text: // Copyright (c) 2009-2010 Satoshi Nakamoto
  // Copyright (c) 2009-2017 The Knotcoin Core developers
  // Distributed under the MIT software license, see the accompanying
  // file COPYING or http://www.opensource.org/licenses/mit-license.php.
  
  #ifndef KNOTTCOIN_TXDB_H
  #define KNOTTCOIN_TXDB_H
  
  #include <coins.h>
  #include <dbwrapper.h>
  #include <chain.h>
  
  #include <map>
  #include <string>
  #include <utility>
  #include <vector>
  
  class CBlockIndex;
  class CCoinsViewDBCursor;
  class uint256;
  
  //! No need to periodic flush if at least this much space still available.
  static constexpr int MAX_BLOCK_COINSDB_USAGE = 10;
  //! -dbcache default (MiB)
  static const int64_t nDefaultDbCache = 450;
  //! -dbbatchsize default (bytes)
  static const int64_t nDefaultDbBatchSize = 16 << 20;
  //! max. -dbcache (MiB)
  static const int64_t nMaxDbCache = sizeof(void*) > 4 ? 16384 : 1024;
  //! min. -dbcache (MiB)
  static const int64_t nMinDbCache = 4;
  //! Max memory allocated to block tree DB specific cache, if no -txindex (MiB)
  static const int64_t nMaxBlockDBCache = 2;
  //! Max memory allocated to block tree DB specific cache, if -txindex (MiB)
  // Unlike for the UTXO database, for the txindex scenario the leveldb cache make
  // a meaningful difference: https://github.com/knotcoin/knotcoin/pull/8273#issuecomment-229601991
  static const int64_t nMaxBlockDBAndTxIndexCache = 1024;
  //! Max memory allocated to coin DB specific cache (MiB)
  static const int64_t nMaxCoinsDBCache = 8;
  
  struct CDiskTxPos : public CDiskBlockPos
  {
      unsigned int nTxOffset; // after header
  
      ADD_SERIALIZE_METHODS;
  
      template <typename Stream, typename Operation>
      inline void SerializationOp(Stream& s, Operation ser_action) {
          READWRITE(*(CDiskBlockPos*)this);
          READWRITE(VARINT(nTxOffset));
      }
  
      CDiskTxPos(const CDiskBlockPos &blockIn, unsigned int nTxOffsetIn) : CDiskBlockPos(blockIn.nFile, blockIn.nPos), nTxOffset(nTxOffsetIn) {
      }
  
      CDiskTxPos() {
          SetNull();
      }
  
      void SetNull() {
          CDiskBlockPos::SetNull();
          nTxOffset = 0;
      }
  };
  
  /** CCoinsView backed by the coin database (chainstate/) */
  class CCoinsViewDB final : public CCoinsView
  {
  protected:
      CDBWrapper db;
  public:
      explicit CCoinsViewDB(size_t nCacheSize, bool fMemory = false, bool fWipe = false);
  
      bool GetCoin(const COutPoint &outpoint, Coin &coin) const override;
      bool HaveCoin(const COutPoint &outpoint) const override;
      uint256 GetBestBlock() const override;
      std::vector<uint256> GetHeadBlocks() const override;
      bool BatchWrite(CCoinsMap &mapCoins, const uint256 &hashBlock) override;
      CCoinsViewCursor *Cursor() const override;
  
      //! Attempt to update from an older database format. Returns whether an error occurred.
      bool Upgrade();
      size_t EstimateSize() const override;
  };
  
  /** Specialization of CCoinsViewCursor to iterate over a CCoinsViewDB */
  class CCoinsViewDBCursor: public CCoinsViewCursor
  {
  public:
      ~CCoinsViewDBCursor() {}
  
      bool GetKey(COutPoint &key) const override;
      bool GetValue(Coin &coin) const override;
      unsigned int GetValueSize() const override;
  
      bool Valid() const override;
      void Next() override;
  
  private:
      CCoinsViewDBCursor(CDBIterator* pcursorIn, const uint256 &hashBlockIn):
          CCoinsViewCursor(hashBlockIn), pcursor(pcursorIn) {}
      std::unique_ptr<CDBIterator> pcursor;
      std::pair<char, COutPoint> keyTmp;
  
      friend class CCoinsViewDB;
  };
  
  /** Access to the block database (blocks/index/) */
  class CBlockTreeDB : public CDBWrapper
  {
  public:
      explicit CBlockTreeDB(size_t nCacheSize, bool fMemory = false, bool fWipe = false);
  
      CBlockTreeDB(const CBlockTreeDB&) = delete;
      CBlockTreeDB& operator=(const CBlockTreeDB&) = delete;
  
      bool WriteBatchSync(const std::vector<std::pair<int, const CBlockFileInfo*> >& fileInfo, int nLastFile, const std::vector<const CBlockIndex*>& blockinfo);
      bool ReadBlockFileInfo(int nFile, CBlockFileInfo &info);
      bool ReadLastBlockFile(int &nFile);
      bool WriteReindexing(bool fReindexing);
      bool ReadReindexing(bool &fReindexing);
      bool ReadTxIndex(const uint256 &txid, CDiskTxPos &pos);
      bool WriteTxIndex(const std::vector<std::pair<uint256, CDiskTxPos> > &vect);
      bool WriteFlag(const std::string &name, bool fValue);
      bool ReadFlag(const std::string &name, bool &fValue);
      bool LoadBlockIndexGuts(const Consensus::Params& consensusParams, std::function<CBlockIndex*(const uint256&)> insertBlockIndex);
  };
  
  #endif // KNOTTCOIN_TXDB_H
  