aboutsummaryrefslogtreecommitdiff
path: root/src/validation.h
blob: 7df3801f653747a45a2776e50c5efccb5adfa18e (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2009-2019 The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.

#ifndef BITCOIN_VALIDATION_H
#define BITCOIN_VALIDATION_H

#if defined(HAVE_CONFIG_H)
#include <config/bitcoin-config.h>
#endif

#include <amount.h>
#include <coins.h>
#include <crypto/common.h> // for ReadLE64
#include <fs.h>
#include <policy/feerate.h>
#include <protocol.h> // For CMessageHeader::MessageStartChars
#include <script/script_error.h>
#include <sync.h>
#include <txmempool.h> // For CTxMemPool::cs
#include <txdb.h>
#include <versionbits.h>
#include <serialize.h>

#include <atomic>
#include <map>
#include <memory>
#include <set>
#include <stdint.h>
#include <utility>
#include <vector>

class CChainState;
class BlockValidationState;
class CBlockIndex;
class CBlockTreeDB;
class CBlockUndo;
class CChainParams;
class CInv;
class CConnman;
class CScriptCheck;
class CBlockPolicyEstimator;
class CTxMemPool;
class TxValidationState;
struct ChainTxData;

struct DisconnectedBlockTransactions;
struct PrecomputedTransactionData;
struct LockPoints;

/** Default for -minrelaytxfee, minimum relay fee for transactions */
static const unsigned int DEFAULT_MIN_RELAY_TX_FEE = 1000;
/** Default for -limitancestorcount, max number of in-mempool ancestors */
static const unsigned int DEFAULT_ANCESTOR_LIMIT = 25;
/** Default for -limitancestorsize, maximum kilobytes of tx + all in-mempool ancestors */
static const unsigned int DEFAULT_ANCESTOR_SIZE_LIMIT = 101;
/** Default for -limitdescendantcount, max number of in-mempool descendants */
static const unsigned int DEFAULT_DESCENDANT_LIMIT = 25;
/** Default for -limitdescendantsize, maximum kilobytes of in-mempool descendants */
static const unsigned int DEFAULT_DESCENDANT_SIZE_LIMIT = 101;
/**
 * An extra transaction can be added to a package, as long as it only has one
 * ancestor and is no larger than this. Not really any reason to make this
 * configurable as it doesn't materially change DoS parameters.
 */
static const unsigned int EXTRA_DESCENDANT_TX_SIZE_LIMIT = 10000;
/** Default for -mempoolexpiry, expiration time for mempool transactions in hours */
static const unsigned int DEFAULT_MEMPOOL_EXPIRY = 336;
/** Maximum kilobytes for transactions to store for processing during reorg */
static const unsigned int MAX_DISCONNECTED_TX_POOL_SIZE = 20000;
/** The maximum size of a blk?????.dat file (since 0.8) */
static const unsigned int MAX_BLOCKFILE_SIZE = 0x8000000; // 128 MiB
/** The pre-allocation chunk size for blk?????.dat files (since 0.8) */
static const unsigned int BLOCKFILE_CHUNK_SIZE = 0x1000000; // 16 MiB
/** The pre-allocation chunk size for rev?????.dat files (since 0.8) */
static const unsigned int UNDOFILE_CHUNK_SIZE = 0x100000; // 1 MiB

/** Maximum number of dedicated script-checking threads allowed */
static const int MAX_SCRIPTCHECK_THREADS = 15;
/** -par default (number of script-checking threads, 0 = auto) */
static const int DEFAULT_SCRIPTCHECK_THREADS = 0;
/** Number of blocks that can be requested at any given time from a single peer. */
static const int MAX_BLOCKS_IN_TRANSIT_PER_PEER = 16;
/** Timeout in seconds during which a peer must stall block download progress before being disconnected. */
static const unsigned int BLOCK_STALLING_TIMEOUT = 2;
/** Number of headers sent in one getheaders result. We rely on the assumption that if a peer sends
 *  less than this number, we reached its tip. Changing this value is a protocol upgrade. */
static const unsigned int MAX_HEADERS_RESULTS = 2000;
/** Maximum depth of blocks we're willing to serve as compact blocks to peers
 *  when requested. For older blocks, a regular BLOCK response will be sent. */
static const int MAX_CMPCTBLOCK_DEPTH = 5;
/** Maximum depth of blocks we're willing to respond to GETBLOCKTXN requests for. */
static const int MAX_BLOCKTXN_DEPTH = 10;
/** Size of the "block download window": how far ahead of our current height do we fetch?
 *  Larger windows tolerate larger download speed differences between peer, but increase the potential
 *  degree of disordering of blocks on disk (which make reindexing and pruning harder). We'll probably
 *  want to make this a per-peer adaptive value at some point. */
static const unsigned int BLOCK_DOWNLOAD_WINDOW = 1024;
/** Time to wait (in seconds) between writing blocks/block index to disk. */
static const unsigned int DATABASE_WRITE_INTERVAL = 60 * 60;
/** Time to wait (in seconds) between flushing chainstate to disk. */
static const unsigned int DATABASE_FLUSH_INTERVAL = 24 * 60 * 60;
/** Block download timeout base, expressed in millionths of the block interval (i.e. 10 min) */
static const int64_t BLOCK_DOWNLOAD_TIMEOUT_BASE = 1000000;
/** Additional block download timeout per parallel downloading peer (i.e. 5 min) */
static const int64_t BLOCK_DOWNLOAD_TIMEOUT_PER_PEER = 500000;

