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  • non blocking client server chat application in java using nio

    - by Amith
    I built a simple chat application using nio channels. I am very much new to networking as well as threads. This application is for communicating with server (Server / Client chat application). My problem is that multiple clients are not supported by the server. How do I solve this problem? What's the bug in my code? public class Clientcore extends Thread { SelectionKey selkey=null; Selector sckt_manager=null; public void coreClient() { System.out.println("please enter the text"); BufferedReader stdin=new BufferedReader(new InputStreamReader(System.in)); SocketChannel sc = null; try { sc = SocketChannel.open(); sc.configureBlocking(false); sc.connect(new InetSocketAddress(8888)); int i=0; while (!sc.finishConnect()) { } for(int ii=0;ii>-22;ii++) { System.out.println("Enter the text"); String HELLO_REQUEST =stdin.readLine().toString(); if(HELLO_REQUEST.equalsIgnoreCase("end")) { break; } System.out.println("Sending a request to HelloServer"); ByteBuffer buffer = ByteBuffer.wrap(HELLO_REQUEST.getBytes()); sc.write(buffer); } } catch (IOException e) { e.printStackTrace(); } finally { if (sc != null) { try { sc.close(); } catch (Exception e) { e.printStackTrace(); } } } } public void run() { try { coreClient(); } catch(Exception ej) { ej.printStackTrace(); }}} public class ServerCore extends Thread { SelectionKey selkey=null; Selector sckt_manager=null; public void run() { try { coreServer(); } catch(Exception ej) { ej.printStackTrace(); } } private void coreServer() { try { ServerSocketChannel ssc = ServerSocketChannel.open(); try { ssc.socket().bind(new InetSocketAddress(8888)); while (true) { sckt_manager=SelectorProvider.provider().openSelector(); ssc.configureBlocking(false); SocketChannel sc = ssc.accept(); register_server(ssc,SelectionKey.OP_ACCEPT); if (sc == null) { } else { System.out.println("Received an incoming connection from " + sc.socket().getRemoteSocketAddress()); printRequest(sc); System.err.println("testing 1"); String HELLO_REPLY = "Sample Display"; ByteBuffer buffer = ByteBuffer.wrap(HELLO_REPLY.getBytes()); System.err.println("testing 2"); sc.write(buffer); System.err.println("testing 3"); sc.close(); }}} catch (IOException e) { e.printStackTrace(); } finally { if (ssc != null) { try { ssc.close(); } catch (IOException e) { e.printStackTrace(); } } } } catch(Exception E) { System.out.println("Ex in servCORE "+E); } } private static void printRequest(SocketChannel sc) throws IOException { ReadableByteChannel rbc = Channels.newChannel(sc.socket().getInputStream()); WritableByteChannel wbc = Channels.newChannel(System.out); ByteBuffer b = ByteBuffer.allocate(1024); // read 1024 bytes while (rbc.read(b) != -1) { b.flip(); while (b.hasRemaining()) { wbc.write(b); System.out.println(); } b.clear(); } } public void register_server(ServerSocketChannel ssc,int selectionkey_ops)throws Exception { ssc.register(sckt_manager,selectionkey_ops); }} public class HelloClient { public void coreClientChat() { Clientcore t=new Clientcore(); new Thread(t).start(); } public static void main(String[] args)throws Exception { HelloClient cl= new HelloClient(); cl.coreClientChat(); }} public class HelloServer { public void coreServerChat() { ServerCore t=new ServerCore(); new Thread(t).start(); } public static void main(String[] args) { HelloServer st= new HelloServer(); st.coreServerChat(); }}

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  • connection between two android phones

    - by user1770346
    I m not able to connect my android device to other device(either android or non-android)via bluetooth.After detecting the devices from my android phone,i m not able to connect it to selected device from the list.The main problem is it not showing connectivity conformation message in selected device from list.How can i recover from this problem. please help me.Thanks My code for searching device is:(BluetoothSearchActivity.java) public class BluetoothSearchActivity extends Activity { ArrayAdapter<String> btArrayAdapter; BluetoothAdapter mBluetoothAdapter; TextView stateBluetooth; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); ImageView BluetoothSearchImageView=new ImageView(this); BluetoothSearchImageView.setImageResource(R.drawable.inner1); setContentView(BluetoothSearchImageView); setContentView(R.layout.activity_bluetooth_search); mBluetoothAdapter=BluetoothAdapter.getDefaultAdapter(); ListView listDevicesFound=(ListView) findViewById(R.id.myList); btArrayAdapter=new ArrayAdapter<String> (BluetoothSearchActivity.this,android.R.layout.simple_list_item_1); listDevicesFound.setAdapter(btArrayAdapter); registerReceiver(ActionFoundReceiver,new IntentFilter(BluetoothDevice.ACTION_FOUND)); btArrayAdapter.clear(); mBluetoothAdapter.startDiscovery(); listDevicesFound.setOnItemClickListener(new OnItemClickListener() { public void onItemClick(AdapterView<?> parent,View view,int position,long id) { Intent i6=new Intent(getApplicationContext(),AcceptThread.class); startActivity(i6); } }); } private final BroadcastReceiver ActionFoundReceiver=new BroadcastReceiver() { @Override public void onReceive(Context context, Intent intent) { // TODO Auto-generated method stub String action=intent.getAction(); if(BluetoothDevice.ACTION_FOUND.equals(action)) { BluetoothDevice device=intent.getParcelableExtra(BluetoothDevice.EXTRA_DEVICE); btArrayAdapter.add(device.getName()+"\n"+device.getAddress()); btArrayAdapter.notifyDataSetChanged(); Log.d("BluetoothSearchActivity",device.getName()+"\n"+device.getAddress()); } } }; @Override protected void onDestroy() { super.onDestroy(); unregisterReceiver(ActionFoundReceiver); } @Override public boolean onCreateOptionsMenu(Menu menu) { getMenuInflater().inflate(R.menu.activity_bluetooth_search, menu); return true; } } and my connectivity code is:(AcceptThread.java) class ConnectThread extends Thread { private static final UUID MY_UUID=UUID.fromString("fa87c0d0-afac-11de-8a39-0800200c9a66"); private static final String ConnectThread = null; BluetoothSocket mSocket; BluetoothDevice mDevice; BluetoothAdapter mBluetoothAdapter; public ConnectThread(BluetoothDevice device) { BluetoothSocket temp=null; mDevice=device; try{ temp=mDevice.createRfcommSocketToServiceRecord(MY_UUID); }catch(IOException e) { } mSocket=temp; } public void run() { mBluetoothAdapter.cancelDiscovery(); try{ Log.i(ConnectThread,"starting to connect"); mSocket.connect(); }catch(IOException connectException) { Log.e(ConnectThread,"connection Failed"); try{ mSocket.close(); }catch(IOException closeException){ } return; } } public void cancel() { try{ mSocket.close(); }catch(IOException e) { } } } public class AcceptThread extends Thread{ private static final String NAME="BluetoothAcceptThread"; private static final UUID MY_UUID=UUID.fromString("fa87c0d0-afac-11de-8a39-0800200c9a66"); BluetoothServerSocket mServerSocket; BluetoothAdapter mBluetoothAdapter; public AcceptThread() { BluetoothServerSocket temp=null; try{ temp=mBluetoothAdapter.listenUsingRfcommWithServiceRecord(NAME,MY_UUID); }catch(IOException e){ } mServerSocket=temp; } public void run() { BluetoothSocket socket=null; while(true) { try{ socket=mServerSocket.accept(); }catch(IOException e) { break; } if(socket!=null) { try { mServerSocket.close(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } break; } } } public void cancel() { try{ mServerSocket.close(); }catch(IOException e) { } } }

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  • Java deadlock problem....

    - by markovuksanovic
    I am using java sockets for communication. On the client side I have some processing and at this point I send an object to the cient. The code is as follows: while (true) { try { Socket server = new Socket("localhost", 3000); OutputStream os = server.getOutputStream(); InputStream is = server.getInputStream(); CommMessage commMessage = new CommMessageImpl(); ByteArrayOutputStream bos = new ByteArrayOutputStream(); ObjectOutputStream oos = new ObjectOutputStream(bos); oos.writeObject(commMessage); os.write(bos.toByteArray()); os.flush(); byte[] buff = new byte[512]; int bytesRead = 0; ByteArrayOutputStream receivedObject = new ByteArrayOutputStream(); while ((bytesRead = is.read(buff)) > -1) { receivedObject.write(buff, 0, bytesRead); System.out.println(receivedObject); } os.close(); Thread.sleep(10000); } catch (IOException e) { } catch (InterruptedException e) { } } Next on the server side I have the following code to read the object and write the response (Which is just an echo message) public void startServer() { Socket client = null; try { server = new ServerSocket(3000); logger.log(Level.INFO, "Waiting for connections."); client = server.accept(); logger.log(Level.INFO, "Accepted a connection from: " + client.getInetAddress()); os = new ObjectOutputStream(client.getOutputStream()); is = new ObjectInputStream(client.getInputStream()); // Read contents of the stream and store it into a byte array. byte[] buff = new byte[512]; int bytesRead = 0; ByteArrayOutputStream receivedObject = new ByteArrayOutputStream(); while ((bytesRead = is.read(buff)) > -1) { receivedObject.write(buff, 0, bytesRead); } // Check if received stream is CommMessage or not contents. CommMessage commMessage = getCommMessage(receivedObject); if (commMessage != null) { commMessage.setSessionState(this.sessionManager.getState().getState()); ByteArrayOutputStream bos = new ByteArrayOutputStream(); ObjectOutputStream oos = new ObjectOutputStream(bos); oos.writeObject(commMessage); os.write(bos.toByteArray()); System.out.println(commMessage.getCommMessageType()); } else { processData(receivedObject, this.sessionManager); } os.flush(); } catch (IOException e) { } finally { try { is.close(); os.close(); client.close(); server.close(); } catch (IOException e) { } } } The above code works ok if I do not try to read data on the client side (If i exclude the code related to reading). But if I have that code, for some reason, I get some kind of deadlock when accessing input streams. Any ideas what I might have done wrong? Thanks in advance.

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  • Only Execute Code on Certain Requests Java

    - by BillPull
    I am building a little API for class and the teacher supplied us with a link to a tutorial that provided a simple webserver that implements Runnable. I have already written some code that will parse arguments the arguments ( or at least get me the request string ) and some code that will return some simple xml. however I think certain requests like the one for the favicon are sent I think it is messing up my code. I wrapped that in an if else but it does not seem to be working. package server; import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; import java.net.Socket; import java.util.*; import java.io.*; import java.net.*; import parkinglots.*; public class WorkerRunnable implements Runnable{ protected Socket clientSocket = null; protected String serverText = null; public WorkerRunnable(Socket clientSocket, String serverText) { this.clientSocket = clientSocket; this.serverText = serverText; } public Boolean authenticateAPI(String key){ //Authenticate Key against Stored Keys //TODO: Create Stored Keys and Compare return true; } public void run() { try { InputStream input = clientSocket.getInputStream(); OutputStream output = clientSocket.getOutputStream(); long time = System.currentTimeMillis(); //TODO: Parse args and output different formats and Authentication //Parse URL Arguments BufferedReader in = new BufferedReader( new InputStreamReader(clientSocket.getInputStream(), "8859_1")); String request = in.readLine(); //Server gets Favicon Request so skip that and goto args System.out.println(request); if ( request != "GET /favicon.ico HTTP/1.1" && request != "GET / HTTP/1.1" && request != null ){ String format = "", apikey =""; System.out.println("I am Here"); String request_location = request.split(" ")[1]; String request_args = request_location.replace("/",""); request_args = request_args.replace("?",""); String[] queries = request_args.split("&"); System.out.println(queries[0]); for ( int i = 0; i < queries.length; i++ ){ if( queries[i] == "format" ){ format = queries[i].split("=")[1]; } else if( queries[i] == "apikey" ){ apikey = queries[i].split("=")[1]; } } if( apikey == "" ){ apikey = "None"; } if( format == "" ){ format = "xml"; } Boolean auth = authenticateAPI(apikey); if ( auth ){ if ( format == "xml"){ // Retrieve XML Document String xml = LotFromDB.getParkingLotXML(); output.write((xml).getBytes()); }else{ //Retrieve JSON String json = LotFromDB.getParkingLotJSON(); output.write((json).getBytes()); } }else{ output.write(("Access Denied - User is Not Authenticated").getBytes()); } }else{ output.write(("Access Denied Must Pass API Key").getBytes()); } output.close(); input.close(); System.out.println("Request processed: " + time); } catch (IOException e) { //report exceptions e.printStackTrace(); } } } Console output I get I am Here format=json Request processed: 1333516648331 GET /favicon.ico HTTP/1.1 I am Here favicon.ico Request processed: 1333516648332 It always returns the XML as well. This is my first exposure to writing a web server and dealing with networking in Java, which frustrates me a lot in general, So any suggestions here are very appreciated.

