruneManual(std::set<int> &setFilesToPrune,
	int nManualPruneHeight);
	static void FindFilesToPrune(std::set<int> &setFilesToPrune,
	uint64_t nPruneAfterHeight);
	static FILE *OpenUndoFile(const CDiskBlockPos &pos, bool fReadOnly = false);
	static FlatFileSeq BlockFileSeq();
	static FlatFileSeq UndoFileSeq();
	static uint32_t GetNextBlockScriptFlags(const Config &config,
	const CBlockIndex *pindex);

	bool TestLockPointValidity(const LockPoints *lp) {
	AssertLockHeld(cs_main);
	assert(lp);
	// If there are relative lock times then the maxInputBlock will be set
	// If there are no relative lock times, the LockPoints don't depend on the
	// chain
	if (lp->maxInputBlock) {
	// Check whether chainActive is an extension of the block at which the
	// LockPoints calculation was valid. If not LockPoints are no longer
	// valid.
	if (!chainActive.Contains(lp->maxInputBlock)) {
	return false;
	}
	}

	// LockPoints still valid
	return true;
	}

	bool CheckSequenceLocks(const CTransaction &tx, int flags, LockPoints *lp,
	bool useExistingLockPoints) {
	AssertLockHeld(cs_main);
	AssertLockHeld(g_mempool.cs);

	CBlockIndex *tip = chainActive.Tip();
	assert(tip != nullptr);

	CBlockIndex index;
	index.pprev = tip;
	// CheckSequenceLocks() uses chainActive.Height()+1 to evaluate height based
	// locks because when SequenceLocks() is called within ConnectBlock(), the
	// height of the block being evaluated is what is used. Thus if we want to
	// know if a transaction can be part of the next block, we need to use one
	// more than chainActive.Height()
	index.nHeight = tip->nHeight + 1;

	std::pair<int, int64_t> lockPair;
	if (useExistingLockPoints) {
	assert(lp);
	lockPair.first = lp->height;
	lockPair.second = lp->time;
	} else {
	// pcoinsTip contains the UTXO set for chainActive.Tip()
	CCoinsViewMemPool viewMemPool(pcoinsTip.get(), g_mempool);
	std::vector<int> prevheights;
	prevheights.resize(tx.vin.size());
	for (size_t txinIndex = 0; txinIndex < tx.vin.size(); txinIndex++) {
	const CTxIn &txin = tx.vin[txinIndex];
	Coin coin;
	if (!viewMemPool.GetCoin(txin.prevout, coin)) {
	return error("%s: Missing input", __func__);
	}
	if (coin.GetHeight() == MEMPOOL_HEIGHT) {
	// Assume all mempool transaction confirm in the next block
	prevheights[txinIndex] = tip->nHeight + 1;
	} else {
	prevheights[txinIndex] = coin.GetHeight();
	}
	}
	lockPair = CalculateSequenceLocks(tx, flags, &prevheights, index);
	if (lp) {
	lp->height = lockPair.first;
	lp->time = lockPair.second;
	// Also store the hash of the block with the highest height of all
	// the blocks which have sequence locked prevouts. This hash needs
	// to still be on the chain for these LockPoint calculations to be
	// valid.
	// Note: It is impossible to correctly calculate a maxInputBlock if
	// any of the sequence locked inputs depend on unconfirmed txs,
	// except in the special case where the relative lock time/height is
	// 0, which is equivalent to no sequence lock. Since we assume input
	// height of tip+1 for mempool txs and test the resulting lockPair
	// from CalculateSequenceLocks against tip+1. We know
	// EvaluateSequenceLocks will fail if there was a non-zero sequence
	// lock on a mempool input, so we can use the return value of
	// CheckSequenceLocks to indicate the LockPoints validity.
	int maxInputHeight = 0;
	for (int height : prevheights) {
	// Can ignore mempool inputs since we'll fail if they had
	// non-zero locks.
	if (height != tip->nHeight + 1) {
	maxInputHeight = std::max(maxInputHeight, height);
	}
	}
	lp->maxInputBlock = tip->GetAncestor(maxInputHeight);
	}
	}
	return EvaluateSequenceLocks(index, lockPair);
	}

	/** Convert CValidationState to a human-readable message for logging */
	std::string FormatStateMessage(const CValidationState &state) {
	return strprintf(
	"%s%s (code %i)", state.GetRejectReason(),
	state.GetDebugMessage().empty() ? "" : ", " + state.GetDebugMessage(),
	state.GetRejectCode());
	}

	static bool IsMagneticAnomalyEnabledForCurrentBlock(const Config &config) {
	AssertLockHeld(cs_main);
	return IsMagneticAnomalyEnabled(config, chainActive.Tip());
	}

	// Command-line argument "-replayprotectionactivationtime=<timestamp>" will
	// cause the node to switch to replay protected SigHash ForkID value when the
	// median timestamp of the previous 11 blocks is greater than or equal to
	// <timestamp>. Defaults to the pre-defined timestamp when not set.
	static bool IsReplayProtectionEnabled(const Config &config,
	int64_t nMedianTimePast) {
	return nMedianTimePast >=
	gArgs.GetArg(
	"-replayprotectionactivationtime",
	config.GetChainParams().GetConsensus().gravitonActivationTime);
	}

	static bool IsReplayProtectionEnabled(const Config &config,
	const CBlockIndex *pindexPrev) {
	if (pindexPrev == nullptr) {
	return false;
	}

	return IsReplayProtectionEnabled(config, pindexPrev->GetMedianTimePast());
	}

	static bool IsReplayProtectionEnabledForCurrentBlock(const Config &config) {
	AssertLockHeld(cs_main);
	return IsReplayProtectionEnabled(config, chainActive.Tip());
	}

	// Used to avoid mempool polluting consensus critical paths if CCoinsViewMempool
	// were somehow broken and returning the wrong scriptPubKeys
	static bool CheckInputsFromMempoolAndCache(
	const CTransaction &tx, CValidationState &state,
	const CCoinsViewCache &view, const CTxMemPool &pool, const uint32_t flags,
	bool cacheSigStore, PrecomputedTransactionData &txdata) {
	AssertLockHeld(cs_main);

	// pool.cs should be locked already, but go ahead and re-take the lock here
	// to enforce that mempool doesn't change between when we check the view and
	// when we actually call through to CheckInputs
	LOCK(pool.cs);

	assert(!tx.IsCoinBase());
	for (const CTxIn &txin : tx.vin) {
	const Coin &coin = view.AccessCoin(txin.prevout);

	// At this point we haven't actually checked if the coins are all
	// available (or shouldn't assume we have, since CheckInputs does). So
	// we just return failure if the inputs are not available here, and then
	// only have to check equivalence for available inputs.
	if (coin.IsSpent()) {
	return false;
	}

	const CTransactionRef &txFrom = pool.get(txin.prevout.GetTxId());
	if (txFrom) {
	assert(txFrom->GetId() == txin.prevout.GetTxId());
	assert(txFrom->vout.size() > txin.prevout.GetN());
	assert(txFrom->vout[txin.prevout.GetN()] == coin.GetTxOut());
	} else {
	const Coin &coinFromDisk = pcoinsTip->AccessCoin(txin.prevout);
	assert(!coinFromDisk.IsSpent());
	assert(coinFromDisk.GetTxOut() == coin.GetTxOut());
	}
	}

	return CheckInputs(tx, state, view, true, flags, cacheSigStore, true,
	txdata);
	}

	static bool AcceptToMemoryPoolWorker(
	const Config &config, CTxMemPool &pool, CValidationState &state,
	const CTransactionRef &ptx, bool fLimitFree, bool *pfMissingInputs,
	int64_t nAcceptTime, bool fOverrideMempoolLimit, const Amount nAbsurdFee,
	std::vector<COutPoint> &coins_to_uncache, bool test_accept) {
	AssertLockHeld(cs_main);

	const CTransaction &tx = *ptx;
	const TxId txid = tx.GetId();

	// mempool "read lock" (held through
	// GetMainSignals().TransactionAddedToMempool())
	LOCK(pool.cs);
	if (pfMissingInputs) {
	*pfMissingInputs = false;
	}

	// Coinbase is only valid in a block, not as a loose transaction.
	if (!CheckRegularTransaction(tx, state)) {
	// state filled in by CheckRegularTransaction.
	return false;
	}

	// Rather not work on nonstandard transactions (unless -testnet/-regtest)
	std::string reason;
	if (fRequireStandard && !IsStandardTx(tx, reason)) {
	return state.DoS(0, false, REJECT_NONSTANDARD, reason);
	}

	// Only accept nLockTime-using transactions that can be mined in the next
	// block; we don't want our mempool filled up with transactions that can't
	// be mined yet.
	CValidationState ctxState;
	if (!ContextualCheckTransactionForCurrentBlock(
	config, tx, ctxState, STANDARD_LOCKTIME_VERIFY_FLAGS)) {
	// We copy the state from a dummy to ensure we don't increase the
	// ban score of peer for transaction that could be valid in the future.
	return state.DoS(
	0, false, REJECT_NONSTANDARD, ctxState.GetRejectReason(),
	ctxState.CorruptionPossible(), ctxState.GetDebugMessage());
	}

	// Is it already in the memory pool?
	if (pool.exists(txid)) {
	return state.Invalid(false, REJECT_DUPLICATE, "txn-already-in-mempool");
	}

	// Check for conflicts with in-memory transactions
	for (const CTxIn &txin : tx.vin) {
	auto itConflicting = pool.mapNextTx.find(txin.prevout);
	if (itConflicting != pool.mapNextTx.end()) {
	// Disable replacement feature for good
	return state.Invalid(false, REJECT_DUPLICATE,
	"txn-mempool-conflict");
	}
	}

	{
	CCoinsView dummy;
	CCoinsViewCache view(&dummy);

	LockPoints lp;
	CCoinsViewMemPool viewMemPool(pcoinsTip.get(), pool);
	view.SetBackend(viewMemPool);

	// Do all inputs exist?
	for (const CTxIn txin : tx.vin) {
	if (!pcoinsTip->HaveCoinInCache(txin.prevout)) {
	coins_to_uncache.push_back(txin.prevout);
	}

	if (!view.HaveCoin(txin.prevout)) {
	// Are inputs missing because we already have the tx?
	for (size_t out = 0; out < tx.vout.size(); out++) {
	// Optimistically just do efficient check of cache for
	// outputs.
	if (pcoinsTip->HaveCoinInCache(COutPoint(txid, out))) {
	return state.Invalid(false, REJECT_DUPLICATE,
	"txn-already-known");
	}
	}

	// Otherwise assume this might be an orphan tx for which we just
	// haven't seen parents yet.
	if (pfMissingInputs) {
	*pfMissingInputs = true;
	}

	// fMissingInputs and !state.IsInvalid() is used to detect this
	// condition, don't set state.Invalid()
	return false;
	}
	}

	// Are the actual inputs available?
	if (!view.HaveInputs(tx)) {
	return state.Invalid(false, REJECT_DUPLICATE,
	"bad-txns-inputs-spent");
	}

	// Bring the best block into scope.
	view.GetBestBlock();

	// We have all inputs cached now, so switch back to dummy, so we don't
	// need to keep lock on mempool.
	view.SetBackend(dummy);

	// Only accept BIP68 sequence locked transactions that can be mined in
	// the next block; we don't want our mempool filled up with transactions
	// that can't be mined yet. Must keep pool.cs for this unless we change
	// CheckSequenceLocks to take a CoinsViewCache instead of create its
	// own.
	if (!CheckSequenceLocks(tx, STANDARD_LOCKTIME_VERIFY_FLAGS, &lp)) {
	return state.DoS(0, false, REJECT_NONSTANDARD, "non-BIP68-final");
	}

	Amount nFees = Amount::zero();
	if (!Consensus::CheckTxInputs(tx, state, view, GetSpendHeight(view),
	nFees)) {
	return error("%s: Consensus::CheckTxInputs: %s, %s", __func__,
	tx.GetId().ToString(), FormatStateMessage(state));
	}

	// Check for non-standard pay-to-script-hash in inputs
	if (fRequireStandard && !AreInputsStandard(tx, view)) {
	return state.Invalid(false, REJECT_NONSTANDARD,
	"bad-txns-nonstandard-inputs");
	}

	int64_t nSigOpsCount =
	GetTransactionSigOpCount(tx, view, STANDARD_SCRIPT_VERIFY_FLAGS);

	// nModifiedFees includes any fee deltas from PrioritiseTransaction
	Amount nModifiedFees = nFees;
	double nPriorityDummy = 0;
	pool.ApplyDeltas(txid, nPriorityDummy, nModifiedFees);

	Amount inChainInputValue;
	double dPriority =
	view.GetPriority(tx, chainActive.Height(), inChainInputValue);

	// Keep track of transactions that spend a coinbase, which we re-scan
	// during reorgs to ensure COINBASE_MATURITY is still met.
	bool fSpendsCoinbase = false;
	for (const CTxIn &txin : tx.vin) {
	const Coin &coin = view.AccessCoin(txin.prevout);
	if (coin.IsCoinBase()) {
	fSpendsCoinbase = true;
	break;
	}
	}

	CTxMemPoolEntry entry(ptx, nFees, nAcceptTime, dPriority,
	chainActive.Height(), inChainInputValue,
	fSpendsCoinbase, nSigOpsCount, lp);
	unsigned int nSize = entry.GetTxSize();

	// Check that the transaction doesn't have an excessive number of
	// sigops, making it impossible to mine. Since the coinbase transaction
	// itself can contain sigops MAX_STANDARD_TX_SIGOPS is less than
	// MAX_BLOCK_SIGOPS_PER_MB; we still consider this an invalid rather
	// than merely non-standard transaction.
	if (nSigOpsCount > MAX_STANDARD_TX_SIGOPS) {
	return state.DoS(0, false, REJECT_NONSTANDARD,
	"bad-txns-too-many-sigops", false,
	strprintf("%d", nSigOpsCount));
	}

	Amount mempoolRejectFee =
	pool.GetMinFee(
	gArgs.GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE) *
	1000000)
	.GetFee(nSize);
	if (mempoolRejectFee > Amount::zero() &&
	nModifiedFees < mempoolRejectFee) {
	return state.DoS(
	0, false, REJECT_INSUFFICIENTFEE, "mempool min fee not met",
	false, strprintf("%d < %d", nModifiedFees, mempoolRejectFee));
	}

	if (gArgs.GetBoolArg("-relaypriority", DEFAULT_RELAYPRIORITY) &&
	nModifiedFees < minRelayTxFee.GetFee(nSize) &&
	!AllowFree(entry.GetPriority(chainActive.Height() + 1))) {
	// Require that free transactions have sufficient priority to be
	// mined in the next block.
	return state.DoS(0, false, REJECT_INSUFFICIENTFEE,
	"insufficient priority");
	}

	// Continuously rate-limit free (really, very-low-fee) transactions.
	// This mitigates 'penny-flooding' -- sending thousands of free
	// transactions just to be annoying or make others' transactions take
	// longer to confirm.
	if (fLimitFree && nModifiedFees < minRelayTxFee.GetFee(nSize)) {
	static CCriticalSection csFreeLimiter;
	static double dFreeCount;
	static int64_t nLastTime;
	int64_t nNow = GetTime();

	LOCK(csFreeLimiter);

	// Use an exponentially decaying ~10-minute window:
	dFreeCount *= pow(1.0 - 1.0 / 600.0, double(nNow - nLastTime));
	nLastTime = nNow;
	// -limitfreerelay unit is thousand-bytes-per-minute
	// At default rate it would take over a month to fill 1GB

	// NOTE: Use the actual size here, and not the fee size since this
	// is counting real size for the rate limiter.
	if (dFreeCount + nSize >=
	gArgs.GetArg("-limitfreerelay", DEFAULT_LIMITFREERELAY) * 10 *
	1000) {
	return state.DoS(0, false, REJECT_INSUFFICIENTFEE,
	"rate limited free transaction");
	}

	LogPrint(BCLog::MEMPOOL, "Rate limit dFreeCount: %g => %g\n",
	dFreeCount, dFreeCount + nSize);
	dFreeCount += nSize;
	}

	if (nAbsurdFee != Amount::zero() && nFees > nAbsurdFee) {
	return state.Invalid(false, REJECT_HIGHFEE, "absurdly-high-fee",
	strprintf("%d > %d", nFees, nAbsurdFee));
	}

	// Calculate in-mempool ancestors, up to a limit.
	CTxMemPool::setEntries setAncestors;
	size_t nLimitAncestors =
	gArgs.GetArg("-limitancestorcount", DEFAULT_ANCESTOR_LIMIT);
	size_t nLimitAncestorSize =
	gArgs.GetArg("-limitancestorsize", DEFAULT_ANCESTOR_SIZE_LIMIT) *
	1000;
	size_t nLimitDescendants =
	gArgs.GetArg("-limitdescendantcount", DEFAULT_DESCENDANT_LIMIT);
	size_t nLimitDescendantSize =
	gArgs.GetArg("-limitdescendantsize",
	DEFAULT_DESCENDANT_SIZE_LIMIT) *
	1000;
	std::string errString;
	if (!pool.CalculateMemPoolAncestors(
	entry, setAncestors, nLimitAncestors, nLimitAncestorSize,
	nLimitDescendants, nLimitDescendantSize, errString)) {
	return state.DoS(0, false, REJECT_NONSTANDARD,
	"too-long-mempool-chain", false, errString);
	}

	// Set extraFlags as a set of flags that needs to be activated.
	uint32_t extraFlags = SCRIPT_VERIFY_NONE;
	if (IsReplayProtectionEnabledForCurrentBlock(config)) {
	extraFlags \|= SCRIPT_ENABLE_REPLAY_PROTECTION;
	}

	if (IsMagneticAnomalyEnabledForCurrentBlock(config)) {
	extraFlags \|= SCRIPT_VERIFY_CHECKDATASIG_SIGOPS;
	}

	// Make sure whatever we need to activate is actually activated.
	const uint32_t scriptVerifyFlags =
	STANDARD_SCRIPT_VERIFY_FLAGS \| extraFlags;

	// Check against previous transactions. This is done last to help
	// prevent CPU exhaustion denial-of-service attacks.
	PrecomputedTransactionData txdata(tx);
	if (!CheckInputs(tx, state, view, true, scriptVerifyFlags, true, false,
	txdata)) {
	// State filled in by CheckInputs.
	return false;
	}

	// Check again against the next block's script verification flags
	// to cache our script execution flags.
	//
	// This is also useful in case of bugs in the standard flags that cause
	// transactions to pass as valid when they're actually invalid. For
	// instance the STRICTENC flag was incorrectly allowing certain CHECKSIG
	// NOT scripts to pass, even though they were invalid.
	//
	// There is a similar check in CreateNewBlock() to prevent creating
	// invalid blocks (using TestBlockValidity), however allowing such
	// transactions into the mempool can be exploited as a DoS attack.
	uint32_t nextBlockScriptVerifyFlags =
	GetNextBlockScriptFlags(config, chainActive.Tip());

	if (!CheckInputsFromMempoolAndCache(tx, state, view, pool,
	nextBlockScriptVerifyFlags, true,
	txdata)) {
	return error("%s: BUG! PLEASE REPORT THIS! CheckInputs failed "
	"against next-block but not STANDARD flags %s, %s",
	__func__, txid.ToString(), FormatStateMessage(state));
	}

	if (test_accept) {
	// Tx was accepted, but not added
	return true;
	}

	// Store transaction in memory.
	pool.addUnchecked(txid, entry, setAncestors);

	// Trim mempool and check if tx was trimmed.
	if (!fOverrideMempoolLimit) {
	pool.LimitSize(
	gArgs.GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE) * 1000000,
	gArgs.GetArg("-mempoolexpiry", DEFAULT_MEMPOOL_EXPIRY) * 60 *
	60);
	if (!pool.exists(txid)) {
	return state.DoS(0, false, REJECT_INSUFFICIENTFEE,
	"mempool full");
	}
	}
	}

	GetMainSignals().TransactionAddedToMempool(ptx);
	return true;
	}

	/**
	* (try to) add transaction to memory pool with a specified acceptance time.
	*/
	static bool
	AcceptToMemoryPoolWithTime(const Config &config, CTxMemPool &pool,
	CValidationState &state, const CTransactionRef &tx,
	bool fLimitFree, bool *pfMissingInputs,
	int64_t nAcceptTime, bool fOverrideMempoolLimit,
	const Amount nAbsurdFee, bool test_accept) {
	std::vector<COutPoint> coins_to_uncache;
	bool res = AcceptToMemoryPoolWorker(
	config, pool, state, tx, fLimitFree, pfMissingInputs, nAcceptTime,
	fOverrideMempoolLimit, nAbsurdFee, coins_to_uncache, test_accept);
	if (!res) {
	for (const COutPoint &outpoint : coins_to_uncache) {
	pcoinsTip->Uncache(outpoint);
	}
	}

	// After we've (potentially) uncached entries, ensure our coins cache is
	// still within its size limits
	CValidationState stateDummy;
	FlushStateToDisk(config.GetChainParams(), stateDummy,
	FlushStateMode::PERIODIC);
	return res;
	}

	bool AcceptToMemoryPool(const Config &config, CTxMemPool &pool,
	CValidationState &state, const CTransactionRef &tx,
	bool fLimitFree, bool *pfMissingInputs,
	bool fOverrideMempoolLimit, const Amount nAbsurdFee,
	bool test_accept) {
	return AcceptToMemoryPoolWithTime(
	config, pool, state, tx, fLimitFree, pfMissingInputs, GetTime(),
	fOverrideMempoolLimit, nAbsurdFee, test_accept);
	}

	/**
	* Return transaction in txOut, and if it was found inside a block, its hash is
	* placed in hashBlock. If blockIndex is provided, the transaction is fetched
	* from the corresponding block.
	*/
	bool GetTransaction(const Config &config, const TxId &txid,
	CTransactionRef &txOut, uint256 &hashBlock, bool fAllowSlow,
	CBlockIndex *blockIndex) {
	CBlockIndex *pindexSlow = blockIndex;

	LOCK(cs_main);

	if (!blockIndex) {
	CTransactionRef ptx = g_mempool.get(txid);
	if (ptx) {
	txOut = ptx;
	return true;
	}

	if (g_txindex) {
	return g_txindex->FindTx(txid, hashBlock, txOut);
	}

	// use coin database to locate block that contains transaction, and scan
	// it
	if (fAllowSlow) {
	const Coin &coin = AccessByTxid(*pcoinsTip, txid);
	if (!coin.IsSpent()) {
	pindexSlow = chainActive[coin.GetHeight()];
	}
	}
	}

	if (pindexSlow) {
	CBlock block;
	if (ReadBlockFromDisk(block, pindexSlow, config)) {
	for (const auto &tx : block.vtx) {
	if (tx->GetId() == txid) {
	txOut = tx;
	hashBlock = pindexSlow->GetBlockHash();
	return true;
	}
	}
	}
	}

	return false;
	}

	//////////////////////////////////////////////////////////////////////////////
	//
	// CBlock and CBlockIndex
	//

	static bool WriteBlockToDisk(const CBlock &block, CDiskBlockPos &pos,
	const CMessageHeader::MessageMagic &messageStart) {
	// Open history file to append
	CAutoFile fileout(OpenBlockFile(pos), SER_DISK, CLIENT_VERSION);
	if (fileout.IsNull()) {
	return error("WriteBlockToDisk: OpenBlockFile failed");
	}

	// Write index header
	unsigned int nSize = GetSerializeSize(fileout, block);
	fileout << FLATDATA(messageStart) << nSize;

	// Write block
	long fileOutPos = ftell(fileout.Get());
	if (fileOutPos < 0) {
	return error("WriteBlockToDisk: ftell failed");
	}

	pos.nPos = (unsigned int)fileOutPos;
	fileout << block;

	return true;
	}

	bool ReadBlockFromDisk(CBlock &block, const CDiskBlockPos &pos,
	const Config &config) {
	block.SetNull();

	// Open history file to read
	CAutoFile filein(OpenBlockFile(pos, true), SER_DISK, CLIENT_VERSION);
	if (filein.IsNull()) {
	return error("ReadBlockFromDisk: OpenBlockFile failed for %s",
	pos.ToString());
	}

	// Read block
	try {
	filein >> block;
	} catch (const std::exception &e) {
	return error("%s: Deserialize or I/O error - %s at %s", __func__,
	e.what(), pos.ToString());
	}

	// Check the header
	if (!CheckProofOfWork(block.GetHash(), block.nBits, config)) {
	return error("ReadBlockFromDisk: Errors in block header at %s",
	pos.ToString());
	}

	return true;
	}

	bool ReadBlockFromDisk(CBlock &block, const CBlockIndex *pindex,
	const Config &config) {
	CDiskBlockPos blockPos;
	{
	LOCK(cs_main);
	blockPos = pindex->GetBlockPos();
	}

	if (!ReadBlockFromDisk(block, blockPos, config)) {
	return false;
	}

	if (block.GetHash() != pindex->GetBlockHash()) {
	return error("ReadBlockFromDisk(CBlock&, CBlockIndex*): GetHash() "
	"doesn't match index for %s at %s",
	pindex->ToString(), pindex->GetBlockPos().ToString());
	}

	return true;
	}

	Amount GetBlockSubsidy(int nHeight, const Consensus::Params &consensusParams) {
	int halvings = nHeight / consensusParams.nSubsidyHalvingInterval;
	// Force block reward to zero when right shift is undefined.
	if (halvings >= 64) {
	return Amount::zero();
	}

	Amount nSubsidy = 50 * COIN;
	// Subsidy is cut in half every 210,000 blocks which will occur
	// approximately every 4 years.
	return ((nSubsidy / SATOSHI) >> halvings) * SATOSHI;
	}

	bool IsInitialBlockDownload() {
	// Once this function has returned false, it must remain false.
	static std::atomic<bool> latchToFalse{false};
	// Optimization: pre-test latch before taking the lock.
	if (latchToFalse.load(std::memory_order_relaxed)) {
	return false;
	}

	LOCK(cs_main);
	if (latchToFalse.load(std::memory_order_relaxed)) {
	return false;
	}
	if (fImporting \|\| fReindex) {
	return true;
	}
	if (chainActive.Tip() == nullptr) {
	return true;
	}
	if (chainActive.Tip()->nChainWork < nMinimumChainWork) {
	return true;
	}
	if (chainActive.Tip()->GetBlockTime() < (GetTime() - nMaxTipAge)) {
	return true;
	}
	LogPrintf("Leaving InitialBlockDownload (latching to false)\n");
	latchToFalse.store(true, std::memory_order_relaxed);
	return false;
	}

