[mojo-edk] Add MojoWatch and MojoCancelWatch APIs

mojo/edk/system/watcher_set.h

Index: mojo/edk/system/watcher_set.h
diff --git a/mojo/edk/system/watcher_set.h b/mojo/edk/system/watcher_set.h
new file mode 100644
index 0000000000000000000000000000000000000000..8ae54a1b35270faf5d3fe8fc3b753764623362c1
--- /dev/null
+++ b/mojo/edk/system/watcher_set.h
@@ -0,0 +1,54 @@
+// Copyright 2016 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_SET_H_
+#define MOJO_EDK_SYSTEM_WATCHER_SET_H_
+
+#include <unordered_map>
+
+#include "base/callback.h"
+#include "base/macros.h"
+#include "base/memory/ref_counted.h"
+#include "mojo/edk/system/handle_signals_state.h"
+#include "mojo/edk/system/watcher.h"
+#include "mojo/public/c/system/types.h"
+
+namespace mojo {
+namespace edk {
+
+// A WatcherSet maintains a set of Watchers attached to a single handle and
+// keyed on an arbitrary user context.
+class WatcherSet {
+ public:
+  WatcherSet();
+  ~WatcherSet();
+
+  // Notifies all Watchers of a state change.
+  void NotifyForStateChange(const HandleSignalsState& state);
+
+  // Notifies all Watchers that their watched handle has been closed.
+  void NotifyClosed();
+
+  // Adds a new watcher to watch for signals in |signals| to be satisfied or
+  // unsatisfiable. |current_state| is the current signals state of the
+  // handle being watched.
+  MojoResult Add(MojoHandleSignals signals,
+                 const Watcher::WatchCallback& callback,
+                 uintptr_t context,
+                 const HandleSignalsState& current_state);
+
+  // Removes a watcher from the set.
+  MojoResult Remove(uintptr_t context);
+
+ private:
+  // A map of watchers keyed on context value.
+  std::unordered_map<uintptr_t, scoped_refptr<Watcher>> watchers_;
+
+  DISALLOW_COPY_AND_ASSIGN(WatcherSet);
+};
+
+}  // namespace edk
+}  // namespace mojo
+
+#endif  // MOJO_EDK_SYSTEM_WATCHER_SET_H_