src/miner.cpp

   1 // Copyright (c) 2009-2010 Satoshi Nakamoto
   2 // Copyright (c) 2009-2015 The Bitcoin Core developers
   3 // Distributed under the MIT software license, see the accompanying
   4 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
   5
   6 #include "miner.h"
   7
   8 #include "amount.h"
   9 #include "chain.h"
  10 #include "chainparams.h"
  11 #include "coins.h"
  12 #include "consensus/consensus.h"
  13 #include "consensus/merkle.h"
  14 #include "consensus/validation.h"
  15 #include "hash.h"
  16 #include "validation.h"
  17 #include "net.h"
  18 #include "policy/policy.h"
  19 #include "pow.h"
  20 #include "primitives/transaction.h"
  21 #include "script/standard.h"
  22 #include "timedata.h"
  23 #include "txmempool.h"
  24 #include "util.h"
  25 #include "utilmoneystr.h"
  26 #include "validationinterface.h"
  27
  28 #include <algorithm>
  29 #include <boost/thread.hpp>
  30 #include <boost/tuple/tuple.hpp>
  31 #include <queue>
  32 #include <utility>
  33
  34 using namespace std;
  35
  36 //////////////////////////////////////////////////////////////////////////////
  37 //
  38 // BitcoinMiner
  39 //
  40
  41 //
  42 // Unconfirmed transactions in the memory pool often depend on other
  43 // transactions in the memory pool. When we select transactions from the
  44 // pool, we select by highest priority or fee rate, so we might consider
  45 // transactions that depend on transactions that aren't yet in the block.
  46
  47 uint64_t nLastBlockTx = 0;
  48 uint64_t nLastBlockSize = 0;
  49 uint64_t nLastBlockWeight = 0;
  50
  51 class ScoreCompare
  52 {
  53 public:
  54     ScoreCompare() {}
  55
  56     bool operator()(const CTxMemPool::txiter a, const CTxMemPool::txiter b)
  57     {
  58         return CompareTxMemPoolEntryByScore()(*b,*a); // Convert to less than
  59     }
  60 };
  61
  62 int64_t UpdateTime(CBlockHeader* pblock, const Consensus::Params& consensusParams, const CBlockIndex* pindexPrev)
  63 {
  64     int64_t nOldTime = pblock->nTime;
  65     int64_t nNewTime = std::max(pindexPrev->GetMedianTimePast()+1, GetAdjustedTime());
  66
  67     if (nOldTime < nNewTime)
  68         pblock->nTime = nNewTime;
  69
  70     // Updating time can change work required on testnet:
  71     if (consensusParams.fPowAllowMinDifficultyBlocks)
  72         pblock->nBits = GetNextWorkRequired(pindexPrev, pblock, consensusParams);
  73
  74     return nNewTime - nOldTime;
  75 }
  76
  77 BlockAssembler::BlockAssembler(const CChainParams& _chainparams)
  78     : chainparams(_chainparams)
  79 {
  80     // Block resource limits
  81     // If neither -blockmaxsize or -blockmaxweight is given, limit to DEFAULT_BLOCK_MAX_*
  82     // If only one is given, only restrict the specified resource.
  83     // If both are given, restrict both.
