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• Strategies for Synchronizing Data Between a Rails App and iPhone App

  - by jessecurry

  I've written many iPhone Applications that have pulled data from web services and I've worked on synchronizing data between an iPhone App and a Web Application, but I've always felt that there is probably a better way to handle the synchronization. I'd like to know what strategies you have used to synchronize data between your iPhone(read: mobile) Apps and your Rails(read: web) Applications. Are there any strategies that scale particularly well? How have you dealt with large amounts of data? (Do you use paged responses?) How do you make sure that data is not overwritten? Is there a reason to avoid Ruby on Rails? if so, can you suggest an alternative? What is better about the alternative? What strategies have failed? Why do you believe that those strategies failed? I would like to be able to keep all of the data modifications on the server, but the particular application I am about to start work on will need the ability to operate while disconnected from the network. The user will be able to update data on the mobile device and update data through the web application. When the user's mobile device connects to the server any local changes will be pushed to the server.

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• How do I stop Chrome from yellowing my site's input boxes?

  - by davebug

  Among other text and visual aids on a form submission, post-validation, I'm coloring my input boxes red to signify the interactive area needing attention. On Chrome (and for Google Toolbar users) the auto-fill feature re-colors my input forms yellow. Here's the complex issue: I want auto-complete allowed on my forms, as it speeds users logging in. I am going to check into the ability to turn the autocomplete attribute to off if/when there's an error triggered, but it is a complex bit of coding to programmatically turn off the auto-complete for the single effected input on a page. This, to put it simply, would be a major headache. So to try to avoid that issue, is there any simpler method of stopping Chrome from re-coloring the input boxes? [edit] I tried the !important suggestion below and it had no effect. I have not yet checked Google Toolbar to see if the !important attribute woudl work for that. As far as I can tell, there isn't any means other than using the autocomplete attribute (which does appear to work).

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• What's a good way to parameterize "static" content (e.g. CSS) in a Tomcat webapp?

  - by Steven Huwig

  Some of our CSS files contain parameters that can vary based on the deployment location (dev, QA, prod). For example: background: url(#DOJO_PATH#/dijit/themes...) to avoid hardcoding a path to a particular CDN or locally-hosted Dojo installation. These values are textually substituted with the real values by a deployment script, when it copies the contents of the webapp into the Tomcat webapps directory. That way the same deployment archive file (WAR + TAR file containing other configuration) can be deployed to dev, QA, and prod, with the varying parameters provided by environment-specific configuration files. However, I'd like to make the contents of the WAR (including the templatized CSS files) independent of this in-house deployment script. Since we don't really have control over the deployment script, all I can think to do is configure Tomcat with #DOJO_PATH# etc. as environment variables in the application's context.xml, and use Tomcat to insert those parameters into the CSS at runtime. I could make the CSS files into generated JSPs, but it seems a little ugly to me. Moreover, the substitution only needs to be done once per application deployment, so repeatedly dynamically generating the stylesheets using JSP will be rather wasteful. Does anyone have any alternative ideas or tools to use for this? We're committed to Tomcat and to substituting these parameters at deployment or at runtime (that is, not at build time).

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• #include - brackets vs quotes in XCode?

  - by Chris Becke

  In MSVC++ #include files are searched for differently depending on whether the file is enclosed in "" or <. The quoted form searches first in the local folder, then in /I specified locations, The angle bracket form avoids the local folder. This means, in MSVC++, its possible to have header files with the same name as runtime and SDK headers. So, for example, I need to wrap up the windows sdk windows.h file to undefine some macro's that cause trouble. With MSVS I can just add a (optional) windows.h file to my project as long as I include it using the quoted form :- // some .cpp file #include "windows.h" // will include my local windows.h file And in my windows.h, I can pull in the real one using the angle bracket form: // my windows.h #include <windows.h> // will load the real one #undef ConflictingSymbol Trying this trick with GCC in XCode didn't work. angle bracket #includes in system header files in fact are finding my header files with similar names in my local folder structure. The MSVC system means its quite safe to have a "String.h" header file in my own folder structre. On XCode this seems to be a major no no. Is there some way to control this search path behaviour in XCode to be more like MSVC's? Or do I just have to avoid naming any of my headers anything that might possibly conflict with a system header. Writing cross platform code and using lots of frameworks means the possibility of incidental conflicts seems large.

