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• Web-app currency input/manipulation/calculation with javascript .. there has got to be a better (fra

  - by dreftymac

  BACKGROUND: I am of the "user-input-lockdown" school of thought. Whenever possible, I try to mistrust and sanitize user input, both client side and server side; and I try to take multiple opportunities to restrict possible inputs to a known subset of possibilities, usually this means providing a lot of checkboxes and select lists. (This is from the usability side of things, I know security-wise that malicious users can easily bypass fixed user input GUI controls). PROBLEM: Anyway, the problem always arises with non-fixed input of currency. Whenever I have to accept a freely-specified dollar amount as user input, I always have to confront these problems/annoyances and it is always painful: 1) Make sure to give the user two input boxes for each currency_datapoint, one for the whole_dollar_part and another for the fractional_pennies_part 2) Whenever the user changes a currency_datapoint, provide keystroke-by-keystroke GUI feedback to let them know whether the currency_datapoint is well-formed, with context-appropriate validation rules (e.g., no negatives?, nonzero only?, numeric only!, no non-numeric punctuation! no symbols!) 3) For display purposes, every user-provided currency_datapoint should be translated to human-readable currency formatting (dollar sign, period, commas provided by the app, where appropriate) 4) For calculation purposes, every user-provided currency_datapoint has to be converted to integer (all pennies, to avoid floating point errors) and summed into a grand total with zero or more subtotals. 5) Every user-provided currency_datapoint should be displayed or displayable in a nice "tabular" format, which auto-updates as the user enters each currency_datapoint, including a baloon that warns when one or more currency_datapoints is not well-formed. I seem to be re-inventing this wheel every time I have to work with currency in Javascript on the client side (server side is a bit more flexible since most programming languages have higher-level currency formatting logic). QUESTION: Has anyone out there solved the problem of dealing with the above issues, client side, in a way that is server-side-technology-stack agnostic, (preferrably plain javascript or jquery)? This is getting old, there has to be a better way.

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• MVVM Listbox DataTemplate SelectedItem

  - by StinkerPeter

  I am using a ListBox with a DataTemplate as shown below (xaml simplified and variable names changed). <ListBox ItemsSource="{Binding Path=ObservCollectionItems}" SelectedItem="{Binding Path=SelectedItemVar, Mode=TwoWay}"> <ListBox.ItemTemplate> <DataTemplate> <StackPanel> <TextBlock Text="{Binding SomeVar}" /> <Border> <StackPanel> <Button Content="String1" Command="{Binding DataContext.Command1} RelativeSource={RelativeSource FindAncestor, ListBox, 1}}" /> <Button Content="String2" Command="{Binding DataContext.Command2} RelativeSource={RelativeSource FindAncestor, ListBox, 1}}" /> </StackPanel> </Border> </StackPanel> </DataTemplate> <ListBox.ItemTemplate> </ListBox> I need the SelectedItemVar (dependency property) to update when I click on one of the buttons. SelectedItemVar is then used for the respective button's command. SelectedItemVar does update when I click on the TextBlock or the Border, but not when I click either button. I found a non-MVVM solution to this problem here. I do not want to add code in the file-behind to solve this, as they did in the link. Is there a clean solution that can be done in XAML. Beyond the non-MVVM solutions, I have not found anyone with this problem. I would have thought this was fairly common. Finally, I found this Command="{Binding DataContext.CommandName} RelativeSource={RelativeSource FindAncestor, ListBox, 1} for the Command binding. I do not fully understand what it is doing, but I do know that the command wasn't firing when I was binding directly to CommandName.

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• Presentation Issue in an Unordered List

  - by phreeskier

  I'm having an issue with correctly presenting items in an unordered list. The labels are floating left and the related spans that are long in length are wrapping and showing below the label. I need a solution that keeps the related spans in their respective columns. In other words, I don't want long spans to show under the labels. What property can I take advantage of so that I get the desired layout in all of the popular browsers, including IE6? Thanks in advance for the help. My code is as follows: <ul> <li> <label>Name</label> <span><%= Html.Encode(Model.Name) %></span> </li> <li> <label>Entity</label> <span><%= Html.Encode(Model.Entity) %></span> </li> <li> <label>Phone</label> <span><%= Html.Encode(Model.Phone) %></span> </li> </ul> My CSS styling is as follows: ul { display:block; list-style-type:none; margin:0; padding:0; } ul li label { float:left; width:100px; }

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• What Do You Need To Write Your Own Blog Engine?

