VariantImpl: add toArrayIfNull() and toObjectIfNull()

This removes the two-way dependency between `JsonVariant` and `VariantImpl`

.github/workflows/ci.yml

@@ -93,44 +93,40 @@ jobs:
       fail-fast: false
       matrix:
         include:
-          - clang: "3.9"
-            runner: ubuntu-20.04
-            archive: bionic
-          - clang: "4.0"
-            runner: ubuntu-20.04
-            archive: bionic
-          - clang: "5.0"
-            runner: ubuntu-20.04
-            archive: bionic
-          - clang: "6.0"
-            runner: ubuntu-20.04
-            archive: bionic
           - clang: "7"
-            runner: ubuntu-20.04
+            runner: ubuntu-22.04
+            archive: focal
           - clang: "8"
             cxxflags: -fsanitize=leak -fno-sanitize-recover=all
-            runner: ubuntu-20.04
+            runner: ubuntu-22.04
+            archive: focal
           - clang: "9"
             cxxflags: -fsanitize=undefined -fno-sanitize-recover=all
-            runner: ubuntu-20.04
+            runner: ubuntu-22.04
+            archive: focal
           - clang: "10"
             cxxflags: -fsanitize=address -fno-sanitize-recover=all
-            runner: ubuntu-20.04
+            runner: ubuntu-22.04
+            archive: focal
           - clang: "11"
             runner: ubuntu-22.04
           - clang: "12"
             runner: ubuntu-22.04
           - clang: "13"
             runner: ubuntu-22.04
-          - clang: "14"
-            runner: ubuntu-22.04
-          - clang: "15"
-            runner: ubuntu-22.04
-    runs-on: ${{ matrix.runner }}
+          - clang: 14
+          - clang: 15
+          - clang: 16
+          - clang: 17
+          - clang: 18
+          - clang: 19
+    runs-on: ${{ matrix.runner || 'ubuntu-latest' }}
     steps:
       - name: Add archive repositories
         if: matrix.archive
         run: |
+          sudo gpg --keyserver keyserver.ubuntu.com --recv-keys 3B4FE6ACC0B21F32
+          sudo gpg --export 3B4FE6ACC0B21F32 | sudo tee /etc/apt/trusted.gpg.d/ubuntu-keyring.gpg > /dev/null
           sudo add-apt-repository -yn 'deb http://archive.ubuntu.com/ubuntu/ ${{ matrix.archive }} main'
           sudo add-apt-repository -yn 'deb http://archive.ubuntu.com/ubuntu/ ${{ matrix.archive }} universe'
       - name: Install Clang ${{ matrix.clang }}
@@ -138,10 +134,9 @@ jobs:
           sudo apt-get update
           sudo apt-get install -y clang-${{ matrix.clang }}
       - name: Install libc++ ${{ matrix.clang }}
-        if: matrix.clang >= 11
         run: sudo apt-get install -y libc++-${{ matrix.clang }}-dev libc++abi-${{ matrix.clang }}-dev
       - name: Install libunwind ${{ matrix.clang }}
-        if: matrix.clang == 12  # dependency is missing in Ubuntu 22.04
+        if: matrix.clang == 12 # dependency is missing in Ubuntu 22.04
         run: sudo apt-get install -y libunwind-${{ matrix.clang }}-dev
       - name: Checkout
         uses: actions/checkout@v4
@@ -163,7 +158,7 @@ jobs:
   conf_test:
     name: Test configuration on Linux
     needs: [gcc, clang]
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-22.04
     steps:
       - name: Install
         run: |
@@ -184,19 +179,19 @@ jobs:
 
   conf_test_windows:
     name: Test configuration on Windows
-    runs-on: windows-2019
+    runs-on: windows-2022
     needs: [gcc, clang]
     steps:
       - name: Checkout
         uses: actions/checkout@v4
       - name: 32-bit
         run: |
-          call "C:\Program Files (x86)\Microsoft Visual Studio\2019\Enterprise\VC\Auxiliary\Build\vcvars32.bat"
+          call "C:\Program Files\Microsoft Visual Studio\2022\Enterprise\VC\Auxiliary\Build\vcvars32.bat"
           cl /Isrc extras/conf_test/x86.cpp
         shell: cmd
       - name: 64-bit
         run: |
-          call "C:\Program Files (x86)\Microsoft Visual Studio\2019\Enterprise\VC\Auxiliary\Build\vcvars64.bat"
+          call "C:\Program Files\Microsoft Visual Studio\2022\Enterprise\VC\Auxiliary\Build\vcvars64.bat"
           cl /Isrc extras/conf_test/x64.cpp
         shell: cmd
 
@@ -257,7 +252,7 @@ jobs:
             board: arduino:avr:uno
           - core: arduino:samd
             board: arduino:samd:mkr1000
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-22.04
     steps:
       - name: Checkout
         uses: actions/checkout@v4
@@ -412,7 +407,7 @@ jobs:
   arm:
     name: GCC for ARM processor
     needs: gcc
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-22.04
     steps:
       - name: Install
         run: |
@@ -431,7 +426,7 @@ jobs:
   coverage:
     needs: gcc
     name: Coverage
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-22.04
     steps:
       - name: Install
         run: sudo apt-get install -y lcov ninja-build
@@ -463,7 +458,7 @@ jobs:
   valgrind:
     needs: gcc
     name: Valgrind
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-22.04
     steps:
       - name: Install
         run: |
@@ -485,24 +480,24 @@ jobs:
   clang-tidy:
     needs: clang
     name: Clang-Tidy
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-latest
     steps:
       - name: Install
-        run: sudo apt-get install -y clang-tidy cmake ninja-build
+        run: sudo apt-get install -y clang-tidy libc++-dev libc++abi-dev
       - name: Checkout
         uses: actions/checkout@v4
       - name: Configure
-        run: cmake -G Ninja -DCMAKE_CXX_CLANG_TIDY="clang-tidy-10;--warnings-as-errors=*" -DCMAKE_BUILD_TYPE=Debug .
+        run: cmake -G Ninja -DCMAKE_CXX_CLANG_TIDY="clang-tidy;--warnings-as-errors=*" -DCMAKE_BUILD_TYPE=Debug .
         env:
-          CC: clang-10
-          CXX: clang++-10
+          CC: clang
+          CXX: clang++
       - name: Check
         run: cmake --build . -- -k 0
 
   amalgamate:
     needs: gcc
     name: Amalgamate ArduinoJson.h
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-22.04
     steps:
       - name: Checkout
         uses: actions/checkout@v4
@@ -578,7 +573,7 @@ jobs:
 
   codeql:
     name: CodeQL
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-22.04
     needs: gcc
 
     permissions:
@@ -587,20 +582,20 @@ jobs:
       security-events: write
 
     steps:
-    - name: Checkout repository
-      uses: actions/checkout@v4
+      - name: Checkout repository
+        uses: actions/checkout@v4
 
-    - name: Initialize CodeQL
-      uses: github/codeql-action/init@v3
-      with:
-        languages: cpp
+      - name: Initialize CodeQL
+        uses: github/codeql-action/init@v3
+        with:
+          languages: cpp
 
-    - name: Build
-      run: |
-        cmake -DCMAKE_BUILD_TYPE=Debug .
-        cmake --build .
+      - name: Build
+        run: |
+          cmake -DCMAKE_BUILD_TYPE=Debug .
+          cmake --build .
 
-    - name: Perform CodeQL Analysis
-      uses: github/codeql-action/analyze@v3
-      with:
-        category: "/language:cpp"
+      - name: Perform CodeQL Analysis
+        uses: github/codeql-action/analyze@v3
+        with:
+          category: "/language:cpp"

.github/workflows/release.yml

@@ -8,7 +8,7 @@ on:
 jobs:
   release:
     name: Create release
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-22.04
     steps:
       - name: Set variables
         id: init

CHANGELOG.md

@@ -1,6 +1,53 @@
 ArduinoJson: change log
 =======================
 
+HEAD
+----
+
+* Optimize storage of static strings
+
+> ### BREAKING CHANGES
+>
+> Static string cannot contain NUL characters anymore (they could since 7.3.0).
+> This is an extremely rare case, so you probably won't be affected.
+>
+> For example, the following code produces different output in 7.3 and 7.4:
+>
+> ```cpp
+> JsonDocument doc;
+> doc["a\0b"] = "c\0d";
+> serializeJson(doc, Serial);
+> // With Arduino 7.3 -> {"a\u0000b":"c\u0000d"}
+> // With Arduino 7.4 -> {"a":"c"}
+> ```
+>
+> `JsonString` contructor now only accepts two arguments, not three.
+> If your code uses `JsonString` to store a string as a pointer, you must remove the size argument.
+>
+> For example, if you have something like this:
+>
+> ```cpp
+> doc["key"] = JsonString(str.c_str(), str.size(), true);
+> ```
+>
+> You must replace with either:
+>
+> ```cpp
+> doc["key"] = JsonString(str.c_str(), true);  // store as pointer, cannot contain NUL characters
+> doc["key"] = JsonString(str.c_str(), str.size()); // store by copy, NUL characters allowed
+> doc["key"] = str; // same as previous line for supported string classes (`String`, `std::string`, etc.)
+> ```
+
+v7.4.2 (2025-06-20)
+------
+
+* Fix truncated strings on Arduino Due (issue #2181)
+
+v7.4.1 (2025-04-11)
+------
+
+* Fix crash with tiny Flash strings (issue #2170)
+
 v7.4.0 (2025-04-09)
 ------
 

CMakeLists.txt

@@ -10,7 +10,7 @@ if(ESP_PLATFORM)
 	return()
 endif()
 
-project(ArduinoJson VERSION 7.4.0)
+project(ArduinoJson VERSION 7.4.2)
 
 if(CMAKE_PROJECT_NAME STREQUAL PROJECT_NAME)
 	include(CTest)

README.md

@@ -80,7 +80,7 @@ ArduinoJson is a C++ JSON library for Arduino and IoT (Internet Of Things).
     * Continuously tested on
         * [Visual Studio 2017, 2019, 2022](https://ci.appveyor.com/project/bblanchon/arduinojson/branch/7.x)
         * [GCC 4.8, 5, 6, 7, 8, 9, 10, 11, 12](https://github.com/bblanchon/ArduinoJson/actions?query=workflow%3A%22Continuous+Integration%22)
-        * [Clang 3.9, 4.0, 5.0, 6.0, 7, 8, 9, 10, 11, 12, 13, 14, 15](https://github.com/bblanchon/ArduinoJson/actions?query=workflow%3A%22Continuous+Integration%22)
+        * [Clang 7 to 19](https://github.com/bblanchon/ArduinoJson/actions?query=workflow%3A%22Continuous+Integration%22)
     * [Continuously fuzzed with Google OSS Fuzz](https://bugs.chromium.org/p/oss-fuzz/issues/list?sort=-opened&can=1&q=proj:arduinojson)
     * Passes all default checks of [clang-tidy](https://releases.llvm.org/10.0.0/tools/clang/tools/extra/docs/clang-tidy/)
 * Well documented
@@ -139,11 +139,6 @@ See the [tutorial on arduinojson.org](https://arduinojson.org/v7/doc/serializati
 
 ArduinoJson is thankful to its sponsors. Please give them a visit; they deserve it!
 
-<p>
-  <a href="https://www.programmingelectronics.com/" rel="sponsored">
-    <img src="https://arduinojson.org/images/2021/10/programmingeleactronicsacademy.png" alt="Programming Electronics Academy" width="200">
-  </a>
-</p>
 <p>
   <a href="https://github.com/1technophile" rel="sponsored">
     <img alt="1technophile" src="https://avatars.githubusercontent.com/u/12672732?s=40&v=4">

appveyor.yml

@@ -1,4 +1,4 @@
-version: 7.4.0.{build}
+version: 7.4.2.{build}
 environment:
   matrix:
     - APPVEYOR_BUILD_WORKER_IMAGE: Visual Studio 2022

extras/conf_test/avr.cpp

@@ -12,7 +12,7 @@ static_assert(ARDUINOJSON_LITTLE_ENDIAN == 1, "ARDUINOJSON_LITTLE_ENDIAN");
 
 static_assert(ARDUINOJSON_USE_DOUBLE == 0, "ARDUINOJSON_USE_DOUBLE");
 
-static_assert(ArduinoJson::detail::ResourceManager::slotSize == 6, "slot size");
+static_assert(sizeof(ArduinoJson::detail::VariantData) == 6, "slot size");
 
 void setup() {}
 void loop() {}

extras/conf_test/esp8266.cpp

@@ -10,7 +10,7 @@ static_assert(ARDUINOJSON_LITTLE_ENDIAN == 1, "ARDUINOJSON_LITTLE_ENDIAN");
 
 static_assert(ARDUINOJSON_USE_DOUBLE == 1, "ARDUINOJSON_USE_DOUBLE");
 
-static_assert(ArduinoJson::detail::ResourceManager::slotSize == 8, "slot size");
+static_assert(sizeof(ArduinoJson::detail::VariantData) == 8, "slot size");
 
 void setup() {}
 void loop() {}

extras/conf_test/x64.cpp

@@ -10,7 +10,6 @@ static_assert(ARDUINOJSON_LITTLE_ENDIAN == 1, "ARDUINOJSON_LITTLE_ENDIAN");
 
 static_assert(ARDUINOJSON_USE_DOUBLE == 1, "ARDUINOJSON_USE_DOUBLE");
 
-static_assert(ArduinoJson::detail::ResourceManager::slotSize == 16,
-              "slot size");
+static_assert(sizeof(ArduinoJson::detail::VariantData) == 16, "slot size");
 
 int main() {}

extras/conf_test/x86.cpp

@@ -10,6 +10,6 @@ static_assert(ARDUINOJSON_LITTLE_ENDIAN == 1, "ARDUINOJSON_LITTLE_ENDIAN");
 
 static_assert(ARDUINOJSON_USE_DOUBLE == 1, "ARDUINOJSON_USE_DOUBLE");
 
-static_assert(ArduinoJson::detail::ResourceManager::slotSize == 8, "slot size");
+static_assert(sizeof(ArduinoJson::detail::VariantData) == 8, "slot size");
 
 int main() {}

extras/tests/Deprecated/BasicJsonDocument.cpp

@@ -54,7 +54,7 @@ TEST_CASE("BasicJsonDocument") {
     doc["hello"] = "world";
     auto copy = doc;
     REQUIRE(copy.as<std::string>() == "{\"hello\":\"world\"}");
-    REQUIRE(allocatorLog == "AA");
+    REQUIRE(allocatorLog == "AAAA");
   }
 
   SECTION("capacity") {

extras/tests/Helpers/Allocators.hpp

@@ -269,10 +269,16 @@ inline size_t sizeofPoolList(size_t n = ARDUINOJSON_INITIAL_POOL_COUNT) {
   return sizeof(MemoryPool<VariantData>) * n;
 }
 
+template <typename T = ArduinoJson::detail::VariantData>
 inline size_t sizeofPool(
     ArduinoJson::detail::SlotCount n = ARDUINOJSON_POOL_CAPACITY) {
+  return ArduinoJson::detail::MemoryPool<T>::slotsToBytes(n);
+}
+
+inline size_t sizeofStaticStringPool(
+    ArduinoJson::detail::SlotCount n = ARDUINOJSON_POOL_CAPACITY) {
   using namespace ArduinoJson::detail;
-  return MemoryPool<VariantData>::slotsToBytes(n);
+  return MemoryPool<const char*>::slotsToBytes(n);
 }
 
 inline size_t sizeofStringBuffer(size_t iteration = 1) {

extras/tests/JsonArray/add.cpp

@@ -8,7 +8,7 @@
 #include "Allocators.hpp"
 #include "Literals.hpp"
 
-using ArduinoJson::detail::sizeofArray;
+using namespace ArduinoJson::detail;
 
 TEST_CASE("JsonArray::add(T)") {
   SpyingAllocator spy;
@@ -33,7 +33,8 @@ TEST_CASE("JsonArray::add(T)") {
     REQUIRE(array[0].is<double>());
     REQUIRE_FALSE(array[0].is<bool>());
     REQUIRE(spy.log() == AllocatorLog{
-                             Allocate(sizeofPool()),
+                             Allocate(sizeofPool<VariantData>()),
+                             Allocate(sizeofPool<EightByteValue>()),
                          });
   }
 
@@ -56,6 +57,7 @@ TEST_CASE("JsonArray::add(T)") {
     REQUIRE(array[0].is<int>() == false);
     REQUIRE(spy.log() == AllocatorLog{
                              Allocate(sizeofPool()),
+                             Allocate(sizeofStaticStringPool()),
                          });
   }
 

extras/tests/JsonDeserializer/array.cpp

@@ -7,7 +7,7 @@
 
 #include "Allocators.hpp"
 
-using ArduinoJson::detail::sizeofArray;
+using namespace ArduinoJson::detail;
 
 TEST_CASE("deserialize JSON array") {
   SpyingAllocator spy;
@@ -92,8 +92,12 @@ TEST_CASE("deserialize JSON array") {
       REQUIRE(arr[0].as<double>() == Approx(4.2123456));
       REQUIRE(arr[1] == -7E89);
       REQUIRE(spy.log() == AllocatorLog{
-                               Allocate(sizeofPool()),
-                               Reallocate(sizeofPool(), sizeofPool(4)),
+                               Allocate(sizeofPool<VariantData>()),
+                               Allocate(sizeofPool<EightByteValue>()),
+                               Reallocate(sizeofPool<VariantData>(),
+                                          sizeofPool<VariantData>(2)),
+                               Reallocate(sizeofPool<EightByteValue>(),
+                                          sizeofPool<EightByteValue>(2)),
                            });
     }
 

extras/tests/JsonDeserializer/destination_types.cpp

@@ -104,6 +104,8 @@ TEST_CASE("deserializeJson(MemberProxy)") {
 
     REQUIRE(err == DeserializationError::Ok);
     REQUIRE(doc.as<std::string>() == "{\"hello\":\"world\",\"value\":[42]}");
-    REQUIRE(spy.log() == AllocatorLog{});
+    REQUIRE(spy.log() == AllocatorLog{
+                             Allocate(sizeofStaticStringPool()),
+                         });
   }
 }

extras/tests/JsonDeserializer/errors.cpp

@@ -121,7 +121,7 @@ TEST_CASE("deserializeJson() returns NoMemory if string length overflows") {
   }
 }
 
-TEST_CASE("deserializeJson() returns NoMemory if extension allocation fails") {
+TEST_CASE("deserializeJson() returns NoMemory if 8-bit slot allocation fails") {
   JsonDocument doc(FailingAllocator::instance());
 
   SECTION("uint32_t should pass") {

extras/tests/JsonDeserializer/filter.cpp

@@ -825,7 +825,9 @@ TEST_CASE("shrink filter") {
 
   deserializeJson(doc, "{}", DeserializationOption::Filter(filter));
 
-  REQUIRE(spy.log() == AllocatorLog{
-                           Reallocate(sizeofPool(), sizeofObject(1)),
-                       });
+  REQUIRE(spy.log() ==
+          AllocatorLog{
+              Reallocate(sizeofPool(), sizeofObject(1)),
+              Reallocate(sizeofStaticStringPool(), sizeofStaticStringPool(1)),
+          });
 }

extras/tests/JsonDocument/ElementProxy.cpp

@@ -31,6 +31,7 @@ TEST_CASE("ElementProxy::add()") {
     REQUIRE(doc.as<std::string>() == "[[\"world\"]]");
     REQUIRE(spy.log() == AllocatorLog{
                              Allocate(sizeofPool()),
+                             Allocate(sizeofStaticStringPool()),
                          });
   }
 

extras/tests/JsonDocument/MemberProxy.cpp

@@ -25,6 +25,7 @@ TEST_CASE("MemberProxy::add()") {
     REQUIRE(doc.as<std::string>() == "{\"hello\":[42]}");
     REQUIRE(spy.log() == AllocatorLog{
                              Allocate(sizeofPool()),
+                             Allocate(sizeofStaticStringPool()),
                          });
   }
 
@@ -34,6 +35,7 @@ TEST_CASE("MemberProxy::add()") {
     REQUIRE(doc.as<std::string>() == "{\"hello\":[\"world\"]}");
     REQUIRE(spy.log() == AllocatorLog{
                              Allocate(sizeofPool()),
+                             Allocate(sizeofStaticStringPool()),
                          });
   }
 
@@ -44,6 +46,7 @@ TEST_CASE("MemberProxy::add()") {
     REQUIRE(doc.as<std::string>() == "{\"hello\":[\"world\"]}");
     REQUIRE(spy.log() == AllocatorLog{
                              Allocate(sizeofPool()),
+                             Allocate(sizeofStaticStringPool()),
                              Allocate(sizeofString("world")),
                          });
   }
@@ -55,8 +58,8 @@ TEST_CASE("MemberProxy::add()") {
     REQUIRE(doc.as<std::string>() == "{\"hello\":[\"world\"]}");
     REQUIRE(spy.log() == AllocatorLog{
                              Allocate(sizeofPool()),
+                             Allocate(sizeofStaticStringPool()),
                              Allocate(sizeofString("world")),
-
                          });
   }
 
@@ -71,6 +74,7 @@ TEST_CASE("MemberProxy::add()") {
     REQUIRE(doc.as<std::string>() == "{\"hello\":[\"world\"]}");
     REQUIRE(spy.log() == AllocatorLog{
                              Allocate(sizeofPool()),
+                             Allocate(sizeofStaticStringPool()),
                              Allocate(sizeofString("world")),
                          });
   }
@@ -399,7 +403,7 @@ TEST_CASE("MemberProxy under memory constraints") {
   }
 
   SECTION("value slot allocation fails") {
-    timebomb.setCountdown(1);
+    timebomb.setCountdown(2);
 
     // fill the pool entirely, but leave one slot for the key
     doc["foo"][ARDUINOJSON_POOL_CAPACITY - 4] = 1;
@@ -412,6 +416,7 @@ TEST_CASE("MemberProxy under memory constraints") {
     REQUIRE(doc.overflowed() == true);
     REQUIRE(spy.log() == AllocatorLog{
                              Allocate(sizeofPool()),
+                             Allocate(sizeofStaticStringPool()),
                              AllocateFail(sizeofPool()),
                          });
   }

extras/tests/JsonDocument/add.cpp

@@ -32,6 +32,7 @@ TEST_CASE("JsonDocument::add(T)") {
     REQUIRE(doc.as<std::string>() == "[\"hello\"]");
     REQUIRE(spy.log() == AllocatorLog{
                              Allocate(sizeofPool()),
+                             Allocate(sizeofStaticStringPool()),
                          });
   }
 

extras/tests/JsonDocument/assignment.cpp

@@ -69,6 +69,8 @@ TEST_CASE("JsonDocument assignment") {
       doc2 = std::move(doc1);
 
       REQUIRE(doc2.as<std::string>() == "{\"hello\":\"world\"}");
+
+      // NOLINTNEXTLINE(clang-analyzer-cplusplus.Move)
       REQUIRE(doc1.as<std::string>() == "null");
     }
     REQUIRE(spyingAllocator.log() == AllocatorLog{

extras/tests/JsonDocument/constructor.cpp

@@ -44,6 +44,8 @@ TEST_CASE("JsonDocument constructor") {
       JsonDocument doc2(std::move(doc1));
 
       REQUIRE(doc2.as<std::string>() == "The size of this string is 32!!");
+
+      // NOLINTNEXTLINE(clang-analyzer-cplusplus.Move)
       REQUIRE(doc1.as<std::string>() == "null");
     }
     REQUIRE(spyingAllocator.log() == AllocatorLog{
@@ -62,6 +64,7 @@ TEST_CASE("JsonDocument constructor") {
     REQUIRE(doc2.as<std::string>() == "{\"hello\":\"world\"}");
     REQUIRE(spyingAllocator.log() == AllocatorLog{
                                          Allocate(sizeofPool()),
+                                         Allocate(sizeofStaticStringPool()),
                                      });
   }
 
@@ -85,6 +88,7 @@ TEST_CASE("JsonDocument constructor") {
     REQUIRE(doc2.as<std::string>() == "[\"hello\"]");
     REQUIRE(spyingAllocator.log() == AllocatorLog{
                                          Allocate(sizeofPool()),
+                                         Allocate(sizeofStaticStringPool()),
                                      });
   }
 

extras/tests/JsonDocument/remove.cpp

@@ -22,10 +22,10 @@ TEST_CASE("JsonDocument::remove()") {
 
   SECTION("string literal") {
     doc["a"] = 1;
-    doc["a\0b"_s] = 2;
+    doc["x"] = 2;
     doc["b"] = 3;
 
-    doc.remove("a\0b");
+    doc.remove("x");
 
     REQUIRE(doc.as<std::string>() == "{\"a\":1,\"b\":3}");
   }

extras/tests/JsonDocument/set.cpp

@@ -37,7 +37,9 @@ TEST_CASE("JsonDocument::set()") {
     doc.set("example");
 
     REQUIRE(doc.as<const char*>() == "example"_s);
-    REQUIRE(spy.log() == AllocatorLog{});
+    REQUIRE(spy.log() == AllocatorLog{
+                             Allocate(sizeofStaticStringPool()),
+                         });
   }
 
   SECTION("const char*") {
@@ -87,6 +89,13 @@ TEST_CASE("JsonDocument::set()") {
                          });
   }
 
+  SECTION("Flash tiny string") {  // issue #2170
+    doc.set(F("abc"));
+
+    REQUIRE(doc.as<const char*>() == "abc"_s);
+    REQUIRE(spy.log() == AllocatorLog{});
+  }
+
 #ifdef HAS_VARIABLE_LENGTH_ARRAY
   SECTION("VLA") {
     size_t i = 16;

extras/tests/JsonDocument/shrinkToFit.cpp

@@ -75,7 +75,11 @@ TEST_CASE("JsonDocument::shrinkToFit()") {
     doc.shrinkToFit();
 
     REQUIRE(doc.as<std::string>() == "hello");
-    REQUIRE(spyingAllocator.log() == AllocatorLog{});
+    REQUIRE(spyingAllocator.log() ==
+            AllocatorLog{
+                Allocate(sizeofStaticStringPool()),
+                Reallocate(sizeofStaticStringPool(), sizeofStaticStringPool(1)),
+            });
   }
 
   SECTION("owned string") {
@@ -110,7 +114,9 @@ TEST_CASE("JsonDocument::shrinkToFit()") {
     REQUIRE(spyingAllocator.log() ==
             AllocatorLog{
                 Allocate(sizeofPool()),
+                Allocate(sizeofStaticStringPool()),
                 Reallocate(sizeofPool(), sizeofObject(1)),
+                Reallocate(sizeofStaticStringPool(), sizeofStaticStringPool(1)),
             });
   }
 
@@ -137,7 +143,9 @@ TEST_CASE("JsonDocument::shrinkToFit()") {
     REQUIRE(spyingAllocator.log() ==
             AllocatorLog{
                 Allocate(sizeofPool()),
+                Allocate(sizeofStaticStringPool()),
                 Reallocate(sizeofPool(), sizeofArray(1)),
+                Reallocate(sizeofStaticStringPool(), sizeofStaticStringPool(1)),
             });
   }
 
@@ -164,20 +172,23 @@ TEST_CASE("JsonDocument::shrinkToFit()") {
     REQUIRE(spyingAllocator.log() ==
             AllocatorLog{
                 Allocate(sizeofPool()),
+                Allocate(sizeofStaticStringPool()),
                 Reallocate(sizeofPool(), sizeofObject(1)),
+                Reallocate(sizeofStaticStringPool(), sizeofStaticStringPool(2)),
             });
   }
 
   SECTION("owned string in object") {
-    doc["key"] = "abcdefg"_s;
+    doc["key1"_s] = "value"_s;
 
     doc.shrinkToFit();
 
-    REQUIRE(doc.as<std::string>() == "{\"key\":\"abcdefg\"}");
+    REQUIRE(doc.as<std::string>() == "{\"key1\":\"value\"}");
     REQUIRE(spyingAllocator.log() ==
             AllocatorLog{
                 Allocate(sizeofPool()),
-                Allocate(sizeofString("abcdefg")),
+                Allocate(sizeofString("key1")),
+                Allocate(sizeofString("value")),
                 Reallocate(sizeofPool(), sizeofPool(2)),
             });
   }

extras/tests/JsonDocument/subscript.cpp

@@ -25,8 +25,6 @@ TEST_CASE("JsonDocument::operator[]") {
     SECTION("string literal") {
       REQUIRE(doc["abc"] == "ABC");
       REQUIRE(cdoc["abc"] == "ABC");
-      REQUIRE(doc["abc\0d"] == "ABCD");
-      REQUIRE(cdoc["abc\0d"] == "ABCD");
     }
 
     SECTION("std::string") {
@@ -114,6 +112,7 @@ TEST_CASE("JsonDocument::operator[] key storage") {
     REQUIRE(doc.as<std::string>() == "{\"hello\":0}");
     REQUIRE(spy.log() == AllocatorLog{
                              Allocate(sizeofPool()),
+                             Allocate(sizeofStaticStringPool()),
                          });
   }
 

extras/tests/JsonObject/set.cpp

@@ -26,25 +26,12 @@ TEST_CASE("JsonObject::set()") {
     REQUIRE(obj2["hello"] == "world"_s);
     REQUIRE(spy.log() == AllocatorLog{
                              Allocate(sizeofPool()),
+                             Allocate(sizeofStaticStringPool()),
                          });
   }
 