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  • C# 5 Async, Part 1: Simplifying Asynchrony – That for which we await

    - by Reed
    Today’s announcement at PDC of the future directions C# is taking excite me greatly.  The new Visual Studio Async CTP is amazing.  Asynchronous code – code which frustrates and demoralizes even the most advanced of developers, is taking a huge leap forward in terms of usability.  This is handled by building on the Task functionality in .NET 4, as well as the addition of two new keywords being added to the C# language: async and await. This core of the new asynchronous functionality is built upon three key features.  First is the Task functionality in .NET 4, and based on Task and Task<TResult>.  While Task was intended to be the primary means of asynchronous programming with .NET 4, the .NET Framework was still based mainly on the Asynchronous Pattern and the Event-based Asynchronous Pattern. The .NET Framework added functionality and guidance for wrapping existing APIs into a Task based API, but the framework itself didn’t really adopt Task or Task<TResult> in any meaningful way.  The CTP shows that, going forward, this is changing. One of the three key new features coming in C# is actually a .NET Framework feature.  Nearly every asynchronous API in the .NET Framework has been wrapped into a new, Task-based method calls.  In the CTP, this is done via as external assembly (AsyncCtpLibrary.dll) which uses Extension Methods to wrap the existing APIs.  However, going forward, this will be handled directly within the Framework.  This will have a unifying effect throughout the .NET Framework.  This is the first building block of the new features for asynchronous programming: Going forward, all asynchronous operations will work via a method that returns Task or Task<TResult> The second key feature is the new async contextual keyword being added to the language.  The async keyword is used to declare an asynchronous function, which is a method that either returns void, a Task, or a Task<T>. Inside the asynchronous function, there must be at least one await expression.  This is a new C# keyword (await) that is used to automatically take a series of statements and break it up to potentially use discontinuous evaluation.  This is done by using await on any expression that evaluates to a Task or Task<T>. For example, suppose we want to download a webpage as a string.  There is a new method added to WebClient: Task<string> WebClient.DownloadStringTaskAsync(Uri).  Since this returns a Task<string> we can use it within an asynchronous function.  Suppose, for example, that we wanted to do something similar to my asynchronous Task example – download a web page asynchronously and check to see if it supports XHTML 1.0, then report this into a TextBox.  This could be done like so: private async void button1_Click(object sender, RoutedEventArgs e) { string url = "http://reedcopsey.com"; string content = await new WebClient().DownloadStringTaskAsync(url); this.textBox1.Text = string.Format("Page {0} supports XHTML 1.0: {1}", url, content.Contains("XHTML 1.0")); } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Let’s walk through what’s happening here, step by step.  By adding the async contextual keyword to the method definition, we are able to use the await keyword on our WebClient.DownloadStringTaskAsync method call. When the user clicks this button, the new method (Task<string> WebClient.DownloadStringTaskAsync(string)) is called, which returns a Task<string>.  By adding the await keyword, the runtime will call this method that returns Task<string>, and execution will return to the caller at this point.  This means that our UI is not blocked while the webpage is downloaded.  Instead, the UI thread will “await” at this point, and let the WebClient do it’s thing asynchronously. When the WebClient finishes downloading the string, the user interface’s synchronization context will automatically be used to “pick up” where it left off, and the Task<string> returned from DownloadStringTaskAsync is automatically unwrapped and set into the content variable.  At this point, we can use that and set our text box content. There are a couple of key points here: Asynchronous functions are declared with the async keyword, and contain one or more await expressions In addition to the obvious benefits of shorter, simpler code – there are some subtle but tremendous benefits in this approach.  When the execution of this asynchronous function continues after the first await statement, the initial synchronization context is used to continue the execution of this function.  That means that we don’t have to explicitly marshal the call that sets textbox1.Text back to the UI thread – it’s handled automatically by the language and framework!  Exception handling around asynchronous method calls also just works. I’d recommend every C# developer take a look at the documentation on the new Asynchronous Programming for C# and Visual Basic page, download the Visual Studio Async CTP, and try it out.

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  • New features of C# 4.0

    This article covers New features of C# 4.0. Article has been divided into below sections. Introduction. Dynamic Lookup. Named and Optional Arguments. Features for COM interop. Variance. Relationship with Visual Basic. Resources. Other interested readings… 22 New Features of Visual Studio 2008 for .NET Professionals 50 New Features of SQL Server 2008 IIS 7.0 New features Introduction It is now close to a year since Microsoft Visual C# 3.0 shipped as part of Visual Studio 2008. In the VS Managed Languages team we are hard at work on creating the next version of the language (with the unsurprising working title of C# 4.0), and this document is a first public description of the planned language features as we currently see them. Please be advised that all this is in early stages of production and is subject to change. Part of the reason for sharing our plans in public so early is precisely to get the kind of feedback that will cause us to improve the final product before it rolls out. Simultaneously with the publication of this whitepaper, a first public CTP (community technology preview) of Visual Studio 2010 is going out as a Virtual PC image for everyone to try. Please use it to play and experiment with the features, and let us know of any thoughts you have. We ask for your understanding and patience working with very early bits, where especially new or newly implemented features do not have the quality or stability of a final product. The aim of the CTP is not to give you a productive work environment but to give you the best possible impression of what we are working on for the next release. The CTP contains a number of walkthroughs, some of which highlight the new language features of C# 4.0. Those are excellent for getting a hands-on guided tour through the details of some common scenarios for the features. You may consider this whitepaper a companion document to these walkthroughs, complementing them with a focus on the overall language features and how they work, as opposed to the specifics of the concrete scenarios. C# 4.0 The major theme for C# 4.0 is dynamic programming. Increasingly, objects are “dynamic” in the sense that their structure and behavior is not captured by a static type, or at least not one that the compiler knows about when compiling your program. Some examples include a. objects from dynamic programming languages, such as Python or Ruby b. COM objects accessed through IDispatch c. ordinary .NET types accessed through reflection d. objects with changing structure, such as HTML DOM objects While C# remains a statically typed language, we aim to vastly improve the interaction with such objects. A secondary theme is co-evolution with Visual Basic. Going forward we will aim to maintain the individual character of each language, but at the same time important new features should be introduced in both languages at the same time. They should be differentiated more by style and feel than by feature set. The new features in C# 4.0 fall into four groups: Dynamic lookup Dynamic lookup allows you to write method, operator and indexer calls, property and field accesses, and even object invocations which bypass the C# static type checking and instead gets resolved at runtime. Named and optional parameters Parameters in C# can now be specified as optional by providing a default value for them in a member declaration. When the member is invoked, optional arguments can be omitted. Furthermore, any argument can be passed by parameter name instead of position. COM specific interop features Dynamic lookup as well as named and optional parameters both help making programming against COM less painful than today. On top of that, however, we are adding a number of other small features that further improve the interop experience. Variance It used to be that an IEnumerable<string> wasn’t an IEnumerable<object>. Now it is – C# embraces type safe “co-and contravariance” and common BCL types are updated to take advantage of that. Dynamic Lookup Dynamic lookup allows you a unified approach to invoking things dynamically. With dynamic lookup, when you have an object in your hand you do not need to worry about whether it comes from COM, IronPython, the HTML DOM or reflection; you just apply operations to it and leave it to the runtime to figure out what exactly those operations mean for that particular object. This affords you enormous flexibility, and can greatly simplify your code, but it does come with a significant drawback: Static typing is not maintained for these operations. A dynamic object is assumed at compile time to support any operation, and only at runtime will you get an error if it wasn’t so. Oftentimes this will be no loss, because the object wouldn’t have a static type anyway, in other cases it is a tradeoff between brevity and safety. In order to facilitate this tradeoff, it is a design goal of C# to allow you to opt in or opt out of dynamic behavior on every single call. The dynamic type C# 4.0 introduces a new static type called dynamic. When you have an object of type dynamic you can “do things to it” that are resolved only at runtime: dynamic d = GetDynamicObject(…); d.M(7); The C# compiler allows you to call a method with any name and any arguments on d because it is of type dynamic. At runtime the actual object that d refers to will be examined to determine what it means to “call M with an int” on it. The type dynamic can be thought of as a special version of the type object, which signals that the object can be used dynamically. It is easy to opt in or out of dynamic behavior: any object can be implicitly converted to dynamic, “suspending belief” until runtime. Conversely, there is an “assignment conversion” from dynamic to any other type, which allows implicit conversion in assignment-like constructs: dynamic d = 7; // implicit conversion int i = d; // assignment conversion Dynamic operations Not only method calls, but also field and property accesses, indexer and operator calls and even delegate invocations can be dispatched dynamically: dynamic d = GetDynamicObject(…); d.M(7); // calling methods d.f = d.P; // getting and settings fields and properties d[“one”] = d[“two”]; // getting and setting thorugh indexers int i = d + 3; // calling operators string s = d(5,7); // invoking as a delegate The role of the C# compiler here is simply to package up the necessary information about “what is being done to d”, so that the runtime can pick it up and determine what the exact meaning of it is given an actual object d. Think of it as deferring part of the compiler’s job to runtime. The result of any dynamic operation is itself of type dynamic. Runtime lookup At runtime a dynamic operation is dispatched according to the nature of its target object d: COM objects If d is a COM object, the operation is dispatched dynamically through COM IDispatch. This allows calling to COM types that don’t have a Primary Interop Assembly (PIA), and relying on COM features that don’t have a counterpart in C#, such as indexed properties and default properties. Dynamic objects If d implements the interface IDynamicObject d itself is asked to perform the operation. Thus by implementing IDynamicObject a type can completely redefine the meaning of dynamic operations. This is used intensively by dynamic languages such as IronPython and IronRuby to implement their own dynamic object models. It will also be used by APIs, e.g. by the HTML DOM to allow direct access to the object’s properties using property syntax. Plain objects Otherwise d is a standard .NET object, and the operation will be dispatched using reflection on its type and a C# “runtime binder” which implements C#’s lookup and overload resolution semantics at runtime. This is essentially a part of the C# compiler running as a runtime component to “finish the work” on dynamic operations that was deferred by the static compiler. Example Assume the following code: dynamic d1 = new Foo(); dynamic d2 = new Bar(); string s; d1.M(s, d2, 3, null); Because the receiver of the call to M is dynamic, the C# compiler does not try to resolve the meaning of the call. Instead it stashes away information for the runtime about the call. This information (often referred to as the “payload”) is essentially equivalent to: “Perform an instance method call of M with the following arguments: 1. a string 2. a dynamic 3. a literal int 3 4. a literal object null” At runtime, assume that the actual type Foo of d1 is not a COM type and does not implement IDynamicObject. In this case the C# runtime binder picks up to finish the overload resolution job based on runtime type information, proceeding as follows: 1. Reflection is used to obtain the actual runtime types of the two objects, d1 and d2, that did not have a static type (or rather had the static type dynamic). The result is Foo for d1 and Bar for d2. 2. Method lookup and overload resolution is performed on the type Foo with the call M(string,Bar,3,null) using ordinary C# semantics. 3. If the method is found it is invoked; otherwise a runtime exception is thrown. Overload resolution with dynamic arguments Even if the receiver of a method call is of a static type, overload resolution can still happen at runtime. This can happen if one or more of the arguments have the type dynamic: Foo foo = new Foo(); dynamic d = new Bar(); var result = foo.M(d); The C# runtime binder will choose between the statically known overloads of M on Foo, based on the runtime type of d, namely Bar. The result is again of type dynamic. The Dynamic Language Runtime An important component in the underlying implementation of dynamic lookup is the Dynamic Language Runtime (DLR), which is a new API in .NET 4.0. The DLR provides most of the infrastructure behind not only C# dynamic lookup but also the implementation of several dynamic programming languages on .NET, such as IronPython and IronRuby. Through this common infrastructure a high degree of interoperability is ensured, but just as importantly the DLR provides excellent caching mechanisms which serve to greatly enhance the efficiency of runtime dispatch. To the user of dynamic lookup in C#, the DLR is invisible except for the improved efficiency. However, if you want to implement your own dynamically dispatched objects, the IDynamicObject interface allows you to interoperate with the DLR and plug in your own behavior. This is a rather advanced task, which requires you to understand a good deal more about the inner workings of the DLR. For API writers, however, it can definitely be worth the trouble in order to vastly improve the usability of e.g. a library representing an inherently dynamic domain. Open issues There are a few limitations and things that might work differently than you would expect. · The DLR allows objects to be created from objects that represent classes. However, the current implementation of C# doesn’t have syntax to support this. · Dynamic lookup will not be able to find extension methods. Whether extension methods apply or not depends on the static context of the call (i.e. which using clauses occur), and this context information is not currently kept as part of the payload. · Anonymous functions (i.e. lambda expressions) cannot appear as arguments to a dynamic method call. The compiler cannot bind (i.e. “understand”) an anonymous function without knowing what type it is converted to. One consequence of these limitations is that you cannot easily use LINQ queries over dynamic objects: dynamic collection = …; var result = collection.Select(e => e + 5); If the Select method is an extension method, dynamic lookup will not find it. Even if it is an instance method, the above does not compile, because a lambda expression cannot be passed as an argument to a dynamic operation. There are no plans to address these limitations in C# 4.0. Named and Optional Arguments Named and optional parameters are really two distinct features, but are often useful together. Optional parameters allow you to omit arguments to member invocations, whereas named arguments is a way to provide an argument using the name of the corresponding parameter instead of relying on its position in the parameter list. Some APIs, most notably COM interfaces such as the Office automation APIs, are written specifically with named and optional parameters in mind. Up until now it has been very painful to call into these APIs from C#, with sometimes as many as thirty arguments having to be explicitly passed, most of which have reasonable default values and could be omitted. Even in APIs for .NET however you sometimes find yourself compelled to write many overloads of a method with different combinations of parameters, in order to provide maximum usability to the callers. Optional parameters are a useful alternative for these situations. Optional parameters A parameter is declared optional simply by providing a default value for it: public void M(int x, int y = 5, int z = 7); Here y and z are optional parameters and can be omitted in calls: M(1, 2, 3); // ordinary call of M M(1, 2); // omitting z – equivalent to M(1, 2, 7) M(1); // omitting both y and z – equivalent to M(1, 5, 7) Named and optional arguments C# 4.0 does not permit you to omit arguments between commas as in M(1,,3). This could lead to highly unreadable comma-counting code. Instead any argument can be passed by name. Thus if you want to omit only y from a call of M you can write: M(1, z: 3); // passing z by name or M(x: 1, z: 3); // passing both x and z by name or even M(z: 3, x: 1); // reversing the order of arguments All forms are equivalent, except that arguments are always evaluated in the order they appear, so in the last example the 3 is evaluated before the 1. Optional and named arguments can be used not only with methods but also with indexers and constructors. Overload resolution Named and optional arguments affect overload resolution, but the changes are relatively simple: A signature is applicable if all its parameters are either optional or have exactly one corresponding argument (by name or position) in the call which is convertible to the parameter type. Betterness rules on conversions are only applied for arguments that are explicitly given – omitted optional arguments are ignored for betterness purposes. If two signatures are equally good, one that does not omit optional parameters is preferred. M(string s, int i = 1); M(object o); M(int i, string s = “Hello”); M(int i); M(5); Given these overloads, we can see the working of the rules above. M(string,int) is not applicable because 5 doesn’t convert to string. M(int,string) is applicable because its second parameter is optional, and so, obviously are M(object) and M(int). M(int,string) and M(int) are both better than M(object) because the conversion from 5 to int is better than the conversion from 5 to object. Finally M(int) is better than M(int,string) because no optional arguments are omitted. Thus the method that gets called is M(int). Features for COM interop Dynamic lookup as well as named and optional parameters greatly improve the experience of interoperating with COM APIs such as the Office Automation APIs. In order to remove even more of the speed bumps, a couple of small COM-specific features are also added to C# 4.0. Dynamic import Many COM methods accept and return variant types, which are represented in the PIAs as object. In the vast majority of cases, a programmer calling these methods already knows the static type of a returned object from context, but explicitly has to perform a cast on the returned value to make use of that knowledge. These casts are so common that they constitute a major nuisance. In order to facilitate a smoother experience, you can now choose to import these COM APIs in such a way that variants are instead represented using the type dynamic. In other words, from your point of view, COM signatures now have occurrences of dynamic instead of object in them. This means that you can easily access members directly off a returned object, or you can assign it to a strongly typed local variable without having to cast. To illustrate, you can now say excel.Cells[1, 1].Value = "Hello"; instead of ((Excel.Range)excel.Cells[1, 1]).Value2 = "Hello"; and Excel.Range range = excel.Cells[1, 1]; instead of Excel.Range range = (Excel.Range)excel.Cells[1, 1]; Compiling without PIAs Primary Interop Assemblies are large .NET assemblies generated from COM interfaces to facilitate strongly typed interoperability. They provide great support at design time, where your experience of the interop is as good as if the types where really defined in .NET. However, at runtime these large assemblies can easily bloat your program, and also cause versioning issues because they are distributed independently of your application. The no-PIA feature allows you to continue to use PIAs at design time without having them around at runtime. Instead, the C# compiler will bake the small part of the PIA that a program actually uses directly into its assembly. At runtime the PIA does not have to be loaded. Omitting ref Because of a different programming model, many COM APIs contain a lot of reference parameters. Contrary to refs in C#, these are typically not meant to mutate a passed-in argument for the subsequent benefit of the caller, but are simply another way of passing value parameters. It therefore seems unreasonable that a C# programmer should have to create temporary variables for all such ref parameters and pass these by reference. Instead, specifically for COM methods, the C# compiler will allow you to pass arguments by value to such a method, and will automatically generate temporary variables to hold the passed-in values, subsequently discarding these when the call returns. In this way the caller sees value semantics, and will not experience any side effects, but the called method still gets a reference. Open issues A few COM interface features still are not surfaced in C#. Most notably these include indexed properties and default properties. As mentioned above these will be respected if you access COM dynamically, but statically typed C# code will still not recognize them. There are currently no plans to address these remaining speed bumps in C# 4.0. Variance An aspect of generics that often comes across as surprising is that the following is illegal: IList<string> strings = new List<string>(); IList<object> objects = strings; The second assignment is disallowed because strings does not have the same element type as objects. There is a perfectly good reason for this. If it were allowed you could write: objects[0] = 5; string s = strings[0]; Allowing an int to be inserted into a list of strings and subsequently extracted as a string. This would be a breach of type safety. However, there are certain interfaces where the above cannot occur, notably where there is no way to insert an object into the collection. Such an interface is IEnumerable<T>. If instead you say: IEnumerable<object> objects = strings; There is no way we can put the wrong kind of thing into strings through objects, because objects doesn’t have a method that takes an element in. Variance is about allowing assignments such as this in cases where it is safe. The result is that a lot of situations that were previously surprising now just work. Covariance In .NET 4.0 the IEnumerable<T> interface will be declared in the following way: public interface IEnumerable<out T> : IEnumerable { IEnumerator<T> GetEnumerator(); } public interface IEnumerator<out T> : IEnumerator { bool MoveNext(); T Current { get; } } The “out” in these declarations signifies that the T can only occur in output position in the interface – the compiler will complain otherwise. In return for this restriction, the interface becomes “covariant” in T, which means that an IEnumerable<A> is considered an IEnumerable<B> if A has a reference conversion to B. As a result, any sequence of strings is also e.g. a sequence of objects. This is useful e.g. in many LINQ methods. Using the declarations above: var result = strings.Union(objects); // succeeds with an IEnumerable<object> This would previously have been disallowed, and you would have had to to some cumbersome wrapping to get the two sequences to have the same element type. Contravariance Type parameters can also have an “in” modifier, restricting them to occur only in input positions. An example is IComparer<T>: public interface IComparer<in T> { public int Compare(T left, T right); } The somewhat baffling result is that an IComparer<object> can in fact be considered an IComparer<string>! It makes sense when you think about it: If a comparer can compare any two objects, it can certainly also compare two strings. This property is referred to as contravariance. A generic type can have both in and out modifiers on its type parameters, as is the case with the Func<…> delegate types: public delegate TResult Func<in TArg, out TResult>(TArg arg); Obviously the argument only ever comes in, and the result only ever comes out. Therefore a Func<object,string> can in fact be used as a Func<string,object>. Limitations Variant type parameters can only be declared on interfaces and delegate types, due to a restriction in the CLR. Variance only applies when there is a reference conversion between the type arguments. For instance, an IEnumerable<int> is not an IEnumerable<object> because the conversion from int to object is a boxing conversion, not a reference conversion. Also please note that the CTP does not contain the new versions of the .NET types mentioned above. In order to experiment with variance you have to declare your own variant interfaces and delegate types. COM Example Here is a larger Office automation example that shows many of the new C# features in action. using System; using System.Diagnostics; using System.Linq; using Excel = Microsoft.Office.Interop.Excel; using Word = Microsoft.Office.Interop.Word; class Program { static void Main(string[] args) { var excel = new Excel.Application(); excel.Visible = true; excel.Workbooks.Add(); // optional arguments omitted excel.Cells[1, 1].Value = "Process Name"; // no casts; Value dynamically excel.Cells[1, 2].Value = "Memory Usage"; // accessed var processes = Process.GetProcesses() .OrderByDescending(p =&gt; p.WorkingSet) .Take(10); int i = 2; foreach (var p in processes) { excel.Cells[i, 1].Value = p.ProcessName; // no casts excel.Cells[i, 2].Value = p.WorkingSet; // no casts i++; } Excel.Range range = excel.Cells[1, 1]; // no casts Excel.Chart chart = excel.ActiveWorkbook.Charts. Add(After: excel.ActiveSheet); // named and optional arguments chart.ChartWizard( Source: range.CurrentRegion, Title: "Memory Usage in " + Environment.MachineName); //named+optional chart.ChartStyle = 45; chart.CopyPicture(Excel.XlPictureAppearance.xlScreen, Excel.XlCopyPictureFormat.xlBitmap, Excel.XlPictureAppearance.xlScreen); var word = new Word.Application(); word.Visible = true; word.Documents.Add(); // optional arguments word.Selection.Paste(); } } The code is much more terse and readable than the C# 3.0 counterpart. Note especially how the Value property is accessed dynamically. This is actually an indexed property, i.e. a property that takes an argument; something which C# does not understand. However the argument is optional. Since the access is dynamic, it goes through the runtime COM binder which knows to substitute the default value and call the indexed property. Thus, dynamic COM allows you to avoid accesses to the puzzling Value2 property of Excel ranges. Relationship with Visual Basic A number of the features introduced to C# 4.0 already exist or will be introduced in some form or other in Visual Basic: · Late binding in VB is similar in many ways to dynamic lookup in C#, and can be expected to make more use of the DLR in the future, leading to further parity with C#. · Named and optional arguments have been part of Visual Basic for a long time, and the C# version of the feature is explicitly engineered with maximal VB interoperability in mind. · NoPIA and variance are both being introduced to VB and C# at the same time. VB in turn is adding a number of features that have hitherto been a mainstay of C#. As a result future versions of C# and VB will have much better feature parity, for the benefit of everyone. Resources All available resources concerning C# 4.0 can be accessed through the C# Dev Center. Specifically, this white paper and other resources can be found at the Code Gallery site. Enjoy! span.fullpost {display:none;}