  - by deworde

  I've been messing around with basic websites for a few years, using companies like www.Fasthosts.co.uk to do my web hosting. But I'd like to expand my skills from C++ and Java app programming into Web-based programming, and I think the best way to do that is with a project. I've chosen to go with a blog engine because it's a relative comprehensive yet non-complex project. I'm aware that you can just go to Blogger and bam! One blog. I've done that, so that I can at least have some content, and work out what I want to do with this blog. At the moment, I'm thinking I'll use it to chart my progress creating the blogging engine. But I have some questions. Do you need to be running your own server? Or is it more sensible in the short-term to use a hosting company? What types of language are worth considering? What's important to focus on from a design perspective? What unexpected problems might I encounter?

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• How to bind data from a view of type List<List<MyViewModelClass>>?

  - by Robert Koritnik

  I have a strong type view of type List<List<MyViewModelClass>> The outer list will always have two lists of List<MyViewModelClass>. For each of the two outer lists I want to display a group of checkboxes. Each set can have an arbitrary number of choices. My view model class looks similar to this: public class MyViewModelClass { public Area Area { get; set; } public bool IsGeneric { get; set; } public string Code { get; set; } public bool IsChecked { get; set; } } So the final view will look something like: Please select those that apply: First set of choices: x Option 1 x Option 2 x Option 3 etc. Second set of choices: x Second Option 1 x Second Option 2 x Second Option 3 x Second Option 4 etc. Checkboxes should display MyViewModelClass.Area.Name, and their value should be related to MyViewModelClass.Area.Id. Checked state is of course related to MyViewModel.IsChecked. Question I wonder how should I use Html.CheckBox() or Html.CheckBoxFor() helper to display my checkboxes? I have to get these values back to the server on a postback of course. If it makes things simpler, I could make a separate view model type like: public class Options { public List<MyViewModelClass> General { get; set; } public List<MyViewModelClass> Others { get; set; } }

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• Objective C loop logic

  - by Graham

  Hi guys, I'm really new to programming in Obj-C, my background is in labview which is a graphical programming language, I've worked with Visual Basic some and HTML/CSS a fair amount as well. I'm trying to figure out the logic to create an array of data for the pattern below. I need the pattern later to extract data from another 2 arrays in a specific order. I can do it by referencing a = 1, b = 2, c = 3 etc and then creating the array with a, b, c but I want to use a loop so that I don't have 8 references above the array. These references will be used to generate another generation of data so unless I can get help figuring out the logic I'll actually end up with 72 references above the array. // This is the first one which gives the pattern 0 0 0 0 (etc) // 1 1 1 1 // 2 2 2 2 NSMutableArray * expSecondRef_one = [NSMutableArray array]; int a1 = 0; while (a1 < 9) { int a2 = 0; while (a2 < 8) { NSNumber * a3 = [NSNumber numberWithInt:a1]; [expSecondRef_one addObject:a3]; a2++; } a1++; } // This is the second one which I'm stumbling over, I am looking for the pattern 1 2 3 4 5 6 7 8 // 0 2 3 4 5 6 7 8 // 0 1 3 4 5 6 7 8 // 0 1 2 4 5 6 7 8 // etc to -> // 0 1 2 3 4 5 6 7 If you run it in a line every 9th number is -1 but I don't know how to do that over a pattern of 8. Thanks in advance! Graham

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• How can I speed up the "finally get it" process?

