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  • Handling very large lists of objects without paging?

    - by user246114
    Hi, I have a class which can contain many small elements in a list. Looks like: public class Farm { private ArrayList<Horse> mHorses; } just wondering what will happen if the mHorses array grew to something crazy like 15,000 elements. I'm assuming that trying to write and read this from the datastore would be crazy, because I'd get killed on the serialization process. It's important that I can get the entire array in one shot without paging, and each Horse element may only have two string properties in it, so they are pretty lightweight: public class Horse { private String mId; private String mName; } I don't need these horses indexed at all. Does it sound reasonable to just store the mHorse array as a raw Text field, and force my clients to do the deserialization? Something like: public class Farm { private Text mHorsesSerialized; } then whenever the client receives a Farm instance, it has to take the raw string of horses, and split it in order to reinstantiate the list, something like: // GWT client perhaps Farm farm = rpcCall.getMyFarm(); String horsesSerialized = farm.getHorses(); String[] horseBlocks = horsesSerialized.split(","); for (int i = 0; i < horseBlocks.length; i++) { // .. continue deserializing the individual objects ... } yeah... so hopefully it would be quick to read a Farm instance from the datastore, and the serialization penalty is paid by the client, Thanks

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  • How can I tell when the Text of a System.Windows.Forms.GroupBox wraps to the next line?

    - by fre0n
    I'm creating a GroupBox at runtime and setting its Text property. Usually, the text is only on one line, but sometimes it wraps. The problem is that the controls contained in the GroupBox cover up the GroupBox's text. What I'd like to do is determine if and when the text wraps. Specifically, I'd like to determine how much extra height the wrapped text takes up as compared to a single line. That way, I can reposition the GroupBox's controls and adjust its height. Initially, I thought I'd do this by calling the GroupBox's CreateGraphics() method, and using the Graphics to measure the string. Something like this: private void SetGroupBoxText(GroupBox grp, string text) { const int somePadding = 10; Graphics g = grp.CreateGraphics(); SizeF textSize = g.MeasureString(text, grp.Font); if (textSize.Width > (grp.Width - somePadding)) { // Adjust height, etc. } } The problem is that the size generated by g.MeasureString(text, grp.Font) doesn't seem to be accurate. I determined that it wasn't accurate by putting enough of a single character to cause a wrap, then measuring the resulting string. For example, it took 86 pipes (|) to until a wrap happened. When I measured that string, its width was ~253. And it took 16 capital W's to force a wrap - its string had a width of ~164. These were the two extremes that I tested. My GroupBox's width was 189. (a's took 29 and had a width of ~180, O's took 22 and had a width of ~189) Does anyone have any ideas? (hacks, WinAPI, etc. are welcome solutions)

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  • Processing forms that generate many rows in DB

    - by Zack
    I'm wondering what the best approach to take here is. I've got a form that people use to register for a class and a lot of times the manager of a company will register multiple people for the class at the same time. Presently, they'd have to go through the registration process multiple times and resubmit the form once for every person they want to register. What I want to do is give the user a form that has a single <input/> for one person to register with, along with all the other fields they'll need to fill out (Email, phone number, etc); if they want to add more people, they'll be able to press a button and a new <input/> will be generated. This part I know how to do, but I'm including it to best describe what I'm aiming to do. The part I don't know how to approach is processing that data the form submits, I need some way of making a new row in the Registrant table for every <input/> that's added and include the same contact information (phone, email, etc) as the first row with that row. For the record, I'm using the Django framework for my back-end code. What's the best approach here? Should it just POST the form x times for x people, or is there a less "brute force" way of handling this?

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  • ASP.Net - Help with datagrid/checkboxes/double submit

