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• How to design a high-level application protocol for metadata syncing between devices and server?

  - by Jaanus

  I am looking for guidance on how to best think about designing a high-level application protocol to sync metadata between end-user devices and a server. My goal: the user can interact with the application data on any device, or on the web. The purpose of this protocol is to communicate changes made on one endpoint to other endpoints through the server, and ensure all devices maintain a consistent picture of the application data. If user makes changes on one device or on the web, the protocol will push data to the central repository, from where other devices can pull it. Some other design thoughts: I call it "metadata syncing" because the payloads will be quite small, in the form of object IDs and small metadata about those ID-s. When client endpoints retrieve new metadata over this protocol, they will fetch actual object data from an external source based on this metadata. Fetching the "real" object data is out of scope, I'm only talking about metadata syncing here. Using HTTP for transport and JSON for payload container. The question is basically about how to best design the JSON payload schema. I want this to be easy to implement and maintain on the web and across desktop and mobile devices. The best approach feels to be simple timer- or event-based HTTP request/response without any persistent channels. Also, you should not have a PhD to read it, and I want my spec to fit on 2 pages, not 200. Authentication and security are out of scope for this question: assume that the requests are secure and authenticated. The goal is eventual consistency of data on devices, it is not entirely realtime. For example, user can make changes on one device while being offline. When going online again, user would perform "sync" operation to push local changes and retrieve remote changes. Having said that, the protocol should support both of these modes of operation: Starting from scratch on a device, should be able to pull the whole metadata picture "sync as you go". When looking at the data on two devices side by side and making changes, should be easy to push those changes as short individual messages which the other device can receive near-realtime (subject to when it decides to contact server for sync). As a concrete example, you can think of Dropbox (it is not what I'm working on, but it helps to understand the model): on a range of devices, the user can manage a files and folders—move them around, create new ones, remove old ones etc. And in my context the "metadata" would be the file and folder structure, but not the actual file contents. And metadata fields would be something like file/folder name and time of modification (all devices should see the same time of modification). Another example is IMAP. I have not read the protocol, but my goals (minus actual message bodies) are the same. Feels like there are two grand approaches how this is done: transactional messages. Each change in the system is expressed as delta and endpoints communicate with those deltas. Example: DVCS changesets. REST: communicating the object graph as a whole or in part, without worrying so much about the individual atomic changes. What I would like in the answers: Is there anything important I left out above? Constraints, goals? What is some good background reading on this? (I realize this is what many computer science courses talk about at great length and detail... I am hoping to short-circuit it by looking at some crash course or nuggets.) What are some good examples of such protocols that I could model after, or even use out of box? (I mention Dropbox and IMAP above... I should probably read the IMAP RFC.)

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• What is there so useful in the Decorator Pattern? My example doesn't work

  - by Green

  The book says: The decorator pattern can be used to extend (decorate) the functionality of a certain object I have a rabbit animal. And I want my rabbit to have, for example, reptile skin. Just want to decorate a common rabbit with reptile skin. I have the code. First I have abstract class Animal with everythig that is common to any animal: abstract class Animal { abstract public function setSleep($hours); abstract public function setEat($food); abstract public function getSkinType(); /* and more methods which for sure will be implemented in any concrete animal */ } I create class for my rabbit: class Rabbit extends Animal { private $rest; private $stomach; private $skinType = "hair"; public function setSleep($hours) { $this->rest = $hours; } public function setFood($food) { $this->stomach = $food; } public function getSkinType() { return $this->$skinType; } } Up to now everything is OK. Then I create abstract AnimalDecorator class which extends Animal: abstract class AnimalDecorator extends Animal { protected $animal; public function __construct(Animal $animal) { $this->animal = $animal; } } And here the problem comes. Pay attention that AnimalDecorator also gets all the abstract methods from the Animal class (in this example just two but in real can have many more). Then I create concrete ReptileSkinDecorator class which extends AnimalDecorator. It also has those the same two abstract methods from Animal: class ReptileSkinDecorator extends AnimalDecorator { public function getSkinColor() { $skin = $this->animal->getSkinType(); $skin = "reptile"; return $skin; } } And finaly I want to decorate my rabbit with reptile skin: $reptileSkinRabbit = ReptileSkinDecorator(new Rabbit()); But I can't do this because I have two abstract methods in ReptileSkinDecorator class. They are: abstract public function setSleep($hours); abstract public function setEat($food); So, instead of just re-decorating only skin I also have to re-decorate setSleep() and setEat(); methods. But I don't need to. In all the book examples there is always ONLY ONE abstract method in Animal class. And of course it works then. But here I just made very simple real life example and tried to use the Decorator pattern and it doesn't work without implementing those abstract methods in ReptileSkinDecorator class. It means that if I want to use my example I have to create a brand new rabbit and implement for it its own setSleep() and setEat() methods. OK, let it be. But then this brand new rabbit has the instance of commont Rabbit I passed to ReptileSkinDecorator: $reptileSkinRabbit = ReptileSkinDecorator(new Rabbit()); I have one common rabbit instance with its own methods in the reptileSkinRabbit instance which in its turn has its own reptileSkinRabbit methods. I have rabbit in rabbit. But I think I don't have to have such possibility. I don't understand the Decarator pattern right way. Kindly ask you to point on any mistakes in my example, in my understanding of this pattern. Thank you.

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• PostgreSQL triggers and passing parameters

  - by iandouglas

  This is a multi-part question. I have a table similar to this: CREATE TABLE sales_data ( Company character(50), Contract character(50), top_revenue_sum integer, top_revenue_sales integer, last_sale timestamp) ; I'd like to create a trigger for new inserts into this table, something like this: CREATE OR REPLACE FUNCTION add_contract() RETURNS VOID DECLARE myCompany character(50), myContract character(50), BEGIN myCompany = TG_ARGV[0]; myContract = TG_ARGV[1]; IF (TG_OP = 'INSERT') THEN EXECUTE 'CREATE TABLE salesdata_' || $myCompany || '_' || $myContract || ' ( sale_amount integer, updated TIMESTAMP not null, some_data varchar(32), country varchar(2) ) ;' EXECUTE 'CREATE TRIGGER update_sales_data BEFORE INSERT OR DELETE ON salesdata_' || $myCompany || '_' || $myContract || ' FOR EACH ROW EXECUTE update_sales_data( ' || $myCompany || ',' || $myContract || ', revenue);' ; END IF; END; $add_contract$ LANGUAGE plpgsql; CREATE TRIGGER add_contract AFTER INSERT ON sales_data FOR EACH ROW EXECUTE add_contract() ; Basically, every time I insert a new row into sales_data, I want to generate a new table where the name of the table will be defined as something like "salesdata_Company_Contract" So my first question is how can I pass the Company and Contract data to the trigger so it can be passed to the add_contract() stored procedure? From my stored procedure, you'll see that I also want to update the original sales_data table whenever new data is inserted into the salesdata_Company_Contract table. This trigger will do something like this: CREATE OR REPLACE FUNCTION update_sales_data() RETURNS trigger as $update_sales_data$ DECLARE myCompany character(50) NOT NULL, myContract character(50) NOT NULL, myRevenue integer NOT NULL BEGIN myCompany = TG_ARGV[0] ; myContract = TG_ARGV[1] ; myRevenue = TG_ARGV[2] ; IF (TG_OP = 'INSERT') THEN UPDATE sales_data SET top_revenue_sales = top_revenue_sales + 1, top_revenue_sum = top_revenue_sum + $myRevenue, updated = now() WHERE Company = $myCompany AND Contract = $myContract ; ELSIF (TG_OP = 'DELETE') THEN UPDATE sales_data SET top_revenue_sales = top_revenue_sales - 1, top_revenue_sum = top_revenue_sum - $myRevenue, updated = now() WHERE Company = $myCompany AND Contract = $myContract ; END IF; END; $update_sales_data$ LANGUAGE plpgsql; This will, of course, require that I pass several parameters around within these stored procedures and triggers, and I'm not sure (a) if this is even possible, or (b) practical, or (c) best practice and we should just put this logic into our other software instead of asking the database to do this work for us. To keep our table sizes down, as we'll have hundreds of thousands of transactions per day, we've decided to partition our data using the Company and Contract strings as part of the table names themselves so they're all very small in size; file IO for us is faster and we felt we'd get better performance. Thanks for any thoughts or direction. My thinking, now that I've written all of this out, is that maybe we need to write stored procedures where we pass our insert data as parameters, and call that from our other software, and have the stored procedure do the insert into "sales_data" then create the other table. Then, have a second stored procedure to insert new data into the salesdata_Company_Contract tables, where the table name is passed to the stored proc as a parameter, and again have that stored proc do the insert, then update the main sales_data table afterward. What approach would you take?

