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• Complex derived attributes in Django models

  - by rabidpebble

  What I want to do is implement submission scoring for a site with users voting on the content, much like in e.g. reddit (see the 'hot' function in http://code.reddit.com/browser/sql/functions.sql). My submission model currently keeps track of up and down vote totals. Currently, when a user votes I create and save a related Vote object and then use F() expressions to update the Submission object's voting totals. The problem is that I want to update the score for the submission at the same time, but F() expressions are limited to only simple operations (it's missing support for log(), date_part(), sign() etc.) From my limited experience with Django I can see 4 options here: extend F() somehow (haven't looked at the code yet) to support the missing SQL functions; this is my preferred option and seems to fit within the Django framework the best define a scoring function (much like reddit's 'hot' function) in my database, and have Django use the value of that function for the value of the score field; as far as I can tell, #2 is not possible wrap my two step voting process in a suitably isolated transaction so that I can calculate the voting totals in Python and then update the Submission's voting totals without fear that another vote against the submission could be added/changed in the meantime; I'm hesitant to take this route because it seems overly complex - what is a "suitably isolated transaction" in this case anyway? use raw SQL; I would prefer to avoid this entirely -- what's the point of an ORM if I have to revert to SQL for such a common use case as this! (Note that this coming from somebody who loves sprocs, but is using Django for ease of development.) Before I embark on this mission to extend F() (which I'm not sure is even possible), am I about to reinvent the wheel? Is there a more standard way to do this? It seems like such a common use case and yet in an hour of searching I have yet to find a common solution...

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• How close can I get C# to the performance of C++ for small intensive tasks?

  - by SLC

  I was thinking about the speed difference of C++ to C# being mostly about C# compiling to byte-code that is taken in by the JIT compiler (is that correct?) and all the checks C# does. I notice that it is possible to turn a lot of these functions off, both in the compile options, and possibly through using the unsafe keyword as unsafe code is not verifiable by the common language runtime. Therefore if you were to write a simple console application in both languages, that flipped an imaginary coin an infinite number of times and displayed the results to the screen every 10,000 or so iterations, how much speed difference would there be? I chose this because it's a very simple program. I'd like to test this but I don't know C++ or have the tools to compile it. This is my C# version though: static void Main(string[] args) { unsafe { Random rnd = new Random(); int heads = 0, tails = 0; while (true) { if (rnd.NextDouble() > 0.5) heads++; else tails++; if ((heads + tails) % 1000000 == 0) Console.WriteLine("Heads: {0} Tails: {1}", heads, tails); } } } Is the difference enough to warrant deliberately compiling sections of code "unsafe" or into DLLs that do not have some of the compile options like overflow checking enabled? Or does it go the other way, where it would be beneficial to compile sections in C++? I'm sure interop speed comes into play too then. To avoid subjectivity, I reiterate the specific parts of this question as: Does C# have a performance boost from using unsafe code? Do the compile options such as disabling overflow checking boost performance, and do they affect unsafe code? Would the program above be faster in C++ or negligably different? Is it worth compiling long intensive number-crunching tasks in a language such as C++ or using /unsafe for a bonus? Less subjectively, could I complete an intensive operation faster by doing this?

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• SQL Server Compact timed out waiting for a lock

  - by jankhana

  Hi all, I'm having an application in that i use Sql Compact 3.5 with VS2008. I'm running multiple threads in my application which contacts the compact database and accesses the row. It selects and deletes those rows in a fashion i.e selecting and giving to the application 5 rows and deleting those rows from the table. It works great with a single thread but if i use multiple threads i.e if 3 or more threads are running I get very often the TimeOut Error!!! I have increased the Time out property in the connection string but it didn't give me expected result. The error log is as follow: SQL Server Compact timed out waiting for a lock. The default lock time is 2000ms for devices and 5000ms for desktops. The default lock timeout can be increased in the connection string using the ssce: default lock timeout property. [ Session id = 5,Thread id = 4204,Process id = 4808,Table name = XXX,Conflict type = x lock (s blocks),Resource = TAB ] The Query that I use to retrieve is as follows: " select Top(5) * from TableName order by id; delete from TableName where id in(select top(5) id from TableName order by id); " Is there any way by which we can avoid this Time Out exception??????? The above query I un as a transaction in VS2008 one using SQLCECommand and the other using SqlCEDataAdapter. Any Idea!!!!!! Reply