    - by Gareth D
    We have a simple datagrid. Each row has a checkbox. The checkbox is set to autopostback, and the code-behind has an event handler for the checkbox check-changed event. This all works as expected, nothing complicated. However, we want to disable the checkboxes as soon as one is checked to prevent a double submit i.e. check box checked, all checkboxes are disabled via client side javascript, form submitted. To achieve this I we are injecting some code into the onclick event as follows (note that the alert is just for testing!): Protected Sub DgAccounts_ItemCreated(ByVal sender As System.Object, ByVal e As System.Web.UI.WebControls.DataGridItemEventArgs) Handles DgAccounts.ItemCreated If e.Item.ItemType = ListItemType.Item Or e.Item.ItemType = ListItemType.AlternatingItem Then Dim chk As CheckBox = CType(e.Item.FindControl("chkItemChecked"), CheckBox) chk.Attributes.Add("onclick", "alert('fired ...');DisableAllDataGridCheckBoxes();") End If End Sub When inspecting the source of the rendered page we get the following: <input id="DgAccounts__ctl2_chkItemChecked" type="checkbox" name="DgAccounts:_ctl2:chkItemChecked" onclick="alert('fired ...');DisableAllDataGridCheckBoxes();setTimeout('__doPostBack(\'DgAccounts$_ctl2$chkItemChecked\',\'\')', 0)" language="javascript" /> It all appears in order, however the server side event does not fire – I believe this is due to the checkbox being disabled, as if we just leave the alert in and remove the call to disable the checkbox it all works fine. Can I force the check-changed event to fire even though the check box is disabled?

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  • Login fails when recreating database with Code First

    - by Mun
    I'm using ASP.NET Entity Framework's Code First to create my database from the model, and the login seems to fail when the database needs to be recreated after the model changes. In Global.asax, I've got the following: protected void Application_Start() { Database.SetInitializer(new DropCreateDatabaseIfModelChanges<EntriesContext>()); // ... } In my controller, I've got the following: public ActionResult Index() { // This is just to force the database to be created var context = new EntriesContext(); var all = (from e in context.Entries select e).ToList(); } When the database doesn't exist, it is created with no problems. However, when I make a change to the model, rebuild and refresh, I get the following error: Login failed for user 'sa'. My connection string looks like this: <add name="EntriesContext" connectionString="Server=(LOCAL);Database=MyDB;User Id=sa;Password=password" providerName="System.Data.SqlClient" /> The login definitely works as I can connect to the server and the database from Management Studio using these credentials. If I delete the database manually, everything works correctly and the database is recreated as expected with the schema reflecting the changes made to the model. It seems like either the password or access to the database is being lost. Is there something else I need to do to get this working?

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  • Best ways to construct Dynamic Search Conditions for Sql

    - by CoolBeans
    I have always wondered what's the best way to achieve this task. In most web based applications you have to provide search options on many different criteria. Based on what criteria is chosen behind the scene you modify your SQL. Generally, this is how I tend to go about it:- Have a base SQL template. In the base template have conditions like this WHERE [#PRE_COND1] AND [#PRE_COND2] .. so on and so forth. So an example SQL might look something like SELECT NAME,AGE FROM PERSONS [,#TABLE2] [,#TABLE3] WHERE [#PRE_COND1] AND [#PRE_COND2] ORDER BY [#ORD_COND1] AND [#ORD_COND2] etc. During run time after figuring out the all the search criteria user has entered, I replace the [#PRE_COND1]s and [#ORD_COND1]s with the appropriate SQLs and then execute the query. I personally do not like this brute force method. However, I never came across a better approach either. How do you accomplish such tasks generally given you are either using native JDBC or Spring JDBC? It is almost like I need a C MACRO like functionality in Java to do this.

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  • Updating table row by given id with jQuery

    - by fabrik
    Hello all! I need to update a specific table row (via tr id="unique_key") after a successful AJAX call. HTML fragment: <a name=\"p{$product_id}\" class=\"tr{$product_id}\"></a> <tr id="p{product_id}" class="item-row"> <td><h3>{product_id}</h3><a rel="facebox" href="ajax_url">{product_name}</a></td> <td>{image_information}</td> <td>{image_sortiment}</td> <td>{product_status}</td> </tr> Javascript: // AJAX Call success: function(msg){ $('#p' + prod_id).remove(); $('.tr' + prod_id).after(msg); $('#p' + prod_id + ' a[rel*=facebox]').facebox(); } ... What happens: The table row removed Anchors grouped into one single row (not before their <tr>'s) so my 'hook' disappears AJAX result inserted over the whole table (after my 'hook' but still a wrong place) What's wrong with my idea? How can i force jQuery to 'overwrite' the required table row?

