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  • ID generator with local static variable - thread-safe?

    - by Poseidon
    Will the following piece of code work as expected in a multi-threaded scenario? int getUniqueID() { static int ID=0; return ++ID; } It's not necessary that the IDs to be contiguous - even if it skips a value, it's fine. Can it be said that when this function returns, the value returned will be unique across all threads?

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  • Php static variables across sessions

    - by pistacchio
    Hi, In ASP.NET if I declare a variable (or object) static (or if I make a singleton) I can have it persist across multiple sessions of multiple users (it it registered in a server scope) so that I don't have to initialize it at every request. Is there such a feature in PHP? Thanks

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  • What networking hardware do I need in this situation (Fairpoint [ISP] "E-DIA" connection)?

    - by Tegeril
    Right away you'd probably want to say, "Well just ask Fairpoint." I've done that, a number of times in as many different ways I can phrase it and just keep hitting a brick wall where they will not commit to giving any useful information and instead recommend contracting an outside firm and spending a pile of money. Anyway... I'm trying to help a family member out with an office connection that is being setup. I've managed to scrape tiny details here and there from our discussions with the ISP (Fairpoint in Maine) about what is going to be done and what is going to be needed. This is the connection that is being setup: http://www.fairpoint.com/enterprise/vantagepoint/e-dia/index.jsp Information I have been given: Via this connection I can get IPs across different C blocks if that were necessary (it is not) Fairpoint is bringing hardware with them that they claim simply does the conversion from whatever line is coming in the building to ethernet, they have referred to this as the "Fairpoint Netvanta" which I know suggests a line of products that I have looked up, but some (most? all?) of those seems to handle all the routing that I saw. Fairpoint says that I need to bring my own router to sit behind their device. They have literally declined to even suggest products that have worked for other clients in the past and fall back on "any business router works, not a home router." That alone makes my head spin. Detail and clarity hit a brick wall from there. At one moment I got them to cough up that the router I provide needs to be able to do VPN tunneling but they typically fall back to "not a home router" and I was even given "just a business router, Cisco or something, it'll be $500-$1000". Now I know that VPN tunneling routers exist well below that price point and since this connection is going to one machine, possibly two only via ethernet, my desire to purchase networking hardware that over-delivers what I need is not very high. They are literally setting all this up, have provided no configuration details for after they finish, and expect me to just plunk a $500+ router behind it and cross my fingers or contract out to a third party company. If there were other options available for the location, I would have dropped them in a second, but there aren't. The device that is connected requires a static IP and I'm honestly a bit hazy on the necessity of an additional router behind their device and generally a bit over my head. I presume that the router needs to be able to serve external static IPs to its clients, but I really don't know what is going to show up when they come to do the install. This was originally going to be run via an ADSL bridge modem with a range of static IPs (which is easy and is currently setup properly) but the location is too far from the telco to get speeds that we really want for upload and this is also a connection that needs high availability. Any suggestions would be greatly appreciated (I see a number of options in the Cisco Small Business line and other competitors that aren't going to break the bank…), especially if you've worked with Fairpoint before! Thanks for reading my wall of text.

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  • How to populate a generic list of objects in C# from SQL database

    - by developr
    I am just learning ASP.NET c# and trying to incorporate best practices into my applications. Everything that I read says to layer my applications into DAL, BLL, UI, etc based on separation of concerns. Instead of passing datatables around, I am thinking about using custom objects so that I am loosely coupled to my data layer and can take advantage of intellisense in VS. I assume these objects would be considered DTOs? First, where do these objects reside in my layers? BLL, DAL, other? Second, when populating from SQL, should I loop through a data reader to populate the list or first fill a data table, then loop through the table to populate the list? I know you should close the database connection as soon as possible, but it seems like even more overhead to populate the data table and then loop through that for the list. Third, everything I see these days says use Linq2SQL. I am planning to learn Linq2SQL, but at this time I am working with a legacy database that doesn't have foreign keys setup and I do not have the ability to fix it atm. Also, I want to learn more about c# before I start getting into ORM solutions like nHibernate. At the same time I don't want to type out all the connection and SQL plumbing for every query. Is it ok to use the Enterprise DAAB for now?

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  • qsort on an array of pointers to Objective-C objects

    - by ElBueno
    I have an array of pointers to Objective-C objects. These objects have a sort key associated with them. I'm trying to use qsort to sort the array of pointers to these objects. However, the first time my comparator is called, the first argument points to the first element in my array, but the second argument points to garbage, giving me an EXC_BAD_ACCESS when I try to access its sort key. Here is my code (paraphrased): - (void)foo:(int)numThingies { Thingie **array; array = malloc(sizeof(deck[0])*numThingies); for(int i = 0; i < numThingies; i++) { array[i] = [[Thingie alloc] initWithSortKey:(float)random()/RAND_MAX]; } qsort(array[0], numThingies, sizeof(array[0]), thingieCmp); } int thingieCmp(const void *a, const void *b) { const Thingie *ia = (const Thingie *)a; const Thingie *ib = (const Thingie *)b; if (ia.sortKey > ib.sortKey) return 1; //ib point to garbage, so ib.sortKey produces the EXC_BAD_ACCESS else return -1; } Any ideas why this is happening?

