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  • Java performance issue

    - by Colby77
    Hi, I've got a question related to java performance and method execution. In my app there are a lot of place where I have to validate some parameter, so I've written a Validator class and put all the validation methods into it. Here is an example: public class NumberValidator { public static short shortValidator(String s) throws ValidationException{ try{ short sh = Short.parseShort(s); if(sh < 1){ throw new ValidationException(); } return sh; }catch (Exception e) { throw new ValidationException("The parameter is wrong!"); } } ... But I'm thinking about that. Is this OK? It's OO and modularized, but - considering performance - is it a good idea? What if I had awful lot of invocation at the same time? The snippet above is short and fast, but there are some methods that take more time. What happens when there are a lot of calling to a static method or an instance method in the same class and the method is not synchronized? All the calling methods have to fall in line and the JVM executes them sequentially? Is it a good idea to have some class that are identical to the above-mentioned and randomly call their identical methods? I think it is not, because "Don't repeat yourself " and "Duplication is Evil" etc. But what about performance? Thanks is advance.

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  • How Can I: Generate 40/64 Bit WEP Key In Python?

    - by Aktariel
    So, I've been beating my head against the wall of this issue for several months now, partly because it's a side interest and partly because I suck at programming. I've searched and researched all across the web, but have not had any luck (except one small bit of success; see below), so I thought I might try asking the experts. What I am trying to do is, as the title suggests, generate a 40/64 bit WEP key from a passphrase, according to the "de facto" standard. (A site such as [http://www.powerdog.com/wepkey.cgi] produces the expected outputs.) I have already written portions of the script that take inputs and write them to a file; one of the inputs would be the passphrase, sanitized to lower case. For the longest time I had no idea what the defacto standard was, much less how to even go about implementing it. I finally stumbled across a paper (http://www.lava.net/~newsham/wlan/WEP_password_cracker.pdf) that sheds as much light as I've had yet on the issue (page 18 has the relevant bits). Apparently, the passphrase is "mapped to a 32-bit value with XOR," the result of which is then used as the seed for a "linear congruential PRNG (which one of the several PRNGs Python has would fit this description, I don't know), and then from that result several bits of the result are taken. I have no idea how to go about implementing this, since the description is rather vague. What I need is help in writing the generator in Python, and also in understanding how exactly the key is generated. I'm not much of a programmer, so explanations are appreciated as well. (Yes, I know that WEP isn't secure.)

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  • Is undefined behavior worth it?

    - by Space_C0wb0y
    Many bad things happened and continue to happen (or not, who knows, anything can happen) due to undefined behavior. I understand that this was introduced to leave some wiggle-room for compilers to optimize, and maybe also to make C++ easier to port to different platforms and architectures. However the problems caused by undefined behavior seem to be too large to be justified by these arguments. What are other arguments for undefined behavior? If there are none, why does undefined behavior still exist?

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  • PHP URL Security Question

    - by TaG
    I want to have users store the url in my database I'm using php mysql and htmlpurifier I was wondering if the following code was good way to filter out bad data? Here is the Partial PHP code. $url = mysqli_real_escape_string($mysqli, $purifier->purify(htmlspecialchars(strip_tags($_POST['url'])));

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  • Method that does conditional return of method calling it?

    - by Mattias Konradsson
    Ok this might be a bit of hack but bear with me :) The background is that i'm tired of methods that that some if-statement to that messes up indention for the whole method, like: public SomeClass DoStuff(string inputStr) { SomeClass result =null; if (IsOpenFilter(inputStr)) { .... } return result; } So I was thinking , wouldn't it be neat if I could do something like this instead: public SomeClass DoStuff(string inputStr) { Require(IsOpenFilter(inputStr),null); .... return result; } The idea is that if the statement does not evaluates to true it would return null. If there wasn't a return type for the method it would simply be: Require(IsOpenFilter(inputStr)); I realize that this is kinda overlapping with code contracts but these would be more like "conditional" or "soft" contracts evaluated at runtime rather than compile time. So I guess there's two questions, can this be done somehow? I'm stumped on how to do a conditional return from calling a method. The other question is, is this a good idea? It's a bit weird to monkeypatch the language like this but I'd rather like the way the code reads. I would be even cleaner if it could be put into an attribute above the method: [Require(IsOpenFilter(inputStr))]

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  • Will GTK's pango and cairo work well in Coca and MFC applications.

