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  • Ubuntu Laptop as a wireless hotspot on bridge mode

    - by nixnotwin
    I have a wired router to which my ubuntu laptop connects via ethernet. The wierless NIC of the laptop acts as a wireless hotspot on master mode. I use hostapd fo this. I have bridged eth0 and wlan0, so my wireless clients that connect to my laptop over wifi get ip from the wired router via dhcp, so the devices get registered at the wired router ( and the laptop is just an access point). I use the following commands to get my laptop+accesspoint working: sudo brctl addbr br0 sudo brctl addif br0 eth0 sudo hostapd /etc/hostapd/hostapd.conf & sudo dhclient -d br0 & sudo ifconfig wlan0 192.168.1.15 netmask 255.255.255.0 up sudo brctl addif br0 wlan0 These commands enable me to access internet on my wireless clients and also on the laptop which is acting as wireless accesspoint. But if I reboot the wired router (without rebooting the laptop that is acting as accesspoint), Internet access on the laptop+accesspoint gets lost, but on wireless clients it works fine. Even I have not been able to figure out a command which will reset the laptop interfaces to default settings, so everytime the router reboots, I have to reboot the laptop too to get into default settings so that I can re-enter the above mentioned commands. My first question is How can I have my bridge+accesspoint up and running even-though the router reboots? And is there a command to set the interfaces to a default state? (ifdown -a doesn't work, after issuing the command the bridge still remained).

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  • Ubuntu Laptop as a wireless hotspot on bridge mode

    - by nixnotwin
    I have a wired router to which my ubuntu laptop connects via ethernet. The wierless NIC of the laptop acts as a wireless hotspot on master mode. I use hostapd fo this. I have bridged eth0 and wlan0, so my wireless clients that connect to my laptop over wifi get ip from the wired router via dhcp, so the devices get registered at the wired router ( and the laptop is just an access point). I use the following commands to get my laptop+accesspoint working: sudo brctl addbr br0 sudo brctl addif br0 eth0 sudo hostapd /etc/hostapd/hostapd.conf & sudo dhclient -d br0 & sudo ifconfig wlan0 192.168.1.15 netmask 255.255.255.0 up sudo brctl addif br0 wlan0 These commands enable me to access internet on my wireless clients and also on the laptop which is acting as wireless accesspoint. But if I reboot the wired router (without rebooting the laptop that is acting as accesspoint), Internet access on the laptop+accesspoint gets lost, but on wireless clients it works fine. Even I have not been able to figure out a command which will reset the laptop interfaces to default settings, so everytime the router reboots, I have to reboot the laptop too to get into default settings so that I can re-enter the above mentioned commands. My first question is How can I have my bridge+accesspoint up and running even-though the router reboots? And is there a command to set the interfaces to a default state? (ifdown -a doesn't work, after issuing the command the bridge still remained).

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  • Configuration for httphandler in classic mode

    - by happyspider
    I have to install an httphandler that needs to run on classic mode. I have created an application on the iis that uses a classic apppool and put the handler assembly there. The vendor gave me a configuration in the deployment document that looks like this: <system.web> <globalization requestEncoding="iso-8859-1" responseEncoding="iso-8859-1" /> <httpModules> </httpModules> <httpHandlers> <add verb="*" path="*" type="ProductName.ProductName, ProductName" /> </httpHandlers> </system.web> <system.webServer> <validation validateIntegratedModeConfiguration="false"/> <handlers> <add name="someUnspecificName" path="*" verb="*" modules="IsapiModule" scriptProcessor="C:\Windows\Microsoft.NET\Framework\v2.0.50727\aspnet_isapi.dll" resourceType="Unspecified" requireAccess="None" preCondition="classicMode,runtimeVersionv2.0,bitness32" /> </handlers> </system.webServer> The error I get when requesting a URL on the application is a 404, so I guess the handle is not used at all. Does the configuration look ok for a 64bit system?

