zmq: Pass lambda to zmq's ZMQPublishRawBlockNotifier

The lambda captures a reference to the chainman unique_ptr to retrieve
block data. An assert is added on the chainman to ensure that the lambda
is not used while the chainman is uninitialized.

This is done in preparation for the following commits where blockstorage
functions are made BlockManager methods.

src/init.cpp

@@ -1424,7 +1424,11 @@ bool AppInitMain(NodeContext& node, interfaces::BlockAndHeaderTipInfo* tip_info)
     }
 
 #if ENABLE_ZMQ
-    g_zmq_notification_interface = CZMQNotificationInterface::Create();
+    g_zmq_notification_interface = CZMQNotificationInterface::Create(
+        [&chainman = node.chainman](CBlock& block, const CBlockIndex& index) {
+            assert(chainman);
+            return node::ReadBlockFromDisk(block, &index, chainman->GetConsensus());
+        });
 
     if (g_zmq_notification_interface) {
         RegisterValidationInterface(g_zmq_notification_interface.get());

src/zmq/zmqabstractnotifier.h

@@ -6,6 +6,7 @@
 #define BITCOIN_ZMQ_ZMQABSTRACTNOTIFIER_H
 
 #include <cstdint>
+#include <functional>
 #include <memory>
 #include <string>
 
@@ -13,7 +14,7 @@ class CBlockIndex;
 class CTransaction;
 class CZMQAbstractNotifier;
 
-using CZMQNotifierFactory = std::unique_ptr<CZMQAbstractNotifier> (*)();
+using CZMQNotifierFactory = std::function<std::unique_ptr<CZMQAbstractNotifier>()>;
 
 class CZMQAbstractNotifier
 {

src/zmq/zmqnotificationinterface.cpp

@@ -39,12 +39,14 @@ std::list<const CZMQAbstractNotifier*> CZMQNotificationInterface::GetActiveNotif
     return result;
 }
 
-std::unique_ptr<CZMQNotificationInterface> CZMQNotificationInterface::Create()
+std::unique_ptr<CZMQNotificationInterface> CZMQNotificationInterface::Create(std::function<bool(CBlock&, const CBlockIndex&)> get_block_by_index)
 {
     std::map<std::string, CZMQNotifierFactory> factories;
     factories["pubhashblock"] = CZMQAbstractNotifier::Create<CZMQPublishHashBlockNotifier>;
     factories["pubhashtx"] = CZMQAbstractNotifier::Create<CZMQPublishHashTransactionNotifier>;
-    factories["pubrawblock"] = CZMQAbstractNotifier::Create<CZMQPublishRawBlockNotifier>;
+    factories["pubrawblock"] = [&get_block_by_index]() -> std::unique_ptr<CZMQAbstractNotifier> {
+        return std::make_unique<CZMQPublishRawBlockNotifier>(get_block_by_index);
+    };
     factories["pubrawtx"] = CZMQAbstractNotifier::Create<CZMQPublishRawTransactionNotifier>;
     factories["pubsequence"] = CZMQAbstractNotifier::Create<CZMQPublishSequenceNotifier>;
 

src/zmq/zmqnotificationinterface.h

@@ -9,6 +9,7 @@
 #include <validationinterface.h>
 
 #include <cstdint>
+#include <functional>
 #include <list>
 #include <memory>
 
@@ -23,7 +24,7 @@ public:
 
     std::list<const CZMQAbstractNotifier*> GetActiveNotifiers() const;
 
-    static std::unique_ptr<CZMQNotificationInterface> Create();
+    static std::unique_ptr<CZMQNotificationInterface> Create(std::function<bool(CBlock&, const CBlockIndex&)> get_block_by_index);
 
 protected:
     bool Initialize();

src/zmq/zmqpublishnotifier.cpp

@@ -39,8 +39,6 @@ namespace Consensus {
 struct Params;
 }
 
-using node::ReadBlockFromDisk;
-
 static std::multimap<std::string, CZMQAbstractPublishNotifier*> mapPublishNotifiers;
 
 static const char *MSG_HASHBLOCK = "hashblock";
@@ -247,10 +245,9 @@ bool CZMQPublishRawBlockNotifier::NotifyBlock(const CBlockIndex *pindex)
 {
     LogPrint(BCLog::ZMQ, "Publish rawblock %s to %s\n", pindex->GetBlockHash().GetHex(), this->address);
 
-    const Consensus::Params& consensusParams = Params().GetConsensus();
     CDataStream ss(SER_NETWORK, PROTOCOL_VERSION | RPCSerializationFlags());
     CBlock block;
-    if (!ReadBlockFromDisk(block, pindex, consensusParams)) {
+    if (!m_get_block_by_index(block, *pindex)) {
         zmqError("Can't read block from disk");
         return false;
     }

src/zmq/zmqpublishnotifier.h

@@ -9,7 +9,9 @@
 
 #include <cstddef>
 #include <cstdint>
+#include <functional>
 
+class CBlock;
 class CBlockIndex;
 class CTransaction;
 
@@ -46,7 +48,12 @@ public:
 
 class CZMQPublishRawBlockNotifier : public CZMQAbstractPublishNotifier
 {
+private:
+    const std::function<bool(CBlock&, const CBlockIndex&)> m_get_block_by_index;
+
 public:
+    CZMQPublishRawBlockNotifier(std::function<bool(CBlock&, const CBlockIndex&)> get_block_by_index)
+        : m_get_block_by_index{std::move(get_block_by_index)} {}
     bool NotifyBlock(const CBlockIndex *pindex) override;
 };