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  • optimistic and pessimistic locks

    - by billmce
    Working on my first php/Codeigniter project and I’ve scoured the ‘net for information on locking access to editing data and haven’t found very much information. I expect it to be a fairly regular occurrence for 2 users to attempt to edit the same form simultaneously. My experience (in the stateful world of BBx, filePro, and other RAD apps) is that the data being edited is locked using a pessimistic lock—one user has access to the edit form at the time. The second user basically has to wait for the first to finish. I understand this can be done using Ajax sending XMLHttpRequests to maintain a ‘lock’ database. The php world, lacking state, seems to prefer optimistic locking. If I understand it correctly it works like this: both users get to access the data and they each record a ‘before changes’ version of the data. Before saving their changes, the data is once again retrieved and compared the ‘before changes’ version. If the two versions are identical then the users changes are written. If they are different; the user is shown what has changed since he/she started editing and some mechanism is added to resolve the differences—or the user is shown a ‘Sorry, try again’ message. I’m interested in any experience people here have had with implementing both pessimistic and optimistic locking. If there are any libraries, tools, or ‘how-to’s available I’m appreciate a link. Thanks

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  • Intercept creation of activities when the application is restored

    - by Johan Bilien
    Most of our activities access a user-specific model. All these activities inherit from a ModelActivity base class, which provides a getModel() call. When one of these activities detect that the user has signed out (through the AccountManager callback), it sticks to its existing model, but prepares to exit back to the root activity (which is not user-specific) by starting its intent with FLAG_ACTIVITY_CLEAR_TOP. If however the user deletes an account while the app is not running, we run into trouble when the activity is restored. Now the activity needs to handle there not being a model, which makes the code more complicated and bug-prone. Ideally we would intercept the application restore process before the activity is created. Then we would check whether we have an account and a model, and if not clear up the saved stack of activities, and restart from our root activity instead of the last saved activity. But as far as I can tell the first place where we can run code is in the onCreate callback of the activity. Is there a way to run some code when the application is restored from background-saving, but before the saved activity is created?

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  • why my iphone device and simulator has different screen resolution?

    - by happyzone8
    i use itouch 4G has my device and i use simulator-4.2 i will just draw a rectangle as an example. i use Quartz-2d to draw - (void)drawRect:(CGRect)rect { // Get a graphics context, saving its state CGContextRef context = UIGraphicsGetCurrentContext(); CGContextSaveGState(context); // Reset the transformation CGAffineTransform t0 = CGContextGetCTM(context); t0 = CGAffineTransformInvert(t0); CGContextConcatCTM(context,t0); // Draw a green rectangle CGContextBeginPath(context); CGContextSetRGBFillColor(context, 0,1,0,1); CGContextAddRect(context, CGRectMake(0,0,320,480)); CGContextClosePath(context); CGContextDrawPath(context,kCGPathFill); CGContextRestoreGState(context); } i run it in the simulator, the whole screen becomes green, then i run this on my device, only the quarter of the screen becomes green, in order to make the whole screen green on my device, i have to draw a larger rectangle CGContextAddRect(context, CGRectMake(0,0,640,960)); seem like my device has twice resolution than the simulator, how can i fix this?

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  • Problem with SqlLite database in Qt SDK 1.0.2

    - by Risino
    Hi I have a problem with SqlLite database. Here is my code: void incomeDialog::on_add_pushButton_clicked() { int a = ui->income_lineEdit->text().toInt(); int b = ui->other_lineEdit->text().toInt(); int c = (a+b); db = QSqlDatabase::addDatabase("QSQLITE"); db.setDatabaseName("money.db"); QSqlQuery query(db); query.exec("create table Income" "(Month TEXT, Payment NUMBER, Other NUMBER, Together NUMBER)"); query.prepare("INSERT INTO Income values (?,?,?,?)"); query.addBindValue(ui->comboBox->currentText()); query.addBindValue(ui->income_lineEdit->text().toInt()); query.addBindValue(ui->other_lineEdit->text().toInt()); query.addBindValue(c); query.exec(); } I use qt sdk 1.0.2. After building shows errors: Undefined reference to 'QSqlDatabase::addDatabase(QString const&, QString const&)... all errors is similar (Undefined reference to 'QSqlDatabase:: Do you have any idea how to repair it?

