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• Feasibility of using Silverlight for web and windows client with common code base for data intensive

  - by Kabeer

  Hello. Recently in a conversation, someone suggested me to make use of Silverlight if I am targeting a web client and a windows client for the same application. This will cut down my effort for supporting the contrast in both presentation layers. Mine is a product, that will be deployed in enterprises. Both web and windows clients are desirable. With the above context, I have few queries: Is it advisable to adopt the recommended approach and whether this approach is becoming a trend? Besides, some configuration & deployment tweaking, will this significantly reduce effort on the presentation layer? Is there a possibility that my future prospects (for this product) will resist Silverlight footprint? Will I be able to make use of the ASP.Net MVC pattern? Will there be any performance implication for the web client? Will Silverlight support incremental load of controls? If my back-end includes SSRS, will I be able to harness all its front end features with Silverlight? Will I be able to support additional devices with same code base in future? Mine is a very data intensive application from both, data entry and reporting perspective. Is it advisable to use 3rd party controls (like Telerik) for improved user experience and developer productivity? Are their any professional quality open source Silverlight controls (library) available? Further, I seek information of best practices in the context I shared above.

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• What is the fastest way to pull a few element values out of XML files in Perl?

  - by Anon Guy

  I have a bunch of XML files that are about 1-2 megabytes in size. Actually, more than a bunch, there are millions. They're all well-formed and many are even validated against their schema (confirmed with libxml2). All were created by the same app, so they're in a consistent format (though this could theoretically change in the future). I want to check the values of one element in each file from within a Perl script. Speed is important (I'd like to take less than a second per file) and as noted I already know the files are well-formed. I am sorely tempted to simply 'open' the files in Perl and scan through until I see the element I am looking for, grab the value (which is near the start of the file), and close the file. On the other hand, I could use an XML parser (which might protect me from future changes to the XML formatting) but I suspect it will be slower than I'd like. Can anyone recommend an appropriate approach and/or parser? Thanks in advance.

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• PostgreSQL: Auto-partition a table

  - by Adam Matan

  Hi, I have a huge database which holds pairs of numbers (A,B), each ranging from 0 to 10,000 and stored as floats. e.g., (1, 9984.4), (2143.44, 124.243), (0.55, 0), ... Since the PostgreSQL table which stores these pairs grew quite large, I have decided to partition it into inheriting sub-tables. I intend to create 100 such tables, each storing a range of 1000x1000. The problem is that these numbers tend to come in large chunks of nearby numbers. It means that in the future, some tables will be nearly empty and some will hold a very large portion of the database. Unfortunately, the distribution of future pairs is yet unknown. I am looking for a way to automatically repartition my table. That means that if a certain subtable holds more than a specific number of pairs, it will be automatically partitioned into four sub-sub tables, and so on. My questions are: Is recursive partitioning and inheritance possible in PostgreSQL 8.3? Will indexes and query plans understand it? What's the best way to split a subtable once it grew too large? I should point out that this isn't a live database, so a downtime of few hours every week is totally acceptable. Thanks in advance, Adam

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• Hopping from a C++ to a Perl/Unix job

  - by rocknroll

  Hi all, I have been a C++ / Linux Developer till now and I am adept in this stack. Of late I have been getting opportunities that require Perl, Unix (with knowledge of C++,shell scripting) expertise. Organizations are showing interest even though I don't have much scripting experience to boast off. The role is more in a Support, maintenance project involving SQL as well. Off late I am in a fix whether to forgo these offers or not. I don't know the dynamics of an IT organization and thus on one hand I fear that my C++ experience will be nullified and on the positive side I am getting to work on a new technology stack which will only add to my skill set. I am sure, most of you at some point of time have encountered such dilemmas and would have taken some decision. I want you to share your perspectives on such a scenario where a person is required to change his/her technology stack when changing his/her job. What are the merits and demerits in going with either of the choices? Also I know that C++ isn't going anywhere in the near future. What about perl? I have no clue as to what the future holds for perl developer? Whether there are enough opportunities for a perl developer? I am asking this question here because most of my fellow programmers face this career choice dilemma. Thanks.

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• Choosing an installer product that is free and will download/install the .NET Framework

  - by Coder7862396

  I'm currently using the Visual Studio Installer (Setup Project) in Visual Studio 2010 as the installer for MyProgram. It has some quirky bugs and is not very customizable so I would like to switch to another installer product. Here are my requirements: Must be free (and licensed for commercial use) Must install the Windows Installer 3.1 and .NET Framework 4.0 if the client doesn't have them The installer will download them if they are not available The code for detecting the .NET Framework and downloading it must be written by Microsoft (I do not want to have to update hard-coded URLs and registry keys in the future). I know that the Windows SDK includes a setup bootstrap that does this (C:\Program Files\Microsoft SDKs\Windows\v7.0A\Bootstrapper) In the future, when .NET Framework 5 is released and MyProgram uses it, no installer code will need to be changed, the updated installer product should see that MyProgram now uses the .NET Framework version 5 and will install that Here are my current choices: Visual Studio Installer: Automatically detects/downloads/installs Windows Installer and .NET Framework using a bootstrapper Setup.exe (Good!) Limited/buggy functionality (Uninstall shortcuts in the Start Menu cause empty folders to be left behind during uninstall, asking the user if they want a desktop shortcut requires a lot of work, etc.) NSIS: Doesn't natively support the .NET Framework so adding it as a prerequisite requires excessive coding, hardcoded URLS, etc. Inno Setup: Doesn't natively support the .NET Framework so adding it as a prerequisite requires excessive coding, hardcoded URLs, etc. WiX: Steep learning curve... not sure if I want to spend weeks learning it only to find out that it has the same uninstall problem as the Visual Studio Installer (because they both use MSI files) InstallShield LE 2010: Downloading it requires me to setup a fake email account to register just to download it. Then once it is installed it has to contact the company's servers and transmit some private information to them before I'm even allowed to try the free version. This is the most insidious form of DRM that there is and I will not accept it.