-  SECTION("copy local string value") {
-    obj1["hello"] = "world"_s;
-    spy.clearLog();
-
-    bool success = obj2.set(obj1);
-
-    REQUIRE(success == true);
-    REQUIRE(obj2["hello"] == "world"_s);
-    REQUIRE(spy.log() == AllocatorLog{
-                             Allocate(sizeofPool()),
-                             Allocate(sizeofString("world")),
-                         });
-  }
-
-  SECTION("copy local key") {
-    obj1["hello"_s] = "world";
+  SECTION("copy local string key and value") {
+    obj1["hello"_s] = "world"_s;
     spy.clearLog();
 
     bool success = obj2.set(obj1);
@@ -54,6 +41,7 @@ TEST_CASE("JsonObject::set()") {
     REQUIRE(spy.log() == AllocatorLog{
                              Allocate(sizeofPool()),
                              Allocate(sizeofString("hello")),
+                             Allocate(sizeofString("world")),
                          });
   }
 
@@ -110,7 +98,7 @@ TEST_CASE("JsonObject::set()") {
   }
 
   SECTION("copy fails in the middle of an array") {
-    TimebombAllocator timebomb(1);
+    TimebombAllocator timebomb(2);
     JsonDocument doc3(&timebomb);
     JsonObject obj3 = doc3.to<JsonObject>();
 

extras/tests/JsonObject/subscript.cpp

@@ -102,21 +102,25 @@ TEST_CASE("JsonObject::operator[]") {
     REQUIRE(42 == obj[key]);
   }
 
-  SECTION("should not duplicate const char*") {
+  SECTION("string literals") {
     obj["hello"] = "world";
-    REQUIRE(spy.log() == AllocatorLog{Allocate(sizeofPool())});
+    REQUIRE(spy.log() == AllocatorLog{
+                             Allocate(sizeofPool()),
+                             Allocate(sizeofStaticStringPool()),
+                         });
   }
 
   SECTION("should duplicate char* value") {
     obj["hello"] = const_cast<char*>("world");
     REQUIRE(spy.log() == AllocatorLog{
                              Allocate(sizeofPool()),
+                             Allocate(sizeofStaticStringPool()),
                              Allocate(sizeofString("world")),
                          });
   }
 
   SECTION("should duplicate char* key") {
-    obj[const_cast<char*>("hello")] = "world";
+    obj[const_cast<char*>("hello")] = 42;
     REQUIRE(spy.log() == AllocatorLog{
                              Allocate(sizeofPool()),
                              Allocate(sizeofString("hello")),
@@ -136,12 +140,13 @@ TEST_CASE("JsonObject::operator[]") {
     obj["hello"] = "world"_s;
     REQUIRE(spy.log() == AllocatorLog{
                              Allocate(sizeofPool()),
+                             Allocate(sizeofStaticStringPool()),
                              Allocate(sizeofString("world")),
                          });
   }
 
   SECTION("should duplicate std::string key") {
-    obj["hello"_s] = "world";
+    obj["hello"_s] = 42;
     REQUIRE(spy.log() == AllocatorLog{
                              Allocate(sizeofPool()),
                              Allocate(sizeofString("hello")),
@@ -158,7 +163,7 @@ TEST_CASE("JsonObject::operator[]") {
   }
 
   SECTION("should duplicate a non-static JsonString key") {
-    obj[JsonString("hello", false)] = "world";
+    obj[JsonString("hello", false)] = 42;
     REQUIRE(spy.log() == AllocatorLog{
                              Allocate(sizeofPool()),
                              Allocate(sizeofString("hello")),
@@ -166,9 +171,10 @@ TEST_CASE("JsonObject::operator[]") {
   }
 
   SECTION("should not duplicate a static JsonString key") {
-    obj[JsonString("hello", true)] = "world";
+    obj[JsonString("hello", true)] = 42;
     REQUIRE(spy.log() == AllocatorLog{
                              Allocate(sizeofPool()),
+                             Allocate(sizeofStaticStringPool()),
                          });
   }
 

extras/tests/JsonVariant/copy.cpp

@@ -38,13 +38,15 @@ TEST_CASE("JsonVariant::set(JsonVariant)") {
     REQUIRE(var1.as<std::string>() == "{\"value\":[42]}");
   }
 
-  SECTION("stores const char* by reference") {
+  SECTION("stores string literals by pointer") {
     var1.set("hello!!");
     spyingAllocator.clearLog();
 
     var2.set(var1);
 
-    REQUIRE(spyingAllocator.log() == AllocatorLog{});
+    REQUIRE(spyingAllocator.log() == AllocatorLog{
+                                         Allocate(sizeofStaticStringPool()),
+                                     });
   }
 
   SECTION("stores char* by copy") {

extras/tests/JsonVariant/set.cpp

@@ -8,7 +8,7 @@
 #include "Allocators.hpp"
 #include "Literals.hpp"
 
-using ArduinoJson::detail::sizeofObject;
+using namespace ArduinoJson::detail;
 
 enum ErrorCode { ERROR_01 = 1, ERROR_10 = 10 };
 
@@ -23,7 +23,9 @@ TEST_CASE("JsonVariant::set() when there is enough memory") {
     REQUIRE(result == true);
     CHECK(variant ==
           "hello"_s);  // linked string cannot contain '\0' at the moment
-    CHECK(spy.log() == AllocatorLog{});
+    CHECK(spy.log() == AllocatorLog{
+                           Allocate(sizeofStaticStringPool()),
+                       });
   }
 
   SECTION("const char*") {
@@ -149,7 +151,9 @@ TEST_CASE("JsonVariant::set() when there is enough memory") {
 
     REQUIRE(result == true);
     REQUIRE(variant == "world");  // stores by pointer
-    REQUIRE(spy.log() == AllocatorLog{});
+    REQUIRE(spy.log() == AllocatorLog{
+                             Allocate(sizeofStaticStringPool()),
+                         });
   }
 
   SECTION("non-static JsonString") {
@@ -193,11 +197,11 @@ TEST_CASE("JsonVariant::set() when there is enough memory") {
     REQUIRE(result == true);
     REQUIRE(variant.is<double>() == true);
     REQUIRE(variant.as<double>() == 1.2);
-    REQUIRE(spy.log() ==
-            AllocatorLog{
-                Allocate(sizeofPool()),
-                Reallocate(sizeofPool(), sizeofPool(1)),  // one extension slot
-            });
+    REQUIRE(spy.log() == AllocatorLog{
+                             Allocate(sizeofPool<EightByteValue>()),
+                             Reallocate(sizeofPool<EightByteValue>(),
+                                        sizeofPool<EightByteValue>(1)),
+                         });
   }
 
   SECTION("int32_t") {
@@ -216,11 +220,11 @@ TEST_CASE("JsonVariant::set() when there is enough memory") {
     REQUIRE(result == true);
     REQUIRE(variant.is<int64_t>() == true);
     REQUIRE(variant.as<int64_t>() == -2147483649LL);
-    REQUIRE(spy.log() ==
-            AllocatorLog{
-                Allocate(sizeofPool()),
-                Reallocate(sizeofPool(), sizeofPool(1)),  // one extension slot
-            });
+    REQUIRE(spy.log() == AllocatorLog{
+                             Allocate(sizeofPool<EightByteValue>()),
+                             Reallocate(sizeofPool<EightByteValue>(),
+                                        sizeofPool<EightByteValue>(1)),
+                         });
   }
 
   SECTION("uint32_t") {
@@ -239,11 +243,11 @@ TEST_CASE("JsonVariant::set() when there is enough memory") {
     REQUIRE(result == true);
     REQUIRE(variant.is<uint64_t>() == true);
     REQUIRE(variant.as<uint64_t>() == 4294967296);
-    REQUIRE(spy.log() ==
-            AllocatorLog{
-                Allocate(sizeofPool()),
-                Reallocate(sizeofPool(), sizeofPool(1)),  // one extension slot
-            });
+    REQUIRE(spy.log() == AllocatorLog{
+                             Allocate(sizeofPool<EightByteValue>()),
+                             Reallocate(sizeofPool<EightByteValue>(),
+                                        sizeofPool<EightByteValue>(1)),
+                         });
   }
 
   SECTION("JsonDocument") {
@@ -265,6 +269,20 @@ TEST_CASE("JsonVariant::set() with not enough memory") {
 
   JsonVariant v = doc.to<JsonVariant>();
 
+  SECTION("string literal") {
+    bool result = v.set("hello world");
+
+    REQUIRE(result == false);
+    REQUIRE(v.isNull());
+  }
+
+  SECTION("static JsonString") {
+    bool result = v.set(JsonString("hello world", true));
+
+    REQUIRE(result == false);
+    REQUIRE(v.isNull());
+  }
+
   SECTION("std::string") {
     bool result = v.set("hello world!!"_s);
 
@@ -360,7 +378,7 @@ TEST_CASE("JsonVariant::set() releases the previous value") {
   }
 
   SECTION("float") {
-    v.set(1.2);
+    v.set(1.2f);
     REQUIRE(spy.log() == AllocatorLog{
                              Deallocate(sizeofString("world")),
                          });
@@ -375,7 +393,7 @@ TEST_CASE("JsonVariant::set() releases the previous value") {
   }
 }
 
-TEST_CASE("JsonVariant::set() reuses extension slot") {
+TEST_CASE("JsonVariant::set() reuses 8-bit slot") {
   SpyingAllocator spy;
   JsonDocument doc(&spy);
   JsonVariant variant = doc.to<JsonVariant>();

extras/tests/JsonVariantConst/subscript.cpp

@@ -57,7 +57,7 @@ TEST_CASE("JsonVariantConst::operator[]") {
     SECTION("string literal") {
       REQUIRE(var["ab"] == "AB"_s);
       REQUIRE(var["abc"] == "ABC"_s);
-      REQUIRE(var["abc\0d"] == "ABCD"_s);
+      REQUIRE(var["abc\0d"] == "ABC"_s);
       REQUIRE(var["def"].isNull());
       REQUIRE(var[0].isNull());
     }

extras/tests/Misc/CMakeLists.txt

@@ -29,3 +29,23 @@ set_tests_properties(Misc
 	PROPERTIES
 		LABELS "Catch"
 )
+
+add_executable(Issue2181
+	issue2181.cpp # Cannot be linked with other tests
+)
+
+set_target_properties(Issue2181 PROPERTIES UNITY_BUILD OFF)
+
+add_test(Issue2181 Issue2181)
+
+set_tests_properties(Issue2181
+	PROPERTIES
+		LABELS "Catch"
+)
+
+if(CMAKE_CXX_COMPILER_ID MATCHES "Clang")
+	target_compile_options(Issue2181
+		PRIVATE
+			-Wno-keyword-macro # keyword is hidden by macro definition
+	)
+endif()

extras/tests/Misc/StringAdapters.cpp

@@ -21,7 +21,7 @@ TEST_CASE("adaptString()") {
     auto s = adaptString("bravo\0alpha");
 
     CHECK(s.isNull() == false);
-    CHECK(s.size() == 11);
+    CHECK(s.size() == 5);
     CHECK(s.isStatic() == true);
   }
 

extras/tests/Misc/issue2181.cpp

@@ -0,0 +1,15 @@
+// ArduinoJson - https://arduinojson.org
+// Copyright © 2014-2025, Benoit BLANCHON
+// MIT License
+
+#define true 0x1
+#define false 0x0
+
+#include <ArduinoJson.h>
+#include <catch.hpp>
+
+TEST_CASE("Issue #2181") {
+  JsonDocument doc;
+  doc["hello"] = "world";
+  REQUIRE(doc.as<std::string>() == "{\"hello\":\"world\"}");
+}

extras/tests/MsgPackDeserializer/destination_types.cpp

@@ -104,6 +104,8 @@ TEST_CASE("deserializeMsgPack(MemberProxy)") {
 
     REQUIRE(err == DeserializationError::Ok);
     REQUIRE(doc.as<std::string>() == "{\"hello\":\"world\",\"value\":[42]}");
-    REQUIRE(spy.log() == AllocatorLog{});
+    REQUIRE(spy.log() == AllocatorLog{
+                             Allocate(sizeofStaticStringPool()),
+                         });
   }
 }

extras/tests/ResourceManager/CMakeLists.txt

@@ -5,6 +5,7 @@
 add_executable(ResourceManagerTests
 	allocVariant.cpp
 	clear.cpp
+	saveStaticString.cpp
 	saveString.cpp
 	shrinkToFit.cpp
 	size.cpp

extras/tests/ResourceManager/StringBuffer.cpp

@@ -2,7 +2,7 @@
 // Copyright © 2014-2025, Benoit BLANCHON
 // MIT License
 
-#include <ArduinoJson/Memory/StringBuffer.hpp>
+#include <ArduinoJson.hpp>
 #include <catch.hpp>
 
 #include "Allocators.hpp"
@@ -21,8 +21,8 @@ TEST_CASE("StringBuffer") {
     strcpy(ptr, "hi!");
     sb.save(&variant);
 
-    REQUIRE(variant.type() == VariantType::TinyString);
-    REQUIRE(variant.asString() == "hi!");
+    REQUIRE(variant.type == VariantType::TinyString);
+    REQUIRE(VariantImpl(&variant, &resources).asString() == "hi!");
   }
 
   SECTION("Tiny string can't contain NUL") {
@@ -30,9 +30,9 @@ TEST_CASE("StringBuffer") {
     memcpy(ptr, "a\0b", 3);
     sb.save(&variant);
 
-    REQUIRE(variant.type() == VariantType::OwnedString);
+    REQUIRE(variant.type == VariantType::OwnedString);
 
-    auto str = variant.asString();
+    auto str = VariantImpl(&variant, &resources).asString();
     REQUIRE(str.size() == 3);
     REQUIRE(str.c_str()[0] == 'a');
     REQUIRE(str.c_str()[1] == 0);
@@ -44,7 +44,7 @@ TEST_CASE("StringBuffer") {
     strcpy(ptr, "alfa");
     sb.save(&variant);
 
-    REQUIRE(variant.type() == VariantType::OwnedString);
-    REQUIRE(variant.asString() == "alfa");
+    REQUIRE(variant.type == VariantType::OwnedString);
+    REQUIRE(VariantImpl(&variant, &resources).asString() == "alfa");
   }
 }

extras/tests/ResourceManager/StringBuilder.cpp

@@ -2,7 +2,7 @@
 // Copyright © 2014-2025, Benoit BLANCHON
 // MIT License
 
-#include <ArduinoJson/Memory/StringBuilder.hpp>
+#include <ArduinoJson.hpp>
 #include <catch.hpp>
 
 #include "Allocators.hpp"
@@ -26,7 +26,7 @@ TEST_CASE("StringBuilder") {
     REQUIRE(spyingAllocator.log() == AllocatorLog{
                                          Allocate(sizeofStringBuffer()),
                                      });
-    REQUIRE(data.type() == VariantType::TinyString);
+    REQUIRE(data.type == VariantType::TinyString);
   }
 
   SECTION("Tiny string") {
@@ -45,8 +45,8 @@ TEST_CASE("StringBuilder") {
     str.save(&data);
 
     REQUIRE(resources.overflowed() == false);
-    REQUIRE(data.type() == VariantType::TinyString);
-    REQUIRE(data.asString() == "url");
+    REQUIRE(data.type == VariantType::TinyString);
+    REQUIRE(VariantImpl(&data, &resources).asString() == "url");
   }
 
   SECTION("Short string fits in first allocation") {
@@ -116,12 +116,12 @@ TEST_CASE("StringBuilder") {
   }
 }
 
-static JsonString saveString(StringBuilder& builder, const char* s) {
+static VariantData saveString(StringBuilder& builder, const char* s) {
   VariantData data;
   builder.startString();
   builder.append(s);
   builder.save(&data);
-  return data.asString();
+  return data;
 }
 
 TEST_CASE("StringBuilder::save() deduplicates strings") {
@@ -134,9 +134,10 @@ TEST_CASE("StringBuilder::save() deduplicates strings") {
     auto s2 = saveString(builder, "world");
     auto s3 = saveString(builder, "hello");
 
-    REQUIRE(s1 == "hello");
-    REQUIRE(s2 == "world");
-    REQUIRE(+s1.c_str() == +s3.c_str());  // same address
+    REQUIRE(VariantImpl(&s1, &resources).asString() == "hello");
+    REQUIRE(VariantImpl(&s2, &resources).asString() == "world");
+    REQUIRE(+VariantImpl(&s1, &resources).asString().c_str() ==
+            +VariantImpl(&s3, &resources).asString().c_str());  // same address
 
     REQUIRE(spy.log() ==
             AllocatorLog{
@@ -152,9 +153,11 @@ TEST_CASE("StringBuilder::save() deduplicates strings") {
     auto s1 = saveString(builder, "hello world");
     auto s2 = saveString(builder, "hello");
 
-    REQUIRE(s1 == "hello world");
-    REQUIRE(s2 == "hello");
-    REQUIRE(+s2.c_str() != +s1.c_str());  // different address
+    REQUIRE(VariantImpl(&s1, &resources).asString() == "hello world");
+    REQUIRE(VariantImpl(&s2, &resources).asString() == "hello");
+    REQUIRE(
+        +VariantImpl(&s1, &resources).asString().c_str() !=
+        +VariantImpl(&s2, &resources).asString().c_str());  // different address
 
     REQUIRE(spy.log() ==
             AllocatorLog{
@@ -169,9 +172,11 @@ TEST_CASE("StringBuilder::save() deduplicates strings") {
     auto s1 = saveString(builder, "hello world");
     auto s2 = saveString(builder, "worl");
 
-    REQUIRE(s1 == "hello world");
-    REQUIRE(s2 == "worl");
-    REQUIRE(s2.c_str() != s1.c_str());  // different address
+    REQUIRE(VariantImpl(&s1, &resources).asString() == "hello world");
+    REQUIRE(VariantImpl(&s2, &resources).asString() == "worl");
+    REQUIRE(
+        VariantImpl(&s1, &resources).asString().c_str() !=
+        VariantImpl(&s2, &resources).asString().c_str());  // different address
 
     REQUIRE(spy.log() ==
             AllocatorLog{

extras/tests/ResourceManager/clear.cpp

@@ -3,7 +3,6 @@
 // MIT License
 
 #include <ArduinoJson/Memory/ResourceManager.hpp>
-#include <ArduinoJson/Memory/ResourceManagerImpl.hpp>
 #include <ArduinoJson/Strings/StringAdapters.hpp>
 #include <catch.hpp>
 

extras/tests/ResourceManager/saveStaticString.cpp

@@ -0,0 +1,47 @@
+// ArduinoJson - https://arduinojson.org
+// Copyright © 2014-2025, Benoit BLANCHON
+// MIT License
+
+#include <ArduinoJson/Memory/ResourceManager.hpp>
+#include <ArduinoJson/Strings/StringAdapters.hpp>
+#include <catch.hpp>
+
+#include "Allocators.hpp"
+
+using namespace ArduinoJson::detail;
+
+TEST_CASE("ResourceManager::saveStaticString() deduplicates strings") {
+  SpyingAllocator spy;
+  ResourceManager resources(&spy);
+
+  auto str1 = "hello";
+  auto str2 = "world";
+
+  auto id1 = resources.saveStaticString(str1);
+  auto id2 = resources.saveStaticString(str2);
+  REQUIRE(id1 != id2);
+
+  auto id3 = resources.saveStaticString(str1);
+  REQUIRE(id1 == id3);
+
+  resources.shrinkToFit();
+  REQUIRE(spy.log() ==
+          AllocatorLog{
+              Allocate(sizeofStaticStringPool()),
+              Reallocate(sizeofStaticStringPool(), sizeofStaticStringPool(2)),
+          });
+  REQUIRE(resources.overflowed() == false);
+}
+
+TEST_CASE("ResourceManager::saveStaticString() when allocation fails") {
+  SpyingAllocator spy(FailingAllocator::instance());
+  ResourceManager resources(&spy);
+
+  auto slotId = resources.saveStaticString("hello");
+
+  REQUIRE(slotId == NULL_SLOT);
+  REQUIRE(resources.overflowed() == true);
+  REQUIRE(spy.log() == AllocatorLog{
+                           AllocateFail(sizeofStaticStringPool()),
+                       });
+}

extras/tests/ResourceManager/shrinkToFit.cpp

@@ -3,7 +3,6 @@
 // MIT License
 
 #include <ArduinoJson/Memory/ResourceManager.hpp>
-#include <ArduinoJson/Memory/ResourceManagerImpl.hpp>
 #include <catch.hpp>
 
 #include "Allocators.hpp"

extras/tests/ResourceManager/size.cpp

@@ -3,7 +3,6 @@
 // MIT License
 
 #include <ArduinoJson/Memory/ResourceManager.hpp>
-#include <ArduinoJson/Memory/ResourceManagerImpl.hpp>
 #include <catch.hpp>
 
 #include "Allocators.hpp"

extras/tests/ResourceManager/swap.cpp

@@ -4,7 +4,6 @@
 
 #include <ArduinoJson/Memory/Alignment.hpp>
 #include <ArduinoJson/Memory/ResourceManager.hpp>
-#include <ArduinoJson/Memory/ResourceManagerImpl.hpp>
 #include <catch.hpp>
 
 #include "Allocators.hpp"

idf_component.yml

@@ -1,7 +1,7 @@
-version: "7.4.0"
+version: "7.4.2"
 description: >-
   A simple and efficient JSON library for embedded C++.
-  ★ 6896 stars on GitHub!
+  ★ 6953 stars on GitHub!
   Supports serialization, deserialization, MessagePack, streams, filtering, and more.
   Fully tested and documented.
 url: https://arduinojson.org/

library.json

@@ -1,13 +1,13 @@
 {
   "name": "ArduinoJson",
   "keywords": "json, rest, http, web",
-  "description": "A simple and efficient JSON library for embedded C++. ⭐ 6896 stars on GitHub! Supports serialization, deserialization, MessagePack, streams, filtering, and more. Fully tested and documented.",
+  "description": "A simple and efficient JSON library for embedded C++. ⭐ 6953 stars on GitHub! Supports serialization, deserialization, MessagePack, streams, filtering, and more. Fully tested and documented.",
   "homepage": "https://arduinojson.org/?utm_source=meta&utm_medium=library.json",
   "repository": {
     "type": "git",
     "url": "https://github.com/bblanchon/ArduinoJson.git"
   },
-  "version": "7.4.0",
+  "version": "7.4.2",
   "authors": {
     "name": "Benoit Blanchon",
     "url": "https://blog.benoitblanchon.fr"

library.properties

@@ -1,9 +1,9 @@
 name=ArduinoJson
-version=7.4.0
+version=7.4.2
 author=Benoit Blanchon <blog.benoitblanchon.fr>
 maintainer=Benoit Blanchon <blog.benoitblanchon.fr>
 sentence=A simple and efficient JSON library for embedded C++.
-paragraph=⭐ 6896 stars on GitHub! Supports serialization, deserialization, MessagePack, streams, filtering, and more. Fully tested and documented.
+paragraph=⭐ 6953 stars on GitHub! Supports serialization, deserialization, MessagePack, streams, filtering, and more. Fully tested and documented.
 category=Data Processing
 url=https://arduinojson.org/?utm_source=meta&utm_medium=library.properties
 architectures=*

src/ArduinoJson.hpp

@@ -26,6 +26,15 @@
 #  endif
 #endif
 
+// Remove true and false macros defined by some cores, such as Arduino Due's
+// See issues #2181 and arduino/ArduinoCore-sam#50
+#ifdef true
+#  undef true
+#endif
+#ifdef false
+#  undef false
+#endif
+
 #include "ArduinoJson/Array/JsonArray.hpp"
 #include "ArduinoJson/Object/JsonObject.hpp"
 #include "ArduinoJson/Variant/JsonVariantConst.hpp"
@@ -36,13 +45,10 @@
 #include "ArduinoJson/Array/ElementProxy.hpp"
 #include "ArduinoJson/Array/Utilities.hpp"
 #include "ArduinoJson/Collection/CollectionImpl.hpp"
-#include "ArduinoJson/Memory/ResourceManagerImpl.hpp"
 #include "ArduinoJson/Object/MemberProxy.hpp"
 #include "ArduinoJson/Object/ObjectImpl.hpp"
 #include "ArduinoJson/Variant/ConverterImpl.hpp"
-#include "ArduinoJson/Variant/JsonVariantCopier.hpp"
 #include "ArduinoJson/Variant/VariantCompare.hpp"
-#include "ArduinoJson/Variant/VariantImpl.hpp"
 #include "ArduinoJson/Variant/VariantRefBaseImpl.hpp"
 
 #include "ArduinoJson/Json/JsonDeserializer.hpp"

src/ArduinoJson/Array/ArrayData.hpp

@@ -1,66 +0,0 @@
-// ArduinoJson - https://arduinojson.org
-// Copyright © 2014-2025, Benoit BLANCHON
-// MIT License
-
-#pragma once
-
-#include <ArduinoJson/Collection/CollectionData.hpp>
-
-ARDUINOJSON_BEGIN_PRIVATE_NAMESPACE
-
-class ArrayData : public CollectionData {
- public:
-  VariantData* addElement(ResourceManager* resources);
-
-  static VariantData* addElement(ArrayData* array, ResourceManager* resources) {
-    if (!array)
-      return nullptr;
-    return array->addElement(resources);
-  }
-
-  template <typename T>
-  bool addValue(const T& value, ResourceManager* resources);
-
-  template <typename T>
-  static bool addValue(ArrayData* array, const T& value,
-                       ResourceManager* resources) {
-    if (!array)
-      return false;
-    return array->addValue(value, resources);
-  }
-
-  VariantData* getOrAddElement(size_t index, ResourceManager* resources);
-
-  VariantData* getElement(size_t index, const ResourceManager* resources) const;
-
-  static VariantData* getElement(const ArrayData* array, size_t index,
-                                 const ResourceManager* resources) {
-    if (!array)
-      return nullptr;
-    return array->getElement(index, resources);
-  }
-
-  void removeElement(size_t index, ResourceManager* resources);
-
-  static void removeElement(ArrayData* array, size_t index,
-                            ResourceManager* resources) {
-    if (!array)
-      return;
-    array->removeElement(index, resources);
-  }
-
-  void remove(iterator it, ResourceManager* resources) {
-    CollectionData::removeOne(it, resources);
-  }
-
-  static void remove(ArrayData* array, iterator it,
-                     ResourceManager* resources) {
-    if (array)
-      return array->remove(it, resources);
-  }
-
- private:
-  iterator at(size_t index, const ResourceManager* resources) const;
-};
-
-ARDUINOJSON_END_PRIVATE_NAMESPACE

src/ArduinoJson/Array/ArrayImpl.hpp

@@ -4,42 +4,57 @@
 
 #pragma once
 
-#include <ArduinoJson/Array/ArrayData.hpp>
-#include <ArduinoJson/Variant/VariantCompare.hpp>
-#include <ArduinoJson/Variant/VariantData.hpp>
+#include <ArduinoJson/Collection/CollectionIterator.hpp>
+#include <ArduinoJson/Variant/VariantImpl.hpp>
 
 ARDUINOJSON_BEGIN_PRIVATE_NAMESPACE
 
-inline ArrayData::iterator ArrayData::at(
-    size_t index, const ResourceManager* resources) const {
-  auto it = createIterator(resources);
+inline VariantImpl::iterator VariantImpl::at(size_t index) const {
+  if (!isArray())
+    return iterator();
+
+  auto it = createIterator();
   while (!it.done() && index) {
-    it.next(resources);
+    it.move();
     --index;
   }
   return it;
 }
 
-inline VariantData* ArrayData::addElement(ResourceManager* resources) {
-  auto slot = resources->allocVariant();
+inline VariantData* VariantImpl::addElement() {
+  if (!isArray())
+    return nullptr;
+  auto slot = allocVariant();
   if (!slot)
     return nullptr;
-  CollectionData::appendOne(slot, resources);
+  addElement(slot);
   return slot.ptr();
 }
 
-inline VariantData* ArrayData::getOrAddElement(size_t index,
-                                               ResourceManager* resources) {
-  auto it = createIterator(resources);
+inline void VariantImpl::addElement(Slot<VariantData> slot) {
+  auto coll = getCollectionData();
+
+  if (coll->tail != NULL_SLOT) {
+    auto tail = getVariant(coll->tail);
+    tail->next = slot.id();
+    coll->tail = slot.id();
+  } else {
+    coll->head = slot.id();
+    coll->tail = slot.id();
+  }
+}
+
+inline VariantData* VariantImpl::getOrAddElement(size_t index) {
+  auto it = createIterator();
   while (!it.done() && index > 0) {
-    it.next(resources);
+    it.move();
     index--;
   }
   if (it.done())
     index++;
-  VariantData* element = it.data();
+  VariantData* element = it->data();
   while (index > 0) {
-    element = addElement(resources);
+    element = addElement();
     if (!element)
       return nullptr;
     index--;
@@ -47,33 +62,48 @@ inline VariantData* ArrayData::getOrAddElement(size_t index,
   return element;
 }
 
-inline VariantData* ArrayData::getElement(
-    size_t index, const ResourceManager* resources) const {
-  return at(index, resources).data();
+inline VariantData* VariantImpl::getElement(size_t index) const {
+  return at(index)->data();
 }
 
