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  • unix message queue

    - by Betamoo
    Is there an ipc option to get the last message in message queue but not removing it? I want this to allow many clients reading same messages from the same server.. Thanks

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  • Support FOSS Projects via T-Shirts

    - by The MYYN
    Can we get a list of free and open source projects, which can be supported through purchasing branded garment? Free Software Foundation http://shop.fsf.org/ ps. I know this is extremly off-topic. But I'd like to buy clothing and support open source at the same time, if possible. And I'd like to know, where this is possible.

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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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  • Parallel processing via multithreading in Java

    - by Robz
    There are certain algorithms whose running time can decrease significantly when one divides up a task and gets each part done in parallel. One of these algorithms is merge sort, where a list is divided into infinitesimally smaller parts and then recombined in a sorted order. I decided to do an experiment to test whether or not I could I increase the speed of this sort by using multiple threads. I am running the following functions in Java on a Quad-Core Dell with Windows Vista. One function (the control case) is simply recursive: // x is an array of N elements in random order public int[] mergeSort(int[] x) { if (x.length == 1) return x; // Dividing the array in half int[] a = new int[x.length/2]; int[] b = new int[x.length/2+((x.length%2 == 1)?1:0)]; for(int i = 0; i < x.length/2; i++) a[i] = x[i]; for(int i = 0; i < x.length/2+((x.length%2 == 1)?1:0); i++) b[i] = x[i+x.length/2]; // Sending them off to continue being divided mergeSort(a); mergeSort(b); // Recombining the two arrays int ia = 0, ib = 0, i = 0; while(ia != a.length || ib != b.length) { if (ia == a.length) { x[i] = b[ib]; ib++; } else if (ib == b.length) { x[i] = a[ia]; ia++; } else if (a[ia] < b[ib]) { x[i] = a[ia]; ia++; } else { x[i] = b[ib]; ib++; } i++; } return x; } The other is in the 'run' function of a class that extends thread, and recursively creates two new threads each time it is called: public class Merger extends Thread { int[] x; boolean finished; public Merger(int[] x) { this.x = x; } public void run() { if (x.length == 1) { finished = true; return; } // Divide the array in half int[] a = new int[x.length/2]; int[] b = new int[x.length/2+((x.length%2 == 1)?1:0)]; for(int i = 0; i < x.length/2; i++) a[i] = x[i]; for(int i = 0; i < x.length/2+((x.length%2 == 1)?1:0); i++) b[i] = x[i+x.length/2]; // Begin two threads to continue to divide the array Merger ma = new Merger(a); ma.run(); Merger mb = new Merger(b); mb.run(); // Wait for the two other threads to finish while(!ma.finished || !mb.finished) ; // Recombine the two arrays int ia = 0, ib = 0, i = 0; while(ia != a.length || ib != b.length) { if (ia == a.length) { x[i] = b[ib]; ib++; } else if (ib == b.length) { x[i] = a[ia]; ia++; } else if (a[ia] < b[ib]) { x[i] = a[ia]; ia++; } else { x[i] = b[ib]; ib++; } i++; } finished = true; } } It turns out that function that does not use multithreading actually runs faster. Why? Does the operating system and the java virtual machine not "communicate" effectively enough to place the different threads on different cores? Or am I missing something obvious?

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  • Is it possible to create a domain model for legacy code without refactoring?

    - by plaureano
    I currently have a client that wants me to 'abstract' out a domain model from the existing code but they specifically said that I shouldn't refactor the existing code itself. My question is 1) whether or not this is advisable and 2) what techniques would you apply in this scenario if you can't refactor the code yet they expect you to come up with a model for it? (EDIT: I can't quite put my finger on it, but somehow, not being able to refactor in this case just feels wrong. Has anyone else run into this type of scenario?)