  - by Earlz

  Hello, I am a hobby programmer and began when I was about 13. I'm currently going to college(freshman) for my computer science degree(which means, I'm still in the stuff I already know such as for loops). I've been programming professionally for a start up for about 9 months or so now. I have a serious problem though. I think that almost all of the code I write is perfect. Now I remember reading an article somewhere where there is like 3 stages of learning programming You don't know anything and you know you don't know anything. You don't know anything but you think you do. You finally get and accept that you don't know anything. (if someone finds that article tell me and I'll give a link) So right now, I'm at stage 2. How can I get to stage 3 quicker? The more and more of some people's code I read I think "this is complete rubbish, I would've done it like..." and I really dislike how I think that way. (and this fairly recently began happening, like over the past year)

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• Pointers, am I doing them correctly? Objective-c/cocoa

  - by Chris

  I have this in my @interface struct track currentTrack; struct track previousTrack; int anInt; Since these are not objects, I do not have to have them like int* anInt right? And if setting non-object values like ints, boolean, etc, I do not have to release the old value right (assuming non-GC environment)? The struct contains objects: typedef struct track { NSString* theId; NSString* title; } *track; Am I doing that correctly? Lastly, I access the struct like this: [currentTrack.title ...]; currentTrack.theId = @"asdf"; //LINE 1 I'm also manually managing the memory (from a setter) for the struct like this: [currentTrack.title autorelease]; currentTrack.title = [newTitle retain]; If I'm understanding the garbage collection correctly, I should be able to ditch that and just set it like LINE 1 (above)? Also with garbage collection, I don't need a dealloc method right? If I use garbage collection does this mean it only runs on OS 10.5+? And any other thing I should know before I switch to garbage collected code? Sorry there are so many questions. Very new to objective-c and desktop programming. Thanks

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• How to approach parallel processing of messages?

  - by Dan

  I am redesigning the messaging system for my app to use intel threading building blocks and am stumped trying to decide between two possible approaches. Basically, I have a sequence of message objects and for each message type, a sequence of handlers. For each message object, I apply each handler registered for that message objects type. The sequential version would be something like this (pseudocode): for each message in message_sequence <- SEQUENTIAL for each handler in (handler_table for message.type) apply handler to message <- SEQUENTIAL The first approach which I am considering processes the message objects in turn (sequentially) and applies the handlers concurrently. Pros: predictable ordering of messages (ie, we are guaranteed a FIFO processing order) (potentially) lower latency of processing each message Cons: more processing resources available than handlers for a single message type (bad parallelization) bad use of processor cache since message objects need to be copied for each handler to use large overhead for small handlers The pseudocode of this approach would be as follows: for each message in message_sequence <- SEQUENTIAL parallel_for each handler in (handler_table for message.type) apply handler to message <- PARALLEL The second approach is to process the messages in parallel and apply the handlers to each message sequentially. Pros: better use of processor cache (keeps the message object local to all handlers which will use it) small handlers don't impose as much overhead (as long as there are other handlers also to be run) more messages are expected than there are handlers, so the potential for parallelism is greater Cons: Unpredictable ordering - if message A is sent before message B, they may both be processed at the same time, or B may finish processing before all of A's handlers are finished (order is non-deterministic) The pseudocode is as follows: parallel_for each message in message_sequence <- PARALLEL for each handler in (handler_table for message.type) apply handler to message <- SEQUENTIAL The second approach has more advantages than the first, but non-deterministic ordering is a big disadvantage.. Which approach would you choose and why? Are there any other approaches I should consider (besides the obvious third approach: parallel messages and parallel handlers, which has the disadvantages of both and no real redeeming factors as far as I can tell)? Thanks!

