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  • How does static code run with multiple threads?

    - by Krisc
    I was reading http://stackoverflow.com/questions/1511798/threading-from-within-a-class-with-static-and-non-static-methods and I am in a similar situation. I have a static method that pulls data from a resource and creates some runtime objects based on the data. static class Worker{ public static MyObject DoWork(string filename){ MyObject mo = new MyObject(); // ... does some work return mo; } } The method takes awhile (in this case it is reading 5-10mb files) and returns an object. I want to take this method and use it in a multiple thread situation so I can read multiple files at once. Design issues / guidelines aside, how would multiple threads access this code? Let's say I have something like this... class ThreadedWorker { public void Run() { Thread t = new Thread(OnRun); t.Start(); } void OnRun() { MyObject mo = Worker.DoWork("somefilename"); mo.WriteToConsole(); } } Does the static method run for each thread, allowing for parallel execution?

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  • Dataset bind to Gridview within WCF REST retrieval method and Linq to Sql

    - by user643794
    I used a WCF REST template to build a WCF service library to create PUT and GET calls. PUT method works fine sending my blob to a database. On the GET, I want to be able to access the web service directly and display the results from a stored procedure as a dataset and bind this to a gridview. The stored procedure is a simple select statement, returning three of the four columns from the table. I have the following: [WebGet(UriTemplate = "/?name={name}", ResponseFormat = WebMessageFormat.Xml)] public List<Object> GetCollection(string name) { try { db.OpenDbConnection(); // Call to SQL stored procedure return db.GetCustFromName(name); } catch (Exception e) { Log.Error("Stored Proc execution failed. ", e); } finally { db.CloseDbConnection(); } return null; } I also added Linq to SQL class to include my database table and stored procedures access. I also created the Default.aspx file in addition to the other required files. protected void Page_Load(object sender, EventArgs e) { ServiceDataContext objectContext = new ServiceDataContext(); var source = objectContext.GetCustFromName("Tiger"); Menu1.DataSource = source; Menu1.DataBind(); } But this gives me The entity type '' does not belong to any registered model. Where should the data binding be done? What should be the return type for GetCollection()? I am stuck with this. Please provide help on how to do this.

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  • Database schemas WAY out of sync - need to get up to date without losing data

    - by Zind
    The problem: we have one application that has a portion which is used by a very small subset of the total users, and that part of the application is running off of a separate database as well. In a perfect world, the schemas of the two databases would be synced up, but such is not the case. Some migrations have been run on the smaller database, most haven't; and furthermore, there is nothing such as revision number to be able to easily identify which have and which haven't. We would like to solve this quandary for future projects. During a discussion we've come up with the following possible plan of action, and I am wondering if anyone knows of any project which has already solved this problem: What we would like to do is create an empty database from the schema of the large fully-migrated database, and then move all of the data from the smaller non-migrated database into that empty one. If it makes things easier, it can probably be assumed for the sake of this problem specifically that no migrations have ever removed anything, only added. Else, if there are other known solutions, I'd like to hear them as well.

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  • Which source control paradigm and solution to embed in a custom editor application?

    - by Greg Harman
    I am building an application that manages a number of custom objects, which may be edited concurrently by multiple users (using different instances of the application). These objects have an underlying serialized representation, and my plan is to persist them (through my application UI) in an external source control system. Of course this implies that my application can check the current version of an object for updates, a merging interface for each object, etc. My question is what source control paradigm(s) and specific solution(s) to support and why. The way I (perhaps naively) see the source control world is three general paradigms: Single-repository, locked access (MS SourceSafe) Single-repository, concurrent access (CVS/SVN) Distributed (Mercurial, Git) I haven't heard of anyone using #1 for quite a number of years, so I am planning to disregard this case altogether (unless I get a compelling argument otherwise). However, I'm at a loss as to whether to support #2 or #3, and which specific implementations. I'm concerned that the use paradigms are subtly different enough that I can't adequately capture basic operations in a single UI. The last bit of information I should convey is that this application is intended to be deployed in a commercial setting, where a source control system may already be in use. I would prefer not to support more than one solution unless it's really a deal-breaker, so wide adoption in a corporate setting is a plus.