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• How do I programmatically send email w/attachment to a known recipient using MAPI in C++? MAPISendM

  - by Tim

  This question is similar, but does not show how to add a recipient. How do I do both? We'd like the widest support possible for as many Windows platforms as possible (from XP and greater) We're using visual studio 2008 Essentially we want to send an email with: pre-filled destination address file attachment subject line from our program and give the user the ability to add any information or cancel it. EDIT I am trying to use MAPISendMail() I copied much of the code from the questions linked near the top, but I get no email dlg box and the error return I get from the call is: 0x000f - "The system cannot find the drive specified" If I comment out the lines to set the recipient, it works fine (of course then I have no recipient pre-filled in) Here is the code: #include <tchar.h> #include <windows.h> #include <mapi.h> #include <mapix.h> int _tmain( int argc, wchar_t *argv[] ) { HMODULE hMapiModule = LoadLibrary( _T( "mapi32.dll" ) ); if ( hMapiModule != NULL ) { LPMAPIINITIALIZE lpfnMAPIInitialize = NULL; LPMAPIUNINITIALIZE lpfnMAPIUninitialize = NULL; LPMAPILOGONEX lpfnMAPILogonEx = NULL; LPMAPISENDDOCUMENTS lpfnMAPISendDocuments = NULL; LPMAPISESSION lplhSession = NULL; LPMAPISENDMAIL lpfnMAPISendMail = NULL; lpfnMAPIInitialize = (LPMAPIINITIALIZE)GetProcAddress( hMapiModule, "MAPIInitialize" ); lpfnMAPIUninitialize = (LPMAPIUNINITIALIZE)GetProcAddress( hMapiModule, "MAPIUninitialize" ); lpfnMAPILogonEx = (LPMAPILOGONEX)GetProcAddress( hMapiModule, "MAPILogonEx" ); lpfnMAPISendDocuments = (LPMAPISENDDOCUMENTS)GetProcAddress( hMapiModule, "MAPISendDocuments" ); lpfnMAPISendMail = (LPMAPISENDMAIL)GetProcAddress( hMapiModule, "MAPISendMail" ); if ( lpfnMAPIInitialize && lpfnMAPIUninitialize && lpfnMAPILogonEx && lpfnMAPISendDocuments ) { HRESULT hr = (*lpfnMAPIInitialize)( NULL ); if ( SUCCEEDED( hr ) ) { hr = (*lpfnMAPILogonEx)( 0, NULL, NULL, MAPI_EXTENDED | MAPI_USE_DEFAULT, &lplhSession ); if ( SUCCEEDED( hr ) ) { // this opens the email client // create the msg. We need to add recipients AND subject AND the dmp file // file attachment MapiFileDesc filedesc; ::ZeroMemory(&filedesc, sizeof(filedesc)); filedesc.nPosition = (ULONG)-1; filedesc.lpszPathName = "E:\\Development\\Open\\testmail\\testmail.cpp"; // recipient(s) MapiRecipDesc recip; ::ZeroMemory(&recip, sizeof(recip)); recip.lpszName = "QA email"; recip.lpszAddress = "[email protected]"; // the message MapiMessage msg; ::ZeroMemory(&msg, sizeof(msg)); msg.lpszSubject = "Test"; msg.nRecipCount = 1; // if I comment out this line it works fine... msg.lpRecips = &recip; msg.nFileCount = 1; msg.lpFiles = &filedesc; hr = (*lpfnMAPISendMail)(0, NULL, &msg, MAPI_LOGON_UI|MAPI_DIALOG, 0); if ( SUCCEEDED( hr ) ) { hr = lplhSession->Logoff( 0, 0, 0 ); hr = lplhSession->Release(); lplhSession = NULL; } } } (*lpfnMAPIUninitialize)(); } FreeLibrary( hMapiModule ); } return 0; }

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• onCommand on button not firing inside gridView??

  - by sah302

  This is really driving me crazy. I've got a button inside a gridview to remove that item from the gridview (its datasource is a list). I've got the list being saved to session anytime a change is being made to it, and on page_load check if that session variable is empty, if not, then set that list to bind to the gridview. Code Behind: Public accomplishmentTypeDao As New AccomplishmentTypeDao() Public accomplishmentDao As New AccomplishmentDao() Public userDao As New UserDao() Public facultyDictionary As New Dictionary(Of Guid, String) Public facultyList As New List(Of User) Public associatedFaculty As New List(Of User) Public facultyId As New Guid Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load 'If Not Session("associatedFaculty") Is Nothing Then' ' Dim associatedFacultyArray As User() = DirectCast(Session("associatedFaculty"), User())' ' associatedFaculty = associatedFacultyArray.ToList()' 'End If' Page.Title = "Add a New Faculty Accomplishment" ddlAccomplishmentType.DataSource = accomplishmentTypeDao.getEntireTable() ddlAccomplishmentType.DataTextField = "Name" ddlAccomplishmentType.DataValueField = "Id" ddlAccomplishmentType.DataBind() facultyList = userDao.getListOfUsersByUserGroupName("Faculty") For Each faculty As User In facultyList facultyDictionary.Add(faculty.Id, faculty.LastName & ", " & faculty.FirstName) Next If Not Page.IsPostBack Then ddlFacultyList.DataSource = facultyDictionary ddlFacultyList.DataTextField = "Value" ddlFacultyList.DataValueField = "Key" ddlFacultyList.DataBind() End If gvAssociatedUsers.DataSource = associatedFaculty gvAssociatedUsers.DataBind() End Sub Protected Sub deleteUser(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.CommandEventArgs) facultyId = New Guid(e.CommandArgument.ToString()) associatedFaculty.Remove(associatedFaculty.Find(Function(user) user.Id = facultyId)) Session("associatedFaculty") = associatedFaculty.ToArray() gvAssociatedUsers.DataBind() upAssociatedFaculty.Update() End Sub Protected Sub btnAddUser_Click(ByVal sender As Object, ByVal e As EventArgs) Handles btnAddUser.Click facultyId = New Guid(ddlFacultyList.SelectedValue) associatedFaculty.Add(facultyList.Find(Function(user) user.Id = facultyId)) Session.Add("associatedFaculty", associatedFaculty.ToArray()) gvAssociatedUsers.DataBind() upAssociatedFaculty.Update() End Sub Protected Sub Delete(ByVal sender As Object, ByVal e As System.Web.UI.WebControls.CommandEventArgs) End Sub End Class Markup: <asp:UpdatePanel ID="upAssociatedFaculty" runat="server" UpdateMode="Conditional"> <ContentTemplate> <p><b>Created By:</b> <asp:Label ID="lblCreatedBy" runat="server"></asp:Label></p> <p><b>Accomplishment Type: </b><asp:DropDownList ID="ddlAccomplishmentType" runat="server"></asp:DropDownList></p> <p><b>Accomplishment Applies To: </b><asp:DropDownList ID="ddlFacultyList" runat="server"></asp:DropDownList> &nbsp;<asp:Button ID="btnAddUser" runat="server" Text="Add Faculty" OnClientClick="incrementCounter();" /></p> <p> <asp:GridView ID="gvAssociatedUsers" runat="server" AutoGenerateColumns="false" GridLines="None" ShowHeader="false"> <Columns> <asp:BoundField DataField="Id" HeaderText="Id" Visible="False" /> <asp:TemplateField ShowHeader="False"> <ItemTemplate> <span style="margin-left: 15px;"> <p><%#Eval("LastName")%>, <%#Eval("FirstName")%> <asp:Button ID="btnUnassignUser" runat="server" CausesValidation="false" CommandArgument='<%# Eval("Id") %>' CommandName="Delete" OnCommand="deleteUser" Text='Remove' /></p> </span> </ItemTemplate> </asp:TemplateField> </Columns> <EmptyDataTemplate> <em>There are currently no faculty associated with this accomplishment.</em> </EmptyDataTemplate> </asp:GridView> </p> </ContentTemplate> </asp:UpdatePanel> Now here is the crazy part I am simply boggled by, if I uncomment the If Not Session... block of page_load, then deleteUser will never fire when btnUnassignUser is clicked. If I keep it commented out...it fires no problem, but then of course my list can never have more than one item since I am not loading the saved list from session into the gridview but just a fresh one. But the button click is being registered, because page_load is being stepped through again when I am viewing in debug mode, just deleteUser never fires. Why is this happening?? And how can I fix it??