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  • Xbox Music ignores Asus FN media keys in Desktop Mode

    - by Ruud Lenders
    I have an Asus PRO64JQ laptop, and I recently upgraded to Windows 8. The FN keys stopped working, so I tried to install default drivers using the CD that came with my laptop. Unfortunately, the CD does not support Windows 8. Asus Support does not help me either. It seems that Asus does not support Windows 8 on my model, since I can't find it in their list of Windows 8 upgradable models. Also, the support page of my laptop does not allow me to select Windows 8 as OS. That's why I'm asking my question here. I fixed (most of) the FN keys by installing the ATKPackage, and I was happy to find out that the media keys (play/pauze, next, previous) works with the Xbox Music app. But the keys only work in the Metro UI. In Desktop Mode, pressing FN+? (play/pause) starts up Windows Media Player. Disabling Windows Media Player through the control panel stops it from popping up, but Xbox Music still only responds to them in the Metro UI. I remember that I had similar problems when I tried to make these media keys to work with iTunes on Windows 7. The fix there was a small iTunes plug-in. So tell me, do you know how to fix my problem? Thanks.

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  • Linux boot - stop the kernel switching to a new framebuffer mode clearing output

    - by Avio
    I'm working on an embedded system (based onUbuntu 12.04 LTS) and I'm customizing its kernel. I'm having some problem with upstart, mountall and plymouth. Nothing unsolvable I suppose, but the real problem is that I can't diagnose properly what's going on because the kernel (or maybe plymouth) changes the video mode in the middle of the boot process. This completely wipes entire lines of log and prevents any debugging of kernel misconfigurations. My Grub2 config seems to be ok with: GRUB_CMDLINE_LINUX="" GRUB_CMDLINE_LINUX_DEFAULT="acpi=force noplymouth" GRUB_GFXMODE=1024x768x32 GRUB_GFXPAYLOAD_LINUX=keep Here is some relevant output of lspci: 00:00.0 Host bridge: Intel Corporation Mobile 945GSE Express Memory Controller Hub (rev 03) 00:02.0 VGA compatible controller: Intel Corporation Mobile 945GSE Express Integrated Graphics Controller (rev 03) 00:02.1 Display controller: Intel Corporation Mobile 945GM/GMS/GME, 943/940GML Express Integrated Graphics Controller (rev 03) And here is the relevant portion of my kernel configuration: CONFIG_AGP=y CONFIG_AGP_INTEL=y CONFIG_VGA_ARB=y CONFIG_VGA_ARB_MAX_GPUS=16 CONFIG_DRM=y CONFIG_DRM_KMS_HELPER=y CONFIG_DRM_I915=y CONFIG_DRM_I915_KMS=y CONFIG_VIDEO_OUTPUT_CONTROL=y CONFIG_FB=y CONFIG_FB_BOOT_VESA_SUPPORT=y CONFIG_FB_CFB_FILLRECT=y CONFIG_FB_CFB_COPYAREA=y CONFIG_FB_CFB_IMAGEBLIT=y CONFIG_FB_MODE_HELPERS=y CONFIG_FB_VESA=y CONFIG_BACKLIGHT_LCD_SUPPORT=y CONFIG_BACKLIGHT_CLASS_DEVICE=y CONFIG_VGA_CONSOLE=y CONFIG_VGACON_SOFT_SCROLLBACK=y CONFIG_VGACON_SOFT_SCROLLBACK_SIZE=640 CONFIG_DUMMY_CONSOLE=y CONFIG_FRAMEBUFFER_CONSOLE=y CONFIG_FRAMEBUFFER_CONSOLE_DETECT_PRIMARY=y CONFIG_FONT_8x8=y CONFIG_FONT_8x16=y CONFIG_LOGO=y CONFIG_LOGO_LINUX_MONO=y CONFIG_LOGO_LINUX_VGA16=y CONFIG_LOGO_LINUX_CLUT224=y Every other custom/stock kernel boot fine with that Grub2 config. What I would like to have is a single flow of messages on a single console (retaining one screen resolution) from the bootup logo till the login prompt. Does anybody know what I have to tweak to achieve this?

