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• Naming convention when casually referring to methods in Java

  - by polygenelubricants

  Is there a Java convention to refer to methods, static and otherwise, any specific one or the whole overload, etc? e.g. String.valueOf - referring to all overloads of static valueOf String.valueOf(char) - specific overload, formal parameter name omittable? String.split - looks like a static method, but actually an instance method Maybe aString.split is the convention? String#split - I've seen this HTML anchor form too, which I guess is javadoc-influenced Is there an authoritative recommendation on how to clearly refer to these things?

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• Font not showing bullet points

  - by Hanpan

  I have embedded my font using the embed meta tag, along which the entire range of Unicode characters... here is my CustomTextField class: [Embed(source='../assets/fonts/Arial.ttf',fontName='CustomFont',fontWeight='regular', unicodeRange='U+0020-U+0040,U+0041-U+005A,U+005B-U+0060,U+0061-U+007A,U+007B-U+007E,U+0080-U+00FF,U+0100-U+017F,U+0400-U+04FF,U+0370-U+03FF,U+1E00-U+1EFF', mimeType='application/x-font-truetype' )] public static var MY_FONT:Class; [Embed(source='../assets/fonts/Arial Bold.ttf',fontName='CustomFont',fontWeight='bold', unicodeRange='U+0020-U+0040,U+0041-U+005A,U+005B-U+0060,U+0061-U+007A,U+007B-U+007E,U+0080-U+00FF,U+0100-U+017F,U+0400-U+04FF,U+0370-U+03FF,U+1E00-U+1EFF', mimeType='application/x-font-truetype' )] public static var MY_FONT_BOLD:Class; public static const DEFAULT_FONT:String = "CustomFont"; public static const DEFAULT_TEXT_COLOUR:int = 0x000000; public static const DEFAULT_TEXT_SIZE:int = 14; private var _tf:TextFormat = new TextFormat(DEFAULT_FONT, DEFAULT_TEXT_SIZE, DEFAULT_TEXT_COLOUR); public function CustomTextField():void { Font.registerFont(CustomTextField.MY_FONT); Font.registerFont(CustomTextField.MY_FONT_BOLD); _tf.size = 16; antiAliasType = AntiAliasType.ADVANCED; sharpness = 0; defaultTextFormat = _tf; autoSize = TextFieldAutoSize.LEFT; embedFonts = true; } public override function set htmlText(value:String):void { super.htmlText = value; setTextFormat(_tf); } For some reason, using tags intends the text perfectly, but I am not seeing any bullet points. The font is just standard Arial, so it isn't a case of the font missing the bullet character. Does anyone have any idea as to why Flex is not showing the bullet point characters?

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• Why won't my program terminate?

  - by Qwertie

  I have a .NET Compact Framework app that can runs on three windows machines (Desktop windows and two WinCE machines) and on the WinCE devices, the process never terminates on exit, even if I call Application.Exit(). Besides .NET, it uses one COM component (which does everything on the UI thread). If I break into the debugger after exitting, Visual Studio shows only one thread and a completely blank call stack. What could possibly cause this? Update: My process is terminating on the desktop but not the WinCE machines. I tried to force the process to terminate with the following code, but it doesn't work: [DllImport("coredll.dll")] static extern int TerminateProcess(IntPtr hProcess, uint uExitCode); static public void ExitProcess() { if (Platform.IsWindowsCE) TerminateProcess(new IntPtr(-1), 0); Application.Exit(); } There are also supposed to be ExitProcess() and GetCurrentProcess() APIs like the following, but if I try to call them, I get EntryPointNotFoundException. Therefore I am using TerminateProcess(-1, 0) because the documentation for the desktop version of GetCurrentProcess claims that it simply returns -1. [DllImport("coredll.dll")] static extern int ExitProcess(IntPtr hProcess); [DllImport("coredll.dll")] static extern IntPtr GetCurrentProcess(); Even if I do this: static public void ExitProcess() { if (Platform.IsWindowsCE) TerminateProcess(new IntPtr(-1), 0); Application.Exit(); throw new Exception("Trying to force quit."); } A fatal error dialog appears with a helpful "Quit" button, but pushing the button still does not cause the process to terminate on either machine!

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• What would you like to correct and/or improve in this java implementation of Chain Of Responsibility

  - by Maciek Kreft

  package design.pattern.behavioral; import design.pattern.behavioral.ChainOfResponsibility.*; public class ChainOfResponsibility { public static class Chain { private Request[] requests = null; private Handler[] handlers = null; public Chain(Handler[] handlers, Request[] requests){ this.handlers = handlers; this.requests = requests; } public void start() { for(Request r : requests) for (Handler h : handlers) if(h.handle(r)) break; } } public static class Request { private int value; public Request setValue(int value){ this.value = value; return this; } public int getValue() { return value; } } public static class Handler<T1> { private Lambda<T1> lambda = null; private Lambda<T1> command = null; public Handler(Lambda<T1> condition, Lambda<T1> command) { this.lambda = condition; this.command = command; } public boolean handle(T1 request) { if (lambda.lambda(request)) command.lambda(request); return lambda.lambda(request); } } public static abstract class Lambda<T1>{ public abstract Boolean lambda(T1 request); } } class TestChainOfResponsibility { public static void main(String[] args) { new TestChainOfResponsibility().test(); } private void test() { new Chain(new Handler[]{ // chain of responsibility new Handler<Request>( new Lambda<Request>(){ // command public Boolean lambda(Request condition) { return condition.getValue() >= 600; } }, new Lambda<Request>(){ public Boolean lambda(Request command) { System.out.println("You are rich: " + command.getValue() + " (id: " + command.hashCode() + ")"); return true; } } ), new Handler<Request>( new Lambda<Request>(){ public Boolean lambda(Request condition) { return condition.getValue() >= 100; } }, new Lambda<Request>(){ public Boolean lambda(Request command) { System.out.println("You are poor: " + command.getValue() + " (id: " + command.hashCode() + ")"); return true; } } ), }, new Request[]{ new Request().setValue(600), // chaining method new Request().setValue(100), } ).start(); } }

