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• Get timestamp from Authenticode Signed files in .NET

  - by SlavaGu

  We need to verify that binary files are signed properly with digital signature (Authenticode). This can be achieved with signtool.exe pretty easily. However, we need an automatic way that also verifies signer name and timestamp. This is doable in native C++ with CryptQueryObject() API as shown in this wonderful sample: How To Get Information from Authenticode Signed Executables However we live in a managed world :) hence looking for C# solution to the same problem. Straight approach would be to pInvoke Crypt32.dll and all is done. But there is similar managed API in System.Security.Cryptography.X509Certificates Namespace. X509Certificate2 Class seems to provide some information but no timestamp. Now we came to the original question how can we get that timestamp of a digital signature in C Sharp?

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• ffmpeg hangs when creating a video

  - by FearUs

  I am trying to insert an audio channel with a video: first of all I extract the audio from the original video for processing: ffmpeg -i lotr.mp4 lotr.wav I then extract all frames for later processing too: ffmpeg -i lotr.mp4 -f image2 %d.jpg When done processing audio and video streams, I try to create the video ffmpeg -f image2 -r 15 -i %d.jpg new.mp4 then merge with the audio: ffmpeg -i new.mp4 -i lotr.wav -map 0:0 -map 1:0 new_w_audio.mp4 Result: CPU activity = 100%, the process hangs and never returns. PS: I even tried it without modifying the images or the audio (so just trying to unpack then repack the video) but still the same output FFmpeg version SVN-r26400, Copyright (c) 2000-2011 the FFmpeg developers built on Jan 18 2011 04:07:05 with gcc 4.4.2 configuration: --enable-gpl --enable-version3 --enable-libgsm --enable-libvorb is --enable-libtheora --enable-libspeex --enable-libmp3lame --enable-libopenjpeg --enable-libschroedinger --enable-libopencore_amrwb --enable-libopencore_amrnb --enable-libvpx --disable-decoder=libvpx --arch=x86 --enable-runtime-cpudetect - -enable-libxvid --enable-libx264 --enable-librtmp --extra-libs='-lrtmp -lpolarss l -lws2_32 -lwinmm' --target-os=mingw32 --enable-avisynth --enable-w32threads -- cross-prefix=i686-mingw32- --cc='ccache i686-mingw32-gcc' --enable-memalign-hack libavutil 50.36. 0 / 50.36. 0 libavcore 0.16. 1 / 0.16. 1 libavcodec 52.108. 0 / 52.108. 0 libavformat 52.93. 0 / 52.93. 0 libavdevice 52. 2. 3 / 52. 2. 3 libavfilter 1.74. 0 / 1.74. 0 libswscale 0.12. 0 / 0.12. 0 Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'new.mp4': Metadata: major_brand : isom minor_version : 512 compatible_brands: isomiso2mp41 creation_time : 1970-01-01 00:00:00 encoder : Lavf52.93.0 Duration: 00:00:29.66, start: 0.000000, bitrate: 193 kb/s Stream #0.0(und): Video: mpeg4, yuv420p, 200x134 [PAR 1:1 DAR 100:67], 192 k b/s, 15 fps, 15 tbr, 15 tbn, 15 tbc Metadata: creation_time : 1970-01-01 00:00:00 [wav @ 01fed010] max_analyze_duration reached Input #1, wav, from 'lotr.wav': Duration: 00:00:29.90, bitrate: 176 kb/s Stream #1.0: Audio: pcm_s16le, 11025 Hz, 1 channels, s16, 176 kb/s File 'new_w_audio.mp4' already exists. Overwrite ? [y/N] y [buffer @ 01b03820] w:200 h:134 pixfmt:yuv420p Output #0, mp4, to 'new_w_audio.mp4': Metadata: major_brand : isom minor_version : 512 compatible_brands: isomiso2mp41 creation_time : 1970-01-01 00:00:00 encoder : Lavf52.93.0 Stream #0.0(und): Video: mpeg4, yuv420p, 200x134 [PAR 1:1 DAR 100:67], q=2-3 1, 200 kb/s, 15 tbn, 15 tbc Metadata: creation_time : 1970-01-01 00:00:00 Stream #0.1: Audio: aac, 11025 Hz, 1 channels, s16, 64 kb/s Stream mapping: Stream #0.0 -> #0.0 Stream #1.0 -> #0.1 Press [q] to stop encoding

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• How do I guarantee cleanup code runs in Windows C++ (SIGINT, bad alloc, and closed window)

  - by Meekohi

  I have a Windows C++ console program, and if I don't call ReleaseDriver() at the end of my program, some pieces of hardware enter a bad state and can't be used again without rebooting. I'd like to make sure ReleaseDriver() gets runs even if the program exits abnormally, for example if I hit Ctrl+C or close the console window. I can use signal() to create a signal handler for SIGINT. This works fine, although as the program ends it pops up an annoying error "An unhandled Win32 exception occurred...". I don't know how to handle the case of the console window being closed, and (more importantly) I don't know how to handle exceptions caused by bad memory accesses etc. Thanks for any help!