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  • Web Workers - Transferable Objects for JSON

    - by kclem06
    HTML 5 Web workers are very slow when using worker.postMessage on a large JSON object. I'm trying to figure out how to transfer a JSON Object to a web worker - using the 'Transferable Objects' types in Chrome, in order to increase the speed of this. Here is what I'm referring to and appears it should speed this up quite a bit: http://updates.html5rocks.com/2011/12/Transferable-Objects-Lightning-Fast I'm having trouble finding a good example of this (and I don't believe I want to use an ArrayBuffer). Any help would be appreciated. I'm imagining something like this: worker = new Worker('workers.js'); var large_json = {}; for(var i = 0; i < 20000; ++i){ large_json[i] = i; large_json["test" + i] = "string"; }; //How to make this call to use Transfer Objects? Takes approx 2 seconds to serialize this for me currently. worker.webkitPostMessage(large_json);

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  • How to persist objects between requests in PHP

    - by SztupY
    I've been using rails, merb, django and asp.net mvc applications in the past. What they have common (that is relevant to the question) is that they have code that sets up the framework. This usually means creating objects and state that is persisted until the web server is recycled (like setting up routing, or checking which controllers are available, etc). As far as I know PHP is more like a CGI script that gets compiled to some bytecode each time it's run, and after the request it's discarded. Of course you can have sessions, to persist data between requests from the same user, and as I see there are extensions like APC, with which you can persist objects between requests at the server level. My question is: how can one create a PHP application that works like rails and such? I mean an application that on the first requests sets up the framework, then on the 2nd and later requests use the objects that are already set up. Is there some built in caching facility in mod_php? (for example that stores the compiled bytecode of the executed php applications) Or is using APC or some similar extensions the only way to solve this problem? How would you do it? Thanks.

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  • Why aren't my objects sorting with sortedArrayUsingDescriptors?

    - by clozach
    I expected the code below to return the objects in imageSet as a sorted array. Instead, there's no difference in the ordering before and after. NSSortDescriptor *descriptor = [[NSSortDescriptor alloc] initWithKey:@"imageID" ascending:YES]; NSSet *imageSet = collection.images; for (CBImage *image in imageSet) { NSLog(@"imageID in Set: %@",image.imageID); } NSArray *imageArray = [[imageSet allObjects] sortedArrayUsingDescriptors:(descriptor, nil)]; [descriptor release]; for (CBImage *image in imageArray) { NSLog(@"imageID in Array: %@",image.imageID); } Fwiw, CBImage is defined in my core data model. I don't know why sorting on managed objects would work any differently than on "regular" objects, but maybe it matters. As proof that @"imageID" should work as the key for the descriptor, here's what the two log loops above output for one of the sets I'm iterating through: 2010-05-05 00:49:52.876 Cover Browser[38678:207] imageID in Array: 360339 2010-05-05 00:49:52.876 Cover Browser[38678:207] imageID in Array: 360337 2010-05-05 00:49:52.877 Cover Browser[38678:207] imageID in Array: 360338 2010-05-05 00:49:52.878 Cover Browser[38678:207] imageID in Array: 360336 2010-05-05 00:49:52.879 Cover Browser[38678:207] imageID in Array: 360335 ... For extra credit, I'd love to get a general solution to troubleshooting NSSortDescriptor troubles (esp. if it also applies to troubleshooting NSPredicate). The functionality of these things seems totally opaque to me and consequently debugging takes forever.

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  • Advantages/Disadvantages of different implementations for Comparing Objects using .NET

    - by Kevin Crowell
    This questions involves 2 different implementations of essentially the same code. First, using delegate to create a Comparison method that can be used as a parameter when sorting a collection of objects: class Foo { public static Comparison<Foo> BarComparison = delegate(Foo foo1, Foo foo2) { return foo1.Bar.CompareTo(foo2.Bar); }; } I use the above when I want to have a way of sorting a collection of Foo objects in a different way than my CompareTo function offers. For example: List<Foo> fooList = new List<Foo>(); fooList.Sort(BarComparison); Second, using IComparer: public class BarComparer : IComparer<Foo> { public int Compare(Foo foo1, Foo foo2) { return foo1.Bar.CompareTo(foo2.Bar); } } I use the above when I want to do a binary search for a Foo object in a collection of Foo objects. For example: BarComparer comparer = new BarComparer(); List<Foo> fooList = new List<Foo>(); Foo foo = new Foo(); int index = fooList.BinarySearch(foo, comparer); My questions are: What are the advantages and disadvantages of each of these implementations? What are some more ways to take advantage of each of these implementations? Is there a way to combine these implementations in such a way that I do not need to duplicate the code? Can I achieve both a binary search and an alternative collection sort using only 1 of these implementations?

