[release/6.0.1] Support async operations on unseekable files

[adamsitnik]

This is a manual backport of #58434, the problem has been recently discussed for #60931 which has not been merged to 6.0 as it was simply too late.

Customer Impact

This PR actually fixes two bugs.

The first one is a bug reported by customer via email, where an async read operation performed on a FileStream opened for non-seekable device file was throwing an System.IO.IOException: "The parameter is incorrect".

It turns out that ReadFiledoc was wrong:

For an hFile that does not support byte offsets, Offset and OffsetHigh are ignored.

And OVERLAPPEDdoc was right:

This member is nonzero only when performing I/O requests on a seeking device that supports the concept of an offset (also referred to as a file pointer mechanism), such as a file. Otherwise, this member must be zero.

The second bug is #58383. To tell the long story short, File.ReadAllBytes*(string path, ...) methods were assuming that path can't point to a non-seekable file like named pipe.

Testing

The fix was verified using tests added in the PR. It has been in main for a month (#58434) and we have already been doing that for sync file handles (the issue was originally discovered and fixed by @stephentoub):

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

Lines 723 to 732 in cf7d517

	privatestaticNativeOverlappedGetNativeOverlappedForSyncHandle(SafeFileHandlehandle,longfileOffset)
	{
	Debug.Assert(!handle.IsAsync);
	NativeOverlappedresult=default;
	if(handle.CanSeek)
	{
	result.OffsetLow=unchecked((int)fileOffset);
	result.OffsetHigh=(int)(fileOffset>>32);
	}

Risk

Very low.

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Issue Details

---

Customer Impact

This PR actually fixes two bugs.

The first one is a bug reported by customer via email, where an async read operation performed on a FileStream opened for non-seekable device file was throwing an System.IO.IOException: "The parameter is incorrect".

It turns out that ReadFiledoc was wrong:

For an hFile that does not support byte offsets, Offset and OffsetHigh are ignored.

And OVERLAPPEDdoc was right:

This member is nonzero only when performing I/O requests on a seeking device that supports the concept of an offset (also referred to as a file pointer mechanism), such as a file. Otherwise, this member must be zero.

The second bug is #58383. To tell the long story short, File.ReadAllBytes*(string path, ...) methods were assuming that path can't point to a non-seekable file like named pipe.

Testing

The fix was verified using tests added in the PR. It has been in main for a month (#58434) and we have already been doing that for sync file handles (the issue was originally discovered and fixed by @stephentoub):

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

Lines 723 to 732 in cf7d517

	privatestaticNativeOverlappedGetNativeOverlappedForSyncHandle(SafeFileHandlehandle,longfileOffset)
	{
	Debug.Assert(!handle.IsAsync);
	NativeOverlappedresult=default;
	if(handle.CanSeek)
	{
	result.OffsetLow=unchecked((int)fileOffset);
	result.OffsetHigh=(int)(fileOffset>>32);
	}

Risk

Very low.

Author:	adamsitnik
Assignees:	-
Labels:	area-System.IO
Milestone:	6.0.1

[jamshedd]

Approved for Dec - 6.0.1

[danmoseley]

@adamsitnik approved for 6.0.1, but if it's feasible to ask the customer to validate (presumably by picking up current main) that would be ideal.