Refactor CPDF_Object and its subclasses.

core/include/fpdfapi/fpdf_objects.h

Index: core/include/fpdfapi/fpdf_objects.h
diff --git a/core/include/fpdfapi/fpdf_objects.h b/core/include/fpdfapi/fpdf_objects.h
index 0478acc3e03d0aed5675e08a72acc914ff551bb0..86035a86ad975c10650f1cfbb1249e238b428286 100644
--- a/core/include/fpdfapi/fpdf_objects.h
+++ b/core/include/fpdfapi/fpdf_objects.h
@@ -44,65 +44,61 @@ class CPDF_Object {
     REFERENCE
   };
 
-  Type GetType() const { return m_Type; }
+  virtual Type GetType() const = 0;
   FX_DWORD GetObjNum() const { return m_ObjNum; }
   FX_DWORD GetGenNum() const { return m_GenNum; }
 
-  FX_BOOL IsIdentical(CPDF_Object* pObj) const;
-  CPDF_Object* Clone(FX_BOOL bDirect = FALSE) const;
-  CPDF_Object* CloneRef(CPDF_IndirectObjectHolder* pObjs) const;
+  virtual CPDF_Object* Clone(FX_BOOL bDirect = FALSE) const = 0;
+  virtual CPDF_Object* GetDirect() const {
+    return const_cast<CPDF_Object*>(this);
+  }
 
-  CPDF_Object* GetDirect() const;
   FX_BOOL IsModified() const { return FALSE; }
-
   void Release();
 
-  CFX_ByteString GetString() const;
-  CFX_ByteStringC GetConstString() const;
-  CFX_WideString GetUnicodeText(CFX_CharMap* pCharMap = NULL) const;
-  FX_FLOAT GetNumber() const;
-  FX_FLOAT GetNumber16() const;
-  int GetInteger() const;
-  CPDF_Dictionary* GetDict() const;
-  CPDF_Array* GetArray() const;
-
-  void SetString(const CFX_ByteString& str);
-  void SetUnicodeText(const FX_WCHAR* pUnicodes, int len = -1);
-
-  bool IsArray() const { return m_Type == ARRAY; }
-  bool IsBoolean() const { return m_Type == BOOLEAN; }
-  bool IsDictionary() const { return m_Type == DICTIONARY; }
-  bool IsName() const { return m_Type == NAME; }
-  bool IsNumber() const { return m_Type == NUMBER; }
-  bool IsReference() const { return m_Type == REFERENCE; }
-  bool IsStream() const { return m_Type == STREAM; }
-  bool IsString() const { return m_Type == STRING; }
-
-  CPDF_Array* AsArray();
-  const CPDF_Array* AsArray() const;
-  CPDF_Boolean* AsBoolean();
-  const CPDF_Boolean* AsBoolean() const;
-  CPDF_Dictionary* AsDictionary();
-  const CPDF_Dictionary* AsDictionary() const;
-  CPDF_Name* AsName();
-  const CPDF_Name* AsName() const;
-  CPDF_Number* AsNumber();
-  const CPDF_Number* AsNumber() const;
-  CPDF_Reference* AsReference();
-  const CPDF_Reference* AsReference() const;
-  CPDF_Stream* AsStream();
-  const CPDF_Stream* AsStream() const;
-  CPDF_String* AsString();
-  const CPDF_String* AsString() const;
+  virtual CFX_ByteString GetString() const { return CFX_ByteString(); }
+  virtual CFX_ByteStringC GetConstString() const { return CFX_ByteStringC(); }
+  virtual CFX_WideString GetUnicodeText(CFX_CharMap* pCharMap = nullptr) const {
+    return CFX_WideString();
+  }
+  virtual FX_FLOAT GetNumber() const { return 0; }
+  virtual int GetInteger() const { return 0; }
+  virtual CPDF_Dictionary* GetDict() const { return nullptr; }
+  virtual CPDF_Array* GetArray() const { return nullptr; }
+
+  virtual void SetString(const CFX_ByteString& str) { ASSERT(FALSE); }
+
+  virtual bool IsArray() const { return false; }
+  virtual bool IsBoolean() const { return false; }
+  virtual bool IsDictionary() const { return false; }
+  virtual bool IsName() const { return false; }
+  virtual bool IsNumber() const { return false; }
+  virtual bool IsReference() const { return false; }
+  virtual bool IsStream() const { return false; }
+  virtual bool IsString() const { return false; }
+
+  virtual CPDF_Array* AsArray() { return nullptr; }
+  virtual const CPDF_Array* AsArray() const { return nullptr; }
+  virtual CPDF_Boolean* AsBoolean() { return nullptr; }
+  virtual const CPDF_Boolean* AsBoolean() const { return nullptr; }
+  virtual CPDF_Dictionary* AsDictionary() { return nullptr; }
+  virtual const CPDF_Dictionary* AsDictionary() const { return nullptr; }
+  virtual CPDF_Name* AsName() { return nullptr; }
+  virtual const CPDF_Name* AsName() const { return nullptr; }
+  virtual CPDF_Number* AsNumber() { return nullptr; }
+  virtual const CPDF_Number* AsNumber() const { return nullptr; }
+  virtual CPDF_Reference* AsReference() { return nullptr; }
+  virtual const CPDF_Reference* AsReference() const { return nullptr; }
+  virtual CPDF_Stream* AsStream() { return nullptr; }
+  virtual const CPDF_Stream* AsStream() const { return nullptr; }
+  virtual CPDF_String* AsString() { return nullptr; }
+  virtual const CPDF_String* AsString() const { return nullptr; }
 
