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  • Android application Database Framework

    - by Marek Sebera
    When creating mobile (specially Android) application, I usually come to touch with similar pattern of working with data. Usually I need to fetch some remote data (covered by authorization process) to local cache. And on next request: Check networking Check presence of cache file Check version of cache file (if networking) Get new version and save cache (if networking and file not in cache, or outdated) Data store is no-SQL JSON Document-Based (and yes, I know about CouchDB Android version, but it doesn't fit my needs yet.) Process of authorizing to data source and code for check version of local cache is adapted to application. But the other code (handling network, saving cache, handling exceptions,...) is always the same. Is there any Data Store helper I can use, which provides functions I described above?

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  • How should I delete a child object from within a parent's slot? Possibly boost::asio specific.

    - by kaliatech
    I have written a network server class that maintains a std::set of network clients. The network clients emit a signal to the network server on disconnect (via boost::bind). When a network client disconnects, the client instance needs to be removed from the Set and eventually deleted. I would think this is a common pattern, but I am having problems that might, or might not, be specific to ASIO. I've tried to trim down to just the relevant code: /** NetworkServer.hpp **/ class NetworkServices : private boost::noncopyable { public: NetworkServices(void); ~NetworkServices(void); private: void run(); void onNetworkClientEvent(NetworkClientEvent&); private: std::set<boost::shared_ptr<const NetworkClient>> clients; }; /** NetworkClient.cpp **/ void NetworkServices::run() { running = true; boost::asio::io_service::work work(io_service); //keeps service running even if no operations // This creates just one thread for the boost::asio async network services boost::thread iot(boost::bind(&NetworkServices::run_io_service, this)); while (running) { boost::system::error_code err; try { tcp::socket* socket = new tcp::socket(io_service); acceptor->accept(*socket, err); if (!err) { NetworkClient* networkClient = new NetworkClient(io_service, boost::shared_ptr<tcp::socket>(socket)); networkClient->networkClientEventSignal.connect(boost::bind(&NetworkServices::onNetworkClientEvent, this, _1)); clients.insert(boost::shared_ptr<NetworkClient>(networkClient)); networkClient->init(); //kicks off 1st asynch_read call } } // etc... } } void NetworkServices::onNetworkClientEvent(NetworkClientEvent& evt) { switch(evt.getType()) { case NetworkClientEvent::CLIENT_ERROR : { boost::shared_ptr<const NetworkClient> clientPtr = evt.getClient().getSharedPtr(); // ------ THIS IS THE MAGIC LINE ----- // If I keep this, the io_service hangs. If I comment it out, // everything works fine (but I never delete the disconnected NetworkClient). // If actually deleted the client here I might expect problems because it is the caller // of this method via boost::signal and bind. However, The clientPtr is a shared ptr, and a // reference is being kept in the client itself while signaling, so // I would the object is not going to be deleted from the heap here. That seems to be the case. // Never-the-less, this line makes all the difference, most likely because it controls whether or not the NetworkClient ever gets deleted. clients.erase(clientPtr); //I should probably put this socket clean-up in NetworkClient destructor. Regardless by doing this, // I would expect the ASIO socket stuff to be adequately cleaned-up after this. tcp::socket& socket = clientPtr->getSocket(); try { socket.shutdown(boost::asio::socket_base::shutdown_both); socket.close(); } catch(...) { CommServerContext::error("Error while shutting down and closing socket."); } break; } default : { break; } } } /** NetworkClient.hpp **/ class NetworkClient : public boost::enable_shared_from_this<NetworkClient>, Client { NetworkClient(boost::asio::io_service& io_service, boost::shared_ptr<tcp::socket> socket); virtual ~NetworkClient(void); inline boost::shared_ptr<const NetworkClient> getSharedPtr() const { return shared_from_this(); }; boost::signal <void (NetworkClientEvent&)> networkClientEventSignal; void onAsyncReadHeader(const boost::system::error_code& error, size_t bytes_transferred); }; /** NetworkClient.cpp - onAsyncReadHeader method called from io_service.run() thread as result of an async_read operation. Error condition usually result of an unexpected client disconnect.**/ void NetworkClient::onAsyncReadHeader( const boost::system::error_code& error, size_t bytes_transferred) { if (error) { //Make sure this instance doesn't get deleted from parent/slot deferencing //Alternatively, somehow schedule for future delete? boost::shared_ptr<const NetworkClient> clientPtr = getSharedPtr(); //Signal to service that this client is disconnecting NetworkClientEvent evt(*this, NetworkClientEvent::CLIENT_ERROR); networkClientEventSignal(evt); networkClientEventSignal.disconnect_all_slots(); return; } I believe it's not safe to delete the client from within the slot handler because the function return would be ... undefined? (Interestingly, it doesn't seem to blow up on me though.) So I've used boost:shared_ptr along with shared_from_this to make sure the client doesn't get deleted until all slots have been signaled. It doesn't seem to really matter though. I believe this question is not specific to ASIO, but the problem manifests in a peculiar way when using ASIO. I have one thread executing io_service.run(). All ASIO read/write operations are performed asynchronously. Everything works fine with multiple clients connecting/disconnecting UNLESS I delete my client object from the Set per the code above. If I delete my client object, the io_service seemingly deadlocks internally and no further asynchronous operations are performed unless I start another thread. I have try/catches around the io_service.run() call and have not been able to detect any errors. Questions: Are there best practices for deleting child objects, that are also signal emitters, from within parent slots? Any ideas as to why the io_service is hanging when I delete my network client object?