static const int64_t DEFAULT_MAX_TIP_AGE = 24 * 60 * 60;
/** Maximum age of our tip in seconds for us to be considered current for fee estimation */
static const int64_t MAX_FEE_ESTIMATION_TIP_AGE = 3 * 60 * 60;

static const bool DEFAULT_CHECKPOINTS_ENABLED = true;
static const bool DEFAULT_TXINDEX = false;
static const char* const DEFAULT_BLOCKFILTERINDEX = "0";
static const unsigned int DEFAULT_BANSCORE_THRESHOLD = 100;
/** Default for -persistmempool */
static const bool DEFAULT_PERSIST_MEMPOOL = true;
/** Default for using fee filter */
static const bool DEFAULT_FEEFILTER = true;

/** Maximum number of headers to announce when relaying blocks with headers message.*/
static const unsigned int MAX_BLOCKS_TO_ANNOUNCE = 8;

/** Maximum number of unconnecting headers announcements before DoS score */
static const int MAX_UNCONNECTING_HEADERS = 10;

/** Default for -stopatheight */
static const int DEFAULT_STOPATHEIGHT = 0;

struct BlockHasher
{
    // this used to call `GetCheapHash()` in uint256, which was later moved; the
    // cheap hash function simply calls ReadLE64() however, so the end result is
    // identical
    size_t operator()(const uint256& hash) const { return ReadLE64(hash.begin()); }
};

extern RecursiveMutex cs_main;
extern CBlockPolicyEstimator feeEstimator;
extern CTxMemPool mempool;
typedef std::unordered_map<uint256, CBlockIndex*, BlockHasher> BlockMap;
extern Mutex g_best_block_mutex;
extern std::condition_variable g_best_block_cv;
extern uint256 g_best_block;
extern std::atomic_bool fImporting;
extern std::atomic_bool fReindex;
/** Whether there are dedicated script-checking threads running.
 * False indicates all script checking is done on the main threadMessageHandler thread.
 */
extern bool g_parallel_script_checks;
extern bool fRequireStandard;
extern bool fCheckBlockIndex;
extern bool fCheckpointsEnabled;
extern size_t nCoinCacheUsage;
/** A fee rate smaller than this is considered zero fee (for relaying, mining and transaction creation) */
extern CFeeRate minRelayTxFee;
/** If the tip is older than this (in seconds), the node is considered to be in initial block download. */
extern int64_t nMaxTipAge;

/** Block hash whose ancestors we will assume to have valid scripts without checking them. */
extern uint256 hashAssumeValid;

/** Minimum work we will assume exists on some valid chain. */
extern arith_uint256 nMinimumChainWork;

/** Best header we've seen so far (used for getheaders queries' starting points). */
extern CBlockIndex *pindexBestHeader;

/** Pruning-related variables and constants */
/** True if any block files have ever been pruned. */
extern bool fHavePruned;
/** True if we're running in -prune mode. */
extern bool fPruneMode;
/** Number of MiB of block files that we're trying to stay below. */
extern uint64_t nPruneTarget;
/** Block files containing a block-height within MIN_BLOCKS_TO_KEEP of ::ChainActive().Tip() will not be pruned. */
static const unsigned int MIN_BLOCKS_TO_KEEP = 288;
/** Minimum blocks required to signal NODE_NETWORK_LIMITED */
static const unsigned int NODE_NETWORK_LIMITED_MIN_BLOCKS = 288;

static const signed int DEFAULT_CHECKBLOCKS = 6;
static const unsigned int DEFAULT_CHECKLEVEL = 3;

