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  • Constructor invocation returned null: what to do?

    - by strager
    I have code which looks like: private static DirectiveNode CreateInstance(Type nodeType, DirectiveInfo info) { var ctor = nodeType.GetConstructor(new[] { typeof(DirectiveInfo) }); if(ctor == null) { throw new MissingMethodException(nodeType.FullName, "ctor"); } var node = ctor.Invoke(new[] { info }) as DirectiveNode; if(node == null) { // ???; } return node; } I am looking for what to do (e.g. what type of exception to throw) when the Invoke method returns something which isn't a DirectiveNode or when it returns null (indicated by // ??? above). (By the method's contract, nodeType will always describe a subclass of DirectiveNode.) I am not sure when calling a constructor would return null, so I am not sure if I should handle anything at all, but I still want to be on the safe side and throw an exception if something goes wrong.

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  • Keyboard input with timeout in Python

    - by J. Pablo Fernández
    How would you prompt the user for some input but timing out after N seconds? Google is pointing to a mail thread about it at http://mail.python.org/pipermail/python-list/2006-January/533215.html but it seems not to work. The statement in which the timeout happens, no matter whether it is a sys.input.readline or timer.sleep(), I always get: <type 'exceptions.TypeError'>: [raw_]input expected at most 1 arguments, got 2 which somehow the except fails to catch.

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  • Decrypting data from a secure socket

    - by Ronald
    I'm working on a server application in Java. I've successfully got past the handshake portion of the communication process, but how do I go about decrypting my input stream? Here is how I set up my server: import java.io.IOException; import java.net.ServerSocket; import java.net.Socket; import java.util.ArrayList; import java.util.HashMap; import javax.net.ServerSocketFactory; import javax.net.ssl.SSLServerSocket; import javax.net.ssl.SSLServerSocketFactory; import org.json.me.JSONException; import dictionary.Dictionary; public class Server { private static int port = 1234; public static void main(String[] args) throws JSONException { System.setProperty("javax.net.ssl.keyStore", "src/my.keystore"); System.setProperty("javax.net.ssl.keyStorePassword", "test123"); System.out.println("Starting server on port: " + port); HashMap<String, Game> games = new HashMap<String, Game>(); final String[] enabledCipherSuites = { "SSL_RSA_WITH_RC4_128_SHA" }; try{ SSLServerSocketFactory socketFactory = (SSLServerSocketFactory) SSLServerSocketFactory.getDefault(); SSLServerSocket listener = (SSLServerSocket) socketFactory.createServerSocket(port); listener.setEnabledCipherSuites(enabledCipherSuites); Socket server; Dictionary dict = new Dictionary(); Game game = new Game(dict); //for testing, creates 1 global game. while(true){ server = listener.accept(); ClientConnection conn = new ClientConnection(server, game, "User"); Thread t = new Thread(conn); t.start(); } } catch(IOException e){ System.out.println("Failed setting up on port: " + port); e.printStackTrace(); } } } I used a BufferedReader to get the data send from the client: BufferedReader d = new BufferedReader(new InputStreamReader(socket.getInputStream())); After the handshake is complete it appears like I'm getting encrypted data. I did some research online and it seems like I might need to use a Cipher, but I'm not sure. Any ideas?

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  • Manipulating the address of a variable to store a smaller type?

    - by Sidnicious
    This is what I get for pampering myself with high-level programming languages. I have a function which writes a 32-bit value to a buffer, and a uint64_t on the stack. Is the following code a sane way to store it? uint64_t size = 0; // ... getBytes((uint32_t*)&size+0x1); I'm assuming that this would be the canonical, safe style: uint64_t size = 0; // ... uint32_t smallSize; getBytes(&smallSize); size = smallSize;

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  • java concurrency: many writers, one reader

