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  • Stream classes ... design, pattern for creating views over streams

    - by ToxicAvenger
    A question regarding the design of stream classes - I need a pattern to create independent views over a single stream instance (in my case for reading). A view would be a consecutive part of the stream. The problem I have with the stream classes is that the state (reading or writing) is coupled with the underlying data/storage. So if I need to partition a stream into different segments (whether segments overlap or not doesn't matter), I cannot easily create views over the stream, the views would store start and end position. Because reading from a view - which would translate to reading from the underlying stream adjusted based on the start/end positions - would change the state of the underlying stream instance. So what I could do is take a read on a view instance, adjust the Position of the stream, read the chunks I need. But I cannot do that concurrently. Why is it designed in such a way, and what kind of pattern could I implement to create independet views over a single stream instance which would allow to read/write independently (and concurrently)?

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  • Why two subprocesses created by Java behave differently?

    - by Lily
    I use Java Runtime.getRuntime().exec(command) to create a subprocess and print its pid as follows: public static void main(String[] args) { Process p2; try { p2 = Runtime.getRuntime().exec(cmd); Field f2 = p2.getClass().getDeclaredField("pid"); f2.setAccessible(true); System.out.println( f2.get( p2 ) ); } catch (Exception ie) { System.out.println("Yikes, you are not supposed to be here"); } } I tried both C++ executable and Java executable (.jar file). Both executables will continuously print out "Hello World" to stdout. When cmd is the C++ executable, the pid is printed out to console but the subprocess gets killed as soon as main() returns. However, when I call the .jar executable in cmd, the subprocess does not get killed, which is the desired behavior. I don't understand why same Java code, with different executables can behave so differently. How should I modify my code so that I could have persistent subprocesses in Java. Newbie in this field. Any suggestion is welcomed. Lily

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  • Module not found

    - by TMP
    Hi There! I've been working on this one quite a bit and haven't gotten any closer to a solution. I juut dug up my old copy of the WindowsHookLib again - It's available with source at http://www.codeproject.com/KB/DLL/WindowsHookLib.aspx. This library allows Global Windows Mouse/Keyboard/Clipboard Hooks, which is very useful. I'm trying to use the Mouse Hook in here to Capture Mouse-Motion (I could use a Timer that always polls Cursor.Position, but I plan on using more features of WindowsHookLib later). Code as follows: MouseHook mh = new MouseHook(); mh.InstallHook(); mh.MouseMove += new EventHandler<WindowsHookLib.MouseEventArgs>(mh_MouseMove); But on the call to InstallHook(), I get an Exception: "The specified Module could not be found". Strange. Searching, I found that someone thought this occurs because a DLL is not in a place included in the Windows PATH variable, and because placing it in system32 didn't help I went the whole hog and translated the thing to C# for inclusion directly in my project (I was curious how it works). However the error was obstinately persistent, so I dug a bit on this, and found the Code in the Library that is responsible: In InstallHook(), we have IntPtr hinstDLL = Marshal.GetHINSTANCE(Assembly.GetExecutingAssembly().GetModules()[0]); this._hMouseHook = UnsafeNativeMethods.SetWindowsHookEx(14, this._mouseProc, hinstDLL, 0); if (this._hMouseHook == IntPtr.Zero) { throw new MouseHookException(new Win32Exception(Marshal.GetLastWin32Error()).Message); } And this (after modification and recompile) tells me that what I'm really getting is a Windows error "ERROR_MOD_NOT_FOUND"! Now, Here I'm stumped. Didn't I just compile the Hook Library directly into my project? (UnsafeMethods.SetWindowsHookEx is just a DllImported Method from user32) Any Answers, or Prods in the right direction, or any hints, pointers or similar are very much appreciated!

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  • Linq to sql Incorrect varchar length

    - by scott
    I have a table with a nullable varchar(50) column in it. When I am updating the value through linq to sql and trace the call in profiler it is defining the parameter as varchar(36). This is obviously causing some minor issues when we are trying to insert data that is between 37 and 50 characters long. I have tried removing the table and re-adding it to the design surface but the same thing happens. I also tried removing that property and adding it manually, same issue. When I look at the designer.cs code it shows the attribute properly: [Column(Storage="_Name", DbType="VarChar(50)")] I am out of ideas, anybody seen this before? Every other column is correct.

