txmempool.h

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// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2009-2017 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 FABCOIN_TXMEMPOOL_H
#define FABCOIN_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/ordered_index.hpp>
#include <boost/multi_index/hashed_index.hpp>
#include <boost/multi_index/sequenced_index.hpp>

#include <boost/signals2/signal.hpp>

class CBlockIndex;

static const uint32_t MEMPOOL_HEIGHT = 0x0FFFFFFF;
//??? 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
{
private:
    CTransactionRef tx;
    CAmount nFee;              
    size_t nTxWeight;          
    size_t nUsageSize;         
    int64_t nTime;             
    unsigned int entryHeight;  
    bool spendsCoinbase;       
    int64_t sigOpCost;         
    int64_t feeDelta;          
    LockPoints lockPoints;     
    CAmount nMinGasPrice;      

    // 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;  
    uint64_t nSizeWithDescendants;   
    CAmount nModFeesWithDescendants; 

    // 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, CAmount _nMinGasPrice = 0);

    CTxMemPoolEntry(const CTxMemPoolEntry& other);

    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; }
    const CAmount& GetMinGasPrice() const { return nMinGasPrice; }

    // 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, int 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; 
};

// 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
{
    update_fee_delta(int64_t _feeDelta) : feeDelta(_feeDelta) { }

    void operator() (CTxMemPoolEntry &e) { e.UpdateFeeDelta(feeDelta); }

private:
    int64_t feeDelta;
};

struct update_lock_points
{
    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
{
public:
    bool operator()(const CTxMemPoolEntry& a, const CTxMemPoolEntry& b) const
    {
        bool fUseADescendants = UseDescendantScore(a);
        bool fUseBDescendants = UseDescendantScore(b);

        double aModFee = fUseADescendants ? a.GetModFeesWithDescendants() : a.GetModifiedFee();
        double aSize = fUseADescendants ? a.GetSizeWithDescendants() : a.GetTxSize();

        double bModFee = fUseBDescendants ? b.GetModFeesWithDescendants() : b.GetModifiedFee();
        double bSize = fUseBDescendants ? b.GetSizeWithDescendants() : b.GetTxSize();

        // Avoid division by rewriting (a/b > c/d) as (a*d > c*b).
        double f1 = aModFee * bSize;
        double f2 = aSize * bModFee;

        if (f1 == f2) {
            return a.GetTime() >= b.GetTime();
        }
        return f1 < f2;
    }

    // Calculate which score to use for an entry (avoiding division).
    bool UseDescendantScore(const CTxMemPoolEntry &a) const
    {
        double f1 = (double)a.GetModifiedFee() * a.GetSizeWithDescendants();
        double f2 = (double)a.GetModFeesWithDescendants() * a.GetTxSize();
        return f2 > f1;
    }
};

class CompareTxMemPoolEntryByScore
{
public:
    bool operator()(const CTxMemPoolEntry& a, const CTxMemPoolEntry& b) const
    {
        double f1 = (double)a.GetModifiedFee() * b.GetTxSize();
        double f2 = (double)b.GetModifiedFee() * 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 CompareTxMemPoolEntryByAncestorFee
{
public:
    bool operator()(const CTxMemPoolEntry& a, const CTxMemPoolEntry& b) const
    {
        double aFees = a.GetModFeesWithAncestors();
        double aSize = a.GetSizeWithAncestors();

        double bFees = b.GetModFeesWithAncestors();
        double bSize = b.GetSizeWithAncestors();

        // Avoid division by rewriting (a/b > c/d) as (a*d > c*b).
        double f1 = aFees * bSize;
        double f2 = aSize * bFees;

        if (f1 == f2) {
            return a.GetTx().GetHash() < b.GetTx().GetHash();
        }

        return f1 > f2;
    }
};

class CompareTxMemPoolEntryByAncestorFeeOrGasPrice
{
public:
    bool operator()(const CTxMemPoolEntry& a, const CTxMemPoolEntry& b) const
    {
        bool fAHasCreateOrCall = a.GetTx().HasCreateOrCall();
        bool fBHasCreateOrCall = b.GetTx().HasCreateOrCall();

