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• How to write CData in xml

  - by Rajesh Rolen- DotNet Developer

  i have an xml like : <?xml version="1.0" encoding="UTF-8"?> <entry> <entry_id></entry_id> <entry_status></entry_status> </entry> i am writing data in it like: XmlNode xnode = xdoc.SelectSingleNode("entry/entry_status"); xnode.InnerText = "<![CDATA[ " + Convert.ToString(sqlReader["story_status"]) + " ]]>" ; but its change "<" to "&lt" of CDATA. Please tell me how to fill values in above xml as a CData format. i know that we can create CDATA like : XmlNode itemDescription = doc.CreateElement("description"); XmlCDataSection cdata = doc.CreateCDataSection("<P>hello world</P>"); itemDescription.AppendChild(cdata); item.AppendChild(itemDescription); but my process is to read node of xml and change its value not to append in it. Thanks

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• paperclip overwrites / resets S3 permissions for non-bucket-owners

  - by adriandz

  I have opened this as an issue on Github (http://github.com/thoughtbot/paperclip/issues/issue/225) but on the chance that I'm just doing this wrong, I thought I'd also ask about it here. If someone can tell me where I'm going wrong, I can close the issue and save the Paperclip guys some trouble. Issue: When using S3 for storage, and you wish your bucket to allow access to other users to whom you have granted access, Paperclip appears to overwrite the permissions on the bucket, removing access to these users. Process for duplication: Create a bucket in S3 and set up a Rails app with Paperclip to use this bucket for storage Add a user (for example, [email protected], the user for the video encoding service Zencoder) to the bucket, and grant this user List and Read/Write permissions. Upload a file. Refresh the permissions. The user you added will be gone. As well, a user "Everyone" with read permissions will have been added. The end result is that you cannot, so far as I can tell, retain desired permissions on your bucket when using Paperclip and S3. Can anyone help?

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• Trap SIGPIPE when trying to write without reader

  - by Matt

  I am trying to implement a named-pipe communication solution in BASH between two processes. The first process runs a script which echo something in a named-pipe: send(){ echo 'something' > $NAMEDPIPE } And the second script is supposed to read the named-pipe via another script which contains: while true;do if read line < $NAMEDPIPE;do someCommands fi done Not that the named pipe has been previously created using the traditional command mkfifo $NAMEDPIPE My problem is that the reader script is not always running so that if the writer script try to write in the named-pipe it stay blocked until a reader connect the pipe. I want to avoid this behavior, and a solution would be to trap a SIGPIPE signal. Indeed, according to man 7 signal is supposed to be send when trying to write in a pipe with no reader. So I changed my red function by: read(){ trap 'echo "SIGPIPE received"' SIGPIPE echo 'something' > $NAMEDPIPE } But when I run the reader script, the script stay blocked, and not "SIGPIPE received" appears... Am I mistaking on the signal mechanism or is there any better solution to my problem ? Thank you for your help.

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• How to push a new feature to a central Mercurial repo?

  - by Sly

  I'm assigned the development of a feature for a project. I'm going to work on that feature for several days over a period of a few weeks. I'll clone the central repo. Then I'm going to work locally for 3 weeks. I'll commit my progress to my repo several times during that process. When I'm done, I'm going to pull/merge/commit before I push. What is the right way push my feature as a single changeset to the central repo? I don't want to push 14 "work in progress" changesets and 1 "merged" changeset to the central repo. I want other collaborators on the project to see only one changeset with a significant commit message (such as "Implemented feature ABC"). I'm new to Mercurial and DVCS so don't hesitate to provide guidance if you think I'm not approaching that the right way. <My own answer> So far I came up with a way of reducing 15 changeset to 2 changeset. Suppose changesets 10 to 24 are "work in progress" changesets. I can 'hg collapse -r 10:24 -m "Implemented feature ABC"' (14 changesets collapsed into 1). Then, I must 'hg pull' + 'hg merge' + 'hg commit -m "Merged with most recent changes"'. But now I'm stuck with 2 changesets. I can no longer 'hg collapse', because pull/merge/commit broke my changeset sequence. Of course 2 changesets is better then 15 but still, I'd rather have 1 changeset. </My own answer>

