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• Maintain List of Active Users for Web

  - by Bryan Marble

  Problem Statement - Would like to know if particular web app user is active (i.e. logged in and using site) and be able to query for list of active users or determine a user's activity status. Constraints - Doesn't need to be exact (i.e. if a user was active within a certain timeframe, that's ok to say that they're active even if they've closed their browser). I feel like there should be a design pattern for this type of problem but haven't been able to find anything here or elsewhere on the web. Approaches I'm considering: Maintain a table that is updated any time a user performs an action (or some subset of actions). Would then query for users that have performed an action within some threshold of time. Try to monitor session information and maintain a table that lists logged in users and times out after a certain period of time. Some other more standard way of doing this? How would you approach this problem (again, from a design pattern perspective)? Thanks!

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• Unable to get my webpage height in javascript?

  - by Rajesh Vaddepally

  I have a different problem , when user clicks on page and dragging to some location, then with that co-ordinates i should draw a rectangle div... But it working fine, when user doesn't scroll the window.. If he scroll the window. then he trying to creating a rectangle means ,then it is coming to upper positions.. how can i solve this problem.. i don't have much knowledge on javascript.. If i could not explain you in detail. feel free to ask me.. thanks Rajesh

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• Is there a faster alternative to using textures in XNA?

  - by Matthew Bowen

  I am writing a map editing program for a 2D game using XNA. To create a Texture2D for all of the tiles that a map requires takes too long. Are there any alternatives to using textures for drawing with XNA? I attempted to create just one texture per tile set instead of a texture for every tile in a tile set, but there is a limit to the size of textures and I could not fit all the tiles of a tile set into one texture. Currently the program contains all the would-be textures in memory as Bitmap objects. Is there a way to simply draw a Bitmap object to the screen in XNA? I have searched but I cannot find any information on this. This approach would avoid having to create textures altogether, however any tinting or effects I would have to do to the bitmap directly. Any help would be very much appreciated. Thanks

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• Are there any online database schema drawing tools?

  - by Pure.Krome

  Hi folks, i wish to draw up some database schemas. Eg, table 1 has zero to many rows in table 2, etc. It's purely for visual purposes (eg. no sql code, etc). Are there any online tools / website that offer this? (please don't say: Use Sql Server Database Diagrams, print screen, upload to image hosting service). thanks :) EDIT: Please take note of the keyword - ONLINE. I don't want any desktop solutions (because I already have one of these).

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• How can I use ToUnicode without breaking dead key support?

  - by Cypherjb

  A similar question has already been asked, so I'm not going to waste time re-explaining it, an existing discussion can be found here: http://stackoverflow.com/questions/1964614/toascii-tounicode-in-a-keyboard-hook-destroys-dead-keys The reason I'm posting a new question however is that I seem to have come across a 'solution', but I'm not quite sure how to implement it. This blog post seems to propose a solution to the problem of ToUnicode killing dead-key support: http://blogs.msdn.com/michkap/archive/2005/01/19/355870.aspx However I'm not sure how to implement the suggested solution. A push in the right direction would be greatly appreciated. To be clear, the part I'm referring to is this: "There are two ways to work around this: 1) You can keep calling ToUnicode with the same info until it is cleared out and then call it one more time to put the state back where it was if you had never typed anything, or 2) You can load all of the keyboard info ahead of time and then when they type information you can look up in your own info cache what the keystrokes mean, without having to call APIs later." I'm not quite sure how to do either of those things (keyboards and internationalization are far from my strong point), so any help would be greatly appreciated. Thanks

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• Monitor web sites visited using Internet Explorer, Opera, Chrome, Firefox and Safari in Python

  - by Zachary Brown

  I am working on a project for work and have seemed to run into a small problem. The project is a similar program to Web Nanny, but branded to my client's company. It will have features such as website blocking by URL, keyword and web activity logs. I would also need it to be able to "pause" downloads until an acceptable username and password is entered. I found a script to monitor the URL visited in Internet Explorer (shown below), but it seems to slow the browser down considerably. I have not found any support or ideas onhow to implement this in other browsers. So, my questions are: 1). How to I monitor other browser activity / visited URLs? 2). How do I prevent downloading unless an acceptable username and password is entered? from win32com.client import Dispatch,WithEvents import time,threading,pythoncom,sys stopEvent=threading.Event() class EventSink(object): def OnNavigateComplete2(self,*args): print "complete",args stopEvent.set() def waitUntilReady(ie): if ie.ReadyState!=4: while 1: print "waiting" pythoncom.PumpWaitingMessages() stopEvent.wait(.2) if stopEvent.isSet() or ie.ReadyState==4: stopEvent.clear() break; time.clock() ie=Dispatch('InternetExplorer.Application',EventSink) ev=WithEvents(ie,EventSink) ie.Visible=1 ie.Navigate("http://www.google.com") waitUntilReady(ie) print "location",ie.LocationName ie.Navigate("http://www.aol.com") waitUntilReady(ie) print "location",ie.LocationName print ie.LocationName,time.clock() print ie.ReadyState

