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• How do I design a cryptographic hash function?

  - by Eyal

  After reading the following about why one-way hash functions are one-way, I would like to know how to design a hash function. http://stackoverflow.com/questions/1038307/help-me-better-understand-cryptographic-hash-functions/1047106#1047106 Before everyone gets on my case: Yes, I know that it's a bad idea to not use a proven and tested hash function. I would still like to know how it's done. I'm familiar with Feistel-network ciphers but those are necessarily reversible, horrible for a cryptographic hash. Is there some sort of construction that is well-used in cryptographic hashing? Something that makes it very one-way?

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• mongodb read/write performance and mongo hosting in the cloud

  - by z3cko

  we are currently developing a high traffic rails application with facebooker (facebook game). since amazon simpledb (aws-sdb) is really slow, we are thinking of using a dedicated mongodb server as offered by mongoHQ for example. questions: what is the read/writes peak value for a mongodb server running on a amazon ec2 instance? what would be a recommended setup for a ec2 hosted app with mongodb - a master on amazon EBS and replicas on the ec2 instances? any examples or experiences? is there a company that offers mongodb hosting in the cloud? thanks, mz

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• Is -1 a magic number? An anti-pattern? A code smell? Quotes and guidelines from authorities

  - by polygenelubricants

  I've seen -1 used in various APIs, most commonly when searching into a "collection" with zero-based indices, usually to indicate the "not found" index. This "works" because -1 is never a legal index to begin with. It seems that any negative number should work, but I think -1 is almost always used, as some sort of (unwritten?) convention. I would like to limit the scope to Java at least for now. My questions are: What are the official words from Sun regarding using -1 as a "special" return value like this? What quotes are there regarding this issue, from e.g. James Gosling, Josh Bloch, or even other authoritative figures outside of Java? What were some of the notable discussions regarding this issue in the past?

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• Using multithreading for loop

  - by annelie

  Hello, I'm new to threading and want to do something similar to this question: http://stackoverflow.com/questions/100291/speed-up-loop-using-multithreading-in-c-question However, I'm not sure if that solution is the best one for me as I want them to keep running and never finish. (I'm also using .net 3.5 rather than 2.0 as for that question.) I want to do something like this: foreach (Agent agent in AgentList) { // I want to start a new thread for each of these agent.DoProcessLoop(); } --- public void DoProcessLoop() { while (true) { // do the processing // this is things like check folder for new files, update database // if new files found } } Would a ThreadPool be the best solution or is there something that suits this better? Thanks, Annelie

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• Voice Communication over TCP/IP

  - by Micha

  Hello, I'm currently developing application using DirectSound for communication on an intranet. I've had working solution using UDP but then my boss told me he wants to use TCP/IP for some reason. I've tried to implement it in pretty much the same way as UDP, but with very little success. What I get is basically just noise. 20% of it is the recorded sound and the rest is just weird noise. My guess for the reason is that TCP needs to read all the accepted data several times until it gets the final sound I can play. Now two questions: Am I on the right tracks? Is it even good idea to use TCP/IP for this kind of application (voice conferencing of sorts)? I'm doing it in C# but I don't think this is language specific.

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• How do I use a ListProperty(users.user) in a djangoforms.ModelForm on Google AppEngine?

  - by Gabriel

  I have been looking around a bit for info on how to do this. Essentially I have a Model: class SharableUserAsset(db.Model): name = StringProperty() users = ListProperty(users.User) My questions are: What is the best way to associate users to this value where they are not authenticated, visa vi invite from contacts list etc.? Is there a reasonable way to present a list control easily in a djangoforms.ModelForm? Once a user logs in I want to be able to check if that user is in the list for any number of SharableUserAsset class "records", how do I do that? Does user evaluate as a match to an email address or is there a way to look up a valid user against an email address?

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• Displaying untrusted HTML using PHP

  - by esryl

  I have a read a number of excellent questions and answers today about dealing with user input. I am now using htmlspecialchars() to display user data in the create/edit forms (but accepting the raw input via prepared PDO statements into my database). The main question I know have is, what do you do when you are allowing the user to submit HTML which will then be displayed to the public. Obviously htmlspecialchars() is no longer suitable as it just encodes the tags and renders the content useless for purpose. My application is currently accepting HTML from an admin for product descriptions. This would allow a malicious admin to inject potentially unsafe data into public facing pages. How do people cope with this?

