Change link() to shallowCopy() (issue #1343)

Instead of storing a pointer, the function copies the `VariantData`.

Benefits:
* smaller code
* no impact on programs that don't use this feature

Drawbacks:
* changes to the original variant are not always reflected on the copy
* modifying the original from the shallow copy leads to UB

src/ArduinoJson/Array/ArrayRef.hpp

@@ -202,12 +202,12 @@ struct Converter<ArrayConstRef> {
 
   static ArrayConstRef fromJson(VariantConstRef src) {
     const VariantData* data = getData(src);
-    return data ? data->resolve()->asArray() : 0;
+    return data ? data->asArray() : 0;
   }
 
   static bool checkJson(VariantConstRef src) {
     const VariantData* data = getData(src);
-    return data && data->resolve()->isArray();
+    return data && data->isArray();
   }
 };
 

src/ArduinoJson/Array/ElementProxy.hpp

@@ -106,8 +106,8 @@ class ElementProxy : public VariantOperators<ElementProxy<TArray> >,
     return getOrAddUpstreamElement().template to<T>();
   }
 
-  FORCE_INLINE void link(VariantConstRef value) const {
-    getOrAddUpstreamElement().link(value);
+  FORCE_INLINE void shallowCopy(VariantConstRef value) const {
+    getOrAddUpstreamElement().shallowCopy(value);
   }
 
   // Replaces the value

src/ArduinoJson/Collection/CollectionImpl.hpp

@@ -17,6 +17,7 @@ inline VariantSlot* CollectionData::addSlot(MemoryPool* pool) {
     return 0;
 
   if (_tail) {
+    ARDUINOJSON_ASSERT(pool->owns(_tail));  // Can't alter a linked array/object
     _tail->setNextNotNull(slot);
     _tail = slot;
   } else {

src/ArduinoJson/Document/JsonDocument.hpp

@@ -62,7 +62,7 @@ class JsonDocument : public VariantOperators<const JsonDocument&> {
   }
 
   size_t size() const {
-    return _data.resolve()->size();
+    return _data.size();
   }
 
   bool set(const JsonDocument& src) {

src/ArduinoJson/Json/JsonSerializer.hpp

@@ -24,7 +24,7 @@ class JsonSerializer : public Visitor<size_t> {
     const VariantSlot *slot = array.head();
 
     while (slot != 0) {
-      slot->data()->resolve()->accept(*this);
+      slot->data()->accept(*this);
 
       slot = slot->next();
       if (slot == 0)
@@ -45,7 +45,7 @@ class JsonSerializer : public Visitor<size_t> {
     while (slot != 0) {
       _formatter.writeString(slot->key());
       write(':');
-      slot->data()->resolve()->accept(*this);
+      slot->data()->accept(*this);
 
       slot = slot->next();
       if (slot == 0)

src/ArduinoJson/Json/PrettyJsonSerializer.hpp

@@ -25,7 +25,7 @@ class PrettyJsonSerializer : public JsonSerializer<TWriter> {
       _nesting++;
       while (slot != 0) {
         indent();
-        slot->data()->resolve()->accept(*this);
+        slot->data()->accept(*this);
 
         slot = slot->next();
         base::write(slot ? ",\r\n" : "\r\n");
@@ -48,7 +48,7 @@ class PrettyJsonSerializer : public JsonSerializer<TWriter> {
         indent();
         base::visitString(slot->key());
         base::write(": ");
-        slot->data()->resolve()->accept(*this);
+        slot->data()->accept(*this);
 
         slot = slot->next();
         base::write(slot ? ",\r\n" : "\r\n");