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• EasyHook Windows Hooking problem/.dll injection

  - by Tom

  Ok can someone try and find the error with this code, it should produce all the registry keys every time something accesses them but i keep getting: System.MissingMethodException: The given method does not exist at EasyHook.LocalHook.GetProcAdress(String InModule, String InChannelName) An example code can be found here: http://www.codeproject.com/KB/DLL/EasyHook64.aspx I can get the CcreateFileW example to work! My code is here: public class Main : EasyHook.IEntryPoint { FileMon.FileMonInterface Interface; LocalHook LocalHook; Stack<String> Queue = new Stack<String>(); public Main(RemoteHooking.IContext InContext,String InChannelName) { // connect to host... Interface = RemoteHooking.IpcConnectClient<FileMon.FileMonInterface>(InChannelName); Interface.Ping(); } public void Run(RemoteHooking.IContext InContext,String InChannelName) { // install hook... try { LocalHook localHook = LocalHook.Create(LocalHook.GetProcAddress("Advapi32.dll", "RegOpenKeyExW"),new DMyRegOpenKeyExW(MyRegOpenKeyExW),this); localHook.ThreadACL.SetExclusiveACL(new int[] { }); } catch (Exception ExtInfo) { Interface.ReportException(ExtInfo); return; } Interface.IsInstalled(RemoteHooking.GetCurrentProcessId()); RemoteHooking.WakeUpProcess(); // wait for host process termination... try { while (true) { Thread.Sleep(500); // transmit newly monitored file accesses... if (Queue.Count > 0) { String[] Package = null; lock (Queue) { Package = Queue.ToArray(); Queue.Clear(); } Interface.OnCreateFile(RemoteHooking.GetCurrentProcessId(), Package); } else Interface.Ping(); } } catch { // Ping() will raise an exception if host is unreachable } } [DllImport("Advapi32.dll", CharSet = CharSet.Unicode, SetLastError = true, CallingConvention = CallingConvention.StdCall)] static extern int RegOpenKeyExW(UIntPtr hKey,string subKey,int ulOptions,int samDesired,out UIntPtr hkResult); [UnmanagedFunctionPointer(CallingConvention.StdCall, CharSet = CharSet.Unicode, SetLastError = true)] delegate int DMyRegOpenKeyExW(UIntPtr hKey,string subKey,int ulOptions,int samDesired,out UIntPtr hkResult); int MyRegOpenKeyExW(UIntPtr hKey,string subKey,int ulOptions,int samDesired,out UIntPtr hkResult) { Console.WriteLine(string.Format("Accessing: {0}", subKey)); return RegOpenKeyExW(hKey, subKey, ulOptions, samDesired, out hkResult); } }

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• Safe to pass objects to C functions when working in JNI Invocation API?

  - by bubbadoughball

  I am coding up something using the JNI Invocation API. A C program starts up a JVM and makes calls into it. The JNIenv pointer is global to the C file. I have numerous C functions which need to perform the same operation on a given class of jobject. So I wrote helper functions which take a jobject and process it, returning the needed data (a C data type...for example, an int status value). Is it safe to write C helper functions and pass jobjects to them as arguments? i.e. (a simple example - designed to illustrate the question): int getStatusValue(jobject jStatus) { return (*jenv)->CallIntMethod(jenv,jStatus,statusMethod); } int function1() { int status; jobject aObj = (*jenv)->NewObject (jenv, aDefinedClass, aDefinedCtor); jobject j = (*jenv)->CallObjectMethod (jenv, aObj, aDefinedObjGetMethod) status = getStatusValue(j); (*jenv)->DeleteLocalRef(jenv,aObj); (*jenv)->DeleteLocalRef(jenv,j); return status; } Thanks.

