moveonly: add mp/type-optional.h

Author: ryanofsky

CMakeLists.txt

@@ -46,6 +46,7 @@ set(MP_PUBLIC_HEADERS
   include/mp/proxy-types.h
   include/mp/proxy.h
   include/mp/type-context.h
+  include/mp/type-optional.h
   include/mp/util.h)
 add_library(multiprocess STATIC
   ${MP_PROXY_SRCS}

include/mp/proxy-types.h

@@ -141,27 +141,6 @@ struct ReadDestUpdate
     Value& m_value;
 };
 
-template <typename LocalType, typename Input, typename ReadDest>
-decltype(auto) CustomReadField(TypeList<std::optional<LocalType>>,
-    Priority<1>,
-    InvokeContext& invoke_context,
-    Input&& input,
-    ReadDest&& read_dest)
-{
-    return read_dest.update([&](auto& value) {
-        if (!input.has()) {
-            value.reset();
-        } else if (value) {
-            ReadField(TypeList<LocalType>(), invoke_context, input, ReadDestUpdate(*value));
-        } else {
-            ReadField(TypeList<LocalType>(), invoke_context, input,
-                ReadDestEmplace(TypeList<LocalType>(), [&](auto&&... args) -> auto& {
-                    value.emplace(std::forward<decltype(args)>(args)...);
-                    return *value;
-                }));
-        }
-    });
-}
 
 template <typename LocalType, typename Input, typename ReadDest>
 decltype(auto) CustomReadField(TypeList<std::shared_ptr<LocalType>>,
@@ -824,20 +803,6 @@ LocalType BuildPrimitive(InvokeContext& invoke_context,
     return value;
 }
 
-template <typename LocalType, typename Value, typename Output>
-void CustomBuildField(TypeList<std::optional<LocalType>>,
-    Priority<1>,
-    InvokeContext& invoke_context,
-    Value&& value,
-    Output&& output)
-{
-    if (value) {
-        output.setHas();
-        // FIXME: should std::move value if destvalue is rref?
-        BuildField(TypeList<LocalType>(), invoke_context, output, *value);
-    }
-}
-
 template <typename Output>
 void CustomBuildField(TypeList<std::exception>,
     Priority<1>,

include/mp/type-optional.h

@@ -0,0 +1,48 @@
+// Copyright (c) 2025 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef MP_PROXY_TYPE_OPTIONAL_H
+#define MP_PROXY_TYPE_OPTIONAL_H
+
+#include <mp/util.h>
+
+namespace mp {
+template <typename LocalType, typename Value, typename Output>
+void CustomBuildField(TypeList<std::optional<LocalType>>,
+    Priority<1>,
+    InvokeContext& invoke_context,
+    Value&& value,
+    Output&& output)
+{
+    if (value) {
+        output.setHas();
+        // FIXME: should std::move value if destvalue is rref?
+        BuildField(TypeList<LocalType>(), invoke_context, output, *value);
+    }
+}
+
+template <typename LocalType, typename Input, typename ReadDest>
+decltype(auto) CustomReadField(TypeList<std::optional<LocalType>>,
+    Priority<1>,
+    InvokeContext& invoke_context,
+    Input&& input,
+    ReadDest&& read_dest)
+{
+    return read_dest.update([&](auto& value) {
+        if (!input.has()) {
+            value.reset();
+        } else if (value) {
+            ReadField(TypeList<LocalType>(), invoke_context, input, ReadDestUpdate(*value));
+        } else {
+            ReadField(TypeList<LocalType>(), invoke_context, input,
+                ReadDestEmplace(TypeList<LocalType>(), [&](auto&&... args) -> auto& {
+                    value.emplace(std::forward<decltype(args)>(args)...);
+                    return *value;
+                }));
+        }
+    });
+}
+} // namespace mp
+
+#endif // MP_PROXY_TYPE_OPTIONAL_H