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• Precision of cos(atan2(y,x)) versus using complex <double>, C++

  - by Ivan

  Hi all, I'm writing some coordinate transformations (more specifically the Joukoswky Transform, Wikipedia Joukowsky Transform), and I'm interested in performance, but of course precision. I'm trying to do the coordinate transformations in two ways: 1) Calculating the real and complex parts in separate, using double precision, as below: double r2 = chi.x*chi.x + chi.y*chi.y; //double sq = pow(r2,-0.5*n) + pow(r2,0.5*n); //slow!!! double sq = sqrt(r2); //way faster! double co = cos(atan2(chi.y,chi.x)); double si = sin(atan2(chi.y,chi.x)); Z.x = 0.5*(co*sq + co/sq); Z.y = 0.5*si*sq; where chi and Z are simple structures with double x and y as members. 2) Using complex : Z = 0.5 * (chi + (1.0 / chi)); Where Z and chi are complex . There interesting part is that indeed the case 1) is faster (about 20%), but the precision is bad, giving error in the third decimal number after the comma after the inverse transform, while the complex gives back the exact number. So, the problem is on the cos(atan2), sin(atan2)? But if it is, how the complex handles that? Thanks!

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• Long text input from user and PDF generation

  - by Petteri Hietavirta

  I have built a web application that can be seen as an overcomplicated application form. There are bunch of text areas with a given character limit. After the form submission various things happen and one of them is PDF generation. The text is queried from the DB and inserted in the PDF template created in iReports. This works fine but the major pain is overflowing text. The maximum number of characters is set based on 'average' text. But sometimes people prefer to write with CAPS or add plenty of linefeeds to format their text. These then cause user's text to overflow the space given in PDF. Unfortunately the PDF document must look like a real application form so I cannot allow unlimited space. What kind of approaches you have used to tackle this? Clean/restrict user input? Calculate the space requirement of the text based on font metrics? Provide preview of the PDF? (too bad users are not allowed to change their input after submission...)

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• Handling Status Bar notification

  - by MAkS

  in my app a background service starts and from that service i want to set Status bar notification, that the service has Started following is the code : Context context = getApplicationContext(); String ns = Context.NOTIFICATION_SERVICE; int icon = R.drawable.icon; CharSequence tickerText = "Hello"; long when = System.currentTimeMillis(); Notification notification = new Notification(icon, tickerText, when); CharSequence contentTitle = "My notification"; CharSequence contentText = "Hello World!"; Intent notificationIntent = new Intent(MyService.this, MyClass.class); notificationIntent.setFlags( Intent.FLAG_ACTIVITY_NEW_TASK); PendingIntent contentIntent = PendingIntent.getActivity(this,0,notificationIntent,0); notification.setLatestEventInfo(context, contentTitle, contentText, contentIntent); NotificationManager mNotificationManager = (NotificationManager) getSystemService(ns); mNotificationManager.notify(1, notification); Notification is displayed in Status bar But whin i click on that MyClass.class is not fired.And in log cat it shows "Input Manager Service Window already focused ignoring focuson ...." so plz provide solution. thanks in advance

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• iPad: Detecting External Keyboard

  - by StuartW

  My app uses a UIAccessoryView to provide additional keyboard functionality (such as forward/backward tabs and arrows keys) for the virtual keyboard, but that causes UIKeyboardDidShowNotification to fire even when a physical keyboard is present (the accessory appears at the bottom of the screen). I'd like to check if a physical keyboard is attached when handling UIKeyboardWillShowNotification, to prevent the accessory view from appearing and to prevent my custom view from scrolling up (to make room for the non-existent virtual keyboard). I've tried examining the UIKeyboardFrameEndUserInfoKey key, but it returns a real size for the virtual keyboard, in spite of nothing being displayed. Is there any way to detect the presence of a physical keyboard to prevent this unwanted behaviour? Hmm, the plot thickens. I tried disabling the input accessory by returning nil from the inputAccessoryView property of the Responder object which triggers the keyboard. That suppresses UIKeyboardWillShowNotification and UIKeyboardDidShowNotification when there is a physical keyboard present, but keeps these notifications when there is no such keyboard. All good so far. Then I tried re-enabling inputAccessoryView only after UIKeyboardWillShowNotification had been received. This only fires when a virtual keyboard is needed, so it should allow me to reintroduce the accessory view in those circumstances. Or so I thought. Unfortunately, it seems the OS doesn't check inputAccessoryView after UIKeyboardWillShowNotification, so it fails to show the accessory view when it is needed :o( That leaves me with two options: Include the input accessory view, giving extra functionality for virtual keyboard users, but lose the ability to detect a physical keyboard and hence not supporting physical devices; or Exclude the input accessory altogether, preventing most users from accessing the extra keys, but allowing the app to work with a physical keyboard. Not a great choice, so I'm still keen to see if anyone else has addressed this problem!

