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