1 files changed, 70 insertions, 0 deletions
diff --git a/src/mongo/util/timer.cpp b/src/mongo/util/timer.cpp
new file mode 100644
index 00000000000..ae9f912a464
--- /dev/null
+++ b/src/mongo/util/timer.cpp
@@ -0,0 +1,70 @@
+// @file mongo/util/timer.cpp
+
+/*    Copyright 2009 10gen 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 "pch.h"  // TODO: Replace with platform/base.h after it's checked in.
+
+#include "mongo/util/timer.h"
+
+#include <limits>
+
+namespace mongo {
+
+    unsigned long long Timer::_countsPerSecond;
+
+    namespace {
+
+        // TODO: SERVER-5112, better startup-time initialization of C++ modules.
+        struct AtStartup {
+            AtStartup();
+        } atstartuputil;
+
+#if defined(MONGO_TIMER_IMPL_WIN32)
+
+        AtStartup::AtStartup() {
+            LARGE_INTEGER x;
+            bool ok = QueryPerformanceFrequency(&x);
+            verify(ok);
+            Timer::_countsPerSecond = x.QuadPart;
+        }
+
+#elif defined(MONGO_TIMER_IMPL_POSIX_MONOTONIC_CLOCK)
+
+        AtStartup::AtStartup() {
+            Timer::_countsPerSecond = Timer::nanosPerSecond;
+
+            // Make sure that the current time relative to the (unspecified) epoch isn't already too
+            // big to represent as a 64-bit count of nanoseconds.
+            unsigned long long maxSecs = std::numeric_limits<unsigned long long>::max() /
+                Timer::nanosPerSecond;
+            timespec the_time;
+            fassert(16162, !clock_gettime(CLOCK_MONOTONIC, &the_time));
+            fassert(16163, static_cast<unsigned long long>(the_time.tv_sec) < maxSecs);
+        }
+
+#elif defined(MONGO_TIMER_IMPL_GENERIC)
+
+        AtStartup::AtStartup() {
+            Timer::_countsPerSecond = Timer::microsPerSecond;
+        }
+
+#else
+#error "Unknown mongo::Timer implementation"
+#endif
+
+    }  // namespace
+
+}  // namespace mongo