Allow zero length streams when parsing.chromium/3130

It's possible to create a stream of length 0 in a PDF document.
Currently the code will early exit and return a nullptr. This causes
issues when you want to print the given PDF as the FPDF_ImportPages code
ends up only generating up to the zero length object.

This CL allows creating streams with length 0 and updates the PDF saving
code to output a blank stream.

Bug: chromium:732380
Change-Id: I44182ba4aaac7c51284b002ba01bbc34b6bcf9e0
Reviewed-on: https://pdfium-review.googlesource.com/6490
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: dsinclair <dsinclair@chromium.org>

1 files changed, 37 insertions, 3 deletions

diff --git a/fpdfsdk/fpdfppo_embeddertest.cpp b/fpdfsdk/fpdfppo_embeddertest.cpp
index db39700ca1..7e6ff33fc3 100644
--- a/fpdfsdk/fpdfppo_embeddertest.cpp
+++ b/fpdfsdk/fpdfppo_embeddertest.cpp
@@ -1,11 +1,11 @@
 // Copyright 2016 PDFium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
-
-#include "public/fpdf_ppo.h"
+#include <string>
 
 #include "core/fxcrt/fx_basic.h"
 #include "public/fpdf_edit.h"
+#include "public/fpdf_ppo.h"
 #include "public/fpdfview.h"
 #include "testing/embedder_test.h"
 #include "testing/gtest/include/gtest/gtest.h"
@@ -131,7 +131,7 @@ TEST_F(FPDFPPOEmbeddertest, BUG_664284) {
   EXPECT_TRUE(OpenDocument("bug_664284.pdf"));
 
   FPDF_PAGE page = LoadPage(0);
-  EXPECT_TRUE(page);
+  ASSERT_NE(nullptr, page);
 
   FPDF_DOCUMENT output_doc = FPDF_CreateNewDocument();
   EXPECT_TRUE(output_doc);
@@ -140,3 +140,37 @@ TEST_F(FPDFPPOEmbeddertest, BUG_664284) {
 
   UnloadPage(page);
 }
+
+TEST_F(FPDFPPOEmbeddertest, ImportWithZeroLengthStream) {
+  EXPECT_TRUE(OpenDocument("zero_length_stream.pdf"));
+  FPDF_PAGE page = LoadPage(0);
+  ASSERT_NE(nullptr, page);
+
+  FPDF_BITMAP bitmap = RenderPage(page);
+  ASSERT_EQ(200, FPDFBitmap_GetWidth(bitmap));
+  ASSERT_EQ(200, FPDFBitmap_GetHeight(bitmap));
+  ASSERT_EQ(800, FPDFBitmap_GetStride(bitmap));
+
+  std::string digest = HashBitmap(bitmap, 200, 200);
+  FPDFBitmap_Destroy(bitmap);
+  FPDF_ClosePage(page);
+
+  FPDF_DOCUMENT new_doc = FPDF_CreateNewDocument();
+  EXPECT_TRUE(new_doc);
+  EXPECT_TRUE(FPDF_ImportPages(new_doc, document(), "1", 0));
+
+  EXPECT_EQ(1, FPDF_GetPageCount(new_doc));
+  FPDF_PAGE new_page = FPDF_LoadPage(new_doc, 0);
+  ASSERT_NE(nullptr, new_page);
+  FPDF_BITMAP new_bitmap = RenderPage(new_page);
+  ASSERT_EQ(200, FPDFBitmap_GetWidth(new_bitmap));
+  ASSERT_EQ(200, FPDFBitmap_GetHeight(new_bitmap));
+  ASSERT_EQ(800, FPDFBitmap_GetStride(new_bitmap));
+
+  std::string new_digest = HashBitmap(new_bitmap, 200, 200);
+  FPDFBitmap_Destroy(new_bitmap);
+  FPDF_ClosePage(new_page);
+  FPDF_CloseDocument(new_doc);
+
+  EXPECT_EQ(digest, new_digest);
+}