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Obtaining a File Name From a File Handle

  • Artykuł

GetFinalPathNameByHandle, introduced in Windows Vista and Windows Server 2008, will return a path from a handle. If you need to do this on earlier releases of Windows, the following example obtains a file name from a handle to a file object using a file mapping object. It uses the CreateFileMapping and MapViewOfFile functions to create the mapping. Next, it uses the GetMappedFileName function to obtain the file name. For remote files, it prints the device path received from this function. For local files, it converts the path to use a drive letter and prints this path. To test this code, create a main function that opens a file using CreateFile and passes the resulting handle to GetFileNameFromHandle.

#include <windows.h>
#include <stdio.h>
#include <tchar.h>
#include <string.h>
#include <psapi.h>
#include <strsafe.h>

#define BUFSIZE 512

BOOL GetFileNameFromHandle(HANDLE hFile) 
{
  BOOL bSuccess = FALSE;
  TCHAR pszFilename[MAX_PATH+1];
  HANDLE hFileMap;

  // Get the file size.
  DWORD dwFileSizeHi = 0;
  DWORD dwFileSizeLo = GetFileSize(hFile, &dwFileSizeHi); 

  if( dwFileSizeLo == 0 && dwFileSizeHi == 0 )
  {
     _tprintf(TEXT("Cannot map a file with a length of zero.\n"));
     return FALSE;
  }

  // Create a file mapping object.
  hFileMap = CreateFileMapping(hFile, 
                    NULL, 
                    PAGE_READONLY,
                    0, 
                    1,
                    NULL);

  if (hFileMap) 
  {
    // Create a file mapping to get the file name.
    void* pMem = MapViewOfFile(hFileMap, FILE_MAP_READ, 0, 0, 1);

    if (pMem) 
    {
      if (GetMappedFileName (GetCurrentProcess(), 
                             pMem, 
                             pszFilename,
                             MAX_PATH)) 
      {

        // Translate path with device name to drive letters.
        TCHAR szTemp[BUFSIZE];
        szTemp[0] = '\0';

        if (GetLogicalDriveStrings(BUFSIZE-1, szTemp)) 
        {
          TCHAR szName[MAX_PATH];
          TCHAR szDrive[3] = TEXT(" :");
          BOOL bFound = FALSE;
          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(pszFilename, szName, uNameLen) == 0
                         && *(pszFilename + uNameLen) == _T('\\');

                if (bFound) 
                {
                  // Reconstruct pszFilename using szTempFile
                  // Replace device path with DOS path
                  TCHAR szTempFile[MAX_PATH];
                  StringCchPrintf(szTempFile,
                            MAX_PATH,
                            TEXT("%s%s"),
                            szDrive,
                            pszFilename+uNameLen);
                  StringCchCopyN(pszFilename, MAX_PATH+1, szTempFile, _tcslen(szTempFile));
                }
              }
            }

            // Go to the next NULL character.
            while (*p++);
          } while (!bFound && *p); // end of string
        }
      }
      bSuccess = TRUE;
      UnmapViewOfFile(pMem);
    } 

    CloseHandle(hFileMap);
  }
  _tprintf(TEXT("File name is %s\n"), pszFilename);
  return(bSuccess);
}

int _tmain(int argc, TCHAR *argv[])
{
    HANDLE hFile;

    if( argc != 2 )
    {
        _tprintf(TEXT("This sample takes a file name as a parameter.\n"));
        return 0;
    }
    hFile = CreateFile(argv[1], GENERIC_READ, FILE_SHARE_READ, NULL,
        OPEN_EXISTING, 0, NULL);

    if(hFile == INVALID_HANDLE_VALUE)
    {
        _tprintf(TEXT("CreateFile failed with %d\n"), GetLastError());
        return 0;
    }
    GetFileNameFromHandle( hFile );
}

Using File Mapping

GetFinalPathNameByHandle