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  • How to properly handle signals when using the worker thread pattern?

    - by ipartola
    I have a simple server that looks something like this: void *run_thread(void *arg) { // Communicate via a blocking socket } int main() { // Initialization happens here... // Main event loop while (1) { new_client = accept(socket, ...); pthread_create(&thread, NULL, &run_thread, *thread_data*); pthread_detach(thread); } // Do cleanup stuff: close(socket); // Wait for existing threads to finish exit(0); ) Thus when a SIGINT or SIGTERM is received I need to break out of the main event loop to get to the clean up code. Moreover most likely the master thread is waiting on the accept() call so it's not able to check some other variable to see if it should break;. Most of the advice I found was along the lines of this: http://devcry.blogspot.com/2009/05/pthreads-and-unix-signals.html (creating a special signal handling thread to catch all the signals and do processing on those). However, it's the processing portion that I can't really wrap my head around: how can I possibly tell the main thread to return from the accept() call and check on an external variable to see if it should break;?

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  • How do I combine similar method calls into a delegate pattern?

    - by Daniel T.
    I have three methods: public void Save<T>(T entity) { using (new Transaction()) { Session.Save(entity); } } public void Create<T>(T entity) { using (new Transaction()) { Session.Create(entity); } } public void Delete<T>(T entity) { using (new Transaction()) { Session.Delete(entity); } } As you can see, the only thing that differs is the method call inside the using block. How can I rewrite this so it's something like this instead: public void Save<T>(T entity) { TransactionWrapper(Session.Save(entity)); } public void Create<T>(T entity) { TransactionWrapper(Session.Create(entity)); } public void Save<T>(T entity) { TransactionWrapper(Session.Save(entity)); } So in other words, I pass a method call as a parameter, and the TransactionWrapper method wraps a transaction around the method call.

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  • Make error: target pattern contains no '%'. Stop.

    - by Derek
    Hi all. I have a project that I have been running on IRIX that builds fine with gmake. I copied the source and make files onto a Redhat machine, and running gmake gives me the error posted in the subject. This is during a part of the make that is building .d dependency files, and they are separated by a colon, which I have read is a no-no, but why does it work on one system and not the other? What is the fix? Thanks

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  • Mysql: how to generate count table by PATTERN / LIKE statement ? very tricky

    - by Abdulrahman Al-Qabandi
    to simplify, I got a database of registered users, I want to count how many emails there are for each email domain name (note I do not know all domain names) for example, Users table- id | email ------------------ 1 | [email protected] 2 | [email protected]<--unknown to me 3 | [email protected]<--unknown to me 4 | [email protected] 5 | [email protected]<--unknown to me 6 | [email protected] 7 | [email protected] 8 | [email protected] ( note: I want to count each email without specifying which email exactly ) so the result I want is suffix | count hotmail.com | 3 somesite.aaa | 2 unknownsite.aaa| 1 yahoo.com | 2 again, I stress this, I do not know unknownsite.aaa nor can i mention it in a statement because it is unknown to me, i hope I am clear. So essentially I want to make a statistic of what my website users use as an email host website. but like I said and I will repeat the third time, I do not know every mailhost that exists. I am going to investigate this more, I have a feeling this is something mysql cannot handle.

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  • How can I refactor this to work without breaking the pattern horribly?

