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• C Run-Time library part 2

  - by b-gen-jack-o-neill

  Hi, I was suggested when I have some further questions on my older ones, to create newer Question and reffer to old one. So, this is the original question: What is the C runtime library? OK, from your answers, I now get thet statically linked libraries are Microsoft implementation of C standart functions. Now: If I get it right, the scheme would be as follow: I want to use printf(), so I must include which just tels compiler there us functio printf() with these parameters. Now, when I compile code, becouse printf() is defined in C Standart Library, and becouse Microsoft decided to name it C Run Time library, it gets automatically statically linked from libcmt.lib (if libcmt.lib is set in compiler) at compile time. I ask, becouse on wikipedia, in article about runtime library there is that runtime library is linked in runtime, but .lib files are linked at compile time, am I right? Now, what confuses me. There is .dll version of C standart library. But I thought that to link .dll file, you must actually call winapi program to load that library. So, how can be these functions dynamically linked, if there is no static library to provide code to tell Windows to load desired functions from dll? And really last question on this subject - are C Standart library functions also calls to winapi even they are not .dll files like more advanced WinAPI functions? I mean, in the end to access framebuffer and print something you must tell Windows to do it, since OS cannot let you directly manipulate HW. I think of it like the OS must be written to support all C standart library functions same way across similiar versions, since they are statically linked, and can differently support more complex WinAPI calls becouse new version of OS can have adjustements in the .dll file.

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• boost::shared_ptr in Objective-C++

  - by John Smith

  This is a better understanding of a question I had earlier. I have the following Objective-C++ object @interface OCPP { MyCppobj * cppobj; } @end @implementation OCPP -(OCPP *) init { cppobj = new MyCppobj; } @end Then I create a completely differently obj which needs to use cppobj in a boost::shared_ptr (I have no choice in this matter, it's part of a huge library which I cannot change) @interface NOBJ -(void) use_cppobj_as_shared_ptr { //get an OCPP obj called occ from somewhere.. //troubling line here } @end I have tried the following and that failed: I tried synthesising cppobj. Then I created a shared_ptr in "troubling line" in the following way: MyCppobj * cpp = [occ cppobj]; bsp = boost::shared_ptr<MyCppobj>(cpp); It works fine first time around. Then I destroy the NOBJ and recreate it. When I for cppobj it's gone. Presumably shared_ptr decided it's no longer needed and did away with it. So I need help. How can I keep cppobj alive? Is there a way to destroy bsp (or it's reference to cppobj) without destroying cppobj?

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• Associate "Code/Properties/Stuff" with Fields in C# without reflection. I am too indoctrinated by J

  - by AlexH

  I am building a library to automatically create forms for Objects in the project that I am working on. The codebase is in C#, and essentially we have a HUGE number of different objects to store information about different things. If I send these objects to the client side as JSON, it is easy enough to programatically inspect them to generate a form for all of the properties. The problem is that I want to be able to create a simple way of enforcing permissions and doing validation on the client side. It needs to be done on a field by field level. In javascript I would do this by creating a parallel object structure, which had some sort of { permissions : "someLevel", validator : someFunction } object at the nodes. With empty nodes implying free permissions and universal validation. This would let me simply iterate over the new object and the permissions object, run the check, and deal with the result. Because I am overfamilar with the hammer that is javascript, this is really the only way that I can see to deal with this problem. My first implementation thus uses reflection to let me treat objects as dictionaries, that can be programatically iterated over, and then I just have dictionaries of dictionaries of PermissionRule objects which can be compared with. Very javascripty. Very awkward. Is there some better way that I can do this? Essentially a way to associate a data set with each property, and then iterate over those properties. Or else am I Doing It Wrong?

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• How do I create a python module from a fortran program with f2py?