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  • How does session middleware generally verify browser sessions?

    - by BBnyc
    I've been using session middleware to build web apps for years: from PHP's built-in session handling layer to node's connect session middleware. However, I've never tried (or needed) to roll my own session handling layer. How would one go about it? What sort of checks are necessary to provide at least some modicum of security against HTTP session highjacking? I figure setting a cookie with a token to keep track of the session, and then perhaps some check to see that the originating IP address of the session doesn't change and that the client browser software remains consistent. Hoping to hear about current best-practices...

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  • Any frameworks or library allow me to run large amount of concurrent jobs schedully?

    - by Yoga
    Are there any high level programming frameworks that allow me to run large amount of concurrent jobs schedully? e.g. I have 100K of urls need to check their uptime every 5 minutes Definitely I can write a program to handle this, but then I need to handle concurrency, queuing, error handling, system throttling, job distribution etc. Will there be a framework that I only focus on a particular job (i.e. the ping task) and the system will take care of the scaling and error handling for me? I am open to any language.

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  • timer_getoverrun() doesn't behave as expected when using sleep()

    - by dlp
    Here is a program that uses a POSIX per-process timer alongside the sleep subroutine. The signal used by the timer has been set to SIGUSR1 rather than SIGALRM, since SIGALRM may be used internally by sleep, but it still doesn't seem to work. I have run the program using the command line timer-overruns -d 1 -n 10000000 (1 cs interval) so, in theory, we should expect 100 overruns between calls to sigwaitinfo. However, timer_getoverrun returns 0. I have also tried a version using a time-consuming for loop to introduce the delay. In this case, overruns are recorded. Does anyone know why this happens? I am running a 3.4 Linux kernel. Program source /* * timer-overruns.c */ #include <unistd.h> #include <stdlib.h> #include <stdio.h> #include <signal.h> #include <time.h> // Signal to be used for timer expirations #define TIMER_SIGNAL SIGUSR1 int main(int argc, char **argv) { int opt; int d = 0; int r = 0; // Repeat indefinitely struct itimerspec its; its.it_interval.tv_sec = 0; its.it_interval.tv_nsec = 0; // Parse arguments while ((opt = getopt(argc, argv, "d:r:s:n:")) != -1) { switch (opt) { case 'd': // Delay before calling sigwaitinfo() d = atoi(optarg); break; case 'r': // Number of times to call sigwaitinfo() r = atoi(optarg); break; case 's': // Timer interval (seconds) its.it_interval.tv_sec = its.it_value.tv_sec = atoi(optarg); break; case 'n': // Timer interval (nanoseconds) its.it_interval.tv_nsec = its.it_value.tv_nsec = atoi(optarg); break; default: /* '?' */ fprintf(stderr, "Usage: %s [-d signal_accept_delay] [-r repetitions] [-s interval_seconds] [-n interval_nanoseconds]\n", argv[0]); exit(EXIT_FAILURE); } } // Check sanity of command line arguments short e = 0; if (d < 0) { fprintf(stderr, "Delay (-d) cannot be negative!