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• Fluent Nhibernate - how do i specify table schemas when auto generating tables in SQL CE 4

  - by daffers

  I am using SQL CE as a database for running local and CI integration tests (normally our site runs on normal SQL server). We are using Fluent Nhibernate for our mapping and having it create our schema from our Mapclasses. There are only two classes with a one to many relationship between them. In our real database we use a non dbo schema. The code would not work with this real database at first until i added schema names to the Table() methods. However doing this broke the unit tests with the error... System.Data.SqlServerCe.SqlCeException : There was an error parsing the query. [ Token line number = 1,Token line offset = 26,Token in error = User ] These are the classes and associatad MapClasses (simplified of course) public class AffiliateApplicationRecord { public virtual int Id { get; private set; } public virtual string CompanyName { get; set; } public virtual UserRecord KeyContact { get; private set; } public AffiliateApplicationRecord() { DateReceived = DateTime.Now; } public virtual void AddKeyContact(UserRecord keyContactUser) { keyContactUser.Affilates.Add(this); KeyContact = keyContactUser; } } public class AffiliateApplicationRecordMap : ClassMap<AffiliateApplicationRecord> { public AffiliateApplicationRecordMap() { Schema("myschema"); Table("Partner"); Id(x => x.Id).GeneratedBy.Identity(); Map(x => x.CompanyName, "Name"); References(x => x.KeyContact) .Cascade.All() .LazyLoad(Laziness.False) .Column("UserID"); } } public class UserRecord { public UserRecord() { Affilates = new List<AffiliateApplicationRecord>(); } public virtual int Id { get; private set; } public virtual string Forename { get; set; } public virtual IList<AffiliateApplicationRecord> Affilates { get; set; } } public class UserRecordMap : ClassMap<UserRecord> { public UserRecordMap() { Schema("myschema"); Table("[User]");//Square brackets required as user is a reserved word Id(x => x.Id).GeneratedBy.Identity(); Map(x => x.Forename); HasMany(x => x.Affilates); } } And here is the fluent configuraton i am using .... public static ISessionFactory CreateSessionFactory() { return Fluently.Configure() .Database( MsSqlCeConfiguration.Standard .Dialect<MsSqlCe40Dialect>() .ConnectionString(ConnectionString) .DefaultSchema("myschema")) .Mappings(m => m.FluentMappings.AddFromAssembly(typeof(AffiliateApplicationRecord).Assembly)) .ExposeConfiguration(config => new SchemaExport(config).Create(false, true)) .ExposeConfiguration(x => x.SetProperty("connection.release_mode", "on_close")) //This is included to deal with a SQLCE issue http://stackoverflow.com/questions/2361730/assertionfailure-null-identifier-fluentnh-sqlserverce .BuildSessionFactory(); } The documentation on this aspect of fluent is pretty weak so any help would be appreciated

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• More localized, efficient Lowest Common Ancestor algorithm given multiple binary trees?

  - by mstksg

  I have multiple binary trees stored as an array. In each slot is either nil (or null; pick your language) or a fixed tuple storing two numbers: the indices of the two "children". No node will have only one child -- it's either none or two. Think of each slot as a binary node that only stores pointers to its children, and no inherent value. Take this system of binary trees: 0 1 / \ / \ 2 3 4 5 / \ / \ 6 7 8 9 / \ 10 11 The associated array would be: 0 1 2 3 4 5 6 7 8 9 10 11 [ [2,3] , [4,5] , [6,7] , nil , nil , [8,9] , nil , [10,11] , nil , nil , nil , nil ] I've already written simple functions to find direct parents of nodes (simply by searching from the front until there is a node that contains the child) Furthermore, let us say that at relevant times, both all trees are anywhere between a few to a few thousand levels deep. I'd like to find a function P(m,n) to find the lowest common ancestor of m and n -- to put more formally, the LCA is defined as the "lowest", or deepest node in which have m and n as descendants (children, or children of children, etc.). If there is none, a nil would be a valid return. Some examples, given our given tree: P( 6,11) # => 2 P( 3,10) # => 0 P( 8, 6) # => nil P( 2,11) # => 2 The main method I've been able to find is one that uses an Euler trace, which turns the given tree, with a node A to be the invisible parent of 0 and 1 with a depth of -1, into: A-0-2-6-2-7-10-7-11-7-2-0-3-0-A-1-4-1-5-8-5-9-5-1-A And from that, simply find the node between your given m and n that has the lowest number; For example, to find P(6,11), look for a 6 and an 11 on the trace. The number between them that is the lowest is 2, and that's your answer. If A is in between them, return nil. -- Calculating P(6,11) -- A-0-2-6-2-7-10-7-11-7-2-0-3-0-A-1-4-1-5-8-5-9-5-1-A ^ ^ ^ | | | m lowest n Unfortunately, I do believe that finding the Euler trace of a tree that can be several thousands of levels deep is a bit machine-taxing...and because my tree is constantly being changed throughout the course of the programming, every time I wanted to find the LCA, I'd have to re-calculate the Euler trace and hold it in memory every time. Is there a more memory efficient way, given the framework I'm using? One that maybe iterates upwards? One way I could think of would be the "count" the generation/depth of both nodes, and climb the lowest node until it matched the depth of the highest, and increment both until they find someone similar. But that'd involve climbing up from level, say, 3025, back to 0, twice, to count the generation, and using a terribly inefficient climbing-up algorithm in the first place, and then re-climbing back up. Are there any other better ways?

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• How to cope with developing against a poor 3rd party API/application?

  - by wsanville

  I'm a web developer, and my organization has recently started to use a proprietary ASP.NET CMS for our web sites. I was excited to get started using the CMS, thinking it would bring a lot of value to our end users and be fun to work with, since my skills are a good match for the types of projects we're using it for. That was about a year ago. Since then, we've ran into all kinds of issues, from blatant bugs in the product, to nasty edge cases in the APIs, to extremely poor documentation for developers. On about a weekly basis, we are forced to pursue workarounds and rewrite some of the out of the box functionality, and even find some of the basic features unusable. In many cases, since this is a closed source application (and obfuscated of course), there's nothing we can do as developers to solve these issues. So my question is, how does one attempt to develop a good application in such a scenario? The application mostly works when using the the exact out of the box behavior, or using one of the company's starter sites. However, my attempts to use the underlying APIs to implement slightly different, yet reasonable behavior has proved to be extremely time consuming (not to mention just as buggy), given the lack of good information about the APIs. I've given this a lot of thought, and my conflicting viewpoints are the following: Strongly advise against any customization to the CMS, as development time will rise exponentially, or even have an extremely high chance of failing. While this is accurate, I do not want to give the impression that I am not willing to code my own solutions to problems and take the initiative to implement something difficult or complex. I don't want to be perceived as someone who is not motivated, lazy, or not knowledgeable to do anything complex, because this is simply not the case. I love coding my own solutions, trying new/difficult things, I just dislike the vendor app we're using. Continue on the path I'm on now, which is hacking my way past all issues I encounter and try my best to deliver an application that meets the needs and specs exactly. My goals are to make it as seamless and easy to use as possible to the end user, even when integrating the CMS with our other applications internally. The problem I'm finding with this approach is it is very time consuming. I open support cases with the vendor on a regular basis to solve issues and to gain knowledge of their APIs, but this is extremely time consuming, and in some cases it leads to dead ends. I post on the vendors forums on a regular basis but have become frustrated as most of my posts get 0 replies. So, what would you, a reasonable developer, do in this case? How can I make the best of the situation? And just for fun, here are some of the code smells and anti-patterns I've dealt with using the product (aside from their own code blatantly failing): Use of StringBuilder to concatenate a giant string that is hard coded and does not change. They use it to concatenate their Javascript and write it out into the body tags of their pages. Methods that accept object or Microsoft.VisualBasic.Collection as the parameters. In the case of the VB Collection, the data is not a list of any kind, it's used instead of making a class. Methods that return a Hashtable of VB Collections Method names of the form MethodName_v45, MethodName_v20, etc... Multiple classes with the same name in different namespaces with different functionality/behavior. Intellisense that reads "Note: this parameter is non functional" Complete lack of coding standards, API is filled with magic numbers and magic strings. Properties with a getter of type object that accepts totally different things, like enum or strings, and throw exceptions at runtime when you pass in something not supported. And much, much, more...