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• Problems with generation of dynamic code

  - by user308344

  This code gif an exception: Invocation exception, please help, I don't know what happen, I think is some thing with the Add because he work when I push onto the stack intergers, and when i push lvalue It's didn't work, thanks static void Main(string[] args) { AppDomain dominioAplicacion = System.Threading.Thread.GetDomain(); AssemblyName nombre_Del_Ensamblado = new AssemblyName("ASS"); AssemblyBuilder ensambladoBld = dominioAplicacion.DefineDynamicAssembly(nombre_Del_Ensamblado, AssemblyBuilderAccess.RunAndSave); ModuleBuilder moduloBld = ensambladoBld.DefineDynamicModule("<MOD"); TypeBuilder claseContenedoraBld = moduloBld.DefineType("claseContenedora"); MethodBuilder mainBld = claseContenedoraBld.DefineMethod("main", MethodAttributes.Public | MethodAttributes.Static, typeof(void), Type.EmptyTypes); ILGenerator il = mainBld.GetILGenerator(); FieldBuilder campoBld = claseContenedoraBld.DefineField("x", typeof(int), FieldAttributes.Public | FieldAttributes.Static); il.Emit(OpCodes.Ldc_I4, 2); il.Emit(OpCodes.Stsfld, campoBld); FieldBuilder campoBld1 = claseContenedoraBld.DefineField("x1", typeof(int), FieldAttributes.Public | FieldAttributes.Static); il.Emit(OpCodes.Ldc_I4, 2); il.Emit(OpCodes.Stsfld, campoBld1); il.Emit(OpCodes.Ldftn, campoBld); //il.Emit(OpCodes.Unbox, typeof(int)); //il.Emit(OpCodes.Stloc_0); il.Emit(OpCodes.Ldloc_0); il.Emit(OpCodes.Ldftn, campoBld1); //il.Emit(OpCodes.Unbox, typeof(int)); il.Emit(OpCodes.Stloc_1); il.Emit(OpCodes.Ldloc_1); //il.Emit(OpCodes.Box, typeof(int)); //il.Emit(OpCodes.Ldftn, campoBld1); //il.Emit(OpCodes.Unbox, typeof(int)); il.Emit(OpCodes.Add); il.Emit(OpCodes.Pop); //il.Emit(OpCodes.Stsfld, campoBld1); il.Emit(OpCodes.Ret); Type t = claseContenedoraBld.CreateType(); object ptInstance = Activator.CreateInstance(t, new Type[] { }); t.InvokeMember("main", BindingFlags.InvokeMethod | BindingFlags.Static | BindingFlags.Public, null, ptInstance, new object[0]); var x = t.GetField("x"); }

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• Java - Interfaces

  - by Paul

  Why interfaces cannot be declared as static ?

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• problem parsing with XMLReader (using ReadSubTree)

  - by no9

  Hello. Im trying to build a simple XML to Controls parser in my CF application. In the code below the string im trying to parse looks like this: "<Panel><Label>Text1</Label><Label>Text2</Label></Panel>" The result i want with this code would be a Panel with two labels. But the problem is when the first Label is parsed the subreader.Read() returns false in the ParsePanelElementh method, and so it falls out of while statement. Since im new into XMLReader i must be missing something very simple. Any help would be apreciated ! peace. static class XMLParser { public static Control Parse(string aXmlString) { XmlReader reader = XmlReader.Create(new StringReader(aXmlString)); return ParseXML(reader); } public static Control ParseXML(XmlReader reader) { using (reader) { while (reader.Read()) { if (reader.NodeType == XmlNodeType.Element) { if (reader.LocalName == "Panel") { return ParsePanelElement(reader); } if (reader.LocalName == "Label") { return ParseLabelElement(reader); } } } } return null; } private static Control ParsePanelElement(XmlReader reader) { var myPanel = new Panel(); XmlReader subReader = reader.ReadSubtree(); while (subReader.Read()) { Control subControl = ParseXML(subReader); if (subControl != null) { myPanel.Controls.Add(subControl); }; } return myPanel; } private static Control ParseLabelElement(XmlReader reader) { reader.Read(); var myString = reader.Value as string; var myLabel = new Label(); myLabel.Text = myString; return myLabel; } }

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• How do i refactor this code by using Action<t> or Func<t> delegates