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• SAML Identity Provider based on Active Directory

  - by Jarret

  I have a 3rd party program that supports web SSO using SAML 1.1 (it is ready to serve as the Service Provider, in other words). We would like to implement this SSO for our intranet users based on their Active Directory credentials. In other words, they've already logged on to their system, so let's simply use those credentials to facilitate an SSO. I am a little overwhelmed at where to begin, though. My initial thought is that IIS / Active Directory could easily serve as the Identity Provider since IIS gives us "Integrated Windows Authentication" abilities. I would think we could just create a .NET web app that requires Integrated Authentication which simply extracts the current user ID, builds the SAML response, and re-directs the user back to the Service Provider with this SAML response to complete the SSO. But then, my problem is that I simply have no real idea of how to go about creating this SAML response, the X.509 certs involved, etc... I am wondering if I am in over my head on this, or if creating this SAML response should be relatively easy. Note this SSO is to be used by intranet users only, so no need to worry about federating with other companies / domains.

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• Optional Member Objects

  - by David Relihan

  Okay, so you have a load of methods sprinkled around your systems main class. So you do the right thing and refactor by creating a new class and perform move method(s) into a new class. The new class has a single responsibility and all is right with the world again: class Feature { public: Feature(){}; void doSomething(); void doSomething1(); void doSomething2(); }; So now your original class has a member variable of type object: Feature _feature; Which you will call in the main class. Now if you do this many times, you will have many member-objects in your main class. Now these features may or not be required based on configuration so in a way it's costly having all these objects that may or not be needed. Can anyone suggest a way of improving this? At the moment I plan to test in the newly created class if the feature is enabled - so the when a call is made to method I will return if it is not enabled. I could have a pointer to the object and then only call new if feature is enabled - but this means I will have to test before I call a method on it which would be potentially dangerous and not very readable. Would having an auto_ptr to the object improve things: auto_ptr<Feature> feature; Or am I still paying the cost of object invokation even though the object may\or may not be required. BTW - I don't think this is premeature optimisation - I just want to consider the possibilites.

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• How to deal with "partial" dates (2010-00-00) from MySQL in Django?

  - by Etienne

  In one of my Django projects that use MySQL as the database, I need to have a date fields that accept also "partial" dates like only year (YYYY) and year and month (YYYY-MM) plus normal date (YYYY-MM-DD). The date field in MySQL can deal with that by accepting 00 for the month and the day. So 2010-00-00 is valid in MySQL and it represent 2010. Same thing for 2010-05-00 that represent May 2010. So I started to create a PartialDateField to support this feature. But I hit a wall because, by default, and Django use the default, MySQLdb, the python driver to MySQL, return a datetime.date object for a date field AND datetime.date() support only real date. So it's possible to modify the converter for the date field used by MySQLdb and return only a string in this format 'YYYY-MM-DD'. Unfortunately the converter use by MySQLdb is set at the connection level so it's use for all MySQL date fields. But Django DateField rely on the fact that the database return a datetime.date object, so if I change the converter to return a string, Django is not happy at all. Someone have an idea or advice to solve this problem? How to create a PartialDateField in Django ? EDIT Also I should add that I already thought of 2 solutions, create 3 integer fields for year, month and day (as mention by Alison R.) or use a varchar field to keep date as string in this format YYYY-MM-DD. But in both solutions, if I'm not wrong, I will loose the special properties of a date field like doing query of this kind on them: Get all entries after this date. I can probably re-implement this functionality on the client side but that will not be a valid solution in my case because the database can be query from other systems (mysql client, MS Access, etc.)

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• How to manage multiple python versions ?