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• Synchronising local and remote DB

  - by nico

  Hi everyone, I have a general question about DB synchronisation. So, I'm developing a website locally (PHP + MySQL) and I would like to be able to synchronise at least the structure (and maybe the contents) of the two DB when one of the two is changed (normally I would change the local copy). Right now what I'm doing is to use mysqldump to dump the modified tables and then import them in the remote DB or do it by hand if the changes are minimal. However I find this tedious and error-prone. For the PHP I'm currently using Quanta+ which has the handy feature of finding files that have changed and just upload those. Is there something similar for MySQL? Otherwise how do you keep your DBs synchronised? Thanks nico PS: I'm sorry if this was already asked, I saw other questions that deal with similar topics, but couldn't really find an answer.

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• How do I use a command line tool to install .net 4 to IIS

  - by tehp

  I'm trying to deploy my WCF RIA services application to our in-house server for testing. I've been following the instructions and comments from this blog site: http://timheuer.com/blog/archive/2009/12/10/tips-to-deploy-ria-services-troubleshoot.aspx At the end someone points to this question: http://stackoverflow.com/questions/1528324/how-to-solve-a-http-error-404-3-not-found-error I've been trying to run that same tool with .net 4.0 but it keeps giving me an error: [Warning]The HTTP namespace reservation already exists. I am running the version of the exe that I found inside of C:\Windows\Microsoft.NET\Framework\v4.0.21006 There is also C:\Windows\Microsoft.NET\Framework\v3.0\Windows Communication Foundation that has (what I assume is) the same exe in it, and I can use it just fine. I've tried to un-install the 3.0 version before installing the 4.0 version, but I am still getting the same warning and failure. Has anyone successfully done this with .net 4.0?

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• Desktop mono app and MVC/MVP framework

  - by tempy

  I am looking for a MVC/MVP (mvp prefferably) framework for my first mono app. There doesn't seem to be too much out there, but I have found the following: http://www.mvcsharp.org/ http://desktoprails.osl.ull.es/doku.php I've been looking into both for some time, and MVC# seems to be closer to what I want. The issue is that MVC# seems to be a .net project and not designed specifically for mono (as opposed to desktop rails), so I'm not 100% sure how it will play with mono. Also, it is under the Microsoft Public License (MsPL), and I am not sure how well that license will play with other components I intend to use that are gpl/mit/apache/etc. So if anyone has any experience with either of these frameworks in mono and can answer any of these questions, I would appreciate any feedback.

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• Clojure lots of threads

  - by Timothy Baldridge

  I just got done watching Rick Hickey's "Clojure Concurrency" talk, and I have a few questions about threads. Let's say I have a situation with lots of Agents, let's say 10,000 of them running one machine. I'd rather not have 10,000 CPU threads running at once, but I don't want threads to be blocked by the actions of other threads. In this example I won't really be waiting for replies, instead each Agent will be sending a message or two, and then waiting until it gets a message. How would I structure a program like this without getting 10k OS threads which would probably end up slowing the system down.

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• Do you have any tips for comments to keep them in step with the code? [closed]

  - by Rob Wells

  Possible Duplicate: How do you like your comments? G'day, I've read both of Steve McConnell's excellent Code Complete books "Code Complete" and "Code Complete 2" and was wondering if people have any other suggestions for commenting code. My commenting mantra could be summed up by the basic idea of expressing "what the code below cannot say". While enjoying this interesting blog post by Jeff about commenting I was still left wondering "When coding, when do you feel a comment is required?" Edit: Oops. Seems to be a duplicate of this question http://stackoverflow.com/questions/121945/how-do-you-like-your-comments so sorry for the noise. Thanks to my, seemingly, SO shadow for pointing it out - wouldn't have thought I was that interesting. Now off to read the original post and see if it is relevant. Edit: I meant to emphasise the best appraoch to ensure that your comments will stay in step with the code. Maybe expressing an intent rather than the mechansim for instance.

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• What should a Java/SOA developer be able to do?

