.NET中的IMAPI2 MsftFileSystemImage在创建ISO时不释放文件

Question

我成功地创建了iso映像,但是在调用此Create方法返回后,我尝试删除rootFolderPath中的文件时出现'文件正在使用'IO错误.我错过了Marshal.ReleaseComObject调用吗？

谢谢,

CW

/// <summary>
/// Create iso image from rootFolderPath and write to isoImageFilePath. Does not include the actual rootFolder itself
/// </summary>
public void Create()
{
    IFileSystemImage ifsi = new MsftFileSystemImage();
    try
    {
        ifsi.ChooseImageDefaultsForMediaType(IMAPI_MEDIA_PHYSICAL_TYPE.IMAPI_MEDIA_TYPE_DISK);
        ifsi.FileSystemsToCreate =
                FsiFileSystems.FsiFileSystemJoliet | FsiFileSystems.FsiFileSystemISO9660;
        ifsi.VolumeName = this.volumeName;
        ifsi.Root.AddTree(rootFolderPath, false);//use a valid folder
        //this will implement the Write method for the formatter
        IStream imagestream = ifsi.CreateResultImage().ImageStream;
        if (imagestream != null)
        {
            System.Runtime.InteropServices.ComTypes.STATSTG stat;
            imagestream.Stat(out stat, 0x01);
            IStream newStream;
            if (0 == SHCreateStreamOnFile(isoImageFilepath, 0x00001001, out newStream) && newStream != null)
            {
                IntPtr inBytes = Marshal.AllocHGlobal(Marshal.SizeOf(typeof(long)));
                IntPtr outBytes = Marshal.AllocHGlobal(Marshal.SizeOf(typeof(long)));
                try
                {
                    imagestream.CopyTo(newStream, stat.cbSize, inBytes, outBytes);
                    Marshal.ReleaseComObject(imagestream);
                    imagestream = null;
                    newStream.Commit(0);
                }
                finally
                {
                    Marshal.ReleaseComObject(newStream);
                    Marshal.FreeHGlobal(inBytes);
                    Marshal.FreeHGlobal(outBytes);
                    if (imagestream != null)
                        Marshal.ReleaseComObject(imagestream);
                }
            }
        }
    }
    finally
    {
        Marshal.ReleaseComObject(ifsi); 
    }
}

Answer 1

锁定大文件肯定存在问题.在网上挖掘会产生以下几点:

• http://social.msdn.microsoft.com/Forums/en-US/windowsopticalplatform/thread/5ae4a173-ccb2-4c10-8fd5-c6e59a9c0ac9

  MS的第一个答案承认大文件存在问题.(NB设置"Staging = false"对我不起作用.)

• http://www.codeproject.com/KB/miscctrl/ISOImage.aspx?msg=2532334

  使用流添加要刻录的文件.

• http://social.msdn.microsoft.com/Forums/en-AU/windowsopticalplatform/thread/124017ea-79c5-45e2-b62e-589b3b4505af

  讨论AddRef/Release不平衡.

因此,在所有这些消化后,我得到了一个解决方案:在写入之后,迭代文件系统映像root并释放任何流数据.

多区段光盘存在一些问题 - 由于导入现有文件(通过ImportFileSystem),它们都会被检查锁定,这可能需要一些时间,并且对于未在当前会话中写入的每个文件都会抛出COMException .通过一些努力,我确信可以缓存AddTree之前和之后的文件系统之间的差异,并且只检查那些文件.

无论如何......在调用Write之后,我们调用ReleaseIFsiItems ......

       {
          // Write...

          // Call to release any locks
          ReleaseIFsiItems(fileSystemImage.Root);

           // Complete tidy up...
          Marshal.FinalReleaseComObject(fileSystem);
          Marshal.FinalReleaseComObject(fileSystemImageResult);
        }

 private static void ReleaseIFsiItems(IFsiDirectoryItem rootItem)
  {
     if (rootItem == null)
     {
        return;
     }

     var enm = rootItem.GetEnumerator();
     while (enm.MoveNext())
     {
        var currentItem = enm.Current as IFsiItem;
        var fsiFileItem = currentItem as IFsiFileItem;
        if (fsiFileItem != null)
        {
           try
           {
              var stream = fsiFileItem.Data;
              var iUnknownForObject = Marshal.GetIUnknownForObject(stream);
              // Get a reference - things go badly wrong if we release a 0 ref count stream!
              var i = Marshal.AddRef(iUnknownForObject);
              // Release all references
              while (i > 0)
              {
                 i = Marshal.Release(iUnknownForObject);
              }
              Marshal.FinalReleaseComObject(stream);
           }
           catch (COMException)
           {
              // Thrown when accessing fsiFileItem.Data
           }
        }
        else
        {
           ReleaseIFsiItems(currentItem as IFsiDirectoryItem);
        }
     }
  }

我希望这对你有用!