    - by Janning
    I need to gather some statistics in my software and i am trying to make it fast and correct, which is not easy (for me!) first my code so far with two classes, a StatsService and a StatsHarvester public class StatsService { private Map<String, Long> stats = new HashMap<String, Long>(1000); public void notify ( String key ) { Long value = 1l; synchronized (stats) { if (stats.containsKey(key)) { value = stats.get(key) + 1; } stats.put(key, value); } } public Map<String, Long> getStats ( ) { Map<String, Long> copy; synchronized (stats) { copy = new HashMap<String, Long>(stats); stats.clear(); } return copy; } } this is my second class, a harvester which collects the stats from time to time and writes them to a database. public class StatsHarvester implements Runnable { private StatsService statsService; private Thread t; public void init ( ) { t = new Thread(this); t.start(); } public synchronized void run ( ) { while (true) { try { wait(5 * 60 * 1000); // 5 minutes collectAndSave(); } catch (InterruptedException e) { e.printStackTrace(); } } } private void collectAndSave ( ) { Map<String, Long> stats = statsService.getStats(); // do something like: // saveRecords(stats); } } At runtime it will have about 30 concurrent running threads each calling notify(key) about 100 times. Only one StatsHarvester is calling statsService.getStats() So i have many writers and only one reader. it would be nice to have accurate stats but i don't care if some records are lost on high concurrency. The reader should run every 5 Minutes or whatever is reasonable. Writing should be as fast as possible. Reading should be fast but if it locks for about 300ms every 5 minutes, its fine. I've read many docs (Java concurrency in practice, effective java and so on), but i have the strong feeling that i need your advice to get it right. I hope i stated my problem clear and short enough to get valuable help.

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  • Increase increment size to match GUID advantage

    - by TenaciousImpy
    Hi, I've been thinking of implementing this system, but can't help but feel there's a catch somewhere. One of the points of using GUID over incrementing int is that, in the future, if you were to merge databases together, you wouldn't have any clashes over the primary key/identifier. However, my approach is to set the increment size to X where X is the number of servers I'll most likely have in the future. Then, on each server, have the seed be an increment over the seed number on the previous server. That way, during merging, there would be no clashes with the primary key. Is this a safe, normal method or have I gone mental :)? Thanks

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  • Java NIO (Netty): Exceptionhandling in Downstream Hanlders/Chain

    - by Tom
    Hello Experts, could someone please explain to me, how in netty "Downstream Exceptions" are handeled? According to the javadoc there are no Downstream exceptions: http://docs.jboss.org/netty/3.1/api/org/jboss/netty/channel/ExceptionEvent.html Given the case that in one of my downstream handlers an exception occures OR in the I/0 Thread itself, where can these errors be catched and handeled? thank you very much tom

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  • pthread and child process data sharing in C

    - by mustafabattal
    hi everyone, my question is somewhat conceptual, how is parent process' data shared with child process created by a "fork()" call or with a thread created by "pthread_create()" for example, are global variables directly passed into child process and if so, does modification on that variable made by child process effect value of it in parent process? i appreciate partial and complete answers in advance, if i'm missing any existing resource, i'm sorry, i've done some search on google but couldn't find good results thanks again for your time and answers

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  • java.util.concurrent.ThreadPoolExecutor strange logic

    - by rodrigoap
    Look ath this method of ThreadPoolExcecutor: public void execute(Runnable command) { ... if (runState == RUNNING && workQueue.offer(command)) { if (runState != RUNNING || poolSize == 0) ensureQueuedTaskHandled(command); } ... } It check that runState is RUNNING and then the oposite. As I'm trying to do some tuning on a SEDA like model I wanted to understand the internals of the thread pool. Do you think this code is correct?

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  • Python urllib3 and how to handle cookie support?

    - by bigredbob
    So I'm looking into urllib3 because it has connection pooling and is thread safe (so performance is better, especially for crawling), but the documentation is... minimal to say the least. urllib2 has build_opener so something like: #!/usr/bin/python import cookielib, urllib2 cj = cookielib.CookieJar() opener = urllib2.build_opener(urllib2.HTTPCookieProcessor(cj)) r = opener.open("http://example.com/") But urllib3 has no build_opener method, so the only way I have figured out so far is to manually put it in the header: #!/usr/bin/python import urllib3 http_pool = urllib3.connection_from_url("http://example.com") myheaders = {'Cookie':'some cookie data'} r = http_pool.get_url("http://example.org/", headers=myheaders) But I am hoping there is a better way and that one of you can tell me what it is. Also can someone tag this with "urllib3" please.

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  • Stream writing lags my GUI

    - by blez
    I have a thread that dequeues data from a queue and write it to another application's STDIN. I'm using Stream, but with .Write and even .BeginWrite, when I send 1mb chunks to the second app, my GUI gets laggy for ~1sec. Why?

