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• creative way for implementing Data object with its corresponding business logic class in java

  - by ekeren

  I have a class that need to be serialized (for both persistentcy and client-server communication) for simplicity's sake let's call the classes Business a BusinessData and I prefix for their Interfaces. All the getter and setter are delegated from Business class to BusinessData class. I thought about implementing IBusinessData interface that will contain all the getter and setters and IBusiness interface that will extend it. I can either make Business extend BuisnessData so I will not need to implement all getter and setter delegates, or make some abstract class ForwardingBusinessData that will only delegate getter and setters. Any of the above option I lose my hierarchy freedom, do any of you have any creative solutions for this problem... I also reviewed DAO pattern: http://java.sun.com/blueprints/patterns/DAO.html

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• Legality Of Re-Implementing An Existing API (e.g. GNU implementing the UNIX APIs)

  - by splicer

  I've often wondered about this. I'm not looking for legal advice, just casual opinions ;) If some company publishes an API on the web for their closed-source library, would it be legal for another party to release an open-source implementation of that API? Are function declarations considered source code? Take GNU implementing the UNIX APIs, for example. The UNIX standard gives the following function declaration and defines its required behaviour in English: char * mktemp(char *template); Now, consider an API that lists and declares and describes several thousand (more much complex) functions, enums, etc.; an API which defines a solution to a non-trival set of problems. If an open-source project publishes C headers that copy (verbatim) the function definitions contained in the closed-source company's published API, doesn't that violate some sort copyright law?

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• Implementing clone on a LinkedList

  - by devoured elysium

  I am trying to implement a clone() method on a DoubleLinkedList. Now, the problem is that implementing it by "the convention" is a lot more troublesome than just creating a new DoubleLinkedList and filling it with all the elements of my current DoubleLinkedList. Is there any inconvenient I am not seeing when doing that? Here is my current approach: @Override public DoubleLinkedList<T> clone() { DoubleLinkedList<T> dll = new DoubleLinkedList<T>(); for (T element : dll) { dll.add(element); } return dll; } Here is what it would be by the convention: @Override public DoubleLinkedList<T> clone() { try { DoubleLinkedList<T> dll = (DoubleLinkedList<T>)super.clone(); //kinda complex code to copy elements return dll; } catch (CloneNotSupportedException e) { throw new InternalError(e.toString()); } }

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• Implementing Transparent Persistence

  - by Jules

  Transparent persistence allows you to use regular objects instead of a database. The objects are automatically read from and written to disk. Examples of such systems are Gemstone and Rucksack (for common lisp). Simplified version of what they do: if you access foo.bar and bar is not in memory, it gets loaded from disk. If you do foo.bar = baz then the foo object gets updated on disk. Most systems also have some form of transactions, and they may have support for sharing objects across programs and even across a network. My question is what are the different techniques for implementing these kind of systems and what are the trade offs between these implementation approaches?

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• mapping list of different types implementing same function?

  - by sisif

  I want to apply a function to every element in a list (map) but the elements may have different types but all implement the same function (here "putOut") like an interface. However I cannot create a list of this "interface" type (here "Outputable"). How do I map a list of different types implementing the same function? main :: IO () main = do map putOut lst putStrLn "end" where lst :: [Outputable] -- ERROR: Class "Outputable" used as a type lst = [(Out1 1),(Out2 1 2)] class Outputable a where putOut :: a -> IO () -- user defined: data Out1 = Out1 Int deriving (Show) data Out2 = Out2 Int deriving (Show) instance Outputable Out1 where putOut out1 = putStrLn $ show out1 instance Outputable Out2 where putOut out2 = putStrLn $ show out2 I cannot define it this way: data Out = Out1 Int | Out2 Int Int putOut Out1 = ... putOut Out2 = ... because this is a library and users should be able to extend Out with their own types

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• implementing security with session variables, how it is insecure

  - by haansi

  I am doing web based projects in dotnet. Currently I am implementing security using session variables. I keep current user id and user type in session and authenticate user from these session variables (say Session["UserId"],Session["UserName"] and Session["UserType"]). Please help me understand how this could be insecure. I've heard that such security can be broken and applications can be hacked very easily, like it is possible to get session id and directly connect to that session id etc. Please guide me on this.

