Make it possible to read CLD data from a file

chrome/browser/translate/translate_tab_helper.cc

 // Copyright 2011 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 "chrome/browser/translate/translate_tab_helper.h"
 
+#include "base/path_service.h"
+#include "base/platform_file.h"
 #include "chrome/browser/chrome_notification_types.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/translate/translate_accept_languages_factory.h"
 #include "chrome/browser/translate/translate_infobar_delegate.h"
 #include "chrome/browser/translate/translate_manager.h"
 #include "chrome/browser/translate/translate_service.h"
 #include "chrome/browser/ui/browser.h"
 #include "chrome/browser/ui/browser_finder.h"
 #include "chrome/browser/ui/browser_window.h"
 #include "chrome/browser/ui/tabs/tab_strip_model.h"
 #include "chrome/browser/ui/translate/translate_bubble_factory.h"
+#include "chrome/common/chrome_paths.h"
 #include "chrome/common/pref_names.h"
 #include "chrome/common/render_messages.h"
 #include "components/translate/core/browser/page_translated_details.h"
 #include "components/translate/core/browser/translate_accept_languages.h"
 #include "components/translate/core/browser/translate_prefs.h"
 #include "components/translate/core/common/language_detection_details.h"
 #include "content/public/browser/notification_service.h"
+#include "content/public/browser/render_process_host.h"
+#include "content/public/browser/render_view_host.h"
 #include "content/public/browser/web_contents.h"
 
 DEFINE_WEB_CONTENTS_USER_DATA_KEY(TranslateTabHelper);
 
 TranslateTabHelper::TranslateTabHelper(content::WebContents* web_contents)
     : content::WebContentsObserver(web_contents),
       translate_driver_(&web_contents->GetController()),
       translate_manager_(new TranslateManager(this)) {}
 
 TranslateTabHelper::~TranslateTabHelper() {
@@ skipping 70 matching lines @@
                                    error_type,
                                    original_profile->GetPrefs());
 }
 
 bool TranslateTabHelper::OnMessageReceived(const IPC::Message& message) {
   bool handled = true;
   IPC_BEGIN_MESSAGE_MAP(TranslateTabHelper, message)
     IPC_MESSAGE_HANDLER(ChromeViewHostMsg_TranslateLanguageDetermined,
                         OnLanguageDetermined)
     IPC_MESSAGE_HANDLER(ChromeViewHostMsg_PageTranslated, OnPageTranslated)
+    IPC_MESSAGE_HANDLER(ChromeViewHostMsg_NeedCLDData, OnCLDDataRequested)
     IPC_MESSAGE_UNHANDLED(handled = false)
   IPC_END_MESSAGE_MAP()
 
   return handled;
 }
 
 void TranslateTabHelper::DidNavigateAnyFrame(
     const content::LoadCommittedDetails& details,
     const content::FrameNavigateParams& params) {
   // Let the LanguageState clear its state.
   translate_driver_.DidNavigate(details);
 }
 
 void TranslateTabHelper::WebContentsDestroyed(
     content::WebContents* web_contents) {
   // Translation process can be interrupted.
   // Destroying the TranslateManager now guarantees that it never has to deal
   // with NULL WebContents.
   translate_manager_.reset();
 }
 
+// TODO(andrewhayden): It's annoying that during download of the data file,
+// multiple renderers may be calling this method repeatedly, but there's not
+// an obviously-better choice from a complexity standpoint: we have no idea
+// if or when the file will become available, and the check is cheap.
+void TranslateTabHelper::OnCLDDataRequested() {
+  static base::PlatformFile cached_platform_file = 0;
+  const int routing_id = GetWebContents()->GetRenderViewHost()->GetRoutingID();
+
+  // If we have cached the platform file, we reuse it. Else, we cache it now.
+  if (cached_platform_file == 0) {
+    // First, grab a reference to the user data directory
+    base::FilePath path;
+    if (!PathService::Get(chrome::DIR_USER_DATA, &path)) {
+        NOTREACHED();

[jochen (gone - plz use gerrit), 2014/03/12 13:08:27]

i don't think this if () { NOTREACHED(); } adds much value here

[Andrew Hayden (chromium.org), 2014/03/13 16:39:48]

Done.

+    }
+
+    // Now derive the name of the CLD data file that we are looking for.
+    path = path.Append(chrome::kCLDDataFilename);
+
+    // If the file exists, we can send an IPC-safe construct back to the
+    // renderer process immediately. If not (e.g., the file is being downloaded
+    // right now), then we will do nothing. It is up to the renderer process
+    // to call us again later.
+    if (!base::PathExists(path)) {
+      return;

[jochen (gone - plz use gerrit), 2014/03/12 13:08:27]

no { }

[Andrew Hayden (chromium.org), 2014/03/13 16:39:48]

Done.

+    }
+
+    // Attempt to open the file for reading.
+    int flags = base::PLATFORM_FILE_OPEN | base::PLATFORM_FILE_READ;
+    bool created = false;
+    base::PlatformFileError error;
+    cached_platform_file = base::CreatePlatformFile(
+        path, flags, &created, &error);
+    DCHECK(created == false);

[jochen (gone - plz use gerrit), 2014/03/12 13:08:27]

!created

[Andrew Hayden (chromium.org), 2014/03/13 16:39:48]

Done.

+    if (error != base::PLATFORM_FILE_OK) {
+      cached_platform_file = 0;
+      DCHECK(false) << "Failed to open CLD data file, error code=" << error;

[jochen (gone - plz use gerrit), 2014/03/12 13:08:27]

is it really necessary to crash here?

[Andrew Hayden (chromium.org), 2014/03/13 16:39:48]

No, it isn't. I just put a comment in the code instead. Thanks.

+      return;
+    }
+  }
+
+  // Get a handle to the renderer process for IPC.
+  base::ProcessHandle rendererProcessHandle =
+      GetWebContents()->GetRenderViewHost()->GetProcess()->GetHandle();
+  // Prepare a file handle for transit to that renderer process.
+  IPC::PlatformFileForTransit ipcPlatformFile = IPC::GetFileHandleForProcess(
+      cached_platform_file,
+      rendererProcessHandle,
+      false);
+  // Send the file handle to the renderer via IPC. We're done!
+  Send(new ChromeViewMsg_CLDDataAvailable(routing_id, ipcPlatformFile));
+}
+
 void TranslateTabHelper::OnLanguageDetermined(
     const LanguageDetectionDetails& details,
     bool page_needs_translation) {
   translate_driver_.language_state().LanguageDetermined(
       details.adopted_language, page_needs_translation);
 
   content::NotificationService::current()->Notify(
       chrome::NOTIFICATION_TAB_LANGUAGE_DETERMINED,
       content::Source<content::WebContents>(web_contents()),
       content::Details<const LanguageDetectionDetails>(&details));
@@ skipping 48 matching lines @@
     if (GetLanguageState().InTranslateNavigation())
       return;
   }
 
   TranslateBubbleFactory::Show(
       browser->window(), web_contents(), step, error_type);
 #else
   NOTREACHED();
 #endif
 }