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• Understanding Domain Driven Design

  - by Nihilist

  Hi I have been trying to understand DDD for few weeks now. Its very confusing. I dont understand how I organise my projects. I have lot of questions on UnitOfWork, Repository, Associations and the list goes on... Lets take a simple example. Album and Tracks. Album: AlbumId, Name, ListOf Tracks Tracks: TrackId, Name Question1: Should i expose Tracks as a IList/IEnumerabe property on Album ? If that how do i add an album ? OR should i expose a ReadOnlyCollection of Tracks and expose a AddTrack method? Question2: How do i load Tracks for Album [assuming lazy loading]? should the getter check for null and then use a repository to load the tracks if need be? Question3: How do we organise the assemblies. Like what does each assembly have? Model.dll - does it only have the domain entities? Where do the repositories go? Interfaces and implementations both. Can i define IAlbumRepository in Model.dll? Infrastructure.dll : what shold this have? Question4: Where is unit of work defined? How do repository and unit of work communicate? [ or should they ] for example. if i need to add multiple tracks to album, again should this be defined as AddTrack on Album OR should there a method in the repository? Regardless of where the method is, how do I implement unit of work here? Question5: Should the UI use Infrastructure..dll or should there be ServiceLayer? Do my quesitons make sense? Regards

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• error detection/correction/recovery in serial protocols

  - by Jason S

  I have some designing to do for a serial protocol and am running into some questions that I figure must have been considered elsewhere. So I'm wondering if there are some recommendations for best practices in designing serial protocols. (Please either state a fact that is easily verifiable, or cite a reputable source if you make a claim.) General recommendations for websites/books are also welcome. In particular I have to deal with issues like parsing a stream of bytes into packets verifying a packet is correct (easy with a CRC, for instance) identifying reasonable types of errors that can occur (e.g. in a point-to-point serial stream, sporadic single bit errors, and dropped series of bytes, are both likely, but extra phantom bytes are unlikely; whereas with a record stored in flash memory or on a disk drive the types of errors that predominate are different) error correction or recovery (if I detect an error in a packet, can I correct it? If not, can I resync to the boundary of the next packet?) how to make variable-length packets robust to error correction / recovery. Any suggestions?

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• Routing trouble for RESTful API - Rails

  - by aressidi

  I'm building out an API for web app that I've been working on for some time. I've started with the User model. The user portion of the API will allow remote clients to a) retrieve user data, b) update user information and c) create new users. I've gotten all of this to work, but it doesn't seem like its setup correctly. Here are my questions: Should the API endpoint be users or user? What's the best practice? I have to add the action to the end, which I would expect to be picked up instead by the request type so I don't have to specify it explicitly. How do I get my routes setup properly as not to have to include the method for protected actions? Let me give some examples: Get request for show - want it to work without the "show" curl -u rmbruno:blah http://app.local/api/users/show Put request for update - want it to work without the "update" curl -X put -F 'user[forum_notifications]=true' -u rmbruno:blah http://app.local/api/users/update Create - works with or without 'create' which is what I want for all these actions curl -X post -F 'user[login]=mamafatta' -F 'user[email][email protected]' -F 'user[password]=12345678' http://twye.local/api/users/ How do I structure routes to not require the action name? Isn't that the common way to to RESTful APIs? Here is my route for the API now: map.namespace :api do |route| route.resources :users route.resources :weight end I'm using restful authentication which is handling the http auth in curl. Any guidance on the routes issues and best practice on singular versus plural would be really helpful. Thanks! -A

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• Asynchronous event loop design and issues.

  - by Artyom

  Hello, I'm designing event loop for asynchronous socket IO using epoll/devpoll/kqueue/poll/select (including windows-select). I have two options of performing, IO operation: Non-blocking mode, poll on EAGAIN Set socket to non-blocking mode. Read/Write to socket. If operation succeeds, post completion notification to event loop. If I get EAGAIN, add socket to "select list" and poll socket. Polling mode: poll and then execute Add socket to select list and poll it. Wait for notification that it is readable writable read/write Post completion notification to event loop of sucseeds To me it looks like first would require less system calls when using in normal mode, especially for writing to socket (buffers are quite big). Also it looks like that it would be possible to reduce the overhead over number of "select" executions, especially it is nice when you do not have something that scales well as epoll/devpoll/kqueue. Questions: Are there any advantages of the second approach? Are there any portability issues with non-blocking operations on sockets/file descriptors over numerous operating systems: Linux, FreeBSD, Solaris, MacOSX, Windows. Notes: Please do not suggest using existing event-loop/socket-api implementations

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• Evidence-Based-Scheduling - are estimations only as accurate as the work-plan they're based on?

