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  • How can I safely raise events in an AsyncCallback?

    - by cyclotis04
    I'm writing a wrapper class around a TcpClient which raises an event when data arrives. I'm using BeginRead and EndRead, but when the parent form handles the event, it's not running on the UI thread. I do I need to use delegates and pass the context into the callback? I thought that callbacks were a way to avoid this... void ReadCallback(IAsyncResult ar) { int length = _tcpClient.GetStream().EndRead(ar); _stringBuilder.Append(ByteArrayToString(_buffer, length)); BeginRead(); OnStringArrival(EventArgs.Empty); }

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  • Syncronizing mobile phone contacts with contacts from social networks

    - by Pentium10
    I retrieve a JSON list of contacts from a social network site. It contains firstname, lastname, displayname, data1, data2, etc... What is the efficient way to quickly lookup my local phone contacts database and "match" them based on their name. Since there are firstname, lastname and displayname this can vary. What do you think, how can the best match be achieved? Also how do I make sure I don't parse for each JSON item the whole database I want to avoide having JSON_COUNT x MOBILE COUNT steps.

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  • question about book example - Java Concurrency in Practice, Listing 4.12

    - by mike
    Hi, I am working through an example in Java Concurrency in Practice and am not understanding why a concurrent-safe container is necessary in the following code. I'm not seeing how the container "locations" 's state could be modified after construction; so since it is published through an 'unmodifiableMap' wrapper, it appears to me that an ordinary HashMap would suffice. EG, it is accessed concurrently, but the state of the map is only accessed by readers, no writers. The value fields in the map are syncronized via delegation to the 'SafePoint' class, so while the points are mutable, the keys for the hash, and their associated values (references to SafePoint instances) in the map never change. I think my confusion is based on what precisely the state of the collection is in the problem. Thanks!! -Mike Listing 4.12, Java Concurrency in Practice, (this listing available as .java here, and also in chapter form via google) /////////////begin code @ThreadSafe public class PublishingVehicleTracker { private final Map<String, SafePoint> locations; private final Map<String, SafePoint> unmodifiableMap; public PublishingVehicleTracker( Map<String, SafePoint> locations) { this.locations = new ConcurrentHashMap<String, SafePoint>(locations); this.unmodifiableMap = Collections.unmodifiableMap(this.locations); } public Map<String, SafePoint> getLocations() { return unmodifiableMap; } public SafePoint getLocation(String id) { return locations.get(id); } public void setLocation(String id, int x, int y) { if (!locations.containsKey(id)) throw new IllegalArgumentException( "invalid vehicle name: " + id); locations.get(id).set(x, y); } } // monitor protected helper-class @ThreadSafe public class SafePoint { @GuardedBy("this") private int x, y; private SafePoint(int[] a) { this(a[0], a[1]); } public SafePoint(SafePoint p) { this(p.get()); } public SafePoint(int x, int y) { this.x = x; this.y = y; } public synchronized int[] get() { return new int[] { x, y }; } public synchronized void set(int x, int y) { this.x = x; this.y = y; } } ///////////end code

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  • Java - when to use notify or notifyAll?

    - by mdma
    Why does java.lang.Object have two notify methods - notify and notifyAll? It seems that notifyAll does at least everything notify does, so why not just use notifyAll all the time? If notifyAll is used instead of notify, is the program still correct, and vice versa? What influences the choice between these two methods?

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  • General ORM design question