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  • Node.js Adventure - When Node Flying in Wind

    - by Shaun
    In the first post of this series I mentioned some popular modules in the community, such as underscore, async, etc.. I also listed a module named “Wind (zh-CN)”, which is created by one of my friend, Jeff Zhao (zh-CN). Now I would like to use a separated post to introduce this module since I feel it brings a new async programming style in not only Node.js but JavaScript world. If you know or heard about the new feature in C# 5.0 called “async and await”, or you learnt F#, you will find the “Wind” brings the similar async programming experience in JavaScript. By using “Wind”, we can write async code that looks like the sync code. The callbacks, async stats and exceptions will be handled by “Wind” automatically and transparently.   What’s the Problem: Dense “Callback” Phobia Let’s firstly back to my second post in this series. As I mentioned in that post, when we wanted to read some records from SQL Server we need to open the database connection, and then execute the query. In Node.js all IO operation are designed as async callback pattern which means when the operation was done, it will invoke a function which was taken from the last parameter. For example the database connection opening code would be like this. 1: sql.open(connectionString, function(error, conn) { 2: if(error) { 3: // some error handling code 4: } 5: else { 6: // connection opened successfully 7: } 8: }); And then if we need to query the database the code would be like this. It nested in the previous function. 1: sql.open(connectionString, function(error, conn) { 2: if(error) { 3: // some error handling code 4: } 5: else { 6: // connection opened successfully 7: conn.queryRaw(command, function(error, results) { 8: if(error) { 9: // failed to execute this command 10: } 11: else { 12: // records retrieved successfully 13: } 14: }; 15: } 16: }); Assuming if we need to copy some data from this database to another then we need to open another connection and execute the command within the function under the query function. 1: sql.open(connectionString, function(error, conn) { 2: if(error) { 3: // some error handling code 4: } 5: else { 6: // connection opened successfully 7: conn.queryRaw(command, function(error, results) { 8: if(error) { 9: // failed to execute this command 10: } 11: else { 12: // records retrieved successfully 13: target.open(targetConnectionString, function(error, t_conn) { 14: if(error) { 15: // connect failed 16: } 17: else { 18: t_conn.queryRaw(copy_command, function(error, results) { 19: if(error) { 20: // copy failed 21: } 22: else { 23: // and then, what do you want to do now... 24: } 25: }; 26: } 27: }; 28: } 29: }; 30: } 31: }); This is just an example. In the real project the logic would be more complicated. This means our application might be messed up and the business process will be fragged by many callback functions. I would like call this “Dense Callback Phobia”. This might be a challenge how to make code straightforward and easy to read, something like below. 1: try 2: { 3: // open source connection 4: var s_conn = sqlConnect(s_connectionString); 5: // retrieve data 6: var results = sqlExecuteCommand(s_conn, s_command); 7: 8: // open target connection 9: var t_conn = sqlConnect(t_connectionString); 10: // prepare the copy command 11: var t_command = getCopyCommand(results); 12: // execute the copy command 13: sqlExecuteCommand(s_conn, t_command); 14: } 15: catch (ex) 16: { 17: // error handling 18: }   What’s the Problem: Sync-styled Async Programming Similar as the previous problem, the callback-styled async programming model makes the upcoming operation as a part of the current operation, and mixed with the error handling code. So it’s very hard to understand what on earth this code will do. And since Node.js utilizes non-blocking IO mode, we cannot invoke those operations one by one, as they will be executed concurrently. For example, in this post when I tried to copy the records from Windows Azure SQL Database (a.k.a. WASD) to Windows Azure Table Storage, if I just insert the data into table storage one by one and then print the “Finished” message, I will see the message shown before the data had been copied. This is because all operations were executed at the same time. In order to make the copy operation and print operation executed synchronously I introduced a module named “async” and the code was changed as below. 1: async.forEach(results.rows, 2: function (row, callback) { 3: var resource = { 4: "PartitionKey": row[1], 5: "RowKey": row[0], 6: "Value": row[2] 7: }; 8: client.insertEntity(tableName, resource, function (error) { 9: if (error) { 10: callback(error); 11: } 12: else { 13: console.log("entity inserted."); 14: callback(null); 15: } 16: }); 17: }, 18: function (error) { 19: if (error) { 20: error["target"] = "insertEntity"; 21: res.send(500, error); 22: } 23: else { 24: console.log("all done."); 25: res.send(200, "Done!"); 26: } 27: }); It ensured that the “Finished” message will be printed when all table entities had been inserted. But it cannot promise that the records will be inserted in sequence. It might be another challenge to make the code looks like in sync-style? 1: try 2: { 3: forEach(row in rows) { 4: var entity = { /* ... */ }; 5: tableClient.insert(tableName, entity); 6: } 7:  8: console.log("Finished"); 9: } 10: catch (ex) { 11: console.log(ex); 12: }   How “Wind” Helps “Wind” is a JavaScript library which provides the control flow with plain JavaScript for asynchronous programming (and more) without additional pre-compiling steps. It’s available in NPM so that we can install it through “npm install wind”. Now let’s create a very simple Node.js application as the example. This application will take some website URLs from the command arguments and tried to retrieve the body length and print them in console. Then at the end print “Finish”. I’m going to use “request” module to make the HTTP call simple so I also need to install by the command “npm install request”. The code would be like this. 1: var request = require("request"); 2:  3: // get the urls from arguments, the first two arguments are `node.exe` and `fetch.js` 4: var args = process.argv.splice(2); 5:  6: // main function 7: var main = function() { 8: for(var i = 0; i < args.length; i++) { 9: // get the url 10: var url = args[i]; 11: // send the http request and try to get the response and body 12: request(url, function(error, response, body) { 13: if(!error && response.statusCode == 200) { 14: // log the url and the body length 15: console.log( 16: "%s: %d.", 17: response.request.uri.href, 18: body.length); 19: } 20: else { 21: // log error 22: console.log(error); 23: } 24: }); 25: } 26: 27: // finished 28: console.log("Finished"); 29: }; 30:  31: // execute the main function 32: main(); Let’s execute this application. (I made them in multi-lines for better reading.) 1: node fetch.js 2: "http://www.igt.com/us-en.aspx" 3: "http://www.igt.com/us-en/games.aspx" 4: "http://www.igt.com/us-en/cabinets.aspx" 5: "http://www.igt.com/us-en/systems.aspx" 6: "http://www.igt.com/us-en/interactive.aspx" 7: "http://www.igt.com/us-en/social-gaming.aspx" 8: "http://www.igt.com/support.aspx" Below is the output. As you can see the finish message was printed at the beginning, and the pages’ length retrieved in a different order than we specified. This is because in this code the request command, console logging command are executed asynchronously and concurrently. Now let’s introduce “Wind” to make them executed in order, which means it will request the websites one by one, and print the message at the end.   First of all we need to import the “Wind” package and make sure the there’s only one global variant named “Wind”, and ensure it’s “Wind” instead of “wind”. 1: var Wind = require("wind");   Next, we need to tell “Wind” which code will be executed asynchronously so that “Wind” can control the execution process. In this case the “request” operation executed asynchronously so we will create a “Task” by using a build-in helps function in “Wind” named Wind.Async.Task.create. 1: var requestBodyLengthAsync = function(url) { 2: return Wind.Async.Task.create(function(t) { 3: request(url, function(error, response, body) { 4: if(error || response.statusCode != 200) { 5: t.complete("failure", error); 6: } 7: else { 8: var data = 9: { 10: uri: response.request.uri.href, 11: length: body.length 12: }; 13: t.complete("success", data); 14: } 15: }); 16: }); 17: }; The code above created a “Task” from the original request calling code. In “Wind” a “Task” means an operation will be finished in some time in the future. A “Task” can be started by invoke its start() method, but no one knows when it actually will be finished. The Wind.Async.Task.create helped us to create a task. The only parameter is a function where we can put the actual operation in, and then notify the task object it’s finished successfully or failed by using the complete() method. In the code above I invoked the request method. If it retrieved the response successfully I set the status of this task as “success” with the URL and body length. If it failed I set this task as “failure” and pass the error out.   Next, we will change the main() function. In “Wind” if we want a function can be controlled by Wind we need to mark it as “async”. This should be done by using the code below. 1: var main = eval(Wind.compile("async", function() { 2: })); When the application is running, Wind will detect “eval(Wind.compile(“async”, function” and generate an anonymous code from the body of this original function. Then the application will run the anonymous code instead of the original one. In our example the main function will be like this. 1: var main = eval(Wind.compile("async", function() { 2: for(var i = 0; i < args.length; i++) { 3: try 4: { 5: var result = $await(requestBodyLengthAsync(args[i])); 6: console.log( 7: "%s: %d.", 8: result.uri, 9: result.length); 10: } 11: catch (ex) { 12: console.log(ex); 13: } 14: } 15: 16: console.log("Finished"); 17: })); As you can see, when I tried to request the URL I use a new command named “$await”. It tells Wind, the operation next to $await will be executed asynchronously, and the main thread should be paused until it finished (or failed). So in this case, my application will be pause when the first response was received, and then print its body length, then try the next one. At the end, print the finish message.   Finally, execute the main function. The full code would be like this. 1: var request = require("request"); 2: var Wind = require("wind"); 3:  4: var args = process.argv.splice(2); 5:  6: var requestBodyLengthAsync = function(url) { 7: return Wind.Async.Task.create(function(t) { 8: request(url, function(error, response, body) { 9: if(error || response.statusCode != 200) { 10: t.complete("failure", error); 11: } 12: else { 13: var data = 14: { 15: uri: response.request.uri.href, 16: length: body.length 17: }; 18: t.complete("success", data); 19: } 20: }); 21: }); 22: }; 23:  24: var main = eval(Wind.compile("async", function() { 25: for(var i = 0; i < args.length; i++) { 26: try 27: { 28: var result = $await(requestBodyLengthAsync(args[i])); 29: console.log( 30: "%s: %d.", 31: result.uri, 32: result.length); 33: } 34: catch (ex) { 35: console.log(ex); 36: } 37: } 38: 39: console.log("Finished"); 40: })); 41:  42: main().start();   Run our new application. At the beginning we will see the compiled and generated code by Wind. Then we can see the pages were requested one by one, and at the end the finish message was printed. Below is the code Wind generated for us. As you can see the original code, the output code were shown. 1: // Original: 2: function () { 3: for(var i = 0; i < args.length; i++) { 4: try 5: { 6: var result = $await(requestBodyLengthAsync(args[i])); 7: console.log( 8: "%s: %d.", 9: result.uri, 10: result.length); 11: } 12: catch (ex) { 13: console.log(ex); 14: } 15: } 16: 17: console.log("Finished"); 18: } 19:  20: // Compiled: 21: /* async << function () { */ (function () { 22: var _builder_$0 = Wind.builders["async"]; 23: return _builder_$0.Start(this, 24: _builder_$0.Combine( 25: _builder_$0.Delay(function () { 26: /* var i = 0; */ var i = 0; 27: /* for ( */ return _builder_$0.For(function () { 28: /* ; i < args.length */ return i < args.length; 29: }, function () { 30: /* ; i ++) { */ i ++; 31: }, 32: /* try { */ _builder_$0.Try( 33: _builder_$0.Delay(function () { 34: /* var result = $await(requestBodyLengthAsync(args[i])); */ return _builder_$0.Bind(requestBodyLengthAsync(args[i]), function (result) { 35: /* console.log("%s: %d.", result.uri, result.length); */ console.log("%s: %d.", result.uri, result.length); 36: return _builder_$0.Normal(); 37: }); 38: }), 39: /* } catch (ex) { */ function (ex) { 40: /* console.log(ex); */ console.log(ex); 41: return _builder_$0.Normal(); 42: /* } */ }, 43: null 44: ) 45: /* } */ ); 46: }), 47: _builder_$0.Delay(function () { 48: /* console.log("Finished"); */ console.log("Finished"); 49: return _builder_$0.Normal(); 50: }) 51: ) 52: ); 53: /* } */ })   How Wind Works Someone may raise a big concern when you find I utilized “eval” in my code. Someone may assume that Wind utilizes “eval” to execute some code dynamically while “eval” is very low performance. But I would say, Wind does NOT use “eval” to run the code. It only use “eval” as a flag to know which code should be compiled at runtime. When the code was firstly been executed, Wind will check and find “eval(Wind.compile(“async”, function”. So that it knows this function should be compiled. Then it utilized parse-js to analyze the inner JavaScript and generated the anonymous code in memory. Then it rewrite the original code so that when the application was running it will use the anonymous one instead of the original one. Since the code generation was done at the beginning of the application was started, in the future no matter how long our application runs and how many times the async function was invoked, it will use the generated code, no need to generate again. So there’s no significant performance hurt when using Wind.   