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• [NHibernate and ASP.NET MVC] How can I implement a robust session-per-request pattern in my project,

  - by Guillaume Gervais

  I'm currently building an ASP.NET MVC project, with NHibernate as its persistance layer. For now, some functionnalities have been implemented, but only use local NHibernate sessions: each method that accessed the database (read or write) needs to instanciate its own NHibernate session, with the "using()" directive. The problem is that I want to leverage NHibernate's Lazy-Loading capabilities to improve the performance of my project. This implies an open NHibernate session per request until the view is rendered. Furthermore, simultaneous request must be supported (multiple Sessions at the same time). How can I achieve that as cleanly as possible? I searched the Web a little bit and learned about the session-per-request pattern. Most of the implementations I saw used some sort of Http* (HttpContext, etc.) object to store the session. Also, using the Application_BeginRequest/Application_EndRequest functions is complicated, since they get fired for each HTTP request (aspx files, css files, js files, etc.), when I only want to instanciate a session once per request. The concern that I have is that I don't want my views or controllers to have access to NHibernate sessions (or, more generally, NHibernate namespaces and code). That means that I do not want to handle sessions at the controller level nor the view one. I have a few options in mind. Which one seems the best ? Use interceptors (like in GRAILS) that get triggered before and after the controller action. These would open and close sessions/transactions. Is it possible in the ASP.NET MVC world? Use the CurrentSessionContext Singleton provided by NHibernate in a Web context. Using this page as an example, I think this is quite promising, but that still requires filters at the controller level. Use the HttpContext.Current.Items to store the request session. This, coupled with a few lines of code in Global.asax.cs, can easily provide me with a session on the request level. However, it means that dependencies will be injected between NHibernate and my views (HttpContext). Thank you very much!

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• Wrong data retrieved from database

  - by holyredbeard

  So, I want to retrieve the order of the elements of a list. The order is set before by the user, and are stored in the table below. Because I also want to retrieve name and description of the list elements I need to combine two tables (see below). However, what is actually retrieved is an array containing 16 elements (should be four because it only exists four elements as for now). The array is too long to post here, but I put it in a phpFiddle to be found here if you're interested. Well, I have really tried to find what's wrong (probably something easy as always), but with no luck. Thanks a lot for your time and help! listModel.php: public function GetOrderedElements($userId, $listId) { // $userId = 46 // $listId = 1 $query = "SELECT le.listElemId, le.listElemName, le.listElemDesc, lo.listElemOrderPlace FROM listElement AS le INNER JOIN listElemOrder AS lo ON le.listId = lo.listId WHERE lo.userId = ? AND lo.listId = ? ORDER BY listElemId"; $stmt = $this->m_db->Prepare($query); $stmt->bind_param("ii", $userId, $listId); $listElements = $this->m_db->GetOrderedElements($stmt); return $listElements; } database.php: public function GetOrderedElements(\mysqli_stmt $stmt) { if ($stmt === FALSE) { throw new \Exception($this->mysqli->error); } if ($stmt->execute() == FALSE) { throw new \Exception($this->mysqli->error); } if ($stmt->bind_result($listElemId, $listElemName, $listElemDesc, $listElemOrderPlace) == FALSE) { throw new \Exception($this->mysqli->error); } $listElements = array(); while ($stmt->fetch()) { $listElements[] = array('listElemId' => $listElemId, 'listElemName' => $listElemName, 'listElemDesc' => $listElemDesc, 'listElemOrderPlace' => $listElemOrderPlace); } var_dump($listElements); $stmt->Close(); return $listElements; } from the database: listElemOrder: listElemOrderId | listId | listElemId | userId | listElemOrderPlace 1 1 1 46 1 2 1 2 46 4 3 1 3 46 2 4 1 4 46 3 listElement: listElemId | listElemName | listId | listElemDesc | listElemOrderPlace 1 Elem A 1 Derp NULL 2 Elem B 1 Herp NULL 3 Elem C 1 Lorum NULL 4 Elem D 1 Ipsum NULL Note: 'listElemOrderPlace' in the table listElement is the final order of the elements (all users average), not to be mixed with the one with the same name in the other table, that's only a specific user's order of the list elements (which is the interesting one in this case).

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• Loosely coupled implicit conversion

  - by ltjax

  Implicit conversion can be really useful when types are semantically equivalent. For example, imagine two libraries that implement a type identically, but in different namespaces. Or just a type that is mostly identical, except for some semantic-sugar here and there. Now you cannot pass one type into a function (in one of those libraries) that was designed to use the other, unless that function is a template. If it's not, you have to somehow convert one type into the other. This should be trivial (or otherwise the types are not so identical after-all!) but calling the conversion explicitly bloats your code with mostly meaningless function-calls. While such conversion functions might actually copy some values around, they essentially do nothing from a high-level "programmers" point-of-view. Implicit conversion constructors and operators could obviously help, but they introduce coupling, so that one of those types has to know about the other. Usually, at least when dealing with libraries, that is not the case, because the presence of one of those types makes the other one redundant. Also, you cannot always change libraries. Now I see two options on how to make implicit conversion work in user-code: The first would be to provide a proxy-type, that implements conversion-operators and conversion-constructors (and assignments) for all the involved types, and always use that. The second requires a minimal change to the libraries, but allows great flexibility: Add a conversion-constructor for each involved type that can be externally optionally enabled. For example, for a type A add a constructor: template <class T> A( const T& src, typename boost::enable_if<conversion_enabled<T,A>>::type* ignore=0 ) { *this = convert(src); } and a template template <class X, class Y> struct conversion_enabled : public boost::mpl::false_ {}; that disables the implicit conversion by default. Then to enable conversion between two types, specialize the template: template <> struct conversion_enabled<OtherA, A> : public boost::mpl::true_ {}; and implement a convert function that can be found through ADL. I would personally prefer to use the second variant, unless there are strong arguments against it. Now to the actual question(s): What's the preferred way to associate types for implicit conversion? Are my suggestions good ideas? Are there any downsides to either approach? Is allowing conversions like that dangerous? Should library implementers in-general supply the second method when it's likely that their type will be replicated in software they are most likely beeing used with (I'm thinking of 3d-rendering middle-ware here, where most of those packages implement a 3D vector).