  - by Lars Hellemo

  I am trying to read some smps files with python, and found a fortran implementation, so I thought I would give f2py a shot. The problem is that I have no experience with fortran. I have successfully installed gfortran and f2py on my Linux box and ran the example on thew f2py page, but I have some trouble compiling and running the large program. There are two files, one with a file reader wrapper and one with all the logic. They seem to call each other, but when I compile and link or try f2py, I get errors that they somehow can't find each other: f95 -c FILEWR~1.F f95 -c SMPSREAD.F90 f95 -o smpsread SMPSREAD.o FILEWR~1.o FILEWR~1.o In function `file_wrapper_' FILEWR~1.F(.text+0x3d) undefined reference to `chopen_' usrlibgcci486-linux-gnu4.4.1libgfortranbegin.a(fmain.o) In function `main' (.text+0x27) undefined reference to `MAIN__' collect2 ld returned 1 exit status I also tried changing the name to FILE_WRAPPER.F but that did not help. With f2py I found out I had to include a comment to get it to accept free format, and saved this as a new file and tried: f2py -c -m smpsread smpsread.f90 I get a lot of output and warnings, but the error seems to be this one: getctype: No C-type found in "{'typespec': 'type', 'attrspec': ['allocatable'], 'typename': 'node', 'dimension': [':']}", assuming void. The fortran 90 spms reader can be found here. Any help or suggestions appreciated.

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• Replace low level web-service reference call transport with custom one

  - by hoodoos

  I'm not sure if title sounds right actually, so I will give more explanation here. I will begin from very beginning :) I'm using c# and .net for my development. I have an application that makes requests to some soap web-service and for each user request it produces 3 to 10 requests for web-service, they should all run async to finish in one time, so I use Async method of the web-service generated reference and then wait for result on callback. But it seems like it starts a thread (or takes it from pool) for every async call I make, so if I have 10 clients I got to spawn 30 to 100 threads and it sounds terrible even for my 16 cores server :) So i wanted to replace low level transport implementation with my own which uses non-blocking sockets and can handle at least 50 sockets run parallel in one thread with not much overhead. But I actually dunno where to put my override best. I analyzed System.Web.Services.Protocols.SoapHttpClientProtocol class and see that it has some GetWebRequest method which I actually could use. If only I could somehow interupt the object it creates and get a http request with all headers and body from there and then send it with my own sockets.. Any ideas what approach to use? Or maybe there's something built in the framework I can use?

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• Implementing scroll view that is much larger than the screen view with random images

  - by pulegium

  What I'm trying to do is to implement something like the fruit machine scroll view. Basically I have a sequence of images (randomly generated on the fly) and I want to allow the users to scroll through this line. There can fit approx 10 images on the screen, but the line is virtually unlimited. My question is what would be the best approach in implementing this? So far I've thought of having a UIImageView going across the screen (with width equal to the sum of 10 images) and the image associated with it would be a combination of 12 or so images, with two images falling out of the visible area, this would allow for smooth scrolling. If the user scrolls further, then I would reconstruct the image associated with the view so the new images are appended and the old one's are discarded. This image reconstruction business sounds bit complicated, so I was wondering if there's a more logical way to implement this. There's one more thing, I want to have two lines crossing each other with images, bit like conveyor belts crossing. If that makes any sense... Bit like below: V1 V2 H1 H2 H3 H4 H5 V4 V5 So if the vertical belt is moved it'd be like: V2 H3 H1 H2 V4 H4 H5 V5 V6 H1-H5, V1-V6 being automatically generated images. I'm not asking for the implementation code, just the thoughts on the principles how to implement this. Thanks!! :)

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• Refactor throwing not null exception if using a method that has a dependency on a certain contructor

  - by N00b

  In the method below the second constructor accepts a ForumThread object which the IncrementViewCount() method uses. There is a dependency between the method and that particular constructor. Without extracting into a new private method the null check in IncrementViewCount() and LockForumThread() (plus other methods not shown) is there some simpler re-factoring I can do or the implementation of a better design practice for this method to guard against the use of the wrong constructor with these dependent methods? Thank you for any suggestions in advance. private readonly IThread _forumLogic; private readonly ForumThread _ft; public ThreadLogic(IThread forumLogic) : this(forumLogic, null) { } public ThreadLogic(IThread forumLogic, ForumThread ft) { _forumLogic = forumLogic; _ft = ft; } public void Create(ForumThread ft) { _forumLogic.SaveThread(ft); } public void IncrementViewCount() { if (_ft == null) throw new NoNullAllowedException("_ft ForumThread is null; this must be set in the constructor"); lock (_ft) { _ft.ViewCount = _ft.ViewCount + 1; _forumLogic.SaveThread(_ft); } } public void LockForumThread() { if (_ft == null) throw new NoNullAllowedException("_ft ForumThread is null; this must be set in the constructor"); _ft.ThreadLocked = true; _forumLogic.SaveThread(_ft); }

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• speed string search in PHP