  - by Assaf Lavie

  I've been using FogBugz's Evidence Based Scheduling (for the uninitiated, Joel explains) for a while now and there's an inherent problem I can't seem to work around. The system is good at telling me the probability that a given project will be delivered at some date, given the detailed list of tasks that comprise the project. However, it does not take into account the fact that during development additional tasks always pop up. Now, there's the garbage-can approach of creating a generic task/scheduled-item for "last minute hacks" or "integration tasks", or what have you, but that clearly goes against the idea of aggregating the estimates of many small cases. It's often the case that during the development stage of a project you realize that there's a whole area your planning didn't cover, because, well, that's the nature of developing stuff that hasn't been developed before. So now your ~3 month project may very well turn into a 6 month project, but not because your estimations were off (you could be the best estimator in the world, for those task the comprised your initial work plan); rather because you ended up adding a whole bunch of new tasks that weren't there to begin with. EBS doesn't help you with that. It could, theoretically (I guess). It could, perhaps, measure the amount of work you add to a project over time and take that into consideration when estimating the time remaining on a given project. Just a thought. In other words, EBS works on a task basis, but not on a project/release basis - but the latter is what's important. It's what your boss typically cares about - delivery date, not the time it takes to finish each task along the way, and not the time it would have taken, if your planning was perfect. So the question is (yes, there's a question here, don't close it): What's your methodology when it comes to using EBS in FogBugz and how do you solve the problem above, which seems to be a main cause of schedule delays and mispredictions? Edit Some more thoughts after reading a few answers: If it comes down to having to choose which delivery date you're comfortable presenting to your higher-ups by squinting at the delivery-probability graph and choosing 80%, or 95%, or 60% (based on what, exactly?) then we've resorted to plain old buffering/factoring of our estimates. In which case, couldn't we have skipped the meticulous case by case hour-sized estimation effort step? By forcing ourselves to break down tasks that take more than a day into smaller chunks of work haven't we just deluded ourselves into thinking our planning is as tight and thorough as it could be? People may be consistently bad estimators that do not even learn from their past mistakes. In that respect, having an EBS system is certainly better than not having one. But what can we do about the fact that we're not that good in planning as well? I'm not sure it's a problem that can be solved by a similar system. Our estimates are wrong because of tendencies to be overly optimistic/pessimistic about certain tasks, and because of neglect to account for systematic delays (e.g. sick days, major bug crisis) - and usually not because we lack knowledge about the work that needs to be done. Our planning, on the other hand, is often incomplete because we simply don't have enough knowledge in this early stage; and I don't see how an EBS-like system could fill that gap. So we're back to methodology. We need to find a way to accommodate bad or incomplete work plans that's better than voodoo-multiplication.

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• If the address of a function can not be resolved during deduction, is it SFINAE or a compiler error?

  - by Faisal Vali

  In C++0x SFINAE rules have been simplified such that any invalid expression or type that occurs in the "immediate context" of deduction does not result in a compiler error but rather in deduction failure (SFINAE). My question is this: If I take the address of an overloaded function and it can not be resolved, is that failure in the immediate-context of deduction? (i.e is it a hard error or SFINAE if it can not be resolved)? Here is some sample code: struct X { // template T* foo(T,T); // lets not over-complicate things for now void foo(char); void foo(int); }; template struct S { template struct size_map { typedef int type; }; // here is where we take the address of a possibly overloaded function template void f(T, typename size_map::type* = 0); void f(...); }; int main() { S s; // should this cause a compiler error because 'auto T = &X::foo' is invalid? s.f(3); } Gcc 4.5 states that this is a compiler error, and clang spits out an assertion violation. Here are some more related questions of interest: Does the FCD-C++0x clearly specify what should happen here? Are the compilers wrong in rejecting this code? Does the "immediate-context" of deduction need to be defined a little better? Thanks!

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• How do I Data-Bind dual DateTimePicker to a single DateTime object

  - by S.C. Madsen

  Hi, I have a simple form, with two DateTimePicker-controls: One for date, and one for time. The thing is these two controls are supposed to represent a single point in time. Hence I would like to "Bind" them to a single DateTime property on my form (for simplicity). I did the following: // Start is a DateTime property on the form _StartDate.DataBindings.Add("Value", this, "Start"); _StartTime.DataBindings.Add("Value", this, "Start"); But hooking into "ValueChanged" event, yields mixed results... Sometimes I get exactly what I want, sometimes the updates of the property are "sluggish". I figured this way of splitting into two DateTimePicker's was fairly common. So how to do it? Update: There is possibly multiple questions in there: How do I bind a DateTimePicker (Format: Date) to a DateTime Property on a form? Then, how do I bind yet another DateTimePicker (Format: Time) to the same property? I'm using Visual Studio Express 2008 (.NET 3.5), and I seemingly get ValueChanged events from the DateTimePickers before the value is changed?

