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  • What design pattern should be used to create an emulator?

    - by Facon
    I have programmed an emulator, but I have some doubts about how to organizate it properly, because, I see that it has some problems about classes connection (CPU <- Machine Board). For example: I/O ports, interruptions, communication between two or more CPU, etc. I need for the emulator to has the best performance and good understanding of the code. PD: Sorry for my bad English.

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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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  • What types of objects should the ViewModel reference in the MVVM pattern?

    - by Blanthor
    I've seen quite a few examples of MVVM. I can see that the View should reference the ViewModel. I've seen recently an example of a ViewModel referencing a View, which seems wrong to me, as it would result in tighter coupling. Given that ViewModel is often described as an intermediary between the View and the Model, is there more to the ViewModel than a facade to domain objects? I hope I used the term "facade" correctly here.

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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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  • 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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  • Using Session State in Public Class in ASP.NET?

    - by davemackey
    I'm trying to move some reusable portions of code into a class. This is working okay except when I attempt to use Session within this class. I get an error: "Cannot refer to an instance member of a class from within a shared method or shared member initializer without an explicit instance of the class." My code looks something like this: Public Class webHousing Inherits System.Web.UI.Page Public Sub GetUserInfo() Dim x as String x = 10 Session("x")= x End Sub End Class I've simplified this code significantly - but the basic problem is present - trying to set a session value from within a class. I found the following MSDN article1 but don't believe Public/Shared can be used on Session?

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  • What is the state of model driven development in 2012?

    - by eriktheblond
    I haven't heard a lot of talk lately on model driven development, but some of my company's customers are using it. I know briefly what it is, but after trying to refresh my memory using Google I found that most of the information is from 2006-2007. Was it something that never really took off? More worryingly is the reason why the customers are asking: They want IEC 61508 complience. Is this actually a "not-so-good" idea that will live on simply because it is prescribed by a standard? I have too little experience to say if MDD is good idea or not (I'm guessing the right answer starts with "It depends"...), but the reasons for using it, that is standard complience, seems just wrong.

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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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  • What's the state of PHP unit testing frameworks in 2010?

    - by Pekka
    As far as I can see, PHPUnit is the only serious product in the field at the moment. It is widely used, is integrated into Continuous Integration suites like phpUnderControl, and well regarded. The thing is, I don't really like working with PHPUnit. I find it hard to set up (PEAR is the only officially supported installation method, and I hate PEAR), sometimes complicated to work with and, correct me if I'm wrong, lacking executability from a web page context (i.e. no CLI, which would really be nice when developing a web app.) The only competition to I can see is Simpletest, which looks very nice but hasn't seen a new release for almost two years, which tends to rule it out for me - Unit Testing is quite a static field, true, but as I will be deploying those tests alongside web applications, I would like to see active development on the project, at least for security updates and such. There is a SO question that pretty much confirms what I'm saying: Simple test vs PHPunit Seeing that that is almost two years old as well, though, I think it's time to ask again: Does anybody know any other serious feature-complete unit testing frameworks? Am I wrong in my criticism of PHPUnit? Is there still development going on for SimpleTest?

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  • Which .NET exception to throw for invalid database state?

    - by jslatts
    I am writing some data access code and I want to check for potentially "invalid" data states in the database. For instance, I am returning a widget out of the database and I only expect one. If I get two, I want to throw an exception. Even though referential integrity should prevent this from occurring, I do not want to depend on the DBAs never changing the schema. I would like to use the System.IO.InvalidDataException, except that I am not dealing with a file stream so it would be misleading. I ended up going with a generic applicationexception. Anyone have a better idea?

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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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  • How does dzone.com maintain state of the div?

    - by CShipley
    When you scroll down to the bottom of http://www.dzone.com/links/ it automatically loads more links. However, when you navigate away, then hit the back button, the contents of the modified div stay there. How do they get the browser to go back to a dynamically generated div?

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  • Is this state-of-the-art Ajax/jQuery, or should I do it differently?

