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  • How to mmap the stack for the clone() system call on linux?

    - by Joseph Garvin
    The clone() system call on Linux takes a parameter pointing to the stack for the new created thread to use. The obvious way to do this is to simply malloc some space and pass that, but then you have to be sure you've malloc'd as much stack space as that thread will ever use (hard to predict). I remembered that when using pthreads I didn't have to do this, so I was curious what it did instead. I came across this site which explains, "The best solution, used by the Linux pthreads implementation, is to use mmap to allocate memory, with flags specifying a region of memory which is allocated as it is used. This way, memory is allocated for the stack as it is needed, and a segmentation violation will occur if the system is unable to allocate additional memory." The only context I've ever heard mmap used in is for mapping files into memory, and indeed reading the mmap man page it takes a file descriptor. How can this be used for allocating a stack of dynamic length to give to clone()? Is that site just crazy? ;) In either case, doesn't the kernel need to know how to find a free bunch of memory for a new stack anyway, since that's something it has to do all the time as the user launches new processes? Why does a stack pointer even need to be specified in the first place if the kernel can already figure this out?

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  • flow 2 columns of text automatically with CSS

    - by Joseph Mastey
    I have the code similar to the following: <p>This is paragraph 1. Lorem ipsum ... </p> <p>This is paragraph 2. Lorem ipsum ... </p> <p>This is paragraph 3. Lorem ipsum ... </p> <p>This is paragraph 4. Lorem ipsum ... </p> <p>This is paragraph 5. Lorem ipsum ... </p> <p>This is paragraph 6. Lorem ipsum ... </p> I'd like to, without markup if possible, cause this text to flow into two columns (1-3 on the left, 4-6 on the right). The reason for my hesitation to add a column using a <div> is that this text is entered by the client via a WYSIWYG editor, so any elements I inject are likely to be killed later on inexplicably. Thanks, Joe

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  • Opening XNA Xbox 360 assemblies in Reflector

    - by David Brown
    I'd like to get a look at the differences between the Xbox 360 and Windows XNA assemblies. I know the 360 runs the .NET Compact Framework and I was under the impression that Reflector could read CF assemblies, but when I open them, all of the methods are blank and no internal classes are shown. Is this done on purpose, or is it a limitation of Reflector? Is there another way to see how the Xbox 360 XNA assemblies work?

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  • nHibernate persist IList<DayOfWeek>

    - by Charlie Brown
    Is it possible to persist an IList<DayOfWeek> using nHibernate? public class Vendor { public virtual IList<DayOfWeek> OrderDays { get; private set; } } If not, what are some common solutions; creating a class for OrderDays?, using an IList<string>?

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  • Python re.sub MULTILINE caret match

    - by cdleary
    The Python docs say: re.MULTILINE: When specified, the pattern character '^' matches at the beginning of the string and at the beginning of each line (immediately following each newline)... By default, '^' matches only at the beginning of the string... So what's going on when I get the following unexpected result? >>> import re >>> s = """// The quick brown fox. ... // Jumped over the lazy dog.""" >>> re.sub('^//', '', s, re.MULTILINE) ' The quick brown fox.\n// Jumped over the lazy dog.'

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  • Why does one loop take longer to detect a shared memory update than another loop?

    - by Joseph Garvin
    I've written a 'server' program that writes to shared memory, and a client program that reads from the memory. The server has different 'channels' that it can be writing to, which are just different linked lists that it's appending items too. The client is interested in some of the linked lists, and wants to read every node that's added to those lists as it comes in, with the minimum latency possible. I have 2 approaches for the client: For each linked list, the client keeps a 'bookmark' pointer to keep its place within the linked list. It round robins the linked lists, iterating through all of them over and over (it loops forever), moving each bookmark one node forward each time if it can. Whether it can is determined by the value of a 'next' member of the node. If it's non-null, then jumping to the next node is safe (the server switches it from null to non-null atomically). This approach works OK, but if there are a lot of lists to iterate over, and only a few of them are receiving updates, the latency gets bad. The server gives each list a unique ID. Each time the server appends an item to a list, it also appends the ID number of the list to a master 'update list'. The client only keeps one bookmark, a bookmark into the update list. It endlessly checks if the bookmark's next pointer is non-null ( while(node->next_ == NULL) {} ), if so moves ahead, reads the ID given, and then processes the new node on the linked list that has that ID. This, in theory, should handle large numbers of lists much better, because the client doesn't have to iterate over all of them each time. When I benchmarked the latency of both approaches (using gettimeofday), to my surprise #2 was terrible. The first approach, for a small number of linked lists, would often be under 20us of latency. The second approach would have small spats of low latencies but often be between 4,000-7,000us! Through inserting gettimeofday's here and there, I've determined that all of the added latency in approach #2 is spent in the loop repeatedly checking if the next pointer is non-null. This is puzzling to me; it's as if the change in one process is taking longer to 'publish' to the second process with the second approach. I assume there's some sort of cache interaction going on I don't understand. What's going on?

