C# Signature:
[DllImport("mpr.dll")]
[return:MarshalAs(UnmanagedType.U4)]
static extern int WNetGetUniversalName(
string lpLocalPath,
[MarshalAs(UnmanagedType.U4)] int dwInfoLevel,
IntPtr lpBuffer,
[MarshalAs(UnmanagedType.U4)] ref int lpBufferSize);
VB Signature:
Declare Function WNetGetUniversalName Lib "advapi32.dll" (TODO) As TODO
Constants:
const int UNIVERSAL_NAME_INFO_LEVEL = 0x00000001;
const int REMOTE_NAME_INFO_LEVEL = 0x00000002;
const int ERROR_MORE_DATA = 234;
const int NOERROR = 0;
Wrapper
using System.Runtime.InteropServices;
static string GetUniversalName(string localPath)
{
// The return value.
string retVal = null ;
// The pointer in memory to the structure.
IntPtr buffer = IntPtr.Zero;
// Wrap in a try/catch block for cleanup.
try
{
// First, call WNetGetUniversalName to get the size.
int size = 0;
// Make the call.
// Pass IntPtr.Size because the API doesn't like null, even though
// size is zero. We know that IntPtr.Size will be
// aligned correctly.
int apiRetVal = WNetGetUniversalName(localPath, UNIVERSAL_NAME_INFO_LEVEL, (IntPtr) IntPtr.Size, ref size);
// If the return value is not ERROR_MORE_DATA, then
// raise an exception.
if (apiRetVal != ERROR_MORE_DATA)
// Throw an exception.
throw new Win32Exception(apiRetVal);
// Allocate the memory.
buffer = Marshal.AllocCoTaskMem(size);
// Now make the call.
apiRetVal = WNetGetUniversalName(localPath, UNIVERSAL_NAME_INFO_LEVEL, buffer, ref size);
// If it didn't succeed, then throw.
if (apiRetVal != NOERROR)
// Throw an exception.
throw new Win32Exception(apiRetVal);
// Now get the string. It's all in the same buffer, but
// the pointer is first, so offset the pointer by IntPtr.Size
// and pass to PtrToStringAuto.
retVal = Marshal.PtrToStringAuto(new IntPtr(buffer.ToInt64() + IntPtr.Size));
}
finally
{
// Release the buffer.
Marshal.FreeCoTaskMem(buffer);
}
// First, allocate the memory for the structure.
// That's all folks.
return retVal;
}
Notes:
Note by Günter Prossliner 2005-08-29
PtrToStringAuto doesn't work on my system. I have tested in on a clean WindowsXP professional maschine. The PtrToStringAuto function just returns garbage. After stepping into the function with the debugger I was looking a the Memory - Windows pointing to the address of "buffer". What I've seen there was a "normal" zero - terminated ANSI String.
After i have changed
retVal = Marshal.PtrToStringAuto(new IntPtr(buffer.ToInt64() + IntPtr.Size));
into
retVal = Marshal.PtrToStringAnsi(new IntPtr(buffer.ToInt64() + IntPtr.Size), size);
all worked fine.
If you take a look at the IL - Code of Marshal.PtrToStringAuto(IntPtr) you can see that this function calls 'kernel32:lstrlen' and 'kernel32:lstrcpy' using a buffer (StringBuilder) with the size of lstrlen.
The code of Marshal.PtrToStringAuto(IntPtr, Int32 size) looks quite different: It checks out the Marshal.SystemDefaultCharSize field and simply calls 'PtrToStringAnsi' or 'PtrToStringUni'.
Tips & Tricks:
Please add some!
Sample Code:
/* This needs cleaning up -- errr but I'm paid by the hour so I don't have the time. I mostly ripped the wrapper and modified it. It provides an alternative to pointer arithmetic though...*/
/*
typedef struct _REMOTE_NAME_INFO
{
LPTSTR lpUniversalName;
LPTSTR lpConnectionName;
LPTSTR lpRemainingPath;
} REMOTE_NAME_INFO;
*/
[StructLayout(LayoutKind.Sequential)]
struct _REMOTE_NAME_INFO
{
public IntPtr lpUniversalName;
public IntPtr lpConnectionName;
public IntPtr lpRemainingPath;
}
public struct RemoteNameInfo
{
public string universalName;
public string connectionName;
public string remainingPath;
}
public class WNet
{
const int UNIVERSAL_NAME_INFO_LEVEL = 0x00000001;
const int REMOTE_NAME_INFO_LEVEL = 0x00000002;
const int ERROR_MORE_DATA = 234;
const int NOERROR = 0;
[DllImport("mpr.dll", CharSet = CharSet.Unicode)]
[return: MarshalAs(UnmanagedType.U4)]
private static extern int WNetGetUniversalNameW(
string lpLocalPath,
[MarshalAs(UnmanagedType.U4)] int dwInfoLevel,
IntPtr lpBuffer,
[MarshalAs(UnmanagedType.U4)] ref int lpBufferSize);
public static RemoteNameInfo GetRemoteNameInfo(string localPath)
{
// The return value.
RemoteNameInfo retVal;
_REMOTE_NAME_INFO rni;
// The pointer in memory to the structure.
IntPtr buffer = IntPtr.Zero;
// Wrap in a try/catch block for cleanup.
try
{
// First, call WNetGetUniversalName to get the size.
int size = 0;
// Make the call.
// Pass IntPtr.Size because the API doesn't like null, even though
// size is zero. We know that IntPtr.Size will be
// aligned correctly.
int apiRetVal = WNetGetUniversalNameW(localPath, REMOTE_NAME_INFO_LEVEL, (IntPtr)IntPtr.Size, ref size);
// If the return value is not ERROR_MORE_DATA, then
// raise an exception.
if (apiRetVal != ERROR_MORE_DATA)
// Throw an exception.
throw new System.ComponentModel.Win32Exception();
// Allocate the memory.
buffer = Marshal.AllocCoTaskMem(size);
// Now make the call.
apiRetVal = WNetGetUniversalNameW(localPath, REMOTE_NAME_INFO_LEVEL, buffer, ref size);
// If it didn't succeed, then throw.
if (apiRetVal != NOERROR)
// Throw an exception.
throw new System.ComponentModel.Win32Exception();
// Now get the string. It's all in the same buffer, but
// the pointer is first, so offset the pointer by IntPtr.Size
// and pass to PtrToStringAuto.
//retVal = Marshal.PtrToStringAuto(new IntPtr(buffer.ToInt64() + IntPtr.Size));
rni = (_REMOTE_NAME_INFO)Marshal.PtrToStructure(buffer, typeof(_REMOTE_NAME_INFO));
retVal.connectionName = Marshal.PtrToStringAuto(rni.lpConnectionName);
retVal.remainingPath = Marshal.PtrToStringAuto(rni.lpRemainingPath);
retVal.universalName = Marshal.PtrToStringAuto(rni.lpUniversalName);
return retVal;
}
finally
{
// Release the buffer.
Marshal.FreeCoTaskMem(buffer);
}
// First, allocate the memory for the structure.
// That's all folks.
}
}
Alternative Managed API:
Do you know one? Please contribute it!