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• Database schema for simple stats project

  - by Bubnoff

  Backdrop: I have a file hierarchy of cvs files for multiple locations named by dates they cover ...by month specifically. Each cvs file in the folder is named after the location. eg', folder name: 2010-feb contains: location1.csv location2.csv Each CSV file holds records like this: 2010-06-28, 20:30:00 , 0 2010-06-29, 08:30:00 , 0 2010-06-29, 09:30:00 , 0 2010-06-29, 10:30:00 , 0 2010-06-29, 11:30:00 , 0 meaning of record columns ( column names ): Date, time, # of sessions I have a perl script that pulls the data from this mess and originally I was going to store it as json files, but am thinking a database might be more appropriate long term ...comparing year to year trends ...fun stuff like that. Pt 2 - My question/problem: So I now have a REST service that coughs up json with a test database. My question is [ I suck at db design ], how best to design a database backend for this? I am thinking the following tables would suffice and keep it simple: Location: (PK)location_code, name session: (PK)id, (FK)location_code, month, hour, num_sessions I need to be able to average sessions (plus min and max) for each hour across days of week in addition to days of week in a given month or months. I've been using perl hashes to do this and am trying to decide how best to implement this with a database. Do you think stored procedures should be used? As to the database, depending on info gathered here, it will be postgresql or sqlite. If there is no compelling reason for postgresql I'll stick with sqlite. How and where should I compare the data to hours of operation. I am storing the hours of operation in a yaml file. I currently 'match' the hour in the data to a hash from the yaml to do this. Would a database open simpler methods? I am thinking I would do this comparison as I do now then insert the data. Can be recalled with: SELECT hour, num_sessions FROM session WHERE location_code=LOC1 Since only hours of operation are present, I do not need to worry about it. Should I calculate all results as I do now then store as a stats table for different 'reports'? This, rather than processing on demand? How would this look? Anyway ...I ramble. Thanks for reading! Bubnoff

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• Is it correct or incorrect for a Java JAR to contain its own dependencies?

  - by 4herpsand7derpsago

  I guess this is a two-part question. I am trying to write my own Ant task (MyFirstTask) that can be used in other project's build.xml buildfiles. To do this, I need to compile and package my Ant task inside its own JAR. Because this Ant task that I have written is fairly complicated, it has about 20 dependencies (other JAR files), such as using XStream for OX-mapping, Guice for DI, etc. I am currently writing the package task in the build.xml file inside the MyFirstTask project (the buildfile that will package myfirsttask.jar, which is the reusable Ant task). I am suddenly realizing that I don't fully understand the intention of a Java JAR. Is it that a JAR should not contain dependencies, and leave it to the runtime configuration (the app container, the runtime environment, etc.) to supply it with the dependencies it needs? I would assume if this is the case, an executable JAR is an exception to the rule, yes? Or, is it the intention for Java JARs to also include their dependencies? Either way, I don't want to be forcing my users to be copying-n-pasting 25+ JARs into their Ant libs; that's just cruel. I like the way WAR files are set up, where the classpath for dependencies is defined under the classes/ directory. I guess, ultimately, I'd like my JAR structure to look like: myfirsttask.jar/ com/ --> the root package of my compiled binaries config/ --> config files, XML, XSD, etc. classes/ --> all dependencies, guice-3.0.jar, xstream-1.4.3.jar, etc. META-INF/ MANIFEST.MF I assume that in order to accomplish this (and get the runtime classpath to also look into the classes/ directory), I'll need to modify the MANIFEST.MF somehow (I know there's a manifest attribute called ClassPath, I believe?). I'm just having a tough time putting everything together, and have a looming/lingering question about the very intent of JARs to begin with. Can someone please confirm whether Oracle intends for JARs to contain their dependencies or not? And, either way, what I would have to do in the manifest (or anywhere else) to make sure that, at runtime, the classpath can find the dependencies stored under the classes/ directory? Thanks in advance!

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• How can I execute an insert with data from a repeater-generated form whose data source is SQL?

  - by Duke

  I'm storing multilingual data in a database whose model is language normalized (like this). For this particular problem the key for the table in question consists of a value entered by the user and a language from the language table. I'd like to dynamically generate a form with input fields for all available languages. The user inputs a key value then goes down a list of field sets filling out the information in each language. In this case there are two fields for every language, a name and a value (the value is language dependent.) I have all existing information displayed on the page with a gridview, below which I have a formview that is always in insert mode allowing the user to enter new data. Within the formview I have a repeater with an SQLDataSource that gets a list of available languages: <asp:Repeater ID="SessionLocaleRepeater" runat="server" DataSourceID="LocaleSQLDataSource" EnableViewState="false"> <ItemTemplate> <tr> <th scope="row"><%# DataBinder.Eval(Container.DataItem, "LocaleName") %></th> <td>Name:</td> <td><asp:TextBox ID="TextBox1" runat="server" Text="" /></td> <td>Number:</td> <td><asp:TextBox ID="TextBox2" runat="server" Text="" /></td> </tr> </ItemTemplate> </asp:Repeater> I figured that in order to insert this data I'd have to execute my sql server insert stored procedure for each item in the repeater; I am trying to use the formview inserting event. The problem is that the repeater isn't databound to the SQLDataSource until after the formview inserting event (inserting event is in PostBackEvent and databind is in PreRender), which means the controls and data are not available when the inserting event is fired. I tried databinding the repeater during the formview inserting event; the controls were available but the data was not. Would this have something to do with how/when the viewstate information is re-added to the controls? From what I've read, Viewstate is one of the first things to be restored. Given the order of events how can I get the data I need for the insert? I'm open to other solutions to creating dynamic input controls, but they will have to query the database to determine how many sets of controls to create.

