multiprocess: Add serialization code for BlockValidationState

Co-authored-by: TheCharlatan <seb.kung@gmail.com>

src/ipc/CMakeLists.txt

@@ -3,6 +3,7 @@
 # file COPYING or https://opensource.org/license/mit/.
 
 add_library(bitcoin_ipc STATIC EXCLUDE_FROM_ALL
+  capnp/mining.cpp
   capnp/protocol.cpp
   interfaces.cpp
   process.cpp

src/ipc/capnp/mining-types.h

@@ -13,4 +13,14 @@
 #include <node/types.h>
 #include <validation.h>
 
+namespace mp {
+// Custom serialization for BlockValidationState.
+void CustomBuildMessage(InvokeContext& invoke_context,
+                        const BlockValidationState& src,
+                        ipc::capnp::messages::BlockValidationState::Builder&& builder);
+void CustomReadMessage(InvokeContext& invoke_context,
+                       const ipc::capnp::messages::BlockValidationState::Reader& reader,
+                       BlockValidationState& dest);
+} // namespace mp
+
 #endif // BITCOIN_IPC_CAPNP_MINING_TYPES_H

src/ipc/capnp/mining.capnp

@@ -39,6 +39,12 @@ struct BlockCreateOptions $Proxy.wrap("node::BlockCreateOptions") {
     coinbaseOutputMaxAdditionalSigops @2 :UInt64 $Proxy.name("coinbase_output_max_additional_sigops");
 }
 
-# TODO add fields to this struct
-struct BlockValidationState $Proxy.wrap("BlockValidationState") {
+# Note: serialization of the BlockValidationState C++ type is somewhat fragile
+# and using the struct can be awkward. It would be good if testBlockValidity
+# method were changed to return validity information in a simpler format.
+struct BlockValidationState {
+    mode @0 :Int32;
+    result @1 :Int32;
+    rejectReason @2 :Text;
+    debugMessage @3 :Text;
 }

src/ipc/capnp/mining.cpp

@@ -0,0 +1,47 @@
+// Copyright (c) 2024 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include <ipc/capnp/mining-types.h>
+#include <ipc/capnp/mining.capnp.proxy-types.h>
+
+#include <mp/proxy-types.h>
+
+namespace mp {
+void CustomBuildMessage(InvokeContext& invoke_context,
+                        const BlockValidationState& src,
+                        ipc::capnp::messages::BlockValidationState::Builder&& builder)
+{
+    if (src.IsValid()) {
+        builder.setMode(0);
+    } else if (src.IsInvalid()) {
+        builder.setMode(1);
+    } else if (src.IsError()) {
+        builder.setMode(2);
+    } else {
+        assert(false);
+    }
+    builder.setResult(static_cast<int>(src.GetResult()));
+    builder.setRejectReason(src.GetRejectReason());
+    builder.setDebugMessage(src.GetDebugMessage());
+}
+
+void CustomReadMessage(InvokeContext& invoke_context,
+                       const ipc::capnp::messages::BlockValidationState::Reader& reader,
+                       BlockValidationState& dest)
+{
+    if (reader.getMode() == 0) {
+        assert(reader.getResult() == 0);
+        assert(reader.getRejectReason().size() == 0);
+        assert(reader.getDebugMessage().size() == 0);
+    } else if (reader.getMode() == 1) {
+        dest.Invalid(static_cast<BlockValidationResult>(reader.getResult()), reader.getRejectReason(), reader.getDebugMessage());
+    } else if (reader.getMode() == 2) {
+        assert(reader.getResult() == 0);
+        dest.Error(reader.getRejectReason());
+        assert(reader.getDebugMessage().size() == 0);
+    } else {
+        assert(false);
+    }
+}
+} // namespace mp