    - by Lothar
    I'm writing a GUI program and decided to go native on all platforms. But for all the stuff i need to draw myself i would like to use the same drawing routines because font and unicode handling is so difficult and complex. Do you see any negative points in useing Pango/Cairo. Well on MacOSX i havent succeded installing Pango/Cairo yet. Looks like a bad Omen.

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  • Excel::Shape object getting released automatically after the count reaches 18 in List<T>

    - by A9S6
    I have a Excel addin written in C# 2.0 in which I am experiencing a strange behavior.Please note that this behavior is only seen in Excel 2003 and NOT in Excel 2007 or 2010. Issue: When the user clicks an import command button, a file is read and a number of Shapes are created/added to the worksheet using Worksheet::Shapes::AddPicture() method. A reference to these Shape objects are kept in a generic list: List<Excel.Shape> list = new List<Excel.Shape>(); Everything works fine till the list has less than 18 references. When the count reaches 18, and a new Shape reference is added, the first one i.e. @ index [0] is released. I am unable to call any method or property on that reference and calling a method/property throws a COMException (0x800A1A8) i.e. Object Required. If I add one more, then the reference @ [1] is not accessible and so on. Strange enough... this happens with Shape object only i.e. If I add one Shape and then 17 nulls to the list then this wont happen until 17 more Shape objects are added. Does anyone has an idea why it happens after the count reaches 18? I thought it might be something with the List's default capacity. Something like relocating the references during which they get released so I initialized it with a capacity of 1000 but still no luck. List<Excel.Shape> list = new List<Excel.Shape>(1000); Any Idea??

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  • Model login constraints based on time

    - by DaDaDom
    Good morning, for an existing web application I need to implement "time based login constraints". It means that for each user, later maybe each group, I can define timeslots when they are (not) allowed to log in into the system. As all data for the application is stored in database tables, I need to somehow create a way to model this idea in that way. My first approach, I will try to explain it here: Create a tree of login constraints (called "timeslots") with the main "categories", like "workday", "weekend", "public holiday", etc. on the top level, which are in a "sorted" order (meaning "public holiday" has a higher priority than "weekday") for each top level node create subnodes, which have a finer timespan, like "monday", "tuesday", ... below that, create an "hour" level: 0, 1, 2, ..., 23. No further details are necessary. set every member to "allowed" by default For every member of the system create a 1:n relationship member:timeslots which defines constraints, e.g. a member A may have A:monday-forbidden and A:tuesday-forbidden Do a depth-first search at every login and check if the member has a constraint. Why a depth first search? Well, I thought that it may be that a member has the rules: A:monday->forbidden, A:monday-10->allowed, A:mondey-11->allowed So a login on monday at 12:30 would fail, but one at 10:30 succeed. For performance reasons I could break the relational database paradigm and set a flag for every entry in the member-to-timeslots-table which is set to true if the member has information set for "finer" timeslots, but that's a second step. Is this model in principle a good idea? Are there existing models? Thanks.

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  • JS and Rails site wide announcements

    - by pcasa
    Tried doing http://davidwparker.com/2008/09/17/site-wide-announcements-in-rails-using-jquery-jgrowl/ Am really bad with JS. Think I am messing up on the last part where it says "This code goes in your application.js file (somewhere in $(function){ //here })" Am I not suppose to do a link_to_function and create a function with this code that references that link? Really lost on this one.

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  • How to post a poll on the Facebook wall

    - by Bengt
    Hi, I'm trying to convert my poll app into a Facebook iframe app. My app is written in PHP and uses some Ajax calls to vote at a poll. In the application canvas everything is working fine, but of course I want to get the poll on the wall of a user too. Unfortunately I'm not able to find out how I can post a simple poll with some radio buttons for the options on the wall. I know how to publish images, text, audio files and links to the wall, but I have no idea how to publish my poll on the wall. And I don't just want to use links to vote, I want the user be able to choose a radio button. Does anyone have an idea how to do this or where to find information about doing this? I'm stuck there now for a while and it gets pretty frustrating. I'm using the new Graph API by the way. Or is this impossible? But I don't think so. Any help is appreciated. Bengt

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  • What I must to learn to write php graber (parser)?

    - by butteff
    What I must to learn to write php web-site graber (parser)? It's just must collect any other information from other websites, as weather forecast, wiki "on this day", some news and other useful and interesting "every day" information! and what i must to read for writing m3u player on php? sorry for my bad english

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  • How can I apply a PSSM efficiently?