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  • Data retrieval error in Jquery

    - by Ben
    I'm trying to retrieve data from a php file named return that contains <?php echo 'here is a string'; ?>. I'm doing this through an html file containing ` div { color:blue; } span { color:red; } var x; $.get("return.php", function(data){ x = data; }) function showAlert() {alert(x);} $(document).ready(function(){ alert(x); }); ` When the button is clicked it retrieves and displays the code fine, but on the page loading, it displays "undefined" instead of the data in return.php. Any solutions?

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  • Pthread-ed filetransfer application crash

    - by N.R.S.Sowrabh
    I am developing a file transfer application and am using pthreads on the receiver side for receiving multiple files. The function which is passed to pthreads calls the following function and at the end of this function I get a SIGABRT error and stack-smashing error appears on the terminal. Please help me find the bugs. If you need anymore code I'd be able to post the same. Thanks in advance. void recv_mesg(int new_sockid, char *fname) { cout<<"New Thread created with "<<new_sockid<<" and "<<fname<<endl; char buf[MAXLINE]; int fd; fd = open(fname, O_WRONLY ); int len =0; while (len<1024) { int curr = recv(new_sockid, buf, 1024-len, 0); //fprintf(stdout,"Message from Client:\n"); len += curr; //write (fd, buf, curr); fputs(buf, stderr); } int file_size = 0; sscanf(buf,"%d",&file_size); if(file_size<=0) perror("File Size < 0"); sprintf(buf,"Yes"); send(new_sockid,buf,strlen(buf),0); len = 0; while (len<file_size) { int curr = recv(new_sockid, buf, min(file_size-len,MAXLINE), 0); len += curr; write (fd, buf, curr); //fputs(buf, stdout); //fflush(stdout); } len = 0; close(fd); close(new_sockid); }

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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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  • 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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  • what do you do while code is compiling

    - by Jacob
    I'm looking for the best idea for what to do while code is compiling or tests are running. Typically around 5 minutes of thumb twiddling. Only so many cups of coffee can be made and drunk in a day, and I don't want to be seen always in the kitchen or bothering other people.

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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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  • Where is the Open Source alternative to WPF?

    - by Evan Plaice
    If we've learned anything from HTML/CSS it's that, declarative languages (like XML) work best to describe User Interfaces because: It's easy to build code preprocessors that can template the code effectively. The code is in a well defined well structured (ideally) format so it's easy to parse. The technology to effectively parse or crawl an XML based source file already exists. The UIs scripted code becomes much simpler and easier to understand. It simple enough that designers are able to design the interface themselves. Programmers suck at creating UIs so it should be made easy enough for designers. I recently took a look at the meat of a WPF application (ie. the XAML) and it looks surprisingly familiar to the declarative language style used in HTML. It's blindingly apparent to me that the current state of desktop UI development is largely fractionalized, otherwise there wouldn't be so much duplicated effort in the domain of user interfaces (IE. GTK, XUL, Qt, Winforms, WPF, etc). There are 45 GUI platforms for Python alone It's painfully obvious to me that there should be a general purpose, open source, standardized, platform independent, markup language for designing desktop GUIs. Much like what the W3C made HTML/CSS into. WPF, or more specifically XAML seems like a pretty likely step in the right direction. Why hasn't anyone in the Open Source community (AFAIK) even scratched the surface of this issue. Now that the 'browser wars' are over should we look forward to a future of 'desktop gui wars?' Note: This topic is relatively subjective in the attempt to be 'future-thinking.' I think that desktop GUI development in its current state sucks ((really)hard) and, even though WPF is still in it's infancy, it presents a likely solution to the problem. Has no one in the OS community looked into developing something similar because they don't see the value, or because it's not worth the effort?

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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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  • Other ternary operators besides ternary conditional (?:)

    - by Malcolm
    The "ternary operator" expression is now almost equivalent to the ternary conditional operator: condition ? trueExpression : falseExpression; However, "ternary operator" only means that it takes three arguments. I'm just curious, are there any languages with any other built-in ternary operators besides conditional operator and which ones?

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  • Longest Common Subsequence

    - by tsudot
    Consider 2 sequences X[1..m] and Y[1..n]. The memoization algorithm would compute the LCS in time O(m*n). Is there any better algorithm to find out LCS wrt time? I guess memoization done diagonally can give us O(min(m,n)) time complexity.