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  • DOM manipulation

    - by bluedaniel
    Hello everyone, Im trying to use the DOM in PHP to do a pretty specific job and Ive got no luck so far, the objective is to take a string of HTML from a Wordpress blog post (from the DB, this is a wordpress plugin). And then out of that HTML replace <div id="do_not_edit">old content</div>" with <div id="do_not_edit">new content</div>" in its place. Saving anything above and below that div in its structure. Then save the HTML back into the DB, should be simple really, I have read that a regex wouldnt be the right way to go here so Ive turned to the DOM instead. The problem is I just cant get it to work, cant extract the div or anything. Help me!! UPDATE The HTML coming out of the wordpress table looks like: Congratulations on finding us here on the world wide web, we are on a mission to create a website that will show off your culinary skills better than any other website does. <div id="do_not_edit">blah blah</div> We want this website to be fun and easy to use, we strive for simple elegance and incredible functionality.We aim to provide a 'complete package'. By this we want to create a website where people can meet, share ideas and help each other out. After several different (incorrect) workings all Ive got below is: $content = ($wpdb->get_var( "SELECT `post_content` FROM $wpdb->posts WHERE ID = {$article[post_id]}" )); $doc = new DOMDocument(); $doc->validateOnParse = true; $doc->loadHTMLFile($content); $element = $doc->getElementById('do_not_edit'); echo $element;

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  • Name for a "naive" timekeeping system?

    - by Robert L
    I am thinking of a "naive" timekeeping system of the sort I believe would be likely to be implemented by non-specialists. A day is exactly 24 hours. An hour is exactly 60 minutes. A minute is exactly 60 seconds. No exceptions (i.e. no Daylight Saving or leap seconds). A leap year occurs exactly once every four years: if the year modulo 4 equals 0, it is a leap year. The month lengths are the normal 31 days for January, 28 or 29 days for February, etc., that you would expect to find on a wall calendar. Days of the week, if they are used, are what you would get by taking your contemporary (late 1900's / early 2000's) wall calendar and, using the above rules for leap years and month lengths, extrapolating in both directions: if the calendar goes far back enough, February 29, 1900 exists and is a Wednesday; and if the calendar goes far forward enough, February 29, 2100 exists and is a Monday. What name, if any, is used to describe precisely this system?

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  • Why should I abstract my data layer?

    - by Gazillion
    OOP principles were difficult for me to grasp because for some reason I could never apply them to web development. As I developed more and more projects I started understanding how some parts of my code could use certain design patterns to make them easier to read, reuse, and maintain so I started to use it more and more. The one thing I still can't quite comprehend is why I should abstract my data layer. Basically if I need to print a list of items stored in my DB to the browser I do something along the lines of: $sql = 'SELECT * FROM table WHERE type = "type1"';' $result = mysql_query($sql); while($row = mysql_fetch_assoc($result)) { echo '<li>'.$row['name'].'</li>'; } I'm reading all these How-Tos or articles preaching about the greatness of PDO but I don't understand why. I don't seem to be saving any LoCs and I don't see how it would be more reusable because all the functions that I call above just seem to be encapsulated in a class but do the exact same thing. The only advantage I'm seeing to PDO are prepared statements. I'm not saying data abstraction is a bad thing, I'm asking these questions because I'm trying to design my current classes correctly and they need to connect to a DB so I figured I'd do this the right way. Maybe I'm just reading bad articles on the subject :) I would really appreciate any advice, links, or concrete real-life examples on the subject!