  - by user330612

  I have a sample program, which needs to execute 3 methods in a particular order. And after executing each method, should do error handling. Now i did this in a normal fashion, w/o using delegates like this. class Program { public static void Main() { MyTest(); } private static bool MyTest() { bool result = true; int m = 2; int temp = 0; try { temp = Function1(m); } catch (Exception e) { Console.WriteLine("Caught exception for function1" + e.Message); result = false; } try { Function2(temp); } catch (Exception e) { Console.WriteLine("Caught exception for function2" + e.Message); result = false; } try { Function3(temp); } catch (Exception e) { Console.WriteLine("Caught exception for function3" + e.Message); result = false; } return result; } public static int Function1(int x) { Console.WriteLine("Sum is calculated"); return x + x; } public static int Function2(int x) { Console.WriteLine("Difference is calculated "); return (x - x); } public static int Function3(int x) { return x * x; } } As you can see, this code looks ugly w/ so many try catch loops, which are all doing the same thing...so i decided that i can use delegates to refactor this code so that Try Catch can be all shoved into one method so that it looks neat. I was looking at some examples online and couldnt figure our if i shud use Action or Func delegates for this. Both look similar but im unable to get a clear idea how to implement this. Any help is gr8ly appreciated. I'm using .NET 4.0, so im allowed to use anonymous methods n lambda expressions also for this Thanks

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• Flex special characters not embedding

  - by Hanpan

  Hi, I am using the following code to embed Arial into my application: [Embed(source='../assets/fonts/Arial.ttf',fontFamily='CustomFont',fontWeight='regular', unicodeRange='U+0020-U+0040,U+0041-U+005A,U+005B-U+0060,U+0061-U+007A,U+007B-U+007E,U+0080-U+00FF,U+0100-U+017F,U+0400-U+04FF,U+0370-U+03FF,U+1E00-U+1EFF,U+2022,U+2219,U+20AC-U+21AC', mimeType='application/x-font-truetype' )] public static var MY_FONT:Class; [Embed(source='../assets/fonts/Arial Bold.ttf',fontFamily='CustomFont',fontWeight='bold', unicodeRange='U+0020-U+0040,U+0041-U+005A,U+005B-U+0060,U+0061-U+007A,U+007B-U+007E,U+0080-U+00FF,U+0100-U+017F,U+0400-U+04FF,U+0370-U+03FF,U+1E00-U+1EFF,U+2022,U+2219,U+20AC-U+21AC', mimeType='application/x-font-truetype' )] public static var MY_FONT_BOLD:Class; [Embed(source='../assets/fonts/Arial Italic.ttf',fontFamily='CustomFont',fontWeight='regular',fontStyle="italic", unicodeRange='U+0020-U+0040,U+0041-U+005A,U+005B-U+0060,U+0061-U+007A,U+007B-U+007E,U+0080-U+00FF,U+0100-U+017F,U+0400-U+04FF,U+0370-U+03FF,U+1E00-U+1EFF,U+2022,U+2219,U+20AC-U+21AC', mimeType='application/x-font-truetype' )] public static var MY_FONT_ITALIC:Class; [Embed(source='../assets/fonts/Arial Bold Italic.ttf',fontFamily='CustomFont',fontWeight='bold',fontStyle="italic", unicodeRange='U+0020-U+0040,U+0041-U+005A,U+005B-U+0060,U+0061-U+007A,U+007B-U+007E,U+0080-U+00FF,U+0100-U+017F,U+0400-U+04FF,U+0370-U+03FF,U+1E00-U+1EFF,U+2022,U+2219,U+20AC-U+21AC', mimeType='application/x-font-truetype' )] public static var MY_FONT_ITALIC_BOLD:Class; [Embed(source='../assets/fonts/Arial Unicode.ttf',fontFamily='CustomFont',fontWeight='regular', unicodeRange='U+0020-U+0040,U+0041-U+005A,U+005B-U+0060,U+0061-U+007A,U+007B-U+007E,U+0080-U+00FF,U+0100-U+017F,U+0400-U+04FF,U+0370-U+03FF,U+1E00-U+1EFF,U+2022,U+2219,U+20AC-U+21AC', mimeType='application/x-font-truetype' )] public static var MY_FONT_UNICODE:Class; It's working fine for foreign characters, but no special characters (copyright, trademark, euro sign etc) are working. Can anyone help? I've checked my unicode ranges, they should work fine!

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• How do I correctly use Unity to pass a ConnectionString to my repository classes?

  - by GenericTypeTea

  I've literally just started using the Unity Application Blocks Dependency Injection library from Microsoft, and I've come unstuck. This is my IoC class that'll handle the instantiation of my concrete classes to their interface types (so I don't have to keep called Resolve on the IoC container each time I want a repository in my controller): public class IoC { public static void Intialise(UnityConfigurationSection section, string connectionString) { _connectionString = connectionString; _container = new UnityContainer(); section.Configure(_container); } private static IUnityContainer _container; private static string _connectionString; public static IMovementRepository MovementRepository { get { return _container.Resolve<IMovementRepository>(); } } } So, the idea is that from my Controller, I can just do the following: _repository = IoC.MovementRepository; I am currently getting the error: Exception is: InvalidOperationException - The type String cannot be constructed. You must configure the container to supply this value. Now, I'm assuming this is because my mapped concrete implementation requires a single string parameter for its constructor. The concrete class is as follows: public sealed class MovementRepository : Repository, IMovementRepository { public MovementRepository(string connectionString) : base(connectionString) { } } Which inherits from: public abstract class Repository { public Repository(string connectionString) { _connectionString = connectionString; } public virtual string ConnectionString { get { return _connectionString; } } private readonly string _connectionString; } Now, am I doing this the correct way? Should I not have a constructor in my concrete implementation of a loosely coupled type? I.e. should I remove the constructor and just make the ConnectionString property a Get/Set so I can do the following: public static IMovementRepository MovementRepository { get { return _container.Resolve<IMovementRepository>( new ParameterOverrides { { "ConnectionString", _connectionString } }.OnType<IMovementRepository>() ); } } So, I basically wish to know how to get my connection string to my concrete type in the correct way that matches the IoC rules and keeps my Controller and concrete repositories loosely coupled so I can easily change the DataSource at a later date.