Wind in My Previous Demo Let’s adopt Wind into one of my previous demonstration and to see how it helps us to make our code simple, straightforward and easy to read and understand. In this post when I implemented the functionality that copied the records from my WASD to table storage, the logic would be like this. 1, Open database connection. 2, Execute a query to select all records from the table. 3, Recreate the table in Windows Azure table storage. 4, Create entities from each of the records retrieved previously, and then insert them into table storage. 5, Finally, show message as the HTTP response. But as the image below, since there are so many callbacks and async operations, it’s very hard to understand my logic from the code. Now let’s use Wind to rewrite our code. First of all, of course, we need the Wind package. Then we need to include the package files into project and mark them as “Copy always”. Add the Wind package into the source code. Pay attention to the variant name, you must use “Wind” instead of “wind”. 1: var express = require("express"); 2: var async = require("async"); 3: var sql = require("node-sqlserver"); 4: var azure = require("azure"); 5: var Wind = require("wind"); Now we need to create some async functions by using Wind. All async functions should be wrapped so that it can be controlled by Wind which are open database, retrieve records, recreate table (delete and create) and insert entity in table. Below are these new functions. All of them are created by using Wind.Async.Task.create. 1: sql.openAsync = function (connectionString) { 2: return Wind.Async.Task.create(function (t) { 3: sql.open(connectionString, function (error, conn) { 4: if (error) { 5: t.complete("failure", error); 6: } 7: else { 8: t.complete("success", conn); 9: } 10: }); 11: }); 12: }; 13:  14: sql.queryAsync = function (conn, query) { 15: return Wind.Async.Task.create(function (t) { 16: conn.queryRaw(query, function (error, results) { 17: if (error) { 18: t.complete("failure", error); 19: } 20: else { 21: t.complete("success", results); 22: } 23: }); 24: }); 25: }; 26:  27: azure.recreateTableAsync = function (tableName) { 28: return Wind.Async.Task.create(function (t) { 29: client.deleteTable(tableName, function (error, successful, response) { 30: console.log("delete table finished"); 31: client.createTableIfNotExists(tableName, function (error, successful, response) { 32: console.log("create table finished"); 33: if (error) { 34: t.complete("failure", error); 35: } 36: else { 37: t.complete("success", null); 38: } 39: }); 40: }); 41: }); 42: }; 43:  44: azure.insertEntityAsync = function (tableName, entity) { 45: return Wind.Async.Task.create(function (t) { 46: client.insertEntity(tableName, entity, function (error, entity, response) { 47: if (error) { 48: t.complete("failure", error); 49: } 50: else { 51: t.complete("success", null); 52: } 53: }); 54: }); 55: }; Then in order to use these functions we will create a new function which contains all steps for data copying. 1: var copyRecords = eval(Wind.compile("async", function (req, res) { 2: try { 3: } 4: catch (ex) { 5: console.log(ex); 6: res.send(500, "Internal error."); 7: } 8: })); Let’s execute steps one by one with the “$await” keyword introduced by Wind so that it will be invoked in sequence. First is to open the database connection. 1: var copyRecords = eval(Wind.compile("async", function (req, res) { 2: try { 3: // connect to the windows azure sql database 4: var conn = $await(sql.openAsync(connectionString)); 5: console.log("connection opened"); 6: } 7: catch (ex) { 8: console.log(ex); 9: res.send(500, "Internal error."); 10: } 11: })); Then retrieve all records from the database connection. 1: var copyRecords = eval(Wind.compile("async", function (req, res) { 2: try { 3: // connect to the windows azure sql database 4: var conn = $await(sql.openAsync(connectionString)); 5: console.log("connection opened"); 6: // retrieve all records from database 7: var results = $await(sql.queryAsync(conn, "SELECT * FROM [Resource]")); 8: console.log("records selected. count = %d", results.rows.length); 9: } 10: catch (ex) { 11: console.log(ex); 12: res.send(500, "Internal error."); 13: } 14: })); After recreated the table, we need to create the entities and insert them into table storage. 1: var copyRecords = eval(Wind.compile("async", function (req, res) { 2: try { 3: // connect to the windows azure sql database 4: var conn = $await(sql.openAsync(connectionString)); 5: console.log("connection opened"); 6: // retrieve all records from database 7: var results = $await(sql.queryAsync(conn, "SELECT * FROM [Resource]")); 8: console.log("records selected. count = %d", results.rows.length); 9: if (results.rows.length > 0) { 10: // recreate the table 11: $await(azure.recreateTableAsync(tableName)); 12: console.log("table created"); 13: // insert records in table storage one by one 14: for (var i = 0; i < results.rows.length; i++) { 15: var entity = { 16: "PartitionKey": results.rows[i][1], 17: "RowKey": results.rows[i][0], 18: "Value": results.rows[i][2] 19: }; 20: $await(azure.insertEntityAsync(tableName, entity)); 21: console.log("entity inserted"); 22: } 23: } 24: } 25: catch (ex) { 26: console.log(ex); 27: res.send(500, "Internal error."); 28: } 29: })); Finally, send response back to the browser. 1: var copyRecords = eval(Wind.compile("async", function (req, res) { 2: try { 3: // connect to the windows azure sql database 4: var conn = $await(sql.openAsync(connectionString)); 5: console.log("connection opened"); 6: // retrieve all records from database 7: var results = $await(sql.queryAsync(conn, "SELECT * FROM [Resource]")); 8: console.log("records selected. count = %d", results.rows.length); 9: if (results.rows.length > 0) { 10: // recreate the table 11: $await(azure.recreateTableAsync(tableName)); 12: console.log("table created"); 13: // insert records in table storage one by one 14: for (var i = 0; i < results.rows.length; i++) { 15: var entity = { 16: "PartitionKey": results.rows[i][1], 17: "RowKey": results.rows[i][0], 18: "Value": results.rows[i][2] 19: }; 20: $await(azure.insertEntityAsync(tableName, entity)); 21: console.log("entity inserted"); 22: } 23: // send response 24: console.log("all done"); 25: res.send(200, "All done!"); 26: } 27: } 28: catch (ex) { 29: console.log(ex); 30: res.send(500, "Internal error."); 31: } 32: })); If we compared with the previous code we will find now it became more readable and much easy to understand. It’s very easy to know what this function does even though without any comments. When user go to URL “/was/copyRecords” we will execute the function above. The code would be like this. 1: app.get("/was/copyRecords", function (req, res) { 2: copyRecords(req, res).start(); 3: }); And below is the logs printed in local compute emulator console. As we can see the functions executed one by one and then finally the response back to me browser.   Scaffold Functions in Wind Wind provides not only the async flow control and compile functions, but many scaffold methods as well. We can build our async code more easily by using them. I’m going to introduce some basic scaffold functions here. In the code above I created some functions which wrapped from the original async function such as open database, create table, etc.. All of them are very similar, created a task by using Wind.Async.Task.create, return error or result object through Task.complete function. In fact, Wind provides some functions for us to create task object from the original async functions. If the original async function only has a callback parameter, we can use Wind.Async.Binding.fromCallback method to get the task object directly. For example the code below returned the task object which wrapped the file exist check function. 1: var Wind = require("wind"); 2: var fs = require("fs"); 3:  4: fs.existsAsync = Wind.Async.Binding.fromCallback(fs.exists); In Node.js a very popular async function pattern is that, the first parameter in the callback function represent the error object, and the other parameters is the return values. In this case we can use another build-in function in Wind named Wind.Async.Binding.fromStandard. For example, the open database function can be created from the code below. 1: sql.openAsync = Wind.Async.Binding.fromStandard(sql.open); 2:  3: /* 4: sql.openAsync = function (connectionString) { 5: return Wind.Async.Task.create(function (t) { 6: sql.open(connectionString, function (error, conn) { 7: if (error) { 8: t.complete("failure", error); 9: } 10: else { 11: t.complete("success", conn); 12: } 13: }); 14: }); 15: }; 16: */ When I was testing the scaffold functions under Wind.Async.Binding I found for some functions, such as the Azure SDK insert entity function, cannot be processed correctly. So I personally suggest writing the wrapped method manually.   Another scaffold method in Wind is the parallel tasks coordination. In this example, the steps of open database, retrieve records and recreated table should be invoked one by one, but it can be executed in parallel when copying data from database to table storage. In Wind there’s a scaffold function named Task.whenAll which can be used here. Task.whenAll accepts a list of tasks and creates a new task. It will be returned only when all tasks had been completed, or any errors occurred. For example in the code below I used the Task.whenAll to make all copy operation executed at the same time. 1: var copyRecordsInParallel = eval(Wind.compile("async", function (req, res) { 2: try { 3: // connect to the windows azure sql database 4: var conn = $await(sql.openAsync(connectionString)); 5: console.log("connection opened"); 6: // retrieve all records from database 7: var results = $await(sql.queryAsync(conn, "SELECT * FROM [Resource]")); 8: console.log("records selected. count = %d", results.rows.length); 9: if (results.rows.length > 0) { 10: // recreate the table 11: $await(azure.recreateTableAsync(tableName)); 12: console.log("table created"); 13: // insert records in table storage in parallal 14: var tasks = new Array(results.rows.length); 15: for (var i = 0; i < results.rows.length; i++) { 16: var entity = { 17: "PartitionKey": results.rows[i][1], 18: "RowKey": results.rows[i][0], 19: "Value": results.rows[i][2] 20: }; 21: tasks[i] = azure.insertEntityAsync(tableName, entity); 22: } 23: $await(Wind.Async.Task.whenAll(tasks)); 24: // send response 25: console.log("all done"); 26: res.send(200, "All done!"); 27: } 28: } 29: catch (ex) { 30: console.log(ex); 31: res.send(500, "Internal error."); 32: } 33: })); 34:  35: app.get("/was/copyRecordsInParallel", function (req, res) { 36: copyRecordsInParallel(req, res).start(); 37: });   Besides the task creation and coordination, Wind supports the cancellation solution so that we can send the cancellation signal to the tasks. It also includes exception solution which means any exceptions will be reported to the caller function.   Summary In this post I introduced a Node.js module named Wind, which created by my friend Jeff Zhao. As you can see, different from other async library and framework, adopted the idea from F# and C#, Wind utilizes runtime code generation technology to make it more easily to write async, callback-based functions in a sync-style way. By using Wind there will be almost no callback, and the code will be very easy to understand. Currently Wind is still under developed and improved. There might be some problems but the author, Jeff, should be very happy and enthusiastic to learn your problems, feedback, suggestion and comments. You can contact Jeff by - Email: [email protected] - Group: https://groups.google.com/d/forum/windjs - GitHub: https://github.com/JeffreyZhao/wind/issues   Source code can be download here.   Hope this helps, Shaun All documents and related graphics, codes are provided "AS IS" without warranty of any kind. Copyright © Shaun Ziyan Xu. This work is licensed under the Creative Commons License.