  - by Marc

  Hi! I have a 1.2GB file that contains a one line string. What I need is to search the entire file to find the position of an another string (currently I have a list of strings to search). The way what I'm doing it now is opening the big file and move a pointer throught 4Kb blocks, then moving the pointer X positions back in the file and get 4Kb more. My problem is that a bigger string to search, a bigger time he take to got it. Can you give me some ideas to optimize the script to get better search times? this is my implementation: function busca($inici){ $limit = 4096; $big_one = fopen('big_one.txt','r'); $options = fopen('options.txt','r'); while(!feof($options)){ $search = trim(fgets($options)); $retro = strlen($search);//maybe setting this position absolute? (like 12 or 15) $punter = 0; while(!feof($big_one)){ $ara = fgets($big_one,$limit); $pos = strpos($ara,$search); $ok_pos = $pos + $punter; if($pos !== false){ echo "$pos - $punter - $search : $ok_pos <br>"; break; } $punter += $limit - $retro; fseek($big_one,$punter); } fseek($big_one,0); } } Thanks in advance!

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• JMF microphone volume controller

  - by TacB0sS

  How to obtain the Microphone volume controller in JMF? this is what I have: I tried this implementation concept of yours, but I keep getting a null from the first volume processor when I try to get the stream, here is how I do it: // the device is the media device specifically audio Processor processorForVolume = Manager.createProcessor(device.getLocator()); // wait until configured ProcessorStates newState = new ProcessorStateListener(Processor.Configured).waitForProcessorState(processorForVolume); System.out.println("volumeProcessorState: "+newState); // setting the content descriptor to null - read in another thread this allows to get the gain control processorForVolume.setContentDescriptor(null); // set the track control format to one supported by the device and the track control. // I didn't match it to an RTP allowed format, but I don't think this has anything to do with it... TrackControl[] trackControls = processorForVolume.getTrackControls(); if (trackControls.length == 0) throw new MC_Exception("No track controls where found for this device:", new Object[]{device}); for (TrackControl control : trackControls) trackManipulator.manipulateTrackControls(control); // wait until the processor is realized newState = new ProcessorStateListener(Controller.Realized).waitForProcessorState(processorForVolume); System.out.println("volumeProcessorState: "+newState); // receives the gain control micVolumeController = processorForVolume.getGainControl(); // cannot get the output stream to process further... any suggestions? processor = Manager.createProcessor(processorForVolume.getDataOutput()); new ProcessorStateListener(Processor.Configured).waitForProcessorState(processor); processor.setContentDescriptor(DeviceCapturingManager.RAW_RTP); new ProcessorStateListener(Controller.Realized).waitForProcessorState(processor); this is the output It generates: volumeProcessorState: Configured format set to track control - com.sun.media.ProcessEngine$ProcTControl@1627c16: LINEAR, 48000.0 Hz, 16-bit, Stereo, LittleEndian, Signed volumeProcessorState: Realized and the data output from the processor is Null. I should make clear that when the content descriptor != null I do get an output stream but not the volume controller, and the when it is null I get the controller, but no stream. I try to connect to an audio microphone device Adam.

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• Should a new language compiler target the JVM?

  - by Pindatjuh

  I'm developing a new language. My initial target was to compile to native x86 for the Windows platform, but now I am in doubt. I've seen some new languages target the JVM (most notable Scala and Clojure). Ofcourse it's not possible to port every language easily to the JVM; to do so, it may lead to small changes to the language and it's design. So that's the reason behind this doubt, and thus this question: Is targetting the JVM a good idea, when creating a compiler for a new language? Or should I stick with x86? I have experience in generating JVM bytecode. Are there any workarounds to JVM's GC? The language has deterministic implicit memory management. How to produce JIT-compatible bytecode, such that it will get the highest speedup? Is it similar to compiling for IA-32, such as the 4-1-1 muops pattern on Pentium? I can imagine some advantages (please correct me if I'm wrong): JVM bytecode is easier than x86. Like x86 communicates with Windows, JVM communicates with the Java Foundation Classes. To provide I/O, Threading, GUI, etc. Implementing "lightweight"-threads.I've seen a very clever implementation of this at http://www.malhar.net/sriram/kilim/. Most advantages of the Java Runtime (portability, etc.) The disadvantages, as I imagined, are: Less freedom? On x86 it'll be more easy to create low-level constructs, while JVM has a higher level (more abstract) processor. Most disadvantages of the Java Runtime (no native dynamic typing, etc.)