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• Help with storing/accessing user access roles C# Winforms

  - by user222453

  Hello, firstly I would like to thank you in advance for any assistance provided. I am new to software development and have designed several Client/Server applications over the last 12 months or so, I am currently working on a project that involves a user logging in to gain access to the application and I am looking at the most efficient and "simple" method of storing the users permissions once logged in to the application which can be used throughout restricting access to certain tabs on the main form. I have created a static class called "User" detailed below: static class User { public static int _userID; public static string _moduleName; public static string _userName; public static object[] UserData(object[] _dataRow) { _userID = (int)_dataRow[0]; _userName = (string)_dataRow[1]; _moduleName = (string)_dataRow[2]; return _moduleName; } } When the user logs in and they have been authenticated, I wish to store the _moduleName objects in memory so I can control which tabs on the main form tab control they can access, for example; if the user has been assigned the following roles in the database: "Sales Ledger", "Purchase Ledger" they can only see the relevant tabs on the form, by way of using a Switch - Case block once the login form is hidden and the main form is instantiated. I can store the userID and userName variables in the main form once it loads by means of say for example: Here we process the login data from the user: DataAccess _dal = new DataAccess(); switch (_dal.ValidateLogin(txtUserName.Text, txtPassword.Text)) { case DataAccess.ValidationCode.ConnectionFailed: MessageBox.Show("Database Server Connection Failed!"); break; case DataAccess.ValidationCode .LoginFailed: MessageBox.Show("Login Failed!"); _dal.RecordLogin(out errMsg, txtUserName.Text, workstationID, false); break; case DataAccess.ValidationCode .LoginSucceeded: frmMain frmMain = new frmMain(); _dal.GetUserPrivList(out errMsg,2); //< here I access my DB and get the user permissions based on the current login. frmMain.Show(); this.Hide(); break; default: break; } private void frmMain_Load(object sender, EventArgs e) { int UserID = User._userID; } That works fine, however the _modules object contains mutiple permissions/roles depending on what has been set in the database, how can I store the multiple values and access them via a Switch-Case block? Thank you again in advance.

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• Data won't save to SQL database, getting error "close() was never explicitly called on database"

  - by SnowLeppard

  I have a save button in the activity where the user enters data which does this: String subjectName = etName.getText().toString(); String subjectColour = etColour.getText().toString(); SQLDatabase entrySubject = new SQLDatabase(AddSubject.this); entrySubject.open(); entrySubject.createSubjectEntry(subjectName, subjectColour); entrySubject.close(); Which refers to this SQL database class: package com.***.schooltimetable; import android.content.ContentValues; import android.content.Context; import android.database.Cursor; import android.database.SQLException; import android.database.sqlite.SQLiteDatabase; import android.database.sqlite.SQLiteOpenHelper; public class SQLDatabase { public static final String KEY_SUBJECTS_ROWID = "_id"; public static final String KEY_SUBJECTNAME = "name"; public static final String KEY_COLOUR = "colour"; private static final String DATABASE_NAME = "Database"; private static final String DATABASE_TABLE_SUBJECTS = "tSubjects"; private static final int DATABASE_VERSION = 1; private DbHelper ourHelper; private final Context ourContext; private SQLiteDatabase ourDatabase; private static class DbHelper extends SQLiteOpenHelper { public DbHelper(Context context) { super(context, DATABASE_NAME, null, DATABASE_VERSION); // TODO Auto-generated constructor stub } @Override public void onCreate(SQLiteDatabase db) { // TODO Auto-generated method stub db.execSQL("CREATE TABLE " + DATABASE_TABLE_SUBJECTS + " (" + KEY_SUBJECTS_ROWID + " INTEGER PRIMARY KEY AUTOINCREMENT, " + KEY_SUBJECTNAME + " TEXT NOT NULL, " + KEY_COLOUR + " TEXT NOT NULL);"); } @Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { // TODO Auto-generated method stub db.execSQL("DROP TABLE IF EXISTS " + DATABASE_TABLE_SUBJECTS); onCreate(db); } } public SQLDatabase(Context c) { ourContext = c; } public SQLDatabase open() throws SQLException { ourHelper = new DbHelper(ourContext); ourDatabase = ourHelper.getWritableDatabase(); return this; } public void close() { ourHelper.close(); } public long createSubjectEntry(String subjectName, String subjectColour) { // TODO Auto-generated method stub ContentValues cv = new ContentValues(); cv.put(KEY_SUBJECTNAME, subjectName); cv.put(KEY_COLOUR, subjectColour); return ourDatabase.insert(DATABASE_TABLE_SUBJECTS, null, cv); } public String[][] getSubjects() { // TODO Auto-generated method stub String[] Columns = new String[] { KEY_SUBJECTNAME, KEY_COLOUR }; Cursor c = ourDatabase.query(DATABASE_TABLE_SUBJECTS, Columns, null, null, null, null, null); String[][] Result = new String[1][]; // int iRow = c.getColumnIndex(KEY_LESSONS_ROWID); int iName = c.getColumnIndex(KEY_SUBJECTNAME); int iColour = c.getColumnIndex(KEY_COLOUR); for (c.moveToFirst(); !c.isAfterLast(); c.moveToNext()) { Result[0][c.getPosition()] = c.getString(iName); Result[1][c.getPosition()] = c.getString(iColour); Settings.subjectCount = c.getPosition(); TimetableEntry.subjectCount = c.getPosition(); } return Result; } This class has other variables and other variations of the same methods for multiple tables in the database, i've cut out the irrelevant ones. I'm not sure what I need to close and where, I've got the entrySubject.close() in my activity. I used the methods for the database from the NewBoston tutorials. Can anyone see what I've done wrong, or where my problem is? Thanks.

