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  • Understanding CLR 2.0 Memory Model

    - by Eloff
    Joe Duffy, gives 6 rules that describe the CLR 2.0+ memory model (it's actual implementation, not any ECMA standard) I'm writing down my attempt at figuring this out, mostly as a way of rubber ducking, but if I make a mistake in my logic, at least someone here will be able to catch it before it causes me grief. Rule 1: Data dependence among loads and stores is never violated. Rule 2: All stores have release semantics, i.e. no load or store may move after one. Rule 3: All volatile loads are acquire, i.e. no load or store may move before one. Rule 4: No loads and stores may ever cross a full-barrier (e.g. Thread.MemoryBarrier, lock acquire, Interlocked.Exchange, Interlocked.CompareExchange, etc.). Rule 5: Loads and stores to the heap may never be introduced. Rule 6: Loads and stores may only be deleted when coalescing adjacent loads and stores from/to the same location. I'm attempting to understand these rules. x = y y = 0 // Cannot move before the previous line according to Rule 1. x = y z = 0 // equates to this sequence of loads and stores before possible re-ordering load y store x load 0 store z Looking at this, it appears that the load 0 can be moved up to before load y, but the stores may not be re-ordered at all. Therefore, if a thread sees z == 0, then it also will see x == y. If y was volatile, then load 0 could not move before load y, otherwise it may. Volatile stores don't seem to have any special properties, no stores can be re-ordered with respect to each other (which is a very strong guarantee!) Full barriers are like a line in the sand which loads and stores can not be moved over. No idea what rule 5 means. I guess rule 6 means if you do: x = y x = z Then it is possible for the CLR to delete both the load to y and the first store to x. x = y z = y // equates to this sequence of loads and stores before possible re-ordering load y store x load y store z // could be re-ordered like this load y load y store x store z // rule 6 applied means this is possible? load y store x // but don't pop y from stack (or first duplicate item on top of stack) store z What if y was volatile? I don't see anything in the rules that prohibits the above optimization from being carried out. This does not violate double-checked locking, because the lock() between the two identical conditions prevents the loads from being moved into adjacent positions, and according to rule 6, that's the only time they can be eliminated. So I think I understand all but rule 5, here. Anyone want to enlighten me (or correct me or add something to any of the above?)

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  • Recursive N-way merge/diff algorithm for directory trees?

    - by BobMcGee
    What algorithms or Java libraries are available to do N-way, recursive diff/merge of directories? I need to be able to generate a list of folder trees that have many identical files, and have subdirectories with many similar files. I want to be able to use 2-way merge operations to quickly remove as much redundancy as possible. Goals: Find pairs of directories that have many similar files between them. Generate short list of directory pairs that can be synchronized with 2-way merge to eliminate duplicates Should operate recursively (there may be nested duplicates of higher-level directories) Run time and storage should be O(n log n) in numbers of directories and files Should be able to use an embedded DB or page to disk for processing more files than fit in memory (100,000+). Optional: generate an ancestry and change-set between folders Optional: sort the merge operations by how many duplicates they can elliminate I know how to use hashes to find duplicate files in roughly O(n) space, but I'm at a loss for how to go from this to finding partially overlapping sets between folders and their children. EDIT: some clarification The tricky part is the difference between "exact same" contents (otherwise hashing file hashes would work) and "similar" (which will not). Basically, I want to feed this algorithm at a set of directories and have it return a set of 2-way merge operations I can perform in order to reduce duplicates as much as possible with as few conflicts possible. It's effectively constructing an ancestry tree showing which folders are derived from each other. The end goal is to let me incorporate a bunch of different folders into one common tree. For example, I may have a folder holding programming projects, and then copy some of its contents to another computer to work on it. Then I might back up and intermediate version to flash drive. Except I may have 8 or 10 different versions, with slightly different organizational structures or folder names. I need to be able to merge them one step at a time, so I can chose how to incorporate changes at each step of the way. This is actually more or less what I intend to do with my utility (bring together a bunch of scattered backups from different points in time). I figure if I can do it right I may as well release it as a small open source util. I think the same tricks might be useful for comparing XML trees though.

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  • multiple definition of inline function

    - by K71993
    Hi, I have gone through some posts related to this topic but was not able to sort out my doubt completly. This might be a very navie question. Code Description I have a header file "inline.h" and two translation unit "main.cpp" and "tran.cpp". Details of code are as below inline.h file details #ifndef __HEADER__ #include <stdio.h> extern inline int func1(void) { return 5; } static inline int func2(void) { return 6; } inline int func3(void) { return 7; } #endif main.c file details are below #define <stdio.h> #include <inline.h> int main(int argc, char *argv[]) { printf("%d\n",func1()); printf("%d\n",func2()); printf("%d\n",func3()); return 0; } tran.cpp file details (Not that the functions are not inline here) #include <stdio.h> int func1(void) { return 500; } int func2(void) { return 600; } int func3(void) { return 700; } Question The above code does not compile in gcc compiler whereas compiles in g++ (Assuming you make changes related to gcc in code like changing the code to .c not using any C++ header files... etc). The error displayed is "duplicate definition of inline function - func3". Can you clarify why this difference is present across compile? When you run the program (g++ compiled) by creating two seperate compilation unit (main.o and tran.o and create an executable a.out), the output obtained is 500 6 700 Why does the compiler pick up the definition of the function which is not inline. Actually since #include is used to "add" the inline definiton I had expected 5,6,7 as the output. My understanding was during compilation since the inline definition is found, the function call would be "replaced" by inline function definition. Can you please tell me in detailed steps the process of compilation and linking which would lead us to 500,6,700 output. I can only understand the output 6. Thanks in advance for valuable input.

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  • In a DDD approach, is this example modelled correctly?