    - by Calvin
    Suppose you have 2 classes, Person and Rabbit. A person can do a number of things to a rabbit, s/he can either feed it, buy it and become its owner, or give it away. A rabbit can have none or at most 1 owner at a time. And if it is not fed for a while, it may die. Class Person { Void Feed(Rabbit r); Void Buy(Rabbit r); Void Giveaway(Person p, Rabbit r); Rabbit[] rabbits; } Class Rabbit { Bool IsAlive(); Person pwner; } There are a couple of observations from the domain model: Person and Rabbit can have references to each other Any actions on 1 object can also change the state of the other object Even if no explicit actions are invoked, there can still be a change of state in the objects (e.g. Rabbit can be starved to death, and that causes it to be removed from the Person.rabbits array) As DDD is concerned, I think the correct approach is to synchronize all calls that may change the states in the domain model. For instance, if a Person buys a Rabbit, s/he would need to acquire a lock in Person to make a change to the rabbits array AND also another lock in Rabbit to change its owner before releasing the first one. This would prevent a race condition where 2 Persons claim to be the owner of the little Rabbit. The other approach is to let the database to handle all these synchronizations. Who makes the first call wins, but then the DB needs to have some kind of business logics to figure out if it is a valid transaction (e.g. if a Rabbit already has an owner, it cannot change its owner unless the Person gives it away). There are both pros/cons in either approach, and I’d expect the “best” solution would be somewhere in-between. How would you do it in real life? What’s your take and experience? Also, is it a valid concern that there can be another race condition the domain model has committed its change but before it is fully committed in the database? And for the 3rd observation (i.e. state change due to time factor). How will you do it?

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  • How do I sync Dreamweaver site definitions across 2 computers?

    - by baritoneuk
    I use Dreamweaver on my laptop and Desktop PC and frequently change between them. I keep all my sites synced using Syncplicity (similar to Dropbox, which indecently I also use) I want my site definitions to be synced across the two computers. If I add a new site on one computer I want it to appear on the other one. I know I can export all sites on one computer and then get Syncplicity to sync the files to the other computer at which point I can import them. However this relies on me remembering to do this each time I add a new site, and it's also quite time consuming. As far as I can tell, Dreamweaver (at least upto CS4- not sure about CS5) stupidly stores the site definitions in the registry. I really don't know why they do this- if they stored it in xml files then I could easily sync the information. Does anyone know if what I am asking is possible?

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  • Synchronisation construct inside pragma for

    - by Sayan Ghosh
    Hi, I have a program block like: for (iIndex1=0; iIndex1 < iSize; iIndex1++) { for (iIndex2=iIndex1+1; iIndex2 < iSize; iIndex2++) { iCount++; fDist =(*this)[iIndex1].distance( (*this)[iIndex2] ); m_oPDF.addPairDistance( fDist ); if ((bShowProgress) && (iCount % 1000000 == 0)) xyz_exception::ui()->progress( iCount, (size()-1)*((size()-1))/2 ); } } } } I have tried parallelising the inner and outer loop and by putting iCount in a critical region. What would be the best approach to parallelise this? If I wrap iCount with omp single or omp atomic then the code gives an error and I figured out that would be invalid inside omp for. I guess I am adding many extraneous stuffs to paralellise this. Need some advice... Thanks, Sayan

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  • Synclock a section of code while waiting for ShowDialog to return

    - by clawson
    I'm having trouble working out how to lock my application out of a section of code while it waits for a response from an external program. I've used Synclock on a section of code with the Me object in the expression. In this Synclock I call an overridden ShowDialog method of a dialog box, which has a timeout parameter, but does return the value from the underlying ShowDialog function call ,once the timer is setup. Works like this. SyncLock Me Dim frmDlgWithTimeout As New frmDlgWithTimeout ' dialog box with overridden ShowDialog ' Dim res As DialogResult = frmDlgWithTimeout.ShowDialog(10 * 1000) ' 10 sec timeout ' End SyncLock Now, external programs may raise events that bring my application to this Synclock but it doesn't prevent it from entering it, even though the ShowDialog function hasn't returned a value (and hence what I thought would keep the section of code locked). There is only one instance of the object that is used for lock in the program. Your help is greatly appreciated.

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  • Strophe javascript prevent disconnection on some delay

    - by patrikas
    Hello, I am developing javascript XMPP application which uses Strophe library to connect to Jabber server. I need to engage the thread for about 5-10 seconds when Strophe connects to the server. Thread is engaged by running java applet and after it releases the thread it goes back to handle XMPP events, however at the moment I cannot manage to do that - trying to use a connection after delay gives me 404 HTTP error (this is sent by XMPP-BOSHS service straight after Strophe sends POST request with XMPP message to it). I was trying to 'pause' a connection with Strophe's connection.pause and then resume it - didn't work. Would sending some raw content to the server, maybe if it's possible telling it that client's gonna be unresponsive for a short time work ? Are there any other solutions ? Thanks

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  • What is a good way to sync code files between computer?