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• Postgres error with Sinatra/Haml/DataMapper on Heroku

  - by sevennineteen

  I'm trying to move a simple Sinatra app over to Heroku. Migration of the Ruby app code and existing MySQL database using Taps went smoothly, but I'm getting the following Postgres error: PostgresError - ERROR: operator does not exist: text = integer LINE 1: ...d_at", "post_id" FROM "comments" WHERE ("post_id" IN (4, 17,... ^ HINT: No operator matches the given name and argument type(s). You might need to add explicit type casts. It's evident that the problem is related to a type mismatch in the query, but this is being issued from a Haml template by the DataMapper ORM at a very high level of abstraction, so I'm not sure how I'd go about controlling this... Specifically, this seems to be throwing up on a call of p.comments from my Haml template, where p represents a given post. The Datamapper models are related as follows: class Post property :id, Serial ... has n, :comments end class Comment property :id, Serial ... belongs_to :post end This works fine on my local and current hosted environment using MySQL, but Postgres is clearly more strict. There must be hundreds of Datamapper & Haml apps running on Postgres DBs, and this model relationship is super-conventional, so hopefully someone has seen (and determined how to fix) this. Thanks!

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• Mercurial repository usage with binary files for building setup files

  - by Ryan

  I have an existing Mercurial repository for a C++ application in a small corporate environment. I asked a co-worker to add the setup script to the repository and he added all of the dependency binaries, PDFs, and executable to the repository under an Install directory. I dislike having the binaries and dependencies in the same repository, but I'd like recommendations on best practices. Here are the options I am considering: Create a separate repository for the Installer and related files Create a subrepository for the Installer and related files Use a (yet to be identified) build dependency manager I am concerned with using a subrepository with Mercurial based on what I've read so far and the (apparently) incomplete implementation. I would like to get a project dependency system, e.g. Ivy, but I don't know all of the options and haven't had time yet to try out any options. I thought I'd use TortoiseHg as a basis, and it does not have the TortoiseHg binaries in the repository although it does have some binaries such as kdiff3.exe. Instead it uses setup.py to clone multiple repositories and build the apps. This seems reasonable for OSS, but not so much for corporate environments. Recommendations?

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• Cannot connect to SQL Server from ASP.NET MVC app

  - by Dan Fergus

  I have an ASP.NET MVC app that has on a hosted server for over a year, connecting to SQL Server. I've had to change hosting services, the new one supports MVC 1.0. I've also moved a non MVC ASP app to the same hosting service. Now, MY MVC based app retturnes this error when I try to validate a user login. A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: Named Pipes Provider, error: 40 - Could not open a connection to SQL Server) Now, the non-MVC app can access the exact same database and authenticate users just fine. The MVC app, when run from my dev box connects fine. It also run/connects/authenticates without problem when I install and run the site from an internal SQL 2008 server running IIS 7. I, along with the hosting support techs, am at a loss how the exact same connect string works every where except on the hosted server, and only when run from inside an ASP.NET MVC web app. Any ideas would be greatly appreciated.

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• How to submit Nothing as a route value to ASP MVC

  - by Adam

  I have a route with several optional parameters. These are possible search terms in different fields. So, for example, if I have fields key, itemtype and text then I have in global.asax: routes.MapRoute( _ "Search", _ "Admin.aspx/Search/{Key}/{ItemType}/{Text}", _ New With {.controller = "Admin", .action = "Search" .Key = Nothing, .ItemType = Nothing, .Text = Nothing} _ ) My action takes optional parameters: Function Search(Optional ByVal Key As String = Nothing, _ Optional ByVal ItemType As Integer = 0, _ Optional ByVal Text As String = Nothing, _ Optional ByVal OtherText As String = Nothing) It then checks if the Key and Text strings have a non-null (and non-empty) value and adds search terms to the db request as needed. However, is it possible to send in a null value for, for example, Key but still send in a value for Text? If so, what does the URL look like? (Admin.aspx/Search//0/Foo doesn't work :) ) I know I can handle this using a parameter array instead, but wondered if this was possible using the sort of route described? I could of course define some other value as equivalent to null (for example, a space/%20) but is there any way to send a null value in the URL? I'm suspecting not, but thought I'd see if anyone knew of one. I'm using ASP MVC 2 for this project.

