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• Sys.WebForms.PageRequestManagerServerErrorException: .... The status code returned from the server w

  - by webnoob

  Hi All, I have seen a few posts regarding this issue but not one specific to my problem and I have no ideas as to what I need to do to debug this. I have some combo boxes on an aspx pages, when I select a value from the first one, it fills the second with value and so on with the third and fourth. This works with no problems until I wrap an asp.net UpdatePanel around the combo boxes and try to "ajaxify" the whole process so the page isn't dancing around. The exact error I get is: Sys.WebForms.PageRequestManagerServerErrorException: An unknown error occurred while processing the request on the server. The status code returned from the server was: 404 Some things to note: I am using URL rewriting - This is what I think is causing the problem The error will occur whenever I choose a selection for a SECOND time. This means that I could select a value from the first combo box and get the same error (so it is happening on the second postback - No matter which combo box it's from). I have tried setting the EnablePartialRendering="false" on teh scriptmanager but as I said, it works when not using ajax, so I don't know how to debug the issue. My server is Windows 2008 running IIS& with ASP.NET 2.0. I would really appreciate your help Thanks in advance.

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• dotNet Templated, Repeating, Databound ServerControl: Modifying underlying ServerControl data per te

  - by Campbeln

  I have a server control that wraps an underlying class which manages a number of indexes to track where it is in a dataset (ie: RenderedRecordCount, ErroredRecordCount, NewRecordCount, etc.). I've got the server control rendering great, but OnDataBinding I'm having an issue as to seems to happen after CreateChildControls and before Render (both of which properly manage the iteration of the underlying indexes). While I'm somewhat familiar with the ASP.NET page lifecycle, this one seems to be beyond me at the moment. So... How do I hook into the iterative process OnDataBinding uses so I can manage the underlying indexes? Will I have to iterate over the ITemplates myself, managing the indexes as I go or is there an easier solution? [edit: Agh... writing the problem out is very cathartic... I'm thinking this is exactly what I will need to do...] Also... I implemented the iteration of the underlying indexes during CreateChildControls originally in the belief that was the proper place to hook in for events like OnDataBinding (thinking it was done as the controls were being .Add'd). Now it seems that this may actually be unnecessary. So I guess the secondary question is: What happens during CreateChildControls? Are the unadulterated (read: with various <%-tags in place) controls added to the .Controls collection without any other processing?

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• "Exclusive" DirectDraw palette isn't actually exclusive

  - by CyberShadow

  We're maintaining an old video game that uses a full-screen 256-color graphics mode with DirectDraw. The problem is, some applications running in the background sometimes try to change the system palette while the game is running, which results in corrupted graphics. We can (sometimes) detect when this happens by processing the WM_PALETTECHANGED message. A few update versions ago we added logging (just log the window title/class/process name), which helped users identify offending applications and close them. MSN Live Messenger was a common culprit. The problem got worse when we found out that Windows Vista (and 7) does it "by itself". The WM_PALETTECHANGED parameters point towards CSRSS and the desktop window. In Vista, a workaround that often worked was to open any folder (Computer, Documents, etc.) and leave it open while running the game. Sounds ridiculous, but it worked - in most cases. In Windows 7, not even this workaround worked any more. Users found that stopping some services (Windows Update and the indexing service) also resolved the problem on some configurations. Some time ago I just started trying random things in hope of finding a solution. I found that setting the GDI palette (using Create/SelectPalette) before setting the DirectDraw palette (using IDirectDrawPalette::SetEntries) would restore the palette after it became corrupted (WM_PALETTECHANGED handler). SetSystemPaletteUse and calling SetPalette on the primary surface helped some more. However, there is still perceivable flickering when an application tries to steal the palette, which is especially prominent during fades. Question: is there a way to get a "real" exclusive palette, which completely disallows other applications changing the Windows palette as long as our game retains focus?

