Add a bitsery extension for serializing void*

Using the `native_size_t` representation. This is needed to be able to
directly serialize CLAP events.

src/common/bitsery/ext/native-pointer.h

@@ -0,0 +1,64 @@
+// yabridge: a Wine plugin bridge
+// Copyright (C) 2020-2022 Robbert van der Helm
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+#pragma once
+
+#include <ghc/filesystem.hpp>
+
+#include <bitsery/details/serialization_common.h>
+#include <bitsery/traits/core/traits.h>
+
+#include "../../serialization/common.h"
+
+namespace bitsery {
+namespace ext {
+
+/**
+ * An adapter for serializing and deserializing native pointer types. This makes
+ * it possible to serialize `void*` fields in CLAP structs as a `native_size_t`
+ * without having to modify the struct. Used in the CLAP event serialization.
+ */
+class NativePointer {
+   public:
+    template <typename Ser, typename Fnc>
+    void serialize(Ser& ser, const void* const& pointer, Fnc&&) const {
+        const auto native_pointer =
+            static_cast<native_size_t>(reinterpret_cast<size_t>(pointer));
+        ser.value8b(native_pointer);
+    }
+
+    template <typename Des, typename Fnc>
+    void deserialize(Des& des, void*& pointer, Fnc&&) const {
+        native_size_t native_pointer;
+        des.value8b(native_pointer);
+        pointer = reinterpret_cast<void*>(static_cast<size_t>(native_pointer));
+    }
+};
+
+}  // namespace ext
+
+namespace traits {
+
+template <>
+struct ExtensionTraits<ext::NativePointer, void*> {
+    using TValue = void;
+    static constexpr bool SupportValueOverload = false;
+    static constexpr bool SupportObjectOverload = true;
+    static constexpr bool SupportLambdaOverload = false;
+};
+
+}  // namespace traits
+}  // namespace bitsery