        // If either of the two entries that we are comparing has a contract scriptPubKey, the comparison here takes precedence
        if(fAHasCreateOrCall || fBHasCreateOrCall) {
            // Prioritze non-contract txs
            if(fAHasCreateOrCall != fBHasCreateOrCall) {
                return fAHasCreateOrCall ? false : true;
            }

            // Prioritize the contract txs that have the least number of ancestors
            // The reason for this is that otherwise it is possible to send one tx with a
            // high gas limit but a low gas price which has a child with a low gas limit but a high gas price
            // Without this condition that transaction chain would get priority in being included into the block.
            if(a.GetCountWithAncestors() != b.GetCountWithAncestors()) {
                return a.GetCountWithAncestors() < b.GetCountWithAncestors();
            }

            // Otherwise, prioritize the contract tx with the highest (minimum among its outputs) gas price
            // The reason for using the gas price of the output that sets the minimum gas price is that there
            // otherwise it may be possible to game the prioritization by setting a large gas price in one output
            // that does no execution, while the real execution has a very low gas price
            if(a.GetMinGasPrice() != b.GetMinGasPrice()) {
                return a.GetMinGasPrice() > b.GetMinGasPrice();
            }

            // Otherwise, prioritize the tx with the minimum size
            if(a.GetTxSize() != b.GetTxSize()) {
                return a.GetTxSize() < b.GetTxSize();
            }

            // If the txs are identical in their minimum gas prices and tx size
            // order based on the tx hash for consistency.
            return a.GetTx().GetHash() < b.GetTx().GetHash();
        }

        // If neither of the txs we are comparing are contract txs, use the standard comparison based on ancestor fees / ancestor size
        return CompareTxMemPoolEntryByAncestorFee()(a, b);
    }
};

// Multi_index tag names
struct descendant_score {};
struct entry_time {};
struct mining_score {};
struct ancestor_score {};
struct ancestor_score_or_gas_price {};

class CBlockPolicyEstimator;

struct TxMempoolInfo
{
    CTransactionRef tx;

    int64_t nTime;

    CFeeRate feeRate;

    int64_t nFeeDelta;
};

enum class MemPoolRemovalReason {
    UNKNOWN = 0, 
    EXPIRY,      
    SIZELIMIT,   
    REORG,       
    BLOCK,       
    CONFLICT,    
    REPLACED     
};

class SaltedTxidHasher
{
private:
    const uint64_t k0, k1;

public:
    SaltedTxidHasher();

    size_t operator()(const uint256& txid) const {
        return SipHashUint256(k0, k1, txid);
    }
};

class CTxMemPool
{
private:
    uint32_t nCheckFrequency; 
    unsigned int nTransactionsUpdated; 
    CBlockPolicyEstimator* minerPolicyEstimator;

    uint64_t totalTxSize;      
    uint64_t cachedInnerUsage; 

    mutable int64_t lastRollingFeeUpdate;
    mutable bool blockSinceLastRollingFeeBump;
    mutable double rollingMinimumFeeRate; 

    void trackPackageRemoved(const CFeeRate& rate);

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 score (for mining prioritization)
            boost::multi_index::ordered_unique<
                boost::multi_index::tag<mining_score>,
                boost::multi_index::identity<CTxMemPoolEntry>,
                CompareTxMemPoolEntryByScore
            >,
            // sorted by fee rate with ancestors
            boost::multi_index::ordered_non_unique<
                boost::multi_index::tag<ancestor_score>,
                boost::multi_index::identity<CTxMemPoolEntry>,
                CompareTxMemPoolEntryByAncestorFee
            >,
            // sorted by fee rate with gas price (if contract tx) or ancestors otherwise
            boost::multi_index::ordered_non_unique<
                boost::multi_index::tag<ancestor_score_or_gas_price>,
                boost::multi_index::identity<CTxMemPoolEntry>,
                CompareTxMemPoolEntryByAncestorFeeOrGasPrice
             >
        >
    > indexed_transaction_set;

    mutable CCriticalSection cs;
    indexed_transaction_set mapTx;

    typedef indexed_transaction_set::nth_index<0>::type::iterator txiter;
    std::vector<std::pair<uint256, txiter> > vTxHashes; 

