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| 1 // Copyright 2016 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_EDK_SYSTEM_WATCHER_H_ | |
| 6 #define MOJO_EDK_SYSTEM_WATCHER_H_ | |
| 7 | |
| 8 #include "base/callback.h" | |
| 9 #include "base/macros.h" | |
| 10 #include "base/memory/ref_counted.h" | |
| 11 #include "base/synchronization/lock.h" | |
| 12 #include "mojo/public/c/system/functions.h" | |
| 13 #include "mojo/public/c/system/types.h" | |
| 14 | |
| 15 namespace mojo { | |
| 16 namespace edk { | |
| 17 | |
| 18 struct HandleSignalsState; | |
| 19 | |
| 20 // This object corresponds to a watch added by a single call to |MojoWatch()|. | |
| 21 // | |
| 22 // An event may occur at any time which should trigger a Watcher to run its | |
| 23 // callback, but the callback needs to be deferred until all EDK locks are | |
| 24 // released. At the same time, a watch may be cancelled at any time by | |
| 25 // |MojoCancelWatch()| and it is not OK for the callback to be invoked after | |
| 26 // that happens. | |
| 27 // | |
| 28 // Therefore a Watcher needs to have some associated thread-safe state to track | |
| 29 // its cancellation, which is why it's ref-counted. | |
| 30 class Watcher : public base::RefCountedThreadSafe<Watcher> { | |
| 31 public: | |
| 32 using WatchCallback = base::Callback<void(MojoResult, | |
| 33 const HandleSignalsState&, | |
| 34 MojoWatchNotificationFlags)>; | |
| 35 | |
| 36 // Constructs a new Watcher which watches for |signals| to be satisfied on a | |
| 37 // handle and which invokes |callback| either when one such signal is | |
| 38 // satisfied, or all such signals become unsatisfiable. | |
| 39 Watcher(MojoHandleSignals signals, const WatchCallback& callback); | |
| 40 | |
| 41 // Runs the Watcher's callback with the given arguments if it hasn't been | |
| 42 // cancelled yet. | |
| 43 void MaybeInvokeCallback(MojoResult result, | |
| 44 const HandleSignalsState& state, | |
| 45 MojoWatchNotificationFlags flags); | |
| 46 | |
| 47 // Notifies the Watcher of a state change. This may result in the Watcher | |
| 48 // adding a finalizer to the current RequestContext to invoke its callback, | |
| 49 // cancellation notwithstanding. | |
| 50 void NotifyForStateChange(const HandleSignalsState& signals_state); | |
| 51 | |
| 52 // Notifies the Watcher of handle closure. This always results in the Watcher | |
| 53 // adding a finalizer to the current RequestContext to invoke its callback, | |
| 54 // cancellation notwithstanding. | |
| 55 void NotifyClosed(); | |
| 56 | |
| 57 // Explicitly cancels the watch, guaranteeing that its callback will never be | |
| 58 // be invoked again. | |
| 59 void Cancel(); | |
| 60 | |
| 61 private: | |
| 62 friend class base::RefCountedThreadSafe<Watcher>; | |
| 63 | |
| 64 ~Watcher(); | |
| 65 | |
| 66 // The set of signals which are watched by this Watcher. | |
| 67 const MojoHandleSignals signals_; | |
| 68 | |
| 69 // The callback to invoke with a result and signal state any time signals in | |
| 70 // |signals_| are satisfied or become permanently unsatisfiable. | |
| 71 const WatchCallback callback_; | |
| 72 | |
| 73 // Guards |is_cancelled_|. | |
| 74 base::Lock lock_; | |
| 75 | |
| 76 // Indicates whether the watch has been cancelled. A |Watcher| may exist for a | |
| 77 // brief period of time after being cancelled if it's been attached as a | |
| 78 // RequestContext finalizer. In such cases the callback must not be invoked, | |
| 79 // hence this flag. | |
| 80 bool is_cancelled_ = false; | |
| 81 | |
| 82 DISALLOW_COPY_AND_ASSIGN(Watcher); | |
| 83 }; | |
| 84 | |
| 85 } // namespace edk | |
| 86 } // namespace mojo | |
| 87 | |
| 88 #endif // MOJO_EDK_SYSTEM_WATCHER_H_ | |
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Chromium Code Reviews
Issue 2725133002:
Mojo: Armed Watchers (Closed)
