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  • Queue ExternalInterface calls to Flash Object in UpdatePanel - Needs Improvement?

    - by Laramie
    A Flash (actually Flex) object is created on an ASP.Net page within an Update Panel using a modified version of the embedCallAC_FL_RunContent.js script so it can be written in dynamically. It is re-created with this script with each partial postback to that panel. There are also other Update Panels on the page. With some postbacks (partial and full), External Interface calls such as $get('FlashObj').ExternalInterfaceFunc('arg1', 0, true); are prepared server-side and added to the page using ScriptManager.RegisterStartupScript. They're embedded in a function and stuffed into Sys.Application's load event, for example Sys.Application.add_load(funcContainingExternalInterfaceCalls). The problem is that because the Flash object's state state may change with each partial postback, the Flash (Flex) object and/or External Interface may not be ready or even exist yet in the DOM when the JavaScript - Flash External Interface call is made. It results in an "Object doesn't support this property or method" exception. I have a working strategy to make the ExternalInterface calls immediately if Flash is ready or else queue them until such time that Flash announces its readiness. //Called when the Flash object is initialized and can accept ExternalInterfaceCalls var flashReady = false; //Called by Flash when object is fully initialized function setFlashReady() { flashReady = true; //Make any queued ExternalInterface calls, then dequeue while (extIntQueue.length > 0) (extIntQueue.shift())(); } var extIntQueue = []; function callExternalInterface(flashObjName, funcName, args) { //reference to the wrapped ExternalInterface Call var wrapped = extWrap(flashObjName, funcName, args); //only procede with ExternalInterface call if the global flashReady variable has been set if (flashReady) { wrapped(); } else { //queue the function so when flashReady() is called next, the function is called and the aruments are passed. extIntQueue.push(wrapped); } } //bundle ExtInt call and hold variables in a closure function extWrap(flashObjName, funcName, args) { //put vars in closure return function() { var funcCall = '$get("' + flashObjName + '").' + funcName; eval(funcCall).apply(this, args); } } I set the flashReady var to dirty whenever I update the Update Panel that contains the Flash (Flex) object. ScriptManager.RegisterClientScriptBlock(parentContainer, parentContainer.GetType(), "flashReady", "flashReady = false;", true); I'm pleased that I got it to work, but it feels like a hack. I am still on the learning curve with respect to concepts like closures why "eval()" is apparently evil, so I'm wondering if I'm violating some best practice or if this code should be improved, if so how? Thanks.

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  • Can I use Linq-to-xml to persist my object state without having to use/know Xpath & XSD Syntax?

    - by Greg
    Hi, Can I use Linq-to-xml to persist my object state without having to use/know Xpath & XSD Syntax? ie. really looking for simple but flexible way to persist a graph of object data (e.g. have say 2 or 3 classes with associations) - if Linq-to-xml were as simple as saying "persist this graph to XML", and then you could also query it via Linq, or load it into memory again/change/then re-save to the xml file.

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  • Can you transport a Javascript object to server and receive it in the same state?

    - by zorglub76
    I'm considering creating a simple remote debugging application for Javascript. Actually, I want to provide an object to Firebug Lite and let it do all the job. So, can I get an object from one page, serialize it, send it to server and then to another browser and finally see the same results in Firebug Lite (on that other client) as I would see on the first browser (with doing "console.dir(obj)")? Is it possible to do?

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  • How to create multiple Repository object inside a Repository class using Unit Of Work?

    - by Santosh
    I am newbie to MVC3 application development, currently, we need following Application technologies as requirement MVC3 framework IOC framework – Autofac to manage object creation dynamically Moq – Unit testing Entity Framework Repository and Unit Of Work Pattern of Model class I have gone through many article to explore an basic idea about the above points but still I am little bit confused on the “Repository and Unit Of Work Pattern “. Basically what I understand Unit Of Work is a pattern which will be followed along with Repository Pattern in order to share the single DB Context among all Repository object, So here is my design : IUnitOfWork.cs public interface IUnitOfWork : IDisposable { IPermitRepository Permit_Repository{ get; } IRebateRepository Rebate_Repository { get; } IBuildingTypeRepository BuildingType_Repository { get; } IEEProjectRepository EEProject_Repository { get; } IRebateLookupRepository RebateLookup_Repository { get; } IEEProjectTypeRepository EEProjectType_Repository { get; } void Save(); } UnitOfWork.cs public class UnitOfWork : IUnitOfWork { #region Private Members private readonly CEEPMSEntities context = new CEEPMSEntities(); private IPermitRepository permit_Repository; private IRebateRepository rebate_Repository; private IBuildingTypeRepository buildingType_Repository; private IEEProjectRepository eeProject_Repository; private IRebateLookupRepository rebateLookup_Repository; private IEEProjectTypeRepository eeProjectType_Repository; #endregion #region IUnitOfWork Implemenation public IPermitRepository Permit_Repository { get { if (this.permit_Repository == null) { this.permit_Repository = new PermitRepository(context); } return permit_Repository; } } public IRebateRepository Rebate_Repository { get { if (this.rebate_Repository == null) { this.rebate_Repository = new RebateRepository(context); } return rebate_Repository; } } } PermitRepository .cs public class PermitRepository : IPermitRepository { #region Private Members private CEEPMSEntities objectContext = null; private IObjectSet<Permit> objectSet = null; #endregion #region Constructors public PermitRepository() { } public PermitRepository(CEEPMSEntities _objectContext) { this.objectContext = _objectContext; this.objectSet = objectContext.CreateObjectSet<Permit>(); } #endregion public IEnumerable<RebateViewModel> GetRebatesByPermitId(int _permitId) { // need to implment } } PermitController .cs public class PermitController : Controller { #region Private Members IUnitOfWork CEEPMSContext = null; #endregion #region Constructors public PermitController(IUnitOfWork _CEEPMSContext) { if (_CEEPMSContext == null) { throw new ArgumentNullException("Object can not be null"); } CEEPMSContext = _CEEPMSContext; } #endregion } So here I am wondering how to generate a new Repository for example “TestRepository.cs” using same pattern where I can create more then one Repository object like RebateRepository rebateRepo = new RebateRepository () AddressRepository addressRepo = new AddressRepository() because , what ever Repository object I want to create I need an object of UnitOfWork first as implmented in the PermitController class. So if I would follow the same in each individual Repository class that would again break the priciple of Unit Of Work and create multiple instance of object context. So any idea or suggestion will be highly appreciated. Thank you

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  • Move an object in the direction of a bezier curve?

    - by Sent1nel
    I have an object with which I would like to make follow a bezier curve and am a little lost right now as to how to make it do that based on time rather than the points that make up the curve. .::Current System::. Each object in my scene graph is made from position, rotation and scale vectors. These vectors are used to form their corresponding matrices: scale, rotation and translation. Which are then multiplied in that order to form the local transform matrix. A world transform (Usually the identity matrix) is then multiplied against the local matrix transform. class CObject { public: // Local transform functions Matrix4f GetLocalTransform() const; void SetPosition(const Vector3f& pos); void SetRotation(const Vector3f& rot); void SetScale(const Vector3f& scale); // Local transform Matrix4f m_local; Vector3f m_localPostion; Vector3f m_localRotation; // rotation in degrees (xrot, yrot, zrot) Vector3f m_localScale; } Matrix4f CObject::GetLocalTransform() { Matrix4f out(Matrix4f::IDENTITY); Matrix4f scale(), rotation(), translation(); scale.SetScale(m_localScale); rotation.SetRotationDegrees(m_localRotation); translation.SetTranslation(m_localTranslation); out = scale * rotation * translation; } The big question I have are 1) How do I orientate my object to face the tangent of the Bezier curve? 2) How do I move that object along the curve without just setting objects position to that of a point on the bezier cuve? Heres an overview of the function thus far void CNodeControllerPieceWise::AnimateNode(CObject* pSpatial, double deltaTime) { // Get object latest pos. Vector3f posDelta = pSpatial->GetWorldTransform().GetTranslation(); // Get postion on curve Vector3f pos = curve.GetPosition(m_t); // Get tangent of curve Vector3f tangent = curve.GetFirstDerivative(m_t); } Edit: sorry its not very clear. I've been working on this for ages and its making my brain turn to mush. I want the object to be attached to the curve and face the direction of the curve. As for movement, I want to object to follow the curve based on the time this way it creates smooth movement throughout the curve.

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  • Metro: Understanding CSS Media Queries

    - by Stephen.Walther
    If you are building a Metro style application then your application needs to look great when used on a wide variety of devices. Your application needs to work on tiny little phones, slates, desktop monitors, and the super high resolution displays of the future. Your application also must support portable devices used with different orientations. If someone tilts their phone from portrait to landscape mode then your application must still be usable. Finally, your Metro style application must look great in different states. For example, your Metro application can be in a “snapped state” when it is shrunk so it can share screen real estate with another application. In this blog post, you learn how to use Cascading Style Sheet media queries to support different devices, different device orientations, and different application states. First, you are provided with an overview of the W3C Media Query recommendation and you learn how to detect standard media features. Next, you learn about the Microsoft extensions to media queries which are supported in Metro style applications. For example, you learn how to use the –ms-view-state feature to detect whether an application is in a “snapped state” or “fill state”. Finally, you learn how to programmatically detect the features of a device and the state of an application. You learn how to use the msMatchMedia() method to execute a media query with JavaScript. Using CSS Media Queries Media queries enable you to apply different styles depending on the features of a device. Media queries are not only supported by Metro style applications, most modern web browsers now support media queries including Google Chrome 4+, Mozilla Firefox 3.5+, Apple Safari 4+, and Microsoft Internet Explorer 9+. Loading Different Style Sheets with Media Queries Imagine, for example, that you want to display different content depending on the horizontal resolution of a device. In that case, you can load different style sheets optimized for different sized devices. Consider the following HTML page: <!DOCTYPE html> <html xmlns="http://www.w3.org/1999/xhtml"> <head> <title>U.S. Robotics and Mechanical Men</title> <link href="main.css" rel="stylesheet" type="text/css" /> <!-- Less than 1100px --> <link href="medium.css" rel="stylesheet" type="text/css" media="(max-width:1100px)" /> <!-- Less than 800px --> <link href="small.css" rel="stylesheet" type="text/css" media="(max-width:800px)" /> </head> <body> <div id="header"> <h1>U.S. Robotics and Mechanical Men</h1> </div> <!-- Advertisement Column --> <div id="leftColumn"> <img src="advertisement1.gif" alt="advertisement" /> <img src="advertisement2.jpg" alt="advertisement" /> </div> <!-- Product Search Form --> <div id="mainContentColumn"> <label>Search Products</label> <input id="search" /><button>Search</button> </div> <!-- Deal of the Day Column --> <div id="rightColumn"> <h1>Deal of the Day!</h1> <p> Buy two cameras and get a third camera for free! Offer is good for today only. </p> </div> </body> </html> The HTML page above contains three columns: a leftColumn, mainContentColumn, and rightColumn. When the page is displayed on a low resolution device, such as a phone, only the mainContentColumn appears: When the page is displayed in a medium resolution device, such as a slate, both the leftColumn and the mainContentColumns are displayed: Finally, when the page is displayed in a high-resolution device, such as a computer monitor, all three columns are displayed: Different content is displayed with the help of media queries. The page above contains three style sheet links. Two of the style links include a media attribute: <link href="main.css" rel="stylesheet" type="text/css" /> <!-- Less than 1100px --> <link href="medium.css" rel="stylesheet" type="text/css" media="(max-width:1100px)" /> <!-- Less than 800px --> <link href="small.css" rel="stylesheet" type="text/css" media="(max-width:800px)" /> The main.css style sheet contains default styles for the elements in the page. The medium.css style sheet is applied when the page width is less than 1100px. This style sheet hides the rightColumn and changes the page background color to lime: html { background-color: lime; } #rightColumn { display:none; } Finally, the small.css style sheet is loaded when the page width is less than 800px. This style sheet hides the leftColumn and changes the page background color to red: html { background-color: red; } #leftColumn { display:none; } The different style sheets are applied as you stretch and contract your browser window. You don’t need to refresh the page after changing the size of the page for a media query to be applied: Using the @media Rule You don’t need to divide your styles into separate files to take advantage of media queries. You can group styles by using the @media rule. For example, the following HTML page contains one set of styles which are applied when a device’s orientation is portrait and another set of styles when a device’s orientation is landscape: <!DOCTYPE html> <html> <head> <meta charset="utf-8" /> <title>Application1</title> <style type="text/css"> html { font-family:'Segoe UI Semilight'; font-size: xx-large; } @media screen and (orientation:landscape) { html { background-color: lime; } p.content { width: 50%; margin: auto; } } @media screen and (orientation:portrait) { html { background-color: red; } p.content { width: 90%; margin: auto; } } </style> </head> <body> <p class="content"> Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Maecenas porttitor congue massa. Fusce posuere, magna sed pulvinar ultricies, purus lectus malesuada libero, sit amet commodo magna eros quis urna. </p> </body> </html> When a device has a landscape orientation then the background color is set to the color lime and the text only takes up 50% of the available horizontal space: When the device has a portrait orientation then the background color is red and the text takes up 90% of the available horizontal space: Using Standard CSS Media Features The official list of standard media features is contained in the W3C CSS Media Query recommendation located here: http://www.w3.org/TR/css3-mediaqueries/ Here is the official list of the 13 media features described in the standard: · width – The current width of the viewport · height – The current height of the viewport · device-width – The width of the device · device-height – The height of the device · orientation – The value portrait or landscape · aspect-ratio – The ratio of width to height · device-aspect-ratio – The ratio of device width to device height · color – The number of bits per color supported by the device · color-index – The number of colors in the color lookup table of the device · monochrome – The number of bits in the monochrome frame buffer · resolution – The density of the pixels supported by the device · scan – The values progressive or interlace (used for TVs) · grid – The values 0 or 1 which indicate whether the device supports a grid or a bitmap Many of the media features in the list above support the min- and max- prefix. For example, you can test for the min-width using a query like this: (min-width:800px) You can use the logical and operator with media queries when you need to check whether a device supports more than one feature. For example, the following query returns true only when the width of the device is between 800 and 1,200 pixels: (min-width:800px) and (max-width:1200px) Finally, you can use the different media types – all, braille, embossed, handheld, print, projection, screen, speech, tty, tv — with a media query. For example, the following media query only applies to a page when a page is being printed in color: print and (color) If you don’t specify a media type then media type all is assumed. Using Metro Style Media Features Microsoft has extended the standard list of media features which you can include in a media query with two custom media features: · -ms-high-contrast – The values any, black-white, white-black · -ms-view-state – The values full-screen, fill, snapped, device-portrait You can take advantage of the –ms-high-contrast media feature to make your web application more accessible to individuals with disabilities. In high contrast mode, you should make your application easier to use for individuals with vision disabilities. The –ms-view-state media feature enables you to detect the state of an application. For example, when an application is snapped, the application only occupies part of the available screen real estate. The snapped application appears on the left or right side of the screen and the rest of the screen real estate is dominated by the fill application (Metro style applications can only be snapped on devices with a horizontal resolution of greater than 1,366 pixels). Here is a page which contains style rules for an application in both a snap and fill application state: <!DOCTYPE html> <html> <head> <meta charset="utf-8" /> <title>MyWinWebApp</title> <style type="text/css"> html { font-family:'Segoe UI Semilight'; font-size: xx-large; } @media screen and (-ms-view-state:snapped) { html { background-color: lime; } } @media screen and (-ms-view-state:fill) { html { background-color: red; } } </style> </head> <body> <p class="content"> Lorem ipsum dolor sit amet, consectetuer adipiscing elit. Maecenas porttitor congue massa. Fusce posuere, magna sed pulvinar ultricies, purus lectus malesuada libero, sit amet commodo magna eros quis urna. </p> </body> </html> When the application is snapped, the application appears with a lime background color: When the application state is fill then the background color changes to red: When the application takes up the entire screen real estate – it is not in snapped or fill state – then no special style rules apply and the application appears with a white background color. Querying Media Features with JavaScript You can perform media queries using JavaScript by taking advantage of the window.msMatchMedia() method. This method returns a MSMediaQueryList which has a matches method that represents success or failure. For example, the following code checks whether the current device is in portrait mode: if (window.msMatchMedia("(orientation:portrait)").matches) { console.log("portrait"); } else { console.log("landscape"); } If the matches property returns true, then the device is in portrait mode and the message “portrait” is written to the Visual Studio JavaScript Console window. Otherwise, the message “landscape” is written to the JavaScript Console window. You can create an event listener which triggers code whenever the results of a media query changes. For example, the following code writes a message to the JavaScript Console whenever the current device is switched into or out of Portrait mode: window.msMatchMedia("(orientation:portrait)").addListener(function (mql) { if (mql.matches) { console.log("Switched to portrait"); } }); Be aware that the event listener is triggered whenever the result of the media query changes. So the event listener is triggered both when you switch from landscape to portrait and when you switch from portrait to landscape. For this reason, you need to verify that the matches property has the value true before writing the message. Summary The goal of this blog entry was to explain how CSS media queries work in the context of a Metro style application written with JavaScript. First, you were provided with an overview of the W3C CSS Media Query recommendation. You learned about the standard media features which you can query such as width and orientation. Next, we focused on the Microsoft extensions to media queries. You learned how to use –ms-view-state to detect whether a Metro style application is in “snapped” or “fill” state. You also learned how to use the msMatchMedia() method to perform a media query from JavaScript.