	CBlockIndex const *pindexBestForkTip = nullptr;
	CBlockIndex const *pindexBestForkBase = nullptr;

	static void AlertNotify(const std::string &strMessage) {
	uiInterface.NotifyAlertChanged();
	std::string strCmd = gArgs.GetArg("-alertnotify", "");
	if (strCmd.empty()) {
	return;
	}

	// Alert text should be plain ascii coming from a trusted source, but to be
	// safe we first strip anything not in safeChars, then add single quotes
	// around the whole string before passing it to the shell:
	std::string singleQuote("'");
	std::string safeStatus = SanitizeString(strMessage);
	safeStatus = singleQuote + safeStatus + singleQuote;
	boost::replace_all(strCmd, "%s", safeStatus);

	std::thread t(runCommand, strCmd);
	// thread runs free
	t.detach();
	}

	static void CheckForkWarningConditions() {
	AssertLockHeld(cs_main);
	// Before we get past initial download, we cannot reliably alert about forks
	// (we assume we don't get stuck on a fork before finishing our initial
	// sync)
	if (IsInitialBlockDownload()) {
	return;
	}

	// If our best fork is no longer within 72 blocks (+/- 12 hours if no one
	// mines it) of our head, drop it
	if (pindexBestForkTip &&
	chainActive.Height() - pindexBestForkTip->nHeight >= 72) {
	pindexBestForkTip = nullptr;
	}

	if (pindexBestForkTip \|\|
	(pindexBestInvalid &&
	pindexBestInvalid->nChainWork >
	chainActive.Tip()->nChainWork +
	(GetBlockProof(chainActive.Tip()) 6))) {
	if (!GetfLargeWorkForkFound() && pindexBestForkBase) {
	std::string warning =
	std::string("'Warning: Large-work fork detected, forking after "
	"block ") +
	pindexBestForkBase->phashBlock->ToString() + std::string("'");
	AlertNotify(warning);
	}

	if (pindexBestForkTip && pindexBestForkBase) {
	LogPrintf("%s: Warning: Large fork found\n forking the "
	"chain at height %d (%s)\n lasting to height %d "
	"(%s).\nChain state database corruption likely.\n",
	__func__, pindexBestForkBase->nHeight,
	pindexBestForkBase->phashBlock->ToString(),
	pindexBestForkTip->nHeight,
	pindexBestForkTip->phashBlock->ToString());
	SetfLargeWorkForkFound(true);
	} else {
	LogPrintf("%s: Warning: Found invalid chain at least ~6 blocks "
	"longer than our best chain.\nChain state database "
	"corruption likely.\n",
	__func__);
	SetfLargeWorkInvalidChainFound(true);
	}
	} else {
	SetfLargeWorkForkFound(false);
	SetfLargeWorkInvalidChainFound(false);
	}
	}

	static void
	CheckForkWarningConditionsOnNewFork(const CBlockIndex *pindexNewForkTip) {
	AssertLockHeld(cs_main);
	// If we are on a fork that is sufficiently large, set a warning flag.
	const CBlockIndex *pfork = chainActive.FindFork(pindexNewForkTip);

	// We define a condition where we should warn the user about as a fork of at
	// least 7 blocks with a tip within 72 blocks (+/- 12 hours if no one mines
	// it) of ours. We use 7 blocks rather arbitrarily as it represents just
	// under 10% of sustained network hash rate operating on the fork, or a
	// chain that is entirely longer than ours and invalid (note that this
	// should be detected by both). We define it this way because it allows us
	// to only store the highest fork tip (+ base) which meets the 7-block
	// condition and from this always have the most-likely-to-cause-warning fork
	if (pfork &&
	(!pindexBestForkTip \|\|
	pindexNewForkTip->nHeight > pindexBestForkTip->nHeight) &&
	pindexNewForkTip->nChainWork - pfork->nChainWork >
	(GetBlockProof(pfork) 7) &&
	chainActive.Height() - pindexNewForkTip->nHeight < 72) {
	pindexBestForkTip = pindexNewForkTip;
	pindexBestForkBase = pfork;
	}

	CheckForkWarningConditions();
	}

	static void InvalidChainFound(CBlockIndex *pindexNew) {
	if (!pindexBestInvalid \|\|
	pindexNew->nChainWork > pindexBestInvalid->nChainWork) {
	pindexBestInvalid = pindexNew;
	}

	// If the invalid chain found is supposed to be finalized, we need to move
	// back the finalization point.
	if (IsBlockFinalized(pindexNew)) {
	pindexFinalized = pindexNew->pprev;
	}

	LogPrintf("%s: invalid block=%s height=%d log2_work=%.8g date=%s\n",
	__func__, pindexNew->GetBlockHash().ToString(),
	pindexNew->nHeight,
	log(pindexNew->nChainWork.getdouble()) / log(2.0),
	FormatISO8601DateTime(pindexNew->GetBlockTime()));
	CBlockIndex *tip = chainActive.Tip();
	assert(tip);
	LogPrintf("%s: current best=%s height=%d log2_work=%.8g date=%s\n",
	__func__, tip->GetBlockHash().ToString(), chainActive.Height(),
	log(tip->nChainWork.getdouble()) / log(2.0),
	FormatISO8601DateTime(tip->GetBlockTime()));
	}

	void CChainState::InvalidBlockFound(CBlockIndex *pindex,
	const CValidationState &state) {
	if (!state.CorruptionPossible()) {
	pindex->nStatus = pindex->nStatus.withFailed();
	m_failed_blocks.insert(pindex);
	setDirtyBlockIndex.insert(pindex);
	InvalidChainFound(pindex);
	}
	}

	void SpendCoins(CCoinsViewCache &view, const CTransaction &tx, CTxUndo &txundo,
	int nHeight) {
	// Mark inputs spent.
	if (tx.IsCoinBase()) {
	return;
	}

	txundo.vprevout.reserve(tx.vin.size());
	for (const CTxIn &txin : tx.vin) {
	txundo.vprevout.emplace_back();
	bool is_spent = view.SpendCoin(txin.prevout, &txundo.vprevout.back());
	assert(is_spent);
	}
	}

	void UpdateCoins(CCoinsViewCache &view, const CTransaction &tx, CTxUndo &txundo,
	int nHeight) {
	SpendCoins(view, tx, txundo, nHeight);
	AddCoins(view, tx, nHeight);
	}

	void UpdateCoins(CCoinsViewCache &view, const CTransaction &tx, int nHeight) {
	// Mark inputs spent.
	if (!tx.IsCoinBase()) {
	for (const CTxIn &txin : tx.vin) {
	bool is_spent = view.SpendCoin(txin.prevout);
	assert(is_spent);
	}
	}

	// Add outputs.
	AddCoins(view, tx, nHeight);
	}

	bool CScriptCheck::operator()() {
	const CScript &scriptSig = ptxTo->vin[nIn].scriptSig;
	return VerifyScript(scriptSig, scriptPubKey, nFlags,
	CachingTransactionSignatureChecker(ptxTo, nIn, amount,
	cacheStore, txdata),
	&error);
	}

	int GetSpendHeight(const CCoinsViewCache &inputs) {
	LOCK(cs_main);
	CBlockIndex *pindexPrev = LookupBlockIndex(inputs.GetBestBlock());
	return pindexPrev->nHeight + 1;
	}

	bool CheckInputs(const CTransaction &tx, CValidationState &state,
	const CCoinsViewCache &inputs, bool fScriptChecks,
	const uint32_t flags, bool sigCacheStore,
	bool scriptCacheStore,
	const PrecomputedTransactionData &txdata,
	std::vector<CScriptCheck> *pvChecks) {
	assert(!tx.IsCoinBase());

	if (pvChecks) {
	pvChecks->reserve(tx.vin.size());
	}

	// Skip script verification when connecting blocks under the assumevalid
	// block. Assuming the assumevalid block is valid this is safe because
	// block merkle hashes are still computed and checked, of course, if an
	// assumed valid block is invalid due to false scriptSigs this optimization
	// would allow an invalid chain to be accepted.
	if (!fScriptChecks) {
	return true;
	}

	// First check if script executions have been cached with the same flags.
	// Note that this assumes that the inputs provided are correct (ie that the
	// transaction hash which is in tx's prevouts properly commits to the
	// scriptPubKey in the inputs view of that transaction).
	uint256 hashCacheEntry = GetScriptCacheKey(tx, flags);
	if (IsKeyInScriptCache(hashCacheEntry, !scriptCacheStore)) {
	return true;
	}

	for (size_t i = 0; i < tx.vin.size(); i++) {
	const COutPoint &prevout = tx.vin[i].prevout;
	const Coin &coin = inputs.AccessCoin(prevout);
	assert(!coin.IsSpent());

	// We very carefully only pass in things to CScriptCheck which are
	// clearly committed to by tx's hash. This provides a sanity
	// check that our caching is not introducing consensus failures through
	// additional data in, eg, the coins being spent being checked as a part
	// of CScriptCheck.
	const CScript &scriptPubKey = coin.GetTxOut().scriptPubKey;
	const Amount amount = coin.GetTxOut().nValue;

	// Verify signature
	CScriptCheck check(scriptPubKey, amount, tx, i, flags, sigCacheStore,
	txdata);
	if (pvChecks) {
	pvChecks->push_back(std::move(check));
	} else if (!check()) {
	// Compute flags without the optional standardness flags.
	// This differs from MANDATORY_SCRIPT_VERIFY_FLAGS as it contains
	// additional upgrade flags (see AcceptToMemoryPoolWorker variable
	// extraFlags).
	uint32_t mandatoryFlags =
	flags & ~STANDARD_NOT_MANDATORY_VERIFY_FLAGS;
	if (flags != mandatoryFlags) {
	// Check whether the failure was caused by a non-mandatory
	// script verification check. If so, don't trigger DoS
	// protection to avoid splitting the network on the basis of
	// relay policy disagreements.
	CScriptCheck check2(scriptPubKey, amount, tx, i, mandatoryFlags,
	sigCacheStore, txdata);
	if (check2()) {
	return state.Invalid(
	false, REJECT_NONSTANDARD,
	strprintf("non-mandatory-script-verify-flag (%s)",
	ScriptErrorString(check.GetScriptError())));
	}
	}

	// Failures of other flags indicate a transaction that is invalid in
	// new blocks, e.g. a invalid P2SH. We DoS ban such nodes as they
	// are not following the protocol. That said during an upgrade
	// careful thought should be taken as to the correct behavior - we
	// may want to continue peering with non-upgraded nodes even after
	// soft-fork super-majority signaling has occurred.
	return state.DoS(
	100, false, REJECT_INVALID,
	strprintf("mandatory-script-verify-flag-failed (%s)",
	ScriptErrorString(check.GetScriptError())));
	}
	}

	if (scriptCacheStore && !pvChecks) {
	// We executed all of the provided scripts, and were told to cache the
	// result. Do so now.
	AddKeyInScriptCache(hashCacheEntry);
	}

	return true;
	}

	namespace {

	bool UndoWriteToDisk(const CBlockUndo &blockundo, CDiskBlockPos &pos,
	const uint256 &hashBlock,
	const CMessageHeader::MessageMagic &messageStart) {
	// Open history file to append
	CAutoFile fileout(OpenUndoFile(pos), SER_DISK, CLIENT_VERSION);
	if (fileout.IsNull()) {
	return error("%s: OpenUndoFile failed", __func__);
	}

	// Write index header
	unsigned int nSize = GetSerializeSize(fileout, blockundo);
	fileout << FLATDATA(messageStart) << nSize;

	// Write undo data
	long fileOutPos = ftell(fileout.Get());
	if (fileOutPos < 0) {
	return error("%s: ftell failed", __func__);
	}
	pos.nPos = (unsigned int)fileOutPos;
	fileout << blockundo;

	// calculate & write checksum
	CHashWriter hasher(SER_GETHASH, PROTOCOL_VERSION);
	hasher << hashBlock;
	hasher << blockundo;
	fileout << hasher.GetHash();

	return true;
	}

	static bool UndoReadFromDisk(CBlockUndo &blockundo, const CBlockIndex *pindex) {
	CDiskBlockPos pos = pindex->GetUndoPos();
	if (pos.IsNull()) {
	return error("%s: no undo data available", __func__);
	}

	// Open history file to read
	CAutoFile filein(OpenUndoFile(pos, true), SER_DISK, CLIENT_VERSION);
	if (filein.IsNull()) {
	return error("%s: OpenUndoFile failed", __func__);
	}

	// Read block
	uint256 hashChecksum;
	// We need a CHashVerifier as reserializing may lose data
	CHashVerifier<CAutoFile> verifier(&filein);
	try {
	verifier << pindex->pprev->GetBlockHash();
	verifier >> blockundo;
	filein >> hashChecksum;
	} catch (const std::exception &e) {
	return error("%s: Deserialize or I/O error - %s", __func__, e.what());
	}

	// Verify checksum
	if (hashChecksum != verifier.GetHash()) {
	return error("%s: Checksum mismatch", __func__);
	}

	return true;
	}

	/** Abort with a message */
	static bool AbortNode(const std::string &strMessage,
	const std::string &userMessage = "") {
	SetMiscWarning(strMessage);
	LogPrintf("*** %s\n", strMessage);
	uiInterface.ThreadSafeMessageBox(
	userMessage.empty() ? _("Error: A fatal internal error occurred, see "
	"debug.log for details")
	: userMessage,
	"", CClientUIInterface::MSG_ERROR);
	StartShutdown();
	return false;
	}

	static bool AbortNode(CValidationState &state, const std::string &strMessage,
	const std::string &userMessage = "") {
	AbortNode(strMessage, userMessage);
	return state.Error(strMessage);
	}

	} // namespace

	/** Restore the UTXO in a Coin at a given COutPoint. */
	DisconnectResult UndoCoinSpend(const Coin &undo, CCoinsViewCache &view,
	const COutPoint &out) {
	bool fClean = true;

	if (view.HaveCoin(out)) {
	// Overwriting transaction output.
	fClean = false;
	}

	if (undo.GetHeight() == 0) {
	// Missing undo metadata (height and coinbase). Older versions included
	// this information only in undo records for the last spend of a
	// transactions' outputs. This implies that it must be present for some
	// other output of the same tx.
	const Coin &alternate = AccessByTxid(view, out.GetTxId());
	if (alternate.IsSpent()) {
	// Adding output for transaction without known metadata
	return DISCONNECT_FAILED;
	}

	// This is somewhat ugly, but hopefully utility is limited. This is only
	// useful when working from legacy on disck data. In any case, putting
	// the correct information in there doesn't hurt.
	const_cast<Coin &>(undo) = Coin(undo.GetTxOut(), alternate.GetHeight(),
	alternate.IsCoinBase());
	}

	// The potential_overwrite parameter to AddCoin is only allowed to be false
	// if we know for sure that the coin did not already exist in the cache. As
	// we have queried for that above using HaveCoin, we don't need to guess.
	// When fClean is false, a coin already existed and it is an overwrite.
	view.AddCoin(out, std::move(undo), !fClean);

	return fClean ? DISCONNECT_OK : DISCONNECT_UNCLEAN;
	}

	/**
	* Undo the effects of this block (with given index) on the UTXO set represented
	* by coins. When FAILED is returned, view is left in an indeterminate state.
	*/
	DisconnectResult CChainState::DisconnectBlock(const CBlock &block,
	const CBlockIndex *pindex,
	CCoinsViewCache &view) {
	CBlockUndo blockUndo;
	if (!UndoReadFromDisk(blockUndo, pindex)) {
	error("DisconnectBlock(): failure reading undo data");
	return DISCONNECT_FAILED;
	}

	return ApplyBlockUndo(blockUndo, block, pindex, view);
	}

	DisconnectResult ApplyBlockUndo(const CBlockUndo &blockUndo,
	const CBlock &block, const CBlockIndex *pindex,
	CCoinsViewCache &view) {
	bool fClean = true;

	if (blockUndo.vtxundo.size() + 1 != block.vtx.size()) {
	error("DisconnectBlock(): block and undo data inconsistent");
	return DISCONNECT_FAILED;
	}

	// First, restore inputs.
	for (size_t i = 1; i < block.vtx.size(); i++) {
	const CTransaction &tx = *(block.vtx[i]);
	const CTxUndo &txundo = blockUndo.vtxundo[i - 1];
	if (txundo.vprevout.size() != tx.vin.size()) {
	error("DisconnectBlock(): transaction and undo data inconsistent");
	return DISCONNECT_FAILED;
	}

	for (size_t j = 0; j < tx.vin.size(); j++) {
	const COutPoint &out = tx.vin[j].prevout;
	const Coin &undo = txundo.vprevout[j];
	DisconnectResult res = UndoCoinSpend(undo, view, out);
	if (res == DISCONNECT_FAILED) {
	return DISCONNECT_FAILED;
	}
	fClean = fClean && res != DISCONNECT_UNCLEAN;
	}
	}

	// Second, revert created outputs.
	for (const auto &ptx : block.vtx) {
	const CTransaction &tx = *ptx;
	const TxId &txid = tx.GetId();
	const bool is_coinbase = tx.IsCoinBase();

	// Check that all outputs are available and match the outputs in the
	// block itself exactly.
	for (size_t o = 0; o < tx.vout.size(); o++) {
	if (tx.vout[o].scriptPubKey.IsUnspendable()) {
	continue;
	}

	COutPoint out(txid, o);
	Coin coin;
	bool is_spent = view.SpendCoin(out, &coin);
	if (!is_spent \|\| tx.vout[o] != coin.GetTxOut() \|\|
	uint32_t(pindex->nHeight) != coin.GetHeight() \|\|
	is_coinbase != coin.IsCoinBase()) {
	// transaction output mismatch
	fClean = false;
	}
	}
	}

	// Move best block pointer to previous block.
	view.SetBestBlock(block.hashPrevBlock);

	return fClean ? DISCONNECT_OK : DISCONNECT_UNCLEAN;
	}

	static void FlushBlockFile(bool fFinalize = false) {
	LOCK(cs_LastBlockFile);

	CDiskBlockPos block_pos_old(nLastBlockFile,
	vinfoBlockFile[nLastBlockFile].nSize);
	CDiskBlockPos undo_pos_old(nLastBlockFile,
	vinfoBlockFile[nLastBlockFile].nUndoSize);

	bool status = true;
	status &= BlockFileSeq().Flush(block_pos_old, fFinalize);
	status &= UndoFileSeq().Flush(undo_pos_old, fFinalize);
	if (!status) {
	AbortNode("Flushing block file to disk failed. This is likely the "
	"result of an I/O error.");
	}
	}

	static bool FindUndoPos(CValidationState &state, int nFile, CDiskBlockPos &pos,
	unsigned int nAddSize);

	static bool WriteUndoDataForBlock(const CBlockUndo &blockundo,
	CValidationState &state, CBlockIndex *pindex,
	const CChainParams &chainparams) {
	// Write undo information to disk
	if (pindex->GetUndoPos().IsNull()) {
	CDiskBlockPos _pos;
	if (!FindUndoPos(
	state, pindex->nFile, _pos,
	::GetSerializeSize(blockundo, SER_DISK, CLIENT_VERSION) + 40)) {
	return error("ConnectBlock(): FindUndoPos failed");
	}
	if (!UndoWriteToDisk(blockundo, _pos, pindex->pprev->GetBlockHash(),
	chainparams.DiskMagic())) {
	return AbortNode(state, "Failed to write undo data");
	}

	// update nUndoPos in block index
	pindex->nUndoPos = _pos.nPos;
	pindex->nStatus = pindex->nStatus.withUndo();
	setDirtyBlockIndex.insert(pindex);
	}

	return true;
	}

	static CCheckQueue<CScriptCheck> scriptcheckqueue(128);

	void ThreadScriptCheck() {
	RenameThread("bitcoin-scriptch");
	scriptcheckqueue.Thread();
	}

	int32_t ComputeBlockVersion(const CBlockIndex *pindexPrev,
	const Consensus::Params &params) {
	int32_t nVersion = VERSIONBITS_TOP_BITS;
	return nVersion;
	}

	// Returns the script flags which should be checked for the block after
	// the given block.
	static uint32_t GetNextBlockScriptFlags(const Config &config,
	const CBlockIndex *pindex) {
	AssertLockHeld(cs_main);
	const Consensus::Params &consensusParams =
	config.GetChainParams().GetConsensus();

	uint32_t flags = SCRIPT_VERIFY_NONE;

	// Start enforcing P2SH (BIP16)
	if ((pindex->nHeight + 1) >= consensusParams.BIP16Height) {
	flags \|= SCRIPT_VERIFY_P2SH;
	}

	// Start enforcing the DERSIG (BIP66) rule.
	if ((pindex->nHeight + 1) >= consensusParams.BIP66Height) {
	flags \|= SCRIPT_VERIFY_DERSIG;
	}

	// Start enforcing CHECKLOCKTIMEVERIFY (BIP65) rule.
	if ((pindex->nHeight + 1) >= consensusParams.BIP65Height) {
	flags \|= SCRIPT_VERIFY_CHECKLOCKTIMEVERIFY;
	}

	// Start enforcing CSV (BIP68, BIP112 and BIP113) rule.
	if ((pindex->nHeight + 1) >= consensusParams.CSVHeight) {
	flags \|= SCRIPT_VERIFY_CHECKSEQUENCEVERIFY;
	}

	// If the UAHF is enabled, we start accepting replay protected txns
	if (IsUAHFenabled(config, pindex)) {
	flags \|= SCRIPT_VERIFY_STRICTENC;
	flags \|= SCRIPT_ENABLE_SIGHASH_FORKID;
	}

	// If the DAA HF is enabled, we start rejecting transaction that use a high
	// s in their signature. We also make sure that signature that are supposed
	// to fail (for instance in multisig or other forms of smart contracts) are
	// null.
	if (IsDAAEnabled(config, pindex)) {
	flags \|= SCRIPT_VERIFY_LOW_S;
	flags \|= SCRIPT_VERIFY_NULLFAIL;
	}

	// When the magnetic anomaly fork is enabled, we start accepting
	// transactions using the OP_CHECKDATASIG opcode and it's verify
	// alternative. We also start enforcing push only signatures and
	// clean stack.
	if (IsMagneticAnomalyEnabled(config, pindex)) {
	flags \|= SCRIPT_VERIFY_CHECKDATASIG_SIGOPS;
	flags \|= SCRIPT_VERIFY_SIGPUSHONLY;
	flags \|= SCRIPT_VERIFY_CLEANSTACK;
	}

	// We make sure this node will have replay protection during the next hard
	// fork.
	if (IsReplayProtectionEnabled(config, pindex)) {
	flags \|= SCRIPT_ENABLE_REPLAY_PROTECTION;
	}

	return flags;
	}

	static int64_t nTimeCheck = 0;
	static int64_t nTimeForks = 0;
	static int64_t nTimeVerify = 0;
	static int64_t nTimeConnect = 0;
	static int64_t nTimeIndex = 0;
	static int64_t nTimeCallbacks = 0;
	static int64_t nTimeTotal = 0;
	static int64_t nBlocksTotal = 0;

	/**
	* Apply the effects of this block (with given index) on the UTXO set
	* represented by coins. Validity checks that depend on the UTXO set are also
	* done; ConnectBlock() can fail if those validity checks fail (among other
	* reasons).
	*/
	bool CChainState::ConnectBlock(const Config &config, const CBlock &block,
	CValidationState &state, CBlockIndex *pindex,
	CCoinsViewCache &view, bool fJustCheck) {
	AssertLockHeld(cs_main);
	assert(pindex);
	assert(*pindex->phashBlock == block.GetHash());
	int64_t nTimeStart = GetTimeMicros();

	// Check it again in case a previous version let a bad block in
	// NOTE: We don't currently (re-)invoke ContextualCheckBlock() or
	// ContextualCheckBlockHeader() here. This means that if we add a new
	// consensus rule that is enforced in one of those two functions, then we
	// may have let in a block that violates the rule prior to updating the
	// software, and we would NOT be enforcing the rule here. Fully solving
	// upgrade from one software version to the next after a consensus rule
	// change is potentially tricky and issue-specific (see RewindBlockIndex()
	// for one general approach that was used for BIP 141 deployment).
	// Also, currently the rule against blocks more than 2 hours in the future
	// is enforced in ContextualCheckBlockHeader(); we wouldn't want to
	// re-enforce that rule here (at least until we make it impossible for
	// GetAdjustedTime() to go backward).
	BlockValidationOptions validationOptions =
	BlockValidationOptions(!fJustCheck, !fJustCheck);
	if (!CheckBlock(config, block, state, validationOptions)) {
	return error("%s: Consensus::CheckBlock: %s", __func__,
	FormatStateMessage(state));
	}

	// Verify that the view's current state corresponds to the previous block
	uint256 hashPrevBlock =
	pindex->pprev == nullptr ? uint256() : pindex->pprev->GetBlockHash();
	assert(hashPrevBlock == view.GetBestBlock());

	// Special case for the genesis block, skipping connection of its
	// transactions (its coinbase is unspendable)
	const Consensus::Params &consensusParams =
	config.GetChainParams().GetConsensus();
	if (block.GetHash() == consensusParams.hashGenesisBlock) {
	if (!fJustCheck) {
	view.SetBestBlock(pindex->GetBlockHash());
	}

	return true;
	}

	nBlocksTotal++;

	bool fScriptChecks = true;
	if (!hashAssumeValid.IsNull()) {
	// We've been configured with the hash of a block which has been
	// externally verified to have a valid history. A suitable default value
	// is included with the software and updated from time to time. Because
	// validity relative to a piece of software is an objective fact these
	// defaults can be easily reviewed. This setting doesn't force the
	// selection of any particular chain but makes validating some faster by
	// effectively caching the result of part of the verification.
	BlockMap::const_iterator it = mapBlockIndex.find(hashAssumeValid);
	if (it != mapBlockIndex.end()) {
	if (it->second->GetAncestor(pindex->nHeight) == pindex &&
	pindexBestHeader->GetAncestor(pindex->nHeight) == pindex &&
	pindexBestHeader->nChainWork >= nMinimumChainWork) {
	// This block is a member of the assumed verified chain and an
	// ancestor of the best header. The equivalent time check
	// discourages hash power from extorting the network via DOS
	// attack into accepting an invalid block through telling users
	// they must manually set assumevalid. Requiring a software
	// change or burying the invalid block, regardless of the
	// setting, makes it hard to hide the implication of the demand.
	// This also avoids having release candidates that are hardly
	// doing any signature verification at all in testing without
	// having to artificially set the default assumed verified block
	// further back. The test against nMinimumChainWork prevents the
	// skipping when denied access to any chain at least as good as
	// the expected chain.
	fScriptChecks =
	(GetBlockProofEquivalentTime(
	pindexBestHeader, pindex, *pindexBestHeader,
	consensusParams) <= 60 * 60 * 24 * 7 * 2);
	}
	}
	}

	int64_t nTime1 = GetTimeMicros();
	nTimeCheck += nTime1 - nTimeStart;
	LogPrint(BCLog::BENCH, " - Sanity checks: %.2fms [%.2fs (%.2fms/blk)]\n",
	MILLI * (nTime1 - nTimeStart), nTimeCheck * MICRO,
	nTimeCheck * MILLI / nBlocksTotal);