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• Implementing a recursive menu system a'la Joomla in CodeIgniter

  - by pettersolberg

  Hi I have some sites powered by Joomla, but with my current assignment I wanted to try something new and created with CodeIgniter a really basic CMS (just to suit my client's needs). Everything works fine except menus - multilevel menus like in Joomla, Drupal etc. with items and subitems... My question is: do you know of any tutorials or texts abut implementing such a structure. I've tried the recursion thinggy with while getting children's IDs move downwards from the parent while searching for the currently displayed item's ID. I've tried also the Drupalish way with having a path parameter enclosing ID's all the way from top to bottom '1/23/123/3'. But all in all it was just too chaotic - code something, try it out. If you have some idea on this topic - thanks in advice.

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• Implementing activity indicator

  - by Prash.......

  I am implementing an activity indicator in my application. In my application on button click a webservice is called and it takes some time. To show the user that process is going on I implemented an activity indicator: CGRect frame = CGRectMake(140, 300, 40, 37); UIActivityIndicatorView *activityIndicator = [[UIActivityIndicatorView alloc] initWithFrame:frame]; activityIndicator.activityIndicatorViewStyle = UIActivityIndicatorViewStyleGray; [self.view addSubview:activityIndicator]; This Snippet is written in viewDidLoad() method, and I have an action called, -(IBAction)agree:(id)sender { //here webservice is called } I have to start that activity by [activityIndicator startAnimating]; But I am unable to start that activityIndicator, please suggest a proper solution for that.

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• Implementing traceback on i386

  - by markelliott2000

  Hi, I am currently porting our code from an alpha (Tru64) to an i386 processor (Linux) in C. Everything has gone pretty smoothly up until I looked into porting our exception handling routine. Currently we have a parent process which spawns lots of sub processes, and when one of these sub-processes fatal's (unfielded) I have routines to catch the process. I am currently struggling to find the best method of implementing a traceback routine which can list the function addresses in the error log, currently my routine just prints the the signal which caused the exception and the exception qualifier code. Any help would be greatly received, ideally I would write error handling for all processors, however at this stage I only really care about i386, and x86_64. Thanks Mark

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• Constructors in Inner classes (implementing Interfaces)

  - by thepandaatemyface

  Hi, How would I go about writing a constructor for an inner class which is implementing an interface? I know I could make a whole new class, but I figure there's got to be a way to do something along the line of this: JButton b = new JButton(new AbstractAction() { public AbstractAction() { super("This is a button"); } public void actionPerformed(ActionEvent e) { System.out.println("button clicked"); } }); When I enter this it doesn't recognize the AbstractAction method as a constructor (compiler asks for return type). Anyone have an idea? Thanks

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• Abstract class get parameter from implementing subclass?

  - by soren.qvist

  I'm wondering if there is way to do this without breaking encapsulation, I want the abstract class to rely on parameters defined in the implementing subclass. Like so: public abstract class Parent { private int size; private List<String> someList; public Parent() { size = getSize(); someList = new ArrayList<String>(size); } public abstract int getSize(); } public class Child extends Parent { @Override public int getSize() { return 5; } } Is this ugly? Is there a better way? And perhaps more importantly, is this even a good idea?

