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• Delphi, PGDac vs Zeos, Fetch, Lookup?

  - by durumdara

  Hi! I used Zeos to test to know: is ZTable uses fetch technics, or not? May in the future we migrate our lesser system to PGSQL, and this used now "Table" components (as BDE, but it have an SQL-like server). These tables use real cursors, a "Window" with N record, so lookup is very fast, because the Locate/Lookup is started on server, and only these N records are refreshed, no matter, how many records in the lookup table. PGSQL uses fetch technics as I know, and I tested it with a table (id int, name varchar(100)), and 1 million records. (I also trying this with mysql). The adapter is Zeos. ID, sec to find, allocated memory in bytes on client. MySQL 500000 2,761 113 196 344 1000000 3,214 225 471 232 313800 0,437 225 471 232 328066 0,468 225 471 232 276374 0,390 225 471 232 905984 1,264 225 471 232 260253 0,359 225 471 232 PGSQL 500000 3,042 113 188 184 1000000 3,744 225 463 064 313800 0,436 225 463 064 328066 0,452 225 463 064 276374 0,375 225 463 064 905984 1,295 225 463 064 260253 0,359 225 463 064 142023 0,203 225 463 064 As you see the records are fetched locally, this cause the 225 MB usage, and searches are slow a little, based where is the record we must find. I want to ask more things: a.) Is PGDAC have some technics to we can use the lookups without pay the fetch with memory and secs? b.) Or is PG ODBC driver can help in this problem with ADO? (As I know ADO can use server side cursors)? c.) Have anybody some experience with lookup tables, and performance? Is this critical question or it is not? (With client memory usage too). d.) If no chance to avoid fetch hell with lookups, what we can do? Server Side Joins, and unique code for Lookup field changing without real Lookup? Thanks for your help: dd

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• Android animation's first frame is applied too early on ImageView

  - by Robert

  I have the following View setup in one of my Activities: <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:id="@+id/photoLayout" android:layout_width="fill_parent" android:layout_height="fill_parent"> <ImageView android:id="@+id/photoImageView" android:src="@drawable/backyardPhoto" android:layout_width="fill_parent" android:layout_height="fill_parent" android:gravity="center" android:scaleType="centerInside" android:padding="45dip" > </ImageView> </LinearLayout> Without an animation set, this displays just fine. However I want to display a very simple animation. So in my Activity's onStart override, I have the following: @Override public void onStart() { super.onStart(); mPhotoImageView = (ImageView) findViewById(R.id.photoImageView); float offset = -25; int top = mPhotoImageView.getTop(); TranslateAnimation anim1 = new TranslateAnimation( Animation.ABSOLUTE, 0, Animation.ABSOLUTE, 0, Animation.ABSOLUTE, top, Animation.ABSOLUTE, offset); anim1.setInterpolator(new AnticipateInterpolator()); anim1.setDuration(1500); anim1.setStartOffset(5000); TranslateAnimation anim2 = new TranslateAnimation( Animation.ABSOLUTE, 0, Animation.ABSOLUTE, 0, Animation.ABSOLUTE, offset, Animation.ABSOLUTE, top); anim2.setInterpolator(new BounceInterpolator()); anim2.setDuration(3500); anim2.setStartOffset(6500); mBouncingAnimation = new AnimationSet(false); mBouncingAnimation.addAnimation(anim1); mBouncingAnimation.addAnimation(anim2); mPhotoImageView.setAnimation(mBouncingAnimation); } The problem is that when the Activity displays for the first time, the initial position of the photo is not in the center of the screen with padding around. It seems like the first frame of the animation is loaded already. Only after the animation is completed, does the photoImageView "snap" back to the intended location. I've looked and looked and could not find how to avoid this problem. I want the photoImageView to start in the center of the screen, and then the animation to happen, and return it to the center of the screen. The animation should happen by itself without interaction from the user.