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• Simplifying Testing through design considerations while utilizing dependency injection

  - by Adam Driscoll

  We are a few months into a green-field project to rework the Logic and Business layers of our product. By utilizing MEF (dependency injection) we have achieved high levels of code coverage and I believe that we have a pretty solid product. As we have been working through some of the more complex logic I have found it increasingly difficult to unit test. We are utilizing the CompositionContainer to query for types required by these complex algorithms. My unit tests are sometimes difficult to follow due to the lengthy mock object setup process that must take place, just right, to allow for certain circumstances to be verified. My unit tests often take me longer to write than the code that I'm trying to test. I realize this is not only an issue with dependency injection but with design as a whole. Is poor method design or lack of composition to blame for my overly complex tests? I've tried base classing tests, creating commonly used mock objects and ensuring that I utilize the container as much as possible to ease this issue but my tests always end up quite complex and hard to debug. What are some tips that you've seen to keep such tests concise, readable, and effective?

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• What techniques can be used to detect so called "black holes" (a spider trap) when creating a web crawler?

  - by Tom

  When creating a web crawler, you have to design somekind of system that gathers links and add them to a queue. Some, if not most, of these links will be dynamic, which appear to be different, but do not add any value as they are specifically created to fool crawlers. An example: We tell our crawler to crawl the domain evil.com by entering an initial lookup URL. Lets assume we let it crawl the front page initially, evil.com/index The returned HTML will contain several "unique" links: evil.com/somePageOne evil.com/somePageTwo evil.com/somePageThree The crawler will add these to the buffer of uncrawled URLs. When somePageOne is being crawled, the crawler receives more URLs: evil.com/someSubPageOne evil.com/someSubPageTwo These appear to be unique, and so they are. They are unique in the sense that the returned content is different from previous pages and that the URL is new to the crawler, however it appears that this is only because the developer has made a "loop trap" or "black hole". The crawler will add this new sub page, and the sub page will have another sub page, which will also be added. This process can go on infinitely. The content of each page is unique, but totally useless (it is randomly generated text, or text pulled from a random source). Our crawler will keep finding new pages, which we actually are not interested in. These loop traps are very difficult to find, and if your crawler does not have anything to prevent them in place, it will get stuck on a certain domain for infinity. My question is, what techniques can be used to detect so called black holes? One of the most common answers I have heard is the introduction of a limit on the amount of pages to be crawled. However, I cannot see how this can be a reliable technique when you do not know what kind of site is to be crawled. A legit site, like Wikipedia, can have hundreds of thousands of pages. Such limit could return a false positive for these kind of sites. Any feedback is appreciated. Thanks.

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• Jasmine testing coffeescript expect(setTimeout).toHaveBeenCalledWith

  - by Lee Quarella

  In the process of learning Jasmine, I've come to this issue. I want a basic function to run, then set a timeout to call itself again... simple stuff. class @LoopObj constructor: -> loop: (interval) -> #do some stuff setTimeout((=>@loop(interval)), interval) But I want to test to make sure the setTimeout was called with the proper args describe "loop", -> xit "does nifty things", -> it "loops at a given interval", -> my_nifty_loop = new LoopObj interval = 10 spyOn(window, "setTimeout") my_nifty_loop.loop(interval) expect(setTimeout).toHaveBeenCalledWith((-> my_nifty_loop.loop(interval)), interval) I get this error: Expected spy setTimeout to have been called with [ Function, 10 ] but was called with [ [ Function, 10 ] ] Is this because the (-> my_nifty_loop.loop(interval)) function does not equal the (=>@loop(interval)) function? Or does it have something to do with the extra square brackets around the second [ [ Function, 10 ] ]? Something else altogther? Where have I gone wrong?

