Use NtCreateFile on Win32 #27195
Use NtCreateFile on Win32 #27195
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NtCreateFile allows passing in a base handle which makes opening child directories much faster. This cuts anywhere from 3-10% of the time off of a GetFiles() call. It is significantly faster as it avoids normalization and path parsing overhead.
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This is a fully supported stable API right? It's hard to imagine it changing but the doc links to https://msdn.microsoft.com/en-us/library/bb432200(v=vs.85).aspx |
| [Flags] | ||
| public enum ObjectAttributes : uint | ||
| { | ||
| // https://msdn.microsoft.com/en-us/library/windows/hardware/ff564586.aspx |
| // https://msdn.microsoft.com/en-us/library/bb432380.aspx | ||
| // https://msdn.microsoft.com/en-us/library/windows/hardware/ff566424.aspx | ||
| [DllImport(Libraries.NtDll, CharSet = CharSet.Unicode, ExactSpelling = true)] | ||
| private unsafe static extern int NtCreateFile( |
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why not define it to return Interop.StatusOptions (NTSTATUS)
BTW are we consistent when we use "original" name (seems structs and constants) vs "C# style" name (seems enum here)
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Because it isn't an enum. I'd prefer it to be. I can follow up with another change that does this- I'd have to change some other projects.
| { | ||
| return IntPtr.Zero; | ||
| } | ||
| throw Win32Marshal.GetExceptionForWin32Error(error, fullPath); |
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I don't think it is worth the trouble in this case but worth mentioning that we probably could get better error messages by calling FormatMessage passing the handle to ntdll instead of converting the NTSTATUS to Win32 error.
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We would get more discrete errors, but it wouldn't match the Win32 behavior. Want to be consistent historically, but more importantly, with our UAP builds.
Yes. The API is fully documented. Fyi, the signature hasn't changed since at least NT3.5, probably hasn't changed since the start (NT3.1). Changing it would break every kernel-mode driver/service that creates a file handle. |
NtCreateFile allows passing in a base handle which makes opening child directories much faster. This cuts anywhere from 3-10% of the time off of a GetFiles() call. It is significantly faster as it avoids normalization and path parsing overhead.
NtCreateFile allows passing in a base handle which makes opening child directories much faster. This cuts anywhere from 3-10% of the time off of a GetFiles() call. It is significantly faster as it avoids normalization and path parsing overhead. Commit migrated from dotnet/corefx@a28a2cd
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NtCreateFile allows passing in a base handle which makes opening child directories much faster. This cuts anywhere from 3-10% of the time off of a GetFiles() call.
It is significantly faster as it avoids normalization and path parsing overhead.
cc: @terrajobst, @danmosemsft