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  • Algorithm for measuring distance between disordered sequences of strings

    - by Kinopiko
    The Levenshtein distance gives us a way to calculate the distance between two similar strings in terms of disordered individual characters: quick brown fox quikc brown fax The Levenshtein distance = 3. What is a similar algorithm for the distance between two strings with similar subsequences? For example, in quickbrownfox brownquickfox the Levenshtein distance is 10, but this takes no account of the fact that the strings have two similar subsequences, which makes them more "similar" than completely disordered words like quickbrownfox qburiocwknfox and yet this completely disordered version has a Levenshtein distance of eight. What distance measures exist which take the length of subsequences into account, without assuming that the subsequences can be easily broken into distinct words?

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  • Update panel and usercontrols

    - by Charlie Brown
    I have two web user controls nested inside of an update panel. The events inside the user controls do not appear to trigger the panel. For testing, I have set the method the fires to sleep for 3 seconds, and added an update progress panel to the page. The update progress panel never comes up and the page reflashes as usual. The user controls work correctly and do what they need to do, but I would like to make them ajaxy and pretty. Is there a special method for adding usercontrols to an update so the postback works correctly? <asp:ScriptManager ID="ScriptManager1" runat="server"> </asp:ScriptManager> <asp:UpdateProgress ID="UpdateProgress1" runat="server" DisplayAfter="100"> <ProgressTemplate> UPDATING...</ProgressTemplate> </asp:UpdateProgress> <asp:UpdatePanel ID="UpdatePanel1" runat="server"> <ContentTemplate> <div id="order"> <keg:BeerList runat="server" ID="uxBeerList" /> <kegcart:ShoppingCart runat="server" ID="uxCustomerCart" /> <br class="clearfloat" /> </div> </ContentTemplate> </asp:UpdatePanel> Protected Sub uxBeerList_AddItem(ByVal item As KegData.IOrderableItem) Handles uxBeerList.AddItem uxCustomerCart.AddItemToOrder(item) System.Threading.Thread.Sleep(5000) End Sub

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  • Use php to zip large files

    - by Joseph
    Hi, I have a php form that has a bunch of checkboxes that all contain links to files. Once a user clicks on which checkboxes (files) they want, it then zips up the files and forces a download. I got a simple php zip force download to work, but when one of the files is huge or if someone lets say selects the whole list to zip up and download, my server errors out. I understand that I can increase the server size, but are there any other ways? Thanks!

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  • mod rewritten directory shorten

    - by Joseph
    I can only find mod rewrite examples/tutorials for query's, so can someone help me with this. I would like this http://website.tld/Folder1/Folder2/Folder3/Folder4/Folder5/File.exten to be transformed into http://website.tld/Folder4/File.exten Folder4 and Folder5 are multiple directories, while Folder 1-3 stay the same. Also File.exten also should be changeable in the rewrite. thanks.

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  • What does this code mean?

    - by joseph
    Hello, I do not know, what is function of code lookups.singleton in code below public class ProjectNode extends AbstractNode { public ProjectNode(MainProject obj, ProjectsChildren children) { super (children, Lookups.singleton(obj)); setDisplayName ( obj.getName()); } }

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  • A JTAG emulator for use with a Hawkboard and OpenOCD?

    - by David Brown
    I'd like to try bare metal ARM programming with the Hawkboard, but the deployment process looks awful. I'm totally new to this, so I could be misunderstanding the instructions, but it appears that I have to use a program called AISgen to convert the binary file, then boot with u-Boot over UART and copy the AIS binary into memory. Not only is that a lot of stuff to do every time I make a change, it also doesn't give me the ability to debug with GDB. The best solution for this that I can find is JTAG. But the prices for these JTAG emulators look ridiculous. I'm not even sure which ones will work with the Hawkboard and which ones won't. So far, my best bet appears to be the Flyswatter, but the pin layout is different. Basically, I need something that's relatively cheap and works with the Hawkboard and OpenOCD. Any suggestions? Or is there another way I could do this, perhaps?