  84     nBlockMaxWeight = DEFAULT_BLOCK_MAX_WEIGHT;
  85     nBlockMaxSize = DEFAULT_BLOCK_MAX_SIZE;
  86     bool fWeightSet = false;
  87     if (mapArgs.count("-blockmaxweight")) {
  88         nBlockMaxWeight = GetArg("-blockmaxweight", DEFAULT_BLOCK_MAX_WEIGHT);
  89         nBlockMaxSize = MAX_BLOCK_SERIALIZED_SIZE;
  90         fWeightSet = true;
  91     }
  92     if (mapArgs.count("-blockmaxsize")) {
  93         nBlockMaxSize = GetArg("-blockmaxsize", DEFAULT_BLOCK_MAX_SIZE);
  94         if (!fWeightSet) {
  95             nBlockMaxWeight = nBlockMaxSize * WITNESS_SCALE_FACTOR;
  96         }
  97     }
  98
  99     // Limit weight to between 4K and MAX_BLOCK_WEIGHT-4K for sanity:
 100     nBlockMaxWeight = std::max((unsigned int)4000, std::min((unsigned int)(MAX_BLOCK_WEIGHT-4000), nBlockMaxWeight));
 101     // Limit size to between 1K and MAX_BLOCK_SERIALIZED_SIZE-1K for sanity:
 102     nBlockMaxSize = std::max((unsigned int)1000, std::min((unsigned int)(MAX_BLOCK_SERIALIZED_SIZE-1000), nBlockMaxSize));
 103
 104     // Whether we need to account for byte usage (in addition to weight usage)
 105     fNeedSizeAccounting = (nBlockMaxSize < MAX_BLOCK_SERIALIZED_SIZE-1000);
 106 }
 107
 108 void BlockAssembler::resetBlock()
 109 {
 110     inBlock.clear();
 111
 112     // Reserve space for coinbase tx
 113     nBlockSize = 1000;
 114     nBlockWeight = 4000;
 115     nBlockSigOpsCost = 400;
 116     fIncludeWitness = false;
 117
 118     // These counters do not include coinbase tx
 119     nBlockTx = 0;
 120     nFees = 0;
 121
 122     lastFewTxs = 0;
 123     blockFinished = false;
 124 }
 125
 126 std::unique_ptr<CBlockTemplate> BlockAssembler::CreateNewBlock(const CScript& scriptPubKeyIn)
 127 {
 128     resetBlock();
 129
 130     pblocktemplate.reset(new CBlockTemplate());
 131
 132     if(!pblocktemplate.get())
 133         return nullptr;
 134     pblock = &pblocktemplate->block; // pointer for convenience
 135
 136     // Add dummy coinbase tx as first transaction
 137     pblock->vtx.emplace_back();
 138     pblocktemplate->vTxFees.push_back(-1); // updated at end
 139     pblocktemplate->vTxSigOpsCost.push_back(-1); // updated at end
 140
 141     LOCK2(cs_main, mempool.cs);
 142     CBlockIndex* pindexPrev = chainActive.Tip();
 143     nHeight = pindexPrev->nHeight + 1;
 144
 145     pblock->nVersion = ComputeBlockVersion(pindexPrev, chainparams.GetConsensus());
 146     // -regtest only: allow overriding block.nVersion with
 147     // -blockversion=N to test forking scenarios
 148     if (chainparams.MineBlocksOnDemand())
 149         pblock->nVersion = GetArg("-blockversion", pblock->nVersion);
 150
 151     pblock->nTime = GetAdjustedTime();
 152     const int64_t nMedianTimePast = pindexPrev->GetMedianTimePast();
 153
 154     nLockTimeCutoff = (STANDARD_LOCKTIME_VERIFY_FLAGS & LOCKTIME_MEDIAN_TIME_PAST)
 155                        ? nMedianTimePast
 156                        : pblock->GetBlockTime();
 157
 158     // Decide whether to include witness transactions
 159     // This is only needed in case the witness softfork activation is reverted
 160     // (which would require a very deep reorganization) or when
 161     // -promiscuousmempoolflags is used.
 162     // TODO: replace this with a call to main to assess validity of a mempool
 163     // transaction (which in most cases can be a no-op).
 164     fIncludeWitness = IsWitnessEnabled(pindexPrev, chainparams.GetConsensus());
 165
 166     addPriorityTxs();
 167     addPackageTxs();
 168
 169     nLastBlockTx = nBlockTx;
 170     nLastBlockSize = nBlockSize;
 171     nLastBlockWeight = nBlockWeight;
 172
 173     // Create coinbase transaction.
