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• ASP.NET MVC Paging for a search form

  - by James Alexander

  I've read several different posts on paging w/ in MVC but none describe a scenario where I have something like a search form and then want to display the results of the search criteria (with paging) beneath the form once the user clicks submit. My problem is that, the paging solution I'm using will create <a href="..."> links that will pass the desired page like so: http://mysite.com/search/2/ and while that's all fine and dandy, I don't have the results of the query being sent to the db in memory or anything so I need to query the DB again. If the results are handled by the POST controller action for /Search and the first page of the data is rendered as such, how do I get the same results (based on the form criteria specified by the user) when the user clicks to move to page 2? Some javascript voodoo? Leverage Session State? Make my GET controller action have the same variables expected by the search criteria (but optional), when the GET action is called, instantiate a FormCollection instance, populate it and pass it to the POST action method (there-by satisfying DRY)? Can someone point me in the right direction for this scenario or provide examples that have been implemented in the past? Thanks!

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• AS3 using PrintJob to print a MovieClip

  - by Chris Waugh

  Hello, I am currently trying to create a function which will allow me to pass in a movieclip and print it. Here is the simplified version of the function: function printMovieClip(clip:MovieClip) { var printJob:PrintJob = new PrintJob(); var numPages:int = 0; var printY:int = 0; var printHeight:Number; if ( printJob.start() ) { /* Resize movie clip to fit within page width */ if (clip.width > printJob.pageWidth) { clip.width = printJob.pageWidth; clip.scaleY = clip.scaleX; } numPages = Math.ceil(clip.height / printJob.pageHeight); /* Add pages to print job */ for (var i:int = 0; i < numPages; i++) { printJob.addPage(clip, new Rectangle(0, printY, printJob.pageWidth, printJob.pageHeight)); printY += printJob.pageHeight; } /* Send print job to printer */ printJob.send(); /* Delete job from memory */ printJob = null; } } printMovieClip( testMC ); Unfortunately this is not working as expected i.e. printing the full width of the Movieclip and doing page breaks on the length. Any help with this would be greatly appreciated. Many thanks, Chris

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• Anonymous union definition/declaration in a macro GNU vs VS2008

  - by Alan_m

  I am attempting to alter an IAR specific header file for a lpc2138 so it can compile with Visual Studio 2008 (to enable compatible unit testing). My problem involves converting register definitions to be hardware independent (not at a memory address) The "IAR-safe macro" is: #define __IO_REG32_BIT(NAME, ADDRESS, ATTRIBUTE, BIT_STRUCT) \ volatile __no_init ATTRIBUTE union \ { \ unsigned long NAME; \ BIT_STRUCT NAME ## _bit; \ } @ ADDRESS //declaration //(where __gpio0_bits is a structure that names //each of the 32 bits as P0_0, P0_1, etc) __IO_REG32_BIT(IO0PIN,0xE0028000,__READ_WRITE,__gpio0_bits); //usage IO0PIN = 0x0xAA55AA55; IO0PIN_bit.P0_5 = 0; This is my comparable "hardware independent" code: #define __IO_REG32_BIT(NAME, BIT_STRUCT)\ volatile union \ { \ unsigned long NAME; \ BIT_STRUCT NAME##_bit; \ } NAME; //declaration __IO_REG32_BIT(IO0PIN,__gpio0_bits); //usage IO0PIN.IO0PIN = 0xAA55AA55; IO0PIN.IO0PIN_bit.P0_5 = 1; This compiles and works but quite obviously my "hardware independent" usage does not match the "IAR-safe" usage. How do I alter my macro so I can use IO0PIN the same way I do in IAR? I feel this is a simple anonymous union matter but multiple attempts and variants have proven unsuccessful. Maybe the IAR GNU compiler supports anonymous unions and vs2008 does not. Thank you.

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• Space-saving character encoding for japanese?

