JSON: Add stateless allocator which uses thread local heap

Signed-off-by: Abhijat Malviya <[email protected]>

Author: abhijat

src/core/json/json_object.h

@@ -29,6 +29,42 @@ inline thread_local PMR_NS::memory_resource* tl_mr = nullptr;
 
 void InitJSONTLHeap(PMR_NS::memory_resource* mr);
 
+template <typename T> class JSONConsAllocator {
+ public:
+  using value_type = T;
+  using size_type = std::size_t;
+  using difference_type = std::ptrdiff_t;
+  using is_always_equal = std::true_type;
+
+  template <typename U> JSONConsAllocator(const JSONConsAllocator<U>&) noexcept {
+  }
+
+  JSONConsAllocator() noexcept = default;
+
+  static value_type* allocate(size_type n) {
+    void* ptr = detail::tl_mr->allocate(n * sizeof(value_type), alignof(value_type));
+    return static_cast<value_type*>(ptr);
+  }
+
+  static void deallocate(value_type* ptr, size_type n) noexcept {
+    detail::tl_mr->deallocate(ptr, n * sizeof(value_type), alignof(value_type));
+  }
+
+  static PMR_NS::memory_resource* resource() {
+    return detail::tl_mr;
+  }
+};
+
+template <typename T, typename U>
+bool operator==(const JSONConsAllocator<T>&, const JSONConsAllocator<U>&) noexcept {
+  return true;
+}
+
+template <typename T, typename U>
+bool operator!=(const JSONConsAllocator<T>&, const JSONConsAllocator<U>&) noexcept {
+  return false;
+}
+
 using JsonType = jsoncons::pmr::json;
 
 // Build a json object from string. If the string is not legal json, will return nullopt