\n"); e++; } if (r < 0) { fprintf(stderr, "Number of repetitions (-r) cannot be negative!\n"); e++; } if (its.it_interval.tv_sec < 0) { fprintf(stderr, "Interval seconds value (-s) cannot be negative!\n"); e++; } if (its.it_interval.tv_nsec < 0) { fprintf(stderr, "Interval nanoseconds value (-n) cannot be negative!\n"); e++; } if (its.it_interval.tv_nsec > 999999999) { fprintf(stderr, "Interval nanoseconds value (-n) must be < 1 second.\n"); e++; } if (e > 0) exit(EXIT_FAILURE); // Set default values if not specified if (its.it_interval.tv_sec == 0 && its.it_interval.tv_nsec == 0) { its.it_interval.tv_sec = its.it_value.tv_sec = 1; its.it_value.tv_nsec = 0; } printf("Running with timer delay %d.%09d seconds\n", (int) its.it_interval.tv_sec, (int) its.it_interval.tv_nsec); // Will be waiting for signals synchronously, so block the one in use. sigset_t sigset; sigemptyset(&sigset); sigaddset(&sigset, TIMER_SIGNAL); sigprocmask(SIG_BLOCK, &sigset, NULL ); // Create and arm the timer struct sigevent sev; timer_t timer; sev.sigev_notify = SIGEV_SIGNAL; sev.sigev_signo = TIMER_SIGNAL; sev.sigev_value.sival_ptr = timer; timer_create(CLOCK_REALTIME, &sev, &timer); timer_settime(timer, TIMER_ABSTIME, &its, NULL ); // Signal handling loop int overruns; siginfo_t si; // Make the loop infinite if r = 0 if (r == 0) r = -1; while (r != 0) { // Sleeping should cause overruns if (d > 0) sleep(d); sigwaitinfo(&sigset, &si); // Check that the signal is from the timer if (si.si_code != SI_TIMER) continue; overruns = timer_getoverrun(timer); if (overruns > 0) { printf("Timer overrun occurred for %d expirations.\n", overruns); } // Decrement r if not repeating indefinitely if (r > 0) r--; } return EXIT_SUCCESS; }

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  • Any Programming Languages Recommendations? A Space shooter game that allows two people to play at the same time?

    - by Bombcode
    Hey Everyone, Do you remember a arcade game, that allow two people to versus or play each other? A Galaga/Gradius type game. Me and a couple of other people I know wanna make a game like this. We want to get some other opinions on what programming languages to use.(C or C++ isn't an option .). We plan to use an engine to help us build. It's gonna be a multiplayer game, so we would be handling the networking with this language as well. We are thinking about C#, Java, or Actionscript 3. Any Advice on this? And if anyone knows the arcade game I am referring to please post up :)! Edit Let me add something here, this game will be plain on computers and laptops only. We mainly wanna what's good for handling the networking and Dual screen play.