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• Getter and Setter vs. Builder strategy

  - by Extrakun

  I was reading a JavaWorld's article on Getter and Setter where the basic premise is that getters expose internal content of an object, hence tightening coupling, and go on to provide examples using builder objects. I was rather leery of abolishing getter/setter but on second reading of the article, see to quite like the idea. However, sometimes I just need one cruical element of an entity class, such as the user's id and writing one whole class just to extract that cruical element seems like overkill. It also implies that for different view, a different type of importer/exporter must be implemented (or the whole data of the class to be exported out, thus resulting in waste). Usually I tend towards filtering the result of a getter - for example, if I need to output the price of a product in different currency, I would code it as: return CurrencyOutput::convertTo($product->price(), 'USD'); This is with the understanding that the raw output of a getter is not necessary the final result to be pushed onto a screen or a database. Is getter/setter really as bad as it is protrayed to be? When should one adopt a builder strategy, or a 'get the result and filter it' approach? How do you avoid having a class needing to know about every other objects if you are not using getter/setter?

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• jQuery capture all changes to named inpt on a form

  - by Brian M. Hunt

  I'm trying to determine when any of a set of named input/select/radio/checked/hidden fields in a form change. In particular, I'd like to capture when any changes are made to fields matching jQuery's selector $("form :input"), and where that input is has a name attribute. However, the form isn't static i.e. some of the fields are dynamically added later. My initial thought is to keep track of when new named elements matching :input are added, and then add an event handler, like this: function on_change() { alert("The form element with name " + $(this).attr("name") + " has changed"); } function reg_new_e_handler(input_element) { input_element.change(on_change); } However, I'm quite hopeful I can avoid this with some jQuery magic. In particular, is there a way to register an event handler in jQuery that would handle input elements that match the following: $("form :input").filter( function () { $(this).attr("name") } ).change(on_change); However, have this event set update whenever new input elements are added. I've thought that it may be possible to capture keyup event on the form node with $("form").keyup(on_change), but I'm not so sure how one could capture change events. I'd also like this to capture keyup events. Thank you for reading. Brian

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• Asynchronous crawling F#

  - by jlezard

  When crawling on webpages I need to be careful as to not make too many requests to the same domain, for example I want to put 1 s between requests. From what I understand it is the time between requests that is important. So to speed things up I want to use async workflows in F#, the idea being make your requests with 1 sec interval but avoid blocking things while waiting for request response. let getHtmlPrimitiveAsyncTimer (uri : System.Uri) (timer:int) = async{ let req = (WebRequest.Create(uri)) :?> HttpWebRequest req.UserAgent<-"Mozilla" try Thread.Sleep(timer) let! resp = (req.AsyncGetResponse()) Console.WriteLine(uri.AbsoluteUri+" got response") use stream = resp.GetResponseStream() use reader = new StreamReader(stream) let html = reader.ReadToEnd() return html with | _ as ex -> return "Bad Link" } Then I do something like: let uri1 = System.Uri "http://rue89.com" let timer = 1000 let jobs = [|for i in 1..10 -> getHtmlPrimitiveAsyncTimer uri1 timer|] jobs |> Array.mapi(fun i job -> Console.WriteLine("Starting job "+string i) Async.StartAsTask(job).Result) Is this alright ? I am very unsure about 2 things: -Does the Thread.Sleep thing work for delaying the request ? -Is using StartTask a problem ? I am a beginner (as you may have noticed) in F# (coding in general actually ), and everything envolving Threads scares me :) Thanks !!

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• Multithreading and Interrupts

  - by Nicholas Flynt

  I'm doing some work on the input buffers for my kernel, and I had some questions. On Dual Core machines, I know that more than one "process" can be running simultaneously. What I don't know is how the OS and the individual programs work to protect collisions in data. There are two things I'd like to know on this topic: (1) Where do interrupts occur? Are they guaranteed to occur on one core and not the other, and could this be used to make sure that real-time operations on one core were not interrupted by, say, file IO which could be handled on the other core? (I'd logically assume that the interrupts would happen on the 1st core, but is that always true, and how would you tell? Or perhaps does each core have its own settings for interrupts? Wouldn't that lead to a scenario where each core could react simultaneously to the same interrupt, possibly in different ways?) (2) How does the dual core processor handle opcode memory collision? If one core is reading an address in memory at exactly the same time that another core is writing to that same address in memory, what happens? Is an exception thrown, or is a value read? (I'd assume the write would work either way.) If a value is read, is it guaranteed to be either the old or new value at the time of the collision? I understand that programs should ideally be written to avoid these kinds of complications, but the OS certainly can't expect that, and will need to be able to handle such events without choking on itself.

