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Unified Diff: mojo/edk/system/watcher_dispatcher.h

Issue 2725133002: Mojo: Armed Watchers (Closed)
Patch Set: rebase Created 3 years, 9 months ago
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Index: mojo/edk/system/watcher_dispatcher.h
diff --git a/mojo/edk/system/watcher_dispatcher.h b/mojo/edk/system/watcher_dispatcher.h
new file mode 100644
index 0000000000000000000000000000000000000000..9698818272ea68ca319dd912e55acf4573eac991
--- /dev/null
+++ b/mojo/edk/system/watcher_dispatcher.h
@@ -0,0 +1,91 @@
+// 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_EDK_SYSTEM_WATCHER_DISPATCHER_H_
+#define MOJO_EDK_SYSTEM_WATCHER_DISPATCHER_H_
+
+#include <map>
+#include <set>
+
+#include "base/macros.h"
+#include "base/memory/ref_counted.h"
+#include "base/synchronization/lock.h"
+#include "mojo/edk/system/dispatcher.h"
+#include "mojo/edk/system/handle_signals_state.h"
+#include "mojo/edk/system/system_impl_export.h"
+#include "mojo/public/c/system/watcher.h"
+
+namespace mojo {
+namespace edk {
+
+class Watch;
+
+// The dispatcher type which backs watcher handles.
+class WatcherDispatcher : public Dispatcher {
+ public:
+ // Constructs a new WatcherDispatcher which invokes |callback| when a
+ // registered watch observes some relevant state change.
+ explicit WatcherDispatcher(MojoWatcherCallback callback);
+
+ // Methods used by watched dispatchers to notify watchers of events.
+ void NotifyHandleState(Dispatcher* dispatcher,
+ const HandleSignalsState& state);
+ void NotifyHandleClosed(Dispatcher* dispatcher);
+
+ // Method used by RequestContext (indirectly, via Watch) to complete
+ // notification operations from a safe stack frame to avoid reentrancy.
+ void InvokeWatchCallback(uintptr_t context,
+ MojoResult result,
+ const HandleSignalsState& state,
+ MojoWatcherNotificationFlags flags);
+
+ // Dispatcher:
+ Type GetType() const override;
+ MojoResult Close() override;
+ MojoResult WatchDispatcher(scoped_refptr<Dispatcher> dispatcher,
+ MojoHandleSignals signals,
+ uintptr_t context) override;
+ MojoResult CancelWatch(uintptr_t context) override;
+ MojoResult Arm(uint32_t* num_ready_contexts,
+ uintptr_t* ready_contexts,
+ MojoResult* ready_results,
+ MojoHandleSignalsState* ready_signals_states) override;
+
+ private:
+ friend class Watch;
+
+ ~WatcherDispatcher() override;
+
+ const MojoWatcherCallback callback_;
+
+ // Guards access to the fields below.
+ //
+ // NOTE: This may be acquired while holding another dispatcher's lock, as
+ // watched dispatchers call into WatcherDispatcher methods which lock this
+ // when issuing state change notifications. WatcherDispatcher must therefore
+ // take caution to NEVER acquire other dispatcher locks while this is held.
+ base::Lock lock_;
+
+ bool armed_ = false;
+ bool closed_ = false;
+
+ // A mapping from context to Watch.
+ std::map<uintptr_t, scoped_refptr<Watch>> watches_;
+
+ // A mapping from watched dispatcher to Watch.
+ std::map<Dispatcher*, scoped_refptr<Watch>> watched_handles_;
+
+ // The set of all Watch instances which are currently ready to signal. This is
+ // used for efficient arming behavior, as it allows for O(1) discovery of
+ // whether or not arming can succeed and quick determination of who's
+ // responsible if it can't.
+ std::set<Watch*> ready_watches_;
+
+ DISALLOW_COPY_AND_ASSIGN(WatcherDispatcher);
+};
+
+} // namespace edk
+} // namespace mojo
+
+#endif // MOJO_EDK_SYSTEM_WATCHER_DISPATCHER_H_

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