Implement CPDF_Object::MakeReference method.chromium/3456

Change-Id: I153747ef587a184eaef58ff09dbf8f214c9ddfb3
Reviewed-on: https://pdfium-review.googlesource.com/17230
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Commit-Queue: Art Snake <art-snake@yandex-team.ru>

13 files changed, 97 insertions, 58 deletions

diff --git a/core/fpdfapi/edit/cpdf_pagecontentgenerator.cpp b/core/fpdfapi/edit/cpdf_pagecontentgenerator.cpp
index ba0aeef373..3365b5f986 100644
--- a/core/fpdfapi/edit/cpdf_pagecontentgenerator.cpp
+++ b/core/fpdfapi/edit/cpdf_pagecontentgenerator.cpp
@@ -91,48 +91,44 @@ void CPDF_PageContentGenerator::GenerateContent() {
   if (pContent) {
     CPDF_Array* pArray = ToArray(pContent);
     if (pArray) {
-      pArray->AddNew<CPDF_Reference>(pDoc, pStream->GetObjNum());
+      pArray->Add(pStream->MakeReference(pDoc));
       return;
     }
     CPDF_Reference* pReference = ToReference(pContent);
     if (!pReference) {
-      pPageDict->SetNewFor<CPDF_Reference>("Contents", m_pDocument.Get(),
-                                           pStream->GetObjNum());
+      pPageDict->SetFor("Contents", pStream->MakeReference(pDoc));
       return;
     }
     CPDF_Object* pDirectObj = pReference->GetDirect();
     if (!pDirectObj) {
-      pPageDict->SetNewFor<CPDF_Reference>("Contents", m_pDocument.Get(),
-                                           pStream->GetObjNum());
+      pPageDict->SetFor("Contents", pStream->MakeReference(pDoc));
       return;
     }
     CPDF_Array* pObjArray = pDirectObj->AsArray();
     if (pObjArray) {
-      pObjArray->AddNew<CPDF_Reference>(pDoc, pStream->GetObjNum());
+      pObjArray->Add(pStream->MakeReference(pDoc));
       return;
     }
     if (pDirectObj->IsStream()) {
       CPDF_Array* pContentArray = pDoc->NewIndirect<CPDF_Array>();
-      pContentArray->AddNew<CPDF_Reference>(pDoc, pDirectObj->GetObjNum());
-      pContentArray->AddNew<CPDF_Reference>(pDoc, pStream->GetObjNum());
-      pPageDict->SetNewFor<CPDF_Reference>("Contents", pDoc,
-                                           pContentArray->GetObjNum());
+      pContentArray->Add(pDirectObj->MakeReference(pDoc));
+      pContentArray->Add(pStream->MakeReference(pDoc));
+      pPageDict->SetFor("Contents", pContentArray->MakeReference(pDoc));
       return;
     }
   }
-  pPageDict->SetNewFor<CPDF_Reference>("Contents", m_pDocument.Get(),
-                                       pStream->GetObjNum());
+  pPageDict->SetFor("Contents", pStream->MakeReference(pDoc));
 }
 
 ByteString CPDF_PageContentGenerator::RealizeResource(
-    uint32_t dwResourceObjNum,
+    const CPDF_Object* pResource,
     const ByteString& bsType) {
-  ASSERT(dwResourceObjNum);
+  ASSERT(pResource);
   if (!m_pObjHolder->m_pResources) {
     m_pObjHolder->m_pResources = m_pDocument->NewIndirect<CPDF_Dictionary>();
-    m_pObjHolder->GetDict()->SetNewFor<CPDF_Reference>(
-        "Resources", m_pDocument.Get(),
-        m_pObjHolder->m_pResources->GetObjNum());
+    m_pObjHolder->GetDict()->SetFor(
+        "Resources",
+        m_pObjHolder->m_pResources->MakeReference(m_pDocument.Get()));
   }
   CPDF_Dictionary* pResList = m_pObjHolder->m_pResources->GetDictFor(bsType);
   if (!pResList)
@@ -147,8 +143,7 @@ ByteString CPDF_PageContentGenerator::RealizeResource(
 
     idnum++;
   }
-  pResList->SetNewFor<CPDF_Reference>(name, m_pDocument.Get(),
-                                      dwResourceObjNum);
+  pResList->SetFor(name, pResource->MakeReference(m_pDocument.Get()));
   return name;
 }
 