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  • Why does Font.registerFont throw an error the second time a swf is loaded?

    - by Al Brown
    I've found an issue (in flash cs5) when using TLFTextfields and fonts shared at runtime, and I wondered if anyone has a solution. Here's the scenario. Fonts.swf: library for fonts (runtime shared DF4) Popup.swf: popup with a TLFTextfield (with text in it) using a font from Fonts.swf Main.swf : the main swf with a button that loads and unloads Popup.swf (using Loader or SafeLoader give the same results) Nice and simple, Run main.swf, click button and the popup appears with the text. Click the button again to remove the popup. All well and good now click the button again and I get the following error. ArgumentError: Error #1508: The value specified for argument font is invalid. at flash.text::Font$/registerFont() at Popup_fla::MainTimeline()[Popup_fla.MainTimeline::MainTimeline:12] I'm presuming it's happening because the font is already registered (checked when clicking before the load). Does anyone know how to get past this? If you are wondering here's my Main.as package { import fl.controls.Button; import flash.display.Loader; import flash.display.Sprite; import flash.events.Event; import flash.events.IOErrorEvent; import flash.events.MouseEvent; import flash.events.UncaughtErrorEvent; import flash.net.URLRequest; import flash.text.Font; public class Main extends Sprite { public var testPopupBtn:Button; protected var loader:Loader; public function Main() { trace("Main.Main()"); testPopupBtn.label = "open"; testPopupBtn.addEventListener(MouseEvent.CLICK, testClickHandler); } protected function testClickHandler(event:MouseEvent):void { trace("Main.testClickHandler(event)"); if(loader) { testPopupBtn.label = "open"; this.removeChild(loader); //loader.unloadAndStop(); loader = null; }else{ testPopupBtn.label = "close"; trace("Registered Fonts -->"); var fonts:Array = Font.enumerateFonts(false); for each (var font:Font in fonts) { trace("\t",font.fontName, font.fontStyle, font.fontType); } trace("<--"); loader = new Loader(); loader.uncaughtErrorEvents.addEventListener(UncaughtErrorEvent.UNCAUGHT_ERROR, uncaughtErrorHandler); this.addChild(loader); try{ loader.load(new URLRequest("Popup.swf")); }catch(e:*){ trace(e); } } } private function uncaughtErrorHandler(event:UncaughtErrorEvent):void { trace("Main.uncaughtErrorHandler(event)", event); } } }

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  • how to load an image to a grid using pygame, instead of just using a fill color?

    - by yao jiang
    I am trying to create a "map of a city" using pygame. I want to be able to put images of buildings in specific grid coords rather than just filling them in with a color. This is how I am creating this map grid: def clear(): for r in range(rows): for c in range(rows): if r%3 == 1 and c%3 == 1: color = brown; grid[r][c] = 1; else: color = white; grid[r][c] = 0; pygame.draw.rect(screen, color, [(margin+width)*c+margin, (margin+height)*r+margin, width, height]) pygame.display.flip(); Now how do I put images of buildings in those brown colored grids at those specific locations? I've tried some of the samples online but can't seem to get them to work. Any help is appreciated. If anyone have a good source for free sprites that I can use for pygame, please let me know. Thanks!

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  • question regarding rails framework code

    - by Joseph Misiti
    I noticed that the code in the rails framework is using the following convention all over the place: class SomeClass class << self def some function end end end rather than class SomeClass end def SomeClass.function end and class SomeClass def self.somefunction end end What is the reason for this design choice? They all seem to accomplish them same thing

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  • Custom MembershipProvider attempts to pass empty creds after IIS restart

    - by Joseph DeCarlo
    I have a C# custom ASP.Net MembershipProvider. When the user attempts to navigate to another part of the site after IIS is restarted, it doesn't navigate to the login page to collect credentials, but instead attempts to authenticate with empty credentials. Can anyone tell me what I have to do to identify that the new authentication needs to take place and that new creds need to be gathered? I have a complementary custom IHttpModule implementation that allows me to intercept events like BeginRequest and AuthenticateRequest, if that helps.

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  • Rails, if instance is in a scope?

