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• Designing a database file format

  - by RoliSoft

  I would like to design my own database engine for educational purposes, for the time being. Designing a binary file format is not hard nor the question, I've done it in the past, but while designing a database file format, I have come across a very important question: How to handle the deletion of an item? So far, I've thought of the following two options: Each item will have a "deleted" bit which is set to 1 upon deletion. Pro: relatively fast. Con: potentially sensitive data will remain in the file. 0x00 out the whole item upon deletion. Pro: potentially sensitive data will be removed from the file. Con: relatively slow. Recreating the whole database. Pro: no empty blocks which makes the follow-up question void. Con: it's a really good idea to overwrite the whole 4 GB database file because a user corrected a typo. I will sell this method to Twitter ASAP! Now let's say you already have a few empty blocks in your database (deleted items). The follow-up question is how to handle the insertion of a new item? Append the item to the end of the file. Pro: fastest possible. Con: file will get huge because of all the empty blocks that remain because deleted items aren't actually deleted. Search for an empty block exactly the size of the one you're inserting. Pro: may get rid of some blocks. Con: you may end up scanning the whole file at each insert only to find out it's very unlikely to come across a perfectly fitting empty block. Find the first empty block which is equal or larger than the item you're inserting. Pro: you probably won't end up scanning the whole file, as you will find an empty block somewhere mid-way; this will keep the file size relatively low. Con: there will still be lots of leftover 0x00 bytes at the end of items which were inserted into bigger empty blocks than they are. Rigth now, I think the first deletion method and the last insertion method are probably the "best" mix, but they would still have their own small issues. Alternatively, the first insertion method and scheduled full database recreation. (Probably not a good idea when working with really large databases. Also, each small update in that method will clone the whole item to the end of the file, thus accelerating file growth at a potentially insane rate.) Unless there is a way of deleting/inserting blocks from/to the middle of the file in a file-system approved way, what's the best way to do this? More importantly, how do databases currently used in production usually handle this?

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• ASP.net Repeater Control Problem (nothing outputted from datasource(sqldatareader))

  - by Phil

  I have the following code to get the repeaters' data in my usercontrol (content.ascx.vb): If did = 0 Then s = "select etc (statement works on server)" x = New SqlCommand(s, c) x.Parameters.Add("@contentid", Data.SqlDbType.Int) x.Parameters("@contentid").Value = contentid c.Open() r = x.ExecuteReader If r.HasRows Then Contactinforepeater.DataSource = r End If c.Close() r.Close() Else s = "select etc (statement works on server)" x = New SqlCommand(s, c) x.Parameters.Add("@contentid", SqlDbType.Int) x.Parameters("@contentid").Value = contentid x.Parameters.Add("@did", SqlDbType.Int) x.Parameters("@did").Value = did c.Open() r = x.ExecuteReader If r.HasRows Then Contactinforepeater.DataSource = r c.Close() r.Close() End If End If Then I have the following repeater control markup in my usercontrol (content.ascx): <asp:Repeater ID="Contactinforepeater" runat="server"> <HeaderTemplate> <h1>Contact Information</h1> </HeaderTemplate> <ItemTemplate> <table width="50%"> <tr> <td colspan="2"><%#Container.DataItem("position")%></td> </tr> <tr> <td>Name:</td> <td><%#Container.DataItem("surname")%></td> </tr> <tr> <td>Telephone:</td> <td><%#Container.DataItem("telephone")%></td> </tr> <tr> <td>Fax:</td> <td><%#Container.DataItem("fax")%></td> </tr> <tr> <td>Email:</td> <td><%#Container.DataItem("email")%></td> </tr> </table> </ItemTemplate> <SeparatorTemplate><br /><hr /><br /></SeparatorTemplate> </asp:Repeater> When I insert this usercontrol into default.aspx with this code: <%@ Register src="Modules/Content.ascx" tagname="Content" tagprefix="uc1" %> and <form id="form1" runat="server"> <div> <uc1:Content ID="Content" runat="server" /> </div> </form> I do not get any error messages but the expected content from the database is not displayed. Can someone please show me the syntax to get this working or point out where I am going wrong? Thanks in advance!

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• C# mvc 3 using selectlist with selected value in view

  - by Rob

  I'm working on a MVC3 web application. I want a list of categories shown when editing a blo from whe applications managements system. In my viewmodel i've got the following property defined for a list of selectlistitems for categories. /// <summary> /// The List of categories /// </summary> [Display(Name = "Categorie")] public IEnumerable<SelectListItem> Categories { get; set; } The next step, my controller contains the following edit action where the list of selectlistitems is filled from the database. public ActionResult Edit(Guid id) { var blogToEdit = _blogService.First(x => x.Id.Equals(id)); var listOfCategories = _categorieService.GetAll(); var selectList = listOfCategories.Select(x =>new SelectListItem{Text = x.Name, Value = x.Id.ToString(), Selected = x.Id.Equals(blogToEdit.Category.Id)}).ToList(); selectList.Insert(0, new SelectListItem{Text = Messages.SelectAnItem, Value = Messages.SelectAnItem}); var viewModel = new BlogModel { BlogId = blogToEdit.Id, Active = blogToEdit.Actief, Content = blogToEdit.Text, Title = blogToEdit.Titel, Categories = selectList //at this point i see the expected item being selected //Categories = new IEnumerable<SelectListItem>(listOfCategories, "Id", "Naam", blogToEdit.CategorieId) }; return View(viewModel); } When i set a breakpoint just before the view is being returned, i see that the selectlist is filled as i expected. So at this point everything seems to be okay. The viewmodel is filled entirely correct. Then in my view (i'm using Razor) i've got the following two rules which are supposed to render the selectlist for me. @Html.LabelFor(m => m.Categories) @Html.DropDownListFor(model=>model.Categories, Model.Categories, Model.CategoryId) @Html.ValidationMessageFor(m => m.Categories) When I run the code and open the view to edit my blog, I can see all the correct data. Also the selectlist is rendered correctly, but the item i want to be selected lost it's selection. How can this be? Until the point the viewmodel is being returned with the view everything is okay. But when i view the webpage in the browser, the selectlist is there only with out the correct selection. What am I missing here? Or doing wrong?