  - by Gyom

  short version: how can I get rid of the multiple-versions-of-python nightmare ? long version: over the years, I've used several versions of python, and what is worse, several extensions to python (e.g. pygame, pylab, wxPython...). Each time it was on a different setup, with different OSes, sometimes different architectures (like my old PowerPC mac). Nowadays I'm using a mac (OSX 10.6 on x86-64) and it's a dependency nightmare each time I want to revive script older than a few months. Python itself already comes in three different flavours in /usr/bin (2.5, 2.6, 3.1), but I had to install 2.4 from macports for pygame, something else (cannot remember what) forced me to install all three others from macports as well, so at the end of the day I'm the happy owner of seven (!) instances of python on my system. But that's not the problem, the problem is, none of them has the right (i.e. same set of) libraries installed, some of them are 32bits, some 64bits, and now I'm pretty much lost. For example right now I'm trying to run a three-year-old script (not written by me) which used to use matplotlib/numpy to draw a real-time plot within a rectangle of a wxwidgets window. But I'm failing miserably: py26-wxpython from macports won't install, stock python has wxwidgets included but also has some conflict between 32 bits and 64 bits, and it doesn't have numpy... what a mess ! Obviously, I'm doing things the wrong way. How do you usally cope with all that chaos ?e

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• How to host WCF service and TCP server on same socket?

  - by Ole Jak

  Tooday I use ServiceHost for self hosting WCF cervices. I want to host near to my WCF services my own TCP programm for direct sockets operations (like lien to some sort of broadcasting TCP stream) I need control over namespaces (so I would be able to let my clients to send TCP streams directly into my service using some nice URLs like example.com:port/myserver/stream?id=1 or example.com:port/myserver/stream?id=anything and so that I will not be bothered with Idea of 1 client for 1 socket at one time moment, I realy want to keep my WCF services on the same port as my own server or what it is so to be able to call www.example.com:port/myWCF/stream?id=222...) Can any body please help me with this? I am using just WCF now. And I do not enjoy how it works. That is one of many resons why I want to start migration to clear TCP=) I can not use net-tcp binding or any sort of other cool WS-* binding (tooday I use the simpliest one so that my clients like Flash, AJAX, etc connect to me with ease). I needed Fast and easy in implemrnting connection protocol like one I created fore use with Sockets for real time hi ammount of data transfering. So.. Any Ideas? Please - I need help.

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• What is a good programming language/environment for Linux database applications?

  - by Dkellygb

  I could use some advice on my move from the Windows world to Linux. For my business, I have used VB6 and Microsoft Access with both Access databases and SQL server in the past. The easy to use forms, report writers and programming language were perfect for CRUD apps and analysis for our small hotel/restaurant business. After using Linux at home for some time I would like to convert our small business. Our server is already a Linux box using Samba. I am happy with the OpenOffice.org applications instead of Microsoft Office. The only thing which is holding me back is a desktop database application where I can develop the forms and reports we require. Base does not seem to be up to the job yet from my experience. I would like something like VB.Net with visual studio (express) but I would like to avoid Mono – I just don’t see the point of it. (You can correct me if I’m wrong.) But a good collection of forms, controls and a good report writer would be ideal. I have looked at web based stuff like Ruby on Rails, but I think a webserver for our 5 pc network is overkill. I don’t mind running a proper database on our Ubuntu 9.10 server. I may have exposed a few prejudices above but my mind is open. Any thoughts?

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• Java split giving opposite order of arabic characters

  - by MuhammadA

  I am splitting the following string using \\| in java (android) using the IntelliJ 12 IDE. Everything is fine except the last part, somehow the split picks them up in the opposite order : As you can see the real positioning 34,35,36 is correct and according to the string, but when it gets picked out into split part no 5 its in the wrong order, 36,35,34 ... Any way I can get them to be in the right order? My Code: public ArrayList<Book> getBooksFromDatFile(Context context, String fileName) { ArrayList<Book> books = new ArrayList<Book>(); try { // load csv from assets InputStream is = context.getAssets().open(fileName); try { BufferedReader reader = new BufferedReader(new InputStreamReader(is)); String line; while ((line = reader.readLine()) != null) { String[] RowData = line.split("\\|"); books.add(new Book(RowData[0], RowData[1], RowData[2], RowData[3], RowData[4], RowData[5])); } } catch (IOException ex) { Log.e(TAG, "Error parsing csv file!"); } finally { try { is.close(); } catch (IOException e) { Log.e(TAG, "Error closing input stream!"); } } } catch (IOException ex) { Log.e(TAG, "Error reading .dat file from assets!"); } return books; }

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• Are Fortran control characters (carriage control) still implemented in compilers?