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  • Asterisk: Dropping calls with an "ast_yyerror"

    - by Nick
    I'm having an issue where asterisk will play our greeting to the caller, and then drop the call instead of making our phones ring. The bit of information I could find said it was caused by an error in evaluating a dialplan expression. I'm thinking it's this line: exten = START,n,GotoIf($[${FORCE_CLOSED}=TRUE]?CLOSED,1) But I'm not sure what's wrong with it. I see the following error on the console: [Apr 4 16:29:49] WARNING[27038]: ast_expr2.fl:459 ast_yyerror: ast_yyerror(): syntax error: syntax error, unexpected '=', expecting $end; Input:=TRUE^ Surrounding Console output: -- Executing [START@AGInbound:1] Answer("IAX2/AtlantaTeliax-10086", "") in new stack -- Executing [START@AGInbound:2] BackGround("IAX2/AtlantaTeliax-10086", 0000_AG_THANK_YOU_FOR_CALLING_AG") in new stack -- Playing '0000_AG_THANK_YOU_FOR_CALLING_AG.slin' (language 'en') [Apr 4 16:29:49] WARNING[27038]: ast_expr2.fl:459 ast_yyerror: ast_yyerror(): syntax error: syntax error, unexpected '=', expecting $end; Input: =TRUE ^ [Apr 4 16:29:49] WARNING[27038]: ast_expr2.fl:463 ast_yyerror: If you have questions, please refer to doc/tex/channelvariables.tex in the asterisk source. -- Executing [START@AGInbound:3] GotoIf("IAX2/AtlantaTeliax-10086", "?CLOSED,1") in new stack -- Executing [START@AGInbound:4] GotoIfTime("IAX2/AtlantaTeliax-10086", "9:30-17:0|mon-fri|*|*?OPEN,1") in new stack -- Executing [START@AGInbound:5] GotoIfTime("IAX2/AtlantaTeliax-10086", "10:0-18:30|sat|*|*?OPEN,1") in new stack -- Executing [START@AGInbound:6] GotoIfTime("IAX2/AtlantaTeliax-10086", "12:0-17:0|sun|*|*?OPEN,1") in new stack Relevant lines from the dial plan: exten = START,1,Answer() exten = START,n,Background(0000_AG_THANK_YOU_FOR_CALLING_AG) ; See if we're open ; Force Closed if no one's going to be answering exten = START,n,GotoIf($[${FORCE_CLOSED}=TRUE]?CLOSED,1) exten = START,n,GotoIfTime(${AG_WEEKDAY_OPEN_HOUR}:${AG_WEEKDAY_OPEN_MIN}-${AG$ exten = START,n,GotoIfTime(${AG_SATURDAY_OPEN_HOUR}:${AG_SATURDAY_OPEN_MIN}-${$ exten = START,n,GotoIfTime(${AG_SUNDAY_OPEN_HOUR}:${AG_SUNDAY_OPEN_MIN}-${AG_S$ ; ...and we're not. But maybe the time of day has been overridden? exten = START,n,GotoIf($[${OVERRIDE_TIME_OF_DAY}=TRUE]?OPEN,1) ; No override... We're definatly closed. exten = START,n,Goto(CLOSED,1)

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  • Spring 3.0 vs J2EE 6.0

    - by StudiousJoseph
    Hi everybody, I'm confronted with a situation... I've been asked to give an advise regarding which approach to take, in terms of J2EE development between Spring 3.0 and J2EE 6.0. I was, and still am, a promoter of Spring 2.5 over classic J2EE 5 development, specially with JBoss, I even migrated old apps to Spring and influenced the re-definition of the development policy here to include Spring specific APIs, and helped the development of a strategic plan to foster more lightweight solutions like Spring + Tomcat, instead of the heavier ones of JBoss, right now, we're using JBoss merely as a Web container, having what i call the "container inside the container paradox", that is, having Spring apps, with most of its APIs, running inside JBoss, So we're in the process of migrating to tomcat. However, with the coming of J2EE 6.0 many features, that made Spring attractive at that time, easy deployment, less-coupling, even some sort of D.I, etc, seems to have been mimicked, in one way or the other. JSF 2.0, JPA 2.0, WebBeans, WebProfiles, etc. So, the question goes... From your point of view, how save, and logical, it is to continue to invest in a non-standard J2EE development framework like Spring given the new perspectives offered by J2EE 6.0? Can we talk about maybe 3 or 4 more years of Spring development, or do you recommend early adoption of J2EE 6.0 APIs and it's practices? I'll appreciate any insights with this...