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  • Error Installing ruby with RVM Single User mode on Arch Linux

    - by ChrisBurnor
    I've just installed RVM on ArchLinux x64 in single user mode via the recommended install script curl -L https://get.rvm.io | bash -s stable I've also installed all the requirements listed in rvm requirements However, I'm having trouble actually installing any version of ruby. And getting the following error: arch:~ % rvm install 1.9.3 No binary rubies available for: ///ruby-1.9.3-p194. Continuing with compilation. Please read 'rvm mount' to get more information on binary rubies. Fetching yaml-0.1.4.tar.gz to /home/christopher/.rvm/archives % Total % Received % Xferd Average Speed Time Time Time Current Dload Upload Total Spent Left Speed 100 460k 100 460k 0 0 702k 0 --:--:-- --:--:-- --:--:-- 767k Extracting yaml-0.1.4.tar.gz to /home/christopher/.rvm/src Prepare yaml in /home/christopher/.rvm/src/yaml-0.1.4. Configuring yaml in /home/christopher/.rvm/src/yaml-0.1.4. Error running ' ./configure --prefix=/home/christopher/.rvm/usr ', please read /home/christopher/.rvm/log/ruby-1.9.3-p194/yaml/configure.log Compiling yaml in /home/christopher/.rvm/src/yaml-0.1.4. Error running 'make', please read /home/christopher/.rvm/log/ruby-1.9.3-p194/yaml/make.log Please note that it's required to reinstall all rubies: rvm reinstall all --force Installing Ruby from source to: /home/christopher/.rvm/rubies/ruby-1.9.3-p194, this may take a while depending on your cpu(s)... ruby-1.9.3-p194 - #downloading ruby-1.9.3-p194, this may take a while depending on your connection... ruby-1.9.3-p194 - #extracting ruby-1.9.3-p194 to /home/christopher/.rvm/src/ruby-1.9.3-p194 ruby-1.9.3-p194 - #extracted to /home/christopher/.rvm/src/ruby-1.9.3-p194 Skipping configure step, 'configure' does not exist, did autoreconf not run successfully? ruby-1.9.3-p194 - #compiling Error running 'make', please read /home/christopher/.rvm/log/ruby-1.9.3-p194/make.log There has been an error while running make. Halting the installation. The log files are as follows: arch:~ % cat ~/.rvm/log/ruby-1.9.3-p194/yaml/configure.log __rvm_log_command:32: permission denied: arch:~ % cat ~/.rvm/log/ruby-1.9.3-p194/yaml/make.log make: *** No targets specified and no makefile found. Stop. arch:~ % cat ~/.rvm/log/ruby-1.9.3-p194/make.log make: *** No targets specified and no makefile found. Stop.

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  • Does Windows 7 RC handle non Windows Media Center remotes yet?

    - by zillion
    I'm mostly a Linux geek, but while I will be trying to make my first Arch Linux installation in a virtual machine to learn and make my installation script for the true install, I need a simple OS and Windows 7 was better than Windows XP Media Center cause Media Center is outdated on XP. I tested it has a beta but my Hauppauge wintv-pvr usb2 remote wasn't working but the tv-tuner worked well and I haven't tested Windows XP Mode and my printer Epson Stylus Photo R300. Do someone know this hardware and if the XP Mode is easily supported?

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  • External USB disk drive cannot be remounted in Windows XP

    - by jackhab
    I have Maxtor Basics Desktop 1TB external USB drive connected to Windows XP. The dirve's firmware puts it to sleep after 10-20 min of inactivity and then the drive cannot be mounted unless I reset it via power connector. While in sleep mode I can see the device in the Device Manager under both Disk drives and USB sections. Is there a way to get the drive out of sleep mode without hard reset? Thanks

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  • Integration features enabled but drives not available

    - by dsjbirch
    Frustratingly, after a recent update to Windows XP mode integration features, the availability of shared disks from the hosts has been impaired. Does anyone know any kind of workaround or fix (excluding dropbox et al)? I have tried completely uninstalling and reinstalling as per http://www.sevenforums.com/virtualization/63710-refreshing-xp-mode.html#post568715 At one point restarting the machine appeared to have worked, but today again I am without access to my host. Interestingly audio and copy and paste to and from the machine are working.

