Use GetArena() instead of GetOwningArena() #5.

PiperOrigin-RevId: 575857972

src/google/protobuf/arena.h

@@ -389,7 +389,8 @@ class PROTOBUF_EXPORT PROTOBUF_ALIGNAS(8) Arena final {
     // mutually exclusive fashion, we use implicit conversions to base classes
     // to force an explicit ranking for our preferences.  The lowest ranked
     // version that compiles will be accepted.
-    struct Rank1 {};
+    struct Rank2 {};
+    struct Rank1 : Rank2 {};
     struct Rank0 : Rank1 {};
 
     static Arena* GetOwningArena(const T* p) {
@@ -402,8 +403,15 @@ class PROTOBUF_EXPORT PROTOBUF_ALIGNAS(8) Arena final {
       return p->GetOwningArena();
     }
 
+    // TODO: remove this function.
     template <typename U>
-    static Arena* GetOwningArena(Rank1, const U*) {
+    static auto GetOwningArena(Rank1, const U* p)
+        -> EnableIfArena<decltype(p->GetArena())> {
+      return p->GetArena();
+    }
+
+    template <typename U>
+    static Arena* GetOwningArena(Rank2, const U*) {
       return nullptr;
     }
 

src/google/protobuf/message_lite.h

@@ -221,6 +221,11 @@ class PROTOBUF_EXPORT MessageLite {
   // if arena is a nullptr.
   virtual MessageLite* New(Arena* arena) const = 0;
 
+  // Returns the arena, if any, that directly owns this message and its internal
+  // memory (Arena::Own is different in that the arena doesn't directly own the
+  // internal memory). This method is used in proto's implementation for
+  // swapping, moving and setting allocated, for deciding whether the ownership
+  // of this message or its internal memory could be changed.
   Arena* GetArena() const { return _internal_metadata_.arena(); }
 
   // Clear all fields of the message and set them to their default values.
@@ -511,13 +516,6 @@ class PROTOBUF_EXPORT MessageLite {
 
   inline explicit MessageLite(Arena* arena) : _internal_metadata_(arena) {}
 
-  // Returns the arena, if any, that directly owns this message and its internal
-  // memory (Arena::Own is different in that the arena doesn't directly own the
-  // internal memory). This method is used in proto's implementation for
-  // swapping, moving and setting allocated, for deciding whether the ownership
-  // of this message or its internal memory could be changed.
-  Arena* GetOwningArena() const { return _internal_metadata_.arena(); }
-
   // We use a secondary vtable for descriptor based methods. This way ClassData
   // does not growth with the number of descriptor methods. This avoids extra
   // costs in MessageLite.

src/google/protobuf/repeated_field.h

@@ -293,7 +293,10 @@ class RepeatedField final
   // Gets the Arena on which this RepeatedField stores its elements.
   // Note: this can be inaccurate for split default fields so we make this
   // function non-const.
-  inline Arena* GetArena() { return GetOwningArena(); }
+  inline Arena* GetArena() {
+    return (total_size_ == 0) ? static_cast<Arena*>(arena_or_elements_)
+                              : rep()->arena;
+  }
 
   // For internal use only.
   //
@@ -327,12 +330,6 @@ class RepeatedField final
 
   RepeatedField(Arena* arena, const RepeatedField& rhs);
 
-  // Gets the Arena on which this RepeatedField stores its elements.
-  inline Arena* GetOwningArena() const {
-    return (total_size_ == 0) ? static_cast<Arena*>(arena_or_elements_)
-                              : rep()->arena;
-  }
-
 
   // Swaps entire contents with "other". Should be called only if the caller can
   // guarantee that both repeated fields are on the same arena or are on the

src/google/protobuf/repeated_ptr_field.h

@@ -651,8 +651,6 @@ class PROTOBUF_EXPORT RepeatedPtrFieldBase {
   // Gets the Arena on which this RepeatedPtrField stores its elements.
   inline Arena* GetArena() const { return arena_; }
 
-  inline Arena* GetOwningArena() const { return arena_; }
-
  private:
   using InternalArenaConstructable_ = void;
   using DestructorSkippable_ = void;
@@ -1317,9 +1315,6 @@ class RepeatedPtrField final : private internal::RepeatedPtrFieldBase {
 
   RepeatedPtrField(Arena* arena, const RepeatedPtrField& rhs);
 
-  // Internal version of GetArena().
-  inline Arena* GetOwningArena() const;
-
 
   // Implementations for ExtractSubrange(). The copying behavior must be
   // included only if the type supports the necessary operations (e.g.,
@@ -1676,11 +1671,6 @@ inline Arena* RepeatedPtrField<Element>::GetArena() const {
 }
 #endif  // !PROTOBUF_FUTURE_REMOVE_CONST_REPEATEDFIELD_GETARENA_API
 
-template <typename Element>
-inline Arena* RepeatedPtrField<Element>::GetOwningArena() const {
-  return RepeatedPtrFieldBase::GetArena();
-}
-
 template <typename Element>
 inline size_t RepeatedPtrField<Element>::SpaceUsedExcludingSelfLong() const {
   // `google::protobuf::Message` has a virtual method `SpaceUsedLong`, hence we can