tx_pool: add a max pool size, settable with --max-txpool-size

src/cryptonote_core/tx_pool.h

@@ -198,11 +198,11 @@ namespace cryptonote
     /**
      * @brief loads pool state (if any) from disk, and initializes pool
      *
-     * @param config_folder folder name where pool state will be
+     * @param max_txpool_size the max size in bytes
      *
      * @return true
      */
-    bool init();
+    bool init(size_t max_txpool_size = 0);
 
     /**
      * @brief attempts to save the transaction pool state to disk
@@ -362,6 +362,19 @@ namespace cryptonote
      */
     size_t validate(uint8_t version);
 
+    /**
+     * @brief get the cumulative txpool size in bytes
+     *
+     * @return the cumulative txpool size in bytes
+     */
+    size_t get_txpool_size() const;
+
+    /**
+     * @brief set the max cumulative txpool size in bytes
+     *
+     * @param bytes the max cumulative txpool size in bytes
+     */
+    void set_txpool_max_size(size_t bytes);
 
 #define CURRENT_MEMPOOL_ARCHIVE_VER    11
 #define CURRENT_MEMPOOL_TX_DETAILS_ARCHIVE_VER    12
@@ -496,6 +509,13 @@ namespace cryptonote
      */
     void mark_double_spend(const transaction &tx);
 
+    /**
+     * @brief prune lowest fee/byte txes till we're not above bytes
+     *
+     * if bytes is 0, use m_txpool_max_size
+     */
+    void prune(size_t bytes = 0);
+
     //TODO: confirm the below comments and investigate whether or not this
     //      is the desired behavior
     //! map key images to transactions which spent them
@@ -542,6 +562,9 @@ private:
     std::unordered_set<crypto::hash> m_timed_out_transactions;
 
     Blockchain& m_blockchain;  //!< reference to the Blockchain object
+
+    size_t m_txpool_max_size;
+    size_t m_txpool_size;
   };
 }