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  • Thread-safe data structures

    - by Inso Reiges
    Hello, I have to design a data structure that is to be used in a multi-threaded environment. The basic API is simple: insert element, remove element, retrieve element, check that element exists. The structure's implementation uses implicit locking to guarantee the atomicity of a single API call. After i implemented this it became apparent, that what i really need is atomicity across several API calls. For example if a caller needs to check the existence of an element before trying to insert it he can't do that atomically even if each single API call is atomic: if(!data_structure.exists(element)) { data_structure.insert(element); } The example is somewhat awkward, but the basic point is that we can't trust the result of exists call anymore after we return from atomic context (the generated assembly clearly shows a minor chance of context switch between the two calls). What i currently have in mind to solve this is exposing the lock through the data structure's public API. This way clients will have to explicitly lock things, but at least they won't have to create their own locks. Is there a better commonly-known solution to these kinds of problems? And as long as we're at it, can you advise some good literature on thread-safe design? Thank you.

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  • Looking for a lock-free RT-safe single-reader single-writer structure

    - by moala
    Hi, I'm looking for a lock-free design conforming to these requisites: a single writer writes into a structure and a single reader reads from this structure (this structure exists already and is safe for simultaneous read/write) but at some time, the structure needs to be changed by the writer, which then initialises, switches and writes into a new structure (of the same type but with new content) and at the next time the reader reads, it switches to this new structure (if the writer multiply switches to a new lock-free structure, the reader discards these structures, ignoring their data). The structures must be reused, i.e. no heap memory allocation/free is allowed during write/read/switch operation, for RT purposes. I have currently implemented a ringbuffer containing multiple instances of these structures; but this implementation suffers from the fact that when the writer has used all the structures present in the ringbuffer, there is no more place to change from structure... But the rest of the ringbuffer contains some data which don't have to be read by the reader but can't be re-used by the writer. As a consequence, the ringbuffer does not fit this purpose. Any idea (name or pseudo-implementation) of a lock-free design? Thanks for having considered this problem.

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  • multi thread apps crashes in release mode

    - by etzarfat
    Hello, I'm using Visual Studio 2008 (programming in c). I've a weird problem I worte a program that has 2 threads that runs simultaneously, a recording thread (using audio card to record into memory) and a translation thread (using a speech engine to recognize the words). when I run my program in debug mode (aka setting a breakpoint in the code) it runs great, however when I run in debug mode or release mode (outside the visual studio enviroment) it crashes and give me the following exception: "Unhandled exception at 0x7c911129 in LowLevel.exe: 0xC0000005: Access violation reading location 0x014c7245." My stack looks: LowLevel.exe!__set_flsgetvalue() Line 256 + 0xc bytes C LowLevel.exe!_isleadbyte_l(int c=4359676, localeinfo_struct * plocinfo=0x00000001) Line 57 C++ 014b00d8() LowLevel.exe!PlayDateOfExam(int option=1) Line 2240 + 0x7 bytes C++ LowLevel.exe!NSCThread(void * arg=0x00000000) Line 1585 + 0xb bytes C++ kernel32.dll!7c80b729() winmm.dll!76b5b294() I uses the following file in my project "nsc.lib" and WinMM.lib" I'm not really familiar with threads I used a sample (which works great) and built on it. I saw a similiar question year on the forum but I didn't really understand the answers since I'm not familiar with with threads. Can someone help me? Thanks

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  • Adding a Layout to bottom of the screen inside a ScrollView in Landscape mode

    - by andreea
    I have the following layout which works in Portrait mode: the Layout with the id LinearLayout02 is placed at the bottom of the screen. The problem appears when flipping to Lanscape mode, when the #LinearLayout02 is placed at the top of the screen. The question is how do I position #LinearLayout02 at the bottom of the screen in both Portrait and Landscape mode? (This happens on G1 and Xperia) Thank you The following code is placed inside a ScrollView android:layout_height="fill_parent" android:layout_width="fill_parent" android:fillViewport="true" <LinearLayout android:id="@+id/sLayout" android:layout_height="wrap_content" android:layout_width="fill_parent" android:orientation="vertical" android:paddingTop="2dip" android:layout_alignParentTop="true" android:gravity="top" > ..... </LinearLayout> <LinearLayout android:id="@+id/LinearLayout02" android:background="@drawable/bottombar_bg" android:layout_width="fill_parent" android:paddingTop="10dip" android:layout_height="56dip" android:layout_alignParentBottom="true" android:gravity="bottom" > <Button android:id="@+id/navigate" style="@style/mainBottomTabsButtonNormal" android:drawableLeft="@drawable/icon_navigation" android:text="@string/navigationSettings" android:layout_gravity="left"> </Button> <Button android:id="@+id/search" style="@style/mainBottomTabsButtonActive" android:drawableLeft="@drawable/icon_search" android:text="@string/search.label" android:layout_gravity="right"> </Button> </LinearLayout> </RelativeLayout>