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  • Django | passing form values

    - by MMRUser
    I want to create a user sign up process that requires two different forms with the same data one (1st form) is for filling out the data and other one (2nd form) is for displaying the filled data as a summery (before actually saving the data) so then user can view what he/she has filled up... my problem is that how do I pass 1st form's data in to the 2nd one .. I have used the basic Django form manipulation mechanism and passed the form field values to the next form using Django template tags.. if request.method == 'POST': form = Users(request.POST) if form.is_valid(): cd = form.cleaned_data try: name = cd['fullName'] email = cd['emailAdd'] password1 = cd['password'] password2 = cd['password2'] phoneNumber = cd['phoneNumber'] return render_to_response('signup2.html', {'name': name, 'email': email, 'password1': password1, 'password2': password2, 'phone': phone, 'pt': phoneType}) except Exception, ex: return HttpResponse("Error %s" % str(ex)) and from the second from I just displayed those field values using tags and also used hidden fields in order to submit the form with values, like this: <label for="">Email:</label> {{ email }} <input type="hidden" id="" name="email" class="width250" value="{{ email }}" readonly /> It works nicely from the out look, but the real problem is that if someone view the source of the html he can simply get the password even hackers can get through this easily. So how do I avoid this issue.. and I don't want to use Django session since this is just a simple sign up process and no other interactions involved. Thanks.

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  • What's wrong with output parameters?

    - by Chris McCall
    Both in SQL and C#, I've never really liked output parameters. I never passed parameters ByRef in VB6, either. Something about counting on side effects to get something done just bothers me. I know they're a way around not being able to return multiple results from a function, but a rowset in SQL or a complex datatype in C# and VB work just as well, and seem more self-documenting to me. Is there something wrong with my thinking, or are there resources from authoritative sources that back me up? What's your personal take on this and why? What can I say to colleagues that want to design with output parameters that might convince them to use different structures? EDIT: interesting turn- the output parameter I was asking this question about was used in place of a return value. When the return value is "ERROR", the caller is supposed to handle it as an exception. I was doing that but not pleased with the idea. A coworker wasn't informed of the need to handle this condition and as a result, a great deal of money was lost as the procedure failed silently!

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  • Exited event of Process is not rised?

    - by Kanags.Net
    In my appliation,I am opening an excel sheet to show one of my Excel documents to the user.But before showing the excel I am saving it to a folder in my local machine which in fact will be used for showwing. While the user closes the application I wish to close the opened excel files and delete all the excel files which are present in my local folder.For this, in the logout event I have written code to close all the opened files like shown below, Process[] processes = Process.GetProcessesByName(fileType); foreach (Process p in processes) { IntPtr pFoundWindow = p.MainWindowHandle; if (p.MainWindowTitle.Contains(documentName)) { p.CloseMainWindow(); p.Exited += new EventHandler(p_Exited); } } And in the process exited event I wish to delete the excel file whose process is been exited like shown below void p_Exited(object sender, EventArgs e) { string file = strOriginalPath; if (File.Exists(file)) { //Pdf issue fix FileStream fs = new FileStream(file, FileMode.Open, FileAccess.Read); fs.Flush(); fs.Close(); fs.Dispose(); File.Delete(file); } } But the problem is this exited event is not called at all.On the other hand if I delete the file after closing the MainWindow of the process I am getting an exception "File already used by another process". Could any help me on how to achieve my objective or give me an reason why the process exited event is not being called?

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  • Password security; Is this safe?

    - by Camran
    I asked a question yesterday about password safety... I am new at security... I am using a mysql db, and need to store users passwords there. I have been told in answers that hashing and THEN saving the HASHED value of the password is the correct way of doing this. So basically I want to verify with you guys this is correct now. It is a classifieds website, and for each classified the user puts, he has to enter a password so that he/she can remove the classified using that password later on (when product is sold for example). In a file called "put_ad.php" I use the $_POST method to fetch the pass from a form. Then I hash it and put it into a mysql table. Then whenever the users wants to delete the ad, I check the entered password by hashing it and comparing the hashed value of the entered passw against the hashed value in the mysql db, right? BUT, what if I as an admin want to delete a classified, is there a method to "Unhash" the password easily? sha1 is used currently btw. some code is very much appreciated. Thanks