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• Tree-like queues

  - by Rehno Lindeque

  I'm implementing a interpreter-like project for which I need a strange little scheduling queue. Since I'd like to try and avoid wheel-reinvention I was hoping someone could give me references to a similar structure or existing work. I know I can simply instantiate multiple queues as I go along, I'm just looking for some perspective by other people who might have better ideas than me ;) I envision that it might work something like this: The structure is a tree with a single root. You get a kind of "insert_iterator" to the root and then push elements onto it (e.g. a and b in the example below). However, at any point you can also split the iterator into multiple iterators, effectively creating branches. The branches cannot merge into a single queue again, but you can start popping elements from the front of the queue (again, using a kind of "visitor_iterator") until empty branches can be discarded (at your discretion). x -> y -> z a -> b -> { g -> h -> i -> j } f -> b Any ideas? Seems like a relatively simple structure to implement myself using a pool of circular buffers but I'm following the "think first, code later" strategy :) Thanks

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• How can I use a compound condition in a join in Linq?

  - by Gary McGill

  Let's say I have a Customer table which has a PrimaryContactId field and a SecondaryContactId field. Both of these are foreign keys that reference the Contact table. For any given customer, either one or two contacts may be stored. In other words, PrimaryContactId can never be NULL, but SecondaryContactId can be NULL. If I drop my Customer and Contact tables onto the "Linq to SQL Classes" design surface, the class builder will spot the two FK relationships from the Customer table to the Contact table, and so the generated Customer class will have a Contact field and a Contact1 field (which I can rename to PrimaryContact and SecondaryContact to avoid confusion). Now suppose that I want to get details of all the contacts for a given set of customers. If there was always exactly one contact then I could write something like: from customer in customers join contact in contacts on customer.PrimaryContactId equals contact.id select ... ...which would be translated into something like: SELECT ... FROM Customer INNER JOIN Contact ON Customer.FirstSalesPersonId = Contact.id But, because I want to join on both the contact fields, I want the SQL to look something like: SELECT ... FROM Customer INNER JOIN Contact ON Customer.FirstSalesPersonId = Contact.id OR Customer.SecondSalesPersonId = Contact.id How can I write a Linq expression to do that?

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• What runs faster? Wordpress or Drupal 6.x?

  - by electblake

  So... I run a pretty large Wordpress blog. Currently it gets around 20k+ pageviews a day, and its always a struggle to keep the bad boy running quickly - I currently run a vps.net with CentOS 5.3 I am also Drupal developer by trade so I love the CMS Framework for its versatility and the portability (I can take work from one site and implement on another with great ease) MY QUESTION IS: What is faster then? Wordpress 3.x & Drupal 6.x I'd love to migrate my site to Drupal to be able to roll out new features etc (which I find awkward to do in Wordpress) but I am scared that Drupal may not be able to handle the traffic. Any opinions? I know that some major players use Drupal - as Dries documents well on his blog but I'm not under any illusions that Drupal can be a real hog. Thanks for any/all help! Please try to avoid server optimization talk unless it pertains to Wordpress or Drupal 6.x specifically, I love to learn more about optimizations but I do want to sort out which platform is quicker :) p.s - I realize the fastest option is to use a lower-level framework (with less overhead) like CakePHP etc but assume that isn't an option ;)

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• Strict pointer aliasing: is access through a 'volatile' pointer/reference a solution?

  - by doublep

  On the heels of a specific problem, a self-answer and comments to it, I'd like to understand if it is a proper solution, workaround/hack or just plain wrong. Specifically, I rewrote code: T x = ...; if (*reinterpret_cast <int*> (&x) == 0) ... As: T x = ...; if (*reinterpret_cast <volatile int*> (&x) == 0) ... with a volatile qualifier to the pointer. Let's just assume that treating T as int in my situation makes sense. Does this accessing through a volatile reference solve pointer aliasing problem? For a reference, from specification: [ Note: volatile is a hint to the implementation to avoid aggressive optimization involving the object because the value of the object might be changed by means undetectable by an implementation. See 1.9 for detailed semantics. In general, the semantics of volatile are intended to be the same in C++ as they are in C. — end note ] EDIT: The above code did solve my problem at least on GCC 4.5.

