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  • Too many open connections... Did I mess up something?

    - by Legend
    I am developing a plugin (for a Bittorrent client named Azureus programmed in Java) that lets me add peers into the current list from which it is downloading. Everything was working fine until yesterday when I started getting these weird errors: DEBUG::Thu Apr 15 10:45:40 CET 2010::org.gudy.azureus2.core3.peer.impl.control.PEPeerControlImpl::addPeer::795: Injected peer 90.35.126.126:33064 was not added - Too many connections DEBUG::Thu Apr 15 10:48:40 CET 2010::org.gudy.azureus2.core3.peer.impl.control.PEPeerControlImpl::addPeer::795: Injected peer 80.25.126.126:33064 was not added - Too many connections DEBUG::Thu Apr 15 10:52:40 CET 2010::org.gudy.azureus2.core3.peer.impl.control.PEPeerControlImpl::addPeer::795: Injected peer 90.35.126.126:33064 was not added - Too many connections I am thinking I messed up something with the TCP sockets. Does anyone know why this could be happening?

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  • How is a referencing environment generally implemented for closures?

    - by Alexandr Kurilin
    Let's say I have a statically/lexically scoped language with deep binding and I create a closure. The closure will consist of the statements I want executed plus the so called referencing environment, or, to quote this post, the collection of variables which can be used. What does this referencing environment actually look like implementation-wise? I was recently reading about ObjectiveC's implementation of blocks, and the author suggests that behind the scenes you get a copy of all of the variables on the stack and also of all the references to heap objects. The explanation claims that you get a "snapshot" of the referencing environment at the point in time of the closure's creation. Is that more or less what happens, or did I misread that? Is anything done to "freeze" a separate copy of the heap objects, or is it safe to assume that if they get modified between closure creation and the closure executing, the closure will no longer be operating on the original version of the object? If indeed there's copying being made, are there memory usage considerations in situations where one might want to create plenty of closures and store them somewhere? I think that misunderstanding of some of these concepts might lead to tricky issues like the ones Eric Lippert mentions in this blog post. It's interesting because you'd think that it wouldn't make sense to keep a reference to a value type that might be gone by the time the closure is called, but I'm guessing that in C# the compiler will figure out that the variable is needed later and put it into the heap instead. It seems that in most memory-managed languages everything is a reference and thus ObjectiveC is a somewhat unique situation with having to deal with copying what's on the stack.

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  • Did Java invent interfaces?

    - by Jordão
    I know about C++ pure virtual classes, but Java went one step further and created a first-class (no pun intended) concept for multiple-interface (not implementation) inheritance, the interface. It's now a staple of major statically-typed languages. Did Java invent the interface concept? Or did it appear in older languages also as a first-class concept?

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  • How to best convert Flash compatible mp4 files with FFMPEG

    - by Espen Christensen
    I am trying to convert different files to a flash compatible .mp4 file with ffmpeg, but i cant seem to succeed. Off cource the objective is to get the greatest quality with the smallest filesize. So far I have this, that works but it doesnt play in a flash player of some reason, and the result isnt that great, anybody got any tips on how to improve this conversion? ffmpeg -i input.file -f mp4 -vcodec mpeg4 -r 25 -b 560000 -s 610x340 -acodec aac -ac 2 -ab 64 -ar 44100 output.file Would be great the se other peoples experiences with this type of conversion.

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  • Controlling shell command line wildcard expansion in C or C++

    - by Adrian McCarthy
    I'm writing a program, foo, in C++. It's typically invoked on the command line like this: foo *.txt My main() receives the arguments in the normal way. On many systems, argv[1] is literally *.txt, and I have to call system routines to do the wildcard expansion. On Unix systems, however, the shell expands the wildcard before invoking my program, and all of the matching filenames will be in argv. Suppose I wanted to add a switch to foo that causes it to recurse into subdirectories. foo -a *.txt would process all text files in the current directory and all of its subdirectories. I don't see how this is done, since, by the time my program gets a chance to see the -a, then shell has already done the expansion and the user's *.txt input is lost. Yet there are common Unix programs that work this way. How do they do it? In Unix land, how can I control the wildcard expansion? (Recursing through subdirectories is just one example. Ideally, I'm trying to understand the general solution to controlling the wildcard expansion.)