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• SSL certificate pre-fetch .NET

  - by Wil P

  I am writing a utility that would allow me to monitor the health of our websites. This consists of a series of validation tasks that I can run against a web application. One of the tests is to anticipate the expiration of a particular SSL certificate. I am looking for a way to pre-fetch the SSL certificate installed on a web site using .NET or a WINAPI so that I can validate the expiration date of the certificate associated with a particular website. One way I could do this is to cache the certificates when they are validated in the ServicePointManager.ServerCertificateValidationCallback handler and then match them up with configured web sites, but this seems a bit hackish. Another would be to configure the application with the certificate for the website, but I'd rather avoid this if I can in order to minimize configuration. What would be the easiest way for me to download an SSL certificate associated with a website using .NET so that I can inspect the information the certificate contains to validate it? EDIT: To extend on the answer below there is no need to manually create the ServicePoint prior to creating the request. It is generated on the request object as part of executing the request. private static string GetSSLExpiration(string url) { HttpWebRequest request = WebRequest.Create(url) as HttpWebRequest; using (WebResponse response = request.GetResponse()) { } if (request.ServicePoint.Certificate != null) { return request.ServicePoint.Certificate.GetExpirationDateString(); } else { return string.Empty; } }

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• Creating spotlight in OpenGL scene

  - by Victor Oliveira

  Im studying OpenGL and trying to create a spot light at my application. The code that Im using for my #vertex-shader is below: #:vertex-shader #{ #version 150 core in vec3 in_pos; in vec2 in_tc; out vec2 tc; glLightf(GL_LIGHT0, GL_SPOT_CUTOFF, 20.0f); GLfloat spot_direction[] = { -1.0, -1.0, 0.0 }; glLightfv(GL_LIGHT0, GL_SPOT_DIRECTION, spot_direction); glEnable(GL_LIGHT0); void main() { vec4 pos= vec4(vec3(1.0)*in_pos - vec3(1.0), 1.0); pos.z=0.0; gl_Position = pos; tc = in_tc; } } The thing is, everytime Im trying to run the code an Error that says: Type: other, Source: api, ID: 131169, Severity: low Message: Framebuffer detailed info: The driver allocated storage for renderbuffer 1. len = 157, written = 0 failed to compile vertex shader of deferred: directional info log for shader deferred: directional vertex info log for shader deferred: directional: ERROR: Unbound variable: when Specifications: Renderer: GeForce GTX 580/PCIe/SSE2 Version: 3.3.0 NVIDIA 319.17 GLSL: 3.30 NVIDIA via Cg compiler Status: Using GLEW 1.9.0 1024 x 768 OS: Linux debian I guess to create this spotlight is pretty much simple, but since Im really new to OpenGL I dont have a clue how to do it until now, even reading sources like: http://www.glprogramming.com/red/chapter05.html#name3 Read also in some place that light spots can get really hard to understand, but I cant avoid this step right now since Im following my lecture schedule. Could anybody help me?

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• Make Ant's delete task fail when a directory exists and is not deleted but not when it doesn't exist

  - by Tim Visher

  I have tho following clean function in my build script and I'd like to know how I can improve it. <target name="clean" description="Clean output directories."> <!-- Must not fail on error because it fails if directories don't exist. Is there really no better way to do this? --> <delete includeEmptyDirs="true" failonerror="false"> <fileset dir="${main.build.directory}" /> <fileset dir="dist" /> <fileset dir="${documentation.build.directory}" /> <fileset dir="/build-testing" /> </delete> </target> Specifically regarding my comment, I'm unhappy with the fact that I can't run this on a fresh box because the directory structure hasn't been set up yet by the other targets. We run the build in such a way that it entirely recreates the structures necessary for testing and deployment every time to avoid stale class files and such. With the way that delete currently is set up, a failure to delete a file does not fail the build and I'd like it to. I don't want it to fail the build if the file doesn't exist though. If it doesn't exist then what I'm asking it to do has already happened. Thoughts?

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• Which articles I've should read before starting to make my custom drawn winforms app?

