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      1 // Copyright 2013 The Chromium Authors. All rights reserved.
      2 // Use of this source code is governed by a BSD-style license that can be
      3 // found in the LICENSE file.
      4 
      5 #ifndef MOJO_COMMON_HANDLE_WATCHER_H_
      6 #define MOJO_COMMON_HANDLE_WATCHER_H_
      7 
      8 #include "base/basictypes.h"
      9 #include "base/callback_forward.h"
     10 #include "base/memory/scoped_ptr.h"
     11 #include "mojo/common/mojo_common_export.h"
     12 #include "mojo/public/system/core_cpp.h"
     13 
     14 namespace base {
     15 class Thread;
     16 class TickClock;
     17 class TimeTicks;
     18 }
     19 
     20 namespace mojo {
     21 namespace common {
     22 namespace test {
     23 class HandleWatcherTest;
     24 }
     25 
     26 // HandleWatcher is used to asynchronously wait on a handle and notify a Closure
     27 // when the handle is ready, or the deadline has expired.
     28 class MOJO_COMMON_EXPORT HandleWatcher {
     29  public:
     30   HandleWatcher();
     31   ~HandleWatcher();
     32 
     33   // Starts listening for |handle|. This implicitly invokes Stop(). In other
     34   // words, Start() performs one asynchronous watch at a time. It is ok to call
     35   // Start() multiple times, but it cancels any existing watches. |callback| is
     36   // notified when the handle is ready, invalid or deadline has passed and is
     37   // notified on the thread Start() was invoked on.
     38   void Start(const Handle& handle,
     39              MojoWaitFlags wait_flags,
     40              MojoDeadline deadline,
     41              const base::Callback<void(MojoResult)>& callback);
     42 
     43   // Stops listening. Does nothing if not in the process of listening.
     44   void Stop();
     45 
     46   // Returns now. Used internally; generally not useful.
     47   static base::TimeTicks NowTicks();
     48 
     49   // Converts a MojoDeadline into a TimeTicks.
     50   static base::TimeTicks MojoDeadlineToTimeTicks(MojoDeadline deadline);
     51 
     52  private:
     53   friend class test::HandleWatcherTest;
     54   struct StartState;
     55 
     56   // See description of |StartState::weak_factory| for details.
     57   void OnHandleReady(MojoResult result);
     58 
     59   // If non-NULL Start() has been invoked.
     60   scoped_ptr<StartState> start_state_;
     61 
     62   // Used for getting the time. Only set by tests.
     63   static base::TickClock* tick_clock_;
     64 
     65   DISALLOW_COPY_AND_ASSIGN(HandleWatcher);
     66 };
     67 
     68 }  // namespace common
     69 }  // namespace mojo
     70 
     71 #endif  // MOJO_COMMON_HANDLE_WATCHER_H_
     72