Add VariantAttorney

src/ArduinoJson/Variant/VariantAttorney.hpp

@@ -0,0 +1,51 @@
+// ArduinoJson - https://arduinojson.org
+// Copyright © 2014-2022, Benoit BLANCHON
+// MIT License
+
+#pragma once
+
+#include <ArduinoJson/Polyfills/attributes.hpp>
+#include <ArduinoJson/Polyfills/type_traits.hpp>
+#include <ArduinoJson/Variant/VariantTo.hpp>
+#include "VariantRef.hpp"
+
+namespace ARDUINOJSON_NAMESPACE {
+
+// Grants access to the internal variant API
+class VariantAttorney {
+  // Tells whether getData() returns a const pointer
+  template <typename TClient>
+  struct ResultOfGetData {
+   protected:  // <- to avoid GCC's "all member functions in class are private"
+    typedef char Yes[1];
+    typedef char No[2];
+
+    static Yes &probe(const VariantData *);
+    static No &probe(VariantData *);
+
+    static TClient &client;
+
+   public:
+    typedef typename conditional<sizeof(probe(client.getData())) == sizeof(Yes),
+                                 const VariantData *, VariantData *>::type type;
+  };
+
+ public:
+  template <typename TClient>
+  FORCE_INLINE static MemoryPool *getPool(TClient &client) {
+    return client.getPool();
+  }
+
+  template <typename TClient>
+  FORCE_INLINE static typename ResultOfGetData<TClient>::type getData(
+      TClient &client) {
+    return client.getData();
+  }
+
+  template <typename TClient>
+  FORCE_INLINE static VariantData *getOrCreateData(TClient &client) {
+    return client.getOrCreateData();
+  }
+};
+
+}  // namespace ARDUINOJSON_NAMESPACE