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• QValidator for hex input

  - by Evan Teran

  I have a Qt widget which should only accept a hex string as input. It is very simple to restrict the input characters to [0-9A-Fa-f], but I would like to have it display with a delimiter between "bytes" so for example if the delimiter is a space, and the user types 0011223344 I would like the line edit to display 00 11 22 33 44 Now if the user presses the backspace key 3 times, then I want it to display 00 11 22 3. I almost have what i want, so far there is only one subtle bug involving using the delete key to remove a delimiter. Does anyone have a better way to implement this validator? Here's my code so far: class HexStringValidator : public QValidator { public: HexStringValidator(QObject * parent) : QValidator(parent) {} public: virtual void fixup(QString &input) const { QString temp; int index = 0; // every 2 digits insert a space if they didn't explicitly type one Q_FOREACH(QChar ch, input) { if(std::isxdigit(ch.toAscii())) { if(index != 0 && (index & 1) == 0) { temp += ' '; } temp += ch.toUpper(); ++index; } } input = temp; } virtual State validate(QString &input, int &pos) const { if(!input.isEmpty()) { // TODO: can we detect if the char which was JUST deleted // (if any was deleted) was a space? and special case this? // as to not have the bug in this case? const int char_pos = pos - input.left(pos).count(' '); int chars = 0; fixup(input); pos = 0; while(chars != char_pos) { if(input[pos] != ' ') { ++chars; } ++pos; } // favor the right side of a space if(input[pos] == ' ') { ++pos; } } return QValidator::Acceptable; } }; For now this code is functional enough, but I'd love to have it work 100% as expected. Obviously the ideal would be the just separate the display of the hex string from the actual characters stored in the QLineEdit's internal buffer but I have no idea where to start with that and I imagine is a non-trivial undertaking. In essence, I would like to have a Validator which conforms to this regex: "[0-9A-Fa-f]( [0-9A-Fa-f])*" but I don't want the user to ever have to type a space as delimiter. Likewise, when editing what they types, the spaces should be managed implicitly.

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• How do I recover from an unchecked exception?

  - by erickson

  Unchecked exceptions are alright if you want to handle every failure the same way, for example by logging it and skipping to the next request, displaying a message to the user and handling the next event, etc. If this is my use case, all I have to do is catch some general exception type at a high level in my system, and handle everything the same way. But I want to recover from specific problems, and I'm not sure the best way to approach it with unchecked exceptions. Here is a concrete example. Suppose I have a web application, built using Struts2 and Hibernate. If an exception bubbles up to my "action", I log it, and display a pretty apology to the user. But one of the functions of my web application is creating new user accounts, that require a unique user name. If a user picks a name that already exists, Hibernate throws an org.hibernate.exception.ConstraintViolationException (an unchecked exception) down in the guts of my system. I'd really like to recover from this particular problem by asking the user to choose another user name, rather than giving them the same "we logged your problem but for now you're hosed" message. Here are a few points to consider: There a lot of people creating accounts simultaneously. I don't want to lock the whole user table between a "SELECT" to see if the name exists and an "INSERT" if it doesn't. In the case of relational databases, there might be some tricks to work around this, but what I'm really interested in is the general case where pre-checking for an exception won't work because of a fundamental race condition. Same thing could apply to looking for a file on the file system, etc. Given my CTO's propensity for drive-by management induced by reading technology columns in "Inc.", I need a layer of indirection around the persistence mechanism so that I can throw out Hibernate and use Kodo, or whatever, without changing anything except the lowest layer of persistence code. As a matter of fact, there are several such layers of abstraction in my system. How can I prevent them from leaking in spite of unchecked exceptions? One of the declaimed weaknesses of checked exceptions is having to "handle" them in every call on the stack—either by declaring that a calling method throws them, or by catching them and handling them. Handling them often means wrapping them in another checked exception of a type appropriate to the level of abstraction. So, for example, in checked-exception land, a file-system–based implementation of my UserRegistry might catch IOException, while a database implementation would catch SQLException, but both would throw a UserNotFoundException that hides the underlying implementation. How do I take advantage of unchecked exceptions, sparing myself of the burden of this wrapping at each layer, without leaking implementation details?

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• programming question

  - by shivam

  using System; using System.Data; using System.Collections.Generic; using System.ComponentModel; using System.Drawing; using System.Linq; using System.Text; using System.Windows.Forms; using System.Data.SqlClient; namespace datasynchronization { public partial class Form1 : Form { public Form1() { InitializeComponent(); } private void button1_Click(object sender, EventArgs e) { string connectString = @"Data Source=MOON\SQL2005;Initial Catalog=databaseA;Integrated Security=True"; using (var srcCon = new SqlConnection(connectString)) //connection to source table { srcCon.Open();//source table connection open SqlCommand cmd = new SqlCommand();// sqlobject for source table cmd.Connection = srcCon; string connectionString = @"Data Source=MOON\SQL2005;Initial Catalog=databaseB;Integrated Security=True"; using (var tgtCon = new SqlConnection(connectionString)) //connection to target table { tgtCon.Open(); //target table connection open SqlCommand objcmd1 = new SqlCommand();//sqlobject for target table objcmd1.Connection = tgtCon; objcmd1.CommandText = "SELECT MAX(date) FROM Table_2"; //query to findout the max date from target table var maxdate = objcmd1.ExecuteScalar(); // store the value of max date into the variable maxdate cmd.CommandText = string.Format("SELECT id,date,name,city,salary,region FROM Table_1 where date >'{0}'", maxdate); //select query to fetch rows from source table using (var reader = cmd.ExecuteReader()) { SqlCommand objcmd = new SqlCommand(); objcmd.Connection = tgtCon; objcmd.CommandText = "INSERT INTO Table_2(id,date,name,city,salary,region)VALUES(@id,@date,@name,@city,@salary,@region)"; objcmd.Parameters.Add("@id", SqlDbType.Int); objcmd.Parameters.Add("@date", SqlDbType.DateTime); objcmd.Parameters.Add("@name", SqlDbType.NVarChar); objcmd.Parameters.Add("@city", SqlDbType.NVarChar); objcmd.Parameters.Add("@salary", SqlDbType.Int); objcmd.Parameters.Add("@region", SqlDbType.Char); while (reader.Read()) { var order1 = reader[0].ToString(); var order2 = reader[1].ToString(); var order3 = reader[2].ToString(); var order4 = reader[3].ToString(); var order5 = reader[4].ToString(); var order6 = reader[5].ToString(); objcmd.Parameters["@id"].Value = order1; objcmd.Parameters["@date"].Value = order2; objcmd.Parameters["@name"].Value = order3; objcmd.Parameters["@city"].Value = order4; objcmd.Parameters["@salary"].Value = order5; objcmd.Parameters["@region"].Value = order6; objcmd.ExecuteNonQuery(); } } tgtCon.Close(); } srcCon.Close(); } } } } how can i organize the above written code in an efficient way?

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• Problem determining how to order F# types due to circular references

  - by James Black

  I have some types that extend a common type, and these are my models. I then have DAO types for each model type for CRUD operations. I now have a need for a function that will allow me to find an id given any model type, so I created a new type for some miscellaneous functions. The problem is that I don't know how to order these types. Currently I have models before dao, but I somehow need DAOMisc before CityDAO and CityDAO before DAOMisc, which isn't possible. The simple approach would be to put this function in each DAO, referring to just the types that can come before it, so, State comes before City as State has a foreign key relationship with City, so the miscellaneous function would be very short. But, this just strikes me as wrong, so I am not certain how to best approach this. Here is my miscellaneous type, where BaseType is a common type for all my models. type DAOMisc = member internal self.FindIdByType item = match(item:BaseType) with | :? StateType as i -> let a = (StateDAO()).Retrieve i a.Head.Id | :? CityType as i -> let a = (CityDAO()).Retrieve i a.Head.Id | _ -> -1 Here is one dao type. CommonDAO actually has the code for the CRUD operations, but that is not important here. type CityDAO() = inherit CommonDAO<CityType>("city", ["name"; "state_id"], (fun(reader) -> [ while reader.Read() do let s = new CityType() s.Id <- reader.GetInt32 0 s.Name <- reader.GetString 1 s.StateName <- reader.GetString 3 ]), list.Empty ) This is my model type: type CityType() = inherit BaseType() let mutable name = "" let mutable stateName = "" member this.Name with get() = name and set restnameval=name <- restnameval member this.StateName with get() = stateName and set stateidval=stateName <- stateidval override this.ToSqlValuesList = [this.Name;] override this.ToFKValuesList = [StateType(Name=this.StateName);] The purpose for this FindIdByType function is that I want to find the id for a foreign key relationship, so I can set the value in my model and then have the CRUD functions do the operations with all the correct information. So, City needs the id for the state name, so I would get the state name, put it into the state type, then call this function to get the id for that state, so my city insert will also include the id for the foreign key. This seems to be the best approach, in a very generic way to handle inserts, which is the current problem I am trying to solve.

