Add VariantAttorney

src/ArduinoJson/Variant/ConverterImpl.hpp

@@ -37,7 +37,8 @@ struct Converter {
 template <typename T>
 struct Converter<
     T, typename enable_if<is_integral<T>::value && !is_same<bool, T>::value &&
-                          !is_same<char, T>::value>::type> {
+                          !is_same<char, T>::value>::type>
+    : private VariantAttorney {
   static void toJson(T src, VariantRef dst) {
     VariantData* data = getData(dst);
     ARDUINOJSON_ASSERT_INTEGER_TYPE_IS_SUPPORTED(T);
@@ -58,7 +59,8 @@ struct Converter<
 };
 
 template <typename T>
-struct Converter<T, typename enable_if<is_enum<T>::value>::type> {
+struct Converter<T, typename enable_if<is_enum<T>::value>::type>
+    : private VariantAttorney {
   static void toJson(T src, VariantRef dst) {
     dst.set(static_cast<Integer>(src));
   }
@@ -75,7 +77,7 @@ struct Converter<T, typename enable_if<is_enum<T>::value>::type> {
 };
 
 template <>
-struct Converter<bool> {
+struct Converter<bool> : private VariantAttorney {
   static void toJson(bool src, VariantRef dst) {
     VariantData* data = getData(dst);
     if (data)
@@ -94,7 +96,8 @@ struct Converter<bool> {
 };
 
 template <typename T>
-struct Converter<T, typename enable_if<is_floating_point<T>::value>::type> {
+struct Converter<T, typename enable_if<is_floating_point<T>::value>::type>
+    : private VariantAttorney {
   static void toJson(T src, VariantRef dst) {
     VariantData* data = getData(dst);
     if (data)
@@ -113,7 +116,7 @@ struct Converter<T, typename enable_if<is_floating_point<T>::value>::type> {
 };
 
 template <>
-struct Converter<const char*> {
+struct Converter<const char*> : private VariantAttorney {
   static void toJson(const char* src, VariantRef dst) {
     variantSetString(getData(dst), adaptString(src), getPool(dst),
                      getStringStoragePolicy(src));
@@ -131,7 +134,7 @@ struct Converter<const char*> {
 };
 
 template <>
-struct Converter<String> {
+struct Converter<String> : private VariantAttorney {
   static void toJson(String src, VariantRef dst) {
     variantSetString(getData(dst), adaptString(src), getPool(dst),
                      getStringStoragePolicy(src));
@@ -151,8 +154,8 @@ struct Converter<String> {
 template <typename T>
 inline typename enable_if<IsString<T>::value, bool>::type convertToJson(
     const T& src, VariantRef dst) {
-  VariantData* data = getData(dst);
-  MemoryPool* pool = getPool(dst);
+  VariantData* data = VariantAttorney::getData(dst);
+  MemoryPool* pool = VariantAttorney::getPool(dst);
   return variantSetString(data, adaptString(src), pool,
                           getStringStoragePolicy(src));
 }
@@ -160,7 +163,7 @@ inline typename enable_if<IsString<T>::value, bool>::type convertToJson(
 template <>
 struct Converter<SerializedValue<const char*> > {
   static void toJson(SerializedValue<const char*> src, VariantRef dst) {
-    VariantData* data = getData(dst);
+    VariantData* data = VariantAttorney::getData(dst);
     if (data)
       data->setLinkedRaw(src);
   }
@@ -171,7 +174,8 @@ struct Converter<SerializedValue<const char*> > {
 // SerializedValue<const __FlashStringHelper*>
 template <typename T>
 struct Converter<SerializedValue<T>,
-                 typename enable_if<!is_same<const char*, T>::value>::type> {
+                 typename enable_if<!is_same<const char*, T>::value>::type>
+    : private VariantAttorney {
   static void toJson(SerializedValue<T> src, VariantRef dst) {
     VariantData* data = getData(dst);
     MemoryPool* pool = getPool(dst);
@@ -183,7 +187,7 @@ struct Converter<SerializedValue<T>,
 #if ARDUINOJSON_HAS_NULLPTR
 
 template <>
-struct Converter<decltype(nullptr)> {
+struct Converter<decltype(nullptr)> : private VariantAttorney {
   static void toJson(decltype(nullptr), VariantRef dst) {
     variantSetNull(getData(dst));
   }
@@ -241,8 +245,8 @@ class MemoryPoolPrint : public Print {
 };
 
 inline void convertToJson(const ::Printable& src, VariantRef dst) {
-  MemoryPool* pool = getPool(dst);
-  VariantData* data = getData(dst);
+  MemoryPool* pool = VariantAttorney::getPool(dst);
+  VariantData* data = VariantAttorney::getData(dst);
   if (!pool || !data)
     return;
   MemoryPoolPrint print(pool);