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• If I wanted to make a Pac-Man Game?

  - by SoulBeaver

  I am immediately placing this as a community wiki thing. I don't want to ask for help in programming yet or have even a specific question about programming, but rather the process and the resources needed to make such a game. To put it simply: My college friend and I decided to give ourselves a really big challenge to further our skills in programming. In six months time we want to show ourselves a Pac-Man game. Pac-Man will be AI-controlled like the Ghosts and whichever Pac-Man lives the longest after a set of tries wins. This isn't like anything we've done so far. The goal here, for me, isn't to create a perfect game, but to try and complete it, learn a whole bunch in the process. Even if I don't finish in the time, which is a good possibility, I would want to have at least tried this. So my question is this: How should I start preparing myself? I already have started vector math, matrices, all that fun stuff. My desired platform would be DirectX 9.0c; is that advisable? Keep in mind that this is not a preference just for this project, but I wish to have some kind of future in graphics develepment, so I want to pick a platform that is future-safe. As for the game development in general, what should I take into consideration? I have never done a real game before, so any and all advise to development of mid-scale projects( if this would be a mid-scale project ) is greatly appreciated. My main concerns are the pit-falls and demotivators. Sorry if the question is so vague. If it doesn't belong here, then I will remove it. Otherwise, any and all advise regarding making larger projects is greatly appreciated.

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• Implementing a robust async stream reader

  - by Jon

  I recently provided an answer to this question: C# - Realtime console output redirection. As often happens, explaining stuff (here "stuff" was how I tackled a similar problem) leads you to greater understanding and/or, as is the case here, "oops" moments. I realized that my solution, as implemented, has a bug. The bug has little practical importance, but it has an extremely large importance to me as a developer: I can't rest easy knowing that my code has the potential to blow up. Squashing the bug is the purpose of this question. I apologize for the long intro, so let's get dirty. I wanted to build a class that allows me to receive input from a Stream in an event-based manner. The stream, in my scenario, is guaranteed to be a FileStream and there is also an associated StreamReader already present to leverage. The public interface of the class is this: public class MyStreamManager { public event EventHandler<ConsoleOutputReadEventArgs> StandardOutputRead; public void StartSendingEvents(); public void StopSendingEvents(); } Obviously this specific scenario has to do with a console's standard output, but that is a detail and does not play an important role. StartSendingEvents and StopSendingEvents do what they advertise; for the purposes of this discussion, we can assume that events are always being sent without loss of generality. The class uses these two fields internally: protected readonly StringBuilder inputAccumulator = new StringBuilder(); protected readonly byte[] buffer = new byte[256]; The functionality of the class is implemented in the methods below. To get the ball rolling: public void StartSendingEvents(); { this.stopAutomation = false; this.BeginReadAsync(); } To read data out of the Stream without blocking, and also without requiring a carriage return char, BeginRead is called: protected void BeginReadAsync() { if (!this.stopAutomation) { this.StandardOutput.BaseStream.BeginRead( this.buffer, 0, this.buffer.Length, this.ReadHappened, null); } } The challenging part: BeginRead requires using a buffer. This means that when reading from the stream, it is possible that the bytes available to read ("incoming chunk") are larger than the buffer. Since we are only handing off data from the stream to a consumer, and that consumer may well have inside knowledge about the size and/or format of these chunks, I want to call event subscribers exactly once for each chunk. Otherwise the abstraction breaks down and the subscribers have to buffer the incoming data and reconstruct the chunks themselves using said knowledge. This is much less convenient to the calling code, and detracts from the usefulness of my class. To this end, if the buffer is full after EndRead, we don't send its contents to subscribers immediately but instead append them to a StringBuilder. The contents of the StringBuilder are only sent back whenever there is no more to read from the stream (thus preserving the chunks). private void ReadHappened(IAsyncResult asyncResult) { var bytesRead = this.StandardOutput.BaseStream.EndRead(asyncResult); if (bytesRead == 0) { this.OnAutomationStopped(); return; } var input = this.StandardOutput.CurrentEncoding.GetString( this.buffer, 0, bytesRead); this.inputAccumulator.Append(input); if (bytesRead < this.buffer.Length) { this.OnInputRead(); // only send back if we 're sure we got it all } this.BeginReadAsync(); // continue "looping" with BeginRead } After any read which is not enough to fill the buffer, all accumulated data is sent to the subscribers: private void OnInputRead() { var handler = this.StandardOutputRead; if (handler == null) { return; } handler(this, new ConsoleOutputReadEventArgs(this.inputAccumulator.ToString())); this.inputAccumulator.Clear(); } (I know that as long as there are no subscribers the data gets accumulated forever. This is a deliberate decision). The good This scheme works almost perfectly: Async functionality without spawning any threads Very convenient to the calling code (just subscribe to an event) Maintains the "chunkiness" of the data; this allows the calling code to use inside knowledge of the data without doing any extra work Is almost agnostic to the buffer size (it will work correctly with any size buffer irrespective of the data being read) The bad That last almost is a very big one. Consider what happens when there is an incoming chunk with length exactly equal to the size of the buffer. The chunk will be read and buffered, but the event will not be triggered. This will be followed up by a BeginRead that expects to find more data belonging to the current chunk in order to send it back all in one piece, but... there will be no more data in the stream. In fact, as long as data is put into the stream in chunks with length exactly equal to the buffer size, the data will be buffered and the event will never be triggered. This scenario may be highly unlikely to occur in practice, especially since we can pick any number for the buffer size, but the problem is there. Solution? Unfortunately, after checking the available methods on FileStream and StreamReader, I can't find anything which lets me peek into the stream while also allowing async methods to be used on it. One "solution" would be to have a thread wait on a ManualResetEvent after the "buffer filled" condition is detected. If the event is not signaled (by the async callback) in a small amount of time, then more data from the stream will not be forthcoming and the data accumulated so far should be sent to subscribers. However, this introduces the need for another thread, requires thread synchronization, and is plain inelegant. Specifying a timeout for BeginRead would also suffice (call back into my code every now and then so I can check if there's data to be sent back; most of the time there will not be anything to do, so I expect the performance hit to be negligible). But it looks like timeouts are not supported in FileStream. Since I imagine that async calls with timeouts are an option in bare Win32, another approach might be to PInvoke the hell out of the problem. But this is also undesirable as it will introduce complexity and simply be a pain to code. Is there an elegant way to get around the problem? Thanks for being patient enough to read all of this.