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• Connect to SQLite Database using Eclipse (Java)

  - by bnabilos

  Hello, I'm trying to connect to SQLite database with Ecplise but I have some errors. This is my Java code and the errors that I get on output. Please see if you can help me. Thank you in advance. package jdb; import java.sql.*; public class Test { public static void main(String[] args) throws Exception { Class.forName("org.sqlite.JDBC"); Connection conn = DriverManager.getConnection("jdbc:sqlite:/Applications/MAMP/db/sqlite/test.sqlite"); Statement stat = conn.createStatement(); stat.executeUpdate("drop table if exists people;"); stat.executeUpdate("create table people (name, occupation);"); PreparedStatement prep = conn.prepareStatement( "insert into people values (?, ?);"); prep.setString(1, "Gandhi"); prep.setString(2, "politics"); prep.addBatch(); prep.setString(1, "Turing"); prep.setString(2, "computers"); prep.addBatch(); prep.setString(1, "Wittgenstein"); prep.setString(2, "smartypants"); prep.addBatch(); conn.setAutoCommit(false); prep.executeBatch(); conn.setAutoCommit(true); ResultSet rs = stat.executeQuery("select * from people;"); while (rs.next()) { System.out.println("name = " + rs.getString("name")); System.out.println("job = " + rs.getString("occupation")); } rs.close(); conn.close(); } } ans that what I get in Ecplise : Exception in thread "main" java.lang.ClassNotFoundException: org.sqlite.JDBC at java.net.URLClassLoader$1.run(URLClassLoader.java:200) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:188) at java.lang.ClassLoader.loadClass(ClassLoader.java:315) at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:330) at java.lang.ClassLoader.loadClass(ClassLoader.java:250) at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:398) at java.lang.Class.forName0(Native Method) at java.lang.Class.forName(Class.java:169) at jdb.Test.main(Test.java:7) Thank you

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• Java: Detecting image format, resize (scale) and save as JPEG

  - by BoDiE2003

  This is the code I have, it actually works, not perfectly but it does, the problem is that the resized thumbnails are not pasting on the white Drawn rectangle, breaking the images aspect ratio, here is the code, could someone suggest me a fix for it, please? Thank you import java.awt.Color; import java.awt.Graphics2D; import java.awt.Image; import java.awt.RenderingHints; import java.awt.geom.Rectangle2D; import java.awt.image.BufferedImage; import java.io.BufferedInputStream; import java.io.ByteArrayInputStream; import java.io.ByteArrayOutputStream; import java.io.IOException; import java.io.InputStream; import javax.imageio.ImageIO; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; public class ImageScalerImageIoImpl implements ImageScaler { private static final String OUTPUT_FORMAT_ID = "jpeg"; // Re-scaling image public byte[] scaleImage(byte[] originalImage, int targetWidth, int targetHeight) { try { InputStream imageStream = new BufferedInputStream( new ByteArrayInputStream(originalImage)); Image image = (Image) ImageIO.read(imageStream); int thumbWidth = targetWidth; int thumbHeight = targetHeight; // Make sure the aspect ratio is maintained, so the image is not skewed double thumbRatio = (double)thumbWidth / (double)thumbHeight; int imageWidth = image.getWidth(null); int imageHeight = image.getHeight(null); double imageRatio = (double)imageWidth / (double)imageHeight; if (thumbRatio < imageRatio) { thumbHeight = (int)(thumbWidth / imageRatio); } else { thumbWidth = (int)(thumbHeight * imageRatio); } // Draw the scaled image BufferedImage thumbImage = new BufferedImage(thumbWidth, thumbHeight, BufferedImage.TYPE_INT_RGB); System.out.println("Thumb width Buffered: " + thumbWidth + " || Thumb height Buffered: " + thumbHeight); Graphics2D graphics2D = thumbImage.createGraphics(); // Use of BILNEAR filtering to enable smooth scaling graphics2D.setRenderingHint(RenderingHints.KEY_INTERPOLATION, RenderingHints.VALUE_INTERPOLATION_BILINEAR); // graphics2D.drawImage(image, 0, 0, thumbWidth, thumbHeight, null); // White Background graphics2D.setPaint(Color.WHITE); graphics2D.fill(new Rectangle2D.Double(0, 0, targetWidth, targetHeight)); graphics2D.fillRect(0, 0, targetWidth, targetHeight); System.out.println("Target width: " + targetWidth + " || Target height: " + targetHeight); // insert the resized thumbnail between X and Y of the image graphics2D.drawImage(image, 0, 0, thumbWidth, thumbHeight, null); System.out.println("Thumb width: " + thumbWidth + " || Thumb height: " + thumbHeight); // Write the scaled image to the outputstream ByteArrayOutputStream out = new ByteArrayOutputStream(); ImageIO.write(thumbImage, OUTPUT_FORMAT_ID, out); return out.toByteArray(); } catch (IOException ioe) { throw new ImageResizingException(ioe); } } }

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• Internal class and access to external members.

  - by Knowing me knowing you

  I always thought that internal class has access to all data in its external class but having code: template<class T> class Vector { template<class T> friend std::ostream& operator<<(std::ostream& out, const Vector<T>& obj); private: T** myData_; std::size_t myIndex_; std::size_t mySize_; public: Vector():myData_(nullptr), myIndex_(0), mySize_(0) { } Vector(const Vector<T>& pattern); void insert(const T&); Vector<T> makeUnion(const Vector<T>&)const; Vector<T> makeIntersection(const Vector<T>&)const; class Iterator : public std::iterator<std::bidirectional_iterator_tag,T> { private: T** itData_; public: Iterator()//<<<<<<<<<<<<<------------COMMENT { /*HERE I'M TRYING TO USE ANY MEMBER FROM Vector<T> AND I'M GETTING ERR SAYING: ILLEGAL CALL OF NON-STATIC MEMBER FUNCTION*/} Iterator(T** ty) { itData_ = ty; } Iterator operator++() { return ++itData_; } T operator*() { return *itData_[0]; } bool operator==(const Iterator& obj) { return *itData_ == *obj.itData_; } bool operator!=(const Iterator& obj) { return *itData_ != *obj.itData_; } bool operator<(const Iterator& obj) { return *itData_ < *obj.itData_; } }; typedef Iterator iterator; iterator begin()const { assert(mySize_ > 0); return myData_; } iterator end()const { return myData_ + myIndex_; } }; See line marked as COMMENT. So can I or I can't use members from external class while in internal class? Don't bother about naming, it's not a Vector it's a Set. Thank you.