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• Optimizing a shared buffer in a producer/consumer multithreaded environment

  - by Etan

  I have some project where I have a single producer thread which writes events into a buffer, and an additional single consumer thread which takes events from the buffer. My goal is to optimize this thing for a single machine to achieve maximum throughput. Currently, I am using some simple lock-free ring buffer (lock-free is possible since I have only one consumer and one producer thread and therefore the pointers are only updated by a single thread). #define BUF_SIZE 32768 struct buf_t { volatile int writepos; volatile void * buffer[BUF_SIZE]; volatile int readpos;) }; void produce (buf_t *b, void * e) { int next = (b->writepos+1) % BUF_SIZE; while (b->readpos == next); // queue is full. wait b->buffer[b->writepos] = e; b->writepos = next; } void * consume (buf_t *b) { while (b->readpos == b->writepos); // nothing to consume. wait int next = (b->readpos+1) % BUF_SIZE; void * res = b->buffer[b->readpos]; b->readpos = next; return res; } buf_t *alloc () { buf_t *b = (buf_t *)malloc(sizeof(buf_t)); b->writepos = 0; b->readpos = 0; return b; } However, this implementation is not yet fast enough and should be optimized further. I've tried with different BUF_SIZE values and got some speed-up. Additionaly, I've moved writepos before the buffer and readpos after the buffer to ensure that both variables are on different cache lines which resulted also in some speed. What I need is a speedup of about 400 %. Do you have any ideas how I could achieve this using things like padding etc?

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• Returning the same type the function was passed

  - by Ken Bloom

  I have the following code implementation of Breadth-First search. trait State{ def successors:Seq[State] def isSuccess:Boolean = false def admissableHeuristic:Double } def breadthFirstSearch(initial:State):Option[List[State]] = { val open= new scala.collection.mutable.Queue[List[State]] val closed = new scala.collection.mutable.HashSet[State] open.enqueue(initial::Nil) while (!open.isEmpty){ val path:List[State]=open.dequeue() if(path.head.isSuccess) return Some(path.reverse) closed += path.head for (x <- path.head.successors) if (!closed.contains(x)) open.enqueue(x::path) } return None } If I define a subtype of State for my particular problem class CannibalsState extends State { //... } What's the best way to make breadthFirstSearch return the same subtype as it was passed? Supposing I change this so that there are 3 different state classes for my particular problem and they share a common supertype: abstract class CannibalsState extends State { //... } class LeftSideOfRiver extends CannibalsState { //... } class InTransit extends CannibalsState { //... } class RightSideOfRiver extends CannibalsState { //... } How can I make the types work out so that breadthFirstSearch infers that the correct return type is CannibalsState when it's passed an instance of LeftSideOfRiver? Can this be done with an abstract type member, or must it be done with generics?

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• c# delegate and abstract class

  - by BeraCim

  Hi all: I currently have 2 concrete methods in 2 abstract classes. One class contains the current method, while the other contains the legacy method. E.g. // Class #1 public abstract class ClassCurrent<T> : BaseClass<T> where T : BaseNode, new() { public List<T> GetAllRootNodes(int i) { //some code } } // Class #2 public abstract class MyClassLegacy<T> : BaseClass<T> where T : BaseNode, new() { public List<T> GetAllLeafNodes(int j) { //some code } } I want the corresponding method to run in their relative scenarios in the app. I'm planning to write a delegate to handle this. The idea is that I can just call the delegate and write logic in it to handle which method to call depending on which class/project it is called from (at least thats what I think delegates are for and how they are used). However, I have some questions on that topic (after some googling): 1) Is it possible to have a delegate that knows the 2 (or more) methods that reside in different classes? 2) Is it possible to make a delegate that spawns off abstract classes (like from the above code)? (My guess is a no, since delegates create concrete implementation of the passed-in classes) 3) I tried to write a delegate for the above code. But I'm being technically challenged: public delegate List GetAllNodesDelegate(int k); GetAllNodesDelegate del = new GetAllNodesDelegate(ClassCurrent.GetAllRootNodes); I got the following error: An object reference is required for the non-static field, method, property ClassCurrent<BaseNode>.GetAllRootNodes(int) I might have misunderstood something... but if I have to manually declare a delegate at the calling class, AND to pass in the function manually as above, then I'm starting to question whether delegate is a good way to handle my problem. Thanks.

