Hard disk volume path to full file path

Question

I have an MSVC++ application that spits out the hard disk volume paths of file handles that other applications have open in the following string format:

\\De         


        

Answer 1

You should look for one of the Windows API functions for Volume Management:

Volume Management Functions

Here is an example from MSDN:

Displaying Volume Paths

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

void DisplayVolumePaths(
        __in PWCHAR VolumeName
        )
{
    DWORD  CharCount = MAX_PATH + 1;
    PWCHAR Names     = NULL;
    PWCHAR NameIdx   = NULL;
    BOOL   Success   = FALSE;

    for (;;) 
    {
        //
        //  Allocate a buffer to hold the paths.
        Names = (PWCHAR) new BYTE [CharCount * sizeof(WCHAR)];

        if ( !Names ) 
        {
            //
            //  If memory can't be allocated, return.
            return;
        }

        //
        //  Obtain all of the paths
        //  for this volume.
        Success = GetVolumePathNamesForVolumeNameW(
            VolumeName, Names, CharCount, &CharCount
            );

        if ( Success ) 
        {
            break;
        }

        if ( GetLastError() != ERROR_MORE_DATA ) 
        {
            break;
        }

        //
        //  Try again with the
        //  new suggested size.
        delete [] Names;
        Names = NULL;
    }

    if ( Success )
    {
        //
        //  Display the various paths.
        for ( NameIdx = Names; 
              NameIdx[0] != L'\0'; 
              NameIdx += wcslen(NameIdx) + 1 ) 
        {
            wprintf(L"  %s", NameIdx);
        }
        wprintf(L"\n");
    }

    if ( Names != NULL ) 
    {
        delete [] Names;
        Names = NULL;
    }

    return;
}

void __cdecl wmain(void)
{
    DWORD  CharCount            = 0;
    WCHAR  DeviceName[MAX_PATH] = L"";
    DWORD  Error                = ERROR_SUCCESS;
    HANDLE FindHandle           = INVALID_HANDLE_VALUE;
    BOOL   Found                = FALSE;
    size_t Index                = 0;
    BOOL   Success              = FALSE;
    WCHAR  VolumeName[MAX_PATH] = L"";

    //
    //  Enumerate all volumes in the system.
    FindHandle = FindFirstVolumeW(VolumeName, ARRAYSIZE(VolumeName));

    if (FindHandle == INVALID_HANDLE_VALUE)
    {
        Error = GetLastError();
        wprintf(L"FindFirstVolumeW failed with error code %d\n", Error);
        return;
    }

    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;
        }

        //
        //  QueryDosDeviceW does not allow a trailing backslash,
        //  so temporarily remove it.
        VolumeName[Index] = L'\0';

        CharCount = QueryDosDeviceW(&VolumeName[4], DeviceName, ARRAYSIZE(DeviceName)); 

        VolumeName[Index] = L'\\';

        if ( CharCount == 0 ) 
        {
            Error = GetLastError();
            wprintf(L"QueryDosDeviceW failed with error code %d\n", Error);
            break;
        }

        wprintf(L"\nFound a device:\n %s", DeviceName);
        wprintf(L"\nVolume name: %s", VolumeName);
        wprintf(L"\nPaths:");
        DisplayVolumePaths(VolumeName);

        //
        //  Move on to the next volume.
        Success = FindNextVolumeW(FindHandle, VolumeName, ARRAYSIZE(VolumeName));

        if ( !Success ) 
        {
            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_SUCCESS;
            break;
        }
    }

    FindVolumeClose(FindHandle);
    FindHandle = INVALID_HANDLE_VALUE;

    return;
}

To clarify:

Volume name (or GUID) is something like \\?\Volume{xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx}

Device name is something like \Device\HarddiskVolume1

Drive letter is something like C:

FindFirst/NextVolume gives you a list of Volume names.

QueryDosDevice gives you a Device name from a Volume name.

GetVolumePathNamesForVolumeName gives you the Drive letter from a Volume name.