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• Invert a string: Recursion vs iteration in javascript

  - by steweb

  Hi all, one month ago I've been interviewed by some google PTO members. One of the questions was: Invert a string recursively in js and explain the running time by big O notation this was my solution: function invert(s){ return (s.length > 1) ? s.charAt(s.length-1)+invert(s.substring(0,s.length-1)) : s; } Pretty simple, I think. And, about the big-o notation, I quickly answered O(n) as the running time depends linearly on the input. - Silence - and then, he asked me, what are the differences in terms of running time if you implement it by iteration? I replied that sometimes the compiler "translate" the recursion into iteration (some programming language course memories) so there are no differences about iteration and recursion in this case. Btw since I had no feedback about this particular question, and the interviewer didn't answer "ok" or "nope", I'd like to know if you maybe agree with me or if you can explain me whether there could be differences about the 2 kind of implementations. Thanks a lot and Regards!

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• Creating a Box Control over an area of the map with OpenLayers

  - by Bernie Perez

  I am using OpenLayers to create a box of interest with my program. I am using this code: var control = new OpenLayers.Control(); OpenLayers.Util.extend(control, { draw: function () { this.box = new OpenLayers.Handler.Box( control, {"done": this.notice}, {keyMask: OpenLayers.Handler.MOD_SHIFT}); this.box.activate(); }, notice: function (bounds) { areaSelected(bounds); } }); map.addControl(control); to capture the "Shift Create a Box" control and use the area selected as my area of interest. However the values come back as pixels. But I want Longitude and Latitude, not pixels. The Mouse Position control does show the correct long & lat. I really don't care how to box is created, I just want an easy way for the user to select a area of the map and I need to get the lat & longs of the area. (Box, Circle, doesn't matter)

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• How do I remove those rotation artefacts from my CATiledLayer?

  - by Felix

  Hello all, I have a CATiledLayer into which I render content in the following method - (void)drawLayer:(CALayer *)layer inContext:(CGContextRef)ctx I used the QuartzDemo code to draw a pattern. This works very well until I apply a rotation transform to the layer's parentLayer (a UIView): rotated: These zigzag artefacts become worse when I start drawing lines and texts into the CATiledLayer. I applied the transform as follows (I also tried using an affine transform on the view itself): self.containerView.layer.transform = CATransform3DMakeRotation(angleRadians, 0.0f, 0.0f, 1.0f); I transform the containerView rather than the layer itself, as I have several layers in that view that I would like to rotate at the same time without changing the relative positions. I did not have problems when rotating UIImageViews in the past. Is there a way that I can rotate the CATiledLayer without these problems? Any help would be greatly appreciated. Yours, Felix

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• Get percentiles of data-set with group by month

  - by Cylindric

  Hello, I have a SQL table with a whole load of records that look like this: | Date | Score | + -----------+-------+ | 01/01/2010 | 4 | | 02/01/2010 | 6 | | 03/01/2010 | 10 | ... | 16/03/2010 | 2 | I'm plotting this on a chart, so I get a nice line across the graph indicating score-over-time. Lovely. Now, what I need to do is include the average score on the chart, so we can see how that changes over time, so I can simply add this to the mix: SELECT YEAR(SCOREDATE) 'Year', MONTH(SCOREDATE) 'Month', MIN(SCORE) MinScore, AVG(SCORE) AverageScore, MAX(SCORE) MaxScore FROM SCORES GROUP BY YEAR(SCOREDATE), MONTH(SCOREDATE) ORDER BY YEAR(SCOREDATE), MONTH(SCOREDATE) That's no problem so far. The problem is, how can I easily calculate the percentiles at each time-period? I'm not sure that's the correct phrase. What I need in total is: A line on the chart for the score (easy) A line on the chart for the average (easy) A line on the chart showing the band that 95% of the scores occupy (stumped) It's the third one that I don't get. I need to calculate the 5% percentile figures, which I can do singly: SELECT MAX(SubQ.SCORE) FROM (SELECT TOP 45 PERCENT SCORE FROM SCORES WHERE YEAR(SCOREDATE) = 2010 AND MONTH(SCOREDATE) = 1 ORDER BY SCORE ASC) AS SubQ SELECT MIN(SubQ.SCORE) FROM (SELECT TOP 45 PERCENT SCORE FROM SCORES WHERE YEAR(SCOREDATE) = 2010 AND MONTH(SCOREDATE) = 1 ORDER BY SCORE DESC) AS SubQ But I can't work out how to get a table of all the months. | Date | Average | 45% | 55% | + -----------+---------+-----+-----+ | 01/01/2010 | 13 | 11 | 15 | | 02/01/2010 | 10 | 8 | 12 | | 03/01/2010 | 5 | 4 | 10 | ... | 16/03/2010 | 7 | 7 | 9 | At the moment I'm going to have to load this lot up into my app, and calculate the figures myself. Or run a larger number of individual queries and collate the results.

