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  • Scaling a node.js application, nginx as a base server, but varnish or redis for caching?

    - by AntelopeSalad
    I'm not close to being well versed in using nginx or varnish but this is my setup at the moment. I have a node.js server running which is serving either json, html templates, or socket.io events. Then I have nginx running in front of node which is serving all static content (css, js, etc.). At this point I would like to cache both static content and dynamic content to memory. It's to my understanding that varnish can cache static content quite well and it wouldn't require touching my application code. I also think it's capable of caching dynamic content too but there cannot be any cookie headers? I do use redis at the moment for holding session data and planned to use it for other things in the future like keeping track of non-crucial but fun stats. I just have no idea how I should handle caching everything on the site. I think it comes down to these options but there might be more: Throw varnish in front of nginx and let varnish cache static pages, no app code changes. Redis would cache dynamic db calls which would require modifying my app code. Ignore using varnish completely and let redis handle caching everything, then use one of the nginx-redis modules. I'm not sure if this would require a lot of app code changes (for the static files). I'm not having any luck finding benchmarks that compare nginx+varnish vs nginx+redis and I'm too inexperienced to bench it myself (high chances of my configs being awful). I'm basically looking for the solution that would be the most efficient in terms of req/sec and scalable in the future (throw new hardware at the problem + maybe adjust some values in a config = new servers up and running semi-painlessly).

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  • How do I setup routing for two companies with different Internet connections on the same LAN?

    - by Clint Miller
    Here's the setup: Two companies (A & B) share office space and a LAN. A 2nd ISP is brought in and company A wants its own Internet connection (ISP A) and company B wants its own Internet connection (ISP B). VLANs are deployed internally to separate the two companies' networks (company A: VLAN 1, company B: VLAN 2, shared VOIP: VLAN 3). With separate VLANs it's simple enough to use separate DHCP servers (or separate scopes on the same server) to assign the default gateway to each company's gateway for their Internet connection. Static routes can be created on each gateway to point traffic destined for the other company's VLAN or the voice VLAN so that all nodes are reachable as expected. However, I think this is a form of asymmetrical routing, right? (The path from node A1 to node B1 is not the same as the path back from node B1 to node A1). Can I set up policy-based routing to correct this? In that case, can I assign the same default gateway to every device on all VLANs and create a routing policy on a L3 switch to look at the source address and forward traffic to the appropriate next hop? In that case, I want the routing logic to go like this: If the destination address is known, forward the traffic (traffic destined for a different VLAN). If the destination address is unknown, forward the traffic to ISP A's gateway if the source address is on VLAN A; or forward the traffic to ISP B's gateway if the source address is VLAN B. Am I thinking about this problem in the correct way? Is there another way to solve this problem that I am overlooking?

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  • Facebook contest policy no-no?

    - by Fred
    I would like to post a link on a Facebook page where it will exit Facebook entirely and go to a client's website, where people will be on a page (client's) where they can enter their e-mail address to be entered in a temporary database file with rules and disclosures etc., for a draw once the number of entries reaches 100 for instance. Once the number of entries reaches 100, a random winner is picked and notified via E-mail. The functionality is as follows: A link is place on a Facebook page leading to an external page The page is a form to merely enter their email address for a contest The email is placed in a temporary file An automatic E-mail is sent to the address used for confirmation using SHAH-256 hash The person receives the Email saying something to the affect "Please confirm your Email address etc. - If you did not authorize this, simply ignore this message and no further action will be taken". If the person clicks on the confirmation link, the Email is then stored in the database and the person is again notified saying "Thank you for signing up etc." Once others do the same process and the database reaches a certain number, the form is no longer accessible and automatically picks a random Email. Once picked, an Email is automatically sent to the winner stating the instructions, and notifying me also. Once that person clicks yet another confirmation link, the database is then automatically deleted. I have built this myself and have no intentions of breaking any rules, nor jeopardize the work/time/energy I have put into this project. Is this allowed?

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  • IIS redirect not working as wanted

    - by Leonardo
    i need help with IIS redirect... My website is on the internet and i want to redirect requests based on the following rule: if URL = http :// contoso.com (public address) - Redirect to http :// contoso.com/portal if URL = http :// myserver (internal address) - Dont do anything if URL = http :// 192.168.0.1 (internal address) - Dont do anything is it possible? how can i do it?!? i managed to get the first one... but i cant get the second and third one to work...