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  • Developer Training – Various Options for Maximum Benefit – Part 4

    - by pinaldave
    Developer Training - Importance and Significance - Part 1 Developer Training – Employee Morals and Ethics – Part 2 Developer Training – Difficult Questions and Alternative Perspective - Part 3 Developer Training – Various Options for Developer Training – Part 4 Developer Training – A Conclusive Summary- Part 5 If you have been reading this series, by now you are aware of all the pros and cons that can come along with training.  We’ve asked and answered hard questions, and investigated them “whys” and “hows” of training.  Now it is time to talk about all the different kinds of training that are out there! On Job Training The most common type of training is on the job training.  Everyone receives this kind of education – even experts who come in to consult have to be taught where the printer, pens, and copy machines are.  If you are thinking about more concrete topics, though, on the job training can be some of the easiest to come across.  Picture this: someone in the company whom you really admire is hard at work on a project.  You come up to them and ask to help them out – if they are a busy developer, the odds are that they will say “yes, please!”   If you phrase your question as an offer of help, you can receive training without ever putting someone in the awkward position of acting as a mentor.  However, some people may want the task of being a mentor.  It can never hurt to ask.  Most people will be more than willing to pass their knowledge along. Extreme Programming If your company and coworkers are willing, you can even investigate Extreme Programming.  This is a type of programming that allows small teams to quickly develop code and products that are released with almost immediate user feedback.  You can find more information at http://www.extremeprogramming.org/.  If this is something your company could use, suggest it to your supervisor.  Even if they say no, it will make it clear that you are a go-getter who is interested in new and exciting projects.  If the answer is yes, then you have the opportunity to get some of the best on the job training around. In Person Training Click on Image to Enlarge When you say the word “training,” most people’s minds go back to the classroom, an image they are familiar with.  While training doesn’t always have to be in a traditional setting, because it is so familiar it can also be the most valuable type of training.  There are many ways to get training through a live instructor.  Some companies may be willing to send a representative to you, where employees will get training, sometimes food and coffee, and a live instructor who can answer questions immediately.  Sometimes these trainers are also able to do consultations at the same time, which can invaluable to a company.  If you are the one to asks your supervisor for a training session that can also be turned into a consultation, you may stick in their minds as an incredibly dedicated employee.  If you can’t find a representative, local colleges can also be a good resource for free or cheap classes – or they may have representatives coming who are willing to take on a few more students. Benefits of On Demand Developer Training Of course, you can often get the best of all these types of training with online or On Demand training.  You can get the benefit of a live instructor who is willing to answer questions (although in this case, usually through e-mail or other online venues), there are often real-world examples to follow along – like on the job training – and best of all you can learn whenever you have the time or need.  Did a problem with your server come up at midnight when all your supervisors are safe at home and probably in bed?  No problem!  On Demand training is especially useful if you need to slow down, pause, or rewind a training session.  Not even a real-life instructor can do that! When I was writing this blog post, I felt that each of the subject, which I have covered can be blog posts of itself. However, I wanted to keep the the blog post concise and so touch based on three major training aspects 1) On Job Training 2) In Person Training and 3) Online training. Here is the question for you – is there any other kind of training methods available, which are effective and one should consider it? If yes, what are those, I may write a follow up blog post on the same subject next week. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: Developer Training, PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology

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  • To ORM or Not to ORM. That is the question&hellip;

    - by Patrick Liekhus
    UPDATE:  Thanks for the feedback and comments.  I have adjusted my table below with your recommendations.  I had missed a point or two. I wanted to do a series on creating an entire project using the EDMX XAF code generation and the SpecFlow BDD Easy Test tools discussed in my earlier posts, but I thought it would be appropriate to start with a simple comparison and reasoning on why I choose to use these tools. Let’s start by defining the term ORM, or Object-Relational Mapping.  According to Wikipedia it is defined as the following: Object-relational mapping (ORM, O/RM, and O/R mapping) in computer software is a programming technique for converting data between incompatible type systems in object-oriented programming languages. This creates, in effect, a "virtual object database" that can be used from within the programming language. Why should you care?  Basically it allows you to map your business objects in code to their persistence layer behind them. And better yet, why would you want to do this?  Let me outline it in the following points: Development speed.  No more need to map repetitive tasks query results to object members.  Once the map is created the code is rendered for you. Persistence portability.  The ORM knows how to map SQL specific syntax for the persistence engine you choose.  It does not matter if it is SQL Server, Oracle and another database of your choosing. Standard/Boilerplate code is simplified.  The basic CRUD operations are consistent and case use database metadata for basic operations. So how does this help?  Well, let’s compare some of the ORM tools that I have used and/or researched.  I have been interested in ORM for some time now.  My ORM of choice for a long time was NHibernate and I still believe it has a strong case in some business situations.  However, you have to take business considerations into account and the law of diminishing returns.  Because of these two factors, my recent activity and experience has been around DevExpress eXpress Persistence Objects (XPO).  The primary reason for this is because they have the DevExpress eXpress Application Framework (XAF) that sits on top of XPO.  With this added value, the data model can be created (either database first of code first) and the Web and Windows client can be created from these maps.  While out of the box they provide some simple list and detail screens, you can verify easily extend and modify these to your liking.  DevExpress has done a tremendous job of providing enough framework while also staying out of the way when you need to extend it.  This sounds worse than it really is.  What I mean by this is that if you choose to follow DevExpress coding style and recommendations, the hooks and extension points provided allow you to do some pretty heavy lifting while also not worrying about the basics. I have put together a list of the top features that I have used to compare the limited list of ORM’s that I have exposure with.  Again, the biggest selling point in my opinion is that XPO is just a solid as any of the other ORM’s but with the added layer of XAF they become unstoppable.  And then couple that with the EDMX modeling tools and code generation, it becomes a no brainer. Designer Features Entity Framework NHibernate Fluent w/ Nhibernate Telerik OpenAccess DevExpress XPO DevExpress XPO/XAF plus Liekhus Tools Uses XML to map relationships - Yes - - -   Visual class designer interface Yes - - - - Yes Management integrated w/ Visual Studio Yes - - Yes - Yes Supports schema first approach Yes - - Yes - Yes Supports model first approach Yes - - Yes Yes Yes Supports code first approach Yes Yes Yes Yes Yes Yes Attribute driven coding style Yes - Yes - Yes Yes                 I have a very small team and limited resources with a lot of responsibilities.  In order to keep up with our customers, we must rely on tools like these.  We use the EDMX tool so that we can create a visual representation of the applications with our customers.  Second, we rely on the code generation so that we can focus on the business problems at hand and not whether a field is mapped correctly.  This keeps us from requiring as many junior level developers on our team.  I have also worked on multiple teams where they believed in writing their own “framework”.  In my experiences and opinion this is not the route to take unless you have a team dedicated to supporting just the framework.  Each time that I have worked on custom frameworks, the framework eventually becomes old, out dated and full of “performance” enhancements specific to one or two requirements.  With an ORM, there are a lot smarter people than me working on the bigger issue of persistence and performance.  Again, my recommendation would be to use an available framework and get to working on your business domain problems.  If your coding is not making money for you, why are you working on it?  Do you really need to be writing query to object member code again and again? Thanks

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  • Parallelism in .NET – Part 17, Think Continuations, not Callbacks

    - by Reed
    In traditional asynchronous programming, we’d often use a callback to handle notification of a background task’s completion.  The Task class in the Task Parallel Library introduces a cleaner alternative to the traditional callback: continuation tasks. Asynchronous programming methods typically required callback functions.  For example, MSDN’s Asynchronous Delegates Programming Sample shows a class that factorizes a number.  The original method in the example has the following signature: public static bool Factorize(int number, ref int primefactor1, ref int primefactor2) { //... .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } However, calling this is quite “tricky”, even if we modernize the sample to use lambda expressions via C# 3.0.  Normally, we could call this method like so: int primeFactor1 = 0; int primeFactor2 = 0; bool answer = Factorize(10298312, ref primeFactor1, ref primeFactor2); Console.WriteLine("{0}/{1} [Succeeded {2}]", primeFactor1, primeFactor2, answer); If we want to make this operation run in the background, and report to the console via a callback, things get tricker.  First, we need a delegate definition: public delegate bool AsyncFactorCaller( int number, ref int primefactor1, ref int primefactor2); Then we need to use BeginInvoke to run this method asynchronously: int primeFactor1 = 0; int primeFactor2 = 0; AsyncFactorCaller caller = new AsyncFactorCaller(Factorize); caller.BeginInvoke(10298312, ref primeFactor1, ref primeFactor2, result => { int factor1 = 0; int factor2 = 0; bool answer = caller.EndInvoke(ref factor1, ref factor2, result); Console.WriteLine("{0}/{1} [Succeeded {2}]", factor1, factor2, answer); }, null); This works, but is quite difficult to understand from a conceptual standpoint.  To combat this, the framework added the Event-based Asynchronous Pattern, but it isn’t much easier to understand or author. Using .NET 4’s new Task<T> class and a continuation, we can dramatically simplify the implementation of the above code, as well as make it much more understandable.  We do this via the Task.ContinueWith method.  This method will schedule a new Task upon completion of the original task, and provide the original Task (including its Result if it’s a Task<T>) as an argument.  Using Task, we can eliminate the delegate, and rewrite this code like so: var background = Task.Factory.StartNew( () => { int primeFactor1 = 0; int primeFactor2 = 0; bool result = Factorize(10298312, ref primeFactor1, ref primeFactor2); return new { Result = result, Factor1 = primeFactor1, Factor2 = primeFactor2 }; }); background.ContinueWith(task => Console.WriteLine("{0}/{1} [Succeeded {2}]", task.Result.Factor1, task.Result.Factor2, task.Result.Result)); This is much simpler to understand, in my opinion.  Here, we’re explicitly asking to start a new task, then continue the task with a resulting task.  In our case, our method used ref parameters (this was from the MSDN Sample), so there is a little bit of extra boiler plate involved, but the code is at least easy to understand. That being said, this isn’t dramatically shorter when compared with our C# 3 port of the MSDN code above.  However, if we were to extend our requirements a bit, we can start to see more advantages to the Task based approach.  For example, supposed we need to report the results in a user interface control instead of reporting it to the Console.  This would be a common operation, but now, we have to think about marshaling our calls back to the user interface.  This is probably going to require calling Control.Invoke or Dispatcher.Invoke within our callback, forcing us to specify a delegate within the delegate.  The maintainability and ease of understanding drops.  However, just as a standard Task can be created with a TaskScheduler that uses the UI synchronization context, so too can we continue a task with a specific context.  There are Task.ContinueWith method overloads which allow you to provide a TaskScheduler.  This means you can schedule the continuation to run on the UI thread, by simply doing: Task.Factory.StartNew( () => { int primeFactor1 = 0; int primeFactor2 = 0; bool result = Factorize(10298312, ref primeFactor1, ref primeFactor2); return new { Result = result, Factor1 = primeFactor1, Factor2 = primeFactor2 }; }).ContinueWith(task => textBox1.Text = string.Format("{0}/{1} [Succeeded {2}]", task.Result.Factor1, task.Result.Factor2, task.Result.Result), TaskScheduler.FromCurrentSynchronizationContext()); This is far more understandable than the alternative.  By using Task.ContinueWith in conjunction with TaskScheduler.FromCurrentSynchronizationContext(), we get a simple way to push any work onto a background thread, and update the user interface on the proper UI thread.  This technique works with Windows Presentation Foundation as well as Windows Forms, with no change in methodology.