 174     CMutableTransaction coinbaseTx;
 175     coinbaseTx.vin.resize(1);
 176     coinbaseTx.vin[0].prevout.SetNull();
 177     coinbaseTx.vout.resize(1);
 178     coinbaseTx.vout[0].scriptPubKey = scriptPubKeyIn;
 179     coinbaseTx.vout[0].nValue = nFees + GetBlockSubsidy(nHeight, chainparams.GetConsensus());
 180     coinbaseTx.vin[0].scriptSig = CScript() << nHeight << OP_0;
 181     pblock->vtx[0] = MakeTransactionRef(std::move(coinbaseTx));
 182     pblocktemplate->vchCoinbaseCommitment = GenerateCoinbaseCommitment(*pblock, pindexPrev, chainparams.GetConsensus());
 183     pblocktemplate->vTxFees[0] = -nFees;
 184
 185     uint64_t nSerializeSize = GetSerializeSize(*pblock, SER_NETWORK, PROTOCOL_VERSION);
 186     LogPrintf("CreateNewBlock(): total size: %u block weight: %u txs: %u fees: %ld sigops %d\n", nSerializeSize, GetBlockWeight(*pblock), nBlockTx, nFees, nBlockSigOpsCost);
 187
 188     // Fill in header
 189     pblock->hashPrevBlock  = pindexPrev->GetBlockHash();
 190     UpdateTime(pblock, chainparams.GetConsensus(), pindexPrev);
 191     pblock->nBits          = GetNextWorkRequired(pindexPrev, pblock, chainparams.GetConsensus());
 192     pblock->nNonce         = 0;
 193     pblocktemplate->vTxSigOpsCost[0] = WITNESS_SCALE_FACTOR * GetLegacySigOpCount(*pblock->vtx[0]);
 194
 195     CValidationState state;
 196     if (!TestBlockValidity(state, chainparams, *pblock, pindexPrev, false, false)) {
 197         throw std::runtime_error(strprintf("%s: TestBlockValidity failed: %s", __func__, FormatStateMessage(state)));
 198     }
 199
 200     return std::move(pblocktemplate);
 201 }
 202
 203 bool BlockAssembler::isStillDependent(CTxMemPool::txiter iter)
 204 {
 205     BOOST_FOREACH(CTxMemPool::txiter parent, mempool.GetMemPoolParents(iter))
 206     {
 207         if (!inBlock.count(parent)) {
 208             return true;
 209         }
 210     }
 211     return false;
 212 }
 213
 214 void BlockAssembler::onlyUnconfirmed(CTxMemPool::setEntries& testSet)
 215 {
 216     for (CTxMemPool::setEntries::iterator iit = testSet.begin(); iit != testSet.end(); ) {
 217         // Only test txs not already in the block
 218         if (inBlock.count(*iit)) {
 219             testSet.erase(iit++);
 220         }
 221         else {
 222             iit++;
 223         }
 224     }
 225 }
 226
 227 bool BlockAssembler::TestPackage(uint64_t packageSize, int64_t packageSigOpsCost)
 228 {
 229     // TODO: switch to weight-based accounting for packages instead of vsize-based accounting.
 230     if (nBlockWeight + WITNESS_SCALE_FACTOR * packageSize >= nBlockMaxWeight)
 231         return false;
 232     if (nBlockSigOpsCost + packageSigOpsCost >= MAX_BLOCK_SIGOPS_COST)
 233         return false;
 234     return true;
 235 }
 236
 237 // Perform transaction-level checks before adding to block:
 238 // - transaction finality (locktime)
 239 // - premature witness (in case segwit transactions are added to mempool before
 240 //   segwit activation)
 241 // - serialized size (in case -blockmaxsize is in use)
 242 bool BlockAssembler::TestPackageTransactions(const CTxMemPool::setEntries& package)
 243 {
 244     uint64_t nPotentialBlockSize = nBlockSize; // only used with fNeedSizeAccounting
 245     BOOST_FOREACH (const CTxMemPool::txiter it, package) {
 246         if (!IsFinalTx(it->GetTx(), nHeight, nLockTimeCutoff))
 247             return false;
 248         if (!fIncludeWitness && it->GetTx().HasWitness())
 249             return false;
 250         if (fNeedSizeAccounting) {
 251             uint64_t nTxSize = ::GetSerializeSize(it->GetTx(), SER_NETWORK, PROTOCOL_VERSION);
 252             if (nPotentialBlockSize + nTxSize >= nBlockMaxSize) {
 253                 return false;
 254             }
 255             nPotentialBlockSize += nTxSize;
 256         }
 257     }
 258     return true;
 259 }
 260
 261 bool BlockAssembler::TestForBlock(CTxMemPool::txiter iter)
 262 {
 263     if (nBlockWeight + iter->GetTxWeight() >= nBlockMaxWeight) {
 264         // If the block is so close to full that no more txs will fit
 265         // or if we've tried more than 50 times to fill remaining space
 266         // then flag that the block is finished
 267         if (nBlockWeight >  nBlockMaxWeight - 400 || lastFewTxs > 50) {
 268              blockFinished = true;
 269              return false;
 270         }
 271         // Once we're within 4000 weight of a full block, only look at 50 more txs
 272         // to try to fill the remaining space.