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• Java: Initializing a public static field in superclass that needs a different value in every subclas

  - by BinaryMuse

  Good evening, I am developing a set of Java classes so that a container class Box contains a List of a contained class Widget. A Widget needs to be able to specify relationships with other Widgets. I figured a good way to do this would be to do something like this: public abstract class Widget { public static class WidgetID { // implementation stolen from Google's GWT private static int nextHashCode; private final int index; public WidgetID() { index = ++nextHashCode; } public final int hashCode() { return index; } } public abstract WidgetID getWidgetID(); } so sublcasses of Widget could: public class BlueWidget extends Widget { public static final WidgetID WIDGETID = new WidgetID(); @Override public WidgetID getWidgetID() { return WIDGETID; } } Now, BlueWidget can do getBox().addWidgetRelationship(RelationshipTypes.SomeType, RedWidget.WIDGETID, and Box can iterate through it's list comparing the second parameter to iter.next().getWidgetID(). Now, all this works great so far. What I'm trying to do is keep from having to declare the public static final WidgetID WIDGETID in all the subclasses and implement it instead in the parent Widget class. The problem is, if I move that line of code into Widget, then every instance of a subclass of Widget appears to get the same static final WidgetID for their Subclassname.WIDGETID. However, making it non-static means I can no longer even call Subclassname.WIDGETID. So: how do I create a static WidgetID in the parent Widget class while ensuring it is different for every instance of Widget and subclasses of Widget? Or am I using the wrong tool for the job here? Thanks!

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• What's wrong with this code to un-camel-case a string?

  - by omair iqbal

  Here is my attempt to solve the About.com Delphi challenge to un-camel-case a string. unit challenge1; interface uses Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms, Dialogs, StdCtrls; type check = 65..90; TForm1 = class(TForm) Edit1: TEdit; Button1: TButton; procedure Button1Click(Sender: TObject); private { Private declarations } public { Public declarations } end; var Form1: TForm1; var s1,s2 :string; int : integer; implementation {$R *.dfm} procedure TForm1.Button1Click(Sender: TObject); var i: Integer; checks : set of check; begin s1 := edit1.Text; for i := 1 to 20 do begin int :=ord(s1[i]) ; if int in checks then insert(' ',s1,i-1); end; showmessage(s1); end; end. check is a set that contains capital letters so basically whenever a capital letter is encountered the insert function adds space before its encountered (inside the s1 string), but my code does nothing. ShowMessage just shows text as it was entered in Edit1. What have I done wrong?

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• Why does Tex/Latex not speed up in subsequent runs?

  - by Debilski

  I really wonder, why even recent systems of Tex/Latex do not use any caching to speed up later runs. Every time that I fix a single comma*, calling Latex costs me about the same amount of time, because it needs to load and convert every single picture file. (* I know that even changing a tiny comma could affect the whole structure but of course, a well-written cache format could see the impact of that. Also, there might be situations where 100% correctness is not needed as long as it’s fast.) Is there something in the language of Tex which makes this complicated or impossible to accomplish or is it just that in the original implementation of Tex, there was no need for this (because it would have been slow anyway on those large computers)? But then on the other hand, why doesn’t this annoy other people so much that they’ve started a fork which has some sort of caching (or transparent conversion of Tex files to a format which is faster to parse)? Is there anything I can do to speed up subsequent runs of Latex? Except from putting all the stuff into chapterXX.tex files and then commenting them out?

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• Use LINQ to group a sequence by date with no gaps