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  • Another sound not working post

    - by Thomas Smart
    Tried all the other "sound not working" posts i think, lost count. purge/reinstall alsa and pulse, reboot, add user to audio group, various lines in the alsa config file such as "options snd-hda-intel model=" then tried different options like generic, auto, basic, default, etc. tried pulseaudio -k && sudo alsa force-reload a few times, with and without rebooting. Hardware: 16gb ram, core I7-4790, Intel Haswell mboard with onboard sound and graphics Multimedia: Audio Adapter: HDA-Intel-HDA Intel HDMI OS: Ubuntu server 14.04 with ubuntu-desktop installed. GUI sound settings lists only the dummy sound card alsamixer -c 0 ¦ Card: HDA Intel HDMI F1: Help ¦ ¦ Chip: Intel Haswell HDMI F2: System information ¦ ¦ View: F3:[Playback] F4: Capture F5: All F6: Select sound card ¦ ¦ Item: S/PDIF ¦ ¦ +--+ ¦ ¦ ¦OO¦ ¦ ¦ +--+ ¦ ¦ < S/PDIF > ¦ aplay -l **** List of PLAYBACK Hardware Devices **** card 0: HDMI [HDA Intel HDMI], device 3: HDMI 0 [HDMI 0] Subdevices: 1/1 Subdevice #0: subdevice #0 aplay -L default Playback/recording through the PulseAudio sound server null Discard all samples (playback) or generate zero samples (capture) pulse PulseAudio Sound Server hdmi:CARD=HDMI,DEV=0 HDA Intel HDMI, HDMI 0 HDMI Audio Output dmix:CARD=HDMI,DEV=3 HDA Intel HDMI, HDMI 0 Direct sample mixing device dsnoop:CARD=HDMI,DEV=3 HDA Intel HDMI, HDMI 0 Direct sample snooping device hw:CARD=HDMI,DEV=3 HDA Intel HDMI, HDMI 0 Direct hardware device without any conversions plughw:CARD=HDMI,DEV=3 HDA Intel HDMI, HDMI 0 Hardware device with all software conversions cat /proc/asound/cards 0 [HDMI ]: HDA-Intel - HDA Intel HDMI HDA Intel HDMI at 0xf7d14000 irq 46 cat /proc/asound/devices 1: : sequencer 2: [ 0- 3]: digital audio playback 3: [ 0- 0]: hardware dependent 4: [ 0] : control 33: : timer mplayer -ao alsa:device=hdmi /usr/share/sounds/ubuntu/stereo/system-ready.ogg MPlayer 1.1-4.8 (C) 2000-2012 MPlayer Team mplayer: could not connect to socket mplayer: No such file or directory Failed to open LIRC support. You will not be able to use your remote control. Playing /usr/share/sounds/ubuntu/stereo/system-ready.ogg. libavformat version 54.20.4 (external) Mismatching header version 54.20.3 libavformat file format detected. [lavf] stream 0: audio (vorbis), -aid 0 Load subtitles in /usr/share/sounds/ubuntu/stereo/ ========================================================================== Opening audio decoder: [ffmpeg] FFmpeg/libavcodec audio decoders libavcodec version 54.35.0 (external) AUDIO: 44100 Hz, 1 ch, floatle, 80.0 kbit/5.67% (ratio: 10000->176400) Selected audio codec: [ffvorbis] afm: ffmpeg (FFmpeg Vorbis) ========================================================================== [AO_ALSA] alsa-lib: confmisc.c:768:(parse_card) cannot find card '1' [AO_ALSA] alsa-lib: conf.c:4248:(_snd_config_evaluate) function snd_func_card_driver returned error: No such file or directory [AO_ALSA] alsa-lib: confmisc.c:392:(snd_func_concat) error evaluating strings [AO_ALSA] alsa-lib: conf.c:4248:(_snd_config_evaluate) function snd_func_concat returned error: No such file or directory [AO_ALSA] alsa-lib: confmisc.c:1251:(snd_func_refer) error evaluating name [AO_ALSA] alsa-lib: conf.c:4248:(_snd_config_evaluate) function snd_func_refer returned error: No such file or directory [AO_ALSA] alsa-lib: conf.c:4727:(snd_config_expand) Evaluate error: No such file or directory [AO_ALSA] alsa-lib: pcm.c:2239:(snd_pcm_open_noupdate) Unknown PCM hdmi [AO_ALSA] Playback open error: No such file or directory Failed to initialize audio driver 'alsa:device=hdmi' Could not open/initialize audio device -> no sound. Audio: no sound Video: no video Exiting... (End of file) mplayer -ao alsa:device=hw=0.3 /usr/share/sounds/ubuntu/stereo/system-ready.ogg MPlayer 1.1-4.8 (C) 2000-2012 MPlayer Team mplayer: could not connect to socket mplayer: No such file or directory Failed to open LIRC support. You will not be able to use your remote control. Playing /usr/share/sounds/ubuntu/stereo/system-ready.ogg. libavformat version 54.20.4 (external) Mismatching header version 54.20.3 libavformat file format detected. [lavf] stream 0: audio (vorbis), -aid 0 Load subtitles in /usr/share/sounds/ubuntu/stereo/ ========================================================================== Opening audio decoder: [ffmpeg] FFmpeg/libavcodec audio decoders libavcodec version 54.35.0 (external) AUDIO: 44100 Hz, 1 ch, floatle, 80.0 kbit/5.67% (ratio: 10000->176400) Selected audio codec: [ffvorbis] afm: ffmpeg (FFmpeg Vorbis) ========================================================================== [AO_ALSA] Format floatle is not supported by hardware, trying default. AO: [alsa] 44100Hz 2ch s16le (2 bytes per sample) Video: no video Starting playback... A: 0.4 (00.4) of 0.8 (00.7) 0.1% Exiting... (End of file) Thank you for your time and help :)

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  • Integrated webcam in lenovo t410 not working with 12.04

    - by kristianp
    I have a Lenovo T410 with an inbuilt webcam and I haven't been able to get the webcam working. I tried skype, cheese, both just give me a black window. The microphone works fine with skype, by the way. Can anyone provide any clues please? The webcam is enabled in the bios, but there is no light indicating the webcam is on (not sure if there should be, though). I tried this on Kubuntu 11.10 and have upgraded to 12.04 with the same results. The Fn-F6 keyboard combination doens't seem to do anything either. EDIT: I got the webcam replaced, it looks like it was a hardware problem, because it works fine now. Thanks guys. $ ls /dev/v4l/* /dev/v4l/by-id: usb-Chicony_Electronics_Co.__Ltd._Integrated_Camera-video-index0 /dev/v4l/by-path: pci-0000:00:1a.0-usb-0:1.6:1.0-video-index0 And lsusb: $ lsusb Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 002 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub Bus 001 Device 002: ID 8087:0020 Intel Corp. Integrated Rate Matching Hub Bus 002 Device 002: ID 8087:0020 Intel Corp. Integrated Rate Matching Hub Bus 001 Device 003: ID 147e:2016 Upek Biometric Touchchip/Touchstrip Fingerprint Sensor Bus 001 Device 004: ID 0a5c:217f Broadcom Corp. Bluetooth Controller Bus 001 Device 005: ID 17ef:480f Lenovo Integrated Webcam [R5U877] Bus 002 Device 003: ID 05c6:9204 Qualcomm, Inc. Bus 002 Device 004: ID 17ef:1003 Lenovo Integrated Smart Card Reader Here is the output from guvcview, minus lots of lines describing the available capture formats. It says "unable to start with minimum setup. Please reconnect your camera.". guvcview 1.5.3 ALSA lib pcm_dmix.c:1018:(snd_pcm_dmix_open) unable to open slave ALSA lib pcm.c:2217:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.rear ALSA lib pcm.c:2217:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.center_lfe ALSA lib pcm.c:2217:(snd_pcm_open_noupdate) Unknown PCM cards.pcm.side ALSA lib audio/pcm_bluetooth.c:1614:(audioservice_expect) BT_GET_CAPABILITIES failed : Input/output error(5) ALSA lib audio/pcm_bluetooth.c:1614:(audioservice_expect) BT_GET_CAPABILITIES failed : Input/output error(5) ALSA lib audio/pcm_bluetooth.c:1614:(audioservice_expect) BT_GET_CAPABILITIES failed : Input/output error(5) ALSA lib audio/pcm_bluetooth.c:1614:(audioservice_expect) BT_GET_CAPABILITIES failed : Input/output error(5) ALSA lib pcm_dmix.c:957:(snd_pcm_dmix_open) The dmix plugin supports only playback stream ALSA lib pcm_dmix.c:1018:(snd_pcm_dmix_open) unable to open slave Cannot connect to server socket err = No such file or directory Cannot connect to server socket jack server is not running or cannot be started video device: /dev/video0 Init. Integrated Camera (location: usb-0000:00:1a.0-1.6) { pixelformat = 'YUYV', description = 'YUV 4:2:2 (YUYV)' } { discrete: width = 640, height = 480 } Time interval between frame: 1/30, .... { discrete: width = 1600, height = 1200 } Time interval between frame: 1/15, vid:17ef pid:480f driver:uvcvideo checking format: 1196444237 libv4l2: error setting pixformat: Device or resource busy VIDIOC_S_FORMAT - Unable to set format: Device or resource busy Init v4L2 failed !! Init video returned -2 trying minimum setup ... video device: /dev/video0 Init. Integrated Camera (location: usb-0000:00:1a.0-1.6) { pixelformat = 'YUYV', description = 'YUV 4:2:2 (YUYV)' } { discrete: width = 640, height = 480 } .... vid:17ef pid:480f driver:uvcvideo checking format: 1448695129 libv4l2: error setting pixformat: Device or resource busy VIDIOC_S_FORMAT - Unable to set format: Device or resource busy Init v4L2 failed !! ERROR: Minimum Setup Failed. Exiting... VIDIOC_REQBUFS - Failed to delete buffers: Invalid argument (errno 22) cleaned allocations - 100% Closing portaudio ...OK Terminated.

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  • My Red Gate Experience

    - by Colin Rothwell
    I’m Colin, and I’ve been an intern working with Mike in publishing on Simple-Talk and SQLServerCentral for the past ten weeks. I’ve mostly been working “behind the scenes”, making improvements to the spam filtering, along with various other small tweaks. When I arrived at Red Gate, one of the first things Mike asked me was what I wanted to get out of the internship. It wasn’t a question I’d given a great deal of thought to, but my immediate response was the same as almost anybody: to support my growing family. Well, ok, not quite that, but money was certainly a motivator, along with simply making sure that I didn’t get bored over the summer. Three months is a long time to fill, and many of my friends end up getting bored, or worse, knitting obsessively. With the arrogance which seems fairly common among Cambridge people, I wasn’t expecting to really learn much here! In my mind, the part of the year where I am at Uni is the part where I learn things, whilst Red Gate would be an opportunity to apply what I’d learnt. Thankfully, the opposite is true: I’ve learnt a lot during my time here, and there has been a definite positive impact on the way I write code. The first thing I’ve really learnt is that test-driven development is, in general, a sensible way of working. Before coming, I didn’t really get it: how could you test something you hadn’t yet written? It didn’t make sense! My problem was seeing a test as having to test all the behaviour of a given function. Writing tests which test the bare minimum possible and building them up is a really good way of crystallising the direction the code needs to grow in, and ensures you never attempt to write too much code at time. One really good experience of this was early on in my internship when Mike and I were working on the query used to list active authors: I’d written something which I thought would do the trick, but by starting again using TDD we grew something which revealed that there were several subtle mistakes in the query I’d written. I’ve also been awakened to the value of pair programming. Whilst I could sort of see the point before coming, I also thought that it was impossible that two people would ever get more done at the same computer than if they were working separately. I still think that this is true for projects with pieces that developers can easily work on independently, and with developers who both know the codebase, but I’ve found that pair programming can be really good for learning a code base, and for building up small projects to the point where you can start working on separate components, as well as solving particularly difficult problems. Later on in my internship, for my down tools week project, I was working on adding Python support to Glimpse. Another intern and I we pair programmed the entire project, using ping pong pair programming as much as possible. One bonus that this brought which I wasn’t expecting was that I found myself less prone to distraction: with someone else peering over my shoulder, I didn’t have the ever-present temptation to open gmail, or facebook, or yammer, or twitter, or hacker news, or reddit, and so on, and so forth. I’m quite proud of this project: I think it’s some of the best code I’ve written. I’ve also been really won over to the value of descriptive variables names. In my pre-Red Gate life, as a lone-ranger style cowboy programmer, I’d developed a tendency towards laziness in variable names, sometimes abbreviating or, worse, using acronyms. I’ve swiftly realised that this is a bad idea when working with a team: saving a few key strokes is inevitably not worth it when it comes to reading code again in the future. Longer names also mean you can do away with a majority of comments. I appreciate that if you’ve come up with an O(n*log n) algorithm for something which seemed O(n^2), you probably want to explain how it works, but explaining what a variable name means is a big no no: it’s so very easy to change the behaviour of the code, whilst forgetting about the comments. Whilst at Red Gate, I took the opportunity to attend a code retreat, which really helped me to solidify all the things I’d learnt. To be completely free of any existing code base really lets you focus on best practises and think about how you write code. If you get a chance to go on a similar event, I’d highly recommend it! Cycling to Red Gate, I’ve also become much better at fitting inner tubes: if you’re struggling to get the tube out, or re-fit the tire, letting a bit of air out usually helps. I’ve also become quite a bit better at foosball and will miss having a foosball table! I’d like to finish off by saying thank you to everyone at Red Gate for having me. I’ve really enjoyed working with, and learning from, the team that brings you this web site. If you meet any of them, buy them a drink!

