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  • Strange client's address returned throug accept(..) function.

    - by Negai
    Hi everyone, I'm a socket programming newbie. Here's a snippet: struct sockaddr_storage client_addr; ... client_addr_size = sizeof(client_addr); client_socket = accept( server_socket, (struct sockaddr *)&client_addr, &client_addr_size ); ... result = inet_ntop( AF_INET, &((struct sockaddr_in *)&client_addr)->sin_addr, client_addr_str, sizeof(client_addr_str) ); Whenever the client connects the address I get is 0.0.0.0 regardless from the host. Can anybody explain, what I'm doing wrong? Thanks.

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  • Can someone please explain to me the basic function of Intents in the Android OS?

    - by K-RAN
    I'm new to programming applications for the Android OS. As far as general architecture of the OS goes, I understand that processes are implemented as Linux processes and that each one is sandboxed. However, I'm utterly confused on the IPCs and syscalls (if any) used. I know that the IBinder is a form of this; parcels are sent back and forth between processes and Bundles are array forms of parcels (?). But even that is still unfamiliar to me. Same with Intents. All in all, I don't understand what kinds of IPCs are implemented and how. Could someone briefly explain to me the specific methods used by user level applications in Android OS to communicate with each other and the OS? I've done kernel programming and played with various IPCs in Linux (Ubuntu and Debian) so it would help immensely if this was all explained in relation to what I'm familiar with... Thanks in advance!

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  • a class function with if(this==NULL) test got compiled?

    - by James
    I saw this code snippet during our lab and it actually compiles in MSVC2008 and G++. void LinkList< class T ::Insert(T n) { if (this == NULL) // some code here } As far as I know the this must not be null since you cannot call a class functions in c++ if it wasn't instantiated. Is this a valid code? if so what's the reason behind and where it can be useful?

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  • Is this a legitimate implementation of a 'remember me' function for my web app?

    - by user246114
    Hi, I'm trying to add a "remember me" feature to my web app to let a user stay logged in between browser restarts. I think I got the bulk of it. I'm using google app engine for the backend which lets me use java servlets. Here is some pseudo-code to demo: public class MyServlet { public void handleRequest() { if (getThreadLocalRequest().getSession().getAttribute("user") != null) { // User already has session running for them. } else { // No session, but check if they chose 'remember me' during // their initial login, if so we can have them 'auto log in' // now. Cookie[] cookies = getThreadLocalRequest().getCookies(); if (cookies.find("rememberMePlz").exists()) { // The value of this cookie is the cookie id, which is a // unique string that is in no way based upon the user's // name/email/id, and is hard to randomly generate. String cookieid = cookies.find("rememberMePlz").value(); // Get the user object associated with this cookie id from // the data store, would probably be a two-step process like: // // select * from cookies where cookieid = 'cookieid'; // select * from users where userid = 'userid fetched from above select'; User user = DataStore.getUserByCookieId(cookieid); if (user != null) { // Start session for them. getThreadLocalRequest().getSession() .setAttribute("user", user); } else { // Either couldn't find a matching cookie with the // supplied id, or maybe we expired the cookie on // our side or blocked it. } } } } } // On first login, if user wanted us to remember them, we'd generate // an instance of this object for them in the data store. We send the // cookieid value down to the client and they persist it on their side // in the "rememberMePlz" cookie. public class CookieLong { private String mCookieId; private String mUserId; private long mExpirationDate; } Alright, this all makes sense. The only frightening thing is what happens if someone finds out the value of the cookie? A malicious individual could set that cookie in their browser and access my site, and essentially be logged in as the user associated with it! On the same note, I guess this is why the cookie ids must be difficult to randomly generate, because a malicious user doesn't have to steal someone's cookie - they could just randomly assign cookie values and start logging in as whichever user happens to be associated with that cookie, if any, right? Scary stuff, I feel like I should at least include the username in the client cookie such that when it presents itself to the server, I won't auto-login unless the username+cookieid match in the DataStore. Any comments would be great, I'm new to this and trying to figure out a best practice. I'm not writing a site which contains any sensitive personal information, but I'd like to minimize any potential for abuse all the same, Thanks

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  • window.onbeforeunload ajax request problem with Chrome

    - by lang2
    Hello, I have a web page that handles remote control of a machine through Ajax. When user navigate away from the page, I'd like to automatically disconnect from the machine. So here is the code: window.onbeforeunload = function () { bas_disconnect_only(); } The disconnection function simply send a HTTP GET request to a PHP server side script, which does the actual work of disconnecting: function bas_disconnect_only() { var xhr = bas_send_request("req=10", function() { } ); } This works fine in FireFox. But with Chrome, the ajax request is not sent at all. There is a unacceptable workaround: adding alert to the callback function: function bas_disconnect_only() { var xhr = bas_send_request("req=10", function() { alert("You're been automatically disconnected."); } ); } After adding the alert call, the request would be sent successfully. But as you can see, it's not really a work around at all. Could somebody tell me if this is achievable with Chrome? What I'm doing looks completely legit to me. Thanks,

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  • jQuery programming style?

