core+daemon: eliminate scheduler::{schedule,cancel} wrappers

Also move core/global-io.hpp to daemon/global.hpp

Refs: #4528, #4883
Change-Id: I0b99029f1a19d7451aab57099cd3303b7eb42ff3
diff --git a/daemon/global.hpp b/daemon/global.hpp
new file mode 100644
index 0000000..05bc577
--- /dev/null
+++ b/daemon/global.hpp
@@ -0,0 +1,75 @@
+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil; -*- */
+/*
+ * Copyright (c) 2014-2019  Regents of the University of California,
+ *                          Arizona Board of Regents,
+ *                          Colorado State University,
+ *                          University Pierre & Marie Curie, Sorbonne University,
+ *                          Washington University in St. Louis,
+ *                          Beijing Institute of Technology
+ *
+ * This file is part of NFD (Named Data Networking Forwarding Daemon).
+ * See AUTHORS.md for complete list of NFD authors and contributors.
+ *
+ * NFD is free software: you can redistribute it and/or modify it under the terms
+ * of the GNU General Public License as published by the Free Software Foundation,
+ * either version 3 of the License, or (at your option) any later version.
+ *
+ * NFD is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
+ * without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
+ * PURPOSE.  See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * NFD, e.g., in COPYING.md file.  If not, see <http://www.gnu.org/licenses/>.
+ **/
+
+#ifndef NFD_DAEMON_GLOBAL_HPP
+#define NFD_DAEMON_GLOBAL_HPP
+
+#include "core/common.hpp"
+
+namespace nfd {
+
+/** \brief Returns the global io_service instance for the calling thread.
+ */
+boost::asio::io_service&
+getGlobalIoService();
+
+/** \brief Returns the global Scheduler instance for the calling thread.
+ */
+Scheduler&
+getScheduler();
+
+boost::asio::io_service&
+getMainIoService();
+
+boost::asio::io_service&
+getRibIoService();
+
+void
+setMainIoService(boost::asio::io_service* mainIo);
+
+void
+setRibIoService(boost::asio::io_service* ribIo);
+
+/** \brief Run a function on the main io_service instance.
+ */
+void
+runOnMainIoService(const std::function<void()>& f);
+
+/** \brief Run a function on the RIB io_service instance.
+ */
+void
+runOnRibIoService(const std::function<void()>& f);
+
+#ifdef WITH_TESTS
+/** \brief Destroy the global io_service instance.
+ *
+ *  It will be recreated at the next invocation of getGlobalIoService().
+ */
+void
+resetGlobalIoService();
+#endif
+
+} // namespace nfd
+
+#endif // NFD_DAEMON_GLOBAL_HPP