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  • Subversion unable to merge changes when using Dreamweaver

    - by neilc
    I've got a project running and we're using SVN as the version control. There are 3 devs on it. Dev1 = OSX + Textmate Dev2 = Windows 7 + Dreamweaver (plus tortoise svn) Dev3 = OSX + Coda Case 1 (expected): Dev1 and dev3 work on a file called signup.php. They work on different parts of the file. Dev1 commits it and dev3 updates their copy. signup.php is merged as expected. All good. Case 2 (not expected): Dev1 and dev2 work on a file called signup.php. They work on different parts of the file. Dev1 commits it and dev2 updates their copy. signup.php is always in conflict even though different parts of the file are worked on. This is not the expected behaviour experienced by dev1 and dev3. This works boths ways and each time dev1 updates dev2's changes he gets conflicts too. But never with dev3. Could this be down the way Dreamweaver is saving files ? Perhaps character encoding. We are all working in UTF8. These constant and unnecessary conflicts are becoming a massive distraction. Help !

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  • Namespace scoped aliases for generic types in C#

    - by TN
    Let's have a following example: public class X { } public class Y { } public class Z { } public delegate IDictionary<Y, IList<Z>> Bar(IList<X> x, int i); public interface IFoo { // ... Bar Bar { get; } } public class Foo : IFoo { // ... public Bar Bar { get { return null; //... } } } void Main() { IFoo foo; //= ... IEnumerable<IList<X>> source; //= ... var results = source.Select(foo.Bar); } The compiler says: The type arguments for method 'System.Linq.Enumerable.Select(System.Collections.Generic.IEnumerable, System.Func)' cannot be inferred from the usage. Try specifying the type arguments explicitly. It's because, it cannot convert Bar to Func<IList<X>, int, IDictionary<Y, IList<Z>>>. It would be great if I could create type namespace scoped type aliases for generic types in C#. Then I would define Bar not as a delegate, but rather I would define it as an namespace scoped alias for Func<IList<X>, int, IDictionary<Y, IList<Z>>>. public alias Bar = Func<IList<X>, int, IDictionary<Y, IList<Z>>>; I could then also define namespace scoped alias for e.g. IDictionary<Y, IList<Z>>. And if used appropriately:), it will make the code more readable. Now I have inline the generic types and the real code is not well readable:( Have you find the same trouble:)? Is there any good reason why it is not in C# 3.0? Or there is no good reason, it's just matter of money and/or time? EDIT: I know that I can use using, but it is not namespace based - not so convenient for my case.

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  • How to use Many to Many in Rails?

    - by Newbie
    Hello! In my project, I have users and quests. One User can join multiple quests and one quest can have multiple users. So I created a table called questing, containing the user_id and the quest_id. In my user.rb I did following: require 'digest/sha1' class User < ActiveRecord::Base has_many :questings has_many :quests ,:through =>:questings ... My Quest.rb: class Quest < ActiveRecord::Base has_many :questings has_many :users ,:through =>:questings ... My Questing.rb: class Questing < ActiveRecord::Base belongs_to :quest belongs_to :user end Now I want to create a link or button on my /quests/show.html.erb, calling an action in my controller, which will create the relationship between user and quest. So, in my quest_controller I did: def join_quest @quest = Quest.find(params[:id]) puts '************************' puts 'join quest:' + @quest.id puts '************************' respond_to do |format| format.html { redirect_to(@quest) } format.xml { head :ok } end end and in my show.html.erb I did: <%= link_to 'join this quest!!!', :action => :join_quest %> Now, clicking on this link will cause an error like: Couldn't find Quest with ID=join_quest and the url points to */quests/join_quest* instead of */quests/1/join_quest* Now my questions: Is my quests_controller the right place for my join_quest action, or should I move it to my users_controller? Why do I get this error? How to solve it? What do I have to write in my join_quest action for saving the relationship? On my /users/show.html.erb I want to output all quests the user joined. How to do this? I have to get all this quests from my relationship table, right? How? I hope you can help me! THX!