src/ArduinoJson/MsgPack/MsgPackSerializer.hpp

@@ -56,7 +56,7 @@ class MsgPackSerializer : public Visitor<size_t> {
       writeInteger(uint32_t(n));
     }
     for (const VariantSlot* slot = array.head(); slot; slot = slot->next()) {
-      slot->data()->resolve()->accept(*this);
+      slot->data()->accept(*this);
     }
     return bytesWritten();
   }
@@ -74,7 +74,7 @@ class MsgPackSerializer : public Visitor<size_t> {
     }
     for (const VariantSlot* slot = object.head(); slot; slot = slot->next()) {
       visitString(slot->key());
-      slot->data()->resolve()->accept(*this);
+      slot->data()->accept(*this);
     }
     return bytesWritten();
   }

src/ArduinoJson/Object/MemberProxy.hpp

@@ -132,8 +132,8 @@ class MemberProxy : public VariantOperators<MemberProxy<TObject, TStringRef> >,
     getUpstreamMember().remove(key);
   }
 
-  FORCE_INLINE void link(VariantConstRef value) {
-    getOrAddUpstreamMember().link(value);
+  FORCE_INLINE void shallowCopy(VariantConstRef value) {
+    getOrAddUpstreamMember().shallowCopy(value);
   }
 
   template <typename TValue>

src/ArduinoJson/Object/ObjectRef.hpp

@@ -269,12 +269,12 @@ struct Converter<ObjectConstRef> {
 
   static ObjectConstRef fromJson(VariantConstRef src) {
     const VariantData* data = getData(src);
-    return data != 0 ? data->resolve()->asObject() : 0;
+    return data != 0 ? data->asObject() : 0;
   }
 
   static bool checkJson(VariantConstRef src) {
     const VariantData* data = getData(src);
-    return data && data->resolve()->isObject();
+    return data && data->isObject();
   }
 };
 

src/ArduinoJson/Variant/ConverterImpl.hpp

@@ -48,12 +48,12 @@ struct Converter<
   static T fromJson(VariantConstRef src) {
     ARDUINOJSON_ASSERT_INTEGER_TYPE_IS_SUPPORTED(T);
     const VariantData* data = getData(src);
-    return data ? data->resolve()->asIntegral<T>() : T();
+    return data ? data->asIntegral<T>() : T();
   }
 
   static bool checkJson(VariantConstRef src) {
     const VariantData* data = getData(src);
-    return data && data->resolve()->isInteger<T>();
+    return data && data->isInteger<T>();
   }
 };
 
@@ -65,12 +65,12 @@ struct Converter<T, typename enable_if<is_enum<T>::value>::type> {
 
   static T fromJson(VariantConstRef src) {
     const VariantData* data = getData(src);
-    return data ? static_cast<T>(data->resolve()->asIntegral<int>()) : T();
+    return data ? static_cast<T>(data->asIntegral<int>()) : T();
   }
 
   static bool checkJson(VariantConstRef src) {
     const VariantData* data = getData(src);
-    return data && data->resolve()->isInteger<int>();
+    return data && data->isInteger<int>();
   }
 };
 
@@ -84,12 +84,12 @@ struct Converter<bool> {
 
   static bool fromJson(VariantConstRef src) {
     const VariantData* data = getData(src);
-    return data ? data->resolve()->asBoolean() : false;
+    return data ? data->asBoolean() : false;
   }
 
   static bool checkJson(VariantConstRef src) {
     const VariantData* data = getData(src);
-    return data && data->resolve()->isBoolean();
+    return data && data->isBoolean();
   }
 };
 
@@ -103,12 +103,12 @@ struct Converter<T, typename enable_if<is_floating_point<T>::value>::type> {
 
   static T fromJson(VariantConstRef src) {
     const VariantData* data = getData(src);
-    return data ? data->resolve()->asFloat<T>() : 0;
+    return data ? data->asFloat<T>() : 0;
   }
 
   static bool checkJson(VariantConstRef src) {
     const VariantData* data = getData(src);
-    return data && data->resolve()->isFloat();
+    return data && data->isFloat();
   }
 };
 
@@ -121,12 +121,12 @@ struct Converter<const char*> {
 
   static const char* fromJson(VariantConstRef src) {
     const VariantData* data = getData(src);
-    return data ? data->resolve()->asString().c_str() : 0;
+    return data ? data->asString().c_str() : 0;
   }
 
   static bool checkJson(VariantConstRef src) {
     const VariantData* data = getData(src);
-    return data && data->resolve()->isString();
+    return data && data->isString();
   }
 };
 