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  • Bluetooth service problem

    - by hara
    hi I need to create a custom bluetooth service and I have to develop it using c++. I read a lot of examples but I didn't success in publishing a new service with a custom UUID. I need to specify a UUID in order to be able to connect to the service from an android app. This is what i wrote: GUID service_UUID = { /* 00000003-0000-1000-8000-00805F9B34FB */ 0x00000003, 0x0000, 0x1000, {0x80, 0x00, 0x00, 0x80, 0x5F, 0x9B, 0x34, 0xFB} }; SOCKET s, s2; SOCKADDR_BTH sab if (WSAStartup(MAKEWORD(2, 2), &wsd) != 0) return 1; printf("installing a new service\n"); s = socket(AF_BTH, SOCK_STREAM, BTHPROTO_RFCOMM); if (s == INVALID_SOCKET) { printf ("Socket creation failed, error %d\n", WSAGetLastError()); return 1; } memset (&sab, 0, sizeof(sab)); sab.addressFamily = AF_BTH; sab.port = BT_PORT_ANY; sab.serviceClassId = service_UUID; if (0 != bind(s, (SOCKADDR *) &sab, sizeof(sab))) { printf ("bind() failed with error code %d\n", WSAGetLastError()); closesocket (s); return 1; } int result=sizeof(sab); getsockname(s,(SOCKADDR *) &sab, &result ); printSOCKADDR_BTH(sab); if(listen (s, 5) == 0) printf("listen() is OK! Listening for connection... :)\n"); else printf("listen() failed with error code %d\n", WSAGetLastError()); printf("waiting connection"); for ( ; ; ) { int ilen = sizeof(sab2); s2 = accept (s, (SOCKADDR *)&sab2, &ilen); printf ("accepted"); } if(closesocket(s) == 0) printf("closesocket() pretty fine!\n"); if(WSACleanup () == 0) printf("WSACleanup() is OK!\n"); return 0; When i print the SOCKADDR_BTH structure retrieved with get getsockname i get an UUID that is not the mine. Furthermore if i use the UUID read from getsockname to connect the Android application the connection fails with this exception: java.io.IOException: Service discovery failed Could you help me?? Thanks!

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  • shared hacker houses in europe

    - by Mantas
    Hey, I'm a freelance web developer. I'm borred of my hometown, so I want to hit the road. Do you know any shared hacker houses in Europe? Do you have any ideas what is the best way to look for a shared flat? France, Spain, Holland, Italy... I'm interested in virtually any country :) P.S. I speak English and Lithuanian only, so it's hard to look up shared flat in local languages...

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  • How to implement a syndication receiver? (multi-client / single server)

    - by LeonixSolutions
    I have to come up with a system architecture. A few hundred remote devices will be communicating over internet with a central server which will receive data and store it in a database. I could write my own TCP/IP based protocol use SOAP use AJAX use RSS anything else? This is currently seen as one way (telemetry, as opposed to SCADA). Would it make a difference if we make it bi-directional. There are no plans to do so, but Murphy's law makes me wary of a uni-directional solution (on the data plane; I imagine that the control plane is bi-directional in all solutions (?)). I hope that this is not too subjective. I would like a solution which is quick and easy to implement and for others to support and where the general "communications pipeline" from remote deceives to database server can be re-used as the core of future projects. I have a strong background in telecomms protocols, in C/C++ and PHP.

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  • How well does Scala Perform Comapred to Java?

    - by Teja Kantamneni
    The Question actually says it all. The reason behind this question is I am about to start a small side project and want to do it in Scala. I am learning scala for the past one month and now I am comfortable working with it. The scala compiler itself is pretty slow (unless you use fsc). So how well does it perform on JVM? I previously worked on groovy and I had seen sometimes over performed than java. My Question is how well scala perform on JVM compared to Java. I know scala has some very good features(FP, dynamic lang, statically typed...) but end of the day we need the performance...

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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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