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  • NHibernate many-to-many relationship does not update join-table

    - by Davide Vosti
    I'm having trouble saving a many-to-many relationship with nhibernate. I searched and looked at almost every same question in SO and google but nothing works. The single classes are update correctly but nothing is inserted in the join-table. I have 2 classes: Event and Category. The mapping is this: Event: <bag name="Categories" access="field.camelcase-underscore" table="EventCategories" inverse="true" cascade="all-delete-orphan" lazy="true"> <key column="Event"/> <many-to-many class="Category" column="Category"/> </bag> Category: <bag name="Events" table="EventCategories" access="field.camelcase-underscore" cascade="all-delete-orphan" lazy="true" > <key column="Category"/> <many-to-many class="Event" column="Event"/> </bag> I tried to swap every parameter in both mappings but nothing works... Do you know what I'm doing wrong or have a right mapping for this case? Thank you very much!

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  • Synfony2 validation changes invalid integer to 0

    - by Craig
    I've added validation to a form and found that in some cases it is losing the invalid data I am feeding it and saving 0s instead. The output at the bottom shows that if I post the latitude as 'zzzzzz' (clearly not a number nor between -90 and 90) the form is declared as valid and saved with the value 0 How can that happen given that I have declared the input must be a number? ProxyType.php buildForm() $builder ->add('siteName', null, array('label' => 'Site name')) .... ->add('latitude', 'number', array('label' => 'Latitude')) ->add('longitude', 'number', array('label' => 'Longitude')) .... ; ProxyController.php createAction .... $postData = $request->request->get('niwa_pictbundle_proxytype'); $this->get('logger')->info('Posted latitude = '.$postData['latitude']); $form = $this->createForm(new ProxyType(), $entity); $form->bindRequest($request); if ($form->isValid()) { $this->get('logger')->info('Form declared valid : latlong ('.$entity->getLatitude().','.$entity->getLongitude().')'); .... validation.yml Acme\PictBundle\Entity\Proxy: properties: longitude: - Min: { limit: -180 } - Max: { limit: 180 } latitude: - Max: { limit: 90 } - Min: { limit: -90 } Output [2012-09-28 02:05:30] app.INFO: Posted latitude = zzzzzz [] [] [2012-09-28 02:05:30] app.INFO: Form declared valid : latlong (0,0) [] []

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  • Mixing stored procedures and ORM

    - by Jason
    The company I work for develops a large application which is almost entirely based on stored procedures. We use classic ASP and SQL Server and the major part of the business logic is contained inside those stored procedures. For example, (I know, this is bad...) a single stored procedure can be used for different purposes (insert, update, delete, make some calculations, ...). Most of the time, a stored procedure is used for operations on related tables, but this is not always the case. We are planning to move to ASP.NET in a near future. I have read a lot of posts on StackOverflow recommending that I move the business logic outside the database. The thing is, I have tried to convince the people who takes the decisions at our company and there is nothing I can do to change their mind. Since I want to be able to use the advantages of object-oriented programming, I want to map the tables to actual classes. So far, my solution is to use an ORM (Entity Framework 4 or nHibernate) to avoid mapping the objects manually (mostly to retrieve the data) and use some kind of Data Access Layer to call the existing stored procedures (for saving). I want your advice on this. Do you think it is a good solution? Any ideas?

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  • Stepping through ASP.NET MVC in Action (2009) - and stuck on nunit issue

    - by Jen
    I seem to have missed something - in this step through it talks through downloading nunit and changing the original MSTest reference to NUnit. Which seems fine until it talks about running the test with UnitRun from JetBrains. I would have thought I could run nUnit to be able to run the test - but I load my project in the nUnit gui and I get "This assembly was not built with any known testing framework". This after running the Nunit-2.5.3.9346.msi. Or am I supposed to be able to run tests from within visual studio 2008? After some research I find this: http://www.jetbrains.com/unitrun/ (ie. it seems to be saying this is no longer supported and I'm thinking JetBrains Resharper may cost money?). I'm a little rusty on my NUnit experience. So how do I go ahead and run my test? Is the error message I'm getting considered abnormal? I've added a reference in my MvcApplication.Tests project to the nunit.framework. Is this the wrong reference to add? Thanks :)

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  • How can I overlay a watermark on an already resampled image in PHP (using GD) ?

