text: // Copyright (c) 2009-2010 Satoshi Nakamoto
  // Copyright (c) 2009-2018 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 UNITE_TXMEMPOOL_H
  #define UNITE_TXMEMPOOL_H
  
  #include <memory>
  #include <set>
  #include <map>
  #include <vector>
  #include <utility>
  #include <string>
  
  #include <amount.h>
  #include <coins.h>
  #include <indirectmap.h>
  #include <policy/feerate.h>
  #include <primitives/transaction.h>
  #include <sync.h>
  #include <random.h>
  
  #include <boost/multi_index_container.hpp>
  #include <boost/multi_index/hashed_index.hpp>
  #include <boost/multi_index/ordered_index.hpp>
  #include <boost/multi_index/sequenced_index.hpp>
  #include <boost/signals2/signal.hpp>
  
  class CBlockIndex;
  
  /** Fake height value used in Coin to signify they are only in the memory pool (since 0.8) */
  static const uint32_t MEMPOOL_HEIGHT = 0x7FFFFFFF;
  
  struct LockPoints
  {
      // Will be set to the blockchain height and median time past
      // values that would be necessary to satisfy all relative locktime
      // constraints (BIP68) of this tx given our view of block chain history
      int height;
      int64_t time;
      // As long as the current chain descends from the highest height block
      // containing one of the inputs used in the calculation, then the cached
      // values are still valid even after a reorg.
      CBlockIndex* maxInputBlock;
  
      LockPoints() : height(0), time(0), maxInputBlock(nullptr) { }
  };
  
  class CTxMemPool;
  
  /** \class CTxMemPoolEntry
   *
   * CTxMemPoolEntry stores data about the corresponding transaction, as well
   * as data about all in-mempool transactions that depend on the transaction
   * ("descendant" transactions).
   *
   * When a new entry is added to the mempool, we update the descendant state
   * (nCountWithDescendants, nSizeWithDescendants, and nModFeesWithDescendants) for
   * all ancestors of the newly added transaction.
   *
   */
  
  class CTxMemPoolEntry
  {
  private:
      CTransactionRef tx;
      CAmount nFee;              //!< Cached to avoid expensive parent-transaction lookups
      size_t nTxWeight;          //!< ... and avoid recomputing tx weight (also used for GetTxSize())
      size_t nUsageSize;         //!< ... and total memory usage
      int64_t nTime;             //!< Local time when entering the mempool
      unsigned int entryHeight;  //!< Chain height when entering the mempool
      bool spendsCoinbase;       //!< keep track of transactions that spend a coinbase
      int64_t sigOpCost;         //!< Total sigop cost
      int64_t feeDelta;          //!< Used for determining the priority of the transaction for mining in a block
      LockPoints lockPoints;     //!< Track the height and time at which tx was final
  
      // Information about descendants of this transaction that are in the
      // mempool; if we remove this transaction we must remove all of these
      // descendants as well.
      uint64_t nCountWithDescendants;  //!< number of descendant transactions
      uint64_t nSizeWithDescendants;   //!< ... and size
      CAmount nModFeesWithDescendants; //!< ... and total fees (all including us)
  
      // Analogous statistics for ancestor transactions
      uint64_t nCountWithAncestors;
      uint64_t nSizeWithAncestors;
      CAmount nModFeesWithAncestors;
      int64_t nSigOpCostWithAncestors;
  
  public:
      CTxMemPoolEntry(const CTransactionRef& _tx, const CAmount& _nFee,
                      int64_t _nTime, unsigned int _entryHeight,
                      bool spendsCoinbase,
                      int64_t nSigOpsCost, LockPoints lp);
  
      const CTransaction& GetTx() const { return *this->tx; }
      CTransactionRef GetSharedTx() const { return this->tx; }
      const CAmount& GetFee() const { return nFee; }
      size_t GetTxSize() const;
      size_t GetTxWeight() const { return nTxWeight; }
      int64_t GetTime() const { return nTime; }
      unsigned int GetHeight() const { return entryHeight; }
      int64_t GetSigOpCost() const { return sigOpCost; }
      int64_t GetModifiedFee() const { return nFee + feeDelta; }
      size_t DynamicMemoryUsage() const { return nUsageSize; }
      const LockPoints& GetLockPoints() const { return lockPoints; }
  
