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• SEO: Where do I start?

  - by James

  Hi, I am primarily a software developer however I tend to delve in some web development from time to time. I have recently been asked to have a look at a friends website as they are wanting to improve their position in search engine results i.e. google/yahoo etc. I am aware there is no guarentee that their position will change, however, I do know there are techniques/ways to make your website more visible to search engine spiders and to consequently improve your position in the rankings i.e. performing SEO. Before I started looking at the SEO of the site I did the following prerequsite checks: Ran the website through the W3C Markup Validator and the W3C CSS Validator services. Looked through the markup code manually (check for meta tags etc) Performed a thorough cross browser compatibility test. From those checks, the following was evident: No SEO has been performed on the site before. The website has been developed using a visual editing tool such as dreamweaver (as it failed the validation services miserably and tables where being used everywhere!) The site is fairly cross browser compatibile (only some slight issues with IE8 which are easily resolved). How the site navigation is, isn't very search engine friendly (e.g. index.php?page=home) I can see right away a major improvement for SEO (or I at least think) would be to change the way the website is structured i.e. change from using dynamic pages such as "index.php?page=home" and actually having pages called "home.html". Other area's would be to add meta tags to identify keywords, and then sprinkling these keywords over the pages. As I am a rookie in this department, could anyone give me some advice on how I could perform thorough SEO on this website? Thanks in advance.

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• Efficient Method for Preventing Hotlinking via .htaccess

  - by Michael Robinson

  I need to confirm something before I go accuse someone of ... well I'd rather not say. The problem: We allow users to upload images and embed them within text on our site. In the past we allowed users to hotlink to our images as well, but due to server load we unfortunately had to stop this. Current "solution": The method the programmer used to solve our "too many connections" issue was to rename the file that receives and processes image requests (image_request.php) to image_request2.php, and replace the contents of the original with <?php header("HTTP/1.1 500 Internal Server Error") ; ?> Obviously this has caused all images with their src attribute pointing to the original image_request.php to be broken, and is also the wrong code to be sending in this case. Proposed solution: I feel a more elegant solution would be: In .htaccess If the request is for image_request.php Check referrer If referrer is not our site, send the appropriate header If referrer is our site, proceed to image_request.php and process image request What I would like to know is: Compared to simply returning a 500 for each request to image_request.php: How much more load would be incurred if we were to use my proposed alternative solution outlined above? Is there a better way to do this? Our main concern is that the site stays up. I am not willing to agree that breaking all internally linked images is the best / only way to solve this. I refuse to tell our users that because of something WE changed they must now manually change the embed code in all their previously uploaded content.

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• Windows.Forms RichTextBox Control - Avoid inserting large data.

  - by SchlaWiener

  I have a Windows Form with a RichTextBox on it. The content of the RichTextBox is written to a database field that ist limited to 64k data. For my purpose that is way more than enough text to store. I have set the MaxLength property to avoid insertng more data than allowed. rtcControl.MaxLength = 65536 Howevery, that only restricts the amount of characters that so is allowed to put in the text. But with the formatting overhead from the Rtf I can type more text than I should be allowed to. It even get's worse if I insert a large image, which dosn't increase the TextLength at all but the Rtf Length grows quite a lot. At the moment I check the Length of the richttextboxes' Rtf property in the FormClosing event and display a message to the user if it's to large. However that is just a workaround because I want to disallow putting more data than allowed into the control (like in a textbox if you exceed the MaxLength property nothing is inserted into the control and you hear the default beep(). Any ideas how to achive this? I already tried: using a custom control which extends the richtextbox and shadows th Rtf property to intercept the insertation. But it seems it isn't executed if I add text. Even the TextChanged Event does not fire if I type smth. in the control.

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• How do I dispatch to a method based on a parameter's runtime type in C# < 4?