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• Implementing the double-click event on Silverlight 4 Datagrid

  - by Mohammed Mudassir Azeemi

  Any good soul have an example of implementing the "Command Pattern" introduced by Prism on "Double-click event" of Silverlight 4.0 DataGrid. I did try the following: <data:DataGrid x:Name="dgUserRoles" AutoGenerateColumns="False" Margin="0" Grid.Row="0" ItemsSource="{Binding Path=SelectedUser.UserRoles}" IsReadOnly="False" > <data:DataGrid.Columns> <data:DataGridTemplateColumn Header=" "> <data:DataGridTemplateColumn.CellTemplate> <DataTemplate> <Button Width="20" Height="20" Click="Button_Click" Command="{Binding EditRoleClickedCommand}" CommandParameter="{Binding SelectedRole}" > </Button> </DataTemplate> </data:DataGridTemplateColumn.CellTemplate> </data:DataGridTemplateColumn> <data:DataGridTextColumn Header="Role Name" Binding="{Binding RoleName}" /> <data:DataGridTextColumn Header="Role Code" Binding="{Binding UserroleCode}" IsReadOnly="True"/> <data:DataGridCheckBoxColumn Header="UDFM Managed" Binding="{Binding RoleIsManaged}" IsReadOnly="True" /> <data:DataGridCheckBoxColumn Header="UDFM Role Assigned" Binding="{Binding UserroleIsUdfmRoleAssignment}" IsReadOnly="True" /> <data:DataGridTextColumn Header="Source User" Binding="{Binding SourceUser}" IsReadOnly="True" /> </data:DataGrid.Columns> </data:DataGrid> As you see I did try to hook up the Command there and it is not firing the event in my View Model. Looking for a good alternative.

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• Implementing a 2 Legged OAuth Provider

  - by Rob Wilkerson

  I'm trying to find my way around the OAuth spec, its requirements and any implementations I can find and, so far, it really seems like more trouble than its worth because I'm having trouble finding a single resource that pulls it all together. Or maybe it's just that I'm looking for something more specialized than most tutorials. I have a set of existing APIs--some in Java, some in PHP--that I now need to secure and, for a number of reasons, OAuth seems like the right way to go. Unfortunately, my inability to track down the right resources to help me get a provider up and running is challenging that theory. Since most of this will be system-to-system API usage, I'll need to implement a 2-legged provider. With that in mind... Does anyone know of any good tutorials for implementing a 2-legged OAuth provider with PHP? Given that I have securable APIs in 2 languages, do I need to implement a provider in both or is there a way to create the provider as a "front controller" that I can funnel all requests through? When securing PHP services, for example, do I have to secure each API individually by including the requisite provider resources on each? Thanks for your help.

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• Implementing BindingList<T>

  - by EtherealMonkey

  I am trying to learn more about BindingList because I believe that it will help me with a project that I am working on. Currently, I have an object class (ScannedImage) that is a subtype of a class (HashedImage) that subtypes a native .Net object (Image). There is no reason why I couldn't move the two subtypes together. I am simply subtyping an object that I had previously constructed, but I will now be storing my ScannedImage object in an RDB (well, not technically - only the details and probably the thumbnail). Also, the object class has member types that are my own custom types (Keywords). I am using a custom datagridview to present these objects, but am handling all changes to the ScannedImage object with my own code. As you can probably imagine, I have quite a few events to handle that occur in these base types. So, if I changed my object to implement INotifyPropertyChanged, would the object collection (implementing BindingList) receive notifications of changes to the ScannedImage object? Also, if Keywords were to implement INotifyPropertyChanged, would changes be accessible to the BindingList through the ScannedImage object? Sorry if this seems rather newbish. I only recently discovered the BindingList and not having formal training in C# programming - am having a difficult time moving forward with this. Also, if anyone has any good reference material, I would be thankful for links. Obviously, I have perused the MSDN Library. I have found a few good links on the web, but it seems that a lot of people are now using WPF and ObservableCollection. My project is based on Winforms and .Net3.5 framework. TIA

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• Implementing the tree with reference to the root for each leaf

