How to unfold a Windows path to get a kind of canonical form?

Hi,

Having a path in whatever (but absolute) form, I would like to get a canonical form. The goal is to bind the license to the data on that path and to check, whether the path was not redirected via "subst" or "net use" commands. If the path is related to the directory at the network drive, the result should be UNC form of the path. If the path is related to a local drive, then the result should be the path that uses the non-virtual drive letter (i.e. c:\some\app\root\subdir instead of p:\subdir, for example).

The following text to be commented is rather long as it explains behaviour of the attached fully working example. I still need someone more experienced. There may be better approach to be used. Please, tear the code to pieces. Any objections are welcome.

I have found the following functions to be used: WNetGetConnection(), QueryDosDevice(), and GetDriveType().

The complication is that the "net use" and "subst" commands may be combined together. This is not the desired case; however, you can never be sure what the customer does at his computer.

Let's have the following context. The I: is the network drive mapped to...

=================================================
I:\PRIKRYL>net use i:
Local name        I:
Remote name       \\skil02\demo
Resource type     Disk
Status            OK
...
=================================================


Now the user creates subdirectories and puts the file inside:
=================================================
i:\prikryl\subdir\a\b\c\file.txt
=================================================

He also created subst drive letters like that:
=================================================
I:\PRIKRYL>subst p: i:\prikryl

I:\PRIKRYL>subst q: p:\subdir

I:\PRIKRYL>subst r: q:\a

I:\PRIKRYL>subst
P:\: => I:\prikryl
Q:\: => P:\subdir
R:\: => Q:\a
=================================================

The sample program below is given the path through the R: drive and it displays
=================================================
     path: R:\b\c\file.txt
    drive: R:
driveRoot: R:\
driveType: 4 (DRIVE_REMOTE)

WNetGetConnection("R:", ....): failed (67)
QueryDosDevice("R:", ....): \??\Q:\a

new drive: Q:
 new path: Q:\a\b\c\file.txt

WNetGetConnection("Q:", ....): failed (67)
QueryDosDevice("Q:", ....): \??\P:\subdir

new drive: P:
 new path: P:\subdir\a\b\c\file.txt

WNetGetConnection("P:", ....): failed (67)
QueryDosDevice("P:", ....): \??\I:\prikryl

new drive: I:
 new path: I:\prikryl\subdir\a\b\c\file.txt

WNetGetConnection("I:", ....): succeeded!

The wanted path: \\skil02\demo\prikryl\subdir\a\b\c\file.txt
=================================================

The last one is the wanted form. Now the substed drives are deleted
and the same is done via "net use". It is rather simpler case, because
there cannot be created the chain of substed drives via "net use"...
=================================================
I:\PRIKRYL>net use p: i:\prikryl
System error 67 has occurred.

The network name cannot be found.
=================================================

so only R:
=================================================
I:\PRIKRYL>net use r: \\skil02\demo\prikryl\subdir\a
The command completed successfully.
=================================================

The program returns...
=================================================

     path: R:\b\c\file.txt
    drive: R:
driveRoot: R:\
driveType: 4 (DRIVE_REMOTE)

WNetGetConnection("R:", ....): succeeded!

The wanted path: \\skil02\demo\prikryl\subdir\a\b\c\file.txt
=================================================

After removing all mapping of R: (no such drive)
=================================================

     path: R:\b\c\file.txt
    drive: R:
driveRoot: R:\
driveType: 1 (DRIVE_NO_ROOT_DIR)

QueryDosDevice("R:", ....): failed (2)

The wanted path: R:\b\c\file.txt
=================================================

Of course, it is not correct (simplified program), but it can be detected
even earlier by simple asking for existence of the directory or of the file.

