find GPGGA in NMEA

// find_GPGGA_in_nmea.cpp : 此檔案包含 'main' 函式。程式會於該處開始執行及結束執行。
//

#include "pch.h"
#include <iostream>
#include <string>
#include <fstream>
#include <cctype>
using namespace std;

void main()
{
    fstream nmea("E:\\VisualStudio_used\\find_GPGGA_in_nmea\\nmea_sample.txt", ios::in);
    fstream GPGGA_log("E:\\VisualStudio_used\\find_GPGGA_in_nmea\\GPGGA_log.txt", ios::out);
    if (nmea)
        cout << "成功開啟nmea_sample.txt\n";
    else
        cout << "nmea_sample.txt開啟失敗\n";
    if (GPGGA_log)
        cout << "成功建立GPGGA_log.txt\n";
    else
        cout << "GPGGA_log.txt建立失敗\n";

    string temp;
    while (!nmea.eof())
    {
        nmea >> temp;

        //=====find $GPGGA=====
        if (temp.find("$GPGGA") != string::npos)
        {
            cout << temp << endl;
            GPGGA_log << temp << endl;
        }
        else
            continue;

        //=====count check_char=====
        char check_char=temp[1];
        for (int i = 2; i < temp.find('*'); i++)
        {
            check_char ^= temp[i];
        }

        //=====count check_num=====
        int check_num;
        if(isalpha(temp[temp.find('*')+1]))
            check_num = (temp[temp.find('*') + 1] - 'A' + 10) * 16;
        else
            check_num = (temp[temp.find('*') + 1] - '0') * 16;
        if(isalpha(temp[temp.find('*') + 2]))
            check_num += (temp[temp.find('*') + 2] - 'A' + 10);
        else
            check_num += (temp[temp.find('*') + 2] - '0');
        //=====print check resault=====
        if (unsigned(check_char) == check_num)
        {
            cout << "檢查碼正確\t";
            GPGGA_log << "檢查碼正確\t";
        }
        else
        {
            cout << "檢查碼錯誤\t";
            GPGGA_log << "檢查碼錯誤\t";
        }

        //=====print time=====
        int comma_pos=0,comma_num=0;
        while (comma_num != 1)
        {
            comma_pos=temp.find(',', comma_pos);
            comma_num++;
        }
        int hour, min, sec;
        hour = (temp[comma_pos + 1] - '0') * 10 + temp[comma_pos + 2] - '0';
        min= (temp[comma_pos + 3] - '0') * 10 + temp[comma_pos + 4] - '0';
        sec= (temp[comma_pos + 5] - '0') * 10 + temp[comma_pos + 6] - '0';
        if (hour < 12)
        {
            cout << "Time: " << hour << ':' << min << ':' << sec << " AM UTC\t";
            GPGGA_log << "Time: " << hour << ':' << min << ':' << sec << " AM UTC\t";
        }
        else if (hour == 12)
        {
            cout << "Time: " << hour << ':' << min << ':' << sec << " PM UTC\t";
            GPGGA_log << "Time: " << hour << ':' << min << ':' << sec << " PM UTC\t";
        }
        else
        {
            cout << "Time: " << hour - 12 << ':' << min << ':' << sec << " PM UTC\t";
            GPGGA_log << "Time: " << hour - 12 << ':' << min << ':' << sec << " PM UTC\t";
        }

        //=====print 緯度=====
        while (comma_num != 2)
        {
            comma_pos = temp.find(',', comma_pos+1);
            comma_num++;
        }
        int comma_latitude_pos = temp.find(',', comma_pos + 1);
        for (int i = comma_pos + 1; i < comma_latitude_pos; i++)
        {
            if (i == temp.find('.', comma_pos + 1) - 2)
            {
                cout << " ";
                GPGGA_log << " ";
            }
            cout << temp[i];
            GPGGA_log << temp[i];
        }
        cout <<" " << temp[comma_latitude_pos + 1] << '\t';
        GPGGA_log << " " << temp[comma_latitude_pos + 1] << '\t';

        //=====print 經度=====
        while (comma_num != 4)
        {
            comma_pos = temp.find(',', comma_pos + 1);
            comma_num++;
        }
        int comma_longitude_pos = temp.find(',', comma_pos + 1);
        //cout << "temp.find('.', comma_pos + 1)=" << temp.find('.', comma_pos + 1) << endl;
        for (int i = comma_pos + 1; i < comma_longitude_pos; i++)
        {
            if (i == temp.find('.', comma_pos + 1) - 2)
            {
                cout << " ";
                GPGGA_log << " ";
            }
            cout << temp[i];
            GPGGA_log << temp[i];
        }
        cout << " " << temp[comma_longitude_pos + 1] << '\t';
        GPGGA_log << " " << temp[comma_longitude_pos + 1] << '\t';

        //=====衛星數=====
        while (comma_num != 7)
        {
            comma_pos = temp.find(',', comma_pos + 1);
            comma_num++;
        }
        int satellite_num = (temp[comma_pos + 1] - '0') * 10 + (temp[comma_pos + 2] - '0');
        cout <<"使用 "<< satellite_num<<"顆衛星\t";
        GPGGA_log << "使用 " << satellite_num << "顆衛星\t";

        cout << endl<<endl;
        GPGGA_log << endl << endl;
    }
}

// 執行程式: Ctrl + F5 或 [偵錯] > [啟動但不偵錯] 功能表
// 偵錯程式: F5 或 [偵錯] > [啟動偵錯] 功能表

// 開始使用的秘訣:
//   1. 使用 [方案總管] 視窗，新增/管理檔案
//   2. 使用 [Team Explorer] 視窗，連線到原始檔控制
//   3. 使用 [輸出] 視窗，參閱組建輸出與其他訊息
//   4. 使用 [錯誤清單] 視窗，檢視錯誤
//   5. 前往 [專案] > [新增項目]，建立新的程式碼檔案，或是前往 [專案] > [新增現有項目]，將現有程式碼檔案新增至專案
//   6. 之後要再次開啟此專案時，請前往 [檔案] > [開啟] > [專案]，然後選取 .sln 檔案