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  • How to benchmark on multi-core processors

    - by Pascal Cuoq
    I am looking for ways to perform micro-benchmarks on multi-core processors. Context: At about the same time desktop processors introduced out-of-order execution that made performance hard to predict, they, perhaps not coincidentally, also introduced special instructions to get very precise timings. Example of these instructions are rdtsc on x86 and rftb on PowerPC. These instructions gave timings that were more precise than could ever be allowed by a system call, allowed programmers to micro-benchmark their hearts out, for better or for worse. On a yet more modern processor with several cores, some of which sleep some of the time, the counters are not synchronized between cores. We are told that rdtsc is no longer safe to use for benchmarking, but I must have been dozing off when we were explained the alternative solutions. Question: Some systems may save and restore the performance counter and provide an API call to read the proper sum. If you know what this call is for any operating system, please let us know in an answer. Some systems may allow to turn off cores, leaving only one running. I know Mac OS X Leopard does when the right Preference Pane is installed from the Developers Tools. Do you think that this make rdtsc safe to use again? More context: Please assume I know what I am doing when trying to do a micro-benchmark. If you are of the opinion that if an optimization's gains cannot be measured by timing the whole application, it's not worth optimizing, I agree with you, but I cannot time the whole application until the alternative data structure is finished, which will take a long time. In fact, if the micro-benchmark were not promising, I could decide to give up on the implementation now; I need figures to provide in a publication whose deadline I have no control over.

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  • Mysql and PHP - Reading multiple insert queries from a file and executing at runtime

    - by SpikETidE
    Hi everyone... I am trying out a back-up and restore system. Basically, what i try to do is, when creating the back up i make a file which looks like DELETE FROM bank_account; INSERT INTO bank_account VALUES('1', 'IB6872', 'Indian Bank', 'Indian Bank', '2', '1', '0', '0000-00-00 00:00:00', '1', '2010-04-13 17:09:05');INSERT INTO bank_account VALUES('2', 'IB7391', 'Indian Bank', 'Indian Bank', '3', '1', '0', '0000-00-00 00:00:00', '1', '2010-04-13 17:09:32'); and so on and so forth. When i restore the db i just read the query from the file, save it to a string and then execute it over the DB using mysql_query(); The problem is, when i run the query through mysql_query(), the execution stops after the delete query with the error 'Error in syntax near '; INSERT INTO bank_account VALUES('1', 'IB6872', 'Indian Bank', 'Indian Bank', '2',' at line 1. But when i run the queries directly over the Db, using phpmyadmin it executes without any errors. As far as i can see, i can't notice any syntax error in the query. Can anyone point out where there might be a glitch...? Thanks and regards....

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  • Trying to write up a C daemon, but don't know enough C to continue

    - by JamesM-SiteGen
    Okay, so I want this daemon to run in the background with little to no interaction. I plan to have it work with Apache, lighttpd, etc to send the session & request information to allow C to generate a website from an object DB, saving will have to be an option so, you can start the daemon with an existing DB but will not save to it unless you login to the admin area and enable, and restart the daemon. Summary of the daemon: Load a database from file. Have a function to restart the daemon. Allow Apache, lighttpd, etc to get necessary data about the request and session. A varible to allow the database to be saved to the file, otherwise it will only be stored in ram. If it is set to save back to the file, then only have neccessary data in ram. Use sql-light for the database file. Build a webpage from some template files. $(myVar) for getting variables. Get templates from a directory. ./templates/01-test/{index.html,template.css,template.js} Live version of the code and more information: http://typewith.me/YbGB1h1g1p Also I am working on a website CMS in php, but I am tring to switch to C as it is faster than php. ( php is quite fast, but the fact that making a few mySQL requests for every webpage is quite unefficent and I'm sure that it can be far better, so an object that we can recall data from in C would have to be faster ) P.S I am using Arch-Linux not MS-Windows, with the package group base-devel for the common developer tools such as make and makepgk. Edit: Oupps, forgot the question ;) Okay, so the question is, how can I turn this basic C daemon into a base to what I am attempting to do here?

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  • Trouble with custom WPF Panel-derived class