    - by Tag
    Just created an acc on SO to ask this :) Assuming this simplified example: building a web application to manage projects... The application has the following requirements/rules. 1) Users should be able to create projects inserting the project name. 2) Project names cannot be empty. 3) Two projects can't have the same name. I'm using a 4-layered architecture (User Interface, Application, Domain, Infrastructure). On my Application Layer i have the following ProjectService.cs class: public class ProjectService { private IProjectRepository ProjectRepo { get; set; } public ProjectService(IProjectRepository projectRepo) { ProjectRepo = projectRepo; } public void CreateNewProject(string name) { IList<Project> projects = ProjectRepo.GetProjectsByName(name); if (projects.Count > 0) throw new Exception("Project name already exists."); Project project = new Project(name); ProjectRepo.InsertProject(project); } } On my Domain Layer, i have the Project.cs class and the IProjectRepository.cs interface: public class Project { public int ProjectID { get; private set; } public string Name { get; private set; } public Project(string name) { ValidateName(name); Name = name; } private void ValidateName(string name) { if (name == null || name.Equals(string.Empty)) { throw new Exception("Project name cannot be empty or null."); } } } public interface IProjectRepository { void InsertProject(Project project); IList<Project> GetProjectsByName(string projectName); } On my Infrastructure layer, i have the implementation of IProjectRepository which does the actual querying (the code is irrelevant). I don't like two things about this design: 1) I've read that the repository interfaces should be a part of the domain but the implementations should not. That makes no sense to me since i think the domain shouldn't call the repository methods (persistence ignorance), that should be a responsability of the services in the application layer. (Something tells me i'm terribly wrong.) 2) The process of creating a new project involves two validations (not null and not duplicate). In my design above, those two validations are scattered in two different places making it harder (imho) to see whats going on. So, my question is, from a DDD perspective, is this modelled correctly or would you do it in a different way?

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  • Mocking objects with complex Lambda Expressions as parameters

    - by iCe
    Hi there, I´m encountering this problem trying to mock some objects that receive complex lambda expressions in my projects. Mostly with with proxy objects that receive this type of delegate: Func<Tobj, Fun<TParam1, TParam2, TResult>> I have tried to use Moq as well as RhinoMocks to acomplish mocking those types of objects, however both fail. (Moq fails with NotSupportedException, and in RhinoMocks simpy does not satisgy expectation). This is simplified example of what I´m trying to do: I have a Calculator object that does calculations: public class Calculator { public Calculator() { } public int Add(int x, int y) { var result = x + y; return result; } public int Substract(int x, int y) { var result = x - y; return result; } } I need to validate parameters on every method in the Calculator class, so to keep with the Single Responsability principle, I create a validator class. I wire everything up using a Proxy class, that prevents having duplicate code: public class CalculatorProxy : CalculatorExample.ICalculatorProxy { private ILimitsValidator _validator; public CalculatorProxy(Calculator _calc, ILimitsValidator _validator) { this.Calculator = _calc; this._validator = _validator; } public int Operation(Func&lt;Calculator, Func&lt;int, int, int&gt;&gt; operation, int x, int y) { _validator.ValidateArgs(x, y); var calcMethod = operation(this.Calculator); var result = calcMethod(x, y); _validator.ValidateResult(result); return result; } public Calculator Calculator { get; private set; } } Now, I´m testing a component that does use the CalculatorProxy, so I want to mock it, for example using Rhino Mocks: [TestMethod] public void ParserWorksWithCalcultaroProxy() { var calculatorProxyMock = MockRepository.GenerateMock&lt;ICalculatorProxy&gt;(); calculatorProxyMock.Expect(x =&gt; x.Calculator).Return(_calculator); calculatorProxyMock.Expect(x =&gt; x.Operation(c =&gt; c.Add, 2, 2)).Return(4); var mathParser = new MathParser(calculatorProxyMock); mathParser.ProcessExpression("2 + 2"); calculatorProxyMock.VerifyAllExpectations(); } However I cannot get it to work! Any ideas about how this can be done? Thanks a lot!

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  • Wondering about a way to conserve memory in C# using List<> with structs

    - by Michael Ryan
    I'm not even sure how I should phrase this question. I'm passing some CustomStruct objects as parameters to a class method, and storing them in a List. What I'm wondering is if it's possible and more efficient to add multiple references to a particular instance of a CustomStruct if a equivalent instance it found. This is a dummy/example struct: public struct CustomStruct { readonly int _x; readonly int _y; readonly int _w; readonly int _h; readonly Enum _e; } Using the below method, you can pass one, two, or three CustomStruct objects as parameters. In the final method (that takes three parameters), it may be the case that the 3rd and possibly the 2nd will have the same value as the first. List<CustomStruct> _list; public void AddBackground(CustomStruct normal) { AddBackground(normal, normal, normal); } public void AddBackground(CustomStruct normal, CustomStruct hover) { AddBackground(normal, hover, hover); } public void AddBackground(CustomStruct normal, CustomStruct hover, CustomStruct active) { _list = new List<CustomStruct>(3); _list.Add(normal); _list.Add(hover); _list.Add(active); } As the method stands now, I believe it will create new instances of CustomStruct objects, and then adds a reference of each to the List. It is my understanding that if I instead check for equality between normal and hover and (if equal) insert normal again in place of hover, when the method completes, hover will lose all references and eventually be garbage collected, whereas normal will have two references in the List. The same could be done for active. That would be better, right? The CustomStruct is a ValueType, and therefore one instance would remain on the Stack, and the three List references would just point to it. The overall List size is determined not by the object Type is contains, but by its Capacity. By eliminating the "duplicate" CustomStuct objects, you allow them to be cleaned up. When the CustomStruct objects are passed to these methods, new instances are created each time. When the structs are added to the List, is another copy made? For example, if i pass just one CustomStruct, AddBackground(normal) creates a copy of the original variable, and then passes it three times to Addbackground(normal, hover, active). In this method, three copies are made of the original copy. When the three local variables are added to the List using Add(), are additional copies created inside Add(), and does that defeat the purpose of any equality checks as previously mentioned? Am I missing anything here?

