complex networks - Page 254

Languages and VMs: Features that are hard to optimize and why

- by mrjoltcola

I'm doing a survey of features in preparation for a research project. Name a mainstream language or language feature that is hard to optimize, and why the feature is or isn't worth the price paid, or instead, just debunk my theories below with anecdotal evidence. Before anyone flags this as subjective, I am asking for specific examples of languages or features, and ideas for optimization of these features, or important features that I haven't considered. Also, any references to implementations that prove my theories right or wrong. Top on my list of hard to optimize features and my theories (some of my theories are untested and are based on thought experiments): 1) Runtime method overloading (aka multi-method dispatch or signature based dispatch). Is it hard to optimize when combined with features that allow runtime recompilation or method addition. Or is it just hard, anyway? Call site caching is a common optimization for many runtime systems, but multi-methods add additional complexity as well as making it less practical to inline methods. 2) Type morphing / variants (aka value based typing as opposed to variable based) Traditional optimizations simply cannot be applied when you don't know if the type of someting can change in a basic block. Combined with multi-methods, inlining must be done carefully if at all, and probably only for a given threshold of size of the callee. ie. it is easy to consider inlining simple property fetches (getters / setters) but inlining complex methods may result in code bloat. The other issue is I cannot just assign a variant to a register and JIT it to the native instructions because I have to carry around the type info, or every variable needs 2 registers instead of 1. On IA-32 this is inconvenient, even if improved with x64's extra registers. This is probably my favorite feature of dynamic languages, as it simplifies so many things from the programmer's perspective. 3) First class continuations - There are multiple ways to implement them, and I have done so in both of the most common approaches, one being stack copying and the other as implementing the runtime to use continuation passing style, cactus stacks, copy-on-write stack frames, and garbage collection. First class continuations have resource management issues, ie. we must save everything, in case the continuation is resumed, and I'm not aware if any languages support leaving a continuation with "intent" (ie. "I am not coming back here, so you may discard this copy of the world"). Having programmed in the threading model and the contination model, I know both can accomplish the same thing, but continuations' elegance imposes considerable complexity on the runtime and also may affect cache efficienty (locality of stack changes more with use of continuations and co-routines). The other issue is they just don't map to hardware. Optimizing continuations is optimizing for the less-common case, and as we know, the common case should be fast, and the less-common cases should be correct. 4) Pointer arithmetic and ability to mask pointers (storing in integers, etc.) Had to throw this in, but I could actually live without this quite easily. My feelings are that many of the high-level features, particularly in dynamic languages just don't map to hardware. Microprocessor implementations have billions of dollars of research behind the optimizations on the chip, yet the choice of language feature(s) may marginalize many of these features (features like caching, aliasing top of stack to register, instruction parallelism, return address buffers, loop buffers and branch prediction). Macro-applications of micro-features don't necessarily pan out like some developers like to think, and implementing many languages in a VM ends up mapping native ops into function calls (ie. the more dynamic a language is the more we must lookup/cache at runtime, nothing can be assumed, so our instruction mix is made up of a higher percentage of non-local branching than traditional, statically compiled code) and the only thing we can really JIT well is expression evaluation of non-dynamic types and operations on constant or immediate types. It is my gut feeling that bytecode virtual machines and JIT cores are perhaps not always justified for certain languages because of this. I welcome your answers.

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How to scale rotated objects properly in Actionscript 3?

- by Tom

This is unfortunately a quite complex issue to explain, so please don't get discouraged by the wall of text - it's there for a reason. ;) I'm working on a transformation manager for flash, written with Actionscript 3. Users can place objects on the screen, for example a rectangle. This rectangle can then be selected and transformed: move, scale or rotate. Because flash by default rotates around the top left point of the object, and I want it to rotate around the center, I created a wrapper setup for each display object (eg. a rectangle). This is how the wrappers are setup: //the position wrapper makes sure that we do get the top left position when we access x and y var positionWrapper:Sprite = new Sprite(); positionWrapper.x = renderObject.x; positionWrapper.y = renderObject.y; //set the render objects location to center at the rotation wrappers top left renderObject.x = 0 - renderObject.width / 2; renderObject.y = 0 - renderObject.height / 2; //now create a rotation wrapper, at the center of the display object var rotationWrapper:Sprite = new Sprite(); rotationWrapper.x = renderObject.width / 2; rotationWrapper.y = renderObject.height / 2; //put the rotation wrapper inside the position wrapper and the render object inside the rotation wrapper positionWrapper.addChild(rotationWrapper); rotationWrapper.addChild(renderObject); Now, the x and y of the object can be accessed and set directly: mainWrapper.x or mainWrapper.y. The rotation can be set and accessed from the child of this main wrapper: mainWrapper.getChildAt(0).rotation. Finally, the width and height of the display object can be retreived and set by getting the child of the rotation wrapper and accessing the display object directly. An example on how I access them: //get wrappers and render object var positionWrapper:Sprite = currentSelection["render"]; var rotationWrapper:Sprite = positionWrapper.getChildAt(0) as Sprite; var renderObject:DisplayObject = rotationWrapper.getChildAt(0); This works perfectly for all initial transformations: moving, scaling and rotating. However, the problem arises when you first rotate an object (eg. 45 degrees) and then scale it. The scaled object is getting out of shape and doesn't scale as it should. This for example happens when you scale to the left. Scaling left is basically adding n width to the object and then reduce the x coord of the position wrapper by n too: renderObject.width -= diffX; positionWrapper.x += diffX; This works when the object is not rotated. However, when it is, the position wrapper won't be rotated as it is a parent of the rotation wrapper. This will make the position wrapper move left horizontally while the width of the object is increased diagonally. I hope this makes any sense, if not, please tell me and I'll try to elaborate more. Now, to the question: should I use a different kind of setup, system or structure? Should I maybe use matrixes, if so, how would you keep a static width/height after rotation? Or how do I fix my current wrapper system for scaling after rotation? Any help is appreciated.

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When to draw/layout child controls in UserControl

- by Ted Elliott

I have a list-type UserControl (like a ListBox). The items inside the control are another complex UserControl containing a few other controls (ComboBox, TextBox, etc). I'm wondering what the preferred or best method would be to override to draw/layout the child controls. I basically want to trigger this method any time the list changes. I originally had a RedrawItems method that I just called whenever I needed to redraw which added or removed Controls from the Controls collection. But it was getting triggered too early in the lifecycle of the code from some of the designer code. Now I've switched to overriding OnLayout and doing my stuff there. I call PerformLayout when I want to trigger a redraw, such as when the DataSource property changes or when it fires a changed event. Is OnLayout the best place for this? Here is the code: [ComplexBindingProperties("DataSource")] public partial class CustomList : UserControl { private object _dataSource; private CustomListItem _newRow; public CustomList() { InitializeComponent(); } protected override void OnCreateControl() { base.OnCreateControl(); _newRow = new CustomListItem(); Controls.Add(_newRow); } public object DataSource { get { return _dataSource; } set { bool register = _dataSource != value; if (_dataSource != null && _dataSource != value) { UnregisterDataSource(_dataSource); } _dataSource = value; if (_dataSource != null) RegisterDataSource(_dataSource); PerformLayout(); } } public CustomListItem ItemTemplate { get { return _newRow; } } protected override void OnLayout(LayoutEventArgs e) { base.OnLayout(e); int ctrlCount = this.Controls.AsEnumerable().OfType<CustomListItem>().Count(); ctrlCount--; // subtract 1 for the add row var ds = this.DataSource as System.Collections.IList; int itemCount = ds == null? 0 : ds.Count; int maxCount = Math.Max(ctrlCount,itemCount); if (maxCount == 0) return; this.SuspendLayout(); // temporarily remove the template Controls.RemoveAt(Controls.Count-1); for (int i = 0; i < maxCount; i++) { CustomListItem item; if (i >= itemCount) { Controls.RemoveAt(i); } else { if (i >= ctrlCount) { item = ItemTemplate.Copy(); this.Controls.Add(item); item.Location = new Point(0, item.Height * i); item.TabIndex = i + 1; item.ViewMode = true; } else { item = (CustomListItem) Controls[i]; } item.Data = ds[i]; } } this.Controls.Add(ItemTemplate); ItemTemplate.Location = new Point(0, ItemTemplate.Height * maxCount); ItemTemplate.TabIndex = maxCount + 1; this.ResumeLayout(true); } private void RegisterDataSource(object dataSource) { IBindingList ds = dataSource as IBindingList; if (ds != null) { ds.ListChanged += new ListChangedEventHandler(DataSource_ListChanged); } } void DataSource_ListChanged(object sender, ListChangedEventArgs e) { switch (e.ListChangedType) { case ListChangedType.ItemAdded: PerformLayout(); break; case ListChangedType.ItemChanged: break; case ListChangedType.ItemDeleted: PerformLayout(); break; case ListChangedType.ItemMoved: PerformLayout(); break; case ListChangedType.Reset: PerformLayout(); break; default: break; } } private void UnregisterDataSource(object dataSource) { IBindingList ds = dataSource as IBindingList; if (ds != null) { ds.ListChanged -= new ListChangedEventHandler(DataSource_ListChanged); } } }

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Hover/Fadeto/Toggle Multiple Class Changing