// Require that user allocate at least 550 MiB for block & undo files (blk???.dat and rev???.dat)
// At 1MB per block, 288 blocks = 288MB.
// Add 15% for Undo data = 331MB
// Add 20% for Orphan block rate = 397MB
// We want the low water mark after pruning to be at least 397 MB and since we prune in
// full block file chunks, we need the high water mark which triggers the prune to be
// one 128MB block file + added 15% undo data = 147MB greater for a total of 545MB
// Setting the target to >= 550 MiB will make it likely we can respect the target.
static const uint64_t MIN_DISK_SPACE_FOR_BLOCK_FILES = 550 * 1024 * 1024;

/**
 * Process an incoming block. This only returns after the best known valid
 * block is made active. Note that it does not, however, guarantee that the
 * specific block passed to it has been checked for validity!
 *
 * If you want to *possibly* get feedback on whether pblock is valid, you must
 * install a CValidationInterface (see validationinterface.h) - this will have
 * its BlockChecked method called whenever *any* block completes validation.
 *
 * Note that we guarantee that either the proof-of-work is valid on pblock, or
 * (and possibly also) BlockChecked will have been called.
 *
 * May not be called in a
 * validationinterface callback.
 *
 * @param[in]   pblock  The block we want to process.
 * @param[in]   fForceProcessing Process this block even if unrequested; used for non-network block sources and whitelisted peers.
 * @param[out]  fNewBlock A boolean which is set to indicate if the block was first received via this call
 * @returns     If the block was processed, independently of block validity
 */
bool ProcessNewBlock(const CChainParams& chainparams, const std::shared_ptr<const CBlock> pblock, bool fForceProcessing, bool* fNewBlock) LOCKS_EXCLUDED(cs_main);

/**
 * Process incoming block headers.
 *
 * May not be called in a
 * validationinterface callback.
 *
 * @param[in]  block The block headers themselves
 * @param[out] state This may be set to an Error state if any error occurred processing them
 * @param[in]  chainparams The params for the chain we want to connect to
 * @param[out] ppindex If set, the pointer will be set to point to the last new block index object for the given headers
 */
bool ProcessNewBlockHeaders(const std::vector<CBlockHeader>& block, BlockValidationState& state, const CChainParams& chainparams, const CBlockIndex** ppindex = nullptr) LOCKS_EXCLUDED(cs_main);

/** Open a block file (blk?????.dat) */
FILE* OpenBlockFile(const FlatFilePos &pos, bool fReadOnly = false);
/** Translation to a filesystem path */
fs::path GetBlockPosFilename(const FlatFilePos &pos);
/** Import blocks from an external file */
bool LoadExternalBlockFile(const CChainParams& chainparams, FILE* fileIn, FlatFilePos *dbp = nullptr);
/** Ensures we have a genesis block in the block tree, possibly writing one to disk. */
bool LoadGenesisBlock(const CChainParams& chainparams);
/** Load the block tree and coins database from disk,
 * initializing state if we're running with -reindex. */
bool LoadBlockIndex(const CChainParams& chainparams) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
/** Unload database information */
void UnloadBlockIndex();
/** Run an instance of the script checking thread */
void ThreadScriptCheck(int worker_num);
/** Retrieve a transaction (from memory pool, or from disk, if possible) */
bool GetTransaction(const uint256& hash, CTransactionRef& tx, const Consensus::Params& params, uint256& hashBlock, const CBlockIndex* const blockIndex = nullptr);
/**
 * Find the best known block, and make it the tip of the block chain
 *
 * May not be called with cs_main held. May not be called in a
 * validationinterface callback.
 */
bool ActivateBestChain(BlockValidationState& state, const CChainParams& chainparams, std::shared_ptr<const CBlock> pblock = std::shared_ptr<const CBlock>());
CAmount GetBlockSubsidy(int nHeight, const Consensus::Params& consensusParams);

/** Guess verification progress (as a fraction between 0.0=genesis and 1.0=current tip). */
double GuessVerificationProgress(const ChainTxData& data, const CBlockIndex* pindex);

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

/**
 *  Mark one block file as pruned.
 */
void PruneOneBlockFile(const int fileNumber) EXCLUSIVE_LOCKS_REQUIRED(cs_main);

/**
 *  Actually unlink the specified files
 */
void UnlinkPrunedFiles(const std::set<int>& setFilesToPrune);

/** Prune block files up to a given height */
void PruneBlockFilesManual(int nManualPruneHeight);

