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• What happens if an asynchronous delegate call never returns?

  - by RichardHowells

  I found a decent looking example of how to call a delegate asynchronously with a timeout... http://www.eggheadcafe.com/tutorials/aspnet/847c94bf-4b8d-4a66-9ae5-5b61f049019f/basics-make-any-method-c.aspx. In summary it uses WaitOne with a timeout to determine if the call does not return before the timeout expires. I also know that you should have an EndInvoke to match each BeginInvoke. So what happens if the wait timeout expires? We (presumably) DON'T want to call EndInvoke as that will block. The code can go on to do 'other things', but have we leaked anything? Is there some poor thread someplace blocked waiting for a return that's never going to happen? Have we leaked some memory where the result-that-will-never-return was going to be placed?

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• Android: how to have app talk to a web page, ie send gps location

  - by Ted pottel

  I'm trying to write a app, where a webpage will have a button that when press will give the GPS location of the phone. I was going to have the android app create a thread that waits on a scket connection. The issue is that 1. Getting the ip addrs of the phone 2. I was told this would really drain the battery I was also thinking about having the phone send the gps location to a webserver like evrry 10 seconds. This sort of seams like a waste of bandwidth. Is there a good way to do this?

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• Sending while receiving in C

  - by Spidfire

  I've made a piece of code in what's on my server, the problem is that it doesn't send while im receiving. so if i send something to client 1 to client 2, client2 only receives if he sends something himself.. how can i solve this ? /* Thread*/ while (! stop_received) { nr_bytes_recv = recv(s, buffer, BUFFSIZE, 0); if(strncmp(buffer, "SEND", 4) == 0) { char *message = "Text asads \n"; rv = send(users[0].s, message, strlen(message), 0); rv = send(users[1].s, message, strlen(message), 0); if (rv < 0) { perror("Error sending"); exit(EXIT_FAILURE); } }else{ char *message = "Unknown command \n"; rv = send(s, message, strlen(message), 0); if (rv < 0) { perror("Error sending"); exit(EXIT_FAILURE); } } }

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• Do fields need to be explicitly final to have a "proper" immutable object?

  - by Yishai

  You often read about immutable objects requiring final fields to be immutable in Java. Is this in fact the case, or is it simply enough to have no public mutability and not actually mutate the state? For example, if you have an immutable object built by the builder pattern, you could do it by having the builder assign the individual fields as it builds, or having the builder hold the fields itself and ultimately return the immutable object by passing the values to its (private) constructor. Having the fields final has the obvious advantage of preventing implementation errors (such as allowing code to retain a reference to the builder and "building" the object multiple times while in fact mutating an existing object), but having the Builder store its data inside the object as it is built would seem to be DRYer. So the question is: Assuming the Builder does not leak the Object early and stops itself from modifying the object once built (say by setting its reference to the object as null) is there actually anything gained (such as improved thread safety) in the "immutability" of the object if the object's fields were made final instead?

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• Easy Threading in WPF

  - by Sandeep Bansal

  Hi everyone, I've been reading a lot about threading in C#, WPF and Silverlight but can't get it to work. My main problem is I have the _load (_Initialized) action and it has a lot of object creation and along with that I have timers working doing different things, this causes the startup time of the program to be very slow and obviously causes the UI to hang and it isn't a good thing for deploying to a lot of users. My timers change values of labels and textfields but having them do that on another thread is an obvious no go. So can someone give me some examples on how to achieve what I need to do? Thanks

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• Delay in for loop while playing mp3 file C#

  - by daniyalahmad

  I want to give delay in for loop, While in for loop there is mp3 file is playing. What I actually want to do, that every clip plays after 2 sec. There are total 10 clips. Here is my code for (int i=1; i < 10; i++) { System.Threading.Thread.Sleep(1000); WMPLib.WindowsMediaPlayer wplayer = new WMPLib.WindowsMediaPlayer(); wplayer.URL = @"D:\Project C#\A-Z\" + i + ".mp3"; }

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• Passing an array of structures to an Oracle stored procedure (CFMX)

  - by Patti

  I'm looking to write a Oracle stored procedure where I would pass in (from ColdFusion) an array of structures and loop over each iteration to insert the bits and pieces within the structures to the DB., I haven't written this type of procedure / package before. I am planning to do an sp / package similar to what is sketched out in the second reply to this thread: How to pass a array of object to oracle stored procedure Assuming I do, how can I call the procedure from ColdFusion (I'm using MX) and pass in my array? As far as I can see, none of the CF_SQL_Types make sense.