 273         if (nBlockWeight > nBlockMaxWeight - 4000) {
 274             lastFewTxs++;
 275         }
 276         return false;
 277     }
 278
 279     if (fNeedSizeAccounting) {
 280         if (nBlockSize + ::GetSerializeSize(iter->GetTx(), SER_NETWORK, PROTOCOL_VERSION) >= nBlockMaxSize) {
 281             if (nBlockSize >  nBlockMaxSize - 100 || lastFewTxs > 50) {
 282                  blockFinished = true;
 283                  return false;
 284             }
 285             if (nBlockSize > nBlockMaxSize - 1000) {
 286                 lastFewTxs++;
 287             }
 288             return false;
 289         }
 290     }
 291
 292     if (nBlockSigOpsCost + iter->GetSigOpCost() >= MAX_BLOCK_SIGOPS_COST) {
 293         // If the block has room for no more sig ops then
 294         // flag that the block is finished
 295         if (nBlockSigOpsCost > MAX_BLOCK_SIGOPS_COST - 8) {
 296             blockFinished = true;
 297             return false;
 298         }
 299         // Otherwise attempt to find another tx with fewer sigops
 300         // to put in the block.
 301         return false;
 302     }
 303
 304     // Must check that lock times are still valid
 305     // This can be removed once MTP is always enforced
 306     // as long as reorgs keep the mempool consistent.
 307     if (!IsFinalTx(iter->GetTx(), nHeight, nLockTimeCutoff))
 308         return false;
 309
 310     return true;
 311 }
 312
 313 void BlockAssembler::AddToBlock(CTxMemPool::txiter iter)
 314 {
 315     pblock->vtx.emplace_back(iter->GetSharedTx());
 316     pblocktemplate->vTxFees.push_back(iter->GetFee());
 317     pblocktemplate->vTxSigOpsCost.push_back(iter->GetSigOpCost());
 318     if (fNeedSizeAccounting) {
 319         nBlockSize += ::GetSerializeSize(iter->GetTx(), SER_NETWORK, PROTOCOL_VERSION);
 320     }
 321     nBlockWeight += iter->GetTxWeight();
 322     ++nBlockTx;
 323     nBlockSigOpsCost += iter->GetSigOpCost();
 324     nFees += iter->GetFee();
 325     inBlock.insert(iter);
 326
 327     bool fPrintPriority = GetBoolArg("-printpriority", DEFAULT_PRINTPRIORITY);
 328     if (fPrintPriority) {
 329         double dPriority = iter->GetPriority(nHeight);
 330         CAmount dummy;
 331         mempool.ApplyDeltas(iter->GetTx().GetHash(), dPriority, dummy);
 332         LogPrintf("priority %.1f fee %s txid %s\n",
 333                   dPriority,
 334                   CFeeRate(iter->GetModifiedFee(), iter->GetTxSize()).ToString(),
 335                   iter->GetTx().GetHash().ToString());
 336     }
 337 }
 338
 339 void BlockAssembler::UpdatePackagesForAdded(const CTxMemPool::setEntries& alreadyAdded,
 340         indexed_modified_transaction_set &mapModifiedTx)
 341 {
 342     BOOST_FOREACH(const CTxMemPool::txiter it, alreadyAdded) {
 343         CTxMemPool::setEntries descendants;
 344         mempool.CalculateDescendants(it, descendants);
 345         // Insert all descendants (not yet in block) into the modified set
 346         BOOST_FOREACH(CTxMemPool::txiter desc, descendants) {
 347             if (alreadyAdded.count(desc))
 348                 continue;
 349             modtxiter mit = mapModifiedTx.find(desc);
 350             if (mit == mapModifiedTx.end()) {
 351                 CTxMemPoolModifiedEntry modEntry(desc);
 352                 modEntry.nSizeWithAncestors -= it->GetTxSize();
 353                 modEntry.nModFeesWithAncestors -= it->GetModifiedFee();
 354                 modEntry.nSigOpCostWithAncestors -= it->GetSigOpCost();
 355                 mapModifiedTx.insert(modEntry);
 356             } else {
 357                 mapModifiedTx.modify(mit, update_for_parent_inclusion(it));
 358             }
 359         }
 360     }
 361 }
 362
 363 // Skip entries in mapTx that are already in a block or are present
 364 // in mapModifiedTx (which implies that the mapTx ancestor state is
 365 // stale due to ancestor inclusion in the block)
 366 // Also skip transactions that we've already failed to add. This can happen if
 367 // we consider a transaction in mapModifiedTx and it fails: we can then
 368 // potentially consider it again while walking mapTx.  It's currently
 369 // guaranteed to fail again, but as a belt-and-suspenders check we put it in
 370 // failedTx and avoid re-evaluation, since the re-evaluation would be using
 371 // cached size/sigops/fee values that are not actually correct.