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• SmartSVN - Unable to create new repository profile

  - by Sandeepan Nath

  I have just installed SmartSVN on this fedora system. The application starts (on running ./smartsvn.sh) with its usual UI but many things are not working. Creating New repository profile Trying to create a new repository profile (Repositories- Repository Profiles- Add) An Error occurred while processing an SVN command - Cannot connect to 'svn+ssh://192.168.0.103': There was a problem while connecting to 192.168.0.103:22 Quick Checkout Trying to do Quick Checkout (less configuration) An Error occurred while processing an SVN command - Malformed XML. Some Observations When I run the smartsvn.sh file like this:- ./smartsvn.sh It shows this in the console - Warning: /bin/java does not exist Could not lock /root/.smartsvn/_lock_ Switched to running instance I was using SmartSVN in another system before this where it was working. There too, it was showing the warning like Warning: /bin/java does not exist but this part was not showing:- Could not lock /root/.smartsvn/_lock_ Switched to running instance I have only JRE installed in both the systems and not JDK. So, what could be the reason? Any pointers? Thanks, Sandeepan

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• Using PyQt signals correctly

  - by Skilldrick

  A while ago I did some work in Qt for C++; now I'm working with PyQt. I have a subclass of QStackedWidget, and inside that a subclass of QWidget. In the QWidget I want to click a button that goes to the next page of the QStackedWidget. My (simplified) approach is as follows: class Stacked(QtGui.QStackedWidget): def __init__(self, parent=None): QtGui.QStackedWidget.__init__(self, parent) self.widget1 = EventsPage() self.widget1.nextPage.connect(self.nextPage) self.widget2 = MyWidget() self.addWidget(self.widget1) self.addWidget(self.widget2) def nextPage(self): self.setCurrentIndex(self.currentIndex() + 1) class EventsPage(QtGui.QWidget): nextPage = QtCore.pyqtSignal() def __init__(self, parent=None): QtGui.QWidget.__init__(self, parent) self.continueButton = QtGui.QPushButton('Continue') self.continueButton.clicked.connect(self.nextPage) So, basically, I'm connecting the continueButton clicked signal to the EventsPage nextPage signal, which I'm then connecting in Stacked to the nextPage method. I could just delve into the internals of EventsPage in Stacked and connect self.widget1.continueButton.clicked, but that seemed to completely defeat the purpose of signals and slots. So does this approach make sense, or is there a better way?

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• scanning only works under "sudo" (Ubuntu)

  - by JoelFan

  When I try to scan, using simple-scan, the UI says Failed to scan -- Unable to connect to scanner. When I run it from the command line I get: joel@home:/usr/bin$ simple-scan -d ** (simple-scan:6554): DEBUG: Starting Simple Scan 2.32.0.1, PID=6554 ** (simple-scan:6554): DEBUG: Restoring window to 600x400 pixels ** (simple-scan:6554): DEBUG: sane_init () -> SANE_STATUS_GOOD ** (simple-scan:6554): DEBUG: SANE version 1.0.22 ** (simple-scan:6554): DEBUG: Requesting redetection of scan devices ** (simple-scan:6554): DEBUG: Processing request ** (simple-scan:6554): DEBUG: Requesting scan at 300 dpi from device '(null)' ** (simple-scan:6554): DEBUG: scanner_scan ("(null)", 300, SCAN_SINGLE) ** (simple-scan:6554): DEBUG: sane_get_devices () -> SANE_STATUS_GOOD ** (simple-scan:6554): DEBUG: Device: name="brother2:bus4;dev1" vendor="Brother" model="MFC-210C" type="USB scanner" ** (simple-scan:6554): DEBUG: Processing request ** (simple-scan:6554): DEBUG: sane_open ("brother2:bus4;dev1") -> SANE_STATUS_IO_ERROR ** (simple-scan:6554): WARNING **: Unable to get open device: Error during device I/O FYI, I have already done: joel@home:~$ sudo chmod a+rwx /dev/bus/usb joel@home:~$ sudo chmod a+rwx /dev/bus/usb/* If I run under sudo: joel@home:~$ sudo simple-scan it works. How can I get simple-scan to work without sudo?

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• Updating DataGridView from another Form using BackGroundWorker

  - by FezKazi

  Hi! I Have one Form (LoginForm) which has a Background Worker Monitoring a database for new entries. Then I have another Form (AdminForm) which I need to signal to update its datagrids whenever new data is available. I could poll the database in the AdminForm too, but considering that LoginForm is already doing some polling, which can be costly, I just want to signal AdminForm to update the DataGridViews with the new data. You may ask, why is LoginForm doing the polling when youre showing the stuff in the AdminForm? Well, LoginForm is actually processing the data and sending it over the Serial Port :$ heheh. I want it to be able to process the data without having an administrator logged in all the time.

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• forward mails from sendmail + mimedefang on two unix boxes

  - by SWKK

  I am not a unix expert, more like a novice. I have one user account replicated on two unix boxes receiving same mails on both boxes for fail over. Sendmail has mimedefang utility running to process these mails. After all the processing is complete, more like weeding the spam, viruses etc. I need to forward these mails coming to the same account on both boxes to goto a central mailbox on MS Exchange for this account. Problem is I am using .forward file hence both unix boxes forward the mail after processing. I just want to be able to ignore one of the two mails. Has anyone tried something similar? any directions? Please?