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• Cannot figure out how to take in generic parameters for an Enterprise Framework library sql statemen

  - by KallDrexx

  I have written a specialized class to wrap up the enterprise library database functionality for easier usage. The reasoning for using the Enterprise Library is because my applications commonly connect to both oracle and sql server database systems. My wrapper handles both creating connection strings on the fly, connecting, and executing queries allowing my main code to only have to write a few lines of code to do database stuff and deal with error handling. As an example my ExecuteNonQuery method has the following declaration: /// <summary> /// Executes a query that returns no results (e.g. insert or update statements) /// </summary> /// <param name="sqlQuery"></param> /// <param name="parameters">Hashtable containing all the parameters for the query</param> /// <returns>The total number of records modified, -1 if an error occurred </returns> public int ExecuteNonQuery(string sqlQuery, Hashtable parameters) { // Make sure we are connected to the database if (!IsConnected) { ErrorHandler("Attempted to run a query without being connected to a database.", ErrorSeverity.Critical); return -1; } // Form the command DbCommand dbCommand = _database.GetSqlStringCommand(sqlQuery); // Add all the paramters foreach (string key in parameters.Keys) { if (parameters[key] == null) _database.AddInParameter(dbCommand, key, DbType.Object, null); else _database.AddInParameter(dbCommand, key, DbType.Object, parameters[key].ToString()); } return _database.ExecuteNonQuery(dbCommand); } _database is defined as private Database _database;. Hashtable parameters are created via code similar to p.Add("@param", value);. the issue I am having is that it seems that with enterprise library database framework you must declare the dbType of each parameter. This isn't an issue when you are calling the database code directly when forming the paramters but doesn't work for creating a generic abstraction class such as I have. In order to try and get around that I thought I could just use DbType.Object and figure the DB will figure it out based on the columns the sql is working with. Unfortunately, this is not the case as I get the following error: Implicit conversion from data type sql_variant to varchar is not allowed. Use the CONVERT function to run this query Is there any way to use generic parameters in a wrapper class or am I just going to have to move all my DB code into my main classes?

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• .Net Entity Framework SaveChanges is adding without add method

  - by tmfkmoney

  I'm new to the entity framework and I'm really confused about how savechanges works. There's probably a lot of code in my example which could be improved, but here's the problem I'm having. The user enters a bunch of picks. I make sure the user hasn't already entered those picks. Then I add the picks to the database. var db = new myModel() var predictionArray = ticker.Substring(1).Split(','); // Get rid of the initial comma. var user = Membership.GetUser(); var userId = Convert.ToInt32(user.ProviderUserKey); // Get the member with all his predictions for today. var memberQuery = (from member in db.Members where member.user_id == userId select new { member, predictions = from p in member.Predictions where p.start_date == null select p }).First(); // Load all the company ids. foreach (var prediction in memberQuery.predictions) { prediction.CompanyReference.Load(); } var picks = from prediction in predictionArray let data = prediction.Split(':') let companyTicker = data[0] where !(from i in memberQuery.predictions select i.Company.ticker).Contains(companyTicker) select new Prediction { Member = memberQuery.member, Company = db.Companies.Where(c => c.ticker == companyTicker).First(), is_up = data[1] == "up", // This turns up and down into true and false. }; // Save the records to the database. // HERE'S THE PART I DON'T UNDERSTAND. // This saves the records, even though I don't have db.AddToPredictions(pick) foreach (var pick in picks) { db.SaveChanges(); } // This does not save records when the db.SaveChanges outside of a loop of picks. db.SaveChanges(); foreach (var pick in picks) { } // This saves records, but it will insert all the picks exactly once no matter how many picks you have. //The fact you're skipping a pick makes no difference in what gets inserted. var counter = 1; foreach (var pick in picks) { if (counter == 2) { db.SaveChanges(); } counter++; } There's obviously something going on with the context I don't understand. I'm guessing I've somehow loaded my new picks as pending changes, but even if that's true I don't understand I have to loop over them to save changes. Can someone explain this to me?

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• Array within Form collecting multiple values with the same name possible?

  - by JM4

  Good afternoon, I will first start with the goal I am trying to accomplish and then give a very basic sample of what I need to do. Goal Instead of collecting several variables and naming them with keys individually, I have decided to give in and use an array structure to handle all inputs of the same type and rules. Once I have the variables, I will validate against them and if 'ok' store them in a MySQL table. The table will hold consumer information and will need to store multiple rows of the same type of information. First Pass I will leave out the validation portion of this question because I feel I need to first understand the basics. <form action="?" method="POST" name="Form"> Member 1 First Name:<input type="text" name="MemberFirstName[]" /><br /> Member 1 Last Name: <input type="text" name="MemberLastName[]" /><br /> Member 1 Email: <input type="text" name="MemberEmail[]" /><br /> Member 2 First Name:<input type="text" name="MemberFirstName[]" /><br /> Member 2 Last Name: <input type="text" name="MemberLastName[]" /><br /> Member 2 Email: <input type="text" name="MemberEmail[]" /><br /> Member 3 First Name:<input type="text" name="MemberFirstName[]" /><br /> Member 3 Last Name: <input type="text" name="MemberLastName[]" /><br /> Member 3 Email: <input type="text" name="MemberEmail[]" /><br /> <input type="submit" name="submit" value="Continue" /> </form> I am hoping that each input given for First Name (a required field) will generate a unique key for that particular entry and not overwrite any data entered. Because I am carrying information from page to page (checkout form), I am turning the POST variables into SESSION variables then storing in a mysql database in the end. My hope is to have: <?php $conn = mysql_connect("localhost", "username", "password"); mysql_select_db("DBname",$conn); $sql = "INSERT INTO tablename VALUES ('$_SESSION[Member1FirstName]', '$_SESSION[Member1LastName]', '$_SESSION[Member1Email]', '$_SESSION[Member2FirstName]', '$_SESSION[Member2LastName]', '$_SESSION[Member2Email]', '$_SESSION[Member1FirstName]', '$_SESSION[Member3LastName]', '$_SESSION[Member3Email]')"; $result = mysql_query($sql, $conn) or die(mysql_error()); Header ("Location: completed.php"); ?> Where Member1, Member2, and Member3 values will appear on their own row within the table. I KNOW my code is wrong but I am giving a first shot at the overall business purpose I am trying to achieve and trying to learn how to code the right way. I am very, very new to programming so any 'baby advice' is greatly appreciated.