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  • Why does my co-worker see a different Project file (*.csproj) using Visual Source Safe

    - by Leo Zhang
    Hello everybody, I met a problem which is very strange, my company uses Visual Source Safe to control version,but I found that my team's different member see the same .csproj file in VSS is not the same, it's very strange,can you help me? thanks!! there is a file named IPRA.WinUi.Sal.Sra.csproj in VSS: when Tom log on ,the file 'IPRA.WinUi.Sal.Sra.csproj' is : <Reference Include="Ark.Client.WinUi, Version=2.0.0.0, Culture=neutral, processorArchitecture=MSIL"> <SpecificVersion>False</SpecificVersion> <HintPath>..\ARAF\BusinessFramework\Ark.Client.WinUi.dll</HintPath> </Reference> <Reference Include="Ark.Common.Business, Version=1.0.0.0, Culture=neutral, processorArchitecture=MSIL" /> <Reference Include="Ark.Controls.Business, Version=0.0.0.0, Culture=neutral, processorArchitecture=MSIL"> <SpecificVersion>False</SpecificVersion> <HintPath>..\ARAF\SystemFramework\Ark.Controls.Business.dll</HintPath> </Reference> But when leo log on,the same file 'IPRA.WinUi.Sal.Sra.csproj' is : <Reference Include="Ark.Client.WinUi, Version=2.0.0.0, Culture=neutral, processorArchitecture=MSIL"> <SpecificVersion>False</SpecificVersion> <HintPath>..\ARAF\BusinessFramework\Ark.Client.WinUi.dll</HintPath> </Reference> <Reference Include="Ark.Common.Business, Version=1.0.0.0, Culture=neutral, processorArchitecture=MSIL" /> <SpecificVersion>False</SpecificVersion> <HintPath>..\ARAF\BusinessFramework\Ark.Controls.WinUi.dll</HintPath> <Reference Include="Ark.Controls.Business, Version=0.0.0.0, Culture=neutral, processorArchitecture=MSIL"> <SpecificVersion>False</SpecificVersion> <HintPath>..\ARAF\SystemFramework\Ark.Controls.Business.dll</HintPath> </Reference>

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  • UINavigationController navigation stack problems in Landscape Mode

    - by David F
    I have a iPhone application that I am currently converting to a Universal Binary to work with the iPad. I have successfully implemented everything I need in terms of layout so that full landscape functionality is now supported in my app (previously I primarily used portrait mode to display content). But, I have one strange problem, and it ONLY occurs in landscape mode: when I push a view controller onto the stack, it takes two taps on the back button to return to the previous view controller!!! The first tap shows a blank view, but with the same name on the left-side back navigation button, the second tap takes the controller back to previous view like it should. I don't have an iPad to test, so I am relying on the simulator. The problem does not show up on the iPhone and doesn't show up if you rotate back to portrait mode. My app consists of a tabbarcontroller with navigation controllers loaded for its vc's: //application delegate - (void)applicationDidFinishLaunching:(UIApplication *)application //.... WebHelpViewController *vc8 = [[WebHelpViewController alloc] init]; UINavigationController *nv8 = [[UINavigationController alloc] initWithRootViewController:vc8]; [self.tabBarController setViewControllers:[NSArray arrayWithObjects:nv1,nv2,nv3,nv4,nv5,nv6,nv7,nv8,nil]]; To implement landscape capability, the UITabBarController is overridden to autorotate when required: //CustomTabBarController.m - (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation { return [[(UINavigationController *)self.selectedViewController topViewController] shouldAutorotateToInterfaceOrientation:interfaceOrientation]; } ... works fine. I navigate into new views using this method SomeViewController *vc = [[SomeViewController alloc] init]; [self.navigationController pushViewController:vc animated:YES]; [vc release]; Has anyone encountered this problem, and do they know if it's only a simulation error?