-inline void ArrayData::removeElement(size_t index, ResourceManager* resources) {
-  remove(at(index, resources), resources);
+inline void VariantImpl::removeElement(iterator it) {
+  if (!isArray())
+    return;
+  removeOne(it);
 }
 
-template <typename T>
-inline bool ArrayData::addValue(const T& value, ResourceManager* resources) {
-  ARDUINOJSON_ASSERT(resources != nullptr);
-  auto slot = resources->allocVariant();
-  if (!slot)
-    return false;
-  JsonVariant variant(slot.ptr(), resources);
-  if (!variant.set(value)) {
-    resources->freeVariant(slot);
+inline void VariantImpl::removeElement(size_t index) {
+  removeElement(at(index));
+}
+
+inline bool VariantImpl::copyArray(const VariantImpl& src) {
+  ARDUINOJSON_ASSERT(isNull());
+
+  if (!data_)
     return false;
+
+  data_->toArray();
+
+  for (auto it = src.createIterator(); !it.done(); it.move()) {
+    auto slot = allocVariant();
+    if (!slot)
+      return false;
+
+    VariantImpl element(slot.ptr(), resources_);
+    if (!element.copyVariant(*it)) {
+      freeVariant(slot);
+      return false;
+    }
+
+    addElement(slot);
   }
-  CollectionData::appendOne(slot, resources);
+
   return true;
 }
 
 // Returns the size (in bytes) of an array with n elements.
 constexpr size_t sizeofArray(size_t n) {
-  return n * ResourceManager::slotSize;
+  return n * sizeof(VariantData);
 }
 
 ARDUINOJSON_END_PRIVATE_NAMESPACE

src/ArduinoJson/Array/ElementProxy.hpp

@@ -50,22 +50,15 @@ class ElementProxy : public VariantRefBase<ElementProxy<TUpstream>>,
       : upstream_(src.upstream_), index_(src.index_) {}
   // clang-format on
 
-  ResourceManager* getResourceManager() const {
-    return VariantAttorney::getResourceManager(upstream_);
+  VariantImpl getImpl() const {
+    auto impl = VariantAttorney::getImpl(upstream_);
+    return VariantImpl(impl.getElement(index_), impl.resources());
   }
 
-  FORCE_INLINE VariantData* getData() const {
-    return VariantData::getElement(
-        VariantAttorney::getData(upstream_), index_,
-        VariantAttorney::getResourceManager(upstream_));
-  }
-
-  VariantData* getOrCreateData() const {
-    auto data = VariantAttorney::getOrCreateData(upstream_);
-    if (!data)
-      return nullptr;
-    return data->getOrAddElement(
-        index_, VariantAttorney::getResourceManager(upstream_));
+  VariantImpl getOrCreateImpl() const {
+    auto impl = VariantAttorney::getOrCreateImpl(upstream_);
+    impl.toArrayIfNull();
+    return VariantImpl(impl.getOrAddElement(index_), impl.resources());
   }
 
   TUpstream upstream_;

src/ArduinoJson/Array/JsonArray.hpp

@@ -20,24 +20,21 @@ class JsonArray : public detail::VariantOperators<JsonArray> {
   using iterator = JsonArrayIterator;
 
   // Constructs an unbound reference.
-  JsonArray() : data_(0), resources_(0) {}
+  JsonArray() {}
 
   // INTERNAL USE ONLY
-  JsonArray(detail::ArrayData* data, detail::ResourceManager* resources)
-      : data_(data), resources_(resources) {}
+  JsonArray(detail::VariantImpl impl) : impl_(impl) {}
 
   // Returns a JsonVariant pointing to the array.
   // https://arduinojson.org/v7/api/jsonvariant/
   operator JsonVariant() {
-    void* data = data_;  // prevent warning cast-align
-    return JsonVariant(reinterpret_cast<detail::VariantData*>(data),
-                       resources_);
+    return JsonVariant(impl_);
   }
 
   // Returns a read-only reference to the array.
   // https://arduinojson.org/v7/api/jsonarrayconst/
   operator JsonArrayConst() const {
-    return JsonArrayConst(data_, resources_);
+    return JsonArrayConst(impl_);
   }
 
   // Appends a new (empty) element to the array.
@@ -55,15 +52,14 @@ class JsonArray : public detail::VariantOperators<JsonArray> {
   template <typename T, detail::enable_if_t<
                             detail::is_same<T, JsonVariant>::value, int> = 0>
   JsonVariant add() const {
-    return JsonVariant(detail::ArrayData::addElement(data_, resources_),
-                       resources_);
+    return JsonVariant(impl_.addElement(), impl_.resources());
   }
 
   // Appends a value to the array.
   // https://arduinojson.org/v7/api/jsonarray/add/
   template <typename T>
   bool add(const T& value) const {
-    return detail::ArrayData::addValue(data_, value, resources_);
+    return doAdd(value);
   }
 
   // Appends a value to the array.
@@ -71,15 +67,13 @@ class JsonArray : public detail::VariantOperators<JsonArray> {
   template <typename T,
             detail::enable_if_t<!detail::is_const<T>::value, int> = 0>
   bool add(T* value) const {
-    return detail::ArrayData::addValue(data_, value, resources_);
+    return doAdd(value);
   }
 
   // Returns an iterator to the first element of the array.
   // https://arduinojson.org/v7/api/jsonarray/begin/
   iterator begin() const {
-    if (!data_)
-      return iterator();
-    return iterator(data_->createIterator(resources_), resources_);
+    return iterator(impl_.createIterator());
   }
 
   // Returns an iterator following the last element of the array.
@@ -91,28 +85,20 @@ class JsonArray : public detail::VariantOperators<JsonArray> {
   // Copies an array.
   // https://arduinojson.org/v7/api/jsonarray/set/
   bool set(JsonArrayConst src) const {
-    if (!data_)
-      return false;
-
-    clear();
-    for (auto element : src) {
-      if (!add(element))
-        return false;
-    }
-
-    return true;
+    impl_.clear();
+    return impl_.copyArray(detail::VariantAttorney::getImpl(src));
   }
 
   // Removes the element at the specified iterator.
   // https://arduinojson.org/v7/api/jsonarray/remove/
   void remove(iterator it) const {
-    detail::ArrayData::remove(data_, it.iterator_, resources_);
+    impl_.removeElement(it.iterator_);
   }
 
   // Removes the element at the specified index.
   // https://arduinojson.org/v7/api/jsonarray/remove/
   void remove(size_t index) const {
-    detail::ArrayData::removeElement(data_, index, resources_);
+    impl_.removeElement(index);
   }
 
   // Removes the element at the specified index.
@@ -127,7 +113,8 @@ class JsonArray : public detail::VariantOperators<JsonArray> {
   // Removes all the elements of the array.
   // https://arduinojson.org/v7/api/jsonarray/clear/
   void clear() const {
-    detail::ArrayData::clear(data_, resources_);
+    if (impl_.isArray())
+      impl_.empty();
   }
 
   // Gets or sets the element at the specified index.
@@ -150,31 +137,31 @@ class JsonArray : public detail::VariantOperators<JsonArray> {
   }
 
   operator JsonVariantConst() const {
-    return JsonVariantConst(collectionToVariant(data_), resources_);
+    return JsonVariantConst(impl_);
   }
 
   // Returns true if the reference is unbound.
   // https://arduinojson.org/v7/api/jsonarray/isnull/
   bool isNull() const {
-    return data_ == 0;
+    return impl_.isNull();
   }
 
   // Returns true if the reference is bound.
   // https://arduinojson.org/v7/api/jsonarray/isnull/
   operator bool() const {
-    return data_ != 0;
+    return !isNull();
   }
 
   // Returns the depth (nesting level) of the array.
   // https://arduinojson.org/v7/api/jsonarray/nesting/
   size_t nesting() const {
-    return detail::VariantData::nesting(collectionToVariant(data_), resources_);
+    return impl_.nesting();
   }
 
   // Returns the number of elements in the array.
   // https://arduinojson.org/v7/api/jsonarray/size/
   size_t size() const {
-    return data_ ? data_->size(resources_) : 0;
+    return impl_.size();
   }
 
   // DEPRECATED: use add<JsonVariant>() instead
@@ -200,20 +187,36 @@ class JsonArray : public detail::VariantOperators<JsonArray> {
   }
 
  private:
-  detail::ResourceManager* getResourceManager() const {
-    return resources_;
+  const detail::VariantImpl& getImpl() const {
+    return impl_;
   }
 
-  detail::VariantData* getData() const {
-    return collectionToVariant(data_);
+  const detail::VariantImpl& getOrCreateImpl() const {
+    return impl_;
   }
 
-  detail::VariantData* getOrCreateData() const {
-    return collectionToVariant(data_);
+  template <typename T>
+  bool doAdd(const T& value) const {
+    if (!impl_.isArray())
+      return false;
+
+    auto resources = impl_.resources();
+    ARDUINOJSON_ASSERT(resources != nullptr);
+
+    auto slot = resources->allocVariant();
+    if (!slot)
+      return false;
+
+    if (!JsonVariant(slot.ptr(), resources).set(value)) {
+      detail::VariantImpl(slot.ptr(), resources).clear();
+      resources->freeVariant(slot);
+      return false;
+    }
+    impl_.addElement(slot);
+    return true;
   }
 
-  detail::ArrayData* data_;
-  detail::ResourceManager* resources_;
+  mutable detail::VariantImpl impl_;
 };
 
 ARDUINOJSON_END_PUBLIC_NAMESPACE

src/ArduinoJson/Array/JsonArrayConst.hpp

@@ -24,9 +24,7 @@ class JsonArrayConst : public detail::VariantOperators<JsonArrayConst> {
   // Returns an iterator to the first element of the array.
   // https://arduinojson.org/v7/api/jsonarrayconst/begin/
   iterator begin() const {
-    if (!data_)
-      return iterator();
-    return iterator(data_->createIterator(resources_), resources_);
+    return iterator(impl_.createIterator());
   }
 
   // Returns an iterator to the element following the last element of the array.
@@ -36,21 +34,17 @@ class JsonArrayConst : public detail::VariantOperators<JsonArrayConst> {
   }
 
   // Creates an unbound reference.
-  JsonArrayConst() : data_(0), resources_(0) {}
+  JsonArrayConst() {}
 
   // INTERNAL USE ONLY
-  JsonArrayConst(const detail::ArrayData* data,
-                 const detail::ResourceManager* resources)
-      : data_(data), resources_(resources) {}
+  JsonArrayConst(const detail::VariantImpl& impl) : impl_(impl) {}
 
   // Returns the element at the specified index.
   // https://arduinojson.org/v7/api/jsonarrayconst/subscript/
   template <typename T,
             detail::enable_if_t<detail::is_integral<T>::value, int> = 0>
   JsonVariantConst operator[](T index) const {
-    return JsonVariantConst(
-        detail::ArrayData::getElement(data_, size_t(index), resources_),
-        resources_);
+    return JsonVariantConst(impl_.getElement(size_t(index)), impl_.resources());
   }
 
   // Returns the element at the specified index.
@@ -65,31 +59,31 @@ class JsonArrayConst : public detail::VariantOperators<JsonArrayConst> {
   }
 
   operator JsonVariantConst() const {
-    return JsonVariantConst(getData(), resources_);
+    return JsonVariantConst(impl_);
   }
 
   // Returns true if the reference is unbound.
   // https://arduinojson.org/v7/api/jsonarrayconst/isnull/
   bool isNull() const {
-    return data_ == 0;
+    return impl_.isNull();
   }
 
   // Returns true if the reference is bound.
   // https://arduinojson.org/v7/api/jsonarrayconst/isnull/
   operator bool() const {
-    return data_ != 0;
+    return !isNull();
   }
 
   // Returns the depth (nesting level) of the array.
   // https://arduinojson.org/v7/api/jsonarrayconst/nesting/
   size_t nesting() const {
-    return detail::VariantData::nesting(getData(), resources_);
+    return impl_.nesting();
   }
 
   // Returns the number of elements in the array.
   // https://arduinojson.org/v7/api/jsonarrayconst/size/
   size_t size() const {
-    return data_ ? data_->size(resources_) : 0;
+    return impl_.size();
   }
 
   // DEPRECATED: always returns zero
@@ -99,12 +93,11 @@ class JsonArrayConst : public detail::VariantOperators<JsonArrayConst> {
   }
 
  private:
-  const detail::VariantData* getData() const {
-    return collectionToVariant(data_);
+  const detail::VariantImpl& getImpl() const {
+    return impl_;
   }
 
-  const detail::ArrayData* data_;
-  const detail::ResourceManager* resources_;
+  detail::VariantImpl impl_;
 };
 
 // Compares the content of two arrays.

src/ArduinoJson/Array/JsonArrayIterator.hpp

@@ -4,6 +4,7 @@
 
 #pragma once
 
+#include <ArduinoJson/Collection/CollectionIterator.hpp>
 #include <ArduinoJson/Variant/JsonVariant.hpp>
 
 ARDUINOJSON_BEGIN_PUBLIC_NAMESPACE
@@ -30,12 +31,11 @@ class JsonArrayIterator {
 
  public:
   JsonArrayIterator() {}
-  explicit JsonArrayIterator(detail::ArrayData::iterator iterator,
-                             detail::ResourceManager* resources)
-      : iterator_(iterator), resources_(resources) {}
+  explicit JsonArrayIterator(const detail::VariantImpl::iterator& iterator)
+      : iterator_(iterator) {}
 
   JsonVariant operator*() {
-    return JsonVariant(iterator_.data(), resources_);
+    return JsonVariant(*iterator_);
   }
   Ptr<JsonVariant> operator->() {
     return operator*();
@@ -50,13 +50,12 @@ class JsonArrayIterator {
   }
 
   JsonArrayIterator& operator++() {
-    iterator_.next(resources_);
+    iterator_.move();
     return *this;
   }
 
  private:
-  detail::ArrayData::iterator iterator_;
-  detail::ResourceManager* resources_;
+  detail::VariantImpl::iterator iterator_;
 };
 
 class JsonArrayConstIterator {
@@ -64,12 +63,11 @@ class JsonArrayConstIterator {
 
  public:
   JsonArrayConstIterator() {}
-  explicit JsonArrayConstIterator(detail::ArrayData::iterator iterator,
-                                  const detail::ResourceManager* resources)
-      : iterator_(iterator), resources_(resources) {}
+  explicit JsonArrayConstIterator(const detail::VariantImpl::iterator& iterator)
+      : iterator_(iterator) {}
 
   JsonVariantConst operator*() const {
-    return JsonVariantConst(iterator_.data(), resources_);
+    return JsonVariantConst(*iterator_);
   }
   Ptr<JsonVariantConst> operator->() {
     return operator*();
@@ -84,13 +82,12 @@ class JsonArrayConstIterator {
   }
 
   JsonArrayConstIterator& operator++() {
-    iterator_.next(resources_);
+    iterator_.move();
     return *this;
   }
 
  private:
-  detail::ArrayData::iterator iterator_;
-  const detail::ResourceManager* resources_;
+  mutable detail::VariantImpl::iterator iterator_;
 };
 
 ARDUINOJSON_END_PUBLIC_NAMESPACE

src/ArduinoJson/Collection/CollectionData.hpp

@@ -1,122 +0,0 @@
-// ArduinoJson - https://arduinojson.org
-// Copyright © 2014-2025, Benoit BLANCHON
-// MIT License
-
-#pragma once
-
-#include <ArduinoJson/Memory/MemoryPool.hpp>
-#include <ArduinoJson/Namespace.hpp>
-#include <ArduinoJson/Polyfills/assert.hpp>
-
-#include <stddef.h>  // size_t
-
-ARDUINOJSON_BEGIN_PRIVATE_NAMESPACE
-
-class VariantData;
-class ResourceManager;
-
-class CollectionIterator {
-  friend class CollectionData;
-
- public:
-  CollectionIterator() : slot_(nullptr), currentId_(NULL_SLOT) {}
-
-  void next(const ResourceManager* resources);
-
-  bool done() const {
-    return slot_ == nullptr;
-  }
-
-  bool operator==(const CollectionIterator& other) const {
-    return slot_ == other.slot_;
-  }
-
-  bool operator!=(const CollectionIterator& other) const {
-    return slot_ != other.slot_;
-  }
-
-  VariantData* operator->() {
-    ARDUINOJSON_ASSERT(slot_ != nullptr);
-    return data();
-  }
-
-  VariantData& operator*() {
-    ARDUINOJSON_ASSERT(slot_ != nullptr);
-    return *data();
-  }
-
-  const VariantData& operator*() const {
-    ARDUINOJSON_ASSERT(slot_ != nullptr);
-    return *data();
-  }
-
-  VariantData* data() {
-    return reinterpret_cast<VariantData*>(slot_);
-  }
-
-  const VariantData* data() const {
-    return reinterpret_cast<const VariantData*>(slot_);
-  }
-
- private:
-  CollectionIterator(VariantData* slot, SlotId slotId);
-
-  VariantData* slot_;
-  SlotId currentId_, nextId_;
-};
-
-class CollectionData {
-  SlotId head_ = NULL_SLOT;
-  SlotId tail_ = NULL_SLOT;
-
- public:
-  // Placement new
-  static void* operator new(size_t, void* p) noexcept {
-    return p;
-  }
-
-  static void operator delete(void*, void*) noexcept {}
-
-  using iterator = CollectionIterator;
-
-  iterator createIterator(const ResourceManager* resources) const;
-
-  size_t size(const ResourceManager*) const;
-  size_t nesting(const ResourceManager*) const;
-
-  void clear(ResourceManager* resources);
-
-  static void clear(CollectionData* collection, ResourceManager* resources) {
-    if (!collection)
-      return;
-    collection->clear(resources);
-  }
-
-  SlotId head() const {
-    return head_;
-  }
-
- protected:
-  void appendOne(Slot<VariantData> slot, const ResourceManager* resources);
-  void appendPair(Slot<VariantData> key, Slot<VariantData> value,
-                  const ResourceManager* resources);
-
-  void removeOne(iterator it, ResourceManager* resources);
-  void removePair(iterator it, ResourceManager* resources);
-
- private:
-  Slot<VariantData> getPreviousSlot(VariantData*, const ResourceManager*) const;
-};
-
-inline const VariantData* collectionToVariant(
-    const CollectionData* collection) {
-  const void* data = collection;  // prevent warning cast-align
-  return reinterpret_cast<const VariantData*>(data);
-}
-
-inline VariantData* collectionToVariant(CollectionData* collection) {
-  void* data = collection;  // prevent warning cast-align
-  return reinterpret_cast<VariantData*>(data);
-}
-
-ARDUINOJSON_END_PRIVATE_NAMESPACE

src/ArduinoJson/Collection/CollectionImpl.hpp

@@ -4,7 +4,6 @@
 
 #pragma once
 
-#include <ArduinoJson/Collection/CollectionData.hpp>
 #include <ArduinoJson/Memory/Alignment.hpp>
 #include <ArduinoJson/Strings/StringAdapters.hpp>
 #include <ArduinoJson/Variant/VariantCompare.hpp>
@@ -12,125 +11,104 @@
 
 ARDUINOJSON_BEGIN_PRIVATE_NAMESPACE
 
-inline CollectionIterator::CollectionIterator(VariantData* slot, SlotId slotId)
-    : slot_(slot), currentId_(slotId) {
-  nextId_ = slot_ ? slot_->next() : NULL_SLOT;
+inline VariantImpl::iterator VariantImpl::createIterator() const {
+  if (!data_ || !data_->isCollection())
+    return iterator();
+  auto coll = getCollectionData();
+  return iterator(coll->head, resources_);
 }
 
-inline void CollectionIterator::next(const ResourceManager* resources) {
-  ARDUINOJSON_ASSERT(currentId_ != NULL_SLOT);
-  slot_ = resources->getVariant(nextId_);
-  currentId_ = nextId_;
-  if (slot_)
-    nextId_ = slot_->next();
-}
+inline void VariantImpl::addMember(Slot<VariantData> key,
+                                   Slot<VariantData> value) {
+  ARDUINOJSON_ASSERT(isObject());
+  ARDUINOJSON_ASSERT(key);
+  ARDUINOJSON_ASSERT(value);
 
-inline CollectionData::iterator CollectionData::createIterator(
-    const ResourceManager* resources) const {
-  return iterator(resources->getVariant(head_), head_);
-}
+  auto coll = getCollectionData();
 
-inline void CollectionData::appendOne(Slot<VariantData> slot,
-                                      const ResourceManager* resources) {
-  if (tail_ != NULL_SLOT) {
-    auto tail = resources->getVariant(tail_);
-    tail->setNext(slot.id());
-    tail_ = slot.id();
+  key->next = value.id();
+
+  if (coll->tail != NULL_SLOT) {
+    auto tail = getVariant(coll->tail);
+    tail->next = key.id();
+    coll->tail = value.id();
   } else {
-    head_ = slot.id();
-    tail_ = slot.id();
+    coll->head = key.id();
+    coll->tail = value.id();
   }
 }
-
-inline void CollectionData::appendPair(Slot<VariantData> key,
-                                       Slot<VariantData> value,
-                                       const ResourceManager* resources) {
-  key->setNext(value.id());
-
-  if (tail_ != NULL_SLOT) {
-    auto tail = resources->getVariant(tail_);
-    tail->setNext(key.id());
-    tail_ = value.id();
-  } else {
-    head_ = key.id();
-    tail_ = value.id();
-  }
-}
-
-inline void CollectionData::clear(ResourceManager* resources) {
-  auto next = head_;
-  while (next != NULL_SLOT) {
-    auto currId = next;
-    auto slot = resources->getVariant(next);
-    next = slot->next();
-    resources->freeVariant({slot, currId});
-  }
-
-  head_ = NULL_SLOT;
-  tail_ = NULL_SLOT;
-}
-
-inline Slot<VariantData> CollectionData::getPreviousSlot(
-    VariantData* target, const ResourceManager* resources) const {
+inline Slot<VariantData> VariantImpl::getPreviousSlot(
+    VariantData* target) const {
+  auto coll = getCollectionData();
   auto prev = Slot<VariantData>();
-  auto currentId = head_;
+  auto currentId = coll->head;
   while (currentId != NULL_SLOT) {
-    auto currentSlot = resources->getVariant(currentId);
+    auto currentSlot = getVariant(currentId);
     if (currentSlot == target)
       break;
     prev = Slot<VariantData>(currentSlot, currentId);
-    currentId = currentSlot->next();
+    currentId = currentSlot->next;
   }
   return prev;
 }
 
-inline void CollectionData::removeOne(iterator it, ResourceManager* resources) {
+inline void VariantImpl::removeOne(iterator it) {
   if (it.done())
     return;
-  auto curr = it.slot_;
-  auto prev = getPreviousSlot(curr, resources);
-  auto next = curr->next();
+  auto coll = getCollectionData();
+  auto curr = it->data();
+  auto prev = getPreviousSlot(curr);
+  auto next = curr->next;
   if (prev)
-    prev->setNext(next);
+    prev->next = next;
   else
-    head_ = next;
+    coll->head = next;
   if (next == NULL_SLOT)
-    tail_ = prev.id();
-  resources->freeVariant({it.slot_, it.currentId_});
+    coll->tail = prev.id();
+  freeVariant({it->data(), it.slotId()});
 }
 
-inline void CollectionData::removePair(ObjectData::iterator it,
-                                       ResourceManager* resources) {
+inline void VariantImpl::removePair(VariantImpl::iterator it) {
   if (it.done())
     return;
 
-  auto keySlot = it.slot_;
+  auto keySlot = it->data();
 
-  auto valueId = it.nextId_;
-  auto valueSlot = resources->getVariant(valueId);
+  auto valueId = keySlot->next;
+  auto valueSlot = getVariant(valueId);
 
   // remove value slot
-  keySlot->setNext(valueSlot->next());
-  resources->freeVariant({valueSlot, valueId});
+  keySlot->next = valueSlot->next;
+  freeVariant({valueSlot, valueId});
 
   // remove key slot
-  removeOne(it, resources);
+  removeOne(it);
 }
 
-inline size_t CollectionData::nesting(const ResourceManager* resources) const {
+inline size_t VariantImpl::nesting() const {
+  if (!data_ || !data_->isCollection())
+    return 0;
   size_t maxChildNesting = 0;
-  for (auto it = createIterator(resources); !it.done(); it.next(resources)) {
-    size_t childNesting = it->nesting(resources);
+  for (auto it = createIterator(); !it.done(); it.move()) {
+    auto childNesting = it->nesting();
     if (childNesting > maxChildNesting)
       maxChildNesting = childNesting;
   }
   return maxChildNesting + 1;
 }
 
-inline size_t CollectionData::size(const ResourceManager* resources) const {
+inline size_t VariantImpl::size() const {
+  if (!data_)
+    return 0;
+
   size_t count = 0;
-  for (auto it = createIterator(resources); !it.done(); it.next(resources))
+
+  for (auto it = createIterator(); !it.done(); it.move())
     count++;
+
+  if (data_->type == VariantType::Object)
+    count /= 2;  // TODO: do this in JsonObject?
+
   return count;
 }
 

src/ArduinoJson/Collection/CollectionIterator.hpp

@@ -0,0 +1,57 @@
+// ArduinoJson - https://arduinojson.org
+// Copyright © 2014-2025, Benoit BLANCHON
+// MIT License
+
+#pragma once
+
+#include <ArduinoJson/Namespace.hpp>
+#include <ArduinoJson/Polyfills/assert.hpp>
+#include <ArduinoJson/Variant/VariantImpl.hpp>
+
+ARDUINOJSON_BEGIN_PRIVATE_NAMESPACE
+
+class CollectionIterator {
+ public:
+  CollectionIterator() {}
+
+  CollectionIterator(SlotId slotId, ResourceManager* resources)
+      : value_(resources->getVariant(slotId), resources), slotId_(slotId) {}
+
+  void move() {
+    ARDUINOJSON_ASSERT(!done());
+    auto nextId = value_.data()->next;
+    auto resources = value_.resources();
+    value_ = VariantImpl(resources->getVariant(nextId), resources);
+    slotId_ = nextId;
+  }
+
+  const VariantImpl& operator*() const {
+    return value_;
+  }
+
+  const VariantImpl* operator->() const {
+    return &value_;
+  }
+
+  bool done() const {
+    return value_.isUnbound();
+  }
+
+  bool operator==(const CollectionIterator& other) const {
+    return value_.data() == other->data();
+  }
+
+  bool operator!=(const CollectionIterator& other) const {
+    return !operator==(other);
+  }
+
+  SlotId slotId() const {
+    return slotId_;
+  }
+
+ private:
+  VariantImpl value_;
+  SlotId slotId_ = NULL_SLOT;
+};
+
+ARDUINOJSON_END_PRIVATE_NAMESPACE

src/ArduinoJson/Configuration.hpp

@@ -274,9 +274,9 @@
 #endif
 
 #if ARDUINOJSON_USE_LONG_LONG || ARDUINOJSON_USE_DOUBLE
-#  define ARDUINOJSON_USE_EXTENSIONS 1
+#  define ARDUINOJSON_USE_8_BYTE_POOL 1
 #else
-#  define ARDUINOJSON_USE_EXTENSIONS 0
+#  define ARDUINOJSON_USE_8_BYTE_POOL 0
 #endif
 
 #if defined(nullptr)

src/ArduinoJson/Deserialization/deserialize.hpp

@@ -44,13 +44,13 @@ template <template <typename> class TDeserializer, typename TDestination,
           typename TReader, typename TOptions>
 DeserializationError doDeserialize(TDestination&& dst, TReader reader,
                                    TOptions options) {
-  auto data = VariantAttorney::getOrCreateData(dst);
-  if (!data)
+  auto impl = VariantAttorney::getOrCreateImpl(dst);
+  if (impl.isUnbound())
     return DeserializationError::NoMemory;
-  auto resources = VariantAttorney::getResourceManager(dst);
+  auto resources = impl.resources();
   dst.clear();
   auto err = TDeserializer<TReader>(resources, reader)
-                 .parse(*data, options.filter, options.nestingLimit);
+                 .parse(impl.data(), options.filter, options.nestingLimit);
   shrinkJsonDocument(dst);
   return err;
 }

src/ArduinoJson/Document/JsonDocument.hpp

@@ -88,7 +88,7 @@ class JsonDocument : public detail::VariantOperators<const JsonDocument&> {
   // https://arduinojson.org/v7/api/jsondocument/clear/
   void clear() {
     resources_.clear();
-    data_.reset();
+    data_.type = detail::VariantType::Null;
   }
 
   // Returns true if the root is of the specified type.
@@ -120,13 +120,13 @@ class JsonDocument : public detail::VariantOperators<const JsonDocument&> {
   // Returns the depth (nesting level) of the array.
   // https://arduinojson.org/v7/api/jsondocument/nesting/
   size_t nesting() const {
-    return data_.nesting(&resources_);
+    return getImpl().nesting();
   }
 
   // Returns the number of elements in the root array or object.
   // https://arduinojson.org/v7/api/jsondocument/size/
   size_t size() const {
-    return data_.size(&resources_);
+    return getImpl().size();
   }
 