	// Do not allow blocks that contain transactions which 'overwrite' older
	// transactions, unless those are already completely spent. If such
	// overwrites are allowed, coinbases and transactions depending upon those
	// can be duplicated to remove the ability to spend the first instance --
	// even after being sent to another address. See BIP30 and
	// http://r6.ca/blog/20120206T005236Z.html for more information. This logic
	// is not necessary for memory pool transactions, as AcceptToMemoryPool
	// already refuses previously-known transaction ids entirely. This rule was
	// originally applied to all blocks with a timestamp after March 15, 2012,
	// 0:00 UTC. Now that the whole chain is irreversibly beyond that time it is
	// applied to all blocks except the two in the chain that violate it. This
	// prevents exploiting the issue against nodes during their initial block
	// download.
	bool fEnforceBIP30 = !((pindex->nHeight == 91842 &&
	pindex->GetBlockHash() ==
	uint256S("0x00000000000a4d0a398161ffc163c503763"
	"b1f4360639393e0e4c8e300e0caec")) \|\|
	(pindex->nHeight == 91880 &&
	pindex->GetBlockHash() ==
	uint256S("0x00000000000743f190a18c5577a3c2d2a1f"
	"610ae9601ac046a38084ccb7cd721")));

	// Once BIP34 activated it was not possible to create new duplicate
	// coinbases and thus other than starting with the 2 existing duplicate
	// coinbase pairs, not possible to create overwriting txs. But by the time
	// BIP34 activated, in each of the existing pairs the duplicate coinbase had
	// overwritten the first before the first had been spent. Since those
	// coinbases are sufficiently buried its no longer possible to create
	// further duplicate transactions descending from the known pairs either. If
	// we're on the known chain at height greater than where BIP34 activated, we
	// can save the db accesses needed for the BIP30 check.
	assert(pindex->pprev);
	CBlockIndex *pindexBIP34height =
	pindex->pprev->GetAncestor(consensusParams.BIP34Height);
	// Only continue to enforce if we're below BIP34 activation height or the
	// block hash at that height doesn't correspond.
	fEnforceBIP30 =
	fEnforceBIP30 &&
	(!pindexBIP34height \|\|
	!(pindexBIP34height->GetBlockHash() == consensusParams.BIP34Hash));

	if (fEnforceBIP30) {
	for (const auto &tx : block.vtx) {
	for (size_t o = 0; o < tx->vout.size(); o++) {
	if (view.HaveCoin(COutPoint(tx->GetId(), o))) {
	return state.DoS(
	100,
	error("ConnectBlock(): tried to overwrite transaction"),
	REJECT_INVALID, "bad-txns-BIP30");
	}
	}
	}
	}

	// Start enforcing BIP68 (sequence locks).
	int nLockTimeFlags = 0;
	if (pindex->nHeight >= consensusParams.CSVHeight) {
	nLockTimeFlags \|= LOCKTIME_VERIFY_SEQUENCE;
	}

	const uint32_t flags = GetNextBlockScriptFlags(config, pindex->pprev);

	int64_t nTime2 = GetTimeMicros();
	nTimeForks += nTime2 - nTime1;
	LogPrint(BCLog::BENCH, " - Fork checks: %.2fms [%.2fs (%.2fms/blk)]\n",
	MILLI * (nTime2 - nTime1), nTimeForks * MICRO,
	nTimeForks * MILLI / nBlocksTotal);

	CBlockUndo blockundo;

	CCheckQueueControl<CScriptCheck> control(fScriptChecks ? &scriptcheckqueue
	: nullptr);

	std::vector<int> prevheights;
	Amount nFees = Amount::zero();
	int nInputs = 0;

	// Sigops counting. We need to do it again because of P2SH.
	uint64_t nSigOpsCount = 0;
	const uint64_t currentBlockSize =
	::GetSerializeSize(block, SER_NETWORK, PROTOCOL_VERSION);
	const uint64_t nMaxSigOpsCount = GetMaxBlockSigOpsCount(currentBlockSize);

	blockundo.vtxundo.reserve(block.vtx.size() - 1);

	for (const auto &ptx : block.vtx) {
	const CTransaction &tx = *ptx;

	nInputs += tx.vin.size();

	if (tx.IsCoinBase()) {
	// We've already checked for sigops count before P2SH in CheckBlock.
	nSigOpsCount += GetSigOpCountWithoutP2SH(tx, flags);
	}

	// We do not need to throw when a transaction is duplicated. If they are
	// in the same block, CheckBlock will catch it, and if they are in a
	// different block, it'll register as a double spend or BIP30 violation.
	// In both cases, we get a more meaningful feedback out of it.
	AddCoins(view, tx, pindex->nHeight, true);
	}

	for (const auto &ptx : block.vtx) {
	const CTransaction &tx = *ptx;
	if (tx.IsCoinBase()) {
	continue;
	}

	Amount txfee = Amount::zero();
	if (!Consensus::CheckTxInputs(tx, state, view, pindex->nHeight,
	txfee)) {
	return error("%s: Consensus::CheckTxInputs: %s, %s", __func__,
	tx.GetId().ToString(), FormatStateMessage(state));
	}
	nFees += txfee;
	if (!MoneyRange(nFees)) {
	return state.DoS(
	100,
	error("%s: accumulated fee in the block out of range.",
	__func__),
	REJECT_INVALID, "bad-txns-accumulated-fee-outofrange");
	}

	// Check that transaction is BIP68 final BIP68 lock checks (as
	// opposed to nLockTime checks) must be in ConnectBlock because they
	// require the UTXO set.
	prevheights.resize(tx.vin.size());
	for (size_t j = 0; j < tx.vin.size(); j++) {
	prevheights[j] = view.AccessCoin(tx.vin[j].prevout).GetHeight();
	}

	if (!SequenceLocks(tx, nLockTimeFlags, &prevheights, *pindex)) {
	return state.DoS(
	100,
	error("%s: contains a non-BIP68-final transaction", __func__),
	REJECT_INVALID, "bad-txns-nonfinal");
	}

	// GetTransactionSigOpCount counts 2 types of sigops:
	// * legacy (always)
	// * p2sh (when P2SH enabled in flags and excludes coinbase)
	auto txSigOpsCount = GetTransactionSigOpCount(tx, view, flags);
	if (txSigOpsCount > MAX_TX_SIGOPS_COUNT) {
	return state.DoS(100, false, REJECT_INVALID, "bad-txn-sigops");
	}

	nSigOpsCount += txSigOpsCount;
	if (nSigOpsCount > nMaxSigOpsCount) {
	return state.DoS(100, error("ConnectBlock(): too many sigops"),
	REJECT_INVALID, "bad-blk-sigops");
	}

	// Don't cache results if we're actually connecting blocks (still
	// consult the cache, though).
	bool fCacheResults = fJustCheck;

	std::vector<CScriptCheck> vChecks;
	if (!CheckInputs(tx, state, view, fScriptChecks, flags, fCacheResults,
	fCacheResults, PrecomputedTransactionData(tx),
	&vChecks)) {
	return error("ConnectBlock(): CheckInputs on %s failed with %s",
	tx.GetId().ToString(), FormatStateMessage(state));
	}

	control.Add(vChecks);

	blockundo.vtxundo.push_back(CTxUndo());
	SpendCoins(view, tx, blockundo.vtxundo.back(), pindex->nHeight);
	}

	int64_t nTime3 = GetTimeMicros();
	nTimeConnect += nTime3 - nTime2;
	LogPrint(BCLog::BENCH,
	" - Connect %u transactions: %.2fms (%.3fms/tx, %.3fms/txin) "
	"[%.2fs (%.2fms/blk)]\n",
	(unsigned)block.vtx.size(), MILLI * (nTime3 - nTime2),
	MILLI * (nTime3 - nTime2) / block.vtx.size(),
	nInputs <= 1 ? 0 : MILLI * (nTime3 - nTime2) / (nInputs - 1),
	nTimeConnect * MICRO, nTimeConnect * MILLI / nBlocksTotal);

	Amount blockReward =
	nFees + GetBlockSubsidy(pindex->nHeight, consensusParams);
	if (block.vtx[0]->GetValueOut() > blockReward) {
	return state.DoS(100,
	error("ConnectBlock(): coinbase pays too much "
	"(actual=%d vs limit=%d)",
	block.vtx[0]->GetValueOut(), blockReward),
	REJECT_INVALID, "bad-cb-amount");
	}

	if (!control.Wait()) {
	return state.DoS(100, false, REJECT_INVALID, "blk-bad-inputs", false,
	"parallel script check failed");
	}

	int64_t nTime4 = GetTimeMicros();
	nTimeVerify += nTime4 - nTime2;
	LogPrint(
	BCLog::BENCH,
	" - Verify %u txins: %.2fms (%.3fms/txin) [%.2fs (%.2fms/blk)]\n",
	nInputs - 1, MILLI * (nTime4 - nTime2),
	nInputs <= 1 ? 0 : MILLI * (nTime4 - nTime2) / (nInputs - 1),
	nTimeVerify * MICRO, nTimeVerify * MILLI / nBlocksTotal);

	if (fJustCheck) {
	return true;
	}

	if (!WriteUndoDataForBlock(blockundo, state, pindex,
	config.GetChainParams())) {
	return false;
	}

	if (!pindex->IsValid(BlockValidity::SCRIPTS)) {
	pindex->RaiseValidity(BlockValidity::SCRIPTS);
	setDirtyBlockIndex.insert(pindex);
	}

	assert(pindex->phashBlock);
	// add this block to the view's block chain
	view.SetBestBlock(pindex->GetBlockHash());

	int64_t nTime5 = GetTimeMicros();
	nTimeIndex += nTime5 - nTime4;
	LogPrint(BCLog::BENCH, " - Index writing: %.2fms [%.2fs (%.2fms/blk)]\n",
	MILLI * (nTime5 - nTime4), nTimeIndex * MICRO,
	nTimeIndex * MILLI / nBlocksTotal);

	int64_t nTime6 = GetTimeMicros();
	nTimeCallbacks += nTime6 - nTime5;
	LogPrint(BCLog::BENCH, " - Callbacks: %.2fms [%.2fs (%.2fms/blk)]\n",
	MILLI * (nTime6 - nTime5), nTimeCallbacks * MICRO,
	nTimeCallbacks * MILLI / nBlocksTotal);

	return true;
	}

	/**
	* Update the on-disk chain state.
	* The caches and indexes are flushed depending on the mode we're called with if
	* they're too large, if it's been a while since the last write, or always and
	* in all cases if we're in prune mode and are deleting files.
	*/
	static bool FlushStateToDisk(const CChainParams &chainparams,
	CValidationState &state, FlushStateMode mode,
	int nManualPruneHeight) {
	int64_t nMempoolUsage = g_mempool.DynamicMemoryUsage();
	LOCK(cs_main);
	static int64_t nLastWrite = 0;
	static int64_t nLastFlush = 0;
	std::set<int> setFilesToPrune;
	bool full_flush_completed = false;
	try {
	{
	bool fFlushForPrune = false;
	bool fDoFullFlush = false;
	LOCK(cs_LastBlockFile);
	if (fPruneMode && (fCheckForPruning \|\| nManualPruneHeight > 0) &&
	!fReindex) {
	if (nManualPruneHeight > 0) {
	FindFilesToPruneManual(setFilesToPrune, nManualPruneHeight);
	} else {
	FindFilesToPrune(setFilesToPrune,
	chainparams.PruneAfterHeight());
	fCheckForPruning = false;
	}
	if (!setFilesToPrune.empty()) {
	fFlushForPrune = true;
	if (!fHavePruned) {
	pblocktree->WriteFlag("prunedblockfiles", true);
	fHavePruned = true;
	}
	}
	}
	int64_t nNow = GetTimeMicros();
	// Avoid writing/flushing immediately after startup.
	if (nLastWrite == 0) {
	nLastWrite = nNow;
	}
	if (nLastFlush == 0) {
	nLastFlush = nNow;
	}
	int64_t nMempoolSizeMax =
	gArgs.GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE) * 1000000;
	int64_t cacheSize = pcoinsTip->DynamicMemoryUsage();
	int64_t nTotalSpace =
	nCoinCacheUsage +
	std::max<int64_t>(nMempoolSizeMax - nMempoolUsage, 0);
	// The cache is large and we're within 10% and 10 MiB of the limit,
	// but we have time now (not in the middle of a block processing).
	bool fCacheLarge =
	mode == FlushStateMode::PERIODIC &&
	cacheSize > std::max((9 * nTotalSpace) / 10,
	nTotalSpace -
	MAX_BLOCK_COINSDB_USAGE * 1024 * 1024);
	// The cache is over the limit, we have to write now.
	bool fCacheCritical =
	mode == FlushStateMode::IF_NEEDED && cacheSize > nTotalSpace;
	// It's been a while since we wrote the block index to disk. Do this
	// frequently, so we don't need to redownload after a crash.
	bool fPeriodicWrite =
	mode == FlushStateMode::PERIODIC &&
	nNow > nLastWrite + (int64_t)DATABASE_WRITE_INTERVAL * 1000000;
	// It's been very long since we flushed the cache. Do this
	// infrequently, to optimize cache usage.
	bool fPeriodicFlush =
	mode == FlushStateMode::PERIODIC &&
	nNow > nLastFlush + (int64_t)DATABASE_FLUSH_INTERVAL * 1000000;
	// Combine all conditions that result in a full cache flush.
	fDoFullFlush = (mode == FlushStateMode::ALWAYS) \|\| fCacheLarge \|\|
	fCacheCritical \|\| fPeriodicFlush \|\| fFlushForPrune;
	// Write blocks and block index to disk.
	if (fDoFullFlush \|\| fPeriodicWrite) {
	// Depend on nMinDiskSpace to ensure we can write block index
	if (!CheckDiskSpace(GetBlocksDir())) {
	return AbortNode(state, "Disk space is low!",
	_("Error: Disk space is low!"));
	}

	// First make sure all block and undo data is flushed to disk.
	FlushBlockFile();
	// Then update all block file information (which may refer to
	// block and undo files).
	{
	std::vector<std::pair<int, const CBlockFileInfo *>> vFiles;
	vFiles.reserve(setDirtyFileInfo.size());
	for (int i : setDirtyFileInfo) {
	vFiles.push_back(std::make_pair(i, &vinfoBlockFile[i]));
	}

	setDirtyFileInfo.clear();

	std::vector<const CBlockIndex *> vBlocks;
	vBlocks.reserve(setDirtyBlockIndex.size());
	for (const CBlockIndex *cbi : setDirtyBlockIndex) {
	vBlocks.push_back(cbi);
	}

	setDirtyBlockIndex.clear();

	if (!pblocktree->WriteBatchSync(vFiles, nLastBlockFile,
	vBlocks)) {
	return AbortNode(
	state, "Failed to write to block index database");
	}
	}

	// Finally remove any pruned files
	if (fFlushForPrune) {
	UnlinkPrunedFiles(setFilesToPrune);
	}
	nLastWrite = nNow;
	}
	// Flush best chain related state. This can only be done if the
	// blocks / block index write was also done.
	if (fDoFullFlush && !pcoinsTip->GetBestBlock().IsNull()) {
	// Typical Coin structures on disk are around 48 bytes in size.
	// Pushing a new one to the database can cause it to be written
	// twice (once in the log, and once in the tables). This is
	// already an overestimation, as most will delete an existing
	// entry or overwrite one. Still, use a conservative safety
	// factor of 2.
	if (!CheckDiskSpace(GetDataDir(),
	48 * 2 * 2 * pcoinsTip->GetCacheSize())) {
	return AbortNode(state, "Disk space is low!",
	_("Error: Disk space is low!"));
	}

	// Flush the chainstate (which may refer to block index
	// entries).
	if (!pcoinsTip->Flush()) {
	return AbortNode(state, "Failed to write to coin database");
	}
	nLastFlush = nNow;
	full_flush_completed = true;
	}
	}

	if (full_flush_completed) {
	// Update best block in wallet (so we can detect restored wallets).
	GetMainSignals().ChainStateFlushed(chainActive.GetLocator());
	}
	} catch (const std::runtime_error &e) {
	return AbortNode(state, std::string("System error while flushing: ") +
	e.what());
	}
	return true;
	}

	void FlushStateToDisk() {
	CValidationState state;
	const CChainParams &chainparams = Params();
	FlushStateToDisk(chainparams, state, FlushStateMode::ALWAYS);
	}

	void PruneAndFlush() {
	CValidationState state;
	fCheckForPruning = true;
	const CChainParams &chainparams = Params();
	FlushStateToDisk(chainparams, state, FlushStateMode::NONE);
	}

	/** Check warning conditions and do some notifications on new chain tip set. */
	static void UpdateTip(const Config &config, CBlockIndex *pindexNew) {
	// New best block
	g_mempool.AddTransactionsUpdated(1);

	{
	LOCK(g_best_block_mutex);
	g_best_block = pindexNew->GetBlockHash();
	g_best_block_cv.notify_all();
	}

	LogPrintf(
	"%s: new best=%s height=%d version=0x%08x log2_work=%.8g tx=%lu "
	"date='%s' progress=%f cache=%.1fMiB(%utxo)\n",
	__func__, pindexNew->GetBlockHash().ToString(), pindexNew->nHeight,
	pindexNew->nVersion, log(pindexNew->nChainWork.getdouble()) / log(2.0),
	(unsigned long)pindexNew->nChainTx,
	FormatISO8601DateTime(pindexNew->GetBlockTime()),
	GuessVerificationProgress(config.GetChainParams().TxData(), pindexNew),
	pcoinsTip->DynamicMemoryUsage() * (1.0 / (1 << 20)),
	pcoinsTip->GetCacheSize());
	}

	/**
	* Disconnect chainActive's tip.
	* After calling, the mempool will be in an inconsistent state, with
	* transactions from disconnected blocks being added to disconnectpool. You
	* should make the mempool consistent again by calling updateMempoolForReorg.
	* with cs_main held.
	*
	* If disconnectpool is nullptr, then no disconnected transactions are added to
	* disconnectpool (note that the caller is responsible for mempool consistency
	* in any case).
	*/
	bool CChainState::DisconnectTip(const Config &config, CValidationState &state,
	DisconnectedBlockTransactions *disconnectpool) {
	CBlockIndex *pindexDelete = chainActive.Tip();
	assert(pindexDelete);

	// Read block from disk.
	std::shared_ptr<CBlock> pblock = std::make_shared<CBlock>();
	CBlock &block = *pblock;
	if (!ReadBlockFromDisk(block, pindexDelete, config)) {
	return AbortNode(state, "Failed to read block");
	}

	// Apply the block atomically to the chain state.
	int64_t nStart = GetTimeMicros();
	{
	CCoinsViewCache view(pcoinsTip.get());
	assert(view.GetBestBlock() == pindexDelete->GetBlockHash());
	if (DisconnectBlock(block, pindexDelete, view) != DISCONNECT_OK) {
	return error("DisconnectTip(): DisconnectBlock %s failed",
	pindexDelete->GetBlockHash().ToString());
	}

	bool flushed = view.Flush();
	assert(flushed);
	}

	LogPrint(BCLog::BENCH, "- Disconnect block: %.2fms\n",
	(GetTimeMicros() - nStart) * MILLI);

	// Write the chain state to disk, if necessary.
	if (!FlushStateToDisk(config.GetChainParams(), state,
	FlushStateMode::IF_NEEDED)) {
	return false;
	}

	// If this block is deactivating a fork, we move all mempool transactions
	// in front of disconnectpool for reprocessing in a future
	// updateMempoolForReorg call
	if (pindexDelete->pprev != nullptr &&
	GetNextBlockScriptFlags(config, pindexDelete) !=
	GetNextBlockScriptFlags(config, pindexDelete->pprev)) {
	LogPrint(BCLog::MEMPOOL,
	"Disconnecting mempool due to rewind of upgrade block\n");
	if (disconnectpool) {
	disconnectpool->importMempool(g_mempool);
	}
	g_mempool.clear();
	}

	if (disconnectpool) {
	disconnectpool->addForBlock(block.vtx);
	}

	// If the tip is finalized, then undo it.
	if (pindexFinalized == pindexDelete) {
	pindexFinalized = pindexDelete->pprev;
	}

	chainActive.SetTip(pindexDelete->pprev);

	// Update chainActive and related variables.
	UpdateTip(config, pindexDelete->pprev);
	// Let wallets know transactions went from 1-confirmed to
	// 0-confirmed or conflicted:
	GetMainSignals().BlockDisconnected(pblock);
	return true;
	}

	static int64_t nTimeReadFromDisk = 0;
	static int64_t nTimeConnectTotal = 0;
	static int64_t nTimeFlush = 0;
	static int64_t nTimeChainState = 0;
	static int64_t nTimePostConnect = 0;

	struct PerBlockConnectTrace {
	CBlockIndex *pindex = nullptr;
	std::shared_ptr<const CBlock> pblock;
	std::shared_ptr<std::vector<CTransactionRef>> conflictedTxs;
	PerBlockConnectTrace()
	: conflictedTxs(std::make_shared<std::vector<CTransactionRef>>()) {}
	};

	/**
	* Used to track blocks whose transactions were applied to the UTXO state as a
	* part of a single ActivateBestChainStep call.
	*
	* This class also tracks transactions that are removed from the mempool as
	* conflicts (per block) and can be used to pass all those transactions through
	* SyncTransaction.
	*
	* This class assumes (and asserts) that the conflicted transactions for a given
	* block are added via mempool callbacks prior to the BlockConnected()
	* associated with those transactions. If any transactions are marked
	* conflicted, it is assumed that an associated block will always be added.
	*
	* This class is single-use, once you call GetBlocksConnected() you have to
	* throw it away and make a new one.
	*/
	class ConnectTrace {
	private:
	std::vector<PerBlockConnectTrace> blocksConnected;
	CTxMemPool &pool;

	public:
	explicit ConnectTrace(CTxMemPool &_pool) : blocksConnected(1), pool(_pool) {
	pool.NotifyEntryRemoved.connect(
	boost::bind(&ConnectTrace::NotifyEntryRemoved, this, _1, _2));
	}

	~ConnectTrace() {
	pool.NotifyEntryRemoved.disconnect(
	boost::bind(&ConnectTrace::NotifyEntryRemoved, this, _1, _2));
	}

	void BlockConnected(CBlockIndex *pindex,
	std::shared_ptr<const CBlock> pblock) {
	assert(!blocksConnected.back().pindex);
	assert(pindex);
	assert(pblock);
	blocksConnected.back().pindex = pindex;
	blocksConnected.back().pblock = std::move(pblock);
	blocksConnected.emplace_back();
	}

	std::vector<PerBlockConnectTrace> &GetBlocksConnected() {
	// We always keep one extra block at the end of our list because blocks
	// are added after all the conflicted transactions have been filled in.
	// Thus, the last entry should always be an empty one waiting for the
	// transactions from the next block. We pop the last entry here to make
	// sure the list we return is sane.
	assert(!blocksConnected.back().pindex);
	assert(blocksConnected.back().conflictedTxs->empty());
	blocksConnected.pop_back();
	return blocksConnected;
	}

	void NotifyEntryRemoved(CTransactionRef txRemoved,
	MemPoolRemovalReason reason) {
	assert(!blocksConnected.back().pindex);
	if (reason == MemPoolRemovalReason::CONFLICT) {
	blocksConnected.back().conflictedTxs->emplace_back(
	std::move(txRemoved));
	}
	}
	};

	static bool FinalizeBlockInternal(const Config &config, CValidationState &state,
	const CBlockIndex *pindex) {
	AssertLockHeld(cs_main);
	if (pindex->nStatus.isInvalid()) {
	// We try to finalize an invalid block.
	return state.DoS(100,
	error("%s: Trying to finalize invalid block %s",
	__func__, pindex->GetBlockHash().ToString()),
	REJECT_INVALID, "finalize-invalid-block");
	}

	// Check that the request is consistent with current finalization.
	if (pindexFinalized && !AreOnTheSameFork(pindex, pindexFinalized)) {
	return state.DoS(
	20,
	error("%s: Trying to finalize block %s which conflicts "
	"with already finalized block",
	__func__, pindex->GetBlockHash().ToString()),
	REJECT_AGAINST_FINALIZED, "bad-fork-prior-finalized");
	}

	if (IsBlockFinalized(pindex)) {
	// The block is already finalized.
	return true;
	}

	// We have a new block to finalize.
	pindexFinalized = pindex;
	return true;
	}

	static const CBlockIndex *FindBlockToFinalize(const Config &config,
	CBlockIndex *pindexNew) {
	AssertLockHeld(cs_main);

	const int32_t maxreorgdepth =
	gArgs.GetArg("-maxreorgdepth", DEFAULT_MAX_REORG_DEPTH);

	const int64_t finalizationdelay =
	gArgs.GetArg("-finalizationdelay", DEFAULT_MIN_FINALIZATION_DELAY);

	// Find our candidate.
	// If maxreorgdepth is < 0 pindex will be null and auto finalization
	// disabled
	const CBlockIndex *pindex =
	pindexNew->GetAncestor(pindexNew->nHeight - maxreorgdepth);

	int64_t now = GetTime();

	// If the finalization delay is not expired since the startup time,
	// finalization should be avoided. Header receive time is not saved to disk
	// and so cannot be anterior to startup time.
	if (now < (GetStartupTime() + finalizationdelay)) {
	return nullptr;
	}

	// While our candidate is not eligible (finalization delay not expired), try
	// the previous one.
	while (pindex && (pindex != pindexFinalized)) {
	// Check that the block to finalize is known for a long enough time.
	// This test will ensure that an attacker could not cause a block to
	// finalize by forking the chain with a depth > maxreorgdepth.
	// If the block is loaded from disk, header receive time is 0 and the
	// block will be finalized. This is safe because the delay since the
	// node startup is already expired.
	auto headerReceivedTime = pindex->GetHeaderReceivedTime();