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• codeIgniter: pass parameter to a select query from previous query

  - by krike

  I'm creating a little management tool for the browser game travian. So I select all the villages from the database and I want to display some content that's unique to each of the villages. But in order to query for those unique details I need to pass the id of the village. How should I do this? this is my code (controller): function members_area() { global $site_title; $this->load->model('membership_model'); if($this->membership_model->get_villages()) { $data['rows'] = $this->membership_model->get_villages(); $id = 1;//this should be dynamic, but how? if($this->membership_model->get_tasks($id)): $data['tasks'] = $this->membership_model->get_tasks($id); endif; } $data['title'] = $site_title." | Your account"; $data['main_content'] = 'account'; $this->load->view('template', $data); } and this is the 2 functions I'm using in the model: function get_villages() { $q = $this->db->get('villages'); if($q->num_rows() > 0) { foreach ($q->result() as $row) { $data[] = $row; } return $data; } } function get_tasks($id) { $this->db->select('name'); $this->db->from('tasks'); $this->db->where('villageid', $id); $q = $this->db->get(); if($q->num_rows() > 0) { foreach ($q->result() as $task) { $data[] = $task; } return $data; } } and of course the view: <?php foreach($rows as $r) : ?> <div class="village"> <h3><?php echo $r->name; ?></h3> <ul> <?php foreach($tasks as $task): ?> <li><?php echo $task->name; ?></li> <?php endforeach; ?> </ul> <?php echo anchor('site/add_village/'.$r->id.'', '+ add new task'); ?> </div> <?php endforeach; ?> ps: please do not remove the comment in the first block of code!

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• Why did File::Find finish short of completely traversing a large directory?

  - by Stan

  A directory exists with a total of 2,153,425 items (according to Windows folder Properties). It contains .jpg and .gif image files located within a few subdirectories. The task was to move the images into a different location while querying each file's name to retrieve some relevant info and store it elsewhere. The script that used File::Find finished at 20462 files. Out of curiosity I wrote a tiny recursive function to count the items which returned a count of 1,734,802. I suppose the difference can be accounted for by the fact that it didn't count folders, only files that passed the -f test. The problem itself can be solved differently by querying for file names first instead of traversing the directory. I'm just wondering what could've caused File::Find to finish at a small fraction of all files. The data is stored on an NTFS file system. Here is the meat of the script; I don't think including DBI stuff would be relevant since I reran the script with nothing but a counter in process_img() which returned the same number. find(\&process_img, $path_from); sub process_img { eval { return if ($_ eq "." or $_ eq ".."); ## Omitted querying and composing new paths for brevity. make_path("$path_to\\img\\$dir_area\\$dir_address\\$type"); copy($File::Find::name, "$path_to\\img\\$dir_area\\$dir_address\\$type\\$new_name"); }; if ($@) { print STDERR "eval barks: $@\n"; return } } And here is another method I used to count files: count_images($path_from); sub count_images { my $path = shift; opendir my $images, $path or die "died opening $path"; while (my $item = readdir $images) { next if $item eq '.' or $item eq '..'; $img_counter++ && next if -f "$path/$item"; count_images("$path/$item") if -d "$path/$item"; } closedir $images or die "died closing $path"; } print $img_counter;

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• How to refresh xmlDataProvider when xml document changes at runtime in WPF?

  - by Kajsa

  I am trying to make a image viewer/album creator in visual studio, wpf. The image paths for each album is stored in an xml document which i bind to to show the images from each album in a listbox. The problem is when i add a image or an album at runtime and write it to the xml document. I can't seem to make the bindings to the xml document update so they show the new images and albums aswell. Calling Refresh() on the XmlDataProvider doesn't change anything. I don't wish to redo the binding of the XmlDataProvider, just make it read from the same source again. XAML: ... <Grid.DataContext> <XmlDataProvider x:Name="Images" Source="Data/images.xml" XPath="/albums/album[@name='no album']/image" /> </Grid.DataContext> ... <Label Grid.Row="1" Grid.Column="0" HorizontalAlignment="Right" VerticalAlignment="Bottom" Padding="0" Margin="0,0,0,5" Content="{x:Static resx:Resource.AddImageLabel}"/> <TextBox Grid.Row="1" Grid.Column="1" HorizontalAlignment="Stretch" VerticalAlignment="Bottom" Name="newImagePath" Margin="0" /> <Button Grid.Row="1" Grid.Column="2" HorizontalAlignment="Left" VerticalAlignment="Bottom" Name="newImagePathButton" Content="{x:Static resx:Resource.BrowseImageButton}" Click="newImagePathButton_Click" /> ... <ListBox Grid.Column="0" Grid.ColumnSpan="4" Grid.Row="3" HorizontalAlignment="Stretch" Name="thumbnailList" VerticalAlignment="Bottom" IsSynchronizedWithCurrentItem="True" ItemsSource="{Binding BindingGroupName=Images}" SelectedIndex="0" Background="#FFE0E0E0" Height="110"> ... Code behind: private void newImagePathButton_Click(object sender, RoutedEventArgs e) { string imagePath = newImagePath.Text; albumCreator.addImage(imagePath, null); //Reset import image elements to default newImagePath.Text = ""; //Refresh thumbnail listbox Images.Refresh(); Console.WriteLine("Image added!"); } public void addImage(string source, XmlElement parent) { if (parent == null) { //Use default album parent = (XmlElement)root.FirstChild; } //Create image element with source element within XmlElement newImage = xmlDoc.CreateElement(null, "image", null); XmlElement newSource = xmlDoc.CreateElement(null, "source", null); newSource.InnerText = source; newImage.AppendChild(newSource); //Add image element to parent parent.AppendChild(newImage); xmlDoc.Save(xmlFile); } Thank you very much for any help!