  - by CmdrGuard

  In the book Fortran 95/2003 for Scientists and Engineers, there is much talk given to the importance of recognizing that the first column in a format statement is reserved for control characters. I've also seen control characters referred to as carriage control on the internet. To avoid confusion, by control characters, I refer to the characters "1, a blank (i.e. \s), 0, and +" as having an effect on the vertical spacing of output when placed in the first column (character) of a FORMAT statement. Also, see this text-only web page written entirely in fixed-width typeface : Fortran carriage-control (because nothing screams accuracy and antiquity better than prose in monospaced font). I found this page and others like it to be not quite clear. According to Fortran 95/2003 for Scientists and Engineers, failure to recall that the first column is reserved for carriage control can lead to horrible unintended output. Paraphrasing Dave Barry, type the wrong character, and nuclear missiles get fired at Norway. However, when I attempt to adhere to this stern warning, I find that gfortran has no idea what I'm talking about. Allow me to illustrate my point with some example code. I am trying to print out the number Pi: PROGRAM test_format IMPLICIT NONE REAL :: PI = 2 * ACOS(0.0) WRITE (*, 100) PI WRITE (*, 200) PI WRITE (*, 300) PI 100 FORMAT ('1', "New page: ", F11.9) 200 FORMAT (' ', "Single Space: ", F11.9) 300 FORMAT ('0', "Double Space: ", F11.9) END PROGRAM test_format This is the output: 1New page: 3.141592741 Single Space: 3.141592741 0Double Space: 3.141592741 The "1" and "0" are not typos. It appears that gfortran is completely ignoring the control character column. My question, then, is this: Are control characters still implemented in standards compliant compilers or is gfortran simply not standards compliant? For clarity, here is the output of my gfortran -v Using built-in specs. Target: powerpc-apple-darwin9 Configured with: ../gcc-4.4.0/configure --prefix=/sw --prefix=/sw/lib/gcc4.4 --mandir=/sw/share/man --infodir=/sw/share/info --enable-languages=c,c++,fortran,objc,java --with-gmp=/sw --with-libiconv-prefix=/sw --with-ppl=/sw --with-cloog=/sw --with-system-zlib --x-includes=/usr/X11R6/include --x-libraries=/usr/X11R6/lib --disable-libjava-multilib --build=powerpc-apple-darwin9 --host=powerpc-apple-darwin9 --target=powerpc-apple-darwin9 Thread model: posix gcc version 4.4.0 (GCC)

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• ASP.net drop down dynamically styling and then remembering the styles on aborted submit

  - by peacedog

  So, I've got an ASP drop down list (this is .net 2.0). I'm binding it with data. Basically, when the page loads and it's not a post back we'll fetch record data, bind all the drop downs, and set them to their appropriate values (strictly speaking we: initialize page with basic set of data from DB, bind drop downs from DB, fetch actual record data from DB, set drown downs to appropriate settings at this time). What I want to do is selectively style the list options. So the database returns 3 items: ID, Text, and a flag indicating whether I the record is "active" (and I'll style appropriately). It's easy enough to do and I've done it. My problem is what happens when a form submission is halted. We have slightly extended the Page class and created an AddError() method, which will create a list of errors from failed business rule checks and then display them in a ValidationSummary. It works something like this, in the submit button's click event: CheckBizRules(); if(Page.IsValid) { SaveData(); } If any business rule check fails, the Page will not be valid. The problem is, when the page re-renders (viewsate is enabled, but no data is rebound) my beautiful conditional styling is now sadly gone, off to live in the land of the missing socks. I need to preserve it. I was hoping to avoid another DB call here (e.g. getting the list data back from the DB again if the page isn't valid, just for purposes of re-styling the list). But it's not the end of the world if that's my course of action. I was hoping someone might have an alternative suggestion. I couldn't think of how to phrase this question better, if anyone has any suggestions or needs clarification don't hesitate to get it, by force if need be. ;)

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• Reducing moire when downsampling halftone comic images.