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  • Hibernate Session flush behaviour [ and Spring @Transactional ]

    - by EugeneP
    I use Spring and Hibernate in a web-app, SessionFactory is injected into a DAO bean, and then this DAO is used in a Servlet through webservicecontext. DAO methods are transactional, inside one of the methods I use ... getCurrentSession().save(myObject); One servlet calls this method with an object passed. The update seems to not be flushed at once, it takes about 5 seconds to see the changes in the database. The servlet's method in which that DAO's update method is called, takes a fraction of second to complete. After the @Transactional method of DAO is completed, flushing may NOT happen ? It does not seem to be a rule [ I already see it ]. Then the question is this: what to do to force the session to flush after every DAO method? It may not be a good thing to do, but talking about a Service layer, some methods must end with immediate flush, and Hibernate Session behavior is not predictable. So what to do to guarantee that my @Transactional method persists all the changes after the last line of that method code? getCurrentSession().flush() is the only solution? p.s. I read somewhere that @Transactional IS ASSOCIATED with a DB Transaction. Method returns, transaction must be committed. I do not see this happens.

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  • Is there a way to create subdatabases as a kind of subfolders in sql server?

    - by user193655
    I am creating an application where there is main DB and where other data is stored in secondary databases. The secondary databases follow a "plugin" approach. I use SQL Server. A simple installation of the application will just have the mainDB, while as an option one can activate more "plug-ins" and for every plug-in there will be a new database. Now why I made this choice is because I have to work with an exisiting legacy system and this is the smartest thing I could figure to implement the plugin system. MainDB and Plugins DB have exactly the same schema (basically Plugins DB have some "special content", some important data that one can use as a kind of template - think to a letter template for example - in the application). Plugin DBs are so used in readonly mode, they are "repository of content". The "smart" thing is that the main application can also be used by "plugin writers", they just write a DB inserting content, and by making a backup of the database they creaetd a potential plugin (this is why all DBs has the same schema). Those plugins DB are downloaded from internet as there is a content upgrade available, every time the full PlugIn DB is destroyed and a new one with the same name is creaetd. This is for simplicity and even because the size of this DBs is generally small. Now this works, anyway I would prefer to organize the DBs in a kind of Tree structure, so that I can force the PlugIn DBs to be "sub-DBs" of the main application DB. As a workaround I am thinking of using naming rules, like: ApplicationDB (for the main application DB) ApplicationDB_PlugIn_N (for the N-th plugin DB) When I search for plugin 1 I try to connect to ApplicationDB_PlugIn_1, if I don't find the DB i raise an error. This situation can happen for example if som DBA renamed ApplicationDB_Plugin_1. So since those Plugin DBs are really dependant on ApplicationDB only I was trying to "do the subfolder trick". Can anyone suggest a way to do this? Can you comment on this self-made plugin approach I decribed above?

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  • eclipse stuck at running program

    - by user1434388
    This is the picture after I end task the eclipse. My Android Program has no errors, and before this problem it was all fine. It happened when I added some code into my program. It gets stuck after I click the run button. This also happens when I run my handphone for debugging the program. Other programs are all working fine, only one is stuck. When I try to remove and import it again seem there is a classes.dex file which I cannot delete, I have to restart my computer for it to allow to delete and I have to force the program to close. I have searched at this website and they said keep open the emulator but it doesn't work for me. below is the connecting coding that i added. //check internet connection private boolean chkConnectionStatus(){ ConnectivityManager connMgr = (ConnectivityManager) this.getSystemService(Context.CONNECTIVITY_SERVICE); final android.net.NetworkInfo wifi = connMgr.getNetworkInfo(ConnectivityManager.TYPE_WIFI); final android.net.NetworkInfo mobile = connMgr.getNetworkInfo(ConnectivityManager.TYPE_MOBILE); if( wifi.isAvailable() ){ return true; } else if( mobile.isAvailable() ){ return true; } else { Toast.makeText(this, "Check your internet" , Toast.LENGTH_LONG).show(); return false; } }

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  • Custom bean instantiation logic in Spring MVC

    - by Michal Bachman
    I have a Spring MVC application trying to use a rich domain model, with the following mapping in the Controller class: @RequestMapping(value = "/entity", method = RequestMethod.POST) public String create(@Valid Entity entity, BindingResult result, ModelMap modelMap) { if (entity== null) throw new IllegalArgumentException("An entity is required"); if (result.hasErrors()) { modelMap.addAttribute("entity", entity); return "entity/create"; } entity.persist(); return "redirect:/entity/" + entity.getId(); } Before this method gets executed, Spring uses BeanUtils to instantiate a new Entity and populate its fields. It uses this: ... ReflectionUtils.makeAccessible(ctor); return ctor.newInstance(args); Here's the problem: My entities are Spring managed beans. The reason for this is to inject DAOs on them. Instead of calling new, I use EntityFactory.createEntity(). When they're retrieved from the database, I have an interceptor that overrides the public Object instantiate(String entityName, EntityMode entityMode, Serializable id) method and hooks the factories into that. So the last piece of the puzzle missing here is how to force Spring to use the factory rather than its own BeanUtils reflective approach? Any suggestions for a clean solution? Thanks very much in advance.