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• extensible database design: automatic ALTER TABLE or serialize() field BLOB ?

  - by mario

  I want an adaptable database scheme. But still use a simple table data gateway in my application, where I just pass an $data[] array for storing. The basic columns are settled in the initial table scheme. There will however arise a couple of meta fields later (ca 10-20). I want some flexibility there and not adapt the database manually each time, or -worse- change the application logic just because of new fields. So now there are two options which seem workable yet not overkill. But I'm not sure about the scalability or database drawbacks. (1) Automatic ALTER TABLE. Whenever the $data array is to be saved, the keys are compared against the current database columns. New columns get defined before the $data is INSERTed into the table. Actually seems simple enough in test code: function save($data, $table="forum") { // columns if ($new_fields = array_diff(array_keys($data), known_fields($table))) { extend_schema($table, $new_fields, $data); } // save $columns = implode("`, `", array_keys($data)); $qm = str_repeat(",?", count(array_keys($data)) - 1); echo ("INSERT INTO `$table` (`$columns`) VALUES (?$qm);"); function known_fields($table) { return unserialize(@file_get_contents("db:$table")) ?: array("id"); function extend_schema($table, $new_fields, $data) { foreach ($new_fields as $field) { echo("ALTER TABLE `$table` ADD COLUMN `$field` VARCHAR;"); Since it is mostly meta information fields, adding them just as VARCHAR seems sufficient. Nobody will query by them anyway. So the database is really just used as storage here. However, while I might want to add a lot of new $data fields on the go, they will not always be populated. (2) serialize() fields into BLOB. Any new/extraneous meta fields could be opaque to the database. Simply sorting out the virtual fields from the real database columns is simple. And the meta fields can just be serialize()d into a blob/text field then: function ext_save($data, $table="forum") { $db_fields = array("id", "content", "flags", "ext"); // disjoin foreach (array_diff(array_keys($data),$db_fields) as $key) { $data["ext"][$key] = $data[$key]; unset($data[$key]); } $data["ext"] = serialize($data["ext"]); Unserializing and unpacking this 'ext' column on read queries is a minor overhead. The advantage is that there won't be any sparsely filled columns in the database, so I guess it's compacter and faster than the AUTO ALTER TABLE approach. Of course, this method prevents ever using one of the new fields in a WHERE or GROUP BY clause. But I think none of the possible meta fields (user_agent, author_ip, author_img, votes, hits, last_modified, ..) would/should ever be used there anyway. So I currently prefer the 'ext' blob approach, even if it's a one-way ticket. How are such columns called usually? (looking for examples/doc) Would you use XML serialization for (very theoretical) in-database queries? The adapting table scheme seems a "cleaner" interface, even if most columns might remain empty then. How does that impact speed? How many such sparse VARCHAR fields can MySQL/innodb stomach? But most importantly: Is there any standard implementation for this? A pseudo ORM with automatic ALTER TABLE tricks? Storing a simple column list seems workable, but something like pdo::getColumnMeta would be more robust.

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• client-side validation in custom validation attribute - asp.net mvc 4

  - by Giorgos Manoltzas

  I have followed some articles and tutorials over the internet in order to create a custom validation attribute that also supports client-side validation in an asp.net mvc 4 website. This is what i have until now: RequiredIfAttribute.cs [AttributeUsage(AttributeTargets.Property, AllowMultiple = true)] //Added public class RequiredIfAttribute : ValidationAttribute, IClientValidatable { private readonly string condition; private string propertyName; //Added public RequiredIfAttribute(string condition) { this.condition = condition; this.propertyName = propertyName; //Added } protected override ValidationResult IsValid(object value, ValidationContext validationContext) { PropertyInfo propertyInfo = validationContext.ObjectType.GetProperty(this.propertyName); //Added Delegate conditionFunction = CreateExpression(validationContext.ObjectType, _condition); bool conditionMet = (bool)conditionFunction.DynamicInvoke(validationContext.ObjectInstance); if (conditionMet) { if (value == null) { return new ValidationResult(FormatErrorMessage(null)); } } return ValidationResult.Success; } private Delegate CreateExpression(Type objectType, string expression) { LambdaExpression lambdaExpression = System.Linq.Dynamic.DynamicExpression.ParseLambda(objectType, typeof(bool), expression); //Added Delegate function = lambdaExpression.Compile(); return function; } public IEnumerable<ModelClientValidationRule> GetClientValidationRules(ModelMetadata metadata, ControllerContext context) { var modelClientValidationRule = new ModelClientValidationRule { ValidationType = "requiredif", ErrorMessage = ErrorMessage //Added }; modelClientValidationRule.ValidationParameters.Add("param", this.propertyName); //Added return new List<ModelClientValidationRule> { modelClientValidationRule }; } } Then i applied this attribute in a property of a class like this [RequiredIf("InAppPurchase == true", "InAppPurchase", ErrorMessage = "Please enter an in app purchase promotional price")] //Added "InAppPurchase" public string InAppPurchasePromotionalPrice { get; set; } public bool InAppPurchase { get; set; } So what i want to do is display an error message that field InAppPurchasePromotionalPrice is required when InAppPurchase field is true (that means checked in the form). The following is the relevant code form the view: <div class="control-group"> <label class="control-label" for="InAppPurchase">Does your app include In App Purchase?</label> <div class="controls"> @Html.CheckBoxFor(o => o.InAppPurchase) @Html.LabelFor(o => o.InAppPurchase, "Yes") </div> </div> <div class="control-group" id="InAppPurchasePromotionalPriceDiv" @(Model.InAppPurchase == true ? Html.Raw("style='display: block;'") : Html.Raw("style='display: none;'"))> <label class="control-label" for="InAppPurchasePromotionalPrice">App Friday Promotional Price for In App Purchase: </label> <div class="controls"> @Html.TextBoxFor(o => o.InAppPurchasePromotionalPrice, new { title = "This should be at the lowest price tier of free or $.99, just for your App Friday date." }) <span class="help-inline"> @Html.ValidationMessageFor(o => o.InAppPurchasePromotionalPrice) </span> </div> </div> This code works perfectly but when i submit the form a full post is requested on the server in order to display the message. So i created JavaScript code to enable client-side validation: requiredif.js (function ($) { $.validator.addMethod('requiredif', function (value, element, params) { /*var inAppPurchase = $('#InAppPurchase').is(':checked'); if (inAppPurchase) { return true; } return false;*/ var isChecked = $(param).is(':checked'); if (isChecked) { return false; } return true; }, ''); $.validator.unobtrusive.adapters.add('requiredif', ['param'], function (options) { options.rules["requiredif"] = '#' + options.params.param; options.messages['requiredif'] = options.message; }); })(jQuery); This is the proposed way in msdn and tutorials i have found Of course i have also inserted the needed scripts in the form: jquery.unobtrusive-ajax.min.js jquery.validate.min.js jquery.validate.unobtrusive.min.js requiredif.js BUT...client side validation still does not work. So could you please help me find what am i missing? Thanks in advance.

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• Javascript parent and child window functions

  - by Mike Thornley

  <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <HTML> <HEAD> <TITLE>Lab 9-3</TITLE> <SCRIPT LANGUAGE="JavaScript"> <!-- function myFunction(){ myWin = open("","","width=200,height=200"); with(myWin.document){ open(); write("<HTML><HEAD><TITLE>Child Window</TITLE>"); write("<SCRIPT>function myTest(){"); write("alert('This function is defined in the child window "); write("and is called from the parent window.'); this.focus();}"); write("</SCRIPT></HEAD><BODY><H3>Child Window</H3><HR>"); write("<FORM><INPUT TYPE='button' VALUE='parent window function' "); // Use opener property write("onClick='opener.winFunction();'>"); write("<P><INPUT TYPE='button' VALUE='close window' "); write("onClick='window.close();'>"); write("</FORM></BODY></HTML>"); close(); } } function winFunction(){ alert("This function is defined in the parent window\n" + "and is called from the child window."); myWin.focus(); } //--> </SCRIPT> </HEAD> <BODY> <H3>CIW Web Languages</H3> <HR> <FORM NAME="myForm"> <INPUT TYPE="button" VALUE="open new window" onClick="myFunction();"> <!-- Invoke child window function --> <input type="button" value="Click to open child window" onclick="javascript:void(myWin.myTest());"/> </FORM> <P> </BODY> </HTML> To explain further what my initial query was, the code above, should open the child window (myWin) with the second button, the 'Open child window' button without the need to open the window with the first button or do anything else. It should simply call the myWin.myTest()function The child window will open when the second button is pressed but needs to have the child window open first (first button push) before it'll work. This is not the intended purpose, the 'Open child window' button should work without anything else needing to be done. For some reason the parent window isn't communicating with the myWin window and myTest fucntion. It's not homework, it's part of a certification course lab and is coded in the manner I have been shown to understand as correct. DTD isn't included as the focus is the JavaScript. I code correctly with regards to that and other W3C requirements.