  - by Dmitriy Matveev

  Hello! I'm currently developing a windows forms application with a lot of user controls. Some of them are just custom drawn buttons or panels and some of them are a compositions of these buttons and panels inside of FlowLayoutPanels and TableLayoutPanels. And the window itself is also custom drawn. I don't have much experience in winforms development, but I've made a proper decomposition of proposed design into user controls and implementation is already almost finished. I've already solved many arisen problems during development by the help of the google, msdn, SO and several dirty hacks (when nothing were helping) and still experiencing some of them. There are a lot of gaps in my knowledge base, since I don't know answers to many questions like: When I should use things like double buffer, suspended layout, suspended redraw ? What should I do with the controls which shouldn't be visible at some moment ? Common performance pitfalls (I think I've fallen in in several ones) ? So I think there should be some great articles which can give some knowledge enough to avoid most common problems and improve performance and maintainability of my application. Maybe some of you can recommend a few?

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• Flash - Uploading to and Downloading from localhost

  - by Md Derf

  I have an online flash application that acts as a front end for a server application built in delphi. The server can be installed/used on a remote computer or a personal version can be downloaded and the Flash app pointed at localhost to use it. However, Flash has issues with using the POST and GET functions on the localhost, which makes uploading data files and downloading results files difficult. To get past the difficulty with downloading results files I'm planning to just have the server app serve the results file as an attachment and have the Flash app open the address of the file up in another browser window using external interface. First off, is this likely to cause similar security issues? I.E. Flash will see "localhost" in the external interface call and stop it from working the same as when I try to use POST/GET functions with localhost? Secondly, for upload this seems just a bit little trickier, I'm planning on doing something similar, having flash use external interface to open a php script for a file upload. Is this feasible and, again, will Flash still have security issues? Lastly, if anyone knows how to get flash to execute POST and GET functions with localhost addresses, I'd love to have that information to avoid all this jumping through hoops.

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• 301 Redirecting URLs based on GET variables in .htaccess

  - by technicalbloke

  I have a few messy old URLs like... http://www.example.com/bunch.of/unneeded/crap?opendocument&part=1 http://www.example.com/bunch.of/unneeded/crap?opendocument&part=2 ...that I want to redirect to the newer, cleaner form... http://www.example.com/page.php/welcome http://www.example.com/page.php/prices I understand I can redirect one page to another with a simple redirect i.e. Redirect 301 /bunch.of/unneeded/crap http://www.example.com/page.php But the source page doesn't change, only it's GET vars. I can't figure out how to base the redirect on the value of these GET variables. Can anybody help pls!? I'm fairly handy with the old regexes so I can have a pop at using mod-rewrite if I have to but I'm not clear on the syntax for rewriting GET vars and I'd prefer to avoid the performance hit and use the cleaner Redirect directive. Is there a way? and if not can anyone clue me in as to the right mod-rewrite syntax pls? Cheers, Roger.

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• How do you implement a good profanity filter?

  - by Ben Throop

  Many of us need to deal with user input, search queries, and situations where the input text can potentially contain profanity or undesirable language. Oftentimes this needs to be filtered out. Where can one find a good list of swear words in various languages and dialects? Are there APIs available to sources that contain good lists? Or maybe an API that simply says "yes this is clean" or "no this is dirty" with some parameters? What are some good methods for catching folks trying to trick the system, like a$$, azz, or a55? Bonus points if you offer solutions for PHP. :) Edit: Response to answers that say simply avoid the programmatic issue: I think there is a place for this kind of filter when, for instance, a user can use public image search to find pictures that get added to a sensitive community pool. If they can search for "penis", then they will likely get many pictures of, yep. If we don't want pictures of that, then preventing the word as a search term is a good gatekeeper, though admittedly not a foolproof method. Getting the list of words in the first place is the real question. So I'm really referring to a way to figure out of a single token is dirty or not and then simply disallow it. I'd not bother preventing a sentiment like the totally hilarious "long necked giraffe" reference. Nothing you can do there. :)

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• MySql Query lag time / deadlock?