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• radgridview delete update in asp.net

  - by abhi

  i have written the follwing to display data from the datagrid and den insert new rows but how do i perform update and delete plss help here's my code using System; using System.Data; using System.Configuration; using System.Collections; using System.Web; using System.Web.Security; using System.Web.UI; using System.Web.UI.WebControls; using System.Web.UI.WebControls.WebParts; using System.Web.UI.HtmlControls; using Telerik.Web.UI; using System.Data.SqlClient; public partial class Default6 : System.Web.UI.Page { string strQry, strCon; SqlDataAdapter da; SqlConnection con; DataSet ds; protected void Page_Load(object sender, EventArgs e) { strCon = "Data Source=MINETDEVDATA; Initial Catalog=ML_SuppliersProd; User Id=sa; Password=@MinetApps7;"; con = new SqlConnection(strCon); strQry = "SELECT * FROM table1"; da = new SqlDataAdapter(strQry, con); SqlCommandBuilder cmdbuild = new SqlCommandBuilder(da); ds = new DataSet(); da.Fill(ds, "table1"); RadGrid1.DataSource = ds.Tables["table1"]; RadGrid1.DataBind(); Label3.Visible = false; Label4.Visible = false; Label5.Visible = false; txtFname.Visible = false; txtLname.Visible = false; txtDesignation.Visible = false; } protected void Submit_Click(object sender, EventArgs e) { Label3.Visible = true; Label4.Visible = true; Label5.Visible = true; txtFname.Visible = true; txtLname.Visible = true; txtDesignation.Visible = true; } protected void Button2_Click(object sender, EventArgs e) { DataSet ds = new DataSet("EmployeeSet"); da.Fill(ds, "table1"); DataTable EmployeeTable = ds.Tables["table1"]; DataRow row = EmployeeTable.NewRow(); row["Fname"] = txtFname.Text.ToString(); row["Lname"] = txtLname.Text.ToString(); row["Designation"] = txtDesignation.Text.ToString(); EmployeeTable.Rows.Add(row); da.Update(ds, "table1"); //RadGrid1.DataSource = ds.Tables["table1"]; //RadGrid1.DataBind(); txtFname.Text = ""; txtLname.Text = ""; txtDesignation.Text = ""; } protected void RadGrid1_DeleteCommand(object source, GridCommandEventArgs e) { } } }

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• adding other parameter to function

  - by Ronnie Chester Lynwood

  hello. i got a function that listing downloads in a table with foreach. it's also lists searched term, search type. public function fetchDownloads($displaySite=true) { $downloads = array(); $sqlWhere = ""; if(isset($this->q)) { if(strlen($this->q) <= $this->recents_length && !empty($this->q)) { $insertRecent = $this->processDataHook("insertRecent",$this->q); if($insertRecent) { if(!@mysql_query("INSERT INTO wcddl_recents (query) VALUES ('".$this->qSQL."')")) { @mysql_query("UPDATE wcddl_recents SET searches = searches+1 WHERE query = '".$this->qSQL."'"); } } } if($this->search_type == "narrow") { $sqlWhere = " WHERE title LIKE '%".mysql_real_escape_string(str_replace(" ","%",$this->q))."%'"; } elseif($this->search_type == "wide") { $qExp = explode(" ",$this->q); $sqlWhere = array(); foreach($qExp as $fq) $sqlWhere[] = "title LIKE '%".mysql_real_escape_string($fq)."%'"; $sqlWhere = implode(" OR ",$sqlWhere); $sqlWhere = " WHERE (".$sqlWhere.")"; } } if(isset($this->type)) { if(!empty($sqlWhere)) { $sqlWhere .= " AND type = '".$this->typeSQL."'"; } else { $sqlWhere = " WHERE type = '".$this->typeSQL."'"; } } $sqlWhere = $this->processDataHook("fetchDownloadsSQLWhere",$sqlWhere); $this->maxPages = mysql_query("SELECT COUNT(*) FROM wcddl_downloads".$sqlWhere.""); $this->maxPages = mysql_result($this->maxPages,0); $this->numRows = $this->maxPages; $this->maxPages = ceil($this->maxPages/$this->limit); $sqlMain = "SELECT id,sid,title,type,url,dat,views,rating FROM wcddl_downloads".$sqlWhere." ORDER BY ".(isset($this->sqlOrder) ? mysql_real_escape_string($this->sqlOrder) : "id DESC")." LIMIT ".$this->pg.",".$this->limit.""; $sqlMain = $this->processDataHook("whileFetchDownloadsSQL",$sqlMain); $sqlMain = mysql_query($sqlMain); $this->processHook("whileFetchDownloads"); while($row = mysql_fetch_assoc($sqlMain)) { if($displaySite) { $downloadSite = mysql_query("SELECT name as sname, url as surl, rating as srating FROM wcddl_sites WHERE id = '".$row['sid']."'"); $downloadSite = mysql_fetch_assoc($downloadSite); $row = array_merge($row,$downloadSite); } $downloads_current = $this->mapit($row,array("stripslashes","strip_tags")); $downloads_current = $this->processDataHook("fetchDownloadsRow",$downloads_current); $downloads[] = $downloads_current; } $this->pageList = $this->getPages($this->page,$this->maxPages); $this->processHook("endFetchDownloads"); return $downloads; } I want to add if $_REQUEST['site'] is set, order downloads by sname that catching from wcddl_sites.

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• Error in Print Function in Bubble Sort MIPS?

  - by m00nbeam360

  Sorry that this is such a long block of code, but do you see any obvious syntax errors in this? I feel like the problem is that the code isn't printing correctly since the sort and swap methods were from my textbook. Please help if you can! .data save: .word 1,2,4,2,5,6 size: .word 6 .text swap: sll $t1, $a1, 2 #shift bits by 2 add $t1, $a1, $t1 #set $t1 address to v[k] lw $t0, 0($t1) #load v[k] into t1 lw $t2, 4($t1) #load v[k+1] into t1 sw $t2, 0($t1) #swap addresses sw $t0, 4($t1) #swap addresses jr $ra #return sort: addi $sp, $sp, -20 #make enough room on the stack for five registers sw $ra, 16($sp) #save the return address on the stack sw $s3, 12($sp) #save $s3 on the stack sw $s2, 8($sp) #save Ss2 on the stack sw $s1, 4($sp) #save $s1 on the stack sw $s0, 0($sp) #save $s0 on the stack move $s2, $a0 #copy the parameter $a0 into $s2 (save $a0) move $s3, $a1 #copy the parameter $a1 into $s3 (save $a1) move $s0, $zero #start of for loop, i = 0 for1tst: slt $t0, $s0, $s3 #$t0 = 0 if $s0 S $s3 (i S n) beq $t0, $zero, exit1 #go to exit1 if $s0 S $s3 (i S n) addi $s1, $s0, -1 #j - i - 1 for2tst: slti $t0, $s1, 0 #$t0 = 1 if $s1 < 0 (j < 0) bne $t0, $zero, exit2 #$t0 = 1 if $s1 < 0 (j < 0) sll $t1, $s1, 2 #$t1 = j * 4 (shift by 2 bits) add $t2, $s2, $t1 #$t2 = v + (j*4) lw $t3, 0($t2) #$t3 = v[j] lw $t4, 4($t2) #$t4 = v[j+1] slt $t0, $t4, $t3 #$t0 = 0 if $t4 S $t3 beq $t0, $zero, exit2 #go to exit2 if $t4 S $t3 move $a0, $s2 #1st parameter of swap is v(old $a0) move $a1, $s1 #2nd parameter of swap is j jal swap #swap addi $s1, $s1, -1 j for2tst #jump to test of inner loop j print exit2: addi $s0, $s0, 1 #i = i + 1 j for1tst #jump to test of outer loop exit1: lw $s0, 0($sp) #restore $s0 from stack lw $s1, 4($sp) #resture $s1 from stack lw $s2, 8($sp) #restore $s2 from stack lw $s3, 12($sp) #restore $s3 from stack lw $ra, 16($sp) #restore $ra from stack addi $sp, $sp, 20 #restore stack pointer jr $ra #return to calling routine .data space:.asciiz " " # space to insert between numbers head: .asciiz "The sorted numbers are:\n" .text print:add $t0, $zero, $a0 # starting address of array add $t1, $zero, $a1 # initialize loop counter to array size la $a0, head # load address of print heading li $v0, 4 # specify Print String service syscall # print heading out: lw $a0, 0($t0) # load fibonacci number for syscall li $v0, 1 # specify Print Integer service syscall # print fibonacci number la $a0, space # load address of spacer for syscall li $v0, 4 # specify Print String service syscall # output string addi $t0, $t0, 4 # increment address addi $t1, $t1, -1 # decrement loop counter bgtz $t1, out # repeat if not finished jr $ra # return