  - by Regular Joe

  I got assigned the task to list the activities a Java Developer should be able to perform and create an estimate about the time it would take. I've came up with the following: Create JDBC CRUD backend ( S=1d, M=5d, H=10d ) Create JSP/Servlet frontend for a CRUD app ( S=1d, M=10d, H=20d ) Create Swing desktop frontend ( S=1d, M=15d, H=30d) Create ORM based CRUD etc. Create Webapp fronend with webframework etc Where.. S = Small complexity M = Medium complexity H = High complexity 1d = 1 day This is thought for a Java "enterprise" developer. The other profile I have is SOA Developer, but I could not pass beyond: Create webservice ( S=.5d, M=2d, H=7d ) Q.- What other activities should a Java Developer be able to do? Q.- What activities should a SOA Developer be able to do? Please, help me with this, I know this is in the limit of the kind of questions that could be asked here, but I really need a little push on this, and I don't want to go to Yahoo Answers for this.

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• SSRS 2008 Snapshotting Security

  - by Holy Christ

  Hi, I'm writing a report that will show data based on the User!UserID built into the SSRS infrastructure. The data is sensitive to the user's department. In addition to these department users, there will be admins that should be able to run for all departments, or have a report parameter to run for a specific department. Ideally, I'd like to use SSRS snapshotting so that users can rerun a report they ran on a previous date. It's important that a user can only view the snapshots he created for his department. My questions are: 1.) Does SSRS snapshotting provide a mechanism to limit viewing snapshots by the user that created them? 2.) Will I need to write two reports, one for the admin and one for the department users? I think I do since there isn't a way to secure report parameters. Thanks!

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• Is this a well known design pattern? what is it's name

  - by GenEric35

  Hi I have seen this often in code, but when I speak of it i don't know the name of such 'pattern' I have a method with 2 arguments that calls an overloaded method that has 3 arguments and intentionality sets the 3rd one to empty string. public DoWork(string name, string phoneNumber) { CreateContact(name, phoneNumber, string.Empty) } public DoWork(string name, string phoneNumber, string emailAddress) { //do the work } The reason I'm doing this is I to not duplicate code, and allow the existing callers to still call the method that has only 2 parameters. I have associate a few tags to this question, but it probably fit in more categories of questions. Is this a pattern, and does it have a name?

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• LinkedIn / Twitter / Facebook as OAuth and OpenId use

  - by monkeylee

  Firstly I understand OpenId is for authentication and OAuth is for authorisation and unlike other questions on the site I am not asking which should be used for which but if anyone can advise a solution for my issue. I want to allow users to login to my site via their LinkedIn/Twitter/Facebook account once logged in say via LinkedIn they could also then authorise their Twitter and Facebook account as a optional login method. This would allow the user to authenticate via any of the three but end up with their user account on my site as the end result. I also want to use the authorisation they have provided to get basic user details (profile pic/name etc) and post status updates. I don't want to ask a user to login with their account via openId then have to authorise the same account again via oauth to allow my site to publish to their service feed and have to do this for each of the 3 services. Any ideas or issues to this issue Lee

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• Handling dynamic data from javascript or rails

  - by 99miles

  I have page consisting of a calendar view ( http://code.google.com/p/calendardateselect/ ) as well as divs, each of which contain information about a person. In each div I want to have a link to a new controller and action, and pass the id for the person and the date selected in the calendar. I can think of a one way, but I'm thinking there's likely a better solution: 1) Do something like: =link_to_function "Week", "weekClicked(#{person.id})" Then in the weekClicked() javascript method I get the selected date from the calendar, such as: $('e_date').selected_date; then with javascript I could make a post request as mentioned here: http://stackoverflow.com/questions/133925/javascript-post-request-like-a-form-submit 2) Or, is there a way that I could make each link a button in it's own form and maybe have a hidden field that gets the selected date from the calendar as or before the form is submitted? I tried this too, but couldn't figure it out. This definitely seems like it's more on the right track than #1. Thanks.

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• How can I use Java to communicate to device through USB port?

  - by Bopha

  I just recently learn Java and try to communicate to the device through USB port connection. I've have used C# with OpenNETCF which allows me to send file and retrieve file on the device through USB port; how can I achieve this with java? I seearch on stackoverflow thread, http://stackoverflow.com/questions/544507/how-to-communicate-with-a-usb-device-under-windows-and-java, the comment made by christoffer is to hack the native code, but I don't quite which native code api that he referred to. RAPI, maybe?

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• How to find an available port?

  - by Roman

  I want to start a server which listen to a port. I can specify port explicitly and it works. But I would like to find a port in an automatic way. In this respect I have two questions. In which range of port numbers should I search for? (I used ports 12345, 12346, and 12347 and it was fine). How can I find out if a given port is not occupied by another software?

