取得大文件大小

_int64 GetFileSize(const char *szFileName)
{
   //低位，高位，錯誤代碼
   DWord dwSizeLow = 0, dwSizeHigh = 0;

   HANDLE hFile = CreateFile(szFileName,GENERIC_READ,FILE_SHARE_READ,
                          NULL,OPEN_EXISTING,FILE_ATTRIBUTE_NORMAL,NULL);

   if (INVALID_HANDLE_VALUE == hFile)
   {
    MessageBox(NULL,_T("打開文件失敗!"),_T("提示!"),MB_OK|MB_ICONINFORMATION);
    return -1;
   }

   dwSizeLow = ::GetFileSize((HANDLE)hFile, &dwSizeHigh);

   if ( (dwSizeLow == 0xFFFFFFFF) && (GetLastError() != NO_ERROR) )
   {
    MessageBox(NULL,_T("取得文件大小出錯!"),_T("提示!"),MB_OK|MB_ICONINFORMATION);
    CloseHandle(hFile);
    return -1;
   }

   _int64 lFileSize = 0, lPow = 0;

   lPow  = (LONGLONG)pow(2,32);
   lFileSize = dwSizeHigh * lPow+dwSizeLow;

   CloseHandle(hFile);

   return lFileSize;
}