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Fix up buffer management getting network roots #21068

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jborean93 wants to merge 2 commits into from
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Fix up buffer management getting network roots #21068

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aca9d8c
Fix up buffer management getting network roots
jborean93 Jan 14, 2024
dcbcb77
Use builtin pointer to string method and ensure rented array is returned
jborean93 Jan 15, 2024
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62 changes: 31 additions & 31 deletions src/System.Management.Automation/engine/Interop/Windows/WNetGetConnection.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -26,44 +26,37 @@ internal static int GetUNCForNetworkDrive(char drive, out string? uncPath)

uint bufferSize = MAX_PATH;

#if DEBUG
// In Debug mode buffer size is initially set to 3 and if additional buffer is required, the
// required buffer size is allocated and the WNetGetConnection API is executed with the newly
// allocated buffer size.
bufferSize = 3;
#endif

ReadOnlySpan<char> driveName = stackalloc char[] { drive, ':', '\0' };
Span<char> uncBuffer = stackalloc char[(int)bufferSize];
int errorCode = ERROR_NO_NETWORK;

try
{
errorCode = WNetGetConnection(driveName, uncBuffer, ref bufferSize);
}
catch (System.DllNotFoundException)
char[]? rentedArray = null;
while (true)
{
s_WNetApiNotAvailable = true;
return ERROR_NOT_SUPPORTED;
}

if (errorCode == ERROR_SUCCESS)
{
// exclude null terminator
uncPath = uncBuffer.Slice(0, (int)bufferSize - 1).ToString();
}
else if (errorCode == ERROR_MORE_DATA)
{
char[]? rentedArray = null;
int errorCode;
try
{
uncBuffer = rentedArray = ArrayPool<char>.Shared.Rent((int)bufferSize);
errorCode = WNetGetConnection(driveName, uncBuffer, ref bufferSize);
try
{
errorCode = WNetGetConnection(driveName, uncBuffer, ref bufferSize);
}
catch (System.DllNotFoundException)
{
s_WNetApiNotAvailable = true;
return ERROR_NOT_SUPPORTED;
}

if (errorCode == ERROR_SUCCESS)
{
// exclude null terminator
uncPath = uncBuffer.Slice(0, (int)bufferSize - 1).ToString();
// Cannot rely on bufferSize as it's only set if
// the first call ended with ERROR_MORE_DATA,
// instead slice at the null terminator.
unsafe
{
fixed (char* uncBufferPtr = uncBuffer)
{
uncPath = new string(uncBufferPtr);
}
}
}
}
finally
Expand All @@ -73,9 +66,16 @@ internal static int GetUNCForNetworkDrive(char drive, out string? uncPath)
ArrayPool<char>.Shared.Return(rentedArray);
}
}
}

return errorCode;
if (errorCode == ERROR_MORE_DATA)
{
uncBuffer = rentedArray = ArrayPool<char>.Shared.Rent((int)bufferSize);
}
else
{
return errorCode;
}
}
}
}
}