Revert of Mojo: Armed Watchers

mojo/edk/system/watcher_dispatcher.h

-// 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_