- by Slick Willis

So my problem is rather simple and complex at the same time. I am trying to create links that fade in when you mouseover them and fade out when you mouseout of them. At the same time that you are going over them I would like a pic to slide from the left. This is the easy part, I have every thing working. The image fades and another image slides. I did this by using a hover, fadeto, and toggle("slide"). I would like to do this in a table format with multiple images being able to be scrolled over and sliding images out. The problem is that I am calling my sliding image to a class and when I hover over the letters both images slide out. Does anybody have a solution for this? I posted the code that I used below: <html> <head> <script type='text/javascript' src='http://accidentalwords.squarespace.com/storage/jquery/jquery-1.4.2.min.js'></script> <script type='text/javascript' src='http://accidentalwords.squarespace.com/storage/jquery/jquery-custom-181/jquery-ui-1.8.1.custom.min.js'></script> <style type="text/css"> .text-slide { display: none; margin: 0px; width: 167px; height: 50px; } </style> <script> $(document).ready(function(){ $(".letterbox-fade").fadeTo(1,0.25); $(".letterbox-fade").hover(function () { $(this).stop().fadeTo(250,1); $(".text-slide").toggle("slide", {}, 1000); }, function() { $(this).stop().fadeTo(250,0.25); $(".text-slide").toggle("slide", {}, 1000); }); }); </script> </head> <body style="background-color: #181818"> <table> <tr> <td><div class="letterbox-fade"><img src="http://accidentalwords.squarespace.com/storage/sidebar/icons/A-Letterbox-Selected.png" /></div></td> <td><div class="text-slide"><img src="http://accidentalwords.squarespace.com/storage/sidebar/icons/TEST.png" /></div></td> </tr> <tr> <td><div class="letterbox-fade"><img src="http://accidentalwords.squarespace.com/storage/sidebar/icons/B-Letterbox-Selected.png" /></div></td> <td><div class="text-slide"><img src="http://accidentalwords.squarespace.com/storage/sidebar/icons/TEST.png" /></div></td> </tr> </table> </body> </html>

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Read files from directory to create a ZIP hadoop

- by Félix

I'm looking for hadoop examples, something more complex than the wordcount example. What I want to do It's read the files in a directory in hadoop and get a zip, so I have thought to collect al the files in the map class and create the zip file in the reduce class. Can anyone give me a link to a tutorial or example than can help me to built it? I don't want anyone to do this for me, i'm asking for a link with better examples than the wordaccount. This is what I have, maybe it's useful for someone public class Testing { private static class MapClass extends MapReduceBase implements Mapper<LongWritable, Text, Text, BytesWritable> { // reuse objects to save overhead of object creation Logger log = Logger.getLogger("log_file"); public void map(LongWritable key, Text value, OutputCollector<Text, BytesWritable> output, Reporter reporter) throws IOException { String line = ((Text) value).toString(); log.info("Doing something ... " + line); BytesWritable b = new BytesWritable(); b.set(value.toString().getBytes() , 0, value.toString().getBytes() .length); output.collect(value, b); } } private static class ReduceClass extends MapReduceBase implements Reducer<Text, BytesWritable, Text, BytesWritable> { Logger log = Logger.getLogger("log_file"); ByteArrayOutputStream bout; ZipOutputStream out; @Override public void configure(JobConf job) { super.configure(job); log.setLevel(Level.INFO); bout = new ByteArrayOutputStream(); out = new ZipOutputStream(bout); } public void reduce(Text key, Iterator<BytesWritable> values, OutputCollector<Text, BytesWritable> output, Reporter reporter) throws IOException { while (values.hasNext()) { byte[] data = values.next().getBytes(); ZipEntry entry = new ZipEntry("entry"); out.putNextEntry(entry); out.write(data); out.closeEntry(); } BytesWritable b = new BytesWritable(); b.set(bout.toByteArray(), 0, bout.size()); output.collect(key, b); } @Override public void close() throws IOException { // TODO Auto-generated method stub super.close(); out.close(); } } /** * Runs the demo. */ public static void main(String[] args) throws IOException { int mapTasks = 20; int reduceTasks = 1; JobConf conf = new JobConf(Prue.class); conf.setJobName("testing"); conf.setNumMapTasks(mapTasks); conf.setNumReduceTasks(reduceTasks); MultipleInputs.addInputPath(conf, new Path("/messages"), TextInputFormat.class, MapClass.class); conf.setOutputKeyClass(Text.class); conf.setOutputValueClass(BytesWritable.class); FileOutputFormat.setOutputPath(conf, new Path("/czip")); conf.setMapperClass(MapClass.class); conf.setCombinerClass(ReduceClass.class); conf.setReducerClass(ReduceClass.class); // Delete the output directory if it exists already JobClient.runJob(conf); } }

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How to design a data model that deals with (real) contracts?

- by Geoffrey

I was looking for some advice on designing a data model for contract administration. The general life cycle of a contract is thus: Contract is created and in a "draft" state. It is viewable internally and changes may be made. Contract goes out to vendor, status is set to "pending" Contract is rejected by vendor. At this state, nothing can be done to the contract. No statuses may be added to the collection. Contract is accepted by vendor. At this state, nothing can be done to the contract. No statuses may be added to the collection. I obviously want to avoid a situation where the contract is accepted and, say, the amount is changed. Here are my classes: [EnforceNoChangesAfterDraftState] public class VendorContract { public virtual Vendor Vendor { get; set; } public virtual decimal Amount { get; set; } public virtual VendorContact VendorContact { get; set; } public virtual string CreatedBy { get; set; } public virtual DateTime CreatedOn { get; set; } public virtual FileStore Contract { get; set; } public virtual IList<VendorContractStatus> ContractStatus { get; set; } } [EnforceCorrectWorkflow] public class VendorContractStatus { public virtual VendorContract VendorContract { get; set; } public virtual FileStore ExecutedDocument { get; set; } public virtual string Status { get; set; } public virtual string Reason { get; set; } public virtual string CreatedBy { get; set; } public virtual DateTime CreatedOn { get; set; } } I've omitted the filestore class, which is basically a key/value lookup to find the document based on its guid. The VendorContractStatus is mapped as a many-to-one in Nhibernate. I then use a custom validator as described here. If anything but draft is returned in the VendorContractStatus collection, no changes are allowed. Furthermore the VendorContractStatus must follow the correct workflow (you can add a rejected after a pending, but you can't add anything else to the collection if a reject or accepted exists, etc.). All sounds alright? Well a colleague has argued that we should simply add an "IsDraft" bool property to VendorContract and not accept updates if IsDraft is false. Then we should setup a method inside of VendorContractStatus for updating the status, if something gets added after a draft, it sets the IsDraft property of VendorContract to false. I do not like this as it feels like I'm dirtying up the POCOs and adding logic that should persist in the validation area, that no rules should really exist in these classes and they shouldn't be aware of their states. Any thoughts on this and what is the better practice from a DDD perspective? From my view, if in the future we want more complex rules, my way will be more maintainable over the long run. Say we have contracts over a certain amount to be approved by a manager. I would think it would be better to have a one-to-one mapping with a VendorContractApproval class, rather than adding IsApproved properties, but that's just speculation. This might be splitting hairs, but this is the first real gritty enterprise software project we've done. Any advice would be appreciated!

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JavaScript snippet that populates the table

- by kayn

I would like to write a JavaScript snippet that populates the table based on the selection, and not create several details panes and toggle their visibility. I tried implement this using the following code but its not working as desired,firstly,it only works with internet explorer under certain conditions and it just toggles visibility of detail panes;Below is my code; <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd"> <HTML> <HEAD> </HEAD> <BODY onLoad="tblTB_0.style.display='';tblTB_1.style.display='none'; tblTB_2.style.display='none'; tblTB_3.style.display='none'"> <center> <table> <tr> <td> <H1> <align="left"> Candi Colledge of Computing <br/>Course Page </H1> </td> </tr> </table> </center> <hr> </br> <H2><P STYLE="color: blue">Honours Courses.</H2> <left> <p><a href="" onclick="tblTB_1.style.display=''; tblTB_2.style.display='none'; tblTB_3.style.display='none'"> Concurrent Programming</a> <br/> <a href="" onclick="tblTB_1.style.display='none';tblTB_2.style.display=''; tblTB_3.style.display='none'">Simulation of Networks</a><br/> <a href="" onclick="tblTB_1.style.display='none';tblTB_2.style.display='none'; tblTB_3.style.display=''">Advanced Computer Science Topics</a></p> <br> <table style="table-layout: fixed"; border=1> <colgroup> <col width="100px"><col width="150px"><col width="150px"> </colgroup> <tbody id="tblTB_0"> <tr> <td>Course Code</td> <td>Lecturer</td> <td>Hours/Week</td> <td>Credits</td> </tr> </tbody> <tbody id="tblTB_1"> <tr> <td>RW 714</td> <td>Dr. kate</td> <td>2 hrs</td> <td>15</td </tr> </tbody> <tbody id="tblTB_2"> <tr> <td>RW 742</td> <td>Prof. Broz</td> <td>4 hrs</td> <td>10</td> </tr> </tbody> <tbody id="tblTB_3"> <tr> <td>RW 716</td> <td>Consultant</td> <td>3 hrs</td> <td>12</td> </tr> </tbody> </table> </left> <br> </BODY> </HTML>

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Winforms controls and "generic" events handlers. How can I do this?