    - by erotsppa
    I have a need to code from two computers during the week. What is the best way to sync the two computers (mac)? I've started using source control, like SVN. It works pretty good, except sometimes I check in code that I want to sync but they don't compile and it interferes with other people on the team working on the same project. I don't want to use branch. It wouldn't make sense to branch every night when I head home from office.

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  • iPad / iPhone Sync (WLAN or Inet)

    - by tobi
    I have actually one app with a SQLite DB and i port this at the moment to the ipad. My idea is a sync between iPad and iPhone for one table... But the Problem is "Person A" edit/change, create or delete a data record on iphone and "Person B" make the same or delete the edited record from Person A on the same time. Has anybody a idea for this? Or a nice lib for this?

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  • Is nested synchronized block necessary?

    - by Dan
    I am writing a multithreaded program and I have a method that has a nested synchronized blocks and I was wondering if I need the inner sync or if just the outer sync is good enough. public class Tester { private BlockingQueue<Ticket> q = new LinkedBlockingQueue<>(); private ArrayList<Long> list = new ArrayList<>(); public void acceptTicket(Ticket p) { try { synchronized (q) { q.put(p); synchronized (list) { if (list.size() < 5) { list.add(p.getSize()); } else { list.remove(0); list.add(p.getSize()); } } } } catch (InterruptedException ex) { Logger.getLogger(Consumer.class.getName()).log(Level.SEVERE, null, ex); } } } EDIT: This isn't a complete class as I am still working on it. But essentially I am trying to emulate a ticket machine. The ticket machine maintains a list of tickets in the BlockingQueue q. Whenever a client adds a ticket to the machine, the machine also keeps track of the price of the last 5 tickets (ArrayList list)

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  • local code files synch with server

    - by webdev
    I search for way to synch my local code with server on debain linux. For example i modify some files, then i can run synch command, and only changed files send to server (using ssh for ex). Can you help me with good light solution for this?

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  • Can Windows Mobile Synch Services use a business layer

    - by Andy Kakembo
    We're building a Win Mobile 6 warehouse app which needs to update our server based corporate DB. We've got a C# business layer that sits on our app server and we'd really like our warehouse app to go through this. We also like MS Synch Services. Is there a way to combine the two ie can we use sync services but get them to go through our business layer ? Has anyone done this and got an example I can follow ? Is there a best practice for this kind of scenario ? Thanks, Andy

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  • Syncing magento database froms development to production

    - by ringerce
    I use git for version control. I have a development, staging and production environment. When I finish in development I push to staging for review by the client. When approved, I push changes from staging to production. That works fine as long as there is no database changes. What happens if I install modules via Magento connect on local development and it makes database modifications. How would I push those changes up to the production server since the production server is always changing? Edit: I wrote two shell scripts. One that pulls the production database down to my development server, replaces base url with develpment url and updates my development db accordingly. It also leaves the production sql dump behind to be added to my git repo. I'm not really sure if it's beneficial to keep the raw dumps in source control but I'm going to try it out. The second scripts moves the development database up to staging and essentially performs the same operations as the first. Now when it comes time to move to production I pull the updated production repo into the production server and allow magento to do it's thing. I also started using SQLYog recently and it has a database comparison wizard which will give me the differences in my development and production databases and allow me to merge the changes in selectively. It always creates a migration script that I added to source control as well. If anything goes wrong I can run the comparison to see if anything was missed. Does this sounds like a decent workflow to you guys?

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  • Linked list example using threads

    - by Carl_1789
    I have read the following code of using CRITICAL_SECTION when working with multiple threads to grow a linked list. what would be the main() part which uses two threads to add to linked list? #include <windows.h> typedef struct _Node { struct _Node *next; int data; } Node; typedef struct _List { Node *head; CRITICAL_SECTION critical_sec; } List; List *CreateList() { List *pList = (List*)malloc(sizeof(pList)); pList->head = NULL; InitializeCriticalSection(&pList->critical_sec); return pList; } void AddHead(List *pList, Node *node) { EnterCriticalSection(&pList->critical_sec); node->next = pList->head; pList->head = node; LeaveCriticalSection(&pList->critical_sec); } void Insert(List *pList, Node *afterNode, Node *newNode) { EnterCriticalSection(&pList->critical_sec); if (afterNode == NULL) { AddHead(pList, newNode); } else { newNode->next = afterNode->next; afterNode->next = newNode; } LeaveCriticalSection(&pList->critical_sec); } Node *Next(List *pList, Node *node) { Node* next; EnterCriticalSection(&pList->critical_sec); next = node->next; LeaveCriticalSection(&pList->critical_sec); return next; }

