Do more page load/unload checks in EmbedderTest.

- Keep track of pages in a single map when calling LoadPage(). It is
  simpler and performance is not crucial as the number of loaded pages
  is usually very small.
- Verify UnloadPage() is only called for loaded pages.
- Verify there are no loaded pages in TearDown().
- Verify RenderLoadedPage methods are only rendering loaded pages.
- Fix pages that are using FPDF_LoadPage() and FPDF_ClosePage() when
  they should be using LoadPage() and UnloadPage().
- Disallow calling LoadPage() for the same page number repeatedly. No
  caller does this and it makes verification in UnloadPage() harder.

Change-Id: I58878ea8ade21dde28f1bbebd3a3304ce677561d
Reviewed-on: https://pdfium-review.googlesource.com/25550
Reviewed-by: dsinclair <dsinclair@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>

2 files changed, 44 insertions, 15 deletions

diff --git a/testing/embedder_test.cpp b/testing/embedder_test.cpp
index bd52c26286..32c761e050 100644
--- a/testing/embedder_test.cpp
+++ b/testing/embedder_test.cpp
@@ -22,7 +22,9 @@
 #include "testing/image_diff/image_diff_png.h"
 #include "testing/test_support.h"
 #include "testing/utils/path_service.h"
+#include "third_party/base/logging.h"
 #include "third_party/base/ptr_util.h"
+#include "third_party/base/stl_util.h"
 
 #ifdef PDF_ENABLE_V8
 #include "v8/include/v8-platform.h"
@@ -76,6 +78,10 @@ void EmbedderTest::SetUp() {
 }
 
 void EmbedderTest::TearDown() {
+  // Use an EXPECT_EQ() here and continue to let TearDown() finish as cleanly as
+  // possible. This can fail when an ASSERT test fails in a test case.
+  EXPECT_EQ(0U, page_map_.size());
+
   if (document_) {
     FORM_DoDocumentAAction(form_handle_, FPDFDOC_AACTION_WC);
     FPDFDOC_ExitFormFillEnvironment(form_handle_);
@@ -245,10 +251,8 @@ int EmbedderTest::GetPageCount() {
 
 FPDF_PAGE EmbedderTest::LoadPage(int page_number) {
   ASSERT(form_handle_);
-  // First check whether it is loaded already.
-  auto it = page_map_.find(page_number);
-  if (it != page_map_.end())
-    return it->second;
+  ASSERT(page_number >= 0);
+  ASSERT(!pdfium::ContainsKey(page_map_, page_number));
 
   FPDF_PAGE page = FPDF_LoadPage(document_, page_number);
   if (!page)
@@ -258,22 +262,23 @@ FPDF_PAGE EmbedderTest::LoadPage(int page_number) {
   FORM_DoPageAAction(page, form_handle_, FPDFPAGE_AACTION_OPEN);
   // Cache the page.
   page_map_[page_number] = page;
-  page_reverse_map_[page] = page_number;
   return page;
 }
 
 void EmbedderTest::UnloadPage(FPDF_PAGE page) {
   ASSERT(form_handle_);
+
+  int page_number = GetPageNumberForLoadedPage(page);
+  if (page_number < 0) {
+    NOTREACHED();
+    return;
+  }
+
   FORM_DoPageAAction(page, form_handle_, FPDFPAGE_AACTION_CLOSE);
   FORM_OnBeforeClosePage(page, form_handle_);
   FPDF_ClosePage(page);
 
-  auto it = page_reverse_map_.find(page);
-  if (it == page_reverse_map_.end())
-    return;
-
-  page_map_.erase(it->second);
-  page_reverse_map_.erase(it);
+  page_map_.erase(page_number);
 }
 
 FPDF_BITMAP EmbedderTest::RenderPageDeprecated(FPDF_PAGE page) {
@@ -287,6 +292,10 @@ std::unique_ptr<void, FPDFBitmapDeleter> EmbedderTest::RenderLoadedPage(
 
 std::unique_ptr<void, FPDFBitmapDeleter>
 EmbedderTest::RenderLoadedPageWithFlags(FPDF_PAGE page, int flags) {
+  if (GetPageNumberForLoadedPage(page) < 0) {
+    NOTREACHED();
+    return nullptr;
+  }
   return RenderPageWithFlags(page, form_handle_, flags);
 }
 
@@ -521,3 +530,14 @@ int EmbedderTest::GetBlockFromString(void* param,
   memcpy(buf, new_file->data() + pos, size);
   return 1;
 }
+
+int EmbedderTest::GetPageNumberForLoadedPage(FPDF_PAGE page) const {
+  for (const auto& it : page_map_) {
+    if (it.second == page) {
+      int page_number = it.first;
+      ASSERT(page_number >= 0);
+      return page_number;
+    }
+  }
+  return -1;
+}
diff --git a/testing/embedder_test.h b/testing/embedder_test.h
index 18b16b7066..c8fce4825f 100644
--- a/testing/embedder_test.h
+++ b/testing/embedder_test.h
@@ -106,11 +106,17 @@ class EmbedderTest : public ::testing::Test,
   int GetFirstPageNum();
   int GetPageCount();
 
-  // Load a specific page of the open document.
+  // Load a specific page of the open document with a given non-negative
+  // |page_number|. On success, fire form events for the page and return a page
+  // handle. On failure, return nullptr.
+  // The caller does not own the returned page handle, but must call
+  // UnloadPage() on it when done.
+  // The caller cannot call this for a |page_number| if it already obtained and
+  // holds the page handle for that page.
   FPDF_PAGE LoadPage(int page_number);
 
-  // Release the resources obtained from LoadPage(). Further use of |page|
-  // is prohibited after this call is made.
+  // Fire form unload events and release the resources for a |page| obtained
+  // from LoadPage(). Further use of |page| is prohibited after calling this.
   void UnloadPage(FPDF_PAGE page);
 
   // Convert a loaded page into a bitmap.
@@ -215,7 +221,6 @@ class EmbedderTest : public ::testing::Test,
   size_t file_length_ = 0;
   std::unique_ptr<char, pdfium::FreeDeleter> file_contents_;
   std::map<int, FPDF_PAGE> page_map_;
-  std::map<FPDF_PAGE, int> page_reverse_map_;
 
   FPDF_DOCUMENT saved_document_ = nullptr;
   FPDF_FORMHANDLE saved_form_handle_ = nullptr;
@@ -242,6 +247,10 @@ class EmbedderTest : public ::testing::Test,
                                 const void* data,
                                 unsigned long size);
 
+  // Find |page| inside |page_map_| and return the associated page number, or -1
+  // if |page| cannot be found.
+  int GetPageNumberForLoadedPage(FPDF_PAGE page) const;
+
   std::string data_string_;
 };