@@ -139,12 +139,12 @@ struct Converter<String> {
 
   static String fromJson(VariantConstRef src) {
     const VariantData* data = getData(src);
-    return data ? data->resolve()->asString() : 0;
+    return data ? data->asString() : 0;
   }
 
   static bool checkJson(VariantConstRef src) {
     const VariantData* data = getData(src);
-    return data && data->resolve()->isString();
+    return data && data->isString();
   }
 };
 
@@ -192,7 +192,7 @@ struct Converter<decltype(nullptr)> {
   }
   static bool checkJson(VariantConstRef src) {
     const VariantData* data = getData(src);
-    return data == 0 || data->resolve()->isNull();
+    return data == 0 || data->isNull();
   }
 };
 

src/ArduinoJson/Variant/VariantContent.hpp

@@ -31,8 +31,6 @@ enum {
   VALUE_IS_SIGNED_INTEGER = 0x0A,
   VALUE_IS_FLOAT = 0x0C,
 
-  VALUE_IS_POINTER = 0x10,
-
   COLLECTION_MASK = 0x60,
   VALUE_IS_OBJECT = 0x20,
   VALUE_IS_ARRAY = 0x40,
@@ -51,7 +49,6 @@ union VariantContent {
   UInt asUnsignedInteger;
   Integer asSignedInteger;
   CollectionData asCollection;
-  const class VariantData *asPointer;
   struct {
     const char *data;
     size_t size;

src/ArduinoJson/Variant/VariantData.hpp

@@ -37,6 +37,11 @@ class VariantData {
     _flags = VALUE_IS_NULL;
   }
 
+  void operator=(const VariantData &src) {
+    _content = src._content;
+    _flags = uint8_t((_flags & OWNED_KEY_BIT) | (src._flags & ~OWNED_KEY_BIT));
+  }
+
   template <typename TVisitor>
   typename TVisitor::result_type accept(TVisitor &visitor) const {
     switch (type()) {
@@ -83,12 +88,6 @@ class VariantData {
 
   bool asBoolean() const;
 
-  const VariantData *resolve() const {
-    if (isPointer())
-      return _content.asPointer->resolve();
-    return this;
-  }
-
   CollectionData *asArray() {
     return isArray() ? &_content.asCollection : 0;
   }
@@ -123,10 +122,6 @@ class VariantData {
     return (_flags & COLLECTION_MASK) != 0;
   }
 
-  bool isPointer() const {
-    return type() == VALUE_IS_POINTER;
-  }
-
   template <typename T>
   bool isInteger() const {
     switch (type()) {
@@ -222,12 +217,6 @@ class VariantData {
     setType(VALUE_IS_NULL);
   }
 
-  void setPointer(const VariantData *p) {
-    ARDUINOJSON_ASSERT(p);
-    setType(VALUE_IS_POINTER);
-    _content.asPointer = p;
-  }
-
   void setString(String s) {
     ARDUINOJSON_ASSERT(s);
     if (s.isLinked())

src/ArduinoJson/Variant/VariantFunctions.hpp

@@ -15,7 +15,7 @@ template <typename TVisitor>
 inline typename TVisitor::result_type variantAccept(const VariantData *var,
                                                     TVisitor &visitor) {
   if (var != 0)
-    return var->resolve()->accept(visitor);
+    return var->accept(visitor);
   else
     return visitor.visitNull();
 }
@@ -44,7 +44,7 @@ inline bool variantSetString(VariantData *var, TAdaptedString value,
 }
 
 inline size_t variantSize(const VariantData *var) {
-  return var != 0 ? var->resolve()->size() : 0;
+  return var != 0 ? var->size() : 0;
 }
 
 inline CollectionData *variantToArray(VariantData *var) {
@@ -90,14 +90,14 @@ NO_INLINE VariantData *variantGetOrAddMember(VariantData *var,
 }
 
 inline bool variantIsNull(const VariantData *var) {
-  return var == 0 || var->resolve()->isNull();
+  return var == 0 || var->isNull();
 }
 
 inline size_t variantNesting(const VariantData *var) {
   if (!var)
     return 0;
 