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• The CLR has been unable to transition from COM context [...] for 60 seconds

  - by BlueRaja The Green Unicorn

  I am getting this error on code that used to work. I have not changed the code. Here is the full error: The CLR has been unable to transition from COM context 0x3322d98 to COM context 0x3322f08 for 60 seconds. The thread that owns the destination context/apartment is most likely either doing a non pumping wait or processing a very long running operation without pumping Windows messages. This situation generally has a negative performance impact and may even lead to the application becoming non responsive or memory usage accumulating continually over time. To avoid this problem, all single threaded apartment (STA) threads should use pumping wait primitives (such as CoWaitForMultipleHandles) and routinely pump messages during long running operations. And here is the code that caused it: var openFileDialog1 = new System.Windows.Forms.OpenFileDialog(); openFileDialog1.DefaultExt = "mdb"; openFileDialog1.Filter = "Management Database (manage.mdb)|manage.mdb"; //Stalls indefinitely on the following line, then gives the CLR error //one minute later. The dialog never opens. if(openFileDialog1.ShowDialog() == DialogResult.OK) { .... } Yes, I am sure the dialog is not open in the background, and no, I don't have any explicit COM code or unmanaged marshalling or multithreading. I have no idea why the OpenFileDialog won't open - any ideas?

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• Beginner problem / error with ansi-c and gcc under ubuntu.

  - by Framester

  Hi, I am just starting programming ansi c with gcc under ubuntu (9.04). I get following error messages: error messages: main.c:6: error: expected identifier or ‘(’ before ‘/’ token In file included from /usr/include/stdio.h:75, from main.c:9: /usr/include/libio.h:332: error: expected specifier-qualifier-list before ‘size_t’ /usr/include/libio.h:364: error: expected declaration specifiers or ‘...’ before ‘size_t’ /usr/include/libio.h:373: error: expected declaration specifiers or ‘...’ before ‘size_t’ /usr/include/libio.h:493: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’ before ‘_IO_sgetn’ In file included from main.c:9: /usr/include/stdio.h:314: error: expected declaration specifiers or ‘...’ before ‘size_t’ /usr/include/stdio.h:682: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’ before ‘fread’ /usr/include/stdio.h:688: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’ before ‘fwrite’ main.c:12: error: expected identifier or ‘(’ before ‘/’ token I assume it is a very simple problem, maybe in the configuration of ubuntu or gcc. I am new to programming under linux as well. I googled for help and went through a tutorial but could not find an answer. Thank you! code: #include <stdio.h> #include <math.h> int main() { printf("TestOutput\n"); return (0); } command: ~/Documents/projects/Trials$ gcc -Wall -ansi main.c

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• movieClip in Array displays null, and aren't showing up on stage.addChild(Array[i])

  - by jtdino

  i am new to Actionscript3, i need to know why i keep getting Parameter child must be non-null. And my code won't display 5 enemyBlock objects onto the stage but only just one. any tips and help will be much appreciated. thanks in advance. returns: TypeError: Error #2007: Parameter child must be non-null. at flash.display::DisplayObjectContainer/addChild() at flash.display::Stage/addChild() at BlockDrop_fla::MainTimeline/EnemyBlockPos() at BlockDrop_fla::MainTimeline/frame2() // declare varibles var isEnemyMoving:Boolean = false; var enemyArray:Array; var enemyBlock:MovieClip = new EnemyBlock(); // assign EnemyBlock class to enemyBlock var enemyBlockMC:MovieClip; var count:int = 5; var mapWidth:Number = 800; var mapHeight:Number = 600; function EnemyBlockPos() :void { // assign new MovieClip not null enemyBlockMC = new MovieClip; enemyArray = new Array(); for(var i=1; i<= count; i++){ // add class to MC enemyBlockMC.addChild(enemyBlock); // randomize position enemyBlock.x = Math.round(Math.random()*mapWidth); enemyBlock.y = Math.round(Math.random()*mapHeight); // set motion enemyBlock.movement = 5; // add MC to array enemyArray.push(enemyBlockMC); } for (var w = 1; w <= enemyArray.length; w++) { addChild(enemyArray[w]); } } // endOf EnemyBlockPos

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• C++: parsing with simple regular expression or shoud I use sscanf?