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  • MySQL storing negative and positive decimals

    - by Shishant
    Hello, I want to be able to store -11.99 and +11.99 kind of values in mysql db I am thinking of decimals instead of varchar. But reading mysql site I found out that its incompatible with older versions of mysql As a result of the change from string to numeric format for DECIMAL storage, DECIMAL columns no longer store a leading + or - character or leading 0 digits. Before MySQL 5.0.3, if you inserted +0003.1 into a DECIMAL(5,1) column, it was stored as +0003.1. As of MySQL 5.0.3, it is stored as 3.1. For negative numbers, a literal - character is no longer stored. Applications that rely on the older behavior must be modified to account for this change. So what should be the data type, If I have to give up varchar and make it compatible with older versions too?

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  • "conveyor belt" cache architecture

    - by Andrew Matthews
    I'm producing an application with a few peculiar internal communication characteristics that make the usual suspects for data storage and transport (Qs and RDBMSs) ill-fitted. I'm wondering whether there is a product out there that matches the following characteristics: all data put into it is peristent all reads are delivered out of memory data is universally available data lives where it is most needed data is versioned (nice to have) updates are transactional (I'd like ACID characteristics) data is potentially replicated, but always in sync works on windows is based on or has bindings for .NET is really fast is really robust is redundant is scalable I'm looking at things like Microsoft codename "Velocity", but I am not sure whether it fits all of the above characteristics. Likewise, Memcached is not a perfect fit either. The current version of this app opts for an RDBMS with a signaling system for inter-system sync, but latency is too high and versioning of the DB is a pain. I need all the robustness, but with none of the trade-offs.

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  • Can I use a keyPath in a predicate?

    - by dontWatchMyProfile
    For some reason, this didn't work (although the keypath does exist): NSPredicate *predicate = [NSPredicate predicateWithFormat:@"department.departmentName == %@", departmentName]; [fetchRequest setPredicate:predicate]; NSError *fetchError = nil; NSUInteger count = [moc countForFetchRequest:fetchRequest error:&fetchError]; // execution simply stops at this line, with no error or console log Execution just stops at the last line above when asking for the count. I don't get an console log. Also I don't get any kind of exception. The execution just stops. There are no objects in the persistent store yet. So maybe it crashes because of it tries to follow a keypath in a nonexisting object? Does that make sense? The line where GDB stops is this: 0x002a31cb <+0459> test %eax,%eax Previously to that, I see a lot of NSSQLAdapter... calls in the stack trace. There's definitely something wrong. Well, but when I set the Entity to the destination of the key path and then just do something like NSPredicate *predicate = [NSPredicate predicateWithFormat:@"departmentName == %@", departmentName]; then there is no problem and count simply is 0.

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  • Entity Framework How to specify paramter type in generated SQL (SQLServer 2005) Nvarchar vs Varchar

    - by Gratzy
    In entity framework I have an Entity 'Client' that was generated from a database. There is a property called 'Account' it is defined in the storage model as: <Property Name="Account" Type="char" Nullable="false" MaxLength="6" /> And in the Conceptual Model as: <Property Name="Account" Type="String" Nullable="false" /> When select statements are generated using a variable for Account i.e. where m.Account == myAccount... Entity Framework generates a paramaterized query with a paramater of type NVarchar(6). The problem is that the column in the table is data type of char(6). When this is executed there is a large performance hit because of the data type difference. Account is an index on the table and instead of using the index I believe an Index scan is done. Anyone know how to force EF to not use Unicode for the paramater and use Varchar(6) instead?

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  • How does jQuery store data with .data()?

    - by TK
    I am a little confused how jQuery stores data with .data() functions. Is this something called expando? Or is this using HTML5 Web Storage although I think this is very unlikely? The documentation says: The .data() method allows us to attach data of any type to DOM elements in a way that is safe from circular references and therefore from memory leaks. As I read about expando, it seems to have a rick of memory leak. Unfortunately my skills are not enough to read and understand jQuery code itself, but I want to know how jQuery stores such data by using data(). http://api.jquery.com/data/

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  • Zend_Session: unserialize session data

