text: // Copyright (c) 2017-2018 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 BITCORE_INDEX_TXINDEX_H
  #define BITCORE_INDEX_TXINDEX_H
  
  #include <chain.h>
  #include <index/base.h>
  #include <txdb.h>
  
  /**
   * TxIndex is used to look up transactions included in the blockchain by hash.
   * The index is written to a LevelDB database and records the filesystem
   * location of each transaction by transaction hash.
   */
  class TxIndex final : public BaseIndex
  {
  protected:
      class DB;
  
  private:
      const std::unique_ptr<DB> m_db;
  
  protected:
      /// Override base class init to migrate from old database.
      bool Init() override;
  
      bool WriteBlock(const CBlock& block, const CBlockIndex* pindex) override;
  
      BaseIndex::DB& GetDB() const override;
  
      const char* GetName() const override { return "txindex"; }
  
  public:
      /// Constructs the index, which becomes available to be queried.
      explicit TxIndex(size_t n_cache_size, bool f_memory = false, bool f_wipe = false);
  
      // Destructor is declared because this class contains a unique_ptr to an incomplete type.
      virtual ~TxIndex() override;
  
      /// Look up a transaction by hash.
      ///
      /// @param[in]   tx_hash  The hash of the transaction to be returned.
      /// @param[out]  block_hash  The hash of the block the transaction is found in.
      /// @param[out]  tx  The transaction itself.
      /// @return  true if transaction is found, false otherwise
      bool FindTx(const uint256& tx_hash, uint256& block_hash, CTransactionRef& tx) const;
  };
  
  /// The global transaction index, used in GetTransaction. May be null.
  extern std::unique_ptr<TxIndex> g_txindex;
  
  #endif // BITCORE_INDEX_TXINDEX_H
  