  - by Helltone

  I need to parse a string like func1(arg1, arg2); func2(arg3, arg4);. It's not a very complex parsing problem, so I would prefer to avoid resorting to flex/bison or similar utilities. My first approch was to try to use POSIX C regcomp/regexec or Boost implementation of C++ std::regex. I wrote the following regular expression, which does not work (I'll explain why further on). "^" "[ ;\t\n]*" "(" // (1) identifier "[a-zA-Z_][a-zA-Z0-9_]*" ")" "[ \t\n]*" "(" // (2) non-marking "\[" "(" // (3) non-marking "[ \t]*" "(" // (4..n-1) argument "[a-zA-Z0-9_]+" ")" "[ \t\n]*" "," ")*" "[ \t\n]*" "(" // (n) last argument "[a-zA-Z0-9_]+" ")" "]" ")?" "[ \t\n]*" ";" Note that the group 1 captures the identifier and groups 4..n-1 are intended to capture arguments except the last, which is captured by group n. When I apply this regex to, say func(arg1, arg2, arg3) the result I get is an array {func, arg2, arg3}. This is wrong because arg1 is not in it! The problem is that in the standard regex libraries, submarkings only capture the last match. In other words, if you have for instance the regex "((a*|b*))*" applied on "babb", the results of the inner match will be bb and all previous captures will have been forgotten. Another thing that annoys me here is that in case of error there is no way to know which character was not recognized as these functions provide very little information about the state of the parser when the input is rejected. So I don't know if I'm missing something here... In this case should I use sscanf or similar instead? Note that I prefer to use C/C++ standard libraries (and maybe boost).

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• javascript, php, cookies

  - by kennedy

  When i declare mac = 123, my internet explorer and firefox will keep refresh non-stop. And if i declare mac = getMacAddress it returns a value 1... I'm able to do a document.write(getMacAddress()) and it would able to display the mac address nicely. 1) Why my explorer will keep refreshing non-stop when i code it manually with "123" 2) why is the document.write able to display out, and when i store it to the cookie, somehow it didnt mange to capture into the cookie and it return a value of "1". Anyone help? create_users.php <script language="JavaScript"> function getMacAddress(){ document.macaddressapplet.setSep( "-" ); return (document.macaddressapplet.getMacAddress()); } function setCookie(c_name,value) { document.cookie = c_name + "=" +escape(value); } //error checking //var mac = getMacAddress(); var mac = "123"; setCookie('cookie_name',mac); window.location = "checkAvailability.php"; </script> checkAvailability.php $javascript_cookie_value = isset($_COOKIE["cookie_name"]) ? $_COOKIE["cookie_name"] : 1; mysql_query("INSERT INTO test (mac) VALUES ('$javascript_cookie_value')");

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• asyncore callbacks launching threads... ok to do?

  - by sbartell

  I'm unfamiliar with asyncore, and have very limited knowledge of asynchronous programming except for a few intro to twisted tutorials. I am most familiar with threads and use them in all my apps. One particular app uses a couchdb database as its interface. This involves longpolling the db looking for changes and updates. The module I use for couchdb is couchdbkit. It uses an asyncore loop to watch for these changes and send them to a callback. So, I figure from this callback is where I launch my worker threads. It seems a bit crude to mix asynchronous and threaded programming. I really like couchdbkit, but would rather not introduce issues into my program. So, my question is, is it safe to fire threads from an async callback? Here's some code... {{{ def dispatch(change): global jobs, db_url # jobs is my queue db = Database(db_url) work_order = db.get(change['id']) # change is an id to the document that changed. # i need to get the actual document (workorder) worker = Worker(work_order, db) # fire the thread jobs.append[worker] worker.start() return main() . . . consumer.wait(cb=dispatch, since=update_seq, timeout=10000) #wait constains the asyncloop. }}}

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• Sending files using Winsock - optimal send() data length?