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  • BigInteger Library

    A .NET 2.0 library for the 64 bit optimized handling of very large integers, up to 10240 binary digits or approximately (safe to use) 3000 decimal digits

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  • JavaFX 2.2.4 Documentation

    - by user12610255
    JavaFX 2.2.4 and JDK 7u10 were released on Tuesday. In addition to the release documentation, the following new information is provided: A new document, Using the Image Ops API, describes how to read and write raw pixel data to and from JavaFX images. The Handling JavaFX Events document has been updated with more information on touch events. The Working with Touch Events chapter and Touch Events sample provide information about handling individual touch points to provide sophisticated responses to touch actions. The Implementing Best Practices document has been updated to include information about running tasks on background threads. The Troubleshooting section of Deploying JavaFX Applications now includes a section about disabling the automatic proxy configuration in your application code. Other documents were updated to reflect minor bug fixes. You can download JavaFX 2.2.4 from OTN. For all tutorials and API documentation, see http://docs.oracle.com/javafx.

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  • Sneak peek at next generation Three MiFi unit – Huawei E585

    - by Liam Westley
    Last Wednesday I was fortunate to be invited to a sneak preview of the next generation Three MiFi unit, the Huawei E585. Many thanks to all those who posted questions both via this blog or via @westleyl on Twitter. I think I made sure I asked every question posed to the MiFi product manager from Three UK, and so here's the answers you were after. What is a MiFi? For those who are wondering, a MiFi unit is a 3G broadband modem combined with a WiFi access point, providing 3G broadband data access to up to five devices simultaneously via standard WiFi connections. What is different? It appears the prime task of enhancing the MiFi was to improve the user experience and user interface, both in terms of the device hardware and within the management software to configure the device.  I think this was a very sensible decision as these areas had substantial room for improvement. Single button operation to switch on, enable WiFi and connect to 3G Improved OELD display (see below), replacing the multi coloured LEDs; including signal strength, SMS notifications, the number of connected clients and data usage Management is via a web based dashboard accessible from any web browser. This is a big win for those running Linux, Mac OS/X, iPad users and, for me, as I can now configure the device from Windows 7 64-bit Charging is via micro USB, the new standard for small USB devices; you cannot use your old charger for the new MiFi unit Automatic reconnection when regaining a signal Improved charging time, which should allow recharging of the device when in use Although subjective, the black and silver design does look more classy than the silver and white plastic of the original MiFi What is the same? Virtually the same size and weight The battery is the same unit as the original MiFi so you’ll have a handy spare if you upgrade Data plans remain the same as the current MiFi, so cheapest price for upgraders will be £49 pay as you go Still only works on 3G networks, with no fallback to GPRS or EDGE There is no specific upgrade path for existing three customers, either from dongle or from the original MiFi My opinion I think three have concentrated on the correct areas of usability and user experience rather than trying to add new whizz bang technology features which aren’t of interest to mainstream users. The one button operation and the improved device display will make it much easier to use when out and about. If the automatic reconnection proves reliable that will remove a major bugbear that I experienced the previous evening when travelling on the First Great Western line from Paddington to Didcot Parkway.  The signal was repeatedly lost as we sped through tunnels and cuttings, and without automatic reconnection is was a real pain to keep pressing the data button on the MiFi to re-establish my data connection. And finally, the web based dashboard will mean I no longer need to resort to my XP based netbook to configure the SSID and password. My everyday laptop runs Windows 7 64-bit which appears to confuse the older 3 WiFi manager which cannot locate the MiFi when connected. Links to other sites, and other images of the device Good first impressions from Ben Smith, http://thereallymobileproject.com/2010/06/3uk-announce-a-new-mifi-with-a-screen/ Also, a round up of other sneak preview posts, http://www.3mobilebuzz.com/2010/06/11/mifi-round-two-your-view/ Pictures Here is a comparison of the old MiFi device next to the new device, complete with OLED display and the Huawei logo now being a prominent feature on the front of the device. One of my fellow bloggers had a Linux based netbook, showing off the web based dashboard complete with Text messages panel to manage SMS. And finally, I never thought that my blog sub title would ever end up printed onto a cup cake, ... and here's some of the other cup cakes ...