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• Checking when two headers are included at the same time.

  - by fortran

  Hi, I need to do an assertion based on two related macro preprocessor #define's declared in different header files... The codebase is huge and it would be nice if I could find a place to put the assertion where the two headers are already included, to avoid polluting namespaces unnecessarily. Checking just that a file includes both explicitly might not suffice, as one (or both) of them might be included in an upper level of a nesting include's hierarchy. I know it wouldn't be too hard to write an script to check that, but if there's already a tool that does the job, the better. Example: file foo.h #define FOO 0xf file bar.h #define BAR 0x1e I need to put somewhere (it doesn't matter a lot where) something like this: #if (2*FOO) != BAR #error "foo is not twice bar" #endif Yes, I know the example is silly, as they could be replaced so one is derived from the other, but let's say that the includes can be generated from different places not under my control and I just need to check that they match at compile time... And I don't want to just add one include after the other, as it might conflict with previous code that I haven't written, so that's why I would like to find a file where both are already present. In brief: how can I find a file that includes (direct or indirectly) two other files? Thanks!

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• web service slowdown

  - by user238591

  Hi, I have a web service slowdown. My (web) service is in gsoap & managed C++. It's not IIS/apache hosted, but speaks xml. My client is in .NET The service computation time is light (<0.1s to prepare reply). I expect the service to be smooth, fast and have good availability. I have about 100 clients, response time is 1s mandatory. Clients have about 1 request per minute. Clients are checking web service presence by tcp open port test. So, to avoid possible congestion, I turned gSoap KeepAlive to false. Until there everything runs fine : I bearly see connections in TCPView (sysinternals) New special synchronisation program now calls the service in a loop. It's higher load but everything is processed in less 30 seconds. With sysinternals TCPView, I see that about 1 thousands connections are in TIME_WAIT. They slowdown the service and It takes seconds for the service to reply, now. Could it be that I need to reset the SoapHttpClientProtocol connection ? Someone has TIME_WAIT ghosts with a web service call in a loop ?

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• Modify Gridview as it's being rendered through javascript

  - by JonF

  I'm trying to modify a field in each row of my gridview as it is rendered. I need to modify it with client side Javascript. I'm somewhat new to asp.net, but I think I should be doing something with clientscriptmanager. I came up with a simple scenario which is basically what I want to do to avoid getting bogged down in the details. If I could accomplish the following I could accomplish my goal. Say I have a grid view of names and salaries. I want to double each persons salary before displaying it. Obviously I can do it in the code behind, but due to the nature of the more complex actual thing I'm doing, I need to do it in javascript <asp:GridView ID="GridView1" runat="server" AutoGenerateColumns="false" onrowdatabound="GridView1_RowDataBound" > <Columns> <asp:BoundField HeaderText="Full Name" DataField="Name" ></asp:BoundField> <asp:BoundField HeaderText="Salary" DataField="Salary" /> </Columns>

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• Laravel - Mail class Exception

  - by Christian Giupponi

  I need to send email within my app and this is my code: if( $agent->save() ) { //Preparo la mail da inviare con i dati di login $data = [ 'nome' => $input['nome'], 'cognome' => $input['cognome'], 'email' => $input['email'], 'password' => $input['password'] ]; //ATTENZIONE //Questo è da rimuovere in produzione, finge di inviare la mail Mail::pretend(); //Recuero il template e passo alla funzione i dati Mail::send('emails.agents.registration', $data, function($message) use ($data) { $message->to( $data['email'], $data['nome'].' '.$data['cognome'] )->subject('Benvenuto!'); }); return Redirect::action('admin.agents.index')->with('positive_flash_message', 'Agente inserito correttamente.'); } As you can see I have use the Mail::pretend to avoid the email send in development, the problem is that I get this error every time I try to send an email: Undefined property: Illuminate\Mail\Message::$email (View: /var/www/progetti/app/views/emails/agents/registration.blade.php) nd this is my blade view: Email: {{ $message->email }} Password: {{ $message->password }} What's wrong with $message?

