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• Mono & DeflateStream

  - by ILya

  I have a simple code byte[] buffer = Encoding.UTF8.GetBytes("abracadabra"); MemoryStream ms = new MemoryStream(); DeflateStream ds = new DeflateStream(ms, CompressionMode.Compress, false); ms.Write(buffer, 0, buffer.Length); DeflateStream ds2 = new DeflateStream(ms, CompressionMode.Decompress, false); byte[] buffer2 = new byte[ms.Length]; ds2.Read(buffer2, 0, (int)ms.Length); Console.WriteLine(Encoding.UTF8.GetString(buffer2)); And when reading from ds2, i have the following: Stacktrace: at (wrapper managed-to-native) System.IO.Compression.DeflateStream.ReadZStream (intptr,intptr,int) <0x00004 at (wrapper managed-to-native) System.IO.Compression.DeflateStream.ReadZStream (intptr,intptr,int) <0x00004 at System.IO.Compression.DeflateStream.ReadInternal (byte[],int,int) [0x00031] in C:\cygwin\tmp\monobuild\build\BUILD\mono-2.6.3\mcs\class\System\System.IO.Compression\DeflateStream.cs:192 at System.IO.Compression.DeflateStream.Read (byte[],int,int) [0x00086] in C:\cygwin\tmp\monobuild\build\BUILD\mono-2.6.3\mcs\class\System\System.IO.Compression\DeflateStream.cs:214 at testtesttest.MainClass.Main (string[]) [0x00041] in C:\Users\ilukyanov\Desktop\Cassini\GZipDemo\Main.cs:27 at (wrapper runtime-invoke) .runtime_invoke_void_object (object,intptr,intptr,intptr) This application has requested the Runtime to terminate it in an unusual way. Please contact the application's support team for more information. This problem appears in Mono 2.6.1 & 2.6.3... Is there any known way to successfully read from DeflateStream in Mono? Or maybe there are some third-party open-source assemblies with the same functionality?

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• Hashing 11 byte unique ID to 32 bits or less

  - by MoJo

  I am looking for a way to reduce a 11 byte unique ID to 32 bits or fewer. I am using an Atmel AVR microcontroller that has the ID number burned in at the factory, but because it has to be transmitted very often in a very low power system I want to reduce the length down to 4 bytes or fewer. The ID is guaranteed unique for every microcontroller. It is made up of data from the manufacturing process, basically the coordinates of the silicone on the wafer and the production line that was used. They look like this: 304A34393334-16-11001000 314832383431-0F-09000C00 Obviously the main danger is that by reducing these IDs they become non-unique. Unfortunately I don't have a large enough sample size to test how unique these numbers are. Having said that because there will only be tens of thousands of devices in use and there is secondary information that can be used to help identify them (such as their approximate location, known at the time of communication) collisions might not be too much of an issue if they are few and far between. Is something like MD5 suitable for this? My concern is that the data being hashed is very short, just 11 bytes. Do hash functions work reliably on such short data?

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• Convert a binary tree to linked list, breadth first, constant storage/destructive

  - by Merlyn Morgan-Graham

  This is not homework, and I don't need to answer it, but now I have become obsessed :) The problem is: Design an algorithm to destructively flatten a binary tree to a linked list, breadth-first. Okay, easy enough. Just build a queue, and do what you have to. That was the warm-up. Now, implement it with constant storage (recursion, if you can figure out an answer using it, is logarithmic storage, not constant). I found a solution to this problem on the Internet about a year back, but now I've forgotten it, and I want to know :) The trick, as far as I remember, involved using the tree to implement the queue, taking advantage of the destructive nature of the algorithm. When you are linking the list, you are also pushing an item into the queue. Each time I try to solve this, I lose nodes (such as each time I link the next node/add to the queue), I require extra storage, or I can't figure out the convoluted method I need to get back to a node that has the pointer I need. Even the link to that original article/post would be useful to me :) Google is giving me no joy. Edit: Jérémie pointed out that there is a fairly simple (and well known answer) if you have a parent pointer. While I now think he is correct about the original solution containing a parent pointer, I really wanted to solve the problem without it :) The refined requirements use this definition for the node: struct tree_node { int value; tree_node* left; tree_node* right; };

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• When is it safe to use a broken hash function?

