[bitcoin-tx] add rbfoptin command

src/bitcoin-tx.cpp

@@ -77,6 +77,7 @@ static int AppInitRawTx(int argc, char* argv[])
         strUsage += HelpMessageOpt("in=TXID:VOUT(:SEQUENCE_NUMBER)", _("Add input to TX"));
         strUsage += HelpMessageOpt("locktime=N", _("Set TX lock time to N"));
         strUsage += HelpMessageOpt("nversion=N", _("Set TX version to N"));
+        strUsage += HelpMessageOpt("rbfoptin(=N)", _("Set RBF opt-in sequence number for input N (if not provided, opt-in all available inputs)"));
         strUsage += HelpMessageOpt("outaddr=VALUE:ADDRESS", _("Add address-based output to TX"));
         strUsage += HelpMessageOpt("outpubkey=VALUE:PUBKEY[:FLAGS]", _("Add pay-to-pubkey output to TX") + ". " +
             _("Optionally add the \"W\" flag to produce a pay-to-witness-pubkey-hash output") + ". " +
@@ -202,6 +203,24 @@ static void MutateTxLocktime(CMutableTransaction& tx, const std::string& cmdVal)
     tx.nLockTime = (unsigned int) newLocktime;
 }
 
+static void MutateTxRBFOptIn(CMutableTransaction& tx, const std::string& strInIdx)
+{
+    // parse requested index
+    int inIdx = atoi(strInIdx);
+    if (inIdx < 0 || inIdx >= (int)tx.vin.size()) {
+        throw std::runtime_error("Invalid TX input index '" + strInIdx + "'");
+    }
+
+    // set the nSequence to MAX_INT - 2 (= RBF opt in flag)
+    int cnt = 0;
+    for (CTxIn& txin : tx.vin) {
+        if (strInIdx == "" || cnt == inIdx) {
+            txin.nSequence = std::numeric_limits<unsigned int>::max() - 2;
+        }
+        ++cnt;
+    }
+}
+
 static void MutateTxAddInput(CMutableTransaction& tx, const std::string& strInput)
 {
     std::vector<std::string> vStrInputParts;
@@ -649,6 +668,9 @@ static void MutateTx(CMutableTransaction& tx, const std::string& command,
         MutateTxVersion(tx, commandVal);
     else if (command == "locktime")
         MutateTxLocktime(tx, commandVal);
+    else if (command == "rbfoptin") {
+        MutateTxRBFOptIn(tx, commandVal);
+    }
 
     else if (command == "delin")
         MutateTxDelInput(tx, commandVal);