Mojo: Wrap the satisfied/unsatisfied wait flags state in a single object.

mojo/system/wait_flags_state.h

+// Copyright 2014 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_SYSTEM_WAIT_FLAGS_STATE_H_
+#define MOJO_SYSTEM_WAIT_FLAGS_STATE_H_
+
+#include "base/macros.h"
+#include "mojo/public/c/system/types.h"
+#include "mojo/system/system_impl_export.h"
+
+namespace mojo {
+namespace system {
+
+// Just "add" some constructors and methods to the C struct |MojoWaitFlagsState|
+// (for convenience). This should add no overhead.
+struct MOJO_SYSTEM_IMPL_EXPORT WaitFlagsState : public MojoWaitFlagsState {
+  WaitFlagsState() {
+    satisfied_flags = MOJO_WAIT_FLAG_NONE;
+    satisfiable_flags = MOJO_WAIT_FLAG_NONE;
+  }
+  WaitFlagsState(MojoWaitFlags satisfied, MojoWaitFlags satisfiable) {
+    satisfied_flags = satisfied;
+    satisfiable_flags = satisfiable;
+  }
+
+  bool equals(const WaitFlagsState& other) const {
+    return satisfied_flags == other.satisfied_flags &&
+           satisfiable_flags == other.satisfiable_flags;
+  }
+
+  bool satisfies(MojoWaitFlags flags) const {
+    return !!(satisfied_flags & flags);
+  }
+
+  bool can_satisfy(MojoWaitFlags flags) const {
+    return !!(satisfiable_flags & flags);
+  }
+
+  // (Copy and assignment allowed.)
+};
+COMPILE_ASSERT(sizeof(WaitFlagsState) == sizeof(MojoWaitFlagsState),
+               WaitFlagsState_should_add_no_overhead);
+
+}  // namespace system
+}  // namespace mojo
+
+#endif  // MOJO_SYSTEM_WAIT_FLAGS_STATE_H_