  - by Meta

  I am using Winsock with non-blocking sockets to send a file to a client. The way I'm doing it right now is that I read a chunk of 8192 bytes from the file, and then loop until all of it successfully goes through send() (obviously handling WSAEWOULDBLOCK as it occurs). I then move on and read the next 8192 bytes, and so on... Although I can use any other number than 8192 when I test the transfer on my local machine, once I try it over a network, it seems like 8191 is the largest number I can use. When I try to use any number higher than 8191 (starting with 8192), the file transfer becomes extremely slow (about 5 times slower). Is there any reason why 8191 is so special? I've done some more testing and it turns out that using 8000 is slightly faster (by 0.5%). If you understand why 8191 is so special, can you tell me if there is a number better than the others (better than 8000)? I have a feeling that it has something to do with the fact that the default send buffer allocated to the socket by Winsock is 8KB, but I don't understand why. It might also have something to do with the Nagle algorithm, but again, I'm not sure how. Note that I have not modified the SO_SNDBUF option nor the TCP_NODELAY option. Or am I doing this all wrong? What's the best way of sending a file over a non-blocking socket?

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• Simple encryption - Sum of Hashes in C

  - by Dogbert

  I am attempting to demonstrate a simple proof of concept with respect to a vulnerability in a piece of code in a game written in C. Let's say that we want to validate a character login. The login is handled by the user choosing n items, (let's just assume n=5 for now) from a graphical menu. The items are all medieval themed: eg: _______________________________ | | | | | Bow | Sword | Staff | |-----------|-----------|-------| | Shield | Potion | Gold | |___________|___________|_______| The user must click on each item, then choose a number for each item. The validation algorithm then does the following: Determines which items were selected Drops each string to lowercase (ie: Bow becomes bow, etc) Calculates a simple string hash for each string (ie: `bow = b=2, o=15, w=23, sum = (2+15+23=40) Multiplies the hash by the value the user selected for the corresponding item; This new value is called the key Sums together the keys for each of the selected items; this is the final validation hash IMPORTANT: The validator will accept this hash, along with non-zero multiples of it (ie: if the final hash equals 1111, then 2222, 3333, 8888, etc are also valid). So, for example, let's say I select: Bow (1) Sword (2) Staff (10) Shield (1) Potion (6) The algorithm drops each of these strings to lowercase, calculates their string hashes, multiplies that hash by the number selected for each string, then sums these keys together. eg: Final_Validation_Hash = 1*HASH(Bow) + 2*HASH(Sword) + 10*HASH(Staff) + 1*HASH(Shield) + 6*HASH(Potion) By application of Euler's Method, I plan to demonstrate that these hashes are not unique, and want to devise a simple application to prove it. in my case, for 5 items, I would essentially be trying to calculate: (B)(y) = (A_1)(x_1) + (A_2)(x_2) + (A_3)(x_3) + (A_4)(x_4) + (A_5)(x_5) Where: B is arbitrary A_j are the selected coefficients/values for each string/category x_j are the hash values for each string/category y is the final validation hash (eg: 1111 above) B,y,A_j,x_j are all discrete-valued, positive, and non-zero (ie: natural numbers) Can someone either assist me in solving this problem or point me to a similar example (ie: code, worked out equations, etc)? I just need to solve the final step (ie: (B)(Y) = ...). Thank you all in advance.

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• Joining Tables Based on Foreign Keys

  - by maestrojed

  I have a table that has a lot of fields that are foreign keys referencing a related table. I am writing a script in PHP that will do the db queries. When I query this table for its data I need to know the values associated with these keys not the key. How do most people go about this? A 101 way to do this would be to query this table for its data including the foreign keys and then query the related tables to get each key's value. This could be a lot of queries (~10). Question 1: I think I could write 1 query with a bunch of joins. Would that be better? This approach also requires the querying script to know which table fields are foreign keys. Since I have many tables like this but all with different fields, this means writing nice generic functions is hard. MySQL InnoDB tables allow for foreign constraints. I know the database has these set up correctly. Question 2: What about the idea of querying the table and identifying what the constraints are and then matching them up using whatever process I decide on from Question 1. I like this idea but never see it being used in code. Makes me think its not a good idea for some reason. I would use something like SHOW CREATE TABLE tbl_name; to find what constraints/relationships exist for that table. Thank you for any suggestions or advice.