 372 bool BlockAssembler::SkipMapTxEntry(CTxMemPool::txiter it, indexed_modified_transaction_set &mapModifiedTx, CTxMemPool::setEntries &failedTx)
 373 {
 374     assert (it != mempool.mapTx.end());
 375     if (mapModifiedTx.count(it) || inBlock.count(it) || failedTx.count(it))
 376         return true;
 377     return false;
 378 }
 379
 380 void BlockAssembler::SortForBlock(const CTxMemPool::setEntries& package, CTxMemPool::txiter entry, std::vector<CTxMemPool::txiter>& sortedEntries)
 381 {
 382     // Sort package by ancestor count
 383     // If a transaction A depends on transaction B, then A's ancestor count
 384     // must be greater than B's.  So this is sufficient to validly order the
 385     // transactions for block inclusion.
 386     sortedEntries.clear();
 387     sortedEntries.insert(sortedEntries.begin(), package.begin(), package.end());
 388     std::sort(sortedEntries.begin(), sortedEntries.end(), CompareTxIterByAncestorCount());
 389 }
 390
 391 // This transaction selection algorithm orders the mempool based
 392 // on feerate of a transaction including all unconfirmed ancestors.
 393 // Since we don't remove transactions from the mempool as we select them
 394 // for block inclusion, we need an alternate method of updating the feerate
 395 // of a transaction with its not-yet-selected ancestors as we go.
 396 // This is accomplished by walking the in-mempool descendants of selected
 397 // transactions and storing a temporary modified state in mapModifiedTxs.
 398 // Each time through the loop, we compare the best transaction in
 399 // mapModifiedTxs with the next transaction in the mempool to decide what
 400 // transaction package to work on next.
 401 void BlockAssembler::addPackageTxs()
 402 {
 403     // mapModifiedTx will store sorted packages after they are modified
 404     // because some of their txs are already in the block
 405     indexed_modified_transaction_set mapModifiedTx;
 406     // Keep track of entries that failed inclusion, to avoid duplicate work
 407     CTxMemPool::setEntries failedTx;
 408
 409     // Start by adding all descendants of previously added txs to mapModifiedTx
 410     // and modifying them for their already included ancestors
 411     UpdatePackagesForAdded(inBlock, mapModifiedTx);
 412
 413     CTxMemPool::indexed_transaction_set::index<ancestor_score>::type::iterator mi = mempool.mapTx.get<ancestor_score>().begin();
 414     CTxMemPool::txiter iter;
 415     while (mi != mempool.mapTx.get<ancestor_score>().end() || !mapModifiedTx.empty())
 416     {
 417         // First try to find a new transaction in mapTx to evaluate.
 418         if (mi != mempool.mapTx.get<ancestor_score>().end() &&
 419                 SkipMapTxEntry(mempool.mapTx.project<0>(mi), mapModifiedTx, failedTx)) {
 420             ++mi;
 421             continue;
 422         }
 423
 424         // Now that mi is not stale, determine which transaction to evaluate:
 425         // the next entry from mapTx, or the best from mapModifiedTx?