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• jQuery - animating 'left' position of absolutely positioned div when sliding panel is revealed

  - by trickymatt

  Hello, I have a hidden panel off the left side of the screen which slides into view on the click of a 'tab' positioned on the left side of the screen. I need the panel to slide over the top of the existing page content, and I need the tab to move with it. and so both are absolutely positioned in css. Everything works fine, apart from I need the tab (and thus the tab-container) to move left with the panel when it is revealed, so it appears to be stuck to the right-hand-side of the panel. Its relatively simple when using floats, but of course this affects the layout of the existing content, hence absolute positioning. I have tried animating the left position of the panel-container (see the documented jquery function), but I cant get it to work. My HTML <div><!--sample page content--> <p> Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et </p> </div> <div id="panel" class="height"> <!--the hidden panel --> <div class="content"> <p>Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore</p> </div> </div> <!--if javascript is disabled use this link--> <div id="tab-container" class="height"> <a href="#" onclick="return()"> <div id="tab"><!-- this will activate the panel. --></div> </a> </div> My jQuery $(document).ready(function(){ $("#panel, .content").hide(); //hides the panel and content from the user $('#tab').toggle(function(){ //adding a toggle function to the #tab $('#panel').stop().animate({width:"400px", opacity:0.8}, 100, //sliding the #panel to 400px // THIS NEXT FUNCTION DOES NOT WORK --> function() { $('#tab-container').animate({left:"400px"} //400px to match the panel width }); function() { $('.content').fadeIn('slow'); //slides the content into view. }); }, function(){ //when the #tab is next cliked $('.content').fadeOut('slow', function() { //fade out the content $('#panel').stop().animate({width:"0", opacity:0.1}, 500); //slide the #panel back to a width of 0 }); }); }); and this is the css #panel { position:absolute; left:0px; top:50px; background-color:#999999; height:500px; display:none;/*hide the panel if Javascript is not running*/ } #panel .content { width:290px; margin-left:30px; } #tab-container{ position:absolute; top:20px; width:50px; height:620px; background:#161616; } #tab { width:50px; height:150px; margin-top:100px; display:block; cursor:pointer; background:#DDD; } Many thanks

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• Having trouble storing a CRTP based class in a vector

  - by user366834

  Hi, Im not sure if this can be done, im just delving into templates so perhaps my understanding is a bit wrong. I have a Platoon of soldiers, the platoon inherits from a formation to pick up the formations properties, but because i could have as many formations as i can think of I chose to use the CRTP to create the formations, hoping that i could make a vector or array of Platoon to store the platoons in. but, of course, when i make a Platoon, it wont store it in the vector, "types are unrelated" Is there any way around this ? i read about "Veneers" which are similar and that they work with arrays but i cant get it to work, perhaps im missing something. here's some code: (sorry about the formatting, the code is here in my post but its not showing up for some reason ) template < class TBase > class IFormation { public : ~IFormation(){} bool IsFull() { return m_uiMaxMembers == m_uiCurrentMemCount; } protected: unsigned int m_uiCurrentMemCount; unsigned int m_uiMaxMembers; IFormation( unsigned int _uiMaxMembers ): m_uiMaxMembers( _uiMaxMembers ), m_uiCurrentMemCount( 0 ){} // only allow use as a base class. void SetupFormation( std::vector<MySoldier*>& _soldierList ){}; // must be implemented in derived class }; ///////////////////////////////////////////////////////////////////////////////// // PHALANX FORMATION class Phalanx : public IFormation<Phalanx> { public: Phalanx( ): IFormation( 12 ), m_fDistance( 4.0f ) {} ~Phalanx(){} protected: float m_fDistance; // the distance between soldiers void SetupFormation( std::vector<MySoldier*>& _soldierList ); }; /////////////////////////////////////////////////////////////////////////////////// // COLUMN FORMATINO class Column : public IFormation< Column > { public : Column( int _numOfMembers ): IFormation( _numOfMembers ) {} ~Column(); protected: void SetupFormation( std::vector<MySoldier*>& _soldierList ); }; I then use these formations in the platoon class to derive, so that platoon gets the relevant SetupFormation() function: template < class Formation > class Platoon : public Formation { public: **** platoon code here }; everything works great and as expected up until this point. now, as my general can have multiple platoons, I need to store the platoons. typedef Platoon< IFormation<> > TPlatoon; // FAIL typedef std::vector<TPlatoon*> TPlatoons; TPlatoon m_pPlatoons m_pPlatoons.push_back( new Platoon<Phalanx> ); // FAIL, types unrelated. typedef Platoon< IFormation< TPlatoon; fails because i need to specify a template parameter, yet specifying this will only allow me to store platoons created with the same template parameter. so i then created FormationBase class FormationBase { public: virtual bool IsFull() = 0; virtual void SetupFormation( std::vector<MySoldier*>& _soldierList ) = 0; }; and made IFormation publicly inherit from that, and then changed the typedef to typedef Platoon< IFormation< FormationBase > > TPlatoon; but still no love. now in my searches i have not found info that says this is possible - or not possible.

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• What version-control system is most trivial to set up and use for toy projects?

  - by Norman Ramsey

  I teach the third required intro course in a CS department. One of my homework assignments asks students to speed up code they have written for a previous assignment. Factor-of-ten speedups are routine; factors of 100 or 1000 are not unheard of. (For a factor of 1000 speedup you have to have made rookie mistakes with malloc().) Programs are improved by a sequence is small changes. I ask students to record and describe each change and the resulting improvement. While you're improving a program it is also possible to break it. Wouldn't it be nice to back out? You can see where I'm going with this: my students would benefit enormously from version control. But there are some caveats: Our computing environment is locked down. Anything that depends on a central repository is suspect. Our students are incredibly overloaded. Not just classes but jobs, sports, music, you name it. For them to use a new tool it has to be incredibly easy and have obvious benefits. Our students do most work in pairs. Getting bits back and forth between accounts is problematic. Could this problem also be solved by distributed version control? Complexity is the enemy. I know setting up a CVS repository is too baffling---I myself still have trouble because I only do it once a year. I'm told SVN is even harder. Here are my comments on existing systems: I think central version control (CVS or SVN) is ruled out because our students don't have the administrative privileges needed to make a repository that they can share with one other student. (We are stuck with Unix file permissions.) Also, setup on CVS or SVN is too hard. darcs is way easy to set up, but it's not obvious how you share things. darcs send (to send patches by email) seems promising but it's not clear how to set it up. The introductory documentation for git is not for beginners. Like CVS setup, it's something I myself have trouble with. I'm soliciting suggestions for what source-control to use with beginning students. I suspect we can find resources to put a thin veneer over an existing system and to simplify existing documentation. We probably don't have resources to write new documentation. So, what's really easy to setup, commit, revert, and share changes with a partner but does not have to be easy to merge or to work at scale? A key constraint is that programming pairs have to be able to share work with each other and only each other, and pairs change every week. Our infrastructure is Linux, Solaris, and Windows with a netapp filer. I doubt my IT staff wants to create a Unix group for each pair of students. Is there an easier solution I've overlooked? (Thanks for the accepted answer, which beats the others on account of its excellent reference to Git Magic as well as the helpful comments.)