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  • Moving MVC2 Helpers to MVC3 razor view engine

    - by Dai Bok
    Hi, In my MVC 2 site, I have an html helper, that I use to add javascripts for my pages. In my master page I have the main javascripts I want to include, and then in the aspx pages, I include page specific javascripts. So for example, my Site.Master has something like this: .... <head> <%=html.renderScripts() %> </head> ... //core scripts for main page <%html.AddScript("/scripts/jquery.js") %> <%html.AddScript("/scripts/myLib.js") %> .... Then in the child aspx page, I may also want to include other scripts. ... //the page specific script I want to use <% html.AddScript("/scripts/register.aspx.js") %> ... So when the full page gets rendered the javascript files are all collected and rendered in the head by sitemaster placeholder function RenderScripts. This works fine. Now with MVC 3 and razor view engine, they layout pages behave differently, because now my page level javascripts are not rendered/included. Now all I see the LayoutMaster contents. How do I get the solution wo workwith MVC 3 and the razor view engine. (The helper has already been re-written to return a HTMLString ;-)) For reference: my MasterLayout looks like this: ... ... <head> @{ Html.AddJavaScript("/Scripts/jQuery.js"); Html.AddJavaScript("/Scripts/myLib.js"); } //Render scripts @html.RenderScripts() </head> .... and the child page looks like this: @{ Layout = "~/Views/Shared/MasterLayout.cshtml"; ViewBag.Title = "Child Page"; Html.AddJavaScript("/Scripts/register.aspx.js"); } .... <div>some html </div> Thanks for your help. Edit = Just to explain, if this question is not clear enough. When producing a "page" I collect all the javascript files the designers want to use, by using the html.addJavascript("filename.js") and store these in a dictionary - (1) stops people adding duplicate js files - then finally when the page is ready to render, I write out all the javascript files neatly in the header. (2) - this helper helps keep JS in one place, and prevents designers from adding javascript files all over the place. This used to work fine with Master/SiteMaster Pages in mvc 2. but how can I achieve this with razor?

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  • Sorting based on existing elements in xslt

    - by Teelo
    Hi , I want to sort in xslt based on existing set of pattern . Let me explain with the code: <Types> <Type> <Names> <Name>Ryan</Name> </Names> <Address>2344</Address> </Type> <Type> <Names> </Name>Timber</Name> </Names> <Address>1234</Address> </Type> <Type> <Names> </Name>Bryan</Name> </Names> <Address>34</Address> </Type> </Types> Right now I m just calling it and getting it like (all hyperlinks) Ryan Timber Bryan Now I don't want sorting on name but I have existing pattern how I want it to get displayed.Like Timber Bryan Ryan (Also I don't want to lose the url attached to my names earlier while doing this) I was thinking of putting earlier value in some array and sort based on the other array where I will store my existing pattern. But I am not sure how to achieve that.. My xslt looks like this now(there can be duplicate names also) <xsl:for-each select="/Types/Type/Names/Name/text()[generate-id()=generate-id(key('Name',.)[1])]"> <xsl:call-template name="typename"> </xsl:call-template> </xsl:for-each> <xsl:template name="typename"> <li> <a href="somelogicforurl"> <xsl:value-of select="."/> </a> </li> </xsl:template> I am using xsl 1.0

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  • Python: Script works, but seems to deadlock after some time

    - by sberry2A
    I have the following script, which is working for the most part Link to PasteBin The script's job is to start a number of threads which in turn each start a subprocess with Popen. The output from each subprocess is as follows: 1 2 3 . . . n Done Bascially the subprocess is transferring 10M records from tables in one database to different tables in another db with a lot of data massaging/manipulation in between because of the different schemas. If the subprocess fails at any time in it's execution (bad records, duplicate primary keys, etc), or it completes successfully, it will output "Done\n". If there are no more records to select against for transfer then it will output "NO DATA\n" My intent was to create my script "tableTransfer.py" which would spawn a number of these processes, read their output, and in turn output information such as number of updates completed, time remaining, time elapsed, and number of transfers per second. I started running the process last night and checked in this morning to see it had deadlocked. There were not subprocceses running, there are still records to be updated, and the script had not exited. It was simply sitting there, no longer outputting the current information because no subprocces were running to update the total number complete which is what controls updates to the output. This is running on OS X. I am looking for three things: I would like to get rid of the possibility of this deadlock occurring so I don't need to check in on it as frequently. Is there some issue with locking? Am I doing this in a bad way (gThreading variable to control looping of spawning additional thread... etc.) I would appreciate some suggestions for improving my overall methodology. How should I handle ctrl-c exit? Right now I need to kill the process, but assume I should be able to use the signal module or other to catch the signal and kill the threads, is that right? I am not sure whether I should be pasting my entire script here, since I usually just paste snippets. Let me know if I should paste it here as well.

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  • "Unable to find any mappings for the given content, keyPath=null" RestKit 0.2

    - by abisson
    So I switched to using RestKit 0.2 and CoreData and I've been having a lot of trouble trying to get the mappings correct... I don't understand why. The JSON Response of my server is like this: { "meta": { "limit": 20, "next": null, "offset": 0, "previous": null, "total_count": 2 }, "objects": [{ "creation_date": "2012-10-15T20:16:47", "description": "", "id": 1, "last_modified": "2012-10-15T20:16:47", "order": 1, "other_names": "", "primary_name": "Mixing", "production_line": "/api/rest/productionlines/1/", "resource_uri": "/api/rest/cells/1/" }, { "creation_date": "2012-10-15T20:16:47", "description": "", "id": 2, "last_modified": "2012-10-15T20:16:47", "order": 2, "other_names": "", "primary_name": "Packaging", "production_line": "/api/rest/productionlines/1/", "resource_uri": "/api/rest/cells/2/" }] } Then in XCode I have: RKObjectManager *objectManager = [RKObjectManager sharedManager]; [AFNetworkActivityIndicatorManager sharedManager].enabled = YES; NSManagedObjectModel *managedObjectModel = [NSManagedObjectModel mergedModelFromBundles:nil]; RKManagedObjectStore *managedObjectStore = [[RKManagedObjectStore alloc] initWithManagedObjectModel:managedObjectModel]; objectManager.managedObjectStore = managedObjectStore; RKEntityMapping *cellMapping = [RKEntityMapping mappingForEntityForName:@"Cell" inManagedObjectStore:managedObjectStore]; cellMapping.primaryKeyAttribute = @"identifier"; [cellMapping addAttributeMappingsFromDictionary:@{ @"id": @"identifier", @"primary_name": @"primaryName", }]; RKResponseDescriptor *responseCell = [RKResponseDescriptor responseDescriptorWithMapping:cellMapping pathPattern:@"/api/rest/cells/?format=json" keyPath:@"objects" statusCodes:RKStatusCodeIndexSetForClass(RKStatusCodeClassSuccessful)]; [objectManager addResponseDescriptorsFromArray:@[responseCell, responseUser, responseCompany]]; [managedObjectStore createPersistentStoreCoordinator]; NSString *storePath = [RKApplicationDataDirectory() stringByAppendingPathComponent:@"AppDB.sqlite"]; NSString *seedPath = [[NSBundle mainBundle] pathForResource:@"SeedDatabase" ofType:@"sqlite"]; NSError *error; NSPersistentStore *persistentStore = [managedObjectStore addSQLitePersistentStoreAtPath:storePath fromSeedDatabaseAtPath:seedPath withConfiguration:nil options:nil error:&error]; NSAssert(persistentStore, @"Failed to add persistent store with error: %@", error); // Create the managed object contexts [managedObjectStore createManagedObjectContexts]; // Configure a managed object cache to ensure we do not create duplicate objects managedObjectStore.managedObjectCache = [[RKInMemoryManagedObjectCache alloc] initWithManagedObjectContext:managedObjectStore.persistentStoreManagedObjectContext]; My request is: [[RKObjectManager sharedManager] getObjectsAtPath:@"/api/rest/cells/?format=json" parameters:nil success:^(RKObjectRequestOperation *operation, RKMappingResult *mappingResult) { RKLogInfo(@"Load complete: Table should refresh..."); [[NSUserDefaults standardUserDefaults] setObject:[NSDate date] forKey:@"LastUpdatedAt"]; [[NSUserDefaults standardUserDefaults] synchronize]; } failure:^(RKObjectRequestOperation *operation, NSError *error) { RKLogError(@"Load failed with error: %@", error); }]; And I always get the following error: **Error Domain=org.restkit.RestKit.ErrorDomain Code=1001 "Unable to find any mappings for the given content" UserInfo=0x1102d500 {DetailedErrors=(), NSLocalizedDescription=Unable to find any mappings for the given content, keyPath=null}** Thanks a lot!