  - by drawnonward

  How can I reduce moire effects when downsampling halftone comic book images during live zoom on an iPhone or iPad? I am writing a comic book viewer. It would be nice to provide higher resolution images and allow the user to zoom in while reading the comic book. However, my client is averse to moire effects and will not allow this feature if there are noticeable moire artifacts while zooming, which of course there are. Modifying the images to be less susceptible to moire would only work if the modifications were not perceptible. Blur was specifically prohibited, as is anything that removes the beloved halftone dots. The images are black and white halftone and line art. The originals are 600 dpi but what we ship with the application will be half that at best, so probably 2500 pixels or less tall. So what are my options? If I write a custom downsampling algorithm would it be fast enough for real time on these devices? Are there other tricks I can do? Would it work to just avoid the size ratios that have the most visual moire effects? As you zoom in an out, there are definitely peaks where the moire effects are worst. Is there a way to calculate what those points are and just zoom to a nearby scale that is not as bad? Any suggestions are welcome. I have very little experience with image and signal processing, but am enjoying the opportunity to learn. I know nothing of wavelets and acutance and other jargon, so please be verbose.

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• Is a "factory" method the right pattern?

  - by jdt141

  Hey all - So I'm working to improve an existing implementation. I have a number of polymorphic classes that are all composed into a higher level container class. The problem I'm dealing with at the moment is that the higher level container class, well, sucks. It looks something like this, which I really don't have a problem with (as the polymorphic classes in the container should be public). My real issue is the constructor... /* * class1 and class 2 derive from the same superclass */ class Container { public: boost::shared_ptr<ComposedClass1> class1; boost::shared_ptr<ComposedClass2> class2; private: ... } /* * Constructor - builds the objects that we need in this container. */ Container::Container(some params) { class1.reset(new ComposedClass1(...)); class2.reset(new ComposedClass2(...)); } What I really need is to make this container class more re-usable. By hard-coding up the member objects and instantiating them, it basically isn't and can only be used once. A factory is one way to build what I need (potentially by supplying a list of objects and their specific types to be created?) Other ways to get around this problem? Seems like someone should have solved it before... Thanks!

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• How to restrict text search to a certain subset of the database ?

  - by Nikhil Garg

  I have a large central database of around 1 million heavy records. In my app, for every user I would have a subset of rows from central table, which would be very small (probably 100 records each).When a particular user has logged in , I would want to search on this data set only. Example: Say I have a central database of all cars in the world. I have a user profile for General Motors(GM) , Ferrari etc. When GM is logged in I just want to search(a full text search and not fire a sql query) for those cars which are manufactured by GM. Also GM may launch/withdraw a model in which case central db would be updated & so would be rowset associated with GM. In case of acquisitions, db of certain profiles may change without launch/removal of new car. So central db wont change then , but rowsets may. Whats the best way to implement such a design ? These smaller row sets would need to be dynamic depending on user activities. We are on Rails 2.3.5 and use thinking_sphinx as the connector and Sphinx/MySQL for search and relational associations.

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• Using GNU Octave FFT functions

  - by CFP

  Hello world! I'm playing with octave's fft functions, and I can't really figure out how to scale their output: I use the following (very short) code to approximate a function: function y = f(x) y = x .^ 2; endfunction; X=[-4096:4095]/64; Y = f(X); # plot(X, Y); F = fft(Y); S = [0:2047]/2048; function points = approximate(input, count) size = size(input)(2); fourier = [fft(input)(1:count) zeros(1, size-count)]; points = ifft(fourier); endfunction; Y = f(X); plot(X, Y, X, approximate(Y, 10)); Basically, what it does is take a function, compute the image of an interval, fft-it, then keep a few harmonics, and ifft the result. Yet I get a plot that is vertically compressed (the vertical scale of the output is wrong). Any ideas? Thanks!