@@ -190,10 +185,10 @@ void CPDF_PageContentGenerator::ProcessImage(std::ostringstream* buf,
   if (bWasInline)
     pImage->ConvertStreamToIndirectObject();
 
-  uint32_t dwObjNum = pStream->GetObjNum();
-  ByteString name = RealizeResource(dwObjNum, "XObject");
+  ByteString name = RealizeResource(pStream, "XObject");
   if (bWasInline)
-    pImageObj->SetImage(m_pDocument->GetPageData()->GetImage(dwObjNum));
+    pImageObj->SetImage(
+        m_pDocument->GetPageData()->GetImage(pStream->GetObjNum()));
 
   *buf << "/" << PDF_NameEncode(name) << " Do Q\n";
 }
@@ -323,8 +318,7 @@ void CPDF_PageContentGenerator::ProcessGraphics(std::ostringstream* buf,
                                    pPageObj->m_GeneralState.GetBlendMode());
     }
     CPDF_Object* pDict = m_pDocument->AddIndirectObject(std::move(gsDict));
-    uint32_t dwObjNum = pDict->GetObjNum();
-    name = RealizeResource(dwObjNum, "ExtGState");
+    name = RealizeResource(pDict, "ExtGState");
     m_pObjHolder->m_GraphicsMap[graphD] = name;
   }
   *buf << "/" << PDF_NameEncode(name) << " gs ";
@@ -349,8 +343,7 @@ void CPDF_PageContentGenerator::ProcessDefaultGraphics(
     gsDict->SetNewFor<CPDF_Number>("CA", defaultGraphics.strokeAlpha);
     gsDict->SetNewFor<CPDF_Name>("BM", "Normal");
     CPDF_Object* pDict = m_pDocument->AddIndirectObject(std::move(gsDict));
-    uint32_t dwObjNum = pDict->GetObjNum();
-    name = RealizeResource(dwObjNum, "ExtGState");
+    name = RealizeResource(pDict, "ExtGState");
     m_pObjHolder->m_GraphicsMap[defaultGraphics] = name;
   }
   *buf << "/" << PDF_NameEncode(name).c_str() << " gs ";
@@ -382,17 +375,16 @@ void CPDF_PageContentGenerator::ProcessText(std::ostringstream* buf,
   if (it != m_pObjHolder->m_FontsMap.end()) {
     dictName = it->second;
   } else {
-    uint32_t dwObjNum = pFont->GetFontDict()->GetObjNum();
-    if (!dwObjNum) {
+    CPDF_Object* pIndirectFont = pFont->GetFontDict();
+    if (pIndirectFont->IsInline()) {
       // In this case we assume it must be a standard font
       auto fontDict = pdfium::MakeUnique<CPDF_Dictionary>();
       fontDict->SetNewFor<CPDF_Name>("Type", "Font");
       fontDict->SetNewFor<CPDF_Name>("Subtype", fontD.type);
       fontDict->SetNewFor<CPDF_Name>("BaseFont", fontD.baseFont);
-      CPDF_Object* pDict = m_pDocument->AddIndirectObject(std::move(fontDict));
-      dwObjNum = pDict->GetObjNum();
+      pIndirectFont = m_pDocument->AddIndirectObject(std::move(fontDict));
     }
-    dictName = RealizeResource(dwObjNum, "Font");
+    dictName = RealizeResource(pIndirectFont, "Font");
     m_pObjHolder->m_FontsMap[fontD] = dictName;
   }
   *buf << "/" << PDF_NameEncode(dictName) << " " << pTextObj->GetFontSize()
diff --git a/core/fpdfapi/edit/cpdf_pagecontentgenerator.h b/core/fpdfapi/edit/cpdf_pagecontentgenerator.h
index efc5739c4b..a6cf215734 100644
--- a/core/fpdfapi/edit/cpdf_pagecontentgenerator.h
+++ b/core/fpdfapi/edit/cpdf_pagecontentgenerator.h
@@ -16,6 +16,7 @@
 
 class CPDF_Document;
 class CPDF_ImageObject;
+class CPDF_Object;
 class CPDF_PageObject;
 class CPDF_PageObjectHolder;
 class CPDF_PathObject;
@@ -37,7 +38,7 @@ class CPDF_PageContentGenerator {
   void ProcessGraphics(std::ostringstream* buf, CPDF_PageObject* pPageObj);
   void ProcessDefaultGraphics(std::ostringstream* buf);
   void ProcessText(std::ostringstream* buf, CPDF_TextObject* pTextObj);
-  ByteString RealizeResource(uint32_t dwResourceObjNum,
+  ByteString RealizeResource(const CPDF_Object* pResource,
                              const ByteString& bsType);
 