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• Where do I put jar files in Tomcat 6?

  - by Simon

  I am having trouble getting my JSP page to load a Java class which is in a jar file. The message I get appears to indicate a class not found exception: Jan 6, 2011 12:21:45 PM org.apache.catalina.core.StandardWrapperValve invoke SEVERE: Servlet.service() for servlet jsp threw exception org.apache.jasper.JasperException: Unable to compile class for JSP: An error occurred at line: 72 in the jsp file: /xmlloader.jsp FactArray cannot be resolved to a type 69: sourceType = "1"; 70: } 71: 72: FactArray fa = new FactArray(); 73: Fact f; 74: 75: /***********************/ The Type FactArray is one of my classes in a package com.mypackage.fact.FactArray which exists in myjar.jar. myjar.jar is a separate Java project (using NetBeans, but I don't think that's relevant). I include the package in my JSP as follows: <%@ page import="com.mypackage.fact.*" %> I deploy my web site and JSPs into Tomcat 6 as a WAR file. I include myjar.jar in that WAR in WEB-INF/lib but that doesn't work. I tried putting myjar.jar in my tomcat/lib folder, but that doesn't work either. I have bounced the server several times between changes. I have read a whole bunch of questions on here which say "put it in WEB-INF/lib" but that isn't working, so I'm asking my own question. Where do I need to put common JAR files so they get picked up by Tomcat?

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• How to get a fully transparent backbuffer in directx 9 without vista Desktop Window Manager

  - by flawlesslyfaulted

  I currently have an activex control that initiates a media (video/audio) framework another development group in my company developed and I am providing a window handle to that code. That handle is being used by their rendering plugin in the pipeline that uses Direct3d for rendering the video using that handle. I have seperate LPDIRECT3D9EX and LPDIRECT3DDEVICE9EX pointers that I initialize in my activex control. I am trying to clear a backbuffer to transparent and then use directx drawing primatives to draw on that backbuffer producing a transparent window with my drawing primatives over the streaming video on the directx surface below. It appears that clearing a device backbuffer with full alpha transparency is ignored by directx. d3ddev->Clear(0, NULL, D3DCLEAR_TARGET, D3DCOLOR_RGBA(0, 0, 1, 0 /*full alpha*/), 1.0f, 0); I can see the object I draw but they are drawn on top of a backbuffer that has the RGB color specified without the alpha value. The project linked (http://www.codeproject.com/KB/directx/umvistad3d.aspx) to in the stackoverflow question below does what I want but requires vista's Desktop Window Manager and won't work for XP. http://stackoverflow.com/questions/148275/how-do-i-draw-transparent-directx-content-in-a-transparent-window I have tried with D3DRS_ALPHABLENDENABLE true with configured blend with no avail. I have also tried to have pixels with full alpha values not rendered using D3DRS_ALPHATESTENABLE, D3DRS_ALPHAREF, and D3DRS_ALPHAFUNC setup but this doesn't work either. I have tried using ColorFill with alpha after retrieving the backbuffer with GetBackBuffer but this doesn't work either. (again only RGB is used) Finally I have tried creating a texture, selecting a surface, colorfilling that surface with a fully transparent alpha value, then loading that surface onto the backbuffer but only the RGB values appear to be used. I have checked the capabilities using the DXCapsViewer.exe and the D3DFMT_A8R8G8B8 backbuffer format that I am using for the backbuffer is valid so it can't be that. Has anyone gotten a transparent backbuffer in directx to work in XP?

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• Delphi App has "No Debug Info" when Debugging

  - by James L.

  We have built an application that uses packages and components. When we debug the application, the "Event Log" in the IDE often shows the our BPLs are being loaded without debug information ("No Debug Info"). This doesn't make sense because all our packages and EXEs are built with debug. _(each project) | Options | Compiling_ [ x ] Assertions [ x ] Debug information [ x ] Local symbols Symbol reference info = "Reference info" [ ] Use debug .dcus [ x ] Use imported data references _(each project) | Options | Linking_ [ x ] Debug information Map file = Detailed We have 4 projects, all built with runtime pacakges: Core.bpl Components.bpl Plugin.bpl (uses both #1 & #2) MainApp.exe (uses #1) Problems Observed 1) Many times when we debug, the Components.bpl is loaded with debug info, but all values in the "Local Variables" window are blank. If you hover your mouse over a variable in the code, there is no popup, and Evaluate window also shows nothing (the "Result" pane is always blank). 2) Sometimes the Event Log shows "No Debug Info" for various BPLs. For instance, if we activate the Plugin.bpl project and set it's Run | Parameter's Host Application to be the MainApp.exe, and then press F9, all modules seems to load with "Has Debug Info" except for the Plugin.bpl module. When it loads, the Event Log shows "No Debug Info". However, if we close the app and immediately press F9, it will run it again without recompiling anything and this time Plugin.bpl is loaded with debug ("Has Debug Info"). Questions 1) What would cause the "Local Variables" window to not display the values? 2) Why are BPLs sometimes loaded without debug info when the BPL was complied with debug and all the debug files (dcu, map, etc.) are available?