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• Exception: "Given final block not properly padded" in Linux, but it works in Windows

  - by user1685364

  My application works in windows, but fails in Linux with Given final block not properly padded exception. Configuration: JDK Version: 1.6 Windows : version 7 Linux : CentOS 5.8 64bit My code is below: import java.io.IOException; import java.io.UnsupportedEncodingException; import java.security.InvalidKeyException; import java.security.Key; import java.security.NoSuchAlgorithmException; import java.security.SecureRandom; import javax.crypto.BadPaddingException; import javax.crypto.Cipher; import javax.crypto.IllegalBlockSizeException; import javax.crypto.KeyGenerator; import javax.crypto.NoSuchPaddingException; import sun.misc.BASE64Decoder; import sun.misc.BASE64Encoder; public class SecurityKey { private static Key key = null; private static String encode = "UTF-8"; private static String cipherKey = "DES/ECB/PKCS5Padding"; static { try { KeyGenerator generator = KeyGenerator.getInstance("DES"); String seedStr = "test"; generator.init(new SecureRandom(seedStr.getBytes())); key = generator.generateKey(); } catch(Exception e) { } } // SecurityKey.decodeKey("password") public static String decodeKey(String str) throws Exception { if(str == null) return str; Cipher cipher = null; byte[] raw = null; BASE64Decoder decoder = new BASE64Decoder(); String result = null; cipher = Cipher.getInstance(cipherKey); cipher.init(Cipher.DECRYPT_MODE, key); raw = decoder.decodeBuffer(str); byte[] stringBytes = null; stringBytes = cipher.doFinal(raw); // Exception!!!! result = new String(stringBytes, encode); return result; } } At the line: ciper.doFilnal(raw); the following exception is thrown: javax.crypto.BadPaddingException: Given final block not properly padded How can I fix this issue?

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• C# Delegate under the hood question.

  - by Ted

  Hi Guys I was doing some digging around into delegate variance after reading the following tquestion in SO. "delegate-createdelegate-and-generics-error-binding-to-target-method" (sorry not allowed to post more than one hyperlink as a newbie here!) I found a very nice bit of code from Barry kelly at https://www.blogger.com/comment.g?blogID=8184237816669520763&postID=2109708553230166434 Here it is (in a sugared-up form :-) using System; namespace ConsoleApplication4 { internal class Base { } internal class Derived : Base { } internal delegate void baseClassDelegate(Base b); internal delegate void derivedClassDelegate(Derived d); internal class App { private static void Foo1(Base b) { Console.WriteLine("Foo 1"); } private static void Foo2(Derived b) { Console.WriteLine("Foo 2"); } private static T CastDelegate<T>(Delegate src) where T : class { return (T) (object) Delegate.CreateDelegate( typeof (T), src.Target, src.Method, true); // throw on fail } private static void Main() { baseClassDelegate a = Foo1; // works fine derivedClassDelegate b = Foo2; // works fine b = a.Invoke; // the easy way to assign delegate using variance, adds layer of indirection though b(new Derived()); b = CastDelegate<derivedClassDelegate>(a); // the hard way, avoids indirection b(new Derived()); } } } I understand all of it except this one (what looks very simple) line. b = a.Invoke; // the easy way to assign delegate using variance, adds layer of indirection though Can anyone tell me: how it is possible to call invoke without passing the param required by the static function. When is going on under the hood when you assign the return value from calling invoke What does Barry mean by extra indirection (in his comment)

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• Traditional IO vs memory-mapped