- by Yanko Hernández Alvarez

In the demo of the ObjectListView control there is this code (in the "Complex Example" tab page) to allow for a custom editor (a ComboBox) (Adapted to my case and edited for clarity): EventHandler CurrentEH; private void ObjectListView_CellEditStarting(object sender, CellEditEventArgs e) { if (e.Column == SomeCol) { ISomeInterface M = (e.RowObject as ObjectListView1Row).SomeObject; //(1) ComboBox cb = new ComboBox(); cb.Bounds = e.CellBounds; cb.DropDownStyle = ComboBoxStyle.DropDownList; cb.DataSource = ISomeOtherObjectCollection; cb.DisplayMember = "propertyName"; cb.DataBindings.Add("SelectedItem", M, "ISomeOtherObject", false, DataSourceUpdateMode.Never); e.Control = cb; cb.SelectedIndexChanged += CurrentEH = (object sender2, EventArgs e2) => M.ISomeOtherObject = (ISomeOtherObject)((ComboBox)sender2).SelectedValue; //(2) } } private void ObjectListView_CellEditFinishing(object sender, CellEditEventArgs e) { if (e.Column == SomeCol) { // Stop listening for change events ((ComboBox)e.Control).SelectedIndexChanged -= CurrentEH; // Any updating will have been down in the SelectedIndexChanged // event handler. // Here we simply make the list redraw the involved ListViewItem ((ObjectListView)sender).RefreshItem(e.ListViewItem); // We have updated the model object, so we cancel the auto update e.Cancel = true; } } I have too many other columns with combo editors inside objectlistviews to use a copy& paste strategy (besides, copy&paste is a serious source of bugs), so I tried to parameterize the code to keep the code duplication to a minimum. ObjectListView_CellEditFinishing is a piece of cake: HashSet<OLVColumn> cbColumns = new HashSet<OLVColumn> (new OLVColumn[] { SomeCol, SomeCol2, ...}; private void ObjectListView_CellEditFinishing(object sender, CellEditEventArgs e) { if (cbColumns.Contains(e.Column)) ... but ObjectListView_CellEditStarting is the problematic. I guess in CellEditStarting I will have to discriminate each case separately: private void ObjectListView_CellEditStarting(object sender, CellEditEventArgs e) { if (e.Column == SomeCol) // code to create the combo, put the correct list as the datasource, etc. else if (e.Column == SomeOtherCol) // code to create the combo, put the correct list as the datasource, etc. And so on. But how can I parameterize the "code to create the combo, put the correct list as the datasource, etc."? Problem lines are (1) Get SomeObject. the property NAME varies. (2) Set ISomeOtherObject, the property name varies too. The types vary too, but I can cover those cases with a generic method combined with a not so "typesafe" API (for instance, the cb.DataBindings.Add and cb.DataSource both use an object) Reflection? more lambdas? Any ideas? Any other way to do the same? PS: I want to be able to do something like this: private void ObjectListView_CellEditStarting(object sender, CellEditEventArgs e) { if (e.Column == SomeCol) SetUpCombo<ISomeInterface>(ISomeOtherObjectCollection, "propertyName", SomeObject, ISomeOtherObject); else if (e.Column == SomeOtherCol) SetUpCombo<ISomeInterface2>(ISomeOtherObject2Collection, "propertyName2", SomeObject2 ISomeOtherObject2); and so on. Or something like that. I know, parameters SomeObject and ISomeOtherObject are not real parameters per see, but you get the idea of what I want. I want not to repeat the same code skeleton again and again and again. One solution would be "preprocessor generics" like C's DEFINE, but I don't thing c# has something like that. So, does anyone have some alternate ideas to solve this?

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Web service client receiving generic FaultException rather than FaultException<T>

- by Junto

I am connecting to a Java Axis2 web service using a .NET web service client. The client itself targets the .NET 3.5 framework. The application that wraps the client DLL is 2.0. I'm not sure if that has any bearing. I have been given the WSDL and XSDs by email. From those I have built my proxy class using svcutil. Although I am able to successfully send messages, I am unable to pick up the correct faults when something goes wrong. In the example below, errors are always being picked up by the generic FaultException. catch (FaultException<InvoiceErrorType> fex) { OnLog(enLogLevel.ERROR, fex.Detail.ErrorDescription); } catch (FaultException gfex) { OnLog(enLogLevel.ERROR, gfex.Message); } The proxy client appears to have the appropriate attributes for the FaultContract: // CODEGEN: Generating message contract since the operation SendInvoiceProvider_Prod is neither RPC nor document wrapped. [OperationContractAttribute(Action = "https://private/SendInvoiceProvider", ReplyAction = "*")] [FaultContractAttribute(typeof(InvoiceErrorType), Action = "https://private/SendInvoiceProvider", Name = "InvoiceError", Namespace = "urn:company:schema:entities:base")] [XmlSerializerFormatAttribute(SupportFaults = true)] [ServiceKnownTypeAttribute(typeof(ItemDetail))] [ServiceKnownTypeAttribute(typeof(Supplier))] OutboundComponent.SendInvoiceProviderResponse SendInvoiceProvider_Prod(OutboundComponent.SendInvoiceProvider_Request request); I have enabled tracing and I can see the content of the fault coming back, but .NET is not recognizing it as an InvoiceError. The SOAP fault in full is: <soapenv:Fault> <faultcode xmlns="">soapenv:Client</faultcode> <faultstring xmlns="">Message found to be invalid</faultstring> <faultactor xmlns="">urn:SendInvoiceProvider</faultactor> <detail xmlns=""> <InvoiceError xmlns="urn:company:schema:entities:common:invoiceerror:v01"> <ErrorID>100040</ErrorID> <ErrorType>UNEXPECTED</ErrorType> <ErrorDescription><![CDATA[<error xmlns="urn:company:schema:errordetail:v01"><errorCode>1000</errorCode><highestSeverity>8</highestSeverity><errorDetails count="1"><errorDetail><errorType>1</errorType><errorSeverity>8</errorSeverity><errorDescription>cvc-complex-type.2.4.a: Invalid content was found starting with element 'CompanyName'. One of '{"urn:company:schema:sendinvoice:rq:v01":RoleType}' is expected.</errorDescription><errorNamespace>urn:company:schema:sendinvoice:rq:v01</errorNamespace><errorNode>CompanyName</errorNode><errorLine>1</errorLine><errorColumn>2556</errorColumn><errorXPath/><errorSource/></errorDetail></errorDetails></error>]]></ErrorDescription> <TimeStamp>2010-05-04T21:12:10Z</TimeStamp> </InvoiceError> </detail> </soapenv:Fault> I have noticed the namespace defined on the error: <InvoiceError xmlns="urn:company:schema:entities:common:invoiceerror:v01"> This is nowhere to be seen in the generated proxy class, nor in the WSDLs. The interface WSDL defines the error schema namespace as such: <xs:import namespace="urn:company:schema:entities:base" schemaLocation="InvoiceError.xsd"/> Could this be the reason why the .NET client is not able to parse the typed Fault Exception correctly? I have no control over the web service itself. I see no reason why .NET can't talk to a Java Axis2 web service. This user had a similar issue, but the reason for his problem cannot be the same as mine, since I can see the fault detail in the trace: http://stackoverflow.com/questions/864800/does-wcf-faultexceptiont-support-interop-with-a-java-web-service-fault Any help would be gratefully received.

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XML and XSD - use element name as replacement of xsi:type for polymorphism

- by disown

Taking the W3C vehicle XSD as an example: <schema xmlns="http://www.w3.org/2001/XMLSchema" targetNamespace="http://cars.example.com/schema" xmlns:target="http://cars.example.com/schema"> <complexType name="Vehicle" abstract="true"/> <complexType name="Car"> <complexContent> <extension base="target:Vehicle"/> ... </complexContent> </complexType> <complexType name="Plane"> <complexContent> <extension base="target:Vehicle"/> <sequence> <element name="wingspan" type="integer"/> </sequence> </complexContent> </complexType> </schema> , and the following definition of 'meansOfTravel': <complexType name="MeansOfTravel"> <complexContent> <sequence> <element name="transport" type="target:Vehicle"/> </sequence> </complexContent> </complexType> <element name="meansOfTravel" type="target:MeansOfTravel"/> With this definition you need to specify the type of your instance using xsi:type, like this: <meansOfTravel> <transport xsi:type="Plane"> <wingspan>3</wingspan> </transport> </meansOfTravel> I would just like to acheive a 'name of type' - 'name of element' mapping so that this could be replaced with just <meansOfTravel> <plane> <wingspan>3</wingspan> </plane> </meansOfTravel> The only way I could do this until now is by making it explicit: <complexType name="MeansOfTravel"> <sequence> <choice> <element name="plane" type="target:Plane"/> <element name="car" type="target:Car"/> </choice> </sequence> </complexType> <element name="meansOfTravel" type="target:MeansOfTravel"/> But this means that I have to list all possible sub-types in the 'MeansOfTravel' complex type. Is there no way of making the XML parser assume that you mean a 'Plane' if you call the element 'plane'? Or do I have to make the choice explicit? I would just like to keep my design DRY - if you have any other suggestions (like groups or so) - i would love to hear them.

