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  • What's the difference between initializing this structure with these strategies?

    - by mystify
    // the malloc style, which returns a pointer: struct Cat *newCat = malloc(sizeof(struct Cat)); // no malloc...but isn't it actually the same thing? uses memory as well, or not? struct Cat cat = {520.0f, 680.0f, NULL}; Basically, I can get a initialized structure in these two ways. My guess is: It's the same thing, but when I use malloc I also have to free() that. In the second case I don't have to think about memory, because I don't call malloc. Maybe. When should I use the malloc style, and when the other?

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  • iOS Downloading Videos and saving in Application Support folder

    - by Satyam svv
    In my application, i've to download videos around 10 to my application and play accordingly. Each video is around 50 MB. I'm using following code and then after downloading the video, i'm saving it to Application support folder to avoid icloud sync. But the problem is that when downloading the videos its crashing. [NSURLConnection sendAsynchronousRequest:req queue:[[NSOperationQueue alloc] init] completionHandler:^(NSURLResponse *response, NSData *rcvdDat, NSError * err) { . . . } What I'm thinking is that, while downloading the video, it resides in memory and so the total memory occupying by the app is increasing. Finally iOS is making the app to close. I would like to download the video and when ever a stream of data received, write to temp file and when completes move it to application support folder. Can some one help me on how to write it to file and save it at the end? I cannot use 3rd party libraries (unless its small) due to legal issues.

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  • Not seeing Sync Block in Object Layout

    - by bob-bedell
    It's my understanding the all .NET object instances begin with an 8 byte 'object header': a synch block (4 byte pointer into a SynchTableEntry table), and a type handle (4 byte pointer into the types method table). I'm not seeing this in VS 2010 RC's (CLR 4.0) debugger memory windows. Here's a simple class that will generate a 16 byte instance, less the object header. class Program { short myInt = 2; // 4 bytes long myLong = 3; // 8 bytes string myString = "aString"; // 4 byte object reference // 16 byte instance static void Main(string[] args) { new Program(); return; } } An SOS object dump tells me that the total object size is 24 bytes. That makes sense. My 16 byte instance plus an 8 byte object header. !DumpObj 0205b660 Name: Offset_Test.Program MethodTable: 000d383c EEClass: 000d13f8 Size: 24(0x18) bytes File: C:\Users\Bob\Desktop\Offset_Test\Offset_Test\bin\Debug\Offset_Test.exe Fields: MT Field Offset Type VT Attr Value Name 632020fc 4000001 10 System.Int16 1 instance 2 myInt 632050d8 4000002 4 System.Int64 1 instance 3 myLong 631fd2b8 4000003 c System.String 0 instance 0205b678 myString Here's the raw memory: 0x0205B660 000d383c 00000003 00000000 0205b678 00000002 ... And here are some annotations: offset 0 000d383c ;TypeHandle (pointer to MethodTable), 4 bytes offset 4 00000003 00000000 ;myLong, 8 bytes offset 12 0205b678 ;myString, 4 byte reference to address of "myString" on GC Heap offset 16 00000002 ;myInt, 4 bytes My object begins a address 0x0205B660. But I can only account for 20 bytes of it, the type handle and the instance fields. There is no sign of a synch block pointer. The object size is reported as 24 bytes, but the debugger is showing that it only occupies 20 bytes of memory. I'm reading Drill Into .NET Framework Internals to See How the CLR Creates Runtime Objects, and expected the first 4 bytes of my object to be a zeroed synch block pointer, as shown in Figure 8 of that article. Granted, this is an article about CLR 1.1. I'm just wondering if the difference between what I'm seeing and what this early article reports is a change in either the debugger's display of object layout, or in the way the CLR lays out objects in versions later than 1.1. Anyway, can anyone account for my 4 missing bytes?

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  • Entity framework 4 many-to-many insertion?