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  • Synchronizing DataGridView (DataTable) with the DB

    - by Ezekiel Rage
    Hi! I have the following situation: there is a table in the DB that is queried when the form loads and the retrieved data is filled into a DataGridView via the DataTable underneath. After the data is loaded the user is free to modify the data (add / delete rows, modify entries). The form has 2 buttons: Apply and Refresh. The first one sends the changes to the database, the second one re-reads the data from the DB and erases any changes that have been made by the user. My question is: is this the best way to keep a DataGridView synchronized with the DB (from a users point of view)? For now these are the downsides: the user must keep track of what he is doing and must press the button every while the modifications are lost if the form is closed / app crash / ... I tried sending the changes to the DB on CellEndEdit event but then the user also needs some Undo/Redo functionality and that is ... well ... a different story. So, any suggestions?

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  • How do I make my ArrayList Thread-Safe? Another approach to problem in Java?

    - by thechiman
    I have an ArrayList that I want to use to hold RaceCar objects that extend the Thread class as soon as they are finished executing. A class, called Race, handles this ArrayList using a callback method that the RaceCar object calls when it is finished executing. The callback method, addFinisher(RaceCar finisher), adds the RaceCar object to the ArrayList. This is supposed to give the order in which the Threads finish executing. I know that ArrayList isn't synchronized and thus isn't thread-safe. I tried using the Collections.synchronizedCollection(c Collection) method by passing in a new ArrayList and assigning the returned Collection to an ArrayList. However, this gives me a compiler error: Race.java:41: incompatible types found : java.util.Collection required: java.util.ArrayList finishingOrder = Collections.synchronizedCollection(new ArrayList(numberOfRaceCars)); Here is the relevant code: public class Race implements RaceListener { private Thread[] racers; private ArrayList finishingOrder; //Make an ArrayList to hold RaceCar objects to determine winners finishingOrder = Collections.synchronizedCollection(new ArrayList(numberOfRaceCars)); //Fill array with RaceCar objects for(int i=0; i<numberOfRaceCars; i++) { racers[i] = new RaceCar(laps, inputs[i]); //Add this as a RaceListener to each RaceCar ((RaceCar) racers[i]).addRaceListener(this); } //Implement the one method in the RaceListener interface public void addFinisher(RaceCar finisher) { finishingOrder.add(finisher); } What I need to know is, am I using a correct approach and if not, what should I use to make my code thread-safe? Thanks for the help!

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  • Java threads not working correctly with linkedlist

    - by user69514
    Hi I am working on the sleeping barber problem. with the addition of having priority customer when they arrive they go in the front of the line and they are the next ones to get a haircut. I'm using a linkedlist and if I see a priority customer I put him in the beginning of the list, if the customer is not priority he goes to the end of the list. then I call the wantHaircut method getting the first element of the list. my problem is that the customer are being processed in the order they arrive, and the priority customer have to wait. here is the code where it all happens. any ideas what I am doing wrong? thanks public void arrivedBarbershop(Customer c){ if(waiting < numChairs && c.isPriority()){ System.out.println("Customer " + c.getID() + ": is a priority customer - SITTING -"); mutex.up(); customer_list.addFirst(c); } else if(waiting >= numChairs && c.isPriority()){ System.out.println("Customer " + c.getID() + ": is a priority customer - STANDING -"); mutex.up(); customer_list.addFirst(c); } else if(waiting < numChairs && !c.isPriority()){ waiting++; System.out.println("Customer " + c.getID() + ": arrived, sitting in the waiting room"); customer_list.addLast(c); customers.up(); // increment waiting customers } else if(waiting >= numChairs && !c.isPriority()) { System.out.println("Customer " + c.getID() + ": went to another barber because waiting room was full - " + waiting + " waiting"); mutex.up(); } if(!customer_list.isEmpty()){ this.wantHairCut(customer_list.removeFirst()); } } public void wantHairCut(Customer c) { mutex.up(); barber.down(); // waits for being allowed in barber chair System.out.println("Customer " + c.getID() + ": getting haircut"); try { /** haircut takes between 1 and 2 seconds **/ Thread.sleep(Barbershop.randomInt(1, 2) * 1000); } catch (InterruptedException e) { } System.out.println("Barber: finished cutting customer " + c.getID() + "'s hair"); c.gotHaircut = true; cutting.up(); // signals cutting has finished /** customer must pay now **/ this.wantToCashout(c); }