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• How to use log4j for a axis2 webservice

  - by KItis

  I have created a simple axis2 webservice to understand logging functionality in a webservice. in this sample webservice, when a client calls this webservice, first it reads the log4j.property file. then i can see the logs being printed on console. but i have included file appender too into the property file. but i can not file the log file any where in my sample webapplication. i am using tomcat to run the webservice. following is webservice interface method called by client. package test; import java.io.IOException; import java.io.InputStream; import java.util.Properties; import org.apache.log4j.BasicConfigurator; import org.apache.log4j.Logger; import org.apache.log4j.PropertyConfigurator; public class WSInterface { static final Logger logger = Logger.getLogger(WSInterface.class); public String log4jTest(String input){ InputStream inputStream = this.getClass().getClassLoader() .getResourceAsStream(input); Properties properties = new Properties(); System.out.println("InputStream is: " + inputStream); //load the inputStream using the Properties try { properties.load(inputStream); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } PropertyConfigurator.configure(properties); logger.debug("Hello World!"); Class myclass = WSInterface.class; String url = myclass.getResource("WSInterface.class").toString(); String output = ""; return url; } }

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• How do I use XML Builder to create xml in rails?

  - by Angela

  I am trying the following, but the output XML is badly formed: def submit xml = Builder::XmlMarkup.new xml.instruct! xml.mail xml.documents xml.document xml.template xml.source "gallery" xml.name "Postcard: Image fill front" @xml_display = xml end I need it to look more like this: <?xml version="1.0" encoding="UTF-8"?> <mail> <documents> <document> <template> <source>gallery</source> <name>Postcard: Image fill front</name> </template> <sections> <section> <name>Text</name> <text>Hello, World!</text> </section> <section> <name>Image</name> <attachment>...attachment id...</attachment> </section> </sections> </document> </documents> <addressees> <addressee> <name>John Doe</name> <address>123 Main St</address> <city>Anytown</city> <state>AZ</state> <postal-code>10000</postal-code> </addressee> </addressees> </mail>

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• Where does IE store the ASP.NET_SessionId cookie?

  - by scherand

  I am a bit baffled here; using IE7, ASP.NET 2.0 and Cassini (the VS built-in web server; although the same thing seems to be true for "real" applications deployed in IIS) I am looking for the session-id-cookie. My test page shows a session id (by printing out Session.SessionId) and Response.Cookies.Keys contains ASP.NET_SessionId. So far so good. But I cannot find the cookie in IEs cookie-store! Nor does "remove all cookies" reset the session (as it does in FF)... So where - I am tempted to write that four letter word - does IE store that bloody cookie? Or am I missing something? By the way there is no hidden field with a session id either, as far as I can see. If I check in FF there is a cookie called ASP.NET_SessionId as I would expect. And as mentioned above deleting that cookie does start a new session; as I would expect. Can anybody imagine what is happening here?

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• Groovy / Scala / Java under the hood

  - by Jack

  I used Java for like 6-7 years, then some months ago I discovered Groovy and started to save a lot of typing.. then I wondered how certain things worked under the hood (because groovy performance is really poor) and understood that to give you dynamic typing every Groovy object is a MetaClass object that handles all the things that the JVM couldn't handle by itself. Of course this introduces a layer in the middle between what you write and what you execute that slows down everything. Then somedays ago I started getting some infos about Scala. How these two languages compare in their byte code translations? How much things they add to the normal structure that it would be obtained by plain Java code? I mean, Scala is static typed so wrapper of Java classes should be lighter, since many things are checked during compile time but I'm not sure about the real differences of what's going inside. (I'm not talking about the functional aspect of Scala compared to the other ones, that's a different thing) Can someone enlighten me? From WizardOfOdds it seems like that the only way to get less typing and same performance would be to write an intermediate translator that translates something in Java code (letting javac compile it) without alterating how things are executed, just adding synctatic sugar withour caring about other fallbacks of the language itself.

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• Is it possible to store pointers in shared memory without using offsets?

  - by Joseph Garvin

  When using shared memory, each process may mmap the shared region into a different area of their address space. This means that when storing pointers within the shared region, you need to store them as offsets of the start of the shared region. Unfortunately, this complicates use of atomic instructions (e.g. if you're trying to write a lock free algorithm). For example, say you have a bunch of reference counted nodes in shared memory, created by a single writer. The writer periodically atomically updates a pointer 'p' to point to a valid node with positive reference count. Readers want to atomically write to 'p' because it points to the beginning of a node (a struct) whose first element is a reference count. Since p always points to a valid node, incrementing the ref count is safe, and makes it safe to dereference 'p' and access other members. However, this all only works when everything is in the same address space. If the nodes and the 'p' pointer are stored in shared memory, then clients suffer a race condition: x = read p y = x + offset Increment refcount at y During step 2, p may change and x may no longer point to a valid node. The only workaround I can think of is somehow forcing all processes to agree on where to map the shared memory, so that real pointers rather than offsets can be stored in the mmap'd region. Is there any way to do that? I see MAP_FIXED in the mmap documentation, but I don't know how I could pick an address that would be safe.