  - by Evan Barkley

  I have an object o which guaranteed at runtime to be one of three types A, B, or C, all of which implement a common interface I. I can control I, but not A, B, or C. (Thus I could use an empty marker interface, or somehow take advantage of the similarities in the types by using the interface, but I can't add new methods or change existing ones in the types.) I also have a series of methods MethodA, MethodB, and MethodC. The runtime type of o is looked up and is then used as a parameter to these methods. public void MethodA(A a) { ... } public void MethodB(B b) { ... } public void MethodC(C c) { ... } Using this strategy, right now a check has to be performed on the type of o to determine which method should be invoked. Instead, I would like to simply have three overloaded methods: public void Method(A a) { ... } // these are all overloads of each other public void Method(B b) { ... } public void Method(C c) { ... } Now I'm letting C# do the dispatch instead of doing it manually myself. Can this be done? The naive straightforward approach doesn't work, of course: Cannot resolve method 'Method(object)'. Candidates are: void Method(A) void Method(B) void Method(C)

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• Grails - Language prefix in url mappings

  - by Art79

  Hi there im having problem with language mappings. The way i want it to work is that language is encoded in the url like /appname/de/mycontroller/whatever If you go to /appname/mycontroller/action it should check your session and if there is no session pick language based on browser preference and redirect to the language prefixed site. If you have session then it will display english. English does not have en prefix (to make it harder). So i created mappings like this: class UrlMappings { static mappings = { "/$lang/$controller/$action?/$id?"{ constraints { lang(matches:/pl|en/) } } "/$lang/store/$category" { controller = "storeItem" action = "index" constraints { lang(matches:/pl|en/) } } "/$lang/store" { controller = "storeItem" action = "index" constraints { lang(matches:/pl|en/) } } "/$controller/$action?/$id?"{ lang="en" constraints { } } "/store/$category" { lang="en" controller = "storeItem" action = "index" } "/store" { lang="en" controller = "storeItem" action = "index" } "/"(view:"/index") "500"(view:'/error') } } Its not fully working and langs are hardcoded just for now. I think i did something wrong. Some of the reverse mappings work but some dont add language. If i use link tag and pass params:[lang:'pl'] then it works but if i add params:[lang:'pl', page:2] then it does not. In the second case both lang and page number become parameters in the query string. What is worse they dont affect the locale so page shows in english. Can anyone please point me to the documentation what are the rules of reverse mappings or even better how to implement such language prefix in a good way ? THANKS

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• How does MVC ViewData work?

  - by Matt

  I am toying around with an MVC application just to learn the technology. I am mocking up a check register application that keeps track of a checking account, what has cleared the bank and what has not. I am using EF for my model and everything seems to be working correctly insofar as Edit, Create, etc. However, I have a couple of totals at the top. One to show the bank's balance and another to show the actual balance. It works most of the time but when I do Edit's it does not always accurately reflect the new total and I need it to update everytime a change is made (i.e when something clears the bank): [Authorize(Roles = "admin, checkUser")] public ActionResult Index() { var resultSet = from myChecking in chk.tblCheckings orderby myChecking.id descending select myChecking; ViewData.Model = resultSet.Take(45).ToList(); //for balances var actualBalance = from theChecking in chk.tblCheckings select theChecking.deposit - theChecking.withdrawal; var bankBalance = from theChecking in chk.tblCheckings where theChecking.cleared == true select theChecking.deposit - theChecking.withdrawal; //get bank balance ViewData["bankBalance"] = bankBalance.Sum(); //get actual balance ViewData["actualBalance"] = actualBalance.Sum(); return View(); } I am showing the actual and other balance in the Index view as follows: <td colspan="9" style="text-align: center; font-size: 11pt; color: white;"> <%= string.Format("Bank Balance: {0:c}", ViewData["bankBalance"]) %> ------ <%= string.Format("Actual Balance: {0:c}", ViewData["actualBalance"]) %> </td>

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• Deploy GWT Application to Google App Engine using NetBeans