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  • Simulating O_NOFOLLOW (2): Is this other approach safe?

    - by Daniel Trebbien
    As a follow-up question to this one, I thought of another approach which builds off of @caf's answer for the case where I want to append to file name and create it if it does not exist. Here is what I came up with: Create a temporary directory with mode 0700 in a system temporary directory on the same filesystem as file name. Create an empty, temporary, regular file (temp_name) in the temporary directory (only serves as placeholder). Open file name for reading only, just to create it if it does not exist. The OS may follow name if it is a symbolic link; I don't care at this point. Make a hard link to name at temp_name (overwriting the placeholder file). If the link call fails, then exit. (Maybe someone has come along and removed the file at name, who knows?) Use lstat on temp_name (now a hard link). If S_ISLNK(lst.st_mode), then exit. open temp_name for writing, append (O_WRONLY | O_APPEND). Write everything out. Close the file descriptor. unlink the hard link. Remove the temporary directory. (All of this, by the way, is for an open source project that I am working on. You can view the source of my implementation of this approach here.) Is this procedure safe against symbolic link attacks? For example, is it possible for a malicious process to ensure that the inode for name represents a regular file for the duration of the lstat check, then make the inode a symbolic link with the temp_name hard link now pointing to the new, symbolic link? I am assuming that a malicious process cannot affect temp_name.

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  • Is it safe to reuse javax.xml.ws.Service objects

    - by Noel Ang
    I have JAX-WS style web service client that was auto-generated with the NetBeans IDE. The generated proxy factory (extends javax.xml.ws.Service) delegates proxy creation to the various Service.getPort methods. The application that I am maintaining instantiates the factory and obtains a proxy each time it calls the targetted service. Creating the new proxy factory instances repeatedly has been shown to be expensive, given that the WSDL documentation supplied to the factory constructor, an HTTP URI, is re-retrieved for each instantiation. We had success in improving the performance by caching the WSDL. But this has ugly maintenance and packaging implications for us. I would like to explore the suitability of caching the proxy factory itself. Is it safe, e.g., can two different client classes, executing on the same JVM and targetting the same web service, safely use the same factory to obtain distinct proxy objects (or a shared, reentrant one)? I've been unable to find guidance from either the JAX-WS specification nor the javax.xml.ws API documentation. The factory-proxy multiplicity is unclear to me. Having Service.getPort rather than Service.createPort does not inspire confidence.

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  • problems with Console.SetOut in Release Mode?

    - by Matt Jacobsen
    i have a bunch of Console.WriteLines in my code that I can observe at runtime. I communicate with a native library that I also wrote. I'd like to stick some printf's in the native library and observe them too. I don't see them at runtime however. I've created a convoluted hello world app to demonstrate my problem. When the app runs, I can debug into the native library and see that the hello world is called. The output never lands in the textwriter though. Note that if the same code is run as a console app then everything works fine. C#: [DllImport("native.dll")] static extern void Test(); StreamWriter writer; public Form1() { InitializeComponent(); writer = new StreamWriter(@"c:\output.txt"); writer.AutoFlush = true; System.Console.SetOut(writer); } private void button1_Click(object sender, EventArgs e) { Test(); } and the native part: __declspec(dllexport) void Test() { printf("Hello World"); } Update: hamishmcn below started talking about debug/release builds. I removed the native call in the above button1_click method and just replaced it with a standard Console.WriteLine .net call. When I compiled and ran this in debug mode the messages were redirected to the output file. When I switched to release mode however the calls weren't redirected. Console redirection only seems to work in debug mode. How do I get around this?