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• Actionscript 3 Sprite AddChild

  - by Amy

  Im new to actionscript 3 and am a little confused about how the addchild function works. I want to draw 5 houses. each house has a roof and wall. Each wall has a door and a window. I have the following classes and this is how I grouped them class Main class House class Roof //a triangle class Wall //a rectangle class Door //a rectangle class Window //a square Im having trouble with inheritance of the classes. I cant made the wall class show up with a window and a door. Can someone point me to the right direction?

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• Escaping single quote in PHP when inserting into MySQL

  - by hairdresser-101

  I have a perplexing issue that I can't seem to comprehend... I'm hoping someone here might be able to point me in the right direction... I have two SQL statements: - the first enters information from a form into the database. - the second takes data from the database entered above, sends an email and then logs the details of the transaction The problem is that it a appears that a single quote is triggering a MySQL error on the second entry only!!! The first instance works without issue but the second instance triggers the mysql_error(). Does the data from a form get handled differently from the data captured in a form? Query#1 - This works without issue (and without escaping the single quote) $result = mysql_query("INSERT INTO job_log (order_id, supplier_id, category_id, service_id, qty_ordered, customer_id, user_id, salesperson_ref, booking_ref, booking_name, address, suburb, postcode, state_id, region_id, email, phone, phone2, mobile, delivery_date, stock_taken, special_instructions, cost_price, cost_price_gst, sell_price, sell_price_gst, ext_sell_price, retail_customer, created, modified, log_status_id) VALUES ('$order_id', '$supplier_id', '$category_id', '{$value['id']}', '{$value['qty']}', '$customer_id', '$user_id', '$salesperson_ref', '$booking_ref', '$booking_name', '$address', '$suburb', '$postcode', '$state_id', '$region_id', '$email', '$phone', '$phone2', '$mobile', STR_TO_DATE('$delivery_date', '%d/%m/%Y'), '$stock_taken', '$special_instructions', '$cost_price', '$cost_price_gst', '$sell_price', '$sell_price_gst', '$ext_sell_price', '$retail_customer', '".date('Y-m-d H:i:s', time())."', '".date('Y-m-d H:i:s', time())."', '1')"); Query#2 - This fails when entering a name with a single quote (i.e. O'Brien) $query = mysql_query("INSERT INTO message_log (order_id, timestamp, message_type, email_from, supplier_id, primary_contact, secondary_contact, subject, message_content, status) VALUES ('$order_id', '".date('Y-m-d H:i:s', time())."', '$email', '$from', '$row->supplier_id', '$row->primary_email' ,'$row->secondary_email', '$subject', '$message_content', '1')");

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• Escaping single quote in PHP when inserting into MySQL