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• The instruction at "0x7c910a19" referenced memory at "oxffffffff". The memory could not be "read"

  - by ClareBear

  Hello guys/girls The instruction at "0x7c910a19" referenced memory at "oxffffffff". The memory could not be "read" I have a small issue, I receive the error above before the .vbs terminates. I don't know why this error is thrown. Below is the process of the .vbs file: Call ImportTransactions() Call UpdateTransactions() Function ImportTransactions() Dim objConnection, objCommand, objRecordset, strOracle Dim strSQL, objRecordsetInsert Set objConnection = CreateObject("ADODB.Connection") objConnection.Open "DSN=*****;UID=*****;PWD==*****;" Set objCommand = CreateObject("ADODB.Command") Set objRecordset = CreateObject("ADODB.Recordset") strOracle = "SELECT query here from Oracle database" objCommand.CommandText = strOracle objCommand.CommandType = 1 objCommand.CommandTimeout = 0 Set objCommand.ActiveConnection = objConnection objRecordset.cursorType = 0 objRecordset.cursorlocation = 3 objRecordset.Open objCommand, , 1, 3 If objRecordset.EOF = False Then Do Until objRecordset.EOF = True strSQL = "INSERT query here into SQL database" strSQL = Query(strSQL) Call RunSQL(strSQL, objRecordsetInsert, False, conTimeOut, conServer, conDatabase, conUsername, conPassword) objRecordset.MoveNext Loop End If objRecordset.Close() Set objRecordset = Nothing Set objRecordsetInsert = Nothing End Function Function UpdateTransactions() Dim strSQLUpdateVAT, strSQLUpdateCodes Dim objRecordsetVAT, objRecordsetUpdateCodes strSQLUpdateVAT = "UPDATE query here SET [value:costing output] = ([value:costing output] * -1)" Call RunSQL(strSQLUpdateVAT, objRecordsetVAT, False, conTimeOut, conServer, conDatabase, conUsername, conPassword) strSQLUpdateCodes = "UPDATE query here SET [value:costing output] = ([value:costing output] * -1) different WHERE clause" Call RunSQL(strSQLUpdateCodes, objRecordsetUpdateCodes, False, conTimeOut, conServer, conDatabase, conUsername, conPassword) Set objRecordsetVAT = Nothing Set objRecordsetUpdateCodes = Nothing End Function UDPATE: If I exit the function after I open the connection (see below) it still causes the same error. Function ImportTransactions() Dim objConnection, objCommand, objRecordset, strOracle Dim strSQL, objRecordsetInsert Set objConnection = CreateObject("ADODB.Connection") objConnection.Open "DSN=*****;UID=*****;PWD==*****;" Set objCommand = CreateObject("ADODB.Command") Set objRecordset = CreateObject("ADODB.Recordset") Exit Function End Function It does both the import and update and seems to throw this error after. Thanks in advance for any help, Clare

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• Does SetFileBandwidthReservation affect memory-mapped file performance?

  - by Ghostrider

  Does this function affect Memory-mapped file performance? Here's the problem I need to solve: I have two applications competing for disk access: "reader" and "updater". Whole system runs on Windows Server 2008 R2 x64 "Updater" constantly accesses disk in a linear manner, updating data. They system is set up in such a way that updater always has infinite data to update. Consider that it is constantly approximating a solution of a huge set of equations that takes up entire 2TB disk drive. Updater uses ReadFile and WriteFile to process data in a linear fashion. "Reader" is occasionally invoked by user to get some pieces of data. Usually user would read several 4kb blocks from the drive and stop. Occasionally user needs to read up to 100mb sequentially. In exceptional cases up to several gigabytes. Reader maps files to memory to get data it needs. What I would like to achieve is for "reader" to have absolute priority so that "updater" would completely stop if needed so that "reader" could get the data user needs ASAP. Is this problem solvable by using SetPriorityClass and SetFileBandwidthReservation calls? I would really hate to put synchronization login in "reader" and "updater" and rather have the OS take care of priorities.