 426         bool fUsingModified = false;
 427
 428         modtxscoreiter modit = mapModifiedTx.get<ancestor_score>().begin();
 429         if (mi == mempool.mapTx.get<ancestor_score>().end()) {
 430             // We're out of entries in mapTx; use the entry from mapModifiedTx
 431             iter = modit->iter;
 432             fUsingModified = true;
 433         } else {
 434             // Try to compare the mapTx entry to the mapModifiedTx entry
 435             iter = mempool.mapTx.project<0>(mi);
 436             if (modit != mapModifiedTx.get<ancestor_score>().end() &&
 437                     CompareModifiedEntry()(*modit, CTxMemPoolModifiedEntry(iter))) {
 438                 // The best entry in mapModifiedTx has higher score
 439                 // than the one from mapTx.
 440                 // Switch which transaction (package) to consider
 441                 iter = modit->iter;
 442                 fUsingModified = true;
 443             } else {
 444                 // Either no entry in mapModifiedTx, or it's worse than mapTx.
 445                 // Increment mi for the next loop iteration.
 446                 ++mi;
 447             }
 448         }
 449
 450         // We skip mapTx entries that are inBlock, and mapModifiedTx shouldn't
 451         // contain anything that is inBlock.
 452         assert(!inBlock.count(iter));
 453
 454         uint64_t packageSize = iter->GetSizeWithAncestors();
 455         CAmount packageFees = iter->GetModFeesWithAncestors();
 456         int64_t packageSigOpsCost = iter->GetSigOpCostWithAncestors();
 457         if (fUsingModified) {
 458             packageSize = modit->nSizeWithAncestors;
 459             packageFees = modit->nModFeesWithAncestors;
 460             packageSigOpsCost = modit->nSigOpCostWithAncestors;
 461         }
 462
 463         if (packageFees < ::minRelayTxFee.GetFee(packageSize)) {
 464             // Everything else we might consider has a lower fee rate
 465             return;
 466         }
 467
 468         if (!TestPackage(packageSize, packageSigOpsCost)) {
 469             if (fUsingModified) {
 470                 // Since we always look at the best entry in mapModifiedTx,
 471                 // we must erase failed entries so that we can consider the
 472                 // next best entry on the next loop iteration
 473                 mapModifiedTx.get<ancestor_score>().erase(modit);
 474                 failedTx.insert(iter);
 475             }
 476             continue;
 477         }
 478
 479         CTxMemPool::setEntries ancestors;
 480         uint64_t nNoLimit = std::numeric_limits<uint64_t>::max();
 481         std::string dummy;
 482         mempool.CalculateMemPoolAncestors(*iter, ancestors, nNoLimit, nNoLimit, nNoLimit, nNoLimit, dummy, false);
 483
 484         onlyUnconfirmed(ancestors);
 485         ancestors.insert(iter);
 486
 487         // Test if all tx's are Final
 488         if (!TestPackageTransactions(ancestors)) {
 489             if (fUsingModified) {
 490                 mapModifiedTx.get<ancestor_score>().erase(modit);
 491                 failedTx.insert(iter);
 492             }
 493             continue;
 494         }
 495
 496         // Package can be added. Sort the entries in a valid order.
 497         vector<CTxMemPool::txiter> sortedEntries;
 498         SortForBlock(ancestors, iter, sortedEntries);
 499
 500         for (size_t i=0; i<sortedEntries.size(); ++i) {
 501             AddToBlock(sortedEntries[i]);
 502             // Erase from the modified set, if present
 503             mapModifiedTx.erase(sortedEntries[i]);
 504         }
 505
 506         // Update transactions that depend on each of these
 507         UpdatePackagesForAdded(ancestors, mapModifiedTx);
 508     }
 509 }
 510
 511 void BlockAssembler::addPriorityTxs()
 512 {
 513     // How much of the block should be dedicated to high-priority transactions,
 514     // included regardless of the fees they pay
 515     unsigned int nBlockPrioritySize = GetArg("-blockprioritysize", DEFAULT_BLOCK_PRIORITY_SIZE);
 516     nBlockPrioritySize = std::min(nBlockMaxSize, nBlockPrioritySize);
 517
 518     if (nBlockPrioritySize == 0) {