  protected:
-  explicit CPDF_Object(Type type) : m_Type(type), m_ObjNum(0), m_GenNum(0) {}
-  ~CPDF_Object() {}
-  void Destroy();
+  CPDF_Object() : m_ObjNum(0), m_GenNum(0) {}
+  virtual ~CPDF_Object() {}
+  void Destroy() { delete this; }
 
-  const CPDF_Object* GetBasicObject() const;
-
-  const Type m_Type;
   FX_DWORD m_ObjNum;
   FX_DWORD m_GenNum;
 
@@ -111,66 +107,73 @@ class CPDF_Object {
   friend class CPDF_SyntaxParser;
 
  private:
-  CPDF_Object* CloneInternal(FX_BOOL bDirect,
-                             std::set<FX_DWORD>* visited) const;
+  CPDF_Object(const CPDF_Object& src) {}
 };
+
 class CPDF_Boolean : public CPDF_Object {
  public:
-  CPDF_Boolean() : CPDF_Object(BOOLEAN), m_bValue(false) {}
-  explicit CPDF_Boolean(FX_BOOL value)
-      : CPDF_Object(BOOLEAN), m_bValue(value) {}
+  CPDF_Boolean() : m_bValue(false) {}
+  explicit CPDF_Boolean(FX_BOOL value) : m_bValue(value) {}
 
-  FX_BOOL Identical(CPDF_Boolean* pOther) const {
-    return m_bValue == pOther->m_bValue;
+  // CPDF_Object.
+  Type GetType() const override { return BOOLEAN; }
+  CPDF_Object* Clone(FX_BOOL bDirect = FALSE) const override {
+    return new CPDF_Boolean(m_bValue);
   }
-
-  CFX_ByteString GetString() const { return m_bValue ? "true" : "false"; }
-  FX_BOOL GetValue() const { return m_bValue; }
+  CFX_ByteString GetString() const override {
+    return m_bValue ? "true" : "false";
+  }
+  int GetInteger() const override { return m_bValue; }
+  void SetString(const CFX_ByteString& str) override {
+    m_bValue = (str == "true");
+  }
+  bool IsBoolean() const override { return true; }
+  CPDF_Boolean* AsBoolean() override { return this; }
+  const CPDF_Boolean* AsBoolean() const override { return this; }
 
  protected:
+  ~CPDF_Boolean() {}
+
   FX_BOOL m_bValue;
-  friend class CPDF_Object;
 };
+
 inline CPDF_Boolean* ToBoolean(CPDF_Object* obj) {
   return obj ? obj->AsBoolean() : nullptr;
 }
+
 inline const CPDF_Boolean* ToBoolean(const CPDF_Object* obj) {
   return obj ? obj->AsBoolean() : nullptr;
 }
 