      // Adjusts the descendant state.
      void UpdateDescendantState(int64_t modifySize, CAmount modifyFee, int64_t modifyCount);
      // Adjusts the ancestor state
      void UpdateAncestorState(int64_t modifySize, CAmount modifyFee, int64_t modifyCount, int64_t modifySigOps);
      // Updates the fee delta used for mining priority score, and the
      // modified fees with descendants.
      void UpdateFeeDelta(int64_t feeDelta);
      // Update the LockPoints after a reorg
      void UpdateLockPoints(const LockPoints& lp);
  
      uint64_t GetCountWithDescendants() const { return nCountWithDescendants; }
      uint64_t GetSizeWithDescendants() const { return nSizeWithDescendants; }
      CAmount GetModFeesWithDescendants() const { return nModFeesWithDescendants; }
  
      bool GetSpendsCoinbase() const { return spendsCoinbase; }
  
      uint64_t GetCountWithAncestors() const { return nCountWithAncestors; }
      uint64_t GetSizeWithAncestors() const { return nSizeWithAncestors; }
      CAmount GetModFeesWithAncestors() const { return nModFeesWithAncestors; }
      int64_t GetSigOpCostWithAncestors() const { return nSigOpCostWithAncestors; }
  
      mutable size_t vTxHashesIdx; //!< Index in mempool's vTxHashes
  };
  
  // Helpers for modifying CTxMemPool::mapTx, which is a boost multi_index.
  struct update_descendant_state
  {
      update_descendant_state(int64_t _modifySize, CAmount _modifyFee, int64_t _modifyCount) :
          modifySize(_modifySize), modifyFee(_modifyFee), modifyCount(_modifyCount)
      {}
  
      void operator() (CTxMemPoolEntry &e)
          { e.UpdateDescendantState(modifySize, modifyFee, modifyCount); }
  
      private:
          int64_t modifySize;
          CAmount modifyFee;
          int64_t modifyCount;
  };
  
  struct update_ancestor_state
  {
      update_ancestor_state(int64_t _modifySize, CAmount _modifyFee, int64_t _modifyCount, int64_t _modifySigOpsCost) :
          modifySize(_modifySize), modifyFee(_modifyFee), modifyCount(_modifyCount), modifySigOpsCost(_modifySigOpsCost)
      {}
  
      void operator() (CTxMemPoolEntry &e)
          { e.UpdateAncestorState(modifySize, modifyFee, modifyCount, modifySigOpsCost); }
  
      private:
          int64_t modifySize;
          CAmount modifyFee;
          int64_t modifyCount;
          int64_t modifySigOpsCost;
  };
  
  struct update_fee_delta
  {
      explicit update_fee_delta(int64_t _feeDelta) : feeDelta(_feeDelta) { }
  
      void operator() (CTxMemPoolEntry &e) { e.UpdateFeeDelta(feeDelta); }
  
  private:
      int64_t feeDelta;
  };
  
  struct update_lock_points
  {
      explicit update_lock_points(const LockPoints& _lp) : lp(_lp) { }
  
      void operator() (CTxMemPoolEntry &e) { e.UpdateLockPoints(lp); }
  
  private:
      const LockPoints& lp;
  };
  
  // extracts a transaction hash from CTxMempoolEntry or CTransactionRef
  struct mempoolentry_txid
  {
      typedef uint256 result_type;
      result_type operator() (const CTxMemPoolEntry &entry) const
      {
          return entry.GetTx().GetHash();
      }
  
      result_type operator() (const CTransactionRef& tx) const
      {
          return tx->GetHash();
      }
  };
  
  /** \class CompareTxMemPoolEntryByDescendantScore
   *
   *  Sort an entry by max(score/size of entry's tx, score/size with all descendants).
   */
  class CompareTxMemPoolEntryByDescendantScore
  {
  public:
      bool operator()(const CTxMemPoolEntry& a, const CTxMemPoolEntry& b) const
      {
          double a_mod_fee, a_size, b_mod_fee, b_size;
  
          GetModFeeAndSize(a, a_mod_fee, a_size);
          GetModFeeAndSize(b, b_mod_fee, b_size);
  
          // Avoid division by rewriting (a/b > c/d) as (a*d > c*b).
          double f1 = a_mod_fee * b_size;
          double f2 = a_size * b_mod_fee;
  
          if (f1 == f2) {
              return a.GetTime() >= b.GetTime();
          }
          return f1 < f2;
      }
  
