Added BasicJsonDocument to support custom allocator (issue #876)

src/ArduinoJson/Document/BasicJsonDocument.hpp

@@ -0,0 +1,89 @@
+// ArduinoJson - arduinojson.org
+// Copyright Benoit Blanchon 2014-2019
+// MIT License
+
+#pragma once
+
+#include "JsonDocument.hpp"
+
+namespace ARDUINOJSON_NAMESPACE {
+
+template <typename TAllocator>
+class AllocatorOwner {
+ protected:
+  AllocatorOwner() {}
+  AllocatorOwner(const AllocatorOwner& src) : _allocator(src._allocator) {}
+  AllocatorOwner(TAllocator allocator) : _allocator(allocator) {}
+
+  void* allocate(size_t n) {
+    return _allocator.allocate(n);
+  }
+
+  void deallocate(void* p) {
+    _allocator.deallocate(p);
+  }
+
+ private:
+  TAllocator _allocator;
+};
+
+template <typename TAllocator>
+class BasicJsonDocument : AllocatorOwner<TAllocator>, public JsonDocument {
+ public:
+  explicit BasicJsonDocument(size_t capa, TAllocator allocator = TAllocator())
+      : AllocatorOwner<TAllocator>(allocator), JsonDocument(allocPool(capa)) {}
+
+  BasicJsonDocument(const BasicJsonDocument& src)
+      : AllocatorOwner<TAllocator>(src),
+        JsonDocument(allocPool(src.memoryUsage())) {
+    set(src);
+  }
+
+  template <typename T>
+  BasicJsonDocument(const T& src,
+                    typename enable_if<IsVisitable<T>::value>::type* = 0)
+      : JsonDocument(allocPool(src.memoryUsage())) {
+    set(src);
+  }
+
+  // disambiguate
+  BasicJsonDocument(VariantRef src)
+      : JsonDocument(allocPool(src.memoryUsage())) {
+    set(src);
+  }
+
+  ~BasicJsonDocument() {
+    freePool();
+  }
+
+  BasicJsonDocument& operator=(const BasicJsonDocument& src) {
+    reallocPoolIfTooSmall(src.memoryUsage());
+    set(src);
+    return *this;
+  }
+
+  template <typename T>
+  BasicJsonDocument& operator=(const T& src) {
+    reallocPoolIfTooSmall(src.memoryUsage());
+    set(src);
+    return *this;
+  }
+
+ private:
+  MemoryPool allocPool(size_t requiredSize) {
+    size_t capa = addPadding(requiredSize);
+    return MemoryPool(reinterpret_cast<char*>(this->allocate(capa)), capa);
+  }
+
+  void reallocPoolIfTooSmall(size_t requiredSize) {
+    if (requiredSize <= capacity()) return;
+    freePool();
+    replacePool(allocPool(addPadding(requiredSize)));
+  }
+
+  void freePool() {
+    this->deallocate(memoryPool().buffer());
+  }
+};
+
+}  // namespace ARDUINOJSON_NAMESPACE