   // Copies the specified document.
@@ -165,7 +165,7 @@ class JsonDocument : public detail::VariantOperators<const JsonDocument&> {
   template <typename TChar>
   ARDUINOJSON_DEPRECATED("use doc[\"key\"].is<T>() instead")
   bool containsKey(TChar* key) const {
-    return data_.getMember(detail::adaptString(key), &resources_) != 0;
+    return getImpl().getMember(detail::adaptString(key)) != 0;
   }
 
   // DEPRECATED: use obj[key].is<T>() instead
@@ -174,7 +174,7 @@ class JsonDocument : public detail::VariantOperators<const JsonDocument&> {
             detail::enable_if_t<detail::IsString<TString>::value, int> = 0>
   ARDUINOJSON_DEPRECATED("use doc[key].is<T>() instead")
   bool containsKey(const TString& key) const {
-    return data_.getMember(detail::adaptString(key), &resources_) != 0;
+    return getImpl().getMember(detail::adaptString(key)) != 0;
   }
 
   // DEPRECATED: use obj[key].is<T>() instead
@@ -211,8 +211,8 @@ class JsonDocument : public detail::VariantOperators<const JsonDocument&> {
   template <typename TString,
             detail::enable_if_t<detail::IsString<TString>::value, int> = 0>
   JsonVariantConst operator[](const TString& key) const {
-    return JsonVariantConst(
-        data_.getMember(detail::adaptString(key), &resources_), &resources_);
+    return JsonVariantConst(getImpl().getMember(detail::adaptString(key)),
+                            &resources_);
   }
 
   // Gets a root object's member.
@@ -222,8 +222,8 @@ class JsonDocument : public detail::VariantOperators<const JsonDocument&> {
                                     !detail::is_const<TChar>::value,
                                 int> = 0>
   JsonVariantConst operator[](TChar* key) const {
-    return JsonVariantConst(
-        data_.getMember(detail::adaptString(key), &resources_), &resources_);
+    return JsonVariantConst(getImpl().getMember(detail::adaptString(key)),
+                            &resources_);
   }
 
   // Gets or sets a root array's element.
@@ -237,7 +237,7 @@ class JsonDocument : public detail::VariantOperators<const JsonDocument&> {
   // Gets a root array's member.
   // https://arduinojson.org/v7/api/jsondocument/subscript/
   JsonVariantConst operator[](size_t index) const {
-    return JsonVariantConst(data_.getElement(index, &resources_), &resources_);
+    return JsonVariantConst(getImpl().getElement(index), &resources_);
   }
 
   // Gets or sets a root object's member.
@@ -267,14 +267,14 @@ class JsonDocument : public detail::VariantOperators<const JsonDocument&> {
   template <typename T, detail::enable_if_t<
                             detail::is_same<T, JsonVariant>::value, int> = 0>
   JsonVariant add() {
-    return JsonVariant(data_.addElement(&resources_), &resources_);
+    return getOrCreateArray().add<T>();
   }
 
   // Appends a value to the root array.
   // https://arduinojson.org/v7/api/jsondocument/add/
   template <typename TValue>
   bool add(const TValue& value) {
-    return data_.addValue(value, &resources_);
+    return getOrCreateArray().add(value);
   }
 
   // Appends a value to the root array.
@@ -282,7 +282,7 @@ class JsonDocument : public detail::VariantOperators<const JsonDocument&> {
   template <typename TChar,
             detail::enable_if_t<!detail::is_const<TChar>::value, int> = 0>
   bool add(TChar* value) {
-    return data_.addValue(value, &resources_);
+    return getOrCreateArray().add(value);
   }
 
   // Removes an element of the root array.
@@ -290,8 +290,7 @@ class JsonDocument : public detail::VariantOperators<const JsonDocument&> {
   template <typename T,
             detail::enable_if_t<detail::is_integral<T>::value, int> = 0>
   void remove(T index) {
-    detail::VariantData::removeElement(getData(), size_t(index),
-                                       getResourceManager());
+    getImpl().removeElement(size_t(index));
   }
 
   // Removes a member of the root object.
@@ -301,8 +300,7 @@ class JsonDocument : public detail::VariantOperators<const JsonDocument&> {
                                     !detail::is_const<TChar>::value,
                                 int> = 0>
   void remove(TChar* key) {
-    detail::VariantData::removeMember(getData(), detail::adaptString(key),
-                                      getResourceManager());
+    getImpl().removeMember(detail::adaptString(key));
   }
 
   // Removes a member of the root object.
@@ -310,8 +308,7 @@ class JsonDocument : public detail::VariantOperators<const JsonDocument&> {
   template <typename TString,
             detail::enable_if_t<detail::IsString<TString>::value, int> = 0>
   void remove(const TString& key) {
-    detail::VariantData::removeMember(getData(), detail::adaptString(key),
-                                      getResourceManager());
+    getImpl().removeMember(detail::adaptString(key));
   }
 
   // Removes a member of the root object or an element of the root array.
@@ -391,6 +388,20 @@ class JsonDocument : public detail::VariantOperators<const JsonDocument&> {
   }
 
  private:
+  detail::VariantImpl getImpl() const {
+    return {&data_, &resources_};
+  }
+
+  detail::VariantImpl getOrCreateImpl() {
+    return {&data_, &resources_};
+  }
+
+  JsonArray getOrCreateArray() {
+    auto impl = getImpl();
+    impl.toArrayIfNull();
+    return JsonArray(impl);
+  }
+
   JsonVariant getVariant() {
     return JsonVariant(&data_, &resources_);
   }
@@ -399,28 +410,12 @@ class JsonDocument : public detail::VariantOperators<const JsonDocument&> {
     return JsonVariantConst(&data_, &resources_);
   }
 
-  detail::ResourceManager* getResourceManager() {
-    return &resources_;
-  }
-
-  detail::VariantData* getData() {
-    return &data_;
-  }
-
-  const detail::VariantData* getData() const {
-    return &data_;
-  }
-
-  detail::VariantData* getOrCreateData() {
-    return &data_;
-  }
-
-  detail::ResourceManager resources_;
-  detail::VariantData data_;
+  mutable detail::ResourceManager resources_;
+  mutable detail::VariantData data_;
 };
 
-inline void convertToJson(const JsonDocument& src, JsonVariant dst) {
-  dst.set(src.as<JsonVariantConst>());
+inline bool convertToJson(const JsonDocument& src, JsonVariant dst) {
+  return dst.set(src.as<JsonVariantConst>());
 }
 
 ARDUINOJSON_END_PUBLIC_NAMESPACE

src/ArduinoJson/Json/JsonDeserializer.hpp

@@ -28,13 +28,13 @@ class JsonDeserializer {
         resources_(resources) {}
 
   template <typename TFilter>
-  DeserializationError parse(VariantData& variant, TFilter filter,
+  DeserializationError parse(VariantData* variant, TFilter filter,
                              DeserializationOption::NestingLimit nestingLimit) {
     DeserializationError::Code err;
 
     err = parseVariant(variant, filter, nestingLimit);
 
-    if (!err && latch_.last() != 0 && variant.isFloat()) {
+    if (!err && latch_.last() != 0 && variant->isFloat()) {
       // We don't detect trailing characters earlier, so we need to check now
       return DeserializationError::InvalidInput;
     }
@@ -60,10 +60,12 @@ class JsonDeserializer {
 
   template <typename TFilter>
   DeserializationError::Code parseVariant(
-      VariantData& variant, TFilter filter,
+      VariantData* variant, TFilter filter,
       DeserializationOption::NestingLimit nestingLimit) {
     DeserializationError::Code err;
 
+    ARDUINOJSON_ASSERT(variant != nullptr);
+
     err = skipSpacesAndComments();
     if (err)
       return err;
@@ -71,13 +73,13 @@ class JsonDeserializer {
     switch (current()) {
       case '[':
         if (filter.allowArray())
-          return parseArray(variant.toArray(), filter, nestingLimit);
+          return parseArray(variant->toArray(), filter, nestingLimit);
         else
           return skipArray(nestingLimit);
 
       case '{':
         if (filter.allowObject())
-          return parseObject(variant.toObject(), filter, nestingLimit);
+          return parseObject(variant->toObject(), filter, nestingLimit);
         else
           return skipObject(nestingLimit);
 
@@ -90,12 +92,12 @@ class JsonDeserializer {
 
       case 't':
         if (filter.allowValue())
-          variant.setBoolean(true);
+          variant->setBoolean(true);
         return skipKeyword("true");
 
       case 'f':
         if (filter.allowValue())
-          variant.setBoolean(false);
+          variant->setBoolean(false);
         return skipKeyword("false");
 
       case 'n':
@@ -146,7 +148,7 @@ class JsonDeserializer {
 
   template <typename TFilter>
   DeserializationError::Code parseArray(
-      ArrayData& array, TFilter filter,
+      VariantData* arrayData, TFilter filter,
       DeserializationOption::NestingLimit nestingLimit) {
     DeserializationError::Code err;
 
@@ -171,13 +173,15 @@ class JsonDeserializer {
     // Read each value
     for (;;) {
       if (elementFilter.allow()) {
+        VariantImpl array(arrayData, resources_);
+
         // Allocate slot in array
-        VariantData* value = array.addElement(resources_);
+        VariantData* value = array.addElement();
         if (!value)
           return DeserializationError::NoMemory;
 
         // 1 - Parse value
-        err = parseVariant(*value, elementFilter, nestingLimit.decrement());
+        err = parseVariant(value, elementFilter, nestingLimit.decrement());
         if (err)
           return err;
       } else {
@@ -232,7 +236,7 @@ class JsonDeserializer {
 
   template <typename TFilter>
   DeserializationError::Code parseObject(
-      ObjectData& object, TFilter filter,
+      VariantData* objectData, TFilter filter,
       DeserializationOption::NestingLimit nestingLimit) {
     DeserializationError::Code err;
 
@@ -273,19 +277,27 @@ class JsonDeserializer {
       TFilter memberFilter = filter[key];
 
       if (memberFilter.allow()) {
-        auto member = object.getMember(adaptString(key), resources_);
+        VariantImpl object(objectData, resources_);
+        auto member = object.getMember(adaptString(key));
         if (!member) {
-          auto keyVariant = object.addPair(&member, resources_);
-          if (!keyVariant)
+          auto keySlot = resources_->allocVariant();
+          if (!keySlot)
             return DeserializationError::NoMemory;
 
-          stringBuilder_.save(keyVariant);
+          auto valueSlot = resources_->allocVariant();
+          if (!valueSlot)
+            return DeserializationError::NoMemory;
+
+          object.addMember(keySlot, valueSlot);
+
+          stringBuilder_.save(keySlot.ptr());
+          member = valueSlot.ptr();
         } else {
-          member->clear(resources_);
+          VariantImpl(member, resources_).clear();
         }
 
         // Parse value
-        err = parseVariant(*member, memberFilter, nestingLimit.decrement());
+        err = parseVariant(member, memberFilter, nestingLimit.decrement());
         if (err)
           return err;
       } else {
@@ -379,7 +391,7 @@ class JsonDeserializer {
     }
   }
 
-  DeserializationError::Code parseStringValue(VariantData& variant) {
+  DeserializationError::Code parseStringValue(VariantData* variant) {
     DeserializationError::Code err;
 
     stringBuilder_.startString();
@@ -388,7 +400,7 @@ class JsonDeserializer {
     if (err)
       return err;
 
-    stringBuilder_.save(&variant);
+    stringBuilder_.save(variant);
 
     return DeserializationError::Ok;
   }
@@ -504,7 +516,7 @@ class JsonDeserializer {
     return DeserializationError::Ok;
   }
 
-  DeserializationError::Code parseNumericValue(VariantData& result) {
+  DeserializationError::Code parseNumericValue(VariantData* result) {
     uint8_t n = 0;
 
     char c = current();
@@ -518,26 +530,28 @@ class JsonDeserializer {
     auto number = parseNumber(buffer_);
     switch (number.type()) {
       case NumberType::UnsignedInteger:
-        if (result.setInteger(number.asUnsignedInteger(), resources_))
+        if (VariantImpl(result, resources_)
+                .setInteger(number.asUnsignedInteger()))
           return DeserializationError::Ok;
         else
           return DeserializationError::NoMemory;
 
       case NumberType::SignedInteger:
-        if (result.setInteger(number.asSignedInteger(), resources_))
+        if (VariantImpl(result, resources_)
+                .setInteger(number.asSignedInteger()))
           return DeserializationError::Ok;
         else
           return DeserializationError::NoMemory;
 
       case NumberType::Float:
-        if (result.setFloat(number.asFloat(), resources_))
+        if (VariantImpl(result, resources_).setFloat(number.asFloat()))
           return DeserializationError::Ok;
         else
           return DeserializationError::NoMemory;
 
 #if ARDUINOJSON_USE_DOUBLE
       case NumberType::Double:
-        if (result.setFloat(number.asDouble(), resources_))
+        if (VariantImpl(result, resources_).setFloat(number.asDouble()))
           return DeserializationError::Ok;
         else
           return DeserializationError::NoMemory;

src/ArduinoJson/Json/JsonSerializer.hpp

@@ -16,46 +16,42 @@ class JsonSerializer : public VariantDataVisitor<size_t> {
  public:
   static const bool producesText = true;
 
-  JsonSerializer(TWriter writer, const ResourceManager* resources)
+  JsonSerializer(TWriter writer, ResourceManager* resources)
       : formatter_(writer), resources_(resources) {}
 
-  size_t visit(const ArrayData& array) {
+  size_t visitArray(const VariantImpl& array) {
     write('[');
 
-    auto slotId = array.head();
+    bool first = true;
 
-    while (slotId != NULL_SLOT) {
-      auto slot = resources_->getVariant(slotId);
-
-      slot->accept(*this, resources_);
-
-      slotId = slot->next();
-
-      if (slotId != NULL_SLOT)
+    for (auto it = array.createIterator(); !it.done(); it.move()) {
+      if (!first)
         write(',');
+
+      it->accept(*this);
+      first = false;
     }
 
     write(']');
     return bytesWritten();
   }
 
-  size_t visit(const ObjectData& object) {
+  size_t visitObject(const VariantImpl& object) {
     write('{');
 
-    auto slotId = object.head();
+    bool first = true;
+    bool isValue = false;
 
-    bool isKey = true;
+    for (auto it = object.createIterator(); !it.done(); it.move()) {
+      if (isValue)
+        write(':');
+      else if (!first)
+        write(',');
 
-    while (slotId != NULL_SLOT) {
-      auto slot = resources_->getVariant(slotId);
-      slot->accept(*this, resources_);
+      it->accept(*this);
 
-      slotId = slot->next();
-
-      if (slotId != NULL_SLOT)
-        write(isKey ? ':' : ',');
-
-      isKey = !isKey;
+      first = false;
+      isValue = !isValue;
     }
 
     write('}');
@@ -120,7 +116,7 @@ class JsonSerializer : public VariantDataVisitor<size_t> {
   TextFormatter<TWriter> formatter_;
 
  protected:
-  const ResourceManager* resources_;
+  ResourceManager* resources_;
 };
 
 ARDUINOJSON_END_PRIVATE_NAMESPACE

src/ArduinoJson/Json/PrettyJsonSerializer.hpp

@@ -16,19 +16,18 @@ class PrettyJsonSerializer : public JsonSerializer<TWriter> {
   using base = JsonSerializer<TWriter>;
 
  public:
-  PrettyJsonSerializer(TWriter writer, const ResourceManager* resources)
+  PrettyJsonSerializer(TWriter writer, ResourceManager* resources)
       : base(writer, resources), nesting_(0) {}
 
-  size_t visit(const ArrayData& array) {
-    auto it = array.createIterator(base::resources_);
+  size_t visitArray(const VariantImpl& array) {
+    auto it = array.createIterator();
     if (!it.done()) {
       base::write("[\r\n");
       nesting_++;
       while (!it.done()) {
         indent();
-        it->accept(*this, base::resources_);
-
-        it.next(base::resources_);
+        it->accept(*this);
+        it.move();
         base::write(it.done() ? "\r\n" : ",\r\n");
       }
       nesting_--;
@@ -40,8 +39,8 @@ class PrettyJsonSerializer : public JsonSerializer<TWriter> {
     return this->bytesWritten();
   }
 
-  size_t visit(const ObjectData& object) {
-    auto it = object.createIterator(base::resources_);
+  size_t visitObject(const VariantImpl& object) {
+    auto it = object.createIterator();
     if (!it.done()) {
       base::write("{\r\n");
       nesting_++;
@@ -49,8 +48,8 @@ class PrettyJsonSerializer : public JsonSerializer<TWriter> {
       while (!it.done()) {
         if (isKey)
           indent();
-        it->accept(*this, base::resources_);
-        it.next(base::resources_);
+        it->accept(*this);
+        it.move();
         if (isKey)
           base::write(": ");
         else

src/ArduinoJson/Memory/MemoryPool.hpp

@@ -34,6 +34,11 @@ class Slot {
     return ptr_;
   }
 
+  T& operator*() const {
+    ARDUINOJSON_ASSERT(ptr_ != nullptr);
+    return *ptr_;
+  }
+
   T* operator->() const {
     ARDUINOJSON_ASSERT(ptr_ != nullptr);
     return ptr_;
@@ -76,6 +81,14 @@ class MemoryPool {
     return slots_ + id;
   }
 
+  SlotId find(const T& value) const {
+    for (SlotId i = 0; i < usage_; i++) {
+      if (slots_[i] == value)
+        return i;
+    }
+    return NULL_SLOT;
+  }
+
   void clear() {
     usage_ = 0;
   }

src/ArduinoJson/Memory/MemoryPoolList.hpp

@@ -114,6 +114,15 @@ class MemoryPoolList {
     return pools_[poolIndex].getSlot(indexInPool);
   }
 
+  SlotId find(const T& value) const {
+    for (PoolCount i = 0; i < count_; i++) {
+      SlotId id = pools_[i].find(value);
+      if (id != NULL_SLOT)
+        return SlotId(i * ARDUINOJSON_POOL_CAPACITY + id);
+    }
+    return NULL_SLOT;
+  }
+
   void clear(Allocator* allocator) {
     for (PoolCount i = 0; i < count_; i++)
       pools_[i].destroy(allocator);

src/ArduinoJson/Memory/ResourceManager.hpp

@@ -14,26 +14,21 @@
 
 ARDUINOJSON_BEGIN_PRIVATE_NAMESPACE
 
-class VariantData;
+struct VariantData;
 class VariantWithId;
 
 class ResourceManager {
-  union SlotData {
-    VariantData variant;
-#if ARDUINOJSON_USE_EXTENSIONS
-    VariantExtension extension;
-#endif
-  };
-
  public:
-  constexpr static size_t slotSize = sizeof(SlotData);
-
   ResourceManager(Allocator* allocator = DefaultAllocator::instance())
       : allocator_(allocator), overflowed_(false) {}
 
   ~ResourceManager() {
     stringPool_.clear(allocator_);
     variantPools_.clear(allocator_);
+    staticStringsPools_.clear(allocator_);
+#if ARDUINOJSON_USE_8_BYTE_POOL
+    eightBytePools_.clear(allocator_);
+#endif
   }
 
   ResourceManager(const ResourceManager&) = delete;
@@ -42,6 +37,10 @@ class ResourceManager {
   friend void swap(ResourceManager& a, ResourceManager& b) {
     swap(a.stringPool_, b.stringPool_);
     swap(a.variantPools_, b.variantPools_);
+    swap(a.staticStringsPools_, b.staticStringsPools_);
+#if ARDUINOJSON_USE_8_BYTE_POOL
+    swap(a.eightBytePools_, b.eightBytePools_);
+#endif
     swap_(a.allocator_, b.allocator_);
     swap_(a.overflowed_, b.overflowed_);
   }
@@ -58,14 +57,42 @@ class ResourceManager {
     return overflowed_;
   }
 
-  Slot<VariantData> allocVariant();
-  void freeVariant(Slot<VariantData> slot);
-  VariantData* getVariant(SlotId id) const;
+  Slot<VariantData> allocVariant() {
+    auto slot = variantPools_.allocSlot(allocator_);
+    if (!slot) {
+      overflowed_ = true;
+      return {};
+    }
+    new (slot.ptr()) VariantData();
+    return slot;
+  }
 
-#if ARDUINOJSON_USE_EXTENSIONS
-  Slot<VariantExtension> allocExtension();
-  void freeExtension(SlotId slot);
-  VariantExtension* getExtension(SlotId id) const;
+  void freeVariant(Slot<VariantData> slot) {
+    variantPools_.freeSlot(slot);
+  }
+
+  VariantData* getVariant(SlotId id) const {
+    return variantPools_.getSlot(id);
+  }
+
+#if ARDUINOJSON_USE_8_BYTE_POOL
+  Slot<EightByteValue> allocEightByte() {
+    auto slot = eightBytePools_.allocSlot(allocator_);
+    if (!slot) {
+      overflowed_ = true;
+      return {};
+    }
+    return slot;
+  }
+
+  void freeEightByte(SlotId id) {
+    auto p = getEightByte(id);
+    eightBytePools_.freeSlot({p, id});
+  }
+
+  EightByteValue* getEightByte(SlotId id) const {
+    return eightBytePools_.getSlot(id);
+  }
 #endif
 
   template <typename TAdaptedString>
@@ -107,25 +134,55 @@ class ResourceManager {
     StringNode::destroy(node, allocator_);
   }
 
-  void dereferenceString(const char* s) {
-    stringPool_.dereference(s, allocator_);
+  void dereferenceString(StringNode* node) {
+    stringPool_.dereference(node, allocator_);
+  }
+
+  SlotId saveStaticString(const char* s) {
+    auto existingSlotId = staticStringsPools_.find(s);
+    if (existingSlotId != NULL_SLOT)
+      return existingSlotId;
+
+    auto slot = staticStringsPools_.allocSlot(allocator_);
+    if (slot)
+      *slot = s;
+    else
+      overflowed_ = true;
+
+    return slot.id();
+  }
+
+  const char* getStaticString(SlotId id) const {
+    return *staticStringsPools_.getSlot(id);
   }
 
   void clear() {
-    variantPools_.clear(allocator_);
     overflowed_ = false;
+    variantPools_.clear(allocator_);
     stringPool_.clear(allocator_);
+    staticStringsPools_.clear(allocator_);
+#if ARDUINOJSON_USE_8_BYTE_POOL
+    eightBytePools_.clear(allocator_);
+#endif
   }
 
   void shrinkToFit() {
     variantPools_.shrinkToFit(allocator_);
+    staticStringsPools_.shrinkToFit(allocator_);
+#if ARDUINOJSON_USE_8_BYTE_POOL
+    eightBytePools_.shrinkToFit(allocator_);
+#endif
   }
 
  private:
   Allocator* allocator_;
   bool overflowed_;
   StringPool stringPool_;
-  MemoryPoolList<SlotData> variantPools_;
+  MemoryPoolList<VariantData> variantPools_;
+  MemoryPoolList<const char*> staticStringsPools_;
+#if ARDUINOJSON_USE_8_BYTE_POOL
+  MemoryPoolList<EightByteValue> eightBytePools_;
+#endif
 };
 
 ARDUINOJSON_END_PRIVATE_NAMESPACE

src/ArduinoJson/Memory/ResourceManagerImpl.hpp

@@ -1,52 +0,0 @@
-// ArduinoJson - https://arduinojson.org
-// Copyright © 2014-2025, Benoit BLANCHON
-// MIT License
-
-#pragma once
-
-#include <ArduinoJson/Collection/CollectionData.hpp>
-#include <ArduinoJson/Memory/ResourceManager.hpp>
-#include <ArduinoJson/Polyfills/alias_cast.hpp>
-#include <ArduinoJson/Variant/VariantData.hpp>
-
-ARDUINOJSON_BEGIN_PRIVATE_NAMESPACE
-
-inline Slot<VariantData> ResourceManager::allocVariant() {
-  auto p = variantPools_.allocSlot(allocator_);
-  if (!p) {
-    overflowed_ = true;
-    return {};
-  }
-  return {new (&p->variant) VariantData, p.id()};
-}
-
-inline void ResourceManager::freeVariant(Slot<VariantData> variant) {
-  variant->clear(this);
-  variantPools_.freeSlot({alias_cast<SlotData*>(variant.ptr()), variant.id()});
-}
-
-inline VariantData* ResourceManager::getVariant(SlotId id) const {
-  return reinterpret_cast<VariantData*>(variantPools_.getSlot(id));
-}
-
-#if ARDUINOJSON_USE_EXTENSIONS
-inline Slot<VariantExtension> ResourceManager::allocExtension() {
-  auto p = variantPools_.allocSlot(allocator_);
-  if (!p) {
-    overflowed_ = true;
-    return {};
-  }
-  return {&p->extension, p.id()};
-}
-
-inline void ResourceManager::freeExtension(SlotId id) {
-  auto p = getExtension(id);
-  variantPools_.freeSlot({reinterpret_cast<SlotData*>(p), id});
-}
-
-inline VariantExtension* ResourceManager::getExtension(SlotId id) const {
-  return &variantPools_.getSlot(id)->extension;
-}
-#endif
-
-ARDUINOJSON_END_PRIVATE_NAMESPACE

src/ArduinoJson/Memory/StringBuffer.hpp

@@ -41,7 +41,7 @@ class StringBuffer {
     ARDUINOJSON_ASSERT(node_ != nullptr);
     const char* s = node_->data;
     if (isTinyString(s, size_))
-      data->setTinyString(s, static_cast<uint8_t>(size_));
+      data->setTinyString(adaptString(s, size_));
     else
       data->setOwnedString(commitStringNode());
   }

src/ArduinoJson/Memory/StringBuilder.hpp

@@ -5,6 +5,7 @@
 #pragma once
 
 #include <ArduinoJson/Memory/ResourceManager.hpp>
+#include <ArduinoJson/Strings/JsonString.hpp>
 
 ARDUINOJSON_BEGIN_PRIVATE_NAMESPACE
 
@@ -31,7 +32,7 @@ class StringBuilder {
 
     char* p = node_->data;
     if (isTinyString(p, size_)) {
-      variant->setTinyString(p, static_cast<uint8_t>(size_));
+      variant->setTinyString(adaptString(p, size_));
       return;
     }
 

src/ArduinoJson/Memory/StringPool.hpp

@@ -78,20 +78,20 @@ class StringPool {
     return nullptr;
   }
 
-  void dereference(const char* s, Allocator* allocator) {
+  void dereference(StringNode* nodeToRemove, Allocator* allocator) {
     StringNode* prev = nullptr;
-    for (auto node = strings_; node; node = node->next) {
-      if (node->data == s) {
-        if (--node->references == 0) {
+    for (auto current = strings_; current; current = current->next) {
+      if (current == nodeToRemove) {
+        if (--current->references == 0) {
           if (prev)
-            prev->next = node->next;
+            prev->next = current->next;
           else
-            strings_ = node->next;
-          StringNode::destroy(node, allocator);
+            strings_ = current->next;
+          StringNode::destroy(current, allocator);
         }
         return;
       }
-      prev = node;
+      prev = current;
     }
   }
 

src/ArduinoJson/MsgPack/MsgPackBinary.hpp

@@ -24,52 +24,51 @@ class MsgPackBinary {
 
 template <>
 struct Converter<MsgPackBinary> : private detail::VariantAttorney {
-  static void toJson(MsgPackBinary src, JsonVariant dst) {
-    auto data = VariantAttorney::getData(dst);
-    if (!data)
-      return;
-    auto resources = getResourceManager(dst);
-    data->clear(resources);
-    if (src.data()) {
-      size_t headerSize = src.size() >= 0x10000 ? 5
-                          : src.size() >= 0x100 ? 3
-                                                : 2;
-      auto str = resources->createString(src.size() + headerSize);
-      if (str) {
-        resources->saveString(str);
-        auto ptr = reinterpret_cast<uint8_t*>(str->data);
-        switch (headerSize) {
-          case 2:
-            ptr[0] = uint8_t(0xc4);
-            ptr[1] = uint8_t(src.size() & 0xff);
-            break;
-          case 3:
-            ptr[0] = uint8_t(0xc5);
-            ptr[1] = uint8_t(src.size() >> 8 & 0xff);
-            ptr[2] = uint8_t(src.size() & 0xff);
-            break;
-          case 5:
-            ptr[0] = uint8_t(0xc6);
-            ptr[1] = uint8_t(src.size() >> 24 & 0xff);
-            ptr[2] = uint8_t(src.size() >> 16 & 0xff);
-            ptr[3] = uint8_t(src.size() >> 8 & 0xff);
-            ptr[4] = uint8_t(src.size() & 0xff);
-            break;
-          default:
-            ARDUINOJSON_ASSERT(false);
-        }
-        memcpy(ptr + headerSize, src.data(), src.size());
-        data->setRawString(str);
-        return;
-      }
+  static bool toJson(MsgPackBinary src, JsonVariant dst) {
+    auto impl = getImpl(dst);
+    if (impl.isUnbound())
+      return false;
+
+    if (!src.data())
+      return true;
+
+    size_t headerSize = src.size() >= 0x10000 ? 5 : src.size() >= 0x100 ? 3 : 2;
+
+    auto resources = impl.resources();
+    auto str = resources->createString(src.size() + headerSize);
+    if (!str)
+      return false;
+    resources->saveString(str);
+
+    auto ptr = reinterpret_cast<uint8_t*>(str->data);
+    switch (headerSize) {
+      case 2:
+        ptr[0] = uint8_t(0xc4);
+        ptr[1] = uint8_t(src.size() & 0xff);
+        break;
+      case 3:
+        ptr[0] = uint8_t(0xc5);
+        ptr[1] = uint8_t(src.size() >> 8 & 0xff);
+        ptr[2] = uint8_t(src.size() & 0xff);
+        break;
+      case 5:
+        ptr[0] = uint8_t(0xc6);
+        ptr[1] = uint8_t(src.size() >> 24 & 0xff);
+        ptr[2] = uint8_t(src.size() >> 16 & 0xff);
+        ptr[3] = uint8_t(src.size() >> 8 & 0xff);
+        ptr[4] = uint8_t(src.size() & 0xff);
+        break;
+      default:
+        ARDUINOJSON_ASSERT(false);
     }
+    memcpy(ptr + headerSize, src.data(), src.size());
+    impl.data()->setRawString(str);
+    return true;
   }
 
   static MsgPackBinary fromJson(JsonVariantConst src) {
-    auto data = getData(src);
-    if (!data)
-      return {};
-    auto rawstr = data->asRawString();
+    auto variant = getImpl(src);
+    auto rawstr = variant.asRawString();
     auto p = reinterpret_cast<const uint8_t*>(rawstr.c_str());
     auto n = rawstr.size();
     if (n >= 2 && p[0] == 0xc4) {  // bin 8

src/ArduinoJson/MsgPack/MsgPackDeserializer.hpp

@@ -24,10 +24,10 @@ class MsgPackDeserializer {
         foundSomething_(false) {}
 
   template <typename TFilter>
-  DeserializationError parse(VariantData& variant, TFilter filter,
+  DeserializationError parse(VariantData* variant, TFilter filter,
                              DeserializationOption::NestingLimit nestingLimit) {
     DeserializationError::Code err;
-    err = parseVariant(&variant, filter, nestingLimit);
+    err = parseVariant(variant, filter, nestingLimit);
     return foundSomething_ ? err : DeserializationError::EmptyInput;
   }
 
