class CTxMemPoolEntry
{
private:
    CTransactionRef tx;        // 交易引用
    CAmount nFee;              // Cached to avoid expensive parent-transaction lookups
    size_t nTxWeight;          // avoid recomputing tx weight (also used for GetTxSize())
    size_t nUsageSize;         // total memory usage
    int64_t nTime;             // Local time when entering the mempool
    unsigned int entryHeight;  // Chain height when entering the mempool
    bool spendsCoinbase;       // 前一个交易是否是CoinBase
    int64_t sigOpCost;         // Total sigop cost
    int64_t feeDelta;          // 调整交易的优先级
    LockPoints lockPoints;     // 交易最后的所在区块高度和打包的时间

    // 子节点交易信息，如果我们移除一个交易，必须同时移除它的所有后续交易
    uint64_t nCountWithDescendants;  // 子孙交易的数量
    uint64_t nSizeWithDescendants;   
    CAmount nModFeesWithDescendants; // 费用和，包括当前交易

    // Analogous statistics for ancestor transactions
    uint64_t nCountWithAncestors;
    uint64_t nSizeWithAncestors;
    CAmount nModFeesWithAncestors;
    int64_t nSigOpCostWithAncestors;

class CTxMemPool
{
private:
    uint32_t nCheckFrequency GUARDED_BY(cs); // 表示在2^32时间内检查的次数
    unsigned int nTransactionsUpdated; //!< Used by getblocktemplate to trigger CreateNewBlock() invocation
    CBlockPolicyEstimator* minerPolicyEstimator;

    uint64_t totalTxSize;      // 所有mempool中交易的虚拟大小，不包括见证数据
    uint64_t cachedInnerUsage; // map中元素使用的动态内存大小之和

    mutable int64_t lastRollingFeeUpdate;
    mutable bool blockSinceLastRollingFeeBump;
    mutable double rollingMinimumFeeRate; // 进入pool需要的最小费用，指数级下降
}

/** 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
};