add Buffer::INVALID_CHANGE_OPERATION_INDEX

src/core/Buffer.cc

@@ -40,7 +40,7 @@ void Buffer::common_initialization()
     }
     m_change_buffer = std::make_shared<GapBuffer>();
     m_operation_level = 0;
-    m_current_change_operation_index = 0xFFFFFFFFu;
+    m_current_change_operation_index = INVALID_CHANGE_OPERATION_INDEX;
 }
 
 void Buffer::load_empty_buffer()

src/core/Buffer.h

@@ -13,6 +13,11 @@
 class Buffer
 {
 public:
+    enum : uint32_t
+    {
+        INVALID_CHANGE_OPERATION_INDEX = 0xFFFFFFFFu,
+    };
+
     class Iterator
     {
     public: