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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_MESSAGE_PUMP_HANDLE_WATCHER_H_
      6 #define MOJO_MESSAGE_PUMP_HANDLE_WATCHER_H_
      7 
      8 #include <memory>
      9 
     10 #include "base/callback_forward.h"
     11 #include "base/macros.h"
     12 #include "base/run_loop.h"
     13 #include "mojo/message_pump/mojo_message_pump_export.h"
     14 #include "mojo/public/cpp/system/core.h"
     15 
     16 namespace base {
     17 class Thread;
     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_MESSAGE_PUMP_EXPORT HandleWatcher {
     29  public:
     30   HandleWatcher();
     31 
     32   ~HandleWatcher();
     33 
     34   // Starts listening for |handle|. This implicitly invokes Stop(). In other
     35   // words, Start() performs one asynchronous watch at a time. It is ok to call
     36   // Start() multiple times, but it cancels any existing watches. |callback| is
     37   // notified when the handle is ready, invalid or deadline has passed and is
     38   // notified on the thread Start() was invoked on. If the current thread exits
     39   // before the handle is ready, then |callback| is invoked with a result of
     40   // MOJO_RESULT_ABORTED.
     41   void Start(const Handle& handle,
     42              MojoHandleSignals handle_signals,
     43              MojoDeadline deadline,
     44              const base::Callback<void(MojoResult)>& callback);
     45 
     46   // Stops listening. Does nothing if not in the process of listening.
     47   void Stop();
     48 
     49   bool is_watching() const { return !!state_; }
     50 
     51  private:
     52   class StateBase;
     53   class SameThreadWatchingState;
     54   class SecondaryThreadWatchingState;
     55 
     56   // If non-NULL Start() has been invoked.
     57   std::unique_ptr<StateBase> state_;
     58 
     59   DISALLOW_COPY_AND_ASSIGN(HandleWatcher);
     60 };
     61 
     62 }  // namespace common
     63 }  // namespace mojo
     64 
     65 #endif  // MOJO_MESSAGE_PUMP_HANDLE_WATCHER_H_
     66