Now, all mapping of the letter-drives are removed, the directories
are moved to the local disk and substed (to mimic the net mapping,
to pretend the situation is the same)...
=================================================
I:\PRIKRYL>subst p: c:\tmp\test

I:\PRIKRYL>subst q: p:\subdir

I:\PRIKRYL>subst r: q:\a

I:\PRIKRYL>subst
P:\: => C:\tmp\test
Q:\: => P:\subdir
R:\: => Q:\a
=================================================

However, canonization routine is here to reveal the attempt. The final
detection is not correct and should be enhanced somehow. The
C:\tmp\test\subdir\a\b\c\file.txt
should be the result. Using the QueryDosDevice() once more leads
to the situation when the result cannot be used as a full path...
=================================================
     path: R:\b\c\file.txt
    drive: R:
driveRoot: R:\
driveType: 3 (DRIVE_FIXED)

QueryDosDevice("R:", ....): \??\Q:\a

new drive: Q:
 new path: Q:\a\b\c\file.txt

QueryDosDevice("Q:", ....): \??\P:\subdir

new drive: P:
 new path: P:\subdir\a\b\c\file.txt

QueryDosDevice("P:", ....): \??\C:\tmp\test

new drive: C:
 new path: C:\tmp\test\subdir\a\b\c\file.txt

QueryDosDevice("C:", ....): \Device\HarddiskVolume3

new drive: ic
 new path: ice\HarddiskVolume3\tmp\test\subdir\a\b\c\file.txt

QueryDosDevice("ic", ....): failed (2)

The wanted path: ice\HarddiskVolume3\tmp\test\subdir\a\b\c\file.txt
=================================================

Do you have some experience with that? Is there any better approach?
Please point me to a documentation that discusses the

\??\C:\tmp\test

form of the path (namely the \??\ prefix and whether there can be another
variations of the prefix...).

Thanks for reading it to this line ;)
   Petr

#include <Windows.h>
#include <Winnetwk.h>  // WNetGetConnection()
#include <iostream>
#include <string>
 
using namespace std;
 
std::string driveTypeStr(UINT driveType);
 
int main()
{
    string drive("R:");
    string driveRoot(drive + "\\");
    string path(drive + "\\b\\c\\file.txt");
    UINT driveType = ::GetDriveType(driveRoot.c_str());
 
    cout << "     path: " << path << "\n"
         << "    drive: " << drive << "\n"
         << "driveRoot: " << driveRoot << "\n"
         << "driveType: " << driveType << " (" 
                          << driveTypeStr(driveType) << ")" << "\n"
         << "\n";
 
    char buf[1000];
    DWORD size = sizeof(buf);
    DWORD result = 0;
    string lastDrive;
 
    while (true)   
    {
        if (driveType == DRIVE_REMOTE)
        {
            cout << "WNetGetConnection(\"" << drive << "\", ....): ";
            result = WNetGetConnection(drive.c_str(), buf, &size);
            if (result != NO_ERROR)
                cout << "failed (" << result << ")\n";
            else
            {   
                cout << "succeeded!\n\n";
                string path2(buf);
                path = path2 + path.substr(2);
                break;  // the path was found
            }
        }
 
        // Here we get only when the WNetGetConnection failed.
        //
        cout << "QueryDosDevice(\"" << drive << "\", ....): ";   
        result = QueryDosDevice(drive.c_str(), buf, size);  
                                  // returns 0 or number of chars
        string path2(buf);
        if (result == 0)
        {
            cout << "failed (" << GetLastError() << ")\n\n";
            break;  // when this can fail?
        }
        else
        {
            cout << path2 << "\n";  // returned by QueryDosDevice
            drive = path2.substr(4, 2);
            if (lastDrive == drive)
                break;  // the path was found in the previous loop
            else
            {
                lastDrive = drive;
                cout << "\nnew drive: " << drive << "\n";
                path = path2.substr(4) + path.substr(2);
                cout << " new path: " << path << "\n\n";
            }
        }
 
    }
    cout << "The wanted path: " << path << "\n\n";
 
    return 0;
}
 
 
std::string driveTypeStr(UINT driveType)
{
    #define CASE(x) case x: return #x;
    switch (driveType)
    {
      CASE(DRIVE_UNKNOWN)
      CASE(DRIVE_NO_ROOT_DIR)
      CASE(DRIVE_REMOVABLE)
      CASE(DRIVE_FIXED)
      CASE(DRIVE_REMOTE)
      CASE(DRIVE_CDROM)
      CASE(DRIVE_RAMDISK)
    }
    return "unknown type";
}

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