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  • Getting the total number of processors a computer has (c#)

    - by mbcrump
    Here is a code snippet for getting the total number of processors a computer has without using Environment.ProcessorCount. I found out that Environment.ProcessorCount is not necessary returning the correct value on some Intel based CPU’s.   using System; usingSystem.Collections.Generic; usingSystem.Linq; usingSystem.Text; usingSystem.Globalization; usingSystem.Runtime.InteropServices; namespaceConsoleApplication4 {     classProgram    {         static voidMain(string[] args)         {             int c = ProcessorCount;             Console.WriteLine("The computer has {0} processors", c);             Console.ReadLine();         }         private static classNativeMethods        {             [StructLayout(LayoutKind.Sequential)]             internal struct SYSTEM_INFO            {                 public ushort wProcessorArchitecture;                 public ushort wReserved;                 public uint dwPageSize;                 publicIntPtr lpMinimumApplicationAddress;                 publicIntPtr lpMaximumApplicationAddress;                 publicUIntPtr dwActiveProcessorMask;                 public uint dwNumberOfProcessors;                 public uint dwProcessorType;                 public uint dwAllocationGranularity;                 public ushort wProcessorLevel;                 public ushort wProcessorRevision;             }             [DllImport("kernel32.dll", CharSet = CharSet.Auto, ExactSpelling = true)]             internal static extern voidGetNativeSystemInfo(refSYSTEM_INFOlpSystemInfo);         }         public static int ProcessorCount         {             get            {                 NativeMethods.SYSTEM_INFOlpSystemInfo = newNativeMethods.SYSTEM_INFO();                 NativeMethods.GetNativeSystemInfo(reflpSystemInfo);                 return(int)lpSystemInfo.dwNumberOfProcessors;             }         }     } }

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  • Bridging networks problems

    - by Eric
    In my setup I have 3 computers and 2 (wireless d-link) routers. Computer1 has ethernet and wireless interfaces ethernet : 192.168.0.x (DHCP) wireless : 192.168.10.254 (static) Computer 2 has ethernet with two ips ethernet1 : 192.168.0.90 (static) ethernet2 : 192.168.10.110 (static) Computer 3 is a particular device with a hardcoded ip that I can't change wireless : 192.168.10.41 (static) Router1 manages internet and DHCP for network 192.168.0.0/24 Router2 is more complicated. I don't use DHCP. I use it to bridge between both networks. Its static ip is 192.168.10.1 Computer1 can ping Computer2. Computer1 can ping Computer3. Computer1 can ping Router1. Computer1 cannot ping Router2. Computer2 cannot ping Computer3. Computer2 can ping Router2. Router1 can ping Router1 Router2 can ping Computer2 Router2 cannot ping Computer1 Router2 cannot ping Computer3 This is very weird. Router2 manages the wireless connection, it should be able to ping its own computers right? My question is obviously : How can I make it so Computer2 can access everything else. This is a traditional case of "it was working before christmas and now it doesn't". The ethernet wiring is as follow : [ Computer1 ]----[ Router1 ]---[ Router2 ]---[ Computer3 ] I am using switch (lan) ports on Router1/2.

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  • Spam is Killing Me - Can I use GMail as a spam filter?

    - by kirkouimet
    I'm getting at least 50 Viagra ads a day and it's driving me insane. I currently have a hosted MS Exchange account and a Gmail account. My Gmail account forwards to my Exchange account. Both of my addresses are used evenly, and it has been really nice to have all of my e-mail end up in my Exchange box. I like replying from one address consistently, which is my Exchange address. Spam sent to my Gmail address is always caught, where spam sent to my Exchange is getting passed straight through to me. I don't want to have two spam filtration systems that have quarantines that I need to check frequently for false positives. Here is my question: Can I setup my MX records such that all e-mail sent to my Exchange address is forwarded to my Gmail account, which will then forward it to my Exchange account? Kind of like using Gmail as the middle man.

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  • Problems with connecting to wireless network on windows 7

    - by Naveen
    I have a Dell laptop with Windows 7 (Home premium) 64 bit edition installed on it. I use a Wi-Fi router to browse the net. My problem is, I lose the network connection every 10 minutes or so. The network icon on the system tray shows the refresh icon and the status as "identifying network". The network is fine and works fine with my phone. I saw on the net this may be caused if I have enabled IPv6, so I disabled it but still problem persists. When I look at the event log I see the following entries: "Your computer was not assigned an address from the network (by the DHCP Server) for the Network Card with network address 0xXXXXXXXX. The following error occurred: 0x79. Your computer will continue to try and obtain an address on its own from the network address (DHCP) server." I have also installed VirtualBox(32 bit edition) on the laptop. Does anybody any solution to this?

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  • How is starting and ending row number of a Range obtained?

    - by Robert Kerr
    Given a user-selected Range, what is the simplest way to determine the starting row number, and ending row number? Range.Address returns a string containing any number of possible formats. There has to be something simpler. Desired: Dim oRange As Range Dim startRow As Integer Dim endRow As Integer oRange = Range("A1:X50") startRow = oRange.Address.StartRow endRow = oRange.Address.EndRow of course, those properties do not exist. I want to do the same to return column letters.

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  • How to troubleshoot port forwarding on Windows 7 (64 Bit) with ICS enabled?