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• Sending basic authentication information via form

  - by VolatileStorm

  I am working on a site that currently uses a basic authentication dialog box login system, that is the type of dialog that you get if you go here: http://www.dur.ac.uk/vm.boatclub/password/index.php I did not set this system up and am not in a position to easily/quickly work around it, but it DOES work. The issue however is that the dialog box is not very helpful in telling you what login information you have to use (that is which username and password combination), and so I would like to replace it with a form. I had been thinking that this wasn't possible but I wanted to ask in order to find out. Is it possible to set up an HTML form that sends the data to the server such that it accepts it in the same way that it would using this dialog box? Alternatively is it possible to set up a PHP script that would take normal form data and process it somehow passing it to the server such that it logs in? Edit: After being told that this is basic authentication I went around and have managed to find a way that works and keeps the user persistently logged in. However, this does not work in internet explorer. The solution was simply to redirect the user to: http://username:[email protected]/vm.boatclub/password/index.php But Internet Explorer removed it due to phishing uses about 3 years ago. Is there a way to use javascript to get the browser to access the site in this way? Or will I have to simply change my UI?

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• Sending series of images to display like a movie on iPhone

  - by unknownthreat

  Allow me to elaborate more. On the server, we will have a program that will take data from iPhone and process that data and produce series of images. Each time an image is generated, it will be send back to display on iPhone. I have done all of the things above using UDP, OpenGL, and such. It works. The images are transferred to iPhone and can be displayed, but it is slow. The image's resolution is around 320 x 420 and we send the image pixels by pixels. This naive implementation leads to a slow framerate. I can see around 2-3 frames per second. There are also some UDP packets dropped, and this is expected. Are there any sort of compression method available for something like this? Are there any other method that can make this better? NOTE: please don't just write "compression" as an answer, because we are aware that we will need to do it in some ways.

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• How to Avoid PHP Object Nesting/Creation Limit?

  - by Will Shaver

  I've got a handmade ORM in PHP that seems to be bumping up against an object limit and causing php to crash. Here's a simple script that will cause crashes: <? class Bob { protected $parent; public function Bob($parent) { $this->parent = $parent; } public function __toString() { if($this->parent) return (string) "x " . $this->parent; return "top"; } } $bobs = array(); for($i = 1; $i < 40000; $i++) { $bobs[] = new Bob($bobs[$1 -1]); } ?> Even running this from the command line will cause issues. Some boxes take more than 40,000 objects. I've tried it on Linux/Appache (fail) but my app runs on IIS/FastCGI. On FastCGI this causes the famous "The FastCGI process exited unexpectedly" error. Obviously 20k objects is a bit high, but it crashes with far fewer objects if they have data and nested complexity. Fast CGI isn't the issue - I've tried running it from the command line. I've tried setting the memory to something really high - 6,000MB and to something really low - 24MB. If I set it low enough I'll get the "allocated memory size xxx bytes exhausted" error. I'm thinking that it has to do with the number of functions that are called - some kind of nesting prevention. I didn't think that my ORM's nesting was that complicated but perhaps it is. I've got some pretty clear cases where if I load just ONE more object it dies, but loads in under 3 seconds if it works.

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• help with eclipse debugging /or/ subclassed SimpleAdapter not calling setViewImage()

  - by edzillion

  Hi I was following the method for asynchronously loading images into a listview as outlined in evan charlton's blog here. The problem I am having is that the setViewImage function is not being called by the system: @Override public void setViewImage(final ImageView image, final String value) { if (value != null && value.length() > 0 && image instanceof RemoteImageView) { RemoteImageView riv = (RemoteImageView) image; riv.setLocalURI(API.getCacheFileName(value)); riv.setRemoteURI(value); super.setViewImage(image, R.drawable.icon); } else { image.setVisibility(View.GONE); } } I have built his example code, and setViewImage is called fine - it seems to me that the code is functionally identical. Looking into the docs it says: First, if a SimpleAdapter.ViewBinder is available, setViewValue(android.view.View, Object, String) is invoked. If the returned value is true, binding has occured. If the returned value is false and the view to bind is a TextView, setViewText(TextView, String) is invoked. If the returned value is false and the view to bind is an ImageView, setViewImage(ImageView, int) or setViewImage(ImageView, String) is invoked. If no appropriate binding can be found, an IllegalStateException is thrown. I don't really understand how to debug (in eclipse) to find out how this process is occuring, advice on how to do so would be a help. Thanks.