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• Javascript scope chain

  - by Geromey

  Hi, I am trying to optimize my program. I think I understand the basics of closure. I am confused about the scope chain though. I know that in general you want a low scope (to access variables quickly). Say I have the following object: var my_object = (function(){ //private variables var a_private = 0; return{ //public //public variables a_public : 1, //public methods some_public : function(){ debugger; alert(this.a_public); alert(a_private); }; }; })(); My understanding is that if I am in the some_public method I can access the private variables faster than the public ones. Is this correct? My confusion comes with the scope level of this. When the code is stopped at debugger, firebug shows the public variable inside the this keyword. The this word is not inside a scope level. How fast is accessing this? Right now I am storing any this.properties as another local variable to avoid accessing it multiple times. Thanks very much!

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• Best Pattern for AllowUnsafeUpdates

  - by webwires

  So far, in my research I have seen that it is unwise to set AllowUnsafeUpdates on GET request operation to avoid cross site scripting. But, if it is required to allow this, what is the proper way to handle the situation to mitigate any exposure? Here is my best first guess on a reliable pattern if you absolutely need to allow web or site updates on a GET request. Best Practice? protected override void OnLoad(System.EventArgs e) { if(Request.HttpMethod == "POST") { SPUtility.ValidateFormDigest(); // will automatically set AllowSafeUpdates to true } // If not a POST then AllowUnsafeUpdates should be used only // at the point of update and reset immediately after finished // NOTE: Is this true? How is cross-site scripting used on GET // and what mitigates the vulnerability? } // Point of item update SPSecurity.RunWithElevatedPrivledges(delegate() { using(SPSite site = new SPSite(SPContext.Current.Site.Url)) { using (SPWeb web = site.RootWeb) { bool allowUpdates = web.AllowUnsafeUpdates; //store original value web.AllowUnsafeUpdates = true; //... Do something and call Update() ... web.AllowUnsafeUpdates = allowUpdates; //restore original value } } }); Feedback on the best pattern is appreciated.

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• Building an extension framework for a Rails app

  - by obvio171

  I'm starting research on what I'd need in order to build a user-level plugin system (like Wordpress plugins) for a Rails app, so I'd appreciate some general pointers/advice. By user-level plugin I mean a package a user can extract into a folder and have it show up on an admin interface, allowing them to add some extra configuration and then activate it. What is the best way to go about doing this? Is there any other opensource project that does this already? What does Rails itself already offer for programmer-level plugins that could be leveraged? Any Rails plugins that could help me with this? A plugin would have to be able to: run its own migrations (with this? it's undocumented) have access to my models (plugins already do) have entry points for adding content to views (can be done with content_for and yield) replace entire views or partials (how?) provide its own admin and user-facing views (how?) create its own routes (or maybe just announce its presence and let me create the routes for it, to avoid plugins stepping on each other's toes) Anything else I'm missing? Also, is there a way to limit which tables/actions the plugin has access to concerning migrations and models, and also limit their access to routes (maybe letting them include, but not remove routes)? P.S.: I'll try to keep this updated, compiling stuff I figure out and relevant answers so as to have a sort of guide for others.

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• Does anyone knows any Train-table-api service?

  - by DaNieL

  Hi guys, im wondering if there is any online service who provide API about the train timetables (arrivals, departure, etch..), at least for the european stations. I know www.bahn.de, who provide the accurated timetables for many european countries, but i didin't find any similar to a api service. My goal (well, just a future-project) is to develope an application like gmaps, but instead of giving the car-trip i would like to give the train-trip.. you know, the user set the departure day, time and station, then the first arrival, maybe then add another one, and so on. So, there is something like, that can be queryed by php/python/javascript? Edit: if can help, im wondering to build a service to plan an inter-rail trip! (and any help will be really appreciate) Im stuck. Google's public-service api rely on the information that every local company makes avaiable, much branches are missing (for example, is almost impossible to use it to build an itinerary that touches two or more regions of Europe. As i said before, the only service that i know doing it good is the bahn.de, they really have all the data.. but no api. I tryed to parse theyre result page (in order to use them as API), but seem like the markup is been build exactly to avoid that.. maybe they have business plans behind that or whatever, but i dont think they will ever release some API.. so, my project is going on without this function (p.s: my project is about non-profit cultural organizations, we wont make war to anyone ;P) @El Goorf: if you find a way, and consider the idea of sharing it, count on my hand if need help!