/** (try to) add transaction to memory pool
 * plTxnReplaced will be appended to with all transactions replaced from mempool **/
bool AcceptToMemoryPool(CTxMemPool& pool, TxValidationState &state, const CTransactionRef &tx,
                        std::list<CTransactionRef>* plTxnReplaced,
                        bool bypass_limits, const CAmount nAbsurdFee, bool test_accept=false) EXCLUSIVE_LOCKS_REQUIRED(cs_main);

/** Get the BIP9 state for a given deployment at the current tip. */
ThresholdState VersionBitsTipState(const Consensus::Params& params, Consensus::DeploymentPos pos);

/** Get the numerical statistics for the BIP9 state for a given deployment at the current tip. */
BIP9Stats VersionBitsTipStatistics(const Consensus::Params& params, Consensus::DeploymentPos pos);

/** Get the block height at which the BIP9 deployment switched into the state for the block building on the current tip. */
int VersionBitsTipStateSinceHeight(const Consensus::Params& params, Consensus::DeploymentPos pos);


/** Apply the effects of this transaction on the UTXO set represented by view */
void UpdateCoins(const CTransaction& tx, CCoinsViewCache& inputs, int nHeight);

/** Transaction validation functions */

/**
 * Check if transaction will be final in the next block to be created.
 *
 * Calls IsFinalTx() with current block height and appropriate block time.
 *
 * See consensus/consensus.h for flag definitions.
 */
bool CheckFinalTx(const CTransaction &tx, int flags = -1) EXCLUSIVE_LOCKS_REQUIRED(cs_main);

/**
 * Test whether the LockPoints height and time are still valid on the current chain
 */
bool TestLockPointValidity(const LockPoints* lp) EXCLUSIVE_LOCKS_REQUIRED(cs_main);

/**
 * Check if transaction will be BIP 68 final in the next block to be created.
 *
 * Simulates calling SequenceLocks() with data from the tip of the current active chain.
 * Optionally stores in LockPoints the resulting height and time calculated and the hash
 * of the block needed for calculation or skips the calculation and uses the LockPoints
 * passed in for evaluation.
 * The LockPoints should not be considered valid if CheckSequenceLocks returns false.
 *
 * See consensus/consensus.h for flag definitions.
 */
bool CheckSequenceLocks(const CTxMemPool& pool, const CTransaction& tx, int flags, LockPoints* lp = nullptr, bool useExistingLockPoints = false) EXCLUSIVE_LOCKS_REQUIRED(cs_main);

/**
 * Closure representing one script verification
 * Note that this stores references to the spending transaction
 */
class CScriptCheck
{
private:
    CTxOut m_tx_out;
    const CTransaction *ptxTo;
    unsigned int nIn;
    unsigned int nFlags;
    bool cacheStore;
    ScriptError error;
    PrecomputedTransactionData *txdata;

public:
    CScriptCheck(): ptxTo(nullptr), nIn(0), nFlags(0), cacheStore(false), error(SCRIPT_ERR_UNKNOWN_ERROR) {}
    CScriptCheck(const CTxOut& outIn, const CTransaction& txToIn, unsigned int nInIn, unsigned int nFlagsIn, bool cacheIn, PrecomputedTransactionData* txdataIn) :
        m_tx_out(outIn), ptxTo(&txToIn), nIn(nInIn), nFlags(nFlagsIn), cacheStore(cacheIn), error(SCRIPT_ERR_UNKNOWN_ERROR), txdata(txdataIn) { }

    bool operator()();

    void swap(CScriptCheck &check) {
        std::swap(ptxTo, check.ptxTo);
        std::swap(m_tx_out, check.m_tx_out);
        std::swap(nIn, check.nIn);
        std::swap(nFlags, check.nFlags);
        std::swap(cacheStore, check.cacheStore);
        std::swap(error, check.error);
        std::swap(txdata, check.txdata);
    }

    ScriptError GetScriptError() const { return error; }
};

/** Initializes the script-execution cache */
void InitScriptExecutionCache();


/** Functions for disk access for blocks */
bool ReadBlockFromDisk(CBlock& block, const FlatFilePos& pos, const Consensus::Params& consensusParams);
bool ReadBlockFromDisk(CBlock& block, const CBlockIndex* pindex, const Consensus::Params& consensusParams);
bool ReadRawBlockFromDisk(std::vector<uint8_t>& block, const FlatFilePos& pos, const CMessageHeader::MessageStartChars& message_start);
bool ReadRawBlockFromDisk(std::vector<uint8_t>& block, const CBlockIndex* pindex, const CMessageHeader::MessageStartChars& message_start);

bool UndoReadFromDisk(CBlockUndo& blockundo, const CBlockIndex* pindex);

