Clear the JsonObject or JsonArray in deserializeJson()

src/ArduinoJson/Data/List.hpp

@@ -89,6 +89,10 @@ class List {
   }
 
  protected:
+  void clear() {
+    _firstNode = 0;
+  }
+
   JsonBuffer *_buffer;
 
  private:

src/ArduinoJson/DynamicJsonArray.hpp

@@ -16,6 +16,11 @@ class DynamicJsonArray : public JsonArray {
   DynamicJsonArray(size_t capacity)
       : JsonArray(&_buffer), _buffer(capacity - sizeof(JsonArray)) {}
 
+  void clear() {
+    Internals::List<JsonVariant>::clear();
+    _buffer.clear();
+  }
+
   size_t memoryUsage() const {
     return _buffer.size() + sizeof(JsonArray);
   }

src/ArduinoJson/DynamicJsonObject.hpp

@@ -20,6 +20,11 @@ class DynamicJsonObject : public JsonObject {
     return _buffer;
   }
 
+  void clear() {
+    Internals::List<JsonPair>::clear();
+    _buffer.clear();
+  }
+
   size_t memoryUsage() const {
     return _buffer.size() + sizeof(JsonObject);
   }

src/ArduinoJson/DynamicJsonVariant.hpp

@@ -14,6 +14,7 @@ class DynamicJsonVariant : public JsonVariant {
 
  public:
   DynamicJsonVariant() : JsonVariant() {}
+  DynamicJsonVariant(size_t capacity) : JsonVariant(), _buffer(capacity) {}
 
   template <typename T>
   DynamicJsonVariant& operator=(const T& value) {
@@ -33,8 +34,12 @@ class DynamicJsonVariant : public JsonVariant {
     return _buffer;
   }
 
+  void clear() {
+    _buffer.clear();
+  }
+
   size_t memoryUsage() const {
-    return _buffer.size() + sizeof(JsonVariant);
+    return _buffer.size();
   }
 };
 }  // namespace ArduinoJson

src/ArduinoJson/StaticJsonArray.hpp

@@ -16,6 +16,11 @@ class StaticJsonArray : public JsonArray {
  public:
   StaticJsonArray() : JsonArray(&_buffer) {}
 
+  void clear() {
+    Internals::List<JsonVariant>::clear();
+    _buffer.clear();
+  }
+
   size_t memoryUsage() const {
     return _buffer.size() + sizeof(JsonArray);
   }

src/ArduinoJson/StaticJsonObject.hpp

@@ -16,6 +16,11 @@ class StaticJsonObject : public JsonObject {
  public:
   StaticJsonObject() : JsonObject(&_buffer) {}
 
+  void clear() {
+    Internals::List<JsonPair>::clear();
+    _buffer.clear();
+  }
+
   size_t memoryUsage() const {
     return _buffer.size() + sizeof(JsonObject);
   }

src/ArduinoJson/StaticJsonVariant.hpp

@@ -11,7 +11,7 @@ namespace ArduinoJson {
 
 template <size_t CAPACITY = sizeof(JsonVariant)>
 class StaticJsonVariant : public JsonVariant {
-  StaticJsonBuffer<CAPACITY - sizeof(JsonVariant)> _buffer;
+  StaticJsonBuffer<CAPACITY> _buffer;
 
  public:
   template <typename T>
@@ -32,8 +32,12 @@ class StaticJsonVariant : public JsonVariant {
     return _buffer;
   }
 
+  void clear() {
+    _buffer.clear();
+  }
+
   size_t memoryUsage() const {
-    return _buffer.size() + sizeof(JsonVariant);
+    return _buffer.size();
   }
 };
 }  // namespace ArduinoJson

src/ArduinoJson/deserializeJson.hpp

@@ -15,6 +15,7 @@ typename Internals::EnableIf<!Internals::IsArray<TString>::value,
                              JsonError>::type
 deserializeJson(TDestination &destination, const TString &json,
                 uint8_t nestingLimit = ARDUINOJSON_DEFAULT_NESTING_LIMIT) {
+  destination.clear();
   return Internals::makeParser(&destination.buffer(), json, nestingLimit)
       .parse(destination);
 }
@@ -26,6 +27,7 @@ template <typename TDestination, typename TString>
 JsonError deserializeJson(
     TDestination &destination, TString *json,
     uint8_t nestingLimit = ARDUINOJSON_DEFAULT_NESTING_LIMIT) {
+  destination.clear();
   return Internals::makeParser(&destination.buffer(), json, nestingLimit)
       .parse(destination);
 }
@@ -37,6 +39,7 @@ template <typename TDestination, typename TString>
 JsonError deserializeJson(
     TDestination &destination, TString &json,
     uint8_t nestingLimit = ARDUINOJSON_DEFAULT_NESTING_LIMIT) {
+  destination.clear();
   return Internals::makeParser(&destination.buffer(), json, nestingLimit)
       .parse(destination);
 }