  - by Yan Cheng CHEOK

  Hello, I try to deploy a GWT application, to Google App Engine using NetBeans. I had successful run GWT sample http://code.google.com/webtoolkit/doc/latest/tutorial/create.html using Personal GlassFish v3 Prelude Domain, by 1) Copy generated source code from StockWatcher to C:\Projects\StockWatcherNetbeans\src\java\com\google\ 2) Modify C:\Projects\StockWatcherNetbeans\nbproject\gwt.properties gwt.module=com.google.gwt.stockwatcher.StockWatcher 3) Select Personal GlassFish v3 Prelude Domain, and run. All works fine! Now, I try to select Google App Engine server, and run. However, I get the error "There is no appengine web project opened!" I check... There is file called C:\Projects\StockWatcherNetbeans\war\WEB-INF\appengine-web.xml with content <?xml version="1.0" encoding="UTF-8"?> <appengine-web-app xmlns="http://appengine.google.com/ns/1.0" xmlns:xsi='http://www.w3.org/2001/XMLSchema-instance' xsi:schemaLocation='http://kenai.com/projects/nbappengine/downloads/download/schema/appengine-web.xsd appengine-web.xsd'> <application>StockWatcherNetbeans</application> <version>1</version> </appengine-web-app> I am using NetBeans 6.7.1 GWT4NB (GWT Plugin for NetBeans) 2.6.12 Google App Engine plugin for NetBeans from http://kenai.com/downloads/nbappengine/1.0_NetBeans671/updates.xml Anything I had missed out? Even when I right click to the project, the Deploy to Google App Engine options is disabled. And yes, please do not ask me why not use Eclipse.

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• Opening a Unicode file with Perl

  - by Jaco Pretorius

  I'm using osql to run several sql scripts against a database and then I need to look at the results file to check if any errors occurred. The problem is that perl doesn't seem to like the fact that the results files are unicode. I wrote a little test script to test it and the output comes out all warbled. $file = shift; open OUTPUT, $file or die "Can't open $file: $!\n"; while (<OUTPUT>) { print $_; if (/Invalid|invalid|Cannot|cannot/) { push(@invalids, $file); print "invalid file - $inputfile - schedule for retry\n"; last; } } Any ideas? I've tried decoding using decode_utf8 but it makes no difference. I've also tried to set the encoding when opening the file. I think the problem might be that osql puts the result file in UTF-16 format, but I'm not sure. When I open the file in textpad it just tells me 'Unicode'. Edit: Using perl v5.8.8

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• Dumping an ADODB recordset to XML, then back to a recordset, then saving to the db

  - by Mark Biek

  I've created an XML file using the .Save() method of an ADODB recordset in the following manner. dim res dim objXML: Set objXML = Server.CreateObject("MSXML2.DOMDocument") 'This returns an ADODB recordset set res = ExecuteReader("SELECT * from some_table) With res Call .Save(objXML, 1) Call .Close() End With Set res = nothing Let's assume that the XML generated above then gets saved to a file. I'm able to read the XML back into a recordset like this: dim res : set res = Server.CreateObject("ADODB.recordset") res.open server.mappath("/admin/tbl_some_table.xml") And I can loop over the records without any problem. However what I really want to do is save all of the data in res to a table in a completely different database. We can assume that some_table already exists in this other database and has the exact same structure as the table I originally queried to make the XML. I started by creating a new recordset and using AddNew to add all of the rows from res to the new recordset dim outRes : set outRes = Server.CreateObject("ADODB.recordset") dim outConn : set outConn = Server.CreateObject("ADODB.Connection") dim testConnStr : testConnStr = "DRIVER={SQL Server};SERVER=dev-windows\sql2000;UID=myuser;PWD=mypass;DATABASE=Testing" outConn.open testConnStr outRes.activeconnection = outConn outRes.cursortype = adOpenDynamic outRes.locktype = adLockOptimistic outRes.source = "product_accessories" outRes.open while not res.eof outRes.addnew for i=0 to res.fields.count-1 outRes(res.fields(i).name) = res(res.fields(i).name) next outRes.movefirst res.movenext wend outRes.updatebatch But this bombs the first time I try to assign the value from res to outRes. Microsoft OLE DB Provider for ODBC Drivers error '80040e21' Multiple-step OLE DB operation generated errors. Check each OLE DB status value, if available. No work was done. Can someone tell me what I'm doing wrong or suggest a better way for me to copy the data loaded from XML to a different database?

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• lots of backbone views - performance issues?