    - by Sam Dufel
    I was recently asked to fix something on a site which I haven't worked on before. I haven't really worked with jQuery that much, but I figured I'd take a look and see if I could fix it. I've managed to mostly clear up the problem, but I'm still horrified at the way they chose to build this site. On document load, they replace the click() method of every anchor tag and form element with the same massive function. When clicked, that function then checks if the tag has one of a few different attributes (non-standard attributes, even), and does a variety of different tasks depending on what attributes exist and what their values are. Some hyperlinks have an attribute on them called 'ajaxrel', which makes the click() function look for another (hidden) hyperlink with an ID specified by the ajaxrel attribute, and then calls the click() function for that other hyperlink (which was also modified by this same click() function). On the server side, all the php files are quite long and have absolutely no indentation. This whole site has been a nightmare to debug. Is this standard jQuery practice? This navigation scheme seems terrible. Does anyone else actually use jQuery this way? I'd like to start incorporating it into my projects, but looking at this site is giving me a serious headache. Here's the click() function for hyperlinks: function ajaxBoxA(theElement, urltosend, ajaxbox, dialogbox) { if ($(theElement).attr("href") != undefined) var urltosend = $(theElement).attr("href"); if ($(theElement).attr('toajaxbox') != undefined) var ajaxbox = $(theElement).attr('toajaxbox'); // check to see if dialog box is called for. if ($(theElement).attr('dialogbox') != undefined) var dialogbox = $(theElement).attr('dialogbox'); var dodialog = 0; if (dialogbox != undefined) { // if dialogbox doesn't exist, then flag to create dialog box. var isDiaOpen = $('[ajaxbox="' + ajaxbox + '"]').parent().parent().is(".ui-dialog-container"); dodialog = 1; if (isDiaOpen) { dodialog = 0; } dialogbox = parseUri(dialogbox); dialogoptions = { close: function () { // $("[id^=hierarchy]",this).NestedSortableDestroy(); $(this).dialog('destroy').remove() } }; for ( var keyVar in dialogbox['queryKey'] ) eval( "dialogoptions." + keyVar + " = dialogbox['queryKey'][keyVar]"); }; $("body").append("<div id='TB_load'><img src='"+imgLoader.src+"' /></div>"); $('#TB_load').show(); if (urltosend.search(/\?/) > 0) { urltosend = urltosend + "&-ajax=1"; } else { urltosend = urltosend + "?-ajax=1"; } if ($('[ajaxbox="' + ajaxbox + '"]').length) { $('[ajaxbox="' + ajaxbox + '"]').each( function () { $(this).empty(); }); }; $.ajax({ type: "GET", url: urltosend, data: "", async: false, dataType: "html", success: function (html) { var re = /^<toajaxbox>(.*?)<\/toajaxbox>+(.*)/; if (re.test(html)) { var match = re.exec(html); ajaxbox = match[1]; html = Right(html, String(html).length - String(match[1]).length); } var re = /^<header>(.*?)<\/header>+(.*)/; if (re.test(html)) { var match = re.exec(html); window.location = match[1]; return false; } if (html.length > 0) { var newHtml = $(html); if ($('[ajaxbox="' + ajaxbox + '"]').length) { $('[ajaxbox="' + ajaxbox + '"]').each( function () { $(this).replaceWith(newHtml).ready( function () { ajaxBoxInit(newHtml) if (window.ajaxboxsuccess) ajaxboxsuccess(newHtml); }); }); if ($('[ajaxdialog="' + ajaxbox + '"]').length = 0) { if (dodialog) $(newHtml).wrap("<div class='flora ui-dialog-content' ajaxdialog='" + ajaxbox + "' style='overflow:auto;'></div>").parent().dialog(dialogoptions); } } else { $("body").append(newHtml).ready( function () { ajaxBoxInit(newHtml); if (window.ajaxboxsuccess) ajaxboxsuccess(newHtml); }); if (dodialog) $(newHtml).wrap("<div class='flora ui-dialog-content' ajaxdialog='" + ajaxbox + "' style='overflow:auto;'></div>").parent().dialog(dialogoptions); } } var rel = $(theElement).attr('ajaxtriggerrel'); if (rel != undefined) $('a[ajaxrel="' + rel + '"]').click(); tb_remove(); return false; }, complete: function () { $("#TB_load").remove(); } }); return false; }

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  • Why does a PHP function with no parameters require parentheses?