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  • How and why do I set up a C# build machine?

    - by mmr
    Hi all, I'm working with a small (4 person) development team on a C# project. I've proposed setting up a build machine which will do nightly builds and tests of the project, because I understand that this is a Good Thing. Trouble is, we don't have a whole lot of budget here, so I have to justify the expense to the powers that be. So I want to know: What kind of tools/licenses will I need? Right now, we use Visual Studio and Smart Assembly to build, and Perforce for source control. Will I need something else, or is there an equivalent of a cron job for running automated scripts? What, exactly, will this get me, other than an indication of a broken build? Should I set up test projects in this solution (sln file) that will be run by these scripts, so I can have particular functions tested? We have, at the moment, two such tests, because we haven't had the time (or frankly, the experience) to make good unit tests. What kind of hardware will I need for this? Once a build has been finished and tested, is it a common practice to put that build up on an ftp site or have some other way for internal access? The idea is that this machine makes the build, and we all go to it, but can make debug builds if we have to. How often should we make this kind of build? How is space managed? If we make nightly builds, should we keep around all the old builds, or start to ditch them after about a week or so? Is there anything else I'm not seeing here? I realize that this is a very large topic, and I'm just starting out. I couldn't find a duplicate of this question here, and if there's a book out there I should just get, please let me know. EDIT: I finally got it to work! Hudson is completely fantastic, and FxCop is showing that some features we thought were implemented were actually incomplete. We also had to change the installer type from Old-And-Busted vdproj to New Hotness WiX. Basically, for those who are paying attention, if you can run your build from the command line, then you can put it into hudson. Making the build run from the command line via MSBuild is a useful exercise in itself, because it forces your tools to be current.

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  • Who calls the Destructor of the class when operator delete is used in multiple inheritance.

    - by dicaprio-leonard
    This question may sound too silly, however , I don't find concrete answer any where else. With little knowledge on how late binding works and virtual keyword used in inheritance. As in the code sample, when in case of inheritance where a base class pointer pointing to a derived class object created on heap and delete operator is used to deallocate the memory , the destructor of the of the derived and base will be called in order only when the base destructor is declared virtual function. Now my question is : 1) When the destructor of base is not virtual, why the problem of not calling derived dtor occur only when in case of using "delete" operator , why not in the case given below: derived drvd; base *bPtr; bPtr = &drvd; //DTOR called in proper order when goes out of scope. 2) When "delete" operator is used, who is reponsible to call the destructor of the class? The operator delete will have an implementation to call the DTOR ? or complier writes some extra stuff ? If the operator has the implementation then how does it looks like , [I need sample code how this would have been implemented]. 3) If virtual keyword is used in this example, how does operator delete now know which DTOR to call? Fundamentaly i want to know who calls the dtor of the class when delete is used. Sample Code class base { public: base() { cout<<"Base CTOR called"<<endl; } virtual ~base() { cout<<"Base DTOR called"<<endl; } }; class derived:public base { public: derived() { cout<<"Derived CTOR called"<<endl; } ~derived() { cout<<"Derived DTOR called"<<endl; } }; I'm not sure if this is a duplicate, I couldn't find in search. int main() { base *bPtr = new derived(); delete bPtr;// only when you explicitly try to delete an object return 0; }

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  • How to manage multiple versions of the same record

    - by Darvis Lombardo
    I am doing short-term contract work for a company that is trying to implement a check-in/check-out type of workflow for their database records. Here's how it should work... 1) A user creates a new entity within the application. There are about 20 related tables that will be populated in addition to the main entity table. 2) Once the entity is created the user will mark it as the master. 3) Another user can make changes to the master only by "checking out" the entity. Multiple users can checkout the entity at the same time. 4) Once the user has made all the necessary changes to the entity, they put it in a "needs approval" status. 5) After an authorized user reviews the entity, they can promote it to master which will put the original record in a tombstoned status. The way they are currently accomplishing the "check out" is by duplicating the entity records in all the tables. The primary keys include EntityID + EntityDate, so they duplicate the entity records in all related tables with the same EntityID and an updated EntityDate and give it a status of "checked out". When the record is put into the next state (needs approval), the duplication occurs again. Eventually it will be promoted to master at which time the final record is marked as master and the original master is marked as dead. This design seems hideous to me, but I understand why they've done it. When someone looks up an entity from within the application, they need to see all current versions of that entity. This was a very straightforward way for making that happen. But the fact that they are representing the same entity multiple times within the same table(s) doesn't sit well with me, nor does the fact that they are duplicating EVERY piece of data rather than only storing deltas. I would be interested in hearing your reaction to the design, whether positive or negative. I would also be grateful for any resoures you can point me to that might be useful for seeing how someone else has implemented such a mechanism. Thanks! Darvis

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  • C++0x Overload on reference, versus sole pass-by-value + std::move?

