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  • Wake up thread blocked on accept() call

    - by selbie
    Sockets on Linux question I have a worker thread that is blocked on an accept() call. It simply waits for an incoming network connection, handles it, and then returns to listening for the next connection. When it is time for the program to exit, how do I signal this network worker thread (from the main thread) to return from the accept() call while still being able to gracefully exit its loop and handle it's cleanup code. Some things I tried: 1. pthread_kill to send a signal. Feels kludgy to do this, plus it doesn't reliably allow the thread to do it's shutdown logic. Also makes the program terminate as well. I'd like to avoid signals if at all possible. pthread_cancel. Same as above. It's a harsh kill on the thread. That, and the thread may be doing something else. Closing the listen socket from the main thread in order to make accept() abort. This doesn't reliably work. Some constraints: If the solution involves making the listen socket non-blocking, that is fine. But I don't want to accept a solution that involves the thread waking up via a select call every few seconds to check the exit condition. The thread condition to exit may not be tied to the process exiting. Essentially, the logic I am going for looks like this. void* WorkerThread(void* args) { DoSomeImportantInitialization(); // initialize listen socket and some thread specific stuff while (HasExitConditionBeenSet()==false) { listensize = sizeof(listenaddr); int sock = accept(listensocket, &listenaddr, &listensize); // check if exit condition has been set using thread safe semantics if (HasExitConditionBeenSet()) { break; } if (sock < 0) { printf("accept returned %d (errno==%d)\n", sock, errno); } else { HandleNewNetworkCondition(sock, &listenaddr); } } DoSomeImportantCleanup(); // close listen socket, close connections, cleanup etc.. return NULL; } void SignalHandler(int sig) { printf("Caught CTRL-C\n"); } void NotifyWorkerThreadToExit(pthread_t thread_handle) { // signal thread to exit } int main() { void* ptr_ret= NULL; pthread_t workerthread_handle = 0; pthread_create(&workerthread, NULL, WorkerThread, NULL); signal(SIGINT, SignalHandler); sleep((unsigned int)-1); // sleep until the user hits ctrl-c printf("Returned from sleep call...\n"); SetThreadExitCondition(); // sets global variable with barrier that worker thread checks on // this is the function I'm stalled on writing NotifyWorkerThreadToExit(workerthread_handle); // wait for thread to exit cleanly pthread_join(workerthread_handle, &ptr_ret); DoProcessCleanupStuff(); }

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  • What is your most obfuscated JavaScript example (5 lines maximum)?

    - by snowlord
    JavaScript is known as a language with many weird features. This probably makes it a good language to write extremely obfuscated and hard to understand code in (in the style of The International Obfuscated C Code Contest). What would be your best example of obfuscated JavaScript code (5 lines maximum)? I am thinking that it should be very hard to understand, but also have an element of style or humor in it. And for clarity: using obfuscation tools is not the point, of course. Hand crafting only!

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  • How to implement a UIViewAutoresizingFlexibleHeight to a UIScrollView using Objective C in iPhone SD

    - by AppleHack23
    Hello, I'm working on multiple applications for my school. I just need this last bit of code and I was wondering how I could implement a UIViewAutoresizingFlexibleHeight into the app for each textfield. What this does is it makes the textfield pop above the keyboard, rather than over lapping it. I have already implemented a UIScrollView, so if someone on here could be pretty descriptive, or post a link to a video, that would be well appreciated. I am new to coding. Thanks very much!!!!

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  • Text Aligned Next To Photo in CSS

    - by PF1
    Hi Everyone: I am wondering if there is some way to align text on the right of a photo, and keep the text in that same "box" even after the image ends using HTML and CSS. A quick "diagram" of what I am attempting to accomplish is below: ------- -------- ------- -------- -Image- - Text - ------- -------- ------- -------- -------- -------- Thanks for any help!

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  • Is it possible to get Semantic (emacs) to visit all files automatically?

    - by RealityMonster
    From what I can tell from the docs, semantic works by slowly building up an idea of what's in your project by analysing each file (and possibly its neighbours) as you visit them. This is too slow. I'd like to just have it visit all the files in my project. Is there an easy way to do this? Having to visit hundreds of files before I can get decent autocomplete working seems crazy. I've also got a etags file generated. Can I leverage that somehow?