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  • Unable to either locate any wireless networks nor even connect to wifi

    - by Leo Chan
    I'm new to Linux. I currently have installed ubuntu 12.10. I had a previous problem with my wireless card (see url to see previous problem : How to enable wireless in a Fujitsu LH532?). It now shows Connect to hidden network and create new wireless network but now unfortunately it simply cannot find any wireless connections. I did have a very thorough look around about this problem such as wait a little longer since sometimes it cannot load all the wireless connections available that quickly. My wifi is a hidden network and I have used the connect to hidden network feature but it keeps asking for my wep key which has been checked 4 times (I counted) and it still seems to not work; It keeps asking for the WEP key. I did try both WEP 40/128-bit key and WPA & WPA2 since previously on my windows it worked; My family later decided to use WEP. I only have a quick fix using a usb wireless stick and I wish to have a more solid fix. Thanks Results from sudo iwlist wlan0 scan wlan0 Scan completed : Cell 01 - Address: 00:1E:73:C8:62:BD Channel:6 Frequency:2.437 GHz (Channel 6) Quality=25/70 Signal level=-85 dBm Encryption key:on ESSID:"EnigmaHome" Bit Rates:1 Mb/s; 2 Mb/s; 5.5 Mb/s; 11 Mb/s Bit Rates:6 Mb/s; 9 Mb/s; 12 Mb/s; 18 Mb/s; 24 Mb/s 36 Mb/s; 48 Mb/s; 54 Mb/s Mode:Master Extra:tsf=000000cb3bb10a5c Extra: Last beacon: 696ms ago IE: Unknown: 000A456E69676D61486F6D65 IE: Unknown: 010482848B96 IE: Unknown: 030106 IE: Unknown: 0706484B20010B1E IE: Unknown: 2A0107 IE: Unknown: 32080C1218243048606C IE: Unknown: DD180050F2020101000003A4000027A4000042435E0062322F00 Cell 02 - Address: C8:3A:35:34:C1:60 Channel:6 Frequency:2.437 GHz (Channel 6) Quality=22/70 Signal level=-88 dBm Encryption key:on ESSID:"Tenda" Bit Rates:1 Mb/s; 2 Mb/s; 5.5 Mb/s; 11 Mb/s; 9 Mb/s 18 Mb/s; 36 Mb/s; 54 Mb/s Bit Rates:6 Mb/s; 12 Mb/s; 24 Mb/s; 48 Mb/s Mode:Master Extra:tsf=000001336e70ffdd Extra: Last beacon: 716ms ago IE: Unknown: 000554656E6461 IE: Unknown: 010882848B961224486C IE: Unknown: 030106 IE: Unknown: 32040C183060 IE: Unknown: 0706434E20010D10 IE: Unknown: 33082001020304050607 IE: Unknown: 33082105060708090A0B IE: Unknown: DD270050F204104A0001101044000101104700102880288028801880A880C83A3534C160103C000101 IE: Unknown: 050400010000 IE: Unknown: 2A0106 IE: Unknown: 2D1AEC0117FFFF0000000000000000000000000000000C0000000000 IE: Unknown: 3D1606000500000000000000000000000000000000000000 IE: Unknown: 7F0101 IE: IEEE 802.11i/WPA2 Version 1 Group Cipher : CCMP Pairwise Ciphers (1) : CCMP Authentication Suites (1) : PSK Preauthentication Supported IE: Unknown: DD180050F2020101000003A4000027A4000042435E0062322F00 IE: Unknown: 0B05010089127A IE: Unknown: DD1E00904C33EC0117FFFF0000000000000000000000000000000C0000000000 IE: Unknown: DD1A00904C3406000500000000000000000000000000000000000000 IE: Unknown: DD07000C4304000000 Cell 03 - Address: 00:1E:73:C8:62:BF Channel:6 Frequency:2.437 GHz (Channel 6) Quality=47/70 Signal level=-63 dBm Encryption key:on ESSID:"\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00" Bit Rates:1 Mb/s; 2 Mb/s; 5.5 Mb/s; 11 Mb/s Bit Rates:6 Mb/s; 9 Mb/s; 12 Mb/s; 18 Mb/s; 24 Mb/s 36 Mb/s; 48 Mb/s; 54 Mb/s Mode:Master Extra:tsf=000000cb3bac614e Extra: Last beacon: 1064ms ago IE: Unknown: 00110000000000000000000000000000000000 IE: Unknown: 010482848B96 IE: Unknown: 030106 IE: Unknown: 050C010200000000000000000000 IE: Unknown: 0706484B20010B1E IE: Unknown: 2A0107 IE: Unknown: 32080C1218243048606C IE: Unknown: DD070050F202000100