    - by LearnCocos2D
    I want to forward some ports (1666 for perforce, 8081 for Hudson) on my Internet Gateway machine. This machine is running Windows 7 (64 Bit, legal, user-account) and connected to the Internet via cable modem (it's not a router). The Windows machine is sharing its Internet Connection via ICS and that works fine on all connected computers. I can access the services via the gateway's public IP (95.x.x.x) on the given ports if they are running on the gateway machine itself. I've added the ports and destination IP address (192.168.0.18) in the Internet network adapter's Advanced Settings dialog (Sharing tab). That's the same dialog where you have a list of preconfigured services like HTTP, FTP and other incoming services. When I do that I can't connect to the services anymore. For some reason port forwarding isn't working. I have uninstalled Bitdefender because I wanted to check if the Firewall interferes. I've also disabled the Windows Firewall and Defender to no avail. I tried a freeware tool that helps to setup port forwarding but that didn't work either. The target machine is a Mac OS X computer whose Firewall is disabled. The IP is static. I can successfully connect to the services using the local IP address (192.168.0.18) from two different machines, including the gateway computer. So internally and externally it seems to me that the ports are open and not blocked, and the issue is with port forwarding itself. From what I understand it should be enough to add an entry to the Advanced Settings dialog to enable port forwarding when there are no firewalls interfering. How can I troubleshoot why port forwarding isn't working for me? What steps should I follow to alleviate the issue? PS: I gladly accept command line solutions. Other things I've tried: adding an Inbound Rule to Windows Firewall for the 1666, 8081 ports trying with Windows Firewall enabled and disabled disabling/enabling the network adapter double-checked that the IP addresses are correct mapping a different incoming port to the service's actual port followed or checked the misc tips in this article What I haven't dared trying yet (let me know if it's worth a shot): disable/enable ICS remove all network adapters (via Control Panel), then re-install and re-configure them

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  • Fourth texture = segmentation fault

    - by Robin92
    I keep on getting segmentation fault each time I load fourth texture - what type of texture, I mean filename, does not matter. I checked value of GL_TEXTURES_STACK_SIZE which turned out to be 10 so quite more than 4, isn't it? Here're code fragments: funciton to load texture from png static GLuint gl_loadTexture(const char filename[]) { static int iTexNum = 1; GLuint texture = 0; img_s *img = NULL; img = img_loadPNG(filename); if (img) { glGenTextures(iTexNum++, &texture); glBindTexture(GL_TEXTURE_2D, texture); glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR); glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR); glTexImage2D(GL_TEXTURE_2D, 0, img->iGlFormat, img->uiWidth, img->uiHeight, 0, img->iGlFormat, GL_UNSIGNED_BYTE, img->p_ubaData); img_free(img); //it may cause errors on windows } else printf("Error: loading texture '%s' failed!\n", filename); return texture; } actual loading static GLuint textures[4]; static void gl_init() { (...) //setting up OpenGL /* loading textures */ textures[0] = gl_loadTexture("images/background.png"); textures[1] = gl_loadTexture("images/spaceship.png"); textures[2] = gl_loadTexture("images/asteroid.png"); textures[3] = gl_loadTexture("images/asteroid2.png"); //this is causing SegFault no matter which file I load! } Any ideas? Problem is present on both Linux and Windows.

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  • Hide or Show singleton?

    - by Sinker
    Singleton is a common pattern implemented in both native libraries of .NET and Java. You will see it as such: C#: MyClass.Instance Java: MyClass.getInstance() The question is: when writing APIs, is it better to expose the singleton through a property or getter, or should I hide it as much as possible? Here are the alternatives for illustrative purposes: Exposed(C#): private static MyClass instance; public static MyClass Instance { get { if (instance == null) instance = new MyClass(); return instance; } } public void PerformOperation() { ... } Hidden (C#): private static MyClass instance; public static void PerformOperation() { if (instance == null) { instance = new MyClass(); } ... } EDIT: There seems to be a number of detractors of the Singleton design. Great! Please tell me why and what is the better alternative. Here is my scenario: My whole application utilises one logger (log4net/log4j). Whenever, the program has something to log, it utilises the Logger class (e.g. Logger.Instance.Warn(...) or Logger.Instance.Error(...) etc. Should I use Logger.Warn(...) or Logger.Warn(...) instead? If you have an alternative to singletons that addresses my concern, then please write an answer for it. Thank you :)

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  • How To Setup Domain Name for SchoolTool Local Server

    - by zeroseven0183
    I am currently testing SchoolTool 2.0 and I would like to do some things: This application is installed on a virtual machine running Ubuntu Server 11.10 bridged to our home network. The site is accessible through IP address. What I would like to do is setup a local domain, say schooltool.ourhomedomain.com. I thought my sister would appreciate it more if it were not via IP address. If there's anymore information needed, let me know. Thanks in advance!

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  • Wrapping a point-to-point link