    - by SnOrfus
    I've got a base class object that is used for filtering. It's a template method object that looks something like this. public class Filter { public void Process(User u, GeoRegion r, int countNeeded) { List<account> selected = this.Select(u, r, countNeeded); // 1 List<account> filtered = this.Filter(selected, u, r, countNeeded); // 2 if (filtered.Count > 0) { /* do businessy stuff */ } // 3 if (filtered.Count < countNeeded) this.SendToSuccessor(u, r, countNeeded - filtered) // 4 } } Select(...), Filter(...) are protected abstract methods and implemented by the derived classes. Select(...) finds objects in the based on x criteria, Filter(...) filters those selected further. If the remaining filtered collection has more than 1 object in it, we do some business stuff with it (unimportant to the problem here). SendToSuccessor(...) is called if there weren't enough objects found after filtering (it's a composite where the next class in succession will also be derived from Filter but have different filtering criteria) All has been ok, but now I'm building another set of filters, which I was going to subclass from this. The filters I'm building however would require different params and I don't want to just implement those methods and not use the params or just add to the param list the ones I need and have them not used in the existing filters. They still perform the same logical process though. I also don't want to complicated the consumer code for this (which looks like this) Filter f = new Filter1(); Filter f2 = new Filter2(); Filter f3 = new Filter3(); f.Sucessor = f2; f2.Sucessor = f3; /* and so on adding filters as successors to previous ones */ foreach (User u in users) { foreach (GeoRegion r in regions) { f.Process(u, r, ##); } } How should I go about it?

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  • how to write regular expression using proc in TCL to deal with following pattern ?

    - by Passion
    Hello Guys, I am new to TCL and seeking a help to deal with the following expression. I am getting the i/p string from the user to validate any of these strings below & no others in a line in CLI { GHI GII GJI GKI} and another tricky one is to write regexp to match only the characters which begin with alphabet A & end with B, It also have 1 or more of either YO or OY in between using procedure. Thank you

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  • Can I use the decorator pattern to wrap a method body?

    - by mgroves
    I have a bunch of methods with varying signatures. These methods interact with a fragile data connection, so we often use a helper class to perform retries/reconnects, etc. Like so: MyHelper.PerformCall( () => { doStuffWithData(parameters...) }); And this works fine, but it can make the code a little cluttery. What I would prefer to do is decorate the methods that interact with the data connection like so: [InteractsWithData] protected string doStuffWithData(parameters...) { // do stuff... } And then essentially, whenever doStuffWithData is called, the body of that method would be passed in as an Action to MyHelper.PerformCall(). How do I do this?

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  • PCRE (recursive) pattern that matches a string containing a correctly parenthesized substring. Why d

    - by Anton N. Petrov
    Well, there are other ways (hmmm... or rather working ways) to do it, but the question is why does this one fail? / \A # start of the string ( # group 1 (?: # group 2 [^()]* # something other than parentheses (greedy) | # or \( (?1) \) # parenthesized group 1 ) # -group 2 + # at least once (greedy) ) # -group 1 \Z # end of the string /x Fails to match a string with nested parentheses: "(())"

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  • Real-world examples of populating a GWT CellTable using a clean MVP pattern?

    - by piehole
    We are using the GWT-Presenter framework and attempting to use CellTable to put together an updateable grid. It seems as though several of the GWT constructs for CellTable don't lend themselves to easily breaking up the logic into clean view and presenter code. Examples: 1) Within the View's constructor, the CellTable is defined and each column is created by anonymous inner classes that extend the Column class to provide the onValue() method. 2) The FieldUpdater interface must be implemented to provide logic to execute when a user alters data in a cell. This seems like it would best fit in the Presenter's onBind() method, but FieldUpdaters often need access to the Cell or Column which belong in the view. CellTable does not have accessor methods to get hold of the Columns or Cells, so it seems the only way for the Presenter to get them is for me to create a multitude of member variables on the View and accessors on my Display interface. Can anyone provide good examples for dealing with CellTable in GWT-Presenter or a comparable MVP

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  • scala 2.8.0.RC2 compiler problem on pattern matching statement?

