muduo Timestamp

首先给出我学习源码时添加的注释:

分别对应Timestamp.h Timestamp.cc文件

// Use of this source code is governed by a BSD-style license
// that can be found in the License file.
//
// Author: Shuo Chen (chenshuo at chenshuo dot com)

#ifndef MUDUO_BASE_TIMESTAMP_H
#define MUDUO_BASE_TIMESTAMP_H

#include "muduo/base/copyable.h"
#include "muduo/base/Types.h"

#include <boost/operators.hpp>

namespace muduo
{

///
/// Time stamp in UTC, in microseconds resolution.
///
/// This class is immutable.
/// It's recommended to pass it by value, since it's passed in register on x64.
///
class Timestamp : public muduo::copyable,
                  public boost::equality_comparable<Timestamp>,
                  public boost::less_than_comparable<Timestamp>// 自动生成 > >= <= 
{
 public:
  ///
  /// Constucts an invalid Timestamp.
  ///
  Timestamp()
    : microSecondsSinceEpoch_(0)
  {
  }

  ///
  /// Constucts a Timestamp at specific time
  ///
  /// @param microSecondsSinceEpoch
  explicit Timestamp(int64_t microSecondsSinceEpochArg)
    : microSecondsSinceEpoch_(microSecondsSinceEpochArg)
  {
  }

  void swap(Timestamp& that)// 交换两个Timestamp 实质是交换两者microSecondsSinceEpoch_的值
  {
    std::swap(microSecondsSinceEpoch_, that.microSecondsSinceEpoch_);
  }

  // default copy/assignment/dtor are Okay

  string toString() const;// 返回时间的字符串形式
  string toFormattedString(bool showMicroseconds = true) const;

  bool valid() const { return microSecondsSinceEpoch_ > 0; }// 是否为有效时间

  // for internal usage.
  int64_t microSecondsSinceEpoch() const { return microSecondsSinceEpoch_; }
  time_t secondsSinceEpoch() const// 返回距离1970-1-1 00:00:00的秒数
  { return static_cast<time_t>(microSecondsSinceEpoch_ / kMicroSecondsPerSecond); }

  ///
  /// Get time of now.
  ///
  static Timestamp now();// 获取现在时间
  static Timestamp invalid()
  {
    return Timestamp();
  }

  static Timestamp fromUnixTime(time_t t)
  {
    return fromUnixTime(t, 0);
  }

  static Timestamp fromUnixTime(time_t t, int microseconds)
  {
    return Timestamp(static_cast<int64_t>(t) * kMicroSecondsPerSecond + microseconds);
  }

  static const int kMicroSecondsPerSecond = 1000 * 1000;// 每秒等于多少微秒

 private:
  int64_t microSecondsSinceEpoch_;// 记录距离1970-1-1 00:00:00 的微秒数
};

inline bool operator<(Timestamp lhs, Timestamp rhs)// 比较两个时间
{
  return lhs.microSecondsSinceEpoch() < rhs.microSecondsSinceEpoch();
}

inline bool operator==(Timestamp lhs, Timestamp rhs)
{
  return lhs.microSecondsSinceEpoch() == rhs.microSecondsSinceEpoch();
}

///
/// Gets time difference of two timestamps, result in seconds.
///
/// @param high, low
/// @return (high-low) in seconds
/// @c double has 52-bit precision, enough for one-microsecond
/// resolution for next 100 years.
inline double timeDifference(Timestamp high, Timestamp low)// 获取时间间隔单位为秒
{
  int64_t diff = high.microSecondsSinceEpoch() - low.microSecondsSinceEpoch();
  return static_cast<double>(diff) / Timestamp::kMicroSecondsPerSecond;
}

///
/// Add @c seconds to given timestamp.
///
/// @return timestamp+seconds as Timestamp
///
inline Timestamp addTime(Timestamp timestamp, double seconds)// 从当前时间加上对应秒数
{
  int64_t delta = static_cast<int64_t>(seconds * Timestamp::kMicroSecondsPerSecond);
  return Timestamp(timestamp.microSecondsSinceEpoch() + delta);
}