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  • Plan Caching and Query Memory Part II (Hash Match) – When not to use stored procedure - Most common performance mistake SQL Server developers make.

    - by sqlworkshops
    SQL Server estimates Memory requirement at compile time, when stored procedure or other plan caching mechanisms like sp_executesql or prepared statement are used, the memory requirement is estimated based on first set of execution parameters. This is a common reason for spill over tempdb and hence poor performance. Common memory allocating queries are that perform Sort and do Hash Match operations like Hash Join or Hash Aggregation or Hash Union. This article covers Hash Match operations with examples. It is recommended to read Plan Caching and Query Memory Part I before this article which covers an introduction and Query memory for Sort. In most cases it is cheaper to pay for the compilation cost of dynamic queries than huge cost for spill over tempdb, unless memory requirement for a query does not change significantly based on predicates.   This article covers underestimation / overestimation of memory for Hash Match operation. Plan Caching and Query Memory Part I covers underestimation / overestimation for Sort. It is important to note that underestimation of memory for Sort and Hash Match operations lead to spill over tempdb and hence negatively impact performance. Overestimation of memory affects the memory needs of other concurrently executing queries. In addition, it is important to note, with Hash Match operations, overestimation of memory can actually lead to poor performance.   To read additional articles I wrote click here.   The best way to learn is to practice. To create the below tables and reproduce the behavior, join the mailing list by using this link: www.sqlworkshops.com/ml and I will send you the table creation script. Most of these concepts are also covered in our webcasts: www.sqlworkshops.com/webcasts  Let’s create a Customer’s State table that has 99% of customers in NY and the rest 1% in WA.Customers table used in Part I of this article is also used here.To observe Hash Warning, enable 'Hash Warning' in SQL Profiler under Events 'Errors and Warnings'. --Example provided by www.sqlworkshops.com drop table CustomersState go create table CustomersState (CustomerID int primary key, Address char(200), State char(2)) go insert into CustomersState (CustomerID, Address) select CustomerID, 'Address' from Customers update CustomersState set State = 'NY' where CustomerID % 100 != 1 update CustomersState set State = 'WA' where CustomerID % 100 = 1 go update statistics CustomersState with fullscan go   Let’s create a stored procedure that joins customers with CustomersState table with a predicate on State. --Example provided by www.sqlworkshops.com create proc CustomersByState @State char(2) as begin declare @CustomerID int select @CustomerID = e.CustomerID from Customers e inner join CustomersState es on (e.CustomerID = es.CustomerID) where es.State = @State option (maxdop 1) end go  Let’s execute the stored procedure first with parameter value ‘WA’ – which will select 1% of data. set statistics time on go --Example provided by www.sqlworkshops.com exec CustomersByState 'WA' goThe stored procedure took 294 ms to complete.  The stored procedure was granted 6704 KB based on 8000 rows being estimated.  The estimated number of rows, 8000 is similar to actual number of rows 8000 and hence the memory estimation should be ok.  There was no Hash Warning in SQL Profiler. To observe Hash Warning, enable 'Hash Warning' in SQL Profiler under Events 'Errors and Warnings'.   Now let’s execute the stored procedure with parameter value ‘NY’ – which will select 99% of data. -Example provided by www.sqlworkshops.com exec CustomersByState 'NY' go  The stored procedure took 2922 ms to complete.   The stored procedure was granted 6704 KB based on 8000 rows being estimated.    The estimated number of rows, 8000 is way different from the actual number of rows 792000 because the estimation is based on the first set of parameter value supplied to the stored procedure which is ‘WA’ in our case. This underestimation will lead to spill over tempdb, resulting in poor performance.   There was Hash Warning (Recursion) in SQL Profiler. To observe Hash Warning, enable 'Hash Warning' in SQL Profiler under Events 'Errors and Warnings'.   Let’s recompile the stored procedure and then let’s first execute the stored procedure with parameter value ‘NY’.  In a production instance it is not advisable to use sp_recompile instead one should use DBCC FREEPROCCACHE (plan_handle). This is due to locking issues involved with sp_recompile, refer to our webcasts, www.sqlworkshops.com/webcasts for further details.   exec sp_recompile CustomersByState go --Example provided by www.sqlworkshops.com exec CustomersByState 'NY' go  Now the stored procedure took only 1046 ms instead of 2922 ms.   The stored procedure was granted 146752 KB of memory. The estimated number of rows, 792000 is similar to actual number of rows of 792000. Better performance of this stored procedure execution is due to better estimation of memory and avoiding spill over tempdb.   There was no Hash Warning in SQL Profiler.   Now let’s execute the stored procedure with parameter value ‘WA’. --Example provided by www.sqlworkshops.com exec CustomersByState 'WA' go  The stored procedure took 351 ms to complete, higher than the previous execution time of 294 ms.    This stored procedure was granted more memory (146752 KB) than necessary (6704 KB) based on parameter value ‘NY’ for estimation (792000 rows) instead of parameter value ‘WA’ for estimation (8000 rows). This is because the estimation is based on the first set of parameter value supplied to the stored procedure which is ‘NY’ in this case. This overestimation leads to poor performance of this Hash Match operation, it might also affect the performance of other concurrently executing queries requiring memory and hence overestimation is not recommended.     The estimated number of rows, 792000 is much more than the actual number of rows of 8000.  Intermediate Summary: This issue can be avoided by not caching the plan for memory allocating queries. Other possibility is to use recompile hint or optimize for hint to allocate memory for predefined data range.Let’s recreate the stored procedure with recompile hint. --Example provided by www.sqlworkshops.com drop proc CustomersByState go create proc CustomersByState @State char(2) as begin declare @CustomerID int select @CustomerID = e.CustomerID from Customers e inner join CustomersState es on (e.CustomerID = es.CustomerID) where es.State = @State option (maxdop 1, recompile) end go  Let’s execute the stored procedure initially with parameter value ‘WA’ and then with parameter value ‘NY’. --Example provided by www.sqlworkshops.com exec CustomersByState 'WA' go exec CustomersByState 'NY' go  The stored procedure took 297 ms and 1102 ms in line with previous optimal execution times.   The stored procedure with parameter value ‘WA’ has good estimation like before.   Estimated number of rows of 8000 is similar to actual number of rows of 8000.   The stored procedure with parameter value ‘NY’ also has good estimation and memory grant like before because the stored procedure was recompiled with current set of parameter values.  Estimated number of rows of 792000 is similar to actual number of rows of 792000.    The compilation time and compilation CPU of 1 ms is not expensive in this case compared to the performance benefit.   There was no Hash Warning in SQL Profiler.   Let’s recreate the stored procedure with optimize for hint of ‘NY’. --Example provided by www.sqlworkshops.com drop proc CustomersByState go create proc CustomersByState @State char(2) as begin declare @CustomerID int select @CustomerID = e.CustomerID from Customers e inner join CustomersState es on (e.CustomerID = es.CustomerID) where es.State = @State option (maxdop 1, optimize for (@State = 'NY')) end go  Let’s execute the stored procedure initially with parameter value ‘WA’ and then with parameter value ‘NY’. --Example provided by www.sqlworkshops.com exec CustomersByState 'WA' go exec CustomersByState 'NY' go  The stored procedure took 353 ms with parameter value ‘WA’, this is much slower than the optimal execution time of 294 ms we observed previously. This is because of overestimation of memory. The stored procedure with parameter value ‘NY’ has optimal execution time like before.   The stored procedure with parameter value ‘WA’ has overestimation of rows because of optimize for hint value of ‘NY’.   Unlike before, more memory was estimated to this stored procedure based on optimize for hint value ‘NY’.    The stored procedure with parameter value ‘NY’ has good estimation because of optimize for hint value of ‘NY’. Estimated number of rows of 792000 is similar to actual number of rows of 792000.   Optimal amount memory was estimated to this stored procedure based on optimize for hint value ‘NY’.   There was no Hash Warning in SQL Profiler.   This article covers underestimation / overestimation of memory for Hash Match operation. Plan Caching and Query Memory Part I covers underestimation / overestimation for Sort. It is important to note that underestimation of memory for Sort and Hash Match operations lead to spill over tempdb and hence negatively impact performance. Overestimation of memory affects the memory needs of other concurrently executing queries. In addition, it is important to note, with Hash Match operations, overestimation of memory can actually lead to poor performance.   Summary: Cached plan might lead to underestimation or overestimation of memory because the memory is estimated based on first set of execution parameters. It is recommended not to cache the plan if the amount of memory required to execute the stored procedure has a wide range of possibilities. One can mitigate this by using recompile hint, but that will lead to compilation overhead. However, in most cases it might be ok to pay for compilation rather than spilling sort over tempdb which could be very expensive compared to compilation cost. The other possibility is to use optimize for hint, but in case one sorts more data than hinted by optimize for hint, this will still lead to spill. On the other side there is also the possibility of overestimation leading to unnecessary memory issues for other concurrently executing queries. In case of Hash Match operations, this overestimation of memory might lead to poor performance. When the values used in optimize for hint are archived from the database, the estimation will be wrong leading to worst performance, so one has to exercise caution before using optimize for hint, recompile hint is better in this case.   I explain these concepts with detailed examples in my webcasts (www.sqlworkshops.com/webcasts), I recommend you to watch them. The best way to learn is to practice. To create the above tables and reproduce the behavior, join the mailing list at www.sqlworkshops.com/ml and I will send you the relevant SQL Scripts.  Register for the upcoming 3 Day Level 400 Microsoft SQL Server 2008 and SQL Server 2005 Performance Monitoring & Tuning Hands-on Workshop in London, United Kingdom during March 15-17, 2011, click here to register / Microsoft UK TechNet.These are hands-on workshops with a maximum of 12 participants and not lectures. For consulting engagements click here.   Disclaimer and copyright information:This article refers to organizations and products that may be the trademarks or registered trademarks of their various owners. Copyright of this article belongs to R Meyyappan / www.sqlworkshops.com. You may freely use the ideas and concepts discussed in this article with acknowledgement (www.sqlworkshops.com), but you may not claim any of it as your own work. This article is for informational purposes only; you use any of the suggestions given here entirely at your own risk.   R Meyyappan [email protected] LinkedIn: http://at.linkedin.com/in/rmeyyappan

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  • How does interpolation actually work to smooth out an object's movement?