	// If finalization delay is <= 0, finalization always occurs immediately
	if (now >= (headerReceivedTime + finalizationdelay)) {
	return pindex;
	}

	pindex = pindex->pprev;
	}

	return nullptr;
	}

	/**
	* Connect a new block to chainActive. pblock is either nullptr or a pointer to
	* a CBlock corresponding to pindexNew, to bypass loading it again from disk.
	*
	* The block is always added to connectTrace (either after loading from disk or
	* by copying pblock) - if that is not intended, care must be taken to remove
	* the last entry in blocksConnected in case of failure.
	*/
	bool CChainState::ConnectTip(const Config &config, CValidationState &state,
	CBlockIndex *pindexNew,
	const std::shared_ptr<const CBlock> &pblock,
	ConnectTrace &connectTrace,
	DisconnectedBlockTransactions &disconnectpool) {
	AssertLockHeld(cs_main);

	assert(pindexNew->pprev == chainActive.Tip());
	// Read block from disk.
	int64_t nTime1 = GetTimeMicros();
	std::shared_ptr<const CBlock> pthisBlock;
	if (!pblock) {
	std::shared_ptr<CBlock> pblockNew = std::make_shared<CBlock>();
	if (!ReadBlockFromDisk(*pblockNew, pindexNew, config)) {
	return AbortNode(state, "Failed to read block");
	}
	pthisBlock = pblockNew;
	} else {
	pthisBlock = pblock;
	}

	const CBlock &blockConnecting = *pthisBlock;

	// Apply the block atomically to the chain state.
	int64_t nTime2 = GetTimeMicros();
	nTimeReadFromDisk += nTime2 - nTime1;
	int64_t nTime3;
	LogPrint(BCLog::BENCH, " - Load block from disk: %.2fms [%.2fs]\n",
	(nTime2 - nTime1) * MILLI, nTimeReadFromDisk * MICRO);
	{
	CCoinsViewCache view(pcoinsTip.get());
	bool rv = ConnectBlock(config, blockConnecting, state, pindexNew, view);
	GetMainSignals().BlockChecked(blockConnecting, state);
	if (!rv) {
	if (state.IsInvalid()) {
	InvalidBlockFound(pindexNew, state);
	}

	return error("ConnectTip(): ConnectBlock %s failed (%s)",
	pindexNew->GetBlockHash().ToString(),
	FormatStateMessage(state));
	}

	// Update the finalized block.
	const CBlockIndex *pindexToFinalize =
	FindBlockToFinalize(config, pindexNew);
	if (pindexToFinalize &&
	!FinalizeBlockInternal(config, state, pindexToFinalize)) {
	state.SetCorruptionPossible();
	return error("ConnectTip(): FinalizeBlock %s failed (%s)",
	pindexNew->GetBlockHash().ToString(),
	FormatStateMessage(state));
	}

	nTime3 = GetTimeMicros();
	nTimeConnectTotal += nTime3 - nTime2;
	LogPrint(BCLog::BENCH,
	" - Connect total: %.2fms [%.2fs (%.2fms/blk)]\n",
	(nTime3 - nTime2) * MILLI, nTimeConnectTotal * MICRO,
	nTimeConnectTotal * MILLI / nBlocksTotal);
	bool flushed = view.Flush();
	assert(flushed);
	}

	int64_t nTime4 = GetTimeMicros();
	nTimeFlush += nTime4 - nTime3;
	LogPrint(BCLog::BENCH, " - Flush: %.2fms [%.2fs (%.2fms/blk)]\n",
	(nTime4 - nTime3) * MILLI, nTimeFlush * MICRO,
	nTimeFlush * MILLI / nBlocksTotal);

	// Write the chain state to disk, if necessary.
	if (!FlushStateToDisk(config.GetChainParams(), state,
	FlushStateMode::IF_NEEDED)) {
	return false;
	}

	int64_t nTime5 = GetTimeMicros();
	nTimeChainState += nTime5 - nTime4;
	LogPrint(BCLog::BENCH,
	" - Writing chainstate: %.2fms [%.2fs (%.2fms/blk)]\n",
	(nTime5 - nTime4) * MILLI, nTimeChainState * MICRO,
	nTimeChainState * MILLI / nBlocksTotal);

	// Remove conflicting transactions from the mempool.;
	g_mempool.removeForBlock(blockConnecting.vtx, pindexNew->nHeight);
	disconnectpool.removeForBlock(blockConnecting.vtx);

	// If this block is activating a fork, we move all mempool transactions
	// in front of disconnectpool for reprocessing in a future
	// updateMempoolForReorg call
	if (pindexNew->pprev != nullptr &&
	GetNextBlockScriptFlags(config, pindexNew) !=
	GetNextBlockScriptFlags(config, pindexNew->pprev)) {
	LogPrint(BCLog::MEMPOOL,
	"Disconnecting mempool due to acceptance of upgrade block\n");
	disconnectpool.importMempool(g_mempool);
	}

	// Update chainActive & related variables.
	chainActive.SetTip(pindexNew);
	UpdateTip(config, pindexNew);

	int64_t nTime6 = GetTimeMicros();
	nTimePostConnect += nTime6 - nTime5;
	nTimeTotal += nTime6 - nTime1;
	LogPrint(BCLog::BENCH,
	" - Connect postprocess: %.2fms [%.2fs (%.2fms/blk)]\n",
	(nTime6 - nTime5) * MILLI, nTimePostConnect * MICRO,
	nTimePostConnect * MILLI / nBlocksTotal);
	LogPrint(BCLog::BENCH, "- Connect block: %.2fms [%.2fs (%.2fms/blk)]\n",
	(nTime6 - nTime1) * MILLI, nTimeTotal * MICRO,
	nTimeTotal * MILLI / nBlocksTotal);

	connectTrace.BlockConnected(pindexNew, std::move(pthisBlock));
	return true;
	}

	/**
	* Return the tip of the chain with the most work in it, that isn't known to be
	* invalid (it's however far from certain to be valid).
	*/
	CBlockIndex *CChainState::FindMostWorkChain() {
	AssertLockHeld(cs_main);
	do {
	CBlockIndex *pindexNew = nullptr;

	// Find the best candidate header.
	{
	std::set<CBlockIndex *, CBlockIndexWorkComparator>::reverse_iterator
	it = setBlockIndexCandidates.rbegin();
	if (it == setBlockIndexCandidates.rend()) {
	return nullptr;
	}
	pindexNew = *it;
	}

	// If this block will cause a finalized block to be reorged, then we
	// mark it as invalid.
	if (pindexFinalized && !AreOnTheSameFork(pindexNew, pindexFinalized)) {
	LogPrintf("Mark block %s invalid because it forks prior to the "
	"finalization point %d.\n",
	pindexNew->GetBlockHash().ToString(),
	pindexFinalized->nHeight);
	pindexNew->nStatus = pindexNew->nStatus.withFailed();
	InvalidChainFound(pindexNew);
	}

	const CBlockIndex *pindexFork = chainActive.FindFork(pindexNew);

	// Check whether all blocks on the path between the currently active
	// chain and the candidate are valid. Just going until the active chain
	// is an optimization, as we know all blocks in it are valid already.
	CBlockIndex *pindexTest = pindexNew;
	bool hasValidAncestor = true;
	while (hasValidAncestor && pindexTest && pindexTest != pindexFork) {
	assert(pindexTest->nChainTx \|\| pindexTest->nHeight == 0);

	// If this is a parked chain, but it has enough PoW, clear the park
	// state.
	bool fParkedChain = pindexTest->nStatus.isOnParkedChain();
	if (fParkedChain && gArgs.GetBoolArg("-parkdeepreorg", true)) {
	const CBlockIndex *pindexTip = chainActive.Tip();

	// During initialization, pindexTip and/or pindexFork may be
	// null. In this case, we just ignore the fact that the chain is
	// parked.
	if (!pindexTip \|\| !pindexFork) {
	UnparkBlock(pindexTest);
	continue;
	}

	// A parked chain can be unparked if it has twice as much PoW
	// accumulated as the main chain has since the fork block.
	CBlockIndex const *pindexExtraPow = pindexTip;
	arith_uint256 requiredWork = pindexTip->nChainWork;
	switch (pindexTip->nHeight - pindexFork->nHeight) {
	// Limit the penality for depth 1, 2 and 3 to half a block
	// worth of work to ensure we don't fork accidentally.
	case 3:
	case 2:
	pindexExtraPow = pindexExtraPow->pprev;
	// FALLTHROUGH
	case 1: {
	const arith_uint256 deltaWork =
	pindexExtraPow->nChainWork - pindexFork->nChainWork;
	requiredWork += (deltaWork >> 1);
	break;
	}
	default:
	requiredWork +=
	pindexExtraPow->nChainWork - pindexFork->nChainWork;
	break;
	}

	if (pindexNew->nChainWork > requiredWork) {
	// We have enough, clear the parked state.
	LogPrintf("Unpark block %s as its chain has accumulated "
	"enough PoW.\n",
	pindexTest->GetBlockHash().ToString());
	fParkedChain = false;
	UnparkBlock(pindexTest);
	}
	}

	// Pruned nodes may have entries in setBlockIndexCandidates for
	// which block files have been deleted. Remove those as candidates
	// for the most work chain if we come across them; we can't switch
	// to a chain unless we have all the non-active-chain parent blocks.
	bool fInvalidChain = pindexTest->nStatus.isInvalid();
	bool fMissingData = !pindexTest->nStatus.hasData();
	if (!(fInvalidChain \|\| fParkedChain \|\| fMissingData)) {
	// The current block is acceptable, move to the parent, up to
	// the fork point.
	pindexTest = pindexTest->pprev;
	continue;
	}

	// Candidate chain is not usable (either invalid or missing data)
	hasValidAncestor = false;
	setBlockIndexCandidates.erase(pindexTest);

	if (fInvalidChain &&
	(pindexBestInvalid == nullptr \|\|
	pindexNew->nChainWork > pindexBestInvalid->nChainWork)) {
	pindexBestInvalid = pindexNew;
	}

	if (fParkedChain &&
	(pindexBestParked == nullptr \|\|
	pindexNew->nChainWork > pindexBestParked->nChainWork)) {
	pindexBestParked = pindexNew;
	}

	CBlockIndex *pindexFailed = pindexNew;
	// Remove the entire chain from the set.
	while (pindexTest != pindexFailed) {
	if (fInvalidChain \|\| fParkedChain) {
	pindexFailed->nStatus =
	pindexFailed->nStatus.withFailedParent(fInvalidChain)
	.withParkedParent(fParkedChain);
	} else if (fMissingData) {
	// If we're missing data, then add back to
	// mapBlocksUnlinked, so that if the block arrives in the
	// future we can try adding to setBlockIndexCandidates
	// again.
	mapBlocksUnlinked.insert(
	std::make_pair(pindexFailed->pprev, pindexFailed));
	}
	setBlockIndexCandidates.erase(pindexFailed);
	pindexFailed = pindexFailed->pprev;
	}

	if (fInvalidChain \|\| fParkedChain) {
	// We discovered a new chain tip that is either parked or
	// invalid, we may want to warn.
	CheckForkWarningConditionsOnNewFork(pindexNew);
	}
	}

	// We found a candidate that has valid ancestors. This is our guy.
	if (hasValidAncestor) {
	return pindexNew;
	}
	} while (true);
	}

	/**
	* Delete all entries in setBlockIndexCandidates that are worse than the current
	* tip.
	*/
	void CChainState::PruneBlockIndexCandidates() {
	// Note that we can't delete the current block itself, as we may need to
	// return to it later in case a reorganization to a better block fails.
	auto it = setBlockIndexCandidates.begin();
	while (it != setBlockIndexCandidates.end() &&
	setBlockIndexCandidates.value_comp()(*it, chainActive.Tip())) {
	setBlockIndexCandidates.erase(it++);
	}

	// Either the current tip or a successor of it we're working towards is left
	// in setBlockIndexCandidates.
	assert(!setBlockIndexCandidates.empty());
	}

	/**
	* Try to make some progress towards making pindexMostWork the active block.
	* pblock is either nullptr or a pointer to a CBlock corresponding to
	* pindexMostWork.
	*/
	bool CChainState::ActivateBestChainStep(
	const Config &config, CValidationState &state, CBlockIndex *pindexMostWork,
	const std::shared_ptr<const CBlock> &pblock, bool &fInvalidFound,
	ConnectTrace &connectTrace) {
	AssertLockHeld(cs_main);

	const CBlockIndex *pindexOldTip = chainActive.Tip();
	const CBlockIndex *pindexFork = chainActive.FindFork(pindexMostWork);

	// Disconnect active blocks which are no longer in the best chain.
	bool fBlocksDisconnected = false;
	DisconnectedBlockTransactions disconnectpool;
	while (chainActive.Tip() && chainActive.Tip() != pindexFork) {
	if (!DisconnectTip(config, state, &disconnectpool)) {
	// This is likely a fatal error, but keep the mempool consistent,
	// just in case. Only remove from the mempool in this case.
	disconnectpool.updateMempoolForReorg(config, false);
	return false;
	}

	fBlocksDisconnected = true;
	}

	// Build list of new blocks to connect.
	std::vector<CBlockIndex *> vpindexToConnect;
	bool fContinue = true;
	int nHeight = pindexFork ? pindexFork->nHeight : -1;
	while (fContinue && nHeight != pindexMostWork->nHeight) {
	// Don't iterate the entire list of potential improvements toward the
	// best tip, as we likely only need a few blocks along the way.
	int nTargetHeight = std::min(nHeight + 32, pindexMostWork->nHeight);
	vpindexToConnect.clear();
	vpindexToConnect.reserve(nTargetHeight - nHeight);
	CBlockIndex *pindexIter = pindexMostWork->GetAncestor(nTargetHeight);
	while (pindexIter && pindexIter->nHeight != nHeight) {
	vpindexToConnect.push_back(pindexIter);
	pindexIter = pindexIter->pprev;
	}

	nHeight = nTargetHeight;

	// Connect new blocks.
	for (CBlockIndex *pindexConnect : reverse_iterate(vpindexToConnect)) {
	if (!ConnectTip(config, state, pindexConnect,
	pindexConnect == pindexMostWork
	? pblock
	: std::shared_ptr<const CBlock>(),
	connectTrace, disconnectpool)) {
	if (state.IsInvalid()) {
	// The block violates a consensus rule.
	if (!state.CorruptionPossible()) {
	InvalidChainFound(vpindexToConnect.back());
	}

	state = CValidationState();
	fInvalidFound = true;
	fContinue = false;
	break;
	}

	// A system error occurred (disk space, database error, ...).
	// Make the mempool consistent with the current tip, just in
	// case any observers try to use it before shutdown.
	disconnectpool.updateMempoolForReorg(config, false);
	return false;
	} else {
	PruneBlockIndexCandidates();
	if (!pindexOldTip \|\|
	chainActive.Tip()->nChainWork > pindexOldTip->nChainWork) {
	// We're in a better position than we were. Return
	// temporarily to release the lock.
	fContinue = false;
	break;
	}
	}
	}
	}

	if (fBlocksDisconnected \|\| !disconnectpool.isEmpty()) {
	// If any blocks were disconnected, we need to update the mempool even
	// if disconnectpool is empty. The disconnectpool may also be non-empty
	// if the mempool was imported due to new validation rules being in
	// effect.
	LogPrint(BCLog::MEMPOOL, "Updating mempool due to reorganization or "
	"rules upgrade/downgrade\n");
	disconnectpool.updateMempoolForReorg(config, true);
	}

	g_mempool.check(pcoinsTip.get());

	// Callbacks/notifications for a new best chain.
	if (fInvalidFound) {
	CheckForkWarningConditionsOnNewFork(pindexMostWork);
	} else {
	CheckForkWarningConditions();
	}

	return true;
	}

	static void NotifyHeaderTip() {
	bool fNotify = false;
	bool fInitialBlockDownload = false;
	static CBlockIndex *pindexHeaderOld = nullptr;
	CBlockIndex *pindexHeader = nullptr;
	{
	LOCK(cs_main);
	pindexHeader = pindexBestHeader;

	if (pindexHeader != pindexHeaderOld) {
	fNotify = true;
	fInitialBlockDownload = IsInitialBlockDownload();
	pindexHeaderOld = pindexHeader;
	}
	}

	// Send block tip changed notifications without cs_main
	if (fNotify) {
	uiInterface.NotifyHeaderTip(fInitialBlockDownload, pindexHeader);
	}
	}

	bool CChainState::ActivateBestChain(const Config &config,
	CValidationState &state,
	std::shared_ptr<const CBlock> pblock) {
	// Note that while we're often called here from ProcessNewBlock, this is
	// far from a guarantee. Things in the P2P/RPC will often end up calling
	// us in the middle of ProcessNewBlock - do not assume pblock is set
	// sanely for performance or correctness!
	AssertLockNotHeld(cs_main);

	// ABC maintains a fair degree of expensive-to-calculate internal state
	// because this function periodically releases cs_main so that it does not
	// lock up other threads for too long during large connects - and to allow
	// for e.g. the callback queue to drain we use m_cs_chainstate to enforce
	// mutual exclusion so that only one caller may execute this function at a
	// time
	LOCK(m_cs_chainstate);

	CBlockIndex *pindexMostWork = nullptr;
	CBlockIndex *pindexNewTip = nullptr;
	int nStopAtHeight = gArgs.GetArg("-stopatheight", DEFAULT_STOPATHEIGHT);
	do {
	boost::this_thread::interruption_point();

	if (GetMainSignals().CallbacksPending() > 10) {
	// Block until the validation queue drains. This should largely
	// never happen in normal operation, however may happen during
	// reindex, causing memory blowup if we run too far ahead.
	SyncWithValidationInterfaceQueue();
	}

	{
	LOCK(cs_main);
	CBlockIndex *starting_tip = chainActive.Tip();
	bool blocks_connected = false;
	do {
	// We absolutely may not unlock cs_main until we've made forward
	// progress (with the exception of shutdown due to hardware
	// issues, low disk space, etc).

	// Destructed before cs_main is unlocked
	ConnectTrace connectTrace(g_mempool);

	if (pindexMostWork == nullptr) {
	pindexMostWork = FindMostWorkChain();
	}

	// Whether we have anything to do at all.
	if (pindexMostWork == nullptr \|\|
	pindexMostWork == chainActive.Tip()) {
	break;
	}

	bool fInvalidFound = false;
	std::shared_ptr<const CBlock> nullBlockPtr;
	if (!ActivateBestChainStep(
	config, state, pindexMostWork,
	pblock && pblock->GetHash() ==
	pindexMostWork->GetBlockHash()
	? pblock
	: nullBlockPtr,
	fInvalidFound, connectTrace)) {
	return false;
	}
	blocks_connected = true;

	if (fInvalidFound) {
	// Wipe cache, we may need another branch now.
	pindexMostWork = nullptr;
	}

	pindexNewTip = chainActive.Tip();
	for (const PerBlockConnectTrace &trace :
	connectTrace.GetBlocksConnected()) {
	assert(trace.pblock && trace.pindex);
	GetMainSignals().BlockConnected(trace.pblock, trace.pindex,
	trace.conflictedTxs);
	}
	} while (!chainActive.Tip() \|\|
	(starting_tip && CBlockIndexWorkComparator()(
	chainActive.Tip(), starting_tip)));

	if (!blocks_connected) {
	return true;
	}

	const CBlockIndex *pindexFork = chainActive.FindFork(starting_tip);
	bool fInitialDownload = IsInitialBlockDownload();

	// Notify external listeners about the new tip.
	// Enqueue while holding cs_main to ensure that UpdatedBlockTip is
	// called in the order in which blocks are connected
	if (pindexFork != pindexNewTip) {
	// Notify ValidationInterface subscribers
	GetMainSignals().UpdatedBlockTip(pindexNewTip, pindexFork,
	fInitialDownload);

	// Always notify the UI if a new block tip was connected
	uiInterface.NotifyBlockTip(fInitialDownload, pindexNewTip);
	}
	}
	// When we reach this point, we switched to a new tip (stored in
	// pindexNewTip).

	if (nStopAtHeight && pindexNewTip &&
	pindexNewTip->nHeight >= nStopAtHeight) {
	StartShutdown();
	}

	// We check shutdown only after giving ActivateBestChainStep a chance to
	// run once so that we never shutdown before connecting the genesis
	// block during LoadChainTip(). Previously this caused an assert()
	// failure during shutdown in such cases as the UTXO DB flushing checks
	// that the best block hash is non-null.
	if (ShutdownRequested()) {
	break;
	}
	} while (pindexNewTip != pindexMostWork);

	const CChainParams &params = config.GetChainParams();
	CheckBlockIndex(params.GetConsensus());

	// Write changes periodically to disk, after relay.
	if (!FlushStateToDisk(params, state, FlushStateMode::PERIODIC)) {
	return false;
	}

	return true;
	}

	bool ActivateBestChain(const Config &config, CValidationState &state,
	std::shared_ptr<const CBlock> pblock) {
	return g_chainstate.ActivateBestChain(config, state, std::move(pblock));
	}

	bool CChainState::PreciousBlock(const Config &config, CValidationState &state,
	CBlockIndex *pindex) {
	{
	LOCK(cs_main);
	if (pindex->nChainWork < chainActive.Tip()->nChainWork) {
	// Nothing to do, this block is not at the tip.
	return true;
	}

	if (chainActive.Tip()->nChainWork > nLastPreciousChainwork) {
	// The chain has been extended since the last call, reset the
	// counter.
	nBlockReverseSequenceId = -1;
	}

	nLastPreciousChainwork = chainActive.Tip()->nChainWork;
	setBlockIndexCandidates.erase(pindex);
	pindex->nSequenceId = nBlockReverseSequenceId;
	if (nBlockReverseSequenceId > std::numeric_limits<int32_t>::min()) {
	// We can't keep reducing the counter if somebody really wants to
	// call preciousblock 2**31-1 times on the same set of tips...
	nBlockReverseSequenceId--;
	}

	// In case this was parked, unpark it.
	UnparkBlock(pindex);

	// Make sure it is added to the candidate list if appropriate.
	if (pindex->IsValid(BlockValidity::TRANSACTIONS) && pindex->nChainTx) {
	setBlockIndexCandidates.insert(pindex);
	PruneBlockIndexCandidates();
	}
	}

	return ActivateBestChain(config, state);
	}

	bool PreciousBlock(const Config &config, CValidationState &state,
	CBlockIndex *pindex) {
	return g_chainstate.PreciousBlock(config, state, pindex);
	}

	bool CChainState::UnwindBlock(const Config &config, CValidationState &state,
	CBlockIndex *pindex, bool invalidate) {
	AssertLockHeld(cs_main);

	// We first disconnect backwards and then mark the blocks as invalid.
	// This prevents a case where pruned nodes may fail to invalidateblock
	// and be left unable to start as they have no tip candidates (as there
	// are no blocks that meet the "have data and are not invalid per
	// nStatus" criteria for inclusion in setBlockIndexCandidates).

	bool pindex_was_in_chain = false;
	CBlockIndex *invalid_walk_tip = chainActive.Tip();

	DisconnectedBlockTransactions disconnectpool;
	while (chainActive.Contains(pindex)) {
	pindex_was_in_chain = true;
	// ActivateBestChain considers blocks already in chainActive
	// unconditionally valid already, so force disconnect away from it.
	if (!DisconnectTip(config, state, &disconnectpool)) {
	// It's probably hopeless to try to make the mempool consistent
	// here if DisconnectTip failed, but we can try.
	disconnectpool.updateMempoolForReorg(config, false);
	return false;
	}
	}

	// Now mark the blocks we just disconnected as descendants invalid
	// (note this may not be all descendants).
	while (pindex_was_in_chain && invalid_walk_tip != pindex) {
	invalid_walk_tip->nStatus =
	invalidate ? invalid_walk_tip->nStatus.withFailedParent()
	: invalid_walk_tip->nStatus.withParkedParent();
	setDirtyBlockIndex.insert(invalid_walk_tip);
	invalid_walk_tip = invalid_walk_tip->pprev;
	}

	// Mark the block as either invalid or parked.
	pindex->nStatus = invalidate ? pindex->nStatus.withFailed()
	: pindex->nStatus.withParked();
	setDirtyBlockIndex.insert(pindex);
	if (invalidate) {
	m_failed_blocks.insert(pindex);
	}

	// DisconnectTip will add transactions to disconnectpool; try to add these
	// back to the mempool.
	disconnectpool.updateMempoolForReorg(config, true);

	// The resulting new best tip may not be in setBlockIndexCandidates anymore,
	// so add it again.
	for (const std::pair<const uint256, CBlockIndex *> &it : mapBlockIndex) {
	CBlockIndex *i = it.second;
	if (i->IsValid(BlockValidity::TRANSACTIONS) && i->nChainTx &&
	!setBlockIndexCandidates.value_comp()(i, chainActive.Tip())) {
	setBlockIndexCandidates.insert(i);
	}
	}

	if (invalidate) {
	InvalidChainFound(pindex);
	}
	- uiInterface.NotifyBlockTip(IsInitialBlockDownload(), pindex->pprev);
	+
	+ // Only notify about a new block tip if the active chain was modified.
	+ if (pindex_was_in_chain) {
	+ uiInterface.NotifyBlockTip(IsInitialBlockDownload(), pindex->pprev);
	+ }
	return true;
	}

	bool FinalizeBlockAndInvalidate(const Config &config, CValidationState &state,
	CBlockIndex *pindex) {
	AssertLockHeld(cs_main);
	if (!FinalizeBlockInternal(config, state, pindex)) {
	// state is set by FinalizeBlockInternal.
	return false;
	}

	// We have a valid candidate, make sure it is not parked.
	if (pindex->nStatus.isOnParkedChain()) {
	UnparkBlock(pindex);
	}