 class CPDF_Number : public CPDF_Object {
  public:
-  CPDF_Number() : CPDF_Object(NUMBER), m_bInteger(TRUE), m_Integer(0) {}
-
-  explicit CPDF_Number(int value);
-
-  explicit CPDF_Number(FX_FLOAT value);
-
+  CPDF_Number() : m_bInteger(TRUE), m_Integer(0) {}
+  explicit CPDF_Number(int value) : m_bInteger(TRUE), m_Integer(value) {}
+  explicit CPDF_Number(FX_FLOAT value) : m_bInteger(FALSE), m_Float(value) {}
   explicit CPDF_Number(const CFX_ByteStringC& str);
 
-  FX_BOOL Identical(CPDF_Number* pOther) const;
-
-  CFX_ByteString GetString() const;
-
-  void SetString(const CFX_ByteStringC& str);
-
-  FX_BOOL IsInteger() const { return m_bInteger; }
-
-  int GetInteger() const { return m_bInteger ? m_Integer : (int)m_Float; }
-
-  FX_FLOAT GetNumber() const {
-    return m_bInteger ? (FX_FLOAT)m_Integer : m_Float;
+  // CPDF_Object.
+  Type GetType() const override { return NUMBER; }
+  CPDF_Object* Clone(FX_BOOL bDirect = FALSE) const override {
+    return m_bInteger ? new CPDF_Number(m_Integer) : new CPDF_Number(m_Float);
   }
-
-  void SetNumber(FX_FLOAT value);
-
-  FX_FLOAT GetNumber16() const { return GetNumber(); }
-
-  FX_FLOAT GetFloat() const {
-    return m_bInteger ? (FX_FLOAT)m_Integer : m_Float;
+  CFX_ByteString GetString() const override;
+  FX_FLOAT GetNumber() const override {
+    return m_bInteger ? static_cast<FX_FLOAT>(m_Integer) : m_Float;
   }
+  int GetInteger() const override {
+    return m_bInteger ? m_Integer : static_cast<int>(m_Float);
+  }
+  void SetString(const CFX_ByteString& str) override;
+  bool IsNumber() const override { return true; }
+  CPDF_Number* AsNumber() override { return this; }
+  const CPDF_Number* AsNumber() const override { return this; }
+
+  FX_BOOL IsInteger() { return m_bInteger; }
 
  protected:
+  ~CPDF_Number() {}
+
   FX_BOOL m_bInteger;
 
   union {
@@ -178,141 +181,149 @@ class CPDF_Number : public CPDF_Object {
 
     FX_FLOAT m_Float;
   };
-  friend class CPDF_Object;
 };
+
 inline CPDF_Number* ToNumber(CPDF_Object* obj) {
   return obj ? obj->AsNumber() : nullptr;
 }
+
 inline const CPDF_Number* ToNumber(const CPDF_Object* obj) {
   return obj ? obj->AsNumber() : nullptr;
 }
 
 class CPDF_String : public CPDF_Object {
  public:
-  CPDF_String() : CPDF_Object(STRING), m_bHex(FALSE) {}
-
+  CPDF_String() : m_bHex(FALSE) {}
   CPDF_String(const CFX_ByteString& str, FX_BOOL bHex)
-      : CPDF_Object(STRING), m_String(str), m_bHex(bHex) {}
-
+      : m_String(str), m_bHex(bHex) {}
   explicit CPDF_String(const CFX_WideString& str);
 
-  CFX_ByteString GetString() const { return m_String; }
-
-  FX_BOOL Identical(CPDF_String* pOther) const {
-    return m_String == pOther->m_String;
+  // CPDF_Object.
+  Type GetType() const override { return STRING; }
+  CPDF_Object* Clone(FX_BOOL bDirect = FALSE) const override {
+    return new CPDF_String(m_String, m_bHex);
+  }
+  CFX_ByteString GetString() const override { return m_String; }
+  CFX_ByteStringC GetConstString() const override {
+    return CFX_ByteStringC(m_String);
   }
+  CFX_WideString GetUnicodeText(CFX_CharMap* pCharMap = nullptr) const override;
+  void SetString(const CFX_ByteString& str) override { m_String = str; }
+  bool IsString() const override { return true; }
+  CPDF_String* AsString() override { return this; }
+  const CPDF_String* AsString() const override { return this; }
 
