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// @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 "mongo/util/timer.h"
#include <limits>
namespace mongo {
// default value of 1 so that during startup initialization if referenced no division by zero
unsigned long long Timer::_countsPerSecond = 1;
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
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