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• PHP, MySQL - My own version of SALT (I call salty) - Login Issue

  - by Fabio Anselmo

  Ok I wrote my own version of SALT I call it salty lol don't make fun of me.. Anyway the registration part of my script as follows is working 100% correctly. //generate SALTY my own version of SALT and I likes me salt.. lol function rand_string( $length ) { $chars = "ABCDEFGHIJKLMNOPQRSTUWXYZabcdefghijklmnopqrstuwxyz1234567890"; $size = strlen( $chars ); for( $i = 0; $i < $length; $i++ ) { $str .= $chars[ rand( 0, $size - 1 ) ]; } return $str; } $salty = rand_string( 256 ); //generate my extra salty pw $password = crypt('password'); $hash = $password . $salty; $newpass = $hash; //insert the data in the database include ('../../scripts/dbconnect.php'); //Update db record with my salty pw ;) // TESTED WITH AND WITHOUT SALTY //HENCE $password and $newpass mysql_query("UPDATE `Register` SET `Password` = '$password' WHERE `emailinput` = '$email'"); mysql_close($connect); However my LOGIN script is failing. I have it setup to TEST and echo if its login or not. It always returns FAILED. I entered the DB and changed the crypted salty pw to "TEST" and I got a SUCCESS. So my problem is somewhere in this LOGIN script I assume. Now I am not sure how to implement my $Salty in this. But also be advised that even without SALTY (just using crypt to store my pass) - I was still unable to perform a login successfully. And if you're gonna suggest i use blowfish - note that my webhost doesn't have it supported and i don't know how to install it. here's my login script: if (isset($_POST['formsubmitted'])) { include ('../../scripts/dbconnect.php'); $username = mysql_real_escape_string($_POST['username']); $password = crypt(mysql_real_escape_string($_POST['password'])); $qry = "SELECT ID FROM Register WHERE emailinput='$username' AND Password='$password'"; $result = mysql_query($qry); if(mysql_num_rows($result) > 0) { echo 'SUCCESS'; //START SESSION } else { echo 'FAILED'; //YOU ARE NOT LOGGED IN } } So what's wrong with this login? Why isn't it working just using the crypt/storing only crypt? How can i make it work storing both the crypt and randomly generated SALTY :) ? Ty advance

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• check if directory exists c#

  - by Ant

  I am trying to see if a directory exists based on an input field from the user. When the user types in the path, I want to check if the path actually exists. I have some c# code already. It returns 1 for any local path, but always returns 0 when I am checking a network path. static string checkValidPath(string path) { //Insert your code that runs under the security context of the authenticating user here. using (ImpersonateUser user = new ImpersonateUser(user, "", password)) { //DirectoryInfo d = new DirectoryInfo(quotelessPath); bool doesExist = Directory.Exists(path); //if (d.Exists) if(doesExist) { user.Dispose(); return "1"; } else { user.Dispose(); return "0"; } } } public class ImpersonateUser : IDisposable { [DllImport("advapi32.dll", SetLastError = true)] private static extern bool LogonUser(string lpszUsername, string lpszDomain, string lpszPassword, int dwLogonType, int dwLogonProvider, out IntPtr phToken); [DllImport("kernel32", SetLastError = true)] private static extern bool CloseHandle(IntPtr hObject); private IntPtr userHandle = IntPtr.Zero; private WindowsImpersonationContext impersonationContext; public ImpersonateUser(string user, string domain, string password) { if (!string.IsNullOrEmpty(user)) { // Call LogonUser to get a token for the user bool loggedOn = LogonUser(user, domain, password, 9 /*(int)LogonType.LOGON32_LOGON_NEW_CREDENTIALS*/, 3 /*(int)LogonProvider.LOGON32_PROVIDER_WINNT50*/, out userHandle); if (!loggedOn) throw new Win32Exception(Marshal.GetLastWin32Error()); // Begin impersonating the user impersonationContext = WindowsIdentity.Impersonate(userHandle); } } public void Dispose() { if (userHandle != IntPtr.Zero) CloseHandle(userHandle); if (impersonationContext != null) impersonationContext.Undo(); } } Any help is appreciated. Thanks! EDIT 3: updated code to use BrokenGlass's impersonation functions. However, I need to initialize "password" to something... EDIT 2: I updated the code to try and use impersonation as suggested below. It still fails everytime. I assume I am using impersonation improperly... EDIT: As requested by ChrisF, here is the function that calls the checkValidPath function. Frontend aspx file... $.get('processor.ashx', { a: '7', path: x }, function(o) { alert(o); if (o=="0") { $("#outputPathDivValid").dialog({ title: 'Output Path is not valid! Please enter a path that exists!', width: 500, modal: true, resizable: false, buttons: { 'Close': function() { $(this).dialog('close'); } } }); } }); Backend ashx file... public void ProcessRequest (HttpContext context) { context.Response.Cache.SetExpires(DateTime.Now); string sSid = context.Request["sid"]; switch (context.Request["a"]) {//a bunch of case statements here... case "7": context.Response.Write(checkValidPath(context.Request["path"].ToString())); break;

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• sql statement "into outfile" not working with jdbc