    - by user3712955
    I'm using a pair of IP radios (non-WiFi) to bridge my office engineering LAN (172.0.0.0/8) to a lab in another building. The radios work fine, but they expose a web management interface I'd like to hide, and they also generate traffic (ARP, STP, and more) that I need to keep off my (very, very clean) LAN segments. I have some ARM-Linux boards (similar to Beagle/Panda/RasPi) running Ubuntu, and I've put one at each end of the link, between the radio and the LAN. Each of the boards has 2 wired Ethernet interfaces, eth0 and eth1. The LAN segments are connected to eth0, and the radios are connected to eth1. I'd like to accomplish the following: Keep radio-originated traffic off my LAN segments! Hide all services provided by the radio (web, ssh, etc.) Transparently pass all traffic between the LAN segments (including things like ARP). The above also applies to the ARM-Linux boards: No stray traffic my LAN from them either! I'd like the system to look like a switch: LAN packets arriving at one eth0 appear at the other. And neither eth0 should have an IP address: The working system should behave like a CAT6 cable with some latency (instead of ARM boards and radios). Unfortunately, I'm confused about how to properly configure the ARM Ubuntu systems. What I'm guessing I need is a bridge on each board (br0?) and a VLAN (vlan0 or eth0.0?) to isolate the LAN traffic from everything else as it passes through the ARM boards and the radios. Then I need some kind of a firewall to block sending anything out eth0 that isn't from the other eth0 (via the VLAN). I've looked at the ip and ebtables commands (especially -t broute). While the concepts sorta-kinda make sense, I'm completely lost in the details. Edit: In the perverse case that a system on one of my LAN segments has the same IP address as one of the radios, or as eth1 on the ARM-Ubuntu boards, a VLAN won't work. Which I believe means I need to tunnel all traffic between the two eth0 interfaces to get that "like a wire" behavior. Help? Finally, I'd like to have a way to temporarily expose services on the ARM boards (ssh) and the radios (web) for maintenance purposes. Ideally, it would expose an IP address with ssh available on port 22. Once connected, I figure I'd start an X11 session and run a browser on the ARM board to access the radios. Or something. I could login via the console to enable/disable this, or perhaps could use a GPIO to trigger a script. I feel I've identified most of the pieces needed to make all this happen, but I have no idea how to combine them to make a working system. Thanks!

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  • curl to itself behind firewall

    - by xtreaming
    I have a server A which is configured behind a firewall and has 30.x.x.x public adress and 172.x.x.x internal address. I'm trying to make a php Curl call from a script located on that server, to the 30.x.x.x external IP of that server but the curl call cannot be resolved. It seems that server A does not have a route to that IP. Did you encounter any similar situations? Any chance to solve it through static routes?

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  • is VPN client working one way ?

    - by user56839
    I have centos server and installed the VPN client(cisco-vpnclient) and able to connect to the server on the other side using private address and the server on the other side pingable using the private address . The question But the other side can not connect to my server using private address such as: when the other side try to ping my server using the private ip do not get any response. is VPN client working one way ( just send the data to VPN server and do not receive the data) ?

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  • How can I move authorized applications between google accounts?

    - by zoopp
    I'm looking into creating an email address with a professional name on gmail and due to the fact that I can't change my current one I have to create new google account. Among some things which which need to be patched (eg. forwarding email to the new address until every other account's email contact address is changed etc.) I came across authorized applications. If I am to use exclusively the new email address I have to somehow move my authorized applications as well since if I am to eventually delete my old account I will lose access to my current profiles created by those applications (eg. the stackexchange network, youtube etc). How can this move be accomplished?

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  • HP ProLiant DL380 G3 Running Windows Server 2000 has crashed between 6-7:30am for the past 5 days

    - by user109717
    I have a HP ProLiant DL380 G3 running Windows Server 2000 that has been crashing everyday between 6-730am. This started when I changed out a failing hard drive 6 days ago. I have looked at the scheduled tasks which does not have anything pertaining to this issue. Below are the only things I see in the system log and some of the dump files. Can this be a hardware issue if this happens at a certain time frame everyday? Any help is greatly appreciated. Thanks The previous system shutdown at 6:07:55 AM on 2/7/2012 was unexpected. System Information Agent: Health: The server is operational again. The server has previously been shutdown by the Automatic Server Recovery (ASR) feature and has just become operational again. [SNMP TRAP: 6025 in CPQHLTH.MIB] BugCheck 7A, {3, c0000005, 3400028, 0} Probably caused by : memory_corruption ( nt!MiMakeSystemAddressValidPfn+42 ) Followup: MachineOwner 0: kd !analyze -v * Bugcheck Analysis * * KERNEL_DATA_INPAGE_ERROR (7a) The requested page of kernel data could not be read in. Typically caused by a bad block in the paging file or disk controller error. Also see KERNEL_STACK_INPAGE_ERROR. If the error status is 0xC000000E, 0xC000009C, 0xC000009D or 0xC0000185, it means the disk subsystem has experienced a failure. If the error status is 0xC000009A, then it means the request failed because a filesystem failed to make forward progress. Arguments: Arg1: 00000003, lock type that was held (value 1,2,3, or PTE address) Arg2: c0000005, error status (normally i/o status code) Arg3: 03400028, current process (virtual address for lock type 3, or PTE) Arg4: 00000000, virtual address that could not be in-paged (or PTE contents if arg1 is a PTE address) MODULE_NAME: nt IMAGE_NAME: memory_corruption BugCheck A, {0, 2, 1, 804137d6} Probably caused by : ntkrnlmp.exe ( nt!CcGetVirtualAddress+ba ) * Bugcheck Analysis * * IRQL_NOT_LESS_OR_EQUAL (a) An attempt was made to access a pageable (or completely invalid) address at an interrupt request level (IRQL) that is too high. This is usually caused by drivers using improper addresses. If a kernel debugger is available get the stack backtrace. Arguments: Arg1: 00000000, memory referenced Arg2: 00000002, IRQL Arg3: 00000001, bitfield : bit 0 : value 0 = read operation, 1 = write operation bit 3 : value 0 = not an execute operation, 1 = execute operation (only on chips which support this level of status) Arg4: 804137d6, address which referenced memory MODULE_NAME: nt IMAGE_NAME: ntkrnlmp.exe

