C++ 學習筆記：chrono - Timepoint 與 C Calendar Time (ctime) 轉換

Example:

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43

#include <chrono> #include <ctime> #include <string> #include <iostream> std::string asString(const std::chrono::system_clock::time_point& tp) { constexpr bool blUseLocalTime = true; std::time_t t = std::chrono::system_clock::to_time_t(tp); std::string ts = blUseLocalTime ? std::ctime(&t) : std::asctime(gmtime(&t)); ts.resize(ts.size() - 1); return ts; } std::chrono::system_clock::time_point makeTimePoint (int year, int mon, int day, int hour, int min, int sec = 0) { struct std::tm t; t.tm_sec = sec; // second of minute (0 .. 59 and 60 for leap seconds) t.tm_min = min; // minute of hour (0 .. 59) t.tm_hour = hour; // hour of day (0 .. 23) t.tm_mday = day; // day of month (1 .. 31) t.tm_mon = mon - 1; // month of year (0 .. 11) t.tm_year = year - 1900; // year since 1900 t.tm_isdst = -1; // determine whether daylight saving time auto tt = std::mktime(&t); if (tt == -1) { throw "no valid system time"; } return std::chrono::system_clock::from_time_t(tt); } int main() { auto tp1 = makeTimePoint(2010, 01, 01, 00, 00); std::cout << asString(tp1) << std::endl; auto tp2 = makeTimePoint(2011, 05, 23, 13, 44); std::cout << asString(tp2) << std::endl; }

Note:
mktime 會考慮 local time zone, 沒有明確的方法可以指定 UTC time

Reference:

1. The C++ Standard Library: A Tutorial and Reference, Second Edition