@@ -91,7 +91,7 @@ class MsgPackDeserializer {
 
     if (code <= 0x7f || code >= 0xe0) {  // fixint
       if (allowValue)
-        variant->setInteger(static_cast<int8_t>(code), resources_);
+        VariantImpl(variant, resources_).setInteger(static_cast<int8_t>(code));
       return DeserializationError::Ok;
     }
 
@@ -231,14 +231,14 @@ class MsgPackDeserializer {
     if (isSigned) {
       auto truncatedValue = static_cast<JsonInteger>(signedValue);
       if (truncatedValue == signedValue) {
-        if (!variant->setInteger(truncatedValue, resources_))
+        if (!VariantImpl(variant, resources_).setInteger(truncatedValue))
           return DeserializationError::NoMemory;
       }
       // else set null on overflow
     } else {
       auto truncatedValue = static_cast<JsonUInt>(unsignedValue);
       if (truncatedValue == unsignedValue)
-        if (!variant->setInteger(truncatedValue, resources_))
+        if (!VariantImpl(variant, resources_).setInteger(truncatedValue))
           return DeserializationError::NoMemory;
       // else set null on overflow
     }
@@ -257,7 +257,7 @@ class MsgPackDeserializer {
       return err;
 
     fixEndianness(value);
-    variant->setFloat(value, resources_);
+    VariantImpl(variant, resources_).setFloat(value);
 
     return DeserializationError::Ok;
   }
@@ -273,7 +273,7 @@ class MsgPackDeserializer {
       return err;
 
     fixEndianness(value);
-    if (variant->setFloat(value, resources_))
+    if (VariantImpl(variant, resources_).setFloat(value))
       return DeserializationError::Ok;
     else
       return DeserializationError::NoMemory;
@@ -293,7 +293,7 @@ class MsgPackDeserializer {
 
     doubleToFloat(i, o);
     fixEndianness(value);
-    variant->setFloat(value, resources_);
+    VariantImpl(variant, resources_).setFloat(value);
 
     return DeserializationError::Ok;
   }
@@ -349,12 +349,10 @@ class MsgPackDeserializer {
 
     bool allowArray = filter.allowArray();
 
-    ArrayData* array;
+    VariantImpl array;
     if (allowArray) {
       ARDUINOJSON_ASSERT(variant != 0);
-      array = &variant->toArray();
-    } else {
-      array = 0;
+      array = VariantImpl(variant->toArray(), resources_);
     }
 
     TFilter elementFilter = filter[0U];
@@ -363,8 +361,7 @@ class MsgPackDeserializer {
       VariantData* value;
 
       if (elementFilter.allow()) {
-        ARDUINOJSON_ASSERT(array != 0);
-        value = array->addElement(resources_);
+        value = array.addElement();
         if (!value)
           return DeserializationError::NoMemory;
       } else {
@@ -388,12 +385,10 @@ class MsgPackDeserializer {
     if (nestingLimit.reached())
       return DeserializationError::TooDeep;
 
-    ObjectData* object;
+    VariantImpl object;
     if (filter.allowObject()) {
       ARDUINOJSON_ASSERT(variant != 0);
-      object = &variant->toObject();
-    } else {
-      object = 0;
+      object = VariantImpl(variant->toObject(), resources_);
     }
 
     for (; n; --n) {
@@ -406,13 +401,18 @@ class MsgPackDeserializer {
       VariantData* member = 0;
 
       if (memberFilter.allow()) {
-        ARDUINOJSON_ASSERT(object != 0);
-
-        auto keyVariant = object->addPair(&member, resources_);
-        if (!keyVariant)
+        auto keySlot = resources_->allocVariant();
+        if (!keySlot)
           return DeserializationError::NoMemory;
 
-        stringBuffer_.save(keyVariant);
+        auto valueSlot = resources_->allocVariant();
+        if (!valueSlot)
+          return DeserializationError::NoMemory;
+
+        object.addMember(keySlot, valueSlot);
+
+        member = valueSlot.ptr();
+        stringBuffer_.save(keySlot.ptr());
       }
 
       err = parseVariant(member, memberFilter, nestingLimit.decrement());

src/ArduinoJson/MsgPack/MsgPackExtension.hpp

@@ -30,60 +30,62 @@ class MsgPackExtension {
 
 template <>
 struct Converter<MsgPackExtension> : private detail::VariantAttorney {
-  static void toJson(MsgPackExtension src, JsonVariant dst) {
-    auto data = VariantAttorney::getData(dst);
-    if (!data)
-      return;
-    auto resources = getResourceManager(dst);
-    data->clear(resources);
-    if (src.data()) {
-      uint8_t format, sizeBytes;
-      if (src.size() >= 0x10000) {
-        format = 0xc9;  // ext 32
-        sizeBytes = 4;
-      } else if (src.size() >= 0x100) {
-        format = 0xc8;  // ext 16
-        sizeBytes = 2;
-      } else if (src.size() == 16) {
-        format = 0xd8;  // fixext 16
-        sizeBytes = 0;
-      } else if (src.size() == 8) {
-        format = 0xd7;  // fixext 8
-        sizeBytes = 0;
-      } else if (src.size() == 4) {
-        format = 0xd6;  // fixext 4
-        sizeBytes = 0;
-      } else if (src.size() == 2) {
-        format = 0xd5;  // fixext 2
-        sizeBytes = 0;
-      } else if (src.size() == 1) {
-        format = 0xd4;  // fixext 1
-        sizeBytes = 0;
-      } else {
-        format = 0xc7;  // ext 8
-        sizeBytes = 1;
-      }
+  static bool toJson(MsgPackExtension src, JsonVariant dst) {
+    auto impl = getImpl(dst);
+    if (impl.isUnbound())
+      return false;
 
-      auto str = resources->createString(src.size() + 2 + sizeBytes);
-      if (str) {
-        resources->saveString(str);
-        auto ptr = reinterpret_cast<uint8_t*>(str->data);
-        *ptr++ = uint8_t(format);
-        for (uint8_t i = 0; i < sizeBytes; i++)
-          *ptr++ = uint8_t(src.size() >> (sizeBytes - i - 1) * 8 & 0xff);
-        *ptr++ = uint8_t(src.type());
-        memcpy(ptr, src.data(), src.size());
-        data->setRawString(str);
-        return;
-      }
+    impl.clear();
+
+    if (!src.data())
+      return true;
+
+    uint8_t format, sizeBytes;
+    if (src.size() >= 0x10000) {
+      format = 0xc9;  // ext 32
+      sizeBytes = 4;
+    } else if (src.size() >= 0x100) {
+      format = 0xc8;  // ext 16
+      sizeBytes = 2;
+    } else if (src.size() == 16) {
+      format = 0xd8;  // fixext 16
+      sizeBytes = 0;
+    } else if (src.size() == 8) {
+      format = 0xd7;  // fixext 8
+      sizeBytes = 0;
+    } else if (src.size() == 4) {
+      format = 0xd6;  // fixext 4
+      sizeBytes = 0;
+    } else if (src.size() == 2) {
+      format = 0xd5;  // fixext 2
+      sizeBytes = 0;
+    } else if (src.size() == 1) {
+      format = 0xd4;  // fixext 1
+      sizeBytes = 0;
+    } else {
+      format = 0xc7;  // ext 8
+      sizeBytes = 1;
     }
+
+    auto resources = impl.resources();
+    auto str = resources->createString(src.size() + 2 + sizeBytes);
+    if (!str)
+      return false;
+    resources->saveString(str);
+
+    auto ptr = reinterpret_cast<uint8_t*>(str->data);
+    *ptr++ = uint8_t(format);
+    for (uint8_t i = 0; i < sizeBytes; i++)
+      *ptr++ = uint8_t(src.size() >> (sizeBytes - i - 1) * 8 & 0xff);
+    *ptr++ = uint8_t(src.type());
+    memcpy(ptr, src.data(), src.size());
+    impl.data()->setRawString(str);
+    return true;
   }
 
   static MsgPackExtension fromJson(JsonVariantConst src) {
-    auto data = getData(src);
-    if (!data)
-      return {};
-    auto rawstr = data->asRawString();
+    auto variant = detail::VariantAttorney::getImpl(src);
+    auto rawstr = variant.asRawString();
     if (rawstr.size() == 0)
       return {};
     auto p = reinterpret_cast<const uint8_t*>(rawstr.c_str());

src/ArduinoJson/MsgPack/MsgPackSerializer.hpp

@@ -19,7 +19,7 @@ class MsgPackSerializer : public VariantDataVisitor<size_t> {
  public:
   static const bool producesText = false;
 
-  MsgPackSerializer(TWriter writer, const ResourceManager* resources)
+  MsgPackSerializer(TWriter writer, ResourceManager* resources)
       : writer_(writer), resources_(resources) {}
 
   template <typename T>
@@ -47,8 +47,8 @@ class MsgPackSerializer : public VariantDataVisitor<size_t> {
     return bytesWritten();
   }
 
-  size_t visit(const ArrayData& array) {
-    size_t n = array.size(resources_);
+  size_t visitArray(const VariantImpl& array) {
+    size_t n = array.size();
     if (n < 0x10) {
       writeByte(uint8_t(0x90 + n));
     } else if (n < 0x10000) {
@@ -59,18 +59,14 @@ class MsgPackSerializer : public VariantDataVisitor<size_t> {
       writeInteger(uint32_t(n));
     }
 
-    auto slotId = array.head();
-    while (slotId != NULL_SLOT) {
-      auto slot = resources_->getVariant(slotId);
-      slot->accept(*this, resources_);
-      slotId = slot->next();
-    }
+    for (auto it = array.createIterator(); !it.done(); it.move())
+      it->accept(*this);
 
     return bytesWritten();
   }
 
-  size_t visit(const ObjectData& object) {
-    size_t n = object.size(resources_);
+  size_t visitObject(const VariantImpl& object) {
+    size_t n = object.size();
     if (n < 0x10) {
       writeByte(uint8_t(0x80 + n));
     } else if (n < 0x10000) {
@@ -81,12 +77,8 @@ class MsgPackSerializer : public VariantDataVisitor<size_t> {
       writeInteger(uint32_t(n));
     }
 
-    auto slotId = object.head();
-    while (slotId != NULL_SLOT) {
-      auto slot = resources_->getVariant(slotId);
-      slot->accept(*this, resources_);
-      slotId = slot->next();
-    }
+    for (auto it = object.createIterator(); !it.done(); it.move())
+      it->accept(*this);
 
     return bytesWritten();
   }
@@ -209,7 +201,7 @@ class MsgPackSerializer : public VariantDataVisitor<size_t> {
   }
 
   CountingDecorator<TWriter> writer_;
-  const ResourceManager* resources_;
+  ResourceManager* resources_;
 };
 
 ARDUINOJSON_END_PRIVATE_NAMESPACE

src/ArduinoJson/Object/JsonObject.hpp

@@ -20,56 +20,51 @@ class JsonObject : public detail::VariantOperators<JsonObject> {
   using iterator = JsonObjectIterator;
 
   // Creates an unbound reference.
-  JsonObject() : data_(0), resources_(0) {}
+  JsonObject() {}
 
   // INTERNAL USE ONLY
-  JsonObject(detail::ObjectData* data, detail::ResourceManager* resource)
-      : data_(data), resources_(resource) {}
+  JsonObject(detail::VariantImpl impl) : impl_(impl) {}
 
   operator JsonVariant() const {
-    void* data = data_;  // prevent warning cast-align
-    return JsonVariant(reinterpret_cast<detail::VariantData*>(data),
-                       resources_);
+    return JsonVariant(impl_);
   }
 
   operator JsonObjectConst() const {
-    return JsonObjectConst(data_, resources_);
+    return JsonObjectConst(impl_);
   }
 
   operator JsonVariantConst() const {
-    return JsonVariantConst(collectionToVariant(data_), resources_);
+    return JsonVariantConst(impl_);
   }
 
   // Returns true if the reference is unbound.
   // https://arduinojson.org/v7/api/jsonobject/isnull/
   bool isNull() const {
-    return data_ == 0;
+    return !operator bool();
   }
 
   // Returns true if the reference is bound.
   // https://arduinojson.org/v7/api/jsonobject/isnull/
   operator bool() const {
-    return data_ != 0;
+    return impl_.isObject();
   }
 
   // Returns the depth (nesting level) of the object.
   // https://arduinojson.org/v7/api/jsonobject/nesting/
   size_t nesting() const {
-    return detail::VariantData::nesting(collectionToVariant(data_), resources_);
+    return impl_.nesting();
   }
 
   // Returns the number of members in the object.
   // https://arduinojson.org/v7/api/jsonobject/size/
   size_t size() const {
-    return data_ ? data_->size(resources_) : 0;
+    return impl_.size();
   }
 
   // Returns an iterator to the first key-value pair of the object.
   // https://arduinojson.org/v7/api/jsonobject/begin/
   iterator begin() const {
-    if (!data_)
-      return iterator();
-    return iterator(data_->createIterator(resources_), resources_);
+    return iterator(impl_.createIterator());
   }
 
   // Returns an iterator following the last key-value pair of the object.
@@ -81,22 +76,18 @@ class JsonObject : public detail::VariantOperators<JsonObject> {
   // Removes all the members of the object.
   // https://arduinojson.org/v7/api/jsonobject/clear/
   void clear() const {
-    detail::ObjectData::clear(data_, resources_);
+    if (impl_.isObject())
+      impl_.empty();
   }
 
   // Copies an object.
   // https://arduinojson.org/v7/api/jsonobject/set/
   bool set(JsonObjectConst src) {
-    if (!data_ || !src.data_)
+    if (isNull() ||
+        src.isNull())  // TODO: this check is not consistent with JsonArray
       return false;
-
-    clear();
-    for (auto kvp : src) {
-      if (!operator[](kvp.key()).set(kvp.value()))
-        return false;
-    }
-
-    return true;
+    impl_.clear();
+    return impl_.copyObject(detail::VariantAttorney::getImpl(src));
   }
 
   // Gets or sets the member with specified key.
@@ -131,7 +122,7 @@ class JsonObject : public detail::VariantOperators<JsonObject> {
   // Removes the member at the specified iterator.
   // https://arduinojson.org/v7/api/jsonobject/remove/
   FORCE_INLINE void remove(iterator it) const {
-    detail::ObjectData::remove(data_, it.iterator_, resources_);
+    impl_.removeMember(it.iterator_);
   }
 
   // Removes the member with the specified key.
@@ -139,8 +130,7 @@ class JsonObject : public detail::VariantOperators<JsonObject> {
   template <typename TString,
             detail::enable_if_t<detail::IsString<TString>::value, int> = 0>
   void remove(const TString& key) const {
-    detail::ObjectData::removeMember(data_, detail::adaptString(key),
-                                     resources_);
+    impl_.removeMember(detail::adaptString(key));
   }
 
   // Removes the member with the specified key.
@@ -156,8 +146,7 @@ class JsonObject : public detail::VariantOperators<JsonObject> {
   // https://arduinojson.org/v7/api/jsonobject/remove/
   template <typename TChar>
   FORCE_INLINE void remove(TChar* key) const {
-    detail::ObjectData::removeMember(data_, detail::adaptString(key),
-                                     resources_);
+    impl_.removeMember(detail::adaptString(key));
   }
 
   // DEPRECATED: use obj[key].is<T>() instead
@@ -166,8 +155,7 @@ class JsonObject : public detail::VariantOperators<JsonObject> {
             detail::enable_if_t<detail::IsString<TString>::value, int> = 0>
   ARDUINOJSON_DEPRECATED("use obj[key].is<T>() instead")
   bool containsKey(const TString& key) const {
-    return detail::ObjectData::getMember(data_, detail::adaptString(key),
-                                         resources_) != 0;
+    return impl_.getMember(detail::adaptString(key)) != 0;
   }
 
   // DEPRECATED: use obj["key"].is<T>() instead
@@ -178,8 +166,7 @@ class JsonObject : public detail::VariantOperators<JsonObject> {
                                 int> = 0>
   ARDUINOJSON_DEPRECATED("use obj[\"key\"].is<T>() instead")
   bool containsKey(TChar* key) const {
-    return detail::ObjectData::getMember(data_, detail::adaptString(key),
-                                         resources_) != 0;
+    return impl_.getMember(detail::adaptString(key)) != 0;
   }
 
   // DEPRECATED: use obj[key].is<T>() instead
@@ -226,20 +213,15 @@ class JsonObject : public detail::VariantOperators<JsonObject> {
   }
 
  private:
-  detail::ResourceManager* getResourceManager() const {
-    return resources_;
+  const detail::VariantImpl& getImpl() const {
+    return impl_;
   }
 
-  detail::VariantData* getData() const {
-    return detail::collectionToVariant(data_);
+  const detail::VariantImpl& getOrCreateImpl() const {
+    return impl_;
   }
 
-  detail::VariantData* getOrCreateData() const {
-    return detail::collectionToVariant(data_);
-  }
-
-  detail::ObjectData* data_;
-  detail::ResourceManager* resources_;
+  mutable detail::VariantImpl impl_;
 };
 
 ARDUINOJSON_END_PUBLIC_NAMESPACE

src/ArduinoJson/Object/JsonObjectConst.hpp

@@ -19,47 +19,43 @@ class JsonObjectConst : public detail::VariantOperators<JsonObjectConst> {
   using iterator = JsonObjectConstIterator;
 
   // Creates an unbound reference.
-  JsonObjectConst() : data_(0), resources_(0) {}
+  JsonObjectConst() {}
 
   // INTERNAL USE ONLY
-  JsonObjectConst(const detail::ObjectData* data,
-                  const detail::ResourceManager* resources)
-      : data_(data), resources_(resources) {}
+  JsonObjectConst(const detail::VariantImpl& impl) : impl_(impl) {}
 
   operator JsonVariantConst() const {
-    return JsonVariantConst(getData(), resources_);
+    return JsonVariantConst(impl_);
   }
 
   // Returns true if the reference is unbound.
   // https://arduinojson.org/v7/api/jsonobjectconst/isnull/
   bool isNull() const {
-    return data_ == 0;
+    return impl_.isNull();
   }
 
   // Returns true if the reference is bound.
   // https://arduinojson.org/v7/api/jsonobjectconst/isnull/
   operator bool() const {
-    return data_ != 0;
+    return !isNull();
   }
 
   // Returns the depth (nesting level) of the object.
   // https://arduinojson.org/v7/api/jsonobjectconst/nesting/
   size_t nesting() const {
-    return detail::VariantData::nesting(getData(), resources_);
+    return impl_.nesting();
   }
 
   // Returns the number of members in the object.
   // https://arduinojson.org/v7/api/jsonobjectconst/size/
   size_t size() const {
-    return data_ ? data_->size(resources_) : 0;
+    return impl_.size();
   }
 
   // Returns an iterator to the first key-value pair of the object.
   // https://arduinojson.org/v7/api/jsonobjectconst/begin/
   iterator begin() const {
-    if (!data_)
-      return iterator();
-    return iterator(data_->createIterator(resources_), resources_);
+    return iterator(impl_.createIterator());
   }
 
   // Returns an iterator following the last key-value pair of the object.
@@ -74,8 +70,7 @@ class JsonObjectConst : public detail::VariantOperators<JsonObjectConst> {
             detail::enable_if_t<detail::IsString<TString>::value, int> = 0>
   ARDUINOJSON_DEPRECATED("use obj[key].is<T>() instead")
   bool containsKey(const TString& key) const {
-    return detail::ObjectData::getMember(data_, detail::adaptString(key),
-                                         resources_) != 0;
+    return impl_.getMember(detail::adaptString(key)) != 0;
   }
 
   // DEPRECATED: use obj["key"].is<T>() instead
@@ -83,8 +78,7 @@ class JsonObjectConst : public detail::VariantOperators<JsonObjectConst> {
   template <typename TChar>
   ARDUINOJSON_DEPRECATED("use obj[\"key\"].is<T>() instead")
   bool containsKey(TChar* key) const {
-    return detail::ObjectData::getMember(data_, detail::adaptString(key),
-                                         resources_) != 0;
+    return impl_.getMember(detail::adaptString(key)) != 0;
   }
 
   // DEPRECATED: use obj[key].is<T>() instead
@@ -101,9 +95,8 @@ class JsonObjectConst : public detail::VariantOperators<JsonObjectConst> {
   template <typename TString,
             detail::enable_if_t<detail::IsString<TString>::value, int> = 0>
   JsonVariantConst operator[](const TString& key) const {
-    return JsonVariantConst(detail::ObjectData::getMember(
-                                data_, detail::adaptString(key), resources_),
-                            resources_);
+    return JsonVariantConst(impl_.getMember(detail::adaptString(key)),
+                            impl_.resources());
   }
 
   // Gets the member with specified key.
@@ -113,9 +106,8 @@ class JsonObjectConst : public detail::VariantOperators<JsonObjectConst> {
                                     !detail::is_const<TChar>::value,
                                 int> = 0>
   JsonVariantConst operator[](TChar* key) const {
-    return JsonVariantConst(detail::ObjectData::getMember(
-                                data_, detail::adaptString(key), resources_),
-                            resources_);
+    return JsonVariantConst(impl_.getMember(detail::adaptString(key)),
+                            impl_.resources());
   }
 
   // Gets the member with specified key.
@@ -136,12 +128,11 @@ class JsonObjectConst : public detail::VariantOperators<JsonObjectConst> {
   }
 
  private:
-  const detail::VariantData* getData() const {
-    return collectionToVariant(data_);
+  const detail::VariantImpl& getImpl() const {
+    return impl_;
   }
 
-  const detail::ObjectData* data_;
-  const detail::ResourceManager* resources_;
+  detail::VariantImpl impl_;
 };
 
 inline bool operator==(JsonObjectConst lhs, JsonObjectConst rhs) {

src/ArduinoJson/Object/JsonObjectIterator.hpp

@@ -14,12 +14,11 @@ class JsonObjectIterator {
  public:
   JsonObjectIterator() {}
 
-  explicit JsonObjectIterator(detail::ObjectData::iterator iterator,
-                              detail::ResourceManager* resources)
-      : iterator_(iterator), resources_(resources) {}
+  explicit JsonObjectIterator(const detail::VariantImpl::iterator& iterator)
+      : iterator_(iterator) {}
 
   JsonPair operator*() const {
-    return JsonPair(iterator_, resources_);
+    return JsonPair(iterator_);
   }
   Ptr<JsonPair> operator->() {
     return operator*();
@@ -34,14 +33,13 @@ class JsonObjectIterator {
   }
 
   JsonObjectIterator& operator++() {
-    iterator_.next(resources_);  // key
-    iterator_.next(resources_);  // value
+    iterator_.move();  // key
+    iterator_.move();  // value
     return *this;
   }
 
  private:
-  detail::ObjectData::iterator iterator_;
-  detail::ResourceManager* resources_;
+  detail::VariantImpl::iterator iterator_;
 };
 
 class JsonObjectConstIterator {
@@ -50,12 +48,12 @@ class JsonObjectConstIterator {
  public:
   JsonObjectConstIterator() {}
 
-  explicit JsonObjectConstIterator(detail::ObjectData::iterator iterator,
-                                   const detail::ResourceManager* resources)
-      : iterator_(iterator), resources_(resources) {}
+  explicit JsonObjectConstIterator(
+      const detail::VariantImpl::iterator& iterator)
+      : iterator_(iterator) {}
 
   JsonPairConst operator*() const {
-    return JsonPairConst(iterator_, resources_);
+    return JsonPairConst(iterator_);
   }
   Ptr<JsonPairConst> operator->() {
     return operator*();
@@ -70,14 +68,13 @@ class JsonObjectConstIterator {
   }
 
   JsonObjectConstIterator& operator++() {
-    iterator_.next(resources_);  // key
-    iterator_.next(resources_);  // value
+    iterator_.move();  // key
+    iterator_.move();  // value
     return *this;
   }
 
  private:
-  detail::ObjectData::iterator iterator_;
-  const detail::ResourceManager* resources_;
+  detail::VariantImpl::iterator iterator_;
 };
 
 ARDUINOJSON_END_PUBLIC_NAMESPACE

src/ArduinoJson/Object/JsonPair.hpp

@@ -15,12 +15,11 @@ ARDUINOJSON_BEGIN_PUBLIC_NAMESPACE
 class JsonPair {
  public:
   // INTERNAL USE ONLY
-  JsonPair(detail::ObjectData::iterator iterator,
-           detail::ResourceManager* resources) {
+  JsonPair(detail::VariantImpl::iterator iterator) {
     if (!iterator.done()) {
       key_ = iterator->asString();
-      iterator.next(resources);
-      value_ = JsonVariant(iterator.data(), resources);
+      iterator.move();
+      value_ = JsonVariant(*iterator);
     }
   }
 
@@ -43,12 +42,11 @@ class JsonPair {
 // https://arduinojson.org/v7/api/jsonobjectconst/begin_end/
 class JsonPairConst {
  public:
-  JsonPairConst(detail::ObjectData::iterator iterator,
-                const detail::ResourceManager* resources) {
+  JsonPairConst(detail::VariantImpl::iterator iterator) {
     if (!iterator.done()) {
       key_ = iterator->asString();
-      iterator.next(resources);
-      value_ = JsonVariantConst(iterator.data(), resources);
+      iterator.move();
+      value_ = JsonVariantConst(*iterator);
     }
   }
 

src/ArduinoJson/Object/MemberProxy.hpp

@@ -51,22 +51,15 @@ class MemberProxy
       : upstream_(src.upstream_), key_(src.key_) {}
   // clang-format on
 
-  ResourceManager* getResourceManager() const {
-    return VariantAttorney::getResourceManager(upstream_);
+  VariantImpl getImpl() const {
+    auto impl = VariantAttorney::getImpl(upstream_);
+    return VariantImpl(impl.getMember(key_), impl.resources());
   }
 
