Extend the capability of SystemMonitor to support watching storage free space change

base/system_monitor/system_monitor.cc

Index: base/system_monitor/system_monitor.cc
diff --git a/base/system_monitor/system_monitor.cc b/base/system_monitor/system_monitor.cc
index 2616275dfbc64db88abaa6abb0fa85e8cf561a7d..c71d70eec889c9a72052a3a436d8c2021305b780 100644
--- a/base/system_monitor/system_monitor.cc
+++ b/base/system_monitor/system_monitor.cc
@@ -34,12 +34,13 @@ SystemMonitor::RemovableStorageInfo::RemovableStorageInfo(
       location(device_location) {
 }
 
-SystemMonitor::SystemMonitor()
+SystemMonitor::SystemMonitor(StorageFreeSpaceDelegate* delegate)
     : power_observer_list_(new ObserverListThreadSafe<PowerObserver>()),
       devices_changed_observer_list_(
           new ObserverListThreadSafe<DevicesChangedObserver>()),
       battery_in_use_(false),
-      suspended_(false) {
+      suspended_(false),
+      free_space_delegate_(delegate) {
   DCHECK(!g_system_monitor);
   g_system_monitor = this;
 
@@ -127,6 +128,40 @@ void SystemMonitor::ProcessRemovableStorageDetached(const std::string& id) {
   NotifyRemovableStorageDetached(id);
 }
 
+void SystemMonitor::ProcessStorageFreeSpaceChanged(const FilePath& path,
+                                                   int64 available_capacity) {
+  DVLOG(1) << "Free Space Change: " << path.value() << " "
+           << available_capacity << " bytes";
+  scoped_refptr<StorageFreeSpaceObserverList> observers;
+  {
+    base::AutoLock lock(free_space_observers_lock_);
+    StorageFreeSpaceObserverListMap::iterator it =
+      free_space_observer_list_map_.find(path);
+    if (it == free_space_observer_list_map_.end())
+      return;
+    observers = it->second.observer_list;
+  }
+  if (observers.get())
+    observers->Notify(&StorageFreeSpaceObserver::OnFreeSpaceChanged,
+        path, available_capacity);
+}
+
+void SystemMonitor::ProcessStorageFreeSpaceChangeError(const FilePath& path) {
+  DVLOG(1) << "Failed to watch free space change for " << path.value();
+  scoped_refptr<StorageFreeSpaceObserverList> observers;
+  {
+    base::AutoLock lock(free_space_observers_lock_);
+    StorageFreeSpaceObserverListMap::iterator it =
+      free_space_observer_list_map_.find(path);
+    if (it == free_space_observer_list_map_.end())
+      return;
+    observers = it->second.observer_list;
+  }
+  if (observers.get())
+    observers->Notify(&StorageFreeSpaceObserver::OnFreeSpaceChangeError,
+                      path);
+}
+
 std::vector<SystemMonitor::RemovableStorageInfo>
 SystemMonitor::GetAttachedRemovableStorage() const {
   std::vector<RemovableStorageInfo> results;
@@ -156,6 +191,65 @@ void SystemMonitor::RemoveDevicesChangedObserver(DevicesChangedObserver* obs) {
   devices_changed_observer_list_->RemoveObserver(obs);
 }
 
+void SystemMonitor::AddStorageFreeSpaceObserver(const FilePath& path,
+                                                StorageFreeSpaceObserver* obs) {
+  DCHECK(free_space_delegate_ != NULL);
+  if (!free_space_delegate_)
+    return;
+  scoped_refptr<StorageFreeSpaceObserverList> observers;
+  {
+    base::AutoLock lock(free_space_observers_lock_);
+    // Try to start watching the given storage |path| if the first observer
+    // will be added.
+    StorageFreeSpaceObserverListMap::iterator iter =
+        free_space_observer_list_map_.find(path);
+    if (iter == free_space_observer_list_map_.end()) {
+      PathObserverPair pair;
+      pair.observer_list = observers = new StorageFreeSpaceObserverList;
+      pair.observer_set.insert(obs);
+      free_space_observer_list_map_.insert(std::make_pair(path, pair));
+      free_space_delegate_->StartWatchingStorage(path);
+    } else {
+      observers = iter->second.observer_list;
+      iter->second.observer_set.insert(obs);
+    }
+  }
+  observers->AddObserver(obs);
+}
+
+void SystemMonitor::RemoveStorageFreeSpaceObserver(
+    const FilePath& path,
+    StorageFreeSpaceObserver* obs) {
+  DCHECK(free_space_delegate_ != NULL);
+  if (!free_space_delegate_)
+    return;
+  scoped_refptr<StorageFreeSpaceObserverList> observers;
+  {
+    base::AutoLock lock(free_space_observers_lock_);
+    StorageFreeSpaceObserverListMap::iterator iter =
+      free_space_observer_list_map_.find(path);
+    // In case of no observer is interested in the given storage |path|.
+    if (iter == free_space_observer_list_map_.end()) {
+      return;
+    }
+
+    StorageFreeSpaceObserverSet::iterator sit
+        = iter->second.observer_set.find(obs);
+    // No the given observer is found.
+    if (sit == iter->second.observer_set.end())
+      return;
+    iter->second.observer_set.erase(sit);
+    // Try to stop watching in case of the last observer is removed.
+    if (iter->second.observer_set.size() == 0) {
+      free_space_delegate_->StopWatchingStorage(path);
+      free_space_observer_list_map_.erase(path);
+      return;
+    }
+    observers = iter->second.observer_list;
+  }
+  observers->RemoveObserver(obs);
+}
+
 void SystemMonitor::NotifyDevicesChanged(DeviceType device_type) {
   DVLOG(1) << "DevicesChanged with device type " << device_type;
   devices_changed_observer_list_->Notify(