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• Choosing between a dedicated and virtual dedicated server for my startup

  - by MarathonStudios

  I'm about to launch a startup site I've been working on for some time, and I'm just now looking over hosting plans. The site's main feature is fairly processor-heavy (a lot of text processing), so I probably need something other then shared hosting to ensure I don't get shut down for overusing resources. I would like to spend as little as possible on hosting until the site starts generating income, so under-$60/mo is my goal. One caveat is that I need a Windows box for this particular site, so it's harder to get a good deal. For that price, I can either get a bottom-tier dedicated (2gigs ram, pentium 4) or a middle-tier VPS (3gb RAM, a bit more traffic and HD) for a few bucks more per month. I had a bad experience with a low-end VPS a few months ago, so making sure that whatever I get can handle the basic traffic of a website as well as giving me what I need (extra processing power) is essential. Do you have any suggestions as to which way to go, or a certain hosting company you've worked with that you can recommend?

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• Installing Win32 shared SxS policy via WiX 3.0 MSM fails for 2nd app

  - by dr-stevep

  I am attempting to author a merge module for use by multiple application installers to install a Win32 Shared SxS Assembly and its associated Policy. I'm using WiX 3.0 to generate the MSM and test MSIs. So far it works fine for the first app installer that runs … but the second app installer fails because the Policy file already exists (HRESULT: 0x800700B7). What requirement(s) for correct Win32 Shared SxS Policy installation am I missing? I have submitted WiX bug 3005301 for this (https://sourceforge.net/tracker/?func=detail&atid=642714&aid=3005301&group_id=105970) and posted VS2008 projects that reproduce the problem. URL: ftp.digital-rapids.com/upload/SteveP/ User: drc-support Password: drc-support Link: ftp://drc-support:[email protected]/upload/SteveP/ wix-Bugs-3005201.rar contains a VS2008 solution that builds the MSM and MSIs that reproduce the issue. (~3MB) wix-Bugs-3005301_Output.rar contains the generated MSM, MSI, and wixpdb files (~40MB)

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• GpsSatellite.getSnr() - What is the value range?

  - by rflexor

  I'm building a Sat-View that draws a small bar-chart for available satellites and their signal strength (or better: their signal-to-noise-ratio / SNR). The javadoc doesn't say what value-range to expect for the SNR. The NMEA-Standard says 0-99, but even in best conditions my G1 doesn't reach that value. I also read that different manufacturers use different value-ranges for the SNR, so is that true for android-devices, too? Or is there a unified value range on that plattform and if so, what is it? The lack of information in the docs leads me to suspect I just get the "raw" SNR from the driver, in which case I'd like to know: What do you think is the best approach to visualize that unknown value-range in a bar-chart?

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• Query on simple C++ threadpool implementation

