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• How do I synchronize access to shared memory in LynxOS/POSIX?

  - by GrahamS

  I am implementing two processes on a LynxOS SE (POSIX conformant) system that will communicate via shared memory. One process will act as a "producer" and the other a "consumer". In a multi-threaded system my approach to this would be to use a mutex and condvar (condition variable) pair, with the consumer waiting on the condvar (with pthread_cond_wait) and the producer signalling it (with pthread_cond_signal) when the shared memory is updated. How do I achieve this in a multi-process, rather than multi-threaded, architecture? Is there a LynxOS/POSIX way to create a condvar/mutex pair that can be used between processes? Or is some other synchronization mechanism more appropriate in this scenario?

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• Managing execution priorities and request expiry time in your web application

  - by Dan

  Some installations that run our applications can be under hefty stress on a busy day. Our clients ask us is there is a way to manage priorities in our application. For example, in a typical internet banking application, banks are interested in having the form “Transfer money” responsive, while the “Statement” page is a lot less critical. Not being able to transfer money is a direct loss for the bank, while not being able to produce a statement or something similar can be fixed with an apology. AFAIK, neither can you manage different request or session timeouts in a typical web application, it is one value for the whole of your web app. Managing message priority and expiry time is a typical feature in many middleware platforms. Something like this can be useful for a web front end as well. Do any of web servers (either java or .net) or web frameworks provide these features? How would you go about implementing it if you’d have to go for roll-your-own?

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• Java Memory Overhead

  - by flamealpha

  Hello, I would like to ask about Memory Overhead in java, I have a large ArrayList (61,770 items), and trying to calculate the amount of memory taken by each item (counting the object and its ArrayList entry), by profiling the app i get that after all the data is loaded, the heap takes ~ 25Mb. when the ArrayList has only 2 items the heap takes ~1Mb , so roughly: (24*1024*1024)/61,768 = 407 bytes. however, when i count the fields of the each object, i get 148 bytes(not including the ArrayList, and assuming int=4,float=4,reference=4), I am curious to know where did all of those extra bytes came from... i can guess that since the objects I store in the ArrayList are implementing an interface, they store extra values, maybe the VM stores a 4byte function pointer for each implemented method? the interface they implement have 20 functions so thats 80 more bytes, totaling 228 bytes, still not close to the 400 bytes measured. any help would be appreciated.

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• How to "kill" background worker completely?

  - by Ken Hung

  Hi All, I am writing a windows application that runs a sequence of digital IO actions repeatedly. This sequence of actions starts when the user click a "START" button, and it is done by a background worker in backgroundWorker1_DoWork(). However, there are occasions when I get the "This backgroundworker is currently busy......." error message. I am thinking of implementing the following in the code, by using a while loop to "kill" the background worker before starting another sequence of action: if (backgroundWorker1.IsBusy == true) { backgroundWorker1.CancelAsync(); while (backgroundWorker1.IsBusy == true) { backgroundWorker1.CancelAsync(); } backgroundWorker1.Dispose(); } backgroundWorker1.RunWorkerAsync(); I think my main concern is, will the backgroundWorker1 be "killed" eventually? If it will, will it take a long time to complete it? Will this coding get me into an infinite loop?

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• how do i add two delegates to a ui element at run time?

  - by Michael Xu

  Hi everyone, im trying to implement some behaviors when a mapview element scrolls... by coding a delegate for the scrollview inside of a mapview. so, right now, i got a pointer to the scroll view used by the map view in my code. however, i wish to set the delegate of this scroll view inside the map view, but the issue is that the mapview already sets up a default delegate for this scroll view inside the map view. can i make my delegate implement all of the messages of the protocol, explicitly sending them to the mapview's default delegate while also implementing my own behaviors? how else can i go about adding my own delegate behavior, to an already existing default delegate....? thanks everyone, michael

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• How to log python exception ?

  - by Maxim Veksler

  Hi, Coming from java, being familiar with logback I used to do try { ... catch (Exception e) { log("Error at X", e); } I would like the same functionality of being able to log the exception and the stacktrace into a file. How would you recommend me implementing this? Currently using boto logging infrastructre, boto.log.info(...) I've looked at some options and found out I can access the actual exception details using this code: import sys try: 1/0 except: exc_type, exc_value, exc_traceback = sys.exc_info() traceback.print_exception(exc_type, exc_value, exc_traceback) I would like to somehow get the string print_exception() throws to stdout so that I can log it. Thank you, Maxim.