  - by Click Upvote

  When there are multiple PHP scripts running in parallel, each making an UPDATE query to the same record in the same table repeatedly, is it possible for there to be a 'lag time' before the table is updated with each query? I have basically 5-6 instances of a PHP script running in parallel, having been launched via cron. Each script gets all the records in the items table, and then loops through them and processes them. However, to avoid processing the same item more than once, I store the id of the last item being processed in a seperate table. So this is how my code works: function getCurrentItem() { $sql = "SELECT currentItemId from settings"; $result = $this->db->query($sql); return $result->get('currentItemId'); } function setCurrentItem($id) { $sql = "UPDATE settings SET currentItemId='$id'"; $this->db->query($sql); } $currentItem = $this->getCurrentItem(); $sql = "SELECT * FROM items WHERE status='pending' AND id > $currentItem'"; $result = $this->db->query($sql); $items = $result->getAll(); foreach ($items as $i) { //Check if $i has been processed by a different instance of the script, and if so, //leave it untouched. if ($this->getCurrentItem() > $i->id) continue; $this->setCurrentItem($i->id); // Process the item here } But despite of all the precautions, most items are being processed more than once. Which makes me think that there is some lag time between the update queries being run by the PHP script, and when the database actually updates the record. Is it true? And if so, what other mechanism should I use to ensure that the PHP scripts always get only the latest currentItemId even when there are multiple scripts running in parrallel? Would using a text file instead of the db help?

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• Java: Reading images and displaying as an ImageIcon

  - by 11helen

  I'm writing an application which reads and displays images as ImageIcons (within a JLabel), the application needs to be able to support jpegs and bitmaps. For jpegs I find that passing the filename directly to the ImageIcon constructor works fine (even for displaying two large jpegs), however if I use ImageIO.read to get the image and then pass the image to the ImageIcon constructor, I get an OutOfMemoryError( Java Heap Space ) when the second image is read (using the same images as before). For bitmaps, if I try to read by passing the filename to ImageIcon, nothing is displayed, however by reading the image with ImageIO.read and then using this image in the ImageIcon constructor works fine. I understand from reading other forum posts that the reason that the two methods don't work the same for the different formats is down to java's compatability issues with bitmaps, however is there a way around my problem so that I can use the same method for both bitmaps and jpegs without an OutOfMemoryError? (I would like to avoid having to increase the heap size if possible!) The OutOfMemoryError is triggered by this line: img = getFileContentsAsImage(file); and the method definition is: public static BufferedImage getFileContentsAsImage(File file) throws FileNotFoundException { BufferedImage img = null; try { ImageIO.setUseCache(false); img = ImageIO.read(file); img.flush(); } catch (IOException ex) { //log error } return img; } The stack trace is: Exception in thread "AWT-EventQueue-0" java.lang.OutOfMemoryError: Java heap space at java.awt.image.DataBufferByte.<init>(DataBufferByte.java:58) at java.awt.image.ComponentSampleModel.createDataBuffer(ComponentSampleModel.java:397) at java.awt.image.Raster.createWritableRaster(Raster.java:938) at javax.imageio.ImageTypeSpecifier.createBufferedImage(ImageTypeSpecifier.java:1056) at javax.imageio.ImageReader.getDestination(ImageReader.java:2879) at com.sun.imageio.plugins.jpeg.JPEGImageReader.readInternal(JPEGImageReader.java:925) at com.sun.imageio.plugins.jpeg.JPEGImageReader.read(JPEGImageReader.java:897) at javax.imageio.ImageIO.read(ImageIO.java:1422) at javax.imageio.ImageIO.read(ImageIO.java:1282) at framework.FileUtils.getFileContentsAsImage(FileUtils.java:33)

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• Absolute positioning in IE6, using left: 0; and right: 0; simultaneously

  - by Zane

  Here is my website: http://dagwaging.110mb.com/ View it in any good browser, then in IE6. It dies in IE6. It seems that in IE6, one can't do this: div { position: absolute; left: 0px; right: 0px; } or this: div { position: absolute; top: 0px; bottom: 0px; } Absolute positions cannot be set for left and right or top and bottom at the same time. This is terrible, because that is pretty much the basis of my site design. The HTML can be viewed on the site, and the CSS is in /style.css. I'd like to fix this without invalidating my CSS or HTML. Can this be done? Another problem is that my content uses min-width and max-width to avoid over-stretching or compressing the content within. IE6 can't do min-width, so how can I replicate this behavior?