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• How to group data changes by operation with MySQL triggers

  - by Jan-Henk

  I am using triggers in MySQL to log changes to the data. These changes are recorded on a row level. I can now insert an entry in my log table for each row that is changed. However, I also need to record the operation to which the changes belong. For example, a delete operation like "DELETE * FROM table WHERE type=x" can delete multiple rows. With the trigger I can insert an entry for each deleted row into the log table, but I would like to also provide a unique identifier for the operation as a whole, so that the log table looks something like: log_id operation_id tablename fieldname oldvalue newvalue 1 1 table id 1 null 2 1 table type a null 3 1 table id 2 null 4 1 table type a null 5 2 table id 3 null 6 2 table type b null 7 2 table id 4 null 8 2 table type b null Is there a way in MySQL to identify the higher level operation to which the row changes belong? Or is this only possible by means of application level code? In the future it would also be nice to be able to record the transaction to which an operation belongs. Another question is if it is possible to capture the actual SQL query, besides using the query log. I don't think so myself, but maybe I am missing something. It is of course possible to capture these at the application level, but the goal is to keep intrusions to the application level code as minimal as possible. When this is not possible with MySQL, how is this with other database systems? For the current project it is not an option to use something other than MySQL, but it would be nice to know for future projects.

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• Workaround for basic syntax not being parsed.

  - by Mark Tomlin

  I want to have a class property that allow for an expression to take place on the right side of the equals sign. All versions of PHP choke on the following code, but it is written in this way to allow for easier extendibility in the future. /* Example SDK Class */ class SDK { /* Runtime Option Flags */ // Strings # 0: Makes no change to the strings. var $STRING_NONE = (1 << 0); # 1: Removes color codes from the string. var $STRING_STRIP_COLOR = (1 << 1); # 2: Removes language codes from the string. var $STRING_STRIP_LANG = (1 << 2); # 3: Removes all formatting from the string. var $STRING_STRIP = SELF::STRING_STRIP_COLOR & SELF::STRING_STRIP_LANG; # 4: Converts color codes to HTML & UTF-8. var $STRING_HTML = (1 << 3); # 8: Converts color codes to ECMA-48 escape color codes & UTF-8. var $STRING_CONSOLE = (1 << 4); # 16: Changes player names only. var $STRING_NAMES = (1 << 5); # 32: Changes host names only. var $STRING_HOSTS = (1 << 6); function SDK($fString = SELF::STRING_HTML & SELF::STRING_NAMES & SELF_HOST) { // constructor code. } } $SDK &= new SDK(SDK::STRING_NONE); (1 << 0) seems like very basic syntax to me, and is not fathomable why PHP would not allow for such a thing. Can anyone think of a work around that would maintain readability and future expandability of the following code?

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• ExecutorService - scaling

  - by Stanciu Alexandru-Marian

  I am trying to write a program in Java using ExecutorService and it's function invokeAll. My question is: does the invokeAll functions solve the tasks simultaneously? I mean, if i have two processors, there will be two workers in the same time? Because a can't make it to scale correct. It takes the same time to complete the problem if i give newFixedThreadPool(2) or 1. List<Future<PartialSolution>> list = new ArrayList<Future<PartialSolution>>(); Collection<Callable<PartialSolution>> tasks = new ArrayList<Callable<PartialSolution>>(); for(PartialSolution ps : wp) { tasks.add(new Map(ps, keyWords)); } list = executor.invokeAll(tasks); Map is a class that implements Callable and wp is a vector of Partial Solutions, a class that holds some informations in different times. Why doesn't it scale? What could be the problem? Thank you, Alex

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• Strategies for serializing an object for auditing/logging purpose in .NET?