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• Dependency Injection and decoupling of software layers

  - by cs31415

  I am trying to implement Dependency Injection to make my app tester friendly. I have a rather basic doubt. Data layer uses SqlConnection object to connect to a SQL server database. SqlConnection object is a dependency for data access layer. In accordance with the laws of dependency injection, we must not new() dependent objects, but rather accept them through constructor arguments. Not wanting to upset the DI gods, I dutifully create a constructor in my DAL that takes in SqlConnection. Business layer calls DAL. Business layer must therefore, pass in SqlConnection. Presentation layer calls Business layer. Hence it too, must pass in SqlConnection to business layer. This is great for class isolation and testability. But didn't we just couple the UI and Business layers to a specific implementation of the data layer which happens to use a relational database? Why do the Presentation and Business layers need to know that the underlying data store is SQL? What if the app needs to support multiple data sources other than SQL server (such as XML files, Comma delimited files etc.) Furthermore, what if I add another object upon which my data layer is dependent on (say, a second database). Now, I have to modify the upper layers to pass in this new object. How can I avoid this merry-go-round and reap all the benefits of DI without the pain?

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• php scandir --> search for files/directories

  - by Peter

  Hi! I searched before I ask, without lucky.. I looking for a simple script for myself, which I can search for files/folders. Found this code snippet in the php manual (I think I need this), but it is not work for me. "Was looking for a simple way to search for a file/directory using a mask. Here is such a function. By default, this function will keep in memory the scandir() result, to avoid scaning multiple time for the same directory." <?php function sdir( $path='.', $mask='*', $nocache=0 ){ static $dir = array(); // cache result in memory if ( !isset($dir[$path]) || $nocache) { $dir[$path] = scandir($path); } foreach ($dir[$path] as $i=>$entry) { if ($entry!='.' && $entry!='..' && fnmatch($mask, $entry) ) { $sdir[] = $entry; } } return ($sdir); } ?> Thank you for any help, Peter

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• Combine regular expressions for splitting camelCase string into words

  - by stou

  I managed to implement a function that converts camel case to words, by using the solution suggested by @ridgerunner in this question: Split camelCase word into words with php preg_match (Regular Expression) However, I want to also handle embedded abreviations like this: 'hasABREVIATIONEmbedded' translates to 'Has ABREVIATION Embedded' I came up with this solution: <?php function camelCaseToWords($camelCaseStr) { // Convert: "TestASAPTestMore" to "TestASAP TestMore" $abreviationsPattern = '/' . // Match position between UPPERCASE "words" '(?<=[A-Z])' . // Position is after group of uppercase, '(?=[A-Z][a-z])' . // and before group of lowercase letters, except the last upper case letter in the group. '/x'; $arr = preg_split($abreviationsPattern, $camelCaseStr); $str = implode(' ', $arr); // Convert "TestASAP TestMore" to "Test ASAP Test More" $camelCasePattern = '/' . // Match position between camelCase "words". '(?<=[a-z])' . // Position is after a lowercase, '(?=[A-Z])' . // and before an uppercase letter. '/x'; $arr = preg_split($camelCasePattern, $str); $str = implode(' ', $arr); $str = ucfirst(trim($str)); return $str; } $inputs = array( 'oneTwoThreeFour', 'StartsWithCap', 'hasConsecutiveCAPS', 'ALLCAPS', 'ALL_CAPS_AND_UNDERSCORES', 'hasABREVIATIONEmbedded', ); echo "INPUT"; foreach($inputs as $val) { echo "'" . $val . "' translates to '" . camelCaseToWords($val). "'\n"; } The output is: INPUT'oneTwoThreeFour' translates to 'One Two Three Four' 'StartsWithCap' translates to 'Starts With Cap' 'hasConsecutiveCAPS' translates to 'Has Consecutive CAPS' 'ALLCAPS' translates to 'ALLCAPS' 'ALL_CAPS_AND_UNDERSCORES' translates to 'ALL_CAPS_AND_UNDERSCORES' 'hasABREVIATIONEmbedded' translates to 'Has ABREVIATION Embedded' It works as intended. My question is: Can I combine the 2 regular expressions $abreviationsPattern and camelCasePattern so i can avoid running the preg_split() function twice?