   UnownedPtr<CPDF_PageObjectHolder> const m_pObjHolder;
diff --git a/core/fpdfapi/edit/cpdf_pagecontentgenerator_unittest.cpp b/core/fpdfapi/edit/cpdf_pagecontentgenerator_unittest.cpp
index 5d9e029267..354aa672fb 100644
--- a/core/fpdfapi/edit/cpdf_pagecontentgenerator_unittest.cpp
+++ b/core/fpdfapi/edit/cpdf_pagecontentgenerator_unittest.cpp
@@ -247,8 +247,7 @@ TEST_F(CPDF_PageContentGeneratorTest, ProcessText) {
     CPDF_Dictionary* pDesc = pDoc->NewIndirect<CPDF_Dictionary>();
     pDesc->SetNewFor<CPDF_Name>("Type", "FontDescriptor");
     pDesc->SetNewFor<CPDF_Name>("FontName", pFont->GetBaseFont());
-    pDict->SetNewFor<CPDF_Reference>("FontDescriptor", pDoc.get(),
-                                     pDesc->GetObjNum());
+    pDict->SetFor("FontDescriptor", pDesc->MakeReference(pDoc.get()));
 
     CPDF_Font* loadedFont = pDoc->LoadFont(pDict);
     pTextObj->m_TextState.SetFont(loadedFont);
diff --git a/core/fpdfapi/page/cpdf_image.cpp b/core/fpdfapi/page/cpdf_image.cpp
index 8720342d35..a8b593682b 100644
--- a/core/fpdfapi/page/cpdf_image.cpp
+++ b/core/fpdfapi/page/cpdf_image.cpp
@@ -238,9 +238,8 @@ void CPDF_Image::SetImage(const RetainPtr<CFX_DIBitmap>& pBitmap) {
           pdfium::MakeUnique<CPDF_Dictionary>(m_pDocument->GetByteStringPool());
       CPDF_Stream* pCTS = m_pDocument->NewIndirect<CPDF_Stream>(
           std::move(pColorTable), iPalette * 3, std::move(pNewDict));
-      pCS->AddNew<CPDF_Reference>(m_pDocument.Get(), pCTS->GetObjNum());
-      pDict->SetNewFor<CPDF_Reference>("ColorSpace", m_pDocument.Get(),
-                                       pCS->GetObjNum());
+      pCS->Add(pCTS->MakeReference(m_pDocument.Get()));
+      pDict->SetFor("ColorSpace", pCS->MakeReference(m_pDocument.Get()));
     } else {
       pDict->SetNewFor<CPDF_Name>("ColorSpace", "DeviceGray");
     }
@@ -281,8 +280,7 @@ void CPDF_Image::SetImage(const RetainPtr<CFX_DIBitmap>& pBitmap) {
     pMaskDict->SetNewFor<CPDF_Number>("Length", mask_size);
     CPDF_Stream* pNewStream = m_pDocument->NewIndirect<CPDF_Stream>(
         std::move(mask_buf), mask_size, std::move(pMaskDict));
-    pDict->SetNewFor<CPDF_Reference>("SMask", m_pDocument.Get(),
-                                     pNewStream->GetObjNum());
+    pDict->SetFor("SMask", pNewStream->MakeReference(m_pDocument.Get()));
   }
 
   uint8_t* src_buf = pBitmap->GetBuffer();
diff --git a/core/fpdfapi/page/cpdf_streamcontentparser.cpp b/core/fpdfapi/page/cpdf_streamcontentparser.cpp
index 7e7c337d96..7562fb37a6 100644
--- a/core/fpdfapi/page/cpdf_streamcontentparser.cpp
+++ b/core/fpdfapi/page/cpdf_streamcontentparser.cpp
@@ -630,9 +630,8 @@ void CPDF_StreamContentParser::Handle_BeginImage() {
     ByteString key(word.Right(word.GetLength() - 1));
     auto pObj = m_pSyntax->ReadNextObject(false, false, 0);
     if (!key.IsEmpty()) {
-      uint32_t dwObjNum = pObj ? pObj->GetObjNum() : 0;
-      if (dwObjNum)
-        pDict->SetNewFor<CPDF_Reference>(key, m_pDocument.Get(), dwObjNum);
+      if (pObj && !pObj->IsInline())
+        pDict->SetFor(key, pObj->MakeReference(m_pDocument.Get()));
       else
         pDict->SetFor(key, std::move(pObj));
     }
diff --git a/core/fpdfapi/parser/cpdf_array.cpp b/core/fpdfapi/parser/cpdf_array.cpp
index a5361fbbb9..d53476d1c2 100644
--- a/core/fpdfapi/parser/cpdf_array.cpp
+++ b/core/fpdfapi/parser/cpdf_array.cpp
@@ -191,7 +191,7 @@ void CPDF_Array::ConvertToIndirectObjectAt(size_t i,
     return;
 