    - by Saxman
    Hi all, I'm not very familiar with the many-to-many insertion process using Entity Framework 4, POCO. I have a blog with 3 tables: Post, Comment, and Tag. A Post can have many Tags and a Tag can be in many Posts. Here are the Post and Tag models: public class Tag { public int Id { get; set; } [Required] [StringLength(25, ErrorMessage = "Tag name can't exceed 25 characters.")] public string Name { get; set; } public virtual ICollection<Post> Posts { get; set; } } public class Post { public int Id { get; set; } [Required] [StringLength(512, ErrorMessage = "Title can't exceed 512 characters")] public string Title { get; set; } [Required] [AllowHtml] public string Content { get; set; } public string FriendlyUrl { get; set; } public DateTime PostedDate { get; set; } public bool IsActive { get; set; } public virtual ICollection<Comment> Comments { get; set; } public virtual ICollection<Tag> Tags { get; set; } } Now when I'm adding a new post, I'm not sure what would be the right way to do. I'm thinking that I'll have a textbox where I can select multiple tags for that post (this part is already done), in my controller, I will check to see if the tag is already exists or not, if not, then I will insert the new tag. But I'm not even sure based on the models that I've created for EF, will they create a PostsTags table, or they are creating just a Tags and a Posts table and links between the two? How would I insert the new Post and set the tags to that post? Is it just newPost.Tags = Tags (where Tags are the one that got selected, do I even need to check to see if they already exists?), and then something like _post.Add(newPost);? Thanks.

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  • Data Annotations validation Built into model

    - by Josh
    I want to build an object model that automatically wires in validation when I attempt to save an object. I am using DataAnnotations for my validation, and it all works well, but I think my inheritance is whacked. I am looking here for some guidance on a better way to wire in my validation. So, to build in validation I have this interface public interface IValidatable { bool IsValid { get; } ValidationResponse ValidationResults { get; } void Validate(); } Then, I have a base class that all my objects inherit from. I did a class because I wanted to wire in the validation calls automatically. The issue is that the validation has to know the type of the class is it validating. So I use Generics like so. public class CoreObjectBase<T> : IValidatable where T : CoreObjectBase<T> { #region IValidatable Members public virtual bool IsValid { get { // First, check rules that always apply to this type var result = new Validator<T>().Validate((T)this); // return false if any violations occurred return !result.HasViolations; } } public virtual ValidationResponse ValidationResults { get { var result = new Validator<T>().Validate((T)this); return result; } } public virtual void Validate() { // First, check rules that always apply to this type var result = new Validator<T>().Validate((T)this); // throw error if any violations were detected if (result.HasViolations) throw new RulesException(result.Errors); } #endregion } So, I have this circular inheritance statement. My classes look like this then: public class MyClass : CoreObjectBase<MyClass> { } But the problem occurs when I have a more complicated model. Because I can only inherit from one class, when I have a situation where inheritance makes sense I believe the child classes won't have validation on their properties. public class Parent : CoreObjectBase<Parent> { //properties validated } public class Child : Parent { //properties not validated? } I haven't really tested the validation in these cases yet, but I am pretty sure that anything in child with a data annotation on it will not be automatically validated when I call Child.Validate(); due to the way the inheritance is configured. Is there a better way to do this?

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  • Getting set accessor for property in abstract class, not possible?

    - by Lars Udengaard
    Given the class': public abstract class AbstractEntity { public virtual Guid Id { get; private set; } } public class Entity { public virtual Guid Id { get; private set; } } And a PropertyInfo for the property 'Id'. When calling the method: PropertyInfo.GetAccessors() It returns both the get-method and the set-method when the class is not abstract (Entity), but only the get-method when the class is abstract (AbstractEntity). Why is this? And is there another way to get the set-method from a property with a private set?

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  • How to Dispose myClass with Garbage Collecter C#

    - by Ibrahim AKGUN
    Hi, I have a class and got a method that doin so many things in memory and need to be disposed when its jobs done.But i have looked for MSDN for solution.There is an example thats not solved my problem.When my Class is instanced and run this method my memory is getting bigger and bigger.How can i Dispose it when its job done ? Here is my CODES ; class Deneme { public Deneme() { } ~Deneme() { GC.Collect(); GC.SuppressFinalize(this); } public void TestMetodu() { System.Windows.Forms.MessageBox.Show("Test"); // This is my method that doing big jobs :) } } Deneme CCCX = new Deneme(); CCCX.TestMetodu(); CCCX = null; So i cant dispose it with this.

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  • Java: empty ArrayLists in a foor loop

    - by Patrick
    hi, I'm reusing the same ArrayList in a for loop, and I use for loop results = new ArrayList<Integer>(); experts = new ArrayList<Integer>(); output = new ArrayList<String>(); .... to create new ones. I guess this is wrong, because I'm allocating new memory. Is this correct ? If yes, how can I empty them ? Added: another example I'm creating new variables each time I call this method. Is this good practice ? I mean to create new precision, relevantFound.. etc ? Or should I declare them in my class, outside the method to not allocate more and more memory ? public static void computeMAP(ArrayList results, ArrayList experts) { //compute MAP double precision = 0; int relevantFound = 0; double sumprecision = 0; thanks

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  • Is it a problem if i query again and again to SQL Server 2005 and 2000?