  - by AntonAL

  Hi, i implementing a products catalog, that looks, like this: group 1 subgroup 1 subgroup 2 item 1 item 2 ... item n ... subgroup n group 2 subgroup 1 ... subgroup n group 3 ... group n The Models: class CatalogGroup < ActiveRecord::Base has_many: catalog_items has_many :catalog_items_all, :class_name => "CatalogItem", :foreign_key => "catalog_root_group_id" end class CatalogItem < ActiveRecord::Base belongs_to :catalog_group belongs_to :catalog_root_group, :class_name => "CatalogGroup" end Migrations: class CreateCatalogItems < ActiveRecord::Migration def self.up create_table :catalog_items do |t| t.integer :catalog_group_id t.integer :catalog_root_group_id t.string :code t.timestamps end end For convenience, i referenced each CatalogItem to it's top-most CatalogGroup and named this association "catalog_root_group". This will give us the simple implementation of search request, like "show me all items in group 1". We will have a deal only with CatalogModel.catalog_root_group The problem is - this association does't work. I always get "catalog_root_group" equals to nil Also, i have tried to overcome the using of reference to root group ("catalog_root_group"), but i cannot construct appropriate search request in ruby ... Do you know, how to do it ?

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• implementing twitter bootstrap carousel

  - by arboles

  I am having trouble implementing the bootstrap carousel. Can anyone look at the following html and js and give me instructions on how to implement the slide. The .js has not been edited and the carousel is installed on the body hero unit. Do I implement the carousel api? How do I define the carousel I am using within the .js file? Thanks. <div class="carousel"> <!-- Carousel items --> <div class="carousel-inner"> <!-- Main hero unit for a primary marketing message or call to action --> <div class="hero-unit"> <h1>Hello, world!</h1> <p>This is a template for a simple marketing or informational website. It includes a large callout called the hero unit and three supporting pieces of content. Use it as a starting point to create something more unique.</p> <p><a class="btn btn-primary btn-large">Learn more &raquo;</a></p> </div> </div> <!-- Carousel nav --> <a class="carousel-control left" href="#myCarousel" data-slide="prev">&lsaquo;</a> <a class="carousel-control right" href="#myCarousel" data-slide="next">&rsaquo;</a> </div>

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• Resolving Circular References for Objects Implementing ISerializable

  - by Chris

  I'm writing my own IFormatter implementation and I cannot think of a way to resolve circular references between two types that both implement ISerializable. Here's the usual pattern: [Serializable] class Foo : ISerializable { private Bar m_bar; public Foo(Bar bar) { m_bar = bar; m_bar.Foo = this; } public Bar Bar { get { return m_bar; } } protected Foo(SerializationInfo info, StreamingContext context) { m_bar = (Bar)info.GetValue("1", typeof(Bar)); } public void GetObjectData(SerializationInfo info, StreamingContext context) { info.AddValue("1", m_bar); } } [Serializable] class Bar : ISerializable { private Foo m_foo; public Foo Foo { get { return m_foo; } set { m_foo = value; } } public Bar() { } protected Bar(SerializationInfo info, StreamingContext context) { m_foo = (Foo)info.GetValue("1", typeof(Foo)); } public void GetObjectData(SerializationInfo info, StreamingContext context) { info.AddValue("1", m_foo); } } I then do this: Bar b = new Bar(); Foo f = new Foo(b); bool equal = ReferenceEquals(b, b.Foo.Bar); // true // Serialise and deserialise b equal = ReferenceEquals(b, b.Foo.Bar); If I use an out-of-the-box BinaryFormatter to serialise and deserialise b, the above test for reference-equality returns true as one would expect. But I cannot conceive of a way to achieve this in my custom IFormatter. In a non-ISerializable situation I can simply revisit "pending" object fields using reflection once the target references have been resolved. But for objects implementing ISerializable it is not possible to inject new data using SerializationInfo. Can anyone point me in the right direction?