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  • Thread-safe data structure design

    - by Inso Reiges
    Hello, I have to design a data structure that is to be used in a multi-threaded environment. The basic API is simple: insert element, remove element, retrieve element, check that element exists. The structure's implementation uses implicit locking to guarantee the atomicity of a single API call. After i implemented this it became apparent, that what i really need is atomicity across several API calls. For example if a caller needs to check the existence of an element before trying to insert it he can't do that atomically even if each single API call is atomic: if(!data_structure.exists(element)) { data_structure.insert(element); } The example is somewhat awkward, but the basic point is that we can't trust the result of "exists" call anymore after we return from atomic context (the generated assembly clearly shows a minor chance of context switch between the two calls). What i currently have in mind to solve this is exposing the lock through the data structure's public API. This way clients will have to explicitly lock things, but at least they won't have to create their own locks. Is there a better commonly-known solution to these kinds of problems? And as long as we're at it, can you advise some good literature on thread-safe design? EDIT: I have a better example. Suppose that element retrieval returns either a reference or a pointer to the stored element and not it's copy. How can a caller be protected to safely use this pointer\reference after the call returns? If you think that not returning copies is a problem, then think about deep copies, i.e. objects that should also copy another objects they point to internally. Thank you.

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  • Is this a safe/valid hash method implementation?

    - by Sean
    I have a set of classes to represent some objects loaded from a database. There are a couple variations of these objects, so I have a common base class and two subclasses to represent the differences. One of the key fields they have in common is an id field. Unfortunately, the id of an object is not unique across all variations, but within a single variation. What I mean is, a single object of type A could have an id between, say, 0 and 1,000,000. An object of type B could have an id between, 25,000 and 1,025,000. This means there's some overlap of id numbers. The objects are just variations of the same kind of thing, though, so I want to think of them as such in my code. (They were assigned ids from different sets for legacy reasons.) So I have classes like this: @class BaseClass @class TypeAClass : BaseClass @class TypeBClass : BaseClass BaseClass has a method (NSNumber *)objectId. However instances of TypeA and TypeB could have overlapping ids as discussed above, so when it comes to equality and putting these into sets, I cannot just use the id alone to check it. The unique key of these instances is, essentially, (class + objectId). So I figured that I could do this by making the following hash function on the BaseClass: -(NSUInteger)hash { return (NSUInteger)[self class] ^ [self.objectId hash]; } I also implemented isEqual like so: - (BOOL)isEqual:(id)object { return (self == object) || ([object class] == [self class] && [self.objectId isEqual:[object objectId]]); } This seems to be working, but I guess I'm just asking here to make sure I'm not overlooking something - especially with the generation of the hash by using the class pointer in that way. Is this safe or is there a better way to do this?

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  • Safe and polymorphic toEnum

    - by jetxee
    I'd like to write a safe version of toEnum: safeToEnum :: (Enum t, Bounded t) => Int -> Maybe t A naive implementation: safeToEnum :: (Enum t, Bounded t) => Int -> Maybe t safeToEnum i = if (i >= fromEnum (minBound :: t)) && (i <= fromEnum (maxBound :: t)) then Just . toEnum $ i else Nothing main = do print $ (safeToEnum 1 :: Maybe Bool) print $ (safeToEnum 2 :: Maybe Bool) And it doesn't work: safeToEnum.hs:3:21: Could not deduce (Bounded t1) from the context () arising from a use of `minBound' at safeToEnum.hs:3:21-28 Possible fix: add (Bounded t1) to the context of an expression type signature In the first argument of `fromEnum', namely `(minBound :: t)' In the second argument of `(>=)', namely `fromEnum (minBound :: t)' In the first argument of `(&&)', namely `(i >= fromEnum (minBound :: t))' safeToEnum.hs:3:56: Could not deduce (Bounded t1) from the context () arising from a use of `maxBound' at safeToEnum.hs:3:56-63 Possible fix: add (Bounded t1) to the context of an expression type signature In the first argument of `fromEnum', namely `(maxBound :: t)' In the second argument of `(<=)', namely `fromEnum (maxBound :: t)' In the second argument of `(&&)', namely `(i <= fromEnum (maxBound :: t))' As well as I understand the message, the compiler does not recognize that minBound and maxBound should produce exactly the same type as in the result type of safeToEnum inspite of the explicit type declaration (:: t). Any idea how to fix it?

