Implement mediaGalleriesPrivate api to notify extensions about gallery changed events.

chrome/browser/extensions/api/media_galleries_private/gallery_watch_manager.cc

+// Copyright (c) 2012 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.
+//
+// GalleryWatchManager implementation.
+
+#include "chrome/browser/extensions/api/media_galleries_private/gallery_watch_manager.h"
+
+#include <list>
+
+#include "base/bind.h"
+#include "base/compiler_specific.h"
+#include "base/location.h"
+#include "base/stl_util.h"
+#include "base/time.h"
+#include "chrome/browser/extensions/api/media_galleries_private/gallery_watch_manager_factory.h"
+#include "chrome/browser/extensions/api/media_galleries_private/media_galleries_private_api.h"
+#include "chrome/browser/extensions/api/media_galleries_private/media_galleries_private_api_factory.h"
+#include "chrome/browser/extensions/api/media_galleries_private/media_galleries_private_event_router.h"
+#include "chrome/browser/profiles/profile.h"
+#include "content/public/browser/browser_thread.h"
+
+namespace extensions {
+
+namespace {
+
+using content::BrowserThread;
+
+// Dispatches the gallery changed event on the UI thread.
+void SendGalleryChangedEventOnUIThread(
+    const Profile* profile,
+    const std::string& gallery_id,
+    const std::set<std::string>& extension_ids) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+  DCHECK(profile);
+  MediaGalleriesPrivateEventRouter* router =
+      MediaGalleriesPrivateAPIFactory::GetForProfile(
+          const_cast<Profile*>(profile))->event_router();
+  if (!router)
+    return;
+  router->OnGalleryChanged(gallery_id, extension_ids);
+}
+
+}  // namespace
+
+
+///////////////////////////////////////////////////////////////////////////////
+//                       GalleryWatchManager                                 //
+///////////////////////////////////////////////////////////////////////////////
+
+GalleryWatchManager::GalleryWatchManager(const Profile* profile)
+    : profile_(profile) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
+}
+
+GalleryWatchManager::~GalleryWatchManager() {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  if (!gallery_watchers_.empty()) {
+    // Profile is in shutdown mode.
+    STLDeleteValues(&gallery_watchers_);
+  }
+}
+
+bool GalleryWatchManager::StartGalleryWatch(
+    const std::string& gallery_id,
+    const FilePath& watch_path,
+    const std::string& extension_id) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  WatcherMap::const_iterator iter = gallery_watchers_.find(watch_path);

[Lei Zhang, 2012/12/15 04:13:21]

It's easier to understand if you write the code as:

if (iter != gallery_watchers_.end()) {
  // Already watched
  iter->second->AddExtension(extension_id);
  return true;
}

// Need to add new watcher
scoped_ptr<GalleryFilePathWatcher> watch(
    new GalleryFilePathWatcher(profile_, gallery_id, watch_path, extension_id));
if (!watch->SetupWatch())
  return false;
gallery_watchers_[watch_path] = watch.release();
return true;

[kmadhusu, 2012/12/17 23:58:05]

Done.