/** Functions for validating blocks and updating the block tree */

/** Context-independent validity checks */
bool CheckBlock(const CBlock& block, BlockValidationState& state, const Consensus::Params& consensusParams, bool fCheckPOW = true, bool fCheckMerkleRoot = true);

/** Check a block is completely valid from start to finish (only works on top of our current best block) */
bool TestBlockValidity(BlockValidationState& state, const CChainParams& chainparams, const CBlock& block, CBlockIndex* pindexPrev, bool fCheckPOW = true, bool fCheckMerkleRoot = true) EXCLUSIVE_LOCKS_REQUIRED(cs_main);

/** Check whether witness commitments are required for a block, and whether to enforce NULLDUMMY (BIP 147) rules.
 *  Note that transaction witness validation rules are always enforced when P2SH is enforced. */
bool IsWitnessEnabled(const CBlockIndex* pindexPrev, const Consensus::Params& params);

/** When there are blocks in the active chain with missing data, rewind the chainstate and remove them from the block index */
bool RewindBlockIndex(const CChainParams& params) LOCKS_EXCLUDED(cs_main);

/** Compute at which vout of the block's coinbase transaction the witness commitment occurs, or -1 if not found */
int GetWitnessCommitmentIndex(const CBlock& block);

/** Update uncommitted block structures (currently: only the witness reserved value). This is safe for submitted blocks. */
void UpdateUncommittedBlockStructures(CBlock& block, const CBlockIndex* pindexPrev, const Consensus::Params& consensusParams);

/** Produce the necessary coinbase commitment for a block (modifies the hash, don't call for mined blocks). */
std::vector<unsigned char> GenerateCoinbaseCommitment(CBlock& block, const CBlockIndex* pindexPrev, const Consensus::Params& consensusParams);

/** RAII wrapper for VerifyDB: Verify consistency of the block and coin databases */
class CVerifyDB {
public:
    CVerifyDB();
    ~CVerifyDB();
    bool VerifyDB(const CChainParams& chainparams, CCoinsView *coinsview, int nCheckLevel, int nCheckDepth);
};

CBlockIndex* LookupBlockIndex(const uint256& hash) EXCLUSIVE_LOCKS_REQUIRED(cs_main);

/** Find the last common block between the parameter chain and a locator. */
CBlockIndex* FindForkInGlobalIndex(const CChain& chain, const CBlockLocator& locator) EXCLUSIVE_LOCKS_REQUIRED(cs_main);

enum DisconnectResult
{
    DISCONNECT_OK,      // All good.
    DISCONNECT_UNCLEAN, // Rolled back, but UTXO set was inconsistent with block.
    DISCONNECT_FAILED   // Something else went wrong.
};

class ConnectTrace;

/** @see CChainState::FlushStateToDisk */
enum class FlushStateMode {
    NONE,
    IF_NEEDED,
    PERIODIC,
    ALWAYS
};

struct CBlockIndexWorkComparator
{
    bool operator()(const CBlockIndex *pa, const CBlockIndex *pb) const;
};

/**
 * Maintains a tree of blocks (stored in `m_block_index`) which is consulted
 * to determine where the most-work tip is.
 *
 * This data is used mostly in `CChainState` - information about, e.g.,
 * candidate tips is not maintained here.
 */
class BlockManager {
public:
    BlockMap m_block_index GUARDED_BY(cs_main);

    /** 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 m_block_index 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 m_block_index 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 m_block_index 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;

    /**
     * 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*> m_blocks_unlinked;

    /**
     * Load the blocktree off disk and into memory. Populate certain metadata
     * per index entry (nStatus, nChainWork, nTimeMax, etc.) as well as peripheral
     * collections like setDirtyBlockIndex.
     *
     * @param[out] block_index_candidates  Fill this set with any valid blocks for
     *                                     which we've downloaded all transactions.
     */
    bool LoadBlockIndex(
        const Consensus::Params& consensus_params,
        CBlockTreeDB& blocktree,
        std::set<CBlockIndex*, CBlockIndexWorkComparator>& block_index_candidates)
        EXCLUSIVE_LOCKS_REQUIRED(cs_main);

    /** Clear all data members. */
    void Unload() EXCLUSIVE_LOCKS_REQUIRED(cs_main);

    CBlockIndex* AddToBlockIndex(const CBlockHeader& block) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
    /** Create a new block index entry for a given block hash */
    CBlockIndex* InsertBlockIndex(const uint256& hash) EXCLUSIVE_LOCKS_REQUIRED(cs_main);