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• How to convert struct to char array in C

  - by falcojr

  I'm trying to convert a struct to a char array to send over the network. However, I get some weird output from the char array when I do. #include <stdio.h> struct x { int x; } __attribute__((packed)); int main() { struct x a; a.x=127; char *b = (char *)&a; int i; for (i=0; i<4; i++) printf("%02x ", b[i]); printf("\n"); for (i=0; i<4; i++) printf("%d ", b[i]); printf("\n"); return 0; } Here is the output for various values of a.x (on an X86 using gcc): 127: 7f 00 00 00 127 0 0 0 128: ffffff80 00 00 00 -128 0 0 0 255: ffffffff 00 00 00 -1 0 0 0 256: 00 01 00 00 0 1 0 0 I understand the values for 127 and 256, but why do the numbers change when going to 128? Why wouldn't it just be: 80 00 00 00 128 0 0 0 Am I forgetting to do something in the conversion process or am I forgetting something about integer representation? *Note: This is just a small test program. In a real program I have more in the struct, better variable names, and I convert to little-endian. *Edit: formatting

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• Best way to do interprocess communication on Mac OS X

  - by jbrennan

  I'm looking at building a Cocoa application on the Mac with a back-end daemon process (really just a mostly-headless Cocoa app, probably), along with 0 or more "client" applications running locally (although if possible I'd like to support remote clients as well; the remote clients would only ever be other Macs or iPhone OS devices). The data being communicated will be fairly trivial, mostly just text and commands (which I guess can be represented as text anyway), and maybe the occasional small file (an image possibly). I've looked at a few methods for doing this but I'm not sure which is "best" for the task at hand. Things I've considered: Reading and writing to a file (…yes), very basic but not very scalable. Pure sockets (I have no experience with sockets but I seem to think I can use them to send data locally and over a network. Though it seems cumbersome if doing everything in Cocoa Distributed Objects: seems rather inelegant for a task like this NSConnection: I can't really figure out what this class even does, but I've read of it in some IPC search results I'm sure there are things I'm missing, but I was surprised to find a lack of resources on this topic.

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• Database Functional Programming in Clojure

  - by Ralph

  "It is tempting, if the only tool you have is a hammer, to treat everything as if it were a nail." - Abraham Maslow I need to write a tool to dump a large hierarchical (SQL) database to XML. The hierarchy consists of a Person table with subsidiary Address, Phone, etc. tables. I have to dump thousands of rows, so I would like to do so incrementally and not keep the whole XML file in memory. I would like to isolate non-pure function code to a small portion of the application. I am thinking that this might be a good opportunity to explore FP and concurrency in Clojure. I can also show the benefits of immutable data and multi-core utilization to my skeptical co-workers. I'm not sure how the overall architecture of the application should be. I am thinking that I can use an impure function to retrieve the database rows and return a lazy sequence that can then be processed by a pure function that returns an XML fragment. For each Person row, I can create a Future and have several processed in parallel (the output order does not matter). As each Person is processed, the task will retrieve the appropriate rows from the Address, Phone, etc. tables and generate the nested XML. I can use a a generic function to process most of the tables, relying on database meta-data to get the column information, with special functions for the few tables that need custom processing. These functions could be listed in a map(table name -> function). Am I going about this in the right way? I can easily fall back to doing it in OO using Java, but that would be no fun. BTW, are there any good books on FP patterns or architecture? I have several good books on Clojure, Scala, and F#, but although each covers the language well, none look at the "big picture" of function programming design.

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• Error Converting PIL B&W images to Numpy Arrays

  - by Elliot

  I am getting weird errors when I try to convert a black and white PIL image to a numpy array. An example of the code I am working with is below. if image.mode != '1': image = image.convert('1') #convert to B&W data = np.array(image) #convert data to a numpy array n_lines = data.shape[0] #number of raster passes line_range = range(data.shape[1]) for l in range(n_lines): # process one horizontal line of the image line = data[l] for n in line_range: if line[n] == 1: write_line_to(xl, z+scale*n, speed) #conversion to other program code elif line[n] == 0: run_to(xl, z+scale*n) #conversion to other program code I have tried this using both array and asarray for the conversion, and gotten different errors. If I use array, then the data I get out is nothing like what I put in. It looks like several very shrunken partial images side by side, with the remainder of the image space filled in in black. If I use asarray, then the entirety of python crashes during the raster step (on a random line). If I work with a greyscale image ('L'), then neither of these errors occurs for either array or asarray. Does anyone know what I am doing wrong? Is there something odd about the way PIL encodes B&W images, or something special I need to pass numpy to make it convert properly?