    - by dean
    It seems the main advice concerning C++0x's rvalues is to add move constructors and move operators to your classes, until compilers default-implement them. But waiting is a losing strategy if you use VC10, because automatic generation probably won't be here until VC10 SP1, or in worst case, VC11. Likely, the wait for this will be measured in years. Here lies my problem. Writing all this duplicate code is not fun. And it's unpleasant to look at. But this is a burden well received, for those classes deemed slow. Not so for the hundreds, if not thousands, of smaller classes. ::sighs:: C++0x was supposed to let me write less code, not more! And then I had a thought. Shared by many, I would guess. Why not just pass everything by value? Won't std::move + copy elision make this nearly optimal? Example 1 - Typical Pre-0x constructor OurClass::OurClass(const SomeClass& obj) : obj(obj) {} SomeClass o; OurClass(o); // single copy OurClass(std::move(o)); // single copy OurClass(SomeClass()); // single copy Cons: A wasted copy for rvalues. Example 2 - Recommended C++0x? OurClass::OurClass(const SomeClass& obj) : obj(obj) {} OurClass::OurClass(SomeClass&& obj) : obj(std::move(obj)) {} SomeClass o; OurClass(o); // single copy OurClass(std::move(o)); // zero copies, one move OurClass(SomeClass()); // zero copies, one move Pros: Presumably the fastest. Cons: Lots of code! Example 3 - Pass-by-value + std::move OurClass::OurClass(SomeClass obj) : obj(std::move(obj)) {} SomeClass o; OurClass(o); // single copy, one move OurClass(std::move(o)); // zero copies, two moves OurClass(SomeClass()); // zero copies, one move Pros: No additional code. Cons: A wasted move in cases 1 & 2. Performance will suffer greatly if SomeClass has no move constructor. What do you think? Is this correct? Is the incurred move a generally acceptable loss when compared to the benefit of code reduction?

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  • How to create 2 different scripts for 2 browsers (IE+all the rest)

    - by Barnabas Nagy
    I'm trying to solve an IE CSS issue by using conditional tags. My jQuery that does the job of tabbed box effect calls an id that is inside the conditional tags. I've given new ids to IE so on IE the jQuery is not working. I tried to duplicate the script with the new id in one of the script but the 2 scripts seems to get in conflict. My jQuery (in between the head tags) is (for all all browsers except IE): <script> var currentTab = 0; // Set to a different number to start on a different tab. function openTab(clickedTab) { var thisTab = $(".tabbed-box .tabs a").index(clickedTab); $(".tabbed-box .tabs li a").removeClass("active"); $(".tabbed-box .tabs li a:eq("+thisTab+")").addClass("active"); $(".tabbed-box .tabbed-content").hide(); $(".tabbed-box .tabbed-content:eq("+thisTab+")").show(); currentTab = thisTab; } $(document).ready(function() { $(".tabs li:eq(0) a").css("border-left", "none"); $(".tabbed-box .tabs li a").click(function() { openTab($(this)); return false; }); $(".tabbed-box .tabs li a:eq("+currentTab+")").click() }); </script> And I would need this for IE: <script> var currentTab = 0; // Set to a different number to start on a different tab. function openTab(clickedTab) { var thisTab = $(".tabbed-box .tabs a").index(clickedTab); $(".tabbed-box ie-.tabs li a").removeClass("active"); $(".tabbed-box ie-.tabs li a:eq("+thisTab+")").addClass("active"); $(".tabbed-box .tabbed-content").hide(); $(".tabbed-box .tabbed-content:eq("+thisTab+")").show(); currentTab = thisTab; } $(document).ready(function() { $(".ie-tabs li:eq(0) a").css("border-left", "none"); $(".tabbed-box .ie-tabs li a").click(function() { openTab($(this)); return false; }); $(".tabbed-box .ie-tabs li a:eq("+currentTab+")").click() }); </script> Having the 2 scripts in the head conflicts with each other. Maybe there is a way to combine them?

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  • What are the weaknesses of this user authentication method?

    - by byronh
    I'm developing my own PHP framework. It seems all the security articles I have read use vastly different methods for user authentication than I do so I could use some help in finding security holes. Some information that might be useful before I start. I use mod_rewrite for my MVC url's. Passwords are sha1 and md5 encrypted with 24 character salt unique to each user. mysql_real_escape_string and/or variable typecasting on everything going in, and htmlspecialchars on everything coming out. Step-by step process: Top of every page: session_start(); session_regenerate_id(); If user logs in via login form, generate new random token to put in user's MySQL row. Hash is generated based on user's salt (from when they first registered) and the new token. Store the hash and plaintext username in session variables, and duplicate in cookies if 'Remember me' is checked. On every page, check for cookies. If cookies set, copy their values into session variables. Then compare $_SESSION['name'] and $_SESSION['hash'] against MySQL database. Destroy all cookies and session variables if they don't match so they have to log in again. If login is valid, some of the user's information from the MySQL database is stored in an array for easy access. So far, I've assumed that this array is clean so when limiting user access I refer to user.rank and deny access if it's below what's required for that page. I've tried to test all the common attacks like XSS and CSRF, but maybe I'm just not good enough at hacking my own site! My system seems way too simple for it to actually be secure (the security code is only 100 lines long). What am I missing? I've also spent alot of time searching for the vulnerabilities with mysql_real_escape string but I haven't found any information that is up-to-date (everything is from several years ago at least and has apparently been fixed). All I know is that the problem was something to do with encoding. If that problem still exists today, how can I avoid it? Any help will be much appreciated.