-  VariantData* getData() const {
-    return VariantData::getMember(
-        VariantAttorney::getData(upstream_), key_,
-        VariantAttorney::getResourceManager(upstream_));
-  }
-
-  VariantData* getOrCreateData() const {
-    auto data = VariantAttorney::getOrCreateData(upstream_);
-    if (!data)
-      return nullptr;
-    return data->getOrAddMember(key_,
-                                VariantAttorney::getResourceManager(upstream_));
+  VariantImpl getOrCreateImpl() const {
+    auto impl = VariantAttorney::getOrCreateImpl(upstream_);
+    impl.toObjectIfNull();
+    return VariantImpl(impl.getOrAddMember(key_), impl.resources());
   }
 
  private:

src/ArduinoJson/Object/ObjectData.hpp

@@ -1,70 +0,0 @@
-// ArduinoJson - https://arduinojson.org
-// Copyright © 2014-2025, Benoit BLANCHON
-// MIT License
-
-#pragma once
-
-#include <ArduinoJson/Collection/CollectionData.hpp>
-
-ARDUINOJSON_BEGIN_PRIVATE_NAMESPACE
-
-class ObjectData : public CollectionData {
- public:
-  template <typename TAdaptedString>
-  VariantData* addMember(TAdaptedString key, ResourceManager* resources);
-
-  VariantData* addPair(VariantData** value, ResourceManager* resources);
-
-  template <typename TAdaptedString>
-  VariantData* getOrAddMember(TAdaptedString key, ResourceManager* resources);
-
-  template <typename TAdaptedString>
-  VariantData* getMember(TAdaptedString key,
-                         const ResourceManager* resources) const;
-
-  template <typename TAdaptedString>
-  static VariantData* getMember(const ObjectData* object, TAdaptedString key,
-                                const ResourceManager* resources) {
-    if (!object)
-      return nullptr;
-    return object->getMember(key, resources);
-  }
-
-  template <typename TAdaptedString>
-  void removeMember(TAdaptedString key, ResourceManager* resources);
-
-  template <typename TAdaptedString>
-  static void removeMember(ObjectData* obj, TAdaptedString key,
-                           ResourceManager* resources) {
-    if (!obj)
-      return;
-    obj->removeMember(key, resources);
-  }
-
-  void remove(iterator it, ResourceManager* resources) {
-    CollectionData::removePair(it, resources);
-  }
-
-  static void remove(ObjectData* obj, ObjectData::iterator it,
-                     ResourceManager* resources) {
-    if (!obj)
-      return;
-    obj->remove(it, resources);
-  }
-
-  size_t size(const ResourceManager* resources) const {
-    return CollectionData::size(resources) / 2;
-  }
-
-  static size_t size(const ObjectData* obj, const ResourceManager* resources) {
-    if (!obj)
-      return 0;
-    return obj->size(resources);
-  }
-
- private:
-  template <typename TAdaptedString>
-  iterator findKey(TAdaptedString key, const ResourceManager* resources) const;
-};
-
-ARDUINOJSON_END_PRIVATE_NAMESPACE

src/ArduinoJson/Object/ObjectImpl.hpp

@@ -4,38 +4,76 @@
 
 #pragma once
 
-#include <ArduinoJson/Object/ObjectData.hpp>
 #include <ArduinoJson/Variant/VariantCompare.hpp>
-#include <ArduinoJson/Variant/VariantData.hpp>
+#include <ArduinoJson/Variant/VariantImpl.hpp>
 
 ARDUINOJSON_BEGIN_PRIVATE_NAMESPACE
 
+inline bool VariantImpl::copyObject(const VariantImpl& src) {
+  ARDUINOJSON_ASSERT(isNull());
+
+  if (!data_)
+    return false;
+
+  data_->toObject();
+
+  for (auto it = src.createIterator(); !it.done(); it.move()) {
+    auto keySlot = allocVariant();
+    if (!keySlot)
+      return false;
+
+    auto key = VariantImpl(keySlot.ptr(), resources_);
+    if (!key.copyVariant(*it)) {
+      freeVariant(keySlot);
+      return false;
+    }
+
+    it.move();  // move to value
+    ARDUINOJSON_ASSERT(!it.done());
+
+    auto valueSlot = allocVariant();
+    if (!valueSlot) {
+      freeVariant(keySlot);
+      return false;
+    }
+
+    // TODO: we add the pair before copying the value to be keep the old
+    // behavior but this is not consistent with issue #2081
+    addMember(keySlot, valueSlot);
+
+    auto value = VariantImpl(valueSlot.ptr(), resources_);
+    if (!value.copyVariant(*it))
+      return false;
+  }
+
+  return true;
+}
+
 template <typename TAdaptedString>
-inline VariantData* ObjectData::getMember(
-    TAdaptedString key, const ResourceManager* resources) const {
-  auto it = findKey(key, resources);
+inline VariantData* VariantImpl::getMember(TAdaptedString key) const {
+  auto it = findKey(key);
   if (it.done())
     return nullptr;
-  it.next(resources);
-  return it.data();
+  it.move();
+  return it->data();
 }
 
 template <typename TAdaptedString>
-VariantData* ObjectData::getOrAddMember(TAdaptedString key,
-                                        ResourceManager* resources) {
-  auto data = getMember(key, resources);
+VariantData* VariantImpl::getOrAddMember(TAdaptedString key) {
+  auto data = getMember(key);
   if (data)
     return data;
-  return addMember(key, resources);
+  return addMember(key);
 }
 
 template <typename TAdaptedString>
-inline ObjectData::iterator ObjectData::findKey(
-    TAdaptedString key, const ResourceManager* resources) const {
+inline VariantImpl::iterator VariantImpl::findKey(TAdaptedString key) const {
+  if (!isObject())
+    return iterator();
   if (key.isNull())
     return iterator();
   bool isKey = true;
-  for (auto it = createIterator(resources); !it.done(); it.next(resources)) {
+  for (auto it = createIterator(); !it.done(); it.move()) {
     if (isKey && stringEquals(key, adaptString(it->asString())))
       return it;
     isKey = !isKey;
@@ -44,49 +82,42 @@ inline ObjectData::iterator ObjectData::findKey(
 }
 
 template <typename TAdaptedString>
-inline void ObjectData::removeMember(TAdaptedString key,
-                                     ResourceManager* resources) {
-  remove(findKey(key, resources), resources);
+inline void VariantImpl::removeMember(TAdaptedString key) {
+  removeMember(findKey(key));
+}
+
+inline void VariantImpl::removeMember(iterator it) {
+  removePair(it);
 }
 
 template <typename TAdaptedString>
-inline VariantData* ObjectData::addMember(TAdaptedString key,
-                                          ResourceManager* resources) {
-  auto keySlot = resources->allocVariant();
+inline VariantData* VariantImpl::addMember(TAdaptedString key) {
+  if (!isObject())
+    return nullptr;
+
+  if (key.isNull())
+    return nullptr;  // Ignore null key
+
+  auto keySlot = allocVariant();
   if (!keySlot)
     return nullptr;
 
-  auto valueSlot = resources->allocVariant();
+  auto valueSlot = allocVariant();
   if (!valueSlot)
     return nullptr;
 
-  if (!keySlot->setString(key, resources))
+  VariantImpl keyImpl(keySlot.ptr(), resources_);
+  if (!keyImpl.setString(key))
     return nullptr;
 
-  CollectionData::appendPair(keySlot, valueSlot, resources);
+  addMember(keySlot, valueSlot);
 
   return valueSlot.ptr();
 }
 
-inline VariantData* ObjectData::addPair(VariantData** value,
-                                        ResourceManager* resources) {
-  auto keySlot = resources->allocVariant();
-  if (!keySlot)
-    return nullptr;
-
-  auto valueSlot = resources->allocVariant();
-  if (!valueSlot)
-    return nullptr;
-  *value = valueSlot.ptr();
-
-  CollectionData::appendPair(keySlot, valueSlot, resources);
-
-  return keySlot.ptr();
-}
-
 // Returns the size (in bytes) of an object with n members.
 constexpr size_t sizeofObject(size_t n) {
-  return 2 * n * ResourceManager::slotSize;
+  return 2 * n * sizeof(VariantData);
 }
 
 ARDUINOJSON_END_PRIVATE_NAMESPACE

src/ArduinoJson/Serialization/measure.hpp

@@ -11,10 +11,9 @@ ARDUINOJSON_BEGIN_PRIVATE_NAMESPACE
 template <template <typename> class TSerializer>
 size_t measure(ArduinoJson::JsonVariantConst source) {
   DummyWriter dp;
-  auto data = VariantAttorney::getData(source);
-  auto resources = VariantAttorney::getResourceManager(source);
-  TSerializer<DummyWriter> serializer(dp, resources);
-  return VariantData::accept(data, resources, serializer);
+  auto impl = VariantAttorney::getImpl(source);
+  TSerializer<DummyWriter> serializer(dp, impl.resources());
+  return impl.accept(serializer);
 }
 
 ARDUINOJSON_END_PRIVATE_NAMESPACE

src/ArduinoJson/Serialization/serialize.hpp

@@ -10,10 +10,9 @@ ARDUINOJSON_BEGIN_PRIVATE_NAMESPACE
 
 template <template <typename> class TSerializer, typename TWriter>
 size_t doSerialize(ArduinoJson::JsonVariantConst source, TWriter writer) {
-  auto data = VariantAttorney::getData(source);
-  auto resources = VariantAttorney::getResourceManager(source);
-  TSerializer<TWriter> serializer(writer, resources);
-  return VariantData::accept(data, resources, serializer);
+  auto impl = VariantAttorney::getImpl(source);
+  TSerializer<TWriter> serializer(writer, impl.resources());
+  return impl.accept(serializer);
 }
 
 template <template <typename> class TSerializer, typename TDestination>

src/ArduinoJson/Strings/Adapters/RamString.hpp

@@ -90,8 +90,9 @@ template <size_t N>
 struct StringAdapter<const char (&)[N]> {
   using AdaptedString = RamString;
 
-  static AdaptedString adapt(const char (&p)[N]) {
-    return RamString(p, N - 1, true);
+  static AdaptedString adapt(const char* p) {
+    ARDUINOJSON_ASSERT(p);
+    return RamString(p, ::strlen(p), true);
   }
 };
 

src/ArduinoJson/Strings/JsonString.hpp

@@ -28,8 +28,7 @@ class JsonString {
             detail::enable_if_t<detail::is_integral<TSize>::value &&
                                     !detail::is_same<TSize, bool>::value,
                                 int> = 0>
-  JsonString(const char* data, TSize sz, bool isStatic = false)
-      : str_(data, size_t(sz), isStatic) {}
+  JsonString(const char* data, TSize sz) : str_(data, size_t(sz), false) {}
 
   // Returns a pointer to the characters.
   const char* c_str() const {

src/ArduinoJson/Variant/ConverterImpl.hpp

@@ -25,9 +25,10 @@ struct Converter {
                 "type 'char' is not supported, use 'signed char', 'unsigned "
                 "char' or another integer type instead");
 
-  static void toJson(const T& src, JsonVariant dst) {
+  static auto toJson(const T& src, JsonVariant dst)
+      -> decltype(convertToJson(src, dst)) {
     // clang-format off
-    convertToJson(src, dst); // Error here? See https://arduinojson.org/v7/unsupported-set/
+    return convertToJson(src, dst); // Error here? See https://arduinojson.org/v7/unsupported-set/
     // clang-format on
   }
 
@@ -60,25 +61,18 @@ struct Converter<T, detail::enable_if_t<detail::is_integral<T>::value &&
     : private detail::VariantAttorney {
   static bool toJson(T src, JsonVariant dst) {
     ARDUINOJSON_ASSERT_INTEGER_TYPE_IS_SUPPORTED(T);
-    auto data = getData(dst);
-    if (!data)
-      return false;
-    auto resources = getResourceManager(dst);
-    data->clear(resources);
-    return data->setInteger(src, resources);
+    auto impl = getImpl(dst);
+    impl.clear();
+    return impl.setInteger(src);
   }
 
   static T fromJson(JsonVariantConst src) {
     ARDUINOJSON_ASSERT_INTEGER_TYPE_IS_SUPPORTED(T);
-    auto data = getData(src);
-    auto resources = getResourceManager(src);
-    return data ? data->template asIntegral<T>(resources) : T();
+    return getImpl(src).template asIntegral<T>();
   }
 
   static bool checkJson(JsonVariantConst src) {
-    auto data = getData(src);
-    auto resources = getResourceManager(src);
-    return data && data->template isInteger<T>(resources);
+    return getImpl(src).template isInteger<T>();
   }
 };
 
@@ -90,40 +84,28 @@ struct Converter<T, detail::enable_if_t<detail::is_enum<T>::value>>
   }
 
   static T fromJson(JsonVariantConst src) {
-    auto data = getData(src);
-    auto resources = getResourceManager(src);
-    return data ? static_cast<T>(data->template asIntegral<int>(resources))
-                : T();
+    return static_cast<T>(getImpl(src).template asIntegral<int>());
   }
 
   static bool checkJson(JsonVariantConst src) {
-    auto data = getData(src);
-    auto resources = getResourceManager(src);
-    return data && data->template isInteger<int>(resources);
+    return getImpl(src).template isInteger<int>();
   }
 };
 
 template <>
 struct Converter<bool> : private detail::VariantAttorney {
   static bool toJson(bool src, JsonVariant dst) {
-    auto data = getData(dst);
-    if (!data)
-      return false;
-    auto resources = getResourceManager(dst);
-    data->clear(resources);
-    data->setBoolean(src);
-    return true;
+    auto impl = getImpl(dst);
+    impl.clear();
+    return impl.setBoolean(src);
   }
 
   static bool fromJson(JsonVariantConst src) {
-    auto data = getData(src);
-    auto resources = getResourceManager(src);
-    return data ? data->asBoolean(resources) : false;
+    return getImpl(src).asBoolean();
   }
 
   static bool checkJson(JsonVariantConst src) {
-    auto data = getData(src);
-    return data && data->isBoolean();
+    return getImpl(src).type() == detail::VariantType::Boolean;
   }
 };
 
@@ -131,69 +113,60 @@ template <typename T>
 struct Converter<T, detail::enable_if_t<detail::is_floating_point<T>::value>>
     : private detail::VariantAttorney {
   static bool toJson(T src, JsonVariant dst) {
-    auto data = getData(dst);
-    if (!data)
-      return false;
-    auto resources = getResourceManager(dst);
-    data->clear(resources);
-    return data->setFloat(src, resources);
+    auto impl = getImpl(dst);
+    impl.clear();
+    return impl.setFloat(src);
   }
 
   static T fromJson(JsonVariantConst src) {
-    auto data = getData(src);
-    auto resources = getResourceManager(src);
-    return data ? data->template asFloat<T>(resources) : 0;
+    return getImpl(src).template asFloat<T>();
   }
 
   static bool checkJson(JsonVariantConst src) {
-    auto data = getData(src);
-    return data && data->isFloat();
+    return getImpl(src).isFloat();
   }
 };
 
 template <>
 struct Converter<const char*> : private detail::VariantAttorney {
-  static void toJson(const char* src, JsonVariant dst) {
-    detail::VariantData::setString(getData(dst), detail::adaptString(src),
-                                   getResourceManager(dst));
+  static bool toJson(const char* src, JsonVariant dst) {
+    auto impl = getImpl(dst);
+    impl.clear();
+    return impl.setString(detail::adaptString(src));
   }
 
   static const char* fromJson(JsonVariantConst src) {
-    auto data = getData(src);
-    return data ? data->asString().c_str() : 0;
+    return getImpl(src).asString().c_str();
   }
 
   static bool checkJson(JsonVariantConst src) {
-    auto data = getData(src);
-    return data && data->isString();
+    return getImpl(src).isString();
   }
 };
 
 template <>
 struct Converter<JsonString> : private detail::VariantAttorney {
-  static void toJson(JsonString src, JsonVariant dst) {
-    detail::VariantData::setString(getData(dst), detail::adaptString(src),
-                                   getResourceManager(dst));
+  static bool toJson(JsonString src, JsonVariant dst) {
+    auto impl = getImpl(dst);
+    impl.clear();
+    return impl.setString(detail::adaptString(src));
   }
 
   static JsonString fromJson(JsonVariantConst src) {
-    auto data = getData(src);
-    return data ? data->asString() : JsonString();
+    return getImpl(src).asString();
   }
 
   static bool checkJson(JsonVariantConst src) {
-    auto data = getData(src);
-    return data && data->isString();
+    return getImpl(src).isString();
   }
 };
 
 template <typename T>
-inline detail::enable_if_t<detail::IsString<T>::value> convertToJson(
+inline detail::enable_if_t<detail::IsString<T>::value, bool> convertToJson(
     const T& src, JsonVariant dst) {
-  using namespace detail;
-  auto data = VariantAttorney::getData(dst);
-  auto resources = VariantAttorney::getResourceManager(dst);
-  detail::VariantData::setString(data, adaptString(src), resources);
+  auto impl = detail::VariantAttorney::getImpl(dst);
+  impl.clear();
+  return impl.setString(detail::adaptString(src));
 }
 
 // SerializedValue<std::string>
@@ -201,23 +174,26 @@ inline detail::enable_if_t<detail::IsString<T>::value> convertToJson(
 // SerializedValue<const __FlashStringHelper*>
 template <typename T>
 struct Converter<SerializedValue<T>> : private detail::VariantAttorney {
-  static void toJson(SerializedValue<T> src, JsonVariant dst) {
-    detail::VariantData::setRawString(getData(dst), src,
-                                      getResourceManager(dst));
+  static bool toJson(SerializedValue<T> src, JsonVariant dst) {
+    auto impl = getImpl(dst);
+    impl.clear();
+    return impl.setRawString(detail::adaptString(src.data(), src.size()));
   }
 };
 
 template <>
 struct Converter<detail::nullptr_t> : private detail::VariantAttorney {
-  static void toJson(detail::nullptr_t, JsonVariant dst) {
-    detail::VariantData::clear(getData(dst), getResourceManager(dst));
+  static bool toJson(detail::nullptr_t, JsonVariant dst) {
+    if (dst.isUnbound())
+      return false;
+    getImpl(dst).clear();
+    return true;
   }
   static detail::nullptr_t fromJson(JsonVariantConst) {
     return nullptr;
   }
   static bool checkJson(JsonVariantConst src) {
-    auto data = getData(src);
-    return data == 0 || data->isNull();
+    return getImpl(src).isNull();
   }
 };
 
@@ -258,17 +234,17 @@ class StringBuilderPrint : public Print {
 };
 }  // namespace detail
 
-inline void convertToJson(const ::Printable& src, JsonVariant dst) {
-  auto resources = detail::VariantAttorney::getResourceManager(dst);
-  auto data = detail::VariantAttorney::getData(dst);
-  if (!resources || !data)
-    return;
-  data->clear(resources);
-  detail::StringBuilderPrint print(resources);
+inline bool convertToJson(const ::Printable& src, JsonVariant dst) {
+  auto impl = detail::VariantAttorney::getImpl(dst);
+  if (impl.isUnbound())
+    return false;
+  impl.clear();
+  detail::StringBuilderPrint print(impl.resources());
   src.printTo(print);
   if (print.overflowed())
-    return;
-  print.save(data);
+    return false;
+  print.save(impl.data());
+  return true;
 }
 
 #endif
@@ -321,85 +297,73 @@ inline bool canConvertFromJson(JsonVariantConst src, const std::string_view&) {
 
 template <>
 struct Converter<JsonArrayConst> : private detail::VariantAttorney {
-  static void toJson(JsonArrayConst src, JsonVariant dst) {
+  static bool toJson(JsonArrayConst src, JsonVariant dst) {
     if (src.isNull())
-      dst.set(nullptr);
+      return dst.set(nullptr);
     else
-      dst.to<JsonArray>().set(src);
+      return dst.to<JsonArray>().set(src);
   }
 
   static JsonArrayConst fromJson(JsonVariantConst src) {
-    auto data = getData(src);
-    auto array = data ? data->asArray() : nullptr;
-    return JsonArrayConst(array, getResourceManager(src));
+    return JsonArrayConst(getImpl(src));
   }
 
   static bool checkJson(JsonVariantConst src) {
-    auto data = getData(src);
-    return data && data->isArray();
+    return getImpl(src).type() == detail::VariantType::Array;
   }
 };
 
 template <>
 struct Converter<JsonArray> : private detail::VariantAttorney {
-  static void toJson(JsonVariantConst src, JsonVariant dst) {
+  static bool toJson(JsonVariantConst src, JsonVariant dst) {
     if (src.isNull())
-      dst.set(nullptr);
+      return dst.set(nullptr);
     else
-      dst.to<JsonArray>().set(src);
+      return dst.to<JsonArray>().set(src);
   }
 
   static JsonArray fromJson(JsonVariant src) {
-    auto data = getData(src);
-    auto resources = getResourceManager(src);
-    return JsonArray(data != 0 ? data->asArray() : 0, resources);
+    return JsonArray(getImpl(src));
   }
 
   static bool checkJson(JsonVariant src) {
-    auto data = getData(src);
-    return data && data->isArray();
+    return getImpl(src).type() == detail::VariantType::Array;
   }
 };
 
 template <>
 struct Converter<JsonObjectConst> : private detail::VariantAttorney {
-  static void toJson(JsonVariantConst src, JsonVariant dst) {
+  static bool toJson(JsonVariantConst src, JsonVariant dst) {
     if (src.isNull())
-      dst.set(nullptr);
+      return dst.set(nullptr);
     else
-      dst.to<JsonObject>().set(src);
+      return dst.to<JsonObject>().set(src);
   }
 
   static JsonObjectConst fromJson(JsonVariantConst src) {
-    auto data = getData(src);
-    auto object = data != 0 ? data->asObject() : nullptr;
-    return JsonObjectConst(object, getResourceManager(src));
+    return JsonObjectConst(getImpl(src));
   }
 
   static bool checkJson(JsonVariantConst src) {
-    auto data = getData(src);
-    return data && data->isObject();
+    return getImpl(src).type() == detail::VariantType::Object;
   }
 };
 
 template <>
 struct Converter<JsonObject> : private detail::VariantAttorney {
-  static void toJson(JsonVariantConst src, JsonVariant dst) {
+  static bool toJson(JsonVariantConst src, JsonVariant dst) {
     if (src.isNull())
-      dst.set(nullptr);
+      return dst.set(nullptr);
     else
-      dst.to<JsonObject>().set(src);
+      return dst.to<JsonObject>().set(src);
   }
 
   static JsonObject fromJson(JsonVariant src) {
-    auto data = getData(src);
-    auto resources = getResourceManager(src);
-    return JsonObject(data != 0 ? data->asObject() : 0, resources);
+    return JsonObject(getImpl(src));
   }
 
   static bool checkJson(JsonVariant src) {
-    auto data = getData(src);
-    return data && data->isObject();
+    return getImpl(src).type() == detail::VariantType::Object;
   }
 };
 

src/ArduinoJson/Variant/JsonVariant.hpp

@@ -16,37 +16,33 @@ class JsonVariant : public detail::VariantRefBase<JsonVariant>,
 
  public:
   // Creates an unbound reference.
-  JsonVariant() : data_(0), resources_(0) {}
+  JsonVariant() {}
 
   // INTERNAL USE ONLY
   JsonVariant(detail::VariantData* data, detail::ResourceManager* resources)
-      : data_(data), resources_(resources) {}
+      : impl_(data, resources) {}
+
+  // INTERNAL USE ONLY
+  JsonVariant(detail::VariantImpl impl) : impl_(impl) {}
 
  private:
-  detail::ResourceManager* getResourceManager() const {
-    return resources_;
+  const detail::VariantImpl& getImpl() const {
+    return impl_;
   }
 
-  detail::VariantData* getData() const {
-    return data_;
+  const detail::VariantImpl& getOrCreateImpl() const {
+    return impl_;
   }
 
-  detail::VariantData* getOrCreateData() const {
-    return data_;
-  }
-
-  detail::VariantData* data_;
-  detail::ResourceManager* resources_;
+  mutable detail::VariantImpl impl_;
 };
 
-namespace detail {
-bool copyVariant(JsonVariant dst, JsonVariantConst src);
-}
-
 template <>
 struct Converter<JsonVariant> : private detail::VariantAttorney {
-  static void toJson(JsonVariantConst src, JsonVariant dst) {
-    copyVariant(dst, src);
+  static bool toJson(JsonVariantConst src, JsonVariant dst) {
+    auto impl = getImpl(dst);
+    impl.clear();
+    return impl.copyVariant(getImpl(src));
   }
 
   static JsonVariant fromJson(JsonVariant src) {
@@ -54,24 +50,24 @@ struct Converter<JsonVariant> : private detail::VariantAttorney {
   }
 
   static bool checkJson(JsonVariant src) {
-    auto data = getData(src);
-    return !!data;
+    return !getImpl(src).isUnbound();
   }
 };
 
 template <>
 struct Converter<JsonVariantConst> : private detail::VariantAttorney {
-  static void toJson(JsonVariantConst src, JsonVariant dst) {
-    copyVariant(dst, src);
+  static bool toJson(JsonVariantConst src, JsonVariant dst) {
+    auto impl = getImpl(dst);
+    impl.clear();
+    return impl.copyVariant(getImpl(src));
   }
 
   static JsonVariantConst fromJson(JsonVariantConst src) {
-    return JsonVariantConst(getData(src), getResourceManager(src));
+    return JsonVariantConst(getImpl(src));
   }
 
   static bool checkJson(JsonVariantConst src) {
-    auto data = getData(src);
-    return !!data;
+    return !getImpl(src).isUnbound();
   }
 };
 

src/ArduinoJson/Variant/JsonVariantConst.hpp

@@ -35,34 +35,37 @@ class JsonVariantConst : public detail::VariantTag,
 
  public:
   // Creates an unbound reference.
-  JsonVariantConst() : data_(nullptr), resources_(nullptr) {}
+  JsonVariantConst() {}
 
   // INTERNAL USE ONLY
-  explicit JsonVariantConst(const detail::VariantData* data,
-                            const detail::ResourceManager* resources)
-      : data_(data), resources_(resources) {}
+  explicit JsonVariantConst(detail::VariantData* data,
+                            detail::ResourceManager* resources)
+      : impl_(data, resources) {}
+
+  // INTERNAL USE ONLY
+  explicit JsonVariantConst(detail::VariantImpl impl) : impl_(impl) {}
 
   // Returns true if the value is null or the reference is unbound.
   // https://arduinojson.org/v7/api/jsonvariantconst/isnull/
   bool isNull() const {
-    return detail::VariantData::isNull(data_);
+    return impl_.isNull();
   }
 
   // Returns true if the reference is unbound.
   bool isUnbound() const {
-    return !data_;
+    return impl_.isUnbound();
   }
 
   // Returns the depth (nesting level) of the value.
   // https://arduinojson.org/v7/api/jsonvariantconst/nesting/
   size_t nesting() const {
-    return detail::VariantData::nesting(data_, resources_);
+    return impl_.nesting();
   }
 
   // Returns the size of the array or object.
   // https://arduinojson.org/v7/api/jsonvariantconst/size/
   size_t size() const {
-    return detail::VariantData::size(data_, resources_);
+    return impl_.size();
   }
 
   // Casts the value to the specified type.
@@ -104,9 +107,7 @@ class JsonVariantConst : public detail::VariantTag,
   template <typename T,
             detail::enable_if_t<detail::is_integral<T>::value, int> = 0>
   JsonVariantConst operator[](T index) const {
-    return JsonVariantConst(
-        detail::VariantData::getElement(data_, size_t(index), resources_),
-        resources_);
+    return JsonVariantConst(impl_.getElement(size_t(index)), impl_.resources());
   }
 
   // Gets object's member with specified key.
@@ -114,9 +115,8 @@ class JsonVariantConst : public detail::VariantTag,
   template <typename TString,
             detail::enable_if_t<detail::IsString<TString>::value, int> = 0>
   JsonVariantConst operator[](const TString& key) const {
-    return JsonVariantConst(detail::VariantData::getMember(
-                                data_, detail::adaptString(key), resources_),
-                            resources_);
+    return JsonVariantConst(impl_.getMember(detail::adaptString(key)),
+                            impl_.resources());
   }
 
   // Gets object's member with specified key.
@@ -126,9 +126,8 @@ class JsonVariantConst : public detail::VariantTag,
                                     !detail::is_const<TChar>::value,
                                 int> = 0>
   JsonVariantConst operator[](TChar* key) const {
-    return JsonVariantConst(detail::VariantData::getMember(
-                                data_, detail::adaptString(key), resources_),
-                            resources_);
+    return JsonVariantConst(impl_.getMember(detail::adaptString(key)),
+                            impl_.resources());
   }
 
   // Gets object's member with specified key or the array's element at the
@@ -149,8 +148,7 @@ class JsonVariantConst : public detail::VariantTag,
             detail::enable_if_t<detail::IsString<TString>::value, int> = 0>
   ARDUINOJSON_DEPRECATED("use var[key].is<T>() instead")
   bool containsKey(const TString& key) const {
-    return detail::VariantData::getMember(getData(), detail::adaptString(key),
-                                          resources_) != 0;
+    return impl_.getMember(detail::adaptString(key)) != 0;
   }
 
   // DEPRECATED: use obj["key"].is<T>() instead
@@ -161,8 +159,7 @@ class JsonVariantConst : public detail::VariantTag,
                                 int> = 0>
   ARDUINOJSON_DEPRECATED("use obj[\"key\"].is<T>() instead")
   bool containsKey(TChar* key) const {
-    return detail::VariantData::getMember(getData(), detail::adaptString(key),
-                                          resources_) != 0;
+    return impl_.getMember(detail::adaptString(key)) != 0;
   }
 
   // DEPRECATED: use obj[key].is<T>() instead
@@ -181,17 +178,12 @@ class JsonVariantConst : public detail::VariantTag,
   }
 
  protected:
-  const detail::VariantData* getData() const {
-    return data_;
-  }
-
-  const detail::ResourceManager* getResourceManager() const {
-    return resources_;
+  const detail::VariantImpl& getImpl() const {
+    return impl_;
   }
 
  private:
-  const detail::VariantData* data_;
-  const detail::ResourceManager* resources_;
+  mutable detail::VariantImpl impl_;
 };
 
 ARDUINOJSON_END_PUBLIC_NAMESPACE

src/ArduinoJson/Variant/JsonVariantCopier.hpp

@@ -1,34 +0,0 @@
-// ArduinoJson - https://arduinojson.org
-// Copyright © 2014-2025, Benoit BLANCHON
-// MIT License
-
-#pragma once
-
-#include <ArduinoJson/Variant/JsonVariant.hpp>
-#include <ArduinoJson/Variant/JsonVariantVisitor.hpp>
-
-ARDUINOJSON_BEGIN_PRIVATE_NAMESPACE
-
-class JsonVariantCopier {
- public:
-  using result_type = bool;
-
-  JsonVariantCopier(JsonVariant dst) : dst_(dst) {}
-
-  template <typename T>
-  bool visit(T src) {
-    return dst_.set(src);
-  }
-
- private:
-  JsonVariant dst_;
-};
-
-inline bool copyVariant(JsonVariant dst, JsonVariantConst src) {
-  if (dst.isUnbound())
-    return false;
-  JsonVariantCopier copier(dst);
-  return accept(src, copier);
-}
-
-ARDUINOJSON_END_PRIVATE_NAMESPACE

src/ArduinoJson/Variant/JsonVariantVisitor.hpp

@@ -26,15 +26,14 @@ class VisitorAdapter {
  public:
   using result_type = typename TVisitor::result_type;
 