  - by Senne

  I'm trying to illustrate the difference in performance between traditional IO and memory mapped files in java to students. I found an example somewhere on internet but not everything is clear to me, I don't even think all steps are nececery. I read a lot about it here and there but I'm not convinced about a correct implementation of neither of them. The code I try to understand is: public class FileCopy{ public static void main(String args[]){ if (args.length < 1){ System.out.println(" Wrong usage!"); System.out.println(" Correct usage is : java FileCopy <large file with full path>"); System.exit(0); } String inFileName = args[0]; File inFile = new File(inFileName); if (inFile.exists() != true){ System.out.println(inFileName + " does not exist!"); System.exit(0); } try{ new FileCopy().memoryMappedCopy(inFileName, inFileName+".new" ); new FileCopy().customBufferedCopy(inFileName, inFileName+".new1"); }catch(FileNotFoundException fne){ fne.printStackTrace(); }catch(IOException ioe){ ioe.printStackTrace(); }catch (Exception e){ e.printStackTrace(); } } public void memoryMappedCopy(String fromFile, String toFile ) throws Exception{ long timeIn = new Date().getTime(); // read input file RandomAccessFile rafIn = new RandomAccessFile(fromFile, "rw"); FileChannel fcIn = rafIn.getChannel(); ByteBuffer byteBuffIn = fcIn.map(FileChannel.MapMode.READ_WRITE, 0,(int) fcIn.size()); fcIn.read(byteBuffIn); byteBuffIn.flip(); RandomAccessFile rafOut = new RandomAccessFile(toFile, "rw"); FileChannel fcOut = rafOut.getChannel(); ByteBuffer writeMap = fcOut.map(FileChannel.MapMode.READ_WRITE,0,(int) fcIn.size()); writeMap.put(byteBuffIn); long timeOut = new Date().getTime(); System.out.println("Memory mapped copy Time for a file of size :" + (int) fcIn.size() +" is "+(timeOut-timeIn)); fcOut.close(); fcIn.close(); } static final int CHUNK_SIZE = 100000; static final char[] inChars = new char[CHUNK_SIZE]; public static void customBufferedCopy(String fromFile, String toFile) throws IOException{ long timeIn = new Date().getTime(); Reader in = new FileReader(fromFile); Writer out = new FileWriter(toFile); while (true) { synchronized (inChars) { int amountRead = in.read(inChars); if (amountRead == -1) { break; } out.write(inChars, 0, amountRead); } } long timeOut = new Date().getTime(); System.out.println("Custom buffered copy Time for a file of size :" + (int) new File(fromFile).length() +" is "+(timeOut-timeIn)); in.close(); out.close(); } } When exactly is it nececary to use RandomAccessFile? Here it is used to read and write in the memoryMappedCopy, is it actually nececary just to copy a file at all? Or is it a part of memorry mapping? In customBufferedCopy, why is synchronized used here? I also found a different example that -should- test the performance between the 2: public class MappedIO { private static int numOfInts = 4000000; private static int numOfUbuffInts = 200000; private abstract static class Tester { private String name; public Tester(String name) { this.name = name; } public long runTest() { System.out.print(name + ": "); try { long startTime = System.currentTimeMillis(); test(); long endTime = System.currentTimeMillis(); return (endTime - startTime); } catch (IOException e) { throw new RuntimeException(e); } } public abstract void test() throws IOException; } private static Tester[] tests = { new Tester("Stream Write") { public void test() throws IOException { DataOutputStream dos = new DataOutputStream( new BufferedOutputStream( new FileOutputStream(new File("temp.tmp")))); for(int i = 0; i < numOfInts; i++) dos.writeInt(i); dos.close(); } }, new Tester("Mapped Write") { public void test() throws IOException { FileChannel fc = new RandomAccessFile("temp.tmp", "rw") .getChannel(); IntBuffer ib = fc.map( FileChannel.MapMode.READ_WRITE, 0, fc.size()) .asIntBuffer(); for(int i = 0; i < numOfInts; i++) ib.put(i); fc.close(); } }, new Tester("Stream Read") { public void test() throws IOException { DataInputStream dis = new DataInputStream( new BufferedInputStream( new FileInputStream("temp.tmp"))); for(int i = 0; i < numOfInts; i++) dis.readInt(); dis.close(); } }, new Tester("Mapped Read") { public void test() throws IOException { FileChannel fc = new FileInputStream( new File("temp.tmp")).getChannel(); IntBuffer ib = fc.map( FileChannel.MapMode.READ_ONLY, 0, fc.size()) .asIntBuffer(); while(ib.hasRemaining()) ib.get(); fc.close(); } }, new Tester("Stream Read/Write") { public void test() throws IOException { RandomAccessFile raf = new RandomAccessFile( new File("temp.tmp"), "rw"); raf.writeInt(1); for(int i = 0; i < numOfUbuffInts; i++) { raf.seek(raf.length() - 4); raf.writeInt(raf.readInt()); } raf.close(); } }, new Tester("Mapped Read/Write") { public void test() throws IOException { FileChannel fc = new RandomAccessFile( new File("temp.tmp"), "rw").getChannel(); IntBuffer ib = fc.map( FileChannel.MapMode.READ_WRITE, 0, fc.size()) .asIntBuffer(); ib.put(0); for(int i = 1; i < numOfUbuffInts; i++) ib.put(ib.get(i - 1)); fc.close(); } } }; public static void main(String[] args) { for(int i = 0; i < tests.length; i++) System.out.println(tests[i].runTest()); } } I more or less see whats going on, my output looks like this: Stream Write: 653 Mapped Write: 51 Stream Read: 651 Mapped Read: 40 Stream Read/Write: 14481 Mapped Read/Write: 6 What is makeing the Stream Read/Write so unbelievably long? And as a read/write test, to me it looks a bit pointless to read the same integer over and over (if I understand well what's going on in the Stream Read/Write) Wouldn't it be better to read int's from the previously written file and just read and write ints on the same place? Is there a better way to illustrate it? I've been breaking my head about a lot of these things for a while and I just can't get the whole picture..