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• Using Interface Builder efficiently

  - by Aaron Wetzler

  I am new to iPhone and objective c. I have spent hours and hours and hours reading documents and trying to understand how things work. I have RTFM or at least am in the process. My main problem is that I want to understand how to specify where an event gets passed to and the only way I have been able to do it is by specifying delegates but I am certain there is an easier/quicker way in IB. So, an example. Lets say I have 20 different views and view controllers and one MyAppDelegate. I want to be able to build all of these different Xib files in IB and add however many buttons and text fields and whatever and then specify that they all produce some event in the MyAppDelegate object. To do this I added a MyAppDelegate object in each view controller in IB's list view. Then I created an IBAction method in MyAppDelegate in XCode and went back to IB and linked all of the events to the MyAppDelegate object in each Xib file. However when I tried running it it just crashed with a bad read exception. My guess is that each Xib file is putting a MyAppDelegate object pointer that has nothing to do with the eventual MyAppDelegate adress that will actually be created at runtime. So my question is...how can I do this?!!!

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• Which software for intranet CMS - Django or Joomla?

  - by zalun

  In my company we are thinking of moving from wiki style intranet to a more bespoke CMS solution. Natural choice would be Joomla, but we have a specific architecture. There is a few hundred people who will use the system. System should be self explainable (easier than wiki). We use a lot of tools web, applications and integrated within 3rd party software. The superior element which is a glue for all of them is API. In example for the intranet tools we do use Django, but it's used without ORM, kind of limited to templates and url - every application has an adequate methods within our API. We do not use the Django admin interface, because it is hardly dependent on ORM. Because of that Joomla may be hard to integrate. Every employee should be able to edit most of the pages, authentication and privileges have to be managed by our API. How hard is it to plug Joomla to use a different authentication process? (extension only - no hacks) If one knows Django better than Joomla, should Django be used?

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• Python virtualenv questions

  - by orokusaki

  I'm using VirtualEnv on Windows XP. I'm wondering if I have my brain wrapped around it correctly. I ran virtualenv ENV and it created C:\WINDOWS\system32\ENV. I then changed my PATH variable to include C:\WINDOWS\system32\ENV\Scripts instead of C:\Python27\Scripts. Then, I checked out Django into C:\WINDOWS\system32\ENV\Lib\site-packages\django-trunk, updated my PYTHON_PATH variable to point the new Django directory, and continued to easy_install other things (which of course go into my new C:\WINDOWS\system32\ENV\Lib\site-packages directory). I understand why I should use VirtualEnv so I can run multiple versions of Django, and other libraries on the same machine, but does this mean that to switch between environments I have to basically change my PATH and PYTHON_PATH variable? So, I go from developing one Django project which uses Django 1.2 in an environment called ENV and then change my PATH and such so that I can use an environment called ENV2 which has the dev version of Django? Is that basically it, or is there some better way to automatically do all this (I could update my path in Python code, but that would require me to write machine-specific code in my application)? Also, how does this process compare to using VirtualEnv on Linux (I'm quite the beginner at Linux).

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• Access User Meta Data on User Registration in Wordpress

  - by Shadi Almosri

  Hiya, I am attempting to carry out a few functions when a user registers on a wordpress site. I have created a module for this which carries out the following function: add_action( 'user_register', 'tml_new_user_registered' ); function tml_new_user_registered( $user_id ) { //wp_set_auth_cookie( $user_id, false, is_ssl() ); //wp_redirect( admin_url( 'profile.php' ) ); $user_info = get_userdata($user_id); $subscription_value = get_user_meta( $user_id, "subscribe_to_newsletter", TRUE); if($subscription_value == "Yes") { //include("Subscriber.Add.php"); } echo "<pre>: "; print_r($user_info); print_r($subscription_value); echo "</pre>"; exit; } But it seems that i am not able to access any user meta data as at the end of this stage none of it is stored. Any ideas how i execute a function once Wordpress has completed the whole registration process of adding meta data into the relevant tables too? I attempted to use this: add_filter('user_register ','tml_new_user_registered',99); But with no luck unfortunately. Thanks in advance!