  - by Constantin

  In my opinion a common problem: character encoding in combination with a bitmap-font. Most multi-language encodings have an huge space between different character types and even a lot of unused code points there. So if I want to use them I waste a lot of memory (not only for saving multi-byte text - i mean specially for spaces in my bitmap-font) - and VRAM is mostly really valuable... So the only reasonable thing seems to be: Using an custom mapping on my texture for i.e. UTF-8 characters (so that no space is waste). BUT: This effort seems to be same with use an own proprietary character encoding (so also own order of characters in my texture). In my specially case I got texture space for 4096 different characters and need characters to display latin languages as well as japanese (its a mess with utf-8 that only support generall cjk codepages). Had somebody ever a similiar problem (I really wonder, if not)? If theres already any approach? Edit: The same Problem is described here http://www.tonypottier.info/Unicode_And_Japanese_Kanji/ but it doesnt provide an real solution how to save these bitmapfont mappings to utf-8 space efficent. So any further help is welcome!

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• CUDA Kernel Not Updating Global Variable

  - by Taher Khokhawala

  I am facing the following problem in a CUDA kernel. There is an array "cu_fx" in global memory. Each thread has a unique identifier jj and a local loop variable ii and a local float variable temp. Following code is not working. It is not at all changing cu_fx[jj]. At the end of loop cu_fx[jj] remains 0. ii = 0; cu_fx[jj] = 0; while(ii < l) { if(cu_y[ii] > 0) cu_fx[jj] += (cu_mu[ii]*cu_Kernel[(jj-start_row)*Kernel_w + ii]); else cu_fx[jj] -= (cu_mu[ii]*cu_Kernel[(jj-start_row)*Kernel_w + ii]); ii++; } But when I rewrite it using a temporary variable temp, it works fine. ii = 0; temp = 0; while(ii < l) { if(cu_y[ii] > 0) temp += (cu_mu[ii]*cu_Kernel[(jj-start_row)*Kernel_w + ii]); else temp -= (cu_mu[ii]*cu_Kernel[(jj-start_row)*Kernel_w + ii]); ii++; } cu_fx[jj] = temp; Can somebody please help with this problem. Thanking in advance.

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• Do fluent interfaces significantly impact runtime performance of a .NET application?

  - by stakx

  I'm currently occupying myself with implementing a fluent interface for an existing technology, which would allow code similar to the following snippet: using (var directory = Open.Directory(@"path\to\some\directory")) { using (var file = Open.File("foobar.html").In(directory)) { // ... } } In order to implement such constructs, classes are needed that accumulate arguments and pass them on to other objects. For example, to implement the Open.File(...).In(...) construct, you would need two classes: // handles 'Open.XXX': public static class OpenPhrase { // handles 'Open.File(XXX)': public static OpenFilePhrase File(string filename) { return new OpenFilePhrase(filename); } // handles 'Open.Directory(XXX)': public static DirectoryObject Directory(string path) { // ... } } // handles 'Open.File(XXX).XXX': public class OpenFilePhrase { internal OpenFilePhrase(string filename) { _filename = filename } // handles 'Open.File(XXX).In(XXX): public FileObject In(DirectoryObject directory) { // ... } private readonly string _filename; } That is, the more constituent parts statements such as the initial examples have, the more objects need to be created for passing on arguments to subsequent objects in the chain until the actual statement can finally execute. Question: I am interested in some opinions: Does a fluent interface which is implemented using the above technique significantly impact the runtime performance of an application that uses it? With runtime performance, I refer to both speed and memory usage aspects. Bear in mind that a potentially large number of temporary, argument-saving objects would have to be created for only very brief timespans, which I assume may put a certain pressure on the garbage collector. If you think there is significant performance impact, do you know of a better way to implement fluent interfaces?

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• Python subprocess Popen.communicate() equivalent to Popen.stdout.read()?