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• Fatal error when using FILE* in Windows from DLL

  - by AlannY

  Hi there. Recently, I found a problem with Visual C++ 2008 compiler, but using minor hack avoid it. Currently, I cannot use the same hack, but problem exists as in 2008 as in 2010 (Express). So, I've prepared for you 2 simple C file: one for DLL, one for program: DLL (file-dll.c): #include <stdio.h> __declspec(dllexport) void print_to_stream (FILE *stream) { fprintf (stream, "OK!\n"); } And for program, which links this DLL via file-dll.lib: Program: #include <stdio.h> __declspec(dllimport) void print_to_stream (FILE *stream); int main (void) { print_to_stream (stdout); return 0; } To compile and link DLL: cl /LD file-dll.c To compile and link program: cl file-test.c file-dll.lib When invoking file-test.exe, I got the fatal error (similar to segmentation fault in UNIX). As I said early, I had that the same problem before: about transferring FILE* pointer to DLL. I thought, that it may be because of compiler mismatch, but now I'm using one compiler for everything and it's not the problem. ;-( What can I do now? UPD: I've found solution: cl /LD /MD file-dll.c cl /MD file-test.c file-dll.lib The key is to link to dynamic library, but (I did not know it) by default it links staticaly and (hencefore) error occurs (I see why). P.S. Thanks for patience.

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• How to log correct context with Threadpool threads using log4net?

  - by myotherme

  I am trying to find a way to log useful context from a bunch of threads. The problem is that a lot of code is dealt with on Events that are arriving via threadpool threads (as far as I can tell) so their names are not in relation to any context. The problem can be demonstrated with the following code: class Program { private static readonly log4net.ILog log = log4net.LogManager.GetLogger(System.Reflection.MethodBase.GetCurrentMethod().DeclaringType); static void Main(string[] args) { new Thread(TestThis).Start("ThreadA"); new Thread(TestThis).Start("ThreadB"); Console.ReadLine(); } private static void TestThis(object name) { var nameStr = (string)name; Thread.CurrentThread.Name = nameStr; log4net.ThreadContext.Properties["ThreadContext"] = nameStr; log4net.LogicalThreadContext.Properties["LogicalThreadContext"] = nameStr; log.Debug("From Thread itself"); ThreadPool.QueueUserWorkItem(x => log.Debug("From threadpool Thread: " + nameStr)); } } The Conversion pattern is: %date [%thread] %-5level %logger [%property] - %message%newline The output is like so: 2010-05-21 15:08:02,357 [ThreadA] DEBUG LogicalContextTest.Program [{LogicalThreadContext=ThreadA, log4net:HostName=xxx, ThreadContext=ThreadA}] - From Thread itself 2010-05-21 15:08:02,357 [ThreadB] DEBUG LogicalContextTest.Program [{LogicalThreadContext=ThreadB, log4net:HostName=xxx, ThreadContext=ThreadB}] - From Thread itself 2010-05-21 15:08:02,404 [7] DEBUG LogicalContextTest.Program [{log4net:HostName=xxx}] - From threadpool Thread: ThreadA 2010-05-21 15:08:02,420 [16] DEBUG LogicalContextTest.Program [{log4net:HostName=xxx}] - From threadpool Thread: ThreadB As you can see the last two rows have no Names of useful information to distinguish the 2 threads, other than manually adding the name to the message (which I want to avoid). How can I get the Name/Context into the log for the threadpool threads without adding it to the message at every call?

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• Simple in-place discrete fourier transform ( DFT )

  - by Adam

  I'm writing a very simple in-place DFT. I am using the formula shown here: http://en.wikipedia.org/wiki/Discrete_Fourier_transform#Definition along with Euler's formula to avoid having to use a complex number class just for this. So far I have this: private void fft(double[] data) { double[] real = new double[256]; double[] imag = new double[256]; double pi_div_128 = -1 * Math.PI / 128; for (int k = 0; k < 256; k++) { for (int n = 0; n < 256; n++) { real[k] += data[k] * Math.Cos(pi_div_128 * k * n); imag[k] += data[k] * Math.Sin(pi_div_128 * k * n); } data[k] = Math.Sqrt(real[k] * real[k] + imag[k] * imag[k]); } } But the Math.Cos and Math.Sin terms eventually go both positive and negative, so as I'm adding those terms multiplied with data[k], they cancel out and I just get some obscenely small value. I see how it is happening, but I can't make sense of how my code is perhaps mis-representing the mathematics. Any help is appreciated. FYI, I do have to write my own, I realize I can get off-the shelf FFT's.