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• Using variables inside macros in SQL

  - by Tim

  Hello I'm wanting to use variables inside my macro SQL on Teradata. I thought I could do something like the following: REPLACE MACRO DbName.MyMacro ( MacroNm VARCHAR(50) ) AS ( /* Variable to store last time the macro was run */ DECLARE V_LAST_RUN_DATE TIMESTAMP; /* Get last run date and store in V_LAST_RUN_DATE */ SELECT LastDate INTO V_LAST_RUN_DATE FROM DbName.RunLog WHERE MacroNm = :MacroNm; /* Update the last run date to now and save the old date in history */ EXECUTE MACRO DbName.RunLogUpdater( :MacroNm ,V_LAST_RUN_DATE ,CURRENT_TIMESTAMP ); ); However, that didn't work, so I thought of this instead: REPLACE MACRO DbName.MyMacro ( MacroNm VARCHAR(50) ) AS ( /* Variable to store last time the macro was run */ CREATE VOLATILE TABLE MacroVars AS ( SELECT LastDate AS V_LAST_RUN_DATE FROM DbName.RunLog WHERE MacroNm = :MacroNm; ) WITH DATA ON COMMIT PRESERVE ROWS; /* Update the last run date to now and save the old date in history */ EXECUTE MACRO DbName.RunLogUpdater( :MacroNm ,SELECT V_LAST_RUN_DATE FROM MacroVars ,CURRENT_TIMESTAMP ); ); I can do what I'm looking for with a Stored Procedure, however I want to avoid for performance. Do you have any ideas about this? Is there anything else I can try? Cheers Tim

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• Bioperl, equivalent of IO::ScalarArray for array of Seq objects?

  - by Ryan Thompson

  In perl, we have IO::ScalarArray for treating the elements of an array like the lines of a file. In BioPerl, we have Bio::SeqIO, which can produce a filehandle that reads and writes Bio::Seq objects instead of strings representing lines of text. I would like to do a combination of the two: I would like to obtain a handle that reads successive Bio::Seq objects from an array of such objects. Is there any way to do this? Would it be trivial for me to implement a module that does this? My reason for wanting this is that I would like to be able to write a subroutine that accepts either a Bio::SeqIO handle or an array of Bio::Seq objects, and I'd like to avoid writing separate loops based on what kind of input I get. Perhaps the following would be better than writing my own IO module? sub process_sequences { my $input = $_[0]; # read either from array of Bio::Seq or from Bio::SeqIO my $nextseq; if (ref $input eq 'ARRAY') { my $pos = 0 $nextseq = sub { return $input->[$pos++] if $pos < @$input}; } } else { $nextseq = sub { $input->getline(); } } while (my $seq = $nextseq->()) { do_cool_stuff_with($seq) } }

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• deadlock because of foreign key?

  - by George2

  Hello everyone, I am using SQL Server 2008 Enterprise. I met with deadlock in the following store procedure, but because of my fault, I did not record the deadlock graph. But now I can not reproduce deadlock issue. I want to have a postmortem to find the root cause of deadlock to avoid deadlock in the future. The deadlock happens on delete statement. For the delete statement, Param1 is a column of table FooTable, Param1 is a foreign key of another table (refers to another primary key clustered index column of the other table). There is no index on Param1 itself for table FooTable. FooTable has another column which is used as clustered primary key, but not Param1 column. Here is my guess why there is deadlock, and I want to let people review whether my analysis is correct? Since Param1 column has no index, there will be a table scan, and will acquire table level lock, because of foreign key, the delete operation will also need to check master table (e.g. to acquire lock on master table); Some operation on master table acquires master table lock, but want to acquire lock on FooTable; (1) and (2) cause cycle lock which makes deadlock happen. My analysis correct? Any reproduce scenario? create PROCEDURE [dbo].[FooProc] ( @Param1 int ,@Param2 int ,@Param3 int ) AS DELETE FooTable WHERE Param1 = @Param1 INSERT INTO FooTable ( Param1 ,Param2 ,Param3 ) VALUES ( @Param1 ,@Param2 ,@Param3 ) DECLARE @ID bigint SET @ID = ISNULL(@@Identity,-1) IF @ID > 0 BEGIN SELECT IdentityStr FROM FooTable WHERE ID = @ID END thanks in advance, George