  - by The Rook

  It is trivial to use a secure hash function like SHA256 and continuing to use md5 is reckless behavior. However, there are some complexities to hash function vulnerabilities that I would like to better understand. Collisions have been generated for md4 and md5. According to NIST md5() is not a secure hash function. It only takes 2^39th operations to generate a collision and should never be used for passwords. However SHA1 is vulnerable to a similar collision attack in which a collision can be found in 2^69 operations, where as brute force is 2^80th. No one has generated a sha1 collision and NIST still lists sha1 as a secure message digest function. So when is it safe to use a broken hash function? Even though a function is broken it can still be "big enough". According to Schneier a hash function vulnerable to a collsion attack can still be used as an HMAC. I believe this is because the security of an HMAC is Dependant on its secret key and a collision cannot be found until this key is obtained. Once you have the key used in a HMAC its already broken, so its a moot point. What hash function vulnerabilities would undermine the security of an HMAC? Lets take this property a bit further. Does it then become safe to use a very weak message digest like md4 for passwords if a salt is perpended to the password? Keep in mind the md4 and md5 attacks are prefixing attacks, and if a salt is perpended then an attacker cannot control the prefix of the message. If the salt is truly a secret, and isn't known to the attacker, then does it matter if its a appended to the end of the password? Is it safe to assume that an attacker cannot generate a collision until the entire message has been obtained? Do you know of other cases where a broken hash function can be used in a security context without introducing a vulnerability? (Please post supporting evidence because it is awesome!)

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• Cannot bind to IPv6 address

  - by ereOn

  I am facing a strange problem on my Ubuntu Karmic system. When I call getaddrinfo() with AI_PASSIVE and AF_UNSPEC, for an empty host and the UDP 12000 port to get a bindable address, I only get back one IPv4 result (0.0.0.0:12000 for instance). If I change my call and specify AF_INET6 instead of AF_UNSPEC, then getaddrinfo() returns "Name or service not known". Shouldn't I get [::]:12000 as a result ? The same thing happens if I set the host to ::1. When I call getaddrinfo() without AI_PASSIVE (to get a "connectable" address) for the host "localhost" and the UDP 12000 port, I first get [::1]:12000 then 127.0.0.1:12000. So apparently, my system is IPv6 ready (I can ping to both IPv4 and IPv6 addresses, as well as DNS resolution). But how is it that I can't get an IPv6 address to bind to with getaddrinfo() ? Do you guys have any idea about what could be wrong ? My OS is Ubuntu Karmic, fresh install without any networking tweaking. Thank you.

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• Always send certain values with an ajax request/post

  - by DZittersteyn

  I'm building a system that displays a list of user, and on selection of a user requests some form of password. These values are saved in a hidden field on the page, and need to be sent with every request as a form of authentication. (I'm aware of the MITM-vulnerability that lies herein, but it's a very low-key system, so security is not a large concern). Now I need to send these values with each and every request, to auth the currently 'logged in' user. I'd like to automate this, via ajaxSetup, however i'm running into some issues. My first try was: init_user_auth: function(){ $.ajaxSetup({ data: { 'user' : site_user.selected_user_id(), 'passcode': site_user.selected_user_pc(), 'barcode' : site_user.selected_user_bc() } }); }, However, as I should have known, this reads the values once, at the time of the call to ajaxSetup, and never rereads them. What I need is a way to actually call the functions every time an ajax-call is made. I'm currently trying to understand what is happening here: https://groups.google.com/forum/?fromgroups=#!topic/jquery-dev/OBcEfgvTJ9I, however through the flamewar and very low-level stuff going on there, I'm not exactly sure I get what is going on. Is this the way to proceed, or should I just face facts and manually add login-info to each ajax-call?