  - by Christophe

  Very specific question (I hope): What are the differences between the following three codes? (I expect it to be only that the first does not wait for the child process to be finished, while the second and third ones do. But I need to be sure this is the only difference...) I also welcome other remarks/suggestions (though I'm already well aware of the shell=True dangers and cross-platform limitations) Note that I already read Python subprocess interaction, why does my process work with Popen.communicate, but not Popen.stdout.read()? and that I do not want/need to interact with the program after. Also note that I already read Alternatives to Python Popen.communicate() memory limitations? but that I didn't really get it... First code: from subprocess import Popen, PIPE def exe_f(command='ls -l', shell=True): "Function to execute a command and return stuff" process = Popen(command, shell=shell, stdout=PIPE, stderr=PIPE) stdout = process.stdout.read() stderr = process.stderr.read() return process, stderr, stdout Second code: from subprocess import Popen, PIPE from subprocess import communicate def exe_f(command='ls -l', shell=True): "Function to execute a command and return stuff" process = Popen(command, shell=shell, stdout=PIPE, stderr=PIPE) (stdout, stderr) = process.communicate() return process, stderr, stdout Third code: from subprocess import Popen, PIPE from subprocess import wait def exe_f(command='ls -l', shell=True): "Function to execute a command and return stuff" process = Popen(command, shell=shell, stdout=PIPE, stderr=PIPE) code = process.wait() stdout = process.stdout.read() stderr = process.stderr.read() return process, stderr, stdout Thanks.

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• Why doesn't gcc remove this check of a non-volatile variable?

  - by Thomas

  This question is mostly academic. I ask out of curiosity, not because this poses an actual problem for me. Consider the following incorrect C program. #include <signal.h> #include <stdio.h> static int running = 1; void handler(int u) { running = 0; } int main() { signal(SIGTERM, handler); while (running) ; printf("Bye!\n"); return 0; } This program is incorrect because the handler interrupts the program flow, so running can be modified at any time and should therefore be declared volatile. But let's say the programmer forgot that. gcc 4.3.3, with the -O3 flag, compiles the loop body (after one initial check of the running flag) down to the infinite loop .L7: jmp .L7 which was to be expected. Now we put something trivial inside the while loop, like: while (running) putchar('.'); And suddenly, gcc does not optimize the loop condition anymore! The loop body's assembly now looks like this (again at -O3): .L7: movq stdout(%rip), %rsi movl $46, %edi call _IO_putc movl running(%rip), %eax testl %eax, %eax jne .L7 We see that running is re-loaded from memory each time through the loop; it is not even cached in a register. Apparently gcc now thinks that the value of running could have changed. So why does gcc suddenly decide that it needs to re-check the value of running in this case?

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• error detection/correction/recovery in serial protocols

  - by Jason S

  I have some designing to do for a serial protocol and am running into some questions that I figure must have been considered elsewhere. So I'm wondering if there are some recommendations for best practices in designing serial protocols. (Please either state a fact that is easily verifiable, or cite a reputable source if you make a claim.) General recommendations for websites/books are also welcome. In particular I have to deal with issues like parsing a stream of bytes into packets verifying a packet is correct (easy with a CRC, for instance) identifying reasonable types of errors that can occur (e.g. in a point-to-point serial stream, sporadic single bit errors, and dropped series of bytes, are both likely, but extra phantom bytes are unlikely; whereas with a record stored in flash memory or on a disk drive the types of errors that predominate are different) error correction or recovery (if I detect an error in a packet, can I correct it? If not, can I resync to the boundary of the next packet?) how to make variable-length packets robust to error correction / recovery. Any suggestions?

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• bug in NHunspell spelling checker