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  • SQL RDBMS : one query or multiple calls

    - by None None
    After looking around the internet, I decided to create DAOs that returned objects (POJOs) to the calling business logic function/method. For example: a Customer object with a Address reference would be split in the RDBMS into two tables; Customer and ADDRESS. The CustomerDAO would be in charge of joining the data from the two tables and create both an Address POJO and Customer POJO adding the address to the customer object. Finally return the fulll Customer POJO. Simple, however, now i am at a point where i need to join three or four tables and each representing an attribute or list of attributes for the resulting POJO. The sql will include a group by but i will still result with multiple rows for the same pojo, because some of the tables are joining a one to many relationship. My app code will now have to loop through all the rows trying to figure out if the rows are the same with different attributes or if the record should be a new POJO. Should I continue to create my daos using this technique or break up my Pojo creation into multiple db calls to make the code easier to understand and maintain?

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  • Is it possible to specify a generic constraint for a type parameter to be convertible FROM another t

    - by fostandy
    Suppose I write a library with the following: public class Bar { /* ... */ } public class SomeWeirdClass<T> where T : ??? { public T BarMaker(Bar b) { // ... play with b T t = (T)b return (T) b; } } Later, I expect users to use my library by defining their own types which are convertible to Bar and using the SomeWeirdClass 'factory'. public class Foo { public static explicit operator Foo(Bar f) { return new Bar(); } } public class Demo { public static void demo() { Bar b = new Bar(); SomeWeirdClass<Foo> weird = new SomeWeirdClass<Foo>(); Foo f = weird.BarMaker(b); } } this will compile if i set where T : Foo but the problem is that I don't know about Foo at the library's compile time, and I actually want something more like where T : some class that can be instantiated, given a Bar Is this possible? From my limited knowledge it does not seem to be, but the ingenuity of the .NET framework and its users always surprises me... This may or not be related to the idea of static interface methods - at least, I can see the value in being able to specify the presence of factory methods to create objects (similar to the same way that you can already perform where T : new()) edit: Solution - thanks to Nick and bzIm - For other readers I'll provide a completed solution as I understand it: edit2: This solution requires Foo to expose a public default constructor. For an even stupider better solution that does not require this see the very bottom of this post. public class Bar {} public class SomeWeirdClass<T> where T : IConvertibleFromBar<T>, new() { public T BarMaker(Bar b) { T t = new T(); t.Convert(b); return t; } } public interface IConvertibleFromBar<T> { T Convert(Bar b); } public class Foo : IConvertibleFromBar<Foo> { public static explicit operator Foo(Bar f) { return null; } public Foo Convert(Bar b) { return (Foo) b; } } public class Demo { public static void demo() { Bar b = new Bar(); SomeWeirdClass<Foo> weird = new SomeWeirdClass<Foo>(); Foo f = weird.BarMaker(b); } } edit2: Solution 2: Create a type convertor factory to use: #region library defined code public class Bar {} public class SomeWeirdClass<T, TFactory> where TFactory : IConvertorFactory<Bar, T>, new() { private static TFactory convertor = new TFactory(); public T BarMaker(Bar b) { return convertor.Convert(b); } } public interface IConvertorFactory<TFrom, TTo> { TTo Convert(TFrom from); } #endregion #region user defined code public class BarToFooConvertor : IConvertorFactory<Bar, Foo> { public Foo Convert(Bar from) { return (Foo) from; } } public class Foo { public Foo(int a) {} public static explicit operator Foo(Bar f) { return null; } public Foo Convert(Bar b) { return (Foo) b; } } #endregion public class Demo { public static void demo() { Bar b = new Bar(); SomeWeirdClass<Foo, BarToFooConvertor> weird = new SomeWeirdClass<Foo, BarToFooConvertor>(); Foo f = weird.BarMaker(b); } }

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  • Is it possible to specify a generic constraint for a type parameter to be convertible FROM another t

