SAMPLE: CheckLCL.exe Finds Corresponding Local Path for UNC Name

ID: Q148391

The information in this article applies to:

Microsoft Win32 Software Development Kit (SDK), version 4.0
Microsoft Windows NT Workstation versions 3.50, 3.51
Microsoft Windows NT Server versions 3.5, 3.51
Microsoft Windows 95

SUMMARY

UNC names specify network-wide distinct locations that are useful to provide configuration information for applications. However, when the UNC name refers to the local computer, it introduces some overhead because the requests are passed down the Redirector, looped back by the transport, and sent to the server service instead of going directly to the local disk.

The function provided in the library file in the CheckLCL.exe sample checks the name passed it against the local computer name and replaces the \\<computer>\<share> part with the local path to the share.

MORE INFORMATION

The following file is available for download from the Microsoft Software Library:

~ CheckLCL.exe

For more information about downloading files from the Microsoft Software Library, please see the following article in the Microsoft Knowledge Base:

Q119591 How to Obtain Microsoft Support Files from Online Services

Limitations or Caveats

The function only resolves names in the Microsoft Windows Network. It doesn't work with FPNW.

Because the changed names do not hit server service anymore, share security does not apply. But this is alright because the function, which is called to resolve the name, can only be called by Admin type accounts on Windows NT. On Windows 95, there is no local security anyway.

The CheckLCL library has three callable functions: GlpGetLocalPathName, GlpFreeBuffer, and GlpGetBuffer.

The GlpGetLocalPathName Function


   GlpGetLocalPathName( IN LPCTSTR pszInputName,

               IN OUT LPTSTR *ppszOutputName,
               IN OUT LPDWORD pdwOutputNameLength,
               OPTIONAL OUT LPDWORD pdwLanManError,
               OPTIONAL IN NETSHAREGETINFO_FPTR __stdcall
                               GlpNetShareGetInfoPtr
          );

To successfully execute the GlpGetLocalPathName function, you need to have administrative or server operator privileges on Windows NT. Also, the network should be running. The GlpGetLocalPathName function supports file, pipe, and mailslot share names. It also supports the use of path names longer than 260 characters (syntax \\?\ in CreateFile). For more information, please see the header file.

PszInputName:

The GlpGetLocalPathName function scans the name passed in pszInputName and tries to convert it to a local file path, if it's a UNC name referencing the local computer name.

PpszOutputName:

ppszOutputName contains the local path name if the return code is ERROR_GLP_SUCCESS. In any other case, the contents should be ignored. The GlpGetLocalPathName function will allocate memory if you pass a pointer to NULL. You should free the pointer using GlpFreeBuffer.

PdwOutputNameLength:

When you pass a pointer to memory in ppszOutputName, this parameter specifies the number of characters that can be stored there including the terminating NULL character.

When the GlpGetLocalPathName function returns ERROR_GLP_SUCCESS, this pdwOutputNameLength variable contains the number of characters copied into the buffer.

If the function returns ERROR_GLP_INSUFFICIENT_BUFFER or ERROR_GLP_INSUFFICIENT_MEMORY, the pdwOutputNameLength variable contains the number of characters needed to store the converted name.

PdwLanManError:

This optional parameter points to a DWORD that receives the error code returned by NetShareEnum if the return code is ERROR_GLP_LANMAN_ERROR. The value is not changed when NetShareEnum returns successfully. If you're not interested in this value, pass NULL to the function.

GlpNetShareGetInfoPtr:

If not NULL, this function pointer will be called instead of NetShareEnum. This gives the caller the possibility to provide the local name or to call some other API. The parameters passed are for a call to NetShareEnum with information level 2. Remember that this function is UNICODE only.

The GlpFreeBuffer Function

GlpFreeBuffer (PVOID *ppszBuffer);

This function frees a pointer returned from GlpGetLocalPathName in the parameter ppszOutputName. The function sets the pointer to NULL after the memory is freed.

The GlpGetBuffer Function

GlpGetBuffer (PVOID *ppszBuffer, DWORD dwSizeNeeded);

Use this function if you pass a pointer to your custom NetShareGetInfo function to GlpGetLocalPathNameW to allocate memory for the bufptr output parameter of NetShareGetInfo. GlpGetLocalPathNameW uses its GlpFreeBuffer function to free the memory.

This function returns ERROR_GLP_SUCCESS on success and ERROR_GLP_INSUFFICIENT_MEMORY if there is not enough memory.


Keywords          : kbfile kbnetwork kbsample kbAPI kbNTOS350 kbNTOS351 kbSDKPlatform kbWinOS95 kbNetAPI kbGrpNet 
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Last Reviewed: March 10, 1999