  - by ksol

  tl;dr: I wonder if having lots (100+ for the moment, potentially up to 1000/2000 or more) of backbone views (as a cell of a table) is too heavy or not The project I'm working on revolves around a planning view. There one row per user that covers 6 hours of a day, each hour splitted in 4 slots of 15mn. This planning is used to add "reservations" when clicking on a slot, and should handle hovering of the correct slots, and also handle when it is NOT possible to make a reservation - ie. prevent user click on an "unavailable" slot. There is many reasons why a slot can't be clicked on: the user is not available at this time, or the user is in a reservation; or the app needs to "force" a delay slot between two reservations. Reservations (a div) are rendered in a slot (a cell of a table), and by toying with dimensions, hovers the right number of slots. All this screen is handled with backbone. So For each slot I'm hovering on, I need to check wether I can do a reservation here or not. As of this moment, I use this by toying with the data attributes on the slots : when a reservation object is added, the slots covered are "enhanced with (among others) the reservation object (the backbone view object). But in some cases I don't quite have a grasp on now, it mixes up, and when the reservation view is removed, the slots are not "cleaned up" : the previous class is not reset correctly. It is probably something I've done wrong or badly, but this is only going to get heavier; I think I should use another class of Backbone views here, but I'm afraid the number of slots and thereof of views objects will be high and cause performance issue. I don't know mush about js perf so I'd like to have some feedback before jumping on that train. Any other advice on how to do this would be quite welcomed too. Thanks for your time. If this is not clear enough, tell me, I'll try and rephrase it.

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• ClassNotFoundException com.mysql.jdbc.Driver

  - by Dusk

  This question might have asked here number of times . After doing some google search for the above error and doing some update, I can't understand why I'm still getting that error. I've already put my driver-- mysql-connector-java-5.1.5-bin in the classpath: Java_Home\jre\lib\ Java_Home\jre\lib\ext\ Java_Home\lib and the code which I'm using to connect to mysql database is: try{ Class.forName("com.mysql.jdbc.Driver"); Connection con=DriverManager.getConnection("jdbc:mysql://localhost:3306/mail","root",""); Statement stmt = con.createStatement(); ResultSet rs = stmt.executeQuery("select message_body from deadletter"); String dbtime; while (rs.next()) { dbtime = rs.getString(1); System.out.println(dbtime); } con.close(); } catch (SQLException e) { System.out.println("Connection Failed! Check output console"); e.printStackTrace(); } } and the complete stacktrace of the above exception is: java.lang.ClassNotFoundException: com.mysql.jdbc:Driver at java.net.URLClassLoader$1.run(URLClassLoader.java:200) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:307) at java.lang.ClassLoader.loadClass(ClassLoader.java:307) at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:301) at java.lang.ClassLoader.loadClass(ClassLoader.java:252) at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:320) at java.lang.Class.forName0(Native Method) at java.lang.Class.forName(Class.java:169) at mail.main(mail.java:114) Now, what's wrong I'm doing here?

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• Modelling deterministic and nondeterministic data separately

  - by Superstringcheese

  I'm working with the Microsoft ADO.NET Entity Framework for a game project. Following the advice of other posters on SO, I'm considering modelling deterministic and nondeterministic data separately. The idea for this came from a discussion on multiplayer games, but it seemed to make sense in a single-player scenario as well. Deterministic (things that aren't going to change during gameplay) Attributes (Strength, Agility, etc.) and their descriptions Skills and their descriptions and requirements Races, Factions, Equipment, etc. Base Attribute/Skill/Equipment loadouts for monsters Nondeterministic (things that will change a lot during gameplay) Beings' current AttributeModifers (Potion of Might = +10 Strength), current health and mana, etc. Player inventory, cash, experience, level Player quests states Player FactionRelationships ...and so on. My deterministic model would serve as a set of constants. My nondeterministic model would provide my on-the-fly operable data and would be serialized to a savegame file to maintain game state between play sessions. The data store will be an embedded SQL Compact database. So I might want to create relations between my Attributes table (deterministic model) and my BeingAttributeModifiers table (nondeterministic model), but how do I set that up across models? Det model/db Nondet model/db ____________ ________________________ |Attributes | |PlayerAttributeModifiers| |------------| |------------------------| |Id | |Id | |Name | |AttributeId | |Description | |SourceId | ------------ |Value | ------------------------ Should I use two separate models (edmx) that transact with a single database containing both deterministic-type and nondeterministic-type tables? Or should/can I use two separate databases in one model? Or two models each with their own database? With distinct models/dbs it seems like this will get really complicated and I'll end up fighting EF a lot, rolling my own transaction code, and generally losing out on a lot of the advantages of the framework. I know these are vague questions, I'm just looking for a sanity check before I forge ahead any further.