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  • Abort early in a fold

    - by Heptic
    What's the best way to terminate a fold early? As a simplified example, imagine I want to sum up the numbers in an Iterable, but if I encounter something I'm not expecting (say an odd number) I might want to terminate. This is a first approximation def sumEvenNumbers(nums: Iterable[Int]): Option[Int] = { nums.foldLeft (Some(0): Option[Int]) { case (None, _) => None case (Some(s), n) if n % 2 == 0 => Some(s + n) case (Some(_), _) => None } } However, this solution is pretty ugly (as in, if I did a .foreach and a return -- it'd be much cleaner and clearer) and worst of all, it traverses the entire iterable even if it encounters a non-even number. So what would be the best way to write a fold like this, that terminates early? Should I just go and write this recursively, or is there a more accepted way?

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  • Abstract over X

    - by Bruno Bieth
    Sorry for this english related question but I only came across that expression in the context of IT. What does abstracting over something mean ? For example abstracting over objects or abstracting over classes. Thanks

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  • Using enum values to represent binary operators (or functions)

    - by Bears will eat you
    I'm looking for an elegant way to use values in a Java enum to represent operations or functions. My guess is, since this is Java, there just isn't going to be a nice way to do it, but here goes anyway. My enum looks something like this: public enum Operator { LT, LTEQ, EQEQ, GT, GTEQ, NEQ; ... } where LT means < (less than), LTEQ means <= (less than or equal to), etc - you get the idea. Now I want to actually use these enum values to apply an operator. I know I could do this just using a whole bunch of if-statements, but that's the ugly, OO way, e.g.: int a = ..., b = ...; Operator foo = ...; // one of the enum values if (foo == Operator.LT) { return a < b; } else if (foo == Operator.LTEQ) { return a <= b; } else if ... // etc What I'd like to be able to do is cut out this structure and use some sort of first-class function or even polymorphism, but I'm not really sure how. Something like: int a = ..., b = ...; Operator foo = ...; return foo.apply(a, b); or even int a = ..., b = ...; Operator foo = ...; return a foo.convertToOperator() b; But as far as I've seen, I don't think it's possible to return an operator or function (at least, not without using some 3rd-party library). Any suggestions?

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  • Disabling the "save password" prompt in web browsers

    - by torrtruk
    hi guys. How do I disable the save password prompt in web browsers whenever I'm submitting a form. I've seen a few bank sites where this doesn't come up. Are they doing it through JS or there any http headers or HTML meta tags available to achieve this? I'm trying to do this for a mobile application. Please pour your ideas.

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  • Any good C interpreters?

    - by NoMoreZealots
    I was looking at Ch from SofIntegration and it looks pretty interesting as a possible teaching tool. It would allow the you to let someone learning to program "play" while preparing them to write full fledged C programs. I was wondering if anybody had "good" experiences using a C interpreter or weather it would be a better to go with a language that is typically interpreter to start with?

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  • How can i get more than one jpg. or txt file from any folder?

    - by Phsika
    Dear Sirs; i have two Application to listen network Stream : Server.cs on the other hand; send file Client.cs. But i want to send more files on a stream from any folder. For example. i have C:/folder whish has got 3 jpg files. My client must run. Also My server.cs get files on stream: Client.cs: private void btn_send2_Click(object sender, EventArgs e) { string[] paths= null; paths= System.IO.Directory.GetFiles(@"C:\folder" + @"\", "*.jpg", System.IO.SearchOption.AllDirectories); byte[] Dizi; TcpClient Gonder = new TcpClient("127.0.0.1", 51124); FileStream Dosya; FileInfo Dos; NetworkStream Akis; foreach (string path in paths) { Dosya = new FileStream(path , FileMode.OpenOrCreate); Dos = new FileInfo(path ); Dizi = new byte[(int)Dos.Length]; Dosya.Read(Dizi, 0, (int)Dos.Length); Akis = Gonder.GetStream(); Akis.Write(Dizi, 0, (int)Dosya.Length); Gonder.Close(); Akis.Flush(); Dosya.Close(); } } Also i have Server.cs void Dinle() { TcpListener server = null; try { Int32 port = 51124; IPAddress localAddr = IPAddress.Parse("127.0.0.1"); server = new TcpListener(localAddr, port); server.Start(); Byte[] bytes = new Byte[1024 * 250000]; // string ReceivedPath = "C:/recieved"; while (true) { MessageBox.Show("Waiting for a connection... "); TcpClient client = server.AcceptTcpClient(); MessageBox.Show("Connected!"); NetworkStream stream = client.GetStream(); if (stream.CanRead) { saveFileDialog1.ShowDialog(); // burasi degisecek string pathfolder = saveFileDialog1.FileName; StreamWriter yaz = new StreamWriter(pathfolder); string satir; StreamReader oku = new StreamReader(stream); while ((satir = oku.ReadLine()) != null) { satir = satir + (char)13 + (char)10; yaz.WriteLine(satir); } oku.Close(); yaz.Close(); client.Close(); } } } catch (SocketException e) { Console.WriteLine("SocketException: {0}", e); } finally { // Stop listening for new clients. server.Stop(); } Console.WriteLine("\nHit enter to continue..."); Console.Read(); } Please look Client.cs: icollected all files from "c:\folder" paths= System.IO.Directory.GetFiles(@"C:\folder" + @"\", "*.jpg", System.IO.SearchOption.AllDirectories); My Server.cs how to get all files from stream?