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• implementing a download manager that supports resuming

  - by Idan K

  hi, I intend on writing a small download manager in C++ that supports resuming (and multiple connections per download). From the info I gathered so far, when sending the http request I need to add a header field with a key of "Range" and the value "bytes=startoff-endoff". Then the server returns a http response with the data between those offsets. So roughly what I have in mind is to split the file to the number of allowed connections per file and send a http request per splitted part with the appropriate "Range". So if I have a 4mb file and 4 allowed connections, I'd split the file to 4 and have 4 http requests going, each with the appropriate "Range" field. Implementing the resume feature would involve remembering which offsets are already downloaded and simply not request those. Is this the right way to do this? What if the web server doesn't support resuming? (my guess is it will ignore the "Range" and just send the entire file) When sending the http requests, should I specify in the range the entire splitted size? Or maybe ask smaller pieces, say 1024k per request? When reading the data, should I write it immediately to the file or do some kind of buffering? I guess it could be wasteful to write small chunks. Should I use a memory mapped file? If I remember correctly, it's recommended for frequent reads rather than writes (I could be wrong). Is it memory wise? What if I have several downloads simultaneously? If I'm not using a memory mapped file, should I open the file per allowed connection? Or when needing to write to the file simply seek? (if I did use a memory mapped file this would be really easy, since I could simply have several pointers). Note: I'll probably be using Qt, but this is a general question so I left code out of it.

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• Implementing Operator Overloading with Logarithms in C++

  - by Jacob Relkin

  Hello my friends, I'm having some issues with implementing a logarithm class with operator overloading in C++. My first goal is how I would implement the changeBase method, I've been having a tough time wrapping my head around it. My secoond goal is to be able to perform an operation where the left operand is a double and the right operand is a logarithm object. Here's a snippet of my log class: // coefficient: double // base: unsigned int // number: double class _log { double coefficient, number; unsigned int base; public: _log() { base = rand(); coefficient = rand(); number = rand(); } _log operator+ ( const double b ) const; _log operator* ( const double b ) const; _log operator- ( const double b ) const; _log operator/ ( const double b ) const; _log operator<< ( const _log &b ); double getValue() const; bool changeBase( unsigned int base ); }; You guys are awesome, thank you for your time.

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• Implementing Java Priority Queue

  - by Kay

  public class PriorityQueue<T> { private PriorityNode<T> head, tail; private int numItems; public PriorityQueue(){ numItems = 0; head=null; tail=null; } public void add(int priority, T value){ PriorityNode<T> newNode = new PriorityNode<T>(priority,value); if(numItems == 0){ head = newNode; tail = newNode; } else{ head.setNext(newNode); head = newNode; } } } Where PriorityNode is defined as: public class PriorityNode<T> implements Comparable<T> { private T value; private PriorityNode<T> next; private int priority; public PriorityNode(int priority,T newValue){ value = newValue; next = null; priority = 0; } public PriorityNode(T newValue){ value = newValue; next = null; priority = 0; } public void setPriority(int priority){ this.priority = priority; } public int getPriority(){ return this.priority; } public T getValue(){ return value; } public PriorityNode<T> getNext(){ return next; } public void setNext(PriorityNode<T> nextNode){ this.next = nextNode; } public void setValue(T newValue){ value = newValue; } public int compareTo(int pri) { // TODO Auto-generated method stub if(this.priority<pri){ return -1; } else if(this.priority == pri){ return 0; } else{ return 1; } } } I'm having a lot of difficulty using the Comparator here and implementing a priority queue - please point me in the right direction.

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• Implementing Drag and Drop using MouseListener for custom Components

