tick_source.h

/**
 *    Copyright (C) 2015 MongoDB Inc.
 *
 *    This program is free software: you can redistribute it and/or  modify
 *    it under the terms of the GNU Affero General Public License, version 3,
 *    as published by the Free Software Foundation.
 *
 *    This program is distributed in the hope that it will be useful,
 *    but WITHOUT ANY WARRANTY; without even the implied warranty of
 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *    GNU Affero General Public License for more details.
 *
 *    You should have received a copy of the GNU Affero General Public License
 *    along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 *    As a special exception, the copyright holders give permission to link the
 *    code of portions of this program with the OpenSSL library under certain
 *    conditions as described in each individual source file and distribute
 *    linked combinations including the program with the OpenSSL library. You
 *    must comply with the GNU Affero General Public License in all respects for
 *    all of the code used other than as permitted herein. If you modify file(s)
 *    with this exception, you may extend this exception to your version of the
 *    file(s), but you are not obligated to do so. If you do not wish to do so,
 *    delete this exception statement from your version. If you delete this
 *    exception statement from all source files in the program, then also delete
 *    it in the license file.
 */

#pragma once

#include <cstdint>

namespace mongo {

/**
 * Interface for objects generating ticks that roughly represents the passage of time.
 */
//ServiceContext:_tickSource 类中包含该类成员
//SystemTickSource继承该类  //时间搓相关
//每个tick代表一个时间单位，1个tick可以代表一个us，也可以代表一个ns，参考SystemTickSource
//Timer._tickSource为该类型，Timer定时器也计与时间嘀嗒实现
class TickSource {
public:
    using Tick = int64_t;

    virtual ~TickSource() = default;

    /**
     * Returns the current tick count from this source.
     */
    virtual Tick getTicks() = 0;

    /**
     * Returns the conversion ratio from ticks to seconds.
     */
    virtual Tick getTicksPerSecond() = 0;
};
}  // namespace mongo