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Defend PHP; convince me it isn't horrible

- by Jason L

I made a tongue-in-cheek comment in another question thread calling PHP a terrible language and it got down-voted like crazy. Apparently there are lots of people here who love PHP. So I'm genuinely curious. What am I missing? What makes PHP a good language? Here are my reasons for disliking it: PHP has inconsistent naming of built-in and library functions. Predictable naming patterns are important in any design. PHP has inconsistent parameter ordering of built-in functions, eg array_map vs. array_filter which is annoying in the simple cases and raises all sorts of unexpected behaviour or worse. The PHP developers constantly deprecate built-in functions and lower-level functionality. A good example is when they deprecated pass-by-reference for functions. This created a nightmare for anyone doing, say, function callbacks. A lack of consideration in redesign. The above deprecation eliminated the ability to, in many cases, provide default keyword values for functions. They fixed this in PHP 5, but they deprecated the pass-by-reference in PHP 4! Poor execution of name spaces (formerly no name spaces at all). Now that name spaces exist, what do we use as the dereference character? Backslash! The character used universally for escaping, even in PHP! Overly-broad implicit type conversion leads to bugs. I have no problem with implicit conversions of, say, float to integer or back again. But PHP (last I checked) will happily attempt to magically convert an array to an integer. Poor recursion performance. Recursion is a fundamentally important tool for writing in any language; it can make complex algorithms far simpler. Poor support is inexcusable. Functions are case insensitive. I have no idea what they were thinking on this one. A programming language is a way to specify behavior to both a computer and a reader of the code without ambiguity. Case insensitivity introduces much ambiguity. PHP encourages (practically requires) a coupling of processing with presentation. Yes, you can write PHP that doesn't do so, but it's actually easier to write code in the incorrect (from a sound design perspective) manner. PHP performance is abysmal without caching. Does anyone sell a commercial caching product for PHP? Oh, look, the designers of PHP do. Worst of all, PHP convinces people that designing web applications is easy. And it does indeed make much of the effort involved much easier. But the fact is, designing a web application that is both secure and efficient is a very difficult task. By convincing so many to take up programming, PHP has taught an entire subgroup of programmers bad habits and bad design. It's given them access to capabilities that they lack the understanding to use safely. This has led to PHP's reputation as being insecure. (However, I will readily admit that PHP is no more or less secure than any other web programming language.) What is it that I'm missing about PHP? I'm seeing an organically-grown, poorly-managed mess of a language that's spawning poor programmers. So convince me otherwise!

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reorder XML elements or set an explicit template with XSLT

- by Sash

I tried the solution in my previous question (flattening XML to load via SSIS package), however this isn't working. I now know what I need to do, however I need some guidance on how to do it. So say I have the following XML structure: <person id="1"> <name>John</name> <surname>Smith</surname> <age>25</age> <comment> <comment_id>1</comment_id> <comment_text>Hello</comment_text> </comment> <comment> <comment_id>2</comment_id> <comment_text>Hello again!</comment_text> </comment> <somethingelse> <id>1</id> </somethingelse> <comment> <comment_id>3</comment_id> <comment_text>Third Item</comment_text> </comment> </person> <person id="2"> <name>John</name> <surname>Smith</surname> <age>25</age> <somethingelse> <id>1</id> </somethingelse> </person> ... ... If I am to load this into a SSIS package, as an XML source, what I will essentially get is a table created for each element, as opposed to get a structured table output such as person table (name, surname, age) somethingelse table (id) comment table (comment_id, comment_text) What I end up getting is: person table (person_Id <-- internal SSIS id) name table surname table age table person_name table person_surname table person_comment_comment_id table etc... What I found was that if each element and all inner elements are not in the same format and consistency, i will get the above anomaly which makes it rather complex especially if I am dealing with 80 - 100+ columns. Unfortunately I have no way of modifying the system (Lotus Notes) that produces these reports, so I was wondering whether I may be able to explicitly have an XSLT template that will be able to align each person sub elements (and the sub collection elements such as comments ? Unless there is a quicker way to realign all inner elements. Seems that SSIS XML source requires a very consistent XML file in the sense of: if the name element is in position 1, then all subsequent name elements within person parent have to be in position 1. SSIS seems to pickup the inconsistencies if there are certain elements missing from one parent to another, however, if their ordering is not right (A, B, C)(A, B, C)(A,C,B), it will chuck a massive fuss! All help is appreciated! Thank you in advance.

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How do I prevent TCP connection freezes over an OpenVPN network?

- by Jason R

New details added at the end of this question; it's possible that I'm zeroing in on the cause. I have a UDP OpenVPN-based VPN set up in tap mode (I need tap because I need the VPN to pass multicast packets, which doesn't seem to be possible with tun networks) with a handful of clients across the Internet. I've been experiencing frequent TCP connection freezes over the VPN. That is, I will establish a TCP connection (e.g. an SSH connection, but other protocols have similar issues), and at some point during the session, it seems that traffic will cease being transmitted over that TCP session. This seems to be related to points at which large data transfers occur, such as if I execute an ls command in an SSH session, or if I cat a long log file. Some Google searches turn up a number of answers like this previous one on Server Fault, indicating that the likely culprit is an MTU issue: that during periods of high traffic, the VPN is trying to send packets that get dropped somewhere in the pipes between the VPN endpoints. The above-linked answer suggests using the following OpenVPN configuration settings to mitigate the problem: fragment 1400 mssfix This should limit the MTU used on the VPN to 1400 bytes and fix the TCP maximum segment size to prevent the generation of any packets larger than that. This seems to mitigate the problem a bit, but I still frequently see the freezes. I've tried a number of sizes as arguments to the fragment directive: 1200, 1000, 576, all with similar results. I can't think of any strange network topology between the two ends that could trigger such a problem: the VPN server is running on a pfSense machine connected directly to the Internet, and my client is also connected directly to the Internet at another location. One other strange piece of the puzzle: if I run the tracepath utility, then that seems to band-aid the problem. A sample run looks like: [~]$ tracepath -n 192.168.100.91 1: 192.168.100.90 0.039ms pmtu 1500 1: 192.168.100.91 40.823ms reached 1: 192.168.100.91 19.846ms reached Resume: pmtu 1500 hops 1 back 64 The above run is between two clients on the VPN: I initiated the trace from 192.168.100.90 to the destination of 192.168.100.91. Both clients were configured with fragment 1200; mssfix; in an attempt to limit the MTU used on the link. The above results would seem to suggest that tracepath was able to detect a path MTU of 1500 bytes between the two clients. I would assume that it would be somewhat smaller due to the fragmentation settings specified in the OpenVPN configuration. I found that result somewhat strange. Even stranger, however: if I have a TCP connection in the stalled state (e.g. an SSH session with a directory listing that froze in the middle), then executing the tracepath command shown above causes the connection to start up again! I can't figure out any reasonable explanation for why this would be the case, but I feel like this might be pointing toward a solution to ultimately eradicate the problem. Does anyone have any recommendations for other things to try? Edit: I've come back and looked at this a bit further, and have found only more confounding information: I set the OpenVPN connection to fragment at 1400 bytes, as shown above. Then, I connected to the VPN from across the Internet and used Wireshark to look at the UDP packets that were sent to the VPN server while the stall occurred. None were greater than the specified 1400 byte count, so the fragmentation seems to be functioning properly. To verify that even a 1400-byte MTU would be sufficient, I pinged the VPN server using the following (Linux) command: ping <host> -s 1450 -M do This (I believe) sends a 1450-byte packet with fragmentation disabled (I at least verified that it didn't work if I set it to an obviously-too-large value like 1600 bytes). These seem to work just fine; I get replies back from the host with no issue. So, maybe this isn't an MTU issue at all. I'm just confused as to what else it might be! Edit 2: The rabbit hole just keeps getting deeper: I've now isolated the problem a bit more. It seems to be related to the exact OS that the VPN client uses. I have successfully duplicated the problem on at least three Ubuntu machines (versions 12.04 through 13.04). I can reliably duplicate an SSH connection freeze within a minute or so by just cat-ing a large log file. However, if I do the same test using a CentOS 6 machine as a client, then I don't see the problem! I've tested using the exact same OpenVPN client version as I was using on the Ubuntu machines. I can cat log files for hours without seeing the connection freeze. This seems to provide some insight as to the ultimate cause, but I'm just not sure what that insight is. I have examined the traffic over the VPN using Wireshark. I'm not a TCP expert, so I'm not sure what to make of the gory details, but the gist is that at some point, a UDP packet gets dropped due to the limited bandwidth of the Internet link, causing TCP retransmissions inside the VPN tunnel. On the CentOS client, these retransmissions occur properly and things move on happily. At some point with the Ubuntu clients, though, the remote end starts retransmitting the same TCP segment over and over (with the transmit delay increasing between each retransmission). The client sends what looks like a valid TCP ACK to each retransmission, but the remote end still continues to transmit the same TCP segment periodically. This extends ad infinitum and the connection stalls. My question here would be: Does anyone have any recommendations for how to troubleshoot and/or determine the root cause of the TCP issue? It's as if the remote end isn't accepting the ACK messages sent by the VPN client. One common difference between the CentOS node and the various Ubuntu releases is that Ubuntu has a much more recent Linux kernel version (from 3.2 in Ubuntu 12.04 to 3.8 in 13.04). A pointer to some new kernel bug maybe? I'm assuming that if that were so, then I wouldn't be the only one experiencing the problem; I don't think this seems like a particularly exotic setup.

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How can I keep my MVC Views, models, and model binders as clean as possible?