    - by chaiguy
    I'm trying to write a custom Panel class for WPF, by overriding MeasureOverride and ArrangeOverride but, while it's mostly working I'm experiencing one strange problem I can't explain. In particular, after I call Arrange on my child items in ArrangeOverride after figuring out what their sizes should be, they aren't sizing to the size I give to them, and appear to be sizing to the size passed to their Measure method inside MeasureOverride. Am I missing something in how this system is supposed to work? My understanding is that calling Measure simply causes the child to evaluate its DesiredSize based on the supplied availableSize, and shouldn't affect its actual final size. Here is my full code (the Panel, btw, is intended to arrange children in the most space-efficient manner, giving less space to rows that don't need it and splitting remaining space up evenly among the rest--it currently only supports vertical orientation but I plan on adding horizontal once I get it working properly): protected override Size MeasureOverride( Size availableSize ) { foreach ( UIElement child in Children ) child.Measure( availableSize ); return availableSize; } protected override System.Windows.Size ArrangeOverride( System.Windows.Size finalSize ) { double extraSpace = 0.0; var sortedChildren = Children.Cast<UIElement>().OrderBy<UIElement, double>( new Func<UIElement, double>( delegate( UIElement child ) { return child.DesiredSize.Height; } ) ); double remainingSpace = finalSize.Height; double normalSpace = 0.0; int remainingChildren = Children.Count; foreach ( UIElement child in sortedChildren ) { normalSpace = remainingSpace / remainingChildren; if ( child.DesiredSize.Height < normalSpace ) // if == there would be no point continuing as there would be no remaining space remainingSpace -= child.DesiredSize.Height; else { remainingSpace = 0; break; } remainingChildren--; } extraSpace = remainingSpace / Children.Count; double offset = 0.0; foreach ( UIElement child in Children ) { //child.Measure( new Size( finalSize.Width, normalSpace ) ); double value = Math.Min( child.DesiredSize.Height, normalSpace ) + extraSpace; child.Arrange( new Rect( 0, offset, finalSize.Width, value ) ); offset += value; } return finalSize; }

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  • Dependency Properties, change notification and setting values in the constructor

    - by stefan.at.wpf
    Hello, I have a clas with 3 dependency properties A,B,C. The values of these properties are set by the constructor and every time one of the properties A, B or C changes, the method recalculate() is called. Now during execution of the constructor these method is called 3 times, because the 3 properties A, B, C are changed. Hoewever this isn't necessary as the method recalculate() can't do anything really useful without all 3 properties set. So what's the best way for property change notification but circumventing this change notification in the constructor? I thought about adding the property changed notification in the constructor, but then each object of the DPChangeSample class would always add more and more change notifications. Thanks for any hint! class DPChangeSample : DependencyObject { public static DependencyProperty AProperty = DependencyProperty.Register("A", typeof(int), typeof(DPChangeSample), new PropertyMetadata(propertyChanged)); public static DependencyProperty BProperty = DependencyProperty.Register("B", typeof(int), typeof(DPChangeSample), new PropertyMetadata(propertyChanged)); public static DependencyProperty CProperty = DependencyProperty.Register("C", typeof(int), typeof(DPChangeSample), new PropertyMetadata(propertyChanged)); private static void propertyChanged(DependencyObject d, DependencyPropertyChangedEventArgs e) { ((DPChangeSample)d).recalculate(); } private void recalculate() { // Using A, B, C do some cpu intensive caluclations } public DPChangeSample(int a, int b, int c) { SetValue(AProperty, a); SetValue(BProperty, b); SetValue(CProperty, c); } }

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  • Does adding to a method group count as using a variable?

    - by Vaccano
    I have the following code example taken from the code of a Form: protected void SomeMethod() { SomeOtherMethod(this.OnPaint); } private void SomeOtherMethod(Action<PaintEventArgs> onPaint) { onPaint += MyPaint; } protected void MyPaint(PaintEventArgs e) { // paint some stuff } The second method (SomeOtherMethod) has resharper complaining at me. It says of onPaint that "Value assigned is not used in any execution path". To my mind it was used because I added a method to the list of methods called when a paint was done. But usually when resharper tells me something like this it is because I am not understanding some part of C#. Like maybe when the param goes out of goes out of scope the item I added to the list gets removed (or something like that). I thought I would ask here to see if any one knows what resharper is trying to tell me. (Side Note: I usually just override OnPaint. But I am trying to get OnPaint to call a method in another class. I don't want to expose that method publicly so I thought I would pass in the OnPaint group and add to it.)

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  • BPEL, initialize variable and repeating onAlarm eventHandler

    - by Michael
    I have a little problem I can't solve so far. In BPEL I want to create an onAlarm eventHandler which fires immediatly (i.e. the "for" element is set to 'PT0S') and repeats every 2 seconds. This eventHandler shall contain a counter which increments every time the alarm fires. The question is: How to initialize the counter? If the variable will be initialized within the onAlarm scope the value would not increment anymore. In the "normal" control flow the value also cannot be initialized, because it is not defined if the process or the onAlarm scope runs first. So I would get every now and then an uninitializedVariable exception. My solution would be to not initialize the variable neither in the process scope nor in the onAlarm scope, but create a faultHandler wherein the variable will be initialized and afterwards the onAlarm flow will be executed. Problem is every uninitializedVariable execution will be caught now by this faultHandler and there may be another too. So is there another possibility to deal with this problem or can I somehow find out which variable wasn't initialized properly so the faultHandler can get two control flows? The solution should work on every BPEL engine. Thanks, Michael