   FX_BOOL IsHex() const { return m_bHex; }
 
  protected:
-  CFX_ByteString m_String;
+  ~CPDF_String() {}
 
+  CFX_ByteString m_String;
   FX_BOOL m_bHex;
-  friend class CPDF_Object;
 };
+
 inline CPDF_String* ToString(CPDF_Object* obj) {
   return obj ? obj->AsString() : nullptr;
 }
+
 inline const CPDF_String* ToString(const CPDF_Object* obj) {
   return obj ? obj->AsString() : nullptr;
 }
 
 class CPDF_Name : public CPDF_Object {
  public:
-  explicit CPDF_Name(const CFX_ByteString& str)
-      : CPDF_Object(NAME), m_Name(str) {}
-  explicit CPDF_Name(const CFX_ByteStringC& str)
-      : CPDF_Object(NAME), m_Name(str) {}
-  explicit CPDF_Name(const FX_CHAR* str) : CPDF_Object(NAME), m_Name(str) {}
-
-  CFX_ByteString GetString() const { return m_Name; }
-
-  FX_BOOL Identical(CPDF_Name* pOther) const {
-    return m_Name == pOther->m_Name;
+  explicit CPDF_Name(const CFX_ByteString& str) : m_Name(str) {}
+  explicit CPDF_Name(const CFX_ByteStringC& str) : m_Name(str) {}
+  explicit CPDF_Name(const FX_CHAR* str) : m_Name(str) {}
+
+  // CPDF_Object.
+  Type GetType() const override { return NAME; }
+  CPDF_Object* Clone(FX_BOOL bDirect = FALSE) const override {
+    return new CPDF_Name(m_Name);
   }
+  CFX_ByteString GetString() const override { return m_Name; }
+  CFX_ByteStringC GetConstString() const override {
+    return CFX_ByteStringC(m_Name);
+  }
+  CFX_WideString GetUnicodeText(CFX_CharMap* pCharMap = nullptr) const override;
+  void SetString(const CFX_ByteString& str) override { m_Name = str; }
+  bool IsName() const override { return true; }
+  CPDF_Name* AsName() override { return this; }
+  const CPDF_Name* AsName() const override { return this; }
 
  protected:
+  ~CPDF_Name() {}
+
   CFX_ByteString m_Name;
-  friend class CPDF_Object;
 };
+
 inline CPDF_Name* ToName(CPDF_Object* obj) {
   return obj ? obj->AsName() : nullptr;
 }
+
 inline const CPDF_Name* ToName(const CPDF_Object* obj) {
   return obj ? obj->AsName() : nullptr;
 }
 
 class CPDF_Array : public CPDF_Object {
  public:
-  CPDF_Array() : CPDF_Object(ARRAY) {}
+  CPDF_Array() {}
+
+  // CPDF_Object.
+  Type GetType() const override { return ARRAY; }
+  CPDF_Object* Clone(FX_BOOL bDirect = FALSE) const override;
+  CPDF_Array* GetArray() const override {
+    // The method should be made non-const if we want to not be const.
+    // See bug #234.
+    return const_cast<CPDF_Array*>(this);
+  }
+  bool IsArray() const override { return true; }
+  CPDF_Array* AsArray() override { return this; }
+  const CPDF_Array* AsArray() const override { return this; }
 