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• Check mail attachment

  - by comii

  Hi! I am using vb.net to display email from outlook express! Everything work fine but when some message has attachment, i can not display message that email has attachment! This is my code: Private Sub LoginButton_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles LoginButton.Click Dim oItem Dim i As Integer Dim Message As MAPI.Message Dim items As String() = New String(6) {} ' Items are the sender name,subject and date and read/unread value Dim PrSenderEmail, PrBodyEmail Session = CreateObject("MAPI.Session") ' we use a session object of MAPI Component Session.Logon(ProfileName:=Me.UserId.Text, ProfilePassword:=Me.Password.Text) Session.MAPIOBJECT = Session.MAPIOBJECT ' Folder = CObj(Session.Inbox) ' choose the folder Application = CreateObject("Outlook.Application") Namespace1 = Application.GetNamespace("MAPI") Namespace1.Logon() ' for getting the sender name and avoid security validation of Outlook/Exchange server 2003 ' we are using the "Redemption" component sItem = CreateObject("Redemption.SafeMailItem") Cursor.Current = Cursors.WaitCursor ' show we're busy doing the sort ListInbox.BeginUpdate() ' Notify that update begins ListInbox.Items.Clear() i = 0 ' first email message is 0 For Each Message In Folder.Messages Try i = i + 1 ' increment to the next email message 'get e-mail from the Inbox, can be any other item oItem = Application.Session.GetDefaultFolder(6).Items(i) ' GetDefaultFolder(6) refers to Inbox sItem.Item = oItem 'sItem is an object of Redemption COM and is used to get the senders name items(0) = sItem.SenderName() Catch items(0) = "error" End Try Dim objApp As Outlook.Application = New Outlook.Application 'Get Mapi NameSpace Dim objNS As Outlook.NameSpace = objApp.GetNamespace("MAPI") Dim oMsg As Outlook.MailItem Dim pp As String Dim b As Integer Dim objAttachment As Outlook.Attachment pp = Message.StoreID items(1) = Message.Subject items(2) = Message.TimeReceived items(4) = Message.Subject items(5) = Message.Size Dim objInbox As Outlook.MAPIFolder = objNS.GetDefaultFolder(Outlook.OlDefaultFolders.olFolderInbox) Dim objItems As Outlook.Items = objInbox.Items items(5) = Message.Size.ToString / 1000 & "kb" If Message.Unread = True Then items(3) = "unread" Else items(3) = "read" End If ListInbox.Items.Add(New ListViewItem(items)) Next ListInbox.EndUpdate() ' Notify that update ends Cursor.Current = Cursors.Default End If End Sub How I can display message that email has attachment?

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• EF + UnitOfWork + SharePoint RunWithElevatedPrivileges

  - by Lorenzo

  In our SharePoint application we have used the UnitOfWork + Repository patterns together with Entity Framework. To avoid the usage of the passthrough authentication we have developed a piece of code that impersonate a single user before creating the ObjectContext instance in a similar way that is described in "Impersonating user with Entity Framework" on this site. The only difference between our code and the referred question is that, to do the impersonation, we are using RunWithElevatedPrivileges to impersonate the Application Pool identity as in the following sample. SPSecurity.RunWithElevatedPrivileges(delegate() { using (SPSite site = new SPSite(url)) { _context = new MyDataContext(ConfigSingleton.GetInstance().ConnectionString); } }); We have done this way because we expected that creating the ObjectContext after impersonation and, due to the fact that Repositories are receiving the impersonated ObjectContext would solve our requirement. Unfortunately it's not so easy. In fact we experienced that, even if the ObjectContext is created before and under impersonation circumstances, the real connection is made just before executing the query, and so does not use impersonation, which break our requirement. I have checked the ObjectContext class to see if there was any event through which we can inject the impersonation but unfortunately found nothing. Any help?

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• Use Objective-C without NSObject?