 519         return;
 520     }
 521
 522     bool fSizeAccounting = fNeedSizeAccounting;
 523     fNeedSizeAccounting = true;
 524
 525     // This vector will be sorted into a priority queue:
 526     vector<TxCoinAgePriority> vecPriority;
 527     TxCoinAgePriorityCompare pricomparer;
 528     std::map<CTxMemPool::txiter, double, CTxMemPool::CompareIteratorByHash> waitPriMap;
 529     typedef std::map<CTxMemPool::txiter, double, CTxMemPool::CompareIteratorByHash>::iterator waitPriIter;
 530     double actualPriority = -1;
 531
 532     vecPriority.reserve(mempool.mapTx.size());
 533     for (CTxMemPool::indexed_transaction_set::iterator mi = mempool.mapTx.begin();
 534          mi != mempool.mapTx.end(); ++mi)
 535     {
 536         double dPriority = mi->GetPriority(nHeight);
 537         CAmount dummy;
 538         mempool.ApplyDeltas(mi->GetTx().GetHash(), dPriority, dummy);
 539         vecPriority.push_back(TxCoinAgePriority(dPriority, mi));
 540     }
 541     std::make_heap(vecPriority.begin(), vecPriority.end(), pricomparer);
 542
 543     CTxMemPool::txiter iter;
 544     while (!vecPriority.empty() && !blockFinished) { // add a tx from priority queue to fill the blockprioritysize
 545         iter = vecPriority.front().second;
 546         actualPriority = vecPriority.front().first;
 547         std::pop_heap(vecPriority.begin(), vecPriority.end(), pricomparer);
 548         vecPriority.pop_back();
 549
 550         // If tx already in block, skip
 551         if (inBlock.count(iter)) {
 552             assert(false); // shouldn't happen for priority txs
 553             continue;
 554         }
 555
 556         // cannot accept witness transactions into a non-witness block
 557         if (!fIncludeWitness && iter->GetTx().HasWitness())
 558             continue;
 559
 560         // If tx is dependent on other mempool txs which haven't yet been included
 561         // then put it in the waitSet
 562         if (isStillDependent(iter)) {
 563             waitPriMap.insert(std::make_pair(iter, actualPriority));
 564             continue;
 565         }
 566
 567         // If this tx fits in the block add it, otherwise keep looping
 568         if (TestForBlock(iter)) {
 569             AddToBlock(iter);
 570
 571             // If now that this txs is added we've surpassed our desired priority size
 572             // or have dropped below the AllowFreeThreshold, then we're done adding priority txs
 573             if (nBlockSize >= nBlockPrioritySize || !AllowFree(actualPriority)) {
 574                 break;
 575             }
 576
 577             // This tx was successfully added, so
 578             // add transactions that depend on this one to the priority queue to try again
 579             BOOST_FOREACH(CTxMemPool::txiter child, mempool.GetMemPoolChildren(iter))
 580             {
 581                 waitPriIter wpiter = waitPriMap.find(child);
 582                 if (wpiter != waitPriMap.end()) {
 583                     vecPriority.push_back(TxCoinAgePriority(wpiter->second,child));
 584                     std::push_heap(vecPriority.begin(), vecPriority.end(), pricomparer);
 585                     waitPriMap.erase(wpiter);
 586                 }
 587             }
 588         }
 589     }
 590     fNeedSizeAccounting = fSizeAccounting;
 591 }
 592
 593 void IncrementExtraNonce(CBlock* pblock, const CBlockIndex* pindexPrev, unsigned int& nExtraNonce)
 594 {
 595     // Update nExtraNonce
 596     static uint256 hashPrevBlock;
 597     if (hashPrevBlock != pblock->hashPrevBlock)
 598     {
 599         nExtraNonce = 0;
 600         hashPrevBlock = pblock->hashPrevBlock;
 601     }
 602     ++nExtraNonce;
 603     unsigned int nHeight = pindexPrev->nHeight+1; // Height first in coinbase required for block.version=2
 604     CMutableTransaction txCoinbase(*pblock->vtx[0]);
 605     txCoinbase.vin[0].scriptSig = (CScript() << nHeight << CScriptNum(nExtraNonce)) + COINBASE_FLAGS;
 606     assert(txCoinbase.vin[0].scriptSig.size() <= 100);
 607
 608     pblock->vtx[0] = MakeTransactionRef(std::move(txCoinbase));
 609     pblock->hashMerkleRoot = BlockMerkleRoot(*pblock);
 610 }