Fix loading page using hint tables.

When linearized document have hint table,
The FPDFAvail_IsPageAvail return true,
but FPDF_LoadPage return nullptr, for non first pages.

This happens, bacause document not use hint tables, to load page.
To fix this, I force save the page's ObjNum in document.

This is restoring of original fix:
https://codereview.chromium.org/2437773003/

Review-Url: https://codereview.chromium.org/2444903002

2 files changed, 65 insertions, 31 deletions

diff --git a/core/fpdfapi/parser/cpdf_data_avail.cpp b/core/fpdfapi/parser/cpdf_data_avail.cpp
index c6a434be5d..318f2cf54d 100644
--- a/core/fpdfapi/parser/cpdf_data_avail.cpp
+++ b/core/fpdfapi/parser/cpdf_data_avail.cpp
@@ -1626,7 +1626,7 @@ CPDF_DataAvail::DocAvailStatus CPDF_DataAvail::IsPageAvail(
       if (nResult != DataAvailable)
         return nResult;
       m_pagesLoadState.insert(dwPage);
-      return DataAvailable;
+      return GetPage(dwPage) ? DataAvailable : DataError;
     }
 
     if (m_bMainXRefLoadedOK) {
@@ -1751,31 +1751,33 @@ int CPDF_DataAvail::GetPageCount() const {
 CPDF_Dictionary* CPDF_DataAvail::GetPage(int index) {
   if (!m_pDocument || index < 0 || index >= GetPageCount())
     return nullptr;
+  CPDF_Dictionary* page = m_pDocument->GetPage(index);
+  if (page)
+    return page;
+  if (!m_pLinearized || !m_pHintTables)
+    return nullptr;
 
-  if (m_pLinearized) {
-    CPDF_Dictionary* pDict = m_pLinearized->GetDict();
-    CPDF_Object* pObj = pDict ? pDict->GetDirectObjectFor("P") : nullptr;
-
-    int pageNum = pObj ? pObj->GetInteger() : 0;
-    if (m_pHintTables && index != pageNum) {
-      FX_FILESIZE szPageStartPos = 0;
-      FX_FILESIZE szPageLength = 0;
-      uint32_t dwObjNum = 0;
-      bool bPagePosGot = m_pHintTables->GetPagePos(index, &szPageStartPos,
-                                                   &szPageLength, &dwObjNum);
-      if (!bPagePosGot)
-        return nullptr;
-
-      m_syntaxParser.InitParser(m_pFileRead, (uint32_t)szPageStartPos);
-      CPDF_Object* pPageDict = ParseIndirectObjectAt(0, dwObjNum, m_pDocument);
-      if (!pPageDict)
-        return nullptr;
-
-      if (!m_pDocument->ReplaceIndirectObjectIfHigherGeneration(dwObjNum,
-                                                                pPageDict)) {
-        return nullptr;
-      }
-      return pPageDict->GetDict();
+  CPDF_Dictionary* pDict = m_pLinearized->GetDict();
+  CPDF_Object* pObj = pDict ? pDict->GetDirectObjectFor("P") : nullptr;
+  int firstPageNum = pObj ? pObj->GetInteger() : 0;
+  if (index == firstPageNum)
+    return nullptr;
+  FX_FILESIZE szPageStartPos = 0;
+  FX_FILESIZE szPageLength = 0;
+  uint32_t dwObjNum = 0;
+  const bool bPagePosGot = m_pHintTables->GetPagePos(index, &szPageStartPos,
+                                                     &szPageLength, &dwObjNum);
+  if (!bPagePosGot || !dwObjNum)
+    return nullptr;
+  // We should say to the document, which object is the page.
+  m_pDocument->SetPageObjNum(index, dwObjNum);
+  // Page object already can be parsed in document.
+  CPDF_Object* pPageDict = m_pDocument->GetIndirectObject(dwObjNum);
+  if (!pPageDict) {
+    m_syntaxParser.InitParser(m_pFileRead, (uint32_t)szPageStartPos);
+    pPageDict = ParseIndirectObjectAt(0, dwObjNum, m_pDocument);
+    if (pPageDict) {
+      m_pDocument->ReplaceIndirectObjectIfHigherGeneration(dwObjNum, pPageDict);
     }
   }
   return m_pDocument->GetPage(index);
diff --git a/core/fpdfapi/parser/cpdf_document_unittest.cpp b/core/fpdfapi/parser/cpdf_document_unittest.cpp
index 799ecc694e..9336626f45 100644
--- a/core/fpdfapi/parser/cpdf_document_unittest.cpp
+++ b/core/fpdfapi/parser/cpdf_document_unittest.cpp
@@ -15,6 +15,9 @@
 