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  • The Joy Of Hex

    - by Jim Giercyk
    While working on a mainframe integration project, it occurred to me that some basic computer concepts are slipping into obscurity. For example, just about anyone can tell you that a 64-bit processor is faster than a 32-bit processer. A grade school child could tell you that a computer “speaks” in ‘1’s and ‘0’s. Some people can even tell you that there are 8 bits in a byte. However, I have found that even the most seasoned developers often can’t explain the theory behind those statements. That is not a knock on programmers; in the age of IntelliSense, what reason do we have to work with data at the bit level? Many computer theory classes treat bit-level programming as a thing of the past, no longer necessary now that storage space is plentiful. The trouble with that mindset is that the world is full of legacy systems that run programs written in the 1970’s.  Today our jobs require us to extract data from those systems, regardless of the format, and that often involves low-level programming. Because it seems knowledge of the low-level concepts is waning in recent times, I thought a review would be in order.       CHARACTER: See Spot Run HEX: 53 65 65 20 53 70 6F 74 20 52 75 6E DECIMAL: 83 101 101 32 83 112 111 116 32 82 117 110 BINARY: 01010011 01100101 01100101 00100000 01010011 01110000 01101111 01110100 00100000 01010010 01110101 01101110 In this example, I have broken down the words “See Spot Run” to a level computers can understand – machine language.     CHARACTER:  The character level is what is rendered by the computer.  A “Character Set” or “Code Page” contains 256 characters, both printable and unprintable.  Each character represents 1 BYTE of data.  For example, the character string “See Spot Run” is 12 Bytes long, exclusive of the quotation marks.  Remember, a SPACE is an unprintable character, but it still requires a byte.  In the example I have used the default Windows character set, ASCII, which you can see here:  http://www.asciitable.com/ HEX:  Hex is short for hexadecimal, or Base 16.  Humans are comfortable thinking in base ten, perhaps because they have 10 fingers and 10 toes; fingers and toes are called digits, so it’s not much of a stretch.  Computers think in Base 16, with numeric values ranging from zero to fifteen, or 0 – F.  Each decimal place has a possible 16 values as opposed to a possible 10 values in base 10.  Therefore, the number 10 in Hex is equal to the number 16 in Decimal.  DECIMAL:  The Decimal conversion is strictly for us humans to use for calculations and conversions.  It is much easier for us humans to calculate that [30 – 10 = 20] in decimal than it is for us to calculate [1E – A = 14] in Hex.  In the old days, an error in a program could be found by determining the displacement from the entry point of a module.  Since those values were dumped from the computers head, they were in hex. A programmer needed to convert them to decimal, do the equation and convert back to hex.  This gets into relative and absolute addressing, a topic for another day.  BINARY:  Binary, or machine code, is where any value can be expressed in 1s and 0s.  It is really Base 2, because each decimal place can have a possibility of only 2 characters, a 1 or a 0.  In Binary, the number 10 is equal to the number 2 in decimal. Why only 1s and 0s?  Very simply, computers are made up of lots and lots of transistors which at any given moment can be ON ( 1 ) or OFF ( 0 ).  Each transistor is a bit, and the order that the transistors fire (or not fire) is what distinguishes one value from  another in the computers head (or CPU).  Consider 32 bit vs 64 bit processing…..a 64 bit processor has the capability to read 64 transistors at a time.  A 32 bit processor can only read half as many at a time, so in theory the 64 bit processor should be much faster.  There are many more factors involved in CPU performance, but that is the fundamental difference.    DECIMAL HEX BINARY 0 0 0000 1 1 0001 2 2 0010 3 3 0011 4 4 0100 5 5 0101 6 6 0110 7 7 0111 8 8 1000 9 9 1001 10 A 1010 11 B 1011 12 C 1100 13 D 1101 14 E 1110 15 F 1111   Remember that each character is a BYTE, there are 2 HEX characters in a byte (called nibbles) and 8 BITS in a byte.  I hope you enjoyed reading about the theory of data processing.  This is just a high-level explanation, and there is much more to be learned.  It is safe to say that, no matter how advanced our programming languages and visual studios become, they are nothing more than a way to interpret bits and bytes.  There is nothing like the joy of hex to get the mind racing.

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  • Remote Desktop (Vino-Server) connects but display doesn't work?

    - by kmassada
    Ubuntu comes default with vino-server, I can remote into my machine, and connect to it, however, the display inside my remote client, is a mirror of my own desktop. I tried using one monitor, thinking that's what is the issue but still won't work. (vino-server:3608): EggSMClient-CRITICAL **: egg_sm_client_set_mode: assertion `global_client == NULL || global_client_mode == EGG_SM_CLIENT_MODE_DISABLED' failed 25/07/2012 12:23:58 PM Autoprobing TCP port in (all) network interface 25/07/2012 12:23:58 PM Listening IPv6://[::]:5900 25/07/2012 12:23:58 PM Listening IPv4://0.0.0.0:5900 25/07/2012 12:23:58 PM Autoprobing selected port 5900 25/07/2012 12:23:58 PM Advertising security type: 'TLS' (18) 25/07/2012 12:23:58 PM Re-binding socket to listen for VNC connections on TCP port 5900 in (all) interface 25/07/2012 12:23:58 PM Listening IPv6://[::]:5900 25/07/2012 12:23:58 PM Listening IPv4://0.0.0.0:5900 25/07/2012 12:23:58 PM Clearing securityTypes 25/07/2012 12:23:58 PM Advertising security type: 'TLS' (18) 25/07/2012 12:23:58 PM Clearing securityTypes 25/07/2012 12:23:58 PM Advertising security type: 'TLS' (18) 25/07/2012 12:23:58 PM Advertising authentication type: 'No Authentication' (1) 25/07/2012 12:23:58 PM Re-binding socket to listen for VNC connections on TCP port 5900 in (all) interface 25/07/2012 12:23:58 PM Listening IPv6://[::]:5900 25/07/2012 12:23:58 PM Listening IPv4://0.0.0.0:5900 25/07/2012 12:23:58 PM Clearing securityTypes 25/07/2012 12:23:58 PM Clearing authTypes 25/07/2012 12:23:58 PM Advertising security type: 'TLS' (18) 25/07/2012 12:23:58 PM Advertising authentication type: 'VNC Authentication' (2) 25/07/2012 12:23:58 PM Clearing securityTypes 25/07/2012 12:23:58 PM Clearing authTypes 25/07/2012 12:23:58 PM Advertising security type: 'TLS' (18) 25/07/2012 12:23:58 PM Advertising authentication type: 'VNC Authentication' (2) 25/07/2012 12:23:58 PM Advertising security type: 'VNC Authentication' (2) (vino-server:3608): LIBDBUSMENU-GLIB-WARNING **: Trying to remove a child that doesn't believe we're it's parent. (vino-server:3608): LIBDBUSMENU-GLIB-WARNING **: Trying to remove a child that doesn't believe we're it's parent. 25/07/2012 12:24:16 PM [IPv4] Got connection from client static-XXXX.bltmmd.fios.verizon.net 25/07/2012 12:24:16 PM other clients: 25/07/2012 12:24:29 PM Client Protocol Version 3.7 25/07/2012 12:24:29 PM Advertising security type 18 25/07/2012 12:24:29 PM Advertising security type 2 25/07/2012 12:24:30 PM Client returned security type 18 25/07/2012 12:24:30 PM Advertising authentication type 2 25/07/2012 12:24:30 PM Client returned authentication type 2 25/07/2012 12:24:37 PM rfbProcessClientNormalMessage: ignoring unknown encoding type -258 25/07/2012 12:24:37 PM Enabling NewFBSize protocol extension for client static-XXXX.bltmmd.fios.verizon.net 25/07/2012 12:24:37 PM rfbProcessClientNormalMessage: ignoring unknown encoding type 1464686185 25/07/2012 12:24:37 PM rfbProcessClientNormalMessage: ignoring unknown encoding type -259 25/07/2012 12:24:37 PM rfbProcessClientNormalMessage: ignoring unknown encoding type -257 (vino-server:3608): LIBDBUSMENU-GLIB-WARNING **: Trying to remove a child that doesn't believe we're it's parent. 25/07/2012 12:24:55 PM Client static-XXXX.bltmmd.fios.verizon.net gone 25/07/2012 12:24:55 PM Statistics: 25/07/2012 12:24:55 PM key events received 0, pointer events 80 25/07/2012 12:24:55 PM framebuffer updates 43, rectangles 152, bytes 292401 25/07/2012 12:24:55 PM tight rectangles 152, bytes 292401 25/07/2012 12:24:55 PM raw bytes equivalent 11621332, compression ratio 39.744502 25/07/2012 12:25:21 PM [IPv4] Got connection from client static-XXXX.bltmmd.fios.verizon.net 25/07/2012 12:25:21 PM other clients: 25/07/2012 12:25:28 PM Client Protocol Version 3.7 25/07/2012 12:25:28 PM Advertising security type 18 25/07/2012 12:25:28 PM Advertising security type 2 25/07/2012 12:25:28 PM Client returned security type 18 25/07/2012 12:25:29 PM Advertising authentication type 2 25/07/2012 12:25:29 PM Client returned authentication type 2 25/07/2012 12:25:37 PM rfbProcessClientNormalMessage: ignoring unknown encoding type -258 25/07/2012 12:25:37 PM Enabling NewFBSize protocol extension for client static-XXXX.bltmmd.fios.verizon.net 25/07/2012 12:25:37 PM rfbProcessClientNormalMessage: ignoring unknown encoding type 1464686185 25/07/2012 12:25:37 PM rfbProcessClientNormalMessage: ignoring unknown encoding type -259 25/07/2012 12:25:37 PM rfbProcessClientNormalMessage: ignoring unknown encoding type -257 (vino-server:3608): LIBDBUSMENU-GLIB-WARNING **: Trying to remove a child that doesn't believe we're it's parent. 25/07/2012 12:25:47 PM Client static-XXXX.bltmmd.fios.verizon.net gone 25/07/2012 12:25:47 PM Statistics: 25/07/2012 12:25:47 PM key events received 0, pointer events 7283 25/07/2012 12:25:47 PM framebuffer updates 27, rectangles 82, bytes 113354 25/07/2012 12:25:47 PM tight rectangles 82, bytes 113354 25/07/2012 12:25:47 PM raw bytes equivalent 5831432, compression ratio 51.444431 couple of things I notice, the following error occurs over and over again. the menu error seems to be caused by ubuntu, similar problems occur http://trac.wxwidgets.org/ticket/14292, (vino-server:3608): LIBDBUSMENU-GLIB-WARNING **: Trying to remove a child that doesn't believe we're it's parent. the second one also seem to be a display related issue, can't seem to figure out a solution. I really rather try to fix this issue than have to use the other vnc clients most suggest. (vino-server:3608): EggSMClient-CRITICAL **: egg_sm_client_set_mode: assertion `global_client == NULL || global_client_mode == EGG_SM_CLIENT_MODE_DISABLED' failed

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  • StreamInsight 2.1 Released

    - by Roman Schindlauer
    The wait is over—we are pleased to announce the release of StreamInsight 2.1. Since the release of version 1.2, we have heard your feedbacks and suggestions and based on that we have come up with a whole new set of features. Here are some of the highlights: A New Programming Model – A more clear and consistent object model, eliminating the need for complex input and output adapters (though they are still completely supported). This new model allows you to provision, name, and manage data sources and sinks in the StreamInsight server. Tight integration with Reactive Framework (Rx) – You can write reactive queries hosted inside StreamInsight as well as compose temporal queries on reactive objects. High Availability – Check-pointing over temporal streams and multiple processes with shared computation. Here is how simple coding can be with the 2.1 Programming Model: class Program {     static void Main(string[] args)     {         using (Server server = Server.Create("Default"))         {             // Create an app             Application app = server.CreateApplication("app");             // Define a simple observable which generates an integer every second             var source = app.DefineObservable(() =>                 Observable.Interval(TimeSpan.FromSeconds(1)));             // Define a sink.             var sink = app.DefineObserver(() =>                 Observer.Create<long>(x => Console.WriteLine(x)));             // Define a query to filter the events             var query = from e in source                         where e % 2 == 0                         select e;             // Bind the query to the sink and create a runnable process             using (IDisposable proc = query.Bind(sink).Run("MyProcess"))             {                 Console.WriteLine("Press a key to dispose the process...");                 Console.ReadKey();             }         }     } }   That’s how easily you can define a source, sink and compose a query and run it. Note that we did not replace the existing APIs, they co-exist with the new surface. Stay tuned, you will see a series of articles coming out over the next few weeks about the new features and how to use them. Come and grab it from our download center page and let us know what you think! You can find the updated MSDN documentation here, and we would appreciate if you could provide feedback to the docs as well—best via email to [email protected]. Moreover, we updated our samples to demonstrate the new programming surface. Regards, The StreamInsight Team

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  • StreamInsight 2.1 Released