    /**
     * If a block header hasn't already been seen, call CheckBlockHeader on it, ensure
     * that it doesn't descend from an invalid block, and then add it to m_block_index.
     */
    bool AcceptBlockHeader(
        const CBlockHeader& block,
        BlockValidationState& state,
        const CChainParams& chainparams,
        CBlockIndex** ppindex) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
};

/**
 * A convenience class for constructing the CCoinsView* hierarchy used
 * to facilitate access to the UTXO set.
 *
 * This class consists of an arrangement of layered CCoinsView objects,
 * preferring to store and retrieve coins in memory via `m_cacheview` but
 * ultimately falling back on cache misses to the canonical store of UTXOs on
 * disk, `m_dbview`.
 */
class CoinsViews {

public:
    //! The lowest level of the CoinsViews cache hierarchy sits in a leveldb database on disk.
    //! All unspent coins reside in this store.
    CCoinsViewDB m_dbview GUARDED_BY(cs_main);

    //! This view wraps access to the leveldb instance and handles read errors gracefully.
    CCoinsViewErrorCatcher m_catcherview GUARDED_BY(cs_main);

    //! This is the top layer of the cache hierarchy - it keeps as many coins in memory as
    //! can fit per the dbcache setting.
    std::unique_ptr<CCoinsViewCache> m_cacheview GUARDED_BY(cs_main);

    //! This constructor initializes CCoinsViewDB and CCoinsViewErrorCatcher instances, but it
    //! *does not* create a CCoinsViewCache instance by default. This is done separately because the
    //! presence of the cache has implications on whether or not we're allowed to flush the cache's
    //! state to disk, which should not be done until the health of the database is verified.
    //!
    //! All arguments forwarded onto CCoinsViewDB.
    CoinsViews(std::string ldb_name, size_t cache_size_bytes, bool in_memory, bool should_wipe);

    //! Initialize the CCoinsViewCache member.
    void InitCache() EXCLUSIVE_LOCKS_REQUIRED(::cs_main);
};

enum class CoinsCacheSizeState
{
    //! The coins cache is in immediate need of a flush.
    CRITICAL = 2,
    //! The cache is at >= 90% capacity.
    LARGE = 1,
    OK = 0
};

/**
 * CChainState stores and provides an API to update our local knowledge of the
 * current best chain.
 *
 * 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).
 *
 * Anything that is contingent on the current tip of the chain is stored here,
 * whereas block information and metadata independent of the current tip is
 * kept in `BlockMetadataManager`.
 */
class CChainState {
private:

    /**
     * Every received block is assigned a unique and increasing identifier, so we
     * know which one to give priority in case of a fork.
     */
    RecursiveMutex cs_nBlockSequenceId;
    /** Blocks loaded from disk are assigned id 0, so start the counter at 1. */
    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;

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

    /**
     * Whether this chainstate is undergoing initial block download.
     *
     * Mutable because we need to be able to mark IsInitialBlockDownload()
     * const, which latches this for caching purposes.
     */
    mutable std::atomic<bool> m_cached_finished_ibd{false};

    //! Reference to a BlockManager instance which itself is shared across all
    //! CChainState instances. Keeping a local reference allows us to test more
    //! easily as opposed to referencing a global.
    BlockManager& m_blockman;

    //! Manages the UTXO set, which is a reflection of the contents of `m_chain`.
    std::unique_ptr<CoinsViews> m_coins_views;

public:
    CChainState(BlockManager& blockman) : m_blockman(blockman) {}
    CChainState();

    /**
     * Initialize the CoinsViews UTXO set database management data structures. The in-memory
     * cache is initialized separately.
     *
     * All parameters forwarded to CoinsViews.
     */
    void InitCoinsDB(
        size_t cache_size_bytes,
        bool in_memory,
        bool should_wipe,
        std::string leveldb_name = "chainstate");

    //! Initialize the in-memory coins cache (to be done after the health of the on-disk database
    //! is verified).
    void InitCoinsCache() EXCLUSIVE_LOCKS_REQUIRED(::cs_main);

    //! @returns whether or not the CoinsViews object has been fully initialized and we can
    //!          safely flush this object to disk.
    bool CanFlushToDisk() EXCLUSIVE_LOCKS_REQUIRED(cs_main) {
        return m_coins_views && m_coins_views->m_cacheview;
    }

    //! The current chain of blockheaders we consult and build on.
    //! @see CChain, CBlockIndex.
    CChain m_chain;

    /**
     * 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;