      // Return the fee/size we're using for sorting this entry.
      void GetModFeeAndSize(const CTxMemPoolEntry &a, double &mod_fee, double &size) const
      {
          // Compare feerate with descendants to feerate of the transaction, and
          // return the fee/size for the max.
          double f1 = (double)a.GetModifiedFee() * a.GetSizeWithDescendants();
          double f2 = (double)a.GetModFeesWithDescendants() * a.GetTxSize();
  
          if (f2 > f1) {
              mod_fee = a.GetModFeesWithDescendants();
              size = a.GetSizeWithDescendants();
          } else {
              mod_fee = a.GetModifiedFee();
              size = a.GetTxSize();
          }
      }
  };
  
  /** \class CompareTxMemPoolEntryByScore
   *
   *  Sort by feerate of entry (fee/size) in descending order
   *  This is only used for transaction relay, so we use GetFee()
   *  instead of GetModifiedFee() to avoid leaking prioritization
   *  information via the sort order.
   */
  class CompareTxMemPoolEntryByScore
  {
  public:
      bool operator()(const CTxMemPoolEntry& a, const CTxMemPoolEntry& b) const
      {
          double f1 = (double)a.GetFee() * b.GetTxSize();
          double f2 = (double)b.GetFee() * a.GetTxSize();
          if (f1 == f2) {
              return b.GetTx().GetHash() < a.GetTx().GetHash();
          }
          return f1 > f2;
      }
  };
  
  class CompareTxMemPoolEntryByEntryTime
  {
  public:
      bool operator()(const CTxMemPoolEntry& a, const CTxMemPoolEntry& b) const
      {
          return a.GetTime() < b.GetTime();
      }
  };
  
  /** \class CompareTxMemPoolEntryByAncestorScore
   *
   *  Sort an entry by min(score/size of entry's tx, score/size with all ancestors).
   */
  class CompareTxMemPoolEntryByAncestorFee
  {
  public:
      template<typename T>
      bool operator()(const T& a, const T& b) const
      {
          double a_mod_fee, a_size, b_mod_fee, b_size;
  
          GetModFeeAndSize(a, a_mod_fee, a_size);
          GetModFeeAndSize(b, b_mod_fee, b_size);
  
          // Avoid division by rewriting (a/b > c/d) as (a*d > c*b).
          double f1 = a_mod_fee * b_size;
          double f2 = a_size * b_mod_fee;
  
          if (f1 == f2) {
              return a.GetTx().GetHash() < b.GetTx().GetHash();
          }
          return f1 > f2;
      }
  
      // Return the fee/size we're using for sorting this entry.
      template <typename T>
      void GetModFeeAndSize(const T &a, double &mod_fee, double &size) const
      {
          // Compare feerate with ancestors to feerate of the transaction, and
          // return the fee/size for the min.
          double f1 = (double)a.GetModifiedFee() * a.GetSizeWithAncestors();
          double f2 = (double)a.GetModFeesWithAncestors() * a.GetTxSize();
  
          if (f1 > f2) {
              mod_fee = a.GetModFeesWithAncestors();
              size = a.GetSizeWithAncestors();
          } else {
              mod_fee = a.GetModifiedFee();
              size = a.GetTxSize();
          }
      }
  };
  
  // Multi_index tag names
  struct descendant_score {};
  struct entry_time {};
  struct ancestor_score {};
  
  class CBlockPolicyEstimator;
  
  /**
   * Information about a mempool transaction.
   */
  struct TxMempoolInfo
  {
      /** The transaction itself */
      CTransactionRef tx;
  
      /** Time the transaction entered the mempool. */
      int64_t nTime;
  
      /** Feerate of the transaction. */
      CFeeRate feeRate;
  
      /** The fee delta. */
      int64_t nFeeDelta;
  };
  
  /** Reason why a transaction was removed from the mempool,
   * this is passed to the notification signal.
   */
  enum class MemPoolRemovalReason {
      UNKNOWN = 0,      //! Manually removed or unknown reason
      EXPIRY,           //! Expired from mempool
      SIZELIMIT,        //! Removed in size limiting
      REORG,            //! Removed for reorganization
      BLOCK,            //! Removed for block
      CONFLICT,         //! Removed for conflict with in-block transaction
      REPLACED,         //! Removed for replacement
      OUTDATED_VOTE,    //! Removed because outdated
      SLASH_CONFLICT    //! Removed because conflicting with a slash
  };
  
  class SaltedTxidHasher
  {
  private:
      /** Salt */
      uint64_t k0, k1;
  
  public:
      SaltedTxidHasher();
  