	// If the finalized block is not on the active chain, we need to rewind.
	if (!AreOnTheSameFork(pindex, chainActive.Tip())) {
	const CBlockIndex *pindexFork = chainActive.FindFork(pindex);
	CBlockIndex *pindexToInvalidate =
	chainActive.Tip()->GetAncestor(pindexFork->nHeight + 1);
	return InvalidateBlock(config, state, pindexToInvalidate);
	}

	return true;
	}

	bool InvalidateBlock(const Config &config, CValidationState &state,
	CBlockIndex *pindex) {
	return g_chainstate.UnwindBlock(config, state, pindex, true);
	}

	bool ParkBlock(const Config &config, CValidationState &state,
	CBlockIndex *pindex) {
	return g_chainstate.UnwindBlock(config, state, pindex, false);
	}

	template <typename F>
	void CChainState::UpdateFlagsForBlock(CBlockIndex *pindexBase,
	CBlockIndex *pindex, F f) {
	BlockStatus newStatus = f(pindex->nStatus);
	if (pindex->nStatus != newStatus &&
	pindex->GetAncestor(pindexBase->nHeight) == pindexBase) {
	pindex->nStatus = newStatus;
	setDirtyBlockIndex.insert(pindex);
	if (newStatus.isValid()) {
	m_failed_blocks.erase(pindex);
	}

	if (pindex->IsValid(BlockValidity::TRANSACTIONS) && pindex->nChainTx &&
	setBlockIndexCandidates.value_comp()(chainActive.Tip(), pindex)) {
	setBlockIndexCandidates.insert(pindex);
	}
	}
	}

	template <typename F, typename C>
	void CChainState::UpdateFlags(CBlockIndex *pindex, F f, C fchild) {
	AssertLockHeld(cs_main);

	// Update the current block.
	UpdateFlagsForBlock(pindex, pindex, f);

	// Update the flags from this block and all its descendants.
	BlockMap::iterator it = mapBlockIndex.begin();
	while (it != mapBlockIndex.end()) {
	UpdateFlagsForBlock(pindex, it->second, fchild);
	it++;
	}

	// Update the flags from all ancestors too.
	while (pindex != nullptr) {
	BlockStatus newStatus = f(pindex->nStatus);
	if (pindex->nStatus != newStatus) {
	pindex->nStatus = newStatus;
	setDirtyBlockIndex.insert(pindex);
	if (newStatus.isValid()) {
	m_failed_blocks.erase(pindex);
	}
	}
	pindex = pindex->pprev;
	}
	}

	template <typename F> void CChainState::UpdateFlags(CBlockIndex *pindex, F f) {
	// Handy shorthand.
	UpdateFlags(pindex, f, f);
	}

	bool CChainState::ResetBlockFailureFlags(CBlockIndex *pindex) {
	AssertLockHeld(cs_main);

	if (pindexBestInvalid &&
	(pindexBestInvalid->GetAncestor(pindex->nHeight) == pindex \|\|
	pindex->GetAncestor(pindexBestInvalid->nHeight) ==
	pindexBestInvalid)) {
	// Reset the invalid block marker if it is about to be cleared.
	pindexBestInvalid = nullptr;
	}

	// In case we are reconsidering something before the finalization point,
	// move the finalization point to the last common ancestor.
	if (pindexFinalized) {
	pindexFinalized = LastCommonAncestor(pindex, pindexFinalized);
	}

	UpdateFlags(pindex, [](const BlockStatus status) {
	return status.withClearedFailureFlags();
	});

	return true;
	}

	bool ResetBlockFailureFlags(CBlockIndex *pindex) {
	return g_chainstate.ResetBlockFailureFlags(pindex);
	}

	bool CChainState::UnparkBlockImpl(CBlockIndex *pindex, bool fClearChildren) {
	AssertLockHeld(cs_main);

	if (pindexBestParked &&
	(pindexBestParked->GetAncestor(pindex->nHeight) == pindex \|\|
	pindex->GetAncestor(pindexBestParked->nHeight) == pindexBestParked)) {
	// Reset the parked block marker if it is about to be cleared.
	pindexBestParked = nullptr;
	}

	UpdateFlags(pindex,
	[](const BlockStatus status) {
	return status.withClearedParkedFlags();
	},
	[fClearChildren](const BlockStatus status) {
	return fClearChildren ? status.withClearedParkedFlags()
	: status.withParkedParent(false);
	});

	return true;
	}

	bool UnparkBlockAndChildren(CBlockIndex *pindex) {
	return g_chainstate.UnparkBlockImpl(pindex, true);
	}

	bool UnparkBlock(CBlockIndex *pindex) {
	return g_chainstate.UnparkBlockImpl(pindex, false);
	}

	const CBlockIndex *GetFinalizedBlock() {
	AssertLockHeld(cs_main);
	return pindexFinalized;
	}

	bool IsBlockFinalized(const CBlockIndex *pindex) {
	AssertLockHeld(cs_main);
	return pindexFinalized &&
	pindexFinalized->GetAncestor(pindex->nHeight) == pindex;
	}

	CBlockIndex *CChainState::AddToBlockIndex(const CBlockHeader &block) {
	AssertLockHeld(cs_main);

	// Check for duplicate
	uint256 hash = block.GetHash();
	BlockMap::iterator it = mapBlockIndex.find(hash);
	if (it != mapBlockIndex.end()) {
	return it->second;
	}

	// Construct new block index object
	CBlockIndex *pindexNew = new CBlockIndex(block);
	// We assign the sequence id to blocks only when the full data is available,
	// to avoid miners withholding blocks but broadcasting headers, to get a
	// competitive advantage.
	pindexNew->nSequenceId = 0;
	BlockMap::iterator mi =
	mapBlockIndex.insert(std::make_pair(hash, pindexNew)).first;
	pindexNew->phashBlock = &((*mi).first);
	BlockMap::iterator miPrev = mapBlockIndex.find(block.hashPrevBlock);
	if (miPrev != mapBlockIndex.end()) {
	pindexNew->pprev = (*miPrev).second;
	pindexNew->nHeight = pindexNew->pprev->nHeight + 1;
	pindexNew->BuildSkip();
	}
	pindexNew->nTimeReceived = GetTime();
	pindexNew->nTimeMax =
	(pindexNew->pprev
	? std::max(pindexNew->pprev->nTimeMax, pindexNew->nTime)
	: pindexNew->nTime);
	pindexNew->nChainWork =
	(pindexNew->pprev ? pindexNew->pprev->nChainWork : 0) +
	GetBlockProof(*pindexNew);
	pindexNew->RaiseValidity(BlockValidity::TREE);
	if (pindexBestHeader == nullptr \|\|
	pindexBestHeader->nChainWork < pindexNew->nChainWork) {
	pindexBestHeader = pindexNew;
	}

	setDirtyBlockIndex.insert(pindexNew);
	return pindexNew;
	}

	/**
	* Mark a block as having its data received and checked (up to
	* BLOCK_VALID_TRANSACTIONS).
	*/
	bool CChainState::ReceivedBlockTransactions(const CBlock &block,
	CValidationState &state,
	CBlockIndex *pindexNew,
	const CDiskBlockPos &pos) {
	pindexNew->nTx = block.vtx.size();
	pindexNew->nChainTx = 0;
	pindexNew->nFile = pos.nFile;
	pindexNew->nDataPos = pos.nPos;
	pindexNew->nUndoPos = 0;
	pindexNew->nStatus = pindexNew->nStatus.withData();
	pindexNew->RaiseValidity(BlockValidity::TRANSACTIONS);
	setDirtyBlockIndex.insert(pindexNew);

	if (pindexNew->pprev == nullptr \|\| pindexNew->pprev->nChainTx) {
	// If pindexNew is the genesis block or all parents are
	// BLOCK_VALID_TRANSACTIONS.
	std::deque<CBlockIndex *> queue;
	queue.push_back(pindexNew);

	// Recursively process any descendant blocks that now may be eligible to
	// be connected.
	while (!queue.empty()) {
	CBlockIndex *pindex = queue.front();
	queue.pop_front();
	pindex->nChainTx =
	(pindex->pprev ? pindex->pprev->nChainTx : 0) + pindex->nTx;
	if (pindex->nSequenceId == 0) {
	// We assign a sequence is when transaction are received to
	// prevent a miner from being able to broadcast a block but not
	// its content. However, a sequence id may have been set
	// manually, for instance via PreciousBlock, in which case, we
	// don't need to assign one.
	pindex->nSequenceId = nBlockSequenceId++;
	}

	if (chainActive.Tip() == nullptr \|\|
	!setBlockIndexCandidates.value_comp()(pindex,
	chainActive.Tip())) {
	setBlockIndexCandidates.insert(pindex);
	}

	std::pair<std::multimap<CBlockIndex , CBlockIndex >::iterator,
	std::multimap<CBlockIndex , CBlockIndex >::iterator>
	range = mapBlocksUnlinked.equal_range(pindex);
	while (range.first != range.second) {
	std::multimap<CBlockIndex , CBlockIndex >::iterator it =
	range.first;
	queue.push_back(it->second);
	range.first++;
	mapBlocksUnlinked.erase(it);
	}
	}
	} else if (pindexNew->pprev &&
	pindexNew->pprev->IsValid(BlockValidity::TREE)) {
	mapBlocksUnlinked.insert(std::make_pair(pindexNew->pprev, pindexNew));
	}

	return true;
	}

	static bool FindBlockPos(CDiskBlockPos &pos, unsigned int nAddSize,
	unsigned int nHeight, uint64_t nTime,
	bool fKnown = false) {
	LOCK(cs_LastBlockFile);

	unsigned int nFile = fKnown ? pos.nFile : nLastBlockFile;
	if (vinfoBlockFile.size() <= nFile) {
	vinfoBlockFile.resize(nFile + 1);
	}

	if (!fKnown) {
	while (vinfoBlockFile[nFile].nSize + nAddSize >= MAX_BLOCKFILE_SIZE) {
	nFile++;
	if (vinfoBlockFile.size() <= nFile) {
	vinfoBlockFile.resize(nFile + 1);
	}
	}
	pos.nFile = nFile;
	pos.nPos = vinfoBlockFile[nFile].nSize;
	}

	if ((int)nFile != nLastBlockFile) {
	if (!fKnown) {
	LogPrintf("Leaving block file %i: %s\n", nLastBlockFile,
	vinfoBlockFile[nLastBlockFile].ToString());
	}
	FlushBlockFile(!fKnown);
	nLastBlockFile = nFile;
	}

	vinfoBlockFile[nFile].AddBlock(nHeight, nTime);
	if (fKnown) {
	vinfoBlockFile[nFile].nSize =
	std::max(pos.nPos + nAddSize, vinfoBlockFile[nFile].nSize);
	} else {
	vinfoBlockFile[nFile].nSize += nAddSize;
	}

	if (!fKnown) {
	bool out_of_space;
	size_t bytes_allocated =
	BlockFileSeq().Allocate(pos, nAddSize, out_of_space);
	if (out_of_space) {
	return AbortNode("Disk space is low!",
	_("Error: Disk space is low!"));
	}
	if (bytes_allocated != 0 && fPruneMode) {
	fCheckForPruning = true;
	}
	}

	setDirtyFileInfo.insert(nFile);
	return true;
	}

	static bool FindUndoPos(CValidationState &state, int nFile, CDiskBlockPos &pos,
	unsigned int nAddSize) {
	pos.nFile = nFile;

	LOCK(cs_LastBlockFile);

	pos.nPos = vinfoBlockFile[nFile].nUndoSize;
	vinfoBlockFile[nFile].nUndoSize += nAddSize;
	setDirtyFileInfo.insert(nFile);

	bool out_of_space;
	size_t bytes_allocated =
	UndoFileSeq().Allocate(pos, nAddSize, out_of_space);
	if (out_of_space) {
	return AbortNode(state, "Disk space is low!",
	_("Error: Disk space is low!"));
	}
	if (bytes_allocated != 0 && fPruneMode) {
	fCheckForPruning = true;
	}

	return true;
	}

	/**
	* Return true if the provided block header is valid.
	* Only verify PoW if blockValidationOptions is configured to do so.
	* This allows validation of headers on which the PoW hasn't been done.
	* For example: to validate template handed to mining software.
	* Do not call this for any check that depends on the context.
	* For context-dependent calls, see ContextualCheckBlockHeader.
	*/
	static bool CheckBlockHeader(
	const Config &config, const CBlockHeader &block, CValidationState &state,
	BlockValidationOptions validationOptions = BlockValidationOptions()) {
	// Check proof of work matches claimed amount
	if (validationOptions.shouldValidatePoW() &&
	!CheckProofOfWork(block.GetHash(), block.nBits, config)) {
	return state.DoS(50, false, REJECT_INVALID, "high-hash", false,
	"proof of work failed");
	}

	return true;
	}

	bool CheckBlock(const Config &config, const CBlock &block,
	CValidationState &state,
	BlockValidationOptions validationOptions) {
	// These are checks that are independent of context.
	if (block.fChecked) {
	return true;
	}

	// Check that the header is valid (particularly PoW). This is mostly
	// redundant with the call in AcceptBlockHeader.
	if (!CheckBlockHeader(config, block, state, validationOptions)) {
	return false;
	}

	// Check the merkle root.
	if (validationOptions.shouldValidateMerkleRoot()) {
	bool mutated;
	uint256 hashMerkleRoot2 = BlockMerkleRoot(block, &mutated);
	if (block.hashMerkleRoot != hashMerkleRoot2) {
	return state.DoS(100, false, REJECT_INVALID, "bad-txnmrklroot",
	true, "hashMerkleRoot mismatch");
	}

	// Check for merkle tree malleability (CVE-2012-2459): repeating
	// sequences of transactions in a block without affecting the merkle
	// root of a block, while still invalidating it.
	if (mutated) {
	return state.DoS(100, false, REJECT_INVALID, "bad-txns-duplicate",
	true, "duplicate transaction");
	}
	}

	// All potential-corruption validation must be done before we do any
	// transaction validation, as otherwise we may mark the header as invalid
	// because we receive the wrong transactions for it.

	// First transaction must be coinbase.
	if (block.vtx.empty()) {
	return state.DoS(100, false, REJECT_INVALID, "bad-cb-missing", false,
	"first tx is not coinbase");
	}

	// Size limits.
	auto nMaxBlockSize = config.GetMaxBlockSize();

	// Bail early if there is no way this block is of reasonable size.
	if ((block.vtx.size() * MIN_TRANSACTION_SIZE) > nMaxBlockSize) {
	return state.DoS(100, false, REJECT_INVALID, "bad-blk-length", false,
	"size limits failed");
	}

	auto currentBlockSize =
	::GetSerializeSize(block, SER_NETWORK, PROTOCOL_VERSION);
	if (currentBlockSize > nMaxBlockSize) {
	return state.DoS(100, false, REJECT_INVALID, "bad-blk-length", false,
	"size limits failed");
	}

	// And a valid coinbase.
	if (!CheckCoinbase(*block.vtx[0], state)) {
	return state.Invalid(false, state.GetRejectCode(),
	state.GetRejectReason(),
	strprintf("Coinbase check failed (txid %s) %s",
	block.vtx[0]->GetId().ToString(),
	state.GetDebugMessage()));
	}

	// Keep track of the sigops count.
	uint64_t nSigOps = 0;
	auto nMaxSigOpsCount = GetMaxBlockSigOpsCount(currentBlockSize);

	// Check transactions
	auto txCount = block.vtx.size();
	auto *tx = block.vtx[0].get();

	size_t i = 0;
	while (true) {
	// Count the sigops for the current transaction. If the total sigops
	// count is too high, the the block is invalid.
	nSigOps += GetSigOpCountWithoutP2SH(*tx, STANDARD_SCRIPT_VERIFY_FLAGS);
	if (nSigOps > nMaxSigOpsCount) {
	return state.DoS(100, false, REJECT_INVALID, "bad-blk-sigops",
	false, "out-of-bounds SigOpCount");
	}

	// Go to the next transaction.
	i++;

	// We reached the end of the block, success.
	if (i >= txCount) {
	break;
	}

	// Check that the transaction is valid. Because this check differs for
	// the coinbase, the loop is arranged such as this only runs after at
	// least one increment.
	tx = block.vtx[i].get();
	if (!CheckRegularTransaction(*tx, state)) {
	return state.Invalid(
	false, state.GetRejectCode(), state.GetRejectReason(),
	strprintf("Transaction check failed (txid %s) %s",
	tx->GetId().ToString(), state.GetDebugMessage()));
	}
	}

	if (validationOptions.shouldValidatePoW() &&
	validationOptions.shouldValidateMerkleRoot()) {
	block.fChecked = true;
	}

	return true;
	}

	/**
	* Context-dependent validity checks.
	* By "context", we mean only the previous block headers, but not the UTXO
	* set; UTXO-related validity checks are done in ConnectBlock().
	* NOTE: This function is not currently invoked by ConnectBlock(), so we
	* should consider upgrade issues if we change which consensus rules are
	* enforced in this function (eg by adding a new consensus rule). See comment
	* in ConnectBlock().
	* Note that -reindex-chainstate skips the validation that happens here!
	*/
	static bool ContextualCheckBlockHeader(const Config &config,
	const CBlockHeader &block,
	CValidationState &state,
	const CBlockIndex *pindexPrev,
	int64_t nAdjustedTime) {
	assert(pindexPrev != nullptr);
	const int nHeight = pindexPrev->nHeight + 1;

	// Check proof of work
	const Consensus::Params &consensusParams =
	config.GetChainParams().GetConsensus();
	if (block.nBits != GetNextWorkRequired(pindexPrev, &block, config)) {
	LogPrintf("bad bits after height: %d\n", pindexPrev->nHeight);
	return state.DoS(100, false, REJECT_INVALID, "bad-diffbits", false,
	"incorrect proof of work");
	}

	// Check against checkpoints
	if (fCheckpointsEnabled) {
	const CCheckpointData &checkpoints =
	config.GetChainParams().Checkpoints();

	// Check that the block chain matches the known block chain up to a
	// checkpoint.
	if (!Checkpoints::CheckBlock(checkpoints, nHeight, block.GetHash())) {
	return state.DoS(100,
	error("%s: rejected by checkpoint lock-in at %d",
	__func__, nHeight),
	REJECT_CHECKPOINT, "checkpoint mismatch");
	}

	// Don't accept any forks from the main chain prior to last checkpoint.
	// GetLastCheckpoint finds the last checkpoint in MapCheckpoints that's
	// in our MapBlockIndex.
	CBlockIndex *pcheckpoint = Checkpoints::GetLastCheckpoint(checkpoints);
	if (pcheckpoint && nHeight < pcheckpoint->nHeight) {
	return state.DoS(
	100,
	error("%s: forked chain older than last checkpoint (height %d)",
	__func__, nHeight),
	REJECT_CHECKPOINT, "bad-fork-prior-to-checkpoint");
	}
	}

	// Check timestamp against prev
	if (block.GetBlockTime() <= pindexPrev->GetMedianTimePast()) {
	return state.Invalid(false, REJECT_INVALID, "time-too-old",
	"block's timestamp is too early");
	}

	// Check timestamp
	if (block.GetBlockTime() > nAdjustedTime + MAX_FUTURE_BLOCK_TIME) {
	return state.Invalid(false, REJECT_INVALID, "time-too-new",
	"block timestamp too far in the future");
	}

	// Reject outdated version blocks when 95% (75% on testnet) of the network
	// has upgraded:
	// check for version 2, 3 and 4 upgrades
	if ((block.nVersion < 2 && nHeight >= consensusParams.BIP34Height) \|\|
	(block.nVersion < 3 && nHeight >= consensusParams.BIP66Height) \|\|
	(block.nVersion < 4 && nHeight >= consensusParams.BIP65Height)) {
	return state.Invalid(
	false, REJECT_OBSOLETE,
	strprintf("bad-version(0x%08x)", block.nVersion),
	strprintf("rejected nVersion=0x%08x block", block.nVersion));
	}

	return true;
	}

	bool ContextualCheckTransactionForCurrentBlock(const Config &config,
	const CTransaction &tx,
	CValidationState &state,
	int flags) {
	AssertLockHeld(cs_main);

	// By convention a negative value for flags indicates that the current
	// network-enforced consensus rules should be used. In a future soft-fork
	// scenario that would mean checking which rules would be enforced for the
	// next block and setting the appropriate flags. At the present time no
	// soft-forks are scheduled, so no flags are set.
	flags = std::max(flags, 0);

	// ContextualCheckTransactionForCurrentBlock() uses chainActive.Height()+1
	// to evaluate nLockTime because when IsFinalTx() is called within
	// CBlock::AcceptBlock(), the height of the block being evaluated is what
	// is used. Thus if we want to know if a transaction can be part of the
	// next block, we need to call ContextualCheckTransaction() with one more
	// than chainActive.Height().
	const int nBlockHeight = chainActive.Height() + 1;

	// BIP113 will require that time-locked transactions have nLockTime set to
	// less than the median time of the previous block they're contained in.
	// When the next block is created its previous block will be the current
	// chain tip, so we use that to calculate the median time passed to
	// ContextualCheckTransaction() if LOCKTIME_MEDIAN_TIME_PAST is set.
	const int64_t nMedianTimePast =
	chainActive.Tip() == nullptr ? 0
	: chainActive.Tip()->GetMedianTimePast();
	const int64_t nLockTimeCutoff = (flags & LOCKTIME_MEDIAN_TIME_PAST)
	? nMedianTimePast
	: GetAdjustedTime();

	return ContextualCheckTransaction(config, tx, state, nBlockHeight,
	nLockTimeCutoff, nMedianTimePast);
	}

	/**
	* NOTE: This function is not currently invoked by ConnectBlock(), so we
	* should consider upgrade issues if we change which consensus rules are
	* enforced in this function (eg by adding a new consensus rule). See comment
	* in ConnectBlock().
	* Note that -reindex-chainstate skips the validation that happens here!
	*/
	static bool ContextualCheckBlock(const Config &config, const CBlock &block,
	CValidationState &state,
	const CBlockIndex *pindexPrev) {
	const int nHeight = pindexPrev == nullptr ? 0 : pindexPrev->nHeight + 1;
	const Consensus::Params &consensusParams =
	config.GetChainParams().GetConsensus();

	// Start enforcing BIP113 (Median Time Past).
	int nLockTimeFlags = 0;
	if (nHeight >= consensusParams.CSVHeight) {
	nLockTimeFlags \|= LOCKTIME_MEDIAN_TIME_PAST;
	}

	const int64_t nMedianTimePast =
	pindexPrev == nullptr ? 0 : pindexPrev->GetMedianTimePast();

	const int64_t nLockTimeCutoff = (nLockTimeFlags & LOCKTIME_MEDIAN_TIME_PAST)
	? nMedianTimePast
	: block.GetBlockTime();

	const bool fIsMagneticAnomalyEnabled =
	IsMagneticAnomalyEnabled(config, pindexPrev);

	// Check that all transactions are finalized
	const CTransaction *prevTx = nullptr;
	for (const auto &ptx : block.vtx) {
	const CTransaction &tx = *ptx;
	if (fIsMagneticAnomalyEnabled) {
	if (prevTx && (tx.GetId() <= prevTx->GetId())) {
	if (tx.GetId() == prevTx->GetId()) {
	return state.DoS(100, false, REJECT_INVALID, "tx-duplicate",
	false,
	strprintf("Duplicated transaction %s",
	tx.GetId().ToString()));
	}

	return state.DoS(
	100, false, REJECT_INVALID, "tx-ordering", false,
	strprintf("Transaction order is invalid (%s < %s)",
	tx.GetId().ToString(),
	prevTx->GetId().ToString()));
	}

	if (prevTx \|\| !tx.IsCoinBase()) {
	prevTx = &tx;
	}
	}

	if (!ContextualCheckTransaction(config, tx, state, nHeight,
	nLockTimeCutoff, nMedianTimePast)) {
	// state set by ContextualCheckTransaction.
	return false;
	}
	}

	// Enforce rule that the coinbase starts with serialized block height
	if (nHeight >= consensusParams.BIP34Height) {
	CScript expect = CScript() << nHeight;
	if (block.vtx[0]->vin[0].scriptSig.size() < expect.size() \|\|
	!std::equal(expect.begin(), expect.end(),
	block.vtx[0]->vin[0].scriptSig.begin())) {
	return state.DoS(100, false, REJECT_INVALID, "bad-cb-height", false,
	"block height mismatch in coinbase");
	}
	}

	return true;
	}

	/**
	* If the provided block header is valid, add it to the block index.
	*
	* Returns true if the block is successfully added to the block index.
	*/
	bool CChainState::AcceptBlockHeader(const Config &config,
	const CBlockHeader &block,
	CValidationState &state,
	CBlockIndex **ppindex) {
	AssertLockHeld(cs_main);
	const CChainParams &chainparams = config.GetChainParams();

	// Check for duplicate
	uint256 hash = block.GetHash();
	BlockMap::iterator miSelf = mapBlockIndex.find(hash);
	CBlockIndex *pindex = nullptr;
	if (hash != chainparams.GetConsensus().hashGenesisBlock) {
	if (miSelf != mapBlockIndex.end()) {
	// Block header is already known.
	pindex = miSelf->second;
	if (ppindex) {
	*ppindex = pindex;
	}

	if (pindex->nStatus.isInvalid()) {
	return state.Invalid(error("%s: block %s is marked invalid",
	__func__, hash.ToString()),
	0, "duplicate");
	}

	return true;
	}

	if (!CheckBlockHeader(config, block, state)) {
	return error("%s: Consensus::CheckBlockHeader: %s, %s", __func__,
	hash.ToString(), FormatStateMessage(state));
	}

	// Get prev block index
	BlockMap::iterator mi = mapBlockIndex.find(block.hashPrevBlock);
	if (mi == mapBlockIndex.end()) {
	return state.DoS(10, error("%s: prev block not found", __func__), 0,
	"prev-blk-not-found");
	}

	CBlockIndex pindexPrev = (mi).second;
	assert(pindexPrev);
	if (pindexPrev->nStatus.isInvalid()) {
	return state.DoS(100, error("%s: prev block invalid", __func__),
	REJECT_INVALID, "bad-prevblk");
	}

	if (!ContextualCheckBlockHeader(config, block, state, pindexPrev,
	GetAdjustedTime())) {
	return error("%s: Consensus::ContextualCheckBlockHeader: %s, %s",
	__func__, hash.ToString(), FormatStateMessage(state));
	}

	if (!pindexPrev->IsValid(BlockValidity::SCRIPTS)) {
	for (const CBlockIndex *failedit : m_failed_blocks) {
	if (pindexPrev->GetAncestor(failedit->nHeight) == failedit) {
	assert(failedit->nStatus.hasFailed());
	CBlockIndex *invalid_walk = pindexPrev;
	while (invalid_walk != failedit) {
	invalid_walk->nStatus =
	invalid_walk->nStatus.withFailedParent();
	setDirtyBlockIndex.insert(invalid_walk);
	invalid_walk = invalid_walk->pprev;
	}
	return state.DoS(100,
	error("%s: prev block invalid", __func__),
	REJECT_INVALID, "bad-prevblk");
	}
	}
	}
	}

	if (pindex == nullptr) {
	pindex = AddToBlockIndex(block);
	}

	if (ppindex) {
	*ppindex = pindex;
	}

	CheckBlockIndex(chainparams.GetConsensus());
	return true;
	}

	// Exposed wrapper for AcceptBlockHeader
	bool ProcessNewBlockHeaders(const Config &config,
	const std::vector<CBlockHeader> &headers,
	CValidationState &state,
	const CBlockIndex **ppindex,
	CBlockHeader *first_invalid) {
	if (first_invalid != nullptr) {
	first_invalid->SetNull();
	}