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  • Oracle Insert via Select from multiple tables where one table may not have a row

    - by Mikezx6r
    I have a number of code value tables that contain a code and a description with a Long id. I now want to create an entry for an Account Type that references a number of codes, so I have something like this: insert into account_type_standard (account_type_Standard_id, tax_status_id, recipient_id) ( select account_type_standard_seq.nextval, ts.tax_status_id, r.recipient_id from tax_status ts, recipient r where ts.tax_status_code = ? and r.recipient_code = ?) This retrieves the appropriate values from the tax_status and recipient tables if a match is found for their respective codes. Unfortunately, recipient_code is nullable, and therefore the ? substitution value could be null. Of course, the implicit join doesn't return a row, so a row doesn't get inserted into my table. I've tried using NVL on the ? and on the r.recipient_id. I've tried to force an outer join on the r.recipient_code = ? by adding (+), but it's not an explicit join, so Oracle still didn't add another row. Anyone know of a way of doing this? I can obviously modify the statement so that I do the lookup of the recipient_id externally, and have a ? instead of r.recipient_id, and don't select from the recipient table at all, but I'd prefer to do all this in 1 SQL statement.

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  • jQuery UI Dialog Issue With IE

    - by Dan Appleyard
    I am using the new jQuery 1.3.2 and jQuery-ui-1.7 libraries along with the UI Dialog. I have a div tag with several form elements (textbox, checkbox, etc.) in it. Upon page load, jQuery shows the div as a dialog. This works absolutely fine in FF, but in IE, the height of the div is wrong. It is just showing the title bar a bit of the content. I explicitly set the height when creating the div. If I set the height option after opening the dialog, the height is corrected, but the content is blank (shows the top third of a textbox). If I allow the dialog to be resizable, if you resize it in IE it works fine, but I don't want to force IE users to resize just to see the contents. Any ideas? Here is the code I use to create the dialog: $('#dialogDiv').dialog({ bgiframe: true, height: 400, width: 620, modal: true, draggable: true, resizable: false, close: function(event, ui) { if($('#agree').val() != '1') location.href = 'somepage.html'; } });

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  • Does Monitor.Wait ensure that fields are re-read?

    - by Marc Gravell
    It is generally accepted (I believe!) that a lock will force any values from fields to be reloaded (essentially acting as a memory-barrier or fence - my terminology in this area gets a bit loose, I'm afraid), with the consequence that fields that are only ever accessed inside a lock do not themselves need to be volatile. (If I'm wrong already, just say!) A good comment was raised here, questioning whether the same is true if code does a Wait() - i.e. once it has been Pulse()d, will it reload fields from memory, or could they be in a register (etc). Or more simply: does the field need to be volatile to ensure that the current value is obtained when resuming after a Wait()? Looking at reflector, Wait calls down into ObjWait, which is managed internalcall (the same as Enter). The scenario in question was: bool closing; public bool TryDequeue(out T value) { lock (queue) { // arbitrary lock-object (a private readonly ref-type) while (queue.Count == 0) { if (closing) { // <==== (2) access field here value = default(T); return false; } Monitor.Wait(queue); // <==== (1) waits here } ...blah do something with the head of the queue } } Obviously I could just make it volatile, or I could move this out so that I exit and re-enter the Monitor every time it gets pulsed, but I'm intrigued to know if either is necessary.