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  • What "exotic" language feature do you use every day?

    - by fmark
    For most programmers using procedural or object-oriented languages there is a language-feature lowest common denominator: variables, procedures, standard control structures, and classes. However, almost all languages add features on top of this. Recent C# versions have LINQ and delegates. C++ has template metaprogramming. Java has annotations. What features such as these do you use every day?

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  • Generic callbacks

    - by bobobobo
    Extends So, I'm trying to learn template metaprogramming better and I figure this is a good exercise for it. I'm trying to write code that can callback a function with any number of arguments I like passed to it. // First function to call int add( int x, int y ) ; // Second function to call double square( double x ) ; // Third func to call void go() ; The callback creation code should look like: // Write a callback object that // will be executed after 42ms for "add" Callback<int, int, int> c1 ; c1.func = add ; c1.args.push_back( 2 ); // these are the 2 args c1.args.push_back( 5 ); // to pass to the "add" function // when it is called Callback<double, double> c2 ; c2.func = square ; c2.args.push_back( 52.2 ) ; What I'm thinking is, using template metaprogramming I want to be able to declare callbacks like, write a struct like this (please keep in mind this is VERY PSEUDOcode) <TEMPLATING ACTION <<ANY NUMBER OF TYPES GO HERE>> > struct Callback { double execTime ; // when to execute TYPE1 (*func)( TYPE2 a, TYPE3 b ) ; void* argList ; // a stored list of arguments // to plug in when it is time to call __func__ } ; So for when called with Callback<int, int, int> c1 ; You would automatically get constructed for you by < HARDCORE TEMPLATING ACTION > a struct like struct Callback { double execTime ; // when to execute int (*func)( int a, int b ) ; void* argList ; // this would still be void*, // but I somehow need to remember // the types of the args.. } ; Any pointers in the right direction to get started on writing this?

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  • Why do some languages not use semicolons and braces?

    - by Incognito
    It is interesting that some languages do not use semicolons and braces, even though their predecessors had them. Personally, it makes me nervous to write code in Python because of this. Semicolons are also missing from Google's GO language, although the lexer uses a rule to insert semicolons automatically as it scans. Why do some languages not use semicolons and braces?

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  • Finding Local IP via Socket Creation / getsockname

    - by BSchlinker
    I need to get the IP address of a system within C++. I followed the logic and advice of another comment on here and created a socket and then utilized getsockname to determine the IP address which the socket is bound to. However, this doesn't appear to work (code below). I'm receiving an invalid IP address (58.etc) when I should be receiving a 128.etc Any ideas? string Routes::systemIP(){ // basic setup int sockfd; char str[INET_ADDRSTRLEN]; sockaddr* sa; socklen_t* sl; struct addrinfo hints, *servinfo, *p; int rv; memset(&hints, 0, sizeof hints); hints.ai_family = AF_UNSPEC; hints.ai_socktype = SOCK_DGRAM; if ((rv = getaddrinfo("4.2.2.1", "80", &hints, &servinfo)) != 0) { fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rv)); return "1"; } // loop through all the results and make a socket for(p = servinfo; p != NULL; p = p->ai_next) { if ((sockfd = socket(p->ai_family, p->ai_socktype, p->ai_protocol)) == -1) { perror("talker: socket"); continue; } break; } if (p == NULL) { fprintf(stderr, "talker: failed to bind socket\n"); return "2"; } // get information on the local IP from the socket we created getsockname(sockfd, sa, sl); // convert the sockaddr to a sockaddr_in via casting struct sockaddr_in *sa_ipv4 = (struct sockaddr_in *)sa; // get the IP from the sockaddr_in and print it inet_ntop(AF_INET, &(sa_ipv4->sin_addr.s_addr), str, INET_ADDRSTRLEN); printf("%s\n", str); // return the IP return str; }

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  • assembly of pdp-11(simulator)