      SaltedTxidHasher(const SaltedTxidHasher&) = default;
      SaltedTxidHasher(SaltedTxidHasher&&) = default;
  
      SaltedTxidHasher& operator=(const SaltedTxidHasher&) = default;
      SaltedTxidHasher& operator=(SaltedTxidHasher&&) = default;
  
      ~SaltedTxidHasher() = default;
  
      size_t operator()(const uint256& txid) const {
          return SipHashUint256(k0, k1, txid);
      }
  };
  
  /**
   * CTxMemPool stores valid-according-to-the-current-best-chain transactions
   * that may be included in the next block.
   *
   * Transactions are added when they are seen on the network (or created by the
   * local node), but not all transactions seen are added to the pool. For
   * example, the following new transactions will not be added to the mempool:
   * - a transaction which doesn't meet the minimum fee requirements.
   * - a new transaction that double-spends an input of a transaction already in
   * the pool where the new transaction does not meet the Replace-By-Fee
   * requirements as defined in BIP 125.
   * - a non-standard transaction.
   *
   * CTxMemPool::mapTx, and CTxMemPoolEntry bookkeeping:
   *
   * mapTx is a boost::multi_index that sorts the mempool on 4 criteria:
   * - transaction hash
   * - descendant feerate [we use max(feerate of tx, feerate of tx with all descendants)]
   * - time in mempool
   * - ancestor feerate [we use min(feerate of tx, feerate of tx with all unconfirmed ancestors)]
   *
   * Note: the term "descendant" refers to in-mempool transactions that depend on
   * this one, while "ancestor" refers to in-mempool transactions that a given
   * transaction depends on.
   *
   * In order for the feerate sort to remain correct, we must update transactions
   * in the mempool when new descendants arrive.  To facilitate this, we track
   * the set of in-mempool direct parents and direct children in mapLinks.  Within
   * each CTxMemPoolEntry, we track the size and fees of all descendants.
   *
   * Usually when a new transaction is added to the mempool, it has no in-mempool
   * children (because any such children would be an orphan).  So in
   * addUnchecked(), we:
   * - update a new entry's setMemPoolParents to include all in-mempool parents
   * - update the new entry's direct parents to include the new tx as a child
   * - update all ancestors of the transaction to include the new tx's size/fee
   *
   * When a transaction is removed from the mempool, we must:
   * - update all in-mempool parents to not track the tx in setMemPoolChildren
   * - update all ancestors to not include the tx's size/fees in descendant state
   * - update all in-mempool children to not include it as a parent
   *
   * These happen in UpdateForRemoveFromMempool().  (Note that when removing a
   * transaction along with its descendants, we must calculate that set of
   * transactions to be removed before doing the removal, or else the mempool can
   * be in an inconsistent state where it's impossible to walk the ancestors of
   * a transaction.)
   *
   * In the event of a reorg, the assumption that a newly added tx has no
   * in-mempool children is false.  In particular, the mempool is in an
   * inconsistent state while new transactions are being added, because there may
   * be descendant transactions of a tx coming from a disconnected block that are
   * unreachable from just looking at transactions in the mempool (the linking
   * transactions may also be in the disconnected block, waiting to be added).
   * Because of this, there's not much benefit in trying to search for in-mempool
   * children in addUnchecked().  Instead, in the special case of transactions
   * being added from a disconnected block, we require the caller to clean up the
   * state, to account for in-mempool, out-of-block descendants for all the
   * in-block transactions by calling UpdateTransactionsFromBlock().  Note that
   * until this is called, the mempool state is not consistent, and in particular
   * mapLinks may not be correct (and therefore functions like
   * CalculateMemPoolAncestors() and CalculateDescendants() that rely
   * on them to walk the mempool are not generally safe to use).
   *
   * Computational limits:
   *
   * Updating all in-mempool ancestors of a newly added transaction can be slow,
   * if no bound exists on how many in-mempool ancestors there may be.
   * CalculateMemPoolAncestors() takes configurable limits that are designed to
   * prevent these calculations from being too CPU intensive.
   *
   */
  class CTxMemPool
  {
  private:
      uint32_t nCheckFrequency GUARDED_BY(cs); //!< Value n means that n times in 2^32 we check.
      unsigned int nTransactionsUpdated; //!< Used by getblocktemplate to trigger CreateNewBlock() invocation
      CBlockPolicyEstimator* minerPolicyEstimator;
  