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• Improved way to build nested array of unique values in javascript

  - by dualmon

  The setup: I have a nested html table structure that displays hierarchical data, and the individual rows can be hidden or shown by the user. Each row has a dom id that is comprised of the level number plus the primary key for the record type on that level. I have to have both, because each level is from a different database table, so the primary key alone is not unique in the dom. example: id="level-1-row-216" I am storing the levels and rows of the visible elements in a cookie, so that when the page reloads the same rows the user had open are can be shown automatically. I don't store the full map of dom ids, because I'm concerned about it getting too verbose, and I want to keep my cookie under 4Kb. So I convert the dom ids to a compact json object like this, with one property for each level, and a unique array of primary keys under each level: { 1:[231,432,7656], 2:[234,121], 3:[234,2], 4:[222,423], 5:[222] } With this structure stored in a cookie, I feed it to my show function and restore the user's previous disclosure state when the page loads. The area for improvement: I'm looking for better option for reducing my map of id selectors down to this compact format. Here is my function: function getVisibleIds(){ // example dom id: level-1-row-216-sub var ids = $("tr#[id^=level]:visible").map(function() { return this.id; }); var levels = {}; for(var i in ids ) { var id = ids[i]; if (typeof id == 'string'){ if (id.match(/^level/)){ // here we extract the number for level and row var level = id.replace(/.*(level-)(\d*)(.*)/, '$2'); var row = id.replace(/.*(row-)(\d*)(.*)/, '$2'); // *** Improvement here? *** // This works, but it seems klugy. In PHP it's one line (see below): if(levels.hasOwnProperty(level)){ if($.inArray(parseInt(row, 10) ,levels[level]) == -1){ levels[level].push(parseInt(row, 10)); } } else { levels[level] = [parseInt(row, 10)]; } } } } return levels; } If I were doing it in PHP, I'd build the compact array like this, but I can't figure it out in javascript: foreach($ids as $id) { if (/* the criteria */){ $level = /* extract it from $id */; $row = /* extract it from $id */; $levels[$level][$row]; } }

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• Loading datasets from datastore and merge into single dictionary. Resource problem.

  - by fredrik

  Hi, I have a productdatabase that contains products, parts and labels for each part based on langcodes. The problem I'm having and haven't got around is a huge amount of resource used to get the different datasets and merging them into a dict to suit my needs. The products in the database are based on a number of parts that is of a certain type (ie. color, size). And each part has a label for each language. I created 4 different models for this. Products, ProductParts, ProductPartTypes and ProductPartLabels. I've narrowed it down to about 10 lines of code that seams to generate the problem. As of currently I have 3 Products, 3 Types, 3 parts for each type, and 2 languages. And the request takes a wooping 5500ms to generate. for product in productData: productDict = {} typeDict = {} productDict['productName'] = product.name cache_key = 'productparts_%s' % (slugify(product.key())) partData = memcache.get(cache_key) if not partData: for type in typeData: typeDict[type.typeId] = { 'default' : '', 'optional' : [] } ## Start of problem lines ## for defaultPart in product.defaultPartsData: for label in labelsForLangCode: if label.key() in defaultPart.partLabelList: typeDict[defaultPart.type.typeId]['default'] = label.partLangLabel for optionalPart in product.optionalPartsData: for label in labelsForLangCode: if label.key() in optionalPart.partLabelList: typeDict[optionalPart.type.typeId]['optional'].append(label.partLangLabel) ## end problem lines ## memcache.add(cache_key, typeDict, 500) partData = memcache.get(cache_key) productDict['parts'] = partData productList.append(productDict) I guess the problem lies in the number of for loops is too many and have to iterate over the same data over and over again. labelForLangCode get all labels from ProductPartLabels that match the current langCode. All parts for a product is stored in a db.ListProperty(db.key). The same goes for all labels for a part. The reason I need the some what complex dict is that I want to display all data for a product with it's default parts and show a selector for the optional one. The defaultPartsData and optionaPartsData are properties in the Product Model that looks like this: @property def defaultPartsData(self): return ProductParts.gql('WHERE __key__ IN :key', key = self.defaultParts) @property def optionalPartsData(self): return ProductParts.gql('WHERE __key__ IN :key', key = self.optionalParts) When the completed dict is in the memcache it works smoothly, but isn't the memcache reset if the application goes in to hibernation? Also I would like to show the page for first time user(memcache empty) with out the enormous delay. Also as I said above, this is only a small amount of parts/product. What will the result be when it's 30 products with 100 parts. Is one solution to create a scheduled task to cache it in the memcache every hour? It this efficient? I know this is alot to take in, but I'm stuck. I've been at this for about 12 hours straight. And can't figure out a solution. ..fredrik

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• Specializing a template on a lambda in C++0x

  - by Tony A.

  I've written a traits class that lets me extract information about the arguments and type of a function or function object in C++0x (tested with gcc 4.5.0). The general case handles function objects: template <typename F> struct function_traits { template <typename R, typename... A> struct _internal { }; template <typename R, typename... A> struct _internal<R (F::*)(A...)> { // ... }; typedef typename _internal<decltype(&F::operator())>::<<nested types go here>>; }; Then I have a specialization for plain functions at global scope: template <typename R, typename... A> struct function_traits<R (*)(A...)> { // ... }; This works fine, I can pass a function into the template or a function object and it works properly: template <typename F> void foo(F f) { typename function_traits<F>::whatever ...; } int f(int x) { ... } foo(f); What if, instead of passing a function or function object into foo, I want to pass a lambda expression? foo([](int x) { ... }); The problem here is that neither specialization of function_traits<> applies. The C++0x draft says that the type of the expression is a "unique, unnamed, non-union class type". Demangling the result of calling typeid(...).name() on the expression gives me what appears to be gcc's internal naming convention for the lambda, main::{lambda(int)#1}, not something that syntactically represents a C++ typename. In short, is there anything I can put into the template here: template <typename R, typename... A> struct function_traits<????> { ... } that will allow this traits class to accept a lambda expression?

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• How can I append and execute a script inside an iframe in a cross browser way (specifically IE!)?