    - by MarkRobinson
    I just spent 3 hours wondering why I couldn't start a session, then realised that I used: session_start; when I should have used: session_start(); I received no error messages at all! Perhaps then, I thought, it's a lazy way to differentiate functions from variables - but then remembered that it can't be as variables require a $ Can anyone tell me why parentheses are required then, and also why no error is given when they aren't used?

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  • R: How to pass a list of selection expressions (strings in this case) to the subset function?

    - by John
    Here is some example data: data = data.frame(series = c("1a", "1b", "1e"), reading = c(0.1, 0.4, 0.6)) > data series reading 1 1a 0.1 2 1b 0.4 3 1e 0.6 Which I can pull out selective single rows using subset: > subset (data, series == "1a") series reading 1 1a 0.1 And pull out multiple rows using a logical OR > subset (data, series == "1a" | series == "1e") series reading 1 1a 0.1 3 1e 0.6 But if I have a long list of series expressions, this gets really annoying to input, so I'd prefer to define them in a better way, something like this: series_you_want = c("1a", "1e") (although even this sucks a little) and be able to do something like this, subset (data, series == series_you_want) The above obviously fails, I'm just not sure what the best way to do this is?

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  • How to skip integers in C++ taken from a fstream txt file?

    - by Elaina
    I need to create a function that uses a loop. This function will open a text file and then must be able to skip a variable number of leading random integers. The program must be able to handle any number of leading random integers. Example if the opened file reads this on its first line: 100 120 92 82 38 49 102 and the SKIP_NUMBER variable is assigned 3 the number the function would grab is 82. The function must continue to grab the integers every SKIP_NUMBER until it reaches the end of the file. These integers taken from the txt file are then placed into another text file. Please help I'm really lost on how to create this loop! :D Here is my function so far... //Function skips variables and returns needed integer int skipVariable (int SKIP_NUMBER) { return 0; //temporary return } These are my program variables: // initialize function/variables ifstream fin; string IN_FILE_NAME, OUT_FILE_NAME; int SKIP_NUMBER;

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  • Static source code analysis with LLVM

    - by Phong
    I recently discover the LLVM (low level virtual machine) project, and from what I have heard It can be used to performed static analysis on a source code. I would like to know if it is possible to extract the different function call through function pointer (find the caller function and the callee function) in a program. I could find the kind of information in the website so it would be really helpful if you could tell me if such an library already exist in LLVM or can you point me to the good direction on how to build it myself (existing source code, reference, tutorial, example...). EDIT: With my analysis I actually want to extract caller/callee function call. In the case of a function pointer, I would like to return a set of possible callee. both caller and callee must be define in the source code (this does not include third party function in a library).

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  • Jquery ajax load of JSON in unit tests

    - by wmitchell
    I'm trying to load a dataset in jasmine for my tests like such ... However as its a json call I cant seem to always get the test denoted by "it" to wait till the JSON call has finished before using its array. I tried using the ajaxStop function to no avail. Any ideas ? describe("simple checks", function() { var exampleArray = new Array(); beforeEach(function(){ $(document).ajaxStop(function() { $(this).unbind("ajaxStop"); $.getJSON('/jasmine/obj.json', function(data) { $.each( json.jsonattr, function(i, widgetElement) { exampleArray.push(new widget(widgetElement)); }); }); }); }); it("use the exampleArray", function() { doSomething(exampleArray[0]); // frequently this is coming up as undefined });

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  • How to get all the fields of a row using the SQL MAX function?

    - by Yiannis Mpourkelis
    Consider this table (from http://www.tizag.com/mysqlTutorial/mysqlmax.php): Id name type price 123451 Park's Great Hits Music 19.99 123452 Silly Puddy Toy 3.99 123453 Playstation Toy 89.95 123454 Men's T-Shirt Clothing 32.50 123455 Blouse Clothing 34.97 123456 Electronica 2002 Music 3.99 123457 Country Tunes Music 21.55 123458 Watermelon Food 8.73 This SQL query returns the most expensive item from each type: SELECT type, MAX(price) FROM products GROUP BY type Clothing $34.97 Food $8.73 Music $21.55 Toy $89.95 I also want to get the fields id and name that belong to the above max price, for each row. What SQL query will return a table like this? Id name type price 123455 Blouse Clothing 34.97 123458 Watermelon Food 8.73 123457 Country Tunes Music 21.55 123453 Playstation Toy 89.95

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  • Should not a tail-recursive function also be faster?