    - by takeshin
    I'm using session SaveHandler to persist session data in the database. Sample session_data column from the database: Messenger|a:1:{s:13:"page_messages";a:0:{}}userSession|a:1:{s:7:"referer";s:32:"http://cms.dev/user/profile/view";}Zend_Auth|a:1:{s:7:"storage";O:19:"User_Model_Identity":3:{s:2:"id";s:1:"1";s:8:"username";s:13:"administrator";s:4:"slug";s:13:"administrator";}} I want to delete Zend_Auth object from this session data. How can I unserialize those objects and remove object I need? I suspect, that I don't have to write my custom parser, that Zend_Session already has a method to do this. I have tried different combinations of unserialize but it still returns false. I'm using autoloader from ZF 1.10.2 and Doctrine 1.2

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  • Django gives "I/O operation on closed file" error when reading from a saved ImageField

    - by Rob Osborne
    I have a model with two image fields, a source image and a thumbnail. When I update the new source image, save it and then try to read the source image to crop/scale it to a thumbnail I get an "I/O operation on closed file" error from PIL. If I update the source image, don't save the source image, and then try to read the source image to crop/scale, I get an "attempting to read from closed file" error from PIL. In both cases the source image is actually saved and available in later request/response loops. If I don't crop/scale in a single request/response loop but instead upload on one page and then crop/scale in another page this all works fine. This seems to be a cached buffer being reused some how, either by PIL or by the Django file storage. Any ideas on how to make an ImageField readable after saving?

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  • Real time embeddable http server library required

    - by Howard May
    Having looked at several available http server libraries I have not yet found what I am looking for and am sure I can't be the first to have this set of requirements. I need a library which presents an API which is 'pipelined'. Pipelining is used to describe an HTTP feature where multiple HTTP requests can be sent across a TCP link at a time without waiting for a response. I want a similar feature on the library API where my application can receive all of those request without having to send a response (I will respond but want the ability to process multiple requests at a time to reduce the impact of internal latency). So the web server library will need to support the following flow 1) HTTP Client transmits http request 1 2) HTTP Client transmits http request 2 ... 3) Web Server Library receives request 1 and passes it to My Web Server App 4) My Web Server App receives request 1 and dispatches it to My System 5) Web Server receives request 2 and passes it to My Web Server App 6) My Web Server App receives request 2 and dispatches it to My System 7) My Web Server App receives response to request 1 from My System and passes it to Web Server 8) Web Server transmits HTTP response 1 to HTTP Client 9) My Web Server App receives response to request 2 from My System and passes it to Web Server 10) Web Server transmits HTTP response 2 to HTTP Client Hopefully this illustrates my requirement. There are two key points to recognise. Responses to the Web Server Library are asynchronous and there may be several HTTP requests passed to My Web Server App with responses outstanding. Additional requirements are Embeddable into an existing 'C' application Small footprint; I don't need all the functionality available in Apache etc. Efficient; will need to support thousands of requests a second Allows asynchronous responses to requests; their is a small latency to responses and given the required request throughput a synchronous architecture is not going to work for me. Support persistent TCP connections Support use with Server-Push Comet connections Open Source / GPL support for HTTPS Portable across linux, windows; preferably more. I will be very grateful for any recommendation Best Regards

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  • Multi-process builds in Visual Studio 2010: Worth it?

    - by coryr
    I've started testing our C++ software with VS2010 and the build times are really bad (30-45 minutes, about double the VS2005 times). I've been reading about the /MP switch for multi-process compilation. Unfortunately, it is incompatible with some features that we use quite a bit like #import, incremental compilation, and precompiled headers. Have you had a similar project where you tried the /MP switch after turning off things like precompiled headers? Did you get faster builds? My machine is running 64-bit Windows 7 on a 4 core machine with 4 GB of RAM and a fast SSD storage. Virus scanner disabled and a pretty minimal software environment.

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  • How should my application keep clients in sync with schema changes to HTML5 databases?

    - by Chad Johnson
    I'm wanting to incorporate HTML5 database storage into my web application to make it online-accessible. I've done lots of development in server-side environments with databases, and we all know that database schema additions and modifications are often necessary. I am wondering what should happen if my application uses an offline database schema, and that schema changes. How do I prevent the application from breaking on the client side? How do I ensure the database is always up to date on the client end? Anyone have any solutions?

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  • Strategy in storing ad-hoc numbers/constants?