   FX_DWORD GetCount() const { return m_Objects.GetSize(); }
-
   CPDF_Object* GetElement(FX_DWORD index) const;
-
   CPDF_Object* GetElementValue(FX_DWORD index) const;
-
   CFX_Matrix GetMatrix();
-
   CFX_FloatRect GetRect();
-
   CFX_ByteString GetStringAt(FX_DWORD index) const;
-
   CFX_ByteStringC GetConstStringAt(FX_DWORD index) const;
-
   int GetIntegerAt(FX_DWORD index) const;
-
   FX_FLOAT GetNumberAt(FX_DWORD index) const;
-
   CPDF_Dictionary* GetDictAt(FX_DWORD index) const;
-
   CPDF_Stream* GetStreamAt(FX_DWORD index) const;
-
   CPDF_Array* GetArrayAt(FX_DWORD index) const;
-
   FX_FLOAT GetFloatAt(FX_DWORD index) const { return GetNumberAt(index); }
 
   void SetAt(FX_DWORD index,
              CPDF_Object* pObj,
-             CPDF_IndirectObjectHolder* pObjs = NULL);
-
+             CPDF_IndirectObjectHolder* pObjs = nullptr);
   void InsertAt(FX_DWORD index,
                 CPDF_Object* pObj,
-                CPDF_IndirectObjectHolder* pObjs = NULL);
-
+                CPDF_IndirectObjectHolder* pObjs = nullptr);
   void RemoveAt(FX_DWORD index, int nCount = 1);
 
-  void Add(CPDF_Object* pObj, CPDF_IndirectObjectHolder* pObjs = NULL);
-
+  void Add(CPDF_Object* pObj, CPDF_IndirectObjectHolder* pObjs = nullptr);
   void AddNumber(FX_FLOAT f);
-
   void AddInteger(int i);
-
   void AddString(const CFX_ByteString& str);
-
   void AddName(const CFX_ByteString& str);
-
   void AddReference(CPDF_IndirectObjectHolder* pDoc, FX_DWORD objnum);
-
   void AddReference(CPDF_IndirectObjectHolder* pDoc, CPDF_Object* obj) {
     AddReference(pDoc, obj->GetObjNum());
   }
-
-  FX_FLOAT GetNumber16(FX_DWORD index) const { return GetNumberAt(index); }
-
   void AddNumber16(FX_FLOAT value) { AddNumber(value); }
 
-  FX_BOOL Identical(CPDF_Array* pOther) const;
-
  protected:
   ~CPDF_Array();
 
   CFX_ArrayTemplate<CPDF_Object*> m_Objects;
-  friend class CPDF_Object;
 };
+
 inline CPDF_Array* ToArray(CPDF_Object* obj) {
   return obj ? obj->AsArray() : nullptr;
 }
+
 inline const CPDF_Array* ToArray(const CPDF_Object* obj) {
   return obj ? obj->AsArray() : nullptr;
 }
@@ -322,44 +333,41 @@ class CPDF_Dictionary : public CPDF_Object {
   using iterator = std::map<CFX_ByteString, CPDF_Object*>::iterator;
   using const_iterator = std::map<CFX_ByteString, CPDF_Object*>::const_iterator;
 
-  CPDF_Dictionary() : CPDF_Object(DICTIONARY) {}
+  CPDF_Dictionary() {}
 
-  CPDF_Object* GetElement(const CFX_ByteStringC& key) const;
+  // CPDF_Object.
+  Type GetType() const override { return DICTIONARY; }
+  CPDF_Object* Clone(FX_BOOL bDirect = FALSE) const override;
+  CPDF_Dictionary* GetDict() const override {
+    // The method should be made non-const if we want to not be const.
+    // See bug #234.
+    return const_cast<CPDF_Dictionary*>(this);
+  }
+  bool IsDictionary() const override { return true; }
+  CPDF_Dictionary* AsDictionary() override { return this; }
+  const CPDF_Dictionary* AsDictionary() const override { return this; }
 
