3

我正在从一些慢速源（如 FTP 服务器）读取 .gz 文件，并立即处理接收到的数据。看起来像这样：

FtpWebResponse response = ftpclientRequest.GetResponse() as FtpWebResponse;
using (Stream ftpStream = response.GetResponseStream())
using (GZipStream unzipped = new GZipStream(ftpStream, CompressionMode.Decompress))
using (StreamReader linereader = new StreamReader(unzipped))
{
  String l;
  while ((l = linereader.ReadLine()) != null)
  {
    ...
  }
}

我的问题是显示准确的进度条。事先我可以得到压缩的 .gz 文件大小，但我不知道解压缩的内容有多大。逐行读取文件我很清楚我读取了多少未压缩字节，但我不知道这与压缩文件大小有何关系。

那么，有什么方法可以从 GZipStream 中获取文件指针进入压缩文件的距离？我只需要当前位置，在读取文件之前我可以获取的 gz 文件大小。

4

4 回答 4

4

You can plug a stream in between which counts, how many bytes GZipStream has read.

  public class ProgressStream : Stream
  {
    public long BytesRead { get; set; }
    Stream _baseStream;
    public ProgressStream(Stream s)
    {
      _baseStream = s;
    }
    public override bool CanRead
    {
      get { return _baseStream.CanRead; }
    }
    public override bool CanSeek
    {
      get { return false; }
    }
    public override bool CanWrite
    {
      get { return false; }
    }
    public override void Flush()
    {
      _baseStream.Flush();
    }
    public override long Length
    {
      get { throw new NotImplementedException(); }
    }
    public override long Position
    {
      get
      {
        throw new NotImplementedException();
      }
      set
      {
        throw new NotImplementedException();
      }
    }
    public override int Read(byte[] buffer, int offset, int count)
    {
      int rc = _baseStream.Read(buffer, offset, count);
      BytesRead += rc;
      return rc;
    }
    public override long Seek(long offset, SeekOrigin origin)
    {
      throw new NotImplementedException();
    }
    public override void SetLength(long value)
    {
      throw new NotImplementedException();
    }
    public override void Write(byte[] buffer, int offset, int count)
    {
      throw new NotImplementedException();
    }
  }

// usage
FtpWebResponse response = ftpclientRequest.GetResponse() as FtpWebResponse;
using (Stream ftpStream = response.GetResponseStream())
using (ProgressStream progressStream = new ProgressStream(ftpstream))
using (GZipStream unzipped = new GZipStream(progressStream, CompressionMode.Decompress))
using (StreamReader linereader = new StreamReader(unzipped))
{
  String l;
  while ((l = linereader.ReadLine()) != null)
  {
    progressStream.BytesRead(); // does contain the # of bytes read from FTP so far.
  }
}
于 2009-01-05T14:58:22.717 回答
0

我建议你看看下面的代码：

public static readonly byte[] symbols = new byte[8 * 1024];

public static void Decompress(FileInfo inFile, FileInfo outFile)
{
    using (var inStream = inFile.OpenRead())
    {
        using (var zipStream = new GZipStream(inStream, CompressionMode.Decompress))
        {
            using (var outStream = outFile.OpenWrite())
            {
                var total = 0;
                do
                {
                    var async = zipStream.BeginRead(symbols, 0, symbols.Length, null, null);
                    total = zipStream.EndRead(async);
                    if (total != 0)
                    {
                        // Report progress. Read total bytes (8K) from the zipped file.
                        outStream.Write(symbols, 0, total);
                    }
                } while (total != 0);
            }
        }
    }
}
于 2009-01-05T11:40:08.017 回答
0

I've revisited my code and I've performed some tests. IMHO darin is right. However I think it's possible to read only the header (size ?) of the zipped stream and find out the resulting file size. (WinRar "knows" what's the unzipped file size without unzipping the entire zip archive. It reads this information from archive's header.) If you find the resulting file size this code will help you to report a precise progress.

public static readonly byte[] symbols = new byte[8 * 1024];

public static void Decompress(FileInfo inFile, FileInfo outFile, double size, Action<double> progress)
{
    var percents = new List<double>(100);

    using (var inStream = inFile.OpenRead())
    {
        using (var zipStream = new GZipStream(inStream, CompressionMode.Decompress))
        {
            using (var outStream = outFile.OpenWrite())
            {
                var current = 0;

                var total = 0;
                while ((total = zipStream.Read(symbols, 0, symbols.Length)) != 0)
                {
                    outStream.Write(symbols, 0, total);
                    current += total;

                    var p = Math.Round(((double)current / size), 2) * 100;
                    if (!percents.Contains(p))
                    {
                        if (progress != null)
                        {
                            progress(p);
                        }
                        percents.Add(p);
                    }
                }
            }
        }
    }
}

I hope this helps.

于 2009-01-05T14:27:35.603 回答
0

As a proxy for decompressing progress you may try to get the information for file's download progress from the underlying stream using:

var percentageProgress = ftpStream.Position / (double)ftpWebResponse.ContentLength;

or

var percentageProgress = ftpStream.Position / (double)ftpStream.Length;

It works on a FileStream and it should work on a GetResponseStream() provided it implements Position property and the FTP server returns information on the downloaded file's length: http://msdn.microsoft.com/en-us/library/system.net.ftpwebresponse.contentlength(v=vs.110).aspx

于 2014-03-27T03:03:48.497 回答