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  • Testing for a closed socket

    - by Robert S. Barnes
    I'm trying to test for a closed socket that has been gracefully closed by the peer without incurring the latency hit of a double send to induce a SIGPIPE. One of the assumptions here is that the socket if closed was gracefully closed by the peer immediately after it's last write / send. Actual errors like a premature close are dealt with else where in the code. If the socket is still open, there will be 0 or more bytes data which I don't actually want to pull out of the socket buffer yet. I was thinking that I could call int ret = recv(sockfd, buf, 1, MSG_DONTWAIT | MSG_PEEK); to determine if the socket is still connected. If it's connected but there's no data in the buffer I'll get a return of -1 with errno == EAGAIN and return the sockfd for reuse. If it's been gracefully closed by the peer I'll get ret == 0 and open a new connection. I've tested this and it seems to work. However, I suspect there is a small window between when I recv the last bit of my data and when the peer FIN arrives in which I could get a false-positive EAGAIN from my test recv. Is this going to bite me, or is there a better way of doing this?

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  • Heap Algorithmic Issue

    - by OberynMarDELL
    I am having this algorithmic problem that I want to discuss about. Its not about find a solution but about optimization in terms of runtime. So here it is: Suppose we have a race court of Length L and a total of N cars that participate on the race. The race rules are simple. Once a car overtakes an other car the second car is eliminated from the race. The race ends when no more overtakes are possible to happen. The tricky part is that the k'th car has a starting point x[k] and a velocity v[k]. The points are given in an ascending order, but the velocities may differ. What I've done so far: Given that a car can get overtaken only by its previous, I calculated the time that it takes for each car to reach its next one t = (x[i] - x[i+1])/(v[i] - v[i+1]) and I insert these times onto a min heap in O(n log n). So in theory I have to pop the first element in O(logn), find its previous, pop it as well , update its time and insert it in the heap once more, much like a priority queue. My main problem is how I can access specific points of a heap in O(log n) or faster in order to keep the complexity in O(n log n) levels. This program should be written on Haskell so I would like to keep things simple as far as possible EDIT: I Forgot to write the actual point of the race. The goal is to find the order in which cars exit the game

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  • Having trouble getting GET variables from url.

    - by mchl
    Hey everyone, I'm having trouble with this algorithm to extract the get variables from a url and print them each on a new line like: x=y z=hello etc. but instead it prints a seemingly random section of the url with no newlines to the file. There must be a logic error of some kind but i just can't spot it. for(i_m=0;i_m<len_m;i_m++) { if(var_m[i_m]=='&') { fwrite(var_m+offset_m, 1, amp_m, echo_out); fputc('\n',echo_out); offset_m+=amp_m; amp_m=0; } amp_m++; } any help appreciated.

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  • Create servlet from existing Java project

    - by user69514
    I have a Java Swing project for my class. I would like put it on my website so people can use it. However I'm not sure if there is a way to turn it into a servlet. Or do I need to know JavaScript? I'm confused. Is there a way to make my swing application into a servlet automatically?

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  • How to get input from web?

    - by Dunix
    Hi, i am trying to find out, how to get input from html inputs using c++. In windows you can send WM_GETTEXT to the window and it returns text, that you wanted. But is there any way to do the same thing in web interface?. I am not interesting in sniffing packets now.

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  • Sleep Function Error In C

    - by Arman
    I have a file of data Dump, in with different timestamped data available, I get the time from timestamp and sleep my c thread for that time. But the problem is that The actual time difference is 10 second and the data which I receive at the receiving end is almost 14, 15 second delay. I am using window OS. Kindly guide me. Sorry for my week English.

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