  - by hairdresser-101

  PLEASE NOTE: I am reposting as the original was not answered correctly... I AM LOOKING FOR THE WHY - NOT THE SOLUTION - I KNOW THE SOLUTION, WHAT I DON'T UNDERSTAND IS THE WHY! I have a perplexing issue that I can't seem to comprehend... I'm hoping someone here might be able to point me in the right direction... I have two SQL statements: - the first enters information from a form into the database. - the second takes data from the database entered above, sends an email and then logs the details of the transaction The problem is that it a appears that a single quote is triggering a MySQL error on the second entry only!!! The first instance works without issue but the second instance triggers the mysql_error(). Does the data from a form get handled differently from the data captured in a form? Query#1 - This works without issue (and without escaping the single quote) $result = mysql_query("INSERT INTO job_log (order_id, supplier_id, category_id, service_id, qty_ordered, customer_id, user_id, salesperson_ref, booking_ref, booking_name, address, suburb, postcode, state_id, region_id, email, phone, phone2, mobile, delivery_date, stock_taken, special_instructions, cost_price, cost_price_gst, sell_price, sell_price_gst, ext_sell_price, retail_customer, created, modified, log_status_id) VALUES ('$order_id', '$supplier_id', '$category_id', '{$value['id']}', '{$value['qty']}', '$customer_id', '$user_id', '$salesperson_ref', '$booking_ref', '$booking_name', '$address', '$suburb', '$postcode', '$state_id', '$region_id', '$email', '$phone', '$phone2', '$mobile', STR_TO_DATE('$delivery_date', '%d/%m/%Y'), '$stock_taken', '$special_instructions', '$cost_price', '$cost_price_gst', '$sell_price', '$sell_price_gst', '$ext_sell_price', '$retail_customer', '".date('Y-m-d H:i:s', time())."', '".date('Y-m-d H:i:s', time())."', '1')"); Query#2 - This fails when entering a name with a single quote (i.e. O'Brien) $query = mysql_query("INSERT INTO message_log (order_id, timestamp, message_type, email_from, supplier_id, primary_contact, secondary_contact, subject, message_content, status) VALUES ('$order_id', '".date('Y-m-d H:i:s', time())."', '$email', '$from', '$row->supplier_id', '$row->primary_email' ,'$row->secondary_email', '$subject', '$message_content', '1')");

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• Google App Engine - Caching generated HTML

  - by Alexander

  I have written a Google App Engine application that programatically generates a bunch of HTML code that is really the same output for each user who logs into my system, and I know that this is going to be in-efficient when the code goes into production. So, I am trying to figure out the best way to cache the generated pages. The most probable option is to generate the pages and write them into the database, and then check the time of the database put operation for a given page against the time that the code was last updated. Then, if the code is newer than the last put to the database (for a particular HTML request), new HTML will be generated and served, and cached to the database. If the code is older than the last put to the database, then I will just get the HTML direct from the database and serve it (therefore avoiding all the CPU wastage of generating the HTML). I am not only looking to minimize load times, but to minimize CPU usage. However, one issue that I am having is that I can't figure out how to programatically check when the version of code uploaded to the app engine was updated. I am open to any suggestions on this approach, or other approaches for caching generated html. Note that while memcache could help in this situation, I believe that it is not the final solution since I really only need to re-generate html when the code is updated (as opposed to every time the memcache expires). Kind Regards, and thank you in advance for any suggestions you may be able to offer. -Alex

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• R: disentangling scopes

  - by rescdsk

  Hi, Right now, in my R project, I have functions1.R with doFoo() and doBar(), functions2.R with other functions, and main.R with the main program in it, which first does source('functions1.R'); source('functions2.R'), and then calls the other functions. I've been starting the program from the R GUI in Mac OS X, with source('main.R'). This is fine the first time, but after that, the variables that were defined the first time through the program are defined for the second time functions*.R are sourced, and so the functions get a whole bunch of extra variables defined. I don't want that! I want an "undefined variable" error when my function uses a variable it shouldn't! Twice this has given me very late nights of debugging! So how do other people deal with this sort of problem? Is there something like source(), but that makes an independent namespace that doesn't fall through to the main one? Making a package seems like one solution, but it seems like a big pain in the butt compared to e.g. Python, where a source file is automatically a separate namespace. Any tips? Thank you!

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• Android back button does not restart activity?

  - by Chris

  My app intiates an activity. On the click of a button, the app opens up the browser with a webpage. When I hit the back button, it comes back to my initial activity screen, but does not resume or restart the activity. When I put all the layout code and activity code in onResume instead of onCreate, the activity gets restarted. My question is whether this is the right way to go about it? Can I use onResume to draw my layout and initiate the activity, or is this poor design? When the browser fires up, does the initial activity forget its layout? Please let me know what you suggest. Thanks Chris

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• silverlight 3: long running wcf call triggers 401.1 (access denied)