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  • function objects versus function pointers

    - by kumar_m_kiran
    Hi All, I have two questions related to function objects and function pointers, Question : 1 When I read the different uses sort algorithm of STL, I see that the third parameter can be a function objects, below is an example class State { public: //... int population() const; float aveTempF() const; //... }; struct PopLess : public std::binary_function<State,State,bool> { bool operator ()( const State &a, const State &b ) const { return popLess( a, b ); } }; sort( union, union+50, PopLess() ); Question : Now, How does the statement, sort(union, union+50,PopLess()) work? PopLess() must be resolved into something like PopLess tempObject.operator() which would be same as executing the operator () function on a temporary object. I see this as, passing the return value of overloaded operation i.e bool (as in my example) to sort algorithm. So then, How does sort function resolve the third parameter in this case? Question : 2 Question Do we derive any particular advantage of using function objects versus function pointer? If we use below function pointer will it derive any disavantage? inline bool popLess( const State &a, const State &b ) { return a.population() < b.population(); } std::sort( union, union+50, popLess ); // sort by population PS : Both the above references(including example) are from book "C++ Common Knowledge: Essential Intermediate Programming" by "Stephen C. Dewhurst". I was unable to decode the topic content, thus have posted for help. Thanks in advance for your help.

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  • Access cost of dynamically created objects with dynamically allocated members

    - by user343547
    I'm building an application which will have dynamic allocated objects of type A each with a dynamically allocated member (v) similar to the below class class A { int a; int b; int* v; }; where: The memory for v will be allocated in the constructor. v will be allocated once when an object of type A is created and will never need to be resized. The size of v will vary across all instances of A. The application will potentially have a huge number of such objects and mostly need to stream a large number of these objects through the CPU but only need to perform very simple computations on the members variables. Could having v dynamically allocated could mean that an instance of A and its member v are not located together in memory? What tools and techniques can be used to test if this fragmentation is a performance bottleneck? If such fragmentation is a performance issue, are there any techniques that could allow A and v to allocated in a continuous region of memory? Or are there any techniques to aid memory access such as pre-fetching scheme? for example get an object of type A operate on the other member variables whilst pre-fetching v. If the size of v or an acceptable maximum size could be known at compile time would replacing v with a fixed sized array like int v[max_length] lead to better performance? The target platforms are standard desktop machines with x86/AMD64 processors, Windows or Linux OSes and compiled using either GCC or MSVC compilers.

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  • How to keep track of objects for garbage collection

    - by Yman
    May I know what is the proper way to keep track of display objects created and hence allow me to remove it efficiently later, for garbage collection. For example: for(i=0; i<100; i++){ var dobj = new myClass(); //a sprite addChild(dobj); } From what i know, flash's garbage collection will only collect the objects without strong references and event listeners attached to it. Since the var dobj is strongly referenced to the new object created, I will have to "nullify" it too, am I correct? Should I create an array to keep track of all the objects created in the loop such as: var objectList:Array = new Array(); for(i=0; i<100; i++) { var dobj = new myClass(); //a sprite addChild(dobj); objectList.push(dobj); } //remove all children for each (var key in objectList) { removeChild(key as myClass); } Does this allow GC to collect it on sweep?

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  • How to merge objects in php ?

    - by The Devil
    Hey everybody, I'm currently re-writing a class which handles xml files. Depending on the xml file and it's structure I sometimes need to merge objects. Lets say once I have this: <page name="a title"/> And another time I have this: <page name="a title"> <permission>administrator</permission> </page> Before, I needed only the attributes from the "page" element. That's why a lot of my code expects an object containing only the attributes ($loadedXml-attributes()). Now there are xml files in which the <permission> element is required. I did manage to merge the objects (though not as I wanted) but I can't get to access one of them (most probably it's something I'm missing). To merge my objects I used this code: (object) array_merge( (array) $loadedXml->attributes(), (array) $loadedXml->children() ); This is what I get from print_r(): stdClass Object ( [@attributes] => Array ( [name] => a title ) [permission] => Array ( [0] => administrator ) ) So now my question is how to access the @attributes method ? Thanks in advance, The Devil

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  • C# - Advantages/Disadvantages of different implementations for Comparing Objects