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• Backreferences syntax in replacement strings (why dollar sign?)

  - by polygenelubricants

  In Java, and it seems in a few other languages, backreferences in the pattern is preceded by a slash (e.g. \1, \2, \3, etc), but in a replacement string it's preceded by a dollar sign (e.g. $1, $2, $3, and also $0). Here's a snippet to illustrate: System.out.println( "left-right".replaceAll("(.*)-(.*)", "\\2-\\1") // WRONG!!! ); // prints "2-1" System.out.println( "left-right".replaceAll("(.*)-(.*)", "$2-$1") // CORRECT! ); // prints "right-left" System.out.println( "You want million dollar?!?".replaceAll("(\\w*) dollar", "US\\$ $1") ); // prints "You want US$ million?!?" System.out.println( "You want million dollar?!?".replaceAll("(\\w*) dollar", "US$ \\1") ); // throws IllegalArgumentException: Illegal group reference Questions: Is the use of $ for backreferences in replacement strings unique to Java? If not, what language started it? What flavors use it and what don't? Why is this a good idea? Why not stick to the same pattern syntax? Wouldn't that lead to a more cohesive and an easier to learn language? Wouldn't the syntax be more streamlined if statements 1 and 4 in the above were the "correct" ones instead of 2 and 3?

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• WCF: Using multiple bindings for a single service.

  - by Lijo

  Hi, I have a WCF service (in 3.0) which is running fine with wsHttpBinding. I want to add netTcpBinding binding also to the same service. But the challenge that I am facing is in adding behaviorConfiguration. How should I modify the following code to enable the service for both the bindings? Please help… <service name="Lijo.Samples.WeatherService" behaviorConfiguration="WeatherServiceBehavior"> <host> <baseAddresses> <add baseAddress="http://localhost:8000/ServiceModelSamples/FreeServiceWorld"/> <add baseAddress="net.tcp://localhost:8052/ServiceModelSamples/FreeServiceWorld"/> <!-- added new baseaddress for TCP--> </baseAddresses> </host> <endpoint address="" binding="wsHttpBinding" contract="Lijo.Samples.IWeather" /> <endpoint address="" binding="netTcpBinding" contract="Lijo.Samples.IWeather" /> <!-- added new end point--> <endpoint address="mex" binding="mexHttpBinding" contract="IMetadataExchange" /> </service> </services> <behaviors> <serviceBehaviors> <behavior name="WeatherServiceBehavior"> <serviceMetadata httpGetEnabled="true"/> <serviceDebug includeExceptionDetailInFaults="False"/> </behavior> </serviceBehaviors> </behaviors> Please see the following to see further details http://stackoverflow.com/questions/2887588/wcf-using-windows-service Thanks Lijo

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• Using "ocamlfind" to make the OCaml compiler and toplevel find (project specific) libraries

  - by CharlieP

  Hello, I'm trying to use ocamlfind with both the OCaml compiler and toplevel. From what I understood, I need to place the required libraries in the _tags file at the root of my project, so that the ocamlfind tool will take care of loading them - allowing me to open them in my modules like so : open Sdl open Sdlvideo open Str Currently, my _tags file looks like this : <*>: pkg_sdl,pkg_str I can apparently launch the ocamlfind command with the ocamlc or ocamlopt argument, provided I wan't to compile my project, but I did not see an option to launch the toplevel in the same manner. Is there any way to do this (something like "ocamlfind ocaml")? I also don't know how to place my project specific modules in the _tags file : imagine I have a module name Land. I am currently using the #use "land.ml" directive to open the file and load the module, but it has been suggested that this is not good practice. What syntax should I use in _tags to specify it should be loaded by ocamlfind (considering land.ml is not in the ocamlfind search path) ? Thank you, Charlie P. Edit : According to the first answer of this post, the _tags file is not to be used with ocamlfind. The questions above still stand, there is just a new one to the list : what is the correct way to specify the libraries to ocamlfind ?

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• SO what RDF database do i use for product attribute situation initially i thought about using EAV?