    - by gruenewa
    Why does the following module not compile on Scala 2.8.RC[1,2]? object Test { import util.matching.Regex._ val pVoid = """\s*void\s*""".r val pVoidPtr = """\s*(const\s+)?void\s*\*\s*""".r val pCharPtr = """\s*(const\s+)GLchar\s*\*\s*""".r val pIntPtr = """\s*(const\s+)?GLint\s*\*\s*""".r val pUintPtr = """\s*(const\s+)?GLuint\s*\*\s*""".r val pFloatPtr = """\s*(const\s+)?GLfloat\s*\*\s*""".r val pDoublePtr = """\s*(const\s+)?GLdouble\s*\*\s*""".r val pShortPtr = """\s*(const\s+)?GLshort\s*\*\s*""".r val pUshortPtr = """\s*(const\s+)?GLushort\s*\*\s*""".r val pInt64Ptr = """\s*(const\s+)?GLint64\s*\*\s*""".r val pUint64Ptr = """\s*(const\s+)?GLuint64\s*\*\s*""".r def mapType(t: String): String = t.trim match { case pVoid() => "Unit" case pVoidPtr() => "ByteBuffer" case pCharPtr() => "CharBuffer" case pIntPtr() | pUintPtr() => "IntBuffer" case pFloatPtr() => "FloatBuffer" case pShortPtr() | pUshortPtr() => "ShortBuffer" case pDoublePtr() => "DoubleBuffer" case pInt64Ptr() | pUint64Ptr() => "LongBuffer" case x => x } }

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  • Would Python's Twisted library be the best case for an observer type pattern?

    - by beagleguy
    hi all, I'm developing a system where a queue will be filled with millions of items I need a process that reads items from the queue constantly and then sends those items out to registered clients. I'm thinking about using twisted for this, having the queue reader be a twisted server listening on a tcp port then clients can connect on that port and when an item is pulled from the queue the server writes it out to all the clients. Does that sound like something that twisted would be ideal for? Does anyone know of any sample code out there that may do something similar? thanks

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  • Post-back + Page Refresh. Post/Redirect/Get pattern alternatives?

    - by Andrew Florko
    When user posts back a web form and then tries to refresh the page - dialog "would you like to resend information" pops up (Opera works silently though). To avoid this we can redirect browser to the page we'd like to show after postback. Now, when user refreshes the page, he duplicates get-request and no pop-ups. Everything is ok but post/redirect/get approach requires additional roundtrip. Is there better alternatives. Send form data with ajax aynchronously, for example? Thank you in advance!

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  • Where does the query language sit within the MVC pattern?

    - by weesilmania
    I'd assume that since the query language sits within the controller (typically) that it belongs to that component, but if I play devil's advocate I'd argue that the query language is execute within the domain of the model, and is tightly coupled to that component so it might also be a part of it. Anyone know the answer? Is there a straight answer or is it technology specific?

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  • Scala, represent pattern of boolean tuple into something else.

    - by Berlin Brown
    This is a cellular automata rule (input Boolean == Left, Center, Right Cell) and output Boolean . What is a better way to represent this in Scala. trait Rule { def ruleId() : Int def rule(inputState:(Boolean, Boolean, Boolean)) : Boolean override def toString : String = "Rule:" + ruleId } class Rule90 extends Rule { def ruleId() = 90 def rule(inputState:(Boolean, Boolean, Boolean)) : Boolean = { // Verbose version, show all 8 states inputState match { case (true, true, true) => false case (true, false, true) => false case (false, true, false) => false case (false, false, false) => false case _ => true } } }

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  • How to implement the API/SPI Pattern in Java?

    - by Adam Tannon
    I am creating a framework that exposes an API for developers to use: public interface MyAPI { public void doSomeStuff(); public int getWidgets(boolean hasRun); } All the developers should have to do is code their projects against these API methods. I also want them to be able to place different "drivers"/"API bindings" on the runtime classpath (the same way JDBC or SLF4J work) and have the API method calls (doSomeStuff(), etc.) operate on different 3rd party resources (files, servers, whatever). Thus the same code and API calls will map to operations on different resources depending on what driver/binding the runtime classpath sees (i.e. myapi-ftp, myapi-ssh, myapi-teleportation). How do I write (and package) an SPI that allows for such runtime binding, and then maps MyAPI calls to the correct (concrete) implementation? In other words, if myapi-ftp allows you to getWidgets(boolean) from an FTP server, how would I could this up (to make use of both the API and SPI)? Bonus points for concrete, working Java code example! Thanks in advance!

