將本地時間轉換爲時間戳

Question

將由GetLocalTime返回的SYSTEMTIME結構轉換爲時間戳（自1970年以來的秒數ULONG）會怎樣？

Answer 1

一種方法是將參考時間和目標時間都轉換爲FILETIME結構，然後您可以根據它們的值執行簡單的算術運算。這些以100ns爲單位進行測量，因此您需要將最終結果除以10000000以獲得秒數。

// reference time, convert to FILETIME 
SYSTEMTIME stRef{}; 
stRef.wYear = 1970; 
stRef.wMonth = 1; 
stRef.wDay = 1; 

FILETIME ftRef; 
SystemTimeToFileTime(&stRef, &ftRef); 


// target time, convert to FILETIME 
SYSTEMTIME stTarget; 
GetLocalTime(&stTarget); 

FILETIME ftTarget; 
SystemTimeToFileTime(&stTarget, &ftTarget); 


// convert both to ULARGE_INTEGER 
ULARGE_INTEGER ulRef, ulTarget; 
ulRef.HighPart = ftRef.dwHighDateTime; 
ulRef.LowPart = ftRef.dwLowDateTime; 
ulTarget.HighPart = ftTarget.dwHighDateTime; 
ulTarget.LowPart = ftTarget.dwLowDateTime; 


// subtract reference time from target time 
ulTarget.QuadPart -= ulRef.QuadPart; 

// convert to seconds (divide by 10000000) 
DWORD dwSecondsSinceRefTime = ulTarget.QuadPart/10000000i64;