  - by Nikhil K

  I am using NHunspell for checking spelling.I added NHunspell.dll as a reference to my asp.net page.I added the namespace System.NHunspell. The problem i am facing is related to IDisposible. I put the downloaded code of NHunspell inside the button event. protected void Button1_Click(object sender, EventArgs e) { using (Hunspell hunspell = new Hunspell("en_us.aff", "en_us.dic")) { bool correct = hunspell.Spell("Recommendation"); var suggestions = hunspell.Suggest("Recommendatio"); foreach (string suggestion in suggestions) { Console.WriteLine("Suggestion is: " + suggestion); } } // Hyphen using (Hyphen hyphen = new Hyphen("hyph_en_us.dic")) { var hyphenated = hyphen.Hyphenate("Recommendation"); } * using (MyThes thes = new MyThes("th_en_us_new.idx", "th_en_us_new.dat")) { using (Hunspell hunspell = new Hunspell("en_us.aff", "en_us.dic")) { ThesResult tr = thes.Lookup("cars", hunspell); foreach (ThesMeaning meaning in tr.Meanings) { Console.WriteLine(" Meaning: " + meaning.Description); foreach (string synonym in meaning.Synonyms) { Console.WriteLine(" Synonym: " + synonym); } } } } The * shown above is the line of error.The error is: " type used in a using statement must be implicitly convertible to 'System.IDisposable'". Also there is a warning on that line :"'NHunspell.MyThes.MyThes(string, string)' is obsolete: 'idx File is not longer needed, MyThes works completely in memory'"; Can any one help me to correct this???

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• working with large sprite sheets on iphone

  - by lukya

  Hi All, I am trying to use sprite sheet animation in my application. The first POC with a small sprite sheet worked fine but as i change the sprite sheet to a bigger one, i get "check_safe_call: could not restore current frame" warning and the application quits. A quick search revealed that this problem meant my app is taking too much memory or the image is too huge in dimension. My image is 4.9 Mb and dimensions are 6720 * 10080 (oops!!). i read that iphone allows maximum 3 Mb image with dimensions up to 1024 * 1024. Also that the sprite sheet image dimensions should be a power of two. So please let me know how i can use a sprite sheet this big. One approach could be to cut the sprite sheet into many smaller sprite sheets and use them one at a time. Please suggest if you know any other/better approach to accommodate bigger sprite sheets and whether the problem with my sprite sheet is size (4.9 Mb) OR dimensions (6720 * 10080). (Just FYI, i am not trying to play a movie so using MP4 file instead is not an option for me. i need to animate the sprite sheet based on accelerometer input and i have been able to achieve that in my POC with smaller sprite sheet.) Thanks, Swapnil

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• Is there a fast alternative to creating a Texture2D from a Bitmap object in XNA?

  - by Matthew Bowen

  I've looked around a lot and the only methods I've found for creating a Texture2D from a Bitmap are: using (MemoryStream s = new MemoryStream()) { bmp.Save(s, System.Drawing.Imaging.ImageFormat.Png); s.Seek(0, SeekOrigin.Begin); Texture2D tx = Texture2D.FromFile(device, s); } and Texture2D tx = new Texture2D(device, bmp.Width, bmp.Height, 0, TextureUsage.None, SurfaceFormat.Color); tx.SetData<byte>(rgbValues, 0, rgbValues.Length, SetDataOptions.NoOverwrite); Where rgbValues is a byte array containing the bitmap's pixel data in 32-bit ARGB format. My question is, are there any faster approaches that I can try? I am writing a map editor which has to read in custom-format images (map tiles) and convert them into Texture2D textures to display. The previous version of the editor, which was a C++ implementation, converted the images first into bitmaps and then into textures to be drawn using DirectX. I have attempted the same approach here, however both of the above approaches are significantly too slow. To load into memory all of the textures required for a map takes for the first approach ~250 seconds and for the second approach ~110 seconds on a reasonable spec computer. If there is a method to edit the data of a texture directly (such as with the Bitmap class's LockBits method) then I would be able to convert the custom-format images straight into a Texture2D and hopefully save processing time. Any help would be very much appreciated. Thanks

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• When should I be cautious using data binding in .NET?