- by MBonig

I'm rather new to MVC and as I'm getting into the whole framework more and more I'm finding the modelbinders are becoming tough to maintain. Let me explain... I am writing a basic CRUD-over-database app. My domain models are going to be very rich. In an attempt to keep my controllers as thin as possible I've set it up so that on Create/Edit commands the parameter for the action is a richly populated instance of my domain model. To do this I've implemented a custom model binder. As a result, though, this custom model binder is very specific to the view and the model. I've decided to just override the DefaultModelBinder that ships with MVC 2. In the case where the field being bound to my model is just a textbox (or something as simple), I just delegate to the base method. However, when I'm working with a dropdown or something more complex (the UI dictates that date and time are separate data entry fields but for the model it is one Property), I have to perform some checks and some manual data munging. The end result of this is that I have some pretty tight ties between the View and Binder. I'm architecturally fine with this but from a code maintenance standpoint, it's a nightmare. For example, my model I'm binding here is of type Log (this is the object I will get as a parameter on my Action). The "ServiceStateTime" is a property on Log. The form values of "log.ServiceStartDate" and "log.ServiceStartTime" are totally arbitrary and come from two textboxes on the form (Html.TextBox("log.ServiceStartTime",...)) protected override object GetPropertyValue(ControllerContext controllerContext, ModelBindingContext bindingContext, PropertyDescriptor propertyDescriptor, IModelBinder propertyBinder) { if (propertyDescriptor.Name == "ServiceStartTime") { string date = bindingContext.ValueProvider.GetValue("log.ServiceStartDate").ConvertTo(typeof (string)) as string; string time = bindingContext.ValueProvider.GetValue("log.ServiceStartTime").ConvertTo(typeof (string)) as string; DateTime dateTime = DateTime.Parse(date + " " + time); return dateTime; } if (propertyDescriptor.Name == "ServiceEndTime") { string date = bindingContext.ValueProvider.GetValue("log.ServiceEndDate").ConvertTo(typeof(string)) as string; string time = bindingContext.ValueProvider.GetValue("log.ServiceEndTime").ConvertTo(typeof(string)) as string; DateTime dateTime = DateTime.Parse(date + " " + time); return dateTime; } The Log.ServiceEndTime is a similar field. This doesn't feel very DRY to me. First, if I refactor the ServiceStartTime or ServiceEndTime into different field names, the text strings may get missed (although my refactoring tool of choice, R#, is pretty good at this sort of thing, it wouldn't cause a build-time failure and would only get caught by manual testing). Second, if I decided to arbitrarily change the descriptors "log.ServiceStartDate" and "log.ServiceStartTime", I would run into the same problem. To me, runtime silent errors are the worst kind of error out there. So, I see a couple of options to help here and would love to get some input from people who have come across some of these issues: Refactor any text strings in common between the view and model binders out into const strings attached to the ViewModel object I pass from controller to the aspx/ascx view. This pollutes the ViewModel object, though. Provide unit tests around all of the interactions. I'm a big proponent of unit tests and haven't started fleshing this option out but I've got a gut feeling that it won't save me from foot-shootings. If it matters, the Log and other entities in the system are persisted to the database using Fluent NHibernate. I really want to keep my controllers as thin as possible. So, any suggestions here are greatly welcomed! Thanks

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window.open() in an iPad on load of a frame does not work

- by user278859

I am trying to modify a site that uses "Morten's JavaScript Tree Menu" to display PDFs in a frames set using the Adobe Reader plug-in. On the iPad the frame is useless, so I want to open the PDF in a new tab. Not wanting to mess with the tree menu I thought I could use JavaScript in the web page being opened in the viewer frame to open a new tab with the PDF. I am using window.open() in $(document).ready(function() to open the pdf in the new tab. The problem is that window.open() does not want to work in the iPad. The body of the HTML normally looks like this... <body> <object data="MypdfFileName.pdf#toolbar=1&navpanes=1&scrollbar=0&page=1&view=FitH" type="application/pdf" width="100%" height="100%"> </object> </body> I changed it to only have a div like this... <body> <div class="myviewer" ></div> </body> Then used the following script... $(document).ready(function() { var isMobile = { Android : function() { return navigator.userAgent.match(/Android/i) ? true : false; }, BlackBerry : function() { return navigator.userAgent.match(/BlackBerry/i) ? true : false; }, iOS : function() { return navigator.userAgent.match(/iPhone|iPad|iPod/i) ? true : false; }, Windows : function() { return navigator.userAgent.match(/IEMobile/i) ? true : false; }, any : function() { return (isMobile.Android() || isMobile.BlackBerry() || isMobile.iOS() || isMobile.Windows()); } }; if(isMobile.any()) { var file = "MypdfFileName.pdf"; window.open(file); }else { var markup = "<object data='MypdfFileName.pdf#toolbar=1&navpanes=1&scrollbar=0&page=1&view=FitH' type='application/pdf' width='100%' height='100%'></object>"; $('.myviewer').append(markup); }; }); Everthing works except for window.open() on the iPad. If I switch things around widow.open() works fine on a computer. In another project I am using window.open() successfully on the iPad from an onclick function. I tried using a timer function. I also tried adding an onclick function to the div and posting a click event. In both cases they worked on a computer but not an iPad. I am stumped. I know it would make more sense to handle the ipad in the tree menu frame, but that code is so complex I can't figure out where to put/modify the onclick event. Is there a way to change the object so that it opens in a new tab? Is anyone familiar enough with Mortens Tree Menu code that can tell me how to channge the on click event so that it opens the pdf in a new tab instead of opening a page in the frame? Thanks

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Designing an API with compile-time option to remove first parameter to most functions and use a glob

- by tomlogic

I'm trying to design a portable API in ANSI C89/ISO C90 to access a wireless networking device on a serial interface. The library will have multiple network layers, and various versions need to run on embedded devices as small as an 8-bit micro with 32K of code and 2K of data, on up to embedded devices with a megabyte or more of code and data. In most cases, the target processor will have a single network interface and I'll want to use a single global structure with all state information for that device. I don't want to pass a pointer to that structure through the network layers. In a few cases (e.g., device with more resources that needs to live on two networks) I will interface to multiple devices, each with their own global state, and will need to pass a pointer to that state (or an index to a state array) through the layers. I came up with two possible solutions, but neither one is particularly pretty. Keep in mind that the full driver will potentially be 20,000 lines or more, cover multiple files, and contain hundreds of functions. The first solution requires a macro that discards the first parameter for every function that needs to access the global state: // network.h typedef struct dev_t { int var; long othervar; char name[20]; } dev_t; #ifdef IF_MULTI #define foo_function( x, a, b, c) _foo_function( x, a, b, c) #define bar_function( x) _bar_function( x) #else extern dev_t DEV; #define IFACE (&DEV) #define foo_function( x, a, b, c) _foo_function( a, b, c) #define bar_function( x) _bar_function( ) #endif int bar_function( dev_t *IFACE); int foo_function( dev_t *IFACE, int a, long b, char *c); // network.c #ifndef IF_MULTI dev_t DEV; #endif int bar_function( dev_t *IFACE) { memset( IFACE, 0, sizeof *IFACE); return 0; } int foo_function( dev_t *IFACE, int a, long b, char *c) { bar_function( IFACE); IFACE->var = a; IFACE->othervar = b; strcpy( IFACE->name, c); return 0; } The second solution defines macros to use in the function declarations: // network.h typedef struct dev_t { int var; long othervar; char name[20]; } dev_t; #ifdef IF_MULTI #define DEV_PARAM_ONLY dev_t *IFACE #define DEV_PARAM DEV_PARAM_ONLY, #else extern dev_t DEV; #define IFACE (&DEV) #define DEV_PARAM_ONLY void #define DEV_PARAM #endif int bar_function( DEV_PARAM_ONLY); // I don't like the missing comma between DEV_PARAM and arg2... int foo_function( DEV_PARAM int a, long b, char *c); // network.c #ifndef IF_MULTI dev_t DEV; #endif int bar_function( DEV_PARAM_ONLY) { memset( IFACE, 0, sizeof *IFACE); return 0; } int foo_function( DEV_PARAM int a, long b, char *c) { bar_function( IFACE); IFACE->var = a; IFACE->othervar = b; strcpy( IFACE->name, c); return 0; } The C code to access either method remains the same: // multi.c - example of multiple interfaces #define IF_MULTI #include "network.h" dev_t if0, if1; int main() { foo_function( &if0, -1, 3.1415926, "public"); foo_function( &if1, 42, 3.1415926, "private"); return 0; } // single.c - example of a single interface #include "network.h" int main() { foo_function( 11, 1.0, "network"); return 0; } Is there a cleaner method that I haven't figured out? I lean toward the second since it should be easier to maintain, and it's clearer that there's some macro magic in the parameters to the function. Also, the first method requires prefixing the function names with "_" when I want to use them as function pointers. I really do want to remove the parameter in the "single interface" case to eliminate unnecessary code to push the parameter onto the stack, and to allow the function to access the first "real" parameter in a register instead of loading it from the stack. And, if at all possible, I don't want to have to maintain two separate codebases. Thoughts? Ideas? Examples of something similar in existing code? (Note that using C++ isn't an option, since some of the planned targets don't have a C++ compiler available.)

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Doing XML extracts with XSLT without having to read the whole DOM tree into memory?