  - by Alex I

  I am testing some simple Objective-C code on Windows (cygwin, gcc). This code already works in Xcode on Mac. I would like to convert my objects to not subclass NSObject (or anything else, lol). Is this possible, and how? What I have so far: // MyObject.h @interface MyObject - (void)myMethod:(int) param; @end and // MyObject.m #include "MyObject.h" @interface MyObject() { // this line is a syntax error, why? int _field; } @end @implementation MyObject - (id)init { // what goes in here? return self; } - (void)myMethod:(int) param { _field = param; } @end What happens when I try compiling it: gcc -o test MyObject.m -lobjc MyObject.m:4:1: error: expected identifier or ‘(’ before ‘{’ token MyObject.m: In function ‘-[MyObject myMethod:]’: MyObject.m:17:3: error: ‘_field’ undeclared (first use in this function) EDIT My compiler is cygwin's gcc, also has cygwin gcc-objc package: gcc --version gcc (GCC) 4.7.3 I have tried looking for this online and in a couple of Objective-C tutorials, but every example of a class I have found inherits from NSObject. Is it really impossible to write Objective-C without Cocoa or some kind of Cocoa replacement that provides NSObject? (Yes, I know about GNUstep. I would really rather avoid that if possible...)

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• Altruistic network connection bandwidth estimation

  - by datenwolf

  Assume two peers Alice and Bob connected over a IP network. Alice and Bob are exchanging packets of lossy compressed data which are generated and to be consumes in real time (think a VoIP or video chat application). The service is designed to cope with as little bandwidth available, but relies on low latencies. Alice and Bob would mark their connection with an apropriate QoS profile. Alice and Bob want use a variable bitrate compression and would like to consume all of the leftover bandwidth available for the connection between them, but would voluntarily reduce the consumed bitrate depending on the state of the network. However they'd like to retain a stable link, i.e. avoid interruptions in their decoded data stream caused by congestion and the delay until the bandwidth got adjusted. However it is perfectly possible for them to loose a few packets. TL;DR: Alice and Bob want to implement a VoIP protocol from scratch, and are curious about bandwidth and congestion control. What papers and resources do you suggest for Alice and Bob to read? Mainly in the area of bandwidth estimation and congestion control.

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• Vim script to TeX source, and launch PDF only if no errors

  - by Jeet

  Hi, I am switching to using Vim for for my LaTeX editing environment. I would like to be able to tex the source file from within Vim, and launch an external viewing if the compile was successful. I know about the Vim-Latex suite, but, if possible, would prefer to avoid using it: it is pretty heavy-weight, hijacks a lot of my keys, and clutters up my vimruntime with a lot of files. Here is what I have now: if exists('b:tex_build_mapped') finish endif " use maparg or mapcheck to see if key is free command! -buffer -nargs=* BuildTex call BuildTex(0, <f-args>) command! -buffer -nargs=* BuildAndViewTex call BuildTex(1, <f-args>) noremap <buffer> <silent> <F9> <Esc>:call BuildTex(0)<CR> noremap <buffer> <silent> <S-F9> <Esc>:call BuildTex(1)<CR> let b:tex_build_mapped = 1 if exists('g:tex_build_loaded') finish endif let g:tex_build_loaded = 1 function! BuildTex(view_results, ...) write if filereadable("Makefile") " If Makefile is available in current working directory, run 'make' with arguments echo "(using Makefile)" let l:cmd = "!make ".join(a:000, ' ') echo l:cmd execute l:cmd if a:view_results && v:shell_error == 0 call ViewTexResults() endif else let b:tex_flavor = 'pdflatex' compiler tex make % if a:view_results && v:shell_error == 0 call ViewTexResults() endif endif endfunction function! ViewTexResults(...) if a:0 == 0 let l:target = expand("%:p:r") . ".pdf" else let l:target = a:1 endif if has('mac') execute "! open -a Preview ".l:target endif endfunction The problem is that v:shell_error is not set, even if there are compile errors. Any suggestions or insight on how to detect whether a compile was successful or not would be greatly appreciated! Thanks!

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• Grails - Recursive computing call "StackOverflowError" and don't update on show

  - by Kedare

  Hello, I have a little problem, I have made a Category domain on Grails, but I want to "cache" the string representation on the database by generating it when the representation field is empty or NULL (to avoid recursive queries at each toString), here is the code : package devkedare class Category { String title; String description; String representation; Date dateCreated; Date lastUpdate; Category parent; static constraints = { title(blank:false, nullable:false, size:2..100); description(blank:true, nullable:false); dateCreated(nullable:true); lastUpdate(nullable:true); autoTimestamp: true; } static hasMany = [childs:Category] @Override String toString() { if((!this.representation) || (this.representation == "")) { this.computeRepresentation(true) } return this.representation; } String computeRepresentation(boolean updateChilds) { if(updateChilds) { for(child in this.childs) { child.representation = child.computeRepresentation(true); } } if(this.parent) { this.representation = "${this.parent.computeRepresentation(false)}/${this.title}"; } else { this.representation = this.title } return this.representation; } void beforeUpdate() { this.computeRepresentation(true); } } There is 2 problems : It don't update the representation when the representation if NULL or empty and toString id called, it only update it on save, how to fix that ? On some category, updating it throw a StackOverflowError, here is an example of my actual category table as CSV : Uploaded the csv file here, pasting csv looks buggy: http://kedare.free.fr/Dist/01.csv Updating the representation works everywhere except on "IT" that throw a StackOverlowError (this is the only category that has many childs). Any idea of how can I fix those 2 problems ? Thank you !

