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  • Most efficient way for testing links

    - by Burnzy
    I'm currently developping an app that is going through all the files on a server and checking every single hrefs to check wether they are valid or not. Using a WebClient or a HttpWebRequest/HttpWebResponse is kinda overkilling the process because it downloads the whole page each time, which is useless, I only need to check if the link do not return 404. What would be the most efficient way? Socket seems to be a good way of doing it, however I'm not quite sure how this works. Thanks for sharing your expertise!

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  • sending a packet to multiple client at a time from udp socket

    - by mawia
    Hi! all, I was trying to write a udp server who send an instance of a file to multiple clients.Now suppose any how I manage to know the address of those client statically(for the sake of simplicity) and now I want to send this packet to these addresses.So how exactly I need to fill the sockaddr structure to contain the address of these clients.I am taking an array of sockaddr structure(to contain client address) and trying to send at each one them at a time.Now problem is to fill the individual sockaddr structure to contain the client address. I was trying to do something like that sa[1].sin_family = AF_INET; sa[1].sin_addr.s_addr = htonl(INADDR_ANY);//should'nt I replace this INADDR_ANY with client ip?? sa[1].sin_port = htons(50002); Correct me if this is not the correct way. All your help in this regard will be highly appreciated. With Thanks in advance, Mawia

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  • Why don't scripting languages output Unicode to the Windows console?

    - by hippietrail
    The Windows console has been Unicode aware for at least a decade and perhaps as far back as Windows NT. However for some reason the major cross-platform scripting languages including Perl and Python only ever output various 8-bit encodings, requiring much trouble to work around. Perl gives a "wide character in print" warning, Pythong gives a charmap error and quits. Why on earth after all these years do they not just simply call the Win32 -W APIs that output UTF-16 Unicode instead of forcing everything through the ANSI/codepage bottleneck? Is it just that cross-platform performance is low priority? Is it that the languages use UTF-8 internally and find it too much bother to output UTF-16? Or are the -W APIs inherently broken to such a degree that they can't be used as-is?

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  • How to implement a list fold in Java

    - by Peter Kofler
    I have a List and want to reduce it to a single value (functional programing term "fold", Ruby term "inject"), like Arrays.asList("a", "b", "c") ... fold ... "a,b,c" As I am infected with functional programing ideas (Scala), I am looking for an easier/shorter way to code it than sb = new StringBuilder for ... { append ... } sb.toString

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  • How to handle server-client requests

    - by Layne
    Currently I'm working on a Server-Client system which will be the backbone of my application. I have to find the best way to send requests and handle them on the server-side. The server-side should be able to handle requests like this one: getPortfolio -i 2 -d all In an old project I decided to send such a request as string and the server application had to look up the first part of the string ("getPortfolio"). Afterwards the server application had to find the correct method in a map which linked the methods with the the first part of the string ("getPortfolio"). The second part ("-i 2 -d all") got passed as parameter and the method itself had to handle this string/parameter. I doubt that this is the best solution in order to handle many different requests. Rgds Layne

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  • What happens when we say "listen to a port" ?

    - by smwikipedia
    Hi, When we start a server application, we always need to speicify the port number it listens to. But how is this "listening mechanism" implemented under the hood? My current imagination is like this: The operating system associate the port number with some buffer. The server application's responsibiligy is to monitor this buffer. If there's no data in this buffer, the server application's listen operation will just block the application. When some data arrives from the wire, the operating system will know that check the data and see if it is targed at this port number. And then it will fill the buffer. And then OS will notify the blocked server application and the server application will get the data and continue to run. Question is: If the above scenario is correct, how could the opearting system know there's data arriving from wire? It cannot be a busy pooling. Is it some kind of interrupt-based mechanism? If there's too much data arriving and the buffer is not big enough, will there be data loss? Is the "listen to a port" operation really a blocking operation? Many thanks.