    - by Balint Erdi
    I have the following Clojure code to calculate a number with a certain "factorable" property. (what exactly the code does is secondary). (defn factor-9 ([] (let [digits (take 9 (iterate #(inc %) 1)) nums (map (fn [x] ,(Integer. (apply str x))) (permutations digits))] (some (fn [x] (and (factor-9 x) x)) nums))) ([n] (or (= 1 (count (str n))) (and (divisible-by-length n) (factor-9 (quot n 10)))))) Now, I'm into TCO and realize that Clojure can only provide tail-recursion if explicitly told so using the recur keyword. So I've rewritten the code to do that (replacing factor-9 with recur being the only difference): (defn factor-9 ([] (let [digits (take 9 (iterate #(inc %) 1)) nums (map (fn [x] ,(Integer. (apply str x))) (permutations digits))] (some (fn [x] (and (factor-9 x) x)) nums))) ([n] (or (= 1 (count (str n))) (and (divisible-by-length n) (recur (quot n 10)))))) To my knowledge, TCO has a double benefit. The first one is that it does not use the stack as heavily as a non tail-recursive call and thus does not blow it on larger recursions. The second, I think is that consequently it's faster since it can be converted to a loop. Now, I've made a very rough benchmark and have not seen any difference between the two implementations although. Am I wrong in my second assumption or does this have something to do with running on the JVM (which does not have automatic TCO) and recur using a trick to achieve it? Thank you.

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  • Mysql replace() function, help with query (what chars do I escape?)

    - by jyoseph
    I am trying to update an old cms where images were stored in /images/editor/, they are now stored in a bucket on amazon s3. I'm trying to update the database using mysql replace. I've done this in the past with replacing simple words, but now Mysql is reporting an error, I suspect because this is more than a simple word: UPDATE contents SET desc = replace(desc, '/images/editor/', 'http://s3.amazonaws.com/my_bucket/editor/') Do I need to escape the : or slashes? I've tried escaping it with a '\' to no avail. Can someone get me pointed in the right direction? Thanks! Edit Here's the error I am getting, nothing too telling error : You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'desc = replace(desc, '/images/editor', 'http://s3.amazonaws.com/app_navigator/ed' at line 1

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  • Why not speed up testing by using function dependency graph?

    - by Maltrap
    It seems logical to me that if you have a dependency graph of your source code (tree showing call stack of all functions in your code base) you should be able to save a tremendous amount of time doing functional and integration tests after each release. Essentially you will be able to tell the testers exactly what functionality to test as the rest of the features remain unchanged from a source code point of view. If for instance you change a spelling mistake in once piece of the code, there is no reason to run through your whole test script again "just in case" you introduced a critical bug. My question, why are dependency trees not used in software engineering and if you use them, how do you maintain them? What tools are available that generate these trees for C# .NET, C++ and C source code?

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  • Is there an expand.grid like function in R, returning permutations ?

    - by Brani
    To become more specific, here is an example: > expand.grid(5, 5, c(1:4,6),c(1:4,6)) Var1 Var2 Var3 Var4 1 5 5 1 1 2 5 5 2 1 3 5 5 3 1 4 5 5 4 1 5 5 5 6 1 6 5 5 1 2 7 5 5 2 2 8 5 5 3 2 9 5 5 4 2 10 5 5 6 2 11 5 5 1 3 12 5 5 2 3 13 5 5 3 3 14 5 5 4 3 15 5 5 6 3 16 5 5 1 4 17 5 5 2 4 18 5 5 3 4 19 5 5 4 4 20 5 5 6 4 21 5 5 1 6 22 5 5 2 6 23 5 5 3 6 24 5 5 4 6 25 5 5 6 6 This data frame was created from all combinations of the supplied vectors. I would like to create a similar data frame from all permutations of the supplied vectors. Notice that each row must contain exactly 2 fives, yet not necessarily as the fist two elements. Thank you.