  - by keisimone

  Hi, i have a similar issue as espoused in http://stackoverflow.com/questions/695752/product-table-many-kinds-of-product-each-product-has-many-parameters i am convinced to use RDF now. only because of one of the comments made by Bill Karwin in the answer to the above issue but i already have a database in mysql and the code is in php. 1) So what RDF database should I use? 2) do i combine the approach? meaning i have a class table inheritance in the mysql database and just the weird product attributes in the RDF? I dont think i should move everything to a RDF database since it is only just products and the wide array of possible attributes and value that is giving me the problem. 3) what php resources, articles should i look at that will help me better in the creation of this? 4) more articles or resources that helps me to better understand RDF in the context of the above challenge of building something that will better hold all sorts of products' attributes and values will be greatly appreciated. i tend to work better when i have a conceptual understanding of what is going on. Do bear in mind i am a complete novice to this and my knowledge of programming and database is average at best.

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• Rails form with a better URL

  - by Sam

  Wow, switching to REST is a different paradigm for sure and is mainly a headache right now. view <% form_tag (businesses_path, :method => "get") do %> <%= select_tag :business_category_id, options_for_select(@business_categories.collect {|bc| [bc.name, bc.id ]}.insert(0, ["All Containers", 0]), which_business_category(@business_category) ), { :onchange => "this.form.submit();"} %> <% end %> controller def index @business_categories = BusinessCategory.find(:all) if params[:business_category_id].to_i != 0 @business_category = BusinessCategory.find(params[:business_category_id]) @businesses = @business_category.businesses else @businesses = Business.all end respond_to do |format| format.html # index.html.erb format.xml { render :xml => @businesses } end end routes map.resources What I want to to is get a better URL than what this form is presenting which is the following: http://localhost:3000/businesses?business_category_id=1 Without REST I would have do something like http://localhost:3000/business/view/bbq bbq as permalink or I would have done http://localhost:300/business_categories/view/bbq and get the business that are associated with the category but I don't really know the best way of doing this. So the two questions are what is the best logic of finding a business by its categories using the latter form and number two how to get that in a pretty URL all through RESTful routes in Rails.

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• Right way of making muti-site and multi-lingual website on codeigniter

  - by DR.GEWA

  Hi there. Beforehand let me thank you all !! Really guys you help a lot. When I will finish my web site and will have much time on watching how userbase is growing I will come here again and again to answer to another people questions(if I can ) So here is the problem. I made a web-site on CodeIgniter. A social network engine. Something like phpfox, classmates_com or facebook. It's right now somehow not multilingual, So the UI strings are in the view files, and next step will be move them to the language files. I want the user to have ability to change the language. So I assume that in database user will have row "lang_local" which would be by default set to en, and then to any other language he will change . So what is eating my nervs and enery is following. I will make on this engine several demographic social networks,and I would like to manage theese web-sites in centralized manner with one backend . So whenever I would like to make a new web-network, I just add the domain settings install the script in new folder and add it in database sites I see it like this on every table in database like users,comments,messages,categories ,etc I will have a row site_id , and on each query add/update/delete I add a WHERE SITE_ID=XXX and in table sites(site_id,site_name,domain_name) will have all domains , so that in backend I can filter data by website. Is this a good way? What if i will need then to be multiserver, what about load balancing? Who can tell me what would be a right,PROFESSIONAL way? My maximum user limit for a database is something like for start 10.000 in one-two year 100.000users

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• Implementing Model-level caching

  - by Byron

  I was posting some comments in a related question about MVC caching and some questions about actual implementation came up. How does one implement a Model-level cache that works transparently without the developer needing to manually cache, yet still remains efficient? I would keep my caching responsibilities firmly within the model. It is none of the controller's or view's business where the model is getting data. All they care about is that when data is requested, data is provided - this is how the MVC paradigm is supposed to work. (Source: Post by Jarrod) The reason I am skeptical is because caching should usually not be done unless there is a real need, and shouldn't be done for things like search results. So somehow the Model itself has to know whether or not the SELECT statement being issued to it worthy of being cached. Wouldn't the Model have to be astronomically smart, and/or store statistics of what is being most often queried over a long period of time in order to accurately make a decision? And wouldn't the overhead of all this make the caching useless anyway? Also, how would you uniquely identify a query from another query (or more accurately, a resultset from another resultset)? What about if you're using prepared statements, with only the parameters changing according to user input? Another poster said this: I would suggest using the md5 hash of your query combined with a serialized version of your input arguments. This would require twice the number of serialization options. I was under the impression that serialization was quite expensive, and for large inputs this might be even worse than just re-querying. And is the minuscule chance of collision worth worrying about? Conceptually, caching in the Model seems like a good idea to me, but it seems in practicality the developer should have direct control over caching and write it into the controller. Thoughts/ideas? Edit: I'm using PHP and MySQL if that helps to narrow your focus.