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• [Cocoa] Core Animation with an NSView and subviews

  - by ndg

  I've subclassed NSView to create a 'container' view (which I've called TRTransitionView) which is being used to house two subviews. At the click of a button, I want to transition one subview out of the parent view and transition the other in, using the Core Animation transition type: kCATransitionPush. For the most part, I have this working as you'd expect (here's a basic test project I threw together). The issue I'm seeing relates to resizing my window and then toggling between my two views. After resizing a window, my subviews will appear at seemingly random locations within my TRTransitionView. Additionally, it appears as if the TRTransitionView hasn't stretched correctly and is clipping the contents of its subviews. Ideally, I would like subviews anchored to the top-left of their parent view at all times, and to also grow to expand the size of the parent view. The second issue relates to an NSTableView I've placed in my first subview. When my window is resized, and my TRTransitionView resizes to match its new dimensions, my TableView seems to resize its content quite awkwardly (the entire table seems to jolt around) and the newly expanded space that the table now occupies seems to 'flash' (as if in the process of being animated). Extremely difficult to describe, but is there any way to stop this? Here's my TRTransitionView class: -(void) awakeFromNib { [self setWantsLayer:YES]; [self addSubview:[self currentView]]; transition = [CATransition animation]; [transition setType:kCATransitionPush]; [transition setSubtype:kCATransitionFromLeft]; [self setAnimations: [NSDictionary dictionaryWithObject:transition forKey:@"subviews"]]; } - (void)setCurrentView:(NSView*)newView { if (!currentView) { currentView = newView; return; } [[self animator] replaceSubview:currentView with:newView]; currentView = newView; } -(IBAction) switchToViewOne:(id)sender { [transition setSubtype:kCATransitionFromLeft]; [self setCurrentView:viewOne]; } -(IBAction) switchToViewTwo:(id)sender { [transition setSubtype:kCATransitionFromRight]; [self setCurrentView:viewTwo]; }

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• Testing for interface implementation in WCF/SOA

  - by rabidpebble

  I have a reporting service that implements a number of reports. Each report requires certain parameters. Groups of logically related parameters are placed in an interface, which the report then implements: [ServiceContract] [ServiceKnownType(typeof(ExampleReport))] public interface IService1 { [OperationContract] void Process(IReport report); } public interface IReport { string PrintedBy { get; set; } } public interface IApplicableDateRangeParameter { DateTime StartDate { get; set; } DateTime EndDate { get; set; } } [DataContract] public abstract class Report : IReport { [DataMember] public string PrintedBy { get; set; } } [DataContract] public class ExampleReport : Report, IApplicableDateRangeParameter { [DataMember] public DateTime StartDate { get; set; } [DataMember] public DateTime EndDate { get; set; } } The problem is that the WCF DataContractSerializer does not expose these interfaces in my client library, thus I can't write the generic report generating front-end that I plan to. Can WCF expose these interfaces, or is this a limitation of the serializer? If the latter case, then what is the canonical approach to this OO pattern? I've looked into NetDataContractSerializer but it doesn't seem to be an officially supported implementation (which means it's not an option in my project). Currently I've resigned myself to including the interfaces in a library that is common between the service and the client application, but this seems like an unnecessary extra dependency to me. Surely there is a more straightforward way to do this? I was under the impression that WCF was supposed to replace .NET remoting; checking if an object implements an interface seems to be one of the most basic features required of a remoting interface?

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• Use of Syntactic Sugar / Built in Functionality

  - by Kyle Rozendo

  I was busy looking deeper into things like multi-threading and deadlocking etc. The book is aimed at both pseudo-code and C code and I was busy looking at implementations for things such as Mutex locks and Monitors. This brought to mind the following; in C# and in fact .NET we have a lot of syntactic sugar for doing things. For instance (.NET 3.5): lock(obj) { body } Is identical to: var temp = obj; Monitor.Enter(temp); try { body } finally { Monitor.Exit(temp); } There are other examples of course, such as the using() {} construct etc. My question is when is it more applicable to "go it alone" and literally code things oneself than to use the "syntactic sugar" in the language? Should one ever use their own ways rather than those of people who are more experienced in the language you're coding in? I recall having to not use a Process object in a using block to help with some multi-threaded issues and infinite looping before. I still feel dirty for not having the using construct in there. Thanks, Kyle

