Extend system monitor capacity for watching the free space changes

base/system_monitor/system_monitor_win.cc

Index: base/system_monitor/system_monitor_win.cc
diff --git a/base/system_monitor/system_monitor_win.cc b/base/system_monitor/system_monitor_win.cc
index a8cd54a6db1b8e27716e9b489650c30e8ce849ec..a512fa38bdbae427d392cc5de6606cda1a115c7c 100644
--- a/base/system_monitor/system_monitor_win.cc
+++ b/base/system_monitor/system_monitor_win.cc
@@ -4,8 +4,121 @@
 
 #include "base/system_monitor/system_monitor.h"
 
+#include "base/file_util.h"
+#include "base/message_loop_proxy.h"
+#include "base/win/object_watcher.h"
+
 namespace base {
 
+namespace {
+class StorageDeviceWatcher
+    : public FilePathWatcher::PlatformDelegate,
+      public base::win::ObjectWatcher::Delegate,
+      public MessageLoop::DestructionObserver
+  {
+ public:
+  StorageDeviceWatcher() {}
+  virtual StorageDeviceWatcher() {}
+
+  // Overriden from FilePathWatcher::PlatformDelegate.
+  virtual bool Watch(const FilePath& path,
+                     FilePathWatcher::Delegate* delegate) OVERRIDE;
+  virtual void Cancel() OVERRIDE;
+  virtual void CancelOnMessageLoopThread() OVERRIDE;
+
+ private:
+  // Overriden from ObjectWatcher::Delegate.
+  virtual void OnObjectSignaled(HANDLE object) OVERRIDE;
+
+  void DestroyWatch();
+
+  base::win::ObjectWatcher watcher_;
+  HANDLE handle_;
+  FilePath path_;
+};
+
+// StorageDeviceWatcher
+bool StorageDeviceWatcher::Watch(const FilePath& path,
+                                 FilePathWatcher::Delegate* delegate) {
+  if (handle_ != INVALID_HANDLE_VALUE)
+    DestroyWatch()
+
+  set_message_loop(base::MessageLoopProxy::current());
+  MessageLoop::current()->AddDestructionObserver(this);
+
+  if (!file_util::DirectoryExists(path))
+    return false;
+
+  handle_ = FindFirstChangeNotification(path.value().c_str(),
+                                        TRUE,  // Watch sub directories
+                                        FILE_NOTIFY_CHANGE_SIZE);
+  if (handle_ == INVALID_HANDLE_VALUE) {
+    DPLOG(ERROR) << "FindFirstChangeNotification failed: " << GetLastError();
+    return false;
+  }
+
+  path_ = path;
+  watcher_.StartWatching(handle_, this);
+  return true;
+}
+
+void StorageDeviceWatcher::Cancel() {
+  if (!message_loop()->BelongsToCurrentThread()) {
+    message_loop()->PostTask(FROM_HERE,
+        base::Bind(&StorageDeviceWatcher::CancelOnMessageLoopThread, this));
+  } else {
+    CancelOnMessageLoopThread();
+  }
+}
+
+void StorageDeviceWatcher::CancelOnMessageLoopThread() {
+  set_cancelled();
+  if (handle_ != INVALID_HANDLE_VALUE)
+    DestroyWatch();
+
+  MessageLoop::current()->RemoveDestructionObserver(this);
+}
+
+void StorageDeviceWatcher::OnObjectSignaled(HANDLE object) {
+  DCHECK(object == handle_);
+
+  // TODO (hongbo): need to control the frequency of the storage
+  // free space change event.
+  SystemMonitor::Get()->NotifyStorageFreeSpaceChanged(path_.value());
+
+  watcher_.StartWatching(handle_, this);
+}
+
+void StorageDeviceWatcher::DestroyWatch() {
+  watcher_.StopWatching();
+  FindCloseChangeNotification(handle_);
+  handle_ = INVALID_HANDLE_VALUE;
+}
+
+}
+
+bool SystemMonitor::StartWatchStorageDevice(const FilePath::StringType& path) {
+  scoped_refptr<FilePathWatcher::PlatformDelegate> watcher(
+      new StorageDeviceWatcher());
+  if (watcher->Watch(FilePath(path), NULL)) {
+    storage_watcher_map_.insert(
+      std::pair<FilePath::StringType,
+          scoped_refptr<FilePathWatcher::PlatformDelegate>(path, watcher));
+    return true;
+  }
+  return false;
+}
+
+bool SystemMonitor::StopWatchStorageDevice(const FilePath::StringType& path) {
+  StorageDeviceWatcherMap::iterator iter = storage_watcher_map_.find(path);
+  if (iter == storage_watcher_map_.end())
+    return false;
+
+  iter->second->Cancel();
+  storage_watcher_map_.erase(iter);
+  return true;
+}
+
 void SystemMonitor::ProcessWmPowerBroadcastMessage(int event_id) {
   PowerEvent power_event;
   switch (event_id) {