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#ifndef BASE_OBJECT_WATCHER_H_
#define BASE_OBJECT_WATCHER_H_

#include <windows.h>

#include <map>

#include "base/linked_ptr.h"
#include "base/tracked.h"

class Task;

namespace base {

// A class that enables support for asynchronously waiting for Windows objects
// to become signaled.  Supports waiting on more than 64 objects.
class ObjectWatcher {
 public:
  ObjectWatcher();
  ~ObjectWatcher();

  // When the object is signaled, the given task is run on the thread where
  // Watch is called.  The ObjectWatcher assumes ownership of the task and
  // will ensure that it gets deleted eventually.
  //
  // NOTE: It is an error to call this method on an object that is already
  // being watched by this ObjectWatcher.
  //
  // Returns true if the watch was added.  Otherwise, false is returned.
  //
  bool AddWatch(const tracked_objects::Location& from_here, HANDLE object,
                Task* task);

  // Stops watching the given object.  Does nothing if the watch has already
  // completed.  If the watch is still active, then it is canceled, and the
  // associated task is deleted.
  //
  // Returns true if the watch was canceled.  Otherwise, false is returned.
  //
  bool CancelWatch(HANDLE object);

 private:
  // Called on a background thread when done waiting.
  static void CALLBACK DoneWaiting(void* param, BOOLEAN timed_out);

  // Passed as the param argument to the above methods.
  struct Watch;

  typedef std::map<HANDLE, linked_ptr<Watch>> WatchMap;
  WatchMap watches_;
};

}  // namespace base

#endif  // BASE_OBJECT_WATCHER_H_