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  • More elegant way to make a C++ member function change different member variables based on template p

    - by Eric Moyer
    Today, I wrote some code that needed to add elements to different container variables depending on the type of a template parameter. I solved it by writing a friend helper class specialized on its own template parameter which had a member variable of the original class. It saved me a few hundred lines of repeating myself without adding much complexity. However, it seemed kludgey. I would like to know if there is a better, more elegant way. The code below is a greatly simplified example illustrating the problem and my solution. It compiles in g++. #include <vector> #include <algorithm> #include <iostream> namespace myNS{ template<class Elt> struct Container{ std::vector<Elt> contents; template<class Iter> void set(Iter begin, Iter end){ contents.erase(contents.begin(), contents.end()); std::copy(begin, end, back_inserter(contents)); } }; struct User; namespace WkNS{ template<class Elt> struct Worker{ User& u; Worker(User& u):u(u){} template<class Iter> void set(Iter begin, Iter end); }; }; struct F{ int x; explicit F(int x):x(x){} }; struct G{ double x; explicit G(double x):x(x){} }; struct User{ Container<F> a; Container<G> b; template<class Elt> void doIt(Elt x, Elt y){ std::vector<Elt> v; v.push_back(x); v.push_back(y); Worker<Elt>(*this).set(v.begin(), v.end()); } }; namespace WkNS{ template<class Elt> template<class Iter> void Worker<Elt>::set(Iter begin, Iter end){ std::cout << "Set a." << std::endl; u.a.set(begin, end); } template<> template<class Iter> void Worker<G>::set(Iter begin, Iter end){ std::cout << "Set b." << std::endl; u.b.set(begin, end); } }; }; int main(){ using myNS::F; using myNS::G; myNS::User u; u.doIt(F(1),F(2)); u.doIt(G(3),G(4)); } User is the class I was writing. Worker is my helper class. I have it in its own namespace because I don't want it causing trouble outside myNS. Container is a container class whose definition I don't want to modify, but is used by User in its instance variables. doIt<F> should modify a. doIt<G> should modify b. F and G are open to limited modification if that would produce a more elegant solution. (As an example of one such modification, in the real application F's constructor takes a dummy parameter to make it look like G's constructor and save me from repeating myself.) In the real code, Worker is a friend of User and member variables are private. To make the example simpler to write, I made everything public. However, a solution that requires things to be public really doesn't answer my question. Given all these caveats, is there a better way to write User::doIt?

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  • What is the naming convention in Python for variable and function names?

    - by Ray Vega
    Coming from a C# background the naming convention for variables and method names are usually either CamelCase or Pascal Case: // C# example string thisIsMyVariable = "a" public void ThisIsMyMethod() In Python, I have seen the above but I have also seen underscores being used: # python example this_is_my_variable = 'a' def this_is_my_function(): Is there a more preferable, definitive coding style for Python?

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  • How do you return a pointer to a base class with a virtual function?

    - by Nick Sweet
    I have a base class called Element, a derived class called Vector, and I'm trying to redefine two virtual functions from Element in Vector. //element.h template <class T> class Element { public: Element(); virtual Element& plus(const Element&); virtual Element& minus(const Element&); }; and in another file //Vector.h #include "Element.h" template <class T> class Vector: public Element<T> { T x, y, z; public: //constructors Vector(); Vector(const T& x, const T& y = 0, const T& z =0); Vector(const Vector& u); ... //operations Element<T>& plus(const Element<T>& v) const; Element<T>& minus(const Element<T>& v) const; ... }; //sum template <class T> Element<T>& Vector<T>::plus(const Element<T>& v) const { Element<T>* ret = new Vector((x + v.x), (y + v.y), (z + v.z)); return *ret; } //difference template <class T> Element<T>& Vector<T>::minus(const Element<T>& v) const { Vector<T>* ret = new Vector((x - v.x), (y - v.y), (z - v.z)); return *ret; } but I always get error: 'const class Element' has no member named 'getx' So, can I define my virtual functions to take Vector& as an argument instead, or is there a way for me to access the data members of Vector through a pointer to Element? I'm still fairly new to inheritance polymorphism, fyi.

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  • Retain count = 0 in other function? memory-management problem?

    - by rdesign
    Hey guys, I declared a NSMutableArray in the header-file with: NSMutableArray *myMuArr; and @property (nonatomic, retain) NSMutableArray *myMuArr; In the .m file I've got a delegate from an other class: -(void)didGrabData:(NSArray*)theArray { self.myMuArr = [[[NSMutableArray alloc] initWithArray:myMuArr]retain]; } If I want to access the self.myMuArr in cellForRowAtIndexPath it's empty (I checked the retain count of the array and it's 0) What am I doing wrong? Of course it's released in the dealloc, no where else. I would be very thankfull for any help :0)

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