+  size_t GetCount() const { return m_Map.size(); }
+  CPDF_Object* GetElement(const CFX_ByteStringC& key) const;
   CPDF_Object* GetElementValue(const CFX_ByteStringC& key) const;
-
   CFX_ByteString GetStringBy(const CFX_ByteStringC& key) const;
-
   CFX_ByteStringC GetConstStringBy(const CFX_ByteStringC& key) const;
-
   CFX_ByteString GetStringBy(const CFX_ByteStringC& key,
                              const CFX_ByteStringC& default_str) const;
-
   CFX_ByteStringC GetConstStringBy(const CFX_ByteStringC& key,
                                    const CFX_ByteStringC& default_str) const;
-
   CFX_WideString GetUnicodeTextBy(const CFX_ByteStringC& key,
                                   CFX_CharMap* pCharMap = NULL) const;
-
   int GetIntegerBy(const CFX_ByteStringC& key) const;
-
   int GetIntegerBy(const CFX_ByteStringC& key, int default_int) const;
-
   FX_BOOL GetBooleanBy(const CFX_ByteStringC& key,
                        FX_BOOL bDefault = FALSE) const;
-
   FX_FLOAT GetNumberBy(const CFX_ByteStringC& key) const;
-
   CPDF_Dictionary* GetDictBy(const CFX_ByteStringC& key) const;
-
   CPDF_Stream* GetStreamBy(const CFX_ByteStringC& key) const;
-
   CPDF_Array* GetArrayBy(const CFX_ByteStringC& key) const;
-
   CFX_FloatRect GetRectBy(const CFX_ByteStringC& key) const;
-
   CFX_Matrix GetMatrixBy(const CFX_ByteStringC& key) const;
-
   FX_FLOAT GetFloatBy(const CFX_ByteStringC& key) const {
     return GetNumberBy(key);
   }
@@ -368,63 +376,47 @@ class CPDF_Dictionary : public CPDF_Object {
 
   // Set* functions invalidate iterators for the element with the key |key|.
   void SetAt(const CFX_ByteStringC& key, CPDF_Object* pObj);
-
   void SetAtName(const CFX_ByteStringC& key, const CFX_ByteString& name);
-
   void SetAtString(const CFX_ByteStringC& key, const CFX_ByteString& string);
-
   void SetAtInteger(const CFX_ByteStringC& key, int i);
-
   void SetAtNumber(const CFX_ByteStringC& key, FX_FLOAT f);
-
   void SetAtReference(const CFX_ByteStringC& key,
                       CPDF_IndirectObjectHolder* pDoc,
                       FX_DWORD objnum);
-
   void SetAtReference(const CFX_ByteStringC& key,
                       CPDF_IndirectObjectHolder* pDoc,
                       CPDF_Object* obj) {
     SetAtReference(key, pDoc, obj->GetObjNum());
   }
+  void SetAtRect(const CFX_ByteStringC& key, const CFX_FloatRect& rect);
+  void SetAtMatrix(const CFX_ByteStringC& key, const CFX_Matrix& matrix);
+  void SetAtBoolean(const CFX_ByteStringC& key, FX_BOOL bValue);
 
   void AddReference(const CFX_ByteStringC& key,
                     CPDF_IndirectObjectHolder* pDoc,
                     FX_DWORD objnum);
 
-  void SetAtRect(const CFX_ByteStringC& key, const CFX_FloatRect& rect);
-
-  void SetAtMatrix(const CFX_ByteStringC& key, const CFX_Matrix& matrix);
-
-  void SetAtBoolean(const CFX_ByteStringC& key, FX_BOOL bValue);
-
   // Invalidates iterators for the element with the key |key|.
   void RemoveAt(const CFX_ByteStringC& key);
 
   // Invalidates iterators for the element with the key |oldkey|.
   void ReplaceKey(const CFX_ByteStringC& oldkey, const CFX_ByteStringC& newkey);
 
-  FX_BOOL Identical(CPDF_Dictionary* pDict) const;
-
-  size_t GetCount() const { return m_Map.size(); }
-
   iterator begin() { return m_Map.begin(); }
-
   iterator end() { return m_Map.end(); }
-
   const_iterator begin() const { return m_Map.begin(); }
-
   const_iterator end() const { return m_Map.end(); }
 
  protected:
   ~CPDF_Dictionary();
 
   std::map<CFX_ByteString, CPDF_Object*> m_Map;
-
-  friend class CPDF_Object;
 };
+
 inline CPDF_Dictionary* ToDictionary(CPDF_Object* obj) {
   return obj ? obj->AsDictionary() : nullptr;
 }
+
 inline const CPDF_Dictionary* ToDictionary(const CPDF_Object* obj) {
   return obj ? obj->AsDictionary() : nullptr;
 }
@@ -433,7 +425,17 @@ class CPDF_Stream : public CPDF_Object {
  public:
   CPDF_Stream(uint8_t* pData, FX_DWORD size, CPDF_Dictionary* pDict);
 