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  • SSH Password/User problem with Cygwin sshd service

    - by Supernovah
    hello I just set up SSHd through Cygwin on a Windows XP Pro box overseas using a RAT and discluded the openssh package from the install. I ran the cywin shell (from c:\cywin) and ran Now, It's under a port I know is safe and fowarded properly, but I won't share it's number. It's not a common port, but it's under 40000. Firewalls are off etc etc. I'm on the first Admin account made on the box. (It's full admin) I've run the following commands chmod +r /etc/passwd chmod +r /etc/group hmod 777 /var /*Created New Admin User Account To Be Used via SSH*/ mkpasswd -cl > /etc/passwd mkgroup --local > /etc/group I can connect locally, but not externally. I know my ports etc are fine. Any possible problems, as i really need this tunnel up :P

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  • How to retry opening a properties file in Java

    - by Hoggy
    I'm trying to handle an FileNotFoundException in Java by suspending the thread for x seconds and rereading the file. The idea behind this is to edit properties during runtime. The problem is that the programm simply terminates. Any idea how to realize this solution?

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  • VB6: Question about version numbers of dependent OCXs

    - by Craig Johnston
    Is it important for a VB6 app to refer to certain OCX versions? I have noticed that if I put my VB6 app code through the IDE on one machine then the form files will refer to different version of some OCXs than if I use another machine. What is the rule of thumb with this? Is it safe to assume that most of these old OCX versions will be compatible with each other and so I shouldn't worry? Some of the OCXs in question are: RICHTX32.OCX v1.1 and v1.2 COMCTL32.OCX v1.2 and v1.3

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  • HttpURLConnection does not read the whole respnse

    - by Peter Szanto
    I use HttpURLConnection to do HTTP POST but I dont always get back the full response. I wanted to debug the problem, but when I step through each line it worked. I thought it must be a timing issue so I added Thread.sleep and it really made my code work, but this is only a temporary workaround. I wonder why is this happening and how to solve. Here is my code: URL u = new URL(url); URLConnection c = u.openConnection(); InputStream in = null; String mediaType = null; if (c instanceof HttpURLConnection) { //c.setConnectTimeout(1000000); //c.setReadTimeout(1000000); HttpURLConnection h = (HttpURLConnection)c; h.setRequestMethod("POST"); //h.setChunkedStreamingMode(-1); setAccept(h, expectedMimeType); h.setRequestProperty("Content-Type", inputMimeType); for(String key: httpHeaders.keySet()) { h.setRequestProperty(key, httpHeaders.get(key)); if (logger.isDebugEnabled()) { logger.debug("Request property key : " + key + " / value : " + httpHeaders.get(key)); } } h.setDoOutput(true); h.connect(); OutputStream out = h.getOutputStream(); out.write(input.getBytes()); out.close(); mediaType = h.getContentType(); logger.debug(" ------------------ sleep ------------------ START"); try { Thread.sleep(2000); } catch (InterruptedException e) { e.printStackTrace(); } logger.debug(" ------------------ sleep ------------------ END"); if (h.getResponseCode() < 400) { in = h.getInputStream(); } else { in = h.getErrorStream(); } It genearates the following HTTP headers POST /emailauthentication/ HTTP/1.1 Accept: application/xml Content-Type: application/xml Authorization: OAuth oauth_consumer_key="b465472b-d872-42b9-030e-4e74b9b60e39",oauth_nonce="YnDb5eepuLm%2Fbs",oauth_signature="dbN%2FWeWs2G00mk%2BX6uIi3thJxlM%3D", oauth_signature_method="HMAC-SHA1", oauth_timestamp="1276524919", oauth_token="", oauth_version="1.0" User-Agent: Java/1.6.0_20 Host: test:6580 Connection: keep-alive Content-Length: 1107 In other posts it was suggested to turn off keep-alive by using the http.keepAlive=false system property, I tried that and the headers changed to POST /emailauthentication/ HTTP/1.1 Accept: application/xml Content-Type: application/xml Authorization: OAuth oauth_consumer_key="b465472b-d872-42b9-030e-4e74b9b60e39", oauth_nonce="Eaiezrj6X4Ttt0", oauth_signature="ND9fAdZMqbYPR2j%2FXUCZmI90rSI%3D", oauth_signature_method="HMAC-SHA1", oauth_timestamp="1276526608", oauth_token="", oauth_version="1.0" User-Agent: Java/1.6.0_20 Host: test:6580 Connection: close Content-Length: 1107 the Connection header is "close" but I still cannot read the whole response. Any idea what do I do wrong?

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  • Pros and Cons of Java HTML to XML cleaners

    - by cjavapro
    I am looking to allow HTML emails (and other HTML uploads) without letting in scripts and stuff. I plan to have a white list of safe tags and attributes as well as a whitelist of CSS tags and value regexes (to prevent automatic return receipt). I asked a question: Parse a badly formatted XML document (like an HTML file) I found there are many many ways to do this. Some systems have built in sanitizers (which I don't care so much about). I will post some answers and say Community Wiki. Please post any other options you like and say Community Wiki so they can be voted on. Also any comments or wiki edits on what part of a certain product is better and what is not would be greatly appreciated. This page is a very nice listing page but I get kinda lost http://java-source.net/open-source/html-parsers

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  • What is the sense of permiting the user to use no passwords longer than xx chars?