    - by Rick
    Here's my current code: define('IMG_WIDTH', (isset ($_GET['width'])) ? (int) $_GET['width'] : 99); define('IMG_HEIGHT', (isset ($_GET['height'])) ? (int) $_GET['height'] : 75); $image = imagecreatefromjpeg($_GET['image']); $origWidth = imagesx($image); $origHeight = imagesy($image); $croppedThumb = imagecreatetruecolor(IMG_WIDTH, IMG_HEIGHT); if ($origWidth > $origHeight) { $leftOffset = ($origWidth - $origHeight) / 2; imagecopyresampled($croppedThumb, $image, 0, 0, $leftOffset, 0, IMG_WIDTH, IMG_HEIGHT, $origHeight, $origHeight); } else { $topOffset = ($origHeight - $origWidth) / 2; imagecopyresampled($croppedThumb, $image, 0, 0, 0, $topOffset, IMG_WIDTH, IMG_HEIGHT, $origWidth, $origWidth); } It basically takes an image and re-sizes it to create a thumbnail. It works quite nicely. What I would like to do now is add a watermark to the bottom right corner. I've seen the imagecopymerge function used for this... However, that doesn't seem to allow me to supply a resampled image as the source. How can I take my already modified image and add a watermark? :/ I've thought of saving the image to /tmp and then unlink()'ing it once I've added the watermark but that seems like a bit of a mess...

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  • Packaging Java apps for the Windows/Linux desktop.

    - by alexmcchessers
    I am writing an application in Java for the desktop using the Eclipse SWT library for GUI rendering. I think SWT helps Java get over the biggest hurdle for acceptance on the desktop: namely providing a Java application with a consistent, responsive interface that looks like that belonging to any other app on your desktop. However, I feel that packaging an application is still an issue. OS X natively provides an easy mechanism for wrapping Java apps in native application bundles, but producing an app for Windows/Linux that doesn't require the user to run an ugly batch file or click on a .jar is still a hassle. Possibly that's not such an issue on Linux, where the user is likely to be a little more tech-savvy, but on Windows I'd like to have a regular .exe for him/her to run. Has anyone had any experience with any of the .exe generation tools for Java that are out there? I've tried JSmooth but had various issues with it. Is there a better solution before I crack out Visual Studio and roll my own? Edit: I should perhaps mention that I am unable to spend a lot of money on a commercial solution.

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  • World Economic Crisis. IT prospects

    - by Andrew Florko
    There was alike question in 2008, 2 years passed. Please, share your expectations about IT market and employment in the next year or two (or so far you can predict). IMHO Russia (my native country) fully met Crisis in spring, 2008. Stock markets shrank 3(!) times during half a year. Many developers were fired those days but I suppose just because business was shocked and freezed some projects. Developers expected +20% salary growth per year in 2004-2007 (Developer salary in Moscow was about 2-3K$ in early 2008). Then there was 30% (very subjective) salary cut-off in 2008 and salaries were frozen till 2009. Now things are slowly coming back to 2008. Looking in the future I expect pessimistic scenario and another crash. Our economic depends more and more on oil & gas every year. IT that serves industry will be shrinked because we can't compete to China in real production. Due to high currency board (rubble is strong compared to dollar) we can't rely on offshore programming. Our officials are concerned on innovative economic breakthrough but it's an ordinary budget money assignemtn in practice. I don't believe in innovations either because who require innovations if you have debts and tomorrow is vapor?