    - by user22241
    I've asked a few similar questions over the past 8 months or so with no real joy, so I am going make the question more general. I have an Android game which is OpenGL ES 2.0. within it I have the following Game Loop: My loop works on a fixed time step principle (dt = 1 / ticksPerSecond) loops=0; while(System.currentTimeMillis() > nextGameTick && loops < maxFrameskip){ updateLogic(dt); nextGameTick+=skipTicks; timeCorrection += (1000d/ticksPerSecond) % 1; nextGameTick+=timeCorrection; timeCorrection %=1; loops++; } render(); My intergration works like this: sprite.posX+=sprite.xVel*dt; sprite.posXDrawAt=sprite.posX*width; Now, everything works pretty much as I would like. I can specify that I would like an object to move across a certain distance (screen width say) in 2.5 seconds and it will do just that. Also because of the frame skipping that I allow in my game loop, I can do this on pretty much any device and it will always take 2.5 seconds. Problem However, the problem is that when a render frame skips, the graphic stutter. It's extremely annoying. If I remove the ability to skip frames, then everything is smooth as you like, but will run at different speeds on different devices. So it's not an option. I'm still not sure why the frame skips, but I would like to point out that this is Nothing to do with poor performance, I've taken the code right back to 1 tiny sprite and no logic (apart from the logic required to move the sprite) and I still get skipped frames. And this is on a Google Nexus 10 tablet (and as mentioned above, I need frame skipping to keep the speed consistent across devices anyway). So, the only other option I have is to use interpolation (or extrapolation), I've read every article there is out there but none have really helped me to understand how it works and all of my attempted implementations have failed. Using one method I was able to get things moving smoothly but it was unworkable because it messed up my collision. I can foresee the same issue with any similar method because the interpolation is passed to (and acted upon within) the rendering method - at render time. So if Collision corrects position (character now standing right next to wall), then the renderer can alter it's position and draw it in the wall. So I'm really confused. People have said that you should never alter an object's position from within the rendering method, but all of the examples online show this. So I'm asking for a push in the right direction, please do not link to the popular game loop articles (deWitters, Fix your timestep, etc) as I've read these multiple times. I'm not asking anyone to write my code for me. Just explain please in simple terms how Interpolation actually works with some examples. I will then go and try to integrate any ideas into my code and will ask more specific questions if need-be further down the line. (I'm sure this is a problem many people struggle with).

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  • StackOverflowException throws often when .net application built with Debug mode

    - by user1487950
    I have an application which access an external webservice often, when i are trying to debug it, means debuging in vistual studio. it often throws out StackOverflowException at the webserverice call point. when building in Release mode , the exception thrown out only occasionally. I checked the call stack, looks like there is no recursive call. can you please suggest? thank you very much. call statck attached. [In a sleep, wait, or join] mscorlib.dll!System.Threading.WaitHandle.InternalWaitOne(System.Runtime.InteropServices.SafeHandle waitableSafeHandle, long millisecondsTimeout, bool hasThreadAffinity, bool exitContext) + 0x2b bytes mscorlib.dll!System.Threading.WaitHandle.WaitOne(int millisecondsTimeout, bool exitContext) + 0x2d bytes System.dll!System.Net.NetworkAddressChangePolled.CheckAndReset() + 0x9d bytes System.dll!System.Net.NclUtilities.LocalAddresses.get() + 0x49 bytes System.dll!System.Net.WebProxyScriptHelper.myIpAddress() + 0x27 bytes [Native to Managed Transition] System.dll!System.Net.WebProxyScriptHelper.MyMethodInfo.Invoke(object target, System.Reflection.BindingFlags bindingAttr, System.Reflection.Binder binder, object[] args, System.Globalization.CultureInfo culture) + 0x6b bytes MTOqoHCT.dll!JScript 0.myIpAddress(object this, Microsoft.JScript.Vsa.VsaEngine vsa Engine, object arguments) + 0x91 bytes MTOqoHCT.dll!JScript 0.FindProxyForURL(object this, Microsoft.JScript.Vsa.VsaEngine vsa Engine, object arguments, object url, object host) + 0x3c6e bytes MTOqoHCT.dll!__WebProxyScript.__WebProxyScript.ExecuteFindProxyForURL(object url, object host) + 0x11d bytes [Native to Managed Transition] Microsoft.JScript.dll!System.Net.VsaWebProxyScript.CallMethod(object targetObject, string name, object[] args) + 0x11a bytes Microsoft.JScript.dll!System.Net.VsaWebProxyScript.Run(string url, string host) + 0x74 bytes [Native to Managed Transition] [Managed to Native Transition] mscorlib.dll!System.Runtime.Remoting.Messaging.StackBuilderSink.SyncProcessMessage(System.Runtime.Remoting.Messaging.IMessage msg, int methodPtr, bool fExecuteInContext) + 0x1ef bytes mscorlib.dll!System.Runtime.Remoting.Messaging.StackBuilderSink.SyncProcessMessage(System.Runtime.Remoting.Messaging.IMessage msg) + 0xf bytes mscorlib.dll!System.Runtime.Remoting.Messaging.ServerObjectTerminatorSink.SyncProcessMessage(System.Runtime.Remoting.Messaging.IMessage reqMsg) + 0x66 bytes mscorlib.dll!System.Runtime.Remoting.Messaging.ServerContextTerminatorSink.SyncProcessMessage(System.Runtime.Remoting.Messaging.IMessage reqMsg) + 0x8a bytes mscorlib.dll!System.Runtime.Remoting.Channels.CrossContextChannel.SyncProcessMessageCallback(object[] args) + 0x94 bytes mscorlib.dll!System.Threading.Thread.CompleteCrossContextCallback(System.Threading.InternalCrossContextDelegate ftnToCall, object[] args) + 0x8 bytes [Native to Managed Transition] [Managed to Native Transition] mscorlib.dll!System.Runtime.Remoting.Channels.CrossContextChannel.SyncProcessMessage(System.Runtime.Remoting.Messaging.IMessage reqMsg) + 0xa7 bytes mscorlib.dll!System.Runtime.Remoting.Channels.ChannelServices.SyncDispatchMessage(System.Runtime.Remoting.Messaging.IMessage msg) + 0x92 bytes mscorlib.dll!System.Runtime.Remoting.Channels.CrossAppDomainSink.DoDispatch(byte[] reqStmBuff, System.Runtime.Remoting.Messaging.SmuggledMethodCallMessage smuggledMcm, out System.Runtime.Remoting.Messaging.SmuggledMethodReturnMessage smuggledMrm) + 0xed bytes mscorlib.dll!System.Runtime.Remoting.Channels.CrossAppDomainSink.DoTransitionDispatchCallback(object[] args) + 0x8a bytes mscorlib.dll!System.Threading.Thread.CompleteCrossContextCallback(System.Threading.InternalCrossContextDelegate ftnToCall, object[] args) + 0x8 bytes [Appdomain Transition] mscorlib.dll!System.Runtime.Remoting.Channels.CrossAppDomainSink.DoTransitionDispatch(byte[] reqStmBuff, System.Runtime.Remoting.Messaging.SmuggledMethodCallMessage smuggledMcm, out System.Runtime.Remoting.Messaging.SmuggledMethodReturnMessage smuggledMrm) + 0x74 bytes mscorlib.dll!System.Runtime.Remoting.Channels.CrossAppDomainSink.SyncProcessMessage(System.Runtime.Remoting.Messaging.IMessage reqMsg) + 0xa3 bytes mscorlib.dll!System.Runtime.Remoting.Proxies.RemotingProxy.CallProcessMessage(System.Runtime.Remoting.Messaging.IMessageSink ms, System.Runtime.Remoting.Messaging.IMessage reqMsg, System.Runtime.Remoting.Contexts.ArrayWithSize proxySinks, System.Threading.Thread currentThread, System.Runtime.Remoting.Contexts.Context currentContext, bool bSkippingContextChain) + 0x50 bytes mscorlib.dll!System.Runtime.Remoting.Proxies.RemotingProxy.InternalInvoke(System.Runtime.Remoting.Messaging.IMethodCallMessage reqMcmMsg, bool useDispatchMessage, int callType) + 0x1d5 bytes mscorlib.dll!System.Runtime.Remoting.Proxies.RemotingProxy.Invoke(System.Runtime.Remoting.Messaging.IMessage reqMsg) + 0x66 bytes mscorlib.dll!System.Runtime.Remoting.Proxies.RealProxy.PrivateInvoke(ref System.Runtime.Remoting.Proxies.MessageData msgData, int type) + 0xee bytes System.dll!System.Net.NetWebProxyFinder.GetProxies(System.Uri destination, out System.Collections.Generic.IList<string> proxyList) + 0x83 bytes System.dll!System.Net.AutoWebProxyScriptEngine.GetProxies(System.Uri destination, out System.Collections.Generic.IList<string> proxyList, ref int syncStatus) + 0x84 bytes System.dll!System.Net.WebProxy.GetProxiesAuto(System.Uri destination, ref int syncStatus) + 0x2e bytes System.dll!System.Net.ProxyScriptChain.GetNextProxy(out System.Uri proxy) + 0x2e bytes System.dll!System.Net.ProxyChain.ProxyEnumerator.MoveNext() + 0x98 bytes System.dll!System.Net.ServicePointManager.FindServicePoint(System.Uri address, System.Net.IWebProxy proxy, out System.Net.ProxyChain chain, ref System.Net.HttpAbortDelegate abortDelegate, ref int abortState) + 0x120 bytes System.dll!System.Net.HttpWebRequest.FindServicePoint(bool forceFind) + 0xb1 bytes System.dll!System.Net.HttpWebRequest.GetRequestStream(out System.Net.TransportContext context) + 0x247 bytes System.dll!System.Net.HttpWebRequest.GetRequestStream() + 0xe bytes System.Web.Services.dll!System.Web.Services.Protocols.SoapHttpClientProtocol.Invoke(string methodName, object[] parameters) + 0xc0 bytes Gfinet.Config.dll!Gfinet.Config.Service.cfg_webservice.addOrUpdateProperties(string string, int intVal, Gfinet.Config.Service.PropertiesDataM[] propertiesDataMs) + 0xa3 bytes Gfinet.Config.dll!Gfinet.Config.Service.WSServiceImpl.AddOrUpdateProperties(int setId, Gfinet.Config.Service.PropertiesDataM[] properties) + 0x46 bytes [Native to Managed Transition] Gfinet.Config.dll!Gfinet.Config.Service.ServiceAspect.InvocationHandler(object target, System.Reflection.MethodBase method, object[] parameters) + 0x49e bytes Gfinet.Config.dll!Gfinet.Config.DynamicProxy.DynamicProxyImpl.Invoke(System.Runtime.Remoting.Messaging.IMessage message) + 0x110 bytes mscorlib.dll!System.Runtime.Remoting.Proxies.RealProxy.PrivateInvoke(ref System.Runtime.Remoting.Proxies.MessageData msgData, int type) + 0xee bytes Tici.Kraps.Services.dll!Tici.Kraps.Services.Configuration.GFINetConfiguration.StoreElement(string application, string category, string id, string elementValue, bool save) Line 303 + 0x55 bytes C# Tici.Kraps.Services.dll!Tici.Kraps.Services.Configuration.GFINetConfiguration.SaveAllInternal() Line 582 + 0x6e bytes C# Tici.Kraps.Services.dll!Tici.Kraps.Services.Configuration.GFINetConfiguration.SaveAll(bool async) Line 434 + 0x8 bytes C# Tici.Kraps.Services.dll!Tici.Kraps.Services.Configuration.GFINetConfiguration.SaveAll() Line 406 + 0xa bytes C# Tici.Kraps.Services.dll!Tici.Kraps.Services.Container.Persistor.Save() Line 59 + 0xc bytes C# Spark.exe!Tici.Kraps.RibbonShell.OnBtnSaveWorkspaceItemClick(object sender, DevExpress.XtraBars.ItemClickEventArgs e) Line 642 + 0xf bytes C# DevExpress.XtraBars.v11.2.dll!DevExpress.XtraBars.BarItem.OnClick(DevExpress.XtraBars.BarItemLink link) + 0x108 bytes DevExpress.XtraBars.v11.2.dll!DevExpress.XtraBars.BarBaseButtonItem.OnClick(DevExpress.XtraBars.BarItemLink link) + 0x47 bytes DevExpress.XtraBars.v11.2.dll!DevExpress.XtraBars.BarItemLink.OnLinkClick() + 0x245 bytes DevExpress.XtraBars.v11.2.dll!DevExpress.XtraBars.BarItemLink.OnLinkAction(DevExpress.XtraBars.BarLinkAction action, object actionArgs) + 0xb3 bytes DevExpress.XtraBars.v11.2.dll!DevExpress.XtraBars.BarButtonItemLink.OnLinkAction(DevExpress.XtraBars.BarLinkAction action, object actionArgs) + 0x47e bytes DevExpress.XtraBars.v11.2.dll!DevExpress.XtraBars.BarItemLink.OnLinkActionCore(DevExpress.XtraBars.BarLinkAction action, object actionArgs) + 0x82 bytes DevExpress.XtraBars.v11.2.dll!DevExpress.XtraBars.ViewInfo.BarSelectionInfo.ClickLink(DevExpress.XtraBars.BarItemLink link) + 0x85 bytes DevExpress.XtraBars.v11.2.dll!DevExpress.XtraBars.ViewInfo.BarSelectionInfo.UnPressLink(DevExpress.XtraBars.BarItemLink link) + 0x1e5 bytes DevExpress.XtraBars.v11.2.dll!DevExpress.XtraBars.Ribbon.Handler.BaseRibbonHandler.OnUnPressItem(DevExpress.Utils.DXMouseEventArgs e, DevExpress.XtraBars.Ribbon.ViewInfo.RibbonHitInfo hitInfo) + 0xa7 bytes DevExpress.XtraBars.v11.2.dll!DevExpress.XtraBars.Ribbon.Handler.BaseRibbonHandler.OnUnPress(DevExpress.Utils.DXMouseEventArgs e, DevExpress.XtraBars.Ribbon.ViewInfo.RibbonHitInfo hitInfo) + 0x5f bytes DevExpress.XtraBars.v11.2.dll!DevExpress.XtraBars.Ribbon.Handler.BaseRibbonHandler.OnMouseUp(DevExpress.Utils.DXMouseEventArgs e) + 0x19a bytes DevExpress.XtraBars.v11.2.dll!DevExpress.XtraBars.Ribbon.Handler.RibbonHandler.OnMouseUp(DevExpress.Utils.DXMouseEventArgs e) + 0x47 bytes DevExpress.XtraBars.v11.2.dll!DevExpress.XtraBars.Ribbon.RibbonControl.OnMouseUp(System.Windows.Forms.MouseEventArgs e) + 0x95 bytes System.Windows.Forms.dll!System.Windows.Forms.Control.WmMouseUp(ref System.Windows.Forms.Message m, System.Windows.Forms.MouseButtons button, int clicks) + 0x2d1 bytes System.Windows.Forms.dll!System.Windows.Forms.Control.WndProc(ref System.Windows.Forms.Message m) + 0x93a bytes DevExpress.Utils.v11.2.dll!DevExpress.Utils.Controls.ControlBase.WndProc(ref System.Windows.Forms.Message m) + 0x81 bytes DevExpress.XtraBars.v11.2.dll!DevExpress.XtraBars.Ribbon.RibbonControl.WndProc(ref System.Windows.Forms.Message m) + 0x85 bytes System.Windows.Forms.dll!System.Windows.Forms.Control.ControlNativeWindow.OnMessage(ref System.Windows.Forms.Message m) + 0x13 bytes System.Windows.Forms.dll!System.Windows.Forms.Control.ControlNativeWindow.WndProc(ref System.Windows.Forms.Message m) + 0x31 bytes System.Windows.Forms.dll!System.Windows.Forms.NativeWindow.Callback(System.IntPtr hWnd, int msg, System.IntPtr wparam, System.IntPtr lparam) + 0x96 bytes [Native to Managed Transition] [Managed to Native Transition] DevExpress.Utils.v11.2.dll!DevExpress.Utils.Win.Hook.ControlWndHook.WindowProc(System.IntPtr hWnd, int message, System.IntPtr wParam, System.IntPtr lParam) + 0x159 bytes [Native to Managed Transition] [Managed to Native Transition] System.Windows.Forms.dll!System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(System.IntPtr dwComponentID, int reason, int pvLoopData) + 0x287 bytes System.Windows.Forms.dll!System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(int reason, System.Windows.Forms.ApplicationContext context) + 0x16c bytes System.Windows.Forms.dll!System.Windows.Forms.Application.ThreadContext.RunMessageLoop(int reason, System.Windows.Forms.ApplicationContext context) + 0x61 bytes System.Windows.Forms.dll!System.Windows.Forms.Application.Run(System.Windows.Forms.Form mainForm) + 0x31 bytes Tici.Kraps.Services.dll!Tici.Kraps.Services.Container.DefaultApplicationRunner.Run() Line 41 + 0x17 bytes C# Kraps.exe!Tici.Kraps.Program.Main() Line 105 + 0x9 bytes C# [Native to Managed Transition] [Managed to Native Transition] mscorlib.dll!System.AppDomain.ExecuteAssembly(string assemblyFile, System.Security.Policy.Evidence assemblySecurity, string[] args) + 0x6d bytes Microsoft.VisualStudio.HostingProcess.Utilities.dll!Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly() + 0x2a bytes mscorlib.dll!System.Threading.ThreadHelper.ThreadStart_Context(object state) + 0x63 bytes mscorlib.dll!System.Threading.ExecutionContext.Run(System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, object state, bool ignoreSyncCtx) + 0xb0 bytes mscorlib.dll!System.Threading.ExecutionContext.Run(System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, object state) + 0x2c bytes mscorlib.dll!System.Threading.ThreadHelper.ThreadStart() + 0x44 bytes [Native to Managed Transition]