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  • Synchronizing in SQL Replication works when manually syncing, but not automatically

    - by Dominic Zukiewicz
    I'm using SQL Server 2005 to create a replication copy of the main databases, so that the reports can point to the replication copy instead of locking out our main databases. I have set up the 3 databases as publications and then 3 subscribers moving the transactions over to the subscribers, instantaneously I hope! What seems to be happening is that when using the "Insert Tracer" function, replication take publisher to distributor < 2 seconds, but to replicate to the subscribers can take over 7 minutes (and these are local databases on a SAN). This could be for 2 reasons: The SQL statements used to query the database are obtaining locks which are stopping the transactions updating the subscribers. The subscribers are just too busy for the replication to apply the changes. What seems to trouble me more, is that although the Replication Monitor / Insert Tracer are showing these statistics, if you use the "View Subscription Details" and then click Start, it will sync within seconds. My goal would be to have the data syncing (ideally) continuously, or every minute, perhaps I should reduce the batch size of the transactions? What am I doing wrong? [Note that the -Continuous flag is set!]

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  • How would you implement this "WorkerChain" functionality in .NET?

    - by Dan Tao
    Sorry for the vague question title -- not sure how to encapsulate what I'm asking below succinctly. (If someone with editing privileges can think of a more descriptive title, feel free to change it.) The behavior I need is this. I am envisioning a worker class that accepts a single delegate task in its constructor (for simplicity, I would make it immutable -- no more tasks can be added after instantiation). I'll call this task T. The class should have a simple method, something like GetToWork, that will exhibit this behavior: If the worker is not currently running T, then it will start doing so right now. If the worker is currently running T, then once it is finished, it will start T again immediately. GetToWork can be called any number of times while the worker is running T; the simple rule is that, during any execution of T, if GetToWork was called at least once, T will run again upon completion (and then if GetToWork is called while T is running that time, it will repeat itself again, etc.). Now, this is pretty straightforward with a boolean switch. But this class needs to be thread-safe, by which I mean, steps 1 and 2 above need to comprise atomic operations (at least I think they do). There is an added layer of complexity. I have need of a "worker chain" class that will consist of many of these workers linked together. As soon as the first worker completes, it essentially calls GetToWork on the worker after it; meanwhile, if its own GetToWork has been called, it restarts itself as well. Logically calling GetToWork on the chain is essentially the same as calling GetToWork on the first worker in the chain (I would fully intend that the chain's workers not be publicly accessible). One way to imagine how this hypothetical "worker chain" would behave is by comparing it to a team in a relay race. Suppose there are four runners, W1 through W4, and let the chain be called C. If I call C.StartWork(), what should happen is this: If W1 is at his starting point (i.e., doing nothing), he will start running towards W2. If W1 is already running towards W2 (i.e., executing his task), then once he reaches W2, he will signal to W2 to get started, immediately return to his starting point and, since StartWork has been called, start running towards W2 again. When W1 reaches W2's starting point, he'll immediately return to his own starting point. If W2 is just sitting around, he'll start running immediately towards W3. If W2 is already off running towards W3, then W2 will simply go again once he's reached W3 and returned to his starting point. The above is probably a little convoluted and written out poorly. But hopefully you get the basic idea. Obviously, these workers will be running on their own threads. Also, I guess it's possible this functionality already exists somewhere? If that's the case, definitely let me know!

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