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• Inode to device information

  - by Methos

  I have 3 questions: I want to figure out if a file belongs to a USB device given the file inode. By looking in the latest kernel sources (2.6.33) on LXR, I think one can find that information by following pointers as follows: inode-super_block-block_device-backing_dev_info-device-device_driver(or device_type). However, the kernel that I am working with - 2.6.22.14 - does not have struct device pointer in the backing_dev_info object. So how can I figure out to which device does a file belong to from just the inode? I see that each of the inode, super_block and block_device contain an object of type 'dev_t'. But even after searching a lot, I could not find out how to convert 'dev_t' into struct device *. Is there any way to get that infomation? I tried to print device major and minor numbers using imajor(inode) and iminor(inode). However, for every file - belonging to hdd or usb - it always prints major and minor number as zero. Why would that be happening? I searched online for USB major numbers and I found out that major number for a USB is 180. However, on multiple machines, it showed me the major number associated with the USB dev as 253. $ ls -ltr /dev/usb* crw-rw---- 1 root root 253, 4 2010-04-13 17:20 /dev/usbmon4 crw-rw---- 1 root root 253, 3 2010-04-13 17:20 /dev/usbmon3 crw-rw---- 1 root root 253, 8 2010-04-13 17:20 /dev/usbmon8 crw-rw---- 1 root root 253, 5 2010-04-13 17:20 /dev/usbmon5 crw-rw---- 1 root root 253, 1 2010-04-13 17:20 /dev/usbmon1 crw-rw---- 1 root root 253, 7 2010-04-13 17:20 /dev/usbmon7 Why is that so?

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• Java: Efficiency of the readLine method of the BufferedReader and possible alternatives

  - by Luhar

  We are working to reduce the latency and increase the performance of a process written in Java that consumes data (xml strings) from a socket via the readLine() method of the BufferedReader class. The data is delimited by the end of line separater (\n), and each line can be of a variable length (6KBits - 32KBits). Our code looks like: Socket sock = connection; InputStream in = sock.getInputStream(); BufferedReader inputReader = new BufferedReader(new InputStreamReader(in)); ... do { String input = inputReader.readLine(); // Executor call to parse the input thread in a seperate thread }while(true) So I have a couple of questions: Will the inputReader.readLine() method return as soon as it hits the \n character or will it wait till the buffer is full? Is there a faster of picking up data from the socket than using a BufferedReader? What happens when the size of the input string is smaller than the size of the Socket's receive buffer? What happens when the size of the input string is bigger than the size of the Socket's receive buffer? I am getting to grips (slowly) with Java's IO libraries, so any pointers are much appreciated. Thank you!

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• Data synchronization using XMPP

  - by Jason

  Hi: I'm looking for some insight/advice on synchronizing data over XMPP. I've never developed anything for XMPP before so excuse me if some of my questions seem ridiculous. Basically, what I have is a decentralized social network. Each person has it's own Web site (or server) with a unique URI (one domain could host many servers). Each of these servers can have many clients. E.g., a desktop application, mobile application, etc. What I would like to accomplish is near real-time synchronization/communication between client and server, e.g., I update something on my desktop application, I see it change on my Web site. My server and client code is Python. So, I would like to make use of SleekXMPP if possible (it's license seems to have changed to MIT). I was thinking, and here is where I need advice, that each server would register an account at a dedicated XMPP server, e.g., [email protected]. and then I could use different resources for clients [email protected]/client1, [email protected]/client2, etc. If anyone can register any username, then maybe I also need some intermediate service (since it's decentralized, i'm not sure how to control registrations). Another option, I guess, is that each server runs it's own xmpp server. Assuming, that was all worked out, if I want to broadcast messages to all my resources (except the sending one), how do I do that? Do I have to subscribe to myself? This also seems like a good candidate for publish-subscribe, let me know if you think that could work and what the design/flow of that process would be. thanks :)

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• UVA Online Judge 3n+1 : Right answer is Wrong answer