    - by Kevin Crowell
    This questions involves 2 different implementations of essentially the same code. First, using delegate to create a Comparison method that can be used as a parameter when sorting a collection of objects: class Foo { public static Comparison<Foo> BarComparison = delegate(Foo foo1, Foo foo2) { return foo1.Bar.CompareTo(foo2.Bar); }; } I use the above when I want to have a way of sorting a collection of Foo objects in a different way than my CompareTo function offers. For example: List<Foo> fooList = new List<Foo>(); fooList.Sort(BarComparison); Second, using IComparer: public class BarComparer : IComparer<Foo> { public int Compare(Foo foo1, Foo foo2) { return foo1.Bar.CompareTo(foo2.Bar); } } I use the above when I want to do a binary search for a Foo object in a collection of Foo objects. For example: BarComparer comparer = new BarComparer(); List<Foo> fooList = new List<Foo>(); Foo foo = new Foo(); int index = fooList.BinarySearch(foo, comparer); My questions are: What are the advantages and disadvantages of each of these implementations? What are some more ways to take advantage of each of these implementations? Is there a way to combine these implementations in such a way that I do not need to duplicate the code? Can I achieve both a binary search and an alternative collection sort using only 1 of these methods?

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  • MVC2 Modelbinder for List of derived objects

    - by user250773
    I want a list of different (derived) object types working with the Default Modelbinder in Asp.net MVC 2. I have the following ViewModel: public class ItemFormModel { [Required(ErrorMessage = "Required Field")] public string Name { get; set; } public string Description { get; set; } [ScaffoldColumn(true)] //public List<Core.Object> Objects { get; set; } public ArrayList Objects { get; set; } } And the list contains objects of diffent derived types, e.g. public class TextObject : Core.Object { public string Text { get; set; } } public class BoolObject : Core.Object { public bool Value { get; set; } } It doesn't matter if I use the List or the ArrayList implementation, everything get's nicely scaffolded in the form, but the modelbinder doesn't resolve the derived object type properties for me when posting back to the ActionResult. What could be a good solution for the Viewmodel structure to get a list of different object types handled? Having an extra list for every object type (e.g. List, List etc.) seems to be not a good solution for me, since this is a lot of overhead both in building the viewmodel and mapping it back to the domain model. Thinking about the other approach of binding all properties in a custom model binder, how can I make use the data annotations approach here (validating required attributes etc.) without a lot of overhead?

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  • Diff/Merge functionality for objects (not files!)

    - by gehho
    I have a collection of objects of the same type, let's call it DataItem. The user can view and edit these items in an editor. It should also be possible to compare and merge different items, i.e. some sort of diff/merge for DataItem instances. The DIFF functionality should compare all (relevant) properties/fields of the items and detect possible differences. The MERGE functionality should then be able to merge two instances by applying selected differences to one of the items. For example (pseudo objects): DataItem1 { DataItem2 { Prop1 = 10 Prop1 = 10 Prop2 = 25 Prop2 = 13 Prop3 = 0 Prop3 = 5 Coll = { 7, 4, 8 } Coll = { 7, 4, 8, 12 } } } Now, the user should be provided with a list of differences (i.e. Prop2, Prop3, and Coll) and he should be able to select which differences he wants to eliminate by assigning the value from one item to the other. He should also be able to choose if he wants to assign the value from DataItem1 to DataItem2 or vice versa. Are there common practices which should be used to implement this functionality? Since the same editor should also provide undo/redo functionality (using the Command pattern), I was thinking about reusing the ICommand implementations because both scenarios basically handle with property assignments, collection changes, and so on... My idea was to create Difference objects with ICommand properties which can be used to perform a merge operation for this specific Difference. Btw: The programming language will be C# with .NET 3.5SP1/4.0. However, I think this is more of a language-independent question. Any design pattern/idea/whatsoever is welcome!

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  • Updating UI objects in windows forms

    - by P a u l
    Pre .net I was using MFC, ON_UPDATE_COMMAND_UI, and the CCmdUI class to update the state of my windows UI. From the older MFC/Win32 reference: Typically, menu items and toolbar buttons have more than one state. For example, a menu item is grayed (dimmed) if it is unavailable in the present context. Menu items can also be checked or unchecked. A toolbar button can also be disabled if unavailable, or it can be checked. Who updates the state of these items as program conditions change? Logically, if a menu item generates a command that is handled by, say, a document, it makes sense to have the document update the menu item. The document probably contains the information on which the update is based. If a command has multiple user-interface objects (perhaps a menu item and a toolbar button), both are routed to the same handler function. This encapsulates your user-interface update code for all of the equivalent user-interface objects in a single place. The framework provides a convenient interface for automatically updating user-interface objects. You can choose to do the updating in some other way, but the interface provided is efficient and easy to use. What is the guidance for .net Windows Forms? I am using an Application.Idle handler in the main form but am not sure this is the best way to do this. About the time I put all my UI updates in the Idle event handler my app started to show some performance problems, and I don't have the metrics to track this down yet. Not sure if it's related.

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