CODEWITHSUNDEEP
c#streamipcnamed-pipes
user2481095
user2481095

Reputation: 2106

How to Efficiently Read From a Pipe Stream when using IPC C#

I wrote the simplified version of my program below. Process A launches a child process (Process B). I use an anonymous pipe to write information about the progress of a method running on process B. Meanwhile I have a function in process A that continually reads from a stream to see if there is a new update coming in from the pipe. If there is, the form on process A is updated to reflect the progress. This works as expected, however I am wondering if there is a better way to accomplish this without having to continually check the stream to see if there are any new updates to the progress.

/////////////////
///Process A ////
/////////////////

public void LaunchProcessB()
{
    using (AnonymousPipeServerStream pipeServer = new AnonymousPipeServerStream(PipeDirection.In,
            HandleInheritability.Inheritable))
    {
        var _Process = new Process();
        _Process.StartInfo.FileName = exeString;
        _Process.StartInfo.Arguments = pipeServer.GetClientHandleAsString()
        _Process.StartInfo.RedirectStandardOutput = true;
        _Process.StartInfo.RedirectStandardInput = true;
        _Process.StartInfo.CreateNoWindow = true;
        _Process.StartInfo.UseShellExecute = false;
        _Process.Start(); //launches process B

        pipeServer.DisposeLocalCopyOfClientHandle();

        using (StreamReader sr = new StreamReader(pipeServer))
        {
            try
            {
                while (true)
                {
                    string temp = sr.ReadLine();
                    if (temp == null) break;

                    int result;
                    if (Int32.TryParse(temp, out result))
                        ShowDocumentProgress(result);
                    else ShowProgress(temp);
                }
            }
            catch (Exception)
            {
                //error occured when reading from stream.
            }
        }

        if (!_Process.Responding && !_Process.HasExited)
        {
            _Process.Kill();
            return;
        }

        _Process.WaitForExit(10000);
    }
}

private void ShowProgressPercent(int percentage)
{
    if (percentage > currentPercentage)
    {
        progressBar.Value = percentage;
    }
}

private void ShowProgress(string progressString)
{
    labelMessage.Text = progressString;
}


/////////////////
///Process B ////
/////////////////

private StreamWriter _progressWriter;
private PipeStream _progressPipe;

static int Main(string[] args)
{
    using (progressPipe = new AnonymousPipeClientStream(PipeDirection.Out, args[0]))
    using (_progressWriter = new StreamWriter(_progressPipe))   
    {
        RunLongProcess()
    }
}

private void RunLongProcess() 
{
    //attaches events to PercentProgress and StageProgress methods.  
}

private void PercentProgress(int percentage)
{
    _progressWriter.WriteLine(percentage.ToString());
    _progressPipe.WaitForPipeDrain();
}

private void StageProgress(string stage) 
{
    _progressWriter.WriteLine(stage);
    _progressPipe.WaitForPipeDrain();
}

Upvotes: 0

Views: 1108

Answers (1)

usr
usr

Reputation: 171188

The while condition is not necessary. Simply read until temp is null. That's the end signal of the stream.

Make this a while(true) loop.

I think you also need to add exception handling to catch the process terminating and severing the pipe. !_Process.HasExited && pipeServer.IsConnected is not enough because it might be true but immediately switch to false after the test.

I also would add a WaitForExit at the end to make sure the system is quiesced before you continue.

Upvotes: 2

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