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  • Detecting abuse for post rating system

    - by Steven smethurst
    I am using a wordpress plugin called "GD Star Rating" to allow my users to vote on stories that I post to one of my websites. http://everydayfiction.com/ Recently we have been having a lot of abuse of the system. Stories that have obviously been voted up artificially. "GD Star Rating" creates some detailed logs when a user votes on a story. Including; IP, Time of vote, and user_adgent, ect.. For example this story has 181 votes with an average of 5.7 http://www.everydayfiction.com/snowman-by-shaun-simon/ Most other stories only get around ~40 votes each day. At first I thought that the story got on to a social bookmarking site Digg, Stumbleupon ect... but after checking the logs I found that this story is getting the same amount of traffic that a normal story gets ~2k-3k. I checked if all the votes for this perpendicular story where coming from a the same IP address. I could see this happening if a user was at a school's computer lab using all their lab computers to vote up this story. Not one duplicate IP address in the log for this story. SELECT ip, COUNT(*) as count FROM wp_gdsr_votes_log WHERE id=3932 GROUP BY (ip ) ORDER BY count DESC Next I thought that a use might be using a proxy to vote up a story. I checked this by grouping all the browser user_agent together to see if there a single browser voting in a perpendicular way. At most 7 users where using a similar browser but voted sporadically (1-5), no evidence of wrong doing. SELECT user_agent, COUNT(*) as count FROM wp_gdsr_votes_log WHERE id=3932 GROUP BY ( user_agent) ORDER BY count DESC I check was to see if all the votes came in at a once. Maybe someone has a really interesting bot that can change the user_adgent and uses proxies, ect... At most 5 votes came with in 2 mins of each other. It doesn't seem to be any regularity on how people vote (IE a 5 vote does not come in once a min) SELECT * FROM wp_gdsr_votes_log WHERE id =3932 AND vote=5 ORDER BY wp_gdsr_votes_log.voted DESC The obvious solution to this problem is to force people to login before they are allowed to vote. But I would prefer to not have to go down that route unless it is absolutely necessary. I'm looking for suggestions on things to test for to detect the abuse.

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  • Error building C program

    - by John
    Here are my 2 source files: main.c: #include <stdio.h> #include "part2.c" extern int var1; extern int array1[]; int main() { var1 = 4; array1[0] = 2; array1[1] = 4; array1[2] = 5; array1[3] = 7; display(); printf("---------------"); printf("Var1: %d", var1); printf("array elements:"); int x; for(x = 0;x < 4;++x) printf("%d: %d", x, array1[x]); return 0; } part2.c #include <stdio.h> int var1; int array1[4]; void display(void); void display(void) { printf("Var1: %d", var1); printf("array elements:"); int x; for(x = 0;x < 4;++x) printf("%d: %d", x, array1[x]); } When i try to compile the program this is what i get: Ld /Users/John/Library/Developer/Xcode/DerivedData/Test-blxrdmnozbbrbwhcekmouessaprf/Build/Products/Debug/Test normal x86_64 cd /Users/John/Xcode/Test setenv MACOSX_DEPLOYMENT_TARGET 10.7 /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang -arch x86_64 -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.7.sdk -L/Users/John/Library/Developer/Xcode/DerivedData/Test-blxrdmnozbbrbwhcekmouessaprf/Build/Products/Debug -F/Users/John/Library/Developer/Xcode/DerivedData/Test-blxrdmnozbbrbwhcekmouessaprf/Build/Products/Debug -filelist /Users/John/Library/Developer/Xcode/DerivedData/Test-blxrdmnozbbrbwhcekmouessaprf/Build/Intermediates/Test.build/Debug/Test.build/Objects-normal/x86_64/Test.LinkFileList -mmacosx-version-min=10.7 -o /Users/John/Library/Developer/Xcode/DerivedData/Test-blxrdmnozbbrbwhcekmouessaprf/Build/Products/Debug/Test ld: duplicate symbol _display in /Users/John/Library/Developer/Xcode/DerivedData/Test-blxrdmnozbbrbwhcekmouessaprf/Build/Intermediates/Test.build/Debug/Test.build/Objects-normal/x86_64/part2.o and /Users/John/Library/Developer/Xcode/DerivedData/Test-blxrdmnozbbrbwhcekmouessaprf/Build/Intermediates/Test.build/Debug/Test.build/Objects-normal/x86_64/main.o for architecture x86_64 clang: error: linker command failed with exit code 1 (use -v to see invocation) I am using Xcode and both files are inside of a C project called Test What is causing the error and how do i fix it?

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  • C# Property Access vs Interface Implementation

    - by ehdv
    I'm writing a class to represent a Pivot Collection, the root object recognized by Pivot. A Collection has several attributes, a list of facet categories (each represented by a FacetCategory object) and a list of items (each represented by a PivotItem object). Therefore, an extremely simplified Collection reads: public class Collection { private List<FacetCategory> categories; private List<PivotItem> items; // other attributes } What I'm unsure of is how to properly grant access to those two lists. Because declaration order of both facet categories and items is visible to the user, I can't use sets, but the class also shouldn't allow duplicate categories or items. Furthermore, I'd like to make the Collection object as easy to use as possible. So my choices are: Have Collection implement IList<PivotItem> and have accessor methods for FacetCategory: In this case, one would add an item to Collection foo by writing foo.Add(bar). This works, but since a Collection is equally both kinds of list making it only pass as a list for one type (category or item) seems like a subpar solution. Create nested wrapper classes for List (CategoryList and ItemList). This has the advantage of making a consistent interface but the downside is that these properties would no longer be able to serve as lists (because I need to override the non-virtual Add method I have to implement IList rather than subclass List. Implicit casting wouldn't work because that would return the Add method to its normal behavior. Also, for reasons I can't figure out, IList is missing an AddRange method... public class Collection { private class CategoryList: IList<FacetCategory> { // ... } private readonly CategoryList categories = new CategoryList(); private readonly ItemList items = new ItemList(); public CategoryList FacetCategories { get { return categories; } set { categories.Clear(); categories.AddRange(value); } } public ItemList Items { get { return items; } set { items.Clear(); items.AddRange(value); } } } Finally, the third option is to combine options one and two, so that Collection implements IList<PivotItem> and has a property FacetCategories. Question: Which of these three is most appropriate, and why?