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• segfault during __cxa_allocate_exception in SWIG wrapped library

  - by lefticus

  While developing a SWIG wrapped C++ library for Ruby, we came across an unexplained crash during exception handling inside the C++ code. I'm not sure of the specific circumstances to recreate the issue, but it happened first during a call to std::uncaught_exception, then after a some code changes, moved to __cxa_allocate_exception during exception construction. Neither GDB nor valgrind provided any insight into the cause of the crash. I've found several references to similar problems, including: http://wiki.fifengine.de/Segfault_in_cxa_allocate_exception http://forums.fifengine.de/index.php?topic=30.0 http://code.google.com/p/osgswig/issues/detail?id=17 https://bugs.launchpad.net/ubuntu/+source/libavg/+bug/241808 The overriding theme seems to be a combination of circumstances: A C application is linked to more than one C++ library More than one version of libstdc++ was used during compilation Generally the second version of C++ used comes from a binary-only implementation of libGL The problem does not occur when linking your library with a C++ application, only with a C application The "solution" is to explicitly link your library with libstdc++ and possibly also with libGL, forcing the order of linking. After trying many combinations with my code, the only solution that I found that works is the LD_PRELOAD="libGL.so libstdc++.so.6" ruby scriptname option. That is, none of the compile-time linking solutions made any difference. My understanding of the issue is that the C++ runtime is not being properly initialized. By forcing the order of linking you bootstrap the initialization process and it works. The problem occurs only with C applications calling C++ libraries because the C application is not itself linking to libstdc++ and is not initializing the C++ runtime. Because using SWIG (or boost::python) is a common way of calling a C++ library from a C application, that is why SWIG often comes up when researching the problem. Is anyone out there able to give more insight into this problem? Is there an actual solution or do only workarounds exist? Thanks.

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• Java InputReader. Detect if file being read is binary?

  - by Trizicus

  I had posted a question in regards to this code. I found that JTextArea does not support the binary type data that is loaded. So my new question is how can I go about detecting the 'bad' file and canceling the file I/O and telling the user that they need to select a new file? class Open extends SwingWorker<Void, String> { File file; JTextArea jta; Open(File file, JTextArea jta) { this.file = file; this.jta = jta; } @Override protected Void doInBackground() throws Exception { BufferedReader br = null; try { br = new BufferedReader(new FileReader(file)); String line = br.readLine(); while(line != null) { publish(line); line = br.readLine(); } } finally { try { br.close(); } catch (IOException e) { } } return null; } @Override protected void process(List<String> chunks) { for(String s : chunks) jta.append(s + "\n"); } }

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• Streaming Media Player Tutorial Stops Unexpectedly. How Should I Debug (And Other Questions From A

  - by Danny

  Hello! I'm a fledgling in the Android and Eclipse ways. I was reading and downloaded the source code for a Streaming Media Player tutorial from Pocket Journey, here. However, when I try to run it through the "Run As..." or "Debug As..." features in Eclipse, the emulator reports: "Sorry! The application Android Tutorials (process com.pocketjourney.tutorials) has stopped unexpectedly. Please try again." Now, from stepping through the Tutorial 1 activity (for those of you that may be familiar with it), it seems something funky happens here: button.setOnClickListener(new View.OnClickListener() { public void onClick(View view) { Toast.makeText(Tutorial1.this, "Button Clicked",Toast.LENGTH_SHORT).show(); }}); My questions are: What's up with that line? Apparently, other comments haven't had this problem; am I missing some library that I should be downloading from someplace? How should I go about debugging this other than/in addition to stepping through code? I'm used to Visual Studio, which has a nice box with exception details for me to sift through and copy/paste to google with. Eclipse debugging showed a "No Source Code" page, or a list of exceptions. I've heard of something called LogCat; is that relevant here? Thanks in advance!

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• Symfony - Several form on the same page -> ID issue

  - by Julien

  Hi folks. I have an issue while displaying several forms of the same model on the same page. The problem is that with the NameFormat, the fields have the same ID : $this->widgetSchema->setNameFormat('display[%s]'); Will display <form class="update_display_form" id="update_display_0" action="/iperf/web/frontend_dev.php/update_display" method="post"> <input type="checkbox" name="display[displayed]" checked="checked" id="display_displayed" /> <label for="display_displayed">test</label> </form> <form class="update_display_form" id="update_display_1" action="/iperf/web/frontend_dev.php/update_display" method="post"> <input type="checkbox" name="display[displayed]" checked="checked" id="display_displayed" /> <label for="display_displayed">truc</label> </form> And if you click on the second label, it will activate the first checkbox So I thought I could use the object id to make them unique : $this->widgetSchema->setNameFormat('display'.$this->getObject()->getId().'[%s]'); But then I can not process the request, since I don't know the name of the parameters. The best option I found was to set an ID : $this->widgetSchema['displayed']->setAttributes(array("id" => "display".$this->getObject()->getId() )); but then I totally loose the connections between the label and the checkbox. The problem would be solved if I could change the "for" attribute of my label. Does somebody know how to do that ? Or any other option ?