    //! @returns A reference to the in-memory cache of the UTXO set.
    CCoinsViewCache& CoinsTip() EXCLUSIVE_LOCKS_REQUIRED(cs_main)
    {
        assert(m_coins_views->m_cacheview);
        return *m_coins_views->m_cacheview.get();
    }

    //! @returns A reference to the on-disk UTXO set database.
    CCoinsViewDB& CoinsDB() EXCLUSIVE_LOCKS_REQUIRED(cs_main)
    {
        return m_coins_views->m_dbview;
    }

    //! @returns A reference to a wrapped view of the in-memory UTXO set that
    //!     handles disk read errors gracefully.
    CCoinsViewErrorCatcher& CoinsErrorCatcher() EXCLUSIVE_LOCKS_REQUIRED(cs_main)
    {
        return m_coins_views->m_catcherview;
    }

    //! Destructs all objects related to accessing the UTXO set.
    void ResetCoinsViews() { m_coins_views.reset(); }

    /**
     * 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.
     *
     * If FlushStateMode::NONE is used, then FlushStateToDisk(...) won't do anything
     * besides checking if we need to prune.
     *
     * @returns true unless a system error occurred
     */
    bool FlushStateToDisk(
        const CChainParams& chainparams,
        BlockValidationState &state,
        FlushStateMode mode,
        int nManualPruneHeight = 0);

    //! Unconditionally flush all changes to disk.
    void ForceFlushStateToDisk();

    //! Prune blockfiles from the disk if necessary and then flush chainstate changes
    //! if we pruned.
    void PruneAndFlush();

    /**
     * Make the best chain active, in multiple steps. The result is either failure
     * or an activated best chain. pblock is either nullptr or a pointer to a block
     * that is already loaded (to avoid loading it again from disk).
     *
     * ActivateBestChain is split into steps (see ActivateBestChainStep) so that
     * we avoid holding cs_main for an extended period of time; the length of this
     * call may be quite long during reindexing or a substantial reorg.
     *
     * May not be called with cs_main held. May not be called in a
     * validationinterface callback.
     *
     * @returns true unless a system error occurred
     */
    bool ActivateBestChain(
        BlockValidationState& state,
        const CChainParams& chainparams,
        std::shared_ptr<const CBlock> pblock) LOCKS_EXCLUDED(cs_main);

    bool AcceptBlock(const std::shared_ptr<const CBlock>& pblock, BlockValidationState& state, const CChainParams& chainparams, CBlockIndex** ppindex, bool fRequested, const FlatFilePos* dbp, bool* fNewBlock) EXCLUSIVE_LOCKS_REQUIRED(cs_main);

    // Block (dis)connection on a given view:
    DisconnectResult DisconnectBlock(const CBlock& block, const CBlockIndex* pindex, CCoinsViewCache& view);
    bool ConnectBlock(const CBlock& block, BlockValidationState& state, CBlockIndex* pindex,
                      CCoinsViewCache& view, const CChainParams& chainparams, bool fJustCheck = false) EXCLUSIVE_LOCKS_REQUIRED(cs_main);

    // Apply the effects of a block disconnection on the UTXO set.
    bool DisconnectTip(BlockValidationState& state, const CChainParams& chainparams, DisconnectedBlockTransactions* disconnectpool) EXCLUSIVE_LOCKS_REQUIRED(cs_main, ::mempool.cs);

    // Manual block validity manipulation:
    bool PreciousBlock(BlockValidationState& state, const CChainParams& params, CBlockIndex* pindex) LOCKS_EXCLUDED(cs_main);
    bool InvalidateBlock(BlockValidationState& state, const CChainParams& chainparams, CBlockIndex* pindex) LOCKS_EXCLUDED(cs_main);
    void ResetBlockFailureFlags(CBlockIndex* pindex) EXCLUSIVE_LOCKS_REQUIRED(cs_main);

    /** Replay blocks that aren't fully applied to the database. */
    bool ReplayBlocks(const CChainParams& params);
    bool RewindBlockIndex(const CChainParams& params) LOCKS_EXCLUDED(cs_main);
    bool LoadGenesisBlock(const CChainParams& chainparams);

    void PruneBlockIndexCandidates();

    void UnloadBlockIndex();

    /** Check whether we are doing an initial block download (synchronizing from disk or network) */
    bool IsInitialBlockDownload() const;

    /**
     * Make various assertions about the state of the block index.
     *
     * By default this only executes fully when using the Regtest chain; see: fCheckBlockIndex.
     */
    void CheckBlockIndex(const Consensus::Params& consensusParams);