  - by Jiho Han

  Let's say I have an application that processes messages. Messages are just objects in this case that implements IMessage interface which is just a marker. In this app, if a message fails to process, then I want to log it, first of all for auditing and troubleshooting purposes. Secondly I might want to use it for re-processing. Ideally, I want the message to be serialized into a format that is human-readable. The first candidate is XML although there are others like JSON. If I were to serialize the messages as XML, I want to know whether the message object is XML-serializable. One way is to reflect on the type and to see if it has a parameter-less constructor and the other is to require IXmlSerializable interface. I'm not too happy with either of these approaches. There is a third option which is to try to serialize it and catch exceptions. This doesn't really help - I want to, in some way, stipulate that IMessage (or a derived type) should be xml-serializable. The reflection route has obvious disadvantages such as security, performance, etc. IXmlSerializable route locks down my messages to one format, when in the future, I might want to change the serialization format to be JSON. The other thing is even the simplest objects now must implement ReadXml and WriteXml methods. Is there a route that involves the least amount of work that lets me serialize an arbitrary object (as long as it implements the marker interface) into XML but not lock future messages into XML?

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• iPhone app rejection for using ICU (Unicode extensions)

  - by nickbit

  I received the following mail form Apple, considering my application: *Thank you for submitting your update to ??µ??es?a to the App Store. During our review of your application we found it is using private APIs, which is in violation of the iPhone Developer Program License Agreement section 3.3.1; "3.3.1 Applications may only use Documented APIs in the manner prescribed by Apple and must not use or call any private APIs." While your application has not been rejected, it would be appropriate to resolve this issue in your next update. The following non-public APIs are included in your application: u_isspace ubrk_close ubrk_current ubrk_first ubrk_next ubrk_open If you have defined methods in your source code with the same names as the above mentioned APIs, we suggest altering your method names so that they no longer collide with Apple's private APIs to avoid your application being flagged with future submissions. Please resolve this issue in your next update to ??µ??es?a. Sincerely, iPhone App Review Team* The functions mentioned in this mail are used in the ICU library (International Components for Unicode). Although my app is not rejected at this point, I don't feel very secure for the future of my app, because it relies heavily on the Unicode protocol and on this components in particular. Another thing is that I do not call these functions directly, but they are called by a custom 'sqlite' build (with FTS3 extensions enabled). Am I missing something here? Any suggestions?

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• DAL Layer : EF 4.0 or Normal Data access layer with Stored Procedure

  - by Harryboy

  Hello Experts, Application : I am working on one mid-large size application which will be used as a product, we need to decide on our DAL layer. Application UI is in Silverlight and DAL layer is going to be behind service layer. We are also moving ahead with domain model, so our DB tables and domain classes are not having same structure. So patterns like Data Mapper and Repository will definitely come into picture. I need to design DAL Layer considering below mentioned factors in priority manner Speed of Development with above average performance Maintenance Future support and stability of the technology Performance Limitation : 1) As we need to strictly go ahead with microsoft, we can not use NHibernate or any other ORM except EF 4.0 2) We can use any code generation tool (Should be Open source or very cheap) but it should only generate code in .Net, so there would not be any licensing issue on per copy basis. Questions I read so many articles about EF 4.0, on outset it looks like that it is still lacking in features from NHibernate but it is considerably better then EF 1.0 So, Do you people feel that we should go ahead with EF 4.0 or we should stick to ADO .Net and use any code geneartion tool like code smith or any other you feel best Also i need to answer questions like what time it will take to port application from EF 4.0 to ADO .Net if in future we stuck up with EF 4.0 for some features or we are having serious performance issue. In reverse case if we go ahead and choose ADO .Net then what time it will take to swith to EF 4.0 Lastly..as i was going through the article i found the code only approach (with POCO classes) seems to be best suited for our requirement as switching is really easy from one technology to other. Please share your thoughts on the same and please guide on the above questions

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• inverse relation to multiple inheriting classes in django

  - by Ofri Raviv

  Here are my schematic models: class Law(models.Model): ... class Bill(models.Model): ... # data for a proposed law, or change of an existing law class PrivateBill(Bill): ... # data for a Bill that was initiated by a parliament member class GovernmentBill(Bill): ... # data for a Bill that was initiated by the government It is possible and likely that in the future I (or maybe someone else) would want to add more Bill types. Every Bill should point to a Law (indicating what law this bill is going to change) and my question is: What is the best way to implement this? If I add the ForeignKey(Law) to Bill, I'll have a relation from every Bill to Law, but a Law would only have an inverse relation to Bills (bill_set), and not a different inverse relation to each type of bill. Of course I'll be able to filter each type of bill to get only the ones pointing to a specific Law, but this is something I think I'll need to use often, so I think having privatebill_set, governmentbill_set etc would make the code more readable. Another possible solution is to add the foreign key to each of the inheriting classes (this would give me a privatebill_set, governmentbill_set, futurebill_set), but that seems hairy because I would be relying on future programmers to remember to add that relation. How would you solve this?