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• NHibernate: how to handle entity-based validation using session-per-request pattern, without control

  - by Seth Petry-Johnson

  What is the best way to do entity-based validation (each entity class has an IsValid() method that validates its internal members) in ASP.NET MVC, with a "session-per-request" model, where the controller has zero (or limited) knowledge of the ISession? Here's the pattern I'm using: Get an entity by ID, using an IFooRepository that wraps the current NH session. This returns a connected entity instance. Load the entity with potentially invalid data, coming from the form post. Validate the entity by callings its IsValid() method. If valid, call IFooRepository.Save(entity). Otherwise, display error message. The session is currently opened when the request begins and flushed when the request ends. Since my entity is connected to a session, flushing the session attempts to save the changes even if the object is invalid. What's the best way to keep validation logic in the entity class, limit controller knowledge of NH, and avoid saving invalid changes at the end of a request? Option 1: Explicitly evict on validation failure, implicitly flush: if the validation fails, I could manually evict the invalid object in the action method. If successful, I do nothing and the session is automatically flushed. Con: error prone and counter-intuitive ("I didn't call .Save(), why are my invalid changes being saved anyways?") Option 2: Explicitly flush, do nothing by default: By default I can dispose of the session on request end, only flushing if the controller indicates success. I'd probably create a SaveChanges() method in my base controller that sets a flag indicating success, and then query this flag when closing the session at request end. Pro: More intuitive to troubleshoot if dev forgets this step [relative to option 1] Con: I have to call IRepository.Save(entity)' and SaveChanges(). Option 3: Always work with disconnected objects: I could modify my repositories to return disconnected/transient objects, and modify the Repo.Save() method to re-attach them. Pro: Most intuitive, given that controllers don't know about NH. Con: Does this defeat many of the benefits I'd get from NH?

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• In IIS6, how to provide authenticated access to static files on remote server

  - by frankadelic

  We have a library of ZIP files that we would like to make available for download at an ASP.NET site. The files are sitting on a NAS device that is accessible from out web farm. Here is our initial strategy: Map an IIS virtual directory to the shared drive at path /zipfiles Users can download the zip files when given the URL However, if users share links to the files, anyone can download them. We would instead like to make use of the ASP.NET forms authentication in our site to validate users' requests before initiating the file transfer. A few problems: A request for a zip file is handled by IIS, not ASP.NET. So it is not subject to forms authentication. In addition, we don't want ASP.NET to handle the request, because it uses up an ASP.NET thread and is not scalable for download of large files. So, configuring the asp.net dll to handle *.zip requests is not an option. Any ideas on this? One idea we've tossed around is this: Initial request for download will be for an ashx handler. This handler will, after authentication, generate a download token which is saved to a database. Then, the user is redirected to the file with token appended in QueryString (e.g. /files/xyz.zip?token=123456789). An ISAPI plugin will be used to check the token. Also, the token will expire after x amount of time. Any thoughts on this? I have not implemented an ISAPI plugin so I'm not sure if this will even work. I would like to avoid custom coding since security is an issue and I'd prefer to use a time-tested solution.

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• using the ASP.NET Caching API via method annotations in C#