- by Thorbjørn Ravn Andersen

I have a situation where I want to extract some information from some very large but regular XML files (just had to do it with a 500 Mb file), and where XSLT would be perfect. Unfortunately those XSLT implementations I am aware of (except the most expensive version of Saxon) does not support only having the necessary part of the DOM read in but reads in the whole tree. This cause the computer to swap to death. The XPath in question is //m/e[contains(.,'foobar') so it is essentially just a grep. Is there an XSLT implementation which can do this? Or an XSLT implementation which given suitable "advice" can do this trick of pruning away the parts in memory which will not be needed again? I'd prefer a Java implementation but both Windows and Linux are viable native platforms. EDIT: The input XML looks like: <log>  <e h='12:09:27,284' l='org.apache.catalina.session.ManagerBase' z='1246010967284' t='ContainerBackgroundProcessor[StandardEngine[Catalina]]' v='10000'> <m>Registering Catalina:type=Manager,path=/axsWHSweb-20090626,host=localhost</m></e> <e h='12:09:27,284' l='org.apache.catalina.session.ManagerBase' z='1246010967284' t='ContainerBackgroundProcessor[StandardEngine[Catalina]]' v='10000'> <m>Force random number initialization starting</m></e> <e h='12:09:27,284' l='org.apache.catalina.session.ManagerBase' z='1246010967284' t='ContainerBackgroundProcessor[StandardEngine[Catalina]]' v='10000'> <m>Getting message digest component for algorithm MD5</m></e> <e h='12:09:27,284' l='org.apache.catalina.session.ManagerBase' z='1246010967284' t='ContainerBackgroundProcessor[StandardEngine[Catalina]]' v='10000'> <m>Completed getting message digest component</m></e> <e h='12:09:27,284' l='org.apache.catalina.session.ManagerBase' z='1246010967284' t='ContainerBackgroundProcessor[StandardEngine[Catalina]]' v='10000'> <m>getDigest() 0</m></e> ...... </log> Essentialy I want to select some m-nodes (and I know the XPath is wrong for that, it was just a quick hack), but maintain the XML layout. EDIT: It appears that STX may be what I am looking for (I can live with another transformation language), and that Joost is an implementation hereof. Any experiences? EDIT: I found that Saxon 6.5.4 with -Xmx1500m could load my XML, so this allowed me to use my XPaths right now. This is just a lucky stroke so I'd still like to solve this generically - this means scriptable which in turn means no handcrafted Java filtering first. EDIT: Oh, by the way. This is a log file very similar to what is generated by the log4j XMLLayout. The reason for XML is to be able to do exactly this, namely do queries on the log. This is the initial try, hence the simple question. Later I'd like to be able to ask more complex questions - therefore I'd like the query language to be able to handle the input file.

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Trying to packetize TCP with non-blocking IO is hard! Am I doing something wrong?

- by Ricket

Oh how I wish TCP was packet-based like UDP is! But alas, that's not the case, so I'm trying to implement my own packet layer. Here's the chain of events so far (ignoring writing packets) Oh, and my Packets are very simply structured: two unsigned bytes for length, and then byte[length] data. (I can't imagine if they were any more complex, I'd be up to my ears in if statements!) Server is in an infinite loop, accepting connections and adding them to a list of Connections. PacketGatherer (another thread) uses a Selector to figure out which Connection.SocketChannels are ready for reading. It loops over the results and tells each Connection to read(). Each Connection has a partial IncomingPacket and a list of Packets which have been fully read and are waiting to be processed. On read(): Tell the partial IncomingPacket to read more data. (IncomingPacket.readData below) If it's done reading (IncomingPacket.complete()), make a Packet from it and stick the Packet into the list waiting to be processed and then replace it with a new IncomingPacket. There are a couple problems with this. First, only one packet is being read at a time. If the IncomingPacket needs only one more byte, then only one byte is read this pass. This can of course be fixed with a loop but it starts to get sorta complicated and I wonder if there is a better overall way. Second, the logic in IncomingPacket is a little bit crazy, to be able to read the two bytes for the length and then read the actual data. Here is the code, boiled down for quick & easy reading: int readBytes; // number of total bytes read so far byte length1, length2; // each byte in an unsigned short int (see getLength()) public int getLength() { // will be inaccurate if readBytes < 2 return (int)(length1 << 8 | length2); } public void readData(SocketChannel c) { if (readBytes < 2) { // we don't yet know the length of the actual data ByteBuffer lengthBuffer = ByteBuffer.allocate(2 - readBytes); numBytesRead = c.read(lengthBuffer); if(readBytes == 0) { if(numBytesRead >= 1) length1 = lengthBuffer.get(); if(numBytesRead == 2) length2 = lengthBuffer.get(); } else if(readBytes == 1) { if(numBytesRead == 1) length2 = lengthBuffer.get(); } readBytes += numBytesRead; } if(readBytes >= 2) { // then we know we have the entire length variable // lazily-instantiate data buffers based on getLength() // read into data buffers, increment readBytes // (does not read more than the amount of this packet, so it does not // need to handle overflow into the next packet's data) } } public boolean complete() { return (readBytes > 2 && readBytes == getLength()+2); } Basically I need feedback on my code. Please suggest any improvements. Even overhauling my entire system would be okay, if you have suggestions for how better to implement the whole thing. Book recommendations are welcome too; I love books. I just get the feeling that something isn't quite right.

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Can I execute a "variable statements" within a function and without defines.

- by René Nyffenegger

I am facing a problem that I cannot see how it is solvable without #defines or incuring a performance impact although I am sure that someone can point me to a solution. I have an algorithm that sort of produces a (large) series of values. For simplicity's sake, in the following I pretend it's a for loop in a for loop, although in my code it's more complex than that. In the core of the loop I need to do calculations with the values being produced. Although the algorithm for the values stays the same, the calculations vary. So basically, what I have is: void normal() { // "Algorithm" producing numbers (x and y): for (int x=0 ; x<1000 ; x++) { for (int y=0 ; y<1000 ; y++) { // Calculation with numbers being produced: if ( x+y == 800 && y > 790) { std::cout << x << ", " << y << std::endl; } // end of calculation }} } So, the only part I need to change is if ( x+y == 800 && y > 790) { std::cout << x << ", " << y << std::endl; } So, in order to solve that, I could construct an abstract base class: class inner_0 { public: virtual void call(int x, int y) = 0; }; and derive a "callable" class from it: class inner : public inner_0 { public: virtual void call(int x, int y) { if ( x+y == 800 && y > 790) { std::cout << x << ", " << y << std::endl; } } }; I can then pass an instance of the class to the "algorithm" like so: void O(inner i) { for (int x=0 ; x<1000 ; x++) { for (int y=0 ; y<1000 ; y++) { i.call(x,y); }} } // somewhere else.... inner I; O(I); In my case, I incur a performance hit because there is an indirect call via virtual function table. So I was thinking about a way around it. It's possible with two #defines: #define OUTER \ for (int x=0 ; x<1000 ; x++) { \ for (int y=0 ; y<1000 ; y++) { \ INNER \ }} // later... #define INNER \ if (x + y == 800 && y > 790) \ std::cout << x << ", " << y << std::endl; OUTER While this certainly works, I am not 100% happy with it because I don't necessarly like #defines. So, my question: is there a better way for what I want to achieve?

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Generating strongly biased radom numbers for tests

- by nobody

I want to run tests with randomized inputs and need to generate 'sensible' random numbers, that is, numbers that match good enough to pass the tested function's preconditions, but hopefully wreak havoc deeper inside its code. math.random() (I'm using Lua) produces uniformly distributed random numbers. Scaling these up will give far more big numbers than small numbers, and there will be very few integers. I would like to skew the random numbers (or generate new ones using the old function as a randomness source) in a way that strongly favors 'simple' numbers, but will still cover the whole range, I.e. extending up to positive/negative infinity (or ±1e309 for double). This means: numbers up to, say, ten should be most common, integers should be more common than fractions, numbers ending in 0.5 should be the most common fractions, followed by 0.25 and 0.75; then 0.125, and so on. A different description: Fix a base probability x such that probabilities will sum to one and define the probability of a number n as xk where k is the generation in which n is constructed as a surreal number1. That assigns x to 0, x2 to -1 and +1, x3 to -2, -1/2, +1/2 and +2, and so on. This gives a nice description of something close to what I want (it skews a bit too much), but is near-unusable for computing random numbers. The resulting distribution is nowhere continuous (it's fractal!), I'm not sure how to determine the base probability x (I think for infinite precision it would be zero), and computing numbers based on this by iteration is awfully slow (spending near-infinite time to construct large numbers). Does anyone know of a simple approximation that, given a uniformly distributed randomness source, produces random numbers very roughly distributed as described above? I would like to run thousands of randomized tests, quantity/speed is more important than quality. Still, better numbers mean less inputs get rejected. Lua has a JIT, so performance can't be reasonably predicted. Jumps based on randomness will break every prediction, and many calls to math.random() will be slow, too. This means a closed formula will be better than an iterative or recursive one. 1 Wikipedia has an article on surreal numbers, with a nice picture. A surreal number is a pair of two surreal numbers, i.e. x := {n|m}, and its value is the number in the middle of the pair, i.e. (for finite numbers) {n|m} = (n+m)/2 (as rational). If one side of the pair is empty, that's interpreted as increment (or decrement, if right is empty) by one. If both sides are empty, that's zero. Initially, there are no numbers, so the only number one can build is 0 := { | }. In generation two one can build numbers {0| } =: 1 and { |0} =: -1, in three we get {1| } =: 2, {|1} =: -2, {0|1} =: 1/2 and {-1|0} =: -1/2 (plus some more complex representations of known numbers, e.g. {-1|1} ? 0). Note that e.g. 1/3 is never generated by finite numbers because it is an infinite fraction – the same goes for floats, 1/3 is never represented exactly.