      uint64_t totalTxSize;      //!< sum of all mempool tx's virtual sizes. Differs from serialized tx size since witness data is discounted. Defined in BIP 141.
      uint64_t cachedInnerUsage; //!< sum of dynamic memory usage of all the map elements (NOT the maps themselves)
  
      mutable int64_t lastRollingFeeUpdate;
      mutable bool blockSinceLastRollingFeeBump;
      mutable double rollingMinimumFeeRate; //!< minimum fee to get into the pool, decreases exponentially
  
      void trackPackageRemoved(const CFeeRate& rate) EXCLUSIVE_LOCKS_REQUIRED(cs);
  
  public:
  
      static const int ROLLING_FEE_HALFLIFE = 60 * 60 * 12; // public only for testing
  
      typedef boost::multi_index_container<
          CTxMemPoolEntry,
          boost::multi_index::indexed_by<
              // sorted by txid
              boost::multi_index::hashed_unique<mempoolentry_txid, SaltedTxidHasher>,
              // sorted by fee rate
              boost::multi_index::ordered_non_unique<
                  boost::multi_index::tag<descendant_score>,
                  boost::multi_index::identity<CTxMemPoolEntry>,
                  CompareTxMemPoolEntryByDescendantScore
              >,
              // sorted by entry time
              boost::multi_index::ordered_non_unique<
                  boost::multi_index::tag<entry_time>,
                  boost::multi_index::identity<CTxMemPoolEntry>,
                  CompareTxMemPoolEntryByEntryTime
              >,
              // sorted by fee rate with ancestors
              boost::multi_index::ordered_non_unique<
                  boost::multi_index::tag<ancestor_score>,
                  boost::multi_index::identity<CTxMemPoolEntry>,
                  CompareTxMemPoolEntryByAncestorFee
              >
          >
      > indexed_transaction_set;
  
      mutable CCriticalSection cs;
      indexed_transaction_set mapTx GUARDED_BY(cs);
  
      using txiter = indexed_transaction_set::nth_index<0>::type::const_iterator;
      std::vector<std::pair<uint256, txiter> > vTxHashes; //!< All tx witness hashes/entries in mapTx, in random order
  
      struct CompareIteratorByHash {
          bool operator()(const txiter &a, const txiter &b) const {
              return a->GetTx().GetHash() < b->GetTx().GetHash();
          }
      };
      typedef std::set<txiter, CompareIteratorByHash> setEntries;
  
      const setEntries & GetMemPoolParents(txiter entry) const EXCLUSIVE_LOCKS_REQUIRED(cs);
      const setEntries & GetMemPoolChildren(txiter entry) const EXCLUSIVE_LOCKS_REQUIRED(cs);
      uint64_t CalculateDescendantMaximum(txiter entry) const EXCLUSIVE_LOCKS_REQUIRED(cs);
  private:
      typedef std::map<txiter, setEntries, CompareIteratorByHash> cacheMap;
  
      struct TxLinks {
          setEntries parents;
          setEntries children;
      };
  
      typedef std::map<txiter, TxLinks, CompareIteratorByHash> txlinksMap;
      txlinksMap mapLinks;
  
      void UpdateParent(txiter entry, txiter parent, bool add);
      void UpdateChild(txiter entry, txiter child, bool add);
  
      std::vector<indexed_transaction_set::const_iterator> GetSortedDepthAndScore() const EXCLUSIVE_LOCKS_REQUIRED(cs);
  
  public:
      indirectmap<COutPoint, const CTransaction*> mapNextTx GUARDED_BY(cs);
      std::map<uint256, CAmount> mapDeltas;
  
      /** Create a new CTxMemPool.
       */
      explicit CTxMemPool(CBlockPolicyEstimator* estimator = nullptr);
  
      /**
       * If sanity-checking is turned on, check makes sure the pool is
       * consistent (does not contain two transactions that spend the same inputs,
       * all inputs are in the mapNextTx array). If sanity-checking is turned off,
       * check does nothing.
       */
      void check(const CCoinsViewCache *pcoins) const;
      void setSanityCheck(double dFrequency = 1.0) { LOCK(cs); nCheckFrequency = static_cast<uint32_t>(dFrequency * 4294967295.0); }
  