  - by ticketman

  Stackoverflow has been a tremendous help to me and I'd to give something back to the community. I have been implementing a simple threadpool using the tinythread C++ portable thread library, using what I have learnt from Stackoverflow. I am new to thread programming, so not that comfortable with mutexes, etc. I have a question best asked after presenting the code (which runs quite well under Linux): // ThreadPool.h class ThreadPool { public: ThreadPool(); ~ThreadPool(); // Creates a pool of threads and gets them ready to be used void CreateThreads(int numOfThreads); // Assigns a job to a thread in the pool, but doesn't start the job // Each SubmitJob call will use up one thread of the pool. // This operation can only be undone by calling StartJobs and // then waiting for the jobs to complete. On completion, // new jobs may be submitted. void SubmitJob( void (*workFunc)(void *), void *workData ); // Begins execution of all the jobs in the pool. void StartJobs(); // Waits until all jobs have completed. // The wait will block the caller. // On completion, new jobs may be submitted. void WaitForJobsToComplete(); private: enum typeOfWorkEnum { e_work, e_quit }; class ThreadData { public: bool ready; // thread has been created and is ready for work bool haveWorkToDo; typeOfWorkEnum typeOfWork; // Pointer to the work function each thread has to call. void (*workFunc)(void *); // Pointer to work data void *workData; ThreadData() : ready(false), haveWorkToDo(false) { }; }; struct ThreadArgStruct { ThreadPool *threadPoolInstance; int threadId; }; // Data for each thread ThreadData *m_ThreadData; ThreadPool(ThreadPool const&); // copy ctor hidden ThreadPool& operator=(ThreadPool const&); // assign op. hidden // Static function that provides the function pointer that a thread can call // By including the ThreadPool instance in the void * parameter, // we can use it to access other data and methods in the ThreadPool instance. static void ThreadFuncWrapper(void *arg) { ThreadArgStruct *threadArg = static_cast<ThreadArgStruct *>(arg); threadArg->threadPoolInstance->ThreadFunc(threadArg->threadId); } // The function each thread calls void ThreadFunc( int threadId ); // Called by the thread pool destructor void DestroyThreadPool(); // Total number of threads available // (fixed on creation of thread pool) int m_numOfThreads; int m_NumOfThreadsDoingWork; int m_NumOfThreadsGivenJobs; // List of threads std::vector<tthread::thread *> m_ThreadList; // Condition variable to signal each thread has been created and executing tthread::mutex m_ThreadReady_mutex; tthread::condition_variable m_ThreadReady_condvar; // Condition variable to signal each thread to start work tthread::mutex m_WorkToDo_mutex; tthread::condition_variable m_WorkToDo_condvar; // Condition variable to signal the main thread that // all threads in the pool have completed their work tthread::mutex m_WorkCompleted_mutex; tthread::condition_variable m_WorkCompleted_condvar; }; cpp file: // // ThreadPool.cpp // #include "ThreadPool.h" // This is the thread function for each thread. // All threads remain in this function until // they are asked to quit, which only happens // when terminating the thread pool. void ThreadPool::ThreadFunc( int threadId ) { ThreadData *myThreadData = &m_ThreadData[threadId]; std::cout << "Hello world: Thread " << threadId << std::endl; // Signal that this thread is ready m_ThreadReady_mutex.lock(); myThreadData->ready = true; m_ThreadReady_condvar.notify_one(); // notify the main thread m_ThreadReady_mutex.unlock(); while(true) { //tthread::lock_guard<tthread::mutex> guard(m); m_WorkToDo_mutex.lock(); while(!myThreadData->haveWorkToDo) // check for work to do m_WorkToDo_condvar.wait(m_WorkToDo_mutex); // if no work, wait here myThreadData->haveWorkToDo = false; // need to do this before unlocking the mutex m_WorkToDo_mutex.unlock(); // Do the work switch(myThreadData->typeOfWork) { case e_work: std::cout << "Thread " << threadId << ": Woken with work to do\n"; // Do work myThreadData->workFunc(myThreadData->workData); std::cout << "#Thread " << threadId << ": Work is completed\n"; break; case e_quit: std::cout << "Thread " << threadId << ": Asked to quit\n"; return; // ends the thread } // Now to signal the main thread that my work is completed m_WorkCompleted_mutex.lock(); m_NumOfThreadsDoingWork--; // Unsure if this 'if' would make the program more efficient // if(NumOfThreadsDoingWork == 0) m_WorkCompleted_condvar.notify_one(); // notify the main thread m_WorkCompleted_mutex.unlock(); } } ThreadPool::ThreadPool() { m_numOfThreads = 0; m_NumOfThreadsDoingWork = 0; m_NumOfThreadsGivenJobs = 0; } ThreadPool::~ThreadPool() { if(m_numOfThreads) { DestroyThreadPool(); delete [] m_ThreadData; } } void ThreadPool::CreateThreads(int numOfThreads) { // Check a thread pool has already been created if(m_numOfThreads > 0) return; m_NumOfThreadsGivenJobs = 0; m_NumOfThreadsDoingWork = 0; m_numOfThreads = numOfThreads; m_ThreadData = new ThreadData[m_numOfThreads]; ThreadArgStruct threadArg; for(int i=0; i<m_numOfThreads; ++i) { threadArg.threadId = i; threadArg.threadPoolInstance = this; // Creates the thread and save in a list so we can destroy it later m_ThreadList.push_back( new tthread::thread( ThreadFuncWrapper, (void *)&threadArg ) ); // It takes a little time for a thread to get established. // Best wait until it gets established before creating the next thread. m_ThreadReady_mutex.lock(); while(!m_ThreadData[i].ready) // Check if thread is ready m_ThreadReady_condvar.wait(m_ThreadReady_mutex); // If not, wait here m_ThreadReady_mutex.unlock(); } } // Adds a job to the batch, but doesn't start the job void ThreadPool::SubmitJob(void (*workFunc)(void *), void *workData) { // Check that the thread pool has been created if(!m_numOfThreads) return; if(m_NumOfThreadsGivenJobs >= m_numOfThreads) return; m_ThreadData[m_NumOfThreadsGivenJobs].workFunc = workFunc; m_ThreadData[m_NumOfThreadsGivenJobs].workData = workData; std::cout << "Submitted job " << m_NumOfThreadsGivenJobs << std::endl; m_NumOfThreadsGivenJobs++; } void ThreadPool::StartJobs() { // Check that the thread pool has been created // and some jobs have been assigned if(!m_numOfThreads || !m_NumOfThreadsGivenJobs) return; // Set 'haveworkToDo' flag for all threads m_WorkToDo_mutex.lock(); for(int i=0; i<m_NumOfThreadsGivenJobs; ++i) m_ThreadData[i].haveWorkToDo = true; m_NumOfThreadsDoingWork = m_NumOfThreadsGivenJobs; // Reset this counter so we can resubmit jobs later m_NumOfThreadsGivenJobs = 0; // Notify all threads they have work to do m_WorkToDo_condvar.notify_all(); m_WorkToDo_mutex.unlock(); } void ThreadPool::WaitForJobsToComplete() { // Check that a thread pool has been created if(!m_numOfThreads) return; m_WorkCompleted_mutex.lock(); while(m_NumOfThreadsDoingWork > 0) // Check if all threads have completed their work m_WorkCompleted_condvar.wait(m_WorkCompleted_mutex); // If not, wait here m_WorkCompleted_mutex.unlock(); } void ThreadPool::DestroyThreadPool() { std::cout << "Ask threads to quit\n"; m_WorkToDo_mutex.lock(); for(int i=0; i<m_numOfThreads; ++i) { m_ThreadData[i].haveWorkToDo = true; m_ThreadData[i].typeOfWork = e_quit; } m_WorkToDo_condvar.notify_all(); m_WorkToDo_mutex.unlock(); // As each thread terminates, catch them here for(int i=0; i<m_numOfThreads; ++i) { tthread::thread *t = m_ThreadList[i]; // Wait for thread to complete t->join(); } m_numOfThreads = 0; } Example of usage: (this calculates pi-squared/6) struct CalculationDataStruct { int inputVal; double outputVal; }; void LongCalculation( void *theSums ) { CalculationDataStruct *sums = (CalculationDataStruct *)theSums; int terms = sums->inputVal; double sum; for(int i=1; i<terms; i++) sum += 1.0/( double(i)*double(i) ); sums->outputVal = sum; } int main(int argc, char** argv) { int numThreads = 10; // Create pool ThreadPool threadPool; threadPool.CreateThreads(numThreads); // Create thread workspace CalculationDataStruct sums[numThreads]; // Set up jobs for(int i=0; i<numThreads; i++) { sums[i].inputVal = 3000*(i+1); threadPool.SubmitJob(LongCalculation, &sums[i]); } // Run the jobs threadPool.StartJobs(); threadPool.WaitForJobsToComplete(); // Print results for(int i=0; i<numThreads; i++) std::cout << "Sum of " << sums[i].inputVal << " terms is " << sums[i].outputVal << std::endl; return 0; } Question: In the ThreadPool::ThreadFunc method, would better performance be obtained if the following if statement if(NumOfThreadsDoingWork == 0) was included? Also, I'd be grateful of criticisms and ways to improve the code. At the same time, I hope the code is of use to others.