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mapping rect in small image to larger image (in order to do a copyPixels operation)

- by skinnyTOD

Hi all - this is (I think) a relatively simple math question but I've spent a day banging my head against it and have only the dents and no solution... I'm coding in actionscript 3 - the functionality is: large image loaded at runtime. The bitmapData is stored and a smaller version is created to display on the available screen area (I may end up just scaling the large image since it is in memory anyway). The user can create a rectangle hotspot on the smaller image (the functionality will be more complex: multiple rects with transparency: example a donut shape with hole, etc) 3 When the user clicks on the hotspot, the rect of the hotspot is mapped to the larger image and a new bitmap "callout" is created, using the larger bitmap data. The reason for this is so the "callout" will be better quality than just scaling up the area of the hotspot. The image below shows where I am at so far- the blue rect is the clicked hotspot. In the upper left is the "callout" - copied from the larger image. I have the aspect ratio right but I am not mapping to the larger image correctly. Ugly code below... Sorry this post is so long - I just figured I ought to provide as much info as possible. Thanks for any tips! --trace of my data values *source BitmapDada 1152 864 scaled to rect 800 600 scaled BitmapData 800 600 selection BitmapData 58 56 scaled selection 83 80 ratio 1.44 before (x=544, y=237, w=58, h=56) (x=544, y=237, w=225.04, h=217.28) * Image here: http://i795.photobucket.com/albums/yy237/skinnyTOD/exampleST.jpg public function onExpandCallout(event:MouseEvent):void{ if (maskBitmapData.getPixel32(event.localX, event.localY) != 0){ var maskClone:BitmapData = maskBitmapData.clone(); //amount to scale callout - this will vary/can be changed by user var scale:Number =150 //scale percentage var normalizedScale :Number = scale/=100; var w:Number = maskBitmapData.width*normalizedScale; var h:Number = maskBitmapData.height*normalizedScale; var ratio:Number = (sourceBD.width /targetRect.width); //creat bmpd of the scaled size to copy source into var scaledBitmapData:BitmapData = new BitmapData(maskBitmapData.width * ratio, maskBitmapData.height * ratio, true, 0xFFFFFFFF); trace("source BitmapDada " + sourceBD.width, sourceBD.height); trace("scaled to rect " + targetRect.width, targetRect.height); trace("scaled BitmapData", bkgnImageSprite.width, bkgnImageSprite.height); trace("selection BitmapData", maskBitmapData.width, maskBitmapData.height); trace("scaled selection", scaledBitmapData.width, scaledBitmapData.height); trace("ratio", ratio); var scaledBitmap:Bitmap = new Bitmap(scaledBitmapData); var scaleW:Number = sourceBD.width / scaledBitmapData.width; var scaleH:Number = sourceBD.height / scaledBitmapData.height; var scaleMatrix:Matrix = new Matrix(); scaleMatrix.scale(ratio,ratio); var sRect:Rectangle = maskSprite.getBounds(bkgnImageSprite); var sR:Rectangle = sRect.clone(); var ss:Sprite = new Sprite(); ss.graphics.lineStyle(8, 0x0000FF); //ss.graphics.beginFill(0x000000, 1); ss.graphics.drawRect(sRect.x, sRect.y, sRect.width, sRect.height); //ss.graphics.endFill(); this.addChild(ss); trace("before " + sRect); w = uint(sRect.width * scaleW); h = uint(sRect.height * scaleH); sRect.inflate(maskBitmapData.width * ratio, maskBitmapData.height * ratio); sRect.offset(maskBitmapData.width * ratio, maskBitmapData.height * ratio); trace(sRect); scaledBitmapData.copyPixels(sourceBD, sRect, new Point()); addChild(scaledBitmap); scaledBitmap.x = offsetPt.x; scaledBitmap.y = offsetPt.y; } }

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Runtime error in C code (strange double conversion)

- by Miro Hassan

I have a strange runtime error in my C code. The Integers comparison here works fine. But in the Decimals comparison, I always get that the second number is larger than the first number, which is false. I am pretty new to C and programming in general, so this is a complex application to me. #include <stdio.h> #include <stdbool.h> #include <stdlib.h> int choose; long long neLimit = -1000000000; long long limit = 1000000000; bool big(a,b) { if ((a >= limit) || (b >= limit)) return true; else if ((a <= neLimit) || (b <= neLimit)) return true; return false; } void largerr(a,b) { if (a > b) printf("\nThe First Number is larger ..\n"); else if (a < b) printf("\nThe Second Number is larger ..\n"); else printf("\nThe Two Numbers are Equal .. \n"); } int main() { system("color e && title Numbers Comparison && echo off && cls"); start:{ printf("Choose a Type of Comparison :\n\t1. Integers\n\t2. Decimals \n\t\t I Choose Number : "); scanf("%i", &choose); switch(choose) { case 1: goto Integers; break; case 2: goto Decimals; break; default: system("echo Please Choose a Valid Option && pause>nul && cls"); goto start; } } Integers: { system("title Integers Comparison && cls"); long x , y; printf("\nFirst Number : \t"); scanf("%li", &x); printf("\nSecond Number : "); scanf("%li", &y); if (big(x,y)) { printf("\nOut of Limit .. Too Big Numbers ..\n"); system("pause>nul && cls") ; goto Integers; } largerr(x,y); printf("\nFirst Number : %li\nSecond Number : %li\n",x,y); goto exif; } Decimals: { system("title Decimals Comparison && cls"); double x , y; printf("\nFirst Number : \t"); scanf("%le", &x); printf("\nSecond Number : "); scanf("%le", &y); if (big(x,y)) { printf("\nOut of Limit .. Too Big Numbers ..\n"); system("pause>nul && cls") ; goto Decimals; } largerr(x,y); goto exif; } exif:{ system("pause>nul"); system("cls"); main(); } }

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What language/framework (technology) to use for website (flash games portal)

- by cripox

Hello, I know there are a lot of similar questions on the net, but because I am a newbie in web development I didn't find the solution for my specific problem. I am planing on creating a flash games portal from scratch. It is a big chance that there will be big traffic from the beginning (millions of pageviews). I want to reduce the server costs as much as possible but in the same time to not be tide to an expensive contract as there is a chance that the project will not be as successfully as I want and in that case the money would be very little. The question is : what technology to use? I don't know any web dev technology yet so it doesn't matter what I will learn. My web dev experience is a little php 8 years ago, and from then I programmed in C++ / Java- game and mobile development. I like Java and C syntax and language very much and I tend to dislike dynamic typing or non robust scripting (like php)- but I can get along if these are the best choices. The candidates are now: - Grails (my best for now) Ruby on Rails Cake PHP Other technologies (Google App Engine, Python/Django etc...) I was considering at first using pure C and compiling the web app in the server- just to squeeze more from the servers, but soon I understand that this is overkill. Next my eyes came on Ruby - as there is a lot of buzz for it's easiness of use. Next I discovered Grails and looked at Java because it is said that it is "faster". But I don't know what this "Faster" really means on my needs, so here comes the first question: 1) What will be my biggest consumption on the server, other than bandwidth, for a lot of flash content requests? Is it memory? I heard that Java needs a lot of memory, but is faster. Is it CPU? I am planning to take some daily VPS.NET nodes at first, to see if there is a demand, and if the "spike" is permanent to move to a dedicated server (serverloft.com has some good offers), else to remain with less nodes. I was also considering developing in Google App Engine- cheap or free hosting to use at first - so I can test my assumption- and also very easy to use (no need for sys administration) but the costs became high if used more ( 3 million games played / month .. x mb/ each). And the issue with Google is that it looks me in this technology. My other concern is scalability (not only for traffic/users, but as adding functionality) My plans are to release a functional site in just 4 weeks (just the basics frontend and some quick basic backend - so I can be able to modify some things and add games manually) - but then to raise it and add more things to it. I am planning to take a little different approach than other portals so I need to write it from scratch (a script will not do). 2) Will Grails take much more resources than RoR or Php server wise? I heard that making it on Java stack will be hardware expensive and is overkill if you don't make a bank application. My application will not be very complex (I hope and i will try to) but will have a lot of traffic. I also took in account using CDN for files, but the cheapest CDN found was 5c/GB (vps.net) and the cost per gb on serverloft (http://www.serverloft.com/dedizierte-server/server-details.php?products=4) is only 1.79 cents/GB and comes with the other resources either. I am new to this domain (web). I am learning the ropes and searching on the web for ~half of year but don't have any really practical experience, so I know that I must have some naive thinking and other issues that i don't know from now, so please give me any advice you want regarding anything, not just the specific questions asked. And thank you so much for such great community!