    - by fostandy
    Suppose I write a library with the following: public class Bar { /* ... */ } public class SomeWeirdClass<T> where T : ??? { public T BarMaker(Bar b) { // ... play with b T t = (T)b return (T) b; } } Later, I expect users to use my library by defining their own types which are convertible to Bar and using the SomeWeirdClass 'factory'. public class Foo { public static explicit operator Foo(Bar f) { return new Bar(); } } public class Demo { public static void demo() { Bar b = new Bar(); SomeWeirdClass<Foo> weird = new SomeWeirdClass<Foo>(); Foo f = weird.BarMaker(b); } } this will compile if i set where T : Foo but the problem is that I don't know about Foo at the library's compile time, and I actually want something more like where T : some class that can be instantiated, given a Bar Is this possible? From my limited knowledge it does not seem to be, but the ingenuity of the .NET framework and its users always surprises me... This may or not be related to the idea of static interface methods - at least, I can see the value in being able to specify the presence of factory methods to create objects (similar to the same way that you can already perform where T : new()) edit: Solution - thanks to Nick and bzIm - For other readers I'll provide a completed solution as I understand it: edit2: This solution requires Foo to expose a public default constructor. For an even stupider better solution that does not require this see the very bottom of this post. public class Bar {} public class SomeWeirdClass<T> where T : IConvertibleFromBar<T>, new() { public T BarMaker(Bar b) { T t = new T(); t.Convert(b); return t; } } public interface IConvertibleFromBar<T> { T Convert(Bar b); } public class Foo : IConvertibleFromBar<Foo> { public static explicit operator Foo(Bar f) { return null; } public Foo Convert(Bar b) { return (Foo) b; } } public class Demo { public static void demo() { Bar b = new Bar(); SomeWeirdClass<Foo> weird = new SomeWeirdClass<Foo>(); Foo f = weird.BarMaker(b); } } edit2: Solution 2: Create a type convertor factory to use: #region library defined code public class Bar {} public class SomeWeirdClass<T, TFactory> where TFactory : IConvertorFactory<Bar, T>, new() { private static TFactory convertor = new TFactory(); public T BarMaker(Bar b) { return convertor.Convert(b); } } public interface IConvertorFactory<TFrom, TTo> { TTo Convert(TFrom from); } #endregion #region user defined code public class BarToFooConvertor : IConvertorFactory<Bar, Foo> { public Foo Convert(Bar from) { return (Foo) from; } } public class Foo { public Foo(int a) {} public static explicit operator Foo(Bar f) { return null; } public Foo Convert(Bar b) { return (Foo) b; } } #endregion public class Demo { public static void demo() { Bar b = new Bar(); SomeWeirdClass<Foo, BarToFooConvertor> weird = new SomeWeirdClass<Foo, BarToFooConvertor>(); Foo f = weird.BarMaker(b); } }

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  • android - Caused by: android.view.ViewRootImpl$CalledFromWrongThreadException

    - by chinna_82
    Im trying to get image from my URL and display in application but it throw error Caused by: android.view.ViewRootImpl$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views. Below is my code Code package com.smartag.bird.dev; public class MainActivity extends Activity { static String ndefMsg = null; static String ndefMsg1 = null; NfcAdapter mNfcAdapter; PendingIntent mNfcPendingIntent; IntentFilter[] mNdefExchangeFilters; static final String TAG = "Read Tag"; TextView mTitle; private static ImageView imageView; static String url = "http://sposter.smartag.my/images/chicken_soup.jpg"; private static Bitmap downloadBitmap; private static BitmapDrawable bitmapDrawable; private static boolean largerImg = false; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); //setContentView(R.layout.main); mNfcAdapter = NfcAdapter.getDefaultAdapter(this); mNfcPendingIntent = PendingIntent.getActivity(this, 0, new Intent(this, getClass()).addFlags(Intent.FLAG_ACTIVITY_SINGLE_TOP), 0); IntentFilter ndefDetected = new IntentFilter(NfcAdapter.ACTION_NDEF_DISCOVERED); try { ndefDetected.addDataType("text/plain"); } catch (MalformedMimeTypeException e) { } mNdefExchangeFilters = new IntentFilter[] { ndefDetected }; if (NfcAdapter.ACTION_NDEF_DISCOVERED.equals(getIntent().getAction())) { NdefMessage[] messages = getNdefMessages(getIntent()); byte[] payload = messages[0].getRecords()[0].getPayload(); ndefMsg = new String(payload); setIntent(new Intent()); // Consume this intent. } ConnectivityManager connManager = (ConnectivityManager) getSystemService(CONNECTIVITY_SERVICE); NetworkInfo mWifi = connManager.getNetworkInfo(ConnectivityManager.TYPE_WIFI); if(ndefMsg == null || ndefMsg.length() == 0) { startActivity(new Intent(MainActivity.this, MainMenu.class)); } else { setContentView(R.layout.main); if (mWifi.isConnected()) { ndefMsg1 = ndefMsg; new DownloadFilesTask().execute(); ndefMsg = null; } else { AlertDialog.Builder dialog = new AlertDialog.Builder(this); dialog.setTitle("Attention"); dialog.setMessage("No Internet Connection. Please enable the wifi."); dialog.setPositiveButton("OK", new DialogInterface.OnClickListener() { public void onClick(DialogInterface dialog, int whichButton) { } }); dialog.show(); } } } private class DownloadFilesTask extends AsyncTask<Void, Void, Void> { protected void onPostExecute(Void result) { } @Override protected Void doInBackground(Void... params) { try { URL myFileUrl = new URL("http://sposter.smartag.my/images/chicken_soup.jpg"); HttpURLConnection conn= (HttpURLConnection)myFileUrl.openConnection(); conn.setDoInput(true); conn.connect(); InputStream is = conn.getInputStream(); downloadBitmap = BitmapFactory.decodeStream(is); } catch (FileNotFoundException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } ImageView image = (ImageView) findViewById(R.id.imview); image.setImageBitmap(downloadBitmap); return null; } } }

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  • How do I imply code contracts of chained methods to avoid superfluous checks while chaining?