  - by Samuraisoulification

  Ive been toying with this problem for more than a week now, I have optimized it a lot, I seem to be getting the right answer, since it's the same as when I compare it to other's answers that got accepted, but I keep getting wrong answer. Im not sure what's going on! Anyone have any advice? I think it's a problem with the input or the output, cause Im not exactly sure how this judge thing works. So if anyone could pinpoint the problem, and also give me any advice on my code, Id be very appreciative!!! #include <iostream> #include <cstdlib> #include <stdio.h> #include <vector> using namespace std; class Node{ // node for each number that has teh cycles and number private: int number; int cycles; bool cycleset; // so it knows whether to re-set the cycle public: Node(int num){ number = num; cycles = 0; cycleset = false; } int getnumber(){ return number; } int getcycles(){ return cycles; } void setnumber(int num){ number = num; } void setcycles(int num){ cycles = num; cycleset = true; } bool cycled(){ return cycleset; } }; class Cycler{ private: vector<Node> cycleArray; int biggest; int cycleReal(unsigned int number){ // actually cycles through the number int cycles = 1; if (number != 1) { if (number < 1000000) { // makes sure it's in vector bounds if (!cycleArray[number].cycled()) { // sees if it's been cycled if (number % 2 == 0) { cycles += this->cycleReal((number / 2)); } else { cycles += this->cycleReal((3 * number) + 1); } } else { // if cycled get the number of cycles and don't re-calculate, ends recursion cycles = cycleArray[number].getcycles(); } } else { // continues recursing if it's too big for the vector if (number % 2 == 0) { cycles += this->cycleReal((number / 2)); } else { cycles += this->cycleReal((3 * number) + 1); } } } if(number < 1000000){ // sets cycles table for the number in the vector if (!cycleArray[number].cycled()) { cycleArray[number].setcycles(cycles); } } return cycles; } public: Cycler(){ biggest = 0; for(int i = 0; i < 1000000; i++){ // initialize the vector, set the numbers Node temp(i); cycleArray.push_back(temp); } } int cycle(int start, int end){ // cycles thorugh the inputted numbers. int size = 0; for(int i = start; i < end ; i++){ size = this->cycleReal(i); if(size > biggest){ biggest = size; } } int temp = biggest; biggest = 0; return temp; } int getBiggest(){ return biggest; } }; int main() { Cycler testCycler; int i, j; while(cin>>i>>j){ //read in untill \n int biggest = 0; if(i > j){ biggest = testCycler.cycle(j, i); }else{ biggest = testCycler.cycle(i, j); } cout << i << " " << j << " " << biggest << endl; } return 0; }

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• Entity Framework - Insert/Update new entity with child-entities

  - by Christina Mayers

  I have found many questions here on SO and articles all over the internet but none really tackled my problem. My model looks like this (I striped all non essential Properties): Everyday or so "Play" gets updated (via a XML-file containing the information). internal Play ParsePlayInfo(XDocument doc) { Play play = (from p in doc.Descendants("Play") select new Play { Theatre = new Theatre() { //Properties }, //Properties LastUpdate = DateTime.Now }).SingleOrDefault(); var actors = (from a in doc.XPathSelectElement(".//Play//Actors").Nodes() select new Lecturer() { //Properties }); var parts = (from p in doc.XPathSelectElement(".//Play//Parts").Nodes() select new Part() { //Properties }).ToList(); foreach (var item in parts) { play.Parts.Add(item); } var reviews = (from r in doc.XPathSelectElement(".//Play//Reviews").Nodes() select new Review { //Properties }).ToList(); for (int i = 0; i < reviews.Count(); i++) { PlayReviews pR = new PlayReviews() { Review = reviews[i], Play = play, //Properties }; play.PlayReviews.Add(pR); } return play; } If I add this "play" via Add() every Childobject of Play will be inserted - regardless if some exist already. Since I need to update existing entries I have to do something about that. As far as I can tell I have the following options: add/update the child entities in my PlayRepositories Add-Method restructure and rewrite ParsePlayInfo() so that get all the child entities first, add or update them and then create a new Play. The only problem I have here is that I wanted ParsePlayInfo() to be persistence ignorant, I could work around this by creating multiple parse methods (eg ParseActors() ) and assign them to play in my controller (I'm using ASP.net MVC) after everything was parsed and added Currently I am implementing option 1 - but it feels wrong. I'd appreciate it if someone could guide me in the right direction on this one.

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• Combining aggregate functions in an (ANSI) SQL statement