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• SharePoint 2010 Licensing Costs

  - by Franklin

  Hi, We will be implementing a public-facing website in SharePoint 2010 and I have a few questions regarding licensing: Is there any (relatively) reliable pricing information available for SharePoint 2010? What about rumors? What edition of SharePoint 2010 would be appropriate for a publicly facing website (in 2007, you needed Enterprise for this, but it seems that WCM functionality is included in Standard in 2010)? What would be a reasonable number to budget for SharePoint 2010 licensing for a publicly facing website? Thanks in advance for your help!

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• Updates to NSDictionary attribute in CoreData not saving

  - by sfkaos

  I have created an Entity in CoreData that includes a Transformable attribute type implemented as an NSDictionary. The NSDictionary attribute only contains values of a custom class. The properties of the custom class are all of type NSString. The custom class complies with NSCoding implementing: -(void)encodeWithCoder:(NSCoder*)coder; -(id)initWithCoder:(NSCoder *)coder When saving the Entity for the first time all attributes including the Transformable (NSDictionary) type are properly saved in the DB. When the same Entity is fetched from the DB and updated (including the Transformable attribute) it seems to be updated properly. However, when the app is closed and then reopened fetching the Entity does not show the updated Transformable attribute-type though the rest of the attributes of type NSDate and NSString are up-to-date. The Transformable attribute is the original saved value not the updated value. Is this a problem with KVO or am I missing something else when trying to save an NSDictionary filled with a custom class to CoreData?

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• Why eGet() in EMF returns Object rather than EObject?

  - by Gabriel Šcerbák

  I am working on some code using the EMF framework in Java, but it is really hard to use, e.g. I cannot implement OCL-like query API on top of EMF which would be type-safe. One of the reasons is that eGet() for a EStructuralFeature return just an Object, not EObject. So anything I would write must use much of null checking, type checking and type casting which is unsafe, not performant and cannot be generalized in a reusable way. Why doesn't EMF generate dummy implementations with EObject wrappers for arbitrary Object value? Implementing the EObject and hence the EClass interfaces even with simple throw UnsupportedOperationException is really a pain (the APIs are too big). The same holds for the eContainer() method which makes navigatinng the model upwards painful.

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• What happens when auto_increment on integer column reaches the max_value in databases?

  - by Sanoj

  I am implementing a database application and I will use both JavaDB and MySQL as database. I have an ID column in my tables that has integer as type and I use the databases auto_increment-function for the value. But what happens when I get more than 2 (or 4) billion posts and integer is not enough? Is the integer overflowed and continues or is an exception thrown that I can handle? Yes, I could change to long as datatype, but how do I check when that is needed? And I think there is problem with getting the last_inserted_id()-functions if I use long as datatype for the ID-column.

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• How to do a STAR search in LINQ

  - by aNui

  I'm not sure about clarity of the STAR word. I'm implementing a search method using linq-to-object in c#. And I want to do a search with * (star) operator like most of search apps or web can do. e.g. If I typed "p*", results should be everything starting with "p". And it should work for prefix star, suffix star or star in the middle. And it would be great if the search can do with "-" (minus/NOT) operator or "+" (plus/OR) operator or "AND" operator Thanks in advance.

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• Cleanest way to tell if 3 times are within half an hour of each other

  - by niggles

  I have 3 date / time input boxes on a form and the user cannot select any times within half an hour of each other. I've converted all values to epoch format using a Javascript implementation of strtotime, but not sure how to recursively check that any of the times are actually half an hour apart. I can hand code all checks, but it would be cleaner to write a recursive function (especially if there were theoretically more than 3 time slots). Did some Google research but no luck. Any suggestions on implementing this in Javascript or Jquery. Thanks.

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• Should I use uint in C# for values that can't be negative?

  - by Johannes Rössel

  I have just tried implementing a class where numerous length/count properties, etc. are uint instead of int. However, while doing so I noticed that it's actually painful to do so, like as if no one actually wants to do that. Nearly everything that hands out an integral type returns an int, therefore requiring casts in several points. I wanted to construct a StringBuffer with its buffer length defaulted to one of the fields in that class. Requires a cast too. So I wondered whether I should just revert to int here. I'm certainly not using the entire range anyway. I just thought since what I'm dealing with there simply can't be negative (if it was, it'd be an error) it'd be a nice idea to actually use uint. P.S.: I saw this question and this at least explains why the framework itself always uses int but even in own code it's actually cumbersome to stick to uint which makes me think it apparently isn't really wanted.