  - by sympatric greg

  I have a wcf service consumed by a silverlight 3 control. The Silverlight client uses a basicHttpBindinging that is constructed at runtime from the control's initialization parameters like this: public static T GetServiceClient<T>(string serviceURL) { BasicHttpBinding binding = new BasicHttpBinding(Application.Current.Host.Source.Scheme.Equals("https", StringComparison.InvariantCultureIgnoreCase) ? BasicHttpSecurityMode.Transport : BasicHttpSecurityMode.None); binding.MaxReceivedMessageSize = int.MaxValue; binding.MaxBufferSize = int.MaxValue; binding.Security.Mode = BasicHttpSecurityMode.TransportCredentialOnly; return (T)Activator.CreateInstance(typeof(T), new object[] { binding, new EndpointAddress(serviceURL)}); } The Service implements windows security. Calls were returning as expected until the result set increased to several thousand rows at which time HTTP 401.1 errors were received. The Service's HttpBinding defines closeTime, openTimeout, receiveTimeout and sendTimeOut of 10 minutes. If I limit the size of the resultset the call suceeds. Additional Observations from Fiddler: When Method2 is modified to return a smaller resultset (and avoid the problem), control initialization consists of 4 calls: Service1/Method1 -- result:401 Service1/Method1 -- result:401 (this time header includes element "Authorization: Negotiate TlRMTV..." Service1/Method1 -- result:200 Service1/Method2 -- result:200 (1.25 seconds) When Method2 is configured to return the larger resultset we get: Service1/Method1 -- result:401 Service1/Method1 -- result:401 (this time header includes element "Authorization: Negotiate TlRMTV..." Service1/Method1 -- result:200 Service1/Method2 -- result:401.1 (7.5 seconds) Service1/Method2 -- result:401.1 (15ms) Service1/Method2 -- result:401.1 (7.5 seconds)

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• Window 'onscreen' size puzzle

  - by Bender

  Okay, a REALLY fundamental question about window sizes here... If I create an NSWindow in IB, set its size to 216 x 144 points (exactly 3 inches by 2 inches) then print the window, it measures exactly what I set it to in IB. However, the onscreen display size measures approximately 156 x 105 points. What causes this, and is there any way to force the window to display at the required size onscreen? I ultimately want to draw to this (semi-transparent) window then use it as a full-sized overlay for comparison against a separately loaded scanned image of known size.

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• Drawing star shapes with variable parameters

  - by owca

  Hi. I have task to write program allowing users to draw stars, which can differ in size and amount of arms. When I was dealing with basic stars I was doing it with GeneralPath and tables of points : int xPoints[] = { 55, 67, 109, 73, 83, 55, 27, 37, 1, 43 }; int yPoints[] = { 0, 36, 36, 54, 96, 72, 96, 54, 36, 36 }; Graphics2D g2d = ( Graphics2D ) g; GeneralPath star = new GeneralPath(); star.moveTo( xPoints[ 0 ], yPoints[ 0 ] ); for ( int k = 1; k < xPoints.length; k++ ) star.lineTo( xPoints[ k ], yPoints[ k ] ); star.closePath(); g2d.fill( star ); What method should I choose for drawing stars with variable inner and outer radius, as well as different amount of arms ? This is what I should obtain :

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• how random is Math.random() in java across different jvms or different machines

  - by user881480

  I have a large distributed program across many different physical servers, each program spawns many threads, each thread use Math.random() in its operations to draw a piece from many common resource pools. The goal is to utilize the pools evenly across all operations. Sometimes, it doesn't appear so random by looking at a snapshot on a resource pool to see which pieces it's getting at that instant (it might actually be, but it's hard to measure and find out for sure). Is there something that's better than Math.random() and performs just as good (not much worse at least)?

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• Faster way to iterate through a jagged array?

  - by George Johnston

  I would like to iterate through an array that covers every pixel on my screen. i.e: for (int y = 598; y > 0; y--) { for (int x = 798; x > 0; x--) { if (grains[x][y]) { spriteBatch.Draw(Grain, new Vector2(x,y), Color.White); } } } ...my texture is a 1x1 pixel image that is drawn to the screen when the array value is true. It runs decent -- but there is definitely lag the more screen I cover. Is there a better way to accomplish what I am trying to achieve?