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  • Module not found

    - by TMP
    Hi There! I've been working on this one quite a bit and haven't gotten any closer to a solution. I juut dug up my old copy of the WindowsHookLib again - It's available with source at http://www.codeproject.com/KB/DLL/WindowsHookLib.aspx. This library allows Global Windows Mouse/Keyboard/Clipboard Hooks, which is very useful. I'm trying to use the Mouse Hook in here to Capture Mouse-Motion (I could use a Timer that always polls Cursor.Position, but I plan on using more features of WindowsHookLib later). Code as follows: MouseHook mh = new MouseHook(); mh.InstallHook(); mh.MouseMove += new EventHandler<WindowsHookLib.MouseEventArgs>(mh_MouseMove); But on the call to InstallHook(), I get an Exception: "The specified Module could not be found". Strange. Searching, I found that someone thought this occurs because a DLL is not in a place included in the Windows PATH variable, and because placing it in system32 didn't help I went the whole hog and translated the thing to C# for inclusion directly in my project (I was curious how it works). However the error was obstinately persistent, so I dug a bit on this, and found the Code in the Library that is responsible: In InstallHook(), we have IntPtr hinstDLL = Marshal.GetHINSTANCE(Assembly.GetExecutingAssembly().GetModules()[0]); this._hMouseHook = UnsafeNativeMethods.SetWindowsHookEx(14, this._mouseProc, hinstDLL, 0); if (this._hMouseHook == IntPtr.Zero) { throw new MouseHookException(new Win32Exception(Marshal.GetLastWin32Error()).Message); } And this (after modification and recompile) tells me that what I'm really getting is a Windows error "ERROR_MOD_NOT_FOUND"! Now, Here I'm stumped. Didn't I just compile the Hook Library directly into my project? (UnsafeMethods.SetWindowsHookEx is just a DllImported Method from user32) Any Answers, or Prods in the right direction, or any hints, pointers or similar are very much appreciated!

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  • C++ Exception Handling

    - by user1413793
    So I was writing some code and I noticed that apart from syntactical, type, and other compile-time errors, C++ does not throw any other exceptions. So I decided to test this out with a very trivial program: #include<iostream> int main() { std::count<<5/0<<std::endl; return 1 } When I compiled it using g++, g++ gave me a warning saying I was dividing by 0. But it still compiled the code. Then when I ran it, it printed some really large arbitrary number. When I want to know is, how does C++ deal with exceptions? Integer division by 0 should be a very trivial example of when an exception should be thrown and the program should terminate. Do I have to essentially enclose my entire program in a huge try block and then catch certain exceptions? I know in Python when an exception is thrown, the program will immediately terminate and print out the error. What does C++ do? Are there even runtime exceptions which stop execution and kill the program?

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  • How do I get Google Chrome's root bookmarks folder?

    - by Wayne
    Hi, I'm trying to write a better bookmark manager in chrome extensions. The problem is there are no simple examples (that I can find) about how to actually use the bookmarks api (available here: http://code.google.com/chrome/extensions/bookmarks.html ) I've looked at the example source (when I d/led and installed it on my computer it didn't do anything except provide a search box. Typing/typing and pressing return failed to do anything) and can't find anything useful. My ultimate goal is to make an extension that allows me to save pages to come and read later without having to go sign up for an account on some service somewhere. So I plan to create either one or two bookmark folders in the root folder/other bookmarks - at minimum an "unread pages" folder. In that folder I'll create the unread bookmarks. When the user marks the item as read, it will be removed from that folder. So that's what I'm trying to do... any help will be greatly appreciated, even if it's just pointing me to some good examples. UPDATE: ...<script> function display(tree){ document.getElementById("Output").innerHTML = tree; } function start(){ chrome.bookmarks.getTree(display); } </script> </head> <body> <h4 id="Output"></h4> <script> start(); </script> ... That displays [object Object], that suggests (at least to me with a limited JavaScript experience) that an object exists. But how to access the members of that object? changing tree to tree.id or any other of what look to be parameters displays "undefined".

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  • Can shared memory be read and validated without mutexes?