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• Help to argue why to develop software on a physical computer rather than via a remote desktop

  - by s5804

  Remote desktops are great and many times a blessing and cost effective (instead of leasing expensive cables). I am not arguing against remote desktops, just if one have the alternative to use either remote desktop or physical computer, I would choose the later. Also note that I am not arguing for or against remote work practices. But in my case I am required to be physically present in the office when developing software. Background, I work in a company which main business is not to develop software. Therefore the company IT policies are mainly focused on security and to efficiently deploying/maintaing thousands of computer to users. Further, the typical employee runs typical Office applications, like a word processors. Because safety/stability is such a big priority, every non production system/application, shall be deployed into a physical different network, called the test network. Software development of course also belongs in the test network. To access the test network the company has created a standard policy, which dictates that access to the test network shall go only via a remote desktop client. Practically from ones production computer one would open up a remote desktop client to a virtual computer located in the test network. On the virtual computer's remote desktop one would be able to access/run/install all development tools, like Eclipse IDE. Another solution would be to have a dedicated physical computer, which is physically only connected to the test network. Both solutions are available in the company. I have tested both approaches and found running Eclipse IDE, SQL developer, in the remote desktop client to be sluggish (keyboard strokes are delayed), commands like alt-tab takes me out of the remote client, enjoying... Further, screen resolution and colors are different, just to mention a few. Therefore there is nothing technical wrong with the remote client, just not optimal and frankly de-motivating. Now with the new policies put in place, plans are to remove the physical computers connected to the test network. I am looking for help to argue for why software developers shall have a dedicated physical software development computer, to be productive and cost effective. Remember that we are physically in office. Further one can notice that we are talking about approx. 50 computers out of 2000 employees. Therefore the extra budget is relatively small. This is more about policy than cost. Please note that there are lots of similar setups in other companies that work great due to a perfectly tuned systems. However, in my case it is sluggish and it would cost more money to trouble shoot the performance and fine tune it rather than to have a few physical computers. As a business case we have argued that productivity will go down by 25%, however it's my feeling that the reality is probably closer to 50%. This business case isn't really accepted and I find it very difficult to defend it to managers that has never ever used a rich IDE in their life, never mind developed software. Further the test network and remote client has no guaranteed service level, therefore it is down for a few hours per month with the lowest priority on the fix list. Help is appreciated.

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• Why does this Java code not utilize all CPU cores?

  - by ReneS

  The attached simple Java code should load all available cpu core when starting it with the right parameters. So for instance, you start it with java VMTest 8 int 0 and it will start 8 threads that do nothing else than looping and adding 2 to an integer. Something that runs in registers and not even allocates new memory. The problem we are facing now is, that we do not get a 24 core machine loaded (AMD 2 sockets with 12 cores each), when running this simple program (with 24 threads of course). Similar things happen with 2 programs each 12 threads or smaller machines. So our suspicion is that the JVM (Sun JDK 6u20 on Linux x64) does not scale well. Did anyone see similar things or has the ability to run it and report whether or not it runs well on his/her machine (= 8 cores only please)? Ideas? I tried that on Amazon EC2 with 8 cores too, but the virtual machine seems to run different from a real box, so the loading behaves totally strange. package com.test; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; import java.util.concurrent.Future; import java.util.concurrent.TimeUnit; public class VMTest { public class IntTask implements Runnable { @Override public void run() { int i = 0; while (true) { i = i + 2; } } } public class StringTask implements Runnable { @Override public void run() { int i = 0; String s; while (true) { i++; s = "s" + Integer.valueOf(i); } } } public class ArrayTask implements Runnable { private final int size; public ArrayTask(int size) { this.size = size; } @Override public void run() { int i = 0; String[] s; while (true) { i++; s = new String[size]; } } } public void doIt(String[] args) throws InterruptedException { final String command = args[1].trim(); ExecutorService executor = Executors.newFixedThreadPool(Integer.valueOf(args[0])); for (int i = 0; i < Integer.valueOf(args[0]); i++) { Runnable runnable = null; if (command.equalsIgnoreCase("int")) { runnable = new IntTask(); } else if (command.equalsIgnoreCase("string")) { runnable = new StringTask(); } Future<?> submit = executor.submit(runnable); } executor.awaitTermination(1, TimeUnit.HOURS); } public static void main(String[] args) throws InterruptedException { if (args.length < 3) { System.err.println("Usage: VMTest threadCount taskDef size"); System.err.println("threadCount: Number 1..n"); System.err.println("taskDef: int string array"); System.err.println("size: size of memory allocation for array, "); System.exit(-1); } new VMTest().doIt(args); } }

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• L2S DataContext out of synch: row not found or changed

  - by awrigley

  The Problem I am getting a number of errors that imply that the DataContext, or rather, the way I am using the DataContext is getting out of synch. The error occurs on db.SubmitChanges() where db is my DataContext instance. The error is: Row not found or changed. The problem only occurs intermitently, for example, adding a row then deleting it. If I stop the dev server and restart, the added row is there and I can delete it no problem. Ie, it seems that the problem is related to the DataContext losing track of the rows that have been added. IMPORTANT: Before anyone votes to close this thread, on the basis of it being a duplicate, I have checked the sql server profiler and there is no "Where 0 = 1" in the SQL. I have also recreated the dbml file, so am satisfied that the database schema is in synch with the schema represented by the dbml file. Ie, no cases of mismatched nullable/not nullable columns, etc. My Diagnosis (for what it is worth): It seems to be a problem related to how I am using the DataContext. I am new to MVC, Repositories and Services patterns, so suspect that I have wired things up wrong. The Setup Simple eLearning app in its early stages. Pupils need to be able to add and delete courses (Courses table) to their UserCourses. To do this, I have a service that gets a specific DataContext instance Dependency Injected into its constructor. Service Class Constructor: public class SqlPupilBlockService : IPupilBlockService { DataContext db; public SqlPupilBlockService(DataContext db) { this.db = db; CoursesRepository = new SqlRepository<Course>(db); UserCoursesRepository = new SqlRepository<UserCourse>(db); } // Etc, etc } The CoursesRepository and UserCoursesRepository are both private properties of the service class that are of Type IRepository (just a simple generic repository interface). Sql Respoitory Code: public class SqlRepository<T> : IRepository<T> where T : class { DataContext db; public SqlRepository(DataContext db) { this.db = db; } #region IRepository<T> Members public IQueryable<T> Query { get { return db.GetTable<T>(); } } public List<T> FetchAll() { return Query.ToList(); } public void Add(T entity) { db.GetTable<T>().InsertOnSubmit(entity); } public void Delete(T entity) { db.GetTable<T>().DeleteOnSubmit(entity); } public void Save() { db.SubmitChanges(); } #endregion } The two methods for adding and deleting UserCourses are: Service Methods for Adding and Deleting UserCourses: public void AddUserCourse(int courseId) { UserCourse uc = new UserCourse(); uc.IdCourse = courseId; uc.IdUser = UserId; uc.DateCreated = DateTime.Now; uc.DateAmended = DateTime.Now; uc.Role = "Pupil"; uc.CourseNotes = string.Empty; uc.ActiveStepIndex = 0; UserCoursesRepository.Add(uc); UserCoursesRepository.Save(); } public void DeleteUserCourse(int courseId) { var uc = (UserCoursesRepository.Query.Where(x => x.IdUser == UserId && x.IdCourse == courseId)).Single(); UserCoursesRepository.Delete(uc); UserCoursesRepository.Save(); } Ajax I am using Ajax via Ajax.BeginForm I don't think that is relevant. ASP.NET MVC 3 I am using mvc3, but don't think that is relevant: the errors are related to model code.

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• Help with optimizing C# function via C and/or Assembly

  - by MusiGenesis

  I have this C# method which I'm trying to optimize: // assume arrays are same dimensions private void DoSomething(int[] bigArray1, int[] bigArray2) { int data1; byte A1; byte B1; byte C1; byte D1; int data2; byte A2; byte B2; byte C2; byte D2; for (int i = 0; i < bigArray1.Length; i++) { data1 = bigArray1[i]; data2 = bigArray2[i]; A1 = (byte)(data1 >> 0); B1 = (byte)(data1 >> 8); C1 = (byte)(data1 >> 16); D1 = (byte)(data1 >> 24); A2 = (byte)(data2 >> 0); B2 = (byte)(data2 >> 8); C2 = (byte)(data2 >> 16); D2 = (byte)(data2 >> 24); A1 = A1 > A2 ? A1 : A2; B1 = B1 > B2 ? B1 : B2; C1 = C1 > C2 ? C1 : C2; D1 = D1 > D2 ? D1 : D2; bigArray1[i] = (A1 << 0) | (B1 << 8) | (C1 << 16) | (D1 << 24); } } The function basically compares two int arrays. For each pair of matching elements, the method compares each individual byte value and takes the larger of the two. The element in the first array is then assigned a new int value constructed from the 4 largest byte values (irrespective of source). I think I have optimized this method as much as possible in C# (probably I haven't, of course - suggestions on that score are welcome as well). My question is, is it worth it for me to move this method to an unmanaged C DLL? Would the resulting method execute faster (and how much faster), taking into account the overhead of marshalling my managed int arrays so they can be passed to the method? If doing this would get me, say, a 10% speed improvement, then it would not be worth my time for sure. If it was 2 or 3 times faster, then I would probably have to do it. Note: please, no "premature optimization" comments, thanks in advance. This is simply "optimization".