-  VisitorAdapter(TVisitor& visitor, const ResourceManager* resources)
-      : visitor_(&visitor), resources_(resources) {}
+  VisitorAdapter(TVisitor& visitor) : visitor_(&visitor) {}
 
-  result_type visit(const ArrayData& value) {
-    return visitor_->visit(JsonArrayConst(&value, resources_));
+  result_type visitArray(const VariantImpl& array) {
+    return visitor_->visit(JsonArrayConst(array));
   }
 
-  result_type visit(const ObjectData& value) {
-    return visitor_->visit(JsonObjectConst(&value, resources_));
+  result_type visitObject(const VariantImpl& object) {
+    return visitor_->visit(JsonObjectConst(object));
   }
 
   template <typename T>
@@ -44,18 +43,14 @@ class VisitorAdapter {
 
  private:
   TVisitor* visitor_;
-  const ResourceManager* resources_;
 };
 
 template <typename TVisitor>
 typename TVisitor::result_type accept(JsonVariantConst variant,
                                       TVisitor& visit) {
-  auto data = VariantAttorney::getData(variant);
-  if (!data)
-    return visit.visit(nullptr);
-  auto resources = VariantAttorney::getResourceManager(variant);
-  VisitorAdapter<TVisitor> adapter(visit, resources);
-  return data->accept(adapter, resources);
+  auto impl = VariantAttorney::getImpl(variant);
+  VisitorAdapter<TVisitor> adapter(visit);
+  return impl.accept(adapter);
 }
 
 ARDUINOJSON_END_PRIVATE_NAMESPACE

src/ArduinoJson/Variant/VariantAttorney.hpp

@@ -6,7 +6,7 @@
 
 #include <ArduinoJson/Polyfills/attributes.hpp>
 #include <ArduinoJson/Polyfills/type_traits.hpp>
-#include <ArduinoJson/Variant/VariantData.hpp>
+#include <ArduinoJson/Variant/VariantImpl.hpp>
 #include <ArduinoJson/Variant/VariantTo.hpp>
 #include "JsonVariantConst.hpp"
 
@@ -16,19 +16,13 @@ ARDUINOJSON_BEGIN_PRIVATE_NAMESPACE
 class VariantAttorney {
  public:
   template <typename TClient>
-  static auto getResourceManager(TClient& client)
-      -> decltype(client.getResourceManager()) {
-    return client.getResourceManager();
+  static VariantImpl getImpl(TClient& client) {
+    return client.getImpl();
   }
 
   template <typename TClient>
-  static auto getData(TClient& client) -> decltype(client.getData()) {
-    return client.getData();
-  }
-
-  template <typename TClient>
-  static VariantData* getOrCreateData(TClient& client) {
-    return client.getOrCreateData();
+  static VariantImpl getOrCreateImpl(TClient& client) {
+    return client.getOrCreateImpl();
   }
 };
 

src/ArduinoJson/Variant/VariantCompare.hpp

@@ -199,7 +199,7 @@ struct Comparer<
     T, enable_if_t<is_convertible<T, ArduinoJson::JsonVariantConst>::value>>
     : VariantComparer {
   explicit Comparer(const T& value)
-      : VariantComparer(static_cast<JsonVariantConst>(value)) {}
+      : VariantComparer(JsonVariantConst(VariantAttorney::getImpl(value))) {}
 };
 
 template <typename T>

src/ArduinoJson/Variant/VariantContent.hpp

@@ -6,18 +6,16 @@
 
 #include <stddef.h>  // size_t
 
-#include <ArduinoJson/Array/ArrayData.hpp>
 #include <ArduinoJson/Numbers/JsonFloat.hpp>
 #include <ArduinoJson/Numbers/JsonInteger.hpp>
-#include <ArduinoJson/Object/ObjectData.hpp>
 
 ARDUINOJSON_BEGIN_PRIVATE_NAMESPACE
 
 enum class VariantTypeBits : uint8_t {
   OwnedStringBit = 0x01,  // 0000 0001
   NumberBit = 0x08,       // 0000 1000
-#if ARDUINOJSON_USE_EXTENSIONS
-  ExtensionBit = 0x10,  // 0001 0000
+#if ARDUINOJSON_USE_8_BYTE_POOL
+  EightByteBit = 0x10,  // 0001 0000
 #endif
   CollectionMask = 0x60,
 };
@@ -47,6 +45,18 @@ inline bool operator&(VariantType type, VariantTypeBits bit) {
   return (uint8_t(type) & uint8_t(bit)) != 0;
 }
 
+struct CollectionData {
+  SlotId head = NULL_SLOT;
+  SlotId tail = NULL_SLOT;
+
+  // Placement new
+  static void* operator new(size_t, void* p) noexcept {
+    return p;
+  }
+
+  static void operator delete(void*, void*) noexcept {}
+};
+
 const size_t tinyStringMaxLength = 3;
 
 union VariantContent {
@@ -56,19 +66,14 @@ union VariantContent {
   bool asBoolean;
   uint32_t asUint32;
   int32_t asInt32;
-#if ARDUINOJSON_USE_EXTENSIONS
   SlotId asSlotId;
-#endif
-  ArrayData asArray;
-  ObjectData asObject;
   CollectionData asCollection;
-  const char* asLinkedString;
   struct StringNode* asOwnedString;
   char asTinyString[tinyStringMaxLength + 1];
 };
 
-#if ARDUINOJSON_USE_EXTENSIONS
-union VariantExtension {
+#if ARDUINOJSON_USE_8_BYTE_POOL
+union EightByteValue {
 #  if ARDUINOJSON_USE_LONG_LONG
   uint64_t asUint64;
   int64_t asInt64;
@@ -77,6 +82,9 @@ union VariantExtension {
   double asDouble;
 #  endif
 };
+
+static_assert(sizeof(EightByteValue) == 8,
+              "sizeof(EightByteValue) must be 8 bytes");
 #endif
 
 ARDUINOJSON_END_PRIVATE_NAMESPACE

src/ArduinoJson/Variant/VariantData.hpp

@@ -4,12 +4,7 @@
 
 #pragma once
 
-#include <ArduinoJson/Memory/MemoryPool.hpp>
 #include <ArduinoJson/Memory/StringNode.hpp>
-#include <ArduinoJson/Misc/SerializedValue.hpp>
-#include <ArduinoJson/Numbers/convertNumber.hpp>
-#include <ArduinoJson/Strings/JsonString.hpp>
-#include <ArduinoJson/Strings/StringAdapters.hpp>
 #include <ArduinoJson/Variant/VariantContent.hpp>
 
 ARDUINOJSON_BEGIN_PRIVATE_NAMESPACE
@@ -27,12 +22,11 @@ static bool isTinyString(const T& s, size_t n) {
   return !containsNul;
 }
 
-class VariantData {
-  VariantContent content_;  // must be first to allow cast from array to variant
-  VariantType type_;
-  SlotId next_;
+struct VariantData {
+  VariantContent content;  // must be first to allow cast from array to variant
+  VariantType type = VariantType::Null;
+  SlotId next = NULL_SLOT;
 
- public:
   // Placement new
   static void* operator new(size_t, void* p) noexcept {
     return p;
@@ -40,561 +34,70 @@ class VariantData {
 
   static void operator delete(void*, void*) noexcept {}
 
-  VariantData() : type_(VariantType::Null), next_(NULL_SLOT) {}
-
-  SlotId next() const {
-    return next_;
-  }
-
-  void setNext(SlotId slot) {
-    next_ = slot;
-  }
-
-  template <typename TVisitor>
-  typename TVisitor::result_type accept(
-      TVisitor& visit, const ResourceManager* resources) const {
-#if ARDUINOJSON_USE_EXTENSIONS
-    auto extension = getExtension(resources);
-#else
-    (void)resources;  // silence warning
-#endif
-    switch (type_) {
-      case VariantType::Float:
-        return visit.visit(content_.asFloat);
-
-#if ARDUINOJSON_USE_DOUBLE
-      case VariantType::Double:
-        return visit.visit(extension->asDouble);
-#endif
-
-      case VariantType::Array:
-        return visit.visit(content_.asArray);
-
-      case VariantType::Object:
-        return visit.visit(content_.asObject);
-
-      case VariantType::TinyString:
-        return visit.visit(JsonString(content_.asTinyString));
-
-      case VariantType::LinkedString:
-        return visit.visit(JsonString(content_.asLinkedString, true));
-
-      case VariantType::OwnedString:
-        return visit.visit(JsonString(content_.asOwnedString->data,
-                                      content_.asOwnedString->length));
-
-      case VariantType::RawString:
-        return visit.visit(RawString(content_.asOwnedString->data,
-                                     content_.asOwnedString->length));
-
-      case VariantType::Int32:
-        return visit.visit(static_cast<JsonInteger>(content_.asInt32));
-
-      case VariantType::Uint32:
-        return visit.visit(static_cast<JsonUInt>(content_.asUint32));
-
-#if ARDUINOJSON_USE_LONG_LONG
-      case VariantType::Int64:
-        return visit.visit(extension->asInt64);
-
-      case VariantType::Uint64:
-        return visit.visit(extension->asUint64);
-#endif
-
-      case VariantType::Boolean:
-        return visit.visit(content_.asBoolean != 0);
-
-      default:
-        return visit.visit(nullptr);
-    }
-  }
-
-  template <typename TVisitor>
-  static typename TVisitor::result_type accept(const VariantData* var,
-                                               const ResourceManager* resources,
-                                               TVisitor& visit) {
-    if (var != 0)
-      return var->accept(visit, resources);
-    else
-      return visit.visit(nullptr);
-  }
-
-  VariantData* addElement(ResourceManager* resources) {
-    auto array = isNull() ? &toArray() : asArray();
-    return detail::ArrayData::addElement(array, resources);
-  }
-
-  static VariantData* addElement(VariantData* var, ResourceManager* resources) {
-    if (!var)
-      return nullptr;
-    return var->addElement(resources);
-  }
-
-  template <typename T>
-  bool addValue(const T& value, ResourceManager* resources) {
-    auto array = isNull() ? &toArray() : asArray();
-    return detail::ArrayData::addValue(array, value, resources);
-  }
-
-  template <typename T>
-  static bool addValue(VariantData* var, const T& value,
-                       ResourceManager* resources) {
-    if (!var)
-      return false;
-    return var->addValue(value, resources);
-  }
-
-  bool asBoolean(const ResourceManager* resources) const {
-#if ARDUINOJSON_USE_EXTENSIONS
-    auto extension = getExtension(resources);
-#else
-    (void)resources;  // silence warning
-#endif
-    switch (type_) {
-      case VariantType::Boolean:
-        return content_.asBoolean;
-      case VariantType::Uint32:
-      case VariantType::Int32:
-        return content_.asUint32 != 0;
-      case VariantType::Float:
-        return content_.asFloat != 0;
-#if ARDUINOJSON_USE_DOUBLE
-      case VariantType::Double:
-        return extension->asDouble != 0;
-#endif
-      case VariantType::Null:
-        return false;
-#if ARDUINOJSON_USE_LONG_LONG
-      case VariantType::Uint64:
-      case VariantType::Int64:
-        return extension->asUint64 != 0;
-#endif
-      default:
-        return true;
-    }
-  }
-
-  ArrayData* asArray() {
-    return isArray() ? &content_.asArray : 0;
-  }
-
-  const ArrayData* asArray() const {
-    return const_cast<VariantData*>(this)->asArray();
-  }
-
-  CollectionData* asCollection() {
-    return isCollection() ? &content_.asCollection : 0;
-  }
-
-  const CollectionData* asCollection() const {
-    return const_cast<VariantData*>(this)->asCollection();
-  }
-
-  template <typename T>
-  T asFloat(const ResourceManager* resources) const {
-    static_assert(is_floating_point<T>::value, "T must be a floating point");
-#if ARDUINOJSON_USE_EXTENSIONS
-    auto extension = getExtension(resources);
-#else
-    (void)resources;  // silence warning
-#endif
-    const char* str = nullptr;
-    switch (type_) {
-      case VariantType::Boolean:
-        return static_cast<T>(content_.asBoolean);
-      case VariantType::Uint32:
-        return static_cast<T>(content_.asUint32);
-      case VariantType::Int32:
-        return static_cast<T>(content_.asInt32);
-#if ARDUINOJSON_USE_LONG_LONG
-      case VariantType::Uint64:
-        return static_cast<T>(extension->asUint64);
-      case VariantType::Int64:
-        return static_cast<T>(extension->asInt64);
-#endif
-      case VariantType::TinyString:
-        str = content_.asTinyString;
-        break;
-      case VariantType::LinkedString:
-        str = content_.asLinkedString;
-        break;
-      case VariantType::OwnedString:
-        str = content_.asOwnedString->data;
-        break;
-      case VariantType::Float:
-        return static_cast<T>(content_.asFloat);
-#if ARDUINOJSON_USE_DOUBLE
-      case VariantType::Double:
-        return static_cast<T>(extension->asDouble);
-#endif
-      default:
-        return 0.0;
-    }
-
-    ARDUINOJSON_ASSERT(str != nullptr);
-    return parseNumber<T>(str);
-  }
-
-  template <typename T>
-  T asIntegral(const ResourceManager* resources) const {
-    static_assert(is_integral<T>::value, "T must be an integral type");
-#if ARDUINOJSON_USE_EXTENSIONS
-    auto extension = getExtension(resources);
-#else
-    (void)resources;  // silence warning
-#endif
-    const char* str = nullptr;
-    switch (type_) {
-      case VariantType::Boolean:
-        return content_.asBoolean;
-      case VariantType::Uint32:
-        return convertNumber<T>(content_.asUint32);
-      case VariantType::Int32:
-        return convertNumber<T>(content_.asInt32);
-#if ARDUINOJSON_USE_LONG_LONG
-      case VariantType::Uint64:
-        return convertNumber<T>(extension->asUint64);
-      case VariantType::Int64:
-        return convertNumber<T>(extension->asInt64);
-#endif
-      case VariantType::TinyString:
-        str = content_.asTinyString;
-        break;
-      case VariantType::LinkedString:
-        str = content_.asLinkedString;
-        break;
-      case VariantType::OwnedString:
-        str = content_.asOwnedString->data;
-        break;
-      case VariantType::Float:
-        return convertNumber<T>(content_.asFloat);
-#if ARDUINOJSON_USE_DOUBLE
-      case VariantType::Double:
-        return convertNumber<T>(extension->asDouble);
-#endif
-      default:
-        return 0;
-    }
-
-    ARDUINOJSON_ASSERT(str != nullptr);
-    return parseNumber<T>(str);
-  }
-
-  ObjectData* asObject() {
-    return isObject() ? &content_.asObject : 0;
-  }
-
-  const ObjectData* asObject() const {
-    return const_cast<VariantData*>(this)->asObject();
-  }
-
-  JsonString asRawString() const {
-    switch (type_) {
-      case VariantType::RawString:
-        return JsonString(content_.asOwnedString->data,
-                          content_.asOwnedString->length);
-      default:
-        return JsonString();
-    }
-  }
-
-  JsonString asString() const {
-    switch (type_) {
-      case VariantType::TinyString:
-        return JsonString(content_.asTinyString);
-      case VariantType::LinkedString:
-        return JsonString(content_.asLinkedString, true);
-      case VariantType::OwnedString:
-        return JsonString(content_.asOwnedString->data,
-                          content_.asOwnedString->length);
-      default:
-        return JsonString();
-    }
-  }
-
-#if ARDUINOJSON_USE_EXTENSIONS
-  const VariantExtension* getExtension(const ResourceManager* resources) const;
-#endif
-
-  VariantData* getElement(size_t index,
-                          const ResourceManager* resources) const {
-    return ArrayData::getElement(asArray(), index, resources);
-  }
-
-  static VariantData* getElement(const VariantData* var, size_t index,
-                                 const ResourceManager* resources) {
-    return var != 0 ? var->getElement(index, resources) : 0;
-  }
-
-  template <typename TAdaptedString>
-  VariantData* getMember(TAdaptedString key,
-                         const ResourceManager* resources) const {
-    return ObjectData::getMember(asObject(), key, resources);
-  }
-
-  template <typename TAdaptedString>
-  static VariantData* getMember(const VariantData* var, TAdaptedString key,
-                                const ResourceManager* resources) {
-    if (!var)
-      return 0;
-    return var->getMember(key, resources);
-  }
-
-  VariantData* getOrAddElement(size_t index, ResourceManager* resources) {
-    auto array = isNull() ? &toArray() : asArray();
-    if (!array)
-      return nullptr;
-    return array->getOrAddElement(index, resources);
-  }
-
-  template <typename TAdaptedString>
-  VariantData* getOrAddMember(TAdaptedString key, ResourceManager* resources) {
-    if (key.isNull())
-      return nullptr;
-    auto obj = isNull() ? &toObject() : asObject();
-    if (!obj)
-      return nullptr;
-    return obj->getOrAddMember(key, resources);
-  }
-
-  bool isArray() const {
-    return type_ == VariantType::Array;
-  }
-
-  bool isBoolean() const {
-    return type_ == VariantType::Boolean;
-  }
-
-  bool isCollection() const {
-    return type_ & VariantTypeBits::CollectionMask;
-  }
-
-  bool isFloat() const {
-    return type_ & VariantTypeBits::NumberBit;
-  }
-
-  template <typename T>
-  bool isInteger(const ResourceManager* resources) const {
-#if ARDUINOJSON_USE_LONG_LONG
-    auto extension = getExtension(resources);
-#else
-    (void)resources;  // silence warning
-#endif
-    switch (type_) {
-      case VariantType::Uint32:
-        return canConvertNumber<T>(content_.asUint32);
-
-      case VariantType::Int32:
-        return canConvertNumber<T>(content_.asInt32);
-
-#if ARDUINOJSON_USE_LONG_LONG
-      case VariantType::Uint64:
-        return canConvertNumber<T>(extension->asUint64);
-
-      case VariantType::Int64:
-        return canConvertNumber<T>(extension->asInt64);
-#endif
-
-      default:
-        return false;
-    }
-  }
-
-  bool isNull() const {
-    return type_ == VariantType::Null;
-  }
-
-  static bool isNull(const VariantData* var) {
-    if (!var)
-      return true;
-    return var->isNull();
-  }
-
-  bool isObject() const {
-    return type_ == VariantType::Object;
-  }
-
-  bool isString() const {
-    return type_ == VariantType::LinkedString ||
-           type_ == VariantType::OwnedString ||
-           type_ == VariantType::TinyString;
-  }
-
-  size_t nesting(const ResourceManager* resources) const {
-    auto collection = asCollection();
-    if (collection)
-      return collection->nesting(resources);
-    else
-      return 0;
-  }
-
-  static size_t nesting(const VariantData* var,
-                        const ResourceManager* resources) {
-    if (!var)
-      return 0;
-    return var->nesting(resources);
-  }
-
-  void removeElement(size_t index, ResourceManager* resources) {
-    ArrayData::removeElement(asArray(), index, resources);
-  }
-
-  static void removeElement(VariantData* var, size_t index,
-                            ResourceManager* resources) {
-    if (!var)
-      return;
-    var->removeElement(index, resources);
-  }
-
-  template <typename TAdaptedString>
-  void removeMember(TAdaptedString key, ResourceManager* resources) {
-    ObjectData::removeMember(asObject(), key, resources);
-  }
-
-  template <typename TAdaptedString>
-  static void removeMember(VariantData* var, TAdaptedString key,
-                           ResourceManager* resources) {
-    if (!var)
-      return;
-    var->removeMember(key, resources);
-  }
-
-  void reset() {  // TODO: remove
-    type_ = VariantType::Null;
-  }
-
   void setBoolean(bool value) {
-    ARDUINOJSON_ASSERT(type_ == VariantType::Null);  // must call clear() first
-    type_ = VariantType::Boolean;
-    content_.asBoolean = value;
-  }
-
-  template <typename T>
-  enable_if_t<sizeof(T) == 4, bool> setFloat(T value, ResourceManager*) {
-    ARDUINOJSON_ASSERT(type_ == VariantType::Null);  // must call clear() first
-    type_ = VariantType::Float;
-    content_.asFloat = value;
-    return true;
-  }
-
-  template <typename T>
-  enable_if_t<sizeof(T) == 8, bool> setFloat(T value, ResourceManager*);
-
-  template <typename T>
-  enable_if_t<is_signed<T>::value, bool> setInteger(T value,
-                                                    ResourceManager* resources);
-
-  template <typename T>
-  enable_if_t<is_unsigned<T>::value, bool> setInteger(
-      T value, ResourceManager* resources);
-
-  void setRawString(StringNode* s) {
-    ARDUINOJSON_ASSERT(type_ == VariantType::Null);  // must call clear() first
-    ARDUINOJSON_ASSERT(s);
-    type_ = VariantType::RawString;
-    content_.asOwnedString = s;
-  }
-
-  template <typename T>
-  void setRawString(SerializedValue<T> value, ResourceManager* resources);
-
-  template <typename T>
-  static void setRawString(VariantData* var, SerializedValue<T> value,
-                           ResourceManager* resources) {
-    if (!var)
-      return;
-    var->clear(resources);
-    var->setRawString(value, resources);
+    ARDUINOJSON_ASSERT(type == VariantType::Null);
+    type = VariantType::Boolean;
+    content.asBoolean = value;
   }
 
   template <typename TAdaptedString>
-  bool setString(TAdaptedString value, ResourceManager* resources);
+  void setTinyString(const TAdaptedString& s) {
+    ARDUINOJSON_ASSERT(type == VariantType::Null);
+    ARDUINOJSON_ASSERT(s.size() <= tinyStringMaxLength);
 
-  template <typename TAdaptedString>
-  static void setString(VariantData* var, TAdaptedString value,
-                        ResourceManager* resources) {
-    if (!var)
-      return;
-    var->clear(resources);
-    var->setString(value, resources);
-  }
+    type = VariantType::TinyString;
 
-  void setLinkedString(const char* s) {
-    ARDUINOJSON_ASSERT(type_ == VariantType::Null);  // must call clear() first
-    ARDUINOJSON_ASSERT(s);
-    type_ = VariantType::LinkedString;
-    content_.asLinkedString = s;
-  }
+    auto n = uint8_t(s.size());
+    for (uint8_t i = 0; i < n; i++) {
+      char c = s[i];
+      ARDUINOJSON_ASSERT(c != 0);  // no NUL in tiny string
+      content.asTinyString[i] = c;
+    }
 
-  void setTinyString(const char* s, uint8_t n) {
-    ARDUINOJSON_ASSERT(type_ == VariantType::Null);  // must call clear() first
-    ARDUINOJSON_ASSERT(s);
-    type_ = VariantType::TinyString;
-    for (uint8_t i = 0; i < n; i++)
-      content_.asTinyString[i] = s[i];
-    content_.asTinyString[n] = 0;
+    content.asTinyString[n] = 0;
   }
 
   void setOwnedString(StringNode* s) {
-    ARDUINOJSON_ASSERT(type_ == VariantType::Null);  // must call clear() first
+    ARDUINOJSON_ASSERT(type == VariantType::Null);
     ARDUINOJSON_ASSERT(s);
-    type_ = VariantType::OwnedString;
-    content_.asOwnedString = s;
+    type = VariantType::OwnedString;
+    content.asOwnedString = s;
   }
 
-  size_t size(const ResourceManager* resources) const {
-    if (isObject())
-      return content_.asObject.size(resources);
-
-    if (isArray())
-      return content_.asArray.size(resources);
-
-    return 0;
+  void setRawString(StringNode* s) {
+    ARDUINOJSON_ASSERT(type == VariantType::Null);
+    ARDUINOJSON_ASSERT(s);
+    type = VariantType::RawString;
+    content.asOwnedString = s;
   }
 
-  static size_t size(const VariantData* var, const ResourceManager* resources) {
-    return var != 0 ? var->size(resources) : 0;
+  bool isCollection() const {
+    return type & VariantTypeBits::CollectionMask;
   }
 
-  ArrayData& toArray() {
-    ARDUINOJSON_ASSERT(type_ == VariantType::Null);  // must call clear() first
-    type_ = VariantType::Array;
-    new (&content_.asArray) ArrayData();
-    return content_.asArray;
+  bool isFloat() const {
+    return type & VariantTypeBits::NumberBit;
   }
 
-  static ArrayData* toArray(VariantData* var, ResourceManager* resources) {
-    if (!var)
-      return 0;
-    var->clear(resources);
-    return &var->toArray();
+  bool isString() const {
+    return type == VariantType::LinkedString ||
+           type == VariantType::OwnedString || type == VariantType::TinyString;
   }
 
-  ObjectData& toObject() {
-    ARDUINOJSON_ASSERT(type_ == VariantType::Null);  // must call clear() first
-    type_ = VariantType::Object;
-    new (&content_.asObject) ObjectData();
-    return content_.asObject;
+  VariantData* toArray() {
+    return toCollection(VariantType::Array);
   }
 
-  static ObjectData* toObject(VariantData* var, ResourceManager* resources) {
-    if (!var)
-      return 0;
-    var->clear(resources);
-    return &var->toObject();
+  VariantData* toCollection(VariantType collectionType) {
+    ARDUINOJSON_ASSERT(type == VariantType::Null);
+    ARDUINOJSON_ASSERT(collectionType & VariantTypeBits::CollectionMask);
+    type = collectionType;
+    new (&content.asCollection) CollectionData();
+    return this;
   }
 
-  VariantType type() const {
-    return type_;
-  }
-
-  // Release the resources used by this variant and set it to null.
-  void clear(ResourceManager* resources);
-
-  static void clear(VariantData* var, ResourceManager* resources) {
-    if (!var)
-      return;
-    var->clear(resources);
+  VariantData* toObject() {
+    return toCollection(VariantType::Object);
   }
 };
 

src/ArduinoJson/Variant/VariantDataVisitor.hpp

@@ -4,10 +4,8 @@
 
 #pragma once
 
-#include <ArduinoJson/Array/ArrayData.hpp>
 #include <ArduinoJson/Numbers/JsonFloat.hpp>
 #include <ArduinoJson/Numbers/JsonInteger.hpp>
-#include <ArduinoJson/Object/ObjectData.hpp>
 
 ARDUINOJSON_BEGIN_PRIVATE_NAMESPACE
 
@@ -15,6 +13,14 @@ template <typename TResult>
 struct VariantDataVisitor {
   using result_type = TResult;
 
+  TResult visitArray(const VariantImpl&) {
+    return TResult();
+  }
+
+  TResult visitObject(const VariantImpl&) {
+    return TResult();
+  }
+
   template <typename T>
   TResult visit(const T&) {
     return TResult();

src/ArduinoJson/Variant/VariantImpl.hpp

@@ -5,142 +5,611 @@
 #pragma once
 
 #include <ArduinoJson/Memory/ResourceManager.hpp>
+#include <ArduinoJson/Misc/SerializedValue.hpp>
+#include <ArduinoJson/Numbers/convertNumber.hpp>
+#include <ArduinoJson/Strings/JsonString.hpp>
+#include <ArduinoJson/Strings/StringAdapters.hpp>
 #include <ArduinoJson/Variant/VariantData.hpp>
 
 ARDUINOJSON_BEGIN_PRIVATE_NAMESPACE
 
-template <typename T>
-inline void VariantData::setRawString(SerializedValue<T> value,
-                                      ResourceManager* resources) {
-  ARDUINOJSON_ASSERT(type_ == VariantType::Null);  // must call clear() first
-  auto dup = resources->saveString(adaptString(value.data(), value.size()));
-  if (dup)
-    setRawString(dup);
-}
+class CollectionIterator;
 
-template <typename TAdaptedString>
-inline bool VariantData::setString(TAdaptedString value,
-                                   ResourceManager* resources) {
-  ARDUINOJSON_ASSERT(type_ == VariantType::Null);  // must call clear() first
+class VariantImpl {
+  VariantData* data_;
+  ResourceManager* resources_;
 
-  if (value.isNull())
-    return false;
+ public:
+  using iterator = CollectionIterator;
 
-  if (value.isStatic()) {
-    setLinkedString(value.data());
-    return true;
+  VariantImpl() : data_(nullptr), resources_(nullptr) {}
+
+  VariantImpl(VariantData* data, ResourceManager* resources)
+      : data_(data), resources_(resources) {}
+
+  VariantData* data() const {
+    return data_;
   }
 
-  if (isTinyString(value, value.size())) {
-    setTinyString(value.data(), uint8_t(value.size()));
-    return true;
+  ResourceManager* resources() const {
+    return resources_;
   }
 
-  auto dup = resources->saveString(value);
-  if (dup) {
-    setOwnedString(dup);
-    return true;
-  }
+  template <typename TVisitor>
+  typename TVisitor::result_type accept(TVisitor& visit) const {
+    if (!data_)
+      return visit.visit(nullptr);
 
