Add new interface for time conversion

CMakeLists.txt

@@ -69,6 +69,9 @@ if(BUILD_TESTING)
 
   ament_add_gtest(test_join test/test_join.cpp)
 
+  ament_add_gtest(test_time test/test_time.cpp)
+  ament_target_dependencies(test_time rcutils)
+
   ament_add_gtest(test_env test/test_env.cpp
     ENV
       EMPTY_TEST=

include/rcpputils/time.hpp

@@ -0,0 +1,60 @@
+// Copyright 2021 Open Source Robotics Foundation, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef RCPPUTILS__TIME_HPP_
+#define RCPPUTILS__TIME_HPP_
+
+#include <chrono>
+
+#include "rcutils/time.h"
+
+namespace rcpputils
+{
+
+/// Convert to std::chrono::nanoseconds.
+/**
+ * This function help to convert from std::chrono::duration to std::chrono::nanoseconds and throw
+ * exception if overflow occurs while coverting.
+ *
+ * \param[in] time The time to be converted to std::chrono::nanoseconds.
+ * \return std::chrono::nanoseconds.
+ * \throws std::invalid_argument if time is bigger than std::chrono::nanoseconds::max() or less than
+ * std::chrono::nanoseconds::min().
+ */
+template<typename DurationRepT, typename DurationT>
+std::chrono::nanoseconds convert_to_nanoseconds(
+  const std::chrono::duration<DurationRepT, DurationT> & time)
+{
+  constexpr auto ns_max_as_double =
+    std::chrono::duration_cast<std::chrono::duration<double, std::chrono::nanoseconds::period>>(
+    std::chrono::nanoseconds::max());
+  if (time > ns_max_as_double) {
+    throw std::invalid_argument{
+            "time must be less than std::chrono::nanoseconds::max()"};
+  }
+
+  constexpr auto ns_min_as_double =
+    std::chrono::duration_cast<std::chrono::duration<double, std::chrono::nanoseconds::period>>(
+    std::chrono::nanoseconds::min());
+  if (time < ns_min_as_double) {
+    throw std::invalid_argument{
+            "time must be bigger than std::chrono::nanoseconds::min()"};
+  }
+
+  return std::chrono::duration_cast<std::chrono::nanoseconds>(time);
+}
+
+}  // namespace rcpputils
+
+#endif  // RCPPUTILS__TIME_HPP_

test/test_time.cpp

@@ -0,0 +1,29 @@
+// Copyright 2021 Open Source Robotics Foundation, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <gtest/gtest.h>
+
+#include <rcpputils/time.hpp>
+
+TEST(test_time, test_convert_to_nanoseconds) {
+  rcutils_duration_value_t expect_value = RCUTILS_S_TO_NS(5 * 60);  // 5 minutes
+  rcutils_duration_value_t cast_val = 0;
+  EXPECT_NO_THROW(
+    cast_val = rcpputils::convert_to_nanoseconds(std::chrono::duration<double>(5 * 60)).count());
+  EXPECT_EQ(cast_val, expect_value);
+
+  EXPECT_THROW(
+    rcpputils::convert_to_nanoseconds(std::chrono::hours(10000000)),
+    std::invalid_argument);
+}