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• What techniques can I employ to create a series of UI Elements from a collection of objects using WP

  - by elggarc

  I'm new to WPF and before I dive in solving a problem in completely the wrong way I was wondering if WPF is clever enough to handle something for me. Imagine I have a collection containing objects. Each object is of the same known type and has two parameters. Name (a string) and Picked (a boolean). The collection will be populated at run time. I would like to build up a UI element at run time that will represent this collection as a series of checkboxes. I want the Picked parameter of any given object in the collection updated if the user changes the selected state of the checkbox. To me, the answer is simple. I iterate accross the collection and create a new checkbox for each object, dynamically wiring up a ValueChanged event to capture when Picked should be changed. It has occured to me, however, that I may be able to harness some unknown feature of WPF to do this better (or "properly"). For example, could data binding be employed here? I would be very interested in anyone's thoughts. Thanks, E FootNote: The structure of the collection can be changed completely to better fit any chosen solution but ultimately I will always start from, and end with, some list of string and boolean pairs.

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• Stepping through ASP.NET MVC in Action (2009) - and stuck on nunit issue

  - by Jen

  I seem to have missed something - in this step through it talks through downloading nunit and changing the original MSTest reference to NUnit. Which seems fine until it talks about running the test with UnitRun from JetBrains. I would have thought I could run nUnit to be able to run the test - but I load my project in the nUnit gui and I get "This assembly was not built with any known testing framework". This after running the Nunit-2.5.3.9346.msi. Or am I supposed to be able to run tests from within visual studio 2008? After some research I find this: http://www.jetbrains.com/unitrun/ (ie. it seems to be saying this is no longer supported and I'm thinking JetBrains Resharper may cost money?). I'm a little rusty on my NUnit experience. So how do I go ahead and run my test? Is the error message I'm getting considered abnormal? I've added a reference in my MvcApplication.Tests project to the nunit.framework. Is this the wrong reference to add? Thanks :)

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• Bing search API and Azure

  - by Gapton

  I am trying to programatically perform a search on Microsoft Bing search engine. Here is my understanding: There was a Bing Search API 2.0 , which will be replaced soon (1st Aug 2012) The new API is known as Windows Azure Marketplace. You use different URL for the two. In the old API (Bing Search API 2.0), you specify a key (Application ID) in the URL, and such key will be used to authenticate the request. As long as you have the key as a parameter in the URL, you can obtain the results. In the new API (Windows Azure Marketplace), you do NOT include the key (Account Key) in the URL. Instead, you put in a query URL, then the server will ask for your credentials. When using a browser, there will be a pop-up asking for a/c name and password. Instruction was to leave the account name blank and insert your key in the password field. Okay, I have done all that and I can see a JSON-formatted results of my search on my browser page. How do I do this programmatically in PHP? I tried searching for the documentation and sample code from Microsoft MSDN library, but I was either searching in the wrong place, or there are extremely limited resources in there. Would anyone be able to tell me how do you do the "enter the key in the password field in the pop-up" part in PHP please? Thanks alot in advance.

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• What's the best practice for handling system-specific information under version control?

  - by Joe

  I'm new to version control, so I apologize if there is a well-known solution to this. For this problem in particular, I'm using git, but I'm curious about how to deal with this for all version control systems. I'm developing a web application on a development server. I have defined the absolute path name to the web application (not the document root) in two places. On the production server, this path is different. I'm confused about how to deal with this. I could either: Reconfigure the development server to share the same path as the production Edit the two occurrences each time production is updated. I don't like #1 because I'd rather keep the application flexible for any future changes. I don't like #2 because if I start developing on a second development server with a third path, I would have to change this for every commit and update. What is the best way to handle this? I thought of: Using custom keywords and variable expansion (such as setting the property $PATH$ in the version control properties and having it expanded in all the files). Git doesn't support this because it would be a huge performance hit. Using post-update and pre-commit hooks. Possibly the likely solution for git, but every time I looked at the status, it would report the two files as being changed. Not really clean. Pulling the path from a config file outside of version control. Then I would have to have the config file in the same location on all servers. Might as well just have the same path to begin with. Is there an easy way to deal with this? Am I over thinking it?