    /** Update the chain tip based on database information, i.e. CoinsTip()'s best block. */
    bool LoadChainTip(const CChainParams& chainparams) EXCLUSIVE_LOCKS_REQUIRED(cs_main);

    //! Dictates whether we need to flush the cache to disk or not.
    //!
    //! @return the state of the size of the coins cache.
    CoinsCacheSizeState GetCoinsCacheSizeState(const CTxMemPool& tx_pool)
        EXCLUSIVE_LOCKS_REQUIRED(::cs_main);

    CoinsCacheSizeState GetCoinsCacheSizeState(
        const CTxMemPool& tx_pool,
        size_t max_coins_cache_size_bytes,
        size_t max_mempool_size_bytes) EXCLUSIVE_LOCKS_REQUIRED(::cs_main);

private:
    bool ActivateBestChainStep(BlockValidationState& state, const CChainParams& chainparams, CBlockIndex* pindexMostWork, const std::shared_ptr<const CBlock>& pblock, bool& fInvalidFound, ConnectTrace& connectTrace) EXCLUSIVE_LOCKS_REQUIRED(cs_main, ::mempool.cs);
    bool ConnectTip(BlockValidationState& state, const CChainParams& chainparams, CBlockIndex* pindexNew, const std::shared_ptr<const CBlock>& pblock, ConnectTrace& connectTrace, DisconnectedBlockTransactions& disconnectpool) EXCLUSIVE_LOCKS_REQUIRED(cs_main, ::mempool.cs);

    void InvalidBlockFound(CBlockIndex *pindex, const BlockValidationState &state) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
    CBlockIndex* FindMostWorkChain() EXCLUSIVE_LOCKS_REQUIRED(cs_main);
    void ReceivedBlockTransactions(const CBlock& block, CBlockIndex* pindexNew, const FlatFilePos& pos, const Consensus::Params& consensusParams) EXCLUSIVE_LOCKS_REQUIRED(cs_main);

    bool RollforwardBlock(const CBlockIndex* pindex, CCoinsViewCache& inputs, const CChainParams& params) EXCLUSIVE_LOCKS_REQUIRED(cs_main);

    //! Mark a block as not having block data
    void EraseBlockData(CBlockIndex* index) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
};

/** Mark a block as precious and reorganize.
 *
 * May not be called in a
 * validationinterface callback.
 */
bool PreciousBlock(BlockValidationState& state, const CChainParams& params, CBlockIndex *pindex) LOCKS_EXCLUDED(cs_main);

/** Mark a block as invalid. */
bool InvalidateBlock(BlockValidationState& state, const CChainParams& chainparams, CBlockIndex* pindex) LOCKS_EXCLUDED(cs_main);

/** Remove invalidity status from a block and its descendants. */
void ResetBlockFailureFlags(CBlockIndex* pindex) EXCLUSIVE_LOCKS_REQUIRED(cs_main);

/** @returns the most-work valid chainstate. */
CChainState& ChainstateActive();

/** @returns the most-work chain. */
CChain& ChainActive();

/** @returns the global block index map. */
BlockMap& BlockIndex();

// Most often ::ChainstateActive() should be used instead of this, but some code
// may not be able to assume that this has been initialized yet and so must use it
// directly, e.g. init.cpp.
extern std::unique_ptr<CChainState> g_chainstate;

/** Global variable that points to the active block tree (protected by cs_main) */
extern std::unique_ptr<CBlockTreeDB> pblocktree;

/**
 * Return the spend height, which is one more than the inputs.GetBestBlock().
 * While checking, GetBestBlock() refers to the parent block. (protected by cs_main)
 * This is also true for mempool checks.
 */
int GetSpendHeight(const CCoinsViewCache& inputs);

extern VersionBitsCache versionbitscache;

/**
 * Determine what nVersion a new block should use.
 */
int32_t ComputeBlockVersion(const CBlockIndex* pindexPrev, const Consensus::Params& params);

/** Get block file info entry for one block file */
CBlockFileInfo* GetBlockFileInfo(size_t n);

/** Dump the mempool to disk. */
bool DumpMempool(const CTxMemPool& pool);

/** Load the mempool from disk. */
bool LoadMempool(CTxMemPool& pool);

//! Check whether the block associated with this index entry is pruned or not.
inline bool IsBlockPruned(const CBlockIndex* pblockindex)
{
    return (fHavePruned && !(pblockindex->nStatus & BLOCK_HAVE_DATA) && pblockindex->nTx > 0);
}

#endif // BITCOIN_VALIDATION_H