  - by Ben McCormack

  I just started working on a small team of .NET programmers about a month ago and recently got in a discussion with our team lead regarding why we don't use databinding at all in our code. Every time we work with a data grid, we iterate through a data table and populate the grid row by row; the code usually looks something like this: Dim dt as DataTable = FuncLib.GetData("spGetTheData ...") Dim i As Integer For i = 0 To dt.Rows.Length - 1 '(not sure why we do not use a for each here)' gridRow = grid.Rows.Add() gridRow(constantProductID).Value = dt("ProductID").Value gridRow(constantProductDesc).Value = dt("ProductDescription").Value Next '(I am probably missing something in the code, but that is basically it)' Our team lead was saying that he got burned using data binding when working with Sheridan Grid controls, VB6, and ADO recordsets back in the nineties. He's not sure what the exact problem was, but he remembers that binding didn't work as expected and caused him some major problems. Since then, they haven't trusted data binding and load the data for all their controls by hand. The reason the conversation even came up was because I found data binding to be very simple and really liked separating the data presentation (in this case, the data grid) from the in-memory data source (in this case, the data table). "Loading" the data row by row into the grid seemed to break this distinction. I also observed that with the advent of XAML in WPF and Silverlight, data-binding seems like a must-have in order to be able to cleanly wire up a designer's XAML code with your data. When should I be cautious of using data-binding in .NET?

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• Javascript force GC collection? / Forcefully free object?

  - by plash

  I have a js function for playing any given sound using the Audio interface (creating a new instance for every call). This works quite well, until about the 32nd call (sometimes less). This issue is directly related to the release of the Audio instance. I know this because I've allowed time for the GC in Chromium to run and it will allow me to play another 32 or so sounds again. Here's an example of what I'm doing: <html><head> <script language="javascript"> function playSound(url) { snd = new Audio(url); snd.play(); delete snd; snd = null; } </script> </head> <body> <a href="#" onclick="playSound('blah.mp3');">Play sound</a> </body></html> I also have this, which works well for pages that have less than 32 playSound calls: var AudioPlayer = { cache: {}, play: function(url) { if (!AudioPlayer.cache[url]) AudioPlayer.cache[url] = new Audio(url); AudioPlayer.cache[url].play(); } }; But this will not work for what I want to do (dynamically replace a div with other content (from separate files), which have even more sounds on them - 1. memory usage would easily skyrocket, 2. many sounds will never play). I need a way to release the sound immediately. Is it possible to do this? I have found no free/close/unload method for the Audio interface. The pages will be viewed locally, so the constant loading of sounds is not a big factor at all (and most sounds are rather short).

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• Segmentation fault on writing char to char* address

  - by Lukas Dojcak

  hi guys, i've got problem with my little C program. Maybe you could help me. char* shiftujVzorku(char* text, char* pattern, int offset){ char* pom = text; int size = 0; int index = 0; while(*(text + size) != '\0'){ size++; } while(*(pom + index) != '\0'){ if(overVzorku(pom + index, pattern)){ while(*pattern != '\0'){ //vyment *pom s *pom + offset if(pom + index + offset < text + size){ char x = *(pom + index + offset); char y = *(pom + index); int adresa = *(pom + index + offset); *(pom + index + offset) = y; <<<<<< SEGMENTATION FAULT *(pom + index) = x; //*pom = *pom - *(pom + offset); //*(pom + offset) = *(pom + offset) + *pom; //*pom = *(pom + offset) - *pom; } else{ *pom = *pom - *(pom + offset - size); *(pom + offset - size) = *(pom + offset - size) + *pom; *pom = *(pom + offset - size) - *pom; } pattern++; } break; } index++; } return text; } Isn't important what's the programm doing. Mayby there's lot of bugs. But, why do I get SEGMENTATION FAULT (for destination see code) at this line? I'm, trying to write some char value to memory space, with help of address "pom + offset + index". Thanks for everything helpful. :)

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• Which key value store is the most promising/stable?

  - by Mike Trpcic

  I'm looking to start using a key/value store for some side projects (mostly as a learning experience), but so many have popped up in the recent past that I've got no idea where to begin. Just listing from memory, I can think of: CouchDB MongoDB Riak Redis Tokyo Cabinet Berkeley DB Cassandra MemcacheDB And I'm sure that there are more out there that have slipped through my search efforts. With all the information out there, it's hard to find solid comparisons between all of the competitors. My criteria and questions are: (Most Important) Which do you recommend, and why? Which one is the fastest? Which one is the most stable? Which one is the easiest to set up and install? Which ones have bindings for Python and/or Ruby? Edit: So far it looks like Redis is the best solution, but that's only because I've gotten one solid response (from ardsrk). I'm looking for more answers like his, because they point me in the direction of useful, quantitative information. Which Key-Value store do you use, and why? Edit 2: If anyone has experience with CouchDB, Riak, or MongoDB, I'd love to hear your experiences with them (and even more so if you can offer a comparative analysis of several of them)