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• Why does this gstreamer pipeline stall ?

  - by timday

  I've been playing around with gstreamer pipelines using gst-launch. I don't have any problems if I just want to process audio or video separately (to separate files, or to alsasink/ximagesink), but I'm confused by what I need to do to mux the streams back together using, say avimux. This gst-launch-0.10 filesrc location=MVI_2034.AVI ! decodebin name=dec \ dec. ! queue ! audioconvert ! 'audio/x-raw-int,rate=44100,channels=1' ! queue ! mux. \ dec. ! queue ! videoflip 1 ! ffmpegcolorspace ! jpegenc ! queue ! mux. \ avimux name=mux ! filesink location=out.avi just outputs Setting pipeline to PAUSED ... Pipeline is PREROLLING ... and then stalls indefinitely. What's the trick ?

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• I want to read program content from command line.

  - by Alexandre Dominos

  I am trying to update a program which was wrotten in 1995 with pascal or c. I am not sure about programming language. Command line program. Now I am coded in C#. And I want to read program command line content. Is it possible? I tried something. But not succesfull. They are: private void aboutToolStripMenuItem_Click(object sender, EventArgs e) { // Redirect the output stream of the child process. p.StartInfo.UseShellExecute = false; p.StartInfo.RedirectStandardOutput = true; p.StartInfo.FileName = "osl.exe"; p.Start(); logs.AppendText("Timer Started\n"); timer1.Enabled = true; } private void timer1_Tick(object sender, EventArgs e) { // write somethingg and read what is the program doing on command line? // What is the program printint? etc... // I try this code but not enough for mo. // logs.AppendText("d:" + p.StandardOutput.ReadToEnd()+"\n"); } private void p_Exited(object sender, EventArgs e) { timer1.Enabled = false; } i am open to any idea in java,cpp,c,c#.

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• multithreading issue

  - by vbNewbie

  I have written a multithreaded crawler and the process is simply creating threads and having them access a list of urls to crawl. They then access the urls and parse the html content. All this seems to work fine. Now when I need to write to tables in a database is when I experience issues. I have 2 declared arraylists that will contain the content each thread parse. The first arraylist is simply the rss feed links and the other arraylist contains the different posts. I then use a for each loop to iterate one while sequentially incrementing the other and writing to the database. My problem is that each time a new thread accesses one of the lists the content is changed and this affects the iteration. I tried using nested loops but it did not work before and this works fine using a single thread.I hope this makes sense. Here is my code: SyncLock dlock For Each l As String In links finallinks.Add(l) Next End SyncLock SyncLock dlock For Each p As String In posts finalposts.Add(p) Next End SyncLock ... Dim i As Integer = 0 SyncLock dlock For Each rsslink As String In finallinks postlink = finalposts.Item(i) i = i + 1 finallinks and finalposts are the two arraylists. I did not include the rest of the code which shows the threads working but this is the essential part where my error occurs which is basically here postlink = finalposts.Item(i) i = i + 1 ERROR: index was out of range. Must be non-negative and less than the size of the collection Is there an alternative?

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• Why is OCR(MODI.MiLANGUAGES.miLANG_ENGLISH, true, true) causing an OCR running error?