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• shutdown windows 8 from metro app

  - by MindFreak

  I'm doing a metro app for Windows 8. And as part of its functionality, I need to initiate shutdown of Winodws 8 from the Metro App. Here are the questions: 1) Firstly, I researched a lot on this topic and I found out that System.Diagnostics.Process is not available for Metro App. So, is there a another way around? 2) Even if I can't directly shutdown, is there a way to trigger it from the Metro App? I would prefer a solution in C#. Thanks.

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• Is there a recommended way to use the Observer pattern in MVP using GWT?

  - by Tomislav Nakic-Alfirevic

  I am thinking about implementing a user interface according to the MVP pattern using GWT, but have doubts about how to proceed. These are (some of) my goals: - the presenter knows nothing about the UI technology (i.e. uses nothing from com.google.*) - the view knows nothing about the model or the presenter - the model knows nothing of the view or the presenter (...obviously) I would place an interface between the view and the presenter and use the Observer pattern to decouple the two: the view generates events and the presenter gets notified. What confuses me is that java.util.Observer and java.util.Observable are not supported in GWT. This suggests that what I'm doing is not the recommended way to do it, as far as GWT is concerned, which leads me to my questions: what is the recommended way to implement MVP using GWT, specifically with the above goals in mind? How would you do it?

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• Managing EntityConnection lifetime

  - by kervin

  There have been many question on managing EntityContext lifetime, e.g. http://stackoverflow.com/questions/813457/instantiating-a-context-in-linq-to-entities I've come to the conclusion that the entity context should be considered a unit-of-work and therefore not reused. Great. But while doing some research for speeding up my database access, I ran into this blog post... Improving Entity Framework Performance The post argues that EFs poor performance compared to other frameworks is often due to the EntityConnection object being created each time a new EntityContext object is needed. To test this I manually created a static EntityConnection in Global.asax.cs Application_Start(). I then converted all my context using statements to using( MyObjContext currContext = new MyObjeContext(globalStaticEFConnection) { .... } This seems to have sped things up a bit without any errors so far as far as I can tell. But is this safe? Does using a applicationwide static EntityConnection introduce race conditions? Best regards, Kervin

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• Print a bitmap without printing a sprite?

  - by Carlos Barbosa

  Following up from: http://stackoverflow.com/questions/3021557/as3-printing-problem-blanks-swf-after-print-or-cancel I am trying to comeup with a function to print without creating a sprite, because that's what it seems to be causing my problem: public function printScreen():void { var pJob:PrintJob = new PrintJob(); var options:PrintJobOptions = new PrintJobOptions(); options.printAsBitmap = true; var bitmapData:BitmapData = new BitmapData(root.width, root.height); bitmapData.draw(root); var printThis:Bitmap = new Bitmap(bitmapData); try { pJob.start(); pJob.addPage(printThis, null, options); pJob.send(); } catch(e:Error) { trace("Error Printing") } } This is coming up with an: Error: Description Implicit coercion of a value of type flash.display:Bitmap to an unrelated type flash.display:Sprite. So how do you print a bitmap without creating a Sprite?

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• Why does the release build of my iPhone app crash on the device on the first run after installation?

  - by Chris Cooper

  I have an iPhone app that's been in development for about 2 weeks. We recently tried the "release" version of the build on a device, and to our great unhappiness, it crashes in one of the views with an "EXC_BAD_ACCESS". This crash only occurs on devices, and only in the "release" build. Not only that, but it only happens the first time the app is launched! It is also 100% reproducible. We have removed the small block of code that deals with data persistence, and have tried re-openning Xcode, cleaning the project, deleting and reinstalling the app, etc., as some other questions suggest. Do you have any advice for a) what might be causing this problem, and b) how to go about debugging if it only happens in "release"? Thanks

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• UI Terminology - Enabled vs. Active

  - by Pamela

  When designing a feature that can be accessed by different user levels, I'm wondering how the use of "enabled" versus "active" will work. If I'm an administrator, it means I have the ability to turn on and off a feature. Does this mean the feature is enabled for me or active? Once I turn this feature on, is it then enabled or active? Terminology is the pits. On the subject, does anyone know of a reference book or site dedicated to questions regarding standard terminology for UIs? Thanks a million!

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