   CPDF_Object* pNew = pHolder->AddIndirectObject(std::move(m_Objects[i]));
-  m_Objects[i] = pdfium::MakeUnique<CPDF_Reference>(pHolder, pNew->GetObjNum());
+  m_Objects[i] = pNew->MakeReference(pHolder);
 }
 
 CPDF_Object* CPDF_Array::SetAt(size_t i, std::unique_ptr<CPDF_Object> pObj) {
diff --git a/core/fpdfapi/parser/cpdf_dictionary.cpp b/core/fpdfapi/parser/cpdf_dictionary.cpp
index c6127fa344..071461b756 100644
--- a/core/fpdfapi/parser/cpdf_dictionary.cpp
+++ b/core/fpdfapi/parser/cpdf_dictionary.cpp
@@ -224,7 +224,7 @@ void CPDF_Dictionary::ConvertToIndirectObjectFor(
     return;
 
   CPDF_Object* pObj = pHolder->AddIndirectObject(std::move(it->second));
-  it->second = pdfium::MakeUnique<CPDF_Reference>(pHolder, pObj->GetObjNum());
+  it->second = pObj->MakeReference(pHolder);
 }
 
 std::unique_ptr<CPDF_Object> CPDF_Dictionary::RemoveFor(const ByteString& key) {
diff --git a/core/fpdfapi/parser/cpdf_document.cpp b/core/fpdfapi/parser/cpdf_document.cpp
index 59927bc250..b163cafbbb 100644
--- a/core/fpdfapi/parser/cpdf_document.cpp
+++ b/core/fpdfapi/parser/cpdf_document.cpp
@@ -513,7 +513,7 @@ void CPDF_Document::CreateNewDoc() {
   pPages->SetNewFor<CPDF_Name>("Type", "Pages");
   pPages->SetNewFor<CPDF_Number>("Count", 0);
   pPages->SetNewFor<CPDF_Array>("Kids");
-  m_pRootDict->SetNewFor<CPDF_Reference>("Pages", this, pPages->GetObjNum());
+  m_pRootDict->SetFor("Pages", pPages->MakeReference(this));
   m_pInfoDict = NewIndirect<CPDF_Dictionary>();
 }
 
@@ -545,9 +545,8 @@ bool CPDF_Document::InsertDeletePDFPage(CPDF_Dictionary* pPages,
         continue;
       }
       if (bInsert) {
-        pKidList->InsertNewAt<CPDF_Reference>(i, this, pPageDict->GetObjNum());
-        pPageDict->SetNewFor<CPDF_Reference>("Parent", this,
-                                             pPages->GetObjNum());
+        pKidList->InsertAt(i, pPageDict->MakeReference(this));
+        pPageDict->SetFor("Parent", pPages->MakeReference(this));
       } else {
         pKidList->RemoveAt(i);
       }
@@ -589,9 +588,9 @@ bool CPDF_Document::InsertNewPage(int iPage, CPDF_Dictionary* pPageDict) {
     CPDF_Array* pPagesList = pPages->GetArrayFor("Kids");
     if (!pPagesList)
       pPagesList = pPages->SetNewFor<CPDF_Array>("Kids");
-    pPagesList->AddNew<CPDF_Reference>(this, pPageDict->GetObjNum());
+    pPagesList->Add(pPageDict->MakeReference(this));
     pPages->SetNewFor<CPDF_Number>("Count", nPages + 1);
-    pPageDict->SetNewFor<CPDF_Reference>("Parent", this, pPages->GetObjNum());
+    pPageDict->SetFor("Parent", pPages->MakeReference(this));
     ResetTraversal();
   } else {
     std::set<CPDF_Dictionary*> stack = {pPages};
@@ -647,8 +646,7 @@ size_t CPDF_Document::CalculateEncodingDict(int charset,
     ByteString name = PDF_AdobeNameFromUnicode(pUnicodes[j]);
     pArray->AddNew<CPDF_Name>(name.IsEmpty() ? ".notdef" : name);
   }
-  pBaseDict->SetNewFor<CPDF_Reference>("Encoding", this,
-                                       pEncodingDict->GetObjNum());
+  pBaseDict->SetFor("Encoding", pEncodingDict->MakeReference(this));
   return i;
 }
 