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  • Multiple-File Template Implementation

    - by Maxpm
    With normal functions, the declaration and definition are often separated across multiple files like so: // Foo.h namespace Foo { void Bar(); } . // Foo.cpp #include "Foo.h" void Foo::Bar() { cout << "Inside function." << endl; } It is my understanding that this cannot be done with templates. The declaration and definition must not be separate because the appropriate form of the template is created "on-demand" when needed. So, how and where are templates typically defined in a multiple-file project like this? My intuition is that it would be in Foo.cpp because that's where the "meat" of functions normally is, but on the other hand it's the header file that's going to be included.

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  • What about parallelism across network using multiple PCs?

    - by MainMa
    Parallel computing is used more and more, and new framework features and shortcuts make it easier to use (for example Parallel extensions which are directly available in .NET 4). Now what about the parallelism across network? I mean, an abstraction of everything related to communications, creation of processes on remote machines, etc. Something like, in C#: NetworkParallel.ForEach(myEnumerable, () => { // Computing and/or access to web ressource or local network database here }); I understand that it is very different from the multi-core parallelism. The two most obvious differences would probably be: The fact that such parallel task will be limited to computing, without being able for example to use files stored locally (but why not a database?), or even to use local variables, because it would be rather two distinct applications than two threads of the same application, The very specific implementation, requiring not just a separate thread (which is quite easy), but spanning a process on different machines, then communicating with them over local network. Despite those differences, such parallelism is quite possible, even without speaking about distributed architecture. Do you think it will be implemented in a few years? Do you agree that it enables developers to easily develop extremely powerfull stuff with much less pain? Example: Think about a business application which extracts data from the database, transforms it, and displays statistics. Let's say this application takes ten seconds to load data, twenty seconds to transform data and ten seconds to build charts on a single machine in a company, using all the CPU, whereas ten other machines are used at 5% of CPU most of the time. In a such case, every action may be done in parallel, resulting in probably six to ten seconds for overall process instead of forty.

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  • Developing a project which is an implementation of an open standard/protocol

    - by dotnetdev
    Hi, A lot of interesting code/projects are implementations of protocols, eg SNMP. How are projects like these, which depend on implementing a certain format, developed? Is the process something like get the guidelines of the protocol and then implement code which follows it. For example, XML-RPC is about transmitting XML docs between client/server, so the documentation on this protocol must outline the structure of the XML documents and then the way the transportation between client and server works, so the coder will implement this sort of functionality (xml doc construction, networking between the client and server). Projects I am thinking of (not to develop) are C# libraries which can interpret .PSDs, make VHDs, etc. So if I was to develop a C# app to implement .AI files (Illustrator files), what would be the steps I would look at (such as contacting Adobe, etc)? Is this the way such projects are developed?

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  • Haskell map function with predicate

    - by Paul
    I feel like this should be fairly obvious, or easy, but I just can't get it. What I want to do is apply a function to a list (using map) but only if a condition is held. Imagine you only wanted to divide the numbers which were even: map (`div` 2) (even) [1,2,3,4] And that would give out [1,1,3,2] since only the even numbers would have the function applied to them. Obviously this doesn't work, but is there a way to make this work without having to write a seperate function that you can give to map? Filter is almost there, except I also want to keep the elements which the condition doesn't hold for, and just not apply the function to them. Thanks

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  • How do I use Declarations (type, inline, optimize) in Scheme?

    - by kunjaan
    How do I declare the types of the parameters in order to circumvent type checking? How do I optimize the speed to tell the compiler to run the function as fast as possible like (optimize speed (safety 0))? How do I make an inline function in Scheme? How do I use an unboxed representation of a data object? And finally are any of these important or necessary? Can I depend on my compiler to make these optimizations? thanks, kunjaan.

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  • Regarding Shell variable

    - by arav
    I need to call another shell script testarg.sh within my main script. This script testarg.sh has arguments ARG1 ,ARG2, ARG3. I need to call up the below way ./testarg.sh -ARG1 -ARG2 -ARG3 ARG1 and ARG3 argument Variables are mandatory ones. If its not passed to the main script then i quit. ARG2 is an optional one. If the ARG2 variable is not set with value or it's not defined then i need not pass it from main script.So i need to call up the below way ./testarg.sh -ARG1 -ARG3 If the value exist for the ARG2 Varibale then i need to call the below way ./testarg.sh -ARG1 -ARG2 -ARG3 Do i need to have a if else statement for checking the ARG2 variable is empty or null. Is there any other way to do it.

