C++ 获取时间戳：下周一、月初、月中、月末

C++ 获取时间戳：下周一、月初、月中、月末

在一次开发过程中需要利用当前时间获取下周一、这个个月月中、这个月月末和下个月月初的时间戳，在此做一个总结。

#include 
#include 
#include 
#include 

#define ONE_DAY (86400)

using namespace std;

int GetWeek(long now_timestamp) {
    struct tm gmtm;
    gmtime_r(&now_timestamp, &gmtm);
    int day_of_week = gmtm.tm_wday;
    return day_of_week == 0?7:day_of_week;
}

int GetDay(long now_timestamp) {
    struct tm gmtm;
    gmtime_r(&now_timestamp, &gmtm);
    int day_of_month = gmtm.tm_mday;
    return day_of_month;
}

int GetYears(long now_timestamp) {
    struct tm gmtm;
    gmtime_r(&now_timestamp, &gmtm);
    int years = gmtm.tm_year;
    return years;
}

int GetMonth(long now_timestamp) {
    struct tm gmtm;
    gmtime_r(&now_timestamp, &gmtm);
    int month = gmtm.tm_mon;
    return month;
}

int GetDaysInMonth(long now_timestamp)
{
    int now_years = GetYears(now_timestamp);
    int now_month = GetMonth(now_timestamp);
    int now_day;
    int day[]= {31,28,31,30,31,30,31,31,30,31,30,31};
    if (1 == now_month){
        now_day=(((0==now_years%4)&&(0!=now_years%100)||(0==now_years%400))?29:28);
    }   
    else{
        now_day=day[now_month];
    }   
    return now_day;
}


int main(int argc, char *argv[]){
    long now_time = time(NULL);
    long now_floor_time = now_time/ONE_DAY*ONE_DAY;
    cout << "now time: " << now_floor_time << endl;
    //获取下一个周一零点时间
    cout << "next Monday time: " << now_floor_time + (8 - GetWeek(now_time))*ONE_DAY << endl;
    //获取这个月中旬或者这个月末时间
    long now_day_of_month = GetDay(now_time);
    if (now_day_of_month < 15) {
        cout << "next Mid-month time: " << now_floor_time + (15 - now_day_of_month)*ONE_DAY << endl;
    }
    else {
        cout << "next End of month time: " << now_floor_time + (GetDaysInMonth(now_time) - now_day_of_month)*ONE_DAY << endl;
    }
    //获取下个月月初时间
    cout << "next month time: " << now_floor_time + (GetDaysInMonth(now_time) - now_day_of_month+1)*ONE_DAY << endl;
}

在上述代码中gmtime_r()方法可以线程安全获取到关于当前时间的一个结构体tm，返回的月份从0-11，返回每个月所在的日期为1-31，返回的所在礼拜为0-6，其中0代表的是礼拜天，1代表礼拜一以此类推；

struct tm
{
    int tm_sec;   // seconds after the minute - [0, 60] including leap second
    int tm_min;   // minutes after the hour - [0, 59]
    int tm_hour;  // hours since midnight - [0, 23]
    int tm_mday;  // day of the month - [1, 31]
    int tm_mon;   // months since January - [0, 11]
    int tm_year;  // years since 1900
    int tm_wday;  // days since Sunday - [0, 6]
    int tm_yday;  // days since January 1 - [0, 365]
    int tm_isdst; // daylight savings time flag
};

通过获取到的年份，判断当前年份是否是闰年来获取每个月对应的天数，方法如 GetDaysInMonth()；
拿到这些信息我们可以通过计算天数来获取自己所需要的时间戳。

运行结果如下：

now time: 1560211200
next Monday time: 1560729600
next Mid-month time: 1560556800
next month time: 1561939200