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• How to "smart resize" a displayed image to original aspect ratio

  - by Paul Sasik

  I have an application in which end-users can size and position images in a designer. Since the spec calls for the image to be "stretched" to the containing control, the end user can end up with an awkwardly stretched image. To help the user with image sizing I am thinking of implementing a smart resizer function which would allow the the user to easily fix the aspect ratio of the picture so that it no longer appears stretched. The quick way to solve this is to actually provide two options: 1) scale from width 2) scale from height. The user chooses the method and the algorithm adjusts the size of the picture by using the original aspect ratio. For example: A picture is displayed as 200x200 on the designer but the original image is 1024x768 pixels. The user chooses "Smart Size from width" and the new size becomes ~200x150 since the original aspect ratio is ~1.333 That's OK, but how could I make the algorithm smarter and not bother the user by asking which dimension the recalculation should be based on?

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• How to validate HTTP request headers before receiving request body using WCF

  - by anelson

  I'm implementing a REST service using WCF which will be used to upload very large files. The HTTP headers in this request will communicate information which will be validated prior to allowing the upload to proceed (things like permissions, available disk space, etc). It's possible this validation will fail resulting in an error response. I'd like to do this validation prior to the client sending the body of the request, so it has a chance to detect failure before uploading potentially gigabytes of data. RESTful web services use the HTTP 1.1 Expect: 100-continue in the request to implement this. For example Amazon S3's REST API can validate your key and ACLs in response to an object PUT operation, returning 100 Continue if all is well, indicating you may proceed to send your data. I've rummaged around the WCF documentation and I just can't see a way to accomplish this without doing some pretty low-level hooking into the HTTP request processing pipeline. How would you suggest I solve this problem?

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• Check For Duplicate Records VS try/catch Unique Key Constraint

  - by Jed

  I have a database table that has a Unique Key constraint defined to avoid duplicate records from occurring. I'm curious if it is bad practice to NOT manually check for duplicate records prior to running an INSERT statement on the table. In other words, should I run a SELECT statement using a WHERE clause that checks for duplicate values of the record that I am about to INSERT. If a record is found, then do not run the INSERT statement, otherwise go ahead and run the INSERT.... OR Just run the INSERT statement and try/catch the exception that may be thrown due to a Unique Key violation. I'm weighing the two perspectives and can't decide which is best- 1. Don't waste a SELECT call to check for duplicates when I can just trap for an exception VS 2. Don't be lazy by implementing ugly try/catch logic VS 3. ???Your thoughts here??? :)

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• Using comet with PHP?

  - by ryeguy

  I was thinking of implementing real time chat using a PHP backend, but I ran across this comment on a site discussing comet: My understanding is that PHP is a terrible language for Comet, because Comet requires you to keep a persistent connection open to each browser client. Using mod_php this means tying up an Apache child full-time for each client which doesn’t scale at all. The people I know doing Comet stuff are mostly using Twisted Python which is designed to handle hundreds or thousands of simultaneous connections. Is this true? Or is it something that can be configured around?

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• ASP.NET MVC Authentication Cookie Not Being Retrieved

  - by Jamie Wright

  I am having a hard time implementing "Remember Me" functionality in an MVC application with a custom principal. I have boiled it down to ASP.NET not retrieving the authentication cookie for me. I have included a snaphot below from Google Chrome. Shows the results of Request.Cookies that is set within the controller action and placed in ViewData for the view to read. Notice that it is missing the .ASPXAUTH cookie Shows the results from the Chrome developer tools. You can see that .ASPXAUTH is included here. Does anyone know what the issue may be here? Why does ASP.NET not read this value from the cookie collection?

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• How can something like BOSH be implemented using Java Servlets

  - by John

  BOSH (Bidirectional-streams Over Synchronous HTTP) is a sneaky way of implementing 2-way client-server communication in situations where true server-push is not allowed, most obviously to let a server push data to a browser client without having to use client polling. It works by the client sending a request to the server, and the server doesn't respond immediately... rather it remembers the request but only responds when it has some data to send. When this happens the client immediately sends another request so there is virtually always a 'stored request' sitting on the server ready to push data to the client. At least, that's how I think it works! My question is how you can do this using a Java EE stack i.e standard servlets. I'm rusty with them, is it allowed to send no response and cache the request somehow? If anyone could share (pseudo) code what a servlet class for handling BOSH might look like, I'd be real grateful.

