diff --git a/os.cpp b/os.cpp
new file mode 100644
index 0000000..b190fec
--- /dev/null
+++ b/os.cpp
@@ -0,0 +1,60 @@
+/*
+ * Copyright (C) 2016 The Android Open Source Project
+ *
+ * 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 <algorithm>
+#include <cstdint>
+
+#include "android-base/logging.h"
+
+#include "wifilogd/local_utils.h"
+#include "wifilogd/os.h"
+
+namespace android {
+namespace wifilogd {
+
+using local_utils::GetMaxVal;
+
+namespace {
+constexpr auto kMaxNanoSeconds = 1000 * 1000 * 1000 - 1;
+}
+
+Os::Os() : raw_os_(new RawOs()) {}
+Os::Os(std::unique_ptr<RawOs> raw_os) : raw_os_(std::move(raw_os)) {}
+Os::~Os() {}
+
+Os::Timestamp Os::GetTimestamp(clockid_t clock_id) const {
+  struct timespec now_timespec;
+  int failed = raw_os_->ClockGettime(clock_id, &now_timespec);
+  if (failed) {
+    LOG(FATAL) << "Unexpected error: " << std::strerror(errno);
+  }
+  CHECK(now_timespec.tv_nsec <= kMaxNanoSeconds);
+
+  Timestamp now_timestamp;
+  now_timestamp.secs = SAFELY_CLAMP(
+      now_timespec.tv_sec, uint32_t, 0,
+      // The upper-bound comes from the source-type on 32-bit platforms,
+      // and the dest-type on 64-bit platforms. Using min(), we can figure out
+      // which type to use for the upper bound, without resorting to macros.
+      std::min(static_cast<uintmax_t>(GetMaxVal(now_timestamp.secs)),
+               static_cast<uintmax_t>(GetMaxVal(now_timespec.tv_sec))));
+  now_timestamp.nsecs =
+      SAFELY_CLAMP(now_timespec.tv_nsec, uint32_t, 0, kMaxNanoSeconds);
+  return now_timestamp;
+}
+
+}  // namespace wifilogd
+}  // namespace android