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/*
* Copyright 2013-2019 Max Kellermann <max.kellermann@gmail.com>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* - Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* - Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the
* distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* FOUNDATION OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
* SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
* STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
* OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#ifndef FILE_TIME_HXX
#define FILE_TIME_HXX
#include <fileapi.h>
#include <chrono>
#include <cstdint>
constexpr uint_least64_t
ConstructUint64(DWORD lo, DWORD hi) noexcept
{
return uint_least64_t(lo) | (uint_least64_t(hi) << 32);
}
constexpr uint_least64_t
ToUint64(FILETIME ft) noexcept
{
return ConstructUint64(ft.dwLowDateTime, ft.dwHighDateTime);
}
constexpr int_least64_t
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));
}
/**
* Calculate a std::chrono::duration specifying the duration between
* the unix epoch and the given FILETIME.
*/
constexpr auto
FileTimeToUnixEpochDuration(FILETIME ft) noexcept
{
/**
* The number of days between the Windows FILETIME epoch
* (1601-01-01T00:00) and the Unix epoch (1970-01-01T00:00).
*/
constexpr int_least64_t windows_unix_days = 134774;
constexpr int_least64_t windows_unix_hours = windows_unix_days * 24;
constexpr FileTimeDuration windows_unix_delta{std::chrono::hours{windows_unix_hours}};
return FileTimeToChronoDuration(ft) - windows_unix_delta;
}
inline std::chrono::system_clock::time_point
FileTimeToChrono(FILETIME ft) noexcept
{
/* this is guaranteed to be 0 in C++20 */
const auto unix_epoch = std::chrono::system_clock::from_time_t(0);
const auto windows_duration = FileTimeToUnixEpochDuration(ft);
const auto sys_duration =
std::chrono::duration_cast<std::chrono::system_clock::duration>
(windows_duration);
return unix_epoch + sys_duration;
}
constexpr std::chrono::seconds
DeltaFileTimeS(FILETIME a, FILETIME b) noexcept
{
return std::chrono::duration_cast<std::chrono::seconds>
(FileTimeToChronoDuration(a) - FileTimeToChronoDuration(b));
}
#endif
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