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  • c++ and visual studio 08, how to develop the following web extracting application. folloow up of las

    - by user287745
    the purpose is to use c++ in a useful way. i have just started programming and have made a few small applications in c and c#. my understanding is that programming for web and thing related to web is now a days a very easy task. please note this is for personnel learning not for rent a coder or any money making. an application which can run on any windows platform even win98. the application should start automatically at a scheduled time and do the following. connect to a site which displays stock prices summary (high low current open ). captures the data (excluding the other things in the site) and saves it to disk ( a sql database) please note:- internet connection is assumed to be there always. do not want to know how to make database schema or database. the stock exchange has no law prohibiting the use of the data provided on its site, but i do not want to mention the name in case i am wrong, but its for personnel private use only. the data of summary of pricing is arranged in a table such that when copied pasted to ms excel it automatically forms a table. guidance needed thank u.

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  • iPhone: Which are the most useful techniques for faster Bluetooth?

    - by Mike Howard
    Hi. I'm adding peer-to-peer bluetooth using GameKit to an iPhone shoot-em-up, so speed is vital. I'm sending about 40 messages a second each way, most of them with the faster GKSendDataUnreliable, all serializing with NSCoding. In testing between a 3G and 3GS, this is slowing the 3G down a lot more than I'd like. I'm wondering where I should concentrate my efforts to speed it up. How much slower is GKSendDataReliable? For the few packets that have to get there, would it be faster to send a GKSendDataUnreliable and have the peer send an acknowledgement so I can send again if I don't get the Ack within, say, 100ms? How much faster would it be to create the NSData instance using a regular C array rather than archiving with the NSCoding protocol? Is this serialization process (for about a dozen floats) just as slow as you'd expect from an object creation/deallocation overhead, or is something particularly slow happening? I heard that (for example) sending four seperate sets of data is much, much slower, than sending one piece of data four times the size. Would I make a significant saving by sending separate packets of data that wouldn't always go together in the same packet when they happen at the same time? Are there any other bluetooth performance secrets I've missed? Thanks for your help.

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  • How to Check Authenticity of an AJAX Request

    - by Alex Reisner
    I am designing a web site in which users solve puzzles as quickly as they can. JavaScript is used to time each puzzle, and the number of milliseconds is sent to the server via AJAX when the puzzle is completed. How can I ensure that the time received by the server was not forged by the user? I don't think a session-based authenticity token (the kind used for forms in Rails) is sufficient because I need to authenticate the source of a value, not just the legitimacy of the request. Is there a way to cryptographically sign the request? I can't think of anything that couldn't be duplicated by a hacker. Is any JavaScript, by its exposed, client-side nature, subject to tampering? Am I going to have to use something that gets compiled, like Flash? (Yikes.) Or is there some way to hide a secret key? Or something else I haven't thought of? Update: To clarify, I don't want to penalize people with slow network connections (and network speed should be considered inconsistent), so the timing needs to be 100% client-side (the timer starts only when we know the user can see the puzzle). Also, there is money involved so no amount of "trusting the user" is acceptable.

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  • File is used by another process?

    - by Surya sasidhar
    I get this error (file is being used by another process). Actually I write the code in a button click event like this, i am saving the excel file in a file using file upload, immediately i am fetching the file which i was save just now there i am getting this error. in my point of view i think it take time to save the excel file in that file. this is my code: FileUpload1.PostedFile.SaveAs(Server.MapPath("~/User/Excel/" + name.ToString() + ".xls")); string s = Server.MapPath("~/user/excel/" + name.ToString() + ".xls"); OleDbConnection DBConnection = new OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0;" + "Data Source=" + s.ToString() + ";" + "Extended Properties=\"Excel 8.0;HDR=Yes\""); DBConnection.Open(); string SQLString = "SELECT * FROM Contacts"; OleDbCommand DBCommand = new OleDbCommand(SQLString, DBConnection); IDataReader DBReader = DBCommand.ExecuteReader(); mygridOut.DataSource = DBReader; mygridOut.DataBind(); and i am getting error like this: because it is being used by another process.

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