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  • Ruby on Rails App not starting in production mode

    - by Ermin
    Everything works fine in development mode, but when I try to start my app in production mode (RAILS_ENV=production script/server) I get the following error: /opt/ruby1.8/lib/ruby/gems/1.8/gems/searchlogic-2.4.19/lib/searchlogic/named_scopes/conditions.rb:81:in `method_missing': protected method `scope' called for #<Class:0x7f41de524410> (NoMethodError) from /opt/ruby1.8/lib/ruby/gems/1.8/gems/searchlogic-2.4.19/lib/searchlogic/named_scopes/association_conditions.rb:19:in `method_missing' from /opt/ruby1.8/lib/ruby/gems/1.8/gems/searchlogic-2.4.19/lib/searchlogic/named_scopes/association_ordering.rb:27:in `method_missing' from /opt/ruby1.8/lib/ruby/gems/1.8/gems/searchlogic-2.4.19/lib/searchlogic/named_scopes/ordering.rb:30:in `method_missing' from /opt/ruby1.8/lib/ruby/gems/1.8/gems/searchlogic-2.4.19/lib/searchlogic/named_scopes/or_conditions.rb:28:in `method_missing' from /opt/ruby1.8/lib/ruby/gems/1.8/gems/activerecord-2.3.5/lib/active_record/base.rb:1959:in `method_missing_without_paginate' from /opt/ruby1.8/lib/ruby/gems/1.8/gems/will_paginate-2.3.12/lib/will_paginate/finder.rb:170:in `method_missing' from /opt/ruby1.8/lib/ruby/gems/1.8/gems/acts_as_commentable-3.0.0/lib/comment_methods.rb:12:in `included' from .../app/models/comment.rb:2:in `include' from .../app/models/comment.rb:2 from /opt/ruby1.8/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:in `gem_original_require' from /opt/ruby1.8/lib/ruby/site_ruby/1.8/rubygems/custom_require.rb:31:in `require'... Now it seems to me it that the acts_as_commentable gem is causing this. But how come, it works fine in development mode.

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  • Setting White balance and Exposure mode for iphone camera + enum default

    - by Spectravideo328
    I am using the back camera of an iphone4 and doing the standard and lengthy process of creating an AVCaptureSession and adding to it an AVCaptureDevice. Before attaching the AvCaptureDeviceInput of that camera to the session, I am testing my understanding of white balance and exposure, so I am trying this: [self.theCaptureDevice lockForConfiguration:nil]; [self.theCaptureDevice setWhiteBalanceMode:AVCaptureWhiteBalanceModeLocked]; [self.theCaptureDevice setExposureMode:AVCaptureExposureModeContinuousAutoExposure]; [self.theCaptureDevice unlockForConfiguration]; 1- Given that the various options for white balance mode are in an enum, I would have thought that the default is always zero since the enum Typedef variable was never assigned a value. I am finding out, if I breakpoint and po the values in the debugger, that the default white balance mode is actually set to 2. Unfortunately, the header files of AVCaptureDevice does not say what the default are for the different camera setting. 2- This might sound silly, but can I assume that once I stop the app, that all settings for whitebalance, exposure mode, will go back to their default. So that if I start another app right after, the camera device is not somehow stuck on those "hardware settings".

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  • Returning pointers in a thread-safe way.

    - by Roddy
    Assume I have a thread-safe collection of Things (call it a ThingList), and I want to add the following function. Thing * ThingList::findByName(string name) { return &item[name]; // or something similar.. } But by doing this, I've delegated the responsibility for thread safety to the calling code, which would have to do something like this: try { list.lock(); // NEEDED FOR THREAD SAFETY Thing *foo = list.findByName("wibble"); foo->Bar = 123; list.unlock(); } catch (...) { list.unlock(); throw; } Obviously a RAII lock/unlock object would simplify/remove the try/catch/unlocks, but it's still easy for the caller to forget. There are a few alternatives I've looked at: Return Thing by value, instead of a pointer - fine unless you need to modify the Thing Add function ThingList::setItemBar(string name, int value) - fine, but these tend to proliferate Return a pointerlike object which locks the list on creation and unlocks it again on destruction. Not sure if this is good/bad practice... What's the right approach to dealing with this?

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