 namespace {
 
+using ScopedDictionary =
+    std::unique_ptr<CPDF_Dictionary, ReleaseDeleter<CPDF_Dictionary>>;
+
 CPDF_Dictionary* CreatePageTreeNode(CPDF_Array* kids,
                                     CPDF_Document* pDoc,
                                     int count) {
@@ -35,13 +38,9 @@ CPDF_Dictionary* CreateNumberedPage(size_t number) {
   return page;
 }
 
-}  // namespace
-
 class CPDF_TestDocumentForPages : public CPDF_Document {
  public:
   CPDF_TestDocumentForPages() : CPDF_Document(nullptr) {
-    CPDF_ModuleMgr* module_mgr = CPDF_ModuleMgr::Get();
-    module_mgr->InitPageModule();
     // Set up test
     CPDF_Array* zeroToTwo = new CPDF_Array();
     zeroToTwo->AddReference(this, AddIndirectObject(CreateNumberedPage(0)));
@@ -80,8 +79,18 @@ class CPDF_TestDocumentForPages : public CPDF_Document {
   std::unique_ptr<CPDF_Dictionary, ReleaseDeleter<CPDF_Dictionary>>
       m_pOwnedRootDict;
 };
+}  // namespace
+
+class cpdf_document_test : public testing::Test {
+ public:
+  void SetUp() override {
+    CPDF_ModuleMgr* module_mgr = CPDF_ModuleMgr::Get();
+    module_mgr->InitPageModule();
+  }
+  void TearDown() override {}
+};
 
-TEST(cpdf_document, GetPages) {
+TEST_F(cpdf_document_test, GetPages) {
   std::unique_ptr<CPDF_TestDocumentForPages> document =
       pdfium::MakeUnique<CPDF_TestDocumentForPages>();
   for (int i = 0; i < 7; i++) {
@@ -94,7 +103,7 @@ TEST(cpdf_document, GetPages) {
   EXPECT_FALSE(page);
 }
 
-TEST(cpdf_document, GetPagesReverseOrder) {
+TEST_F(cpdf_document_test, GetPagesReverseOrder) {
   std::unique_ptr<CPDF_TestDocumentForPages> document =
       pdfium::MakeUnique<CPDF_TestDocumentForPages>();
   for (int i = 6; i >= 0; i--) {
@@ -106,3 +115,26 @@ TEST(cpdf_document, GetPagesReverseOrder) {
   CPDF_Dictionary* page = document->GetPage(7);
   EXPECT_FALSE(page);
 }
+
+TEST_F(cpdf_document_test, UseCachedPageObjNumIfHaveNotPagesDict) {
+  // ObjNum can be added in CPDF_DataAvail::IsPageAvail, and PagesDict
+  // can be not exists in this case.
+  // (case, when hint table is used to page check in CPDF_DataAvail).
+  CPDF_Document document(pdfium::MakeUnique<CPDF_Parser>());
+  ScopedDictionary dict(new CPDF_Dictionary());
+  const int page_count = 100;
+  dict->SetIntegerFor("N", page_count);
+  document.LoadLinearizedDoc(dict.get());
+  ASSERT_EQ(page_count, document.GetPageCount());
+  CPDF_Object* page_stub = new CPDF_Dictionary();
+  const uint32_t obj_num = document.AddIndirectObject(page_stub);
+  const int test_page_num = 33;
+
+  EXPECT_FALSE(document.IsPageLoaded(test_page_num));
+  EXPECT_EQ(nullptr, document.GetPage(test_page_num));
+
+  document.SetPageObjNum(test_page_num, obj_num);
+
+  EXPECT_TRUE(document.IsPageLoaded(test_page_num));
+  EXPECT_EQ(page_stub, document.GetPage(test_page_num));
+}