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• Using ARIMA to model and forecast stock prices using user-friendly stats program

  - by Brian

  Hi people, Can anyone please offer some insight into this for me? I'm coming from a functional magnetic resonance imaging research background where I analyzed a lot of time series data, and I'd like to analyze the time series of stock prices (or returns) by: 1) modeling a successful stock in a particular market sector and then cross-correlating the time series of this historically successful stock with that of other newer stocks to look for significant relationships; 2) model a stock's price time series and use forecasting (e.g., exponential smoothing) to predict future values of it. I'd like to use non-linear modeling methods (ARIMA and ARCH) to do this. Several questions: How often do ARIMA and ARCH modeling methods (given that the individual who implements them does so accurately) actually fit the stock time series data they target, and what is the optimal fit I can expect? Is the extent to which this model fits the data commensurate with the extent to which it predicts this stock time series' future values? Rather than randomly selecting stocks to compare or model, if profit is my goal, what is an efficient approach, if any, to selecting the stocks I'm going to analyze? Which stats program is the most user-friendly for this? Any thoughts on this would be great and would go a long way for me. Thanks, Brian

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• Choosing the right web service

  - by Ratan Sharma

  My website currently working in ASP.NET 1.1 Old Process In our database we have huge amount of data stored for a decoding purpose. We have to update this huge set of data table each week(Data is supplied from a vendor). In our website (in asp.net 1.1) we query our database to decode information. New process Now instead of storing data in our database and query them, we want to replace this through the web service, AS now the vendor is supplying us a DLL, which will give us the decoded information. Information on the DLL provided by the vendor The DLL provided, can only be added in 4.0 sites. SO that also impleies that i can not directly add the dll to my 1.1 site. This DLL is exposing certain methods, we simply have to add the DLL refernce in our web service and call the method and fetch the needed information. Thus we will not have to store those information in our database. So which type of web service I should go for (asmx OR WCF) that will use the DLLs provided by vendor to fetch the decoded information ?? Flexibility i am looking for in the web service are: It can be consumed from asp.net 1.1 site directly and also using jQuery ajax. It can be consumed from other web services running on the server. It can be consumed from some windows services running from the server. NOTE : Moreover we have a plan to migrate our website from asp.net 1.1 to 4.0 version in future.So it should be that much supportive for future upgrade.

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• How to properly close a UDT server in Netty 4

  - by Steffen

  I'm trying to close my UDT server (Netty 4.0.5.Final) with shutDownGracefully() and reopen it on the same port. Unfortunately, I always get the socket exception below although it waits until the future has completed. I also added the socket option SO_REUSEADDR. What is the proper way to do this? Exception in thread "main" com.barchart.udt.ExceptionUDT: UDT Error : 5011 : another socket is already listening on the same UDP port : listen0:listen [id: 0x323d3939] at com.barchart.udt.SocketUDT.listen0(Native Method) at com.barchart.udt.SocketUDT.listen(SocketUDT.java:1136) at com.barchart.udt.net.NetServerSocketUDT.bind(NetServerSocketUDT.java:66) at io.netty.channel.udt.nio.NioUdtAcceptorChannel.doBind(NioUdtAcceptorChannel.java:71) at io.netty.channel.AbstractChannel$AbstractUnsafe.bind(AbstractChannel.java:471) at io.netty.channel.DefaultChannelPipeline$HeadHandler.bind(DefaultChannelPipeline.java:1006) at io.netty.channel.DefaultChannelHandlerContext.invokeBind(DefaultChannelHandlerContext.java:504) at io.netty.channel.DefaultChannelHandlerContext.bind(DefaultChannelHandlerContext.java:487) at io.netty.channel.ChannelDuplexHandler.bind(ChannelDuplexHandler.java:38) at io.netty.handler.logging.LoggingHandler.bind(LoggingHandler.java:254) at io.netty.channel.DefaultChannelHandlerContext.invokeBind(DefaultChannelHandlerContext.java:504) at io.netty.channel.DefaultChannelHandlerContext.bind(DefaultChannelHandlerContext.java:487) at io.netty.channel.DefaultChannelPipeline.bind(DefaultChannelPipeline.java:848) at io.netty.channel.AbstractChannel.bind(AbstractChannel.java:193) at io.netty.bootstrap.AbstractBootstrap$2.run(AbstractBootstrap.java:321) at io.netty.util.concurrent.SingleThreadEventExecutor.runAllTasks(SingleThreadEventExecutor.java:354) at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:366) at io.netty.util.concurrent.SingleThreadEventExecutor$2.run(SingleThreadEventExecutor.java:101) at java.lang.Thread.run(Thread.java:724) A small test program demonstration the problem: public class MsgEchoServer { public static class MsgEchoServerHandler extends ChannelInboundHandlerAdapter { } public void run() throws Exception { final ThreadFactory acceptFactory = new UtilThreadFactory("accept"); final ThreadFactory connectFactory = new UtilThreadFactory("connect"); final NioEventLoopGroup acceptGroup = new NioEventLoopGroup(1, acceptFactory, NioUdtProvider.MESSAGE_PROVIDER); final NioEventLoopGroup connectGroup = new NioEventLoopGroup(1, connectFactory, NioUdtProvider.MESSAGE_PROVIDER); try { final ServerBootstrap boot = new ServerBootstrap(); boot.group(acceptGroup, connectGroup) .channelFactory(NioUdtProvider.MESSAGE_ACCEPTOR) .option(ChannelOption.SO_BACKLOG, 10) .option(ChannelOption.SO_REUSEADDR, true) .handler(new LoggingHandler(LogLevel.INFO)) .childHandler(new ChannelInitializer<UdtChannel>() { @Override public void initChannel(final UdtChannel ch) throws Exception { ch.pipeline().addLast(new MsgEchoServerHandler()); } }); final ChannelFuture future = boot.bind(1234).sync(); } finally { acceptGroup.shutdownGracefully().syncUninterruptibly(); connectGroup.shutdownGracefully().syncUninterruptibly(); } new MsgEchoServer().run(); } public static void main(final String[] args) throws Exception { new MsgEchoServer().run(); } }

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• Browser-based application or stand-alone GUI app?