    - by lego69
    I have this code on pdp-11 tks = 177560 tkb = 177562 tps = 177564 tpb = 177566 lcs = 177546 . = torg + 2000 main: mov #main, sp mov #kb_int, @#60 mov #200, @#62 mov #101, @#tks mov #clock, @#100 mov #300, @#102 mov #100, @#lcs loop: mov @#tks,r2 aslb r2 bmi loop halt clock: tst bufferg beq clk_end mov #msg,-(sp) jsr pc, print_str tst (sp)+ clr bufferg bic #100,@#tks clr @#lcs clk_end:rti kb_int: mov r1,-(sp) jsr pc, read_char movb r1,@buff_ptr inc buff_ptr bis #1,@#tks cmpb r1,#'q bne next_if mov #0, @#tks next_if:cmpb r1,#32. bne end_kb_int clrb @buff_ptr mov #buffer,-(sp) jsr pc, print_str tst (sp)+ mov #buffer,buff_ptr end_kb_int: mov (sp)+,r1 rti ;############################# read_char: tstb @#tks bpl read_char movb @#tkb, r1 rts pc ;############################# print_char: tstb @#tps bpl print_char movb r1, @#tpb rts pc ;############################# print_str: mov r1,-(sp) mov r2,-(sp) mov 6(sp),r2 str_loop: movb (r2)+,r1 beq pr_str_end jsr pc, print_char br str_loop pr_str_end: mov (sp)+,r2 mov (sp)+,r1 rts pc . = torg + 3000 msg:.ascii<Something is wrong!> .byte 0 .even buff_ptr: .word buffer buffer: .blkw 3 bufferg: .word 0 Can somebody please explain how this part is working, thanks in advance movb r1,@buff_ptr inc buff_ptr bis #1,@#tks cmpb r1,#'q bne next_if mov #0, @#tks next_if:cmpb r1,#32. bne end_kb_int clrb @buff_ptr mov #buffer,-(sp) jsr pc, print_str tst (sp)+ mov #buffer,buff_ptr

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  • Algorithm for non-contiguous netmask match

    - by Gianluca
    Hi, I have to write a really really fast algorithm to match an IP address to a list of groups, where each group is defined using a notation like 192.168.0.0/252.255.0.255. As you can see, the bitmask can contain zeros even in the middle, so the traditional "longest prefix match" algorithms won't work. If an IP matches two groups, it will be assigned to the group containing most 1's in the netmask. I'm not working with many entries (let's say < 1000) and I don't want to use a data structure requiring a large memory footprint (let's say 1-2 MB), but it really has to be fast (of course I can't afford a linear search). Do you have any suggestion? Thanks guys. UPDATE: I found something quite interesting at http://www.cse.usf.edu/~ligatti/papers/grouper-conf.pdf, but it's still too memory-hungry for my utopic use case

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  • Any merit to a lazy-ish juxt function?

    - by NielsK
    In answering a question about a function that maps over multiple functions with the same arguments (A: juxt), I came up with a function that basically took the same form as juxt, but used map: (defn could-be-lazy-juxt [& funs] (fn [& args] (map #(apply %1 %2) funs (repeat args)))) => ((juxt inc dec str) 1) [2 0 "1"] => ((could-be-lazy-juxt inc dec str) 1) (2 0 "1") => ((juxt * / -) 6 2) [12 3 4] => ((could-be-lazy-juxt * / -) 6 2) (12 3 4) As posted in the original question, I have little clue about the laziness or performance of it, but timing in the REPL does suggest something lazy-ish is going on. => (time (apply (juxt + -) (range 1 100))) "Elapsed time: 0.097198 msecs" [4950 -4948] => (time (apply (could-be-lazy-juxt + -) (range 1 100))) "Elapsed time: 0.074558 msecs" (4950 -4948) => (time (apply (juxt + -) (range 10000000))) "Elapsed time: 1019.317913 msecs" [49999995000000 -49999995000000] => (time (apply (could-be-lazy-juxt + -) (range 10000000))) "Elapsed time: 0.070332 msecs" (49999995000000 -49999995000000) I'm sure this function is not really that quick (the print of the outcome 'feels' about as long in both). Doing a 'take x' on the function only limits the amount of functions evaluated, which probably is limited in it's applicability, and limiting the other parameters by 'take' should be just as lazy in normal juxt. Is this juxt really lazy ? Would a lazy juxt bring anything useful to the table, for instance as a compositing step between other lazy functions ? What are the performance (mem / cpu / object count / compilation) implications ? Is that why the Clojure juxt implementation is done with a reduce and returns a vector ? Edit: Somehow things can always be done simpler in Clojure. (defn could-be-lazy-juxt [& funs] (fn [& args] (map #(apply % args) funs)))

