text: // Copyright (c) 2016-2018 The Pyeongtaekcoin Core developers
  // Distributed under the MIT software license, see the accompanying
  // file COPYING or http://www.opensource.org/licenses/mit-license.php.
  
  #include <policy/rbf.h>
  
  bool SignalsOptInRBF(const CTransaction &tx)
  {
      for (const CTxIn &txin : tx.vin) {
          if (txin.nSequence <= MAX_BIP125_RBF_SEQUENCE) {
              return true;
          }
      }
      return false;
  }
  
  RBFTransactionState IsRBFOptIn(const CTransaction &tx, CTxMemPool &pool)
  {
      AssertLockHeld(pool.cs);
  
      CTxMemPool::setEntries setAncestors;
  
      // First check the transaction itself.
      if (SignalsOptInRBF(tx)) {
          return RBFTransactionState::REPLACEABLE_BIP125;
      }
  
      // If this transaction is not in our mempool, then we can't be sure
      // we will know about all its inputs.
      if (!pool.exists(tx.GetHash())) {
          return RBFTransactionState::UNKNOWN;
      }
  
      // If all the inputs have nSequence >= maxint-1, it still might be
      // signaled for RBF if any unconfirmed parents have signaled.
      uint64_t noLimit = std::numeric_limits<uint64_t>::max();
      std::string dummy;
      CTxMemPoolEntry entry = *pool.mapTx.find(tx.GetHash());
      pool.CalculateMemPoolAncestors(entry, setAncestors, noLimit, noLimit, noLimit, noLimit, dummy, false);
  
      for (CTxMemPool::txiter it : setAncestors) {
          if (SignalsOptInRBF(it->GetTx())) {
              return RBFTransactionState::REPLACEABLE_BIP125;
          }
      }
      return RBFTransactionState::FINAL;
  }
  