  - by agmin

  Background: I need to load ad scripts after the DOM has loaded. Because many of the scripts use document.write() and other potentially bad functions to run after the DOM has loaded, I want to load the scripts inside an iframe. So when the ad needs to be shown, an event is triggered which does the following: var iframe = document.createElement('iframe'); iframe.setAttribute('id', 'iframeId'); iframe.setAttribute('src', 'about:blank'); var adContainer = document.getElementById('AdContainer'); adContainer.appendChild(iframe); var val = '<html><head></head><body>'; val += '<scr' + 'ipt type="text/javascript" src="' + url + '"></scr' + 'ipt>'; val += '</body></html>'; If I don't assign the html and body tags to val, the script automatically gets appended to the head of the iframe and fails to execute in FF. In IE, the script doesn't execute with or without the head/body/html tags. var doc = iframe.contentWindow || iframe.contentDocument; if (doc.document){ doc = doc.document } doc.open(); doc.write(val); doc.close(); I found this last bit of code here: http://stackoverflow.com/questions/1591135/why-does-appending-a-script-to-a-dynamically-created-iframe-seem-to-run-the-s. I do NOT want to load jquery in the iframe though, I just want to append a script and have it execute. My current solution seems to work great in FF and Webkit. However, IE doesn't execute the script. The script is written to the page, but doesn't start running. Is there a better way to append the script to the iframe so it will run cross browser? Or is it possible to tell IE to run the script? I know that I could load an external document with the ad script via the iframe, but I don't want to make the extra call to my server if I can do this dynamically. Also, I've tried using appendChild() on the iframe's body to insert the script, but since the script element is created outside the iframe's DOM this doesn't seem to work.

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• C - How to use both aio_read() and aio_write().

  - by Slav

  I implement game server where I need to both read and write. So I accept incoming connection and start reading from it using aio_read() but when I need to send something, I stop reading using aio_cancel() and then use aio_write(). Within write's callback I resume reading. So, I do read all the time but when I need to send something - I pause reading. It works for ~20% of time - in other case call to aio_cancel() fails with "Operation now in progress" - and I cannot cancel it (even within permanent while cycle). So, my added write operation never happens. How to use these functions well? What did I missed? EDIT: Used under Linux 2.6.35. Ubuntu 10 - 32 bit. Example code: void handle_read(union sigval sigev_value) { /* handle data or disconnection */ } void handle_write(union sigval sigev_value) { /* free writing buffer memory */ } void start() { const int acceptorSocket = socket(AF_INET, SOCK_STREAM, 0); struct sockaddr_in addr; memset(&addr, 0, sizeof(struct sockaddr_in)); addr.sin_family = AF_INET; addr.sin_addr.s_addr = INADDR_ANY; addr.sin_port = htons(port); bind(acceptorSocket, (struct sockaddr*)&addr, sizeof(struct sockaddr_in)); listen(acceptorSocket, SOMAXCONN); struct sockaddr_in address; socklen_t addressLen = sizeof(struct sockaddr_in); for(;;) { const int incomingSocket = accept(acceptorSocket, (struct sockaddr*)&address, &addressLen); if(incomingSocket == -1) { /* handle error ... */} else { //say socket to append outcoming messages at writing: const int currentFlags = fcntl(incomingSocket, F_GETFL, 0); if(currentFlags < 0) { /* handle error ... */ } if(fcntl(incomingSocket, F_SETFL, currentFlags | O_APPEND) == -1) { /* handle another error ... */ } //start reading: struct aiocb* readingAiocb = new struct aiocb; memset(readingAiocb, 0, sizeof(struct aiocb)); readingAiocb->aio_nbytes = MY_SOME_BUFFER_SIZE; readingAiocb->aio_fildes = socketDesc; readingAiocb->aio_buf = mySomeReadBuffer; readingAiocb->aio_sigevent.sigev_notify = SIGEV_THREAD; readingAiocb->aio_sigevent.sigev_value.sival_ptr = (void*)mySomeData; readingAiocb->aio_sigevent.sigev_notify_function = handle_read; if(aio_read(readingAiocb) != 0) { /* handle error ... */ } } } } //called at any time from server side: send(void* data, const size_t dataLength) { //... some thread-safety precautions not needed here ... const int cancellingResult = aio_cancel(socketDesc, readingAiocb); if(cancellingResult != AIO_CANCELED) { //this one happens ~80% of the time - embracing previous call to permanent while cycle does not help: if(cancellingResult == AIO_NOTCANCELED) { puts(strerror(aio_return(readingAiocb))); // "Operation now in progress" /* don't know what to do... */ } } //otherwise it's okay to send: else { aio_write(...); } }

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• Execution plan issue requires reset on SQL Server 2005, how to determine cause?

  - by Tony Brandner

  We have a web application that delivers training to thousands of corporate students running on top of SQL Server 2005. Recently, we started seeing that a single specific query in the application went from 1 second to about 30 seconds in terms of execution time. The application started throwing timeouts in that area. Our first thought was that we may have incorrect indexes, so we reviewed the tables and indexes. However, similar queries elsewhere in the application also run quickly. Reviewing the indexes showed us that they were configured as expected. We were able to narrow it down to a single query, not a stored procedure. Running this query in SQL Studio also runs quickly. We tried running the application in a different server environment. So a different web server with the same query, parameters and database. The query still ran slow. The query is a fairly large one related to determining a student's current list of training. It includes joins and left joins on a dozen tables and subqueries. A few of the tables are fairly large (hundreds of thousands of rows) and some of the other tables are small lookup tables. The query uses a grouping clause and a few where conditions. A few of the tables are quite active and the contents change often but the volume of added rows doesn't seem extreme. These symptoms led us to consider the execution plan. First off, as soon as we reset the execution plan cache with the SQL command 'DBCC FREEPROCCACHE', the problem went away. Unfortunately, the problem started to reoccur within a few days. The problem has continued to plague us for awhile now. It's usually the same query, but we did appear to see the problem occur in another single query recently. It happens enough to be a nuisance. We're having a heck of a time trying to fix it since we can't reproduce it in any other environment other than production. I have downloaded the High Availability guide from Red Gate and I read up more on execution plans. I hope to run the profiler on the live server, but I'm a bit concerned about impact. I would like to ask - what is the best way to figure out what is triggering this problem? Has anyone else seen this same issue?