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  • I don't get prices with Amazon Product Advertising API

    - by Xarem
    I try to get prices of an ASIN number with the Amazon Product Advertising API. Code: $artNr = "B003TKSD8E"; $base_url = "http://ecs.amazonaws.de/onca/xml"; $params = array( 'AWSAccessKeyId' => self::API_KEY, 'AssociateTag' => self::API_ASSOCIATE_TAG, 'Version' => "2010-11-01", 'Operation' => "ItemLookup", 'Service' => "AWSECommerceService", 'Condition' => "All", 'IdType' => 'ASIN', 'ItemId' => $artNr); $params['Timestamp'] = gmdate("Y-m-d\TH:i:s.\\0\\0\\0\\Z", time()); $url_parts = array(); foreach(array_keys($params) as $key) $url_parts[] = $key . "=" . str_replace('%7E', '~', rawurlencode($params[$key])); sort($url_parts); $url_string = implode("&", $url_parts); $string_to_sign = "GET\necs.amazonaws.de\n/onca/xml\n" . $url_string; $signature = hash_hmac("sha256", $string_to_sign, self::API_SECRET, TRUE); $signature = urlencode(base64_encode($signature)); $url = $base_url . '?' . $url_string . "&Signature=" . $signature; $response = file_get_contents($url); $parsed_xml = simplexml_load_string($response); I think this should be correct - but I don't get offers in the response: SimpleXMLElement Object ( [OperationRequest] => SimpleXMLElement Object ( [RequestId] => ************************* [Arguments] => SimpleXMLElement Object ( [Argument] => Array ( [0] => SimpleXMLElement Object ( [@attributes] => Array ( [Name] => Condition [Value] => All ) ) [1] => SimpleXMLElement Object ( [@attributes] => Array ( [Name] => Operation [Value] => ItemLookup ) ) [2] => SimpleXMLElement Object ( [@attributes] => Array ( [Name] => Service [Value] => AWSECommerceService ) ) [3] => SimpleXMLElement Object ( [@attributes] => Array ( [Name] => ItemId [Value] => B003TKSD8E ) ) [4] => SimpleXMLElement Object ( [@attributes] => Array ( [Name] => IdType [Value] => ASIN ) ) [5] => SimpleXMLElement Object ( [@attributes] => Array ( [Name] => AWSAccessKeyId [Value] => ************************* ) ) [6] => SimpleXMLElement Object ( [@attributes] => Array ( [Name] => Timestamp [Value] => 2011-11-29T01:32:12.000Z ) ) [7] => SimpleXMLElement Object ( [@attributes] => Array ( [Name] => Signature [Value] => ************************* ) ) [8] => SimpleXMLElement Object ( [@attributes] => Array ( [Name] => AssociateTag [Value] => ************************* ) ) [9] => SimpleXMLElement Object ( [@attributes] => Array ( [Name] => Version [Value] => 2010-11-01 ) ) ) ) [RequestProcessingTime] => 0.0091540000000000 ) [Items] => SimpleXMLElement Object ( [Request] => SimpleXMLElement Object ( [IsValid] => True [ItemLookupRequest] => SimpleXMLElement Object ( [Condition] => All [IdType] => ASIN [ItemId] => B003TKSD8E [ResponseGroup] => Small [VariationPage] => All ) ) [Item] => SimpleXMLElement Object ( [ASIN] => B003TKSD8E [DetailPageURL] => http://www.amazon.de/Apple-iPhone-4-32GB-schwarz/dp/B003TKSD8E%3FSubscriptionId%3DAKIAI6NFQHK2DQIPRUEQ%26tag%3Dbanholzerme-20%26linkCode%3Dxm2%26camp%3D2025%26creative%3D165953%26creativeASIN%3DB003TKSD8E [ItemLinks] => SimpleXMLElement Object ( [ItemLink] => Array ( [0] => SimpleXMLElement Object ( [Description] => Add To Wishlist [URL] => http://www.amazon.de/gp/registry/wishlist/add-item.html%3Fasin.0%3DB003TKSD8E%26SubscriptionId%3DAKIAI6NFQHK2DQIPRUEQ%26tag%3Dbanholzerme-20%26linkCode%3Dxm2%26camp%3D2025%26creative%3D12738%26creativeASIN%3DB003TKSD8E ) [1] => SimpleXMLElement Object ( [Description] => Tell A Friend [URL] => http://www.amazon.de/gp/pdp/taf/B003TKSD8E%3FSubscriptionId%3DAKIAI6NFQHK2DQIPRUEQ%26tag%3Dbanholzerme-20%26linkCode%3Dxm2%26camp%3D2025%26creative%3D12738%26creativeASIN%3DB003TKSD8E ) [2] => SimpleXMLElement Object ( [Description] => All Customer Reviews [URL] => http://www.amazon.de/review/product/B003TKSD8E%3FSubscriptionId%3DAKIAI6NFQHK2DQIPRUEQ%26tag%3Dbanholzerme-20%26linkCode%3Dxm2%26camp%3D2025%26creative%3D12738%26creativeASIN%3DB003TKSD8E ) [3] => SimpleXMLElement Object ( [Description] => All Offers [URL] => http://www.amazon.de/gp/offer-listing/B003TKSD8E%3FSubscriptionId%3DAKIAI6NFQHK2DQIPRUEQ%26tag%3Dbanholzerme-20%26linkCode%3Dxm2%26camp%3D2025%26creative%3D12738%26creativeASIN%3DB003TKSD8E ) ) ) [ItemAttributes] => SimpleXMLElement Object ( [Manufacturer] => Apple Computer [ProductGroup] => CE [Title] => Apple iPhone 4 32GB schwarz ) ) ) ) Can someone please explain me why I don't get any price-information? Thank you very much

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  • How to get javascript object references or reference count?

    - by Tauren
    How to get reference count for an object Is it possible to determine if a javascript object has multiple references to it? Or if it has references besides the one I'm accessing it with? Or even just to get the reference count itself? Can I find this information from javascript itself, or will I need to keep track of my own reference counters. Obviously, there must be at least one reference to it for my code access the object. But what I want to know is if there are any other references to it, or if my code is the only place it is accessed. I'd like to be able to delete the object if nothing else is referencing it. If you know the answer, there is no need to read the rest of this question. Below is just an example to make things more clear. Use Case In my application, I have a Repository object instance called contacts that contains an array of ALL my contacts. There are also multiple Collection object instances, such as friends collection and a coworkers collection. Each collection contains an array with a different set of items from the contacts Repository. Sample Code To make this concept more concrete, consider the code below. Each instance of the Repository object contains a list of all items of a particular type. You might have a repository of Contacts and a separate repository of Events. To keep it simple, you can just get, add, and remove items, and add many via the constructor. var Repository = function(items) { this.items = items || []; } Repository.prototype.get = function(id) { for (var i=0,len=this.items.length; i<len; i++) { if (items[i].id === id) { return this.items[i]; } } } Repository.prototype.add = function(item) { if (toString.call(item) === "[object Array]") { this.items.concat(item); } else { this.items.push(item); } } Repository.prototype.remove = function(id) { for (var i=0,len=this.items.length; i<len; i++) { if (items[i].id === id) { this.removeIndex(i); } } } Repository.prototype.removeIndex = function(index) { if (items[index]) { if (/* items[i] has more than 1 reference to it */) { // Only remove item from repository if nothing else references it this.items.splice(index,1); return; } } } Note the line in remove with the comment. I only want to remove the item from my master repository of objects if no other objects have a reference to the item. Here's Collection: var Collection = function(repo,items) { this.repo = repo; this.items = items || []; } Collection.prototype.remove = function(id) { for (var i=0,len=this.items.length; i<len; i++) { if (items[i].id === id) { // Remove object from this collection this.items.splice(i,1); // Tell repo to remove it (only if no other references to it) repo.removeIndxe(i); return; } } } And then this code uses Repository and Collection: var contactRepo = new Repository([ {id: 1, name: "Joe"}, {id: 2, name: "Jane"}, {id: 3, name: "Tom"}, {id: 4, name: "Jack"}, {id: 5, name: "Sue"} ]); var friends = new Collection( contactRepo, [ contactRepo.get(2), contactRepo.get(4) ] ); var coworkers = new Collection( contactRepo, [ contactRepo.get(1), contactRepo.get(2), contactRepo.get(5) ] ); contactRepo.items; // contains item ids 1, 2, 3, 4, 5 friends.items; // contains item ids 2, 4 coworkers.items; // contains item ids 1, 2, 5 coworkers.remove(2); contactRepo.items; // contains item ids 1, 2, 3, 4, 5 friends.items; // contains item ids 2, 4 coworkers.items; // contains item ids 1, 5 friends.remove(4); contactRepo.items; // contains item ids 1, 2, 3, 5 friends.items; // contains item ids 2 coworkers.items; // contains item ids 1, 5 Notice how coworkers.remove(2) didn't remove id 2 from contactRepo? This is because it was still referenced from friends.items. However, friends.remove(4) causes id 4 to be removed from contactRepo, because no other collection is referring to it. Summary The above is what I want to do. I'm sure there are ways I can do this by keeping track of my own reference counters and such. But if there is a way to do it using javascript's built-in reference management, I'd like to hear about how to use it.