	{
	LOCK(cs_main);
	for (const CBlockHeader &header : headers) {
	// Use a temp pindex instead of ppindex to avoid a const_cast
	CBlockIndex *pindex = nullptr;
	if (!g_chainstate.AcceptBlockHeader(config, header, state,
	&pindex)) {
	if (first_invalid) {
	*first_invalid = header;
	}
	return false;
	}

	if (ppindex) {
	*ppindex = pindex;
	}
	}
	}

	NotifyHeaderTip();
	return true;
	}

	/**
	* Store block on disk. If dbp is non-nullptr, the file is known to already
	* reside on disk.
	*/
	static CDiskBlockPos SaveBlockToDisk(const CBlock &block, int nHeight,
	const CChainParams &chainparams,
	const CDiskBlockPos *dbp) {
	unsigned int nBlockSize =
	::GetSerializeSize(block, SER_DISK, CLIENT_VERSION);
	CDiskBlockPos blockPos;
	if (dbp != nullptr) {
	blockPos = *dbp;
	}
	if (!FindBlockPos(blockPos, nBlockSize + 8, nHeight, block.GetBlockTime(),
	dbp != nullptr)) {
	error("%s: FindBlockPos failed", __func__);
	return CDiskBlockPos();
	}
	if (dbp == nullptr) {
	if (!WriteBlockToDisk(block, blockPos, chainparams.DiskMagic())) {
	AbortNode("Failed to write block");
	return CDiskBlockPos();
	}
	}
	return blockPos;
	}

	/**
	* Store a block on disk.
	*
	* @param[in] config The global config.
	* @param[in-out] pblock The block we want to accept.
	* @param[in] fRequested A boolean to indicate if this block was requested
	* from our peers.
	* @param[in] dbp If non-null, the disk position of the block.
	* @param[in-out] fNewBlock True if block was first received via this call.
	* @return True if the block is accepted as a valid block and written to disk.
	*/
	bool CChainState::AcceptBlock(const Config &config,
	const std::shared_ptr<const CBlock> &pblock,
	CValidationState &state, bool fRequested,
	const CDiskBlockPos dbp, bool fNewBlock) {
	AssertLockHeld(cs_main);

	const CBlock &block = *pblock;
	if (fNewBlock) {
	*fNewBlock = false;
	}

	CBlockIndex *pindex = nullptr;
	if (!AcceptBlockHeader(config, block, state, &pindex)) {
	return false;
	}

	// Try to process all requested blocks that we don't have, but only
	// process an unrequested block if it's new and has enough work to
	// advance our tip, and isn't too many blocks ahead.
	bool fAlreadyHave = pindex->nStatus.hasData();

	// TODO: deal better with return value and error conditions for duplicate
	// and unrequested blocks.
	if (fAlreadyHave) {
	return true;
	}

	// Compare block header timestamps and received times of the block and the
	// chaintip. If they have the same chain height, use these diffs as a
	// tie-breaker, attempting to pick the more honestly-mined block.
	int64_t newBlockTimeDiff = std::llabs(pindex->GetReceivedTimeDiff());
	int64_t chainTipTimeDiff =
	chainActive.Tip() ? std::llabs(chainActive.Tip()->GetReceivedTimeDiff())
	: 0;

	bool isSameHeight = chainActive.Tip() &&
	(pindex->nChainWork == chainActive.Tip()->nChainWork);
	if (isSameHeight) {
	LogPrintf("Chain tip timestamp-to-received-time difference: hash=%s, "
	"diff=%d\n",
	chainActive.Tip()->GetBlockHash().ToString(),
	chainTipTimeDiff);
	LogPrintf("New block timestamp-to-received-time difference: hash=%s, "
	"diff=%d\n",
	pindex->GetBlockHash().ToString(), newBlockTimeDiff);
	}

	bool fHasMoreOrSameWork =
	(chainActive.Tip() ? pindex->nChainWork >= chainActive.Tip()->nChainWork
	: true);

	// Blocks that are too out-of-order needlessly limit the effectiveness of
	// pruning, because pruning will not delete block files that contain any
	// blocks which are too close in height to the tip. Apply this test
	// regardless of whether pruning is enabled; it should generally be safe to
	// not process unrequested blocks.
	bool fTooFarAhead =
	(pindex->nHeight > int(chainActive.Height() + MIN_BLOCKS_TO_KEEP));

	// TODO: Decouple this function from the block download logic by removing
	// fRequested
	// This requires some new chain data structure to efficiently look up if a
	// block is in a chain leading to a candidate for best tip, despite not
	// being such a candidate itself.

	// If we didn't ask for it:
	if (!fRequested) {
	// This is a previously-processed block that was pruned.
	if (pindex->nTx != 0) {
	return true;
	}

	// Don't process less-work chains.
	if (!fHasMoreOrSameWork) {
	return true;
	}

	// Block height is too high.
	if (fTooFarAhead) {
	return true;
	}

	// Protect against DoS attacks from low-work chains.
	// If our tip is behind, a peer could try to send us
	// low-work blocks on a fake chain that we would never
	// request; don't process these.
	if (pindex->nChainWork < nMinimumChainWork) {
	return true;
	}
	}

	if (fNewBlock) {
	*fNewBlock = true;
	}

	if (!CheckBlock(config, block, state) \|\|
	!ContextualCheckBlock(config, block, state, pindex->pprev)) {
	if (state.IsInvalid() && !state.CorruptionPossible()) {
	pindex->nStatus = pindex->nStatus.withFailed();
	setDirtyBlockIndex.insert(pindex);
	}

	return error("%s: %s (block %s)", __func__, FormatStateMessage(state),
	block.GetHash().ToString());
	}

	// If this is a deep reorg (a regorg of more than one block), preemptively
	// mark the chain as parked. If it has enough work, it'll unpark
	// automatically. We mark the block as parked at the very last minute so we
	// can make sure everything is ready to be reorged if needed.
	if (gArgs.GetBoolArg("-parkdeepreorg", true)) {
	const CBlockIndex *pindexFork = chainActive.FindFork(pindex);
	if (pindexFork && pindexFork->nHeight + 1 < pindex->nHeight) {
	LogPrintf("Park block %s as it would cause a deep reorg.\n",
	pindex->GetBlockHash().ToString());
	pindex->nStatus = pindex->nStatus.withParked();
	setDirtyBlockIndex.insert(pindex);
	}
	}

	// Header is valid/has work and the merkle tree is good.
	// Relay now, but if it does not build on our best tip, let the
	// SendMessages loop relay it.
	if (!IsInitialBlockDownload() && chainActive.Tip() == pindex->pprev) {
	GetMainSignals().NewPoWValidBlock(pindex, pblock);
	}

	const CChainParams &chainparams = config.GetChainParams();

	// Write block to history file
	try {
	CDiskBlockPos blockPos =
	SaveBlockToDisk(block, pindex->nHeight, chainparams, dbp);
	if (blockPos.IsNull()) {
	state.Error(strprintf(
	"%s: Failed to find position to write new block to disk",
	__func__));
	return false;
	}
	if (!ReceivedBlockTransactions(block, state, pindex, blockPos)) {
	return error("AcceptBlock(): ReceivedBlockTransactions failed");
	}
	} catch (const std::runtime_error &e) {
	return AbortNode(state, std::string("System error: ") + e.what());
	}

	if (fCheckForPruning) {
	// we just allocated more disk space for block files.
	FlushStateToDisk(config.GetChainParams(), state, FlushStateMode::NONE);
	}

	CheckBlockIndex(chainparams.GetConsensus());

	return true;
	}

	bool ProcessNewBlock(const Config &config,
	const std::shared_ptr<const CBlock> pblock,
	bool fForceProcessing, bool *fNewBlock) {
	AssertLockNotHeld(cs_main);

	{
	if (fNewBlock) {
	*fNewBlock = false;
	}

	CValidationState state;

	// CheckBlock() does not support multi-threaded block validation
	// because CBlock::fChecked can cause data race.
	// Therefore, the following critical section must include the
	// CheckBlock() call as well.
	LOCK(cs_main);

	// Ensure that CheckBlock() passes before calling AcceptBlock, as
	// belt-and-suspenders.
	bool ret = CheckBlock(config, *pblock, state);
	if (ret) {
	// Store to disk
	ret = g_chainstate.AcceptBlock(
	config, pblock, state, fForceProcessing, nullptr, fNewBlock);
	}

	if (!ret) {
	GetMainSignals().BlockChecked(*pblock, state);
	return error("%s: AcceptBlock FAILED (%s)", __func__,
	state.GetDebugMessage());
	}
	}

	NotifyHeaderTip();

	// Only used to report errors, not invalidity - ignore it
	CValidationState state;
	if (!g_chainstate.ActivateBestChain(config, state, pblock)) {
	return error("%s: ActivateBestChain failed", __func__);
	}

	return true;
	}

	bool TestBlockValidity(const Config &config, CValidationState &state,
	const CBlock &block, CBlockIndex *pindexPrev,
	BlockValidationOptions validationOptions) {
	AssertLockHeld(cs_main);
	assert(pindexPrev && pindexPrev == chainActive.Tip());
	CCoinsViewCache viewNew(pcoinsTip.get());
	uint256 block_hash(block.GetHash());
	CBlockIndex indexDummy(block);
	indexDummy.pprev = pindexPrev;
	indexDummy.nHeight = pindexPrev->nHeight + 1;
	indexDummy.phashBlock = &block_hash;

	// NOTE: CheckBlockHeader is called by CheckBlock
	if (!ContextualCheckBlockHeader(config, block, state, pindexPrev,
	GetAdjustedTime())) {
	return error("%s: Consensus::ContextualCheckBlockHeader: %s", __func__,
	FormatStateMessage(state));
	}

	if (!CheckBlock(config, block, state, validationOptions)) {
	return error("%s: Consensus::CheckBlock: %s", __func__,
	FormatStateMessage(state));
	}

	if (!ContextualCheckBlock(config, block, state, pindexPrev)) {
	return error("%s: Consensus::ContextualCheckBlock: %s", __func__,
	FormatStateMessage(state));
	}

	if (!g_chainstate.ConnectBlock(config, block, state, &indexDummy, viewNew,
	true)) {
	return false;
	}

	assert(state.IsValid());
	return true;
	}

	/**
	* BLOCK PRUNING CODE
	*/

	/**
	* Calculate the amount of disk space the block & undo files currently use.
	*/
	uint64_t CalculateCurrentUsage() {
	LOCK(cs_LastBlockFile);

	uint64_t retval = 0;
	for (const CBlockFileInfo &file : vinfoBlockFile) {
	retval += file.nSize + file.nUndoSize;
	}

	return retval;
	}

	/**
	* Prune a block file (modify associated database entries)
	*/
	void PruneOneBlockFile(const int fileNumber) {
	LOCK(cs_LastBlockFile);

	for (const auto &entry : mapBlockIndex) {
	CBlockIndex *pindex = entry.second;
	if (pindex->nFile == fileNumber) {
	pindex->nStatus = pindex->nStatus.withData(false).withUndo(false);
	pindex->nFile = 0;
	pindex->nDataPos = 0;
	pindex->nUndoPos = 0;
	setDirtyBlockIndex.insert(pindex);

	// Prune from mapBlocksUnlinked -- any block we prune would have
	// to be downloaded again in order to consider its chain, at which
	// point it would be considered as a candidate for
	// mapBlocksUnlinked or setBlockIndexCandidates.
	std::pair<std::multimap<CBlockIndex , CBlockIndex >::iterator,
	std::multimap<CBlockIndex , CBlockIndex >::iterator>
	range = mapBlocksUnlinked.equal_range(pindex->pprev);
	while (range.first != range.second) {
	std::multimap<CBlockIndex , CBlockIndex >::iterator _it =
	range.first;
	range.first++;
	if (_it->second == pindex) {
	mapBlocksUnlinked.erase(_it);
	}
	}
	}
	}

	vinfoBlockFile[fileNumber].SetNull();
	setDirtyFileInfo.insert(fileNumber);
	}

	void UnlinkPrunedFiles(const std::set<int> &setFilesToPrune) {
	for (const int i : setFilesToPrune) {
	CDiskBlockPos pos(i, 0);
	fs::remove(BlockFileSeq().FileName(pos));
	fs::remove(UndoFileSeq().FileName(pos));
	LogPrintf("Prune: %s deleted blk/rev (%05u)\n", __func__, i);
	}
	}

	/**
	* Calculate the block/rev files to delete based on height specified by user
	* with RPC command pruneblockchain
	*/
	static void FindFilesToPruneManual(std::set<int> &setFilesToPrune,
	int nManualPruneHeight) {
	assert(fPruneMode && nManualPruneHeight > 0);

	LOCK2(cs_main, cs_LastBlockFile);
	if (chainActive.Tip() == nullptr) {
	return;
	}

	// last block to prune is the lesser of (user-specified height,
	// MIN_BLOCKS_TO_KEEP from the tip)
	unsigned int nLastBlockWeCanPrune =
	std::min((unsigned)nManualPruneHeight,
	chainActive.Tip()->nHeight - MIN_BLOCKS_TO_KEEP);
	int count = 0;
	for (int fileNumber = 0; fileNumber < nLastBlockFile; fileNumber++) {
	if (vinfoBlockFile[fileNumber].nSize == 0 \|\|
	vinfoBlockFile[fileNumber].nHeightLast > nLastBlockWeCanPrune) {
	continue;
	}
	PruneOneBlockFile(fileNumber);
	setFilesToPrune.insert(fileNumber);
	count++;
	}
	LogPrintf("Prune (Manual): prune_height=%d removed %d blk/rev pairs\n",
	nLastBlockWeCanPrune, count);
	}

	/* This function is called from the RPC code for pruneblockchain */
	void PruneBlockFilesManual(int nManualPruneHeight) {
	CValidationState state;
	const CChainParams &chainparams = Params();
	FlushStateToDisk(chainparams, state, FlushStateMode::NONE,
	nManualPruneHeight);
	}

	/**
	* Prune block and undo files (blk???.dat and undo???.dat) so that the disk
	* space used is less than a user-defined target. The user sets the target (in
	* MB) on the command line or in config file. This will be run on startup and
	* whenever new space is allocated in a block or undo file, staying below the
	* target. Changing back to unpruned requires a reindex (which in this case
	* means the blockchain must be re-downloaded.)
	*
	* Pruning functions are called from FlushStateToDisk when the global
	* fCheckForPruning flag has been set. Block and undo files are deleted in
	* lock-step (when blk00003.dat is deleted, so is rev00003.dat.). Pruning cannot
	* take place until the longest chain is at least a certain length (100000 on
	* mainnet, 1000 on testnet, 1000 on regtest). Pruning will never delete a block
	* within a defined distance (currently 288) from the active chain's tip. The
	* block index is updated by unsetting HAVE_DATA and HAVE_UNDO for any blocks
	* that were stored in the deleted files. A db flag records the fact that at
	* least some block files have been pruned.
	*
	* @param[out] setFilesToPrune The set of file indices that can be unlinked
	* will be returned
	*/
	static void FindFilesToPrune(std::set<int> &setFilesToPrune,
	uint64_t nPruneAfterHeight) {
	LOCK2(cs_main, cs_LastBlockFile);
	if (chainActive.Tip() == nullptr \|\| nPruneTarget == 0) {
	return;
	}
	if (uint64_t(chainActive.Tip()->nHeight) <= nPruneAfterHeight) {
	return;
	}

	unsigned int nLastBlockWeCanPrune =
	chainActive.Tip()->nHeight - MIN_BLOCKS_TO_KEEP;
	uint64_t nCurrentUsage = CalculateCurrentUsage();
	// We don't check to prune until after we've allocated new space for files,
	// so we should leave a buffer under our target to account for another
	// allocation before the next pruning.
	uint64_t nBuffer = BLOCKFILE_CHUNK_SIZE + UNDOFILE_CHUNK_SIZE;
	uint64_t nBytesToPrune;
	int count = 0;

	if (nCurrentUsage + nBuffer >= nPruneTarget) {
	for (int fileNumber = 0; fileNumber < nLastBlockFile; fileNumber++) {
	nBytesToPrune = vinfoBlockFile[fileNumber].nSize +
	vinfoBlockFile[fileNumber].nUndoSize;

	if (vinfoBlockFile[fileNumber].nSize == 0) {
	continue;
	}

	// are we below our target?
	if (nCurrentUsage + nBuffer < nPruneTarget) {
	break;
	}

	// don't prune files that could have a block within
	// MIN_BLOCKS_TO_KEEP of the main chain's tip but keep scanning
	if (vinfoBlockFile[fileNumber].nHeightLast > nLastBlockWeCanPrune) {
	continue;
	}

	PruneOneBlockFile(fileNumber);
	// Queue up the files for removal
	setFilesToPrune.insert(fileNumber);
	nCurrentUsage -= nBytesToPrune;
	count++;
	}
	}

	LogPrint(BCLog::PRUNE,
	"Prune: target=%dMiB actual=%dMiB diff=%dMiB "
	"max_prune_height=%d removed %d blk/rev pairs\n",
	nPruneTarget / 1024 / 1024, nCurrentUsage / 1024 / 1024,
	((int64_t)nPruneTarget - (int64_t)nCurrentUsage) / 1024 / 1024,
	nLastBlockWeCanPrune, count);
	}

	static FlatFileSeq BlockFileSeq() {
	return FlatFileSeq(GetBlocksDir(), "blk", BLOCKFILE_CHUNK_SIZE);
	}

	static FlatFileSeq UndoFileSeq() {
	return FlatFileSeq(GetBlocksDir(), "rev", UNDOFILE_CHUNK_SIZE);
	}

	FILE *OpenBlockFile(const CDiskBlockPos &pos, bool fReadOnly) {
	return BlockFileSeq().Open(pos, fReadOnly);
	}

	/** Open an undo file (rev?????.dat) */
	static FILE *OpenUndoFile(const CDiskBlockPos &pos, bool fReadOnly) {
	return UndoFileSeq().Open(pos, fReadOnly);
	}

	fs::path GetBlockPosFilename(const CDiskBlockPos &pos) {
	return BlockFileSeq().FileName(pos);
	}

	CBlockIndex *CChainState::InsertBlockIndex(const uint256 &hash) {
	AssertLockHeld(cs_main);

	if (hash.IsNull()) {
	return nullptr;
	}

	// Return existing
	BlockMap::iterator mi = mapBlockIndex.find(hash);
	if (mi != mapBlockIndex.end()) {
	return (*mi).second;
	}

	// Create new
	CBlockIndex *pindexNew = new CBlockIndex();
	mi = mapBlockIndex.insert(std::make_pair(hash, pindexNew)).first;
	pindexNew->phashBlock = &((*mi).first);

	return pindexNew;
	}

	bool CChainState::LoadBlockIndex(const Config &config,
	CBlockTreeDB &blocktree) {
	if (!blocktree.LoadBlockIndexGuts(config, [this](const uint256 &hash) {
	return this->InsertBlockIndex(hash);
	})) {
	return false;
	}

	boost::this_thread::interruption_point();

	// Calculate nChainWork
	std::vector<std::pair<int, CBlockIndex *>> vSortedByHeight;
	vSortedByHeight.reserve(mapBlockIndex.size());
	for (const std::pair<uint256, CBlockIndex *> &item : mapBlockIndex) {
	CBlockIndex *pindex = item.second;
	vSortedByHeight.push_back(std::make_pair(pindex->nHeight, pindex));
	}

	sort(vSortedByHeight.begin(), vSortedByHeight.end());
	for (const std::pair<int, CBlockIndex *> &item : vSortedByHeight) {
	CBlockIndex *pindex = item.second;
	pindex->nChainWork = (pindex->pprev ? pindex->pprev->nChainWork : 0) +
	GetBlockProof(*pindex);
	pindex->nTimeMax =
	(pindex->pprev ? std::max(pindex->pprev->nTimeMax, pindex->nTime)
	: pindex->nTime);
	// We can link the chain of blocks for which we've received transactions
	// at some point. Pruned nodes may have deleted the block.
	if (pindex->nTx > 0) {
	if (pindex->pprev) {
	if (pindex->pprev->nChainTx) {
	pindex->nChainTx = pindex->pprev->nChainTx + pindex->nTx;
	} else {
	pindex->nChainTx = 0;
	mapBlocksUnlinked.insert(
	std::make_pair(pindex->pprev, pindex));
	}
	} else {
	pindex->nChainTx = pindex->nTx;
	}
	}

	if (!pindex->nStatus.hasFailed() && pindex->pprev &&
	pindex->pprev->nStatus.hasFailed()) {
	pindex->nStatus = pindex->nStatus.withFailedParent();
	setDirtyBlockIndex.insert(pindex);
	}
	if (pindex->IsValid(BlockValidity::TRANSACTIONS) &&
	(pindex->nChainTx \|\| pindex->pprev == nullptr)) {
	setBlockIndexCandidates.insert(pindex);
	}

	if (pindex->nStatus.isInvalid() &&
	(!pindexBestInvalid \|\|
	pindex->nChainWork > pindexBestInvalid->nChainWork)) {
	pindexBestInvalid = pindex;
	}

	if (pindex->nStatus.isOnParkedChain() &&
	(!pindexBestParked \|\|
	pindex->nChainWork > pindexBestParked->nChainWork)) {
	pindexBestParked = pindex;
	}

	if (pindex->pprev) {
	pindex->BuildSkip();
	}

	if (pindex->IsValid(BlockValidity::TREE) &&
	(pindexBestHeader == nullptr \|\|
	CBlockIndexWorkComparator()(pindexBestHeader, pindex))) {
	pindexBestHeader = pindex;
	}
	}

	return true;
	}

	bool static LoadBlockIndexDB(const Config &config) {
	if (!g_chainstate.LoadBlockIndex(config, *pblocktree)) {
	return false;
	}

	// Load block file info
	pblocktree->ReadLastBlockFile(nLastBlockFile);
	vinfoBlockFile.resize(nLastBlockFile + 1);
	LogPrintf("%s: last block file = %i\n", __func__, nLastBlockFile);
	for (int nFile = 0; nFile <= nLastBlockFile; nFile++) {
	pblocktree->ReadBlockFileInfo(nFile, vinfoBlockFile[nFile]);
	}

	LogPrintf("%s: last block file info: %s\n", __func__,
	vinfoBlockFile[nLastBlockFile].ToString());

	for (int nFile = nLastBlockFile + 1; true; nFile++) {
	CBlockFileInfo info;
	if (pblocktree->ReadBlockFileInfo(nFile, info)) {
	vinfoBlockFile.push_back(info);
	} else {
	break;
	}
	}

	// Check presence of blk files
	LogPrintf("Checking all blk files are present...\n");
	std::set<int> setBlkDataFiles;
	for (const std::pair<uint256, CBlockIndex *> &item : mapBlockIndex) {
	CBlockIndex *pindex = item.second;
	if (pindex->nStatus.hasData()) {
	setBlkDataFiles.insert(pindex->nFile);
	}
	}

	for (const int i : setBlkDataFiles) {
	CDiskBlockPos pos(i, 0);
	if (CAutoFile(OpenBlockFile(pos, true), SER_DISK, CLIENT_VERSION)
	.IsNull()) {
	return false;
	}
	}

	// Check whether we have ever pruned block & undo files
	pblocktree->ReadFlag("prunedblockfiles", fHavePruned);
	if (fHavePruned) {
	LogPrintf(
	"LoadBlockIndexDB(): Block files have previously been pruned\n");
	}

	// Check whether we need to continue reindexing
	bool fReindexing = false;
	pblocktree->ReadReindexing(fReindexing);
	if (fReindexing) {
	fReindex = true;
	}

	return true;
	}

	bool LoadChainTip(const Config &config) {
	AssertLockHeld(cs_main);

	if (chainActive.Tip() &&
	chainActive.Tip()->GetBlockHash() == pcoinsTip->GetBestBlock()) {
	return true;
	}

	if (pcoinsTip->GetBestBlock().IsNull() && mapBlockIndex.size() == 1) {
	// In case we just added the genesis block, connect it now, so
	// that we always have a chainActive.Tip() when we return.
	LogPrintf("%s: Connecting genesis block...\n", __func__);
	CValidationState state;
	if (!ActivateBestChain(config, state)) {
	return false;
	}
	}

	// Load pointer to end of best chain
	CBlockIndex *pindex = LookupBlockIndex(pcoinsTip->GetBestBlock());
	if (!pindex) {
	return false;
	}
	chainActive.SetTip(pindex);

	g_chainstate.PruneBlockIndexCandidates();

	LogPrintf(
	"Loaded best chain: hashBestChain=%s height=%d date=%s progress=%f\n",
	chainActive.Tip()->GetBlockHash().ToString(), chainActive.Height(),
	FormatISO8601DateTime(chainActive.Tip()->GetBlockTime()),
	GuessVerificationProgress(config.GetChainParams().TxData(),
	chainActive.Tip()));
	return true;
	}

	CVerifyDB::CVerifyDB() {
	uiInterface.ShowProgress(_("Verifying blocks..."), 0, false);
	}

	CVerifyDB::~CVerifyDB() {
	uiInterface.ShowProgress("", 100, false);
	}

	bool CVerifyDB::VerifyDB(const Config &config, CCoinsView *coinsview,
	int nCheckLevel, int nCheckDepth) {
	LOCK(cs_main);
	if (chainActive.Tip() == nullptr \|\| chainActive.Tip()->pprev == nullptr) {
	return true;
	}

	// Verify blocks in the best chain
	if (nCheckDepth <= 0 \|\| nCheckDepth > chainActive.Height()) {
	nCheckDepth = chainActive.Height();
	}

	nCheckLevel = std::max(0, std::min(4, nCheckLevel));
	LogPrintf("Verifying last %i blocks at level %i\n", nCheckDepth,
	nCheckLevel);