    - by learner
    Window app i am constructing is for very low end machines (Celeron with max 128 RAM). From the following two approaches which one is the best (I don't want that application becomes memory hog for low end machines):- Approach One:- Query the database Select GUID from Table1 where DateTime <= @givendate which is returning me more than 300 thousands records (but only one field i.e. GUID - 300 thousands GUIDs). Now running a loop to achieve next process of this software based on GUID. Second Approach:- Query the database Select Top 1 GUID from Table1 where DateTime <= @givendate with top 1 again and again until all 300 thousands records done. It will return me only one GUID at a time, and I can do my next step of operation. What do you suggest which approach will use the less Memory Resources?? (Speed / performance is not the issue here).

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  • Delphi 2010 - Why can't I declare an abstract method with a generic type parameter?

    - by James
    I am trying to do the following in Delphi 2010: TDataConverter = class abstract public function Convert<T>(const AData: T): string; virtual; abstract; end; However, I keep getting the following compiler error: E2533 Virtual, dynamic and message methods cannot have type parameters I don't quite understand the reason why I can't do this. I can do this in C# e.g. public abstract class DataConverter { public abstract string Convert<T>(T data); } Anyone know the reasoning behind this?

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  • how do I download a large file (via HTTP) in .NET

    - by nickcartwright
    I need to download a LARGE file (2GB) over HTTP in a C# console app. Problem is, after about 1.2GB, the app runs out of memory. Here's the code I'm using: WebClient request = new WebClient(); request.Credentials = new NetworkCredential(username, password); byte[] fileData = request.DownloadData(baseURL + fName); As you can see... I'm reading the file directly into memory. I'm pretty sure I could solve this if I were to read the data back from HTTP in chunks and write it to a file on disk. Does anyone know how I could do this?

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  • When should one let an application crash because of an exception in Java (design issue)?

    - by JVerstry
    In most cases, it is possible to catch exceptions in Java, even unchecked ones. But, it is not necessarily possible to do something about it (for example out of memory). For other cases, the issue I am trying to solve is a design principle one. I am trying to set-up a design principle or a set of rules indicating when one should give up on an exceptional situation, even if it is detected in time. The objective is trying to not crash the application as much as possible. Has someone already brainstormed and communicated about this? I am looking for specific generic cases and possible solutions, or thumb-rules. UPDATE Suggestions so far: Stop running if data coherency can be compromised Stop running if data can be deleted Stop running if you can't do anything about it (Out of memory...) Stop running if key service is not available or becomes unavailable and cannot be restarted If application must be stopped, degrade as gracefully as possible Use rollbacks in db transactions Log as much relevant information as you can Notify the developers

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  • WPF Prism deactivate ?

    - by 2Fast4YouBR
    Hi all, I have an problem and would like to know if it is common problem or jsut with me. I am using Wpf with Prism and Unity, all with the pattern MvvM. I am loading a viewModel that has a reference to a dropdown with few items, my idea is that each time that the user click in some place to open the view that has this dropdown is that the dropdown will be shown with diferent values. The problem is that I see is that after I show the view for the first time and after the first DEACTIVATE, when I try to load it again looks like it is already in the memory (was not deactivated/disposed), so as is already in memory, it not call the constructor again of the modelView and the dropdown is shown with tha same old values. public BranchSelectionViewModel(IUnityContainer unityContainer) { this.unityContainer = unityContainer; User user = this.unityContainer.Resolve<User>(); this.branches = new ObservableCollection<Department>(user.Departments .Where(department => department.DepartmentId != user.SelectedDepartment.DepartmentId)); }

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  • C++ enforce conditions on inherited classes

    - by user231536
    I would like to define an abstract base class X and enforce the following: a) every concrete class Y that inherits from X define a constructor Y(int x) b) it should be possible to test whether two Y objects are equal. For a, one not very good solution is to put a pure virtual fromInt method in X which concrete class will have to define. But I cannot enforce construction. For b), I cannot seem to use a pure virtual method in X bool operator == (const X& other) const =0; because in overridden classes this remains undefined. It is not enough to define bool operator == (const Y& other) const { //stuff} because the types don't match. How do I solve these problems?

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  • Shared data in an ASP.NET application

    - by Barguast
    I have a basic ASP.NET application which is used to request data which is stored on disk. This is loaded from files and sent as the response. I want to be able to store the data loaded from these files in memory to reduce the number of reads from disk. All of the requests will be asking for the same data, so it makes sense to have a single cache of in-memory data which is accessible to all requests. What is the best way to create a single accessible object instance which I can use to store and access this cached data? I've looked into HttpApplication, but apparently a new instance of this is created for parallel requests and so it doesn't fit my needs.