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  • How to implement Cocoa copyWithZone on derived object in MonoMac C#?

    - by Justin Aquadro
    I'm currently porting a small Winforms-based .NET application to use a native Mac front-end with MonoMac. The application has a TreeControl with icons and text, which does not exist out of the box in Cocoa. So far, I've ported almost all of the ImageAndTextCell code in Apple's DragNDrop example: https://developer.apple.com/library/mac/#samplecode/DragNDropOutlineView/Listings/ImageAndTextCell_m.html#//apple_ref/doc/uid/DTS40008831-ImageAndTextCell_m-DontLinkElementID_6, which is assigned to an NSOutlineView as a custom cell. It seems to be working almost perfectly, except that I have not figured out how to properly port the copyWithZone method. Unfortunately, this means the internal copies that NSOutlineView is making do not have the image field, and it leads to the images briefly vanishing during expand and collapse operations. The objective-c code in question is: - (id)copyWithZone:(NSZone *)zone { ImageAndTextCell *cell = (ImageAndTextCell *)[super copyWithZone:zone]; // The image ivar will be directly copied; we need to retain or copy it. cell->image = [image retain]; return cell; } The first line is what's tripping me up, as MonoMac does not expose a copyWithZone method, and I don't know how to otherwise call it. Update Based on current answers and additional research and testing, I've come up with a variety of models for copying an object. static List<ImageAndTextCell> _refPool = new List<ImageAndTextCell>(); // Method 1 static IntPtr selRetain = Selector.GetHandle ("retain"); [Export("copyWithZone:")] public virtual NSObject CopyWithZone(IntPtr zone) { ImageAndTextCell cell = new ImageAndTextCell() { Title = Title, Image = Image, }; Messaging.void_objc_msgSend (cell.Handle, selRetain); return cell; } // Method 2 [Export("copyWithZone:")] public virtual NSObject CopyWithZone(IntPtr zone) { ImageAndTextCell cell = new ImageAndTextCell() { Title = Title, Image = Image, }; _refPool.Add(cell); return cell; } [Export("dealloc")] public void Dealloc () { _refPool.Remove(this); this.Dispose(); } // Method 3 static IntPtr selRetain = Selector.GetHandle ("retain"); [Export("copyWithZone:")] public virtual NSObject CopyWithZone(IntPtr zone) { ImageAndTextCell cell = new ImageAndTextCell() { Title = Title, Image = Image, }; _refPool.Add(cell); Messaging.void_objc_msgSend (cell.Handle, selRetain); return cell; } // Method 4 static IntPtr selRetain = Selector.GetHandle ("retain"); static IntPtr selRetainCount = Selector.GetHandle("retainCount"); [Export("copyWithZone:")] public virtual NSObject CopyWithZone (IntPtr zone) { ImageAndTextCell cell = new ImageAndTextCell () { Title = Title, Image = Image, }; _refPool.Add (cell); Messaging.void_objc_msgSend (cell.Handle, selRetain); return cell; } public void PeriodicCleanup () { List<ImageAndTextCell> markedForDelete = new List<ImageAndTextCell> (); foreach (ImageAndTextCell cell in _refPool) { uint count = Messaging.UInt32_objc_msgSend (cell.Handle, selRetainCount); if (count == 1) markedForDelete.Add (cell); } foreach (ImageAndTextCell cell in markedForDelete) { _refPool.Remove (cell); cell.Dispose (); } } // Method 5 static IntPtr selCopyWithZone = Selector.GetHandle("copyWithZone:"); [Export("copyWithZone:")] public virtual NSObject CopyWithZone(IntPtr zone) { IntPtr copyHandle = Messaging.IntPtr_objc_msgSendSuper_IntPtr(SuperHandle, selCopyWithZone, zone); ImageAndTextCell cell = new ImageAndTextCell(copyHandle) { Image = Image, }; _refPool.Add(cell); return cell; } Method 1: Increases the retain count of the unmanaged object. The unmanaged object will persist persist forever (I think? dealloc never called), and the managed object will be harvested early. Seems to be lose-lose all-around, but runs in practice. Method 2: Saves a reference of the managed object. The unmanaged object is left alone, and dealloc appears to be invoked at a reasonable time by the caller. At this point the managed object is released and disposed. This seems reasonable, but on the downside the base type's dealloc won't be run (I think?) Method 3: Increases the retain count and saves a reference. Unmanaged and managed objects leak forever. Method 4: Extends Method 3 by adding a cleanup function that is run periodically (e.g. during Init of each new ImageAndTextCell object). The cleanup function checks the retain counts of the stored objects. A retain count of 1 means the caller has released it, so we should as well. Should eliminate leaking in theory. Method 5: Attempt to invoke the copyWithZone method on the base type, and then construct a new ImageAndTextView object with the resulting handle. Seems to do the right thing (the base data is cloned). Internally, NSObject bumps the retain count on objects constructed like this, so we also use the PeriodicCleanup function to release these objects when they're no longer used. Based on the above, I believe Method 5 is the best approach since it should be the only one that results in a truly correct copy of the base type data, but I don't know if the approach is inherently dangerous (I am also making some assumptions about the underlying implementation of NSObject). So far nothing bad has happened "yet", but if anyone is able to vet my analysis then I would be more confident going forward.

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  • VPN iptables Forwarding: Net-to-net

    - by Mike Holler
    I've tried to look elsewhere on this site but I couldn't find anything matching this problem. Right now I have an ipsec tunnel open between our local network and a remote network. Currently, the local box running Openswan ipsec with the tunnel open can ping the remote ipsec box and any of the other computers in the remote network. When logged into on of the remote computers, I can ping any box in our local network. That's what works, this is what doesn't: I can't ping any of the remote computers via a local machine that is not the ipsec box. Here's a diagram of our network: [local ipsec box] ----------\ \ [arbitrary local computer] --[local gateway/router] -- [internet] -- [remote ipsec box] -- [arbitrary remote computer] The local ipsec box and the arbitrary local computer have no direct contact, instead they communicate through the gateway/router. The router has been set up to forward requests from local computers for the remote subnet to the ipsec box. This works. The problem is the ipsec box doesn't forward anything. Whenever an arbitrary local computer pings something on the remote subnet, this is the response: [user@localhost ~]# ping 172.16.53.12 PING 172.16.53.12 (172.16.53.12) 56(84) bytes of data. From 10.31.14.16 icmp_seq=1 Destination Host Prohibited From 10.31.14.16 icmp_seq=2 Destination Host Prohibited From 10.31.14.16 icmp_seq=3 Destination Host Prohibited Here's the traceroute: [root@localhost ~]# traceroute 172.16.53.12 traceroute to 172.16.53.12 (172.16.53.12), 30 hops max, 60 byte packets 1 router.address.net (10.31.14.1) 0.374 ms 0.566 ms 0.651 ms 2 10.31.14.16 (10.31.14.16) 2.068 ms 2.081 ms 2.100 ms 3 10.31.14.16 (10.31.14.16) 2.132 ms !X 2.272 ms !X 2.312 ms !X That's the IP for our ipsec box it's reaching, but it's not being forwarded. On the IPSec box I have enabled IP Forwarding in /etc/sysctl.conf net.ipv4.ip_forward = 1 And I have tried to set up IPTables to forward: *filter :INPUT ACCEPT [0:0] :FORWARD ACCEPT [0:0] :OUTPUT ACCEPT [759:71213] -A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT -A INPUT -p icmp -j ACCEPT -A INPUT -i lo -j ACCEPT -A INPUT -p tcp -m state --state NEW -m tcp --dport 22 -j ACCEPT -A INPUT -p tcp -m state --state NEW -m tcp --dport 25 -j ACCEPT -A INPUT -p udp -m state --state NEW -m udp --dport 500 -j ACCEPT -A INPUT -p udp -m state --state NEW -m udp --dport 4500 -j ACCEPT -A INPUT -m policy --dir in --pol ipsec -j ACCEPT -A INPUT -p esp -j ACCEPT -A INPUT -j REJECT --reject-with icmp-host-prohibited -A FORWARD -s 10.31.14.0/24 -d 172.16.53.0/24 -j ACCEPT -A FORWARD -m policy --dir in --pol ipsec -j ACCEPT -A FORWARD -j REJECT --reject-with icmp-host-prohibited COMMIT Am I missing a rule in IPTables? Is there something I forgot? NOTE: All the machines are running CentOS 6.x Edit: Note 2: eth1 is the only network interface on the local ipsec box.

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  • My current iptable configuration doesn't work [on hold]

    - by Brad
    sudo chkconfig iptables off /etc/init.d/iptables on ### Clear/flush iptables sudo iptables -F sudo iptables -P INPUT ACCEPT sudo iptables -P OUTPUT ACCEPT sudo iptables -P FORWARD ACCEPT ### Allow SSH iptables -A INPUT -i eth0 -p tcp --dport 22 -m state --state NEW,ESTABLISHED -j ACCEPT iptables -A OUTPUT -o eth0 -p tcp --sport 22 -m state --state ESTABLISHED -j ACCEPT ### Allow YUM updates sudo iptables -A OUTPUT -o eth0 -p tcp --dport 80 --match owner --uid-owner 0 --state NEW,ESTABLISHED -j ACCEPT sudo iptables -A OUTPUT -o eth0 -p tcp --dport 443 --match owner --uid-owner 0 --state NEW,ESTABLISHED -j ACCEPT ### Add your rules form the link above, here # ftp,smtp,imap,http,https,pop3,imaps,pop3s sudo iptables -A INPUT -i eth0 -p tcp -m multiport --dports 21,25,143,80,443,110,993,995 -m state --state NEW,ESTABLISHED -j ACCEPT sudo iptables -A OUTPUT -o eth0 -p tcp -m multiport --sports 21,25,143,80,110,443,993,995 -m state --state NEW,ESTABLISHED -j ACCEPT ## allow dns sudo iptables -A OUTPUT -p udp -o eth0 --dport 53 -j ACCEPT && sudo iptables -A INPUT -p udp -i eth0 --sport 53 -j ACCEPT # handling pings sudo iptables -A INPUT -p icmp --icmp-type echo-request -j ACCEPT && sudo iptables -A OUTPUT -p icmp --icmp-type echo-reply -j ACCEPT sudo iptables -A OUTPUT -p icmp --icmp-type echo-request -j ACCEPT && sudo iptables -A INPUT -p icmp --icmp-type echo-reply -j ACCEPT # manage ddos attacks sudo iptables -A INPUT -p tcp --dport 80 -m limit --limit 25/minute --limit-burst 100 -j ACCEPT ## Implement some logging so that we know what's getting dropped sudo iptables -N LOGGING sudo iptables -A INPUT -j LOGGING sudo iptables -A LOGGING -m limit --limit 2/min -j LOG --log-prefix "IPTables Packet Dropped: " --log-level 7 sudo iptables -A LOGGING -j DROP # once a rule affects traffic then it is no longer managed # so if the traffic has not been accepted, block it sudo iptables -A INPUT -j DROP sudo iptables -I INPUT 1 -i lo -j ACCEPT sudo iptables -A OUTPUT -j DROP # allow only internal port forwarding sudo iptables -A FORWARD -i eth0 -o eth1 -j ACCEPT sudo iptables -P FORWARD DROP # create an iptables config file sudo iptables-save > /root/dsl.fw ### Append the following to the rc.local file sudo nano /etc/rc.local ####--- /sbin/iptables-restore < sudo /root/dsl.fw ####--- /etc/init.d/iptables save ## check to see if this setting is working great. sudo service iptables restart ## log out/in testing sudo chkconfig iptables on What is the problem with this setup? If I restart the server it doesn't allow me back in SSH, and there may be a problem with Yum Original source of information: https://gist.github.com/Jonathonbyrd/1274837#file-instructions