  - by Celeste Berus

  I am attempting to add an "export to CSV" feature to a webapp that displays data from a MySQL database. I have a written a "queryExecuter" class to execute queries from my servlet. I have used this to successfully execute insert queries so I know the connection works etc however queries with the "into outfile" statement are simply not executing. Here is my code, the java class... import java.sql.Connection; import java.sql.DriverManager; import java.sql.Statement; import java.sql.ResultSet; public class queryExecuter { public void exportToCSV(String query) { DBase db = new DBase(); Connection conn = db.connect( mydatabaseurl ,"myusername","mypassword"); db.exportData(conn,query); } } class DBase { public DBase() { } public Connection connect(String db_connect_str, String db_userid, String db_password) { Connection conn; try { Class.forName("com.mysql.jdbc.Driver").newInstance(); conn = DriverManager.getConnection(db_connect_str, db_userid, db_password); } catch(Exception e) { e.printStackTrace(); conn = null; } return conn; } public void exportData(Connection conn,String query) { Statement stmt; try { stmt = conn.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE, ResultSet.CONCUR_UPDATABLE); stmt.execute(query); } catch(Exception e) { e.printStackTrace(); stmt = null; } } }; The servlet... import java.io.IOException; import java.io.PrintWriter; import java.sql.SQLException; import java.util.logging.Level; import java.util.logging.Logger; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.servlet.*; import javax.servlet.http.*; import java.io.*; public class MyExportServlet extends HttpServlet { public void doPost(HttpServletRequest request, HttpServletResponse response) throws IOException, ServletException { String query = "select into outfile 'theoutfile.txt' * from mytable;"; request.setAttribute("query", query); queryExecuter mydata = new queryExecuter(); mydata.exportToCSV(query); RequestDispatcher view = request.getRequestDispatcher("ConfirmationPage.jsp"); view.forward(request, response); } } Any help would be greatly appreciated. Thank you

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• Magento user created attribute for products is not saved...

  - by Elzo Valugi

  I am fighting an apparently simple thing for about two days now. I hope somebody can help. I created the myUpdate EAV attribute class Company_Module_Model_Resource_Eav_Mysql4_Setup extends Mage_Eav_Model_Entity_Setup { public function getDefaultEntities() { return array( 'catalog_product' => array( 'entity_model' => 'catalog/product', 'attribute_model' => 'catalog/resource_eav_attribute', 'table' => 'catalog/product', 'additional_attribute_table' => 'catalog/eav_attribute', 'entity_attribute_collection' => 'catalog/product_attribute_collection', 'attributes' => array( 'my_update' => array( 'label' => 'My timestamp', 'type' => 'datetime', 'input' => 'date', 'default' => '', 'class' => 'validate-date', 'backend' => 'eav/entity_attribute_backend_datetime', 'frontend' => '', 'table' => '', 'source' => '', 'global' => Mage_Catalog_Model_Resource_Eav_Attribute::SCOPE_GLOBAL, 'visible' => true, 'required' => false, 'user_defined' => true, 'searchable' => false, 'filterable' => false, 'comparable' => false, 'visible_on_front' => false, 'visible_in_advanced_search' => false, 'unique' => false, 'apply_to' => 'simple', ) ) ) ); } } The attribute is created OK and on install appears correctly in the list of attributes. Later I do // for product 1 $product->setMyUpdate($stringDate); // string this format: yyyy-MM-dd HH:mm:ss $product->save(); // and saves without issues * in admin module But later when I do: $product = Mage::getModel('catalog/product')->load(1); var_dump($product->getMyUpdate()); // returns null Somehow the data is not really saved.. or I am not retrieving it correctly. Please advice on how to get the data and where the data is saved in the DB so I can check at if the insert is done correctly. Thanks.

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• Uploading files to varbinary(max) in SQL Server -- works on one server, not the other

  - by pjabbott

  I have some code that allows users to upload file attachments into a varbinary(max) column in SQL Server from their web browser. It has been working perfectly fine for almost two years, but all of a sudden it stopped working. And it stopped working on only the production database server -- it still works fine on the development server. I can only conclude that the code is fine and there is something up with the instance of SQL Server itself. But I have no idea how to isolate the problem. I insert a record into the ATTACHMENT table, only inserting non-binary data like the title and the content type, and then chunk-upload the uploaded file using the following code: // get the file stream System.IO.Stream fileStream = postedFile.InputStream; // make an upload buffer byte[] fileBuffer; fileBuffer = new byte[1024]; // make an update command SqlCommand fileUpdateCommand = new SqlCommand("update ATTACHMENT set ATTACHMENT_DATA.WRITE(@Data, NULL, NULL) where ATTACHMENT_ID = @ATTACHMENT_ID", sqlConnection, sqlTransaction); fileUpdateCommand.Parameters.Add("@Data", SqlDbType.Binary); fileUpdateCommand.Parameters.AddWithValue("@ATTACHMENT_ID", newId); while (fileStream.Read(fileBuffer, 0, fileBuffer.Length) > 0) { fileUpdateCommand.Parameters["@Data"].Value = fileBuffer; fileUpdateCommand.ExecuteNonQuery(); <------ FAILS HERE } fileUpdateCommand.Dispose(); fileStream.Close(); Where it says "FAILS HERE", it sits for a while and then I get a SQL Server timeout error on the very first iteration through the loop. If I connect to the development database instead, everything works fine (it runs through the loop many, many times and the commit is successful). Both servers are identical (SQL Server 9.0.3042) and the schemas are identical as well. When I open Activity Monitor right after the timeout to see what's going it, it says the last command is (@Data binary(1024),@ATTACHMENT_ID decimal(4,0))update ATTACHMENT set ATTACHMENT_DATA.WRITE(@Data, NULL, NULL) where ATTACHMENT_ID = @ATTACHMENT_ID which I would expect but it also says it has a status of "Suspended" and a wait type of "PAGEIOLATCH_SH". I looked this up and it seems to be a bad thing but I can't find anything specific to my stuation. Ideas?

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• How to overwrite an array of char pointers with a larger list of char pointers?

  - by Casey

  My function is being passed a struct containing, among other things, a NULL terminated array of pointers to words making up a command with arguments. I'm performing a glob match on the list of arguments, to expand them into a full list of files, then I want to replace the passed argument array with the new expanded one. The globbing is working fine, that is, g.gl_pathv is populated with the list of expected files. However, I am having trouble copying this array into the struct I was given. #include <glob.h> struct command { char **argv; // other fields... } void myFunction( struct command * cmd ) { char **p = cmd->argv; char* program = *p++; // save the program name (e.g 'ls', and increment to the first argument glob_t g; memset(&g, 0, sizeof(g)); g.gl_offs = 1; int res = glob(*p++, GLOB_DOOFFS, NULL, &g); glob_handle_res(res); while (*p) { res = glob(*p, GLOB_DOOFFS | GLOB_APPEND, NULL, &g); glob_handle_res(res); } if( g.gl_pathc <= 0 ) { globfree(&g); } cmd->argv = malloc((g.gl_pathc + g.gl_offs) * sizeof *cmd->argv); if (cmd->argv == NULL) { sys_fatal_error("pattern_expand: malloc failed\n");} // copy over the arguments size_t i = g.gl_offs; for (; i < g.gl_pathc + g.gl_offs; ++i) cmd->argv[i] = strdup(g.gl_pathv[i]); // insert the original program name cmd->argv[0] = strdup(program); ** cmd->argv[g.gl_pathc + g.gl_offs] = 0; ** globfree(&g); } void command_free(struct esh_command * cmd) { char ** p = cmd->argv; while (*p) { free(*p++); // Segfaults here, was it already freed? } free(cmd->argv); free(cmd); } Edit 1: Also, I realized I need to stick program back in there as cmd-argv[0] Edit 2: Added call to calloc Edit 3: Edit mem management with tips from Alok Edit 4: More tips from alok Edit 5: Almost working.. the app segfaults when freeing the command struct Finally: Seems like I was missing the terminating NULL, so adding the line: cmd->argv[g.gl_pathc + g.gl_offs] = 0; seemed to make it work.