    - by flies
    I am fitting for position specific scoring matrices (PSSM aka Position Specific Weight Matrices). The fit I'm using is like simulated annealing, where I the perturb the PSSM, compare the prediction to experiment and accept the change if it improves agreement. This means I apply the PSSM millions of times per fit; performance is critical. In my particular problem, I'm applying a PSSM for an object of length L (~8 bp) at every position of a DNA sequence of length M (~30 bp) (so there are M-L+1 valid positions). I need an efficient algorithm to apply a PSSM. Can anyone help improve performance? My best idea is to convert the DNA into some kind of a matrix so that applying the PSSM is matrix multiplication. There are efficient linear algebra libraries out there (e.g. BLAS), but I'm not sure how best to turn an M-length DNA sequence into a matrix M x 4 matrix and then apply the PSSM at each position. The solution needs to work for higher order/dinucleotide terms in the PSSM - presumably this means representing the sequence-matrix for mono-nucleotides and separately for dinucleotides. My current solution iterates over each position m, then over each letter in word from m to m+L-1, adding the corresponding term in the matrix. I'm storing the matrix as a multi-dimensional STL vector, and profiling has revealed that a lot of the computation time is just accessing the elements of the PSSM (with similar performance bottlenecks accessing the DNA sequence). If someone has an idea besides matrix multiplication, I'm all ears.

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  • What is the worst code you've ever written?

    - by Even Mien
    Step into the confessional. Now's your time to come clean. What's the worst code you personally have ever written? Why was it so bad? What did you learn from it? Don't tell us about code you inherited or from some co-worker. This is about your personal growth as a programmer and as a person.

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  • Best way to save user settings on client-side (javascript,jquery)

    - by Johua
    I have a settings page that a user can enter some text and save directly to a combobox. Next time when page loads, combobox is filled in with the previous entered text. Also i have a modify button, so the user can delete or edit a value from the combobox. My question is, what's the best way to save to user settings on the client with javascirpt/jquery? I can only think of using an array and then (push/pop).,,Anyone got some bad experience with arrrays? thx

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  • Strange Problem with Webservice and IIS

    - by Rene
    Hello there, I have a Problem which confuses me a little bit, resp. where I don't have any Idea about what it could be. The System I'm using is Windows Vista, IIS 7.0, VS2008, Windows Software Factory, Entity Framework, WCF. The Binding for all Webservices is wshttpbinding. I'm using a Webservice hosted in IIS. This Webservice uses/calls another Webservice (also installed in the IIS). If I use a client calling the first Webservice (which calls the second Webservice) it works fine for about 4-10 Times. And then (it is repeatable to get this Problem, but sometimes it happens after 4, sometimes after 10 Time, but it always will happen), the Service and the IIS gets stuck. Stuck means, that this Webservice isn't callable anymore and generates an timeout after 1 minute. Even increasing Timeout doesn't change anything. If i try to restart the IIS I get an timeout error. So the IIS is also "stuck" (it is not really stuck, but I can't restart it). Only if I kill the w3wp.exe IIS is restartable and the Webservice will work again (until i again call this service several times). The logfiles (i'm no expert in things like logging or where to find/enable such logs, so to say : i'm a newbie) like http-logging, Event Viewer or WCF-Message Logging don't show any hints upon the source of the problem. I don't have this problem when I'm using a Webservice which doesn't call another Service. Calling a Webservice is done by Service Reference (I'm using no Proxy-Classes), but I think this should be no Problem. I have no idea of what is happening, nor how to solve this Problem. Regards Rene

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  • DotNetZip trouble with russian encoding

    - by Xaver
    i use DotNetZip in my project. using (var zip = new ZipFile()) { zip.ProvisionalAlternateEncoding = System.Text.Encoding.GetEncoding(866); zip.AddFile(filename, "directory\\in\\archive"); zip.Save("archive.zip"); } all ok but when i use method AddDirectoryByName i have a bad directory names.

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  • Need some guidelines on iPad animation programming

    - by thomasvsundert
    Hi, I'm creating an interactive e-book for the iPad. This book will contain multiple pages that will consist of a lot of animations (frame and motion animations), transitions,... I was wondering what my development options are, should I use OpenGL, Quartz,...? I've use UIImageView.animationImages before and found that it had really bad performance. What's the best way to draw frame based animations? Does anybody have some good pointers to resources on this? thanks in advance, Thomas

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  • C# can't cast bool to int

    - by Svetlozar Angelov
    We all know that in C# we can't cast bool to int. I wanted to see what is the binary representation of true with bitmask, but I can't use (bool & int).. I think the problem is the architecture desicion "true is true, not any number != 0" (C++) and I was wondering what the benefits of such an architecture are? What is so bad with the C true/false concept?