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• Have ASP page call save function anytime the user tries to navigate away from page

  - by Breander

  What I have is an input page with a bunch of dynamically created textboxes for the user to input data. The textboxes are dynamically created because the number that are needed are not known until the user selects some options on the page. So what I need to have happen is if the user tries to either A) navigate away from the page or B) select different options bringing up new textboxes. Anything the user may have typed into the textboxes needs to automatically be saved to the database. Like they clicked on the save button on the page. This doesn't sound like a vary smart way to do things or even an easy way to do things but this is the requirement I have been given. No message just save to the database. I have looked into things like onbeforepageunload javascript but that mostly tries to stop the user from navigating away I can't call any code behind code from it. Any help is appreciated. Note : The number of the texboxes with data can be any where between 20 and 500. Yes very crazy but not my idea.

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• Any way to define getters for lazy variables in Javascript arrays?

  - by LLer

  I'm trying to add elements to an array that are lazy-evaluated. This means that the value for them will not be calculated or known until they are accessed. This is like a previous question I asked but for objects. What I ended up doing for objects was Object.prototype.lazy = function(var_name, value_function) { this.__defineGetter__(var_name, function() { var saved_value = value_function(); this.__defineGetter__(var_name, function() { return saved_value; }); return saved_value; }); } lazy('exampleField', function() { // the code that returns the value I want }); But I haven't figured out a way to do it for real Arrays. Arrays don't have setters like that. You could push a function to an array, but you'd have to call it as a function for it to return the object you really want. What I'm doing right now is I created an object that I treat as an array. Object.prototype.lazy_push = function(value_function) { if(!this.length) this.length = 0; this.lazy(this.length++, value_function); } So what I want to know is, is there a way to do this while still doing it on an array and not a fake array?

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• Sys. engineer has decided to dynamically transform all XSLs into DLLs on website build process. DLL

  - by John Sullivan

  Hello, OS: Win XP. Here is my situation. I have a browser based application. It is "wrapped" in a Visual Basic application. Our "Systems Engineer Senior" has decided to spawn DLL files from all of our XSL pages (many of which have duplicate names) upon building a new instance of the website and have the active server pages (ASPX) use the DLL instead. This has created a "known issue" in which ~200 DLL naming conflicts occur and, thus, half of our application is broken. I think a solution to this problem is that, thankfully, we're generating the names of the DLLs and linking them up with our application dynamically. Therefore we can do something kludgy like generate a hash and append it to the end of the DLL file name when we build our website, then always reference the DLL that had some kind of random string / hash appended to its name. Aside from outright renaming the DLLs, is there another way to have multiple DLLs with the same name register for one application? I think the answer is "No, only between different applications using a special technique." Please confirm. Another question I have on my mind is whether this whole idea is a good practice -- converting our XSL pages (which we use in mass -- every time a response from our web app occurs) into DLL functions that call a "function" to do what the XSL page did via an active server page (ASPX), when we were before just sending an XML response to an XSL page via aspx.

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• j_security_check to SSO in different module under Oracle App Server?

  - by thebearinboulder

  I have an existing j2ee application running on Oracle App Server. It is targeted towards paying customers so the content is secured and a SSO module properly intercepts all requests for secured content. Now the company is adding a unbranded public-facing module with a number of unsecured pages. At one point the user is expected to register for a free account and log in to proceed further. Think doctors adding a public-facing site with information for potential patients, or lawyers adding a public-facing site with information for potential clients. There's some information on the session and the usual approach would be to authenticate the user, persist the session information using the now-known user id, invalidate the existing session (to prevent certain types of attacks), the reload the session information before returning to the user. I can't just persist it under the session id since that's about to change. The glitch is that the existing application already has an SSO module and I get a 404 error every time I try to direct to j_security_check. I've tried that, /sso/j_security_check, even http://localhost/sso/j_security_check, all without success. I noticed that an earlier question said that tomcat requires access to a secured page before j_security_check is even visible. I don't know if that's the case with Oracle AS. Ideas? Or is the best approach to continue arguing that we have a different user base so it would be better to handle authentication in our own module anyway?

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• R Tree 50,000 foot overview?