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• How to create a rounded title border in Java Swing

  - by Stephane Grenier

  I do understand that to create a title border, you do something like: BorderFactory.createTitledBorder(" Your Title "); However this creates a rectangle border whereas I need a rectangle with curved corners. Now from what I understand you can create your own custom border by: class CustomBorder implements Border { ... } The problem is that I'm not sure how to write the code that overrides the method: public void paintBorder(Component component, Graphics g, int x, int y, int width, int height) Or better yet, is there a way to do it without implementing your own Border class? And if not, how would you write that custom Title Border? I'm ok with drawing a rectangle with rounded corners, but how do you do it so that there's space for the label too?

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• deciding between subprocess, multiprocesser and thread in Python?

  - by user248237

  I'd like to parallelize my Python program so that it can make use of multiple processors on the machine that it runs on. My parallelization is very simple, in that all the parallel "threads" of the program are independent and write their output to separate files. I don't need the threads to exchange information but it is imperative that I know when the threads finish since some steps of my pipeline depend on their output. Portability is important, in that I'd like this to run on any Python version on Mac, Linux and Windows. Given these constraints, which is the most appropriate Python module for implementing this? I am tryign to decide between thread, subprocess and multiprocessing, which all seem to provide related functionality. Any thoughts on this? I'd like the simplest solution that's portable. Thanks.

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• Best way to store large dataset in SQL Server?

  - by gary

  I have a dataset which contains a string key field and up to 50 keywords associated with that information. Once the data has been inserted into the database there will be very few writes (INSERTS) but mostly queries for one or more keywords. I have read "Tagsystems: performance tests" which is MySQL based and it seems 2NF appears to be a good method for implementing this, however I was wondering if anyone had experience with doing this with SQL Server 2008 and very large datasets. I am likely to initially have 1 million key fields which could have up to 50 keywords each. Would a structure of keyfield, keyword1, keyword2, ... , keyword50 be the best solution or two tables keyid keyfield | 1 | | M keyid keyword Be a better idea if my queries are mostly going to be looking for results that have one or more keywords?

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• Shortest way of determining a name ends with an `s`, `x` or `z`, and then use the `I18n.t` method wi

  - by Koning Baard XIV

  I'm creating a Rails application where users can have a first and last name. Since I'm a perfectionist, the application may not show something like Dennis's profile or Xianx's profile, but rather Dennis' profile and Xianx' profile. I use L18n, so I wanted to ask what is the shortest way of implementing this? This grammar is the same for both English and Dutch, where the application will be translated to. Oh, some important things: I am not afraid of using helpers and the application controller My language files are in Ruby, not YAML Thanks!

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• Producer/consumer in Grails?

  - by Mulone

  Hi all, I'm trying to implement a Consumer/Producer app in Grails, after several unsuccessful attempts at implementing concurrent threads. Basically I want to store all the events coming from a clients (through separate AJAX calls) in a single queue and then process such a queue in a linear way as soon as new events are added. This looks like a Producer/Consumer problem: http://en.wikipedia.org/wiki/Producer-consumer_problem How can I implement this in Grails (maybe with a timer or even better by generating an event 'process queue')? Basically I'd like to a have a singleton service waiting for new events in the queue and processing them linearly (even if the queue is loaded by several concurrent processes). Any hints? Cheers!

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• JavaScript multithreading

  - by Krzysztof Hasinski

  I'm working on comparison for several different methods of implementing (real or fake) multithreading in JavaScript. As far as I know only webworkers and Google Gears WorkerPool can give you real threads (ie. spread across multiple processors with real parallel execution). I've found the following methods: switch between tasks using yield() use setInterval() (or other non-blocking function) with threads waiting one for another use Google Gears WorkerPool threads (with plugin) use html5 web workers I read related questions and found several variations of the above methods, but most of those questions are old, so there might be a few new ideas. I'm wondering - how else can you achieve multithreading in JavaScript? Any other important methods? UPDATE: As pointed out in comments what I really meant was concurrency. UPDATE 2: I found information that Silverlight + JScript supports multithreading, but I'm unable to verify this. UPDATE 3: Google deprecated Gears: http://code.google.com/apis/gears/api_workerpool.html

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