C++ datetime calculation api

来源：互联网发布：基础算法面试题编辑：程序博客网时间：2024/06/05 08:51

Description

A sample of how use C++ localtime/mktime to implement datetime calculation, for example plus/minus a few days, months, years, etc.

Source Code:

#include <time.h>#include <iomanip>#include <iostream>void printtm(const char * prefix, tm * tp) {    std::cout << prefix;    std::cout << std::setw(4) << std::setfill('0') << tp->tm_year + 1900;   // year    std::cout << "/";    std::cout << std::setw(2) << std::setfill('0') << tp->tm_mon + 1;   // month    std::cout << "/";    std::cout << std::setw(2) << std::setfill('0') << tp->tm_mday;  // day    std::cout << " ";    std::cout << std::setw(2) << std::setfill('0') << tp->tm_hour;  // hour    std::cout << ":";    std::cout << std::setw(2) << std::setfill('0') << tp->tm_min;   // minute    std::cout << ":";    std::cout << std::setw(2) << std::setfill('0') << tp->tm_sec;   // second    std::cout << std::endl;}int main(int argc, char * argv[]) {    time_t t = time(NULL);    tm * tp = localtime(&t);     printtm("today     :", tp);    tp->tm_mday += 2; mktime(tp);    printtm("+2 days   :", tp);  // 2 days later    tp->tm_mon  += 2; mktime(tp);    printtm("+2 months :", tp);  // 2 months later    tp->tm_year -= 2; mktime(tp);    printtm("-2 year   :", tp);  // 2 years before    return 0;}

Compile and execute:

$ g++ tt.cpp $ ./a.out today     :2015/12/29 04:16:25+2 days   :2015/12/31 04:16:25+2 months :2016/03/02 04:16:25-2 year   :2014/03/02 04:16:25

Limitation:

Function localtime() is not thread-unsafe, it uses an internal memory space to keep the datetime data structure, when multiply calling localtime(..) they overwrite the same memory space.

So localtime() cannot be shared among multiply threads.

The end

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