+  if (iter == gallery_watchers_.end()) {
+    scoped_ptr<GalleryFilePathWatcher> watch(
+        new GalleryFilePathWatcher(profile_, gallery_id, watch_path,
+                                   extension_id));
+
+    if (watch->SetupWatch())
+      gallery_watchers_[watch_path] = watch.release();
+    else
+      return false;
+  } else {
+    iter->second->AddExtension(extension_id);
+  }
+  return true;
+}
+
+void GalleryWatchManager::StopGalleryWatch(
+    const FilePath& watch_path,
+    const std::string& extension_id) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  WatcherMap::iterator iter = gallery_watchers_.find(watch_path);
+  if (iter == gallery_watchers_.end())
+    return;
+  // Remove the renderer process for this watch.
+  iter->second->RemoveExtension(extension_id);
+  if (iter->second->GetRefCount() == 0) {
+    delete iter->second;
+    gallery_watchers_.erase(iter);
+  }
+}
+
+void GalleryWatchManager::OnExtensionDestroyed(
+    const std::string& extension_id) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  std::list<FilePath> watchers_to_erase;
+  for (WatcherMap::iterator iter = gallery_watchers_.begin();
+       iter != gallery_watchers_.end(); ++iter) {
+    // Remove the renderer process for this watch.
+    iter->second->OnExtensionDestroyed(extension_id);
+    if (iter->second->GetRefCount() == 0)
+      watchers_to_erase.push_back(iter->first);
+  }
+
+  for (std::list<FilePath>::const_iterator path = watchers_to_erase.begin();
+       path != watchers_to_erase.end(); ++path) {
+    WatcherMap::iterator iter = gallery_watchers_.find(*path);
+    DCHECK(iter != gallery_watchers_.end());
+    delete iter->second;
+    gallery_watchers_.erase(iter);
+  }
+}
+
+
+///////////////////////////////////////////////////////////////////////////////
+//             GalleryWatchManager::GalleryFilePathWatcher                   //
+///////////////////////////////////////////////////////////////////////////////
+
+GalleryWatchManager::GalleryFilePathWatcher::GalleryFilePathWatcher(
+    const Profile* profile,
+    const std::string& gallery_id,
+    const FilePath& path,
+    const std::string& extension_id)
+    : profile_(profile),
+      gallery_id_(gallery_id),
+      ref_count_(0),
+      weak_ptr_factory_(ALLOW_THIS_IN_INITIALIZER_LIST(this)) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
+  file_watcher_.reset(new base::files::FilePathWatcher());
+  gallery_path_ = path;
+  AddExtension(extension_id);
+}
+
+GalleryWatchManager::GalleryFilePathWatcher::~GalleryFilePathWatcher() {
+  DCHECK(thread_check_.CalledOnValidThread());
+}
+
+void GalleryWatchManager::GalleryFilePathWatcher::AddExtension(
+    const std::string& extension_id) {
+  DCHECK(thread_check_.CalledOnValidThread());
+  ExtensionUsageRegistry::iterator it = extensions_.find(extension_id);
+  if (it != extensions_.end())
+    it->second++;
+  else
+    extensions_.insert(ExtensionUsageRegistry::value_type(extension_id, 1));
+  ref_count_++;
+}
+
+void GalleryWatchManager::GalleryFilePathWatcher::RemoveExtension(
+    const std::string& extension_id) {
+  DCHECK(thread_check_.CalledOnValidThread());
+  ExtensionUsageRegistry::iterator it = extensions_.find(extension_id);
+  if (it == extensions_.end())
+    return;
+  // If entry found - decrease it's count and remove if necessary
+  it->second--;
+  if (0 == it->second)
+    extensions_.erase(it);
+  ref_count_--;
+}
+
+void GalleryWatchManager::GalleryFilePathWatcher::OnExtensionDestroyed(
+    const std::string& extension_id) {
+  DCHECK(thread_check_.CalledOnValidThread());
+  ExtensionUsageRegistry::iterator it = extensions_.find(extension_id);
+  if (it == extensions_.end())
+    return;
+  ref_count_ -= it->second;
+  extensions_.erase(it);
+}
+
+unsigned int GalleryWatchManager::GalleryFilePathWatcher::GetRefCount() const {
+  DCHECK(thread_check_.CalledOnValidThread());
+  return ref_count_;
+}
+
+bool GalleryWatchManager::GalleryFilePathWatcher::SetupWatch() {
+  DCHECK(thread_check_.CalledOnValidThread());
+  return file_watcher_->Watch(
+      gallery_path_, true,
+      base::Bind(
+          &GalleryWatchManager::GalleryFilePathWatcher::OnFilePathChanged,
+          weak_ptr_factory_.GetWeakPtr()));
+}
+
+void GalleryWatchManager::GalleryFilePathWatcher::OnFilePathChanged(
+    const FilePath& path,
+    bool error) {
+  DCHECK(thread_check_.CalledOnValidThread());
+  if (error || (path != gallery_path_))
+    return;
+
+  if (!last_gallery_changed_event_.is_null()) {
+    // Ignore gallery change event if it is received too frequently.
+    // For example, when an user copies/deletes 1000 media files from a gallery,
+    // this callback is called 1000 times within a span of 10ms.
+    // GalleryWatchManager should not send 1000 gallery changed events to
+    // the watching extension.
+    const int kMinSecondsToIgnoreGalleryChangedEvent = 3;
+    base::TimeDelta diff = base::Time::Now() - last_gallery_changed_event_;
+    if (diff.InSeconds() < kMinSecondsToIgnoreGalleryChangedEvent)
+      return;
+  }
+
+  last_gallery_changed_event_ =  base::Time::Now();
+  ExtensionIdSet extension_ids;
+  for (ExtensionUsageRegistry::const_iterator iter = extensions_.begin();
+       iter != extensions_.end(); ++iter)
+    extension_ids.insert(iter->first);
+  content::BrowserThread::PostTask(
+      content::BrowserThread::UI, FROM_HERE,
+      base::Bind(SendGalleryChangedEventOnUIThread, profile_, gallery_id_,
+                 extension_ids));
+}
+
+}  // namespace extensions