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  • Populating a PHP array within a foreach loop

    - by patrick
    I am wanting to add each user into an array and check for duplicates before I do. $spotcount = 10; for ($topuser_count = 0; $topuser_count < $spotcount; $topuser_count++) //total spots { $spottop10 = $ids[$topuser_count]; $top_10 = $gowalla->getSpotInfo($spottop10); $usercount = 0; $c = 0; $array = array(); foreach($top_10['top_10'] as $top10) //loop each spot { //$getuser = substr($top10['url'],7); //strip the url $getuser = ltrim($top10['url'], " users/" ); if ($usercount < 3) //loop only certain number of top users { if (($getuser != $userurl) && (array_search($getuser, $array) !== true)) { //echo " no duplicates! <br /><br />"; echo ' <a href= "http://gowalla.com'.$top10['url'].'"><img width="90" height="90" src= " '.$top10['image_url'].' " title="'.$top10['first_name'].'" alt="Error" /></a> '; $array[$c++] = $getuser; } else { //echo "duplicate <br /><br />"; } } $usercount++; } print_r($array); } The previous code prints: Array ( [0] => 62151 [1] => 204501 [2] => 209368 ) Array ( [0] => 62151 [1] => 33116 [2] => 122485 ) Array ( [0] => 120728 [1] => 205247 [2] => 33116 ) Array ( [0] => 150883 [1] => 248551 [2] => 248558 ) Array ( [0] => 157580 [1] => 77490 [2] => 52046 ) Which is wrong. It does check for duplicates, but only the contents of each foreach loop instead of the entire array. How is this if I am storing everything into $array?

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  • color objects in C or C ++ [closed]

    - by jazz
    Possible Duplicate: Colors in C language i copied a game from a book which name is paratrooper i ask this question again i also provide the code of the objects which i create there i want to change the color of these objects but i didn't understand how to do that so can any one plz help me how to do that.Listen guys they are not the standard functions but i use the graphics library for these functions and i can't find the function in the library file of graphics. i hope u understand know.this code will not run properly so plz tell me something about the function which color it i can't put the image other wize i show u the image it will make alot easieer #include "graphics.h" #include "stdio.h" #include "conio.h" #include "process.h" #include "alloc.h" #include "stdlib.h" #include "math.h" #include "dos.h" main() { int gm=CGAHI, gd=CGA, key=0, area; initgraph(&gd, &gm, "C:\\tc\\bgi"); helidraw(246,50,-1); getch(); return 0; } helidraw ( int x, int y, int d ) { int direction, i, j ; if ( d ) direction = -1 ; else direction = 1 ; i = 3 ; j = 8 ; line ( x - j - 8, y - i - 2, x + j + 8, y - i - 2 ) ; line ( x - j + 5, y - i - 1, x + j - 5, y - i - 1 ) ; line ( x - j, y - i, x + j, y - i ) ; for ( ; i > 0 ; i--, j += 2 ) { putpixel ( x - ( direction * j ), y - i, 1 ) ; line ( x + ( direction * j ), y - i, x + ( direction * ( j - 8 ) ), y - i ) ; } i = 0 ; j -= 2 ; line ( x - ( direction * j ), y - i, x - ( direction * ( j + 17 ) ), y - i ) ; line ( x - ( direction * j ), y - i + 1, x - ( direction * ( j + 7 ) ), y - i + 1 ) ; putpixel ( x - ( direction * ( j + 19 ) ), y - i - 1, 1 ) ; for ( ; i < 3 ; i++, j -= 2 ) { putpixel ( x - j, y + i, 1 ) ; putpixel ( x + j, y + i, 1 ) ; } line ( x - j, y + i, x + j, y + i ) ; putpixel ( x - j + 3, y + i + 1, 1 ) ; putpixel ( x + j - 3, y + i + 1, 1 ) ; line ( x - j - 10, y + i + 2, x + j + 10, y + i + 2 ) ; putpixel ( x + ( direction * ( j + 12 ) ), y + i + 1, 1 ) ; }

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  • IE browser caching and the jQuery Form Plugin

    - by Harfleur
    Like so many lost souls before me, I'm floundering in the snake pit that is Ajax form submission and IE browser caching. I'm trying to write a simple script using the jQuery Form Plugin to Ajaxify Wordpress comments. It's working fine in Firefox, Chrome, Safari, et. al., but in IE, the response text is cached with the result that Ajax is pulling in the wrong comment. jQuery(this).ajaxSubmit({ success: function(data) { var response = $("<ol>"+data+"</ol>"); response.find('.commentlist li:last').hide().appendTo(jQuery('.commentlist')).slideDown('slow'); } }); ajaxSubmit sends the comment to wp-comments-post.php, which inelegantly spits back the entire page as a response. So, despite the fact that it's ugly as toads, I'm sticking the response text in a variable, using :last to isolate the most recent comment, and sliding it down in its place. IE, however, is returning the cached version of the page, which doesn't include the new comment. So ".commentlist li:last" selects the previous comment, a duplicate of which then uselessly slides down beneath the original. I've tried setting "cache: false" in the ajaxSubmit options, but it has no effect. I've tried setting a url option and tacking on a random number or timestamp, but it winds up being attached to the POST that submits the comment to the server rather than the GET that returns the response, and so has no effect. I'm not sure what else to try. Everything works fine in IE if I turn off browser caching, but that's obviously not something I can expect anyone viewing the page to do. Any help will be hugely appreciated. Thanks in advance! EDIT WITH A PROGRESS REPORT: A couple of people have suggested using PHP headers to prevent caching, and this does indeed work. The trouble is that wp-comments-post is spitting back the entire page when a new comment is submitted, and the only way I can see to add headers is to put them in the Wordpress post template, which disables caching on all posts at all times--not quite the behavior I'm looking for. Is there a way to set a php conditional--"if is_ajax" or something like that--that would keep the headers from being applied during regular pageloads, but plug them in if the page was called by an Ajax GET?

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  • Greasemonkey is getting an empty document.body on select Google pages.