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• Trigger Backgroundworker Completed event.

  - by fireBand

  Hello, I am trying to display the progress bar(marque) in a separate form (progressForm) while i do some calculation in background. I know the typical way of doing it is to include the calculation in background worker and show progressForm in main thread. This approach how ever will lead to lot of synch issues in my application hence I am showing the progressForm using progressForm.ShowDialog() inside the background worker process. But I need to trigger the Completed event with in the application to close the form. Is this possible? Thanks in advance.

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• Is PThread a good choice for multi-platorm C/C++ multi-threading program?

  - by RogerV

  Been doing mostly Java and smattering of .NET for last five years and haven't written any significant C or C++ during that time. So have been away from that scene for a while. If I want to write a C or C++ program today that does some multi-threading and is source code portable across Windows, Mac OS X, and Linux/Unix - is PThread a good choice? The C or C++ code won't be doing any GUI, so won't need to worry with any of that. For the Windows platform, I don't want to bring a lot of Unix baggage, though, in terms of unix emulation runtime libraries. Would prefer a PThread API for Windows that is a thin-as-possible wrapper over existing Windows threading APIs. ADDENDUM EDIT: Am leaning toward going with boost:thread - I also want to be able to use C++ try/catch exception handling too. And even though my program will be rather minimal and not particularly OOPish, I like to encapsulate using class and namespace - as opposed to C disembodied functions.

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• [Java]Queue in while loop, cannot modify the value?

  - by javaLearner.java

  This is my code: Iterator it = queue.iterator(); while(it.hasNext()){ random = randNumber(1,2); if(random == 1){ queue.poll(); } else { queue.add("new"); queue.poll(); } } It gives me: Exception in thread "test" java.util.ConcurrentModificationException at java.util.LinkedList$ListItr.checkForComodification(LinkedList.java:761) at java.util.LinkedList$ListItr.next(LinkedList.java:696) Edit @Jon Skeet: What I want to do is: I have a queue list in, let say the size is 10, lets say: a,b,c,d ... j Generate a number between 1 and 2. if 1, pull (remove the top element) else if 2 add new element I will stop the loop until I added 3 new elements

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• .NET web service call slower when performed asynchronously

  - by joelt

  I have an ASP.NET site, and some pages need to call a web service. I used Visual Studio's "Add Web Reference" to auto-generate classes and methods for the web service. When I call the service synchronously, i.e. objService.MethodName("param1"), a call might take a second or so. When I call it asynchronously, i.e., objService.BeginMethodName("param1", AddressOf MyCallback, Nothing), it typically takes about 6 seconds. When debugging, it appears that the bulk of the time is spent waiting between the completion of the BeginMethodName call and the beginning of MyCallback. Does the thread switching really incur that much overhead? Is there another reason for this?

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• Android SurfaceView/Canvas flickering after trying to clear it

  - by Mark D

  So I am trying to clear the Canvas using canvas.drawColor(Color.BLACK) but if I just call this once, the display flickers and displays the old drawing which should have been covered up by the drawColor. Here is the important bits of my code - public void update() { //This method is called by a Thread Canvas canvas = holder.lockCanvas(null); if (canvas != null) { onDraw(canvas); } holder.unlockCanvasAndPost(canvas); } @Override protected void onDraw(Canvas canvas) { if (toClear) { canvas.drawColor(Color.BLACK); //if this is not set to change back to false, it does not flicker toClear = false; } //Draw some objects that are moving around } public void clearScreen() { //This method is called when the user pressed a button toClear = true; } After Googling around a litte, I heard about double buffering but came to the understanding that lockCanvas() and unlockCanvasAndPost() should handle this for me. What is going wrong here?

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• Should I use multiple threads in this situation? [Ruby]

  - by mr popo

  I'm opening multiple files and processing them, one line at a time. The files contain tokens separating the data, such that sometimes the processing of one file may have to wait for others to catch up to that same token. I was doing this initially with only one thread and an array indicating with true/false if the file should be read in the current iteration or if it should wait for some of the others to catch up. Would using threads make this simpler? More efficient? Does Ruby have a mechanism for this?

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• Delays in ActionScript (Flash)? Alternatives to setInterval

  - by yar

  While setInterval is handy, it's kind of limiting. Every time I want to add a Tween I have to add a new method. I do not want to alter the structure of my code just to add in some delays. Isn't there any way to say this without making methods for A and B? // do A // wait N seconds // do B I don't want to use a while loop with Dates because I think it will be blocking. Isn't there anything like Thread.sleep in ActionScript?