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  • Setting background image for QPushButton

    - by Surjya Narayana Padhi
    Hi Geeks, I am struggling to set an background image for an QPushButton. No Success till now. Following is my code. appsWidget::appsWidget(QWidget *parent) :QWidget(parent) { QPushButton *button1 = new QPushButton("SETTINGS",this); QPushButton *button2 = new QPushButton("TEST",this); QPushButton *button3 = new QPushButton("IE",this); button1->setStyleSheet("background-image:url(config.png)"); -> No success qDebug("appWidget initialized."); QHBoxLayout *layout = new QHBoxLayout; layout->addWidget(button1); layout->addWidget(button2); layout->addWidget(button3); this->setLayout(layout); connect(button1,SIGNAL(clicked()),this,SLOT(setClickIndex1())); connect(button2,SIGNAL(clicked()),this,SLOT(setClickIndex2())); connect(button3,SIGNAL(clicked()),this,SLOT(setClickIndex3())); } The image I am using in the stylesheet is located in the same project folder. Do anybody has any solution?

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  • DSP - Filtering frequencies using DFT

    - by Trap
    I'm trying to implement a DFT-based 8-band equalizer for the sole purpose of learning. To prove that my DFT implementation works I fed an audio signal, analyzed it and then resynthesized it again with no modifications made to the frequency spectrum. So far so good. I'm using the so-called 'standard way of calculating the DFT' which is by correlation. This method calculates the real and imaginary parts both N/2 + 1 samples in length. To attenuate a frequency I'm just doing: float atnFactor = 0.6; Re[k] *= atnFactor; Im[k] *= atnFactor; where 'k' is an index in the range 0 to N/2, but what I get after resynthesis is a slighty distorted signal, especially at low frequencies. The input signal sample rate is 44.1 khz and since I just want a 8-band equalizer I'm feeding the DFT 16 samples at a time so I have 8 frequency bins to play with. Can someone show me what I'm doing wrong? I tried to find info on this subject on the internet but couldn't find any. Thanks in advance.

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  • Qt - QWebView Problem

    - by user547057
    Hi, I have a PyQt gui script which consists of a QWebView widget. I'm trying to send a GET request, i.e go to a page, fill a form and hit click using the code at the bottom of this question. Since i'm dealing with the documentElement(a QWebElement) of the webview, I need to place all DOM actions in a separate function(which I have named fillForm) and connect the loadFinished() signal into the function. Without connecting the signal, the document will not have loaded and I won't be able to get the elements I want. I'm able to submit the form correctly and get the proper response from the webpage. The problem i'm having is that, the above leads to a sort of infinite loop. This is because the webpage gets reloaded each time a new page is loaded, so the form gets filled each and every single time without stopping. I'd like to know if there's some way of finding out whether the WebView's page has loaded fully, non-asynchronously or maybe pause execution of the script(without freezing the gui) until the whole document has loaded. I'm unable to come up with a satisfactory solution(my idea consisted of keeping a global variable to track clicks) to this problem. I would appreciate it if someone could help me out with a better way to tackle this. Thanks! Here's the code i'm using import sys from PyQt4.QtCore import * from PyQt4.QtGui import * from PyQt4.QtWebKit import * from PyQt4 import QtCore app = QApplication(sys.argv) web = QWebView() web.load(QUrl("http://mywebsite.com")) def fillForm(): doc = web.page().mainFrame().documentElement() searchform = doc.findFirst("input[type=text]") searchform.setAttribute("value", "hello") button = doc.findFirst("input[type=submit]") button.evaluateJavaScript("click()") QtCore.QObject.connect(web, QtCore.SIGNAL("loadFinished"), fillForm) web.show() sys.exit(app.exec_())

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  • Why does the add() method in PHP-GTK cause 2 parent-set signals to be emmitted?