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• How should i organize authority code?

  - by acidzombie24

  I have users that fall into the following Not logged in Not Verified Verified Moderator Admin All code that only admin and moderators can access (like banning) is in ModeratorUser which inherits from verified which inherits from BaseUser. Some pages are accessible to all users such as public profiles. If a user is logged in he can leave a comment. To check this i use if (IsVerifiedUser). Now here is the problem. To avoid problems if a user is banned he is not recognized as a verified user. However in the rare case i need to know if he is verified i can use usertype & Verified. Should i not be doing this? I have a bunch of code in my VerifiedUser class and find i am moving tons of it to BaseUser. Is this something i help because a not logged in user can access the page? Should i handle the ban user in a different way and allow IsVerifiedUser to be true even if the user is banned?

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• need help building a stored procedure that takes rows from one table into another.

  - by MyHeadHurts

  alright i built this stored procedure to take the columns from a stagging table and copy them into my other table, but if these four columns are duplicates it wont insert the rows, works fine. however, what i want to do is if only the tour, taskname and deptdate are the same, then i will update the rest of the information. and if all four columns are the same dont instert. INSERT INTO dashboardtasks1 SELECT [tour], [taskname], [deptdate], [tasktype], [desc], [duedate], [compdate], [comments], [agent], [compby], [graceperiod] FROM staggingtasks WHERE NOT EXISTS(SELECT * FROM dashboardtasks1 WHERE (staggingtasks.tour=dashboardtasks1.tour and staggingtasks.taskname=dashboardtasks1.taskname and staggingtasks.deptdate=dashboardtasks1.deptdate and staggingtasks.duedate=dashboardtasks1.duedate ) ) i saw something like this INSERT INTO table (a,b,c) VALUES (1,2,3) ON DUPLICATE KEY UPDATE c=c+1; UPDATE table SET c=c+1 WHERE a=1; but how could i do it if my stated 3 columns are the samed then update? or is there a way to do this with an if statement and use 2 different queries, but how would my if statement work would it check if the row exists in the table i am uploading to and then run the insert statement? or what if i did something like IF EXISTS (SELECT * FROM dashboardtasks WHERE staggingtasks.tour=dashboardtasks.tour and staggingtasks.taskname=dashboardtasks.taskname and staggingtasks.deptdate=dashboardtasks.deptdate ) begin UPDATE [dashboardtasks] SET [tour] = staggingtasks.tour, [taskname] = staggingtasks.taskname, [deptdate] = staggingtasks.deptdate, [tasktype] = staggingtasks.tasktype, [desc] = staggingtasks.desc, [duedate] = staggingtasks.duedate, [compdate] = staggingtasks.compdate, [comments] = staggingtasks.comments, [agent] = staggingtasks.agent, [compby] = staggingtasks.compby, [graceperiod] = staggingtasks.graceperiod end else EXISTS (SELECT * FROM dashboardtasks WHERE staggingtasks.tour=dashboardtasks.tour and staggingtasks.taskname=dashboardtasks.taskname and staggingtasks.deptdate=dashboardtasks.deptdate and staggingtasks.duedate=dashboardtasks.duedate ) begin INSERT INTO dashboardtasks1 SELECT [tour], [taskname], [deptdate], [tasktype], [desc], [duedate], [compdate], [comments], [agent], [compby], [graceperiod] FROM staggingtasks WHERE NOT EXISTS(SELECT * FROM dashboardtasks1 WHERE (staggingtasks.tour=dashboardtasks1.tour and staggingtasks.taskname=dashboardtasks1.taskname and staggingtasks.deptdate=dashboardtasks1.deptdate and staggingtasks.duedate=dashboardtasks1.duedate ) ) end end