      // addUnchecked must updated state for all ancestors of a given transaction,
      // to track size/count of descendant transactions.  First version of
      // addUnchecked can be used to have it call CalculateMemPoolAncestors(), and
      // then invoke the second version.
      // Note that addUnchecked is ONLY called from ATMP outside of tests
      // and any other callers may break wallet's in-mempool tracking (due to
      // lack of CValidationInterface::TransactionAddedToMempool callbacks).
      void addUnchecked(const uint256& hash, const CTxMemPoolEntry& entry, bool validFeeEstimate = true) EXCLUSIVE_LOCKS_REQUIRED(cs);
      void addUnchecked(const uint256& hash, const CTxMemPoolEntry& entry, setEntries& setAncestors, bool validFeeEstimate = true) EXCLUSIVE_LOCKS_REQUIRED(cs);
  
      void removeRecursive(const CTransaction &tx, MemPoolRemovalReason reason = MemPoolRemovalReason::UNKNOWN);
      void removeForReorg(const CCoinsViewCache *pcoins, unsigned int nMemPoolHeight, int flags);
      void removeConflicts(const CTransaction &tx) EXCLUSIVE_LOCKS_REQUIRED(cs);
      void removeForBlock(const std::vector<CTransactionRef>& vtx, unsigned int nBlockHeight);
  
      void clear();
      void _clear() EXCLUSIVE_LOCKS_REQUIRED(cs); //lock free
      bool CompareDepthAndScore(const uint256& hasha, const uint256& hashb);
      void queryHashes(std::vector<uint256>& vtxid);
      bool isSpent(const COutPoint& outpoint) const;
      unsigned int GetTransactionsUpdated() const;
      void AddTransactionsUpdated(unsigned int n);
      /**
       * Check that none of this transactions inputs are in the mempool, and thus
       * the tx is not dependent on other mempool transactions to be included in a block.
       */
      bool HasNoInputsOf(const CTransaction& tx) const;
  
      /** Affect CreateNewBlock prioritisation of transactions */
      void PrioritiseTransaction(const uint256& hash, const CAmount& nFeeDelta);
      void ApplyDelta(const uint256 hash, CAmount &nFeeDelta) const;
      void ClearPrioritisation(const uint256 hash);
  
  public:
      /** Remove a set of transactions from the mempool.
       *  If a transaction is in this set, then all in-mempool descendants must
       *  also be in the set, unless this transaction is being removed for being
       *  in a block.
       *  Set updateDescendants to true when removing a tx that was in a block, so
       *  that any in-mempool descendants have their ancestor state updated.
       */
      void RemoveStaged(setEntries &stage, bool updateDescendants, MemPoolRemovalReason reason = MemPoolRemovalReason::UNKNOWN) EXCLUSIVE_LOCKS_REQUIRED(cs);
  
      /** When adding transactions from a disconnected block back to the mempool,
       *  new mempool entries may have children in the mempool (which is generally
       *  not the case when otherwise adding transactions).
       *  UpdateTransactionsFromBlock() will find child transactions and update the
       *  descendant state for each transaction in vHashesToUpdate (excluding any
       *  child transactions present in vHashesToUpdate, which are already accounted
       *  for).  Note: vHashesToUpdate should be the set of transactions from the
       *  disconnected block that have been accepted back into the mempool.
       */
      void UpdateTransactionsFromBlock(const std::vector<uint256> &vHashesToUpdate);
  
      /** Try to calculate all in-mempool ancestors of entry.
       *  (these are all calculated including the tx itself)
       *  limitAncestorCount = max number of ancestors
       *  limitAncestorSize = max size of ancestors
       *  limitDescendantCount = max number of descendants any ancestor can have
       *  limitDescendantSize = max size of descendants any ancestor can have
       *  errString = populated with error reason if any limits are hit
       *  fSearchForParents = whether to search a tx's vin for in-mempool parents, or
       *    look up parents from mapLinks. Must be true for entries not in the mempool
       */
      bool CalculateMemPoolAncestors(const CTxMemPoolEntry& entry, setEntries& setAncestors, uint64_t limitAncestorCount, uint64_t limitAncestorSize, uint64_t limitDescendantCount, uint64_t limitDescendantSize, std::string& errString, bool fSearchForParents = true) const EXCLUSIVE_LOCKS_REQUIRED(cs);
  
      /** Populate setDescendants with all in-mempool descendants of hash.
       *  Assumes that setDescendants includes all in-mempool descendants of anything
       *  already in it.  */
      void CalculateDescendants(txiter it, setEntries& setDescendants) const EXCLUSIVE_LOCKS_REQUIRED(cs);
  
