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Refactor GetFileShares #26155

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Refactor GetFileShares #26155

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77 changes: 34 additions & 43 deletions src/System.Management.Automation/engine/CommandCompletion/CompletionCompleters.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -17,6 +17,9 @@
using System.Management.Automation.Runspaces;
using System.Reflection;
using System.Runtime.InteropServices;
#if !UNIX
using System.Runtime.InteropServices.Marshalling;
#endif
using System.Text;
using System.Text.RegularExpressions;
using System.Threading;
Expand Down Expand Up @@ -5181,14 +5184,6 @@ private static string NewPathCompletionText(string parent, string leaf, StringCo
@"(^Microsoft\.PowerShell\.Core\\FileSystem::|^FileSystem::|^)(?:\\\\|//)(?![.|?])([^\\/]+)(?:\\|/)([^\\/]*)$",
RegexOptions.IgnoreCase | RegexOptions.Compiled);

[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
private struct SHARE_INFO_1
{
public string netname;
public int type;
public string remark;
}

private static readonly System.IO.EnumerationOptions _enumerationOptions = new System.IO.EnumerationOptions
{
MatchCasing = MatchCasing.CaseInsensitive,
Expand All @@ -5200,50 +5195,46 @@ internal static List<string> GetFileShares(string machine, bool ignoreHidden)
#if UNIX
return new List<string>();
#else
nint shBuf = nint.Zero;
uint numEntries = 0;
uint totalEntries;
uint resumeHandle = 0;
try
unsafe
{
int result = Interop.Windows.NetShareEnum(
machine,
level: 1,
out shBuf,
Interop.Windows.MAX_PREFERRED_LENGTH,
out numEntries,
out totalEntries,
ref resumeHandle);

var shares = new List<string>();
if (result == Interop.Windows.ERROR_SUCCESS || result == Interop.Windows.ERROR_MORE_DATA)
Interop.Windows.SHARE_INFO_1* pShareInfo = null;
try
{
for (int i = 0; i < numEntries; ++i)
{
nint curInfoPtr = shBuf + (Marshal.SizeOf<SHARE_INFO_1>() * i);
SHARE_INFO_1 shareInfo = Marshal.PtrToStructure<SHARE_INFO_1>(curInfoPtr);
uint result = Interop.Windows.NetShareEnum<Interop.Windows.SHARE_INFO_1>(
machine,
out pShareInfo,
out int count);

if ((shareInfo.type & Interop.Windows.STYPE_MASK) != Interop.Windows.STYPE_DISKTREE)
{
continue;
}
List<string> shares = new();

if (ignoreHidden && shareInfo.netname.EndsWith('$'))
if (result is Interop.Windows.ERROR_SUCCESS or Interop.Windows.ERROR_MORE_DATA)
{
foreach (Interop.Windows.SHARE_INFO_1 shareInfo in new ReadOnlySpan<Interop.Windows.SHARE_INFO_1>(pShareInfo, count))
{
continue;
}
if ((shareInfo.type & Interop.Windows.STYPE_MASK) != Interop.Windows.STYPE_DISKTREE)
{
continue;
}

string share = Utf16StringMarshaller.ConvertToManaged(shareInfo.netname);
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Potential null reference exception: Utf16StringMarshaller.ConvertToManaged may return null if shareInfo.netname is null, but the result is used without null checking on line 5221. Add null handling, e.g., string? share = Utf16StringMarshaller.ConvertToManaged(shareInfo.netname); if (share == null) continue;

Suggested change
string share = Utf16StringMarshaller.ConvertToManaged(shareInfo.netname);
string? share = Utf16StringMarshaller.ConvertToManaged(shareInfo.netname);
if (share == null)
{
continue;
}

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if (ignoreHidden && share.EndsWith('$'))
{
continue;
}

shares.Add(shareInfo.netname);
shares.Add(share);
}
}
}

return shares;
}
finally
{
if (shBuf != nint.Zero)
return shares;
}
finally
{
Interop.Windows.NetApiBufferFree(shBuf);
if (pShareInfo is not null)
{
Interop.Windows.NetApiBufferFree(pShareInfo);
}
}
}
#endif
Expand Down
2 changes: 1 addition & 1 deletion src/System.Management.Automation/engine/Interop/Windows/NetApiBufferFree.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -11,6 +11,6 @@ internal static unsafe partial class Windows
{

[LibraryImport("Netapi32.dll")]
internal static partial uint NetApiBufferFree(nint Buffer);
internal static unsafe partial uint NetApiBufferFree(void* Buffer);
}
}
48 changes: 37 additions & 11 deletions src/System.Management.Automation/engine/Interop/Windows/NetShareEnum.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -3,24 +3,50 @@

#nullable enable

using System;
using System.Runtime.InteropServices;

internal static partial class Interop
{
internal static unsafe partial class Windows
{
internal const int MAX_PREFERRED_LENGTH = -1;
internal const int STYPE_DISKTREE = 0;
internal const int STYPE_MASK = 0x000000FF;
internal const uint MAX_PREFERRED_LENGTH = uint.MaxValue;
internal const uint STYPE_DISKTREE = 0u;
internal const uint STYPE_MASK = 255u;

[LibraryImport("Netapi32.dll", StringMarshalling = StringMarshalling.Utf16)]
internal static partial int NetShareEnum(
string serverName,
int level,
out nint bufptr,
int prefMaxLen,
out uint entriesRead,
out uint totalEntries,
ref uint resumeHandle);
private static unsafe partial uint NetShareEnum(
string? servername,
uint level,
out byte* bufptr,
uint prefmaxlen,
out uint entriesread,
out uint totalentries,
uint* resume_handle);

[StructLayout(LayoutKind.Sequential)]
internal unsafe struct SHARE_INFO_1
{
public ushort* netname;
public uint type;
public ushort* remark;
}

internal static uint NetShareEnum<T>(string? servername, out T* pShareInfo, out int count) where T : unmanaged
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@iSazonov iSazonov Oct 9, 2025

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Since it is high level helper it could return just List so that we have no interop/unsafe code in call site.

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@xtqqczze xtqqczze Oct 9, 2025

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We need to free the unmanaged buffer, so we cannot return just a managed type.

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@xtqqczze xtqqczze Oct 9, 2025

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I considered implementing a class deriving from SafeBuffer, but this would be much more code and abstraction for a method that is only called once.

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@iSazonov iSazonov Oct 10, 2025

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If we build List in the method we can free the buffer in the method too.

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@xtqqczze xtqqczze Oct 10, 2025

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If we build List in the method we can free the buffer in the method too.

This is exactly what the GetFileShares method does already :p

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@xtqqczze xtqqczze Oct 17, 2025 •
edited
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@iSazonov I think the current changes are a reasonable balance between safety and avoiding unnecessary abstraction. In terms of safety, we now avoid pointer arithmetic and use a span implementation.

{
uint level = (uint)GetLevelFromStructure<T>();
uint result = NetShareEnum(servername, level, out byte* pBuffer, MAX_PREFERRED_LENGTH, out uint entriesRead, out _, null);
pShareInfo = (T*)pBuffer;
count = (int)entriesRead;
return result;
}

private static int GetLevelFromStructure<T>()
{
if (typeof(T) == typeof(SHARE_INFO_1))
return 1;

throw new NotSupportedException();
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The NotSupportedException lacks a descriptive message. Consider adding a message that specifies which type was unsupported, e.g., throw new NotSupportedException($\"Unsupported structure type: {typeof(T).Name}\");

Suggested change
throw new NotSupportedException();
throw new NotSupportedException($"Unsupported structure type: {typeof(T).Name}");

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}
}
}