    - by AP257
    Hi everyone: I'm using Ajax and jQuery to do some cool client-side stuff. Basically, if the user chooses a subject from a from a drop-down list, I want to auto-populate the page with a set of book details. However, I've built the Ajax from Google results and bits of string. I don't know if what I've done is up-to-date, or whether there are now much neater ways of doing it! Here's what I have: can it be improved? $("#subjectlist").change(function() { if (window.XMLHttpRequest) { xmlhttp=new XMLHttpRequest(); } else { xmlhttp=new ActiveXObject("Microsoft.XMLHTTP"); } xmlhttp.onreadystatechange=function() { if (xmlhttp.readyState==4 && xmlhttp.status==200) { var book_details = eval(xmlhttp.responseText); alert(book_details[0]["url"]); // To be added: extra code to populate HTML results. document.getElementById("book_results").innerHTML=xmlhttp.responseText; } } xmlhttp.open("GET","/subject_json/?id=" + $("#subjectlist").val(),true); xmlhttp.send(); }); Thanks for any advice!

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  • "FOR UPDATE" v/s "LOCK IN SHARE MODE" : Allow concurrent threads to read updated "state" value of locked row

    - by shadesco
    I have the following scenario: User X logs in to the application from location lc1: call it Ulc1 User X (has been hacked, or some friend of his knows his login credential, or he just logs in from a different browser on his machine,etc.. u got the point) logs in at the same time from location lc2: call it Ulc2 I am using a main servlet which : - gets a connection from database pooling - sets autocommit to false - executes a command that goes through app layers: if all successful, set autocommit to true in a "finally" statement, and closes connection. Else if an exception happens, rollback(). In my database (mysql/innoDb) i have a "history" table, with row columns: id(primary key) |username | date | topic | locked The column "locked" has by default value "false" and it serves as a flag that marks if a specific row is locked or not. Each row is specific to a user (as u can see from the username column) So back to the scenario: --Ulc1 sends the command to update his history from the db for date "D" and topic "T". --Ulc2 sends the same command to update history from the db for the same date "D" and same topic "T" at the exact same time. I want to implement an mysql/innoDB locking system that will enable whichever thread arriving to do the following check: Is column "locked" for this row true or not? if true, return a message to the user that " he is already updating the same data from another location" if not true (ie not locked) : flag it as locked and update then reset locked to false once finished. Which of these two mysql locking techniques, will actually allow the 2nd arriving thread from reading the "updated" value of the locked column to decide wt action to take?Should i use "FOR UPDATE" or "LOCK IN SHARE MODE"? This scenario explains what i want to accomplish: - Ulc1 thread arrives first: column "locked" is false, set it to true and continue updating process - Ulc2 thread arrives while Ulc1's transaction is still in process, and even though the row is locked through innoDb functionalities, it doesn't have to wait but in fact reads the "new" value of column locked which is "true", and so doesn't in fact have to wait till Ulc1 transaction commits to read the value of the "locked" column(anyway by that time the value of this column will already have been reset to false). I am not very experienced with the 2 types of locking mechanisms, what i understand so far is that LOCK IN SHARE MODE allow other transaction to read the locked row while FOR UPDATE doesn't even allow reading. But does this read gets on the updated value? or the 2nd arriving thread has to wait the first thread to commit to then read the value? Any recommendations about which locking mechanism to use for this scenario is appreciated. Also if there's a better way to "check" if the row has been locked (other than using a true/false column flag) please let me know about it. thank you SOLUTION (Jdbc pseudocode example based on @Darhazer's answer) Table : [ id(primary key) |username | date | topic | locked ] connection.setautocommit(false); //transaction-1 PreparedStatement ps1 = "Select locked from tableName for update where id="key" and locked=false); ps1.executeQuery(); //transaction 2 PreparedStatement ps2 = "Update tableName set locked=true where id="key"; ps2.executeUpdate(); connection.setautocommit(true);// here we allow other transactions threads to see the new value connection.setautocommit(false); //transaction 3 PreparedStatement ps3 = "Update tableName set aField="Sthg" where id="key" And date="D" and topic="T"; ps3.executeUpdate(); // reset locked to false PreparedStatement ps4 = "Update tableName set locked=false where id="key"; ps4.executeUpdate(); //commit connection.setautocommit(true);

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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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