    - by Bribles
    On Linux I'm using shmget and shmat to setup a shared memory segment that one process will write to and one or more processes will read from. The data that is being shared is a few megabytes in size and when updated is completely rewritten; it's never partially updated. I have my shared memory segment laid out as follows: ------------------------- | t0 | actual data | t1 | ------------------------- where t0 and t1 are copies of the time when the writer began its update (with enough precision such that successive updates are guaranteed to have differing times). The writer first writes to t1, then copies in the data, then writes to t0. The reader on the other hand reads t0, then the data, then t1. If the reader gets the same value for t0 and t1 then it considers the data consistent and valid, if not, it tries again. Does this procedure ensure that if the reader thinks the data is valid then it actually is? Do I need to worry about out-of-order execution (OOE)? If so, would the reader using memcpy to get the entire shared memory segment overcome the OOE issues on the reader side? (This assumes that memcpy performs it's copy linearly and ascending through the address space. Is that assumption valid?)

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  • net send command program debugging in C#

    - by riad
    Dear all, I write a program to execute and send msg using windows net send command.Its working fine for single receptor.But the problem happen when i want to send message in many receptors. i use a for loop to take receptor name from a list box. Here all message go to the first receptor.The problem happen on process execution.So far i guess the process is not clear or dead on the time. Can any body guide me how i can send the msg to multiple users at a time? my code below: string sendingMessage = messageRichTextBox.Text; string[] recepentAddressArray = new string[recepentAddressListBox.Items.Count]; for (int j = 0; j < recepentAddressListBox.Items.Count; j++) // Getting address from list box { recepentAddressArray[j] = recepentAddressListBox.Items[j].ToString(); string recepantAddress = recepentAddressArray[j]; try { string strLine = "net send " + recepantAddress + " " + sendingMessage + " >C:netsend.log"; FileStream fs = new FileStream("c:netsend.bat", FileMode.Create, FileAccess.Write); StreamWriter streamWriter = new StreamWriter(fs); streamWriter.BaseStream.Seek(0, SeekOrigin.End); streamWriter.Write(strLine); streamWriter.Flush(); streamWriter.Close(); fs.Close(); Process p = new Process(); p.StartInfo.FileName = "C:netsend.bat"; p.StartInfo.WindowStyle = ProcessWindowStyle.Hidden; p.Start(); p.WaitForExit(); p.Close(); FileStream fsOutput = new FileStream("C:netsend.log", FileMode.Open, FileAccess.Read); StreamReader reader = new StreamReader(fsOutput); reader.BaseStream.Seek(0, SeekOrigin.Begin); string strOut = reader.ReadLine(); reader.Close(); fsOutput.Close(); } catch (Exception) { MessageBox.Show("ERROR"); } }

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  • Generic dataset handling library

    - by Pep.
    Hello, I want to build a generic Perl module for handling and analysing biomedical character separated datasets and which can, most certain, be used on any kind of datasets that contain a mixture of categorical (A,B,C,..) and continuous (1.2,3,881..) and identifier (XXX1,XXX2...). The plan is to have people initialize the module and then use some arguments to point to the data file(s), the place were the analysis reports should be placed and the structure of the data. By structure of data I mean which variable is in which place and its name/type. And this is where I need some enlightenment. I am baffled how to do this in a clean way. Obviously, having people create a simple schema file, be it XML or some other format would be the cleanest but maybe not all people enjoy doing something like this. The solutions I can think of are: Create a configuration file in XML or similar and with a prespecified format. Pass the information during initialization of the module. Use the first row of the data as headers and try to guess types (ouch) Surely there must be a "canonical" way of doing this that is also usable and efficient. Thanks p.

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  • Python Error-Checking Standard Practice

    - by chaindriver
    Hi, I have a question regarding error checking in Python. Let's say I have a function that takes a file path as an input: def myFunction(filepath): infile = open(filepath) #etc etc... One possible precondition would be that the file should exist. There are a few possible ways to check for this precondition, and I'm just wondering what's the best way to do it. i) Check with an if-statement: if not os.path.exists(filepath): raise IOException('File does not exist: %s' % filepath) This is the way that I would usually do it, though the same IOException would be raised by Python if the file does not exist, even if I don't raise it. ii) Use assert to check for the precondition: assert os.path.exists(filepath), 'File does not exist: %s' % filepath Using asserts seems to be the "standard" way of checking for pre/postconditions, so I am tempted to use these. However, it is possible that these asserts are turned off when the -o flag is used during execution, which means that this check might potentially be turned off and that seems risky. iii) Don't handle the precondition at all This is because if filepath does not exist, there will be an exception generated anyway and the exception message is detailed enough for user to know that the file does not exist I'm just wondering which of the above is the standard practice that I should use for my codes.