  - by Ian Wells

  Hi folks, I am using MODI to read tiff images and do what I need to do with the text. Some images work fine and then other tiff images always cause the method, OCR(MODI.MiLANGUAGES.miLANG_ENGLISH, true, true) to fail. I have researched this and tried different variations such as 'false','false' in the parameter list. I have also tried SYSDEFAULT instead of English but I still get the error. Can anyone please tell me why it would fail on some tiff images and not on others? I have done some research and found this answer: One possible cause is MODI trying to process a file without any recognisable text. A blank document, or one which has only drawings/scribbles and is effectively blank, will cause this exception. Obviously this is not good enough as there is no way I can have an app that decides to OCR some images and not others. I handle the exception, but the OCR object is not then initalised so I can't do what I need to do from there. This is a bloody nightmare! Why can't the method just do it's bloody job and if the image has some unreadable pages then just ignore them? I am using Windows 7 Ultimate and Office 2007 Ultimate. Visual Studio version is 2008 Thanks, IW

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• Trimming bit of the beginning off a recorder waveform

  - by Lowgain

  I've got a flash 10.1 app that lets me record microphone input to a wav without a media server, which I am saving to an Amazon S3 bucket. I have another process running on a server which gets wavs from this bucket, converts to mp3 using LAME and puts them into another bucket. This all works fine, but in converting wav mp3, about 0.1sec or so of silence is added to my sound. In the application this are being used in, perfect sync is critical, so I need to trim off that little bit. If I have to trim it off the original waveform that is okay, I don't expect anything important to happen in that first fraction of a second. What is the best way to go about this? I am using Adobe's WavWriter to convert by ByteArray into a proper waveform. Is there a way I can easily trim off the first few samples from my ByteArray without invalidating the structure? Alternatively, is there a good server-side tool I can use to trim the wav before running it through LAME, or an argument I can give LAME? Or, could I even trim that sound off the mp3 after it has been converted? Thanks!

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• Implementing a robust async stream reader for a console

  - by Jon

  I recently provided an answer to this question: C# - Realtime console output redirection. As often happens, explaining stuff (here "stuff" was how I tackled a similar problem) leads you to greater understanding and/or, as is the case here, "oops" moments. I realized that my solution, as implemented, has a bug. The bug has little practical importance, but it has an extremely large importance to me as a developer: I can't rest easy knowing that my code has the potential to blow up. Squashing the bug is the purpose of this question. I apologize for the long intro, so let's get dirty. I wanted to build a class that allows me to receive input from a Stream in an event-based manner. The stream, in my scenario, is guaranteed to be a FileStream and there is also an associated StreamReader already present to leverage. The public interface of the class is this: public class MyStreamManager { public event EventHandler<ConsoleOutputReadEventArgs> StandardOutputRead; public void StartSendingEvents(); public void StopSendingEvents(); } Obviously this specific scenario has to do with a console's standard output. StartSendingEvents and StopSendingEvents do what they advertise; for the purposes of this discussion, we can assume that events are always being sent without loss of generality. The class uses these two fields internally: protected readonly StringBuilder inputAccumulator = new StringBuilder(); protected readonly byte[] buffer = new byte[256]; The functionality of the class is implemented in the methods below. To get the ball rolling: public void StartSendingEvents(); { this.stopAutomation = false; this.BeginReadAsync(); } To read data out of the Stream without blocking, and also without requiring a carriage return char, BeginRead is called: protected void BeginReadAsync() { if (!this.stopAutomation) { this.StandardOutput.BaseStream.BeginRead( this.buffer, 0, this.buffer.Length, this.ReadHappened, null); } } The challenging part: BeginRead requires using a buffer. This means that when reading from the stream, it is possible that the bytes available to read ("incoming chunk") are larger than the buffer. Since we are only handing off data from the stream to a consumer, and that consumer may well have inside knowledge about the size and/or format of these chunks, I want to call event subscribers exactly once for each chunk. Otherwise the abstraction breaks down and the subscribers have to buffer the incoming data and reconstruct the chunks themselves using said knowledge. This is much less convenient to the calling code, and detracts from the usefulness of my class. Edit: There are comments below correctly stating that since the data is coming from a stream, there is absolutely nothing that the receiver can infer about the structure of the data unless it is fully prepared to parse it. What I am trying to do here is leverage the "flush the output" "structure" that the owner of the console imparts while writing on it. I am prepared to assume (better: allow my caller to have the option to assume) that the OS will pass me the data written between two flushes of the stream in exactly one piece. To this end, if the buffer is full after EndRead, we don't send its contents to subscribers immediately but instead append them to a StringBuilder. The contents of the StringBuilder are only sent back whenever there is no more to read from the stream (thus preserving the chunks). private void ReadHappened(IAsyncResult asyncResult) { var bytesRead = this.StandardOutput.BaseStream.EndRead(asyncResult); if (bytesRead == 0) { this.OnAutomationStopped(); return; } var input = this.StandardOutput.CurrentEncoding.GetString( this.buffer, 0, bytesRead); this.inputAccumulator.Append(input); if (bytesRead < this.buffer.Length) { this.OnInputRead(); // only send back if we 're sure we got it all } this.BeginReadAsync(); // continue "looping" with BeginRead } After any read which is not enough to fill the buffer, all accumulated data is sent to the subscribers: private void OnInputRead() { var handler = this.StandardOutputRead; if (handler == null) { return; } handler(this, new ConsoleOutputReadEventArgs(this.inputAccumulator.ToString())); this.inputAccumulator.Clear(); } (I know that as long as there are no subscribers the data gets accumulated forever. This is a deliberate decision). The good This scheme works almost perfectly: Async functionality without spawning any threads Very convenient to the calling code (just subscribe to an event) Maintains the "chunkiness" of the data; this allows the calling code to use inside knowledge of the data without doing any extra work Is almost agnostic to the buffer size (it will work correctly with any size buffer irrespective of the data being read) The bad That last almost is a very big one. Consider what happens when there is an incoming chunk with length exactly equal to the size of the buffer. The chunk will be read and buffered, but the event will not be triggered. This will be followed up by a BeginRead that expects to find more data belonging to the current chunk in order to send it back all in one piece, but... there will be no more data in the stream. In fact, as long as data is put into the stream in chunks with length exactly equal to the buffer size, the data will be buffered and the event will never be triggered. This scenario may be highly unlikely to occur in practice, especially since we can pick any number for the buffer size, but the problem is there. Solution? Unfortunately, after checking the available methods on FileStream and StreamReader, I can't find anything which lets me peek into the stream while also allowing async methods to be used on it. One "solution" would be to have a thread wait on a ManualResetEvent after the "buffer filled" condition is detected. If the event is not signaled (by the async callback) in a small amount of time, then more data from the stream will not be forthcoming and the data accumulated so far should be sent to subscribers. However, this introduces the need for another thread, requires thread synchronization, and is plain inelegant. Specifying a timeout for BeginRead would also suffice (call back into my code every now and then so I can check if there's data to be sent back; most of the time there will not be anything to do, so I expect the performance hit to be negligible). But it looks like timeouts are not supported in FileStream. Since I imagine that async calls with timeouts are an option in bare Win32, another approach might be to PInvoke the hell out of the problem. But this is also undesirable as it will introduce complexity and simply be a pain to code. Is there an elegant way to get around the problem? Thanks for being patient enough to read all of this.