      /** The minimum fee to get into the mempool, which may itself not be enough
        *  for larger-sized transactions.
        *  The incrementalRelayFee policy variable is used to bound the time it
        *  takes the fee rate to go back down all the way to 0. When the feerate
        *  would otherwise be half of this, it is set to 0 instead.
        */
      CFeeRate GetMinFee(size_t sizelimit) const;
  
      /** Remove transactions from the mempool until its dynamic size is <= sizelimit.
        *  pvNoSpendsRemaining, if set, will be populated with the list of outpoints
        *  which are not in mempool which no longer have any spends in this mempool.
        */
      void TrimToSize(size_t sizelimit, std::vector<COutPoint>* pvNoSpendsRemaining=nullptr);
  
      /** Expire all transaction (and their dependencies) in the mempool older than time. Return the number of removed transactions. */
      int Expire(int64_t time);
  
      /** Expire all the votes (and their dependencies) in the mempol wich are referring to
       *  an epoch before the last finalized one.
       *  @return the number of removed elements.
       */
      int ExpireVotes();
  
      /**
       * Calculate the ancestor and descendant count for the given transaction.
       * The counts include the transaction itself.
       */
      void GetTransactionAncestry(const uint256& txid, size_t& ancestors, size_t& descendants) const;
  
      unsigned long size()
      {
          LOCK(cs);
          return mapTx.size();
      }
  
      uint64_t GetTotalTxSize() const
      {
          LOCK(cs);
          return totalTxSize;
      }
  
      bool exists(uint256 hash) const
      {
          LOCK(cs);
          return (mapTx.count(hash) != 0);
      }
  
      CTransactionRef get(const uint256& hash) const;
      TxMempoolInfo info(const uint256& hash) const;
      std::vector<TxMempoolInfo> infoAll() const;
  
      size_t DynamicMemoryUsage() const;
  
      boost::signals2::signal<void (CTransactionRef)> NotifyEntryAdded;
      boost::signals2::signal<void (CTransactionRef, MemPoolRemovalReason)> NotifyEntryRemoved;
  
  private:
      /** UpdateForDescendants is used by UpdateTransactionsFromBlock to update
       *  the descendants for a single transaction that has been added to the
       *  mempool but may have child transactions in the mempool, eg during a
       *  chain reorg.  setExclude is the set of descendant transactions in the
       *  mempool that must not be accounted for (because any descendants in
       *  setExclude were added to the mempool after the transaction being
       *  updated and hence their state is already reflected in the parent
       *  state).
       *
       *  cachedDescendants will be updated with the descendants of the transaction
       *  being updated, so that future invocations don't need to walk the
       *  same transaction again, if encountered in another transaction chain.
       */
      void UpdateForDescendants(txiter updateIt,
              cacheMap &cachedDescendants,
              const std::set<uint256> &setExclude) EXCLUSIVE_LOCKS_REQUIRED(cs);
      /** Update ancestors of hash to add/remove it as a descendant transaction. */
      void UpdateAncestorsOf(bool add, txiter hash, setEntries &setAncestors) EXCLUSIVE_LOCKS_REQUIRED(cs);
      /** Set ancestor state for an entry */
      void UpdateEntryForAncestors(txiter it, const setEntries &setAncestors) EXCLUSIVE_LOCKS_REQUIRED(cs);
      /** For each transaction being removed, update ancestors and any direct children.
        * If updateDescendants is true, then also update in-mempool descendants'
        * ancestor state. */
      void UpdateForRemoveFromMempool(const setEntries &entriesToRemove, bool updateDescendants) EXCLUSIVE_LOCKS_REQUIRED(cs);
      /** Sever link between specified transaction and direct children. */
      void UpdateChildrenForRemoval(txiter entry) EXCLUSIVE_LOCKS_REQUIRED(cs);
  
      /** Before calling removeUnchecked for a given transaction,
       *  UpdateForRemoveFromMempool must be called on the entire (dependent) set
       *  of transactions being removed at the same time.  We use each
       *  CTxMemPoolEntry's setMemPoolParents in order to walk ancestors of a
       *  given transaction that is removed, so we can't remove intermediate
       *  transactions in a chain before we've updated all the state for the
       *  removal.
       */
      void removeUnchecked(txiter entry, MemPoolRemovalReason reason = MemPoolRemovalReason::UNKNOWN) EXCLUSIVE_LOCKS_REQUIRED(cs);
  };
  