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  • Same query has nested loops when used with INSERT, but Hash Match without.

    - by AaronLS
    I have two tables, one has about 1500 records and the other has about 300000 child records. About a 1:200 ratio. I stage the parent table to a staging table, SomeParentTable_Staging, and then I stage all of it's child records, but I only want the ones that are related to the records I staged in the parent table. So I use the below query to perform this staging by joining with the parent tables staged data. --Stage child records INSERT INTO [dbo].[SomeChildTable_Staging] ([SomeChildTableId] ,[SomeParentTableId] ,SomeData1 ,SomeData2 ,SomeData3 ,SomeData4 ) SELECT [SomeChildTableId] ,D.[SomeParentTableId] ,SomeData1 ,SomeData2 ,SomeData3 ,SomeData4 FROM [dbo].[SomeChildTable] D INNER JOIN dbo.SomeParentTable_Staging I ON D.SomeParentTableID = I.SomeParentTableID; The execution plan indicates that the tables are being joined with a Nested Loop. When I run just the select portion of the query without the insert, the join is performed with Hash Match. So the select statement is the same, but in the context of an insert it uses the slower nested loop. I have added non-clustered index on the D.SomeParentTableID so that there is an index on both sides of the join. I.SomeParentTableID is a primary key with clustered index. Why does it use a nested loop for inserts that use a join? Is there a way to improve the performance of the join for the insert?

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  • Simple encryption - Sum of Hashes in C

    - by Dogbert
    I am attempting to demonstrate a simple proof of concept with respect to a vulnerability in a piece of code in a game written in C. Let's say that we want to validate a character login. The login is handled by the user choosing n items, (let's just assume n=5 for now) from a graphical menu. The items are all medieval themed: eg: _______________________________ | | | | | Bow | Sword | Staff | |-----------|-----------|-------| | Shield | Potion | Gold | |___________|___________|_______| The user must click on each item, then choose a number for each item. The validation algorithm then does the following: Determines which items were selected Drops each string to lowercase (ie: Bow becomes bow, etc) Calculates a simple string hash for each string (ie: `bow = b=2, o=15, w=23, sum = (2+15+23=40) Multiplies the hash by the value the user selected for the corresponding item; This new value is called the key Sums together the keys for each of the selected items; this is the final validation hash IMPORTANT: The validator will accept this hash, along with non-zero multiples of it (ie: if the final hash equals 1111, then 2222, 3333, 8888, etc are also valid). So, for example, let's say I select: Bow (1) Sword (2) Staff (10) Shield (1) Potion (6) The algorithm drops each of these strings to lowercase, calculates their string hashes, multiplies that hash by the number selected for each string, then sums these keys together. eg: Final_Validation_Hash = 1*HASH(Bow) + 2*HASH(Sword) + 10*HASH(Staff) + 1*HASH(Shield) + 6*HASH(Potion) By application of Euler's Method, I plan to demonstrate that these hashes are not unique, and want to devise a simple application to prove it. in my case, for 5 items, I would essentially be trying to calculate: (B)(y) = (A_1)(x_1) + (A_2)(x_2) + (A_3)(x_3) + (A_4)(x_4) + (A_5)(x_5) Where: B is arbitrary A_j are the selected coefficients/values for each string/category x_j are the hash values for each string/category y is the final validation hash (eg: 1111 above) B,y,A_j,x_j are all discrete-valued, positive, and non-zero (ie: natural numbers) Can someone either assist me in solving this problem or point me to a similar example (ie: code, worked out equations, etc)? I just need to solve the final step (ie: (B)(Y) = ...). Thank you all in advance.

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  • Using PHP as template language

    - by Kunal
    I wrote up this quick class to do templating via PHP -- I was wondering if this is easily exploitable if I were ever to open up templating to users (not the immediate plan, but thinking down the road). class Template { private $allowed_methods = array( 'if', 'switch', 'foreach', 'for', 'while' ); private function secure_code($template_code) { $php_section_pattern = '/\<\?(.*?)\?\>/'; $php_method_pattern = '/([a-zA-Z0-9_]+)[\s]*\(/'; preg_match_all($php_section_pattern, $template_code, $matches); foreach (array_unique($matches[1]) as $index => $code_chunk) { preg_match_all($php_method_pattern, $code_chunk, $sub_matches); $code_allowed = true; foreach ($sub_matches[1] as $method_name) { if (!in_array($method_name, $this->allowed_methods)) { $code_allowed = false; break; } } if (!$code_allowed) { $template_code = str_replace($matches[0][$index], '', $template_code); } } return $template_code; } public function render($template_code, $params) { extract($params); ob_start(); eval('?>'.$this->secure_code($template_code).'<?php '); $result = ob_get_contents(); ob_end_clean(); return $result; } } Example usage: $template_code = '<?= $title ?><? foreach ($photos as $photo): ?><img src="<?= $photo ?>"><? endforeach ?>'; $params = array('title' => 'My Title', 'photos' => array('img1.jpg', 'img2.jpg')); $template = new Template; echo $template->render($template_code, $params); The idea here is that I'd store the templates (PHP code) in the database, and then run it through the class which uses regular expressions to only allow permitted methods (if, for, etc.). Anyone see an obvious way to exploit this and run arbitrary PHP? If so, I'll probably go the more standard route of a templating language such as Smarty...