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• DSP - How are frequency amplitudes modified using DFT?

  - by Trap

  I'm trying to implement a DFT-based equalizer (not FFT) for the sole purpose of learning. To check if it works I took an audio signal, analyzed it and then resynthesized it again with no modifications made to the frequency spectrum. So far so good. Now I tried to silence some frequency bands, just by setting their amplitudes to zero before resynthesis, but definitely it's not the way to go. What I get is a rather distorted signal. I'm using the so-called 'standard way of calculating the DFT' which is by correlation. I first tried to modify the real part amplitudes only, then modifying both the real and imaginary part amplitudes. I also tried to convert the DFT output to polar notation, then modifying the magnitude and convert back to rectangular notation, but none of this is working. Can someone show me what I'm doing wrong? I tried to find info on this subject in the internet but couldn't find any. Thanks in advance.

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• TcpListener is queuing connections faster than I can clear them

  - by Matthew Brindley

  As I understand it, TcpListener will queue connections once you call Start(). Each time you call AcceptTcpClient (or BeginAcceptTcpClient), it will dequeue one item from the queue. If we load test our TcpListener app by sending 1,000 connections to it at once, the queue builds far faster than we can clear it, leading (eventually) to timeouts from the client because it didn't get a response because its connection was still in the queue. However, the server doesn't appear to be under much pressure, our app isn't consuming much CPU time and the other monitored resources on the machine aren't breaking a sweat. It feels like we're not running efficiently enough right now. We're calling BeginAcceptTcpListener and then immediately handing over to a ThreadPool thread to actually do the work, then calling BeginAcceptTcpClient again. The work involved doesn't seem to put any pressure on the machine, it's basically just a 3 second sleep followed by a dictionary lookup and then a 100 byte write to the TcpClient's stream. Here's the TcpListener code we're using: // Thread signal. private static ManualResetEvent tcpClientConnected = new ManualResetEvent(false); public void DoBeginAcceptTcpClient(TcpListener listener) { // Set the event to nonsignaled state. tcpClientConnected.Reset(); listener.BeginAcceptTcpClient( new AsyncCallback(DoAcceptTcpClientCallback), listener); // Wait for signal tcpClientConnected.WaitOne(); } public void DoAcceptTcpClientCallback(IAsyncResult ar) { // Get the listener that handles the client request, and the TcpClient TcpListener listener = (TcpListener)ar.AsyncState; TcpClient client = listener.EndAcceptTcpClient(ar); if (inProduction) ThreadPool.QueueUserWorkItem(state => HandleTcpRequest(client, serverCertificate)); // With SSL else ThreadPool.QueueUserWorkItem(state => HandleTcpRequest(client)); // Without SSL // Signal the calling thread to continue. tcpClientConnected.Set(); } public void Start() { currentHandledRequests = 0; tcpListener = new TcpListener(IPAddress.Any, 10000); try { tcpListener.Start(); while (true) DoBeginAcceptTcpClient(tcpListener); } catch (SocketException) { // The TcpListener is shutting down, exit gracefully CheckBuffer(); return; } } I'm assuming the answer will be related to using Sockets instead of TcpListener, or at least using TcpListener.AcceptSocket, but I wondered how we'd go about doing that? One idea we had was to call AcceptTcpClient and immediately Enqueue the TcpClient into one of multiple Queue<TcpClient> objects. That way, we could poll those queues on separate threads (one queue per thread), without running into monitors that might block the thread while waiting for other Dequeue operations. Each queue thread could then use ThreadPool.QueueUserWorkItem to have the work done in a ThreadPool thread and then move onto dequeuing the next TcpClient in its queue. Would you recommend this approach, or is our problem that we're using TcpListener and no amount of rapid dequeueing is going to fix that?