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• Load Spikes on a Apache MySQL Server with Wordpress MU

  - by Vikram Goyal

  Hi there, I am trying to investigate the reasons for some mysterious load spikes on a Linux Apache server (2.2.14) running PHP 5.2.9 on a dedicated server with enough processing power and memory. My primary web application is a Wordpress MU (2.9.2) installation. I have investigated and ruled out DOS attack, MySQL or Apache configuration issues. The log files don't give me anything of interest, except to tell me that there is severe load. The load (which can go up to 100) just seems to come and go. It helps that I have a script that checks every 3 minutes for the load, and restarts Apache. Restarting it helps, and the server comes back, till it happens again. There seems to be no set time frame, or visitor numbers on the site that can trigger this. Even a low number of concurrent visitors (20) can trigger it. I am almost convinced that there is a rewrite loop somewhere that is causing Apache to go mad. Apache is trying to serve something that is causing it to spawn more and more processes till it keels over. My question is: Given that I am convinced that this is a rewrite issue or something similar, how can I try and figure out what the issue is? What should I monitor? Apache logs are voluminous, and not very helpful. Of course, if this is not the issue, then at least knowing what to look for will help me eliminate this as an issue and look for something else. Thanks! Vikram

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• Passing data between ViewControllers versus doing local Fetch in each VC

  - by Tofrizer

  Hi All, I'm developing an iPhone app using Core Data and I'm looking for some general advice and recommendations on whether its acceptable to pass data between ViewControllers versus doing a local fetch in each ViewController as you navigate to it. Ordinarily I would say it all depends on various factors (e.g. performance etc) but the passing data approach is so prevalent in my app and I'm spooked by all the stories about Apple rejecting apps because of not conforming to their standard guidelines. So let me put another way -- is it non-standard to pass data between VC's? The reason I pass data so much is because each ViewController is just another view on to data present in my object model / graph. Once I have a handle on my first object in the first view controller (which I of course do have to fetch), I can use the existing object composition / relationships to drill down into the next level of detail into data and so I just pass these objects to the next VC. Separately, one possible downside with this passing-data-to-each-VC approach is I don't benefit from (what I perceive to be) the optimisation/benefits that NSFetchedResultsController provides in terms of efficient memory usage and section handling. My app is read-only but I do have one table with 5000 rows and I'm curious if I am missing out on NSFetchedResultsController benefits. Any thoughts on this as well? Can I somehow still benefit from NSFetchedResultsController goodness without having to do a full fetch (as I would have already passed in the data from my previous VC)? Thanks a lot.

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• How to delete a QProcess instance correctly?

  - by Kopfschmerzen

  Hi everyone! I have a class looking like this: class FakeRunner : public QObject { Q_OBJECT private: QProcess* proc; public: FakeRunner(); int run() { if (proc) return -1; proc = new QProcess(); QStringList args; QString programName = "fake.exe"; connect(comp, SIGNAL(started()), this, SLOT(procStarted())); connect(comp, SIGNAL(error(QProcess::ProcessError)), this, SLOT(procError(QProcess::ProcessError))); connect(comp, SIGNAL(finished(int, QProcess::ExitStatus)), this, SLOT(procFinished(int, QProcess::ExitStatus))); proc->start(programName, args); return 0; }; private slots: void procStarted() {}; void procFinished(int, QProcess::ExitStatus) {}; void procError(QProcess::ProcessError); } Since "fake.exe" does not exist on my system, proc emits the error() signal. If I handle it like following, my program crashes: void FakeRunner::procError(QProcess::ProcessError rc) { delete proc; proc = 0; } It works well, though, if I don't delete the pointer. So, the question is how (and when) should I delete the pointer to QProcess? I believe I have to delete it to avoid a memory leak. FakeRunner::run() can be invoked many times, so the leak, if there is one, will grow. Thanks!

