Using C + + to realize a sample code of command line progress bar

// Progress.hpp
#pragma once

#include <ctime>
#include <chrono>
#include <iostream>
#include <iomanip>
#include "Timer.hpp"


using namespace std::chrono;

class ProgressBar
{
protected:
  //The length of the progress bar (excluding the front suffix)
	unsigned int ncols;
  //Quantity completed
	std::atomic<unsigned int> finishedNum;
  //Last completed quantity
	unsigned int lastNum;
  //Total
	unsigned int totalNum;
  //Coefficient between progress bar length and percentage
	double colsRatio;
  //Start time
	steady_clock::time_point beginTime;
  //Last redraw time
	steady_clock::time_point lastTime;
  //Redraw cycle
	milliseconds interval;
	Timer timer;
public:
	ProgressBar(unsigned int totalNum, milliseconds interval) : totalNum(totalNum), interval(interval), finishedNum(0), lastNum(0), ncols(80), colsRatio(0.8) {}
  //Start
	void start();
  //Done
	void finish();
  //Update
	void update() { return this->update(1); }
  //Update multiple quantities at a time
	void update(unsigned int num) { this->finishedNum += num; }
  //Get the length of progress bar
	unsigned int getCols() { return this->ncols; }
  //Set progress bar length
	void setCols(unsigned int ncols) { this->ncols = ncols; this->colsRatio = ncols / 100; }
  //Redraw
	void show();
};
void ProgressBar::start() {
  //Record the start time and initialize the timer
	this->beginTime = steady_clock::now();
	this->lastTime = this->beginTime;
	//The timer is used to call the redraw function regularly
	this->timer.start(this->interval.count(), std::bind(&ProgressBar::show, this));
}

//Redraw函数
void ProgressBar::show() {
  //Clear last drawn content
	std::cout << "\r";
  //Record the time point of redrawing
	steady_clock::time_point now = steady_clock::now();
	//Get completed quantity
	unsigned int tmpFinished = this->finishedNum.load();
	//Gets the time interval from the start time and the last redraw time
	auto timeFromStart = now - this->beginTime;
	auto timeFromLast = now - this->lastTime;
	//The number of completed this time
	unsigned int gap = tmpFinished - this->lastNum;
	//Calculation speed
	double rate = gap / duration<double>(timeFromLast).count();
	//Percentage to be displayed
	double present = (100.0 * tmpFinished) / this->totalNum;
	//Print percentage
	std::cout << std::setprecision(1) << std::fixed << present << "%|";
	//Calculate how many = symbols should be drawn
	int barWidth = present * this->colsRatio;
	//Print completed and incomplete progress bars
	std::cout << std::setw(barWidth) << std::setfill('=') << "=";
	std::cout << std::setw(this->ncols - barWidth) << std::setfill(' ') << "|";

	//Printing speed
	std::cout << std::setprecision(1) << std::fixed << rate << "op/s|";
	//The next two parts are printing time passed and remaining time
	int timeFromStartCount = duration<double>(timeFromStart).count();

	std::time_t tfs = timeFromStartCount;
	tm tmfs;
	gmtime_s(&tmfs, &tfs);
	std::cout << std::put_time(&tmfs, "%X") << "|";

	int timeLast;
	if (rate != 0) {
    //The remaining time is estimated by the speed of this time and the number of unfinished projects
		timeLast = (this->totalNum - tmpFinished) / rate;
	}
	else {
		timeLast = INT_MAX;
	}

	if ((this->totalNum - tmpFinished) == 0) {
		timeLast = 0;
	}


	std::time_t tl = timeLast;
	tm tml;
	gmtime_s(&tml, &tl);
	std::cout << std::put_time(&tml, "%X");


	this->lastNum = tmpFinished;
	this->lastTime = now;
}

void ProgressBar::finish() {
  //Stop timer
	this->timer.stop();
	std::cout << std::endl;
}

// Timer.hpp
#pragma once
#include <functional>
#include <chrono>
#include <thread>
#include <atomic>
#include <memory>
#include <mutex>
#include <condition_variable>

using namespace std::chrono;

class Timer
{
public:
	Timer() : _expired(true), _try_to_expire(false)
	{}

	Timer(const Timer& timer)
	{
		_expired = timer._expired.load();
		_try_to_expire = timer._try_to_expire.load();
	}

	~Timer()
	{
		stop();
	}

	void start(int interval, std::function<void()> task)
	{
		// is started, do not start again
		if (_expired == false)
			return;

		// start async timer, launch thread and wait in that thread
		_expired = false;
		std::thread([this, interval, task]() {
			while (!_try_to_expire)
			{
				// sleep every interval and do the task again and again until times up
				std::this_thread::sleep_for(std::chrono::milliseconds(interval));
				task();
			}

			{
				// timer be stopped, update the condition variable expired and wake main thread
				std::lock_guard<std::mutex> locker(_mutex);
				_expired = true;
				_expired_cond.notify_one();
			}
		}).detach();
	}

	void startOnce(int delay, std::function<void()> task)
	{
		std::thread([delay, task]() {
			std::this_thread::sleep_for(std::chrono::milliseconds(delay));
			task();
		}).detach();
	}

	void stop()
	{
		// do not stop again
		if (_expired)
			return;

		if (_try_to_expire)
			return;

		// wait until timer 
		_try_to_expire = true; // change this bool value to make timer while loop stop
		{
			std::unique_lock<std::mutex> locker(_mutex);
			_expired_cond.wait(locker, [this] {return _expired == true; });

			// reset the timer
			if (_expired == true)
				_try_to_expire = false;
		}
	}

private:
	std::atomic<bool> _expired; // timer stopped status
	std::atomic<bool> _try_to_expire; // timer is in stop process
	std::mutex _mutex;
	std::condition_variable _expired_cond;
};