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  • MVC design pattern in complex iPad app: is one fat controller acceptable?

    - by nutsmuggler
    I am building a complex iPad application; think of it as a scrapbook. For the purpose of this question, let's consider a page with two images over it. My main view displays my doc data rendered as a single UIImage; this because I need to do some global manipulation over them. This is my DisplayView. When editing I need to instantiate an EditorView with my two images as subviews; this way I can interact with a single image, (rotate it, scale it, move it). When editing is triggered, I hide my DisplayView and show my EditorView. In a iPhone app, I'd associate each main view (that is, a view filling the screen) to a view controller. The problem is here there is just one view controller; I've considered passing the EditorView via a modal view controller, but it's not an option (there a complex layout with a mask covering everything and palettes over it; rebuilding it in the EditorView would create duplicate code). Presently the EditorView incorporates some logic (loads data from the model, invokes some subviews for fine editing, saves data back to the model); EditorView subviews also incorporate some logic (I manipulate images and pass them back to the main EditorView). I feel this logic belongs more to a controller. On the other hand, I am not sure making my only view controller so fat a good idea. What is the best, cocoa-ish implementation of such a class structure? Feel free to ask for clarifications. Cheers.

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  • UI Design - design pattern for city/country drop down? (ASP.NET MVC)

    - by JK
    What is the best way to do a city/country dropdown pair in ASP.NET MVC? I see lots of places with country above city, but that's unnatural: in real life we write city/country. I've used city, then country, but the problem is that the user then has to go backwards after changing the country. The other problem is what do you do about cities/countries not in your list? If city/country are both drop downs, then the user cant type their own city if it is missing. But if you have a dropdown and a textbox, that makes it unwieldy (you end up with 4 controls to enter 2 pieces of data). Are there any examples websites where the city/country dropdown pair are done in a very useable and clear manner?

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  • About presenter pattern in rails. is a better way to do it?

    - by Totty
    I have in my model: def presenter @presenter ||= ProfilePresenter.new(self) @presenter end The ProfilePresenter is a class that has methods like, get_link(), get_img_url(size), get_sex(), get_relationship_status() and other methods that have not to do with the model, not even with the controller but is used multiple times in the view. So now i use them by doing this: Profile.presenter.get_link # or Profile.presenter.get_img_url('thumb') # returns the path of the image. is not used to make a db query

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  • How to make URL pattern like app.example.com?

    - by abc
    I have my domain say "example.com" (java, GlassFish Web Server) Now I have 3 application.. say A,B,C. Now what I want is, if user hit a.example.com OR example.com/X then A application should get invoked. similarly for B and C. b.example.com or example.com/B, c.example.com or example.com/C. like mail.google.com news.google.com. How to configure this? I couldn't query it in Google as I didn't know how to query for this exactly. So posted here. Thankx guyz in advance.

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  • What is Rails way to DRY up the controller pattern of verifying :id is for a valid object (else redirect to error page)

    - by jpwynn
    One of my controllers has close to 100 methods (eg routes) and nearly every one starts out the same code to redirect to an error page if the id param is invalid, followed by a similar check if the user that id doesn't belong in the user's account: def something @foo = Foo.find_by_guid(params[:id]) unless @foo @msg ||= { :title => 'No such page!', :desc => "There is no such page!" } render :action => "error" and return end unless @foo.owner_id == current_user.id @msg ||= { :title => 'Really?', :desc => "There is no such page." } render :action => "error" and return end What is the best way to DRY up that sort of page id and owner id validation, given the code is doing a render ... and return? What I don't want to do at this point is offload it to a blackbox roles and permissions library like CanCan... my goal is simply to have the in-app code to handle this be as clean as possible.

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