Tar: set directory modification times while extracting.

[tmds]

Fixes #74398.

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Issue Details

---

Fixes #74398.

Author:	tmds
Assignees:	-
Labels:	community-contribution, area-System.Formats.Tar
Milestone:	-

[tmds]

The test I've included fails on Windows.
Something causes the last write time on the extracted directory to be the current time.

It can be a bug in the implementation, though I expect that would also happen on Linux.
It can also be something that is specific to Windows which causes the time to change.
Does someone have an idea on what it might be?

[danmoseley]

Something causes the last write time on the extracted directory to be the current time

I didn't look carefully, but I don't see you setting the directory times (Directory.SetLastWriteTime(..)). Without that, the directories are going to have the same time of the last write to a file within them, I think. (Although I thought that was true on Linux, so not sure why it would be only on Windows)

[danmoseley]

Looks like Directory.SetXx must be used to set a directory timestamp. File.SetXx will not work because Windows requires one extra flag:

runtime/src/libraries/System.Private.CoreLib/src/System/IO/FileSystem.Windows.cs

Line 223 in e80ef86

dwFlagsAndAttributes |= Interop.Kernel32.FileOperations.FILE_FLAG_BACKUP_SEMANTICS;

While on Unix, it looks like either work, they end up calling utimensat the same way.

[tmds]

Looks like Directory.SetXx must be used to set a directory timestamp. File.SetXx will not work because Windows requires one extra flag:

Yes, that makes the difference. The tests are passing now on Windows too.

[tmds]

This is copied and changed for directories from:

runtime/src/libraries/System.Formats.Tar/src/System/Formats/Tar/TarEntry.cs

Lines 552 to 562 in e80ef86

	private static void AttemptSetLastWriteTime(string destinationFileName, DateTimeOffset lastWriteTime)
	{
	try
	{
	File.SetLastWriteTime(destinationFileName, lastWriteTime.LocalDateTime); // SetLastWriteTime expects local time
	}
	catch
	{
	// Some OSes like Android might not support setting the last write time, the extraction should not fail because of that
	}
	}

[danmoseley]

When we close this issue we probably should open an issue for our zip implementation as well as that's also mentioned in that issue

[ViktorHofer]

I might be reading this wrong but isn't directoryModificationTimes always empty here with the current implementation? If it's always empty, why even pass it in?

[tmds]

It gets new-ed up by the caller of this method and the same instance is passed to all entries of the archive.
Items get added and removed by the call to TarHelpers.UpdatePendingModificationTimes in this method.