  - by craigmoliver

  In C#, is it possible to decorate a method with an annotation to populate the cache object with the return value of the method? Currently I'm using the following class to cache data objects: public class SiteCache { // 7 days + 6 hours (offset to avoid repeats peak time) private const int KeepForHours = 174; public static void Set(string cacheKey, Object o) { if (o != null) HttpContext.Current.Cache.Insert(cacheKey, o, null, DateTime.Now.AddHours(KeepForHours), TimeSpan.Zero); } public static object Get(string cacheKey) { return HttpContext.Current.Cache[cacheKey]; } public static void Clear(string sKey) { HttpContext.Current.Cache.Remove(sKey); } public static void Clear() { foreach (DictionaryEntry item in HttpContext.Current.Cache) { Clear(item.Key.ToString()); } } } In methods I want to cache I do this: [DataObjectMethod(DataObjectMethodType.Select)] public static SiteSettingsInfo SiteSettings_SelectOne_Name(string Name) { var ck = string.Format("SiteSettings_SelectOne_Name-Name_{0}-", Name.ToLower()); var dt = (DataTable)SiteCache.Get(ck); if (dt == null) { dt = new DataTable(); dt.Load(ModelProvider.SiteSettings_SelectOne_Name(Name)); SiteCache.Set(ck, dt); } var info = new SiteSettingsInfo(); foreach (DataRowView dr in dt.DefaultView) info = SiteSettingsInfo_Load(dr); return info; } Is it possible to separate those concerns like so: (notice the new annotation) [CacheReturnValue] [DataObjectMethod(DataObjectMethodType.Select)] public static SiteSettingsInfo SiteSettings_SelectOne_Name(string Name) { var dt = new DataTable(); dt.Load(ModelProvider.SiteSettings_SelectOne_Name(Name)); var info = new SiteSettingsInfo(); foreach (DataRowView dr in dt.DefaultView) info = SiteSettingsInfo_Load(dr); return info; }

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• Emulating Dynamic Dispatch in C++ based on Template Parameters

  - by Jon Purdy

  This is heavily simplified for the sake of the question. Say I have a hierarchy: struct Base { virtual int precision() const = 0; }; template<int Precision> struct Derived : public Base { typedef Traits<Precision>::Type Type; Derived(Type data) : value(data) {} virtual int precision() const { return Precision; } Type value; }; I want a function like: Base* function(const Base& a, const Base& b); Where the specific type of the result of the function is the same type as whichever of first and second has the greater Precision; something like the following pseudocode: template<class T> T* operation(const T& a, const T& b) { return new T(a.value + b.value); } Base* function(const Base& a, const Base& b) { if (a.precision() > b.precision()) return operation((A&)a, A(b.value)); else if (a.precision() < b.precision()) return operation(B(a.value), (B&)b); else return operation((A&)a, (A&)b); } Where A and B are the specific types of a and b, respectively. I want f to operate independently of how many instantiations of Derived there are. I'd like to avoid a massive table of typeid() comparisons, though RTTI is fine in answers. Any ideas?

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• Sql Serve - Cascade delete has multiple paths

  - by Anders Juul

  Hi all, I have two tables, Results and ComparedResults. ComparedResults has two columns which reference the primary key of the Results table. My problem is that if a record in Results is deleted, I wish to delete all records in ComparedResults which reference the deleted record, regardless of whether it's one column or the other (and the columns may reference the same Results row). A row in Results may deleted directly or through cascade delete caused by deleting in a third table. Googling this could indicate that I need to disable cascade delete and rewrite all cascade deletes to use triggers instead. Is that REALLY nessesary? I'd be prepared to do much restructuring of the database to avoid this, as my main area is OO programming, and databases should 'just work'. It is hard to see, however, how a restructuring could help as I would just move the problem around... Or am I missing something? I am also a bit at a loss as to why my initial construct should even be a problem for the Sql Server?! Any comments welcome and much appreciated! Anders, Denmark

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• Memory allocation in detached NSThread to load an NSDictionary in background?

  - by mobibob

  I am trying to launch a background thread to retrieve XML data from a web service. I developed it synchronously - without threads, so I know that part works. Now I am ready to have a non-blocking service by spawning a thread to wait for the response and parse. I created an NSAutoreleasePool inside the thread and release it at the end of the parsing. The code to spawn and the thread are as follows: Spawn from main-loop code: . . [NSThread detachNewThreadSelector:@selector(spawnRequestThread:) toTarget:self withObject:url]; . . Thread (inside 'self'): -(void) spawnRequestThread: (NSURL*) url { NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init]; parser = [[NSXMLParser alloc] initWithContentsOfURL:url]; [self parseContentsOfResponse]; [parser release]; [pool release]; } The method parseContentsOfResponse fills an NSMutableDictionary with the parsed document contents. I would like to avoid moving the data around a lot and allocate it back in the main-loop that spawned the thread rather than making a copy. First, is that possible, and if not, can I simply pass in an allocated pointer from the main thread and allocate with 'dictionaryWithDictionary' method? That just seems so inefficient. Are there perferred designs?