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• RSA_sign and RSACryptoProvider.VerifySignature

  - by Miky D

  I'm trying to get up to speed on how to get some code that uses OpenSSL for cryptography, to play nice with another program that I'm writing in C#, using the Microsoft cryptography providers available in .NET. More to the point, I'm trying to have the C# program verify an RSA message signature generated by the OpenSSL code. The code that generates the signature looks something like this: // Code in C, using the OpenSSL RSA implementation char msgToSign[] = "Hello World"; // the message to be signed char signature[RSA_size(rsa)]; // buffer that will hold signature int slen = 0; // will contain signature size // rsa is an OpenSSL RSA context, that's loaded with the public/private key pair memset(signature, 0, sizeof(signature)); RSA_sign(NID_sha1 , (unsigned char*)msgToSign , strlen(msgToSign) , signature , &slen , rsa); // now signature contains the message signature // and can be verified using the RSA_verify counterpart // .. I would like to verify the signature in C# In C#, I would do the following: import the other side's public key into an RSACryptoServiceProvider object receive the message and it's signature try to verify the signature I've got the first two parts working (I've verified that the public key is loading properly because I managed to send an RSA encrypted text from the C# code to the OpenSSL code in C and successfully have it decrypted) In order to verify the signature in C#, I've tried using the: VerifySignature method of the RSACryptoServiceProvider but that didn't work. And digging around the internet I was only able to find some vague information pointing out that .NET uses a different method for generating the signature than OpenSSL does. So, does anybody know how to accomplish this?

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• Java library class to handle scheduled execution of "callbacks"?

  - by Hanno Fietz

  My program has a component - dubbed the Scheduler - that lets other components register points in time at which they want to be called back. This should work much like the Unix cron service, i. e. you tell the Scheduler "notify me at ten minutes past every full hour". I realize there are no real callbacks in Java. Here's my approach, is there a library which already does this stuff? Feel free to suggest improvements, too. Register call to Scheduler passes: a time specification containing hour, minute, second, year month, dom, dow, where each item may be unspecified, meaning "execute it every hour / minute etc." (just like crontabs) an object containing data that will tell the calling object what to do when it is notified by the Scheduler. The Scheduler does not process this data, just stores it and passes it back upon notification. a reference to the calling object Upon startup, or after a new registration request, the Scheduler starts with a Calendar object of the current system time and checks if there are any entries in the database that match this point in time. If there are, they are executed and the process starts over. If there aren't, the time in the Calendar object is incremented by one second and the entreis are rechecked. This repeats until there is one entry or more that match(es). (Discrete Event Simulation) The Scheduler will then remember that timestamp, sleep and wake every second to check if it is already there. If it happens to wake up and the time has already passed, it starts over, likewise if the time has come and the jobs have been executed. Edit: Thanks for pointing me to Quartz. I'm looking for something much smaller, however.

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• I've made something that might be useful to the community. Now what?

  - by Chris McCall

  If the specifics are important, I made a cruisecontrol.net publisher plugin that notifies a series of phone numbers via voice, announcing the current state of the build. It uses Twilio to do so. I'd like to avoid getting hung up on the specifics of what it is I've made, as I have this question a lot, with a number of little hobby one-offs. What's the state of the art as far as making my hobby output available to the world at large? There seem to be a lot of options for open-source project hosting, community features, and what role to take in all of this. It's a little bewildering. What I'm looking for is to put this out into the wild for free and basically take a hands-off approach from there. Is that realistic? Which project hosting service can I use for free to allow developers to at least download the code, report issues and collaborate with each other to improve the product? What snags have you run into that could make me regret this decision? I'm interested in war stories, advice and guidance on making this little product available to the community where it can be used.

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