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  • A Communication System for XAML Applications

    - by psheriff
    In any application, you want to keep the coupling between any two or more objects as loose as possible. Coupling happens when one class contains a property that is used in another class, or uses another class in one of its methods. If you have this situation, then this is called strong or tight coupling. One popular design pattern to help with keeping objects loosely coupled is called the Mediator design pattern. The basics of this pattern are very simple; avoid one object directly talking to another object, and instead use another class to mediate between the two. As with most of my blog posts, the purpose is to introduce you to a simple approach to using a message broker, not all of the fine details. IPDSAMessageBroker Interface As with most implementations of a design pattern, you typically start with an interface or an abstract base class. In this particular instance, an Interface will work just fine. The interface for our Message Broker class just contains a single method “SendMessage” and one event “MessageReceived”. public delegate void MessageReceivedEventHandler( object sender, PDSAMessageBrokerEventArgs e); public interface IPDSAMessageBroker{  void SendMessage(PDSAMessageBrokerMessage msg);   event MessageReceivedEventHandler MessageReceived;} PDSAMessageBrokerMessage Class As you can see in the interface, the SendMessage method requires a type of PDSAMessageBrokerMessage to be passed to it. This class simply has a MessageName which is a ‘string’ type and a MessageBody property which is of the type ‘object’ so you can pass whatever you want in the body. You might pass a string in the body, or a complete Customer object. The MessageName property will help the receiver of the message know what is in the MessageBody property. public class PDSAMessageBrokerMessage{  public PDSAMessageBrokerMessage()  {  }   public PDSAMessageBrokerMessage(string name, object body)  {    MessageName = name;    MessageBody = body;  }   public string MessageName { get; set; }   public object MessageBody { get; set; }} PDSAMessageBrokerEventArgs Class As our message broker class will be raising an event that others can respond to, it is a good idea to create your own event argument class. This class will inherit from the System.EventArgs class and add a couple of additional properties. The properties are the MessageName and Message. The MessageName property is simply a string value. The Message property is a type of a PDSAMessageBrokerMessage class. public class PDSAMessageBrokerEventArgs : EventArgs{  public PDSAMessageBrokerEventArgs()  {  }   public PDSAMessageBrokerEventArgs(string name,     PDSAMessageBrokerMessage msg)  {    MessageName = name;    Message = msg;  }   public string MessageName { get; set; }   public PDSAMessageBrokerMessage Message { get; set; }} PDSAMessageBroker Class Now that you have an interface class and a class to pass a message through an event, it is time to create your actual PDSAMessageBroker class. This class implements the SendMessage method and will also create the event handler for the delegate created in your Interface. public class PDSAMessageBroker : IPDSAMessageBroker{  public void SendMessage(PDSAMessageBrokerMessage msg)  {    PDSAMessageBrokerEventArgs args;     args = new PDSAMessageBrokerEventArgs(      msg.MessageName, msg);     RaiseMessageReceived(args);  }   public event MessageReceivedEventHandler MessageReceived;   protected void RaiseMessageReceived(    PDSAMessageBrokerEventArgs e)  {    if (null != MessageReceived)      MessageReceived(this, e);  }} The SendMessage method will take a PDSAMessageBrokerMessage object as an argument. It then creates an instance of a PDSAMessageBrokerEventArgs class, passing to the constructor two items: the MessageName from the PDSAMessageBrokerMessage object and also the object itself. It may seem a little redundant to pass in the message name when that same message name is part of the message, but it does make consuming the event and checking for the message name a little cleaner – as you will see in the next section. Create a Global Message Broker In your WPF application, create an instance of this message broker class in the App class located in the App.xaml file. Create a public property in the App class and create a new instance of that class in the OnStartUp event procedure as shown in the following code: public partial class App : Application{  public PDSAMessageBroker MessageBroker { get; set; }   protected override void OnStartup(StartupEventArgs e)  {    base.OnStartup(e);     MessageBroker = new PDSAMessageBroker();  }} Sending and Receiving Messages Let’s assume you have a user control that you load into a control on your main window and you want to send a message from that user control to the main window. You might have the main window display a message box, or put a string into a status bar as shown in Figure 1. Figure 1: The main window can receive and send messages The first thing you do in the main window is to hook up an event procedure to the MessageReceived event of the global message broker. This is done in the constructor of the main window: public MainWindow(){  InitializeComponent();   (Application.Current as App).MessageBroker.     MessageReceived += new MessageReceivedEventHandler(       MessageBroker_MessageReceived);} One piece of code you might not be familiar with is accessing a property defined in the App class of your XAML application. Within the App.Xaml file is a class named App that inherits from the Application object. You access the global instance of this App class by using Application.Current. You cast Application.Current to ‘App’ prior to accessing any of the public properties or methods you defined in the App class. Thus, the code (Application.Current as App).MessageBroker, allows you to get at the MessageBroker property defined in the App class. In the MessageReceived event procedure in the main window (shown below) you can now check to see if the MessageName property of the PDSAMessageBrokerEventArgs is equal to “StatusBar” and if it is, then display the message body into the status bar text block control. void MessageBroker_MessageReceived(object sender,   PDSAMessageBrokerEventArgs e){  switch (e.MessageName)  {    case "StatusBar":      tbStatus.Text = e.Message.MessageBody.ToString();      break;  }} In the Page 1 user control’s Loaded event procedure you will send the message “StatusBar” through the global message broker to any listener using the following code: private void UserControl_Loaded(object sender,  RoutedEventArgs e){  // Send Status Message  (Application.Current as App).MessageBroker.    SendMessage(new PDSAMessageBrokerMessage("StatusBar",      "This is Page 1"));} Since the main window is listening for the message ‘StatusBar’, it will display the value “This is Page 1” in the status bar at the bottom of the main window. Sending a Message to a User Control The previous example sent a message from the user control to the main window. You can also send messages from the main window to any listener as well. Remember that the global message broker is really just a broadcaster to anyone who has hooked into the MessageReceived event. In the constructor of the user control named ucPage1 you can hook into the global message broker’s MessageReceived event. You can then listen for any messages that are sent to this control by using a similar switch-case structure like that in the main window. public ucPage1(){  InitializeComponent();   // Hook to the Global Message Broker  (Application.Current as App).MessageBroker.    MessageReceived += new MessageReceivedEventHandler(      MessageBroker_MessageReceived);} void MessageBroker_MessageReceived(object sender,  PDSAMessageBrokerEventArgs e){  // Look for messages intended for Page 1  switch (e.MessageName)  {    case "ForPage1":      MessageBox.Show(e.Message.MessageBody.ToString());      break;  }} Once the ucPage1 user control has been loaded into the main window you can then send a message using the following code: private void btnSendToPage1_Click(object sender,  RoutedEventArgs e){  PDSAMessageBrokerMessage arg =     new PDSAMessageBrokerMessage();   arg.MessageName = "ForPage1";  arg.MessageBody = "Message For Page 1";   // Send a message to Page 1  (Application.Current as App).MessageBroker.SendMessage(arg);} Since the MessageName matches what is in the ucPage1 MessageReceived event procedure, ucPage1 can do anything in response to that event. It is important to note that when the message gets sent it is sent to all MessageReceived event procedures, not just the one that is looking for a message called “ForPage1”. If the user control ucPage1 is not loaded and this message is broadcast, but no other code is listening for it, then it is simply ignored. Remove Event Handler In each class where you add an event handler to the MessageReceived event you need to make sure to remove those event handlers when you are done. Failure to do so can cause a strong reference to the class and thus not allow that object to be garbage collected. In each of your user control’s make sure in the Unloaded event to remove the event handler. private void UserControl_Unloaded(object sender, RoutedEventArgs e){  if (_MessageBroker != null)    _MessageBroker.MessageReceived -=         _MessageBroker_MessageReceived;} Problems with Message Brokering As with most “global” classes or classes that hook up events to other classes, garbage collection is something you need to consider. Just the simple act of hooking up an event procedure to a global event handler creates a reference between your user control and the message broker in the App class. This means that even when your user control is removed from your UI, the class will still be in memory because of the reference to the message broker. This can cause messages to still being handled even though the UI is not being displayed. It is up to you to make sure you remove those event handlers as discussed in the previous section. If you don’t, then the garbage collector cannot release those objects. Instead of using events to send messages from one object to another you might consider registering your objects with a central message broker. This message broker now becomes a collection class into which you pass an object and what messages that object wishes to receive. You do end up with the same problem however. You have to un-register your objects; otherwise they still stay in memory. To alleviate this problem you can look into using the WeakReference class as a method to store your objects so they can be garbage collected if need be. Discussing Weak References is beyond the scope of this post, but you can look this up on the web. Summary In this blog post you learned how to create a simple message broker system that will allow you to send messages from one object to another without having to reference objects directly. This does reduce the coupling between objects in your application. You do need to remember to get rid of any event handlers prior to your objects going out of scope or you run the risk of having memory leaks and events being called even though you can no longer access the object that is responding to that event. NOTE: You can download the sample code for this article by visiting my website at http://www.pdsa.com/downloads. Select “Tips & Tricks”, then select “A Communication System for XAML Applications” from the drop down list.

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  • Metro: Understanding Observables

    - by Stephen.Walther
    The goal of this blog entry is to describe how the Observer Pattern is implemented in the WinJS library. You learn how to create observable objects which trigger notifications automatically when their properties are changed. Observables enable you to keep your user interface and your application data in sync. For example, by taking advantage of observables, you can update your user interface automatically whenever the properties of a product change. Observables are the foundation of declarative binding in the WinJS library. The WinJS library is not the first JavaScript library to include support for observables. For example, both the KnockoutJS library and the Microsoft Ajax Library (now part of the Ajax Control Toolkit) support observables. Creating an Observable Imagine that I have created a product object like this: var product = { name: "Milk", description: "Something to drink", price: 12.33 }; Nothing very exciting about this product. It has three properties named name, description, and price. Now, imagine that I want to be notified automatically whenever any of these properties are changed. In that case, I can create an observable product from my product object like this: var observableProduct = WinJS.Binding.as(product); This line of code creates a new JavaScript object named observableProduct from the existing JavaScript object named product. This new object also has a name, description, and price property. However, unlike the properties of the original product object, the properties of the observable product object trigger notifications when the properties are changed. Each of the properties of the new observable product object has been changed into accessor properties which have both a getter and a setter. For example, the observable product price property looks something like this: price: { get: function () { return this.getProperty(“price”); } set: function (value) { this.setProperty(“price”, value); } } When you read the price property then the getProperty() method is called and when you set the price property then the setProperty() method is called. The getProperty() and setProperty() methods are methods of the observable product object. The observable product object supports the following methods and properties: · addProperty(name, value) – Adds a new property to an observable and notifies any listeners. · backingData – An object which represents the value of each property. · bind(name, action) – Enables you to execute a function when a property changes. · getProperty(name) – Returns the value of a property using the string name of the property. · notify(name, newValue, oldValue) – A private method which executes each function in the _listeners array. · removeProperty(name) – Removes a property and notifies any listeners. · setProperty(name, value) – Updates a property and notifies any listeners. · unbind(name, action) – Enables you to stop executing a function in response to a property change. · updateProperty(name, value) – Updates a property and notifies any listeners. So when you create an observable, you get a new object with the same properties as an existing object. However, when you modify the properties of an observable object, then you can notify any listeners of the observable that the value of a particular property has changed automatically. Imagine that you change the value of the price property like this: observableProduct.price = 2.99; In that case, the following sequence of events is triggered: 1. The price setter calls the setProperty(“price”, 2.99) method 2. The setProperty() method updates the value of the backingData.price property and calls the notify() method 3. The notify() method executes each function in the collection of listeners associated with the price property Creating Observable Listeners If you want to be notified when a property of an observable object is changed, then you need to register a listener. You register a listener by using the bind() method like this: (function () { "use strict"; var app = WinJS.Application; app.onactivated = function (eventObject) { if (eventObject.detail.kind === Windows.ApplicationModel.Activation.ActivationKind.launch) { // Simple product object var product = { name: "Milk", description: "Something to drink", price: 12.33 }; // Create observable product var observableProduct = WinJS.Binding.as(product); // Execute a function when price is changed observableProduct.bind("price", function (newValue) { console.log(newValue); }); // Change the price observableProduct.price = 2.99; } }; app.start(); })(); In the code above, the bind() method is used to associate the price property with a function. When the price property is changed, the function logs the new value of the price property to the Visual Studio JavaScript console. The price property is associated with the function using the following line of code: // Execute a function when price is changed observableProduct.bind("price", function (newValue) { console.log(newValue); }); Coalescing Notifications If you make multiple changes to a property – one change immediately following another – then separate notifications won’t be sent. Instead, any listeners are notified only once. The notifications are coalesced into a single notification. For example, in the following code, the product price property is updated three times. However, only one message is written to the JavaScript console. Only the last value assigned to the price property is written to the JavaScript Console window: // Simple product object var product = { name: "Milk", description: "Something to drink", price: 12.33 }; // Create observable product var observableProduct = WinJS.Binding.as(product); // Execute a function when price is changed observableProduct.bind("price", function (newValue) { console.log(newValue); }); // Change the price observableProduct.price = 3.99; observableProduct.price = 2.99; observableProduct.price = 1.99; Only the last value assigned to price, the value 1.99, appears in the console: If there is a time delay between changes to a property then changes result in different notifications. For example, the following code updates the price property every second: // Simple product object var product = { name: "Milk", description: "Something to drink", price: 12.33 }; // Create observable product var observableProduct = WinJS.Binding.as(product); // Execute a function when price is changed observableProduct.bind("price", function (newValue) { console.log(newValue); }); // Add 1 to price every second window.setInterval(function () { observableProduct.price += 1; }, 1000); In this case, separate notification messages are logged to the JavaScript Console window: If you need to prevent multiple notifications from being coalesced into one then you can take advantage of promises. I discussed WinJS promises in a previous blog entry: http://stephenwalther.com/blog/archive/2012/02/22/windows-web-applications-promises.aspx Because the updateProperty() method returns a promise, you can create different notifications for each change in a property by using the following code: // Change the price observableProduct.updateProperty("price", 3.99) .then(function () { observableProduct.updateProperty("price", 2.99) .then(function () { observableProduct.updateProperty("price", 1.99); }); }); In this case, even though the price is immediately changed from 3.99 to 2.99 to 1.99, separate notifications for each new value of the price property are sent. Bypassing Notifications Normally, if a property of an observable object has listeners and you change the property then the listeners are notified. However, there are certain situations in which you might want to bypass notification. In other words, you might need to change a property value silently without triggering any functions registered for notification. If you want to change a property without triggering notifications then you should change the property by using the backingData property. The following code illustrates how you can change the price property silently: // Simple product object var product = { name: "Milk", description: "Something to drink", price: 12.33 }; // Create observable product var observableProduct = WinJS.Binding.as(product); // Execute a function when price is changed observableProduct.bind("price", function (newValue) { console.log(newValue); }); // Change the price silently observableProduct.backingData.price = 5.99; console.log(observableProduct.price); // Writes 5.99 The price is changed to the value 5.99 by changing the value of backingData.price. Because the observableProduct.price property is not set directly, any listeners associated with the price property are not notified. When you change the value of a property by using the backingData property, the change in the property happens synchronously. However, when you change the value of an observable property directly, the change is always made asynchronously. Summary The goal of this blog entry was to describe observables. In particular, we discussed how to create observables from existing JavaScript objects and bind functions to observable properties. You also learned how notifications are coalesced (and ways to prevent this coalescing). Finally, we discussed how you can use the backingData property to update an observable property without triggering notifications. In the next blog entry, we’ll see how observables are used with declarative binding to display the values of properties in an HTML document.