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  • How to end a thread in perl

    - by user1672190
    I am new to perl and i have a question about perl thread. I am trying to create a new thread to check if the running function is timed out, and my way of doing it is as below. Logic is 1.create a new thread 2.run the main function and see if it is timed out, if ture, kill it Sample code: $exit_tread = false; # a flag to make sure timeout thread will run my $thr_timeout = threads->new( \&timeout ); execute main function here; $exit_thread = true # set the flag to true to force thread ends $thr_timeout->join(); #wait for the timeout thread ends Code of timeout function sub timeout { $timeout = false; my $start_time = time(); while (!$exit_thread) { sleep(1); last if (main function is executed); if (time() - $start_time >= configured time ) { logmsg "process is killed as request timed out"; _kill_remote_process(); $timeout = true; last; } } } now the code is running as i expected, but i am just not very clear if the code $exit_thread = true works because there is a "last" at the end of while loop. Can anybody give me a answer? Thanks

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  • Programming powering off and powering on in one single OnClick function on android

    - by user1060919
    I would like to write an activity that after clicking on a button turns off the screen and then turns it back on after 2 secs. I tried using the following code in order to power off the screen: WindowManager.LayoutParams lp = getWindow().getAttributes(); lp.screenBrightness = 0/(float)255; getWindow().setAttributes(lp); But it would only take effect when then onClick function returns. I tried running it into a handler but with no success. I need to find a way to force the setting to get applied before the function returns so that I can call the power on function 2 secs later on the same onClick call. I also found it very hard to wakeup the device afterwards. While this code works if I power off the screen using the physical button it doesn't seem to work when the phone is powered off using the technique described previously. PowerManager pm = (PowerManager)this.getSystemService(Context.POWER_SERVICE); PowerManager.WakeLock wl = pm.newWakeLock(PowerManager.FULL_WAKE_LOCK|PowerManager.ACQUIRE_CAUSES_WAKEUP | PowerManager.ON_AFTER_RELEASE ,"Dev Tag"); try { wl.acquire(); wl.release(); } catch (Exception e) { Toast.makeText(this, e.getMessage(),20).show(); } Thanks you in advance for your help!

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  • Conditional WHERE Clauses in SQL Server 2008

    - by user336786
    Hello, I am trying to execute a query on a table in my SQL Server 2008 database. I have a stored procedure that uses five int parameters. Currently, my parameters are defined as follows: @memberType int, @color int, @preference int, @groupNumber int, @departmentNumber int This procedure will be passed -1 or higher for each parameter. A value of -1 means that the WHERE clause should not consider that parameter in the join/clause. If the value of the parameter is greater than -1, I need to consider the value in my WHERE clause. I would prefer to NOT use an IF-ELSE statement because it seems sloppy for this case. I saw this question here. However, it did not work for me. I think the reason why is because each of the columns in my table can have a NULL value. Someone pointed this scenario out in the fifth answer. That appears to be happening to me. Is there a slick approach to my question? Or do I just need to brute force it (I hope not :(). Thank you!

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  • Ways to access a 32bit DLL from a 64bit exe

    - by bufferz
    I have a project that must be compiled and run in 64 bit mode. Unfortunately, I am required to call upon a DLL that is only available in 32 bit mode, so there's no way I can house everything in a 1 Visual Studio project. I am working to find the best way to wrap the 32 bit DLL in its own exe/service and issue remote (although on the same machine) calls to that exe/service from my 64 bit app. My OS is Win7 Pro 64 bit. The required calls to this 32 bit process are several dozen per second, but low data volume. This is a realtime image analysis application so response time is critical despite low volume. Lots of sending/receiving single primitives. Ideally, I would host a WCF service to house this DLL, but in a 64 bit OS one cannot force the service to run as x86! Source. That is really unfortunate since I timed function calls to the WCF service to be only 4ms on my machine. I have experimented with named pipes is .net. I found them to be 40-50 times slower than WCF (unusable for me). Any other options or suggestions for the best way to approach my puzzle?

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  • Efficient way to get highly correlated pairs from large data set in Python or R

    - by Akavall
    I have a large data set (Let's say 10,000 variables with about 1000 elements each), we can think of it as 2D list, something like: [[variable_1], [variable_2], ............ [variable_n] ] I want to extract highly correlated variable pairs from that data. I want "highly correlated" to be a parameter that I can choose. I don't need all pairs to be extracted, and I don't necessarily want the most correlated pairs. As long as there is an efficient method that gets me highly correlated pairs I am happy. Also, it would be nice if a variable does not show up in more than one pair. Although this might not be crucial. Of course, there is a brute force way to finding such pairs, but it is too slow for me. I've googled around for a bit and found some theoretical work on this issue, but I wasn't able for find a package that could do what I am looking for. I mostly work in python, so a package in python would be most helpful, but if there exists a package in R that does what I am looking for it will be great. Does anyone know of a package that does the above in Python or R? Or any other ideas? Thank You in Advance