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• Merge Sort issue when removing the array copy step

  - by Ime Prezime

  I've been having an issue that I couldn't debug for quite some time. I am trying to implement a MergeSort algorithm with no additional steps of array copying by following Robert Sedgewick's algorithm in "Algorithm's in C++" book. Short description of the algorithm: The recursive program is set up to sort b, leaving results in a. Thus, the recursive calls are written to leave their result in b, and we use the basic merge program to merge those files from b into a. In this way, all the data movement is done during the course of the merges. The problem is that I cannot find any logical errors but the sorting isn't done properly. Data gets overwritten somewhere and I cannot determine what logical error causes this. The data is sorted when the program is finished but it is not the same data any more. For example, Input array: { A, Z, W, B, G, C } produces the array: { A, G, W, W, Z, Z }. I can obviously see that it must be a logical error somewhere, but I have been trying to debug this for a pretty long time and I think a fresh set of eyes could maybe see what I'm missing cause I really can't find anything wrong. My code: static const int M = 5; void insertion(char** a, int l, int r) { int i,j; char * temp; for (i = 1; i < r + 1; i++) { temp = a[i]; j = i; while (j > 0 && strcmp(a[j-1], temp) > 0) { a[j] = a[j-1]; j = j - 1; } a[j] = temp; } } //merging a and b into c void merge(char ** c,char ** a, int N, char ** b, int M) { for (int i = 0, j = 0, k = 0; k < N+M; k++) { if (i == N) { c[k] = b[j++]; continue; } if (j == M) { c[k] = a[i++]; continue; } c[k] = strcmp(a[i], b[j]) < 0 ? a[i++] : b[j++]; } } void mergesortAux(char ** a, char ** b, int l, int r) { if(r - l <= M) { insertion(a, l, r); return; } int m = (l + r)/2; mergesortAux(b, a, l, m); //merge sort left mergesortAux(b, a, m+1, r); //merge sort right merge(a+l, b+l, m-l+1, b+m+1, r-m); //merge } void mergesort(char ** a,int l, int r, int size) { static char ** aux = (char**)malloc(size * sizeof(char*)); for(int i = l; i < size; i++) aux[i] = a[i]; mergesortAux(a, aux, l, r); free(aux); }

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• Accordion "growing out" from its container - in IE7/8

  - by Richard Knop

  I think this problem is best explained by images. This is how my accordion looks: When you click on the small plus/minus icons the slides under each chapter will expand/collapse. However when the content in the accordion grows too tall, it grows out from its container. So if I click on more plus icons the accordion will look like this (not pretty): As you can see, the container is not growing taller together with the accordion and it does not look good. This problem only occurs in IE7 and IE8. It works in Firefox and Chrome. The HTML looks like this (simplified): <div id="content"> <div class="box2 rounded-corners"> <div class="chapters"> <h3><a href="/clientarea/view/archived-course/teid/133">Obsah</a></h3> <div id="accordion"> <ul> ... // accordion content - too long ... // accordion content - too long </ul> <div class="clear">&nbsp;</div> </div> <div class="clear">&nbsp;</div> </div> <div class="training-body"> ... // content to the right of the accordion </div> </div> </div> The CSS, again siplified: html, body { height: 100%; width: 100%; overflow: auto; } #content { background: white url('/images/background_middle.png') left top repeat-x; padding: 13px; min-height: 40em; height: auto !important; height: 40em; } /* this is the div with rounded corners */ #content .box2 { background: white; padding: 0 15px 15px; border: 1px solid #C5E3F8; position: relative; } /* left sidebar 98 #content div.chapters { float: left; width: 224px; } /* orange heading "OBSAH" */ #content div.chapters h3 { color: #ff6e19; text-transform: uppercase; font-size: .9em; text-align: center; padding-bottom: .5em; margin-top: 1em; margin-bottom: 0; } #content div.chapters h3 a { color: #ff6e19; } /* accordion */ #accordion { width: 226px; border-top: 1px solid #c5e3f8; } #accordion ul { padding-left: 0; margin-top: 0; margin-bottom: 0; margin-left: 0; } /* area to the right of the accordion */ #content div.training-body { float: left; padding-left: 0px; width: 748px; line-height: 1.3em; }

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• Const-correctness semantics in C++

  - by thirtythreeforty

  For fun and profit™, I'm writing a trie class in C++ (using the C++11 standard.) My trie<T> has an iterator, trie<T>::iterator. (They're all actually functionally const_iterators, because you cannot modify a trie's value_type.) The iterator's class declaration looks partially like this: template<typename T> class trie<T>::iterator : public std::iterator<std::bidirectional_iterator_tag, T> { friend class trie<T>; struct state { state(const trie<T>* const node, const typename std::vector<std::pair<typename T::value_type, std::unique_ptr<trie<T>>>>::const_iterator& node_map_it ) : node{node}, node_map_it{node_map_it} {} // This pointer is to const data: const trie<T>* node; typename std::vector<std::pair<typename T::value_type, std::unique_ptr<trie<T>>>>::const_iterator node_map_it; }; public: typedef const T value_type; iterator() =default; iterator(const trie<T>* node) { parents.emplace(node, node->children.cbegin()); // ... } // ... private: std::stack<state> parents; // ... }; Notice that the node pointer is declared const. This is because (in my mind) the iterator should not be modifying the node that it points to; it is just an iterator. Now, elsewhere in my main trie<T> class, I have an erase function that has a common STL signature--it takes an iterator to data to erase (and returns an iterator to the next object). template<typename T> typename trie<T>::iterator trie<T>::erase(const_iterator it) { // ... // Cannot modify a const object! it.parents.top().node->is_leaf = false; // ... } The compiler complains because the node pointer is read-only! The erase function definitely should modify the trie that the iterator points to, even though the iterator shouldn't. So, I have two questions: Should iterator's constructors be public? trie<T> has the necessary begin() and end() members, and of course trie<T>::iterator and trie<T> are mutual friends, but I don't know what the convention is. Making them private would solve a lot of the angst I'm having about removing the const "promise" from the iterator's constructor. What are the correct const semantics/conventions regarding the iterator and its node pointer here? Nobody has ever explained this to me, and I can't find any tutorials or articles on the Web. This is probably the more important question, but it does require a good deal of planning and proper implementation. I suppose it could be circumvented by just implementing 1, but it's the principle of the thing!

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• iOS: Interpreted code - where do they draw the line?

  - by d7samurai

  Apple's iOS developer guidelines state: 3.3.2 — An Application may not itself install or launch other executable code by any means, including without limitation through the use of a plug-in architecture, calling other frameworks, other APIs or otherwise. No interpreted code may be downloaded or used in an Application except for code that is interpreted and run by Apple’s Documented APIs and built-in interpreter(s). Assuming that downloading data - like XML and images (or a game level description), for example - at run-time is allowed (as is my impression), I am wondering where they draw the line between "data" and "code". Picture the scenario of an app that delivers interactive "presentations" to users (like a survey, for instance). Presentations are added continuously to the server and different presentations are made available to different users, so they cannot be part of the initial app download (this is the whole point). They are described in XML format, but being interactive, they might contain conditional branching of this sort (shown in pseudo form to exemplify): <options id="Gender"> <option value="1">Male</option> <option value="2">Female</option> </options> <branches id="Gender"> <branch value="1"> <image src="Man" /> </branch> <branch value="2"> <image src="Woman" /> </branch> </branches> When the presentation is "played" within the app, the above would be presented in two steps. First a selection screen where the user can click on either of the two choices presented ("Male" or "Female"). Next, an image will be [downloaded dynamically] and displayed based on the choice made in the previous step. Now, it's easy to imagine additional tags describing further logic still. For example, a containing tag could be added: <loop count="3"> <options... /> <branches... /> </loop> The result here being that the selection screen / image screen pair would be sequentially presented three times over, of course. Or imagine some description of a level in a game. It's easy to view that as passive "data", but if it includes, say, several doorways that the user can go through and with various triggers, traps and points attached to them etc - isn't that the same as using a script - or, indeed, interpreted code - to describe options and their conditional responses? Assuming that the interpretation engine for this XML data is already present in the app and that such presentations can only be consumed (not created or edited) in the app, how would this fare against Apple's iOS guidelines? Doesn't XML basically constitute a scripting language (couldn't any interpreted programming language simply be described by XML) in this sense? Would it be OK if the proprietary scripting language (ref the XML used above) was strictly sandboxed (how can they tell?) and not given access to the operating system in any way (but able to download content dynamically - and upload results to the authoring server)? Where does the line go?