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• C#.NET Problem with locking of page after writing stream to window.

  - by godlikeskills

  The code below works fine, the problem is the 1st two lines are appearing on screen. It basically loads the PDF but I can't see the btnAcceptProposal change name or become enabled. Tried a Thread for the load but it broke. Anyone got any ideas - it's a web application protected void btnPDFProposal_Click(object sender, EventArgs e) { btnAcceptProposal.Enabled = true; btnAcceptProposal.Text = "sss"; byte[] p = Order.Proposal; Response.AppendHeader("content-disposition", "attachment; filename=Proposal.pdf"); Response.ContentType = "Application/pdf"; Response.Clear(); Response.BinaryWrite(p); Response.End(); }

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• Mysql with innodb and serializable transaction does not (always) lock rows

  - by Tobias G.

  Hello, I have a transaction with a SELECT and possible INSERT. For concurrency reasons, I added FOR UPDATE to the SELECT. To prevent phantom rows, I'm using the SERIALIZABLE transaction isolation level. This all works fine when there are any rows in the table, but not if the table is empty. When the table is empty, the SELECT FOR UPDATE does not do any (exclusive) locking and a concurrent thread/process can issue the same SELECT FOR UPDATE without being locked. CREATE TABLE t ( id INT NOT NULL AUTO_INCREMENT PRIMARY KEY, display_order INT ) ENGINE = InnoDB; SET TRANSACTION ISOLATION LEVEL SERIALIZABLE; START TRANSACTION; SELECT COALESCE(MAX(display_order), 0) + 1 from t FOR UPDATE; .. This concept works as expected with SQL Server, but not with MySQL. Any ideas on what I'm doing wrong? EDIT Adding an index on display_order does not change the behavior.

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• Linux How to print all the files with the same prefix after searching for them?

  - by Alyx

  I need to search through a directory which contains many sub directories, each which contain files. The files read as follows question1234_01, where 1234 are random digits and the suffix _01 is the number of messages that contain the prefix, meaning they are apart of the same continuing thread. find . -name 'quest*' | cut -d_ -f1 | awk '{print $1}' | uniq -c | sort -n example output: 1 quest1234 10 quest1523 This searches for all the files then sorts them in order. What I want to do is print all the files which end up having the most occurrences, in my example the one with 10 matches. So it should only output quest1523_01 - 11

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• How do i resolve method Overlapping in java/Processing [duplicate]

  - by user3718913

  This question already has an answer here: How do I compare strings in Java? 24 answers I have two methods/function in a class, called, Qestion1 and Question2, i want it in such a way that after the user has answered Question one correctly, the Question 2 method is called. Whenever i call the method 2, it displays both of them together instead exiting the first method first. Here's a dummy code to illustrate what i'm saying: void Question1() { String question="What is the capital of England?"; String Answer="London"; if(Answer=='London') { Question2(); } } void Question2() { String question="What is the capital of California?"; String Answer="Sacramento"; if(Answer=='Sacramento') { Question3(); } } Pls, this question is in no way related to that other question. Pls peruse the thread again.

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• Handling orientation changes yourself

  - by synic

  From the documentation regarding the android:configChanges='orientation' attribute of the activity tag in the manifest: Note: Using this attribute should be avoided and used only as a last-resort. Please read Handling Runtime Changes for more information about how to properly handle a restart due to a configuration change. Why does it say this? In the case of threads and networking requests via a service API library, a request could be made with a reference to the original Activity, and then an orientation change could occur, leaving the thread pointing to the old Activity. While this can be fixed, it's tedious and ugly compared to just handling the configuration changes yourself. Why should it be avoided?

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• ArrayIndexOutOfBound exception even though I check for array length!

  - by xtracto

  I have the following code in some app: int lowRange=50; int[] ageRangeIndividual = {6, 10, 18, 25, 45, 65, 90}; int index=0; for (; index<ageRangeIndividual.length-1 && ageRangeIndividual[index]<=lowRange;index++); I am getting an "Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 7" in the for line! even though I explicitly specify to break the cycle if index < last indexable item in the array! This does not happen always, but after some time of running said program (lowRange varies each time the function is called) What am I not seeing?