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• IF-block brackets: best practice

  - by MasterPeter

  I am preparing a short tutorial for level 1 uni students learning JavaScript basics. The task is to validate a phone number. The number must not contain non-digits and must be 14 digits long or less. The following code excerpt is what I came up with and I would like to make it as readable as possible. if ( //set of rules for invalid phone number phoneNumber.length == 0 //empty || phoneNumber.length > 14 //too long || /\D/.test(phoneNumber) //contains non-digits ) { setMessageText(invalid); } else { setMessageText(valid); } A simple question I can not quite answer myself and would like to hear your opinions on: How to position the surrounding (outermost) brackets? It's hard to see the difference between a normal and a curly bracket. Do you usually put the last ) on the same line as the last condition? Do you keep the first opening ( on a line by itself? Do you wrap each individual sub-condition in brackets too? Do you align horizontally the first ( with the last ), or do you place the last ) in the same column as the if? Do you keep ) { on a separate line or you place the last ) on the same line with the last sub-condition and then place the opening { on a new line? Or do you just put the ) { on the same line as the last sub-condition? Community wiki.

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• What are Code Smells? What is the best way to correct them?

  - by Rob Cooper

  OK, so I know what a code smell is, and the Wikipedia Article is pretty clear in its definition: In computer programming, code smell is any symptom in the source code of a computer program that indicates something may be wrong. It generally indicates that the code should be refactored or the overall design should be reexamined. The term appears to have been coined by Kent Beck on WardsWiki. Usage of the term increased after it was featured in Refactoring. Improving the Design of Existing Code. I know it also provides a list of common code smells. But I thought it would be great if we could get clear list of not only what code smells there are, but also how to correct them. Some Rules Now, this is going to be a little subjective in that there are differences to languages, programming style etc. So lets lay down some ground rules: ** ONE SMELL PER ANSWER PLEASE! & ADVISE ON HOW TO CORRECT! ** See this answer for a good display of what this thread should be! DO NOT downmod if a smell doesn't apply to your language or development methodology We are all different. DO NOT just quickly smash in as many as you can think of Think about the smells you want to list and get a good idea down on how to work around. DO downmod answers that just look rushed For example "dupe code - remove dupe code". Let's makes it useful (e.g. Duplicate Code - Refactor into separate methods or even classes, use these links for help on these common.. etc. etc.). DO upmod answers that you would add yourself If you wish to expand, then answer with your thoughts linking to the original answer (if it's detailed) or comment if its a minor point. DO format your answers! Help others to be able to read it, use code snippets, headings and markup to make key points stand out!

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• To what extent should code try to explain fatal exceptions?

  - by Andrzej Doyle

  I suspect that all non-trivial software is likely to experience situations where it hits an external problem it cannot work around and thus needs to fail. This might be due to bad configuration, an external server being down, disk full, etc. In these situations, especially if the software is running in non-interactive mode, I expect that all one can really do is log an error and wait for the admin to read the logs and fix the problem. If someone happens to interact with the software in the meantime, e.g. a request comes in to a server that failed to initialize properly, then perhaps an appropriate hint can be given to check the logs and maybe even the error can be echoed (depending on whether you can tell if they're a technical guy as opposed to a business user). For the moment though let's not think too hard about this part. My question is, to what extent should the software be responsible for trying to explain the meaning of the fatal error? In general, how much competence/knowledge are you allowed to presume on administrators of the software, and how much should you include troubleshooting information and potential resolution steps when logging fatal errors? Of course if there's something that's unique to the runtime context this should definitely be logged; but lets assume your software needs to talk to Active Directory via LDAP and gets back an error "[LDAP: error code 49 - 80090308: LdapErr: DSID-0C090334, comment: AcceptSecurityContext error, data 525, vece]". Is it reasonable to assume that the maintainers will be able to Google the error code and work out what it means, or should the software try to parse the error code and log that this is caused by an incorrect user DN in the LDAP config? I don't know if there is a definitive best-practices answer for this, so I'm keen to hear a variety of views.

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