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• MVC2 Areas not Registering Correctly

  - by Geoffrey

  I believe I have my Areas setup correctly (they were working in MVC1 fine). I followed the guide here: http://odetocode.com/Blogs/scott/archive/2009/10/13/asp-net-mvc2-preview-2-areas-and-routes.aspx I've also used Haacked's Route Debugger. Which shows the correct Area/Controller registration when I run it. However when I try to go to my (AreaName)/(Controller) I get this error: "The resource cannot be found." I believe this indicates there's a problem with the routing, but I'm having trouble debugging this. Where should I set my breakpoints to catch routing errors in MVC2? I'm also using SparkViewEngine compiled against MVC2 references. Could this possibly be causing this error? I've set breakpoints on the controller in the area and it never fires off, I assumed the view engine doesn't kick in until after the controller has been initiated, but I could be wrong. The non-area landing page works fine, and I've stripped my project of all areas except one, to avoid any sort of naming conflicts. Any ideas where I can try to look next?

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• standard way to perform a clean shutdown with Boost.Asio

  - by Timothy003

  I'm writing a cross-platform server program in C++ using Boost.Asio. Following the HTTP Server example on this page, I'd like to handle a user termination request without using implementation-specific APIs. I've initially attempted to use the standard C signal library, but have been unable to find a design pattern suitable for Asio. The Windows example's design seems to resemble the signal library closest, but there's a race condition where the console ctrl handler could be called after the server object has been destroyed. I'm trying to avoid race conditions that cause undefined behavior as specified by the C++ standard. Is there a standard (correct) way to stop the server? So far: #include <csignal> #include <functional> #include <boost/asio.hpp> using std::signal; using boost::asio::io_service; extern "C" { static void handle_signal(int); } namespace { std::function<void ()> sighandler; } void handle_signal(int) { sighandler(); } int main() { io_service s; sighandler = std::bind(&io_service::stop, &s); auto res = signal(SIGINT, &handle_signal); // race condition? SIGINT raised before I could set ignore back if (res == SIG_IGN) signal(SIGINT, SIG_IGN); res = signal(SIGTERM, &handle_signal); // race condition? SIGTERM raised before I could set ignore back if (res == SIG_IGN) signal(SIGTERM, SIG_IGN); s.run(); // reset signals signal(SIGTERM, SIG_DFL); signal(SIGINT, SIG_DFL); // is it defined whether handle_signal can still be in execution at this // point? sighandler = nullptr; }

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• Getting exception when trying to monkey patch pymongo.connection._Pool

  - by Creotiv

  I use pymongo 1.9 on Ubuntu 10.10 with python 2.6.6 When i trying to monkey patch pymongo.connection._Pool i'm getting error on connection: AutoReconnect: could not find master/primary But when i change _Pool class in pymongo.connection module, it work pretty fine. Even if i copy _Pool implementation from pymongo.connection module and will try to monkey patch by the same code, it still giving same exception. I need to remove threading.local from _Pool class, because i use gevent and i need to implement Pool for all mongo connections(for all threads). I use this code: import pymongo class GPool: """A simple connection pool. Uses thread-local socket per thread. By calling return_socket() a thread can return a socket to the pool. Right now the pool size is capped at 10 sockets - we can expose this as a parameter later, if needed. """ # Non thread-locals __slots__ = ["sockets", "socket_factory", "pool_size","sock"] #sock = None def __init__(self, socket_factory): self.pool_size = 10 if not hasattr(self,"sock"): self.sock = None self.socket_factory = socket_factory if not hasattr(self, "sockets"): self.sockets = [] def socket(self): # we store the pid here to avoid issues with fork / # multiprocessing - see # test.test_connection:TestConnection.test_fork for an example # of what could go wrong otherwise pid = os.getpid() if self.sock is not None and self.sock[0] == pid: return self.sock[1] try: self.sock = (pid, self.sockets.pop()) except IndexError: self.sock = (pid, self.socket_factory()) return self.sock[1] def return_socket(self): if self.sock is not None and self.sock[0] == os.getpid(): # There's a race condition here, but we deliberately # ignore it. It means that if the pool_size is 10 we # might actually keep slightly more than that. if len(self.sockets) < self.pool_size: self.sockets.append(self.sock[1]) else: self.sock[1].close() self.sock = None pymongo.connection._Pool = GPool

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