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• Reading Certificates on iOS Problem

  - by David Schiefer

  I am trying to read certificates from various URLs in iOS. My code however is not working well - the array that should return the information I need always returns null. What am I missing? - (void)findCertificate:(NSString *)url { NSInputStream*input = [[NSInputStream inputStreamWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:@"https://store.writeitstudios.com"]]] retain]; [input setDelegate:self]; [input scheduleInRunLoop:[NSRunLoop mainRunLoop] forMode:NSDefaultRunLoopMode]; [input open]; NSLog(@"Status: %i",[input streamStatus]); } - (void)stream:(NSStream *)aStream handleEvent:(NSStreamEvent)eventCode { NSLog(@"handle Event: %i",eventCode); if (eventCode == NSStreamStatusOpen) { NSArray *certificates = (NSArray*)CFReadStreamCopyProperty((CFReadStreamRef)aStream, kCFStreamPropertySSLPeerCertificates); NSLog(@"Certs: %@",CFReadStreamCopyProperty((CFReadStreamRef)aStream, kCFStreamPropertySSLPeerCertificates)); if ([certificates count] > 0) { SecCertificateRef certificate = (SecCertificateRef)[certificates objectAtIndex:0]; NSString *description = (NSString*)SecCertificateCopySubjectSummary(certificate); NSData *data = (NSData *)SecCertificateCopyData(certificate); NSLog(@"Description: %@",description); } } } And yes, I am aware that I am leaking memory. This is just a snippet.

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• "Downloading" a computed value form JavaScript

  - by Travis Jensen

  I'm hoping you can prove me wrong here (please, please, please! ;). I have a situation where I need to download encrypted data from a Server D (for "Data"). Server K (for "Key") has the encryption key. For security sake, I would really prefer that Server D never know the key that Server K knows. What I want is my client (e.g. your browser) to connect to Server D for the data and Server K for the key and doe the decryption locally so the unencrypted stuff never leaves your computer. I can do this fine for text areas in the dom by replacing the contents of the HTML. However, sometimes, I would like to do larger files that I stream to the file system. For instance, perhaps I want to encrypt a movie and decrypt it and stream the contents to the my video player. I am not a JavaScript guru by any stretch, especially when it comes to the edge cases of things like the security sandbox. For Small D, I can handle the decryption, but I don't know how to save the decrypted file. Large D seems problematic as memory runs out. Anybody have any ideas that don't involve native plugins? Thanks!

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• Optimizing MySQL for ALTER TABLE of InnoDB

  - by schuilr

  Sometime soon we will need to make schema changes to our production database. We need to minimize downtime for this effort, however, the ALTER TABLE statements are going to run for quite a while. Our largest tables have 150 million records, largest table file is 50G. All tables are InnoDB, and it was set up as one big data file (instead of a file-per-table). We're running MySQL 5.0.46 on an 8 core machine, 16G memory and a RAID10 config. I have some experience with MySQL tuning, but this usually focusses on reads or writes from multiple clients. There is lots of info to be found on the Internet on this subject, however, there seems to be very little information available on best practices for (temporarily) tuning your MySQL server to speed up ALTER TABLE on InnoDB tables, or for INSERT INTO .. SELECT FROM (we will probably use this instead of ALTER TABLE to have some more opportunities to speed things up a bit). The schema changes we are planning to do is adding a integer column to all tables and make it the primary key, instead of the current primary key. We need to keep the 'old' column as well so overwriting the existing values is not an option. What would be the ideal settings to get this task done as quick as possible?

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• OpenGL equivalent of GDI's HatchBrush or PatternBrush?