  - by crystalattice

  I'm sure this has been asked before, but I can't find it. What are the benefits/limitations of using a browser-based interface for a stand-alone application vs. using a normal GUI framework? I'm working on a Python program currently implement with wxPython for the GUI. The application is simply user-entry forms and dialogs. I am considering moving to PyQt because of the widgets it has (for future expansion), then I realized I could probably just use a browser to do much of the same stuff. The application currently doesn't require Internet access, though it's a possibility in the future. I was thinking of using Karrigell for the web framework if I go browser-based. Edit For clarification, as of right now the application would be browser-based, not web-based. All the information would be stored locally on the client computer; no server calls would need to be made and no Internet access required (it may come later though). It would simply be a browser GUI instead of a wxPython/PyQt GUI. Hope that makes sense.

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• Date Filtered Collections without Functions

  - by madcapnmckay

  Hi, I have an entity similar to the below: public class Entity { public List<DateItem> PastDates { get; set; } public List<DateItem> FutureDates { get; set; } } public class DateItem { public DateTime Date { get; set; } /* * Other Properties * */ } Where PastDates and FutureDates are both mapped to the same type/table. I have been trying to find a way to have the Past and Future properties mapped automagically by Nhibernate. The closest I came was where clause on the mapping as follows HasMany(x => x.PastDates) .AsBag().Cascade .AllDeleteOrphan() .KeyColumnNames.Add("EventId").Where("Date < currentdate()") .Inverse(); Where currentdate is a UDF. I do not want to have these database specific functions if I can avoid it, mostly because i can't then test my DAL with SQLite as it doesn't support functions or stored procedures. At the moment I am building the past and future collections using Criteria and adding to my DTO manually. Anyone know how this could be achieved without using any UDFs? Many thanks,

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• help('modules') crashing?

  - by Chris

  I was trying to install a module for opencv and added an opencv.pth file to the folder beyond my sites.py file. I have since deleted it and no change. When I try to run help('modules'), I get the following error: Please wait a moment while I gather a list of all available modules... /System/Library/Frameworks/Python.framework/Versions/2.5/Extras/lib/python/twisted/words/im/init.py:8: UserWarning: twisted.im will be undergoing a rewrite at some point in the future. warnings.warn("twisted.im will be undergoing a rewrite at some point in the future.") /System/Library/Frameworks/Python.framework/Versions/2.5/lib/python2.5/pkgutil.py:110: DeprecationWarning: The wxPython compatibility package is no longer automatically generated or actively maintained. Please switch to the wx package as soon as possible. import(name) Traceback (most recent call last): File "", line 1, in File "/System/Library/Frameworks/Python.framework/Versions/2.5/lib/python2.5/site.py", line 348, in call return pydoc.help(*args, **kwds) File "/System/Library/Frameworks/Python.framework/Versions/2.5/lib/python2.5/pydoc.py", line 1644, in call self.help(request) File "/System/Library/Frameworks/Python.framework/Versions/2.5/lib/python2.5/pydoc.py", line 1681, in help elif request == 'modules': self.listmodules() File "/System/Library/Frameworks/Python.framework/Versions/2.5/lib/python2.5/pydoc.py", line 1802, in listmodules ModuleScanner().run(callback) File "/System/Library/Frameworks/Python.framework/Versions/2.5/lib/python2.5/pydoc.py", line 1853, in run for importer, modname, ispkg in pkgutil.walk_packages(): File "/System/Library/Frameworks/Python.framework/Versions/2.5/lib/python2.5/pkgutil.py", line 110, in walk_packages import(name) File "/BinaryCache/wxWidgets/wxWidgets-11~262/Root/System/Library/Frameworks/Python.framework/Versions/2.5/Extras/lib/python/wxaddons/init.py", line 180, in import_hook File "/Library/Python/2.5/site-packages/ctypes_opencv/init.py", line 19, in from ctypes_opencv.cv import * File "/BinaryCache/wxWidgets/wxWidgets-11~262/Root/System/Library/Frameworks/Python.framework/Versions/2.5/Extras/lib/python/wxaddons/init.py", line 180, in import_hook File "/Library/Python/2.5/site-packages/ctypes_opencv/cv.py", line 2567, in ('desc', CvMat_r, 1), # CvMat* desc File "/Library/Python/2.5/site-packages/ctypes_opencv/cxcore.py", line 114, in cfunc return CFUNCTYPE(result, *atypes)((name, dll), tuple(aflags)) AttributeError: dlsym(0x2674d10, cvCreateFeatureTree): symbol not found What gives?!