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• lambda traits inconsistency across C++0x compilers

  - by Sumant

  I observed some inconsistency between two compilers (g++ 4.5, VS2010 RC) in the way they match lambdas with partial specializations of class templates. I was trying to implement something like boost::function_types for lambdas to extract type traits. Check this for more details. In g++ 4.5, the type of the operator() of a lambda appears to be like that of a free standing function (R (*)(...)) whereas in VS2010 RC, it appears to be like that of a member function (R (C::*)(...)). So the question is are compiler writers free to interpret any way they want? If not, which compiler is correct? See the details below. template <typename T> struct function_traits : function_traits<decltype(&T::operator())> { // This generic template is instantiated on both the compilers as expected. }; template <typename R, typename C> struct function_traits<R (C::*)() const> { // inherits from this one on VS2010 RC typedef R result_type; }; template <typename R> struct function_traits<R (*)()> { // // inherits from this one g++ 4.5 typedef R result_type; }; int main(void) { auto lambda = []{}; function_traits<decltype(lambda)>::result_type *r; // void * } This program compiles on both g++ 4.5 and VS2010 but the function_traits that are instantiated are different as noted in the code.

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• RPC for java/python with rest support, HTML monitoring and goodies

  - by Ran

  Here's my set of requirements: I'm looking for an RPC framework such as thrift, avro, protobuf (when adding services to it) which supports: Easy and intuitive IDL. No serial numbers, no manual versioning, simple... avro is a good example for this. Works with Java and Python Supports both fast binary prorocol, as well as HTTP based restful style. I'd like to be able to use it for both backend-to-backend communication (java-java or python-java) as well as frontend-to-backend communication (javascript to java). The rest support needs to include &param=value input as get/post requests (configurable per request) and output in three possible formats: json, jsonp, XML. Compact, fast, backward compatible, easy to upgrade etc... Provides some nice monitoring interfaces such as: JMX, web page status reports (e.g. packets in, packets out, error rate etc) Ops friendly... no need to take the whole site down to release new versions Both sync and asyc communication ... other goodies are welcome... Is there something out there? So far I've looked at thrift and avro and they are both nice in some ways, but don't check all my list. Thanks

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• How to initialize audio with Vala/SDL

  - by ioev

  I've been trying to figure this out for a few hours now. In order to start up the audio, I need to create an SDL.AudioSpec object and pass it to SDL.Audio.Open. The problem is, AudioSpec is a class with a private constructor, so when I try to create one I get: sdl.vala:18.25-18.43: error: `SDL.AudioSpec' does not have a default constructor AudioSpec audiospec = new SDL.AudioSpec(); ^^^^^^^^^^^^^^^^^^^ And if I try to just assign values to it's member vars like a struct (it's a struct in normal sdl) I get: sdl.vala:20.3-20.25: error: use of possibly unassigned local variable `audiospec' audiospec.freq = 22050; ^^^^^^^^^^^^^^^^^^^^^^^ I found the valac doc here: http://valadoc.org/sdl/SDL.AudioSpec.html But it isn't much help at all. The offending code block looks like this: // setup the audio configuration AudioSpec audiospec; AudioSpec specback; audiospec.freq = 22050; audiospec.format = SDL.AudioFormat.S16LSB; audiospec.channels = 2; audiospec.samples = 512; // try to initialize sound with these values if (SDL.Audio.open(audiospec, specback) < 0) { stdout.printf("ERROR! Check audio settings!\n"); return 1; } Any help would be greatly appreciated!

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• Is my method for avoiding dynamic_cast<> faster than dynamic_cast<> itself ?