  - by Codesleuth

  I'm trying to select a subgroup of a list where items have contiguous dates, e.g. ID StaffID Type Title ActivityDate -- ------- ---- ----------------- ------------ 1 41 1 Doctors 07/06/2010 2 41 0 Meeting with John 08/06/2010 3 41 0 Meeting Continues 09/06/2010 4 41 0 Meeting Continues 10/06/2010 5 41 3 Annual Leave 11/06/2010 6 41 0 Meeting Continues 14/06/2010 I'm using a pivot point each time, so take the example pivot item as 3, I'd like to get the following resulting contiguous events around the pivot: ID StaffID Type Title ActivityDate -- ------- ---- ----------------- ------------ 2 41 0 Meeting with John 08/06/2010 3 41 0 Meeting Continues 09/06/2010 4 41 0 Meeting Continues 10/06/2010 My current implementation is a laborious "walk" into the past, then into the future, to build the list: var orderedEvents = activities.OrderBy(a => a.ActivityDate).ToArray(); // Walk into the past until a gap is found var preceedingEvents = orderedEvents.TakeWhile(a => a.ID != activity.ID); DateTime dayBefore; var previousEvent = activity; while (previousEvent != null) { dayBefore = previousEvent.ActivityDate.AddDays(-1).Date; previousEvent = preceedingEvents.TakeWhile(a => a.ID != previousEvent.ID).LastOrDefault(); if (previousEvent != null) { if (previousEvent.ActivityDate.Date == dayBefore) relatedActivities.Insert(0, previousEvent); else previousEvent = null; } } // Walk into the future until a gap is found var followingEvents = orderedEvents.SkipWhile(a => a.ID != activity.ID); DateTime dayAfter; var nextEvent = activity; while (nextEvent != null) { dayAfter = nextEvent.ActivityDate.AddDays(1).Date; nextEvent = followingEvents.SkipWhile(a => a.ID != nextEvent.ID).Skip(1).FirstOrDefault(); if (nextEvent != null) { if (nextEvent.ActivityDate.Date == dayAfter) relatedActivities.Add(nextEvent); else nextEvent = null; } } The list relatedActivities should then contain the contiguous events, in order. Is there a better way (maybe using LINQ) for this? I had an idea of using .Aggregate() but couldn't think how to get the aggregate to break out when it finds a gap in the sequence.

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• Do complex JOINs cause high coupling and maintenance problems ?

  - by ashkan.kh.nazary

  Our project has ~40 tables with complex relations.A colleague believes in using long join queries which enforces me to learn about tables outside of my module but I think I should not concern about tables not directly related to my module and use data access functions (written by those responsible for other modules) when I need data from them. Let me clarify: I am responsible for the ContactVendor module which enables the customers to contact the vendor and start a conversation about some specific product. Products module has it's own complex tables and relations with functions that encapsulate details (for example i18n, activation, product availability etc ...). Now I need to show the product title of some product related to some conversation between the vendor and customers. I may either write a long query that retrieves the product info along with conversation stuff in one shot (which enforces me to learn about Product tables) OR I may pass the relevant product_id to the get_product_info(int) function. First approach is obviously demanding and introduces many bad practices and things I normally consider fault in programming. The problem with the second approach seems to be the countless mini queries these access functions cause and performance loss is a concern when a loop tries to fetch product titles for 100 products using functions that each perform a separate query. So I'm stuck between "don't code to the implementation, code to interface" and performance. What is the right way of doing things ? UPDATE: I'm specially concerned about possible future modifications to those tables outside of my module. What if the Products module decided to change the way they are doing things? or for some reason modify the schema? It means some other modules would break or malfunction until the change is integrated to them. The usual ripple effect problem.

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• Does complex JOINs causes high coupling and maintenance problems ?

  - by ashkan.kh.nazary

  Our project has ~40 tables with complex relations.A colleague believes in using long join queries which enforces me to learn about tables outside of my module but I think I should not concern about tables not directly related to my module and use data access functions (written by those responsible for other modules) when I need data from them. Let me clarify: I am responsible for the ContactVendor module which enables the customers to contact the vendor and start a conversation about some specific product. Products module has it's own complex tables and relations with functions that encapsulate details (for example i18n, activation, product availability etc ...). Now I need to show the product title of some product related to some conversation between the vendor and customers. I may either write a long query that retrieves the product info along with conversation stuff in one shot (which enforces me to learn about Product tables) OR I may pass the relevant product_id to the get_product_info(int) function. First approach is obviously demanding and introduces many bad practices and things I normally consider fault in programming. The problem with the second approach seems to be the countless mini queries these access functions cause and performance loss is a concern when a loop tries to fetch product titles for 100 products using functions that each perform a separate query. So I'm stuck between "don't code to the implementation, code to interface" and performance. What is the right way of doing things ? UPDATE: I'm specially concerned about possible future modifications to those tables outside of my module. What if the Products module decided to change the way they are doing things? or for some reason modify the schema? It means some other modules would break or malfunction until the change is integrated to them. The usual ripple effect problem.