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database design help for game / user levels / progress

- by sprugman

Sorry this got long and all prose-y. I'm creating my first truly gamified web app and could use some help thinking about how to structure the data. The Set-up Users need to accomplish tasks in each of several categories before they can move up a level. I've got my Users, Tasks, and Categories tables, and a UserTasks table which joins the three. ("User 3 has added Task 42 in Category 8. Now they've completed it.") That's all fine and working wonderfully. The Challenge I'm not sure of the best way to track the progress in the individual categories toward each level. The "business" rules are: You have to achieve a certain number of points in each category to move up. If you get the number of points needed in Cat 8, but still have other work to do to complete the level, any new Cat 8 points count toward your overall score, but don't "roll over" into the next level. The number of Categories is small (five currently) and unlikely to change often, but by no means absolutely fixed. The number of points needed to level-up will vary per level, probably by a formula, or perhaps a lookup table. So the challenge is to track each user's progress toward the next level in each category. I've thought of a few potential approaches: Possible Solutions Add a column to the users table for each category and reset them all to zero each time a user levels-up. Have a separate UserProgress table with a row for each category for each user and the number of points they have. (Basically a Many-to-Many version of #1.) Add a userLevel column to the UserTasks table and use that to derive their progress with some kind of SUM statement. Their current level will be a simple int in the User table. Pros & Cons (1) seems like by far the most straightforward, but it's also the least flexible. Perhaps I could use a naming convention based on the category ids to help overcome some of that. (With code like "select cats; for each cat, get the value from Users.progress_{cat.id}.") It's also the one where I lose the most data -- I won't know which points counted toward leveling up. I don't have a need in mind for that, so maybe I don't care about that. (2) seems complicated: every time I add or subtract a user or a category, I have to maintain the other table. I foresee synchronization challenges. (3) Is somewhere in between -- cleaner than #2, but less intuitive than #1. In order to find out where a user is, I'd have mildly complex SQL like: SELECT categoryId, SUM(points) from UserTasks WHERE userId={user.id} & countsTowardLevel={user.level} groupBy categoryId Hmm... that doesn't seem so bad. I think I'm talking myself into #3 here, but would love any input, advice or other ideas.

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Dynamic Type to do away with Reflection

- by Rick Strahl

The dynamic type in C# 4.0 is a welcome addition to the language. One thing I’ve been doing a lot with it is to remove explicit Reflection code that’s often necessary when you ‘dynamically’ need to walk and object hierarchy. In the past I’ve had a number of ReflectionUtils that used string based expressions to walk an object hierarchy. With the introduction of dynamic much of the ReflectionUtils code can be removed for cleaner code that runs considerably faster to boot. The old Way - Reflection Here’s a really contrived example, but assume for a second, you’d want to dynamically retrieve a Page.Request.Url.AbsoluteUrl based on a Page instance in an ASP.NET Web Page request. The strongly typed version looks like this: string path = Page.Request.Url.AbsolutePath; Now assume for a second that Page wasn’t available as a strongly typed instance and all you had was an object reference to start with and you couldn’t cast it (right I said this was contrived :-)) If you’re using raw Reflection code to retrieve this you’d end up writing 3 sets of Reflection calls using GetValue(). Here’s some internal code I use to retrieve Property values as part of ReflectionUtils: /// <summary> /// Retrieve a property value from an object dynamically. This is a simple version /// that uses Reflection calls directly. It doesn't support indexers. /// </summary> /// <param name="instance">Object to make the call on</param> /// <param name="property">Property to retrieve</param> /// <returns>Object - cast to proper type</returns> public static object GetProperty(object instance, string property) { return instance.GetType().GetProperty(property, ReflectionUtils.MemberAccess).GetValue(instance, null); } If you want more control over properties and support both fields and properties as well as array indexers a little more work is required: /// <summary> /// Parses Properties and Fields including Array and Collection references. /// Used internally for the 'Ex' Reflection methods. /// </summary> /// <param name="Parent"></param> /// <param name="Property"></param> /// <returns></returns> private static object GetPropertyInternal(object Parent, string Property) { if (Property == "this" || Property == "me") return Parent; object result = null; string pureProperty = Property; string indexes = null; bool isArrayOrCollection = false; // Deal with Array Property if (Property.IndexOf("[") > -1) { pureProperty = Property.Substring(0, Property.IndexOf("[")); indexes = Property.Substring(Property.IndexOf("[")); isArrayOrCollection = true; } // Get the member MemberInfo member = Parent.GetType().GetMember(pureProperty, ReflectionUtils.MemberAccess)[0]; if (member.MemberType == MemberTypes.Property) result = ((PropertyInfo)member).GetValue(Parent, null); else result = ((FieldInfo)member).GetValue(Parent); if (isArrayOrCollection) { indexes = indexes.Replace("[", string.Empty).Replace("]", string.Empty); if (result is Array) { int Index = -1; int.TryParse(indexes, out Index); result = CallMethod(result, "GetValue", Index); } else if (result is ICollection) { if (indexes.StartsWith("\"")) { // String Index indexes = indexes.Trim('\"'); result = CallMethod(result, "get_Item", indexes); } else { // assume numeric index int index = -1; int.TryParse(indexes, out index); result = CallMethod(result, "get_Item", index); } } } return result; } /// <summary> /// Returns a property or field value using a base object and sub members including . syntax. /// For example, you can access: oCustomer.oData.Company with (this,"oCustomer.oData.Company") /// This method also supports indexers in the Property value such as: /// Customer.DataSet.Tables["Customers"].Rows[0] /// </summary> /// <param name="Parent">Parent object to 'start' parsing from. Typically this will be the Page.</param> /// <param name="Property">The property to retrieve. Example: 'Customer.Entity.Company'</param> /// <returns></returns> public static object GetPropertyEx(object Parent, string Property) { Type type = Parent.GetType(); int at = Property.IndexOf("."); if (at < 0) { // Complex parse of the property return GetPropertyInternal(Parent, Property); } // Walk the . syntax - split into current object (Main) and further parsed objects (Subs) string main = Property.Substring(0, at); string subs = Property.Substring(at + 1); // Retrieve the next . section of the property object sub = GetPropertyInternal(Parent, main); // Now go parse the left over sections return GetPropertyEx(sub, subs); } As you can see there’s a fair bit of code involved into retrieving a property or field value reliably especially if you want to support array indexer syntax. This method is then used by a variety of routines to retrieve individual properties including one called GetPropertyEx() which can walk the dot syntax hierarchy easily. Anyway with ReflectionUtils I can retrieve Page.Request.Url.AbsolutePath using code like this: string url = ReflectionUtils.GetPropertyEx(Page, "Request.Url.AbsolutePath") as string; This works fine, but is bulky to write and of course requires that I use my custom routines. It’s also quite slow as the code in GetPropertyEx does all sorts of string parsing to figure out which members to walk in the hierarchy. Enter dynamic – way easier! .NET 4.0’s dynamic type makes the above really easy. The following code is all that it takes: object objPage = Page; // force to object for contrivance :) dynamic page = objPage; // convert to dynamic from untyped object string scriptUrl = page.Request.Url.AbsolutePath; The dynamic type assignment in the first two lines turns the strongly typed Page object into a dynamic. The first assignment is just part of the contrived example to force the strongly typed Page reference into an untyped value to demonstrate the dynamic member access. The next line then just creates the dynamic type from the Page reference which allows you to access any public properties and methods easily. It also lets you access any child properties as dynamic types so when you look at Intellisense you’ll see something like this when typing Request.: In other words any dynamic value access on an object returns another dynamic object which is what allows the walking of the hierarchy chain. Note also that the result value doesn’t have to be explicitly cast as string in the code above – the compiler is perfectly happy without the cast in this case inferring the target type based on the type being assigned to. The dynamic conversion automatically handles the cast when making the final assignment which is nice making for natural syntnax that looks *exactly* like the fully typed syntax, but is completely dynamic. Note that you can also use indexers in the same natural syntax so the following also works on the dynamic page instance: string scriptUrl = page.Request.ServerVariables["SCRIPT_NAME"]; The dynamic type is going to make a lot of Reflection code go away as it’s simply so much nicer to be able to use natural syntax to write out code that previously required nasty Reflection syntax. Another interesting thing about the dynamic type is that it actually works considerably faster than Reflection. Check out the following methods that check performance: void Reflection() { Stopwatch stop = new Stopwatch(); stop.Start(); for (int i = 0; i < reps; i++) { // string url = ReflectionUtils.GetProperty(Page,"Title") as string;// "Request.Url.AbsolutePath") as string; string url = Page.GetType().GetProperty("Title", ReflectionUtils.MemberAccess).GetValue(Page, null) as string; } stop.Stop(); Response.Write("Reflection: " + stop.ElapsedMilliseconds.ToString()); } void Dynamic() { Stopwatch stop = new Stopwatch(); stop.Start(); dynamic page = Page; for (int i = 0; i < reps; i++) { string url = page.Title; //Request.Url.AbsolutePath; } stop.Stop(); Response.Write("Dynamic: " + stop.ElapsedMilliseconds.ToString()); } The dynamic code runs in 4-5 milliseconds while the Reflection code runs around 200+ milliseconds! There’s a bit of overhead in the first dynamic object call but subsequent calls are blazing fast and performance is actually much better than manual Reflection. Dynamic is definitely a huge win-win situation when you need dynamic access to objects at runtime.© Rick Strahl, West Wind Technologies, 2005-2010Posted in .NET CSharp

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