    - by Brock Adams
    Hi, I have a Greasemonkey script that processes Google search results. But it's failing in a few instances, when xpath searches (and document body) appear to be empty. Running the code in Firebug's console works every time. It only fails in a Greasemonkey script. Greasemonkey sees an empty document.body. I've boiled the problem down to a test, greasemonkey script, below. I'm using Firefox 3.5.9 and Greasemonkey 0.8.20100408.6 (but earlier versions had the same problem). Problem: Greasemonkey sees an empty document.body. Recipe to Duplicate: Install the Greasemonkey script. Open a new tab or window. Navigate to Google.com (http://www.google.com/). Search on a simple term like "cats". Check Firefox's Error console (Ctrl-shift-J) or Firebug's console. The script will report that document body is empty. Hit refresh. The script will show a good result (document body found). Note that the failure only reliably appears on Google results obtained this way, and on a new tab/window. Turn javascript off globally (javascript.enabled set to false in about:config). Repeat steps 2 thru 5. Only now the Greasemonkey script will work. It seems that Google javascript is killing the DOM tree for greasemonkey, somehow. I've tried a time-delayed retest and even a programmatic refresh; the script still fails to see the document body. Test Script: // // ==UserScript== // @name TROUBLESHOOTING 2 snippets // @namespace http://www.google.com/ // @description For code that has funky misfires and defies standard debugging. // @include http://*/* // ==/UserScript== // function LocalMain (sTitle) { var sUserMessage = ''; //var sRawHtml = unsafeWindow.document.body.innerHTML; //-- unsafeWindow makes no difference. var sRawHtml = document.body.innerHTML; if (sRawHtml) { sRawHtml = sRawHtml.replace (/^\s\s*/, ''). substr (0, 60); sUserMessage = sTitle + ', Doc body = ' + sRawHtml + ' ...'; } else { sUserMessage = sTitle + ', Document body seems empty!'; } if (typeof (console) != "undefined") { console.log (sUserMessage); } else { if (typeof (GM_log) != "undefined") GM_log (sUserMessage); else if (!sRawHtml) alert (sUserMessage); } } LocalMain ('Preload'); window.addEventListener ("load", function() {LocalMain ('After load');}, false);

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  • itertools.product eliminating repeated reversed tuples

    - by genclik27
    I asked a question yesterday and thanks to Tim Peters, it is solved. The question is here; itertools.product eliminating repeated elements The new question is further version of this. This time I will generate tuples inside of tuples. Here is an example; lis = [[(1,2), (3,4)], [(5,2), (1,2)], [(2,1), (1,2)]] When I use it in itertools.product function this is what I get, ((1, 2), (5, 2), (2, 1)) ((1, 2), (5, 2), (1, 2)) ((1, 2), (1, 2), (2, 1)) ((1, 2), (1, 2), (1, 2)) ((3, 4), (5, 2), (2, 1)) ((3, 4), (5, 2), (1, 2)) ((3, 4), (1, 2), (2, 1)) ((3, 4), (1, 2), (1, 2)) I want to change it in a way that if a sequence has (a,b) inside of it, then it can not have (b,a). In this example if you look at this sequence ((3, 4), (1, 2), (2, 1)) it has (1,2) and (2,1) inside of it. So, this sequence ((3, 4), (1, 2), (2, 1)) should not be considered in the results. As I said, I asked similar question before, in that case it was not considering duplicate elements. I try to adapt it to my problem. Here is modified code. Changed parts in old version are taken in comments. def reverse_seq(seq): s = [] for i in range(len(seq)): s.append(seq[-i-1]) return tuple(s) def uprod(*seqs): def inner(i): if i == n: yield tuple(result) return for elt in sets[i] - reverse: #seen.add(elt) rvrs = reverse_seq(elt) reverse.add(rvrs) result[i] = elt for t in inner(i+1): yield t #seen.remove(elt) reverse.remove(rvrs) sets = [set(seq) for seq in seqs] n = len(sets) #seen = set() reverse = set() result = [None] * n for t in inner(0): yield t In my opinion this code should work but I am getting error for the input lis = [[(1,2), (3,4)], [(5,2), (1,2)], [(2,1), (1,2)]]. I could not understand where I am wrong. for i in uprod(*lis): print i Output is, ((1, 2), (1, 2), (1, 2)) Traceback (most recent call last): File "D:\Users\SUUSER\workspace tree\sequence_covering _array\denemeler_buraya.py", line 39, in <module> for i in uprod(*lis): File "D:\Users\SUUSER\workspace tree\sequence_covering _array\denemeler_buraya.py", line 32, in uprod for t in inner(0): File "D:\Users\SUUSER\workspace tree\sequence_covering _array\denemeler_buraya.py", line 22, in inner for t in inner(i+1): File "D:\Users\SUUSER\workspace tree\sequence_covering _array\denemeler_buraya.py", line 25, in inner reverse.remove(rvrs) KeyError: (2, 1) Thanks,

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  • CSS selectors : should I minimise my use of the class attribute in the HTML or optimise the speed

    - by Laurent Bourgault-Roy
    As I was working on a small website, I decided to use the PageSpeed extension to check if their was some improvement I could do to make the site load faster. However I was quite surprise when it told me that my use of CSS selector was "inefficient". I was always told that you should keep the usage of the class attribute in the HTML to a minimum, but if I understand correctly what PageSpeed tell me, it's much more efficient for the browser to match directly against a class name. It make sense to me, but it also mean that I need to put more CSS classes in my HTML. It also make my .css file a little harder to read. I usually tend to mark my CSS like this : #mainContent p.productDescription em.priceTag { ... } Which make it easy to read : I know this will affect the main content and that it affect something in a paragraph tag (so I wont start to put all sort of layout code in it) that describe a product and its something that need emphasis. However it seem I should rewrite it as .priceTag { ... } Which remove all context information about the style. And if I want to use differently formatted price tag (for example, one in a list on the sidebar and one in a paragraph), I need to use something like that .paragraphPriceTag { ... } .listPriceTag { ... } Which really annoy me since I seem to duplicate the semantic of the HTML in my classes. And that mean I can't put common style in an unqualified .priceTag { ... } and thus I need to replicate the style in both CSS rule, making it harder to make change. (Altough for that I could use multiple class selector, but IE6 dont support them) I believe making code harder to read for the sake of speed has never been really considered a very good practice . Except where it is critical, of course. This is why people use PHP/Ruby/C# etc. instead of C/assembly to code their site. It's easier to write and debug. So I was wondering if I should stick with few CSS classes and complex selector or if I should go the optimisation route and remove my fancy CSS selectors for the sake of speed? Does PageSpeed make over the top recommandation? On most modern computer, will it even make a difference?

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