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• Invoking code both before and after WebControl.Render method

  - by Dirk

  I have a set of custom ASP.NET server controls, most of which derive from CompositeControl. I want to implement a uniform look for "required" fields across all control types by wrapping each control in a specific piece of HTML/CSS markup. For example: <div class="requiredInputContainer"> ...custom control markup... </div> I'd love to abstract this behavior in such a way as to avoid having to do something ugly like this in every custom control, present and future: public class MyServerControl : TextBox, IRequirableField { public IRequirableField.IsRequired {get;set;} protected override void Render(HtmlTextWriter writer){ RequiredFieldHelper.RenderBeginTag(this, writer) //render custom control markup RequiredFieldHelper.RenderEndTag(this, writer) } } public static class RequiredFieldHelper{ public static void RenderBeginTag(IRequirableField field, HtmlTextWriter writer){ //check field.IsRequired, render based on its values } public static void RenderEndTag(IRequirableField field, HtmlTextWriter writer){ //check field.IsRequired , render based on its values } } If I was deriving all of my custom controls from the same base class, I could conceivably use Template Method to enforce the before/after behavior;but I have several base classes and I'd rather not end up with really a convoluted class hierarchy anyway. It feels like I should be able to design something more elegant (i.e. adheres to DRY and OCP) by leveraging the functional aspects of C#, but I'm drawing a blank.

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• Django: returning a selection of fields from a model based on their values?

  - by AP257

  I am working with some data over which I have little control. I'd like to return ONLY the fields of my model that aren't certain 'uninteresting' values (e.g. '0', 'X' or '-'), and access them individually in the template. My model is like this: class Manors(models.Model): structidx = models.IntegerField(primary_key=True, verbose_name="ID") hills = models.CharField(max_length=100, null=True, blank=True, verbose_name="Number of fields") In my template, I return a QuerySet of Manors, and I'd like to output something like this if the hills field isn't uninteresting: {% for manor in manors %} {% if manor.hills %}<li>Hills blah blah: {{ manor.hills }}</li>{% endif %} {% endfor %} I want to avoid too much logic in the template. Ideally, the manor object would simply not return with the uninteresting fields attached, then I could just do {% if manor.hills %}. I tried writing a model method that returns a dictionary of the interesting values, like this: def get_field_dictionary(self): interesting_fields = {} for field in Manors._meta.fields: if field.value_to_string(self) != "N" and field.value_to_string(self) != "0" and field.value_to_string(self) != "-" and field.value_to_string(self) != "X": interesting_fields[field.name] = field.value_to_string(self) return interesting_fields But I don't know how to access individual values of the dictionary in the template: {% if manor.get_field_dictionary['hills'] %}<li>Hills blah blah: {{ manor.get_field_dictionary['hills'] }}</li>{% endif %} gives a TemplateSyntaxError. Is there a better way to do this?

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• Java: using generic wildcards with subclassing

  - by gibberish

  Say I have a class Foo, a class A and some subclass B of A. Foo accepts A and its sublclasses as the generic type. A and B both require a Foo instance in their constructor. I want A's Foo to be of type A , and B's Foo to be of type B or a superclass of B. So in effect, So I only want this: Foo<X> bar = new Foo<X>; new B(bar); to be possible if X is either A, B, or a both subclass of A and superclass of B. So far this is what I have: class Foo<? extends A>{ //construct } class A(Foo<A> bar){ //construct } class B(Foo<? super B> bar){ super(bar); //construct } The call to super(...) doesn't work, because <A> is stricter than <? super B>. Is it somehow possible to use the constructor (or avoid code duplication by another means) while enforcing these types? Edit: Foo keeps a collection of elements of the generic parameter type, and these elements and Foo have a bidirectional link. It should therefore not be possible to link an A to a Foo.

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• How do I fix the alpha value after calling GDI text functions?

  - by Daniel Stutzbach

  I have a application that uses the Aero glass effect, so each pixel has an alpha value in addition to red, green, and blue values. I have one custom-draw control that has a solid white background (alpha = 255). I would like to draw solid text on the control using the GDI text functions. However, these functions set the alpha value to an arbitrary value, causing the text to translucently show whatever window is beneath my application's. After calling rendering the text, I would like to go through all of the pixels in the control and set their alpha value back to 255. What's the best way to do that? I haven't had any luck with the BitBlt, GetPixel, and SetPixel functions. They appear to be oblivious to the alpha value. Here are other solutions that I have considered and rejected: Draw to a bitmap, then copy the bitmap to the device: With this approach, the text rendering does not make use of the characteristics of the monitor (e.g., ClearText). Use GDI+ for text rendering: This application originally used GDI+ for text rendering (before I started working on Aero support). I switched to GDI because of difficulties I encountered trying to accurately measure strings with GDI+. I'd rather not switch back. Set the Aero region to avoid the control in question: My application's window is actually a child window of a different application running in a different process. I don't have direct control over the Aero settings on the top-level window. The application is written in C# using Windows Forms, though I'm not above using Interop to call Win32 API functions.

