[mojo-edk] Add MojoWatch and MojoCancelWatch APIs

mojo/edk/system/awakable_list.h

 // Copyright 2013 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_AWAKABLE_LIST_H_
 #define MOJO_EDK_SYSTEM_AWAKABLE_LIST_H_
 
+#include <stddef.h>
 #include <stdint.h>
 
 #include <vector>
 
 #include "mojo/edk/system/system_impl_export.h"
+#include "mojo/edk/system/watcher.h"
+#include "mojo/edk/system/watcher_set.h"
 #include "mojo/public/c/system/types.h"
 #include "mojo/public/cpp/system/macros.h"
 
 namespace mojo {
 namespace edk {
 
 class Awakable;
 struct HandleSignalsState;
 
 // |AwakableList| tracks all the |Waiter|s that are waiting on a given
 // handle/|Dispatcher|. There should be a |AwakableList| for each handle that
 // can be waited on (in any way). In the simple case, the |AwakableList| is
 // owned by the |Dispatcher|, whereas in more complex cases it is owned by the
 // secondary object (see simple_dispatcher.* and the explanatory comment in
 // core.cc). This class is thread-unsafe (all concurrent access must be
 // protected by some lock).
 class MOJO_SYSTEM_IMPL_EXPORT AwakableList {
  public:
   AwakableList();
   ~AwakableList();
 
   void AwakeForStateChange(const HandleSignalsState& state);
   void CancelAll();
   void Add(Awakable* awakable, MojoHandleSignals signals, uintptr_t context);
   void Remove(Awakable* awakable);
 
+  // Add and remove Watchers to this AwakableList.
+  MojoResult AddWatcher(MojoHandleSignals signals,
+                        const Watcher::WatchCallback& callback,
+                        uintptr_t context,
+                        const HandleSignalsState& current_state);
+  MojoResult RemoveWatcher(uintptr_t context);
+
  private:
   struct AwakeInfo {
     AwakeInfo(Awakable* awakable, MojoHandleSignals signals, uintptr_t context)
         : awakable(awakable), signals(signals), context(context) {}
 
     Awakable* awakable;
     MojoHandleSignals signals;
     uintptr_t context;
   };
   using AwakeInfoList = std::vector<AwakeInfo>;
 
   AwakeInfoList awakables_;
 
+  // TODO: Remove AwakableList and instead use WatcherSet directly in
+  // dispatchers.
+  WatcherSet watchers_;
+
   MOJO_DISALLOW_COPY_AND_ASSIGN(AwakableList);
 };
 
 }  // namespace edk
 }  // namespace mojo
 
 #endif  // MOJO_EDK_SYSTEM_AWAKABLE_LIST_H_