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• How to efficently build an interpreter (lexer+parser) in C?

  - by Rizo

  I'm trying to make a meta-language for writing markup code (such as xml and html) wich can be directly embedded into C/C++ code. Here is a simple sample written in this language, I call it WDI (Web Development Interface): /* * Simple wdi/html sample source code */ #include <mySite> string name = "myName"; string toCapital(string str); html { head { title { mySiteTitle; } link(rel="stylesheet", href="style.css"); } body(id="default") { // Page content wrapper div(id="wrapper", class="some_class") { h1 { "Hello, " + toCapital(name) + "!"; } // Lists post ul(id="post_list") { for(post in posts) { li { a(href=post.getID()) { post.tilte; } } } } } } } Basically it is a C source with a user-friendly interface for html. As you can see the traditional tag-based style is substituted by C-like, with blocks delimited by curly braces. I need to build an interpreter to translate this code to html and posteriorly insert it into C, so that it can be compiled. The C part stays intact. Inside the wdi source it is not necessary to use prints, every return statement will be used for output (in printf function). The program's output will be clean html code. So, for example a heading 1 tag would be transformed like this: h1 { "Hello, " + toCapital(name) + "!"; } // would become: printf("<h1>Hello, %s!</h1>", toCapital(name)); My main goal is to create an interpreter to translate wdi source to html like this: tag(attributes) {content} = <tag attributes>content</tag> Secondly, html code returned by the interpreter has to be inserted into C code with printfs. Variables and functions that occur inside wdi should also be sorted in order to use them as printf parameters (the case of toCapital(name) in sample source). I am searching for efficient (I want to create a fast parser) way to create a lexer and parser for wdi. Already tried flex and bison, but as I am not sure if they are the best tools. Are there any good alternatives? What is the best way to create such an interpreter? Can you advise some brief literature on this issue?

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• Problem passing variables in php form.

  - by Joshxtothe4

  I have the following php form. I am trying to make it so that when the form is loaded, the values will be assigned the appropriate check- variable. This variable will contain either "checked or "". If it contains checked, the way it is displayed with the html should cause the relevant checkbox to be checked. As it is, the variables do not seem to be being passed. When I echo out $deleted or $notice from within the submitinfo branch, they are blank. Furthermore, nothing is being inserted into the database, and I am not getting any database error. How can I check this? <?php if (isset($_GET["cmd"])) $cmd = $_GET["cmd"]; else if (isset($_POST["cmd"])) $cmd = $_POST["cmd"]; else die("Invalid URL"); if (isset($_GET["pk"])) { $pk = $_GET["pk"]; } if (isset($_POST["deleted"])) { $deleted = $_POST["deleted"]; } if (isset($_POST["notice"])) { $notice = $_POST["notice"]; } $con = mysqli_connect("localhost","user","password", "db"); if (!$con) { echo "Can't connect to MySQL Server. Errorcode: %s\n". mysqli_connect_error(); exit; } $con->set_charset("utf8"); $getformdata = $con->query("select * from STATUS where ARTICLE_NO = '$pk'"); $checkDeleted = ""; $checkNotice = ""; while ($row = mysqli_fetch_assoc($getformdata)) { $checkDeleted = $row['deleted']; $checkNotice = $row['notice']; } if($cmd=="submitinfo") { $statusQuery = "INSERT INTO STATUS VALUES (?, ?)"; if ($statusInfo = $con->prepare($statusQuery)) { $statusInfo->bind_param("ss", $deleted, $notice); $statusInfo->execute(); $statusInfo->close(); echo "true"; } else { echo "false"; } print_r($con->error); } if($cmd=="EditStatusData") { echo "<form name=\"statusForm\" action=\"test.php\" method=\"post\" enctype=\"multipart/form-data\"> <h1>Editing information for auction: ".$pk."</h1> Löschung Ebay: <input type=\"checkbox\" name=\"deleted\" value=\"checked\" ".$checkDeleted." /> <br /> Abmahnung: <input type=\"checkbox\" name=\"notice\" value=\"checked\" ".$checkNotice." /> <br /> <input type=\"hidden\" name=\"cmd\" value=\"submitinfo\" /> <input name=\"Submit\" type=\"submit\" value=\"submit\" /> </form>"; } else { print_r($con->error); }

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• Using Core Data Concurrently and Reliably

  - by John Topley

  I'm building my first iOS app, which in theory should be pretty straightforward but I'm having difficulty making it sufficiently bulletproof for me to feel confident submitting it to the App Store. Briefly, the main screen has a table view, upon selecting a row it segues to another table view that displays information relevant for the selected row in a master-detail fashion. The underlying data is retrieved as JSON data from a web service once a day and then cached in a Core Data store. The data previous to that day is deleted to stop the SQLite database file from growing indefinitely. All data persistence operations are performed using Core Data, with an NSFetchedResultsController underpinning the detail table view. The problem I am seeing is that if you switch quickly between the master and detail screens several times whilst fresh data is being retrieved, parsed and saved, the app freezes or crashes completely. There seems to be some sort of race condition, maybe due to Core Data importing data in the background whilst the main thread is trying to perform a fetch, but I'm speculating. I've had trouble capturing any meaningful crash information, usually it's a SIGSEGV deep in the Core Data stack. The table below shows the actual order of events that happen when the detail table view controller is loaded: Main Thread Background Thread viewDidLoad Get JSON data (using AFNetworking) Create child NSManagedObjectContext (MOC) Parse JSON data Insert managed objects in child MOC Save child MOC Post import completion notification Receive import completion notification Save parent MOC Perform fetch and reload table view Delete old managed objects in child MOC Save child MOC Post deletion completion notification Receive deletion completion notification Save parent MOC Once the AFNetworking completion block is triggered when the JSON data has arrived, a nested NSManagedObjectContext is created and passed to an "importer" object that parses the JSON data and saves the objects to the Core Data store. The importer executes using the new performBlock method introduced in iOS 5: NSManagedObjectContext *child = [[NSManagedObjectContext alloc] initWithConcurrencyType:NSPrivateQueueConcurrencyType]; [child setParentContext:self.managedObjectContext]; [child performBlock:^{ // Create importer instance, passing it the child MOC... }]; The importer object observes its own MOC's NSManagedObjectContextDidSaveNotification and then posts its own notification which is observed by the detail table view controller. When this notification is posted the table view controller performs a save on its own (parent) MOC. I use the same basic pattern with a "deleter" object for deleting the old data after the new data for the day has been imported. This occurs asynchronously after the new data has been fetched by the fetched results controller and the detail table view has been reloaded. One thing I am not doing is observing any merge notifications or locking any of the managed object contexts or the persistent store coordinator. Is this something I should be doing? I'm a bit unsure how to architect this all correctly so would appreciate any advice.

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