    - by Jiho Han
    I have a need to store a number of ad-hoc figures and constants for calculation. These numbers change periodically but they are different type of values. One might be a balance, a money amount, another might be an interest rate, and yet another might be a ratio of some kind. These numbers are then used in a calculation that involve other more structured figures. I'm not certain what the best way to store these in a relational DB is - that's the choice of storage for the app. One way, I've done before, is to create a very generic table that stores the values as text. I might store the data type along with it but the consumer knows what type it is so, in situations I didn't even need to store the data type. This kind of works fine but I am not very fond of the solution. Should I break down each of the numbers into specific categories and create tables that way? For example, create Rates table, and Balances table, etc.?

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  • What's a good Java-based Master-Slave communication mechanism?

    - by plecong
    I'm creating a Java application that requires master-slave communication between JVMs, possibly residing on the same physical machine. There will be a "master" server running inside a JEE application server (i.e. JBoss) that will have "slave" clients connect to it and dynamically register itself for communication (that is the master will not know the IP addresses/ports of the slaves so cannot be configured in advance). The master server acts as a controller that will dole work out to the slaves and the slaves will periodically respond with notifications, so there would be bi-directional communication. I was originally thinking of RPC-based systems where each side would be a server, but it could get complicated, so I'd prefer a mechanism where there's an open socket and they talk back and forth. I'm looking for a communication mechanism that would be low-latency where the messages would be mostly primitive types, so no serious serialization is necessary. Here's what I've looked at: RMI JMS: Built-in to Java, the "slave" clients would connect to the existing ConnectionFactory in the application server. JAX-WS/RS: Both master and slave would be servers exposing an RPC interface for bi-directional communication. JGroups/Hazelcast: Use shared distributed data structures to facilitate communication. Memcached/MongoDB: Use these as "queues" to facilitate communication, though the clients would have to poll so there would be some latency. Thrift: This does seem to keep a persistent connection, but not sure how to integrate/embed a Thrift server into JBoss WebSocket/Raw Socket: This would work, but require a lot more custom code than I'd like. Is there any technology I'm missing? Edit: Also looked at: JMX: Have the client connect to JBoss' JMX server and receive JMX notifications for bidirectional comms.

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  • SoundPool.load() and FileDescriptor from file

    - by Hans
    I tried using the load function of the SoundPool that takes a FileDescriptor, because I wanted to be able to set the offset and length. The File is not stored in the Ressources but a file on the storage card. Even though neither the load nor the play function of the SoundPool throw any Exception or print anything to the console, the sound is not played. Using the same code, but use the file path string in the SoundPool constructor works perfectly. This is how I have tried the loading (start equals 0 and length is the length of the file in miliseconds): FileInputStream fileIS = new FileInputStream(new File(mFile)); mStreamID = mSoundPool.load(fileIS.getFD(), start, length, 0); mPlayingStreamID = mSoundPool.play(mStreamID, 1f, 1f, 1, 0, 1f); If I would use this, it works: mStreamID = mSoundPool.load(mFile, 0); mPlayingStreamID = mSoundPool.play(mStreamID, 1f, 1f, 1, 0, 1f); Any ideas anyone? Thanks

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  • LinqToSQL not updating database

    - by codegarten
    Hi. I created a database and dbml in visual studio 2010 using its wizards. Everything was working fine until i checked the tables data (also in visual studio server explorer) and none of my updates were there. using (var context = new CenasDataContext()) { context.Log = Console.Out; context.Cenas.InsertOnSubmit(new Cena() { id = 1}); context.SubmitChanges(); } This is the code i am using to update my database. At this point my database has one table with one field (PK) named ID. *INSERT INTO [dbo].Cenas VALUES (@p0) -- @p0: Input Int (Size = -1; Prec = 0; Scale = 0) [1] -- Context: SqlProvider(Sql2008) Model: AttributedMetaModel Build: 4.0.30319.1* This is LOG from the execution (printed the context log into the console). The problem i'm having is that these updates are not persistent in the database. I mean that when i query my database (visual studio server explorer - new query) i see the table is empty, every time. I am using a SQL Server database file (.mdf).

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  • How does the "Remember my password" checkbox work?