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• jquery in ajax loaded content

  - by Kim Gysen

  My application is supposed to be a single page application and I have the following code that works fine: home.php: <div id="container"> </div> accordion.php: //Click functions: load content $('#parents').click(function(){ //Load parent in container $('#container').load('http://www.blabla.com/entities/parents/parents.php'); }); parents.php: <div class="entity_wrapper"> Some divs and selectors </div> <script type="text/javascript"> $(document).ready(function(){ //Some jQuery / javascript }); </script> So the content loads fine, while the scripts dynamically loaded execute fine as well. I apply this system repetitively and it continues to work smoothly. I've seen that there are a lot of frameworks available on SPA's (such as backbone.js) but I don't understand why I need them if this works fine. From the backbone.js website: When working on a web application that involves a lot of JavaScript, one of the first things you learn is to stop tying your data to the DOM. It's all too easy to create JavaScript applications that end up as tangled piles of jQuery selectors and callbacks, all trying frantically to keep data in sync between the HTML UI, your JavaScript logic, and the database on your server. For rich client-side applications, a more structured approach is often helpful. Well, I totally don't have the feeling that I'm going through the stuff they mention. Adding the javascript per page works really well for me. They are html containers with clear scope and the javascript is just related to that part. More over, the front end doesn't do that much, most of the logic is managed based on Ajax calls to external PHP scripts. Sometimes the js can be a bit more extended for some functionalities, but all just loads as smooth in less than a second. If you think that this is bad coding, please tell me why I cannot do this and more importantly, what is the alternative I should apply. At the moment, I really don't see a reason on why I would change this approach as it just works too well. I'm kinda stuck on this question because it just worries me sick as it seems to easy to be true. Why would people go through hard times if it would be as easy as this...

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• Unit Testing - Am I doing it right?

  - by baron

  Hi everyone, Basically I have been programing for a little while and after finishing my last project can fully understand how much easier it would have been if I'd have done TDD. I guess I'm still not doing it strictly as I am still writing code then writing a test for it, I don't quite get how the test becomes before the code if you don't know what structures and how your storing data etc... but anyway... Kind of hard to explain but basically lets say for example I have a Fruit objects with properties like id, color and cost. (All stored in textfile ignore completely any database logic etc) FruitID FruitName FruitColor FruitCost 1 Apple Red 1.2 2 Apple Green 1.4 3 Apple HalfHalf 1.5 This is all just for example. But lets say I have this is a collection of Fruit (it's a List<Fruit>) objects in this structure. And my logic will say to reorder the fruitids in the collection if a fruit is deleted (this is just how the solution needs to be). E.g. if 1 is deleted, object 2 takes fruit id 1, object 3 takes fruit id2. Now I want to test the code ive written which does the reordering, etc. How can I set this up to do the test? Here is where I've got so far. Basically I have fruitManager class with all the methods, like deletefruit, etc. It has the list usually but Ive changed hte method to test it so that it accepts a list, and the info on the fruit to delete, then returns the list. Unit-testing wise: Am I basically doing this the right way, or have I got the wrong idea? and then I test deleting different valued objects / datasets to ensure method is working properly. [Test] public void DeleteFruit() { var fruitList = CreateFruitList(); var fm = new FruitManager(); var resultList = fm.DeleteFruitTest("Apple", 2, fruitList); //Assert that fruitobject with x properties is not in list ? how } private static List<Fruit> CreateFruitList() { //Build test data var f01 = new Fruit {Name = "Apple",Id = 1, etc...}; var f02 = new Fruit {Name = "Apple",Id = 2, etc...}; var f03 = new Fruit {Name = "Apple",Id = 3, etc...}; var fruitList = new List<Fruit> {f01, f02, f03}; return fruitList; }

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• Planning to create PDF files in Ruby on Rails

  - by deau

  Hi there, A Ruby on Rails app will have access to a number of images and fonts. The images are components of a visual layout which will be stored separately as a set of rules. The rules specify document dimensions along with which images are used and where. The app needs to take these rules, fetch the images, and generate a PDF that is ready for local printing or emailing. The fonts will also be important. The user needs to customize the layout by inputting text which will be included in the PDF. The PDF must therefore also contain the desired font so that the document renders identically across different machines. Each PDF may have many pages. Each page may have different dimensions but this is not essential. Either way, the ability to manipulate the dimensions and margins given by the PDF is essential. The only thing that needs to be regularly changed is the text. If this is takes too much development then the app can store the layouts in 3rd party PDFs and edit the textual content directly. Eventually though, this will prove too restrictive on the apps intended functionality so I would prefer the app to generate the PDF's itself. I have never worked with PDFs before and, for the most part, I've never had to output anything to the user outside their monitor. A printed medium could require a very different approach to get the best results. If anyone has any advice on how to model the PDF format this it would be really appreciated. The technical aspects of printing such as bleed, resolution and colour have already been factored in to the layouts and images. I am aware that PDF is a proprietary file format and I want to use free or open source software. I have seen a number of Ruby libraries for generating PDF files but because I am new on this scene I have no way to reliably compare them and too little time to implement and test them all. I also have the option of using C to handle this feature and if this is process intensive then that might be preferred. What should I be thinking about and how should I be planning to implement this?

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• Calling managed code from unmanaged win32 assembly dll - crash

  - by JustGreg

  I'm developing a serial port dll in win32 assembly (MASM32). It has its own thread checking multiple events and at a specified buffer treshold it'd notify the managed main application by calling a callback function. It just a call with no arguments/return value. At startup the main application stores the callback function's address by calling a function in the dll: pCallBackFunction dd 0 SetCallBackPointer proc pcb:DWORD mov eax, pcb mov pCallBackFunction, eax call DWORD ptr pCallBackFunction ; verify it immediately ret SetCallBackPointer endp The upper function immediately calls back the managed application callback routine for verification purposes. It is working fine. However, when I place the call instruction to other functions in the dll it crashes the application. It doesn't matter if the call is in a simple function or in the threadproc of the dll. For example: OpenPort proc pn:byte,br:dword, inputbuffersize: dword, outputbuffersize:dword, tresholdsize: dword LOCAL dcb: DCB LOCAL SerialTimeOuts: COMMTIMEOUTS call DWORD ptr pCallBackFunction xor eax, eax mov al, pn mov [com_port+3],al etc. etc. will crash at call DWORD ptr pCallBackFunction always. Since I call SetCallBackPointer first to store a valid address in pCallBackFunction, it should have a valid address. My managed app is written in C# and the relevant part is: public partial class Form1 : Form { public delegate void CallBackDelegate(); public static CallBackDelegate mydelegate; [DllImport("serialport.dll")] private static extern void SetCallBackPointer(CallBackDelegate Delegate); [DllImport("serialport.dll")] public static extern int OpenPort(byte com, uint br, uint inbufsize, uint outbufsize, uint treshsize); public Form1() { InitializeComponent(); mydelegate =new CallBackDelegate(CallbackFunction); SetCallBackPointer(mydelegate); unsafe { int sysstat; int hResult; hResult = OpenPort(Convert.ToByte('5'), 9600, 306, 4, 4); } } public static void CallbackFunction() { MessageBox.Show( "CallBack Function Called by Windows DLL"); } The VS debugger reported that the dll had tried to read/write from/to a protected memory address. But when calling SetCallBackPointer there is no such problem. What am I doing wrong here? Any tips would be great!