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• C++ destructor problem with boost::scoped_ptr

  - by bb-generation

  I have a question about the following code: #include <iostream> #include <boost/scoped_ptr.hpp> class Interface { }; class A : public Interface { public: A() { std::cout << "A()" << std::endl; } virtual ~A() { std::cout << "~A()" << std::endl; } }; Interface* get_a() { A* a = new A; return a; } int main() { { std::cout << "1" << std::endl; boost::scoped_ptr<Interface> x(get_a()); std::cout << "2" << std::endl; } std::cout << "3" << std::endl; } It creates the following output: 1 A() 2 3 As you can see, it doesn't call the destructor of A. The only way I see to get the destructor of A being called, is to add a destructor for the Interface class like this: virtual ~Interface() { } But I really want to avoid any Implementation in my Interface class and virtual ~Interface() = 0; doesn't work (produces some linker errors complaining about a non existing implementation of ~Interface(). So my question is: What do I have to change in order to make the destructor being called, but (if possible) leave the Interface as an Interface (only abstract methods).

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• RewriteRule to store thousands of files in subdirectories

  - by Brandon

  I have a website that will have millions of pages in a directory. I'd like to store those files on-disk in a bunch of subdirectories based on the first characters of the page name. For example http://mysite.com/hugedir/somefile.html would be stored in /var/www/html/hugedir/s/o/m/e/f/ile.html That is fairly trivial to do with a RewriteRule like so: RewriteRule ^hugedir/(.)(.)(.)(.)(.)(.*).html /hugedir/{$1}/{$2}/{$3}/{$4}/{$5}/$6.html RewriteRule ^hugedir/(.)(.)(.)(.)(.*).html /hugedir/{$1}/{$2}/{$3}/{$4}/{$5}.html RewriteRule ^hugedir/(.)(.)(.)(.*).html /hugedir/{$1}/{$2}/{$3}/{$4}.html RewriteRule ^hugedir/(.)(.)(.*).html /hugedir/{$1}/{$2}/{$3}.html RewriteRule ^hugedir/(.)(.*).html /hugedir/{$1}/{$2}.html RewriteRule ^hugedir/(.*).html /hugedir/{$1}.html However, the file name may contain hyphens or other non-standard characters and I'd really like to avoid having a directory named with a strange character. Ideally, I'd like to have a list of 'approved' characters and either eliminate or transform the unapproved characters to an underscore. Can anybody think of a way to do that? Or something else equivalent? Part of the requirement is that these be physical files on disk and it not be parsed with a scripting language.

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• Hibernate NamingStrategy implementation that maintains state between calls

  - by Robert Petermeier

  Hi, I'm working on a project where we use Hibernate and JBoss 5.1. We need our entity classes to be mapped to Oracle tables that follow a certain naming convention. I'd like to avoid having to specify each table and column name in annotations. Therefore, I'm currently considering implementing a custom implementation of org.hibernate.cfg.NamingStrategy. The SQL naming conventions require the name of columns to have a suffix that is equivalent to a prefix of the table name. If there is a table "T100_RESOURCE", the ID column would have to be named "RES_ID_T100". In order to implement this in a NamingStrategy, the implementation would have to maintain state, i.e. the current class name it is creating the mappings for. It would rely on Hibernate to always call classToTableName() before propertyToColumnName() and to determine all column names by calling propertyToColumnName() before the next call to classToTableName() Is it safe to do that or are there situations where Hibernate will mix things up? I am not thinking of problems through multiple threads here (which can be solved by keeping the last class name in a ThreadLocal) but also of Hibernate deliberately calling this out of order in certain circumstances. For example Hibernate asking for mappings of three properties of class A, then one of class B, then again more attributes of class A.