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• Singleton EXC_BAD_ACCESS

  - by lclaud

  Hi, so I have a class that I decleare as a singleton and in that class I have a NSMutableArray that contains some NSDictionaries with some key/value pairs in them. The trouble is it doesn't work and I dont't know why... I mean it crashes with EXC_BAD_ACCESS but i don't know where. I followed the code and it did create a new array on first add, made it to the end of the funtion ..and crashed ... @interface dataBase : NSObject { NSMutableArray *inregistrari; } @property (nonatomic,retain) NSMutableArray *inregistrari; -(void)adaugaInregistrareCuData:(NSDate *)data siValoare:(NSNumber *)suma caVenit:(BOOL)venit cuDetaliu:(NSString *)detaliu; -(NSDictionary *)raportIntreData:(NSDate *)dataInitiala siData:(NSDate *)dataFinala; -(NSArray *)luniDisponibileIntreData:(NSDate *)dataInitiala siData:(NSDate *)dataFinala; -(NSArray *)aniDisponibiliIntreData:(NSDate *)dataInitiala siData:(NSDate *)dataFinala; -(NSArray *)vectorDateIntreData:(NSDate *)dataI siData:(NSDate *)dataF; -(void)salveazaInFisier; -(void)incarcaDinFisier; + (dataBase *)shareddataBase; @end And here is the .m file #import "dataBase.h" #import "SynthesizeSingleton.h" @implementation dataBase @synthesize inregistrari; SYNTHESIZE_SINGLETON_FOR_CLASS(dataBase); -(void)adaugaInregistrareCuData:(NSDate *)data siValoare:(NSNumber *)suma caVenit:(BOOL)venit cuDetaliu:(NSString *)detaliu{ NSNumber *v=[NSNumber numberWithBool:venit]; NSArray *input=[NSArray arrayWithObjects:data,suma,v,detaliu,nil]; NSArray *keys=[NSArray arrayWithObjects:@"data",@"suma",@"venit",@"detaliu",nil]; NSDictionary *inreg=[NSDictionary dictionaryWithObjects:input forKeys:keys]; if(inregistrari == nil) { inregistrari=[[NSMutableArray alloc ] initWithObjects:inreg,nil]; }else { [inregistrari addObject:inreg]; } [inreg release]; [input release]; [keys release]; } It made it to the end of that adaugaInregistrareCuData ... ok . said the array had one object ... and then crashed

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• Opaque tenant identification with SQL Server & NHibernate

  - by Anton Gogolev

  Howdy! We're developing a nowadays-fashionable multi-tenanted SaaS app (shared database, shared schema), and there's one thing I don't like about it: public class Domain : BusinessObject { public virtual long TenantID { get; set; } public virtual string Name { get; set; } } The TenantID is driving me nuts, as it has to be accounted for almost everywhere, and it's a hassle from security standpoint: what happens if a malicious API user changes TenantID to some other value and will mix things up. What I want to do is to get rid of this TenantID in our domain objects altogether, and to have either NHibernate or SQL Server deal with it. From what I've already read on the Internets, this can be done with CONTEXT_INFO (here's a NHibernatebased implementation), NHibernate filters, SQL Views and with combination thereof. Now, my requirements are as follows: Remove any mentions of TenantID from domain objects ...but have SQL Server insert it where appropriate (I guess this is achieved with default constraints) ...and obviously provide support for filtering based on this criteria, so that customers will never see each other's data If possible, avoid SQL Server views. Have a solution which plays nicely with NHibernate, SQL Servers' MARS and general nature of SaaS apps being highly concurrent What are your thoughts on that?

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• finding ALL cycles in a huge sparse matrix