  - by ereOn

  Hi, I was answering a question a few minutes ago and it raised to me another one: In one of my projects, I do some network message parsing. The messages are in the form of: [1 byte message type][2 bytes payload length][x bytes payload] The format and content of the payload are determined by the message type. I have a class hierarchy, based on a common class Message. To instanciate my messages, i have a static parsing method which gives back a Message* depending on the message type byte. Something like: Message* parse(const char* frame) { // This is sample code, in real life I obviously check that the buffer // is not NULL, and the size, and so on. switch(frame[0]) { case 0x01: return new FooMessage(); case 0x02: return new BarMessage(); } // Throw an exception here because the mesage type is unknown. } I sometimes need to access the methods of the subclasses. Since my network message handling must be fast, I decived to avoid dynamic_cast<> and I added a method to the base Message class that gives back the message type. Depending on this return value, I use a static_cast<> to the right child type instead. I did this mainly because I was told once that dynamic_cast<> was slow. However, I don't know exactly what it really does and how slow it is, thus, my method might be as just as slow (or slower) but far more complicated. What do you guys think of this design ? Is it common ? Is it really faster than using dynamic_cast<> ? Any detailed explanation of what happen under the hood when one use dynamic_cast<> is welcome !

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• Which SQL statements to execute with intersection / junction tables

  - by user1455103

  Here a simplified database layout One condo can hold multiple properties (flats, garage boxes, etc) - 1->n relationship One owner can have multiple properties in the same condo and properties can have more than one owner (m->n changed to 1->n with the junction table) One condo can have multiple owners - 1->n Some additional clarification: A owner is a member of a condo. A condo is made of properties belonging to owners BUT a owner is not linked to a property directly (there can be no relation between a property and a owner for a certain time BUT there will ALWAYS be a relation between a owner and a condo). Reason for this: the agent managing the condo will first create a list of owners and a list of properties. It is only later thet he will "link" each property to one or multiple owners (or inversely) I'm quite new to SQL. What SQL statements should I execute to: SELECT, for a specific condo (WHERE condition), the properties and their respective owners (all properties should be listed even if owners are null) SELECT, for a specific condo (WHERE condition), the owners along with their properties (all owners should be listed even if properties are null) UPDATE / DELETE existing owners (I'm uncertain about how to handle the operation for the junction tables. Should I first check if there is an entry in the junction table or not ?) UPDATE / DELETE existing properties (same concern) INSERT new owners (should I use two different SQL statements depending if the owner should be linked to a property or NOT - IF condition ?) INSERT new properties (same question as above) Could you be as clear and generic as possible so that it can be reused ? :-)

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• Failure remediation strategy for File I/O

  - by Brett

  I'm doing buffered IO into a file, both read and write. I'm using fopen(), fseeko(), standard ANSI C file I/O functions. In all cases, I'm writing to a standard local file on a disk. How often do these file I/O operations fail, and what should the strategy be for failures? I'm not exactly looking for stats, but I'm looking for a general purpose statement on how far I should go to handle error conditions. For instance, I think everyone recognizes that malloc() could and probably will fail someday on some user's machine and the developer should check for a NULL being returned, but there is no great remediation strategy since it probably means the system is out of memory. At least, this seems to be the approach taken with malloc() on desktop systems, embedded systems are different. Likewise, is it worth reattempting a file I/O operation, or should I just consider a failure to be basically unrecoverable, etc. I would appreciate some code samples demonstrating proper usage, or a library guide reference that indicates how this is to be handled. Any other data is, of course, welcome.

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• How to make active services highly available?

  - by Jader Dias

  I know that with Network Load Balancing and Failover Clusteringwe can make passive services highly available. But what about active apps? Example: One of my apps retrieves some content from a external resource in a fixed interval. I have imagined the following scenarios: Run it in a single machine. Problem: if this instance falls, the content won't be retrieved Run it in each machine of the cluster. Problem: the content will be retrieved multiple times Have it in each machine of the cluster, but run it only in one of them. Each instance will have to check some sort of common resource to decide whether it its turn to do the task or not. When I was thinking about the solution #3 I have wondered what should be the common resource. I have thought of creating a table in the database, where we could use it to get a global lock. Is this the best solution? How does people usually do this? By the way it's a C# .NET WCF app running on Windows Server 2008

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• Alternative way of implementation of a code