-  return false;
-}
-
-inline void VariantData::clear(ResourceManager* resources) {
-  if (type_ & VariantTypeBits::OwnedStringBit)
-    resources->dereferenceString(content_.asOwnedString->data);
-
-#if ARDUINOJSON_USE_EXTENSIONS
-  if (type_ & VariantTypeBits::ExtensionBit)
-    resources->freeExtension(content_.asSlotId);
+#if ARDUINOJSON_USE_8_BYTE_POOL
+    auto eightByteValue = getEightByte();
 #endif
-
-  auto collection = asCollection();
-  if (collection)
-    collection->clear(resources);
-
-  type_ = VariantType::Null;
-}
-
-#if ARDUINOJSON_USE_EXTENSIONS
-inline const VariantExtension* VariantData::getExtension(
-    const ResourceManager* resources) const {
-  return type_ & VariantTypeBits::ExtensionBit
-             ? resources->getExtension(content_.asSlotId)
-             : nullptr;
-}
-#endif
-
-template <typename T>
-enable_if_t<sizeof(T) == 8, bool> VariantData::setFloat(
-    T value, ResourceManager* resources) {
-  ARDUINOJSON_ASSERT(type_ == VariantType::Null);  // must call clear() first
-  (void)resources;                                 // silence warning
-
-  float valueAsFloat = static_cast<float>(value);
+    switch (data_->type) {
+      case VariantType::Float:
+        return visit.visit(data_->content.asFloat);
 
 #if ARDUINOJSON_USE_DOUBLE
-  if (value == valueAsFloat) {
-    type_ = VariantType::Float;
-    content_.asFloat = valueAsFloat;
-  } else {
-    auto extension = resources->allocExtension();
-    if (!extension)
-      return false;
-    type_ = VariantType::Double;
-    content_.asSlotId = extension.id();
-    extension->asDouble = value;
+      case VariantType::Double:
+        return visit.visit(eightByteValue->asDouble);
+#endif
+
+      case VariantType::Array:
+        return visit.visitArray(VariantImpl(data_, resources_));
+
+      case VariantType::Object:
+        return visit.visitObject(VariantImpl(data_, resources_));
+
+      case VariantType::TinyString:
+        return visit.visit(JsonString(data_->content.asTinyString));
+
+      case VariantType::LinkedString:
+        return visit.visit(JsonString(asLinkedString(), true));
+
+      case VariantType::OwnedString: {
+        auto s = asOwnedString();
+        return visit.visit(JsonString(s->data, s->length));
+      }
+
+      case VariantType::RawString: {
+        auto s = asOwnedString();
+        return visit.visit(RawString(s->data, s->length));
+      }
+
+      case VariantType::Int32:
+        return visit.visit(static_cast<JsonInteger>(data_->content.asInt32));
+
+      case VariantType::Uint32:
+        return visit.visit(static_cast<JsonUInt>(data_->content.asUint32));
+
+#if ARDUINOJSON_USE_LONG_LONG
+      case VariantType::Int64:
+        return visit.visit(eightByteValue->asInt64);
+
+      case VariantType::Uint64:
+        return visit.visit(eightByteValue->asUint64);
+#endif
+
+      case VariantType::Boolean:
+        return visit.visit(data_->content.asBoolean != 0);
+
+      default:
+        return visit.visit(nullptr);
+    }
   }
+
+  VariantData* addElement();
+  void addElement(Slot<VariantData> slot);
+
+  bool asBoolean() const {
+    if (!data_)
+      return false;
+
+#if ARDUINOJSON_USE_8_BYTE_POOL
+    auto eightByteValue = getEightByte();
+#endif
+    switch (data_->type) {
+      case VariantType::Boolean:
+        return data_->content.asBoolean;
+      case VariantType::Uint32:
+      case VariantType::Int32:
+        return data_->content.asUint32 != 0;
+      case VariantType::Float:
+        return data_->content.asFloat != 0;
+#if ARDUINOJSON_USE_DOUBLE
+      case VariantType::Double:
+        return eightByteValue->asDouble != 0;
+#endif
+      case VariantType::Null:
+        return false;
+#if ARDUINOJSON_USE_LONG_LONG
+      case VariantType::Uint64:
+      case VariantType::Int64:
+        return eightByteValue->asUint64 != 0;
+#endif
+      default:
+        return true;
+    }
+  }
+
+  template <typename T>
+  T asFloat() const {
+    if (!data_)
+      return 0.0;
+
+    static_assert(is_floating_point<T>::value, "T must be a floating point");
+#if ARDUINOJSON_USE_8_BYTE_POOL
+    auto eightByteValue = getEightByte();
+#endif
+    const char* str = nullptr;
+    switch (data_->type) {
+      case VariantType::Boolean:
+        return static_cast<T>(data_->content.asBoolean);
+      case VariantType::Uint32:
+        return static_cast<T>(data_->content.asUint32);
+      case VariantType::Int32:
+        return static_cast<T>(data_->content.asInt32);
+#if ARDUINOJSON_USE_LONG_LONG
+      case VariantType::Uint64:
+        return static_cast<T>(eightByteValue->asUint64);
+      case VariantType::Int64:
+        return static_cast<T>(eightByteValue->asInt64);
+#endif
+      case VariantType::TinyString:
+        str = data_->content.asTinyString;
+        break;
+      case VariantType::LinkedString:
+        str = asLinkedString();
+        break;
+      case VariantType::OwnedString:
+        str = asOwnedString()->data;
+        break;
+      case VariantType::Float:
+        return static_cast<T>(data_->content.asFloat);
+#if ARDUINOJSON_USE_DOUBLE
+      case VariantType::Double:
+        return static_cast<T>(eightByteValue->asDouble);
+#endif
+      default:
+        return 0.0;
+    }
+
+    ARDUINOJSON_ASSERT(str != nullptr);
+    return parseNumber<T>(str);
+  }
+
+  template <typename T>
+  T asIntegral() const {
+    if (!data_)
+      return 0;
+
+    static_assert(is_integral<T>::value, "T must be an integral type");
+#if ARDUINOJSON_USE_8_BYTE_POOL
+    auto eightByteValue = getEightByte();
+#endif
+    const char* str = nullptr;
+    switch (data_->type) {
+      case VariantType::Boolean:
+        return data_->content.asBoolean;
+      case VariantType::Uint32:
+        return convertNumber<T>(data_->content.asUint32);
+      case VariantType::Int32:
+        return convertNumber<T>(data_->content.asInt32);
+#if ARDUINOJSON_USE_LONG_LONG
+      case VariantType::Uint64:
+        return convertNumber<T>(eightByteValue->asUint64);
+      case VariantType::Int64:
+        return convertNumber<T>(eightByteValue->asInt64);
+#endif
+      case VariantType::TinyString:
+        str = data_->content.asTinyString;
+        break;
+      case VariantType::LinkedString:
+        str = asLinkedString();
+        break;
+      case VariantType::OwnedString:
+        str = asOwnedString()->data;
+        break;
+      case VariantType::Float:
+        return convertNumber<T>(data_->content.asFloat);
+#if ARDUINOJSON_USE_DOUBLE
+      case VariantType::Double:
+        return convertNumber<T>(eightByteValue->asDouble);
+#endif
+      default:
+        return 0;
+    }
+
+    ARDUINOJSON_ASSERT(str != nullptr);
+    return parseNumber<T>(str);
+  }
+
+  JsonString asRawString() const {
+    switch (type()) {
+      case VariantType::RawString: {
+        auto s = asOwnedString();
+        return JsonString(s->data, s->length);
+      }
+      default:
+        return JsonString();
+    }
+  }
+
+  const char* asLinkedString() const {
+    ARDUINOJSON_ASSERT(type() == VariantType::LinkedString);
+    return resources_->getStaticString(data_->content.asSlotId);
+  }
+
+  JsonString asString() const {
+    switch (type()) {
+      case VariantType::TinyString:
+        return JsonString(data_->content.asTinyString);
+      case VariantType::LinkedString:
+        return JsonString(asLinkedString(), true);
+      case VariantType::OwnedString: {
+        auto s = asOwnedString();
+        return JsonString(s->data, s->length);
+      }
+      default:
+        return JsonString();
+    }
+  }
+
+  StringNode* asOwnedString() const {
+    ARDUINOJSON_ASSERT(type() & VariantTypeBits::OwnedStringBit);
+    return data_->content.asOwnedString;
+  }
+
+#if ARDUINOJSON_USE_8_BYTE_POOL
+  const EightByteValue* getEightByte() const {
+    return type() & VariantTypeBits::EightByteBit
+               ? resources_->getEightByte(data_->content.asSlotId)
+               : 0;
+  }
+#endif
+
+  iterator createIterator() const;
+
+  VariantData* getElement(size_t index) const;
+
+  VariantData* getOrAddElement(size_t index);
+
+  void addMember(Slot<VariantData> key, Slot<VariantData> value);
+
+  template <typename TAdaptedString>
+  VariantData* addMember(TAdaptedString key);
+
+  template <typename TAdaptedString>
+  VariantData* getMember(TAdaptedString key) const;
+
+  template <typename TAdaptedString>
+  VariantData* getOrAddMember(TAdaptedString key);
+
+  bool isArray() const {
+    return type() == VariantType::Array;
+  }
+
+  bool isBoolean() const {
+    return type() == VariantType::Boolean;
+  }
+
+  bool isFloat() const {
+    return data_ && data_->isFloat();
+  }
+
+  template <typename T>
+  bool isInteger() const {
+    if (!data_)
+      return false;
+
+#if ARDUINOJSON_USE_LONG_LONG
+    auto eightByteValue = getEightByte();
+#endif
+    switch (data_->type) {
+      case VariantType::Uint32:
+        return canConvertNumber<T>(data_->content.asUint32);
+
+      case VariantType::Int32:
+        return canConvertNumber<T>(data_->content.asInt32);
+
+#if ARDUINOJSON_USE_LONG_LONG
+      case VariantType::Uint64:
+        return canConvertNumber<T>(eightByteValue->asUint64);
+
+      case VariantType::Int64:
+        return canConvertNumber<T>(eightByteValue->asInt64);
+#endif
+
+      default:
+        return false;
+    }
+  }
+
+  bool isUnbound() const {
+    return !data_;
+  }
+
+  bool isNull() const {
+    return type() == VariantType::Null;
+  }
+
+  bool isObject() const {
+    return type() == VariantType::Object;
+  }
+
+  bool isString() const {
+    return data_ && data_->isString();
+  }
+
+  size_t nesting() const;
+
+  void removeElement(iterator it);
+
+  void removeElement(size_t index);
+
+  template <typename TAdaptedString>
+  void removeMember(TAdaptedString key);
+
+  void removeMember(iterator it);
+
+  bool copyVariant(const VariantImpl& src) {
+    switch (src.type()) {
+      case VariantType::Null:
+        return true;
+
+      case VariantType::Array:
+        return copyArray(src);
+
+      case VariantType::Object:
+        return copyObject(src);
+
+      case VariantType::RawString:
+        return setRawString(adaptString(src.asRawString()));
+
+      case VariantType::LinkedString:
+        return setLinkedString(src.asLinkedString());
+
+      case VariantType::OwnedString:
+        return setOwnedString(adaptString(src.asString()));
+
+      default:
+        data_->content = src.data_->content;
+        data_->type = src.data_->type;
+        return true;
+    }
+  }
+
+  bool copyArray(const VariantImpl& src);
+  bool copyObject(const VariantImpl& src);
+
+  bool setBoolean(bool value) {
+    if (!data_)
+      return false;
+    data_->setBoolean(value);
+    return true;
+  }
+
+  template <typename T>
+  enable_if_t<sizeof(T) == 4, bool> setFloat(T value) {
+    ARDUINOJSON_ASSERT(type() == VariantType::Null);  // must call clear() first
+    if (!data_)
+      return false;
+    data_->type = VariantType::Float;
+    data_->content.asFloat = value;
+    return true;
+  }
+
+  template <typename T>
+  enable_if_t<sizeof(T) == 8, bool> setFloat(T value) {
+    ARDUINOJSON_ASSERT(isNull());  // must call clear() first
+
+    if (!data_)
+      return false;
+
+    float valueAsFloat = static_cast<float>(value);
+
+#if ARDUINOJSON_USE_DOUBLE
+    if (value == valueAsFloat) {
+      data_->type = VariantType::Float;
+      data_->content.asFloat = valueAsFloat;
+    } else {
+      auto slot = resources_->allocEightByte();
+      if (!slot)
+        return false;
+      data_->type = VariantType::Double;
+      data_->content.asSlotId = slot.id();
+      slot->asDouble = value;
+    }
 #else
-  type_ = VariantType::Float;
-  content_.asFloat = valueAsFloat;
+    data_->type = VariantType::Float;
+    data_->content.asFloat = valueAsFloat;
 #endif
-  return true;
-}
-
-template <typename T>
-enable_if_t<is_signed<T>::value, bool> VariantData::setInteger(
-    T value, ResourceManager* resources) {
-  ARDUINOJSON_ASSERT(type_ == VariantType::Null);  // must call clear() first
-  (void)resources;                                 // silence warning
-
-  if (canConvertNumber<int32_t>(value)) {
-    type_ = VariantType::Int32;
-    content_.asInt32 = static_cast<int32_t>(value);
+    return true;
   }
-#if ARDUINOJSON_USE_LONG_LONG
-  else {
-    auto extension = resources->allocExtension();
-    if (!extension)
+
+  template <typename T>
+  enable_if_t<is_signed<T>::value, bool> setInteger(T value) {
+    ARDUINOJSON_ASSERT(isNull());  // must call clear() first
+
+    if (!data_)
       return false;
-    type_ = VariantType::Int64;
-    content_.asSlotId = extension.id();
-    extension->asInt64 = value;
-  }
-#endif
-  return true;
-}
 
-template <typename T>
-enable_if_t<is_unsigned<T>::value, bool> VariantData::setInteger(
-    T value, ResourceManager* resources) {
-  ARDUINOJSON_ASSERT(type_ == VariantType::Null);  // must call clear() first
-  (void)resources;                                 // silence warning
-
-  if (canConvertNumber<uint32_t>(value)) {
-    type_ = VariantType::Uint32;
-    content_.asUint32 = static_cast<uint32_t>(value);
-  }
+    if (canConvertNumber<int32_t>(value)) {
+      data_->type = VariantType::Int32;
+      data_->content.asInt32 = static_cast<int32_t>(value);
+    }
 #if ARDUINOJSON_USE_LONG_LONG
-  else {
-    auto extension = resources->allocExtension();
-    if (!extension)
-      return false;
-    type_ = VariantType::Uint64;
-    content_.asSlotId = extension.id();
-    extension->asUint64 = value;
-  }
+    else {
+      auto slot = resources_->allocEightByte();
+      if (!slot)
+        return false;
+      data_->type = VariantType::Int64;
+      data_->content.asSlotId = slot.id();
+      slot->asInt64 = value;
+    }
 #endif
-  return true;
-}
+    return true;
+  }
+
+  template <typename T>
+  enable_if_t<is_unsigned<T>::value, bool> setInteger(T value) {
+    ARDUINOJSON_ASSERT(isNull());  // must call clear() first
+
+    if (!data_)
+      return false;
+
+    if (canConvertNumber<uint32_t>(value)) {
+      data_->type = VariantType::Uint32;
+      data_->content.asUint32 = static_cast<uint32_t>(value);
+    }
+#if ARDUINOJSON_USE_LONG_LONG
+    else {
+      auto slot = resources_->allocEightByte();
+      if (!slot)
+        return false;
+      data_->type = VariantType::Uint64;
+      data_->content.asSlotId = slot.id();
+      slot->asUint64 = value;
+    }
+#endif
+    return true;
+  }
+
+  template <typename TAdaptedString>
+  bool setRawString(TAdaptedString value) {
+    if (!data_)
+      return false;
+    auto dup = resources_->saveString(value);
+    if (!dup)
+      return false;
+    data_->setRawString(dup);
+    return true;
+  }
+
+  template <typename TAdaptedString>
+  bool setString(TAdaptedString value) {
+    ARDUINOJSON_ASSERT(isNull());  // must call clear() first
+
+    if (!data_)
+      return false;
+
+    if (value.isNull())
+      return true;
+
+    if (value.isStatic())
+      return setLinkedString(value.data());
+
+    if (isTinyString(value, value.size())) {
+      data_->setTinyString(value);
+      return true;
+    }
+
+    return setOwnedString(value);
+  }
+
+  template <typename TAdaptedString>
+  bool setOwnedString(TAdaptedString value) {
+    auto dup = resources_->saveString(value);
+    if (!dup)
+      return false;
+
+    data_->setOwnedString(dup);
+    return true;
+  }
+
+  bool setLinkedString(const char* s) {
+    ARDUINOJSON_ASSERT(isNull());  // must call clear() first
+    ARDUINOJSON_ASSERT(s);
+
+    auto slotId = resources_->saveStaticString(s);
+    if (slotId == NULL_SLOT)
+      return false;
+
+    data_->type = VariantType::LinkedString;
+    data_->content.asSlotId = slotId;
+    return true;
+  }
+
+  void toArrayIfNull() {
+    if (data_ && data_->type == VariantType::Null)
+      data_->toArray();
+  }
+
+  void toObjectIfNull() {
+    if (data_ && data_->type == VariantType::Null)
+      data_->toObject();
+  }
+
+  void empty() {
+    auto coll = getCollectionData();
+
+    auto next = coll->head;
+    while (next != NULL_SLOT) {
+      auto currId = next;
+      auto slot = getVariant(next);
+      next = slot->next;
+      freeVariant({slot, currId});
+    }
+
+    coll->head = NULL_SLOT;
+    coll->tail = NULL_SLOT;
+  }
+
+  size_t size() const;
+
+  VariantType type() const {
+    return data_ ? data_->type : VariantType::Null;
+  }
+
+  // Release the resources used by this variant and set it to null.
+  void clear() {
+    if (!data_)
+      return;
+
+    if (data_->type & VariantTypeBits::OwnedStringBit)
+      resources_->dereferenceString(asOwnedString());
+
+#if ARDUINOJSON_USE_8_BYTE_POOL
+    if (data_->type & VariantTypeBits::EightByteBit)
+      resources_->freeEightByte(data_->content.asSlotId);
+#endif
+
+    if (data_->type & VariantTypeBits::CollectionMask)
+      empty();
+
+    data_->type = VariantType::Null;
+  }
+
+ private:
+  template <typename TAdaptedString>
+  iterator findKey(TAdaptedString key) const;
+
+  iterator at(size_t index) const;
+
+  void removeOne(iterator it);
+  void removePair(iterator it);
+
+  VariantData* getVariant(SlotId id) const {
+    ARDUINOJSON_ASSERT(resources_ != nullptr);
+    return resources_->getVariant(id);
+  }
+
+  void freeVariant(Slot<VariantData> slot) {
+    ARDUINOJSON_ASSERT(resources_ != nullptr);
+    VariantImpl(slot.ptr(), resources_).clear();
+    resources_->freeVariant(slot);
+  }
+
+  Slot<VariantData> allocVariant() {
+    ARDUINOJSON_ASSERT(resources_ != nullptr);
+    return resources_->allocVariant();
+  }
+
+  Slot<VariantData> getPreviousSlot(VariantData*) const;
+
+  CollectionData* getCollectionData() const {
+    ARDUINOJSON_ASSERT(data_ != nullptr);
+    ARDUINOJSON_ASSERT(data_->isCollection());
+    return &data_->content.asCollection;
+  }
+};
 
 ARDUINOJSON_END_PRIVATE_NAMESPACE

src/ArduinoJson/Variant/VariantRefBase.hpp

@@ -29,18 +29,18 @@ class VariantRefBase : public VariantTag {
   // Sets the value to null.
   // https://arduinojson.org/v7/api/jsonvariant/clear/
   void clear() const {
-    VariantData::clear(getOrCreateData(), getResourceManager());
+    getOrCreateImpl().clear();
   }
 
   // Returns true if the value is null or the reference is unbound.
   // https://arduinojson.org/v7/api/jsonvariant/isnull/
   bool isNull() const {
-    return VariantData::isNull(getData());
+    return getImpl().isNull();
   }
 
   // Returns true if the reference is unbound.
   bool isUnbound() const {
-    return !getData();
+    return getImpl().isUnbound();
   }
 
   // Casts the value to the specified type.
@@ -93,13 +93,13 @@ class VariantRefBase : public VariantTag {
   // Returns the size of the array or object.
   // https://arduinojson.org/v7/api/jsonvariant/size/
   size_t size() const {
-    return VariantData::size(getData(), getResourceManager());
+    return getImpl().size();
   }
 
   // Returns the depth (nesting level) of the value.
   // https://arduinojson.org/v7/api/jsonvariant/nesting/
   size_t nesting() const {
-    return VariantData::nesting(getData(), getResourceManager());
+    return getImpl().nesting();
   }
 
   // Appends a new (empty) element to the array.
@@ -120,38 +120,34 @@ class VariantRefBase : public VariantTag {
   // https://arduinojson.org/v7/api/jsonvariant/add/
   template <typename T>
   bool add(const T& value) const {
-    return detail::VariantData::addValue(getOrCreateData(), value,
-                                         getResourceManager());
+    return getOrCreateArray().add(value);
   }
 
   // Appends a value to the array.
   // https://arduinojson.org/v7/api/jsonvariant/add/
   template <typename T, enable_if_t<!is_const<T>::value, int> = 0>
   bool add(T* value) const {
-    return detail::VariantData::addValue(getOrCreateData(), value,
-                                         getResourceManager());
+    return getOrCreateArray().add(value);
   }
 
   // Removes an element of the array.
   // https://arduinojson.org/v7/api/jsonvariant/remove/
   void remove(size_t index) const {
-    VariantData::removeElement(getData(), index, getResourceManager());
+    getImpl().removeElement(index);
   }
 
   // Removes a member of the object.
   // https://arduinojson.org/v7/api/jsonvariant/remove/
   template <typename TChar, enable_if_t<IsString<TChar*>::value, int> = 0>
   void remove(TChar* key) const {
-    VariantData::removeMember(getData(), adaptString(key),
-                              getResourceManager());
+    getImpl().removeMember(adaptString(key));
   }
 
   // Removes a member of the object.
   // https://arduinojson.org/v7/api/jsonvariant/remove/
   template <typename TString, enable_if_t<IsString<TString>::value, int> = 0>
   void remove(const TString& key) const {
-    VariantData::removeMember(getData(), adaptString(key),
-                              getResourceManager());
+    getImpl().removeMember(adaptString(key));
   }
 
   // Removes a member of the object or an element of the array.
@@ -263,22 +259,20 @@ class VariantRefBase : public VariantTag {
     return static_cast<const TDerived&>(*this);
   }
 
-  ResourceManager* getResourceManager() const {
-    return VariantAttorney::getResourceManager(derived());
+  VariantImpl getImpl() const {
+    return VariantAttorney::getImpl(derived());
   }
 
-  VariantData* getData() const {
-    return VariantAttorney::getData(derived());
+  VariantImpl getOrCreateImpl() const {
+    return VariantAttorney::getOrCreateImpl(derived());
   }
 
-  VariantData* getOrCreateData() const {
-    return VariantAttorney::getOrCreateData(derived());
-  }
+  JsonArray getOrCreateArray() const;
 
   FORCE_INLINE ArduinoJson::JsonVariant getVariant() const;
 
   FORCE_INLINE ArduinoJson::JsonVariantConst getVariantConst() const {
-    return ArduinoJson::JsonVariantConst(getData(), getResourceManager());
+    return ArduinoJson::JsonVariantConst(getImpl());
   }
 
   template <typename T>
@@ -306,8 +300,6 @@ class VariantRefBase : public VariantTag {
 
   template <typename TConverter, typename T>
   bool doSet(const T& value, true_type) const;
-
-  ArduinoJson::JsonVariant getOrCreateVariant() const;
 };
 
 ARDUINOJSON_END_PRIVATE_NAMESPACE

src/ArduinoJson/Variant/VariantRefBaseImpl.hpp

@@ -61,31 +61,27 @@ inline JsonObject VariantRefBase<TDerived>::createNestedObject(
 }
 
 template <typename TDerived>
-inline void convertToJson(const VariantRefBase<TDerived>& src,
+inline bool convertToJson(const VariantRefBase<TDerived>& src,
                           JsonVariant dst) {
-  dst.set(src.template as<JsonVariantConst>());
+  return dst.set(src.template as<JsonVariantConst>());
 }
 
 template <typename TDerived>
 template <typename T, enable_if_t<is_same<T, JsonVariant>::value, int>>
 inline T VariantRefBase<TDerived>::add() const {
-  return JsonVariant(
-      detail::VariantData::addElement(getOrCreateData(), getResourceManager()),
-      getResourceManager());
+  return getOrCreateArray().template add<T>();
 }
 
 template <typename TDerived>
 template <typename TString, enable_if_t<IsString<TString>::value, int>>
 inline bool VariantRefBase<TDerived>::containsKey(const TString& key) const {
-  return VariantData::getMember(getData(), adaptString(key),
-                                getResourceManager()) != 0;
+  return getImpl().getMember(adaptString(key)) != 0;
 }
 
 template <typename TDerived>
 template <typename TChar, enable_if_t<IsString<TChar*>::value, int>>
 inline bool VariantRefBase<TDerived>::containsKey(TChar* key) const {
-  return VariantData::getMember(getData(), adaptString(key),
-                                getResourceManager()) != 0;
+  return getImpl().getMember(adaptString(key)) != 0;
 }
 
 template <typename TDerived>
@@ -96,12 +92,7 @@ inline bool VariantRefBase<TDerived>::containsKey(const TVariant& key) const {
 
 template <typename TDerived>
 inline JsonVariant VariantRefBase<TDerived>::getVariant() const {
-  return JsonVariant(getData(), getResourceManager());
-}
-
-template <typename TDerived>
-inline JsonVariant VariantRefBase<TDerived>::getOrCreateVariant() const {
-  return JsonVariant(getOrCreateData(), getResourceManager());
+  return JsonVariant(getImpl());
 }
 
 template <typename TDerived>
@@ -136,40 +127,54 @@ VariantRefBase<TDerived>::operator[](const TString& key) const {
 template <typename TDerived>
 template <typename TConverter, typename T>
 inline bool VariantRefBase<TDerived>::doSet(const T& value, false_type) const {
-  TConverter::toJson(value, getOrCreateVariant());
-  auto resources = getResourceManager();
+  auto impl = getOrCreateImpl();
+  TConverter::toJson(value, JsonVariant(impl));
+  auto resources = impl.resources();
   return resources && !resources->overflowed();
 }
 
 template <typename TDerived>
 template <typename TConverter, typename T>
 inline bool VariantRefBase<TDerived>::doSet(const T& value, true_type) const {
-  return TConverter::toJson(value, getOrCreateVariant());
+  auto impl = getOrCreateImpl();
+  return TConverter::toJson(value, JsonVariant(impl));
+}
+
+template <typename TDerived>
+inline JsonArray VariantRefBase<TDerived>::getOrCreateArray() const {
+  auto impl = getOrCreateImpl();
+  impl.toArrayIfNull();
+  return JsonArray(impl);
 }
 
 template <typename TDerived>
 template <typename T, enable_if_t<is_same<T, JsonArray>::value, int>>
 inline JsonArray VariantRefBase<TDerived>::to() const {
-  return JsonArray(
-      VariantData::toArray(getOrCreateData(), getResourceManager()),
-      getResourceManager());
+  auto impl = getOrCreateImpl();
+  if (impl.isUnbound())
+    return JsonArray();
+  impl.clear();
+  impl.data()->toArray();
+  return JsonArray(impl);
 }
 
 template <typename TDerived>
 template <typename T, enable_if_t<is_same<T, JsonObject>::value, int>>
 JsonObject VariantRefBase<TDerived>::to() const {
-  return JsonObject(
-      VariantData::toObject(getOrCreateData(), getResourceManager()),
-      getResourceManager());
+  auto impl = getOrCreateImpl();
+  if (impl.isUnbound())
+    return JsonObject();
+  impl.clear();
+  impl.data()->toObject();
+  return JsonObject(impl);
 }
 
 template <typename TDerived>
 template <typename T, enable_if_t<is_same<T, JsonVariant>::value, int>>
 JsonVariant VariantRefBase<TDerived>::to() const {
-  auto data = getOrCreateData();
-  auto resources = getResourceManager();
-  detail::VariantData::clear(data, resources);
-  return JsonVariant(data, resources);
+  auto impl = getOrCreateImpl();
+  impl.clear();
+  return JsonVariant(impl);
 }
 
 ARDUINOJSON_END_PRIVATE_NAMESPACE

src/ArduinoJson/version.hpp

@@ -4,8 +4,8 @@
 
 #pragma once
 
-#define ARDUINOJSON_VERSION "7.4.0"
+#define ARDUINOJSON_VERSION "7.4.2"
 #define ARDUINOJSON_VERSION_MAJOR 7
 #define ARDUINOJSON_VERSION_MINOR 4
-#define ARDUINOJSON_VERSION_REVISION 0
-#define ARDUINOJSON_VERSION_MACRO V740
+#define ARDUINOJSON_VERSION_REVISION 2
+#define ARDUINOJSON_VERSION_MACRO V742