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• C signals and processes

  - by Gary

  Hi, so basically I want "cmd_limit" to take a number in seconds which is the maximum time we'll wait for the child process (safe to assume there's only one) to finish. If the child process does finish during the sleep, I want cmd_limit to return pass and not run the rest of the cmd_limit code. Could anyone help me do this, here's what I've got so far.. int cmd_limit( int limit, int pid ) { signal( SIGCHLD, child_died ); sleep( limit ); kill( pid, SIGKILL ); printf("killin'\n"); return PASS; } void child_died( int sig ) { int stat_loc; /* child return information */ int status; /* child return status */ waitpid( -1, &stat_loc, WNOHANG ); if( WIFEXITED(stat_loc) ) { // program exited normally status = WEXITSTATUS( stat_loc ); /* get child exit status */ } printf("child died: %s\n", signal); }

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• Getting weird python error when I run a simple django script in Eclipse, not happening in console

  - by Rhubarb

  I am running a basic script that sets up the django environment by itself, to enable me to test the ORM features of django without having to implement web pages. The script then imports one of the types defined in my models. This error doesn't happen when I run this script from iPython, only from eclipse. Simply doing this import causes a weird exception like the following: Exception AttributeError: "'NoneType' object has no attribute 'print_exc'" in <bound method Signal._remove_receiver of <django.dispatch.dispatcher.Signal object at 0x026802B0>> ignored My script is as follows: from django.core.management import setup_environ import settings setup_environ(settings) from stats.models import Person for p in Person.objects.all(): print p.Name

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• Virtualizing WindowsXP on Linux Fedora 12 for Photoshop....

  - by Rae

  I am running a Linux server from 2000, I have Fedora12 installed as the OS. I know you can virtualize Windows XP on the system to be able to run Windows programs, but the problem is I My server has only one 1333Mhz Pentium 3 processor and 1G of Ram. granted this is a pretty kick ass computer for the day, but lacking the processor I'm afraid that I will not be able to run Windows virtualization to support Photoshop CS3. Is there any program out there that runs similar to Photoshop, like windows Digital Image suite 10, that will run smoothly in my Linux Fedora 12 environment? or can I virtualize windows and run the Windows digital image suite 10, without slowing or corrupting my system?

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• Match regex from right to left?

  - by Balroq

  Hi! Is there any way of matching a regex from right to left? What Im looking for is a regex that gets MODULE WAS INSERTED EVENT LOST SIGNAL ON E1/T1 LINK OFF CRC ERROR EVENT CLK IS DIFF FROM MASTER CLK SRC OF from this input CLI MUX trap received: (022) CL-B MCL-2ETH MODULE WAS INSERTED EVENT 07-05-2010 12:08:40 CLI MUX trap received: (090) IO-2 ML-1E1 EX1 LOST SIGNAL ON E1/T1 LINK OFF 04-06-2010 09:58:58 CLI MUX trap received: (094) IO-2 ML-1E1 EX1 CRC ERROR EVENT 04-06-2010 09:58:59 CLI MUX trap received: (009) CLK IS DIFF FROM MASTER CLK SRC OFF 07-05-2010 12:07:32 If i could have done the matching from right to left I could have written something like everything to right of (EVENT|OFF) until the second appearance of more than one space [ ]+ The best I managed today is to get everything from (022) to EVENT with the regex CLI MUX trap received: \([0-9]+\)[ ]+(.*[ ]+(EVENT|OFF)) But that is not really what I wanted :)

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• QWidget keyPressEvent override

  - by eaigner

  Hi there, I'm trying for half an eternity now overriding QWidgets keyPressEvent function in QT but it just won't work. I've to say i am new to CPP, but I know ObjC and standard C. My problem looks like this: class QSGameBoard : public QWidget { Q_OBJECT public: QSGameBoard(QWidget *p, int w, int h, QGraphicsScene *s); signals: void keyCaught(QKeyEvent *e); protected: virtual void keyPressEvent(QKeyEvent *event); }; QSGameBoard is my QWidget subclass and i need to override the keyPressEvent and fire a SIGNAL on each event to notify some registered objects. My overridden keyPressEvent in QSGameBoard.cpp looks like this: void QSGameBoard::keyPressEvent(QKeyEvent *event) { printf("\nkey event in board: %i", event->key()); //emit keyCaught(event); } When i change QSGameBoard:: to QWidget:: it receives the events, but i cant emit the signal because the compiler complains about the scope. And if i write it like this the function doesn't get called at all. What's the problem here?

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• Algorithm for voice comparison

  - by Horace Ho

  Given two recorded voices in digital format, is there an algorithm to compare the two and return a coefficient of similarity?