-  CPDF_Dictionary* GetDict() const { return m_pDict; }
+  // CPDF_Object.
+  Type GetType() const override { return STREAM; }
+  CPDF_Object* Clone(FX_BOOL bDirect = FALSE) const override;
+  CPDF_Dictionary* GetDict() const override { return m_pDict; }
+  CFX_WideString GetUnicodeText(CFX_CharMap* pCharMap = nullptr) const override;
+  bool IsStream() const override { return true; }
+  CPDF_Stream* AsStream() override { return this; }
+  const CPDF_Stream* AsStream() const override { return this; }
+
+  FX_DWORD GetRawSize() const { return m_dwSize; }
+  uint8_t* GetRawData() const { return m_pDataBuf; }
 
   void SetData(const uint8_t* pData,
                FX_DWORD size,
@@ -441,13 +443,8 @@ class CPDF_Stream : public CPDF_Object {
                FX_BOOL bKeepBuf);
 
   void InitStream(uint8_t* pData, FX_DWORD size, CPDF_Dictionary* pDict);
-
   void InitStreamFromFile(IFX_FileRead* pFile, CPDF_Dictionary* pDict);
 
-  FX_BOOL Identical(CPDF_Stream* pOther) const;
-
-  FX_DWORD GetRawSize() const { return m_dwSize; }
-
   FX_BOOL ReadRawData(FX_FILESIZE start_pos,
                       uint8_t* pBuf,
                       FX_DWORD buf_size) const;
@@ -455,29 +452,26 @@ class CPDF_Stream : public CPDF_Object {
   FX_BOOL IsMemoryBased() const { return m_GenNum == kMemoryBasedGenNum; }
 
  protected:
-  friend class CPDF_Object;
-  friend class CPDF_StreamAcc;
-
   static const FX_DWORD kMemoryBasedGenNum = (FX_DWORD)-1;
+
   ~CPDF_Stream();
 
   void InitStreamInternal(CPDF_Dictionary* pDict);
 
   CPDF_Dictionary* m_pDict;
-
   FX_DWORD m_dwSize;
-
   FX_DWORD m_GenNum;
 
   union {
     uint8_t* m_pDataBuf;
-
     IFX_FileRead* m_pFile;
   };
 };
+
 inline CPDF_Stream* ToStream(CPDF_Object* obj) {
   return obj ? obj->AsStream() : nullptr;
 }
+
 inline const CPDF_Stream* ToStream(const CPDF_Object* obj) {
   return obj ? obj->AsStream() : nullptr;
 }
@@ -485,7 +479,6 @@ inline const CPDF_Stream* ToStream(const CPDF_Object* obj) {
 class CPDF_StreamAcc {
  public:
   CPDF_StreamAcc();
-
   ~CPDF_StreamAcc();
 
   void LoadAllData(const CPDF_Stream* pStream,
@@ -494,66 +487,93 @@ class CPDF_StreamAcc {
                    FX_BOOL bImageAcc = FALSE);
 
   const CPDF_Stream* GetStream() const { return m_pStream; }
-
   CPDF_Dictionary* GetDict() const {
     return m_pStream ? m_pStream->GetDict() : nullptr;
   }
-
   const uint8_t* GetData() const;
-
   FX_DWORD GetSize() const;
+  const CFX_ByteString& GetImageDecoder() const { return m_ImageDecoder; }
+  const CPDF_Dictionary* GetImageParam() const { return m_pImageParam; }
 
   uint8_t* DetachData();
 