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• Trouble with piping through sed

  - by Joel

  I am having trouble piping through sed. Once I have piped output to sed, I cannot pipe the output of sed elsewhere. wget -r -nv http://127.0.0.1:3000/test.html Outputs: 2010-03-12 04:41:48 URL:http://127.0.0.1:3000/test.html [99/99] -> "127.0.0.1:3000/test.html" [1] 2010-03-12 04:41:48 URL:http://127.0.0.1:3000/robots.txt [83/83] -> "127.0.0.1:3000/robots.txt" [1] 2010-03-12 04:41:48 URL:http://127.0.0.1:3000/shop [22818/22818] -> "127.0.0.1:3000/shop.29" [1] I pipe the output through sed to get a clean list of URLs: wget -r -nv http://127.0.0.1:3000/test.html 2>&1 | grep --line-buffered -v ERROR | sed 's/^.*URL:\([^ ]*\).*/\1/g' Outputs: http://127.0.0.1:3000/test.html http://127.0.0.1:3000/robots.txt http://127.0.0.1:3000/shop I would like to then dump the output to file, so I do this: wget -r -nv http://127.0.0.1:3000/test.html 2>&1 | grep --line-buffered -v ERROR | sed 's/^.*URL:\([^ ]*\).*/\1/g' > /tmp/DUMP_FILE I interrupt the process after a few seconds and check the file, yet it is empty. Interesting, the following yields no output (same as above, but piping sed output through cat): wget -r -nv http://127.0.0.1:3000/test.html 2>&1 | grep --line-buffered -v ERROR | sed 's/^.*URL:\([^ ]*\).*/\1/g' | cat Why can I not pipe the output of sed to another program like cat?

