Squashed 'src/ipc/libmultiprocess/' content from commit 35944ffd23fa

git-subtree-dir: src/ipc/libmultiprocess
git-subtree-split: 35944ffd23fa26652b82210351d50e896ce16c8f

include/mp/type-function.h

@@ -0,0 +1,67 @@
+// 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_FUNCTION_H
+#define MP_PROXY_TYPE_FUNCTION_H
+
+#include <mp/util.h>
+
+namespace mp {
+//! Adapter to convert ProxyCallback object call to function object call.
+template <typename Result, typename... Args>
+class ProxyCallbackImpl final : public ProxyCallback<std::function<Result(Args...)>>
+{
+    using Fn = std::function<Result(Args...)>;
+    Fn m_fn;
+
+public:
+    ProxyCallbackImpl(Fn fn) : m_fn(std::move(fn)) {}
+    Result call(Args&&... args) override { return m_fn(std::forward<Args>(args)...); }
+};
+
+template <typename Value, typename FnR, typename... FnParams, typename Output>
+void CustomBuildField(TypeList<std::function<FnR(FnParams...)>>,
+    Priority<1>,
+    InvokeContext& invoke_context,
+    Value& value,
+    Output&& output)
+{
+    if (value) {
+        using Interface = typename decltype(output.get())::Calls;
+        using Callback = ProxyCallbackImpl<FnR, FnParams...>;
+        output.set(kj::heap<ProxyServer<Interface>>(
+            std::make_shared<Callback>(std::forward<Value>(value)), invoke_context.connection));
+    }
+}
+
+// ProxyCallFn class is needed because c++11 doesn't support auto lambda parameters.
+// It's equivalent c++14: [invoke_context](auto&& params) {
+// invoke_context->call(std::forward<decltype(params)>(params)...)
+template <typename InvokeContext>
+struct ProxyCallFn
+{
+    InvokeContext m_proxy;
+
+    template <typename... CallParams>
+    decltype(auto) operator()(CallParams&&... params) { return this->m_proxy->call(std::forward<CallParams>(params)...); }
+};
+
+template <typename FnR, typename... FnParams, typename Input, typename ReadDest>
+decltype(auto) CustomReadField(TypeList<std::function<FnR(FnParams...)>>,
+    Priority<1>,
+    InvokeContext& invoke_context,
+    Input&& input,
+    ReadDest&& read_dest)
+{
+    if (input.has()) {
+        using Interface = typename Decay<decltype(input.get())>::Calls;
+        auto client = std::make_shared<ProxyClient<Interface>>(
+            input.get(), &invoke_context.connection, /* destroy_connection= */ false);
+        return read_dest.construct(ProxyCallFn<decltype(client)>{std::move(client)});
+    }
+    return read_dest.construct();
+};
+} // namespace mp
+
+#endif // MP_PROXY_TYPE_FUNCTION_H