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• EXC_MEMORY_ACCESS when trying to delete from Core Data ($cash solution)

  - by llloydxmas

  I have an application that downloads an xml file, parses the file, and creates core data objects while doing so. In the parse code I have a function called 'emptydatacontext' that removes all items from Core Data before creating replacements items from the xml data. This method looks like this: -(void) emptyDataContext { NSFetchRequest * allCon = [[NSFetchRequest alloc] init]; [allCon setEntity:[NSEntityDescription entityForName:@"Condition" inManagedObjectContext:managedObjectContext]]; NSError * error = nil; NSArray * conditions = [managedObjectContext executeFetchRequest:allCon error:&error]; DebugLog(@"ERROR: %@",error); DebugLog(@"RETRIEVED: %@", conditions); [allCon release]; for (NSManagedObject * condition in conditions) { [managedObjectContext deleteObject:condition]; } // Update the data model effectivly removing the objects we removed above. //NSError *error; if (![managedObjectContext save:&error]) { DebugLog(@"%@", [error domain]); } } The first time this runs it deletes all objects and functions as it should - creating new objects from the xml file. I created a 'update' button that starts the exact same process of retrieving the file the proceeding with the parse & build. All is well until its time to delete the core data objects. This 'deleteObject' call creates a "EXC_BAD_ACCESS" error each time. This only happens on the second time through. Captured errors return null. If I log the 'conditions' array I get a list of NSManagedObjects on the first run. On the second this log request causes a crash exactly as the deleteObject call does. I have a feeling it is something very simple I'm missing or not doing correctly to cause this behavior. The data works great on my tableviews - its only when trying to update I get the crashes. I have spent days & days on this trying numerous alternative methods. Whats left of my hair is falling out. I'd be willing to ante up some cash for anyone willing to look at my code and see what I'm doing wrong. Just need to get past this hurdle. Thanks in advance for the help!

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• Passing ViewModel for backbone.js from MVC3 Server-Side

  - by Roman

  In ASP.NET MVC there is Model, View and Controller. MODEL represents entities which are stored in database and essentially is all the data used in a application (for example, generated by EntityFramework, "DB First" approach). Not all data from model you want to show in the view (for example, hashs of passwords). So you create VIEW MODEL, each for every strongly-typed-razor-view you have in application. Like this: using System; using System.Collections.Generic; using System.Linq; using System.Web; namespace MyProject.ViewModels.SomeController.SomeAction { public class ViewModel { public ViewModel() { Entities1 = new List<ViewEntity1>(); Entities2 = new List<ViewEntity2>(); } public List<ViewEntity1> Entities1 { get; set; } public List<ViewEntity2> Entities2 { get; set; } } public class ViewEntity1 { //some properties from original DB-entity you want to show } public class ViewEntity2 { } } When you create complex client-side interfaces (I do), you use some pattern for javascript on client, MVC or MVVM (I know only these). So, with MVC on client you have another model (Backbone.Model for example), which is third model in application. It is a bit much. Why don`t we use the same ViewModel model on a client (in backbone.js or another framework)? Is there a way to transfer CS-coded model to JS-coded? Like in MVVM pattern, with knockout.js, when you can do like this: in SomeAction.cshtml: <div style="display: none;" id="view_model">@Json.Encode(Model)</div> after that in Javascript-code var ViewModel = ko.mapping.fromJSON($("#view_model").get(0).innerHTML); now you can extend your ViewModel with some actions, event handlers, etc: ko.utils.extend(ViewModel, { some_function: function () { //some code } }); So, we are not building the same view model on the client again, we are transferring existing view model from server. At least, data. But knockout.js is not suitable for me, you can`t build complex UI with it, it is just data-binding. I need something more structural, like backbone.js. The only way to build ViewModel for backbone.js I can see now is re-writing same ViewModel in JS from server with hands. Is there any ways to transfer it from server? To reuse the same viewmodel on server view and client view?

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• jQuery action being called when selector isn't met?

  - by dougoftheabaci

  I've been working on a prototype for a client's web site and I've run into a rather significant snag. You can view the prototype here. As you can see, the way it works is you can scroll a set of slides horizontally and, by clicking one, open a stack containing yet more slides. If you then click again on an image in that stack it opens up a lightbox. Clicking on another stack or the close button will close that stack (and open another, as case may be). That all works great. However you get some weird behavior if you do the following: Click to open any stack. Click to open an image's light box (this works best if you click on the image that's level with the main list). Close the light box and the stack either by clicking the close button or clicking on another stack. Click back to the first stack. Instead of reopening the stack, you get the lightbox. This confuses me as the light box should only ever be called if there is a class on the containing UL and that class is removed when the lightbox is closed. I've checked and double-checked this, it's definitely missing. Here are the respective functions: $("ul.hide a.lightbox").live("click",function(){ $("ul.show").removeClass("show").addClass("hide"); $(this).parent().parent().removeClass("hide").addClass("show"); $("ul.hide").animate({opacity: 0.2}); $("ul.show").animate({opacity: 1}); $("#next").animate({opacity: 0.2}); $("#prev").animate({opacity: 0.2}); return false; }); $("ul.show a.lightbox").live("click",function(){ $(this).fancybox().trigger("click"); return false; }); As you can see, in order for the lightbox to be called the containing UL has to have the class of show. However, if you check it with Firebug it won't. For those who are curious, the added .trigger("click"); is because the lightbox will require a double-click to launch otherwise. Any idea how I can fix this?