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• Ant fails without message at javac

  - by digitala

  I've written an Ant build.xml file which obtains a number of source files via WSDL and compiles them. These have been working on an old, now destroyed (and therefore unavailable for comparison), system but the build process isn't completing on this newer, faster system. The relevant section of the build file looks like this: <target name="compile" depends="init"> <java classname="org.apache.axis.wsdl.WSDL2Java"> <arg line="--all --server-side --skeletonDeploy --factory --wrapArrays --output src ${srcurl}" /> </java> <javac srcdir="${src}" destdir="${build}" verbose="yes" /> </target> The files are downloaded via the WSDL service successfully, however after that point Ant simply stops & returns to the commandline. Versions of the relevant apps: # java -version java version "1.6.0_14" Java(TM) SE Runtime Environment (build 1.6.0_14-b08) Java HotSpot(TM) 64-Bit Server VM (build 14.0-b16, mixed mode) # javac -version javac 1.6.0_14 # ant -version Apache Ant version 1.6.5 compiled on January 6 2007 I'm assuming that there's a problem with javac that Ant isn't passing back. Is there any way I can get some debugging information from javac? I've tried adding a <record /> tag to the target but that doesn't give any more information than running ant -v does. Any other suggestions would be great, also!

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• Segmentation in Linux : Segmentation & Paging are redundant?

  - by claws

  Hello, I'm reading "Understanding Linux Kernel". This is the snippet that explains how Linux uses Segmentation which I didn't understand. Segmentation has been included in 80 x 86 microprocessors to encourage programmers to split their applications into logically related entities, such as subroutines or global and local data areas. However, Linux uses segmentation in a very limited way. In fact, segmentation and paging are somewhat redundant, because both can be used to separate the physical address spaces of processes: segmentation can assign a different linear address space to each process, while paging can map the same linear address space into different physical address spaces. Linux prefers paging to segmentation for the following reasons: Memory management is simpler when all processes use the same segment register values that is, when they share the same set of linear addresses. One of the design objectives of Linux is portability to a wide range of architectures; RISC architectures in particular have limited support for segmentation. All Linux processes running in User Mode use the same pair of segments to address instructions and data. These segments are called user code segment and user data segment , respectively. Similarly, all Linux processes running in Kernel Mode use the same pair of segments to address instructions and data: they are called kernel code segment and kernel data segment , respectively. Table 2-3 shows the values of the Segment Descriptor fields for these four crucial segments. I'm unable to understand 1st and last paragraph.

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• Catching / blocking SIGINT during system call

  - by danben

  I've written a web crawler that I'd like to be able to stop via the keyboard. I don't want the program to die when I interrupt it; it needs to flush its data to disk first. I also don't want to catch KeyboardInterruptedException, because the persistent data could be in an inconsistent state. My current solution is to define a signal handler that catches SIGINT and sets a flag; each iteration of the main loop checks this flag before processing the next url. However, I've found that if the system happens to be executing socket.recv() when I send the interrupt, I get this: ^C Interrupted; stopping... // indicates my interrupt handler ran Traceback (most recent call last): File "crawler_test.py", line 154, in <module> main() ... File "/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/socket.py", line 397, in readline data = recv(1) socket.error: [Errno 4] Interrupted system call and the process exits completely. Why does this happen? Is there a way I can prevent the interrupt from affecting the system call?

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• What setting needs to be made to make .Net Automation responsive?