    - by Joseph Silvashy
    I using rails 3 and I can't seem to check if a given instance is in a scope, see here: p = Post.find 6 +----+----------+-------------------------+-------------------------+-------------------------+-----------+ | id | title | publish_date | created_at | updated_at | published | +----+----------+-------------------------+-------------------------+-------------------------+-----------+ | 6 | asfdfdsa | 2010-03-28 22:33:00 UTC | 2010-03-28 22:33:46 UTC | 2010-03-28 22:33:46 UTC | true | +----+----------+-------------------------+-------------------------+-------------------------+-----------+ I have a menu scope which looks like: scope :menu, where("published != ?", false).limit(4) When I run it I get: Post.menu.all +----+------------------+------------------+------------------+-------------------+-----------+ | id | title | publish_date | created_at | updated_at | published | +----+------------------+------------------+------------------+-------------------+-----------+ | 1 | Lorem ipsum | 2010-03-23 07... | 2010-03-23 07... | 2010-03-28 21:... | true | | 2 | fdasf | 2010-03-28 21... | 2010-03-28 21... | 2010-03-28 21:... | true | | 3 | Ruby’s Imple... | 2010-03-28 21... | 2010-03-28 21... | 2010-03-28 21:... | true | | 4 | dsaD | 2010-03-28 22... | 2010-03-28 22... | 2010-03-28 22:... | true | +----+------------------+------------------+------------------+-------------------+-----------+ Which is correct, but if I try to check if p is in the the menu scope using: Post.menu.exists?(p) I get true when it should be false What is the proper way to find out if a given instance of something is in a scope?

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  • Free internet radio station server software with remote broadcasting?

    - by Zachary Brown
    I am in the process of creating an internet radio station, but the two djs I have for it are not able to be in one place. I need for them to be able to login to a web based broadcasting session that still has full functionality. They need to be able to broadcast thier live shows with talk and music. The music will be stroed on the server. I have checked out the Broadwave media streaming server from NCH, but ti does not have the ability to login as a dj from a remote computer. I don't have any money for this, so I need it to be free. If this is not possible, I need it to be cheap!

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  • Can you force a crash if a write occurs to a given memory location with finer than page granularity?

    - by Joseph Garvin
    I'm writing a program that for performance reasons uses shared memory (alternatives have been evaluated, and they are not fast enough for my task, so suggestions to not use it will be downvoted). In the shared memory region I am writing many structs of a fixed size. There is one program responsible for writing the structs into shared memory, and many clients that read from it. However, there is one member of each struct that clients need to write to (a reference count, which they will update atomically). All of the other members should be read only to the clients. Because clients need to change that one member, they can't map the shared memory region as read only. But they shouldn't be tinkering with the other members either, and since these programs are written in C++, memory corruption is possible. Ideally, it should be as difficult as possible for one client to crash another. I'm only worried about buggy clients, not malicious ones, so imperfect solutions are allowed. I can try to stop clients from overwriting by declaring the members in the header they use as const, but that won't prevent memory corruption (buffer overflows, bad casts, etc.) from overwriting. I can insert canaries, but then I have to constantly pay the cost of checking them. Instead of storing the reference count member directly, I could store a pointer to the actual data in a separate mapped write only page, while keeping the structs in read only mapped pages. This will work, the OS will force my application to crash if I try to write to the pointed to data, but indirect storage can be undesirable when trying to write lock free algorithms, because needing to follow another level of indirection can change whether something can be done atomically. Is there any way to mark smaller areas of memory such that writing them will cause your app to blow up? Some platforms have hardware watchpoints, and maybe I could activate one of those with inline assembly, but I'd be limited to only 4 at a time on 32-bit x86 and each one could only cover part of the struct because they're limited to 4 bytes. It'd also make my program painful to debug ;)

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  • What is the life cycle of the XNA GraphicsDevice on the Xbox 360?

    - by David Brown
    I'm working on an XNA project that doesn't use the built-in Game class, mostly for learning purposes (so I can mess with different game loop types, etc). It's only designed for the Xbox 360, because the hardware is consistent and I don't have to worry about compatibility among different PC hardware configurations. So far, it's working well and I can clear the screen to a color, but I'd like to make sure I handle the GraphicsDevice correctly before moving on. What exactly is the life cycle for the GraphicsDevice on the Xbox 360? Is it ever lost or reset automatically? I know that on Windows, it's lost when the window loses focus, but the Xbox obviously doesn't manage focus. It appears to even keep the graphics device when the Guide pops up, which is the closest thing I can find to "losing focus" on the Xbox. I'd like to think it's simply a matter of "fire and forget," which would make a lot of other things much easier (only needing to load content once, for instance). But I want to make sure.

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