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time/FileTime: add FileTimeToChronoDuration()

This commit is contained in:
Max Kellermann 2021-08-10 14:18:57 +02:00
parent 1976003e91
commit 9fc3c60910
1 changed files with 20 additions and 1 deletions
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21
src/time/FileTime.hxx
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@ -53,6 +53,24 @@ ToInt64(FILETIME ft) noexcept
return ToUint64(ft);
}
/* "A file time is a 64-bit value that represents the number of
100-nanosecond intervals"
https://docs.microsoft.com/en-us/windows/win32/sysinfo/file-times */
using FileTimeResolution = std::ratio<1, 10000000>;
using FileTimeDuration = std::chrono::duration<int_least64_t,
FileTimeResolution>;
/**
* Calculate a std::chrono::duration specifying the duration of the
* FILETIME since its epoch (1601-01-01T00:00).
*/
constexpr auto
FileTimeToChronoDuration(FILETIME ft) noexcept
{
return FileTimeDuration(ToInt64(ft));
}
constexpr time_t
FileTimeToTimeT(FILETIME ft) noexcept
{
@ -69,7 +87,8 @@ FileTimeToChrono(FILETIME ft) noexcept
constexpr std::chrono::seconds
DeltaFileTimeS(FILETIME a, FILETIME b) noexcept
{
return std::chrono::seconds((ToInt64(a) - ToInt64(b)) / 10000000);
return std::chrono::duration_cast<std::chrono::seconds>
(FileTimeToChronoDuration(a) - FileTimeToChronoDuration(b));
}
#endif