  - by roufamatic

  I'm working on a school project that involves taking a lat/long point and finding the top five closest points in a known list of places. The list is to be stored in memory, with the caveat that we must choose an "appropriate data structure" -- that is, we cannot simply store all the places in an array and compare distances one-by-one in a linear fashion. The teacher suggested grouping the place data by US State to prevent calculating the distance for places that are obviously too far away. I think I can do better. From my research online it seems like an R-Tree or one of its variants might be a neat solution. Unfortunately, that sentence is as far as I've gotten with understanding the actual technique, as the literature is simply too dense for my non-academic head. Can somebody give me a really high overview of what the process is for populating an R-Tree with lat/long data, and then traversing the tree to find those 5 nearest neighbors of a given point? Additionally the project is in C, and I don't have to reinvent the wheel on this, so if you've used an existing open source C implementation of an R Tree I'd be interested in your experiences.

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• Xcode Unit Testing - Accessing Resources from the application's bundle?

  - by Ben Scheirman

  I'm running into an issue and I wanted to confirm that I'm doing things the correct way. I can test simple things with my SenTestingKit tests, and that works okay. I've set up a Unit Test Bundle and set it as a dependency on the main application target. It successfully runs all tests whenever I press cmd+B. Here's where I'm running into issues. I have some XML files that I need to load from the resources folder as part of the application. Being a good unit tester, I want to write unit tests around this to make sure that they are loading properly. So I have some code that looks like this: NSString *filePath = [[NSBundle mainBundle] pathForResource:@"foo" ofType:@"xml"]; This works when the application runs, but during a unit test, mainBundle points to the wrong bundle, so this line of code returns nil. So I changed it up to utilize a known class like this: NSString *filePath = [[NSBundle bundleForClass:[Config class]] pathForResource:@"foo" ofType:@"xml"]; This doesn't work either, because in order for the test to even compile code like this, it Config needs to be part of the Unit Test Target. If I add that, then the bundle for that class becomes the Unit Test bundle. (Ugh!) Am I approaching this the wrong way?

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• Subversion update misses new directories

  - by Mike Q

  Hi all, Periodically we have trouble with SVN when doing updates. Very occasionally when someone adds a new directory doing an update through Tortoise doesn't work. If we do a "Fully Recursive" update using "Update from revision..." option then it picks it up fine. I'm poked around and seen this question which is virtually identical but with no answer. I've found the item on the SVN website, referenced by that post, that talks about an issue in 1.6.0 which is now fixed. However my SVN version is 1.6.9 and Tortoise is 1.6.7 so I wouldn't expect to have this problem any more. This only seems to occur with new directories, never seen it for individual files. We may have had older versions of Tortoise at one point (can't remember which tho) so maybe some issue has been introduced into our repo that an upgrade doesn't solve. We have the workaround but it wastes a few minutes of head-scratching after failed builds to figure it out and people who haven't come across this problem before really struggle until they ask someone else. Anyone know if this is a known bug and any permanent solutions? Thanks.

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• Should core application configuration be stored in the database, and if so what should be done to se

  - by Rl

  I'm writing an application around a lot of hierarchical data. Currently the hierarchy is fixed, but it's likely that new items will be added to the hierarchy in the future. (please let them be leaves) My current application and database design is fairly generic and nothing dealing with specific nodes in the hierarchy is hardcoded, with the exception of validation and lookup functions written to retrieve external data from each node's particular database. This pleases me from a design point of view, but I'm nervous at the realization that the entire application rests on a handful of records in the database. I'm also frustrated that I have to enforce certain aspects of data integrity with database triggers rather than by foreign key constraints (an example is where several different nodes in the hierarchy have their own proprietary IDs and I store them in a single column which, when coupled with the node ID can be used to locate the foreign data). I'm starting to wonder whether it may have been appropriate to simply hardcoded these known nodes into the system so that it would be more "type safe" and less generic. How does one know when something should be hardcoded, and when it should be a configuration item? Is it just a cost-benefit analysis of clarity/safety now vs less work later, or am I missing some metric I should be using to determine whether or not this is appropriate. The steps I'm taking to protect these valuable configurations are to add triggers that prevent updates/deletes. The database user that this application uses will only have the ability to manipulate data through stored procedures. What else can I do?

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• Codeigniter: how should I restructure db schema?