  - by vikramjb

  The title is not exactly meaningful, but I am not share what else to name it. I wrote a TOC Generation code sometime later. Based on this I was writing code to check for duplicates also. The code is as follows curNumber = getTOCReference(selItem.SNo, IsParent); CheckForDuplicates(curNumber, IsParent,out realTOCRef); curNumber = realTOCRef; And the code for CheckForDuplicates is ListViewItem curItem = this.tlvItems.FindItemWithText(curNumber); if (curItem != null) { curNumber = this.getTOCReference(curNumber, !IsParent); CheckForDuplicates(curNumber, IsParent,out realTOCRef); } else { realTOCRef= curNumber; } What this code does, it gets a TOC and tries it find if it already exists in the ObjectListView and gets a new TOC if there is a existing TOC. Once it determines that the generated TOC is not there in the list it stores it in realTOCRef and sends it back to the main calling code. I have used "out" to return the last generated TOC, which is something I did not want to do. The reason why I did it was after the non duplicate TOC was generated the return was not going back to the calling code instead it looped through the previous instances then it returned back. When the looping back happened the TOC that was to be returned also got reset. I would appreciate any help on this.

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• Access/Download server files, not in site root, with PHP

  - by user271619

  Usually I save documents (images, mpegs, excel, word docs, etc...) for my friends or family on my website's root, inside a directory called /files/ or something similar. Nothing too uncommon. But, I have been playing with user session control, and allowing users to upload files to the dedicated /files/ directory. (the file names are saved in a db, with that user's ID) But, that means other people could try to guess and locate other people's files. I do randomize the file names, upon upload. And I stop the apache from displaying the /files/ directory content. However, I'd like to start saving the files outside of the website's root. This way it can't be accessible via the browser. I don't have any code to show, but I didn't want to even start on this endeavor if it's not able to be accomplished. I did find this snippet that shows how to display an image, from outside your website root: $file = $_GET['file']; $fileDir = '/path/to/files/'; if (file_exists($fileDir . $file)) { // Note: You should probably do some more checks // on the filetype, size, etc. $contents = file_get_contents($fileDir . $file); // Note: You should probably implement some kind // of check on filetype header('Content-type: image/jpeg'); echo $contents; } ? Maybe I can use this for any file type, but has anyone heard of a better way to allow users (logged in) to access their files from online, but not letting other users has similar access?

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• prolog - infinite rule

  - by Tom

  I have the next rules % Signature: natural_number(N)/1 % Purpose: N is a natural number. natural_number(0). natural_number(s(X)) :- natural_number(X) ackermann(0, N, s(N)). //rule 1 ackermann(s(M),0,Result):- ackermann(M,s(0),Result). //rule 2 ackermann(s(M),s(N),Result):-ackermann(M,Result1,Result),ackermann(s(M),N,Result1). //rule 3 The query is: ackermann (M,N,s(s(0))). Now, as I understood, In the third calculation, we got an infinite search (failture branch). I check it, and I got a finite search (failture branch). I'll explain: In the first, we got a substitue of M=0, N=s(0) (rule 1 - succsess!). In the second, we got a substitue of M=s(0),N=0 (rule 2 - sucsses!). But what now? I try to match M=s(s(0)) N=0, But it got a finite search - failture branch. Why the comipler doesn't write me "fail". Thank you.

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• rails validation of presence not failing on nil

  - by holden

  I want to make sure an attibute exists, but it seems to still slip thru and I'm not sure how better to check for it. This should work, but doesn't. It's a attr_accessor and not a real attribute if that makes a difference. validates_presence_of :confirmed, :rooms {"commit"=>"Make Booking", "place_id"=>"the-kosmonaut", "authenticity_token"=>"Tkd9bfGqYFfYUv0n/Kqp6psXHjLU7CmX+D4UnCWMiMk=", "utf8"=>"✓", "booking"=>{"place_id"=>"6933", "bookdate"=>"2010-11-22", "rooms"=>[{}], "no_days"=>"2"}} Not sure why my form_for returns a blank hash in an array... <% form_for :booking, :url => place_bookings_path(@place) do |f| %> <%= f.hidden_field :bookdate, { :value => user_cart.getDate } %> <%= f.hidden_field :no_days, { :value => user_cart.getDays } %> <% for room in pricing_table(@place.rooms,@valid_dates) %> <%= select_tag("booking[rooms][][#{room.id}]", available_beds(room)) %> <% end %> <% end %>

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