Add a simple check for V4 cross reference table

Some unknown software generates cross reference table with the
claimed object numbers are all off by one. Add a simple verification
function to detect this scenario, thus have a chance to rebuild
the correct cross reference table.

To avoid unnecessary checks and potiential performance hit, we only
check for the very first non free entry.

BUG=602650

Review URL: https://codereview.chromium.org/1910063004

1 files changed, 16 insertions, 0 deletions

diff --git a/core/fpdfapi/fpdf_parser/cpdf_parser_embeddertest.cpp b/core/fpdfapi/fpdf_parser/cpdf_parser_embeddertest.cpp
index f427ec5d81..042b221554 100644
--- a/core/fpdfapi/fpdf_parser/cpdf_parser_embeddertest.cpp
+++ b/core/fpdfapi/fpdf_parser/cpdf_parser_embeddertest.cpp
@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#include "public/fpdf_text.h"
 #include "testing/embedder_test.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
@@ -38,3 +39,18 @@ TEST_F(CPDFParserEmbeddertest, Bug_325) {
   EXPECT_FALSE(OpenDocument("bug_325_a.pdf"));
   EXPECT_FALSE(OpenDocument("bug_325_b.pdf"));
 }
+
+TEST_F(CPDFParserEmbeddertest, Bug_602650) {
+  // Test the case that cross reference entries, which are well formed,
+  // but do not match with the objects.
+  EXPECT_TRUE(OpenDocument("bug_602650.pdf"));
+  FPDF_PAGE page = LoadPage(0);
+  EXPECT_NE(nullptr, page);
+  FPDF_TEXTPAGE text_page = FPDFText_LoadPage(page);
+  EXPECT_NE(nullptr, text_page);
+  // The page should not be blank.
+  EXPECT_LT(0, FPDFText_CountChars(text_page));
+
+  FPDFText_ClosePage(text_page);
+  UnloadPage(page);
+}