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• clock and date showing on a live site but not on localhost

  - by grumpypanda

  I've got clock.swf and date.swf working fine on a live site, now I am using the same code to set up a local develop environment. Everything is working well except the clock.swf and date.swf stopped working on localhost. Two same yellow errors "You need to update your Flash plugin. Click here if you want to continue." but of course my Flash player is up to date since the live site is working fine. I'll post the code below which I think has caused the error. I've been searching online for the last couple of hours but no luck, anyone has got into an issue like this before? What can be the possible cause? Any help is appreciated. This is on the index.php, I can post more code here if needed. <?php embed_flash("swf/clock.swf", CLOCK_WIDTH, CLOCK_HEIGHT, "8", '', "flashcontent");?> <?php embed_flash("swf/date.swf", DATE_WIDTH, DATE_HEIGHT, "8", '', "flashcontent_date");?> configure.php define('CLOCK_WIDTH', '450'); define('CLOCK_HEIGHT', ''); define('DATE_WIDTH', '440'); define('DATE_HEIGHT', ''); flash_function.php <?php function embed_flash($name, $w, $h, $version, $bgcolor, $id) { $cacheBuster = rand(); $padTop = $h/3; ?> <style> a.noflash:link, a.noflash:visited, a.noflash:active {color: #1860C2; text-decoration: none; background:#FFFFFF;} a.noflash:hover {color:#000; text-decoration:none; background:#EEEEEE;} .message { width: <?=$w;?>px; font-size:12px; font-weight:normal; margin-bottom: 10px; padding: 5px; color: #EEE; background: orange;"} </style> <div id="<?=$id; ?>" align="center"> <noscript> <div class="message"> Please enable <a href="https://www.google.com/support/adsense/bin/answer.py?answer=12654" target="_blank" class="noflash">&nbsp;JavaScript&nbsp;</a> to view this page properly. </div> </noscript> <div class="message"> You need to update your Flash plugin. Click <a href="http://www.adobe.com/shockwave/download/download.cgi?P1_Prod_Version=ShockwaveFlash&promoid=BIOW" target="_blank" class="noflash">&nbsp;here&nbsp;</a> if you want to continue. </div> </div> <script type="text/javascript"> // <![CDATA[ var so = new SWFObject("<?=$name;?>", "", "<?=$w;?>", "<?=$h;?>", "<?=$version;?>", "<?=$bgcolor;?>"); so.addParam("quality", "high"); so.addParam("allowScriptAccess", "sameDomain"); so.addParam("scale", "showall"); so.addParam("loop", "false"); so.addParam("wmode", "transparent"); so.write("<?=$id;?>"); // ]]> </script>

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• How to select chosen columns from two different entities into one DTO using NHibernate?

  - by Pawel Krakowiak

  I have two classes (just recreating the problem): public class User { public virtual int Id { get; set; } public virtual string FirstName { get; set; } public virtual string LastName { get; set; } public virtual IList<OrgUnitMembership> OrgUnitMemberships { get; set; } } public class OrgUnitMembership { public virtual int UserId { get; set; } public virtual int OrgUnitId { get; set; } public virtual DateTime JoinDate { get; set; } public virtual DateTime LeaveDate { get; set; } } There's a Fluent NHibernate map for both, of course: public class UserMapping : ClassMap<User> { public UserMapping() { Table("Users"); Id(e => e.Id).GeneratedBy.Identity(); Map(e => e.FirstName); Map(e => e.LastName); HasMany(x => x.OrgUnitMemberships) .KeyColumn(TypeReflector<OrgUnitMembership> .GetPropertyName(p => p.UserId))).ReadOnly().Inverse(); } } public class OrgUnitMembershipMapping : ClassMap<OrgUnitMembership> { public OrgUnitMembershipMapping() { Table("OrgUnitMembership"); CompositeId() .KeyProperty(x=>x.UserId) .KeyProperty(x=>x.OrgUnitId); Map(x => x.JoinDate); Map(x => x.LeaveDate); References(oum => oum.OrgUnit) .Column(TypeReflector<OrgUnitMembership> .GetPropertyName(oum => oum.OrgUnitId)).ReadOnly(); References(oum => oum.User) .Column(TypeReflector<OrgUnitMembership> .GetPropertyName(oum => oum.UserId)).ReadOnly(); } } What I want to do is to retrieve some users based on criteria, but I would like to combine all columns from the Users table with some columns from the OrgUnitMemberships table, analogous to a SQL query: select u.*, m.JoinDate, m.LeaveDate from Users u inner join OrgUnitMemberships m on u.Id = m.UserId where m.OrgUnitId = :ouid I am totally lost, I tried many different options. Using a plain SQL query almost works, but because there are some nullable enums in the User class AliasToBean fails to transform, otherwise wrapping a SQL query would work like this: return Session .CreateSQLQuery(sql) .SetParameter("ouid", orgUnitId) .SetResultTransformer(Transformers.AliasToBean<UserDTO>()) .List<UserDTO>() I tried the code below as a test (a few different variants), but I'm not sure what I'm doing. It works partially, I get instances of UserDTO back, the properties coming from OrgUnitMembership (dates) are filled, but all properties from User are null: User user = null; OrgUnitMembership membership = null; UserDTO dto = null; var users = Session.QueryOver(() => user) .SelectList(list => list .Select(() => user.Id) .Select(() => user.FirstName) .Select(() => user.LastName)) .JoinAlias(u => u.OrgUnitMemberships, () => membership) //.JoinQueryOver<OrgUnitMembership>(u => u.OrgUnitMemberships) .SelectList(list => list .Select(() => membership.JoinDate).WithAlias(() => dto.JoinDate) .Select(() => membership.LeaveDate).WithAlias(() => dto.LeaveDate)) .TransformUsing(Transformers.AliasToBean<UserDTO>()) .List<UserDTO>();

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• C++ Serial Port Question

  - by Pfeffer

  Problem: I have a hand held device that scans those graphic color barcodes on all packaging. There is a track device that I can use that will slide the device automatically. This track device functions by taking ascii code through a serial port. I need to get this thing to work in FileMaker on a Mac. So no terminal programs, etc... What I've got so far: I bought a Keyspan USB/Serial adapter. Using a program called ZTerm I was successful in sending commands to the device. Example: "C,7^M^J" I was also able to do the same thing in Terminal using this command: screen /dev/tty.KeySerial1 57600 and then type in the same command above(but when I typed in I just hit Control-M and Control-J for the carriage return and line feed) Now I'm writing a plug-in for FileMaker(in C++ of course). I want to get what I did above happen in C++ so when I install that plug-in in FileMaker I can just call one of those functions and have the whole process take place right there. I'm able to connect to the device, but I can't talk to it. It is not responding to anything. I've tried connecting to the device(successfully) using these: FILE *comport; if ((comport = fopen("/dev/tty.KeySerial1", "w")) == NULL){...} and int fd; fd = open("/dev/tty.KeySerial1", O_RDWR | O_NOCTTY | O_NDELAY); This is what I've tried so far in way of talking to the device: fputs ("C,7^M^J",comport); or fprintf(comport,"C,7^M^J"); or char buffer[] = { 'C' , ',' , '7' , '^' , 'M' , '^' , 'J' }; fwrite (buffer , 1 , sizeof(buffer) , comport ); or fwrite('C,7^M^J', 1, 1, comport); Questions: When I connected to the device from Terminal and using ZTerm, I was able to set my baud rate of 57600. I think that may be why it isn't responding here. But I don't know how to do it here.... Does any one know how to do that? I tried this, but it didn't work: comport->BaudRate = 57600; There are a lot of class solutions out there but they all call these include files like termios.h and stdio.h. I don't have these and, for whatever reason, I can't find them to download. I've downloaded a few examples but there are like 20 files in them and they're all calling other files I can't find(like the ones listed above). Do I need to find these and if so where? I just don't know enough about C++ Is there a website where I can download libraries?? Another solution might be to put those terminal commands in C++. Is there a way to do that? So this has been driving me crazy. I'm not a C++ guy, I only know basic programming concepts. Is anyone out there a C++ expert? I ideally I'd like this to just work using functions I already have, like those fwrite, fputs stuff. Thanks!

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