    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;
    const setEntries & GetMemPoolChildren(txiter entry) const;
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;

public:
    indirectmap<COutPoint, const CTransaction*> mapNextTx;
    std::map<uint256, CAmount> mapDeltas;

    CTxMemPool(CBlockPolicyEstimator* estimator = nullptr);

    void check(const CCoinsViewCache *pcoins) const;
    void setSanityCheck(double dFrequency = 1.0) { nCheckFrequency = 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.
    bool addUnchecked(const uint256& hash, const CTxMemPoolEntry &entry, bool validFeeEstimate = true);
    bool addUnchecked(const uint256& hash, const CTxMemPoolEntry &entry, setEntries &setAncestors, bool validFeeEstimate = true);

    void removeRecursive(const CTransaction &tx, MemPoolRemovalReason reason = MemPoolRemovalReason::UNKNOWN);
    void removeForReorg(const CCoinsViewCache *pcoins, unsigned int nMemPoolHeight, int flags);
    void removeConflicts(const CTransaction &tx);
    void removeForBlock(const std::vector<CTransactionRef>& vtx, unsigned int nBlockHeight);

    void clear();
    void _clear(); //lock free
    bool CompareDepthAndScore(const uint256& hasha, const uint256& hashb);
    void queryHashes(std::vector<uint256>& vtxid);
    bool isSpent(const COutPoint& outpoint);
    unsigned int GetTransactionsUpdated() const;
    void AddTransactionsUpdated(unsigned int n);
    bool HasNoInputsOf(const CTransaction& tx) const;

    void PrioritiseTransaction(const uint256& hash, const CAmount& nFeeDelta);
    void ApplyDelta(const uint256 hash, CAmount &nFeeDelta) const;
    void ClearPrioritisation(const uint256 hash);

public:
    void RemoveStaged(setEntries &stage, bool updateDescendants, MemPoolRemovalReason reason = MemPoolRemovalReason::UNKNOWN);

    void UpdateTransactionsFromBlock(const std::vector<uint256> &vHashesToUpdate);

    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;

    void CalculateDescendants(txiter it, setEntries &setDescendants);

    CFeeRate GetMinFee(size_t sizelimit) const;

    void TrimToSize(size_t sizelimit, std::vector<COutPoint>* pvNoSpendsRemaining=nullptr);

    int Expire(int64_t time);

    bool TransactionWithinChainLimit(const uint256& txid, size_t chainLimit) const;

    unsigned long size()
    {
        LOCK(cs);
        return mapTx.size();
    }

    uint64_t GetTotalTxSize()
    {
        LOCK(cs);
        return totalTxSize;
    }

    bool exists(uint256 hash) const
    {
        LOCK(cs);
        return (mapTx.count(hash) != 0);
    }

    bool exists(const COutPoint& outpoint) const
    {
        LOCK(cs);
        auto it = mapTx.find(outpoint.hash);
        return (it != mapTx.end() && outpoint.n < it->GetTx().vout.size());
    }

    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:
    void UpdateForDescendants(txiter updateIt,
            cacheMap &cachedDescendants,
            const std::set<uint256> &setExclude);
    void UpdateAncestorsOf(bool add, txiter hash, setEntries &setAncestors);
    void UpdateEntryForAncestors(txiter it, const setEntries &setAncestors);
    void UpdateForRemoveFromMempool(const setEntries &entriesToRemove, bool updateDescendants);
    void UpdateChildrenForRemoval(txiter entry);

    void removeUnchecked(txiter entry, MemPoolRemovalReason reason = MemPoolRemovalReason::UNKNOWN);
};

class CCoinsViewMemPool : public CCoinsViewBacked
{
protected:
    const CTxMemPool& mempool;

public:
    CCoinsViewMemPool(CCoinsView* baseIn, const CTxMemPool& mempoolIn);
    bool GetCoin(const COutPoint &outpoint, Coin &coin) const override;
    bool HaveCoin(const COutPoint &outpoint) const override;
};

// 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;
    }

    void addTransaction(const CTransactionRef& tx)
    {
        queuedTx.insert(tx);
        cachedInnerUsage += RecursiveDynamicUsage(tx);
    }

    // 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 // FABCOIN_TXMEMPOOL_H