  - by Ptah- Opener of the Mouth

  I have a VB6 application (please don't laugh) which does a lot of drawing via BitBlt and the standard VB6 drawing functions. I am running up against performance issues (yes, I do the regular tricks like drawing to memory). So, I decided to investigate other ways of drawing, and have come upon OpenGL. I've been doing some experimenting, and it seems straightforward to do most of what I want; the application mostly only uses very simple drawing -- relatively large 2D rectangles of solid colors and such -- but I haven't been able to find an equivalent to something like a HatchBrush or PatternBrush. More specifically, I want to be able to specify a small monochrome pixel pattern, choose a color, and whenever I draw a polygon (or whatever), instead of it being solid, have it automatically tiled with that pattern, not translated or rotated or skewed or stretched, with the "on" bits of the pattern showing up in the specified color, and the "off" bits of the pattern left displaying whatever had been drawn under the area that I am now drawing on. Obviously I could do all the calculations myself. That is, instead of drawing as a polygon which will somehow automatically be tiled for me, I could calculate all of the lines or pixels or whatever that actually need to be drawn, then draw them as lines or pixels or whatever. But is there an easier way? Like in GDI, where you just say "draw this polygon using this brush"? I am guessing that "textures" might be able to accomplish what I want, but it's not clear to me (I'm totally new to this and the documentation I've found is not entirely obvious); it seems like textures might skew or translate or stretch the pattern, based upon the vertices of the polygon? Whereas I want the pattern tiled. Is there a way to do this, or something like it, other than brute force calculation of exactly the pixels/lines/whatever that need to be drawn? Thanks in advance for any help.

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• pthread condition variables on Linux, odd behaviour.

  - by janesconference

  Hi. I'm synchronizing reader and writer processes on Linux. I have 0 or more process (the readers) that need to sleep until they are woken up, read a resource, go back to sleep and so on. Please note I don't know how many reader processes are up at any moment. I have one process (the writer) that writes on a resource, wakes up the readers and does its business until another resource is ready (in detail, I developed a no starve reader-writers solution, but that's not important). To implement the sleep / wake up mechanism I use a Posix condition value, pthread_cond_t. The clients call a pthread_cond_wait() on the variable to sleep, while the server does a pthread_cond_broadcast() to wake them all up. As the manual says, I surround these two calls with a lock/unlock of the associated pthread mutex. The condition variable and the mutex are initialized in the server and shared between processes through a shared memory area (because I'm not working with threads, but with separate processes) an I'm sure my kernel / syscall support it (because I checked _POSIX_THREAD_PROCESS_SHARED). What happens is that the first client process sleeps and wakes up perfectly. When I start the second process, it blocks on its pthread_cond_wait() and never wakes up, even if I'm sure (by the logs) that pthread_cond_broadcast() is called. If I kill the first process, and launch another one, it works perfectly. In other words, the condition variable pthread_cond_broadcast() seems to wake up only one process a time. If more than one process wait on the very same shared condition variable, only the first one manages to wake up correctly, while the others just seem to ignore the broadcast. Why this behaviour? If I send a pthread_cond_broadcast(), every waiting process should wake up, not just one (and, however, not always the same one).

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• Our Flash Streaming Player Occasionally Stutters like a Skipping CD after a Period of Time

  - by Jonathan Fritz

  We offer a streaming player for a number of our clients, who are responsible for their providing us with their own audio streams. We have written a very simple flash player that can play all of the streams that we support (icecast/shoutcast/live365/mp3 over http/etc). Unfortunately, we have found that when listening, our player sometimes begins to stutter (like a skipping cd), sometimes after only 10 minutes, and sometimes after an hour of listening. We have noticed this behaviour in firefox on both linux and windows. Does anybody know anything about this problem? We know that flash isn't ideal for infinite streams of audio, but it's about all that we can find that's on every platform out there. If anybody can suggest a solution to our problem, I'll be your friend forever. Here is a link to the live player: http://cr-jf.jfritz.02.dev.wecreate.com/streaming/player_v5/ Note that you'll need to test in a browser that isn't IE, because we use WMP in IE, and that the JavaScript on the page will cause the player to unload and re-load once an hour because of memory issues. Because I can only put one hyperlink in a post, I'll add a link to the player source code as a comment. Thanks all!

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