	CCoinsViewCache coins(coinsview);
	CBlockIndex *pindexState = chainActive.Tip();
	CBlockIndex *pindexFailure = nullptr;
	int nGoodTransactions = 0;
	CValidationState state;
	int reportDone = 0;
	LogPrintf("[0%%]...");
	for (CBlockIndex *pindex = chainActive.Tip(); pindex && pindex->pprev;
	pindex = pindex->pprev) {
	boost::this_thread::interruption_point();
	int percentageDone = std::max(
	1, std::min(
	99,
	(int)(((double)(chainActive.Height() - pindex->nHeight)) /
	(double)nCheckDepth * (nCheckLevel >= 4 ? 50 : 100))));

	if (reportDone < percentageDone / 10) {
	// report every 10% step
	LogPrintf("[%d%%]...", percentageDone);
	reportDone = percentageDone / 10;
	}

	uiInterface.ShowProgress(_("Verifying blocks..."), percentageDone,
	false);
	if (pindex->nHeight < chainActive.Height() - nCheckDepth) {
	break;
	}

	if (fPruneMode && !pindex->nStatus.hasData()) {
	// If pruning, only go back as far as we have data.
	LogPrintf("VerifyDB(): block verification stopping at height %d "
	"(pruning, no data)\n",
	pindex->nHeight);
	break;
	}

	CBlock block;

	// check level 0: read from disk
	if (!ReadBlockFromDisk(block, pindex, config)) {
	return error(
	"VerifyDB(): *** ReadBlockFromDisk failed at %d, hash=%s",
	pindex->nHeight, pindex->GetBlockHash().ToString());
	}

	// check level 1: verify block validity
	if (nCheckLevel >= 1 && !CheckBlock(config, block, state)) {
	return error("%s: *** found bad block at %d, hash=%s (%s)\n",
	__func__, pindex->nHeight,
	pindex->GetBlockHash().ToString(),
	FormatStateMessage(state));
	}

	// check level 2: verify undo validity
	if (nCheckLevel >= 2 && pindex) {
	CBlockUndo undo;
	if (!pindex->GetUndoPos().IsNull()) {
	if (!UndoReadFromDisk(undo, pindex)) {
	return error(
	"VerifyDB(): *** found bad undo data at %d, hash=%s\n",
	pindex->nHeight, pindex->GetBlockHash().ToString());
	}
	}
	}

	// check level 3: check for inconsistencies during memory-only
	// disconnect of tip blocks
	if (nCheckLevel >= 3 && pindex == pindexState &&
	(coins.DynamicMemoryUsage() + pcoinsTip->DynamicMemoryUsage()) <=
	nCoinCacheUsage) {
	assert(coins.GetBestBlock() == pindex->GetBlockHash());
	DisconnectResult res =
	g_chainstate.DisconnectBlock(block, pindex, coins);
	if (res == DISCONNECT_FAILED) {
	return error("VerifyDB(): *** irrecoverable inconsistency in "
	"block data at %d, hash=%s",
	pindex->nHeight,
	pindex->GetBlockHash().ToString());
	}

	pindexState = pindex->pprev;
	if (res == DISCONNECT_UNCLEAN) {
	nGoodTransactions = 0;
	pindexFailure = pindex;
	} else {
	nGoodTransactions += block.vtx.size();
	}
	}

	if (ShutdownRequested()) {
	return true;
	}
	}

	if (pindexFailure) {
	return error("VerifyDB(): *** coin database inconsistencies found "
	"(last %i blocks, %i good transactions before that)\n",
	chainActive.Height() - pindexFailure->nHeight + 1,
	nGoodTransactions);
	}

	// check level 4: try reconnecting blocks
	if (nCheckLevel >= 4) {
	CBlockIndex *pindex = pindexState;
	while (pindex != chainActive.Tip()) {
	boost::this_thread::interruption_point();
	uiInterface.ShowProgress(
	_("Verifying blocks..."),
	std::max(
	1, std::min(99, 100 - (int)(((double)(chainActive.Height() -
	pindex->nHeight)) /
	(double)nCheckDepth * 50))),
	false);
	pindex = chainActive.Next(pindex);
	CBlock block;
	if (!ReadBlockFromDisk(block, pindex, config)) {
	return error(
	"VerifyDB(): *** ReadBlockFromDisk failed at %d, hash=%s",
	pindex->nHeight, pindex->GetBlockHash().ToString());
	}
	if (!g_chainstate.ConnectBlock(config, block, state, pindex,
	coins)) {
	return error(
	"VerifyDB(): *** found unconnectable block at %d, hash=%s",
	pindex->nHeight, pindex->GetBlockHash().ToString());
	}
	}
	}

	LogPrintf("[DONE].\n");
	LogPrintf("No coin database inconsistencies in last %i blocks (%i "
	"transactions)\n",
	chainActive.Height() - pindexState->nHeight, nGoodTransactions);

	return true;
	}

	/**
	* Apply the effects of a block on the utxo cache, ignoring that it may already
	* have been applied.
	*/
	bool CChainState::RollforwardBlock(const CBlockIndex *pindex,
	CCoinsViewCache &view,
	const Config &config) {
	// TODO: merge with ConnectBlock
	CBlock block;
	if (!ReadBlockFromDisk(block, pindex, config)) {
	return error("ReplayBlock(): ReadBlockFromDisk failed at %d, hash=%s",
	pindex->nHeight, pindex->GetBlockHash().ToString());
	}

	for (const CTransactionRef &tx : block.vtx) {
	// Pass check = true as every addition may be an overwrite.
	AddCoins(view, *tx, pindex->nHeight, true);
	}

	for (const CTransactionRef &tx : block.vtx) {
	if (tx->IsCoinBase()) {
	continue;
	}

	for (const CTxIn &txin : tx->vin) {
	view.SpendCoin(txin.prevout);
	}
	}

	return true;
	}

	bool CChainState::ReplayBlocks(const Config &config, CCoinsView *view) {
	LOCK(cs_main);

	CCoinsViewCache cache(view);

	std::vector<uint256> hashHeads = view->GetHeadBlocks();
	if (hashHeads.empty()) {
	// We're already in a consistent state.
	return true;
	}

	if (hashHeads.size() != 2) {
	return error("ReplayBlocks(): unknown inconsistent state");
	}

	uiInterface.ShowProgress(_("Replaying blocks..."), 0, false);
	LogPrintf("Replaying blocks\n");

	// Old tip during the interrupted flush.
	const CBlockIndex *pindexOld = nullptr;
	// New tip during the interrupted flush.
	const CBlockIndex *pindexNew;
	// Latest block common to both the old and the new tip.
	const CBlockIndex *pindexFork = nullptr;

	if (mapBlockIndex.count(hashHeads[0]) == 0) {
	return error(
	"ReplayBlocks(): reorganization to unknown block requested");
	}

	pindexNew = mapBlockIndex[hashHeads[0]];

	if (!hashHeads[1].IsNull()) {
	// The old tip is allowed to be 0, indicating it's the first flush.
	if (mapBlockIndex.count(hashHeads[1]) == 0) {
	return error(
	"ReplayBlocks(): reorganization from unknown block requested");
	}

	pindexOld = mapBlockIndex[hashHeads[1]];
	pindexFork = LastCommonAncestor(pindexOld, pindexNew);
	assert(pindexFork != nullptr);
	}

	// Rollback along the old branch.
	while (pindexOld != pindexFork) {
	if (pindexOld->nHeight > 0) {
	// Never disconnect the genesis block.
	CBlock block;
	if (!ReadBlockFromDisk(block, pindexOld, config)) {
	return error("RollbackBlock(): ReadBlockFromDisk() failed at "
	"%d, hash=%s",
	pindexOld->nHeight,
	pindexOld->GetBlockHash().ToString());
	}

	LogPrintf("Rolling back %s (%i)\n",
	pindexOld->GetBlockHash().ToString(), pindexOld->nHeight);
	DisconnectResult res = DisconnectBlock(block, pindexOld, cache);
	if (res == DISCONNECT_FAILED) {
	return error(
	"RollbackBlock(): DisconnectBlock failed at %d, hash=%s",
	pindexOld->nHeight, pindexOld->GetBlockHash().ToString());
	}

	// If DISCONNECT_UNCLEAN is returned, it means a non-existing UTXO
	// was deleted, or an existing UTXO was overwritten. It corresponds
	// to cases where the block-to-be-disconnect never had all its
	// operations applied to the UTXO set. However, as both writing a
	// UTXO and deleting a UTXO are idempotent operations, the result is
	// still a version of the UTXO set with the effects of that block
	// undone.
	}
	pindexOld = pindexOld->pprev;
	}

	// Roll forward from the forking point to the new tip.
	int nForkHeight = pindexFork ? pindexFork->nHeight : 0;
	for (int nHeight = nForkHeight + 1; nHeight <= pindexNew->nHeight;
	++nHeight) {
	const CBlockIndex *pindex = pindexNew->GetAncestor(nHeight);
	LogPrintf("Rolling forward %s (%i)\n",
	pindex->GetBlockHash().ToString(), nHeight);
	if (!RollforwardBlock(pindex, cache, config)) {
	return false;
	}
	}

	cache.SetBestBlock(pindexNew->GetBlockHash());
	cache.Flush();
	uiInterface.ShowProgress("", 100, false);
	return true;
	}

	bool ReplayBlocks(const Config &config, CCoinsView *view) {
	return g_chainstate.ReplayBlocks(config, view);
	}

	bool CChainState::RewindBlockIndex(const Config &config) {
	LOCK(cs_main);

	const CChainParams &params = config.GetChainParams();
	int nHeight = chainActive.Height() + 1;

	// nHeight is now the height of the first insufficiently-validated block, or
	// tipheight + 1
	CValidationState state;
	CBlockIndex *pindex = chainActive.Tip();
	while (chainActive.Height() >= nHeight) {
	if (fPruneMode && !chainActive.Tip()->nStatus.hasData()) {
	// If pruning, don't try rewinding past the HAVE_DATA point; since
	// older blocks can't be served anyway, there's no need to walk
	// further, and trying to DisconnectTip() will fail (and require a
	// needless reindex/redownload of the blockchain).
	break;
	}

	if (!DisconnectTip(config, state, nullptr)) {
	return error(
	"RewindBlockIndex: unable to disconnect block at height %i",
	pindex->nHeight);
	}

	// Occasionally flush state to disk.
	if (!FlushStateToDisk(params, state, FlushStateMode::PERIODIC)) {
	return false;
	}
	}

	// Reduce validity flag and have-data flags.
	// We do this after actual disconnecting, otherwise we'll end up writing the
	// lack of data to disk before writing the chainstate, resulting in a
	// failure to continue if interrupted.
	for (const auto &entry : mapBlockIndex) {
	CBlockIndex *pindexIter = entry.second;
	if (pindexIter->IsValid(BlockValidity::TRANSACTIONS) &&
	pindexIter->nChainTx) {
	setBlockIndexCandidates.insert(pindexIter);
	}
	}

	if (chainActive.Tip() != nullptr) {
	// We can't prune block index candidates based on our tip if we have
	// no tip due to chainActive being empty!
	PruneBlockIndexCandidates();

	CheckBlockIndex(params.GetConsensus());
	}

	return true;
	}

	bool RewindBlockIndex(const Config &config) {
	if (!g_chainstate.RewindBlockIndex(config)) {
	return false;
	}

	if (chainActive.Tip() != nullptr) {
	// FlushStateToDisk can possibly read chainActive. Be conservative
	// and skip it here, we're about to -reindex-chainstate anyway, so
	// it'll get called a bunch real soon.
	CValidationState state;
	if (!FlushStateToDisk(config.GetChainParams(), state,
	FlushStateMode::ALWAYS)) {
	return false;
	}
	}

	return true;
	}

	// May NOT be used after any connections are up as much of the peer-processing
	// logic assumes a consistent block index state
	void CChainState::UnloadBlockIndex() {
	nBlockSequenceId = 1;
	m_failed_blocks.clear();
	setBlockIndexCandidates.clear();
	}

	// May NOT be used after any connections are up as much
	// of the peer-processing logic assumes a consistent
	// block index state
	void UnloadBlockIndex() {
	LOCK(cs_main);
	chainActive.SetTip(nullptr);
	pindexFinalized = nullptr;
	pindexBestInvalid = nullptr;
	pindexBestParked = nullptr;
	pindexBestHeader = nullptr;
	pindexBestForkTip = nullptr;
	pindexBestForkBase = nullptr;
	g_mempool.clear();
	mapBlocksUnlinked.clear();
	vinfoBlockFile.clear();
	nLastBlockFile = 0;
	setDirtyBlockIndex.clear();
	setDirtyFileInfo.clear();

	for (BlockMap::value_type &entry : mapBlockIndex) {
	delete entry.second;
	}

	mapBlockIndex.clear();
	fHavePruned = false;

	g_chainstate.UnloadBlockIndex();
	}

	bool LoadBlockIndex(const Config &config) {
	// Load block index from databases
	bool needs_init = fReindex;
	if (!fReindex) {
	bool ret = LoadBlockIndexDB(config);
	if (!ret) {
	return false;
	}

	needs_init = mapBlockIndex.empty();
	}

	if (needs_init) {
	// Everything here is for new reindex/DBs. Thus, though
	// LoadBlockIndexDB may have set fReindex if we shut down
	// mid-reindex previously, we don't check fReindex and
	// instead only check it prior to LoadBlockIndexDB to set
	// needs_init.

	LogPrintf("Initializing databases...\n");
	}
	return true;
	}

	bool CChainState::LoadGenesisBlock(const CChainParams &chainparams) {
	LOCK(cs_main);

	// Check whether we're already initialized by checking for genesis in
	// mapBlockIndex. Note that we can't use chainActive here, since it is
	// set based on the coins db, not the block index db, which is the only
	// thing loaded at this point.
	if (mapBlockIndex.count(chainparams.GenesisBlock().GetHash())) {
	return true;
	}

	try {
	CBlock &block = const_cast<CBlock &>(chainparams.GenesisBlock());
	CDiskBlockPos blockPos =
	SaveBlockToDisk(block, 0, chainparams, nullptr);
	if (blockPos.IsNull()) {
	return error("%s: writing genesis block to disk failed", __func__);
	}
	CBlockIndex *pindex = AddToBlockIndex(block);
	CValidationState state;
	if (!ReceivedBlockTransactions(block, state, pindex, blockPos)) {
	return error("%s: genesis block not accepted", __func__);
	}
	} catch (const std::runtime_error &e) {
	return error("%s: failed to write genesis block: %s", __func__,
	e.what());
	}

	return true;
	}

	bool LoadGenesisBlock(const CChainParams &chainparams) {
	return g_chainstate.LoadGenesisBlock(chainparams);
	}

	bool LoadExternalBlockFile(const Config &config, FILE *fileIn,
	CDiskBlockPos *dbp) {
	// Map of disk positions for blocks with unknown parent (only used for
	// reindex)
	static std::multimap<uint256, CDiskBlockPos> mapBlocksUnknownParent;
	int64_t nStart = GetTimeMillis();

	const CChainParams &chainparams = config.GetChainParams();

	int nLoaded = 0;
	try {
	// This takes over fileIn and calls fclose() on it in the CBufferedFile
	// destructor. Make sure we have at least 2*MAX_TX_SIZE space in there
	// so any transaction can fit in the buffer.
	CBufferedFile blkdat(fileIn, 2 * MAX_TX_SIZE, MAX_TX_SIZE + 8, SER_DISK,
	CLIENT_VERSION);
	uint64_t nRewind = blkdat.GetPos();
	while (!blkdat.eof()) {
	boost::this_thread::interruption_point();

	blkdat.SetPos(nRewind);
	// Start one byte further next time, in case of failure.
	nRewind++;
	// Remove former limit.
	blkdat.SetLimit();
	unsigned int nSize = 0;
	try {
	// Locate a header.
	uint8_t buf[CMessageHeader::MESSAGE_START_SIZE];
	blkdat.FindByte(chainparams.DiskMagic()[0]);
	nRewind = blkdat.GetPos() + 1;
	blkdat >> FLATDATA(buf);
	if (memcmp(buf, std::begin(chainparams.DiskMagic()),
	CMessageHeader::MESSAGE_START_SIZE)) {
	continue;
	}

	// Read size.
	blkdat >> nSize;
	if (nSize < 80) {
	continue;
	}
	} catch (const std::exception &) {
	// No valid block header found; don't complain.
	break;
	}

	try {
	// read block
	uint64_t nBlockPos = blkdat.GetPos();
	if (dbp) {
	dbp->nPos = nBlockPos;
	}
	blkdat.SetLimit(nBlockPos + nSize);
	blkdat.SetPos(nBlockPos);
	std::shared_ptr<CBlock> pblock = std::make_shared<CBlock>();
	CBlock &block = *pblock;
	blkdat >> block;
	nRewind = blkdat.GetPos();

	uint256 hash = block.GetHash();
	{
	LOCK(cs_main);
	// detect out of order blocks, and store them for later
	if (hash != chainparams.GetConsensus().hashGenesisBlock &&
	!LookupBlockIndex(block.hashPrevBlock)) {
	LogPrint(
	BCLog::REINDEX,
	"%s: Out of order block %s, parent %s not known\n",
	__func__, hash.ToString(),
	block.hashPrevBlock.ToString());
	if (dbp) {
	mapBlocksUnknownParent.insert(
	std::make_pair(block.hashPrevBlock, *dbp));
	}
	continue;
	}

	// process in case the block isn't known yet
	CBlockIndex *pindex = LookupBlockIndex(hash);
	if (!pindex \|\| !pindex->nStatus.hasData()) {
	CValidationState state;
	if (g_chainstate.AcceptBlock(config, pblock, state,
	true, dbp, nullptr)) {
	nLoaded++;
	}
	if (state.IsError()) {
	break;
	}
	} else if (hash != chainparams.GetConsensus()
	.hashGenesisBlock &&
	pindex->nHeight % 1000 == 0) {
	LogPrint(
	BCLog::REINDEX,
	"Block Import: already had block %s at height %d\n",
	hash.ToString(), pindex->nHeight);
	}
	}

	// Activate the genesis block so normal node progress can
	// continue
	if (hash == chainparams.GetConsensus().hashGenesisBlock) {
	CValidationState state;
	if (!ActivateBestChain(config, state)) {
	break;
	}
	}

	NotifyHeaderTip();

	// Recursively process earlier encountered successors of this
	// block
	std::deque<uint256> queue;
	queue.push_back(hash);
	while (!queue.empty()) {
	uint256 head = queue.front();
	queue.pop_front();
	std::pair<std::multimap<uint256, CDiskBlockPos>::iterator,
	std::multimap<uint256, CDiskBlockPos>::iterator>
	range = mapBlocksUnknownParent.equal_range(head);
	while (range.first != range.second) {
	std::multimap<uint256, CDiskBlockPos>::iterator it =
	range.first;
	std::shared_ptr<CBlock> pblockrecursive =
	std::make_shared<CBlock>();
	if (ReadBlockFromDisk(*pblockrecursive, it->second,
	config)) {
	LogPrint(
	BCLog::REINDEX,
	"%s: Processing out of order child %s of %s\n",
	__func__, pblockrecursive->GetHash().ToString(),
	head.ToString());
	LOCK(cs_main);
	CValidationState dummy;
	if (g_chainstate.AcceptBlock(
	config, pblockrecursive, dummy, true,
	&it->second, nullptr)) {
	nLoaded++;
	queue.push_back(pblockrecursive->GetHash());
	}
	}
	range.first++;
	mapBlocksUnknownParent.erase(it);
	NotifyHeaderTip();
	}
	}
	} catch (const std::exception &e) {
	LogPrintf("%s: Deserialize or I/O error - %s\n", __func__,
	e.what());
	}
	}
	} catch (const std::runtime_error &e) {
	AbortNode(std::string("System error: ") + e.what());
	}

	if (nLoaded > 0) {
	LogPrintf("Loaded %i blocks from external file in %dms\n", nLoaded,
	GetTimeMillis() - nStart);
	}

	return nLoaded > 0;
	}

	void CChainState::CheckBlockIndex(const Consensus::Params &consensusParams) {
	if (!fCheckBlockIndex) {
	return;
	}

	LOCK(cs_main);

	// During a reindex, we read the genesis block and call CheckBlockIndex
	// before ActivateBestChain, so we have the genesis block in mapBlockIndex
	// but no active chain. (A few of the tests when iterating the block tree
	// require that chainActive has been initialized.)
	if (chainActive.Height() < 0) {
	assert(mapBlockIndex.size() <= 1);
	return;
	}

	// Build forward-pointing map of the entire block tree.
	std::multimap<CBlockIndex , CBlockIndex > forward;
	for (auto &entry : mapBlockIndex) {
	forward.emplace(entry.second->pprev, entry.second);
	}

	assert(forward.size() == mapBlockIndex.size());

	std::pair<std::multimap<CBlockIndex , CBlockIndex >::iterator,
	std::multimap<CBlockIndex , CBlockIndex >::iterator>
	rangeGenesis = forward.equal_range(nullptr);
	CBlockIndex *pindex = rangeGenesis.first->second;
	rangeGenesis.first++;
	// There is only one index entry with parent nullptr.
	assert(rangeGenesis.first == rangeGenesis.second);

	// Iterate over the entire block tree, using depth-first search.
	// Along the way, remember whether there are blocks on the path from genesis
	// block being explored which are the first to have certain properties.
	size_t nNodes = 0;
	int nHeight = 0;
	// Oldest ancestor of pindex which is invalid.
	CBlockIndex *pindexFirstInvalid = nullptr;
	// Oldest ancestor of pindex which is parked.
	CBlockIndex *pindexFirstParked = nullptr;
	// Oldest ancestor of pindex which does not have data available.
	CBlockIndex *pindexFirstMissing = nullptr;
	// Oldest ancestor of pindex for which nTx == 0.
	CBlockIndex *pindexFirstNeverProcessed = nullptr;
	// Oldest ancestor of pindex which does not have BLOCK_VALID_TREE
	// (regardless of being valid or not).
	CBlockIndex *pindexFirstNotTreeValid = nullptr;
	// Oldest ancestor of pindex which does not have BLOCK_VALID_TRANSACTIONS
	// (regardless of being valid or not).
	CBlockIndex *pindexFirstNotTransactionsValid = nullptr;
	// Oldest ancestor of pindex which does not have BLOCK_VALID_CHAIN
	// (regardless of being valid or not).
	CBlockIndex *pindexFirstNotChainValid = nullptr;
	// Oldest ancestor of pindex which does not have BLOCK_VALID_SCRIPTS
	// (regardless of being valid or not).
	CBlockIndex *pindexFirstNotScriptsValid = nullptr;
	while (pindex != nullptr) {
	nNodes++;
	if (pindexFirstInvalid == nullptr && pindex->nStatus.hasFailed()) {
	pindexFirstInvalid = pindex;
	}
	if (pindexFirstParked == nullptr && pindex->nStatus.isParked()) {
	pindexFirstParked = pindex;
	}
	if (pindexFirstMissing == nullptr && !pindex->nStatus.hasData()) {
	pindexFirstMissing = pindex;
	}
	if (pindexFirstNeverProcessed == nullptr && pindex->nTx == 0) {
	pindexFirstNeverProcessed = pindex;
	}
	if (pindex->pprev != nullptr && pindexFirstNotTreeValid == nullptr &&
	pindex->nStatus.getValidity() < BlockValidity::TREE) {
	pindexFirstNotTreeValid = pindex;
	}
	if (pindex->pprev != nullptr &&
	pindexFirstNotTransactionsValid == nullptr &&
	pindex->nStatus.getValidity() < BlockValidity::TRANSACTIONS) {
	pindexFirstNotTransactionsValid = pindex;
	}
	if (pindex->pprev != nullptr && pindexFirstNotChainValid == nullptr &&
	pindex->nStatus.getValidity() < BlockValidity::CHAIN) {
	pindexFirstNotChainValid = pindex;
	}
	if (pindex->pprev != nullptr && pindexFirstNotScriptsValid == nullptr &&
	pindex->nStatus.getValidity() < BlockValidity::SCRIPTS) {
	pindexFirstNotScriptsValid = pindex;
	}