  /**
   * CCoinsView that brings transactions from a mempool into view.
   * It does not check for spendings by memory pool transactions.
   * Instead, it provides access to all Coins which are either unspent in the
   * base CCoinsView, or are outputs from any mempool transaction!
   * This allows transaction replacement to work as expected, as you want to
   * have all inputs "available" to check signatures, and any cycles in the
   * dependency graph are checked directly in AcceptToMemoryPool.
   * It also allows you to sign a double-spend directly in signrawtransaction,
   * as long as the conflicting transaction is not yet confirmed.
   */
  class CCoinsViewMemPool : public CCoinsViewBacked
  {
  protected:
      const CTxMemPool& mempool;
  
  public:
      CCoinsViewMemPool(CCoinsView* baseIn, const CTxMemPool& mempoolIn);
      bool GetCoin(const COutPoint &outpoint, Coin &coin) const override;
  };
  
  /**
   * DisconnectedBlockTransactions
  
   * During the reorg, it's desirable to re-add previously confirmed transactions
   * to the mempool, so that anything not re-confirmed in the new chain is
   * available to be mined. However, it's more efficient to wait until the reorg
   * is complete and process all still-unconfirmed transactions at that time,
   * since we expect most confirmed transactions to (typically) still be
   * confirmed in the new chain, and re-accepting to the memory pool is expensive
   * (and therefore better to not do in the middle of reorg-processing).
   * Instead, store the disconnected transactions (in order!) as we go, remove any
   * that are included in blocks in the new chain, and then process the remaining
   * still-unconfirmed transactions at the end.
   */
  
  // multi_index tag names
  struct txid_index {};
  struct insertion_order {};
  
  struct DisconnectedBlockTransactions {
      typedef boost::multi_index_container<
          CTransactionRef,
          boost::multi_index::indexed_by<
              // sorted by txid
              boost::multi_index::hashed_unique<
                  boost::multi_index::tag<txid_index>,
                  mempoolentry_txid,
                  SaltedTxidHasher
              >,
              // sorted by order in the blockchain
              boost::multi_index::sequenced<
                  boost::multi_index::tag<insertion_order>
              >
          >
      > indexed_disconnected_transactions;
  
      // It's almost certainly a logic bug if we don't clear out queuedTx before
      // destruction, as we add to it while disconnecting blocks, and then we
      // need to re-process remaining transactions to ensure mempool consistency.
      // For now, assert() that we've emptied out this object on destruction.
      // This assert() can always be removed if the reorg-processing code were
      // to be refactored such that this assumption is no longer true (for
      // instance if there was some other way we cleaned up the mempool after a
      // reorg, besides draining this object).
      ~DisconnectedBlockTransactions() { assert(queuedTx.empty()); }
  
      indexed_disconnected_transactions queuedTx;
      uint64_t cachedInnerUsage = 0;
  
      // Estimate the overhead of queuedTx to be 6 pointers + an allocation, as
      // no exact formula for boost::multi_index_contained is implemented.
      size_t DynamicMemoryUsage() const {
          return memusage::MallocUsage(sizeof(CTransactionRef) + 6 * sizeof(void*)) * queuedTx.size() + cachedInnerUsage;
      }
  
      const indexed_disconnected_transactions &GetQueuedTx() const {
          return queuedTx;
      }
  
      void addTransaction(const CTransactionRef& tx)
      {
          queuedTx.insert(tx);
          cachedInnerUsage += RecursiveDynamicUsage(tx);
      }
  
      // Add entries for a block while reconstructing the topological ordering so
      // they can be added back to the mempool simply.
      void LoadFromBlockInTopologicalOrder(const std::vector<CTransactionRef> &vtx);
  
      // Remove entries based on txid_index, and update memory usage.
      void removeForBlock(const std::vector<CTransactionRef>& vtx)
      {
          // Short-circuit in the common case of a block being added to the tip
          if (queuedTx.empty()) {
              return;
          }
          for (auto const &tx : vtx) {
              auto it = queuedTx.find(tx->GetHash());
              if (it != queuedTx.end()) {
                  cachedInnerUsage -= RecursiveDynamicUsage(*it);
                  queuedTx.erase(it);
              }
          }
      }
  
      // Remove an entry by insertion_order index, and update memory usage.
      void removeEntry(indexed_disconnected_transactions::index<insertion_order>::type::iterator entry)
      {
          cachedInnerUsage -= RecursiveDynamicUsage(*entry);
          queuedTx.get<insertion_order>().erase(entry);
      }
  
      void clear()
      {
          cachedInnerUsage = 0;
          queuedTx.clear();
      }
  };
  
  #endif // UNITE_TXMEMPOOL_H
  