@@ -715,7 +713,7 @@ CPDF_Dictionary* CPDF_Document::ProcessbCJK(
   pCIDSysInfo->SetNewFor<CPDF_Number>("Supplement", supplement);
 
   CPDF_Array* pArray = pBaseDict->SetNewFor<CPDF_Array>("DescendantFonts");
-  pArray->AddNew<CPDF_Reference>(this, pFontDict->GetObjNum());
+  pArray->Add(pFontDict->MakeReference(this));
   return pFontDict;
 }
 
@@ -796,8 +794,7 @@ CPDF_Font* CPDF_Document::AddFont(CFX_Font* pFont, int charset, bool bVert) {
   CPDF_Dictionary* pFontDesc = ToDictionary(AddIndirectObject(
       CalculateFontDesc(this, basefont, flags, italicangle, pFont->GetAscent(),
                         pFont->GetDescent(), std::move(pBBox), nStemV)));
-  pFontDict->SetNewFor<CPDF_Reference>("FontDescriptor", this,
-                                       pFontDesc->GetObjNum());
+  pFontDict->SetFor("FontDescriptor", pFontDesc->MakeReference(this));
   return LoadFont(pBaseDict);
 }
 
@@ -889,9 +886,9 @@ CPDF_Font* CPDF_Document::AddWindowsFont(LOGFONTA* pLogFont,
       CalculateFontDesc(this, basefont, flags, italicangle, ascend, descend,
                         std::move(pBBox), pLogFont->lfWeight / 5);
   pFontDesc->SetNewFor<CPDF_Number>("CapHeight", capheight);
-  pFontDict->SetNewFor<CPDF_Reference>(
-      "FontDescriptor", this,
-      AddIndirectObject(std::move(pFontDesc))->GetObjNum());
+  pFontDict->SetFor(
+      "FontDescriptor",
+      AddIndirectObject(std::move(pFontDesc))->MakeReference(this));
   hFont = SelectObject(hDC, hFont);
   DeleteObject(hFont);
   DeleteDC(hDC);
diff --git a/core/fpdfapi/parser/cpdf_object.cpp b/core/fpdfapi/parser/cpdf_object.cpp
index 8190d3429f..6fedd25242 100644
--- a/core/fpdfapi/parser/cpdf_object.cpp
+++ b/core/fpdfapi/parser/cpdf_object.cpp
@@ -12,6 +12,7 @@
 #include "core/fpdfapi/parser/cpdf_dictionary.h"
 #include "core/fpdfapi/parser/cpdf_indirect_object_holder.h"
 #include "core/fpdfapi/parser/cpdf_parser.h"
+#include "core/fpdfapi/parser/cpdf_reference.h"
 #include "core/fpdfapi/parser/fpdf_parser_decode.h"
 #include "core/fxcrt/fx_string.h"
 #include "third_party/base/logging.h"
@@ -170,3 +171,12 @@ CPDF_String* CPDF_Object::AsString() {
 const CPDF_String* CPDF_Object::AsString() const {
   return nullptr;
 }
+
+std::unique_ptr<CPDF_Object> CPDF_Object::MakeReference(
+    CPDF_IndirectObjectHolder* holder) const {
+  if (IsInline()) {
+    NOTREACHED();
+    return nullptr;
+  }
+  return pdfium::MakeUnique<CPDF_Reference>(holder, GetObjNum());
+}
diff --git a/core/fpdfapi/parser/cpdf_object.h b/core/fpdfapi/parser/cpdf_object.h
index 21eec62b0d..5ff028e9e0 100644
--- a/core/fpdfapi/parser/cpdf_object.h
+++ b/core/fpdfapi/parser/cpdf_object.h
@@ -17,6 +17,7 @@
 class CPDF_Array;
 class CPDF_Boolean;
 class CPDF_Dictionary;
+class CPDF_IndirectObjectHolder;
 class CPDF_Name;
 class CPDF_Null;
 class CPDF_Number;
@@ -106,6 +107,11 @@ class CPDF_Object {
       bool bDirect,
       std::set<const CPDF_Object*>* pVisited) const;
 