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• Get directory path by fd

  - by tylerl

  I've run into the need to be able refer to a directory by path given its file descriptor in Linux. The path doesn't have to be canonical, it just has to be functional so that I can pass it to other functions. So, taking the same parameters as passed to a function like fstatat(), I need to be able to call a function like getxattr() which doesn't have a f-XYZ-at() variant. So far I've come up with these solutions; though none are particularly elegant. The simplest solution is to avoid the problem by calling openat() and then using a function like fgetxattr(). This works, but not in every situation. So another method is needed to fill the gaps. The next solution involves looking up the information in proc: if (!access("/proc/self/fd",X_OK)) { sprintf(path,"/proc/self/fd/%i/",fd); } This, of course, totally breaks on systems without proc, including some chroot environments. The last option, a more portable but potentially-race-condition-prone solution, looks like this: DIR* save = opendir("."); fchdir(fd); getcwd(path,PATH_MAX); fchdir(dirfd(save)); closedir(save); The obvious problem here is that in a multithreaded app, changing the working directory around could have side effects. However, the fact that it works is compelling: if I can get the path of a directory by calling fchdir() followed by getcwd(), why shouldn't I be able to just get the information directly: fgetcwd() or something. Clearly the kernel is tracking the necessary information. So how do I get to it?

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• Threads, Sockets, and Designing Low-Latency, High Concurrency Servers

  - by lazyconfabulator

  I've been thinking a lot lately about low-latency, high concurrency servers. Specifically, http servers. http servers (fast ones, anyway) can serve thousands of users simultaneously, with very little latency. So how do they do it? As near as I can tell, they all use events. Cherokee and Lighttpd use libevent. Nginx uses it's own event library performing much the same function of libevent, that is, picking a platform optimal strategy for polling events (like kqueue on *bsd, epoll on linux, /dev/poll on Solaris, etc). They all also seem to employ a strategy of multiprocess or multithread once the connection is made - using worker threads to handle the more cpu intensive tasks while another thread continues to listen and handle connections (via events). This is the extent of my understanding and ability to grok the thousand line sources of these applications. What I really want are finer details about how this all works. In examples of using events I've seen (and written) the events are handling both input and output. To this end, do the workers employ some sort of input/output queue to the event handling thread? Or are these worker threads handling their own input and output? I imagine a fixed amount of worker threads are spawned, and connections are lined up and served on demand, but how does the event thread feed these connections to the workers? I've read about FIFO queues and circular buffers, but I've yet to see any implementations to work from. Are there any? Do any use compare-and-swap instructions to avoid locking or is locking less detrimental to event polling than I think? Or have I misread the design entirely? Ultimately, I'd like to take enough away to improve some of my own event-driven network services. Bonus points to anyone providing solid implementation details (especially for stuff like low-latency queues) in C, as that's the language my network services are written in.

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• Security implications of writing files using PHP

  - by susmits

  I'm currently trying to create a CMS using PHP, purely in the interest of education. I want the administrators to be able to create content, which will be parsed and saved on the server storage in pure HTML form to avoid the overhead that executing PHP script would incur. Unfortunately, I could only think of a few ways of doing so: Setting write permission on every directory where the CMS should want to write a file. This sounds like quite a bad idea. Setting write permissions on a single cached directory. A PHP script could then include or fopen/fread/echo the content from a file in the cached directory at request-time. This could perhaps be carried out in a Mediawiki-esque fashion: something like index.php?page=xyz could read and echo content from cached/xyz.html at runtime. However, I'll need to ensure the sanity of $_GET['page'] to prevent nasty variations like index.php?page=http://www.bad-site.org/malicious-script.js. I'm personally not too thrilled by the second idea, but the first one sounds very insecure. Could someone please suggest a good way of getting this done?

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