mojo/common/handle_watcher.h

   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 "base/run_loop.h"
  12 #include "mojo/common/mojo_common_export.h"
  13 #include "mojo/public/cpp/system/core.h"
  14
  15 namespace base {
  16 class Thread;
  17 }
  18
  19 namespace mojo {
  20 namespace common {
  21 namespace test {
  22 class HandleWatcherTest;
  23 }
  24
  25 // HandleWatcher is used to asynchronously wait on a handle and notify a Closure
  26 // when the handle is ready, or the deadline has expired.
  27 class MOJO_COMMON_EXPORT HandleWatcher {
  28  public:
  29   HandleWatcher();
  30
  31   // The destructor implicitly stops listening. See Stop() for details.
  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. Blocks
  47   // until no longer listening on the handle.
  48   void Stop();
  49
  50  private:
  51   class StateBase;
  52   class SameThreadWatchingState;
  53   class SecondaryThreadWatchingState;
  54
  55   // If non-NULL Start() has been invoked.
  56   scoped_ptr<StateBase> state_;
  57
  58   DISALLOW_COPY_AND_ASSIGN(HandleWatcher);
  59 };
  60
  61 }  // namespace common
  62 }  // namespace mojo
  63
  64 #endif  // MOJO_COMMON_HANDLE_WATCHER_H_