+  // Return a reference to itself.
+  // The object must be direct (!IsInlined).
+  virtual std::unique_ptr<CPDF_Object> MakeReference(
+      CPDF_IndirectObjectHolder* holder) const;
+
  protected:
   CPDF_Object() : m_ObjNum(0), m_GenNum(0) {}
 
diff --git a/core/fpdfapi/parser/cpdf_object_unittest.cpp b/core/fpdfapi/parser/cpdf_object_unittest.cpp
index 856dd0ac3b..78a0af7299 100644
--- a/core/fpdfapi/parser/cpdf_object_unittest.cpp
+++ b/core/fpdfapi/parser/cpdf_object_unittest.cpp
@@ -393,6 +393,18 @@ TEST_F(PDFObjectsTest, IsTypeAndAsType) {
   }
 }
 
+TEST_F(PDFObjectsTest, MakeReferenceGeneric) {
+  auto original_obj = pdfium::MakeUnique<CPDF_Null>();
+  original_obj->SetObjNum(42);
+  ASSERT_FALSE(original_obj->IsInline());
+
+  auto ref_obj = original_obj->MakeReference(m_ObjHolder.get());
+
+  ASSERT_TRUE(ref_obj->IsReference());
+  EXPECT_EQ(original_obj->GetObjNum(),
+            ToReference(ref_obj.get())->GetRefObjNum());
+}
+
 TEST(PDFArrayTest, GetMatrix) {
   float elems[][6] = {{0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f},
                       {1, 2, 3, 4, 5, 6},
@@ -971,3 +983,18 @@ TEST(PDFDictionaryTest, ExtractObjectOnRemove) {
   extracted_object = dict->RemoveFor("non_exists_object");
   EXPECT_FALSE(extracted_object);
 }
+
+TEST(PDFRefernceTest, MakeReferenceToReference) {
+  auto obj_holder = pdfium::MakeUnique<CPDF_IndirectObjectHolder>();
+  auto original_ref = pdfium::MakeUnique<CPDF_Reference>(obj_holder.get(), 42);
+  original_ref->SetObjNum(1952);
+  ASSERT_FALSE(original_ref->IsInline());
+
+  auto ref_obj = original_ref->MakeReference(obj_holder.get());
+
+  ASSERT_TRUE(ref_obj->IsReference());
+  // We do not allow reference to reference.
+  // New reference should have same RefObjNum.
+  EXPECT_EQ(original_ref->GetRefObjNum(),
+            ToReference(ref_obj.get())->GetRefObjNum());
+}
diff --git a/core/fpdfapi/parser/cpdf_reference.cpp b/core/fpdfapi/parser/cpdf_reference.cpp
index 3f45a96c6b..0f3b7627d6 100644
--- a/core/fpdfapi/parser/cpdf_reference.cpp
+++ b/core/fpdfapi/parser/cpdf_reference.cpp
@@ -103,3 +103,11 @@ bool CPDF_Reference::WriteTo(IFX_ArchiveStream* archive) const {
   return archive->WriteString(" ") && archive->WriteDWord(GetRefObjNum()) &&
          archive->WriteString(" 0 R ");
 }
+
+std::unique_ptr<CPDF_Object> CPDF_Reference::MakeReference(
+    CPDF_IndirectObjectHolder* holder) const {
+  ASSERT(holder == m_pObjList.Get());
+  // Do not allow reference to reference, just create other reference for same
+  // object.
+  return pdfium::MakeUnique<CPDF_Reference>(holder, GetRefObjNum());
+}
diff --git a/core/fpdfapi/parser/cpdf_reference.h b/core/fpdfapi/parser/cpdf_reference.h
index 4cfb5c26e3..d1e0a07e4b 100644
--- a/core/fpdfapi/parser/cpdf_reference.h
+++ b/core/fpdfapi/parser/cpdf_reference.h
@@ -34,6 +34,8 @@ class CPDF_Reference : public CPDF_Object {
   CPDF_Reference* AsReference() override;
   const CPDF_Reference* AsReference() const override;
   bool WriteTo(IFX_ArchiveStream* archive) const override;
+  std::unique_ptr<CPDF_Object> MakeReference(
+      CPDF_IndirectObjectHolder* holder) const override;
 
   CPDF_IndirectObjectHolder* GetObjList() const { return m_pObjList.Get(); }
   uint32_t GetRefObjNum() const { return m_RefObjNum; }