CacheLog

Tonight I was reading some articles about the future versions of powershell and I've found
that a new version is comming with new interesting cmdlets like invoke-webrequest.

Naturally, I've installed it from here and I've start playing with this new cmdlet.

1. For getting the syntax
get-help invoke-webrequest

2. I've discovered nice things available   
$test = invoke-webrequest http://cachelog.net
$test.Links | % { write-host $_.href }

3. Do not underestimate the power of this command :
$test2 = invoke-webrequest http://www.loto49.ro/arhiva-loto49.php
$luckyNumbers = $test2.AllElements | `
         ? {$_.tagName -eq "TD"} |  ? { $_.InnerText -match "^\d+$" } | select -property InnerText

(gci | select -f 3) + (gci | select -skip 1 -f 3) | select -unique

My idea is to put the data received from a socket into a more practical form of IObservable<byte>,
so I can use the power of Rx to query the received data. 

Related links:
Using Reactive Extensions (Rx) for socket programming practical?

1. First, I've created a extensions class to wrap each method
            that I'm interested in into a Task:



public static class SocketTaskExtensions
{
    public static Task<Socket> AcceptClient(this Socket socket)
    {
        var tcs = new TaskCompletionSource<Socket>();

        try
        {
            socket.BeginAccept(iar =>
            {
                try
                {
                    Socket handler = socket.EndAccept(iar);
                    tcs.SetResult(handler);
                }
                catch (Exception ex)
                {
                    tcs.SetException(ex);
                }
            }, null);
        }
        catch (Exception ex)
        {
            tcs.SetException(ex);
        }

        return tcs.Task;
    }

    public static Task ConnectTo(this Socket socket, EndPoint remoteEndPoint)
    {
        var tcs = new TaskCompletionSource<bool>();

        try
        {
            socket.BeginConnect(remoteEndPoint, iar =>
            {
                try
                {
                    socket.EndConnect(iar);
                    tcs.SetResult(true);
                }
                catch (Exception ex)
                {
                    tcs.SetException(ex);
                }
            }, null);
        }
        catch (Exception ex)
        {
            tcs.SetException(ex);
        }

        return tcs.Task;
    }

    public static Task<int> ReceiveData(this Socket socket,
         byte[] buffer, int offset, int count, SocketFlags socketFlags)
    {
        var tcs = new TaskCompletionSource<int>();

        try
        {
            socket.BeginReceive(buffer, offset, count, socketFlags, iar =>
            {
                try
                {
                    int bytesRead = socket.EndReceive(iar);
                    tcs.SetResult(bytesRead);
                }
                catch (Exception ex)
                {
                    tcs.SetException(ex);
                }
            }, null);
        }
        catch (Exception ex)
        {
            tcs.SetException(ex);
        }

        return tcs.Task;
    }

    public static Task<int> SendData(this Socket socket, byte[] data)
    {
        var tcs = new TaskCompletionSource<int>();

        try
        {
            socket.BeginSend(data, 0, data.Length, 0, iar =>
            {
                try
                {
                    int bytesSent = socket.EndSend(iar);
                    tcs.SetResult(bytesSent);
                }
                catch (Exception ex)
                {
                    tcs.SetException(ex);
                }
            }, null);
        }
        catch (Exception ex)
        {
            tcs.SetException(ex);
        }

        return tcs.Task;
    }
}


2. I've created an extensions class to add ReadToObservable on socket class:


public static class SocketRxExtensions
{
    public static IObservable<byte> ReadToObservable(this Socket socket,
      Func<Exception, bool> exceptionsHandler)
    {
        BlockingCollection<byte> chunks = new BlockingCollection<byte>();

        ReadDataFromSocket(socket, (buffer, length) =>
            {
                if (length == 0)
                {
                    chunks.CompleteAdding();
                }
                else
                {
                    for (var i = 0; i < length; i++)
                    {
                        chunks.Add(buffer[i]);
                    }
                }
            },exceptionsHandler);

        return chunks.GetConsumingEnumerable().ToObservable<byte>(Scheduler.NewThread);
    }

    private static void ReadDataFromSocket(Socket socket, Action<byte[], int> callback,
        Func<Exception, bool> exceptionsHandler)
    {
        byte[] buffer = new byte[1024];
        var readDataTask = socket.ReceiveData(buffer, 0, 1024, SocketFlags.None);

        readDataTask.ContinueWith((task) =>
            {
                if (task.Exception == null)
                {
                    callback(buffer, task.Result);

                    if (task.Result != 0)
                    {
                        ReadDataFromSocket(socket, callback, exceptionsHandler);
                    }
                    else
                    {
                        socket.Shutdown(SocketShutdown.Receive);
                    }
                }
            });

        try
        {
            readDataTask.Wait();
        }
        catch(AggregateException ex)
        {
            ex.Handle(exceptionsHandler);
        }
    }
}
3. Finally, I've used these classes to write an elegant query to do my socket work:

var dataRead = socket.ReadToObservable(exceptionHandler).ObserveOn(Scheduler.CurrentThread);

var messages = from headerBytes in dataRead.Buffer(4)
                let headerLength = BitConverter.ToInt32(headerBytes.Reverse().ToArray(), 0)
                let message = dataRead.Take(headerLength)
                select new Tuple<int,byte[]>(headerLength,message.ToEnumerable().ToArray());

messages.Subscribe(x =>
{
    Console.WriteLine("message received length: " + x.Item1);
    Console.Write(Encoding.Unicode.GetChars(x.Item2));
});
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