  - by Kevin Brown

  I don't even know if that's the right term. May it be known that I'm a major novice! I have three tables: users, profiles, and survey. Each one has user_id as it's first field, (auto-increment for users), and they're all tied by a foreign key constraint, CASCADE on DELETE. Currently, for each user, let's say user_id 1, they have a corresponding db entry in the other tables. For profiles it lists all their information, and the survey table holds all their survey information. Now I must change things...darn scope creep. Users need the ability to have multiple survey results. I imagine that this would be similar to a comment table for a blog... My entire app runs around the idea that a single user is linked to a constraining profile and survey. How should I structure my db? How should I design my app's db so that a user can have multiple tests/profiles for the test? Please assist! Any advice, information and personal-knowledge is appreciated! Right now the only way I know how to accompany my client is to create a pseudo-user for each test (so unnecessary) and list them in a view table (called "your tests")-- these are obtained from the db by saying: where user_id=manager_id

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• reformatting a matrix in matlab with nan values

  - by Kate

  This post follows a previous question regarding the restructuring of a matrix: re-formatting a matrix in matlab An additional problem I face is demonstrated by the following example: depth = [0:1:20]'; data = rand(1,length(depth))'; d = [depth,data]; d = [d;d(1:20,:);d]; Here I would like to alter this matrix so that each column represents a specific depth and each row represents time, so eventually I will have 3 rows (i.e. days) and 21 columns (i.e. measurement at each depth). However, we cannot reshape this because the number of measurements for a given day are not the same i.e. some are missing. This is known by: dd = sortrows(d,1); for i = 1:length(depth); e(i) = length(dd(dd(:,1)==depth(i),:)); end From 'e' we find that the number of depth is different for different days. How could I insert a nan into the matrix so that each day has the same depth values? I could find the unique depths first by: unique(d(:,1)) From this, if a depth (from unique) is missing for a given day I would like to insert the depth to the correct position and insert a nan into the respective location in the column of data. How can this be achieved?

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• "end()" iterator for back inserters?

  - by Thanatos

  For iterators such as those returned from std::back_inserter(), is there something that can be used as an "end" iterator? This seems a little nonsensical at first, but I have an API which is: template<typename InputIterator, typename OutputIterator> void foo( InputIterator input_begin, InputIterator input_end, OutputIterator output_begin, OutputIterator output_end ); foo performs some operation on the input sequence, generating an output sequence. (Who's length is known to foo but may or may not be equal to the input sequence's length.) The taking of the output_end parameter is the odd part: std::copy doesn't do this, for example, and assumes you're not going to pass it garbage. foo does it to provide range checking: if you pass a range too small, it throws an exception, in the name of defensive programming. (Instead of potentially overwriting random bits in memory.) Now, say I want to pass foo a back inserter, specifically one from a std::vector which has no limit outside of memory constraints. I still need a "end" iterator - in this case, something that will never compare equal. (Or, if I had a std::vector but with a restriction on length, perhaps it might sometimes compare equal?) How do I go about doing this? I do have the ability to change foo's API - is it better to not check the range, and instead provide an alternate means to get the required output range? (Which would be needed anyways for raw arrays, but not required for back inserters into a vector.) This would seem less robust, but I'm struggling to make the "robust" (above) work.

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• Triangulation in 3D Space

  - by w3b_wizzard

  Disclaimer: This is for class, however I'm fresh out of ideas and a nudge in the right direction would be much appreciated. Also, this needs to be implemented in raw C, so no fancy libraries can be used. I have to write a search and rescue simulator for submarines, it has to find a probe that is randomly placed in 3D space in a grid from of the MAX_XYZ (100000). The only tools I'm given are a "ping" which will give the magnitude of the distance between a certain sub and the probe. The goal is to optimize the costs of this entire operation so a brute force attempt, like looking at every single coordinate, won't work. Hence I was thinking triangulation. Now, it makes loads of sense to me, place three subs, each one of them uses their ping to get the distance between them and the probe. Since each sub have a known distance relative to one another, it's easy to build the base of a tetrahedron with them, and the results of the ping will point to a certain coordinate, the problem I'm having is how to figure out the elevation, or the height, of the tetrahedron. So what I have as data is the following: Distances between subs (In vector format) Angles between each subs (very easy to compute) Distance between each sub and the probe (3 segments from the base to the peak) Angles inside each of the outer 3 surfaces of the tetrahedron. I tried finding some sort of relationship with the vertices of the tetrahedron and the relative angles in each of them, however all I found had to deal with tetrahedrons built with equilateral triangles, which isn't much help. I have the impression this can be easily solved with trig but either I'm not seeing it or I need more coffee. Any suggestions would be appreciated!