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• Proper API Design for Version Independence?

  - by Justavian

  I've inherited an enormous .NET solution of about 200 projects. There are now some developers who wish to start adding their own components into our application, which will require that we begin exposing functionality via an API. The major problem with that, of course, is that the solution we've got on our hands contains such a spider web of dependencies that we have to be careful to avoid sabotaging the API every time there's a minor change somewhere in the app. We'd also like to be able to incrementally expose new functionality without destroying any previous third party apps. I have a way to solve this problem, but i'm not sure it's the ideal way - i was looking for other ideas. My plan would be to essentially have three dlls. APIServer_1_0.dll - this would be the dll with all of the dependencies. APIClient_1_0.dll - this would be the dll our developers would actual refer to. No references to any of the mess in our solution. APISupport_1_0.dll - this would contain the interfaces which would allow the client piece to dynamically load the "server" component and perform whatever functions are required. Both of the above dlls would depend upon this. It would be the only dll that the "client" piece refers to. I initially arrived at this design, because the way in which we do inter process communication between windows services is sort of similar (except that the client talks to the server via named pipes, rather than dynamically loading dlls). While i'm fairly certain i can make this work, i'm curious to know if there are better ways to accomplish the same task.

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• How to implement a log window in a web browser?

  - by Jeremy Friesner

  Hi all, I'm interested in adding an HTML/web-browser based "log window" to my net-enabled device. Specifically, my device has a customized web server and an event log, and I'd like to be able to leave a web browser window open to e.g. http://my.devices.ip.address/system_log and have events show up as text in the web browser window as they happen. People could then use this as a quick way to monitor what the system is doing, without needing run any special software. My question is, what is the best way to implement this? I've tried the obvious approach -- just have my device's embedded web server hold the HTTP/TCP connection open indefinitely, and write the necessary text to the TCP socket when an event occurs -- but the problem with that is that most web browsers (e.g. Safari) don't display the web page until the server has closed the TCP connection has been closed, and so the result is that the log data never appears in the web browser, it just acts as if the page is taking forever to load. Is there some trick to make this work? I could implement it as a Java applet, but I'd much prefer something more lightweight/simple, either using only HTML or possibly HTML+JavaScript. Also I'd like to avoid having the web browser 'poll' the server, since that would either introduce too much latency (if the reload delay was large) or put load on the system (if the delay was small)

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• Void* array casting to float, int32, int16, etc.

  - by Griffin

  Hey guys, I've got an array of PCM data, it could be 16 bit, 24 bit packed, 32 bit, etc.. It could be signed, or unsigned, and it could be 32 or 64 bit floating point. It is currently stored as a "void**" matrix, indexed by channel, then by frame. The goal is to allow my library to take in any PCM format and buffer it, without requiring manipulation of the data to fit a designated structure. If the A/D converter spits out 24 bit packed arrays of interleaved PCM, I need to accept it gracefully. I also need to support 16 bit non interleaved, as well as any permutation of the above formats. I know the bit depth and other information at runtime, and I'm trying to code efficiently while not duplicating code. What I need is an effective way to cast the matrix, put PCM data into the matrix, and then pull it out later. I can cast the matrix to int32_t, or int16_t for the 32 and 16 bit signed PCM respectively, I'll probably have to store the 24 bit PCM in an int32_t for 32 bit, 8 bit byte systems as well. Can anyone recommend a good way to put data into this array, and pull it out later? I'd like to avoid large sections of code which look like: switch( mFormat ) { case 1: // unsigned 8 bit for( int i = 0; i < mChannels; i++ ) framesArray = (uint8_t*)pcm[i]; break; case 2: // signed 8 bit for( int i = 0; i < mChannels; i++ ) framesArray = (int8_t*)pcm[i]; break; case 3: // unsigned 16 bit ... Limitations: I'm working in C/C++, no templates, no RTTI, no STL. Think embedded. Things get trickier when I have to port this to a DSP with 16 bit bytes. Does anybody have any useful macros they might be willing to share? Thanks, -Griff

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• Generating different randoms valid for a day on different independent devices?