  - by Andy

  Hi there, First of all I'm quite a Java beginner, so I'm not sure if this is even possible! Basically I have a huge (3+million) data source of relational data (i.e. A is friends with B+C+D, B is friends with D+G+Z (but not A - i.e. unmutual) etc.) and I want to find every cycle within this (not necessarily connected) directed graph. I've found this thread (http://stackoverflow.com/questions/546655/finding-all-cycles-in-graph/549402#549402) which has pointed me to Donald Johnson's (elementary) cycle-finding algorithm which, superficially at least, looks like it'll do what I'm after (I'm going to try when I'm back at work on Tuesday - thought it wouldn't hurt to ask in the meanwhile!). I had a quick scan through the code of the Java implementation of Johnson's algorithm (in that thread) and it looks like a matrix of relations is the first step, so I guess my questions are: a) Is Java capable of handling a 3+million*3+million matrix? (was planning on representing A-friends-with-B by a binary sparse matrix) b) Do I need to find every connected subgraph as my first problem, or will cycle-finding algorithms handle disjoint data? c) Is this actually an appropriate solution for the problem? My understanding of "elementary" cycles is that in the graph below, rather than picking out A-B-C-D-E-F it'll pick out A-B-F, B-C-D etc. but that's not the end of the world given the task. E / \ D---F / \ / \ C---B---A d) If necessary, I can simplify the problem by enforcing mutuality in relations - i.e. A-friends-with-B <== B-friends-with-A, and if really necessary I can maybe cut down the data size, but realistically it is always going to be around the 1mil mark. z) Is this a P or NP task?! Am I biting off more than I can chew? Thanks all, any help appreciated! Andy

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• Thread-safe data structure design

  - by Inso Reiges

  Hello, I have to design a data structure that is to be used in a multi-threaded environment. The basic API is simple: insert element, remove element, retrieve element, check that element exists. The structure's implementation uses implicit locking to guarantee the atomicity of a single API call. After i implemented this it became apparent, that what i really need is atomicity across several API calls. For example if a caller needs to check the existence of an element before trying to insert it he can't do that atomically even if each single API call is atomic: if(!data_structure.exists(element)) { data_structure.insert(element); } The example is somewhat awkward, but the basic point is that we can't trust the result of "exists" call anymore after we return from atomic context (the generated assembly clearly shows a minor chance of context switch between the two calls). What i currently have in mind to solve this is exposing the lock through the data structure's public API. This way clients will have to explicitly lock things, but at least they won't have to create their own locks. Is there a better commonly-known solution to these kinds of problems? And as long as we're at it, can you advise some good literature on thread-safe design? EDIT: I have a better example. Suppose that element retrieval returns either a reference or a pointer to the stored element and not it's copy. How can a caller be protected to safely use this pointer\reference after the call returns? If you think that not returning copies is a problem, then think about deep copies, i.e. objects that should also copy another objects they point to internally. Thank you.

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• How to control the order of module initialization in Prism

  - by Robert Taylor

  I'm using Prism V2 with a DirectoryModuleCatalog and I need the modules to be initialized in a certain order. The desired order is specified with an attribute on each IModule implementation. This is so that as each module is initialized, they add their View into a TabControl region and the order of the tabs needs to be deterministic and controlled by the module author. The order does not imply a dependency, but rather just an order that they should be initialized in. In other words: modules A, B, and C may have priorities of 1, 2, and 3 respectively. B does not have a dependency on A - it just needs to get loaded into the TabControl region after A. So that we have a deterministic and controllable order of the tabs. Also, B might not exist at runtime; so they would load as A, C because the priority should determine the order (1, 3). If i used the ModuleDependency, then module "C" will not be able to load w/o all of it's dependencies. I can manage the logic of how to sort the modules, but i can't figure out where to put said logic.

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• Unit testing that an event is raised in C#, using reflection

  - by Thomas

  I want to test that setting a certain property (or more generally, executing some code) raises a certain event on my object. In that respect my problem is similar to http://stackoverflow.com/questions/248989/unit-testing-that-an-event-is-raised-in-c, but I need a lot of these tests and I hate boilerplate. So I'm looking for a more general solution, using reflection. Ideally, I would like to do something like this: [TestMethod] public void TestWidth() { MyClass myObject = new MyClass(); AssertRaisesEvent(() => { myObject.Width = 42; }, myObject, "WidthChanged"); } For the implementation of the AssertRaisesEvent, I've come this far: private void AssertRaisesEvent(Action action, object obj, string eventName) { EventInfo eventInfo = obj.GetType().GetEvent(eventName); int raisedCount = 0; Action incrementer = () => { ++raisedCount; }; Delegate handler = /* what goes here? */; eventInfo.AddEventHandler(obj, handler); action.Invoke(); eventInfo.RemoveEventHandler(obj, handler); Assert.AreEqual(1, raisedCount); } As you can see, my problem lies in creating a Delegate of the appropriate type for this event. The delegate should do nothing except invoke incrementer. Because of all the syntactic syrup in C#, my notion of how delegates and events really work is a bit hazy. How to do this?

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