    - by Veera
    There are numerous login forms with the little check box "Remember my password" so that the next time you visit the website, the browser automatically fills up the password field for you. But I have noticed a behavior in modern browsers, such as Chrome/Firefox, which shows up a notification bar to save the user name/passoword even though that particular web page does not have any "remember password" check box. so my questions are: If I have to put the "remember password" check box in a login form, what do I have to do when the user checks it? I mean, do I have to store the password in browser cookies (or Local Storage)? If so, should the password be encrypted or plain text? The "Save password" notification bar is a browser's functionality or is there any way to invoke it from the web page?

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  • svn working copy spanning 2 physical drives?

    - by ronenosity
    I have a large repository hosted on dreamhost that I backup daily on a remote machine using a windows scheduled task which updates the working copy located on an external USB 300GB drive connected to the remote machine. The 300GB drive is nearly full with only 26GB of free space remaining. Recently I added a second USB external 1TB drive to increase storage capacity. I would like to ask: what is the best way to use the new 1TB drive? Is it possible to span the working copy across both drives (ex: somehow create a 1.3 TB drive)? If I copied the working copy from the 300GB to the 1TB would svn continue form do I need to retarget the update working copy script to the new 1TB drive and start downloading everything again (least desired option) thanks

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  • Add C pointer to NSMutableArray

    - by Georges Oates Larsen
    I am writing an Objective-C program that deals with low level image memory. I am using ANSI-C structs for my data storage -- Full blown objects seem overkill seeing as the data I am storing is 100% data, with no methods to operate on that data. Specifically, I am writing a customizable posterization algorithm which relies on an array of colors -- This is where things get tricky. I am storing my colors as structs of three floats, and an integer flag (related to the posterization algorithm specifically). Everyhting is going well, except for one thing... [actual question] I can't figure out how to add pointers to an NSMutableArray! I know how to add an object, but adding a pointer to a struct seems to be more difficult -- I do not want NSMutableArray dereferencing my pointer and treating the struct as some sort of strange object. I want NSMutableArray to add the pointer its self to its collection. How do I go about doing this? Thanks in advance, G

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  • How can I use Amazon's API in PHP to search for books?

    - by TerranRich
    I'm working on a Facebook app for book sharing, reviewing, and recommendations. I've scoured the web, searched Google using every search phrase I could think of, but I could not find any tutorials on how to access the Amazon.com API for book information. I signed up for an AWS account, but even the tutorials on their website didn't help me one bit. They're all geared toward using cloud computing for file storage and processing, but that's not what I want. I just want to access their API to search info on books. Kind of like how http://openlibrary.org/ does it, where it's a simple URL call to get information on a book (but their databases aren't nearly as populated as Amazon's). Why is it so damned hard to find the information I need on Amazon's AWS site? If anybody could help, I would greatly appreciate it.

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  • GWT as offline app, to be deployed onto an iPad

    - by Maroloccio
    I often use GWT for web UIs. I have heard of it being used a fair bit in conjunction with Gears for offline solutions (probably nowadays HTML5 "offline storage" is all the rage) and I'd like to experiment with building a GUI in GWT and use it on my iPad. Tips/tutorials on how to deploy it onto the device to act as much as possible like a resident "App"? This is just a curiosity/experiment to fill a week-end... (I can "free" the iPad for the experiment if need be yet I am sure a lot can be done without doing so...)

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  • Free and Simple Hosting Solution with DB Support?

    - by darren
    Hi everyone I have compiled an sqlite database that I would like to make public. I want to provide a very simple webpage that has a few form elements which are used to query the database. Does anybody know of a free hosting solution that would provide me with free web and database functionality? I am familiar with Google App Engine and that would work but I don't want to spend time using their custom storage scheme. I'm looking for something free that I can put together very quickly. Thanks for any suggestions.

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  • Adding items to Model Collection in ASP.NET MVC

    - by Stacey
    In an ASP.NET MVC application where I have the following model.. public class EventViewModel { public Guid Id { get; set; } public List<Guid> Attendants { get; set; } } passed to a view... public ActionResult Create(EventViewModel model) { // ... } I want to be able to add to the "Attendants" Collection from the View. The code to add it works just fine - but how can I ensure that the View model retains the list? Is there any way to do this without saving/opening/saving etc? I am calling my addition method via jQuery $.load. public void Insert(Guid attendant) { // add the attendant to the attendees list of the model - called via $.load } I would also like to add there is no database. There is no storage persistence other than plain files.

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