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• is it a good idea to change a recovery partition from primary to logical? [HP laptop]

  - by DiegoDD

  I have a new HP laptop, model dv6-6c85la, with 1TB hard drive, and it has 4 primary partitions, like this: |<- system [199 MB] -|<- c: [899.8 GB] -|<- d:(recovery) [27.5 GB] -|<- e:(hp_tools) [4 GB] -| I wanted to make another partition, splitting "C" which is the main partition, into TWO partitions, and leave the rest as it is. but it doesn't let me because they are already 4 primary partitions (the ones in the diagram). I read somewhere, that i could in fact split C into 2 partitions, but only if the adjacent partition (in this case d:(recovery) is converted into a "logical" partition. That way, the new unallocated part taken from C, and the recovery partition, would each be logical, "inside" an extended partition (right???) As i understand, the resulting partitions would be: primary (system, no letter), primary (c:), extended [ logical (x:) | logical(d:recovery) ], primary (e: hp_tools) "x" being the new one. am i correct? My question is, if i do convert the recovery partition to logical (and thus, it is inside an extended partition adjacent to the new "x:" one), would i have any problems when in case of a disaster i would like to restore the system using the now logical instead of primary RECOVERY partition? Or it is completely safe to change it to logical? My main concern is because i think i may need to be primary so the recovery can proceed in boot time? Or i am completely wrong? how does the recovery process happens? I also understand that i can simply create recovery media, in DVDs, and then even i would be able to delete that recovery partition completely, but as of now, i don't want to do that. I may create the disks, but i don't want to delete the partition, simply because it would be a lot faster and easier to recover from a hard drive than disks. Wrapping up: if i change a recovery partition from primary to logical, will the system still be capable of using it to recover? or it NEEDS to be primary to work? The whole point is that i want to split C:, but as things are, i cant directly, i'd need to change the recovery partition to logical. Or is there another way? thanks.

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• How to get left-top and right-buttom latitude and longitude of map in MapKit For iPad ?

  - by damniatx

  Hi, i'm looking for answer about getting latitude and longitude from uimapkit. there is same problem that has been answered, but it didn't give right coordinate. http://yit.me/3ddp73 it's code from thread i'm linking above. CLLocationCoordinate2D topLeft, bottomRight; topLeft = [mapView convertPoint:CGPointMake(0,0) toCoordinateFromView:mapView]; CGPoint pointBottomRight = CGPointMake(mapView.frame.size.width, mapView.frame.size.height); bottomRight = [mapView convertPoint:pointBottomRight toCoordinateFromView:mapView]; NSLog(@"topleft = %f", topLeft); NSLog(@"bottom right = %f", bottomRight); any idea to fix this issue ? thanks

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• How can I (reasonably) precisely perform an action every N milliseconds?

  - by Jon Cage

  I have a machine which uses an NTP client to sync up to internet time so it's system clock should be fairly accurate. I've got an application which I'm developing which logs data in real time, processes it and then passes it on. What I'd like to do now is output that data every N milliseconds aligned with the system clock. So for example if I wanted to do 20ms intervals, my oututs ought to be something like this: 13:15:05:0000 13:15:05:0020 13:15:05:0040 13:15:05:0060 I've seen suggestions for using the stopwatch class, but that only measures time spans as opposed to looking for specific time stamps. The code to do this is running in it's own thread, so should be a problem if I need to do some relatively blocking calls. Any suggestions on how to achieve this to a reasonable (close to or better than 1ms precision would be nice) would be very gratefully received.

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• Monitor multiple variable amounts of processes' start and exit

  - by ron975

  I need some code to monitor the start and exit of processes. For example, assume I have a config file with 3 processe names, lets say, foo.exe, bar.exe and abc.exe. How I imagine this be done would be to create 3 threads and somehow listen to each process individually with a timer in each thread, and then do something afterwards. However, I would need to dynamically create threads and timers, as the config file is meant to be modifiable. I can work with VB.NET or C# Code. Thanks.

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• Is there a way to embed an mp3 player in a website that isn't flash based (so that the website is iP

  - by hartleybrody

  I did a lot of searching for what I thought would be a pretty common question, but I came up with nothing. If there is another thread with a similar topic, please let me know. Basically, I'm looking for a way to have an .mp3 file play in a website without relying on a flash-based player. I've searched w3 schools and every forum I can think of, but every media player I've found so far has been some sort of proprietary flash player. Doesn't HTML support some sort of native player? I've found some that rely on Windows Media Player which is close, but I want the player to work on an iPhone and something tells me WMP won't get that done... PS, as I'm thinking more about this this idea just popped into my head: a javascipt player and inside the <noscript> tag, put a flash player? I'm running a music blog (@ http://www.freshoncampus.com) so the less code per post, the better...

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