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| 1 // Copyright 2017 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_WATCH_H_ |
| 6 #define MOJO_EDK_SYSTEM_WATCH_H_ |
| 7 |
| 8 #include "base/macros.h" |
| 9 #include "base/memory/ref_counted.h" |
| 10 #include "base/synchronization/lock.h" |
| 11 #include "mojo/edk/system/atomic_flag.h" |
| 12 #include "mojo/edk/system/handle_signals_state.h" |
| 13 |
| 14 namespace mojo { |
| 15 namespace edk { |
| 16 |
| 17 class Dispatcher; |
| 18 class WatcherDispatcher; |
| 19 |
| 20 // Encapsulates the state associated with a single watch context within a |
| 21 // watcher. |
| 22 // |
| 23 // Every Watch has its own cancellation state, and is captured by RequestContext |
| 24 // notification finalizers to avoid redundant context resolution during |
| 25 // finalizer execution. |
| 26 class Watch : public base::RefCountedThreadSafe<Watch> { |
| 27 public: |
| 28 // Constructs a Watch which represents a watch within |watcher| associated |
| 29 // with |context|, watching |dispatcher| for |signals|. |
| 30 Watch(const scoped_refptr<WatcherDispatcher>& watcher, |
| 31 const scoped_refptr<Dispatcher>& dispatcher, |
| 32 uintptr_t context, |
| 33 MojoHandleSignals signals); |
| 34 |
| 35 // Notifies the Watch of a potential state change. |
| 36 // |
| 37 // If |allowed_to_call_callback| is true, this may add a notification |
| 38 // finalizer to the current RequestContext to invoke the watcher's callback |
| 39 // with this watch's context. See return values below. |
| 40 // |
| 41 // This is called directly by WatcherDispatcher whenever the Watch's observed |
| 42 // dispatcher notifies the WatcherDispatcher of a state change. |
| 43 // |
| 44 // Returns |true| if the Watch entered or remains in a ready state as a result |
| 45 // of the state change. If |allowed_to_call_callback| was true in this case, |
| 46 // the Watch will have also attached a notification finalizer to the current |
| 47 // RequestContext. |
| 48 // |
| 49 // Returns |false| if the |
| 50 bool NotifyState(const HandleSignalsState& state, |
| 51 bool allowed_to_call_callback); |
| 52 |
| 53 // Notifies the watch of cancellation ASAP. This will always be the last |
| 54 // notification sent for the watch. |
| 55 void Cancel(); |
| 56 |
| 57 // Finalizer method for RequestContexts. This method is invoked once for every |
| 58 // notification finalizer added to a RequestContext by this object. This calls |
| 59 // down into the WatcherDispatcher to do the actual notification call. |
| 60 void InvokeCallback(MojoResult result, |
| 61 const HandleSignalsState& state, |
| 62 MojoWatcherNotificationFlags flags); |
| 63 |
| 64 const scoped_refptr<Dispatcher>& dispatcher() const { return dispatcher_; } |
| 65 uintptr_t context() const { return context_; } |
| 66 |
| 67 MojoResult last_known_result() const { |
| 68 AssertWatcherLockAcquired(); |
| 69 return last_known_result_; |
| 70 } |
| 71 |
| 72 MojoHandleSignalsState last_known_signals_state() const { |
| 73 AssertWatcherLockAcquired(); |
| 74 return last_known_signals_state_; |
| 75 } |
| 76 |
| 77 bool ready() const { |
| 78 AssertWatcherLockAcquired(); |
| 79 return last_known_result_ == MOJO_RESULT_OK || |
| 80 last_known_result_ == MOJO_RESULT_FAILED_PRECONDITION; |
| 81 } |
| 82 |
| 83 private: |
| 84 friend class base::RefCountedThreadSafe<Watch>; |
| 85 |
| 86 ~Watch(); |
| 87 |
| 88 #if DCHECK_IS_ON() |
| 89 void AssertWatcherLockAcquired() const; |
| 90 #else |
| 91 void AssertWatcherLockAcquired() const {} |
| 92 #endif |
| 93 |
| 94 const scoped_refptr<WatcherDispatcher> watcher_; |
| 95 const scoped_refptr<Dispatcher> dispatcher_; |
| 96 const uintptr_t context_; |
| 97 const MojoHandleSignals signals_; |
| 98 |
| 99 // The result code with which this Watch would notify if currently armed, |
| 100 // based on the last known signaling state of |dispatcher_|. Guarded by the |
| 101 // owning WatcherDispatcher's lock. |
| 102 MojoResult last_known_result_ = MOJO_RESULT_UNKNOWN; |
| 103 |
| 104 // The last known signaling state of |dispatcher_|. Guarded by the owning |
| 105 // WatcherDispatcher's lock. |
| 106 MojoHandleSignalsState last_known_signals_state_ = {0, 0}; |
| 107 |
| 108 // Guards |is_cancelled_| below and mutually excludes individual watch |
| 109 // notification executions for this same watch context. |
| 110 // |
| 111 // Note that this should only be acquired from a RequestContext finalizer to |
| 112 // ensure that no other internal locks are already held. |
| 113 base::Lock notification_lock_; |
| 114 |
| 115 // Guarded by |notification_lock_|. |
| 116 bool is_cancelled_ = false; |
| 117 |
| 118 DISALLOW_COPY_AND_ASSIGN(Watch); |
| 119 }; |
| 120 |
| 121 } // namespace edk |
| 122 } // namespace mojo |
| 123 |
| 124 #endif // MOJO_EDK_SYSTEM_WATCH_H_ |
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