    - by reox
    Its more like a usability question or maybe database, or even maybe security (consider injection attacks) but what is the sense of permiting the user's password to a be not longer than xx chars? It does not make any sense to me, because longer passwords are mostly considered better and even harder to crack, and some users use password safes, so the password length should not matter. I understand that passwords with more than 20 chars are hardly to remember, but if you use diceware or password safe you dont have any problem with that. I really cant understand why there are sites that say "your password need to be between 5 and 8 chars"... also should the password saved as hash, so the length of the field in the database is fixed, so where is the problem? i think that most of the sites where the password is has to be a fixed length are not even using any hashing method...

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  • segmented reduction with scattered segments

    - by Christian Rau
    I got to solve a pretty standard problem on the GPU, but I'm quite new to practical GPGPU, so I'm looking for ideas to approach this problem. I have many points in 3-space which are assigned to a very small number of groups (each point belongs to one group), specifically 15 in this case (doesn't ever change). Now I want to compute the mean and covariance matrix of all the groups. So on the CPU it's roughly the same as: for each point p { mean[p.group] += p.pos; covariance[p.group] += p.pos * p.pos; ++count[p.group]; } for each group g { mean[g] /= count[g]; covariance[g] = covariance[g]/count[g] - mean[g]*mean[g]; } Since the number of groups is extremely small, the last step can be done on the CPU (I need those values on the CPU, anyway). The first step is actually just a segmented reduction, but with the segments scattered around. So the first idea I came up with, was to first sort the points by their groups. I thought about a simple bucket sort using atomic_inc to compute bucket sizes and per-point relocation indices (got a better idea for sorting?, atomics may not be the best idea). After that they're sorted by groups and I could possibly come up with an adaption of the segmented scan algorithms presented here. But in this special case, I got a very large amount of data per point (9-10 floats, maybe even doubles if the need arises), so the standard algorithms using a shared memory element per thread and a thread per point might make problems regarding per-multiprocessor resources as shared memory or registers (Ok, much more on compute capability 1.x than 2.x, but still). Due to the very small and constant number of groups I thought there might be better approaches. Maybe there are already existing ideas suited for these specific properties of such a standard problem. Or maybe my general approach isn't that bad and you got ideas for improving the individual steps, like a good sorting algorithm suited for a very small number of keys or some segmented reduction algorithm minimizing shared memory/register usage. I'm looking for general approaches and don't want to use external libraries. FWIW I'm using OpenCL, but it shouldn't really matter as the general concepts of GPU computing don't really differ over the major frameworks.

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  • Saving highscores coupled to a facebook account

    - by Eiko
    I want to offer a "highscore" list for friends in my app (at this point iPhone/iPad), so that if the user connected to facebook, he will get a list with his/her friends scores. Connecting is easy, retrieving friends is easy, but figuring out the best way to store the scores is not. As it seems I need to the store the scores on my own server server, no big deal. But what is considered a reasonable safe way to transfer the data? When communicating with facebook, authentication is clear - but communicating with my server basically anyone could post scores for another user if I send user id and score. Obfuscation might help a bit, but is there any better way to make sure that the data comes from the fb-logged-in person? Scores can also go down, so changing scores for other persons won't necessary help them. Thanks :)

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  • How to make a legacy webapp spring aware at the container level for bean autowire into Servlets?

    - by Pete
    We have a legacy web application (not Spring based) and are looking for best practices to autowire some newer Spring configured (thread safe) service beans into instance variables in several of the legacy servlets. Rewriting every servlet to Spring MVC is out of scope. For testability, we do not want any Spring specific bean lookup code in the Servlets to look up beans by name or similar. Note that we are not concerned about web specific bean scopes such as session or request; all services are singleton scope. Below shows relevant code snippet MyServlet extends LegacyServletSuperclass { private MyThreadSafeServiceBean wantThisToBeAutowiredBySpring; .... }

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  • Is there an use case for non-blocking receive when I have threads?

    - by Gabriel Šcerbák
    I know non-blocking receive is not used as much in message passing, but still some intuition tells me, it is needed. Take for example GUI event driven applications, you need some way to wait for a message in a non-blocking way, so your program can execute some computations. One of the ways to solve this is to have a special thread with message queue. Is there some use case, where you would really need non-blocking receive even if you have threads?

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