Do not unload pages while loading of the same pages is in progress.

pdf/pdfium/pdfium_page.cc

 // Copyright (c) 2010 The Chromium 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 "pdf/pdfium/pdfium_page.h"
 
 #include <math.h>
 
 #include "base/logging.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_util.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/values.h"
 #include "pdf/pdfium/pdfium_engine.h"
 
 // Used when doing hit detection.
 #define kTolerance 20.0
 
+namespace {
+
 // Dictionary Value key names for returning the accessible page content as JSON.
 const char kPageWidth[] = "width";
 const char kPageHeight[] = "height";
 const char kPageTextBox[] = "textBox";
 const char kTextBoxLeft[] = "left";
 const char kTextBoxTop[]  = "top";
 const char kTextBoxWidth[] = "width";
 const char kTextBoxHeight[]  = "height";
 const char kTextBoxFontSize[] = "fontSize";
 const char kTextBoxNodes[] = "textNodes";
 const char kTextNodeType[] = "type";
 const char kTextNodeText[] = "text";
 const char kTextNodeURL[] = "url";
 const char kTextNodeTypeText[] = "text";
 const char kTextNodeTypeURL[] = "url";
 const char kDocLinkURLPrefix[] = "#page";
 
+}  // namespace
+
 namespace chrome_pdf {
 
 PDFiumPage::PDFiumPage(PDFiumEngine* engine,
                        int i,
                        const pp::Rect& r,
                        bool available)
     : engine_(engine),
       page_(NULL),
       text_page_(NULL),
       index_(i),
+      loading_count_(0),
       rect_(r),
       calculated_links_(false),
       available_(available) {
 }
 
 PDFiumPage::~PDFiumPage() {
+  DCHECK_EQ(0, loading_count_);
 }
 
 void PDFiumPage::Unload() {
+  // Do not unload while in the middle of a load.
+  if (loading_count_)
+    return;
+
   if (text_page_) {
     FPDFText_ClosePage(text_page_);
     text_page_ = NULL;
   }
 
   if (page_) {
     if (engine_->form()) {
       FORM_OnBeforeClosePage(page_, engine_->form());
     }
     FPDF_ClosePage(page_);
     page_ = NULL;
   }
 }
 
 FPDF_PAGE PDFiumPage::GetPage() {
   ScopedUnsupportedFeature scoped_unsupported_feature(engine_);
   if (!available_)
     return NULL;
   if (!page_) {
+    ScopedLoadCounter scoped_load(this);
     page_ = FPDF_LoadPage(engine_->doc(), index_);
     if (page_ && engine_->form()) {
       FORM_OnAfterLoadPage(page_, engine_->form());
     }
   }
   return page_;
 }
 
 FPDF_PAGE PDFiumPage::GetPrintPage() {
   ScopedUnsupportedFeature scoped_unsupported_feature(engine_);
   if (!available_)
     return NULL;
-  if (!page_)
+  if (!page_) {
+    ScopedLoadCounter scoped_load(this);
     page_ = FPDF_LoadPage(engine_->doc(), index_);
+  }
   return page_;
 }
 
 void PDFiumPage::ClosePrintPage() {
+  // Do not close |page_| while in the middle of a load.
+  if (loading_count_)
+    return;
+
   if (page_) {
     FPDF_ClosePage(page_);
     page_ = NULL;
   }
 }
 
 FPDF_TEXTPAGE PDFiumPage::GetTextPage() {
   if (!available_)
     return NULL;
-  if (!text_page_)
+  if (!text_page_) {
+    ScopedLoadCounter scoped_load(this);
     text_page_ = FPDFText_LoadPage(GetPage());
+  }
   return text_page_;
 }
 
 base::Value* PDFiumPage::GetAccessibleContentAsValue(int rotation) {
   base::DictionaryValue* node = new base::DictionaryValue();
 
   if (!available_)
     return node;
 
   double width = FPDF_GetPageWidth(GetPage());
@@ skipping 348 matching lines @@
   // http://www.netl.doe.gov/publications/proceedings/03/ubc/presentations/Goeckner-pres.pdf
   if (new_right < new_left)
     std::swap(new_right, new_left);
   if (new_bottom < new_top)
     std::swap(new_bottom, new_top);
 
   return pp::Rect(
       new_left, new_top, new_right - new_left + 1, new_bottom - new_top + 1);
 }
 
+PDFiumPage::ScopedLoadCounter::ScopedLoadCounter(PDFiumPage* page)
+    : page_(page) {
+  page_->loading_count_++;
+}
+
+PDFiumPage::ScopedLoadCounter::~ScopedLoadCounter() {
+  page_->loading_count_--;
+}
+
 PDFiumPage::Link::Link() {
 }
 
 PDFiumPage::Link::~Link() {
 }
 
 }  // namespace chrome_pdf