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  • Friendness and derived class

    - by ereOn
    Hi, Let's say I have the following class hierarchy: class Base { protected: virtual void foo() = 0; friend class Other; }; class Derived : public Base { protected: void foo() { /* Some implementation */ }; }; class Other { public: void bar() { Derived* a = new Derived(); a->foo(); // Compiler error: foo() is protected within this context }; }; I guess I could change it too a->Base::foo() but since foo() is pure virtual in the Base class, the call will result in calling Derived::foo() anyway. However, the compiler seems to refuse a->foo(). I guess it is logical, but I can't really understand why. Am I missing something ? Can't (shouldn't) it handle this special case ? Thank you.

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  • When machine code is generated from a program how does it translates to hardware level operations ??

    - by user553492
    Like if say the instruction is something like 100010101 1010101 01010101 011101010101. Now how is this translating to an actual job of deleting something from memory? Memory consists of actual physical transistors the HOLD data. What causes them to lose that data is some external signal? I want to know how that signal is generated. Like how some binary numbers change the state of a physical transistor. Is there a level beyond machine code that isn't explicitly visible to a programmer? I have heard of microcode that handle code at hardware level, even below assembly language. But still I pretty much don't understand. Thanks!

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  • Tie destruction of an object (sealed) to destruction of an unmanaged buffer

    - by testtestSO
    I'll explain my situation first: I'm interested of using the Bitmap constructor that takes scan0, stride and format, because I'm decoding tiled images and I'd like to choose my own stride so I can decode the tiles without caring about the bounds in the decoder part. Anyway, the problem is that the documentation says: The caller is responsible for allocating and freeing the block of memory specified by the scan0 parameter. However, the memory should not be released until the related Bitmap is released. I can't release the buffer easily, because the Bitmap is then passed to another class that will eventually destroy it and I don't have control over it. Is there some way (hacky, I know) to tell the GC to also release my buffer when the Bitmap is destroyed? (Also, any alternative solution is welcome).

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  • Force to reimplement a static function in inherit classes

    - by pacopepe
    Hi, I have a program in C++ with plugins (dynamic libs). In the main program, I want to execute a static function to check if i can create a object of this type. An example without dynamic libs (aren't neccesary to understand the problem): #include "libs/parent.h" #include "libs/one.h" #include "libs/two.h" int main(int argc, char * argv[]) { Parent obj; if (One.match(argv[1])) { obj = new One(); else if (Two.match(argv[1])) { obj = new Two(); } Now, i have a interface class named Parent. All plugins inherit from this class. Ideally, I have a virtual static function in Parent named match, and all the plugins need to reimplement this function. The problem with this code is that i can't do a static virtual function in C++, so i don't know how to solve the problem. Sorry for mi english, i did my best

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  • Sequence Number in testing Spring application with JUnit (Hibernating, Spring MVC)

    - by MBK
    I am testing DAO in Spring Application. @RunWith(SpringJUnit4ClassRunner.class) @ContextConfiguration(locations = "classpath:/applicationContext.xml") @TransactionConfiguration(transactionManager = "transactionManager", defaultRollback = true) @Transactional public class CommentDAOImplTest { @Autowired //testing mehods here} The tests are running good. Iam able to add an comment and I also have a defaultRollback property set. So, the added comment will be deleted automatically. happy!..Now the problem is with the sequence number for mcomment. Can I, in any way rollback the seq number? any suggestins on that. I dont want to mess up the sequrnce number. Business requires comment Id to be showed. (I still dont know why). I know in memory db is an option....but I am guessing defaultRollback purpose is to eliminate in memory db testing and mocking. (Just my opinion.)

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  • Doesn't Matlab optimize the following?

    - by kloop
    I have a very long vector 1xr v, and a very long vector w 1xs, and a matrix A rxs, which is sparse (but very big in dimensions). I was expecting the following to be optimized by Matlab so I won't run into trouble with memory: A./(v'*w) but it seems like Matlab is actually trying to generate the full v'*w matrix, because I am running into Out of memory issue. Is there a way to overcome this? Note that there is no need to calculate all v'*w because many values of A are 0. EDIT: If that were possible, one way to do it would be to do A(find(A)) ./ (v'*w)(find(A)); but you can't select a subset of a matrix (v'*w in this case) without first calculating it and putting it in a variable.

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