如何从FileStream报告进度

Question

我想报告文件加密的进度，这是我的代码，请问我该怎么做？

using (FileStream destination = new FileStream(destinationFilename, FileMode.CreateNew, FileAccess.Write, FileShare.None))
using (CryptoStream cryptoStream = new CryptoStream(destination, transform, CryptoStreamMode.Write))
using (FileStream source = new FileStream(sourceFilename, FileMode.Open, FileAccess.Read, FileShare.Read))
{
    await source.CopyToAsync(cryptoStream);
}

- hadi khodabandeh

---

看一下这个：https://dev59.com/FW025IYBdhLWcg3wX07z - Alex Pshul

尝试轮询Position，但我怀疑它不会起作用（可能要等到操作完成后位置才会更新）。也许你可以在中间放置一些自定义流来拦截对WriteToAsync的调用（参见CopyToAsync sources，它将按缓冲区大小将写操作分成多个块），并提高自定义事件以报告进度。 - Sinatr

Answer 1

为了正确地完成这个任务，您需要插入另一个流来报告进度。因此，代码应该类似于以下内容...

        using (FileStream destination = new FileStream(destinationFilename, FileMode.CreateNew, FileAccess.Write, FileShare.None))
        using (CryptoStream cryptoStream = new CryptoStream(destination, transform, CryptoStreamMode.Write))
        using (FileStream source = new FileStream(sourceFilename, FileMode.Open, FileAccess.Read, FileShare.Read))
        {
            using (ProgressStream progressStream = new ProgressStream(source))
            {
                progressStream.UpdateProgress += ProgressStream_UpdateProgress;
                progressStream.CopyTo(cryptoStream);
            }
        }

Where ProgressStream is...

public class ProgressStream : Stream
{
    private Stream m_input = null;
    private long m_length = 0L;
    private long m_position = 0L;
    public event EventHandler<ProgressEventArgs> UpdateProgress;

    public ProgressStream(Stream input)
    {
        m_input = input;
        m_length = input.Length;
    }
    public override void Flush()
    {
        throw new System.NotImplementedException();
    }

    public override long Seek(long offset, SeekOrigin origin)
    {
        throw new System.NotImplementedException();
    }

    public override void SetLength(long value)
    {
        throw new System.NotImplementedException();
    }

    public override int Read(byte[] buffer, int offset, int count)
    {
        int n = m_input.Read(buffer, offset, count);
        m_position += n;
        UpdateProgress?.Invoke(this, new ProgressEventArgs((1.0f * m_position)/m_length));
        return n;
    }

    public override void Write(byte[] buffer, int offset, int count)
    {
        throw new System.NotImplementedException();
    }

    public override bool CanRead => true;
    public override bool CanSeek => false;
    public override bool CanWrite => false;
    public override long Length => m_length;
    public override long Position
    {
        get {  return m_position; }
        set {  throw new System.NotImplementedException();}
    }
}

ProgressEventArgs是什么？

public class ProgressEventArgs : EventArgs
{
    private float m_progress;

    public ProgressEventArgs(float progress)
    {
        m_progress = progress;
    }

    public float Progress => m_progress;

}

处理事件的程序可能是这样的...

    private void ProgressStream_UpdateProgress(object sender, ProgressEventArgs e)
    {
        Console.WriteLine($"Progress is {e.Progress * 100.0f}%");
    }

运行对样本文件的检测，产生...

Progress is 5.272501%
Progress is 10.545%
Progress is 15.8175%
Progress is 21.09%
Progress is 26.3625%
Progress is 31.635%
Progress is 36.9075%
Progress is 42.18%
Progress is 47.4525%
Progress is 52.72501%
Progress is 57.99751%
Progress is 63.27001%
Progress is 68.5425%
Progress is 73.815%
Progress is 79.08751%
Progress is 84.36001%
Progress is 89.63251%
Progress is 94.90501%
Progress is 100%
Progress is 100%

很多改进和优化的空间，但这是实现你想要做的唯一有效的方法。

- AQuirky