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  • Query broke down and left me stranded in the woods

    - by user1290323
    I am trying to execute a query that deletes all files from the images table that do not exist in the filters tables. I am skipping 3,500 of the latest files in the database as to sort of "Trim" the table back to 3,500 + "X" amount of records in the filters table. The filters table holds markers for the file, as well as the file id used in the images table. The code will run on a cron job. My Code: $sql = mysql_query("SELECT * FROM `images` ORDER BY `id` DESC") or die(mysql_error()); while($row = mysql_fetch_array($sql)){ $id = $row['id']; $file = $row['url']; $getId = mysql_query("SELECT `id` FROM `filter` WHERE `img_id` = '".$id."'") or die(mysql_error()); if(mysql_num_rows($getId) == 0){ $IdQue[] = $id; $FileQue[] = $file; } } for($i=3500; $i<$x; $i++){ mysql_query("DELETE FROM `images` WHERE id='".$IdQue[$i]."' LIMIT 1") or die("line 18".mysql_error()); unlink($FileQue[$i]) or die("file Not deleted"); } echo ($i-3500)." files deleted."; Output: 0 files deleted. Database contents: images table: 10,000 rows filters table: 63 rows Amount of rows in filters table that contain an images table id: 63 Execution time of php script: 4 seconds +/- 0.5 second Relevant DB structure TABLE: images id url etc... TABLE: filter id img_id (CONTAINS ID FROM images table) etc...

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  • How to replace pairs of strings in two files to identical IDs?

    - by Péter Török
    Sorry if the title is not very intelligible, I couldn't come up with anything better. Hopefully my explanation is clear enough: I have a pair of rather large log files with very similar content, except that some strings are different between the two. A couple of examples: UnifiedClassLoader3@19518cc | UnifiedClassLoader3@d0357a JBossRMIClassLoader@13c2d7f | JBossRMIClassLoader@191777e That is, wherever the first file contains UnifiedClassLoader3@19518cc, the second contains UnifiedClassLoader3@d0357a, and so on. [Update] There are about 40 distinct pairs of such identifiers.[/Update] I want to replace these with identical IDs so that I can spot the really important differences between the two files. I.e. I want to replace all occurrences of both UnifiedClassLoader3@19518cc in file1 and UnifiedClassLoader3@d0357a in file2 with UnifiedClassLoader3@1; all occurrences of both JBossRMIClassLoader@13c2d7f in file1 and JBossRMIClassLoader@191777e in file2 with JBossRMIClassLoader@2 etc. Using the Cygwin shell, so far I managed to list all different identifiers occurring in one of the files with grep -o -e 'ClassLoader[0-9]*@[0-9a-f][0-9a-f]*' file1.log | sort | uniq However, now the original order is lost, so I don't know which is the pair of which ID in the other file. With grep -n I can get the line number, so the sort would preserve the order of appearance, but then I can't weed out the duplicate occurrences. Unfortunately grep can not print only the first match of a pattern. I figured I could save the list of identifiers produced by the above command into a file, then iterate over the patterns in the file with grep -n | head -n 1, concatenate the results and sort them again. The result would be something like 2 ClassLoader3@19518cc 137 ClassLoader@13c2d7f 563 ClassLoader3@1267649 ... Then I could (either manually or with sed itself) massage this into a sed command like sed -e 's/ClassLoader3@19518cc/ClassLoader3@2/g' -e 's/ClassLoader@13c2d7f/ClassLoader@137/g' -e 's/ClassLoader3@1267649/ClassLoader3@563/g' file1.log > file1_processed.log and similarly for file2. However, before I start, I would like to verify that my plan is the simplest possible working solution to this. Is there any flaw in this approach? Is there a simpler way?

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