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  • svnserve not strictly required?

    - by Kev
    I was reading the Red Bean book and noticed this paragraph: Do not be seduced by the simple idea of having all of your users access a repository directly via file:// URLs. Even if the repository is readily available to everyone via a network share, this is a bad idea. It removes any layers of protection between the users and the repository: users can accidentally (or intentionally) corrupt the repository database, it becomes hard to take the repository offline for inspection or upgrade, and it can lead to a mess of file permission problems (see the section called “Supporting Multiple Repository Access Methods”). Note that this is also one of the reasons we warn against accessing repositories via svn+ssh:// URLs—from a security standpoint, it's effectively the same as local users accessing via file://, and it can entail all the same problems if the administrator isn't careful. I realized that, since I'm the only one accessing the repository, ever, none of these caveats seem to apply. Can I safely down svnserve then and only ever have to worry about upgrading my TortoiseSVN client, not both the client and the server whenever there's a new version out? (I've tried it already--just needed to use the Relocate feature to switch from svn:// to file://--but I wanted to make sure something wouldn't be sneaking up on me if I left it this way.)

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  • javascript plugin - singleton pattern?

    - by Adam Kiss
    intro Hello, I'm trying to develop some plugin or/*and* object in javascript, which will control some properties over some object. It will also use jQuery, to ease development. idea This is in pseudocode to give you an idea, since I can't really describe it in english with the right words, it's impossible to go and use google to find out what I want to use (and learn). I will have plugin (maybe object?) with some variables and methods: plugin hideshow(startupconfig){ var c, //collection add: function(what){ c += what; }, do: function(){ c.show().hide().stop(); //example code } } and I will use it this way (or sort-of): var p = new Plugin(); p .add($('p#simple')) .add($('p#simple2')) .do(); note I'm not really looking for jQuery plugin tutorials - it's more like usage of singleton pattern in document in javascript, jQuery is mentione only because it will be used to modify dom and simplify selectors, jQuery plugin maybe just for that one little function add. I'm looking for something, that will sit on top of my document and call functions from itselft based on timer, or user actions, or whatever. problems I don't really know where to start with construction of this object/plugin I'm not really sure how to maintain one variable, which is collection of jQuery objects (something like $('#simple, #simple2');) I would maybe like to extedn jQuery with $.fn.addToPlugin to use chaining of objects, but that should be simple (really just each( p.add($(this)); )) I hope I make any sense, ideas, links or advices appreciated.

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  • Extending Java Enums

    - by CaseyB
    Here's what I am looking to accomplish, I have a class that has an enum of some values and I want to subclass that and add more values to the enum. This is a bad example, but: public class Digits { public enum Digit { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 } } public class HexDigits extends Digits { public enum Digit { A, B, C, D, E, F } } so that HexDigits.Digit contains all Hex Digits. Is that possible?

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  • proper use of volatile keyword

    - by luke
    I think i have a pretty good idea about the volatile keyword in java, but i'm thinking about re-factoring some code and i thought it would be a good idea to use it. i have a class that is basically working as a DB Cache. it holds a bunch of objects that it has read from a database, serves requests for those objects, and then occasionally refreshes the database (based on a timeout). Heres the skeleton public class Cache { private HashMap mappings =....; private long last_update_time; private void loadMappingsFromDB() { //.... } private void checkLoad() { if(System.currentTimeMillis() - last_update_time > TIMEOUT) loadMappingsFromDB(); } public Data get(ID id) { checkLoad(); //.. look it up } } So the concern is that loadMappingsFromDB could be a high latency operation and thats not acceptable, So initially i thought that i could spin up a thread on cache startup and then just have it sleep and then update the cache in the background. But then i would need to synchronize my class (or the map). and then i would just be trading an occasional big pause for making every cache access slower. Then i thought why not use volatile i could define the map reference as volatile private volatile HashMap mappings =....; and then in get (or anywhere else that uses the mappings variable) i would just make a local copy of the reference: public Data get(ID id) { HashMap local = mappings; //.. look it up using local } and then the background thread would just load into a temp table and then swap the references in the class HashMap tmp; //load tmp from DB mappings = tmp;//swap variables forcing write barrier Does this approach make sense? and is it actually thread-safe?

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  • Closure Library with ASP.NET

    - by jarrett
    Google's Closure Library looks like it has a lot of great features, but I'm not seeing any examples of it used with ASP.NET sites. I'm just wondering if anyone has any experience using the two together and what parts. Is is a good or bad experience?

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