    - by Sandor Drieënhuizen
    I'm using Code Contracts in C# 4.0. I'm applying the usual static method chaining to simulate optional parameters (I know C# 4.0 supports optional parameters but I really don't want to use them). The thing is that my contract requirements are executed twice (or possibly the number of chained overloads I'd implement) if I call the Init(string , string[]) method -- an obvious effect from the sample source code below. This can be expensive, especially due to relatively expensive requirements like the File.Exists I use. public static void Init(string configurationPath, string[] mappingAssemblies) { // The static contract checker 'makes' me put these here as well as // in the overload below. Contract.Requires<ArgumentNullException>(configurationPath != null, "configurationPath"); Contract.Requires<ArgumentException>(configurationPath.Length > 0, "configurationPath is an empty string."); Contract.Requires<FileNotFoundException>(File.Exists(configurationPath), configurationPath); Contract.Requires<ArgumentNullException>(mappingAssemblies != null, "mappingAssemblies"); Contract.ForAll<string>(mappingAssemblies, (n) => File.Exists(n)); Init(configurationPath, mappingAssemblies, null); } public static void Init(string configurationPath, string[] mappingAssemblies, string optionalArgument) { // This is the main implementation of Init and all calls to chained // overloads end up here. Contract.Requires<ArgumentNullException>(configurationPath != null, "configurationPath"); Contract.Requires<ArgumentException>(configurationPath.Length > 0, "configurationPath is an empty string."); Contract.Requires<FileNotFoundException>(File.Exists(configurationPath), configurationPath); Contract.Requires<ArgumentNullException>(mappingAssemblies != null, "mappingAssemblies"); Contract.ForAll<string>(mappingAssemblies, (n) => File.Exists(n)); //... } If however, I remove the requirements from that method, the static checker complains that the requirements of the Init(string, string[], string) overload are not met. I reckon that the static checker doesn't understand that there requirements of the Init(string, string[], string) overload implicitly apply to the Init(string, string[]) method as well; something that would be perfectly deductable from the code IMO. This is the situation I would like to achieve: public static void Init(string configurationPath, string[] mappingAssemblies) { // I don't want to repeat the requirements here because they will always // be checked in the overload called here. Init(configurationPath, mappingAssemblies, null); } public static void Init(string configurationPath, string[] mappingAssemblies, string optionalArgument) { // This is the main implementation of Init and all calls to chained // overloads end up here. Contract.Requires<ArgumentNullException>(configurationPath != null, "configurationPath"); Contract.Requires<ArgumentException>(configurationPath.Length > 0, "configurationPath is an empty string."); Contract.Requires<FileNotFoundException>(File.Exists(configurationPath), configurationPath); Contract.Requires<ArgumentNullException>(mappingAssemblies != null, "mappingAssemblies"); Contract.ForAll<string>(mappingAssemblies, (n) => File.Exists(n)); //... } So, my question is this: is there a way to have the requirements of Init(string, string[], string) implicitly apply to Init(string, string[]) automatically?

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  • Perl IO modules possibly causing issues in Net::DNS module