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• C# Type Casting at Runtimefor Array.SetValue

  - by sprocketonline

  I'm trying to create an array using reflection, and insert values into it. I'm trying to do this for many different types so would like a createAndFillArray function capable of this : Type t1 = typeof(A); Type t2 = typeof(B); double exampleA = 22.5; int exampleB = 43; Array arrA = createAndFillArray(t1, exampleA); Array arrB = createAndFillArray(t2, exampleB); private Array createAndFillArray(Type t, object val){ Array arr = Array.CreateInstance( t, 1); //length 1 in this example only, real-world is of variable length. arr.SetValue( val, 0 ); //this causes the following error: "System.InvalidCastException : Object cannot be stored in an array of this type." return arr; } with the class A being as follows: public class A{ public A(){} private double val; public double Value{ get{ return val; } set{ this.val = value; } } public static implicit operator A(double d){ A a = new A(); a.Value = d; return a; } } and class B being very similar, but with int: public class B{ public B(){} private double val; public double Value{ get{ return val; } set{ this.val = value; } } public static implicit operator B(double d){ B b = new B(); b.Value = d; return b; } } I hoped that the implicit operator would have ensured that the double be converted to class A, or the int to class B, and the error avoided; but this is obviously not so. The above is used in a custom deserialization class, which takes data from a custom data format and fills in the corresponding .Net object properties. I'm doing this via reflection and at runtime, so I think both are unavoidable. I'm targeting the C# 2.0 framework. I've dozens, if not hundreds, of classes similar to A and B, so would prefer to find a solution which improved on the createAndFillArray method rather than a solution which altered these classes.

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• Use multiple inheritance to discriminate useage roles?

  - by Arne

  Hi fellows, it's my flight simulation application again. I am leaving the mere prototyping phase now and start fleshing out the software design now. At least I try.. Each of the aircraft in the simulation have got a flight plan associated to them, the exact nature of which is of no interest for this question. Sufficient to say that the operator way edit the flight plan while the simulation is running. The aircraft model most of the time only needs to read-acess the flight plan object which at first thought calls for simply passing a const reference. But ocassionally the aircraft will need to call AdvanceActiveWayPoint() to indicate a way point has been reached. This will affect the Iterator returned by function ActiveWayPoint(). This implies that the aircraft model indeed needs a non-const reference which in turn would also expose functions like AppendWayPoint() to the aircraft model. I would like to avoid this because I would like to enforce the useage rule described above at compile time. Note that class WayPointIter is equivalent to a STL const iterator, that is the way point can not be mutated by the iterator. class FlightPlan { public: void AppendWayPoint(const WayPointIter& at, WayPoint new_wp); void ReplaceWayPoint(const WayPointIter& ar, WayPoint new_wp); void RemoveWayPoint(WayPointIter at); (...) WayPointIter First() const; WayPointIter Last() const; WayPointIter Active() const; void AdvanceActiveWayPoint() const; (...) }; My idea to overcome the issue is this: define an abstract interface class for each usage role and inherit FlightPlan from both. Each user then only gets passed a reference of the appropriate useage role. class IFlightPlanActiveWayPoint { public: WayPointIter Active() const =0; void AdvanceActiveWayPoint() const =0; }; class IFlightPlanEditable { public: void AppendWayPoint(const WayPointIter& at, WayPoint new_wp); void ReplaceWayPoint(const WayPointIter& ar, WayPoint new_wp); void RemoveWayPoint(WayPointIter at); (...) }; Thus the declaration of FlightPlan would only need to be changed to: class FlightPlan : public IFlightPlanActiveWayPoint, IFlightPlanEditable { (...) }; What do you think? Are there any cavecats I might be missing? Is this design clear or should I come up with somethink different for the sake of clarity? Alternatively I could also define a special ActiveWayPoint class which would contain the function AdvanceActiveWayPoint() but feel that this might be unnecessary. Thanks in advance!

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• Are there any platforms where using structure copy on an fd_set (for select() or pselect()) causes p

  - by Jonathan Leffler

  The select() and pselect() system calls modify their arguments (the 'struct fd_set *' arguments), so the input value tells the system which file descriptors to check and the return values tell the programmer which file descriptors are currently usable. If you are going to call them repeatedly for the same set of file descriptors, you need to ensure that you have a fresh copy of the descriptors for each call. The obvious way to do that is to use a structure copy: struct fd_set ref_set_rd; struct fd_set ref_set_wr; struct fd_set ref_set_er; ... ...code to set the reference fd_set_xx values... ... while (!done) { struct fd_set act_set_rd = ref_set_rd; struct fd_set act_set_wr = ref_set_wr; struct fd_set act_set_er = ref_set_er; int bits_set = select(max_fd, &act_set_rd, &act_set_wr, &act_set_er, &timeout); if (bits_set > 0) { ...process the output values of act_set_xx... } } My question: Are there any platforms where it is not safe to do a structure copy of the struct fd_set values as shown? I'm concerned lest there be hidden memory allocation or anything unexpected like that. (There are macros/functions FD_SET(), FD_CLR(), FD_ZERO() and FD_ISSET() to mask the internals from the application.) I can see that MacOS X (Darwin) is safe; other BSD-based systems are likely to be safe, therefore. You can help by documenting other systems that you know are safe in your answers. (I do have minor concerns about how well the struct fd_set would work with more than 8192 open file descriptors - the default maximum number of open files is only 256, but the maximum number is 'unlimited'. Also, since the structures are 1 KB, the copying code is not dreadfully efficient, but then running through a list of file descriptors to recreate the input mask on each cycle is not necessarily efficient either. Maybe you can't do select() when you have that many file descriptors open, though that is when you are most likely to need the functionality.) There's a related SO question - asking about 'poll() vs select()' which addresses a different set of issues from this question.

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