-  const CFX_ByteString& GetImageDecoder() { return m_ImageDecoder; }
-
-  const CPDF_Dictionary* GetImageParam() { return m_pImageParam; }
-
  protected:
   uint8_t* m_pData;
-
   FX_DWORD m_dwSize;
-
   FX_BOOL m_bNewBuf;
-
   CFX_ByteString m_ImageDecoder;
-
   CPDF_Dictionary* m_pImageParam;
-
   const CPDF_Stream* m_pStream;
-
   uint8_t* m_pSrcData;
 };
 
 class CPDF_Null : public CPDF_Object {
  public:
-  CPDF_Null() : CPDF_Object(NULLOBJ) {}
+  CPDF_Null() {}
+
+  // CPDF_Object.
+  Type GetType() const override { return NULLOBJ; }
+  CPDF_Object* Clone(FX_BOOL bDirect = FALSE) const override {
+    return new CPDF_Null;
+  }
 };
 
 class CPDF_Reference : public CPDF_Object {
  public:
   CPDF_Reference(CPDF_IndirectObjectHolder* pDoc, int objnum)
-      : CPDF_Object(REFERENCE), m_pObjList(pDoc), m_RefObjNum(objnum) {}
+      : m_pObjList(pDoc), m_RefObjNum(objnum) {}
+
+  // CPDF_Object.
+  Type GetType() const override { return REFERENCE; }
+  CPDF_Object* Clone(FX_BOOL bDirect = FALSE) const override;
+  CPDF_Object* GetDirect() const override;
+  CFX_ByteString GetString() const override {
+    CPDF_Object* obj = SafeGetDirect();
+    return obj ? obj->GetString() : CFX_ByteString();
+  }
+  CFX_ByteStringC GetConstString() const override {
+    CPDF_Object* obj = SafeGetDirect();
+    return obj ? obj->GetConstString() : CFX_ByteStringC();
+  }
+  FX_FLOAT GetNumber() const override {
+    CPDF_Object* obj = SafeGetDirect();
+    return obj ? obj->GetNumber() : 0;
+  }
+  int GetInteger() const override {
+    CPDF_Object* obj = SafeGetDirect();
+    return obj ? obj->GetInteger() : 0;
+  }
+  CPDF_Dictionary* GetDict() const override {
+    CPDF_Object* obj = SafeGetDirect();
+    return obj ? obj->GetDict() : nullptr;
+  }
+  // TODO(weili): check whether GetUnicodeText() and GetArray() are needed.
+  bool IsReference() const override { return true; }
+  CPDF_Reference* AsReference() override { return this; }
+  const CPDF_Reference* AsReference() const override { return this; }
 
   CPDF_IndirectObjectHolder* GetObjList() const { return m_pObjList; }
-
   FX_DWORD GetRefObjNum() const { return m_RefObjNum; }
 
   void SetRef(CPDF_IndirectObjectHolder* pDoc, FX_DWORD objnum);
 
-  FX_BOOL Identical(CPDF_Reference* pOther) const {
-    return m_RefObjNum == pOther->m_RefObjNum;
+ protected:
+  ~CPDF_Reference() {}
+  CPDF_Object* SafeGetDirect() const {
+    CPDF_Object* obj = GetDirect();
+    if (!obj || obj->IsReference())
+      return nullptr;
+    return obj;
   }
 
- protected:
   CPDF_IndirectObjectHolder* m_pObjList;
-
   FX_DWORD m_RefObjNum;
-  friend class CPDF_Object;
 };
+
 inline CPDF_Reference* ToReference(CPDF_Object* obj) {
   return obj ? obj->AsReference() : nullptr;
 }
+
 inline const CPDF_Reference* ToReference(const CPDF_Object* obj) {
   return obj ? obj->AsReference() : nullptr;
 }
@@ -575,7 +595,7 @@ class CPDF_IndirectObjectHolder {
 
   FX_DWORD GetLastObjNum() const { return m_LastObjNum; }
   iterator begin() { return m_IndirectObjs.begin(); }
-  const_iterator begin() const { return m_IndirectObjs.cbegin(); }
+  const_iterator begin() const { return m_IndirectObjs.begin(); }
   iterator end() { return m_IndirectObjs.end(); }
   const_iterator end() const { return m_IndirectObjs.end(); }