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• Qt - Calling widget parent's slots

  - by bullettime

  I wrote a small program to test accessing a widget parent's slot. Basically, it has two classes: Widget: namespace Ui { class Widget; } class Widget : public QWidget { Q_OBJECT public: Widget(QWidget *parent = 0); ~Widget(); QLabel *newlabel; QString foo; public slots: void changeLabel(); private: Ui::Widget *ui; }; Widget::Widget(QWidget *parent) : QWidget(parent), ui(new Ui::Widget) { ui->setupUi(this); customWidget *cwidget = new customWidget(); newlabel = new QLabel("text"); foo = "hello world"; this->ui->formLayout->addWidget(newlabel); this->ui->formLayout->addWidget(cwidget); connect(this->ui->pushButton,SIGNAL(clicked()),cwidget,SLOT(callParentSlot())); connect(this->ui->pb,SIGNAL(clicked()),this,SLOT(changeLabel())); } void Widget::changeLabel(){ newlabel->setText(this->foo); } and customWidget: class customWidget : public QWidget { Q_OBJECT public: customWidget(); QPushButton *customPB; public slots: void callParentSlot(); }; customWidget::customWidget() { customPB = new QPushButton("customPB"); QHBoxLayout *hboxl = new QHBoxLayout(); hboxl->addWidget(customPB); this->setLayout(hboxl); connect(this->customPB,SIGNAL(clicked()),this,SLOT(callParentSlot())); } void customWidget::callParentSlot(){ ((Widget*)this->parentWidget())->changeLabel(); } in the main function, I simply created an instance of Widget, and called show() on it. This Widget instance has a label, a QString, an instance of customWidget class, and two buttons (inside the ui class, pushButton and pb). One of the buttons calls a slot in its own class called changeLabel(), that, as the name suggests, changes the label to whatever is set in the QString contained in it. I made that just to check that changeLabel() worked. This button is working fine. The other button calls a slot in the customWidget instance, named callParentSlot(), that in turn tries to call the changeLabel() slot in its parent. Since in this case I know that its parent is in fact an instance of Widget, I cast the return value of parentWidget() to Widget*. This button crashes the program. I made a button within customWidget to try to call customWidget's parent slot as well, but it also crashes the program. I followed what was on this question. What am I missing?

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• How to directly rotate CVImageBuffer image in IOS 4 without converting to UIImage?

  - by Ian Charnas

  I am using OpenCV 2.2 on the iPhone to detect faces. I'm using the IOS 4's AVCaptureSession to get access to the camera stream, as seen in the code that follows. My challenge is that the video frames come in as CVBufferRef (pointers to CVImageBuffer) objects, and they come in oriented as a landscape, 480px wide by 300px high. This is fine if you are holding the phone sideways, but when the phone is held in the upright position I want to rotate these frames 90 degrees clockwise so that OpenCV can find the faces correctly. I could convert the CVBufferRef to a CGImage, then to a UIImage, and then rotate, as this person is doing: Rotate CGImage taken from video frame However that wastes a lot of CPU. I'm looking for a faster way to rotate the images coming in, ideally using the GPU to do this processing if possible. Any ideas? Ian Code Sample: -(void) startCameraCapture { // Start up the face detector faceDetector = [[FaceDetector alloc] initWithCascade:@"haarcascade_frontalface_alt2" withFileExtension:@"xml"]; // Create the AVCapture Session session = [[AVCaptureSession alloc] init]; // create a preview layer to show the output from the camera AVCaptureVideoPreviewLayer *previewLayer = [AVCaptureVideoPreviewLayer layerWithSession:session]; previewLayer.frame = previewView.frame; previewLayer.videoGravity = AVLayerVideoGravityResizeAspectFill; [previewView.layer addSublayer:previewLayer]; // Get the default camera device AVCaptureDevice* camera = [AVCaptureDevice defaultDeviceWithMediaType:AVMediaTypeVideo]; // Create a AVCaptureInput with the camera device NSError *error=nil; AVCaptureInput* cameraInput = [[AVCaptureDeviceInput alloc] initWithDevice:camera error:&error]; if (cameraInput == nil) { NSLog(@"Error to create camera capture:%@",error); } // Set the output AVCaptureVideoDataOutput* videoOutput = [[AVCaptureVideoDataOutput alloc] init]; videoOutput.alwaysDiscardsLateVideoFrames = YES; // create a queue besides the main thread queue to run the capture on dispatch_queue_t captureQueue = dispatch_queue_create("catpureQueue", NULL); // setup our delegate [videoOutput setSampleBufferDelegate:self queue:captureQueue]; // release the queue. I still don't entirely understand why we're releasing it here, // but the code examples I've found indicate this is the right thing. Hmm... dispatch_release(captureQueue); // configure the pixel format videoOutput.videoSettings = [NSDictionary dictionaryWithObjectsAndKeys: [NSNumber numberWithUnsignedInt:kCVPixelFormatType_32BGRA], (id)kCVPixelBufferPixelFormatTypeKey, nil]; // and the size of the frames we want // try AVCaptureSessionPresetLow if this is too slow... [session setSessionPreset:AVCaptureSessionPresetMedium]; // If you wish to cap the frame rate to a known value, such as 10 fps, set // minFrameDuration. videoOutput.minFrameDuration = CMTimeMake(1, 10); // Add the input and output [session addInput:cameraInput]; [session addOutput:videoOutput]; // Start the session [session startRunning]; } - (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer fromConnection:(AVCaptureConnection *)connection { // only run if we're not already processing an image if (!faceDetector.imageNeedsProcessing) { // Get CVImage from sample buffer CVImageBufferRef cvImage = CMSampleBufferGetImageBuffer(sampleBuffer); // Send the CVImage to the FaceDetector for later processing [faceDetector setImageFromCVPixelBufferRef:cvImage]; // Trigger the image processing on the main thread [self performSelectorOnMainThread:@selector(processImage) withObject:nil waitUntilDone:NO]; } }

