Resolve Windows device path to drive letter - windows

Question

How do you resolve an NT style device path, e.g. \Device\CdRom0, to its logical drive letter, e.g. G:\ ?
Edit: A Volume Name isn't the same as a Device Path so unfortunately GetVolumePathNamesForVolumeName() won't work.

Answer 1

Hopefully the following piece of code will give you enough to solve this - after you've initialised it, you just need to iterate through the collection to find your match. You may want to convert everything to upper/lower case before you insert into the collection to help with lookup performance.
typedef basic_string<TCHAR> tstring;
typedef map<tstring, tstring> HardDiskCollection;
void Initialise( HardDiskCollection &_hardDiskCollection )
{
TCHAR tszLinkName[MAX_PATH] = { 0 };
TCHAR tszDevName[MAX_PATH] = { 0 };
TCHAR tcDrive = 0;
_tcscpy_s( tszLinkName, MAX_PATH, _T("a:") );
for ( tcDrive = _T('a'); tcDrive < _T('z'); ++tcDrive )
{
tszLinkName[0] = tcDrive;
if ( QueryDosDevice( tszLinkName, tszDevName, MAX_PATH ) )
{
_hardDiskCollection.insert( pair<tstring, tstring>( tszLinkName, tszDevName ) );
}
}
}

Answer 2

Maybe you could use GetVolumeNameForMountPoint and iterate through all mount points A:\ through Z:\, breaking when you find a match?
http://msdn.microsoft.com/en-us/library/aa364994(VS.85).aspx
(I haven't tried this)

Answer 3

Following function does the job using C only
BOOL GetWin32FileName(const TCHAR* pszNativeFileName, TCHAR *pszWin32FileName)
{
BOOL bFound = FALSE;
// Translate path with device name to drive letters.
TCHAR szTemp[MAX_PATH];
szTemp[0] = '\0';
if (GetLogicalDriveStrings(MAX_PATH - 1, szTemp))
{
TCHAR szName[MAX_PATH];
TCHAR szDrive[3] = TEXT(" :");
TCHAR* p = szTemp;
do
{
// Copy the drive letter to the template string
*szDrive = *p;
// Look up each device name
if (QueryDosDevice(szDrive, szName, MAX_PATH))
{
size_t uNameLen = _tcslen(szName);
if (uNameLen < MAX_PATH)
{
bFound = _tcsnicmp(pszNativeFileName, szName, uNameLen) == 0
&& *(pszNativeFileName + uNameLen) == _T('\\');
if (bFound)
{
// Replace device path with DOS path
StringCchPrintf(pszWin32FileName,
MAX_PATH,
TEXT("%s%s"),
szDrive,
pszNativeFileName + uNameLen);
}
}
}
// Go to the next NULL character.
while (*p++);
} while (!bFound && *p);
}
return(bFound);
}

Answer 4

You can lookup all volumes' name to match a device name and get drive letter.Here is a sample:
int DeviceNameToVolumePathName(WCHAR *filepath) {
WCHAR fileDevName[MAX_PATH];
WCHAR devName[MAX_PATH];
WCHAR fileName[MAX_PATH];
HANDLE FindHandle = INVALID_HANDLE_VALUE;
WCHAR VolumeName[MAX_PATH];
DWORD Error = ERROR_SUCCESS;
size_t Index = 0;
DWORD CharCount = MAX_PATH + 1;
int index = 0;
// \Device\HarddiskVolume1\windows,locate \windows.
for (int i = 0; i < lstrlenW(filepath); i++) {
if (!memcmp(&filepath[i], L"\\", 2)) {
index++;
if (index == 3) {
index = i;
break;
}
}
}
filepath[index] = L'\0';
memcpy(fileDevName, filepath, (index + 1) * sizeof(WCHAR));
FindHandle = FindFirstVolumeW(VolumeName, ARRAYSIZE(VolumeName));
if (FindHandle == INVALID_HANDLE_VALUE)
{
Error = GetLastError();
wprintf(L"FindFirstVolumeW failed with error code %d\n", Error);
return FALSE;
}
for (;;)
{
// Skip the \\?\ prefix and remove the trailing backslash.
Index = wcslen(VolumeName) - 1;
if (VolumeName[0] != L'\\' ||
VolumeName[1] != L'\\' ||
VolumeName[2] != L'?' ||
VolumeName[3] != L'\\' ||
VolumeName[Index] != L'\\')
{
Error = ERROR_BAD_PATHNAME;
wprintf(L"FindFirstVolumeW/FindNextVolumeW returned a bad path: %s\n", VolumeName);
break;
}
VolumeName[Index] = L'\0';
CharCount = QueryDosDeviceW(&VolumeName[4], devName, 100);
if (CharCount == 0)
{
Error = GetLastError();
wprintf(L"QueryDosDeviceW failed with error code %d\n", Error);
break;
}
if (!lstrcmpW(devName, filepath)) {
VolumeName[Index] = L'\\';
Error = GetVolumePathNamesForVolumeNameW(VolumeName, fileName, CharCount, &CharCount);
if (!Error) {
Error = GetLastError();
wprintf(L"GetVolumePathNamesForVolumeNameW failed with error code %d\n", Error);
break;
}
// concat drive letter to path
lstrcatW(fileName, &filepath[index + 1]);
lstrcpyW(filepath, fileName);
Error = ERROR_SUCCESS;
break;
}
Error = FindNextVolumeW(FindHandle, VolumeName, ARRAYSIZE(VolumeName));
if (!Error)
{
Error = GetLastError();
if (Error != ERROR_NO_MORE_FILES)
{
wprintf(L"FindNextVolumeW failed with error code %d\n", Error);
break;
}
//
// Finished iterating
// through all the volumes.
Error = ERROR_BAD_PATHNAME;
break;
}
}
FindVolumeClose(FindHandle);
if (Error != ERROR_SUCCESS)
return FALSE;
return TRUE;
}
If you want to resolve it in driver,you can check this link for reference.

Answer 5

Here is refactored version of the solution.
I replaced TChAR with wchar_t because afaik it's not a good idea to use it in most projects.
std::map<std::wstring, std::wstring> GetDosPathDevicePathMap()
{
// It's not really related to MAX_PATH, but I guess it should be enough.
// Though the docs say "The first null-terminated string stored into the buffer is the current mapping for the device.
// The other null-terminated strings represent undeleted prior mappings for the device."
wchar_t devicePath[MAX_PATH] = { 0 };
std::map<std::wstring, std::wstring> result;
std::wstring dosPath = L"A:";
for (wchar_t letter = L'A'; letter <= L'Z'; ++letter)
{
dosPath[0] = letter;
if (QueryDosDeviceW(dosPath.c_str(), devicePath, MAX_PATH)) // may want to properly handle errors instead ... e.g. check ERROR_INSUFFICIENT_BUFFER
{
result[dosPath] = devicePath;
}
}
return result;
}