}  // namespace muduo

#endif  // MUDUO_BASE_TIMESTAMP_H

// Use of this source code is governed by a BSD-style license
// that can be found in the License file.
//
// Author: Shuo Chen (chenshuo at chenshuo dot com)

#include "muduo/base/Timestamp.h"

#include <sys/time.h>
#include <stdio.h>

#ifndef __STDC_FORMAT_MACROS
#define __STDC_FORMAT_MACROS
#endif

#include <inttypes.h>

using namespace muduo;

static_assert(sizeof(Timestamp) == sizeof(int64_t),
              "Timestamp should be same size as int64_t");

string Timestamp::toString() const
{
  char buf[32] = {0};
  int64_t seconds = microSecondsSinceEpoch_ / kMicroSecondsPerSecond;
  int64_t microseconds = microSecondsSinceEpoch_ % kMicroSecondsPerSecond;
  snprintf(buf, sizeof(buf), "%" PRId64 ".%06" PRId64 "", seconds, microseconds);
  return buf;
}

string Timestamp::toFormattedString(bool showMicroseconds) const
{
  char buf[64] = {0};
  time_t seconds = static_cast<time_t>(microSecondsSinceEpoch_ / kMicroSecondsPerSecond);
  struct tm tm_time;
  gmtime_r(&seconds, &tm_time);

  if (showMicroseconds)
  {
    int microseconds = static_cast<int>(microSecondsSinceEpoch_ % kMicroSecondsPerSecond);
    snprintf(buf, sizeof(buf), "%4d%02d%02d %02d:%02d:%02d.%06d",
             tm_time.tm_year + 1900, tm_time.tm_mon + 1, tm_time.tm_mday,
             tm_time.tm_hour, tm_time.tm_min, tm_time.tm_sec,
             microseconds);
  }
  else
  {
    snprintf(buf, sizeof(buf), "%4d%02d%02d %02d:%02d:%02d",
             tm_time.tm_year + 1900, tm_time.tm_mon + 1, tm_time.tm_mday,
             tm_time.tm_hour, tm_time.tm_min, tm_time.tm_sec);
  }
  return buf;
}

Timestamp Timestamp::now()
{
  struct timeval tv;
  gettimeofday(&tv, NULL);
  int64_t seconds = tv.tv_sec;
  return Timestamp(seconds * kMicroSecondsPerSecond + tv.tv_usec);
}

下面是测试程序,虽然用的任然是Timestamp相关代码文件,但做了相应修改,只需要包含对应的修改后的文件,而不需要安装muduo库即可运

行测试文件,测试程序如下:

#include <iostream>
#include "Timestamp.h"
#include <vector>

int main()
{
　　muduo::Timestamp time1(muduo::Timestamp::now());
　　std::cout << time1.toString() << std::endl;
　　std::cout << time1.toFormattedString(true) << std::endl;
　　std::cout << time1.toFormattedString(false) << std::endl;

　　// 创建1000000个Timestamp个对象所需要的时间
　　const int kNumber = 1000*1000;
　　std::vector<muduo::Timestamp> stamps;
　　stamps.reserve(kNumber);

　　for (int i = 0; i < kNumber; i++) {
　　　　stamps.push_back(muduo::Timestamp::now());
　　}

　　std::cout << stamps.front().toFormattedString(false) << std::endl;
　　std::cout << stamps.back().toFormattedString(false) << std::endl;
　　std::cout << timeDifference(stamps.back(), stamps.front()) << std::endl;

　　return 0;
}

编译命令和输出如下:

root@ubuntu:/home/wangml/code/muduo_test# g++ Timestamp.cc Timestamp_test.cc -o Timestamp_test
root@ubuntu:/home/wangml/code/muduo_test# ./Timestamp_test 
1615896149.195408
20210316 12:02:29.195408
20210316 12:02:29
20210316 12:02:29
20210316 12:02:29
0.037397

修改后的Timestamp以及测试文件下载:wangmlshadow/learn_muduo: 自己学习muduo源码时添加的注释以及一些自己写的测试文件 (github.com)