timer.h

// @file timer.h

/*    Copyright 2010 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.
 */

#pragma once

#include "mongo/client/export_macros.h"

namespace mongo {

    class Timer /*copyable*/ {
    public:
        static const long long millisPerSecond = 1000;
        static const long long microsPerSecond = 1000 * millisPerSecond;
        static const long long nanosPerSecond = 1000 * microsPerSecond;

        Timer() { reset(); }
        int seconds() const { return (int)(micros() / 1000000); }
        int millis() const { return (int)(micros() / 1000); }
        int minutes() const { return seconds() / 60; }


        inline int millisReset() {
            const long long nextNow = now();
            const long long deltaMicros =
                    static_cast<long long>((nextNow - _old) * _microsPerCount);

            _old = nextNow;
            return static_cast<int>(deltaMicros / 1000);
        }

        inline long long micros() const {
            return static_cast<long long>((now() - _old) * _microsPerCount);
        }

        inline void reset() { _old = now(); }

        inline static void setCountsPerSecond(long long countsPerSecond) {
            _countsPerSecond = countsPerSecond;
            _microsPerCount = static_cast<double>(microsPerSecond) / _countsPerSecond;
        }

        inline static long long getCountsPerSecond() {
            return _countsPerSecond;
        }

    private:
        static long long _countsPerSecond;

        // Derived value from _countsPerSecond. This represents the conversion ratio
        // from clock ticks to microseconds.
        static double _microsPerCount;

        long long now() const;

        long long _old;
    };
}  // namespace mongo