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  • Implementing a Version check between an Abstract class and it's implementation

    - by Michael Stum
    I have this abstract class and concrete implementation (they are in different assemblies): public abstract class MyAbstractClass { private static readonly int MyAbstractClassVersion = 1; public abstract int ImplementedVersion { get; } protected MyAbstractClass() { CheckVersion(); } private void CheckVersion() { var message = string.Format( "MyAbstractClass implements Version {0}, concrete is Version {1}", RepositoryVersion, ImplementedVersion); if (!MyAbstractClassVersion.Equals(ImplementedVersion)) throw new InvalidOperationException(message); } } public class ConcreteClass : MyAbstractClass { public ConcreteClass() : base() { // ConcreteClass is guaranteed to have // a constructor that calls the base constructor // I just simplified the example } public override int ImplementedVersion { get { return 2; } } } As you see, I call CheckVersion() from the abstract constructor, to get rid of the "virtual member call in base constructor" message, but I am not sure if that's really the way to do it. Sure, it works, but that doesn't mean it will always work, will it? Also, I wonder if I can get the name of the Concrete Type from the CheckVersion() function? I know that adding new abstract members will force an error anyway (System.TypeLoadException) and I'm not sure if I want this type of strict Versioning, but I'm just curious how it would be done properly given only the abstract class and an implementation (I know I could do it by using interfaces and/or a Factory pattern).

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  • Complicated API issue with calling assemblies dynamically?

    - by Stefanos Tses
    I have an interesting challenge that I'm wondering if anyone here can give me some direction. I'm writing a .Net windows forms application that runs on a network and uses an SQL Server to save and pull data. I want to offer a mini "plugin" API, where developers can build their own assemblies and implement a specific interface (IDataManipulate). These assemblies then can be used by my application to call the interface functions and do something. I can create assemblies using my API, copy the file to a folder in my local hard drive and configure my application to use Reflection to call a specific function from the implemented interface (IDataManipulate.Execute). The problem: Since the application will be installed in multiple workstations in the network, is impossible to copy the plugin dlls the users will create to each machine. Solutions I tried: Solution 1 Copy the API dll to a network share. Problem: Requires AllowPartiallyTrustedCallersAttribute, which requires .Net singing, which I can't force from my users. Solution 2 (preferred) Serialize the dll object, save it to the database, deserialize it and call IDataManipulate.Execute. Problem: After deserialization, I try cast it to a IDataManipulate object but returns an error looking for the actual dll file. Solution 3 Save the dll bytes as byte[] to the database and recreate the dll at the local PC every time the user starts my application. Problem: Dll may have dependencies, which I don't know if I can detect. Any suggestions will be greatly appreciated. Thanks

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  • Why can't we just use a hash of passphrase as the encryption key (and IV) with symmetric encryption algorithms?

    - by TX_
    Inspired by my previous question, now I have a very interesting idea: Do you really ever need to use Rfc2898DeriveBytes or similar classes to "securely derive" the encryption key and initialization vector from the passphrase string, or will just a simple hash of that string work equally well as a key/IV, when encrypting the data with symmetric algorithm (e.g. AES, DES, etc.)? I see tons of AES encryption code snippets, where Rfc2898DeriveBytes class is used to derive the encryption key and initialization vector (IV) from the password string. It is assumed that one should use a random salt and a shitload of iterations to derive secure enough key/IV for the encryption. While deriving bytes from password string using this method is quite useful in some scenarios, I think that's not applicable when encrypting data with symmetric algorithms! Here is why: using salt makes sense when there is a possibility to build precalculated rainbow tables, and when attacker gets his hands on hash he looks up the original password as a result. But... with symmetric data encryption, I think this is not required, as the hash of password string, or the encryption key, is never stored anywhere. So, if we just get the SHA1 hash of password, and use it as the encryption key/IV, isn't that going to be equally secure? What is the purpose of using Rfc2898DeriveBytes class to generate key/IV from password string (which is a very very performance-intensive operation), when we could just use a SHA1 (or any other) hash of that password? Hash would result in random bit distribution in a key (as opposed to using string bytes directly). And attacker would have to brute-force the whole range of key (e.g. if key length is 256bit he would have to try 2^256 combinations) anyway. So either I'm wrong in a dangerous way, or all those samples of AES encryption (including many upvoted answers here at SO), etc. that use Rfc2898DeriveBytes method to generate encryption key and IV are just wrong.