    - by JW
    I am going through the book PHP-GTK and trying out listing 4-1 One thing I notice is that with the following code some odd output occurs: <?php //listing4-1b.php function setParentFunction($widget) { //get the widgets parent $parent = $widget->get_parent(); //echo a mssg about the widget echo 'The ' . get_class($widget) .' has '; if (isset($parent)) { //ech the class of the parent widget echo 'a '. get_class($parent); } else { //the widget does not have a parent echo 'no'; } echo " parent. \n"; } //start with widgets $frame = new GtkFrame('i am a frame'); $button = new GtkButton('i am a button'); //connect the event to our test function $button->connect('parent-set', 'setParentFunction'); $frame->add($button); ?> The output is: # php listing4-1b.php The GtkButton has a GtkFrame parent. The GtkButton has no parent. Now, I can understand why the first signal is getting emitted and causing the first line of output: The GtkButton has a GtkFrame parent. But, I don't understand why the 2nd 'parent change' is reported to have happened: The GtkButton has no parent. I expected only to see the signal getting emitted / and handled only once in this short script. Does this 2nd signal get emmitted when the script closes down?

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  • Trap SIGPIPE when trying to write without reader

    - by Matt
    I am trying to implement a named-pipe communication solution in BASH between two processes. The first process runs a script which echo something in a named-pipe: send(){ echo 'something' > $NAMEDPIPE } And the second script is supposed to read the named-pipe via another script which contains: while true;do if read line < $NAMEDPIPE;do someCommands fi done Not that the named pipe has been previously created using the traditional command mkfifo $NAMEDPIPE My problem is that the reader script is not always running so that if the writer script try to write in the named-pipe it stay blocked until a reader connect the pipe. I want to avoid this behavior, and a solution would be to trap a SIGPIPE signal. Indeed, according to man 7 signal is supposed to be send when trying to write in a pipe with no reader. So I changed my red function by: read(){ trap 'echo "SIGPIPE received"' SIGPIPE echo 'something' > $NAMEDPIPE } But when I run the reader script, the script stay blocked, and not "SIGPIPE received" appears... Am I mistaking on the signal mechanism or is there any better solution to my problem ? Thank you for your help.

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  • How to interrupt a thread performing a blocking socket connect?

    - by Jason R
    I have some code that spawns a pthread that attempts to maintain a socket connection to a remote host. If the connection is ever lost, it attempts to reconnect using a blocking connect() call on its socket. Since the code runs in a separate thread, I don't really care about the fact that it uses the synchronous socket API. That is, until it comes time for my application to exit. I would like to perform some semblance of an orderly shutdown, so I use thread synchronization primitives to wake up the thread and signal for it to exit, then perform a pthread_join() on the thread to wait for it to complete. This works great, unless the thread is in the middle of a connect() call when I command the shutdown. In that case, I have to wait for the connect to time out, which could be a long time. This makes the application appear to take a long time to shut down. What I would like to do is to interrupt the call to connect() in some way. After the call returns, the thread will notice my exit signal and shut down cleanly. Since connect() is a system call, I thought that I might be able to intentionally interrupt it using a signal (thus making the call return EINTR), but I'm not sure if this is a robust method in a POSIX threads environment. Does anyone have any recommendations on how to do this, either using signals or via some other method? As a note, the connect() call is down in some library code that I cannot modify, so changing to a non-blocking socket is not an option.

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