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  • Sorting data by relevance, from multiple tables

    - by Oden
    Hey, How is it possible to sort data from multiple tables by relevance? My table structure is following: I have 3 tables in my database, one table contains the name of solar systems, the second for e.g. of planets. There is one more table, witch is a connection between solar systems and planets. If I want to get data of a planet, witch is in the Milky Way, i post this data to the server, and it gives me a multi-dimensional array witch contains: The Milky Way, with every planet in it Every planet, witch name contains the string Milky Way (maybe thats a bat example because i don't think that theres but one planet with this name, but the main concept is on file) But, i want to set the most relevant restaurants to the top of the array. (for the relevance i would check the description of the restaurants or something like that) So, how would you do that kind of data sorting?

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  • What are the limitations of assembler? (NASM)

    - by citronas
    Is there a technical limitation of what kind of programs I can write with assembler (NASM)? For now I've only seem some program that do arithmetic operations, like adding two numbers. Is it possible to write complex assembler programs, that provide a GUI, access the file system, plays sounds et cetera? I know I wouldn't write such programs, but I'm curious, if there are technical limitations on what kind of programs I can write with assembler.

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  • C++ Program Flow: Sockets in an Object and the Main Function

    - by jfm429
    I have a rather tricky problem regarding C++ program flow using sockets. Basically what I have is this: a simple command-line socket server program that listens on a socket and accepts one connection at a time. When that connection is lost it opens up for further connections. That socket communication system is contained in a class. The class is fully capable of receiving the connections and mirroring the data received to the client. However, the class uses UNIX sockets, which are not object-oriented. My problem is that in my main() function, I have one line - the one that creates an instance of that object. The object then initializes and waits. But as soon as a connection is gained, the object's initialization function returns, and when that happens, the program quits. How do I somehow wait until this object is deleted before the program quits? Summary: main() creates instance of object Object listens Connection received Object's initialization function returns main() exits (!) What I want is for main() to somehow delay until that object is finished with what it's doing (aka it will delete itself) before it quits. Any thoughts?

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  • How to access File over the Network

    - by Polo
    Hi! I am having a hard time on this one, I have a folder over the network with public access (no credential restriction). I am trying to do a File.Exist or Directory.Exist and I keep on having a exception. Can someone tell me the good way to do IO over the network. EDIT 1 FOR DETAILS: if i do execture = \agoodip\Public\test.txt I get the file etc etc In my code it look like a basic Directory.Exist(@"\\agoodip\Public") or File.exist(@"\\agoodip\Public\test.txt") The exception I get is Path not found. EDIT 2 : I am using Silverlight 3, Is there any security pattern to be aware of to lookup file on the network? Thanks!

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  • Jquery cant get dynamic data

    - by Napoleon Wai Lun Wong
    i am a noob to using the jQuery i have a problem about the Uncaught SyntaxError: Unexpected token i am using the 1.9.0 version of jqery i am creating a dynamic number of record, each record would create a "tr" in a table ,also i want to add some dynamic coding into the textbox part of Html coding : <-tbody<-tr id="row_1"<-input id="1" name="collections[appearance][headersubcolor][entity_id1][name]" value="0" class="Root Catalog input-text" type="text" Click inside to change a color of each Category <-tr id="row_2"<-td class="label"<-td class="value"<-input id="2" name="collections[appearance][headersubcolor][entity_id2][name]" value="0" class="Default Category input-text" type="text".... jQuery coding : $('tr[id^="row_"]'.each(function(){ var rowid = parsInt(this.id.replace("row_","")); console.lof("id:"+ rowid); var ??? = new jscolor.color(document.getElementById('???'), {}) }); $('tr[id^="row_"]'.each(function() <--- i cant getting the DATA

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  • Tips for learning MUMPS (M) / Cache?