  - by morpheous

  I have aggregate functions foo(), foobar(), fredstats(), barneystats() I want to create a domain specific query language (DSQL) above my DB, to facilitate using using a domain language to query the DB. The 'language' comprises of boolean expressions (or more specifically SQL like criteria) which I then 'translate' back into pure (ANSI) SQL and send to the underlying Db. The following lines are examples of what the language statements will look like, and hopefully, it will help further clarify the concept: **Example 1** DQL statement: foobar('yellow') between 1 and 3 and fredstats('weight') > 42 Translation: fetch all rows in an underlying table where computed values for aggregate function foobar() is between 1 and 3 AND computed value for AGG FUNC fredstats() is greater than 42 **Example 2** DQL statement: fredstats('weight') < barneystats('weight') AND foo('fighter') in (9,10,11) AND foobar('green') <> 42 Translation: Fetch all rows where the specified criteria matches **Example 3** DQL statement: foobar('green') / foobar('red') <> 42 Translation: Fetch all rows where the specified criteria matches **Example 4** DQL statement: foobar('green') - foobar('red') >= 42 Translation: Fetch all rows where the specified criteria matches Given the following information: The table upon which the queries above are being executed is called 'tbl' table 'tbl' has the following structure (id int, name varchar(32), weight float) The result set returns only the tbl.id, tbl.name and the names of the aggregate functions as columns in the result set - so for example the foobar() AGG FUNC column will be called foobar in the result set. So for example, the first DQL query will return a result set with the following columns: id, name, foobar, fredstats Given the above, my questions then are: What would be the underlying SQL required for Example1 ? What would be the underlying SQL required for Example3 ? Given an algebraic equation comprising of AGGREGATE functions, Is there a way of generalizing the algorithm needed to generate the required ANSI SQL statement(s)? I am using PostgreSQL as the db, but I would prefer to use ANSI SQL wherever possible.

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• How do I properly add existing source code files to my Xcode project?

  - by BeachRunnerJoe

  I'm new to iPhone development and I'm still getting familiar with the Mac dev environment, including Xcode. I want to add some 3rd party code to my iPhone project, but when I add the "existing files" to my Xcode project, I'm presented with a dialog box that has far too many options that I don't understand and, as such, my project isn't working. When I #import headerfilename.h, I get a build error that reads headerfilename.h: No such file or directory. Can anyone explain to me what all these options mean or give me a link to some documentation that can? I'm having a hard time finding anything in Apple's docs. Which options do I want to choose to add existing source code files to my Xcode project? I should note that the source code files that I'm trying to add are located in my project/Classes/frameworkname/ directory. After they're added, do I need to reference this new code directory in my project settings anywhere (i.e. some kind of header file directory variable)? Thanks so much! Update: I found the following answers/responses on the apple dev forums that were very useful and helped me fix my issue... To make it simple : - if you do not check the copy option, the file stay where it is. - if you check it, it is copied in your project folders In the first case (what it seems you are doing) you need to tell the compiler that the header files are in another directory : - project info - build - search paths - User Header Search Path : add the directory from where you took the header file Hope this will help You have discovered the most confusing dialog box that ever came out of Cupertino. Six years of Xcode, and this thing still is partly a mystery to me. To even get that far, I had to make many test projects to try and reverse-engineer what this thing does. The "Copy" box means that it will copy the files as they are right now, into the project. If this box is not checked, then it just references those files during a build and copies them as they are at THAT time. For source code, you want the Copy box checked. The "relative to" is a total mystery to me and I can't help you with that. I usually leave it however it is already set. Does it mean relative to where they are on disk, or the arrangement in Xcode, or in the bundle? Who knows. The last 2 radio buttons SEEM to mean that it will either re-create the folder structure of the folder you are adding, or just put "fake" folders in Xcode that point to the real folders. This is probably your problem - you are adding source code that is not all at the top level, and when it goes to find it, it does not re-create the hierarchy. Others can supply a better way, hopefully, but what I would do is put all of the source in one folder and add that, using the Copy box. Then in Xcode you can make whatever bogus folders you want and put the source file names in those fake folders.

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• Mixing RewriteRule and ProxyPass in Apache

  - by Taylor L

  I was working on debugging an issue today related to mixing mod_proxy and mod_rewrite together and I ended up having to use balancer://mycluster in the RewriteRule in order to stop receiving a 404 error from Apache. I have two questions: 1) Is there any other way to get the rewritten URL to go through the balancer without adding balancer://mycluster into the RewriteRule? 2) Is there a way to define all the parameters I defined in ProxyPass (stickysession=JSESSIONID|jsessionid scolonpathdelim=On lbmethod=bytraffic nofailover=Off) in either the <Proxy> or RewriteRule? I'm concerned the requests that match the new RewriteRule won't load balance in the same fashion as those that go through ProxyPass (like /app1/something.do)? Below are the relevant sections of the httpd.conf. I am using Apache 2.2. <Proxy balancer://mycluster> Order deny,allow Allow from all BalancerMember ajp://my.domain.com:8009 route=node1 BalancerMember ajp://my.domain.com:8009 route=node2 </Proxy> ProxyPass /app1 balancer://mycluster/app1 stickysession=JSESSIONID|jsessionid scolonpathdelim=On lbmethod=bytraffic nofailover=Off ProxyPassReverse /app1 ajp://my.domain.com:8009/app1 ... RewriteRule ^/static/cms/image/(.*)\.(.*) balancer://mycluster/app1/$1.$2 [P,L]

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