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• A specific data structure

  - by user550413

  Well, this question is a bit specific but I think there is some general idea in it that I can't get it. Lets say I got K servers (which is a constant that I know its size). I have a program that get requests and every request has an id and server id that will handle it. I have n requests - unknown size and can be any number. I need a data structure to support the next operations within the given complexity: GetServer - the function gets the request ID and returns the server id that is supposed to handle this request at the current situation and not necessarily the original server (see below). Complexity: O(log K) at average. KillServer - the function gets as input a server id that should be removed and another server id that all the requests of the removed server should be passed to. Complexity: O(1) at the worst case. -- Place complexity for all the structure is O(K+n) -- The KillServer function made me think using a Union-Find as I can do the union in O(1) as requested but my problem is the first operation. Why it's LogK? Actually, no matter how I "save" the requests if I want to access to any request (lets say it's an AVL tree) so the complexity will be O(log n) at the worst case and said that I can't assume Kn (and probably K Tried thinking about it a couple of hours but I can't find any solution. Known structures that can be used are: B+ tree, AVL tree, skip list, hash table, Union-Find, rank tree and of course all the basics like arrays and such.

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• C++ class derivation and superconstructor confusion

  - by LukeN

  Hey, in a tutorial C++ code, I found this particular piece of confusion: PlasmaTutorial1::PlasmaTutorial1(QObject *parent, const QVariantList &args) : Plasma::Applet(parent, args), // <- Okay, Plasma = namespace, Applet = class m_svg(this), // <- A member function of class "Applet"? m_icon("document") // <- ditto? { m_svg.setImagePath("widgets/background"); // this will get us the standard applet background, for free! setBackgroundHints(DefaultBackground); resize(200, 200); } I'm not new to object oriented programming, so class derivation and super-classes are nothing complicated, but this syntax here got me confused. The header file defines the class like this: class PlasmaTutorial1 : public Plasma::Applet { Similar to above, namespace Plasma and class Applet. But what's the public doing there? I fear that I already know the concept but don't grasp the C++ syntax/way of doing it. In this question I picked up that these are called "superconstructors", at least that's what stuck in my memory, but I don't get this to the full extend. If we glance back at the first snippet, we see Constructor::Class(...) : NS::SuperClass(...), all fine 'till here. But what are m_svg(this), m_icon("document") doing there? Is this some kind of method to make these particular functions known to the derivated class? Is this part of C++ basics or more immediate? While I'm not completly lost in C++, I feel much more at home in C :) Most of the OOP I have done so far was done in D, Ruby or Python. For example in D I would just define class MyClass : MySuperClass, override what I needed to and call the super class' constructor if I'd need to.

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• Why does PDO print my password when the connection fails?

  - by Joe Hopfgartner

  I have a simple website where I establish a connection to a Mysql server using PDO. $dbh = new PDO('mysql:host=localhost;dbname=DB;port=3306', 'USER', 'SECRET',array(PDO::MYSQL_ATTR_INIT_COMMAND => "SET NAMES utf8")); I had some traffic on my site and the servers connection limit was reached, and the website throw this error, with my PLAIN password in it! Fatal error: Uncaught exception 'PDOException' with message 'SQLSTATE[08004] [1040] Too many connections' in /home/premiumize-me/html/index.php:64 Stack trace: #0 /home/premiumize-me/html/index.php(64): PDO-__construct('mysql:host=loca...', 'USER', 'SECRET', Array) #1 {main} thrown in /home/premiumize-me/html/index.php on line 64 Ironically I switched to PDO for security reasons, this really shocked me. Because this exact error is something you can provoke very easily on most sites using simple http flooding. I now wrapped my conenction into a try/catch clause, but still. I think this is catastrophic! So I am new to PDO and my questino is: What do I have to consider to be safe! How to I establish a connection in a secure way? Are there other known security holes like this one that I have to be aware of?

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