  - by Chris Lieb

  I am working on a school assignment that requires me to be able to pick up a tile, drag it to a location, then drop it there. I was able to get this working using TransferHandler and a bunch of stuff from the dnd package, but this is not an acceptable way to perform this action for this assignment according to the professor. So, I am trying to achieve the same effect using the MouseListener interface. The basic setup is this: I have a JPanel-derived class called LocationView that contains JLabel-dervived instances of TileView. I need to get events that give me the LocationView that has the mouse pressed on and the LocationView that has the mouse released on. I am proxying mouse events through the TileView to its containing LocationView so that I can properly handle the mousePressed event. I added System.out.println()'s to the mouse listeners for mousePressed and mouseReleased to both LocationView and TileView so that I could observe the events that were being generated. To my surprise, pressing the mouse on Tile A in Location A, then dragging to Location B and releasing would generate a mouse released event for both Tile A and Location A, but not for Location B. I need the mouse released event triggered for only Location B. To try to work around this, I tried implementing a glass pane based off of the FinalGlassPane found at http://weblogs.java.net/blog/2006/09/20/well-behaved-glasspane. After adding the glass pane and adding an event listener for it, I can see that the mouse events are indeed filtering through the glass pane, but the mouse released event is still only being called on the item the mouse was clicked on. Is there a way to have mousePressed and mouseReleased events associated with the same drag action be called on separate components?

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• Problem implementing Interceptor pattern

  - by ph0enix

  I'm attempting to develop an Interceptor framework (in C#) where I can simply implement some interfaces, and through the use of some static initialization, register all my Interceptors with a common Dispatcher to be invoked at a later time. The problem lies in the fact that my Interceptor implementations are never actually referenced by my application so the static constructors never get called, and as a result, the Interceptors are never registered. If possible, I would like to keep all references to my Interceptor libraries out of my application, as this is my way of (hopefully) enforcing loose coupling across different modules. Hopefully this makes some sense. Let me know if there's anything I can clarify... Does anyone have any ideas, or perhaps a better way to go about implementing my Interceptor pattern? Update: I came across Spring.NET. I've heard of it before, but never really looked into it. It sounds like it has a lot of great features that would be very useful for what I'm trying to do. Does anyone have any experience with Spring.NET? TIA, Jeremy

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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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• implementing cryptographic algorithms, specifically the key expansion part

  - by masseyc

  Hey, recently I picked up a copy of Applied Cryptography by Bruce Schneier and it's been a good read. I now understand how several algorithms outlined in the book work, and I'd like to start implementing a few of them in C. One thing that many of the algorithms have in common is dividing an x-bit key, into several smaller y-bit keys. For example, blowfish's key, X, is 64-bits, but you are required to break it up into two 32-bit halves; Xl and Xr. This is where I'm getting stuck. I'm fairly decent with C, but I'm not the strongest when it comes to bitwise operators and the like. After some help on IRC, I managed to come up with these two macros: #define splitup(a, b, c) {b = a >> 32; c = a & 0xffffffff; } #define combine(a, b, c) {a = (c << 32) | a;} Where a is 64 bits and b and c are 32 bits. However, the compiler warns me about the fact that I'm shifting a 32 bit variable by 32 bits. My questions are these: what's bad about shifting a 32-bit variable 32 bits? I'm guessing it's undefined, but these macros do seem to be working. Also, would you suggest I go about this another way? As I said, I'm fairly familiar with C, but bitwise operators and the like still give me a headache.

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• problem with implementing a simple work queue

  - by John Deerikio

  Hi all, I am having troubles with implementing a simple work queue. Doing some analysis, I am facing a subtle problem. The work queue is backed by a regular linked list. The code looks like this (simplified): 0. while (true) 1. while (enabled == true) 2. acquire lock on the list and get the next action to be executed (blocking operation) (store it in a local variable) 3. execute the action (outside the lock on the list on previous line) 4. get lock on this work queue 5. wait until this work queue has been notified (triggered when setEnabled(true) has been callled) The setEnabled(e) operation looks like this (simplified): enabled = e if (enabled == true) acquire lock on this work queue and do notify() Although this works, there is a condition in which a deadlock occurs. It happens in the following rare situation: while an action is being executed, setEnabled(false) is called just before step (4) is entered, setEnabled(true) is called now step (5) keeps waiting forever, because this work queue has already been notified How do I solve this? I have been looking at this for some time, but I cannot come up with a solution. Please note I am fairly new to thread synchronization. Thanks a lot.

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