-  const CollectionData *collection = var->resolve()->asCollection();
+  const CollectionData *collection = var->asCollection();
   if (!collection)
     return 0;
 

src/ArduinoJson/Variant/VariantRef.hpp

@@ -117,8 +117,7 @@ class VariantConstRef : public VariantRefBase<const VariantData>,
   }
 
   FORCE_INLINE VariantConstRef getElementConst(size_t index) const {
-    return VariantConstRef(_data != 0 ? _data->resolve()->getElement(index)
-                                      : 0);
+    return VariantConstRef(_data != 0 ? _data->getElement(index) : 0);
   }
 
   FORCE_INLINE VariantConstRef operator[](size_t index) const {
@@ -129,8 +128,7 @@ class VariantConstRef : public VariantRefBase<const VariantData>,
   // getMemberConst(const String&) const
   template <typename TString>
   FORCE_INLINE VariantConstRef getMemberConst(const TString &key) const {
-    return VariantConstRef(_data ? _data->resolve()->getMember(adaptString(key))
-                                 : 0);
+    return VariantConstRef(_data ? _data->getMember(adaptString(key)) : 0);
   }
 
   // getMemberConst(char*) const
@@ -138,8 +136,7 @@ class VariantConstRef : public VariantRefBase<const VariantData>,
   // getMemberConst(const __FlashStringHelper*) const
   template <typename TChar>
   FORCE_INLINE VariantConstRef getMemberConst(TChar *key) const {
-    return VariantConstRef(_data ? _data->resolve()->getMember(adaptString(key))
-                                 : 0);
+    return VariantConstRef(_data ? _data->getMember(adaptString(key)) : 0);
   }
 
   // operator[](const std::string&) const
@@ -281,8 +278,7 @@ class VariantRef : public VariantRefBase<VariantData>,
   }
 
   FORCE_INLINE VariantConstRef getElementConst(size_t index) const {
-    return VariantConstRef(_data != 0 ? _data->resolve()->getElement(index)
-                                      : 0);
+    return VariantConstRef(_data != 0 ? _data->getElement(index) : 0);
   }
 
   FORCE_INLINE VariantRef getOrAddElement(size_t index) const {
@@ -310,8 +306,7 @@ class VariantRef : public VariantRefBase<VariantData>,
   // getMemberConst(const __FlashStringHelper*) const
   template <typename TChar>
   FORCE_INLINE VariantConstRef getMemberConst(TChar *key) const {
-    return VariantConstRef(_data ? _data->resolve()->getMember(adaptString(key))
-                                 : 0);
+    return VariantConstRef(_data ? _data->getMember(adaptString(key)) : 0);
   }
 
   // getMemberConst(const std::string&) const
@@ -320,8 +315,7 @@ class VariantRef : public VariantRefBase<VariantData>,
   FORCE_INLINE
       typename enable_if<IsString<TString>::value, VariantConstRef>::type
       getMemberConst(const TString &key) const {
-    return VariantConstRef(_data ? _data->resolve()->getMember(adaptString(key))
-                                 : 0);
+    return VariantConstRef(_data ? _data->getMember(adaptString(key)) : 0);
   }
 
   // getOrAddMember(char*) const
@@ -361,12 +355,12 @@ class VariantRef : public VariantRefBase<VariantData>,
       _data->remove(adaptString(key));
   }
 
-  inline void link(VariantConstRef target) {
+  inline void shallowCopy(VariantConstRef target) {
     if (!_data)
       return;
     const VariantData *targetData = getData(target);
     if (targetData)
-      _data->setPointer(targetData);
+      *_data = *targetData;
     else
       _data->setNull();
   }