  - by Greg

  Have an app that is looking for application windows being created on the desktop using class Unresponsive { private StructureChangedEventHandler m_UIAeventHandler = new StructureChangedEventHandler(OnStructureChanged); public Unresponsive() { Automation.AddStructureChangedEventHandler(AutomationElement.RootElement, TreeScope.Children, m_UIAeventHandler); } private void OnStructureChanged(object sender, StructureChangedEventArgs e) { Debug.WriteLine("Change event"); } } You can see the same issue using UISpy.exe, selecting the desktop and configuring scope for children and just the structure changed event. The problem I'm trying to resolve is that the events are not raised in a timely manner, there seems to be some grouping/delay which makes the app appear to be non responsive. If you start a new app with 1 window and wait a second you get the event, seems alright. If you start the same app several times without delay (say clicking on quickstart), it's not until all of the instances of the app get 'initialised' by the AutomationProxies that you get the notice for the first app (and in short order the other apps/windows). I've sat watching task manager as each instance of the app starts to grow as it is initialised, waiting until the last app is done and then seeing the events all come in. Similarly any time any apps are starting windows within a timeframe there seems to be some blocking. I can't see how to configure this timeframe, or get each structure changed event to be sent on as soon as it happens. Also, this process of listening for structure changed events seems to be leaking, just by listening there is a leak in native memory. (visible in UISpy and my app)

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• Is there a limit for the number of files in a directory on an SD card?

  - by jamesh

  I have a project written for Android devices. It generates a large number of files, each day. These are all text files and images. The app uses a database to reference these files. The app is supposed to clear up these files after a little use (perhaps after a few days), but this process may or may not be working. This is not the subject of this question. Due to a historic accident, the organization of the files are somewhat naive: everything is in the same directory; a .hidden directory which contains a zero byte .nomedia file to prevent the MediaScanner indexing it. Today, I am seeing an error reported: java.io.IOException: Cannot create: /sdcard/.hidden/file-4200.html at java.io.File.createNewFile(File.java:1263) Regarding the sdcard, I see it has plenty of storage left, but counting $ cd /Volumes/NO_NAME/.hidden $ ls | wc -w 9058 Deleting a number of files seems to have allowed the file creation for today to proceed. Regrettably, I did not try touching a new file to try and reproduce the error on a commandline; I also deleted several hundred files rather than a handful. However, my question is: are there hard limits on filesize or number of files in a directory? am I even on the right track here? Nota Bene: The SD card is as-is - i.e. I haven't formatted it, so I would guess it would be a FAT-* format. The FAT-32 format has hard limits of filesize of 2GB (well above the filesizes I am dealing with) and a limit of number of files in the root directory. I am definitely not writing files in the root directory.

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• How to deploy a number of disparate project types?

  - by niteice

  This question is similar to http://stackoverflow.com/questions/1900269/whats-the-best-way-to-deploy-an-executable-process-on-a-web-server. The situation is this: I'm developing a product that needs to be deployed to a web server. It consists of 4 website projects, a background service, a couple of command-line tools, and two assemblies shared by all of these components. Now, I also happen to administer the server that this product will be deployed on. So I'm familiar with everything that may need to be done to perform an update: Copy website files Replace the service binary Install updated components in the GAC Configure IIS Update database schema After some research it seems that, to reduce deployment time and to be able to let the other sysadmins handle deployment, I want to deploy all of these as an MSI, except that I don't know a thing about installers. I know VS can generate web deployment projects, but where do I go from there? Being able to simply click Next a few times on an installer is my goal for deploying updates. It would also be nice to modularize it, so for example, I could distribute the four websites among multiple servers and have everything appear as individual components in the installer, and as one entity in Add/Remove Programs. Is all of this too much to ask in a single package?

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• Tips on designing a .NET API for future use with F#

  - by Drew Noakes

  I'm in the process of designing a .NET API to allow developers to create RoboCup agents for the 3D simulated soccer league. I'm pretty happy with how the API work with C# code, however I would like to use this project to improve my F# skill (which is currently based on reading rather than practice). So I would like to ask what kinds of things I should consider when designing an API that is to be consumed by both C# and F# code. Some points. I make fairly heavy use of matrix and vector math. These are currently immutable classes/structs. The API currently defines a few interfaces with the consumer implements (eg: IAgent), using instances of their implementations (eg: MyAgent) to construct other API classes (eg: new Client(myAgent)). The API fires events. The API exposes a few delegate types. The API includes several enums. I'd like to release a version of the API as soon as possible and don't want to make major changes to it later if I realise it's too difficult to work with from F#. Any advice is appreciated.

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