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

base/system_monitor/system_monitor.h

Index: base/system_monitor/system_monitor.h
diff --git a/base/system_monitor/system_monitor.h b/base/system_monitor/system_monitor.h
index 48d512b708c11aa44368c05300dd9a38f29e00ed..9163db70e7a020a0a8b89e8308eebcb13540658b 100644
--- a/base/system_monitor/system_monitor.h
+++ b/base/system_monitor/system_monitor.h
@@ -6,6 +6,7 @@
 #define BASE_SYSTEM_MONITOR_SYSTEM_MONITOR_H_
 
 #include <map>
+#include <set>
 #include <string>
 #include <vector>
 
@@ -13,6 +14,7 @@
 #include "base/basictypes.h"
 #include "base/file_path.h"
 #include "base/string16.h"
+#include "base/synchronization/lock.h"
 #include "build/build_config.h"
 
 // Windows HiRes timers drain the battery faster so we need to know the battery
@@ -58,6 +60,22 @@ class BASE_EXPORT SystemMonitor {
     DEVTYPE_UNKNOWN,  // Other devices.
   };
 
+  // The delegate interfaces for storage free space.
+  class BASE_EXPORT StorageFreeSpaceDelegate {
+   public:
+    virtual ~StorageFreeSpaceDelegate() {}
+
+    // Return true if the given storage |path| is already being watched.
+    virtual bool IsWatchingStorage(const FilePath& path) = 0;

[vandebo (ex-Chrome), 2012/09/12 17:54:47]

Not sure you need this.

[Hongbo Min, 2012/09/13 13:40:53]

Removed it already.

+
+    // Start watching the storage device identified by the |path| parameter.
+    // The |path| can be a drive path on Windows, or the mount point on Linux.

[vandebo (ex-Chrome), 2012/09/12 17:54:47]

nit: Linux -> Posix

[Hongbo Min, 2012/09/13 13:40:53]

Done.

+    virtual void StartWatchingStorage(const FilePath& path) = 0;
+
+    // Stop watching the storage device identified by the |path| paramter.
+    virtual void StopWatchingStorage(const FilePath& path) = 0;
+  };
+
   struct BASE_EXPORT RemovableStorageInfo {
     RemovableStorageInfo();
     RemovableStorageInfo(const std::string& id,
@@ -147,17 +165,31 @@ class BASE_EXPORT SystemMonitor {
     virtual ~DevicesChangedObserver() {}
   };
 
+  class BASE_EXPORT StorageFreeSpaceChangedObserver {
+   public:
+    // Triggered when the free space of the storage |path| is changed. The
+    // |available_capacity| indicates the free space in bytes.
+    virtual void OnStorageFreeSpaceChanged(const FilePath& path,
+                                           int64 available_capacity) {}
+  };
+
   // Add a new observer.
   // Can be called from any thread.
   // Must not be called from within a notification callback.
   void AddPowerObserver(PowerObserver* obs);
   void AddDevicesChangedObserver(DevicesChangedObserver* obs);
+  void AddStorageFreeSpaceChangedObserver(
+      const FilePath& path,
+      StorageFreeSpaceChangedObserver* obs);
 
   // Remove an existing observer.
   // Can be called from any thread.
   // Must not be called from within a notification callback.
   void RemovePowerObserver(PowerObserver* obs);
   void RemoveDevicesChangedObserver(DevicesChangedObserver* obs);
+  void RemoveStorageFreeSpaceChangedObserver(
+      const FilePath& path,
+      StorageFreeSpaceChangedObserver* obs);
 
 #if defined(OS_WIN)
   // Windows-specific handling of a WM_POWERBROADCAST message.
@@ -176,10 +208,24 @@ class BASE_EXPORT SystemMonitor {
                                        const FilePath::StringType& location);
   void ProcessRemovableStorageDetached(const std::string& id);
 
+  void ProcessStorageFreeSpaceChanged(const FilePath& path,
+                                      int64 available_capacity);
+
+  void set_storage_free_space_delegate(StorageFreeSpaceDelegate* delegate) {
+    free_space_delegate_ = delegate;

[vandebo (ex-Chrome), 2012/09/12 17:54:47]

Add a DCHECK that free_sapce_delegate_ is NULL.  We only expect the delegate to
be set once.

[Hongbo Min, 2012/09/13 13:40:53]

Done, but allow the free_space_delegate_ to be set to NULL again.

+  }
+
  private:
   // Mapping of unique device id to device info tuple.
   typedef std::map<std::string, RemovableStorageInfo> RemovableStorageMap;
 
+  typedef ObserverListThreadSafe<StorageFreeSpaceChangedObserver>
+      StorageFreeSpaceChangedObserverList;
+
+  // Mapping of the storage device path to the observer list.
+  typedef std::map<FilePath, scoped_refptr<
+      StorageFreeSpaceChangedObserverList> > StorageFreeSpaceChangedObserverMap;
+
 #if defined(OS_MACOSX)
   void PlatformInit();
   void PlatformDestroy();
@@ -222,6 +268,22 @@ class BASE_EXPORT SystemMonitor {
   // Map of all the attached removable storage devices.
   RemovableStorageMap removable_storage_map_;
 
+  // The delegate instance for storage free space change.

[vandebo (ex-Chrome), 2012/09/12 17:54:47]

nit: The delegate that implements free space-change notification.

[Hongbo Min, 2012/09/13 13:40:53]

Done.

+  StorageFreeSpaceDelegate* free_space_delegate_;
+
+  // Map of the storage being watched to the observer list.
+  StorageFreeSpaceChangedObserverMap free_space_changed_observer_map_;
+
+  // The set of the storage path being watched. Since we can not know when

[vandebo (ex-Chrome), 2012/09/12 17:54:47]

nit: path -> paths, can not -> can't

[Hongbo Min, 2012/09/13 13:40:53]

Done.

+  // the thread-safe observer list becomse empty, we have to use this set
+  // to decide to stop watching a storage path when its last observer has
+  // been removed.
+  std::multiset<FilePath> watching_storage_set_;
+
+  // The lock for manipulating free_space_changed_observer_map_

[vandebo (ex-Chrome), 2012/09/12 17:54:47]

nit: remove The: "Lock for..."

[Hongbo Min, 2012/09/13 13:40:53]

Done.

+  // and watching_storage_set_.
+  base::Lock free_space_observers_lock_;
+
   DISALLOW_COPY_AND_ASSIGN(SystemMonitor);
 };