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  • Why use shorter VARCHAR(n) fields?

    - by chryss
    It is frequently advised to choose database field sizes to be as narrow as possible. I am wondering to what degree this applies to SQL Server 2005 VARCHAR columns: Storing 10-letter English words in a VARCHAR(255) field will not take up more storage than in a VARCHAR(10) field. Are there other reasons to restrict the size of VARCHAR fields to stick as closely as possible to the size of the data? I'm thinking of Performance: Is there an advantage to using a smaller n when selecting, filtering and sorting on the data? Memory, including on the application side (C++)? Style/validation: How important do you consider restricting colunm size to force non-sensical data imports to fail (such as 200-character surnames)? Anything else? Background: I help data integrators with the design of data flows into a database-backed system. They have to use an API that restricts their choice of data types. For character data, only VARCHAR(n) with n <= 255 is available; CHAR, NCHAR, NVARCHAR and TEXT are not. We're trying to lay down some "good practices" rules, and the question has come up if there is a real detriment to using VARCHAR(255) even for data where real maximum sizes will never exceed 30 bytes or so. Typical data volumes for one table are 1-10 Mio records with up to 150 attributes. Query performance (SELECT, with frequently extensive WHERE clauses) and application-side retrieval performance are paramount.

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  • java.lang.IllegalStateException: The content of the adapter has changed but ListView.... inspite of calling notifydatasetchanged()

    - by Mistaken
    What are the best practices to be followed to update the contents of a listactivty by a background thread (Async Task) ? 1) Am calling the notifyDataSetChanged() to update the adapter as soon as i manipulate the contents of the adapter but still my app force closes while the user scrolls or click on the list. Any pointers to prevent this would be very helpfull. Logcat: java.lang.IllegalStateException: The content of the adapter has changed but ListView did not receive a notification. 2) Where exaclty should i update contents of the listactivity ? inside the doInBackground() or onProgressUpdate()? 3) Am experiencing regular crashes when the user clicks the list item. So will disabling click events on the listactivty during the background operation solve the problem ? If so am not sure how to remove or set item click listeners dynamically to the listactivity. Please instruct me on the too. 4) I dont think blocking all ui interactions during the background async task execution is the only way to solve the problem. I know there is a simple way of doing this but need some help. Thanks in advance. This is my onCreate... protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.fa); tvStatus=(TextView) findViewById(R.id.tvStatus); adapter = new SimpleAdapter( this, mostPopularList, R.layout.list_item, new String[] {"title","author","views","date"}, new int[] {R.id.textView1,R.id.textView2,R.id.textView4,R.id.textView3}); //populateList(); setListAdapter(adapter); } My async task... private class LongOperation extends AsyncTask<String, Void, String> { @Override protected String doInBackground(String... params) { // code for adding new listactivty items } @Override protected void onPostExecute(String networkStatus) { adapter.notifyDataSetChanged(); } @Override protected void onPreExecute() { } @Override protected void onProgressUpdate(Void... values) { } }

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  • Problem with configure script

    - by cube
    I am running into a problem with the ./configure script for ffmpeg. My linux environment uses busybox, which only allows for limited set of linux commands. One command which is used in the ffmpeg ./configure script is mktemp -u, the problem here is the busybox for linux does not recognize the -u switch as valid, so it complains about it and breaks the configure process. This is the relevant code in ./configure which uses the mktemp -u command: if ! check_cmd type mktemp; then # simple replacement for missing mktemp # NOT SAFE FOR GENERAL USE mktemp(){ echo "${2%XXX*}.${HOSTNAME}.${UID}.$$" } fi tmpfile(){ tmp=$(mktemp -u "${TMPDIR}/ffconf.XXXXXXXX")$2 && (set -C; exec > $tmp) 2>/dev/null || die "Unable to create temporary file in $TMPDIR." append TMPFILES $tmp eval $1=$tmp } I am not good with bash scripting at all, so I was wondering if anyone one had an idea on how I can force this configure script to not use mktemp -u and use the 'replacement' alternative option that is available in as per the snippet above. Thanks. btw... simply removing the -u switch does not work. Nor does replacing it with -t, or -p. I believe the mktemp has to be bypassed completely.

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