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

src/ArduinoJson/Variant/VariantCompare.hpp

@@ -180,7 +180,8 @@ struct VariantComparer : ComparerBase {
  private:
   template <typename TComparer>
   CompareResult accept(TComparer &comparer) {
-    CompareResult reversedResult = variantAccept(getData(rhs), comparer);
+    CompareResult reversedResult =
+        variantAccept(VariantAttorney::getData(rhs), comparer);
     switch (reversedResult) {
       case COMPARE_RESULT_GREATER:
         return COMPARE_RESULT_LESS;
@@ -203,7 +204,7 @@ struct Comparer<
 template <typename T>
 CompareResult compare(VariantConstRef lhs, const T &rhs) {
   Comparer<T> comparer(rhs);
-  return variantAccept(getData(lhs), comparer);
+  return variantAccept(VariantAttorney::getData(lhs), comparer);
 }
 
 }  // namespace ARDUINOJSON_NAMESPACE

src/ArduinoJson/Variant/VariantRef.hpp

@@ -11,6 +11,7 @@
 #include <ArduinoJson/Polyfills/type_traits.hpp>
 #include <ArduinoJson/Strings/StringAdapters.hpp>
 #include <ArduinoJson/Variant/Converter.hpp>
+#include <ArduinoJson/Variant/VariantAttorney.hpp>
 #include <ArduinoJson/Variant/VariantFunctions.hpp>
 #include <ArduinoJson/Variant/VariantOperators.hpp>
 #include <ArduinoJson/Variant/VariantRef.hpp>
@@ -50,10 +51,6 @@ class VariantRefBase : public VariantTag {
  protected:
   VariantRefBase(TData *data) : _data(data) {}
   TData *_data;
-
-  friend TData *getData(const VariantRefBase &variant) {
-    return variant._data;
-  }
 };
 
 class VariantConstRef : public VariantRefBase<const VariantData>,
@@ -61,6 +58,8 @@ class VariantConstRef : public VariantRefBase<const VariantData>,
                         public VariantShortcuts<VariantConstRef> {
   typedef VariantRefBase<const VariantData> base_type;
 
+  friend class VariantAttorney;
+
  public:
   VariantConstRef() : base_type(0) {}
   explicit VariantConstRef(const VariantData *data) : base_type(data) {}
@@ -139,6 +138,7 @@ class VariantConstRef : public VariantRefBase<const VariantData>,
     return VariantConstRef(variantGetMember(_data, adaptString(key)));
   }
 
+ protected:
   const VariantData *getData() const {
     return _data;
   }
@@ -285,7 +285,7 @@ class VariantRef : public VariantRefBase<VariantData>,
   inline void shallowCopy(VariantConstRef target) {
     if (!_data)
       return;
-    const VariantData *targetData = target.getData();
+    const VariantData *targetData = VariantAttorney::getData(target);
     if (targetData)
       *_data = *targetData;
     else
@@ -306,14 +306,10 @@ class VariantRef : public VariantRefBase<VariantData>,
 
  private:
   MemoryPool *_pool;
-
-  friend MemoryPool *getPool(const VariantRef &variant) {
-    return variant._pool;
-  }
 };
 
 template <>
-struct Converter<VariantRef> {
+struct Converter<VariantRef> : private VariantAttorney {
   static void toJson(VariantRef src, VariantRef dst) {
     variantCopyFrom(getData(dst), getData(src), getPool(dst));
   }
@@ -336,7 +332,7 @@ struct Converter<VariantRef> {
 };
 
 template <>
-struct Converter<VariantConstRef> {
+struct Converter<VariantConstRef> : private VariantAttorney {
   static void toJson(VariantConstRef src, VariantRef dst) {
     variantCopyFrom(getData(dst), getData(src), getPool(dst));
   }