  - by Pentium10

  Let me describe the system. There are several mobile devices, each independent from each other, and they are generating content for the same record id. I want to avoid generating the same content for the same record on different devices, for this I though I would use a random and make it so too cluster the content pool based on these randoms. Suppose you have choices from 1 to 100. Day 1 Device#1 will choose for the record#33 between 1-10 Device#2 will choose for the record#33 between 40-50 Device#3 will choose for the record#33 between 50-60 Device#1 will choose for the record#55 between 40-50 Device#2 will choose for the record#55 between 1-10 Device#3 will choose for the record#55 between 10-20 Device#1 will choose for the record#11 between 1-10 Device#2 will choose for the record#22 between 1-10 Device#3 will choose for the record#99 between 1-10 Day 2 Device#1 will choose for the record#33 between 90-100 Device#2 will choose for the record#33 between 1-10 Device#3 will choose for the record#33 between 50-60 They don't have access to a central server. Data available for each of them: IMEI (unique per mobile) Date of today (same on all devices) Record id (same on all devices) What do you think, how is it possible? ps. tags can be edited

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• Refreshing a MKMapView when the user location is updated or using default values

  - by koichirose

  I'm trying to refresh my map view and load new data from the server when the device acquires the user location. Here's what I'm doing: - (void)viewDidLoad { CGRect bounds = self.view.bounds; mapView = [[MKMapView alloc] initWithFrame:bounds]; mapView.showsUserLocation=YES; mapView.delegate=self; [self.view insertSubview:mapView atIndex:0]; [self refreshMap]; } - (void)mapView:(MKMapView *)theMapView didUpdateUserLocation:(MKUserLocation *)userLocation { //this is to avoid frequent updates, I just need one position and don't need to continuously track the user's location if (userLocation.location.horizontalAccuracy > self.myUserLocation.location.horizontalAccuracy) { self.myUserLocation = userLocation; CLLocationCoordinate2D centerCoord = { userLocation.location.coordinate.latitude, userLocation.location.coordinate.longitude }; [theMapView setCenterCoordinate:centerCoord zoomLevel:10 animated:YES]; [self refreshMap]; } } - (void)refreshMap { [[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:YES]; [self.mapView removeAnnotations:self.mapView.annotations]; //default position NSString *lat = @"45.464161"; NSString *lon = @"9.190336"; if (self.myUserLocation != nil) { lat = [[NSNumber numberWithDouble:myUserLocation.coordinate.latitude] stringValue]; lon = [[NSNumber numberWithDouble:myUserLocation.coordinate.longitude] stringValue]; } NSString *url = [[NSString alloc] initWithFormat:@"http://myserver/geo_search.json?lat=%@&lon=%@", lat, lon]; NSURLRequest *theRequest=[NSURLRequest requestWithURL:[NSURL URLWithString:url] cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:60.0]; [[NSURLConnection alloc] initWithRequest:theRequest delegate:self]; [url release]; [[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:NO]; } I also have a - (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data, to create and add the annotations. Here's what happens: sometimes I get the location after a while, so I already loaded data close to the default location. Then I get the location and it should remove the old annotations and add the new ones, instead I keep seeing the old annotations and the new ones are added anyway (let's say I receive 10 annotations each time, so it means that I have 20 on my map when I should have 10). What am I doing wrong?

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• Is this an acceptable use of "ASCII arithmetic"?

  - by jmgant

  I've got a string value of the form 10123X123456 where 10 is the year, 123 is the day number within the year, and the rest is unique system-generated stuff. Under certain circumstances, I need to add 400 to the day number, so that the number above, for example, would become 10523X123456. My first idea was to substring those three characters, convert them to an integer, add 400 to it, convert them back to a string and then call replace on the original string. That works. But then it occurred to me that the only character I actually need to change is the third one, and that the original value would always be 0-3, so there would never be any "carrying" problems. It further occurred to me that the ASCII code points for the numbers are consecutive, so adding the number 4 to the character "0", for example, would result in "4", and so forth. So that's what I ended up doing. My question is, is there any reason that won't always work? I generally avoid "ASCII arithmetic" on the grounds that it's not cross-platform or internationalization friendly. But it seems reasonable to assume that the code points for numbers will always be sequential, i.e., "4" will always be 1 more than "3". Anybody see any problem with this reasoning? Here's the code. string input = "10123X123456"; input[2] += 4; //Output should be 10523X123456

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