prepend the “\\?\” string to the path - DriverPackageUninstall

问题

I used DriverPackageUninstall, to uninstall my driver. For this API I need to give "Inf Path" as the input. And I need to give this path as UNICODE string. To do this, I took the following statement from MSDN as reference.

For a Unicode string, the maximum length is 32,767 characters. If you use the Unicode version, prepend the "\?\" string to the path. For general information about the format of file path strings, see Naming a File in the MSDN Library.

But when I try the same in my code its not working. Can someone give me some examples on how to prepend the "\?\" before the path? Thanks..

UPDATE :

I tried with the below code as sample

#define UNICODE
#define _UNIOCDE
#define WINVER 0x501

    #include <stdio.h>
    #include <windows.h>
    #include <tchar.h>

    int main () {
        PTCHAR DriverPackageInfPath = TEXT("\\?\\c:\\Documents and Settings\\Desktop\\My.inf");

        FILE * Log;
         Log = _wfopen( TEXT(DriverPackageInfPath, TEXT("a"));

         if ( Log == NULL ) {
           MessageBox(NULL, TEXT ( "Unable to open INF file\n" ),
               TEXT ( "Installation Error" ), 0 | MB_ICONSTOP );
           exit ( 1 );
         } else {
                printf ("INF file opened successfully\n");
         }

         return 0;
    }

UPDATE:

".\dist\Driver\My.inf" How to add "\\?\" before this kind of paths? "\\?\.\dist\Driver\My.inf" is not working.

回答1:

You have error in string constant:

TEXT("\\?\\c:\\Documents ...."

should be

TEXT("\\\\?\\c:\\Documents  ...."

Read carefully, escape carefully : http://msdn.microsoft.com/en-us/library/windows/hardware/ff552316%28v=vs.85%29.aspx

UPDATE:

From http://msdn.microsoft.com/en-us/library/aa365247.aspx :

Win32 File Namespaces

The Win32 namespace prefixing and conventions are summarized in this section and the following section, with descriptions of how they are used. Note that these examples are intended for use with the Windows API functions and do not all necessarily work with Windows shell applications such as Windows Explorer. For this reason there is a wider range of possible paths than is usually available from Windows shell applications, and Windows applications that take advantage of this can be developed using these namespace conventions.

For file I/O, the "\?\" prefix to a path string tells the Windows APIs to disable all string parsing and to send the string that follows it straight to the file system. For example, if the file system supports large paths and file names, you can exceed the MAX_PATH limits that are otherwise enforced by the Windows APIs. For more information about the normal maximum path limitation, see the previous section Maximum Path Length Limitation.

Because it turns off automatic expansion of the path string, the "\?\" prefix also allows the use of ".." and "." in the path names, which can be useful if you are attempting to perform operations on a file with these otherwise reserved relative path specifiers as part of the fully qualified path.

Win32 Device Namespaces

The "\.\" prefix will access the Win32 device namespace instead of the Win32 file namespace. This is how access to physical disks and volumes is accomplished directly, without going through the file system, if the API supports this type of access. You can access many devices other than disks this way (using the CreateFile and DefineDosDevice functions, for example).

For example, if you want to open the system's serial communications port 1, you can use "COM1" in the call to the CreateFile function. This works because COM1–COM9 are part of the reserved names in the NT namespace, although using the "\.\" prefix will also work with these device names. By comparison, if you have a 100 port serial expansion board installed and want to open COM56, you cannot open it using "COM56" because there is no predefined NT namespace for COM56. You will need to open it using "\.\COM56" because "\.\" goes directly to the device namespace without attempting to locate a predefined alias.

Another example of using the Win32 device namespace is using the CreateFile function with "\.\PhysicalDiskX" (where X is a valid integer value) or "\.\CdRomX". This allows you to access those devices directly, bypassing the file system. This works because these device names are created by the system as these devices are enumerated, and some drivers will also create other aliases in the system. For example, the device driver that implements the name "C:\" has its own namespace that also happens to be the file system.

APIs that go through the CreateFile function generally work with the "\.\" prefix because CreateFile is the function used to open both files and devices, depending on the parameters you use.

If you're working with Windows API functions, you should use the "\.\" prefix to access devices only and not files.

Most APIs won't support "\.\"; only those that are designed to work with the device namespace will recognize it. Always check the reference topic for each API to be sure.

So your relative path can be

\\?\.\dist\driver\My.inf

escaped form is

\\\\?\\.\\dist\\driver\\My.inf

回答2:

You only need to prepend \\?\ to the path if it is longer than MAX_PATH characters.

来源：https://stackoverflow.com/questions/12299123/prepend-the-string-to-the-path-driverpackageuninstall

标签

winapi

unicode

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