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  • How to iptables forward ppp0 to eth0

    - by HPHPHP2012
    need your help with get it routing properly. I've server with eth0 (external interface) and eth1(internal interface). eth1 is merged into the bridge br0 (172.16.1.1) I've installed the pptp and successfully configured it, so I got ppp0 interface (192.168.91.1) and got my VPN clients successfully connected. So I need your help to manage how to allow my VPN clients use internet connection (eth0). Below my configuration files, any help is much appreciated! Thank you! P.S. VPN clients are Windows Xp, Windows 7, Mac OS X Lion, Ubuntu 12.04, iOS 5.x cat /etc/pptpd.conf #local server ip address localip 192.168.91.1 #remote addresses remoteip 192.168.91.11-254,192.168.91.10 #translating ip addresses on this interface bcrelay br0 cat /etc/ppp/pptpd-options name pptpd refuse-pap refuse-chap refuse-mschap require-mschap-v2 require-mppe-128 ms-dns 8.8.8.8 ms-dns 8.8.4.4 nodefaultroute lock nobsdcomp auth logfile /var/log/pptpd.log cat /etc/nat-up #!/bin/sh SERVER_IP="aaa.aaa.aaa.aaa" LOCAL_IP="172.16.1.1" #eth0 with public ip PUBLIC="eth0" #br0 is internal bridge on eth1 interface INTERNAL="br0" #vpn VPN="ppp0" #local LOCAL="lo" iptables -F iptables -X iptables -t nat -F iptables -t nat -X iptables -t mangle -F iptables -t mangle -X iptables -P INPUT DROP iptables -P FORWARD DROP iptables -P OUTPUT ACCEPT echo 1 > /proc/sys/net/ipv4/ip_forward iptables -A INPUT -i $LOCAL -j ACCEPT iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT iptables -A INPUT -m state --state NEW ! -i $PUBLIC -j ACCEPT ####CLEAR CONFIG#### #iptables -A FORWARD -i $PUBLIC -o $INTERNAL -m state --state ESTABLISHED,RELATED -j ACCEPT #iptables -A FORWARD -i $PUBLIC -o $INTERNAL -j ACCEPT #iptables -A FORWARD -i $INTERNAL -o $PUBLIC -j ACCEPT #iptables -t nat -A POSTROUTING -j MASQUERADE ####THIS PART IS NOT HANDLING IT#### iptables -A FORWARD -i $PUBLIC -o $VPN -m state --state ESTABLISHED,RELATED -j ACCEPT iptables -A FORWARD -i $PUBLIC -o $VPN -j ACCEPT iptables -A FORWARD -s 192.168.91.0/24 -o $PUBLIC -j ACCEPT iptables -t nat -A POSTROUTING -s 192.168.91.0/24 -o $PUBLIC -j MASQUERADE # VPN - PPTPD iptables -A INPUT -p gre -s 0/0 -j ACCEPT iptables -A OUTPUT -p gre -m state --state RELATED,ESTABLISHED -j ACCEPT iptables -A INPUT -p tcp -s 0/0 --dport 1723 -j ACCEPT #SSH iptables -A INPUT -p tcp --dport 2222 -j ACCEPT iptables -A OUTPUT -p tcp --sport 2222 -j ACCEPT #BLACKLIST BLOCKDB="/etc/ip.blocked" IPS=$(grep -Ev "^#" $BLOCKDB) for i in $IPS do iptables -A INPUT -s $i -j DROP iptables -A OUTPUT -d $i -j DROP done

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  • Should pathfinder in A* hold closedSet and openedSet or each object should hold its sets?

    - by Patryk
    I am about to implement A* pathfinding algorithm and I wonder how should I implement this - from the point of view of architecture. I have the pathfinder as a class - I think I will instantiate only one object of this class (or maybe make it a Singleton - this is not so important). The hardest part for me is whether the closedSet and openedSet should be attached to objects that can find the path for them or should be stored in pathfinder class ? I am opened to any hints and critique whatsoever. What is the best practice considering pathfinding in terms of design ?

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  • Raid 5 mdadm Problem - Help Please

    - by user66260
    My Raid 5 array (4 1tb Disks WD10EARS) had was showing as degraded. I looked and one of the disks wasnt installed, so i re-added it with the mdadm add command. the array is now showing as (null)Array , but cant be mounted if i run: root@warren-P5K-E:/home/warren# sudo mdadm --misc --detail /dev/md0 I get: mdadm: cannot open /dev/md0: No such file or directory and running: root@warren-P5K-E:/home/warren# cat /proc/mdstat gives me: Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10] unused devices: < none > The data is very important root@warren-P5K-E:/home/warren# mdadm --examine /dev/sda /dev/sda: Magic : a92b4efc Version : 0.90.00 UUID : 00000000:00000000:00000000:00000000 Creation Time : Sat May 26 12:08:14 2012 Raid Level : -unknown- Raid Devices : 0 Total Devices : 4 Preferred Minor : 0 Update Time : Sat May 26 12:08:40 2012 State : active Active Devices : 0 Working Devices : 4 Failed Devices : 0 Spare Devices : 4 Checksum : 82d5b792 - correct Events : 1 Number Major Minor RaidDevice State this 1 8 0 1 spare /dev/sda 0 0 8 16 0 spare /dev/sdb 1 1 8 0 1 spare /dev/sda 2 2 8 32 2 spare /dev/sdc 3 3 8 48 3 spare /dev/sdd root@warren-P5K-E:/home/warren# mdadm --examine /dev/sdb /dev/sdb: Magic : a92b4efc Version : 0.90.00 UUID : 00000000:00000000:00000000:00000000 Creation Time : Sat May 26 12:08:14 2012 Raid Level : -unknown- Raid Devices : 0 Total Devices : 4 Preferred Minor : 0 Update Time : Sat May 26 12:08:40 2012 State : active Active Devices : 0 Working Devices : 4 Failed Devices : 0 Spare Devices : 4 Checksum : 82d5b7a0 - correct Events : 1 Number Major Minor RaidDevice State this 0 8 16 0 spare /dev/sdb 0 0 8 16 0 spare /dev/sdb 1 1 8 0 1 spare /dev/sda 2 2 8 32 2 spare /dev/sdc 3 3 8 48 3 spare /dev/sdd root@warren-P5K-E:/home/warren# oot@warren-P5K-E:/home/warren# mdadm --examine /dev/sdc /dev/sdc: Magic : a92b4efc Version : 0.90.00 UUID : 00000000:00000000:00000000:00000000 Creation Time : Sat May 26 12:08:14 2012 Raid Level : -unknown- Raid Devices : 0 Total Devices : 4 Preferred Minor : 0 Update Time : Sat May 26 12:08:40 2012 State : active Active Devices : 0 Working Devices : 4 Failed Devices : 0 Spare Devices : 4 Checksum : 82d5b7b4 - correct Events : 1 Number Major Minor RaidDevice State this 2 8 32 2 spare /dev/sdc 0 0 8 16 0 spare /dev/sdb 1 1 8 0 1 spare /dev/sda 2 2 8 32 2 spare /dev/sdc 3 3 8 48 3 spare /dev/sdd root@warren-P5K-E:/home/warren# mdadm --examine /dev/sdd /dev/sdd: Magic : a92b4efc Version : 0.90.00 UUID : 00000000:00000000:00000000:00000000 Creation Time : Sat May 26 12:08:14 2012 Raid Level : -unknown- Raid Devices : 0 Total Devices : 4 Preferred Minor : 0 Update Time : Sat May 26 12:08:40 2012 State : active Active Devices : 0 Working Devices : 4 Failed Devices : 0 Spare Devices : 4 Checksum : 82d5b7c6 - correct Events : 1 Number Major Minor RaidDevice State this 3 8 48 3 spare /dev/sdd 0 0 8 16 0 spare /dev/sdb 1 1 8 0 1 spare /dev/sda 2 2 8 32 2 spare /dev/sdc 3 3 8 48 3 spare /dev/sdd That on the 4 drives.

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  • Sliding collision response