    - by Roman Schindlauer
    The wait is over—we are pleased to announce the release of StreamInsight 2.1. Since the release of version 1.2, we have heard your feedbacks and suggestions and based on that we have come up with a whole new set of features. Here are some of the highlights: A New Programming Model – A more clear and consistent object model, eliminating the need for complex input and output adapters (though they are still completely supported). This new model allows you to provision, name, and manage data sources and sinks in the StreamInsight server. Tight integration with Reactive Framework (Rx) – You can write reactive queries hosted inside StreamInsight as well as compose temporal queries on reactive objects. High Availability – Check-pointing over temporal streams and multiple processes with shared computation. Here is how simple coding can be with the 2.1 Programming Model: class Program {     static void Main(string[] args)     {         using (Server server = Server.Create("Default"))         {             // Create an app             Application app = server.CreateApplication("app");             // Define a simple observable which generates an integer every second             var source = app.DefineObservable(() =>                 Observable.Interval(TimeSpan.FromSeconds(1)));             // Define a sink.             var sink = app.DefineObserver(() =>                 Observer.Create<long>(x => Console.WriteLine(x)));             // Define a query to filter the events             var query = from e in source                         where e % 2 == 0                         select e;             // Bind the query to the sink and create a runnable process             using (IDisposable proc = query.Bind(sink).Run("MyProcess"))             {                 Console.WriteLine("Press a key to dispose the process...");                 Console.ReadKey();             }         }     } }   That’s how easily you can define a source, sink and compose a query and run it. Note that we did not replace the existing APIs, they co-exist with the new surface. Stay tuned, you will see a series of articles coming out over the next few weeks about the new features and how to use them. Come and grab it from our download center page and let us know what you think! You can find the updated MSDN documentation here, and we would appreciate if you could provide feedback to the docs as well—best via email to [email protected]. Moreover, we updated our samples to demonstrate the new programming surface. Regards, The StreamInsight Team

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  • Silverlight WCF netTcpBinding problem

    - by JontyMC
    Trying to call a WCF with a netTcpBinding via Silverlight, I am getting the error: "TCP error code 10013: An attempt was made to access a socket in a way forbidden by its access permissions.. This could be due to attempting to access a service in a cross-domain way while the service is not configured for cross-domain access. You may need to contact the owner of the service to expose a sockets cross-domain policy over HTTP and host the service in the allowed sockets port range 4502-4534." My WCF service is hosted in IIS7, bound to: http://localhost.myserivce.com on port 80 and net.tcp on port 4502 I can see http://localhost.myserivce.com/myservice.svc if I browse to it (my hosts file is pointing this domain to localhost). I can also see http://localhost.myserivce.com/clientaccesspolicy.xml: <?xml version="1.0" encoding="utf-8"?> <access-policy> <cross-domain-access> <policy> <allow-from http-request-headers="*"> <domain uri="*" /> </allow-from> <grant-to> <socket-resource port="4502-4534" protocol="tcp" /> </grant-to> </policy> </cross-domain-access> </access-policy> What am I doing wrong?

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  • feedparser - various errors

    - by Eiriks
    I need feedparser (se http://www.feedparser.org) for a project, and want to keep third party modules in a separate folder. I did this by adding a folder to my python path, and putting relevant modules there, among them feedparser. This first attempt to import feedparser resulted in import feedparser Traceback (most recent call last): File "", line 1, in File "/home/users/me/modules/feedparser.py", line 1 ed socket timeout; added support for chardet library ^ SyntaxError: invalid syntax I found the text "socket timeout; added..." in the comments at the bottom of the file, removed these comments, and tried again: import feedparser Traceback (most recent call last): File "", line 1, in File "/home/users/me/modules/feedparser.py", line 1 = [(key, value) for key, value in attrs if key in self.acceptable_attributes] ^ IndentationError: unexpected indent Ok, so some indent error. I made sure the indent in the function in question where ok (moved some line breaks down to no-indent). And tried again: import feedparser Traceback (most recent call last): File "", line 1, in File "/home/users/me/modules/feedparser.py", line 1 , value) for key, value in attrs if key in self.acceptable_attributes] ^ SyntaxError: invalid syntax As much I google, I cannot find anything wrong with the syntax: def unknown_starttag(self, tag, attrs): if not tag in self.acceptable_elements: if tag in self.unacceptable_elements_with_end_tag: self.unacceptablestack += 1 return attrs = self.normalize_attrs(attrs) attrs = [(key, value) for key, value in attrs if key in self.acceptable_attributes] _BaseHTMLProcessor.unknown_starttag(self, tag, attrs) Now what? Is my approach all wrong? Why do I keep producing these errors in a module that seems so well tested and trusted?

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  • C# Sockets Buffer Overflow No Error

    - by Michael Covelli
    I have one thread that is receiving data over a socket like this: while (sock.Connected) { // Receive Data (Block if no data) recvn = sock.Receive(recvb, 0, rlen, SocketFlags.None, out serr); if (recvn <= 0 || sock == null || !sock.Connected) { OnError("Error In Receive, recvn <= 0 || sock == null || !sock.Connected"); return; } else if (serr != SocketError.Success) { OnError("Error In Receive, serr = " + serr); return; } // Copy Data Into Tokenizer tknz.Read(recvb, recvn); // Parse Data while (tknz.MoveToNext()) { try { ParseMessageAndRaiseEvents(tknz.Buffer(), tknz.Length); } catch (System.Exception ex) { string BadMessage = ByteArrayToStringClean(tknz.Buffer(), tknz.Length); string msg = string.Format("Exception in MDWrapper Parsing Message, Ex = {0}, Msg = {1}", ex.Message, BadMessage); OnError(msg); } } } And I kept seeing occasional errors in my parsing function indicating that the message wasn't valid. At first, I thought that my tokenizer class was broken. But after logging all the incoming bytes to the tokenizer, it turns out that the raw bytes in recvb weren't a valid message. I didn't think that corrupted data like this was possible with a tcp data stream. I figured it had to be some type of buffer overflow so I set sock.ReceiveBufferSize = 1024 * 1024 * 8; and the parsing error never, ever occurs in testing (it happens often enough to replicate if I don't change the ReceiveBufferSize). But my question is: why wasn't I seeing an exception or an error state or something if the socket's internal buffer was overflowing before I changed this buffer size?

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  • Suggestions for doing async I/O with Task Parallel Library

    - by anelson
    I have some high performance file transfer code which I wrote in C# using the Async Programming Model (APM) idiom (eg, BeginRead/EndRead). This code reads a file from a local disk and writes it to a socket. For best performance on modern hardware, it's important to keep more than one outstanding I/O operation in flight whenever possible. Thus, I post several BeginRead operations on the file, then when one completes, I call a BeginSend on the socket, and when that completes I do another BeginRead on the file. The details are a bit more complicated than that but at the high level that's the idea. I've got the APM-based code working, but it's very hard to follow and probably has subtle concurrency bugs. I'd love to use TPL for this instead. I figured Task.Factory.FromAsync would just about do it, but there's a catch. All of the I/O samples I've seen (most particularly the StreamExtensions class in the Parallel Extensions Extras) assume one read followed by one write. This won't perform the way I need. I can't use something simple like Parallel.ForEach or the Extras extension Task.Factory.Iterate because the async I/O tasks don't spend much time on a worker thread, so Parallel just starts up another task, resulting in potentially dozens or hundreds of pending I/O operations; way too much! You can work around that by Waiting on your tasks, but that causes creation of an event handle (a kernel object), and a blocking wait on a task wait handle, which ties up a worker thread. My APM-based implementation avoids both of those things. I've been playing around with different ways to keep multiple read/write operations in flight, and I've managed to do so using continuations that call a method that creates another task, but it feels awkward, and definitely doesn't feel like idiomatic TPL. Has anyone else grappled with an issue like this with the TPL? Any suggestions?

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  • easy_install ReviewBoard [Errno 104] Connection reset by peer

    - by blastthisinferno
    I have a Kubuntu 10.04 VM image and am trying to install ReviewBoard by following The Linux Installation Wiki. When I get to the step to easy_install ReviewBoard, I encounter a problem I cannot find a solution to. Below is the console output: sudo easy_install ReviewBoard Searching for ReviewBoard Best match: ReviewBoard 1.0.8 Processing ReviewBoard-1.0.8-py2.6.egg ReviewBoard 1.0.8 is already the active version in easy-install.pth Installing rb-site script to /usr/local/bin Using /usr/local/lib/python2.6/dist-packages/ReviewBoard-1.0.8-py2.6.egg Processing dependencies for ReviewBoard Searching for pytz Reading http://downloads.reviewboard.org/mirror/ Download error: [Errno 104] Connection reset by peer -- Some packages may not be found! Reading http://downloads.reviewboard.org/releases/ReviewBoard/1.0/ Download error: [Errno 104] Connection reset by peer -- Some packages may not be found! Reading http://pypi.python.org/simple/pytz/ Download error: [Errno 104] Connection reset by peer -- Some packages may not be found! Reading http://pypi.python.org/simple/pytz/ Download error: [Errno 104] Connection reset by peer -- Some packages may not be found! Couldn't find index page for 'pytz' (maybe misspelled?) Scanning index of all packages (this may take a while) Reading http://pypi.python.org/simple/ Download error: [Errno 104] Connection reset by peer -- Some packages may not be found! No local packages or download links found for pytz error: Could not find suitable distribution for Requirement.parse('pytz') I am new to python, but it seems like easy_install cannot decide on a version of pytz. I have read http://stackoverflow.com/questions/383738/104-connection-reset-by-peer-socket-error-or-when-does-closing-a-socket-resul http://homepage.mac.com/s_lott/iblog/architecture/C551260341/E20081031204203/index.html and it seems like the problem described in those articles has more to do with development than my problem, but I could be wrong. Has anyone encountered a problem like this? If there is any missing information that would help troubleshoot this, please let me know.

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  • pyscripter Rpyc error

    - by jf328
    pyscripter 2.5.3.0 x64, python 2.7.7 anaconda 2.0.1, windows 7 I was using pyscripter and EPD python happily in 32 bit, no problem. Just changed to 64 bit anaconda version and re-installed everything but now pyscripter cannot import rpyc -- it runs with internal engine (no anaconda), but no such error in pure python. Thanks very much! btw, there is a similar SO post few years ago, but the answer there does not work. *** Python 2.7.3 (default, Apr 10 2012, 23:24:47) [MSC v.1500 64 bit (AMD64)] on win32. *** Internal Python engine is active *** *** Internal Python engine is active *** >>> import rpyc Traceback (most recent call last): File "<interactive input>", line 1, in <module> File "C:\Anaconda\lib\site-packages\rpyc\__init__.py", line 44, in <module> from rpyc.core import (SocketStream, TunneledSocketStream, PipeStream, Channel, File "C:\Anaconda\lib\site-packages\rpyc\core\__init__.py", line 1, in <module> from rpyc.core.stream import SocketStream, TunneledSocketStream, PipeStream File "C:\Anaconda\lib\site-packages\rpyc\core\stream.py", line 7, in <module> import socket File "C:\Anaconda\Lib\socket.py", line 47, in <module> import _socket ImportError: DLL load failed: The specified procedure could not be found. >>> C:\research>python Python 2.7.7 |Anaconda 2.0.1 (64-bit)| (default, Jun 11 2014, 10:40:02) [MSC v.1500 64bit (AMD64)] on win32 Type "help", "copyright", "credits" or "license" for more information. Anaconda is brought to you by Continuum Analytics. Please check out: http://continuum.io/thanks and https://binstar.org >>> import rpyc >>>

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  • In Python epoll can I avoid the errno.EWOULDBLOCK, errno.EAGAIN ?

    - by davyzhang
    I wrote a epoll wrapper in python, It works fine but recently I found the performance is not not ideal for large package sending. I look down into the code and found there's actually a LOT of error Traceback (most recent call last): File "/Users/dawn/Documents/workspace/work/dev/server/sandbox/single_point/tcp_epoll.py", line 231, in send_now num_bytes = self.sock.send(self.response) error: [Errno 35] Resource temporarily unavailable and previously silent it as the document said, so my sending function was done this way: def send_now(self): '''send message at once''' st = time.time() times = 0 while self.response != '': try: num_bytes = self.sock.send(self.response) l.info('msg wrote %s %d : %r size %r',self.ip,self.port,self.response[:num_bytes],num_bytes) self.response = self.response[num_bytes:] except socket.error,e: if e[0] in (errno.EWOULDBLOCK,errno.EAGAIN): #here I printed it, but I silent it in normal days #print 'would block, again %r',tb.format_exc() break else: l.warning('%r %r socket error %r',self.ip,self.port,tb.format_exc()) #must break or cause dead loop break except: #other exceptions l.warning('%r %r msg write error %r',self.ip,self.port,tb.format_exc()) break times += 1 et = time.time() I googled it, and says it caused by temporarily network buffer run out So how can I manually and efficiently detect this error instead it goes to exception phase? Because it cause to much time to rasie/handle the exception.

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  • ASIHTTPRequest POST splits up header + data?

    - by chris.o.
    Hi, I am using ASIHTTPRequest to POST data to a remote server on iPhone 4.2.1. When I make the following post request to our server, I get a 400 response (I removed the IP address): NSString dataString = @"data1=00&data2=00&data3=00"; ASIHTTPRequest *request = [ASIHTTPRequest requestWithURL:[NSURL URLWithString:[NSString stringWithFormat:<ipremoved>]]]; [request appendPostData:[dataString dataUsingEncoding:NSUTF8StringEncoding]]; [request setRequestMethod:@"POST"]; [request addRequestHeader:@"User-Agent" value:@"iphone app"]; [request addRequestHeader:@"Content-Type" value:@"application/octet-stream"]; request.delegate = self; [request startAsynchronous]; When I send the same data using curl, I receive a 200 response: curl -H "User-Agent: iphone app" -H "Accept:" -H "Content-Type:application/octet-stream" --data-ascii "data1=00&data2=00&data3=00" --location <ipremoved> -v My colleague is stating that, in the failure case, the ASIHTTPRequest requires two socket reads: one for the header and one for the data. Apparently the server is not presently equipped to parse this correctly, so I am trying to work around it. If I setup a proxy between iPhone and my Mac and run Paros (to see packets), the problem goes away. Paros combine the header and data so that it is all acquired by the server in a single socket read. I've tried a few things suggested in other posts including disabling persistent connections, but I am not having any luck. I've also tried doing a ASIHTTPFormRequest, but the server does not like the generated data format. Any suggestions would be appreciated. Thanks.

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