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• Fast Lightweight Image Comparisson Metric Algorithm

  - by gav

  Hi All, I am developing an application for the Android platform which contains 1000+ image filters that have been 'evolved'. When a user selects a photo I want to present the most relevant filters first. This 'relevance' should be dependent on previous use cases. I have already developed tools that register when a filtered image is saved; this combination of filter and image can be seen as the training data for my system. The issue is that the comparison must occur between selecting an image and the next screen coming up. From a UI point of view I need the whole process to take less that 4 seconds; select an image- obtain a metric to use for similarity - check against use cases - return 6 closest matches. I figure with 4 seconds I can use animations and progress dialogs to keep the user happy. Due to platform contraints I am fairly limited in the computational expense of the algorithm. I have implemented a technique adapted from various online tutorials for running C code on the G1 and hence this language is available Specific Constraints; Qualcomm® MSM7201A™, 528 MHz Processor 320 x 480 Pixel bitmap in 32 bit ARGB ~ 2 seconds computational time for the native method to get the metric ~ 2 seconds to compare the metric of the current image with training data This is an academic project so all ideas are welcome, anything you can think of or have heard about would be of interest to me. My ideas; I want to keep the complexity down (O(n*m)?) by using pixel data only rather than a neighbourhood function I was looking at using the Colour historgram/Greyscale histogram/Texture/Entropy of the image, combining them to make the measure. There will be an obvious loss of information but I need the resultant metric to be substantially smaller than the memory footprint of the image (~0.512 MB) As I said, any ideas to direct my research would be fantastic. Kind regards, Gavin

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• Directly call distutils' or setuptools' setup() function with command name/options, without parsing

  - by Ryan B. Lynch

  I'd like to call Python's distutils' or setuptools' setup() function in a slightly unconventional way, but I'm not sure whether distutils is meant for this kind of usage. As an example, let's say I currently have a 'setup.py' file, which looks like this (lifted verbatim from the distutils docs--the setuptools usage is almost identical): from distutils.core import setup setup(name='Distutils', version='1.0', description='Python Distribution Utilities', author='Greg Ward', author_email='[email protected]', url='http://www.python.org/sigs/distutils-sig/', packages=['distutils', 'distutils.command'], ) Normally, to build just the .spec file for an RPM of this module, I could run python setup.py bdist_rpm --spec-only, which parses the command line and calls the 'bdist_rpm' code to handle the RPM-specific stuff. The .spec file ends up in './dist'. How can I change my setup() invocation so that it runs the 'bdist_rpm' command with the '--spec-only' option, WITHOUT parsing command-line parameters? Can I pass the command name and options as parameters to setup()? Or can I manually construct a command line, and pass that as a parameter, instead? NOTE: I already know that I could call the script in a separate process, with an actual command line, using os.system() or the subprocess module or something similar. I'm trying to avoid using any kind of external command invocations. I'm looking specifically for a solution that runs setup() in the current interpreter. For background, I'm converting some release-management shell scripts into a single Python program. One of the tasks is running 'setup.py' to generate a .spec file for further pre-release testing. Running 'setup.py' as an external command, with its own command line options, seems like an awkward method, and it complicates the rest of the program. I feel like there may be a more Pythonic way.

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• Copy SQL Server data from one server to another on a schedule

  - by rwmnau

  I have a pair of SQL Servers at different webhosts, and I'm looking for a way to periodically update the one server using the other. Here's what I'm looking for: As automated as possible - ideally, without any involvement on my part once it's set up. Pushes a number of databases, in their entirely (including any schema changes) from one server to the other Freely allows changes on the source server without breaking my process. For this reason, I don't want to use replication, as I'd have to break it every time there's an update on the source, and then recreate the publication and subscription One database is about 4GB in size and contains binary data. I'm not sure if there's a way to export this to a script, but it would be a mammoth file if I did. Originally, I was thinking of writing something that takes a scheduled full backup of each database, FTPs the backups from one server to the other once they're done, and then the new server picks it up and restores it. The only downside I can see to this is that there's no way to know that the backups are done before starting to transfer them - can these backups be done synchronously? Also, the server being refreshes is our test server, so if there's some downtime involved in moving the data, that's fine. Does anybody out there have a better idea, or is what I'm currently considering the best non-replication way to go? Thanks for your help, everybody. UPDATE: I ended up designing a custom solution to get this done using BAT files, 7Zip,command line FTP, and OSQL, so it runs in a completely automatic way and aggregates the data from a dozen servers across the country. I've detailed the steps in a blog entry. Thanks for all your input!

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