From c0a47773d6dadeb8a39a6ced4ebbb1795e2e411f Mon Sep 17 00:00:00 2001
From: art-snake <art-snake@yandex-team.ru>
Date: Wed, 9 Nov 2016 15:20:59 -0800
Subject: Fix receiving page, if it have not obj num.

In some PDF's the page may not have the obj num.
For example: testing\corpus\fx\other\jetman_std.pdf in pdfium repository.
And CPDF_Document::GetPage failed on second call for this page.

Restart the traversing of pages, to fix this

Also added test.

Review-Url: https://codereview.chromium.org/2491583002
---
 core/fpdfapi/parser/cpdf_document.cpp          | 11 ++++++++-
 core/fpdfapi/parser/cpdf_document_unittest.cpp | 33 ++++++++++++++++++++++++++
 2 files changed, 43 insertions(+), 1 deletion(-)

diff --git a/core/fpdfapi/parser/cpdf_document.cpp b/core/fpdfapi/parser/cpdf_document.cpp
index 1c73ce1015..6788394118 100644
--- a/core/fpdfapi/parser/cpdf_document.cpp
+++ b/core/fpdfapi/parser/cpdf_document.cpp
@@ -492,9 +492,18 @@ CPDF_Dictionary* CPDF_Document::GetPage(int iPage) {
   if (!pPages)
     return nullptr;
 
+  if (iPage - m_iNextPageToTraverse + 1 <= 0) {
+    // This can happen when the page does not have an object number. On repeated
+    // calls to this function for the same page index, this condition causes
+    // TraversePDFPages() to incorrectly return nullptr.
+    // Example "testing/corpus/fx/other/jetman_std.pdf"
+    // We should restart traversing in this case.
+    // TODO(art-snake): optimize this.
+    ResetTraversal();
+  }
+  int nPagesToGo = iPage - m_iNextPageToTraverse + 1;
   if (m_pTreeTraversal.empty())
     m_pTreeTraversal.push_back(std::make_pair(pPages, 0));
-  int nPagesToGo = iPage - m_iNextPageToTraverse + 1;
   CPDF_Dictionary* pPage = TraversePDFPages(iPage, &nPagesToGo, 0);
   m_iNextPageToTraverse = iPage + 1;
   return pPage;
diff --git a/core/fpdfapi/parser/cpdf_document_unittest.cpp b/core/fpdfapi/parser/cpdf_document_unittest.cpp
index 7b5ab43b5c..f27e7403f6 100644
--- a/core/fpdfapi/parser/cpdf_document_unittest.cpp
+++ b/core/fpdfapi/parser/cpdf_document_unittest.cpp
@@ -76,6 +76,27 @@ class CPDF_TestDocumentForPages : public CPDF_Document {
   std::unique_ptr<CPDF_Dictionary> m_pOwnedRootDict;
 };
 
+class CPDF_TestDocumentWithPageWithoutPageNum : public CPDF_Document {
+ public:
+  CPDF_TestDocumentWithPageWithoutPageNum() : CPDF_Document(nullptr) {
+    // Set up test
+    CPDF_Array* allPages = new CPDF_Array();
+    allPages->AddReference(this, AddIndirectObject(CreateNumberedPage(0)));
+    allPages->AddReference(this, AddIndirectObject(CreateNumberedPage(1)));
+    // Page without pageNum.
+    allPages->Add(CreateNumberedPage(2));
+    CPDF_Dictionary* pagesDict = CreatePageTreeNode(allPages, this, 3);
+
+    m_pOwnedRootDict.reset(new CPDF_Dictionary());
+    m_pOwnedRootDict->SetReferenceFor("Pages", this, pagesDict->GetObjNum());
+    m_pRootDict = m_pOwnedRootDict.get();
+    m_PageList.SetSize(3);
+  }
+
+ private:
+  std::unique_ptr<CPDF_Dictionary> m_pOwnedRootDict;
+};
+
 class TestLinearized : public CPDF_LinearizedHeader {
  public:
   explicit TestLinearized(CPDF_Dictionary* dict)
@@ -105,6 +126,18 @@ TEST_F(cpdf_document_test, GetPages) {
   EXPECT_FALSE(page);
 }
 
+TEST_F(cpdf_document_test, GetPageWithoutObjNumTwice) {
+  std::unique_ptr<CPDF_TestDocumentWithPageWithoutPageNum> document =
+      pdfium::MakeUnique<CPDF_TestDocumentWithPageWithoutPageNum>();
+  const CPDF_Dictionary* page = document->GetPage(2);
+  ASSERT_TRUE(page);
+  // This is page without obj num.
+  ASSERT_EQ(0ul, page->GetObjNum());
+  const CPDF_Dictionary* second_call_page = document->GetPage(2);
+  EXPECT_TRUE(second_call_page);
+  EXPECT_EQ(page, second_call_page);
+}
+
 TEST_F(cpdf_document_test, GetPagesReverseOrder) {
   std::unique_ptr<CPDF_TestDocumentForPages> document =
       pdfium::MakeUnique<CPDF_TestDocumentForPages>();
-- 
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