	// Begin: actual consistency checks.
	if (pindex->pprev == nullptr) {
	// Genesis block checks.
	// Genesis block's hash must match.
	assert(pindex->GetBlockHash() == consensusParams.hashGenesisBlock);
	// The current active chain's genesis block must be this block.
	assert(pindex == chainActive.Genesis());
	}
	if (pindex->nChainTx == 0) {
	// nSequenceId can't be set positive for blocks that aren't linked
	// (negative is used for preciousblock)
	assert(pindex->nSequenceId <= 0);
	}
	// VALID_TRANSACTIONS is equivalent to nTx > 0 for all nodes (whether or
	// not pruning has occurred). HAVE_DATA is only equivalent to nTx > 0
	// (or VALID_TRANSACTIONS) if no pruning has occurred.
	if (!fHavePruned) {
	// If we've never pruned, then HAVE_DATA should be equivalent to nTx
	// > 0
	assert(pindex->nStatus.hasData() == (pindex->nTx > 0));
	assert(pindexFirstMissing == pindexFirstNeverProcessed);
	} else if (pindex->nStatus.hasData()) {
	// If we have pruned, then we can only say that HAVE_DATA implies
	// nTx > 0
	assert(pindex->nTx > 0);
	}
	if (pindex->nStatus.hasUndo()) {
	assert(pindex->nStatus.hasData());
	}
	// This is pruning-independent.
	assert((pindex->nStatus.getValidity() >= BlockValidity::TRANSACTIONS) ==
	(pindex->nTx > 0));
	// All parents having had data (at some point) is equivalent to all
	// parents being VALID_TRANSACTIONS, which is equivalent to nChainTx
	// being set.
	// nChainTx != 0 is used to signal that all parent blocks have been
	// processed (but may have been pruned).
	assert((pindexFirstNeverProcessed != nullptr) ==
	(pindex->nChainTx == 0));
	assert((pindexFirstNotTransactionsValid != nullptr) ==
	(pindex->nChainTx == 0));
	// nHeight must be consistent.
	assert(pindex->nHeight == nHeight);
	// For every block except the genesis block, the chainwork must be
	// larger than the parent's.
	assert(pindex->pprev == nullptr \|\|
	pindex->nChainWork >= pindex->pprev->nChainWork);
	// The pskip pointer must point back for all but the first 2 blocks.
	assert(nHeight < 2 \|\|
	(pindex->pskip && (pindex->pskip->nHeight < nHeight)));
	// All mapBlockIndex entries must at least be TREE valid
	assert(pindexFirstNotTreeValid == nullptr);
	if (pindex->nStatus.getValidity() >= BlockValidity::TREE) {
	// TREE valid implies all parents are TREE valid
	assert(pindexFirstNotTreeValid == nullptr);
	}
	if (pindex->nStatus.getValidity() >= BlockValidity::CHAIN) {
	// CHAIN valid implies all parents are CHAIN valid
	assert(pindexFirstNotChainValid == nullptr);
	}
	if (pindex->nStatus.getValidity() >= BlockValidity::SCRIPTS) {
	// SCRIPTS valid implies all parents are SCRIPTS valid
	assert(pindexFirstNotScriptsValid == nullptr);
	}
	if (pindexFirstInvalid == nullptr) {
	// Checks for not-invalid blocks.
	// The failed mask cannot be set for blocks without invalid parents.
	assert(!pindex->nStatus.isInvalid());
	}
	if (pindexFirstParked == nullptr) {
	// Checks for not-invalid blocks.
	// The failed mask cannot be set for blocks without invalid parents.
	assert(!pindex->nStatus.isOnParkedChain());
	}
	if (!CBlockIndexWorkComparator()(pindex, chainActive.Tip()) &&
	pindexFirstNeverProcessed == nullptr) {
	if (pindexFirstInvalid == nullptr) {
	// If this block sorts at least as good as the current tip and
	// is valid and we have all data for its parents, it must be in
	// setBlockIndexCandidates or be parked.
	if (pindexFirstMissing == nullptr) {
	assert(pindex->nStatus.isOnParkedChain() \|\|
	setBlockIndexCandidates.count(pindex));
	}
	// chainActive.Tip() must also be there even if some data has
	// been pruned.
	if (pindex == chainActive.Tip()) {
	assert(setBlockIndexCandidates.count(pindex));
	}
	// If some parent is missing, then it could be that this block
	// was in setBlockIndexCandidates but had to be removed because
	// of the missing data. In this case it must be in
	// mapBlocksUnlinked -- see test below.
	}
	} else {
	// If this block sorts worse than the current tip or some ancestor's
	// block has never been seen, it cannot be in
	// setBlockIndexCandidates.
	assert(setBlockIndexCandidates.count(pindex) == 0);
	}
	// Check whether this block is in mapBlocksUnlinked.
	std::pair<std::multimap<CBlockIndex , CBlockIndex >::iterator,
	std::multimap<CBlockIndex , CBlockIndex >::iterator>
	rangeUnlinked = mapBlocksUnlinked.equal_range(pindex->pprev);
	bool foundInUnlinked = false;
	while (rangeUnlinked.first != rangeUnlinked.second) {
	assert(rangeUnlinked.first->first == pindex->pprev);
	if (rangeUnlinked.first->second == pindex) {
	foundInUnlinked = true;
	break;
	}
	rangeUnlinked.first++;
	}
	if (pindex->pprev && pindex->nStatus.hasData() &&
	pindexFirstNeverProcessed != nullptr &&
	pindexFirstInvalid == nullptr) {
	// If this block has block data available, some parent was never
	// received, and has no invalid parents, it must be in
	// mapBlocksUnlinked.
	assert(foundInUnlinked);
	}
	if (!pindex->nStatus.hasData()) {
	// Can't be in mapBlocksUnlinked if we don't HAVE_DATA
	assert(!foundInUnlinked);
	}
	if (pindexFirstMissing == nullptr) {
	// We aren't missing data for any parent -- cannot be in
	// mapBlocksUnlinked.
	assert(!foundInUnlinked);
	}
	if (pindex->pprev && pindex->nStatus.hasData() &&
	pindexFirstNeverProcessed == nullptr &&
	pindexFirstMissing != nullptr) {
	// We HAVE_DATA for this block, have received data for all parents
	// at some point, but we're currently missing data for some parent.
	// We must have pruned.
	assert(fHavePruned);
	// This block may have entered mapBlocksUnlinked if:
	// - it has a descendant that at some point had more work than the
	// tip, and
	// - we tried switching to that descendant but were missing
	// data for some intermediate block between chainActive and the
	// tip.
	// So if this block is itself better than chainActive.Tip() and it
	// wasn't in
	// setBlockIndexCandidates, then it must be in mapBlocksUnlinked.
	if (!CBlockIndexWorkComparator()(pindex, chainActive.Tip()) &&
	setBlockIndexCandidates.count(pindex) == 0) {
	if (pindexFirstInvalid == nullptr) {
	assert(foundInUnlinked);
	}
	}
	}
	// Perhaps too slow
	// assert(pindex->GetBlockHash() == pindex->GetBlockHeader().GetHash());
	// End: actual consistency checks.

	// Try descending into the first subnode.
	std::pair<std::multimap<CBlockIndex , CBlockIndex >::iterator,
	std::multimap<CBlockIndex , CBlockIndex >::iterator>
	range = forward.equal_range(pindex);
	if (range.first != range.second) {
	// A subnode was found.
	pindex = range.first->second;
	nHeight++;
	continue;
	}
	// This is a leaf node. Move upwards until we reach a node of which we
	// have not yet visited the last child.
	while (pindex) {
	// We are going to either move to a parent or a sibling of pindex.
	// If pindex was the first with a certain property, unset the
	// corresponding variable.
	if (pindex == pindexFirstInvalid) {
	pindexFirstInvalid = nullptr;
	}
	if (pindex == pindexFirstParked) {
	pindexFirstParked = nullptr;
	}
	if (pindex == pindexFirstMissing) {
	pindexFirstMissing = nullptr;
	}
	if (pindex == pindexFirstNeverProcessed) {
	pindexFirstNeverProcessed = nullptr;
	}
	if (pindex == pindexFirstNotTreeValid) {
	pindexFirstNotTreeValid = nullptr;
	}
	if (pindex == pindexFirstNotTransactionsValid) {
	pindexFirstNotTransactionsValid = nullptr;
	}
	if (pindex == pindexFirstNotChainValid) {
	pindexFirstNotChainValid = nullptr;
	}
	if (pindex == pindexFirstNotScriptsValid) {
	pindexFirstNotScriptsValid = nullptr;
	}
	// Find our parent.
	CBlockIndex *pindexPar = pindex->pprev;
	// Find which child we just visited.
	std::pair<std::multimap<CBlockIndex , CBlockIndex >::iterator,
	std::multimap<CBlockIndex , CBlockIndex >::iterator>
	rangePar = forward.equal_range(pindexPar);
	while (rangePar.first->second != pindex) {
	// Our parent must have at least the node we're coming from as
	// child.
	assert(rangePar.first != rangePar.second);
	rangePar.first++;
	}
	// Proceed to the next one.
	rangePar.first++;
	if (rangePar.first != rangePar.second) {
	// Move to the sibling.
	pindex = rangePar.first->second;
	break;
	} else {
	// Move up further.
	pindex = pindexPar;
	nHeight--;
	continue;
	}
	}
	}

	// Check that we actually traversed the entire map.
	assert(nNodes == forward.size());
	}

	std::string CBlockFileInfo::ToString() const {
	return strprintf(
	"CBlockFileInfo(blocks=%u, size=%u, heights=%u...%u, time=%s...%s)",
	nBlocks, nSize, nHeightFirst, nHeightLast,
	FormatISO8601DateTime(nTimeFirst), FormatISO8601DateTime(nTimeLast));
	}

	CBlockFileInfo *GetBlockFileInfo(size_t n) {
	LOCK(cs_LastBlockFile);

	return &vinfoBlockFile.at(n);
	}

	static const uint64_t MEMPOOL_DUMP_VERSION = 1;

	bool LoadMempool(const Config &config) {
	int64_t nExpiryTimeout =
	gArgs.GetArg("-mempoolexpiry", DEFAULT_MEMPOOL_EXPIRY) * 60 * 60;
	FILE *filestr = fsbridge::fopen(GetDataDir() / "mempool.dat", "rb");
	CAutoFile file(filestr, SER_DISK, CLIENT_VERSION);
	if (file.IsNull()) {
	LogPrintf(
	"Failed to open mempool file from disk. Continuing anyway.\n");
	return false;
	}

	int64_t count = 0;
	int64_t skipped = 0;
	int64_t failed = 0;
	int64_t nNow = GetTime();

	try {
	uint64_t version;
	file >> version;
	if (version != MEMPOOL_DUMP_VERSION) {
	return false;
	}

	uint64_t num;
	file >> num;
	double prioritydummy = 0;
	while (num--) {
	CTransactionRef tx;
	int64_t nTime;
	int64_t nFeeDelta;
	file >> tx;
	file >> nTime;
	file >> nFeeDelta;

	Amount amountdelta = nFeeDelta * SATOSHI;
	if (amountdelta != Amount::zero()) {
	g_mempool.PrioritiseTransaction(tx->GetId(), prioritydummy,
	amountdelta);
	}
	CValidationState state;
	if (nTime + nExpiryTimeout > nNow) {
	LOCK(cs_main);
	AcceptToMemoryPoolWithTime(
	config, g_mempool, state, tx, true /* fLimitFree */,
	nullptr /* pfMissingInputs */, nTime,
	false /* fOverrideMempoolLimit */,
	Amount::zero() /* nAbsurdFee /, false / test_accept */);
	if (state.IsValid()) {
	++count;
	} else {
	++failed;
	}
	} else {
	++skipped;
	}

	if (ShutdownRequested()) {
	return false;
	}
	}
	std::map<uint256, Amount> mapDeltas;
	file >> mapDeltas;

	for (const auto &i : mapDeltas) {
	g_mempool.PrioritiseTransaction(i.first, prioritydummy, i.second);
	}
	} catch (const std::exception &e) {
	LogPrintf("Failed to deserialize mempool data on disk: %s. Continuing "
	"anyway.\n",
	e.what());
	return false;
	}

	LogPrintf("Imported mempool transactions from disk: %i successes, %i "
	"failed, %i expired\n",
	count, failed, skipped);
	return true;
	}

	bool DumpMempool() {
	int64_t start = GetTimeMicros();

	std::map<uint256, Amount> mapDeltas;
	std::vector<TxMempoolInfo> vinfo;

	static Mutex dump_mutex;
	LOCK(dump_mutex);

	{
	LOCK(g_mempool.cs);
	for (const auto &i : g_mempool.mapDeltas) {
	mapDeltas[i.first] = i.second.second;
	}

	vinfo = g_mempool.infoAll();
	}

	int64_t mid = GetTimeMicros();

	try {
	FILE *filestr = fsbridge::fopen(GetDataDir() / "mempool.dat.new", "wb");
	if (!filestr) {
	return false;
	}

	CAutoFile file(filestr, SER_DISK, CLIENT_VERSION);

	uint64_t version = MEMPOOL_DUMP_VERSION;
	file << version;

	file << uint64_t(vinfo.size());
	for (const auto &i : vinfo) {
	file << *(i.tx);
	file << int64_t(i.nTime);
	file << i.nFeeDelta;
	mapDeltas.erase(i.tx->GetId());
	}

	file << mapDeltas;
	if (!FileCommit(file.Get())) {
	throw std::runtime_error("FileCommit failed");
	}
	file.fclose();
	RenameOver(GetDataDir() / "mempool.dat.new",
	GetDataDir() / "mempool.dat");
	int64_t last = GetTimeMicros();
	LogPrintf("Dumped mempool: %gs to copy, %gs to dump\n",
	(mid - start) * MICRO, (last - mid) * MICRO);
	} catch (const std::exception &e) {
	LogPrintf("Failed to dump mempool: %s. Continuing anyway.\n", e.what());
	return false;
	}
	return true;
	}

	//! Guess how far we are in the verification process at the given block index
	//! require cs_main if pindex has not been validated yet (because nChainTx might
	//! be unset)
	double GuessVerificationProgress(const ChainTxData &data,
	const CBlockIndex *pindex) {
	if (pindex == nullptr) {
	return 0.0;
	}

	// This function assumes the lock on cs_main is already held (see the
	// above comment). This is a temporary check until PR15997 is backported.
	// https://github.com/bitcoin/bitcoin/pull/15997
	AssertLockHeld(cs_main);

	int64_t nNow = time(nullptr);

	double fTxTotal;
	if (pindex->nChainTx <= data.nTxCount) {
	fTxTotal = data.nTxCount + (nNow - data.nTime) * data.dTxRate;
	} else {
	fTxTotal =
	pindex->nChainTx + (nNow - pindex->GetBlockTime()) * data.dTxRate;
	}

	return pindex->nChainTx / fTxTotal;
	}

	class CMainCleanup {
	public:
	CMainCleanup() {}
	~CMainCleanup() {
	// block headers
	for (const std::pair<const uint256, CBlockIndex *> &it :
	mapBlockIndex) {
	delete it.second;
	}
	mapBlockIndex.clear();
	}
	} instance_of_cmaincleanup;
	diff --git a/test/functional/rpc_blockchain.py b/test/functional/rpc_blockchain.py
	index 2e03dce65d..917dac4a86 100755
	--- a/test/functional/rpc_blockchain.py
	+++ b/test/functional/rpc_blockchain.py
	@@ -1,298 +1,354 @@
	#!/usr/bin/env python3
	# Copyright (c) 2014-2016 The Bitcoin Core developers
	# Distributed under the MIT software license, see the accompanying
	# file COPYING or http://www.opensource.org/licenses/mit-license.php.

	"""Test RPCs related to blockchainstate.

	Test the following RPCs:
	- getblockchaininfo
	- gettxoutsetinfo
	- getdifficulty
	- getbestblockhash
	- getblockhash
	- getblockheader
	- getchaintxstats
	- getnetworkhashps
	- verifychain

	Tests correspond to code in rpc/blockchain.cpp.
	"""

	from decimal import Decimal
	import http.client
	import subprocess

	from test_framework.test_framework import BitcoinTestFramework
	from test_framework.util import (
	assert_equal,
	assert_greater_than,
	assert_greater_than_or_equal,
	assert_raises,
	assert_raises_rpc_error,
	assert_is_hash_string,
	assert_is_hex_string,
	)
	+from test_framework.blocktools import (
	+ create_block,
	+ create_coinbase,
	+)
	+from test_framework.messages import (
	+ msg_block,
	+)
	+from test_framework.mininode import (
	+ P2PInterface,
	+ network_thread_start,
	+)


	class BlockchainTest(BitcoinTestFramework):

	def set_test_params(self):
	self.num_nodes = 1
	self.extra_args = [['-stopatheight=207', '-prune=1']]

	def run_test(self):
	self._test_getblockchaininfo()
	self._test_getchaintxstats()
	self._test_gettxoutsetinfo()
	self._test_getblockheader()
	self._test_getdifficulty()
	self._test_getnetworkhashps()
	self._test_stopatheight()
	self._test_getblock()
	+ self._test_waitforblockheight()
	assert self.nodes[0].verifychain(4, 0)

	def _test_getblockchaininfo(self):
	self.log.info("Test getblockchaininfo")

	keys = [
	'bestblockhash',
	'blocks',
	'chain',
	'chainwork',
	'difficulty',
	'headers',
	'initialblockdownload',
	'mediantime',
	'pruned',
	'size_on_disk',
	'verificationprogress',
	'warnings',
	]
	res = self.nodes[0].getblockchaininfo()

	# result should have these additional pruning keys if manual pruning is
	# enabled
	assert_equal(sorted(res.keys()), sorted(
	['pruneheight', 'automatic_pruning'] + keys))

	# size_on_disk should be > 0
	assert_greater_than(res['size_on_disk'], 0)

	# pruneheight should be greater or equal to 0
	assert_greater_than_or_equal(res['pruneheight'], 0)

	# check other pruning fields given that prune=1
	assert res['pruned']
	assert not res['automatic_pruning']

	self.restart_node(0, ['-stopatheight=207'])
	res = self.nodes[0].getblockchaininfo()
	# should have exact keys
	assert_equal(sorted(res.keys()), keys)

	self.restart_node(0, ['-stopatheight=207', '-prune=550'])
	res = self.nodes[0].getblockchaininfo()
	# result should have these additional pruning keys if prune=550
	assert_equal(sorted(res.keys()), sorted(
	['pruneheight', 'automatic_pruning', 'prune_target_size'] + keys))

	# check related fields
	assert res['pruned']
	assert_equal(res['pruneheight'], 0)
	assert res['automatic_pruning']
	assert_equal(res['prune_target_size'], 576716800)
	assert_greater_than(res['size_on_disk'], 0)

	def _test_getchaintxstats(self):
	self.log.info("Test getchaintxstats")

	# Test `getchaintxstats` invalid extra parameters
	assert_raises_rpc_error(
	-1, 'getchaintxstats', self.nodes[0].getchaintxstats, 0, '', 0)

	# Test `getchaintxstats` invalid `nblocks`
	assert_raises_rpc_error(
	-1, "JSON value is not an integer as expected", self.nodes[0].getchaintxstats, '')
	assert_raises_rpc_error(
	-8, "Invalid block count: should be between 0 and the block's height - 1", self.nodes[0].getchaintxstats, -1)
	assert_raises_rpc_error(-8, "Invalid block count: should be between 0 and the block's height - 1", self.nodes[
	0].getchaintxstats, self.nodes[0].getblockcount())

	# Test `getchaintxstats` invalid `blockhash`
	assert_raises_rpc_error(
	-1, "JSON value is not a string as expected", self.nodes[0].getchaintxstats, blockhash=0)
	assert_raises_rpc_error(
	-5, "Block not found", self.nodes[0].getchaintxstats, blockhash='0')
	blockhash = self.nodes[0].getblockhash(200)
	self.nodes[0].invalidateblock(blockhash)
	assert_raises_rpc_error(
	-8, "Block is not in main chain", self.nodes[0].getchaintxstats, blockhash=blockhash)
	self.nodes[0].reconsiderblock(blockhash)

	chaintxstats = self.nodes[0].getchaintxstats(1)
	# 200 txs plus genesis tx
	assert_equal(chaintxstats['txcount'], 201)
	# tx rate should be 1 per 10 minutes, or 1/600
	# we have to round because of binary math
	assert_equal(round(chaintxstats['txrate'] * 600, 10), Decimal(1))

	b1_hash = self.nodes[0].getblockhash(1)
	b1 = self.nodes[0].getblock(b1_hash)
	b200_hash = self.nodes[0].getblockhash(200)
	b200 = self.nodes[0].getblock(b200_hash)
	time_diff = b200['mediantime'] - b1['mediantime']

	chaintxstats = self.nodes[0].getchaintxstats()
	assert_equal(chaintxstats['time'], b200['time'])
	assert_equal(chaintxstats['txcount'], 201)
	assert_equal(chaintxstats['window_final_block_hash'], b200_hash)
	assert_equal(chaintxstats['window_block_count'], 199)
	assert_equal(chaintxstats['window_tx_count'], 199)
	assert_equal(chaintxstats['window_interval'], time_diff)
	assert_equal(
	round(chaintxstats['txrate'] * time_diff, 10), Decimal(199))

	chaintxstats = self.nodes[0].getchaintxstats(blockhash=b1_hash)
	assert_equal(chaintxstats['time'], b1['time'])
	assert_equal(chaintxstats['txcount'], 2)
	assert_equal(chaintxstats['window_final_block_hash'], b1_hash)
	assert_equal(chaintxstats['window_block_count'], 0)
	assert('window_tx_count' not in chaintxstats)
	assert('window_interval' not in chaintxstats)
	assert('txrate' not in chaintxstats)

	def _test_gettxoutsetinfo(self):
	node = self.nodes[0]
	res = node.gettxoutsetinfo()

	assert_equal(res['total_amount'], Decimal('8725.00000000'))
	assert_equal(res['transactions'], 200)
	assert_equal(res['height'], 200)
	assert_equal(res['txouts'], 200)
	assert_equal(res['bogosize'], 17000),
	assert_equal(res['bestblock'], node.getblockhash(200))
	size = res['disk_size']
	assert size > 6400
	assert size < 64000
	assert_equal(len(res['bestblock']), 64)
	assert_equal(len(res['hash_serialized']), 64)

	self.log.info(
	"Test that gettxoutsetinfo() works for blockchain with just the genesis block")
	b1hash = node.getblockhash(1)
	node.invalidateblock(b1hash)

	res2 = node.gettxoutsetinfo()
	assert_equal(res2['transactions'], 0)
	assert_equal(res2['total_amount'], Decimal('0'))
	assert_equal(res2['height'], 0)
	assert_equal(res2['txouts'], 0)
	assert_equal(res2['bogosize'], 0),
	assert_equal(res2['bestblock'], node.getblockhash(0))
	assert_equal(len(res2['hash_serialized']), 64)

	self.log.info(
	"Test that gettxoutsetinfo() returns the same result after invalidate/reconsider block")
	node.reconsiderblock(b1hash)

	res3 = node.gettxoutsetinfo()
	assert_equal(res['total_amount'], res3['total_amount'])
	assert_equal(res['transactions'], res3['transactions'])
	assert_equal(res['height'], res3['height'])
	assert_equal(res['txouts'], res3['txouts'])
	assert_equal(res['bogosize'], res3['bogosize'])
	assert_equal(res['bestblock'], res3['bestblock'])
	assert_equal(res['hash_serialized'], res3['hash_serialized'])

	def _test_getblockheader(self):
	node = self.nodes[0]

	assert_raises_rpc_error(-5, "Block not found",
	node.getblockheader, "nonsense")

	besthash = node.getbestblockhash()
	secondbesthash = node.getblockhash(199)
	header = node.getblockheader(besthash)

	assert_equal(header['hash'], besthash)
	assert_equal(header['height'], 200)
	assert_equal(header['confirmations'], 1)
	assert_equal(header['previousblockhash'], secondbesthash)
	assert_is_hex_string(header['chainwork'])
	assert_is_hash_string(header['hash'])
	assert_is_hash_string(header['previousblockhash'])
	assert_is_hash_string(header['merkleroot'])
	assert_is_hash_string(header['bits'], length=None)
	assert isinstance(header['time'], int)
	assert isinstance(header['mediantime'], int)
	assert isinstance(header['nonce'], int)
	assert isinstance(header['version'], int)
	assert isinstance(int(header['versionHex'], 16), int)
	assert isinstance(header['difficulty'], Decimal)

	def _test_getdifficulty(self):
	difficulty = self.nodes[0].getdifficulty()
	# 1 hash in 2 should be valid, so difficulty should be 1/2**31
	# binary => decimal => binary math is why we do this check
	assert abs(difficulty * 2**31 - 1) < 0.0001

	def _test_getnetworkhashps(self):
	hashes_per_second = self.nodes[0].getnetworkhashps()
	# This should be 2 hashes every 10 minutes or 1/300
	assert abs(hashes_per_second * 300 - 1) < 0.0001

	def _test_stopatheight(self):
	assert_equal(self.nodes[0].getblockcount(), 200)
	self.nodes[0].generate(6)
	assert_equal(self.nodes[0].getblockcount(), 206)
	self.log.debug('Node should not stop at this height')
	assert_raises(subprocess.TimeoutExpired,
	lambda: self.nodes[0].process.wait(timeout=3))
	try:
	self.nodes[0].generate(1)
	except (ConnectionError, http.client.BadStatusLine):
	pass # The node already shut down before response
	self.log.debug('Node should stop at this height...')
	self.nodes[0].wait_until_stopped()
	self.start_node(0)
	assert_equal(self.nodes[0].getblockcount(), 207)

	def _test_getblock(self):
	# Checks for getblock verbose outputs
	node = self.nodes[0]
	getblockinfo = node.getblock(node.getblockhash(1), 2)
	gettransactioninfo = node.gettransaction(getblockinfo['tx'][0]['txid'])
	getblockheaderinfo = node.getblockheader(node.getblockhash(1), True)

	assert_equal(getblockinfo['hash'], gettransactioninfo['blockhash'])
	assert_equal(
	getblockinfo['confirmations'], gettransactioninfo['confirmations'])
	assert_equal(getblockinfo['height'], getblockheaderinfo['height'])
	assert_equal(
	getblockinfo['versionHex'], getblockheaderinfo['versionHex'])
	assert_equal(getblockinfo['version'], getblockheaderinfo['version'])
	assert_equal(getblockinfo['size'], 188)
	assert_equal(
	getblockinfo['merkleroot'], getblockheaderinfo['merkleroot'])
	# Verify transaction data by check the hex values
	for tx in getblockinfo['tx']:
	getrawtransaction = node.getrawtransaction(tx['txid'], True)
	assert_equal(tx['hex'], getrawtransaction['hex'])
	assert_equal(getblockinfo['time'], getblockheaderinfo['time'])
	assert_equal(
	getblockinfo['mediantime'], getblockheaderinfo['mediantime'])
	assert_equal(getblockinfo['nonce'], getblockheaderinfo['nonce'])
	assert_equal(getblockinfo['bits'], getblockheaderinfo['bits'])
	assert_equal(
	getblockinfo['difficulty'], getblockheaderinfo['difficulty'])
	assert_equal(
	getblockinfo['chainwork'], getblockheaderinfo['chainwork'])
	assert_equal(
	getblockinfo['previousblockhash'], getblockheaderinfo['previousblockhash'])
	assert_equal(
	getblockinfo['nextblockhash'], getblockheaderinfo['nextblockhash'])

	+ def _test_waitforblockheight(self):
	+ self.log.info("Test waitforblockheight")
	+
	+ node = self.nodes[0]
	+
	+ # Start a P2P connection since we'll need to create some blocks.
	+ node.add_p2p_connection(P2PInterface())
	+ network_thread_start()
	+ node.p2p.wait_for_verack()
	+
	+ current_height = node.getblock(node.getbestblockhash())['height']
	+
	+ # Create a fork somewhere below our current height, invalidate the tip
	+ # of that fork, and then ensure that waitforblockheight still
	+ # works as expected.
	+ #
	+ # (Previously this was broken based on setting
	+ # `rpc/blockchain.cpp:latestblock` incorrectly.)
	+ #
	+ b20hash = node.getblockhash(20)
	+ b20 = node.getblock(b20hash)
	+
	+ def solve_and_send_block(prevhash, height, time):
	+ b = create_block(prevhash, create_coinbase(height), time)
	+ b.solve()
	+ node.p2p.send_message(msg_block(b))
	+ node.p2p.sync_with_ping()
	+ return b
	+
	+ b21f = solve_and_send_block(int(b20hash, 16), 21, b20['time'] + 1)
	+ b22f = solve_and_send_block(b21f.sha256, 22, b21f.nTime + 1)
	+
	+ node.invalidateblock(b22f.hash)
	+
	+ def assert_waitforheight(height, timeout=2):
	+ assert_equal(
	+ node.waitforblockheight(height, timeout)['height'],
	+ current_height)
	+
	+ assert_waitforheight(0)
	+ assert_waitforheight(current_height - 1)
	+ assert_waitforheight(current_height)
	+ assert_waitforheight(current_height + 1)
	+

	if __name__ == '__main__':
	BlockchainTest().main()

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