text: // Copyright (c) 2016 The Testcoin 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 < std::numeric_limits<unsigned int>::max()-1) {
              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 RBF_TRANSACTIONSTATE_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 RBF_TRANSACTIONSTATE_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 RBF_TRANSACTIONSTATE_REPLACEABLE_BIP125;
          }
      }
      return RBF_TRANSACTIONSTATE_FINAL;
  }
  