    - by Jake
    I'm interested in getting involved/up to speed on VistA, the Veterans' Administrations open source medical records system. To that effect, I understand I should learn the MUMPS (M) language upon which the software is based. Does anyone have any getting started tips or book recommendations on this language and environment? Any tips on getting up to speed on VistA is appreciated as well. Audience: experienced developer/consultant. Thanx in adv.

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  • reassembling http packets with perl and parsing it

    - by johnny2
    I am using net::pcap module to capture packets with this filter: dst $my_host and dst port 80 inside the net::pcap::loop i use the below callback function: net::pcap::loop($pcap_t,-1,\my_callback,'') where my_callback look like this : my_callback { my ($user_data, $header, $packet) = @_; # Strip ethernet IP and TCP my $ether_data = NetPacket::Ethernet::strip($packet); my $ip = NetPacket::IP->decode($ether_data); my $tcp = NetPacket::TCP->decode($ip->{'data'}); } could someone help me how can i assemble the http packets to one packet and extract its header .

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  • Using pointers, references, handles to generic datatypes, as generic and flexible as possible

    - by Patrick
    In my application I have lots of different data types, e.g. Car, Bicycle, Person, ... (they're actually other data types, but this is just for the example). Since I also have quite some 'generic' code in my application, and the application was originally written in C, pointers to Car, Bicycle, Person, ... are often passed as void-pointers to these generic modules, together with an identification of the type, like this: Car myCar; ShowNiceDialog ((void *)&myCar, DATATYPE_CAR); The 'ShowNiceDialog' method now uses meta-information (functions that map DATATYPE_CAR to interfaces to get the actual data out of Car) to get information of the car, based on the given data type. That way, the generic logic only has to be written once, and not every time again for every new data type. Of course, in C++ you could make this much easier by using a common root class, like this class RootClass { public: string getName() const = 0; }; class Car : public RootClass { ... }; void ShowNiceDialog (RootClass *root); The problem is that in some cases, we don't want to store the data type in a class, but in a totally different format to save memory. In some cases we have hundreds of millions of instances that we need to manage in the application, and we don't want to make a full class for every instance. Suppose we have a data type with 2 characteristics: A quantity (double, 8 bytes) A boolean (1 byte) Although we only need 9 bytes to store this information, putting it in a class means that we need at least 16 bytes (because of the padding), and with the v-pointer we possibly even need 24 bytes. For hundreds of millions of instances, every byte counts (I have a 64-bit variant of the application and in some cases it needs 6 GB of memory). The void-pointer approach has the advantage that we can almost encode anything in a void-pointer and decide how to use it if we want information from it (use it as a real pointer, as an index, ...), but at the cost of type-safety. Templated solutions don't help since the generic logic forms quite a big part of the application, and we don't want to templatize all this. Additionally, the data model can be extended at run time, which also means that templates won't help. Are there better (and type-safer) ways to handle this than a void-pointer? Any references to frameworks, whitepapers, research material regarding this?

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  • How to replace for-loops with a functional statement in C#?

    - by Lernkurve
    A colleague once said that God is killing a kitten every time I write a for-loop. When asked how to avoid for-loops, his answer was to use a functional language. However, if you are stuck with a non-functional language, say C#, what techniques are there to avoid for-loops or to get rid of them by refactoring? With lambda expressions and LINQ perhaps? If so, how? Questions So the question boils down to: Why are for-loops bad? Or, in what context are for-loops to avoid and why? Can you provide C# code examples of how it looks before, i.e. with a loop, and afterwards without a loop?

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  • Statements and state

    - by FredOverflow
    Is there any deeper meaning in the fact that the word "statement" starts with the word "state", or is that just a curious coincidence? Note that english is not my native language, so the answer might be obvious to you, but not me ;)

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