Merge #20523: zmq: deduplicate 'sequence' publisher message creation/sending

962444295d92744e6f671dac2462037f9f3d79d7 zmq: deduplicate 'sequence' publisher message creation/sending (Sebastian Falbesoner)

Pull request description:

  This small PR deduplicates common low-level creation and sending code for the 'sequence' zmq publisher message (methods `NotifyBlock{Connect,Disconnect}()`, `NotifyTransaction{Acceptance,Removal}()` in the class `CZMQPublishSequenceNotifier`) by introducing a helper function.

ACKs for top commit:
  jonatack:
    Code review re-ACK 962444295d92744e6f671dac2462037f9f3d79d7 per `git diff f231ffd 9624442`
  instagibbs:
    utACK https://github.com/bitcoin/bitcoin/pull/20523/commits/962444295d92744e6f671dac2462037f9f3d79d7

Tree-SHA512: de0750d923f36d1a5751331e88eec8a1605cb88c93318830913210485e2bff712310484f18a0fb626df6ef32ce0b0cf57f4421ce62656e05fce7011a0c3c2d0e

1 files changed, 17 insertions, 23 deletions

diff --git a/src/zmq/zmqpublishnotifier.cpp b/src/zmq/zmqpublishnotifier.cpp
index c0207f9dd6..168ba841c8 100644
--- a/src/zmq/zmqpublishnotifier.cpp
+++ b/src/zmq/zmqpublishnotifier.cpp
@@ -17,6 +17,7 @@
 #include <cstdarg>
 #include <cstddef>
 #include <map>
+#include <optional>
 #include <string>
 #include <utility>
 
@@ -227,50 +228,43 @@ bool CZMQPublishRawTransactionNotifier::NotifyTransaction(const CTransaction &tr
     return SendZmqMessage(MSG_RAWTX, &(*ss.begin()), ss.size());
 }
 
+// Helper function to send a 'sequence' topic message with the following structure:
+//    <32-byte hash> | <1-byte label> | <8-byte LE sequence> (optional)
+static bool SendSequenceMsg(CZMQAbstractPublishNotifier& notifier, uint256 hash, char label, std::optional<uint64_t> sequence = {})
+{
+    unsigned char data[sizeof(hash) + sizeof(label) + sizeof(uint64_t)];
+    for (unsigned int i = 0; i < sizeof(hash); ++i) {
+        data[sizeof(hash) - 1 - i] = hash.begin()[i];
+    }
+    data[sizeof(hash)] = label;
+    if (sequence) WriteLE64(data + sizeof(hash) + sizeof(label), *sequence);
+    return notifier.SendZmqMessage(MSG_SEQUENCE, data, sequence ? sizeof(data) : sizeof(hash) + sizeof(label));
+}
 
-// TODO: Dedup this code to take label char, log string
 bool CZMQPublishSequenceNotifier::NotifyBlockConnect(const CBlockIndex *pindex)
 {
     uint256 hash = pindex->GetBlockHash();
     LogPrint(BCLog::ZMQ, "zmq: Publish sequence block connect %s to %s\n", hash.GetHex(), this->address);
-    char data[sizeof(uint256)+1];
-    for (unsigned int i = 0; i < sizeof(uint256); i++)
-        data[sizeof(uint256) - 1 - i] = hash.begin()[i];
-    data[sizeof(data) - 1] = 'C'; // Block (C)onnect
-    return SendZmqMessage(MSG_SEQUENCE, data, sizeof(data));
+    return SendSequenceMsg(*this, hash, /* Block (C)onnect */ 'C');
 }
 
 bool CZMQPublishSequenceNotifier::NotifyBlockDisconnect(const CBlockIndex *pindex)
 {
     uint256 hash = pindex->GetBlockHash();
     LogPrint(BCLog::ZMQ, "zmq: Publish sequence block disconnect %s to %s\n", hash.GetHex(), this->address);
-    char data[sizeof(uint256)+1];
-    for (unsigned int i = 0; i < sizeof(uint256); i++)
-        data[sizeof(uint256) - 1 - i] = hash.begin()[i];
-    data[sizeof(data) - 1] = 'D'; // Block (D)isconnect
-    return SendZmqMessage(MSG_SEQUENCE, data, sizeof(data));
+    return SendSequenceMsg(*this, hash, /* Block (D)isconnect */ 'D');
 }
 
 bool CZMQPublishSequenceNotifier::NotifyTransactionAcceptance(const CTransaction &transaction, uint64_t mempool_sequence)
 {
     uint256 hash = transaction.GetHash();
     LogPrint(BCLog::ZMQ, "zmq: Publish hashtx mempool acceptance %s to %s\n", hash.GetHex(), this->address);
-    unsigned char data[sizeof(uint256)+sizeof(mempool_sequence)+1];
-    for (unsigned int i = 0; i < sizeof(uint256); i++)
-        data[sizeof(uint256) - 1 - i] = hash.begin()[i];
-    data[sizeof(uint256)] = 'A'; // Mempool (A)cceptance
-    WriteLE64(data+sizeof(uint256)+1, mempool_sequence);
-    return SendZmqMessage(MSG_SEQUENCE, data, sizeof(data));
+    return SendSequenceMsg(*this, hash, /* Mempool (A)cceptance */ 'A', mempool_sequence);
 }
 
 bool CZMQPublishSequenceNotifier::NotifyTransactionRemoval(const CTransaction &transaction, uint64_t mempool_sequence)
 {
     uint256 hash = transaction.GetHash();
     LogPrint(BCLog::ZMQ, "zmq: Publish hashtx mempool removal %s to %s\n", hash.GetHex(), this->address);
-    unsigned char data[sizeof(uint256)+sizeof(mempool_sequence)+1];
-    for (unsigned int i = 0; i < sizeof(uint256); i++)
-        data[sizeof(uint256) - 1 - i] = hash.begin()[i];
-    data[sizeof(uint256)] = 'R'; // Mempool (R)emoval
-    WriteLE64(data+sizeof(uint256)+1, mempool_sequence);
-    return SendZmqMessage(MSG_SEQUENCE, data, sizeof(data));
+    return SendSequenceMsg(*this, hash, /* Mempool (R)emoval */ 'R', mempool_sequence);
 }