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• How to update the contents of a FigureCanvasTkAgg

  - by Copo

  I'm plotting some data in a Tkinter FigureCanvasTkagg using matplotlib. I need to clear the figure where i plot data and draw new data when a button is pressed. here is the plotting part of the code (there's an App class defined before..) self.fig = figure() self.ax = self.fig.add_subplot(111) self.ax.set_ylim( min(y), max(y) ) self.line, = self.ax.semilogx(x,y,'.-') #tuple of a single element self.canvas = FigureCanvasTkAgg(self.fig,master=master) self.ax.semilogx(x,y,'o-') self.canvas.show() self.canvas.get_tk_widget().pack(side='top', fill='both', expand=1) self.frame.pack() how do i update the contents of such a canvas? regards, Jacopo

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• Avoiding GC thrashing with WSE 3.0 MTOM service

  - by Leon Breedt

  For historical reasons, I have some WSE 3.0 web services that I cannot upgrade to WCF on the server side yet (it is also a substantial amount of work to do so). These web services are being used for file transfers from client to server, using MTOM encoding. This can also not be changed in the short term, for reasons of compatibility. Secondly, they are being called from both Java and .NET, and therefore need to be cross-platform, hence MTOM. How it works is that an "upload" WebMethod is called by the client, sending up a chunk of data at a time, since files being transferred could potentially be gigabytes in size. However, due to not being able to control parts of the stack before the WebMethod is invoked, I cannot control the memory usage patterns of the web service. The problem I am running into is for file sizes from 50MB or so onwards, performance is absolutely killed because of GC, since it appears that WSE 3.0 buffers each chunk received from the client in a new byte[] array, and by the time we've done 50MB we're spending 20-30% of time doing GC. I've played with various chunk sizes, from 16k to 2MB, with no real great difference in results. Smaller chunks are killed by the latency involved with round-tripping, and larger chunks just postpone the slowdown until GC kicks in. Any bright ideas on cutting down on the garbage created by WSE? Can I plug into the pipeline somehow and jury-rig something that has access to the client's request stream and streams it to the WebMethod? I'm aware that it is possible to "stream" responses to the client using WSE (albeit very ugly), but this problem is with requests from the client.

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• Simple ASP.NET MVC views without writing a controller

  - by Jake Stevenson

  We're building a site that will have very minimal code, it's mostly just going to be a bunch of static pages served up. I know over time that will change and we'll want to swap in more dynamic information, so I've decided to go ahead and build a web application using ASP.NET MVC2 and the Spark view engine. There will be a couple of controllers that will have to do actual work (like in the /products area), but most of it will be static. I want my designer to be able to build and modify the site without having to ask me to write a new controller or route every time they decide to add or move a page. So if he wants to add a "http://mysite.com/News" page he can just create a "News" folder under Views and put an index.spark page within it. Then later if he decides he wants a /News/Community page, he can drop a community.spark file within that folder and have it work. I'm able to have a view without a specific action by making my controllers override HandleUnknownAction, but I still have to create a controller for each of these folders. It seems silly to have to add an empty controller and recompile every time they decide to add an area to the site. Is there any way to make this easier, so I only have to write a controller and recompile if there's actual logic to be done? Some sort of "master" controller that will handle any requests where there was no specific controller defined?

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• Linear feedback shift register?

  - by Mattia Gobbi

  Lately I bumped repeatedly into the concept of LFSR, that I find quite interesting because of its links with different fields and also fascinating in itself. It took me some effort to understand, the final help was this really good page, much better than the (at first) cryptic wikipedia entry. So I wanted to write some small code for a program that worked like a LFSR. To be more precise, that somehow showed how a LFSR works. Here's the cleanest thing I could come up with after some lenghtier attempts (Python): def lfsr(seed, taps): sr, xor = seed, 0 while 1: for t in taps: xor += int(sr[t-1]) if xor%2 == 0.0: xor = 0 else: xor = 1 print xor sr, xor = str(xor) + sr[:-1], 0 print sr if sr == seed: break lfsr('11001001', (8,7,6,1)) #example I named "xor" the output of the XOR function, not very correct. However, this is just meant to show how it circles through its possible states, in fact you noticed the register is represented by a string. Not much logical coherence. This can be easily turned into a nice toy you can watch for hours (at least I could :-) def lfsr(seed, taps): import time sr, xor = seed, 0 while 1: for t in taps: xor += int(sr[t-1]) if xor%2 == 0.0: xor = 0 else: xor = 1 print xor print time.sleep(0.75) sr, xor = str(xor) + sr[:-1], 0 print sr print time.sleep(0.75) Then it struck me, what use is this in writing software? I heard it can generate random numbers; is it true? how? So, it would be nice if someone could: explain how to use such a device in software development come up with some code, to support the point above or just like mine to show different ways to do it, in any language Also, as theres not much didactic stuff around about this piece of logic and digital circuitry, it would be nice if this could be a place for noobies (like me) to get a better understanding of this thing, or better, to understand what it is and how it can be useful when writing software. Should have made it a community wiki? That said, if someone feels like golfing... you're welcome.

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