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  • Linux Kernel - Socket file descriptor close location

    - by NTek
    Where in the linux kernel does the closing of a socket's file descriptor occur? I know for a file, the file's file descriptor is closed in fs/open.cs function sys_close(). However, for a socket file descriptor, is this the same location or somewhere else? Also, do sockets utilize the file.c alloc_fd to allocate the file descriptor or do they utilize some other function?

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  • My python program always brings down my internet connection after several hours running, how do I debug and fix this problem?

    - by Shane
    I'm writing a python script checking/monitoring several server/websites status(response time and similar stuff), it's a GUI program and I use separate thread to check different server/website, and the basic structure of each thread is using an infinite while loop to request that site every random time period(15 to 30 seconds), once there's changes in website/server each thread will start a new thread to do a thorough check(requesting more pages and similar stuff). The problem is, my internet connection always got blocked/jammed/messed up after several hours running of this script, the situation is, from my script side I got urlopen error timed out each time it's requesting a page, and from my FireFox browser side I cannot open any site. But the weird thing is, the moment I close my script my Internet connection got back on immediately which means now I can surf any site through my browser, so it must be the script causing all the problem. I've checked the program carefully and even use del to delete any connection once it's used, still get the same problem. I only use urllib2, urllib, mechanize to do network requests. Anybody knows why such thing happens? How do I debug this problem? Is there a tool or something to check my network status once such situation occurs? It's really bugging me for a while... By the way I'm behind a VPN, does it have something to do with this problem? Although I don't think so because my network always get back on once the script closed, and the VPN connection never drops(as it appears) during the whole process.

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  • F# replace ref variable with something fun

    - by Stephen Swensen
    I have the following F# functions which makes use of a ref variable to seed and keep track of a running total, something tells me this isn't in the spirit of fp or even particular clear on its own. I'd like some direction on the clearest (possible fp, but if an imperative approach is clearer I'd be open to that) way to express this in F#. Note that selectItem implements a random weighted selection algorithm. type WeightedItem(id: int, weight: int) = member self.id = id member self.weight = weight let selectItem (items: WeightedItem list) (rand:System.Random) = let totalWeight = List.sumBy (fun (item: WeightedItem) -> item.weight) items let selection = rand.Next(totalWeight) + 1 let runningWeight = ref 0 List.find (fun (item: WeightedItem) -> runningWeight := !runningWeight + item.weight !runningWeight >= selection) items let items = [new WeightedItem(1,100); new WeightedItem(2,50); new WeightedItem(3,25)] let selection = selectItem items (new System.Random())

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  • inode_operations , warning: initialization from incompatible pointer type

    - by djTeller
    Hi everyone, I'm trying to compile a simple Kernel program that read and write from a proc file. I'm trying to set permission to that file by overriding the permission fp in inode_operations struct (.permission) static int module_permission(struct inode *inode, int op, struct nameidata *foo) { . . . } static struct inode_operations Inode_Ops_4_Our_Proc_File = { .permission = module_permission, /* check for permissions */ }; Our_Proc_File->proc_iops = &Inode_Ops_4_Our_Proc_File; For some reason, when I compile this i get - warning: initialization from incompatible pointer type on the following line: .permission = module_permission, /* check for permissions */ Any idea how to solve this? Thanks!

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  • Generic TypeIdenitifier convertion.How?

    - by John
    How do I convert the TypeIdenitifier to a class type? I need to use implicit convertion. type TMyChildArray<T>=class(TMyArray<T>) private FData:Array of T; procedure AddEnd(); end; TTypeIdenitifierParentClass=class(TAnotherParentClass) protected TestField:Cardinal; end; procedure TMyChildArray<T>.AddEnd(); var elem:T; begin for elem in Fdata do TTypeIdenitifierParentClass(elem).TestField:=0; end; I get "Invalid typecast" on the implicit convertion "TTypeIdenitifierParentClass(elem).TestField:=0;". The principle I want to use is that the TypeIdenitifier will represent a class that descends from TTypeIdenitifierParentClass.There are many class types,but all of them descend that class. How do I do this?

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