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• Advanced ASP.NET Gridview Layout

  - by chief7

  So i had a feature request to add fields to a second table row for a single data row on a GridView. At first, I looked at extending the functionality of the GridView but soon realized this would be a huge task and since I consider this request a shim for a larger future feature decided against it. Also want to move to MVC in the near future and this would be throw away code. So instead I created a little jquery script to move the cell to the next row in the table. $(document).ready(function() { $(".fieldAttributesNextRow").each(function() { var parent = $(this).parent(); var newRow = $("<tr></tr>"); newRow.attr("class", $(parent).attr("class")); var headerRow = $(parent).parent().find(":first"); var cellCount = headerRow.children().length - headerRow.children().find(".hide").length; newRow.append($(this).attr("colspan", cellCount)); $(parent).after(newRow); }) }); What do you think of this? Is this a poor design decision? I am actually quite pleased with the ease of this solution. Please provide your thoughts.

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• Implementing a robust async stream reader for a console

  - by Jon

  I recently provided an answer to this question: C# - Realtime console output redirection. As often happens, explaining stuff (here "stuff" was how I tackled a similar problem) leads you to greater understanding and/or, as is the case here, "oops" moments. I realized that my solution, as implemented, has a bug. The bug has little practical importance, but it has an extremely large importance to me as a developer: I can't rest easy knowing that my code has the potential to blow up. Squashing the bug is the purpose of this question. I apologize for the long intro, so let's get dirty. I wanted to build a class that allows me to receive input from a Stream in an event-based manner. The stream, in my scenario, is guaranteed to be a FileStream and there is also an associated StreamReader already present to leverage. The public interface of the class is this: public class MyStreamManager { public event EventHandler<ConsoleOutputReadEventArgs> StandardOutputRead; public void StartSendingEvents(); public void StopSendingEvents(); } Obviously this specific scenario has to do with a console's standard output. StartSendingEvents and StopSendingEvents do what they advertise; for the purposes of this discussion, we can assume that events are always being sent without loss of generality. The class uses these two fields internally: protected readonly StringBuilder inputAccumulator = new StringBuilder(); protected readonly byte[] buffer = new byte[256]; The functionality of the class is implemented in the methods below. To get the ball rolling: public void StartSendingEvents(); { this.stopAutomation = false; this.BeginReadAsync(); } To read data out of the Stream without blocking, and also without requiring a carriage return char, BeginRead is called: protected void BeginReadAsync() { if (!this.stopAutomation) { this.StandardOutput.BaseStream.BeginRead( this.buffer, 0, this.buffer.Length, this.ReadHappened, null); } } The challenging part: BeginRead requires using a buffer. This means that when reading from the stream, it is possible that the bytes available to read ("incoming chunk") are larger than the buffer. Since we are only handing off data from the stream to a consumer, and that consumer may well have inside knowledge about the size and/or format of these chunks, I want to call event subscribers exactly once for each chunk. Otherwise the abstraction breaks down and the subscribers have to buffer the incoming data and reconstruct the chunks themselves using said knowledge. This is much less convenient to the calling code, and detracts from the usefulness of my class. Edit: There are comments below correctly stating that since the data is coming from a stream, there is absolutely nothing that the receiver can infer about the structure of the data unless it is fully prepared to parse it. What I am trying to do here is leverage the "flush the output" "structure" that the owner of the console imparts while writing on it. I am prepared to assume (better: allow my caller to have the option to assume) that the OS will pass me the data written between two flushes of the stream in exactly one piece. To this end, if the buffer is full after EndRead, we don't send its contents to subscribers immediately but instead append them to a StringBuilder. The contents of the StringBuilder are only sent back whenever there is no more to read from the stream (thus preserving the chunks). private void ReadHappened(IAsyncResult asyncResult) { var bytesRead = this.StandardOutput.BaseStream.EndRead(asyncResult); if (bytesRead == 0) { this.OnAutomationStopped(); return; } var input = this.StandardOutput.CurrentEncoding.GetString( this.buffer, 0, bytesRead); this.inputAccumulator.Append(input); if (bytesRead < this.buffer.Length) { this.OnInputRead(); // only send back if we 're sure we got it all } this.BeginReadAsync(); // continue "looping" with BeginRead } After any read which is not enough to fill the buffer, all accumulated data is sent to the subscribers: private void OnInputRead() { var handler = this.StandardOutputRead; if (handler == null) { return; } handler(this, new ConsoleOutputReadEventArgs(this.inputAccumulator.ToString())); this.inputAccumulator.Clear(); } (I know that as long as there are no subscribers the data gets accumulated forever. This is a deliberate decision). The good This scheme works almost perfectly: Async functionality without spawning any threads Very convenient to the calling code (just subscribe to an event) Maintains the "chunkiness" of the data; this allows the calling code to use inside knowledge of the data without doing any extra work Is almost agnostic to the buffer size (it will work correctly with any size buffer irrespective of the data being read) The bad That last almost is a very big one. Consider what happens when there is an incoming chunk with length exactly equal to the size of the buffer. The chunk will be read and buffered, but the event will not be triggered. This will be followed up by a BeginRead that expects to find more data belonging to the current chunk in order to send it back all in one piece, but... there will be no more data in the stream. In fact, as long as data is put into the stream in chunks with length exactly equal to the buffer size, the data will be buffered and the event will never be triggered. This scenario may be highly unlikely to occur in practice, especially since we can pick any number for the buffer size, but the problem is there. Solution? Unfortunately, after checking the available methods on FileStream and StreamReader, I can't find anything which lets me peek into the stream while also allowing async methods to be used on it. One "solution" would be to have a thread wait on a ManualResetEvent after the "buffer filled" condition is detected. If the event is not signaled (by the async callback) in a small amount of time, then more data from the stream will not be forthcoming and the data accumulated so far should be sent to subscribers. However, this introduces the need for another thread, requires thread synchronization, and is plain inelegant. Specifying a timeout for BeginRead would also suffice (call back into my code every now and then so I can check if there's data to be sent back; most of the time there will not be anything to do, so I expect the performance hit to be negligible). But it looks like timeouts are not supported in FileStream. Since I imagine that async calls with timeouts are an option in bare Win32, another approach might be to PInvoke the hell out of the problem. But this is also undesirable as it will introduce complexity and simply be a pain to code. Is there an elegant way to get around the problem? Thanks for being patient enough to read all of this.