    - by dbostream
    I have been reading plenty of tutorials about sliding collision responses yet I am not able to implement it properly in my project. What I want to do is make a puck slide along the rounded corner boards of a hockey rink. In my latest attempt the puck does slide along the boards but there are some strange velocity behaviors. First of all the puck slows down a lot pretty much right away and then it slides for awhile and stops before exiting the corner. Even if I double the speed I get a similar behavior and the puck does not make it out of the corner. I used some ideas from this document http://www.peroxide.dk/papers/collision/collision.pdf. This is what I have: Update method called from the game loop when it is time to update the puck (I removed some irrelevant parts). I use two states (current, previous) which are used to interpolate the position during rendering. public override void Update(double fixedTimeStep) { /* Acceleration is set to 0 for now. */ Acceleration.Zero(); PreviousState = CurrentState; _collisionRecursionDepth = 0; CurrentState.Position = SlidingCollision(CurrentState.Position, CurrentState.Velocity * fixedTimeStep + 0.5 * Acceleration * fixedTimeStep * fixedTimeStep); /* Should not this be affected by a sliding collision? and not only the position. */ CurrentState.Velocity = CurrentState.Velocity + Acceleration * fixedTimeStep; Heading = Vector2.NormalizeRet(CurrentState.Velocity); } private Vector2 SlidingCollision(Vector2 position, Vector2 velocity) { if(_collisionRecursionDepth > 5) return position; bool collisionFound = false; Vector2 futurePosition = position + velocity; Vector2 intersectionPoint = new Vector2(); Vector2 intersectionPointNormal = new Vector2(); /* I did not include the collision detection code, if a collision is detected the intersection point and normal in that point is returned. */ if(!collisionFound) return futurePosition; /* If no collision was detected it is safe to move to the future position. */ /* It is not exactly the intersection point, but slightly before. */ Vector2 newPosition = intersectionPoint; /* oldVelocity is set to the distance from the newPosition(intersection point) to the position it had moved to had it not collided. */ Vector2 oldVelocity = futurePosition - newPosition; /* Project the distance left to move along the intersection normal. */ Vector2 newVelocity = oldVelocity - intersectionPointNormal * oldVelocity.DotProduct(intersectionPointNormal); if(newVelocity.LengthSq() < 0.001) return newPosition; /* If almost no speed, no need to continue. */ _collisionRecursionDepth++; return SlidingCollision(newPosition, newVelocity); } What am I doing wrong with the velocity? I have been staring at this for very long so I have gone blind. I have tried different values of recursion depth but it does not seem to make it better. Let me know if you need more information. I appreciate any help. EDIT: A combination of Patrick Hughes' and teodron's answers solved the velocity problem (I think), thanks a lot! This is the new code: I decided to use a separate recursion method now too since I don't want to recalculate the acceleration in each recursion. public override void Update(double fixedTimeStep) { Acceleration.Zero();// = CalculateAcceleration(fixedTimeStep); PreviousState = new MovingEntityState(CurrentState.Position, CurrentState.Velocity); CurrentState = SlidingCollision(CurrentState, fixedTimeStep); Heading = Vector2.NormalizeRet(CurrentState.Velocity); } private MovingEntityState SlidingCollision(MovingEntityState state, double timeStep) { bool collisionFound = false; /* Calculate the next position given no detected collision. */ Vector2 futurePosition = state.Position + state.Velocity * timeStep; Vector2 intersectionPoint = new Vector2(); Vector2 intersectionPointNormal = new Vector2(); /* I did not include the collision detection code, if a collision is detected the intersection point and normal in that point is returned. */ /* If no collision was detected it is safe to move to the future position. */ if (!collisionFound) return new MovingEntityState(futurePosition, state.Velocity); /* Set new position to the intersection point (slightly before). */ Vector2 newPosition = intersectionPoint; /* Project the new velocity along the intersection normal. */ Vector2 newVelocity = state.Velocity - 1.90 * intersectionPointNormal * state.Velocity.DotProduct(intersectionPointNormal); /* Calculate the time of collision. */ double timeOfCollision = Math.Sqrt((newPosition - state.Position).LengthSq() / (futurePosition - state.Position).LengthSq()); /* Calculate new time step, remaining time of full step after the collision * current time step. */ double newTimeStep = timeStep * (1 - timeOfCollision); return SlidingCollision(new MovingEntityState(newPosition, newVelocity), newTimeStep); } Even though the code above seems to slide the puck correctly please have a look at it. I have a few questions, if I don't multiply by 1.90 in the newVelocity calculation it doesn't work (I get a stack overflow when the puck enters the corner because the timeStep decreases very slowly - a collision is found early in every recursion), why is that? what does 1.90 really do and why 1.90? Also I have a new problem, the puck does not move parallell to the short side after exiting the curve; to be more exact it moves outside the rink (I am not checking for any collisions with the short side at the moment). When I perform the collision detection I first check that the puck is in the correct quadrant. For example bottom-right corner is quadrant four i.e. circleCenter.X < puck.X && circleCenter.Y puck.Y is this a problem? or should the short side of the rink be the one to make the puck go parallell to it and not the last collision in the corner? EDIT2: This is the code I use for collision detection, maybe it has something to do with the fact that I can't make the puck slide (-1.0) but only reflect (-2.0): /* Point is the current position (not the predicted one) and quadrant is 4 for the bottom-right corner for example. */ if (GeometryHelper.PointInCircleQuadrant(circleCenter, circleRadius, state.Position, quadrant)) { /* The line is: from = state.Position, to = futurePosition. So a collision is detected when from is inside the circle and to is outside. */ if (GeometryHelper.LineCircleIntersection2d(state.Position, futurePosition, circleCenter, circleRadius, intersectionPoint, quadrant)) { collisionFound = true; /* Set the intersection point to slightly before the real intersection point (I read somewhere this was good to do because of floting point precision, not sure exactly how much though). */ intersectionPoint = intersectionPoint - Vector2.NormalizeRet(state.Velocity) * 0.001; /* Normal at the intersection point. */ intersectionPointNormal = Vector2.NormalizeRet(circleCenter - intersectionPoint) } } When I set the intersection point, if I for example use 0.1 instead of 0.001 the puck travels further before it gets stuck, but for all values I have tried (including 0 - the real intersection point) it gets stuck somewhere (but I necessarily not get a stack overflow). Can something in this part be the cause of my problem? I can see why I get the stack overflow when using -1.0 when calculating the new velocity vector; but not how to solve it. I traced the time steps used in the recursion (initial time step is always 1/60 ~ 0.01666): Recursion depth Time step next recursive call [Start recursion, time step ~ 0.016666] 0 0,000985806527246773 [No collision, stop recursion] [Start recursion, time step ~ 0.016666] 0 0,0149596704364629 1 0,0144883449376379 2 0,0143155612984837 3 0,014224925727213 4 0,0141673917461608 5 0,0141265435314026 6 0,0140953966184117 7 0,0140704653746625 ...and so on. As you can see the collision is detected early in every recursive call which means the next time step decreases very slowly thus the recursion depth gets very big - stack overflow.

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  • How do I resolve "No JSON object could be decoded" on mythbuntu live CD?

    - by Neil
    I have been running a MythTV frontend on my laptop for some time against a MythTV backend installed in Linux Mint 12 on another computer, and everything works fine. Now, I'm trying out the Mythbuntu Live CD (12.04.1 32-bit) on the laptop, to turn it into a dedicated front end. It's connecting to the network just fine, and I can see my server. When I click on the frontend icon on the desktop, it asks me for the security code, which I've verified against mythtv-setup on the server. However, when I test that code, it shows the error message "No JSON object could be decoded". I've looked in the control center to see if there's something else I should be setting up. The message above implies to me that it can't find the server, but I can find no place in the control center to tell it where to find my myth backend, which I find a little odd. Does the live CD not work against a backend server on another machine?

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  • UML class diagram - can aggregated object be part of two aggregated classes?

    - by user970696
    Some sources say that aggregation means that the class owns the object and shares reference. Lets assume an example where a company class holds a list of cars but departments of that company has list of cars used by them. class Department { list<Car> listOfCars; } class Company { list<Car> listOfCars; //initialization of the list } So in UML class diagram, I would do it like this. But I assume this is not allowed because it would imply that both company and department own the objects.. [COMPANY]<>------[CAR] [DEPARTMENT]<>---| //imagine this goes up to the car class

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  • Is there a language or design pattern that allows the *removal* of object behavior or properties in a class hierarchy?

    - by Sebastien Diot
    A well-know shortcoming of traditional class hierarchies is that they are bad when it comes to model the real world. As an example, trying to represent animals species with classes. There are actually several problems when doing that, but one that I never saw a solution to is when a sub-class "looses" a behavior or properties that was defined in a super-class, like a penguin not being able to fly (there are probably better examples, but that's the first one that comes to my mind, having seen "Madagascar 2" recently). On the one hand, you don't want to define for every property and behavior some flag that specifies if it is at all present, and check it every time before accessing that behavior or property. You would just like to say that birds can fly, simply and clearly, in the Bird class. But then it would be nice if one could define "exceptions" afterward, without having to use some horrible hacks everywhere. This often happens when a system has been productive for a while. You suddenly find an "exception" that doesn't fit in the original design at all, and you don't want to change a large portion of your code to accommodate it. So, is there some language or design patterns that can cleanly handle this problem, without requiring major changes to the "super-class", and all the code that uses it? Even if a solution only handle a specific case, several solutions might together form a complete strategy. [EDIT] Forgot about the Liskov Substitution Principle. That is why you can't do it. Assuming you define "traits/interfaces" for all major "feature groups", you can freely implement traits in different branches of the hierarchy, like the Flying trait could be implemented by Birds, and some special kind of squirrels and fish. So my question could amount to "How could I un-implement a trait?" If your super-class is a Java Serializable, you have to be one too, even if there is no way for you to serialize your state, for example if you contained a "Socket". So one way to do it is to always define all your traits in pair from the start: Flying and NotFlying (which would throw UnsupportedOperationExceiption, if not checked against). The Not-trait would not define any new interface, and could be simply checked for. Sounds like a "cheap" solution, in particular if used from the start.

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  • VPN pptp connection Unable to pass through linux iptables

    - by user221844
    I have set up a windows VPN server behind Linux - Ubuntu box that is working as firewall and proxy server. Now I want people from outside to be able to connect to the VPN server, but the connection is not being established and I get on the client an error 619. I have checked the problem on the internet and it seems a firewall issue. what should I do to make the connection established through the firewall? here is below the information about my setup Firewall-External-IF-IP: 172.16.1.100 Firewall-LAN-IF-IP: 192.168.1.1 VPN-Server-IP: 192.168.1.10 and below is my iptables file content: #Generated by iptables-save v1.4.12 on Thu May 29 12:40:18 2014 *filter :INPUT ACCEPT [162000:140437619] :FORWARD ACCEPT [23282:27196133] :OUTPUT ACCEPT [185778:143961739] :LOGGING - [0:0] -A INPUT -p gre -j ACCEPT -A INPUT -s 192.168.1.10/32 -p tcp -m tcp --sport 1723 -j ACCEPT -A INPUT -s 192.168.1.10/32 -p udp -m udp --sport 1723 -j ACCEPT -A FORWARD -s 192.168.1.0/24 -o EXT_IF -j ACCEPT -A FORWARD -s 192.168.1.0/24 -i EXT_IF -m state --state RELATED,ESTABLISHED -j ACCEPT -A FORWARD -d 192.168.1.10/32 -i EXT_IF -o INT_IF -p tcp -m tcp --dport 1723 -m state --state NEW,RELATED,ESTABLISHED -j ACCEPT -A FORWARD -s 192.168.1.10/32 -i INT_IF -o EXT_IF -p tcp -m tcp --sport 1723 -m state --state RELATED,ESTABLISHED -j ACCEPT -A FORWARD -d 192.168.1.10/32 -i EXT_IF -o INT_IF -p gre -m state --state NEW,RELATED,ESTABLISHED -j ACCEPT -A FORWARD -s 192.168.1.10/32 -i INT_IF -o EXT_IF -p gre -m state --state RELATED,ESTABLISHED -j ACCEPT -A OUTPUT -p gre -j ACCEPT -A OUTPUT -d 192.168.1.10/32 -p tcp -m tcp --dport 1723 -j ACCEPT -A OUTPUT -d 192.168.1.10/32 -p udp -m udp --dport 1723 -j ACCEPT COMMIT # Completed on Thu May 29 12:40:18 2014 # Generated by iptables-save v1.4.12 on Thu May 29 12:40:18 2014 *nat :PREROUTING ACCEPT [17865:1053739] :INPUT ACCEPT [5490:357281] :OUTPUT ACCEPT [3723:223677] :POSTROUTING ACCEPT [3726:223870] -A PREROUTING -p tcp -m tcp --dport 80 -j REDIRECT --to-ports 3128 -A PREROUTING -d 172.16.1.100/32 -i EXT_IF -p tcp -m tcp --dport 1723 -j DNAT --to-destination 192.168.1.10 -A PREROUTING -d 172.16.1.100/32 -i EXT_IF -p gre -j DNAT --to-destination 192.168.1.10 -A PREROUTING -i -h -A POSTROUTING -s 192.168.1.0/24 -o EXT_IF -j MASQUERADE COMMIT # Completed on Thu May 29 12:40:18 2014 # Generated by iptables-save v1.4.12 on Thu May 29 12:40:18 2014 *mangle :PREROUTING ACCEPT [22695965:17811993005] :INPUT ACCEPT [13818180:11522330171] :PREROUTING ACCEPT [17865:1053739] :INPUT ACCEPT [5490:357281] :OUTPUT ACCEPT [3723:223677] :POSTROUTING ACCEPT [3726:223870] -A PREROUTING -p tcp -m tcp --dport 80 -j REDIRECT --to-ports 3128 -A PREROUTING -d 172.16.1.100/32 -i EXT_IF -p tcp -m tcp --dport 1723 -j DNAT --to-destination 192.168.1.10 -A PREROUTING -d 172.16.1.100/32 -i EXT_IF -p gre -j DNAT --to-destination 192.168.1.10 -A PREROUTING -i -h -A POSTROUTING -s 192.168.1.0/24 -o EXT_IF -j MASQUERADE COMMIT # Completed on Thu May 29 12:40:18 2014 # Generated by iptables-save v1.4.12 on Thu May 29 12:40:18 2014 *mangle :PREROUTING ACCEPT [22695965:17811993005] :INPUT ACCEPT [13818180:11522330171] :FORWARD ACCEPT [8527694:6271564562] :OUTPUT ACCEPT [14748508:11899678536] :POSTROUTING ACCEPT [23271280:18170828012] COMMIT # Completed on Thu May 29 12:40:18 2014 hope that I find the solution here ....!! :(

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  • Collision Resolution

    - by ultifinitus
    Hey all, I'm making a simple side-scrolling game, and I would appreciate some input! My collision detection system is a simple bounding box detection, so it's really easy to implement. However my collision resolution is ridiculous! Currently I have a little formula like this: if (colliding(firstObject,secondObject)) firstObject.resolve_collision(yAxisOffset); if (colliding(firstObject,secondObject)) firstObject.resolve_collision(xAxisOffset); where yAxisOffset is only set if the first object's previous y position was outside the second object's collision frame, respectively xAxisOffset as well. Now this is working great, in general. However there is a single problem. When I have a stack of objects and I push the first object against that stack, the first object get's "stuck," on the stack. What's I think is happening is the object's collision system checks and resolves for collisions based on creation time, so If I check one axis, then the other, the object will "sink" object directly along the checking axis. This sinking action causes the collision detection routine to think there's a gap between our position and the other object's position, and when I finally check the object that I've already sunk into, my object's position is resolved to it's original position... All this is great, and I'm sure if I bang my head against a wall long enough i'll come up with a working algorithm, but I'd rather not =). So what in the heck do you think I should do? How could I change my collision resolution system to fix this? Here's the program (temporary link, not sure how long it'll last) (notes: arrow keys to navigate, click to drop block, x to jump) I'd appreciate any help you can offer!

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