    - by Rich
    Hi! I’m porting some software that I wrote for a White Russian OpenWRT system to a new Kamikaze 8.09.1 OpenWRT system but I am having some serious issues that I’m hoping you can help me with. Old system Linux kernel 2.4.34 MIPSEL arch Perl 5.8.7 Net::DNS 0.48 IO 1.21 IO::Socket 1.28 IO::Socket::INET 1.28 New system Linux kernel 2.6.26.8 MIPS arch Perl 5.10.0 Net::DNS 0.66 IO 1.23_01 IO::Socket 1.30_01 IO::Socket::INET 1.31 First, let me provide some background information… I am trying to resolve my server (clearprobe.winbeam.com) from within my Perl program and see the following if I enable debugging in Net::DNS: resolve: Server 'clearprobe-ddns.winbeam.com' ;; query(clearprobe-ddns.winbeam.com) ;; setting up an AF_INET() family type UDP socket ;; send_udp(192.168.88.1:53) ;; send_udp(4.2.2.2:53) ;; send_udp(192.168.88.1:53) ;; send_udp(4.2.2.2:53) resolve: res->errorstring: query timed out Both of these servers resolve clearprobe.winbeam.com fine from the command line: root@cwb-2-11:~# echo “nameserver 192.168.88.1” > /etc/resolv.conf root@cwb-2-11:~# nslookup clearprobe-ddns.winbeam.com Server: 192.168.88.1 Address 1: 192.168.88.1 router Name: clearprobe-ddns.winbeam.com Address 1: 64.13.48.40 64-13-48-40.war.clearwire-dns.net root@cwb-2-11:~# echo “nameserver 4.2.2.2” > /etc/resolv.conf root@cwb-2-11:~# nslookup clearprobe-ddns.winbeam.com Server: 4.2.2.2 Address 1: 4.2.2.2 vnsc-bak.sys.gtei.net Name: clearprobe-ddns.winbeam.com Address 1: 64.13.48.40 64-13-48-40.war.clearwire-dns.net Using Perl’s call to the C gethostbyaddr() function works fine, but I need to do another lookup later in the software which requires that I specify the nameserver (clearprobe-ddns.winbeam.com is the authority for my internal DNS zone), hence my Net::DNS requirement. Now, here is the IO module-specific information: What I am seeing is that the reply is coming back from the nameserver (confirmed via tcpdump – I can send the captures if you’d like), but the UDP packets are sitting in the process’s UDP receive queue pending reception by Net::DNS (the approx 1752 bytes per response stay queued waiting for $sel-can_read()): root@cwb-2-11:~# netstat -una Active Internet connections (servers and established) Proto Recv-Q Send-Q Local Address Foreign Address State udp 1752 0 0.0.0.0:52680 0.0.0.0:* root@cwb-2-11:~# netstat -una Active Internet connections (servers and established) Proto Recv-Q Send-Q Local Address Foreign Address State udp 5256 0 0.0.0.0:52680 0.0.0.0:* If I force $sock[AF_INET]-recv($buf, $self-_packetsz) around line 803 of /usr/lib/perl5/5.10/Net/DNS/Resolver/Base.pm, instead of waiting for IO::Select’s can_read() function ( @ready = $sel-can_read($timeout)) to populate @ready, the response is received and processed. Any idea what could be causing this issue? In a possibly related matter, I noticed in another script that the following code fails in the same manner (network responses stay in the process’s TCP receive queue) with the new system: $sock = new IO::Socket::INET( PeerAddr => "$server", PeerPort => 37, Proto => 'tcp', Timeout => 5 ); Whereas the following code works: $sock = new IO::Socket::INET( PeerAddr => "$server", PeerPort => 37, Proto => 'tcp' ); I have looked through the NET::DNS code and don’t see a timeout passed for the UDP sockets, so I am not sure if that this is related or not. Please let me know if I can provide you with any further information in order to help diagnose this issue. Thanks! -Rich

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  • Syntax error in INSERT INTO statement

    - by user454563
    I wrote a program that connects to MS Access. When I fill in the fields and add a new item to Access the program fails. The exception is "Syntax error in INSERT INTO statement" Here is the relevant code. **************************************************************** AdoHelper.cs **************************************************************** using System; using System.Collections.Generic; using System.Text; using System.Data; using System.Data.OleDb; namespace Yad2 { class AdoHelper { //get the connection string from the app.config file //Provider=Microsoft.ACE.OLEDB.12.0;Data Source=|DataDirectory|\Yad2.accdb static string connectionString = Properties.Settings.Default.DBConnection.ToString(); //declare the db connection static OleDbConnection con = new OleDbConnection(connectionString); /// <summary> /// To Execute queries which returns result set (table / relation) /// </summary> /// <param name="query">the query string</param> /// <returns></returns> public static DataTable ExecuteDataTable(string query) { try { con.Open(); OleDbCommand command = new OleDbCommand(query, con); System.Data.OleDb.OleDbDataAdapter tableAdapter = new System.Data.OleDb.OleDbDataAdapter(command); DataTable dt = new DataTable(); tableAdapter.Fill(dt); return dt; } catch (Exception ex) { throw ex; } finally { con.Close(); } } /// <summary> /// To Execute update / insert / delete queries /// </summary> /// <param name="query">the query string</param> public static void ExecuteNonQuery(string query) { try { con.Open(); System.Data.OleDb.OleDbCommand command = new System.Data.OleDb.OleDbCommand(query, con); command.ExecuteNonQuery(); } catch (Exception ex) { throw ex; } finally { con.Close(); } } /// <summary> /// To Execute queries which return scalar value /// </summary> /// <param name="query">the query string</param> public static object ExecuteScalar(string query) { try { con.Open(); System.Data.OleDb.OleDbCommand command = new System.Data.OleDb.OleDbCommand(query, con); /// here is the Excaption !!!!!!!!! return command.ExecuteScalar(); } catch { throw; } finally { con.Close(); } } } } **************************************************************************** **************************************************************************** DataQueries.cs **************************************************************************** using System; using System.Collections.Generic; using System.Text; using System.Data; namespace Yad2 { class DataQueries { public static DataTable GetAllItems() { try { string query = "Select * from Messages"; DataTable dt = AdoHelper.ExecuteDataTable(query); return dt; } catch (Exception ex) { throw ex; } } public static void AddNewItem(string mesNumber, string title , string mesDate , string contactMail , string mesType , string Details ) { string query = "Insert into Messages values(" + mesNumber + " , '" + title + "' , '" + mesDate + "' , '" + contactMail + "' , , '" + mesType + "' , '" + Details + "')"; AdoHelper.ExecuteNonQuery(query); } public static void DeleteDept(int mesNumber) { string query = "Delete from Item where MessageNumber=" + mesNumber; AdoHelper.ExecuteNonQuery(query); } } } *********************************************************************************************** plase help me .... why the program falls ?

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