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• MVC.NET custom validator is not working

  - by IvanMushketyk

  I want to write a custom validator for MVC.NET framework that checks if entered date is in the future. To do it, I wrote the following class: [AttributeUsage(AttributeTargets.Property, AllowMultiple = false, Inherited = true)] public sealed class InTheFutureAttribute : ValidationAttribute, IClientValidatable { private const string DefaultErrorMessage = "{0} should be date in the future"; public InTheFutureAttribute() : base(DefaultErrorMessage) { } public override string FormatErrorMessage(string name) { return string.Format(ErrorMessageString, name); } public override bool IsValid(object value) { DateTime time = (DateTime)value; if (time < DateTime.Now) { return false; } return true; } public IEnumerable<ModelClientValidationRule> GetClientValidationRules(ModelMetadata metadata, ControllerContext context) { var clientValidationRule = new ModelClientValidationRule() { ErrorMessage = FormatErrorMessage(metadata.GetDisplayName()), ValidationType = "wrongvalue" }; return new[] { clientValidationRule }; } } and added attribute to field that I want to check. On the View page I create input field in the following way: <div class="editor-label-search"> @Html.LabelFor(model => model.checkIn) </div> <div class="editor-field-search-date"> @Html.EditorFor(model => model.checkIn) <script type="text/javascript"> $(document).ready(function () { $('#checkIn').datepicker({ showOn: 'button', buttonImage: '/Content/images/calendar.gif', duration: 0, dateFormat: 'dd/mm/yy' }); }); </script> @Html.ValidationMessageFor(model => model.checkIn) </div> When I submit the form for the controller that requires model with checked attribute code in my validator is called and it returns false, but instead of displaying an error it just call my controller's action and send invalid model to it. Am I doing something wrong? How can I fix it? Thank you in advance.

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• Using JQuery with dynamically added controls (MVC)

  - by Mario

  I have a set of radio buttons that are dynamically generated (via JSON call): StringBuilder sbEligAll = new StringBuilder(); sbEligAll.Append("<div id='currentselectiondepartment'>"); sbEligAll.Append(" <input type='radio' name='selectalldepartment' id='radCurrent' value='0' /><label for='radCurrent'>Current</label>"); sbEligAll.Append(" <input type='radio' name='selectalldepartment' id='radFuture' value='1' /><label for='radFuture'>Future</label>"); sbEligAll.Append(" <input type='radio' name='selectalldepartment' id='radCurrentAll' value='2' /><label for='radCurrentAll'>Current All</label>"); sbEligAll.Append(" <input type='radio' name='selectalldepartment' id='radFutureAll' value='3' /><label for='radFutureAll'>Future All</label>"); sbEligAll.Append("</div>"); Then: return Json(new { TableList = sbElig.ToString() }, JsonRequestBehavior.AllowGet); Is there a way to get jQuery to be able to interact with these? For example: $("input[name=selectalldepartment]").change(function() { var str = $('input[name=selectalldepartment]:checked').val(); $(".radiolist[value='" + str + "']").attr("checked", true); }); I've tried everything I know how to do, but the jQuery just doesnt fire. (I've added alerts to the jQuery code to see if it actually gets called, and it does not). Any thoughts?! Thanks!

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• Python and Unicode: How everything should be Unicode

  - by A A

  Forgive if this a long a question: I have been programming in Python for around six months. Self taught, starting with the Python tutorial and then SO and then just using Google for stuff. Here is the sad part: No one told me all strings should be Unicode. No, I am not lying or making this up, but where does the tutorial mention it? And most examples also I see just make use of byte strings, instead of Unicode strings. I was just browsing and came across this question on SO, which says how every string in Python should be a Unicode string. This pretty much made me cry! I read that every string in Python 3.0 is Unicode by default, so my questions are for 2.x: Should I do a: print u'Some text' or just print 'Text' ? Everything should be Unicode, does this mean, like say I have a tuple: t = ('First', 'Second'), it should be t = (u'First', u'Second')? I read that I can do a from __future__ import unicode_literals and then every string will be a Unicode string, but should I do this inside a container also? When reading/ writing to a file, I should use the codecs module. Right? Or should I just use the standard way or reading/ writing and encode or decode where required? If I get the string from say raw_input(), should I convert that to Unicode also? What is the common approach to handling all of the above issues in 2.x? The from __future__ import unicode_literals statement? Sorry for being a such a noob, but this changes what I have been doing for a long time and so clearly I am confused.

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