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- // Copyright 2017 The Chromium Authors. All rights reserved.
- // Use of this source code is governed by a BSD-style license that can be
- // found in the LICENSE file.
- #ifndef MOJO_CORE_WATCH_H_
- #define MOJO_CORE_WATCH_H_
- #include "base/memory/ref_counted.h"
- #include "base/synchronization/lock.h"
- #include "mojo/core/atomic_flag.h"
- #include "mojo/core/handle_signals_state.h"
- #include "mojo/public/c/system/trap.h"
- namespace mojo {
- namespace core {
- class Dispatcher;
- class WatcherDispatcher;
- // Encapsulates the state associated with a single watch context within a
- // watcher.
- //
- // Every Watch has its own cancellation state, and is captured by RequestContext
- // notification finalizers to avoid redundant context resolution during
- // finalizer execution.
- class Watch : public base::RefCountedThreadSafe<Watch> {
- public:
- // Constructs a Watch which represents a watch within |watcher| associated
- // with |context|, watching |dispatcher| for |signals|.
- Watch(const scoped_refptr<WatcherDispatcher>& watcher,
- const scoped_refptr<Dispatcher>& dispatcher,
- uintptr_t context,
- MojoHandleSignals signals,
- MojoTriggerCondition condition);
- Watch(const Watch&) = delete;
- Watch& operator=(const Watch&) = delete;
- // Notifies the Watch of a potential state change.
- //
- // If |allowed_to_call_callback| is true, this may add a notification
- // finalizer to the current RequestContext to invoke the watcher's callback
- // with this watch's context. See return values below.
- //
- // This is called directly by WatcherDispatcher whenever the Watch's observed
- // dispatcher notifies the WatcherDispatcher of a state change.
- //
- // Returns |true| if the Watch entered or remains in a ready state as a result
- // of the state change. If |allowed_to_call_callback| was true in this case,
- // the Watch will have also attached a notification finalizer to the current
- // RequestContext.
- //
- // Returns |false| if the
- bool NotifyState(const HandleSignalsState& state,
- bool allowed_to_call_callback);
- // Notifies the watch of cancellation ASAP. This will always be the last
- // notification sent for the watch.
- void Cancel();
- // Finalizer method for RequestContexts. This method is invoked once for every
- // notification finalizer added to a RequestContext by this object. This calls
- // down into the WatcherDispatcher to do the actual notification call.
- void InvokeCallback(MojoResult result,
- const HandleSignalsState& state,
- MojoTrapEventFlags flags);
- const scoped_refptr<Dispatcher>& dispatcher() const { return dispatcher_; }
- uintptr_t context() const { return context_; }
- MojoResult last_known_result() const {
- AssertWatcherLockAcquired();
- return last_known_result_;
- }
- MojoHandleSignalsState last_known_signals_state() const {
- AssertWatcherLockAcquired();
- return last_known_signals_state_;
- }
- bool ready() const {
- AssertWatcherLockAcquired();
- return last_known_result_ == MOJO_RESULT_OK ||
- last_known_result_ == MOJO_RESULT_FAILED_PRECONDITION;
- }
- private:
- friend class base::RefCountedThreadSafe<Watch>;
- ~Watch();
- #if DCHECK_IS_ON()
- void AssertWatcherLockAcquired() const;
- #else
- void AssertWatcherLockAcquired() const {}
- #endif
- const scoped_refptr<WatcherDispatcher> watcher_;
- const scoped_refptr<Dispatcher> dispatcher_;
- const uintptr_t context_;
- const MojoHandleSignals signals_;
- const MojoTriggerCondition condition_;
- // The result code with which this Watch would notify if currently armed,
- // based on the last known signaling state of |dispatcher_|. Guarded by the
- // owning WatcherDispatcher's lock.
- MojoResult last_known_result_ = MOJO_RESULT_UNKNOWN;
- // The last known signaling state of |dispatcher_|. Guarded by the owning
- // WatcherDispatcher's lock.
- MojoHandleSignalsState last_known_signals_state_ = {0, 0};
- // Guards |is_cancelled_| below and mutually excludes individual watch
- // notification executions for this same watch context.
- //
- // Note that this should only be acquired from a RequestContext finalizer to
- // ensure that no other internal locks are already held.
- base::Lock notification_lock_;
- // Guarded by |notification_lock_|.
- bool is_cancelled_ = false;
- };
- } // namespace core
- } // namespace mojo
- #endif // MOJO_CORE_WATCH_H_
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