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• C SIGSEGV Handler & Mprotect

  - by pws5068

  I'm constructing a program which uses mprotect() to restrict a block of memory from accessing. When the memory is requested, a SIGSEGV is thrown which I listen for using a signal() call. Once the SIGSEGV has been detected, I need to somehow access the pointer to the memory that was requested (that threw the fault) and the size of the segment requested. Is this possible? void fifoSigHandler(){ // Needs to only remove protection from requested block of virtual memory mprotect(fifoVm,(size_t)fifoVm_size,PROT_WRITE); printf("Caught Seg Fault"); } void fifo_init(void* vm, int vm_size, int n_frames, int page_size) { fifoVm = vm; fifoVm_size = vm_size; fifoFrames = n_frames; fifoPageSize = page_size; mprotect(fifoVm,(size_t)fifoVm_size,PROT_NONE); signal(SIGSEGV, fifoSigHandler); } Additionally, is there a way to determine the level of mprotect() a block of memory is currently assigned (PROT_NONE,PROT_READ, etc..)?

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• Rugged Netbook and software options for Running R statistical software?

  - by Thomas

  I am interested in purchasing a netbook to do field research in another country. My hardware specifications for the nebtook: -Be rugged enough to survive a bit of wear and tear -Fairly fast processing (the ability to upgrade from 1GB of RAM to 2GB) -A battery life of longer than 6 hours -At least a 10 inch screen -A decent camera for Skyping My software needs: -Be able run a Spreadsheet program to do basic data input (like Excel or Open Office) -Use the Open Source Statistical Program R to do basic data analysis (Regression, data analysis etc.) -Word Processing (Word or Open Office) Do you have any suggestions on which models or brands my fit my needs? Some of the models I was considering: Samsung NB-30 Toshiba NB 305 Asus Eee PC 1005HA Lenovo S10-2 Also any recommendations on the best software to load on the aforementioned Netbooks. I saw this resource from [livehacker][6] Any comments. Thanks for your help! -Thomas

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• Why can't I use __getattr__ with Django models?

  - by Joshmaker

  I've seen examples online of people using __getattr__ with Django models, but whenever I try I get errors. (Django 1.2.3) I don't have any problems when I am using __getattr__ on normal objects. For example: class Post(object): def __getattr__(self, name): return 42 Works just fine... >>> from blog.models import Post >>> p = Post() >>> p.random 42 Now when I try it with a Django model: from django.db import models class Post(models.Model): def __getattr__(self, name): return 42 And test it on on the interpreter: >>> from blog.models import Post >>> p = Post() ERROR: An unexpected error occurred while tokenizing input The following traceback may be corrupted or invalid The error message is: ('EOF in multi-line statement', (6, 0)) --------------------------------------------------------------------------- TypeError Traceback (most recent call last) /Users/josh/project/ in () /Users/josh/project/lib/python2.6/site-packages/django/db/models/base.pyc in init(self, *args, **kwargs) 338 if kwargs: 339 raise TypeError("'%s' is an invalid keyword argument for this function" % kwargs.keys()[0]) -- 340 signals.post_init.send(sender=self.class, instance=self) 341 342 def repr(self): /Users/josh/project/lib/python2.6/site-packages/django/dispatch/dispatcher.pyc in send(self, sender, **named) 160 161 for receiver in self._live_receivers(_make_id(sender)): -- 162 response = receiver(signal=self, sender=sender, **named) 163 responses.append((receiver, response)) 164 return responses /Users/josh/project/python2.6/site-packages/photologue/models.pyc in add_methods(sender, instance, signal, *args, **kwargs) 728 """ 729 if hasattr(instance, 'add_accessor_methods'): -- 730 instance.add_accessor_methods() 731 732 # connect the add_accessor_methods function to the post_init signal TypeError: 'int' object is not callable Can someone explain what is going on? EDIT: I may have been too abstract in the examples, here is some code that is closer to what I actually would use on the website: class Post(models.Model): title = models.CharField(max_length=255) slug = models.SlugField() date_published = models.DateTimeField() content = RichTextField('Content', blank=True, null=True) # Etc... Class CuratedPost(models.Model): post = models.ForeignKey('Post') position = models.PositiveSmallIntegerField() def __getattr__(self, name): ''' If the user tries to access a property of the CuratedPost, return the property of the Post instead... ''' return self.post.name # Etc... While I could create a property for each attribute of the Post class, that would lead to a lot of code duplication. Further more, that would mean anytime I add or edit a attribute of the Post class I would have to remember to make the same change to the CuratedPost class, which seems like a recipe for code rot.

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