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• C#.Net Calling a C++ DLL

  - by hayer

  Hi I got a DLL(without the sourcecode) which exports like this: ?ReceiveCoreDataPtr@@YAXPAX@Z ?xenoAddRigidBodyAngularImpulse@@YAXHMMM@Z ?xenoAddRigidBodyForce@@YAXHMMM@Z ?xenoAddRigidBodyForce@@YAXHMMMMMM@Z ?xenoAddRigidBodyLinearImpulse@@YAXHMMM@Z ?xenoAddRigidBodyPointImpulse@@YAXHMMMMMM@Z ?xenoAddRigidBodyTorque@@YAXHMMM@Z ?xenoCharacterControllerCrouch@@YAXH@Z ?xenoCharacterControllerJump@@YAXH@Z ?xenoCharacterDisable@@YAXH@Z ?xenoCharacterEnable@@YAXH@Z ?xenoDeleteRigidBody@@YAXH@Z ?xenoEnd@@YAXXZ ?xenoGetCameraFOV@@YAKH@Z ?xenoGetCameraPointX@@YAKH@Z ?xenoGetCameraPointY@@YAKH@Z ?xenoGetCameraPointZ@@YAKH@Z ?xenoGetCameraPositionX@@YAKH@Z ?xenoGetCameraPositionY@@YAKH@Z ?xenoGetCameraPositionZ@@YAKH@Z ?xenoGetCharacterControllerHeadPosition@@YAKH@Z ?xenoGetCharacterControllerPositionX@@YAKH@Z ?xenoGetCharacterControllerPositionY@@YAKH@Z ?xenoGetCharacterControllerPositionZ@@YAKH@Z ?xenoGetCharacterControllerRotation@@YAKH@Z ?xenoGetRigidBodyAllowedPenetrationDepth@@YAKH@Z ?xenoGetRigidBodyAngularDamping@@YAKH@Z ?xenoGetRigidBodyAngularVelocityX@@YAKH@Z ?xenoGetRigidBodyAngularVelocityY@@YAKH@Z ?xenoGetRigidBodyAngularVelocityZ@@YAKH@Z ?xenoGetRigidBodyFriction@@YAKH@Z ?xenoGetRigidBodyGravityFactor@@YAKH@Z ?xenoGetRigidBodyLinearDamping@@YAKH@Z ?xenoGetRigidBodyLinearVelocityX@@YAKH@Z ?xenoGetRigidBodyLinearVelocityY@@YAKH@Z ?xenoGetRigidBodyLinearVelocityZ@@YAKH@Z ?xenoGetRigidBodyMass@@YAKH@Z ?xenoGetRigidBodyMaxAngularVelocity@@YAKH@Z ?xenoGetRigidBodyMaxLinearVelocity@@YAKH@Z ?xenoGetRigidBodyPointVelocityX@@YAKHMMM@Z ?xenoGetRigidBodyPointVelocityY@@YAKHMMM@Z ?xenoGetRigidBodyPointVelocityZ@@YAKHMMM@Z ?xenoGetRigidBodyRestitution@@YAKH@Z ?xenoIsRigidBodyALadder@@YAHH@Z ?xenoMakeCamera@@YAXHH@Z ?xenoMakeCharacterController@@YAXHMM@Z ?xenoMakeCharacterController@@YAXHMMM@Z ?xenoMakeCharacterController@@YAXHMMMM@Z ?xenoMakeCharacterController@@YAXHMMMMM@Z ?xenoMakeCharacterController@@YAXHMMMMMM@Z ?xenoMakeCharacterController@@YAXHMMMMMMM@Z ?xenoMakeRigidBodyDynamicBox@@YAXH@Z ?xenoMakeRigidBodyDynamicBox@@YAXHM@Z ?xenoMakeRigidBodyDynamicCapsule@@YAXH@Z ?xenoMakeRigidBodyDynamicCapsule@@YAXHM@Z ?xenoMakeRigidBodyDynamicCylinder@@YAXH@Z ?xenoMakeRigidBodyDynamicCylinder@@YAXHM@Z ?xenoMakeRigidBodyDynamicSphere@@YAXH@Z ?xenoMakeRigidBodyDynamicSphere@@YAXHM@Z ?xenoMakeRigidBodyStaticBox@@YAXH@Z ?xenoMakeRigidBodyStaticCapsule@@YAXH@Z ?xenoMakeRigidBodyStaticCylinder@@YAXH@Z ?xenoMakeRigidBodyStaticSphere@@YAXH@Z ?xenoMakeRigidBodyStaticTriangleMesh@@YAXH@Z ?xenoMakeVehicle@@YAXHH@Z ?xenoMoveCharacterControllerBackward@@YAXH@Z ?xenoMoveCharacterControllerForward@@YAXH@Z ?xenoMoveCharacterControllerLeft@@YAXH@Z ?xenoMoveCharacterControllerRight@@YAXH@Z ?xenoSetCharacterControllerPosition@@YAXHMMM@Z ?xenoSetCharacterControllerRotation@@YAXHM@Z ?xenoSetGravity@@YAXM@Z ?xenoSetGravity@@YAXMMM@Z ?xenoSetRigidBodyAllowedPenetrationDepth@@YAXHM@Z ?xenoSetRigidBodyAngularDamping@@YAXHM@Z ?xenoSetRigidBodyAngularVelocity@@YAXHMMM@Z ?xenoSetRigidBodyAsLadder@@YAXHH@Z ?xenoSetRigidBodyFriction@@YAXHM@Z ?xenoSetRigidBodyGravityFactor@@YAXHM@Z ?xenoSetRigidBodyLinearDamping@@YAXHM@Z ?xenoSetRigidBodyLinearVelocity@@YAXHMMM@Z ?xenoSetRigidBodyMass@@YAXHM@Z ?xenoSetRigidBodyMaxAngularVelocity@@YAXHM@Z ?xenoSetRigidBodyMaxLinearVelocity@@YAXHM@Z ?xenoSetRigidBodyPosition@@YAXHMMM@Z ?xenoSetRigidBodyRestitution@@YAXHM@Z ?xenoSetRigidBodyRotation@@YAXHMMM@Z ?xenoSetTimeStep@@YAXM@Z ?xenoStart@@YAXH@Z ?xenoStart@@YAXHM@Z ?xenoStart@@YAXHMH@Z ?xenoStart@@YAXXZ ?xenoUpdate@@YAXXZ ?xenoVehicleAccelerate@@YAXHM@Z ?xenoVehicleHandbrake@@YAXH@Z ?xenoVehicleReverse@@YAXH@Z ?xenoVehicleTurn@@YAXHM@Z When I try to use it in another C++ App like this #include <windows.h> class XenoPhysics { private: typedef void (*FunctionFunc)(void); typedef void (*FunctionFuncFloat)(float); typedef void (*FunctionFuncInt)(int); typedef void (*FunctionIntFloatFloatFloat)(int,float,float,float); HMODULE libInstance; public: void LoadLib() { this->libInstance = LoadLibrary(L"F:\\xenophysics.dll"); } void UnloadLib() { FreeLibrary(libInstance); } void xStart() { FunctionFunc curFunc; curFunc = (FunctionFunc)GetProcAddress(this->libInstance, "?xenoStart@@YAXXZ"); curFunc(); } void xEnd() { FunctionFunc curFunc; curFunc = (FunctionFunc)GetProcAddress(libInstance, "xenoEnd"); curFunc(); } void xUpdate() { FunctionFunc curFunc; curFunc = (FunctionFunc)GetProcAddress(libInstance, "xenoUpdate"); curFunc(); } void xMakeRigidBodyStaticBox(int objid) { FunctionFuncInt curFunc; curFunc = (FunctionFuncInt)GetProcAddress(libInstance, "xenoMakeRigidBodyStaticBox"); curFunc(objid); } void xMakeRigidBodyDynamicBox(int objid) { FunctionFuncInt curFunc; curFunc = (FunctionFuncInt)GetProcAddress(libInstance, "xenoMakeRigidBodyDynamicBox"); curFunc(objid); } void xSetRigidBodyPosition(int objid, float x, float y, float z) { FunctionIntFloatFloatFloat curFunc; curFunc = (FunctionIntFloatFloatFloat)GetProcAddress(libInstance, "xenoSetRigidBodyPosition"); curFunc(objid, x, y, z); } void xSetGravity(float grav) { FunctionFuncFloat curFunc; curFunc = (FunctionFuncFloat)GetProcAddress(libInstance, "xenoSetGravity"); curFunc(grav); } }; This is the "wrapper"(or whatever you would call it) class.. To call the functions I'm doing XenoPhysics * d = new XenoPhysics(); d->LoadLib(); d->xStart(); It then throws the following error at me(Note that it passes the LoadLib() without any errors) Unhandled exception at 0x50261bc9 in Xeno Test.exe: 0xC0000005: Access violation reading location 0x00000064. And yes; I've checked that the "curFunc" gets the address, not just a NULL pointer(atleast I think I've checked that).. Anyone who can help out? Edit: Forgot the C#.Net code, how stupid of me :3 Here is the C++ CLR DLL "wrapper" I tried to make: #include <windows.h> // The following ifdef block is the standard way of creating macros which make exporting // from a DLL simpler. All files within this DLL are compiled with the XENOWRAPPERWIN32_EXPORTS // symbol defined on the command line. this symbol should not be defined on any project // that uses this DLL. This way any other project whose source files include this file see // XENOWRAPPERWIN32_API functions as being imported from a DLL, whereas this DLL sees symbols // defined with this macro as being exported. #ifdef XENOWRAPPERWIN32_EXPORTS #define XENOWRAPPERWIN32_API __declspec(dllexport) #else #define XENOWRAPPERWIN32_API __declspec(dllimport) #endif typedef void (*FunctionFunc)(); typedef void (*FunctionFuncFloat)(float); typedef void (*FunctionFuncInt)(int); typedef void (*FunctionIntFloatFloatFloat)(int,float,float,float); // This class is exported from the xeno wrapper win32.dll class XENOWRAPPERWIN32_API Cxenowrapperwin32 { public: Cxenowrapperwin32(void); HINSTANCE libInstance; // FunctionFunc curFunc; // Library base functions void LoadLib() { libInstance = LoadLibrary(L"F:\\xenophysics.dll"); } void UnloadLib() { FreeLibrary(libInstance); } // Function calls to the xeno physics void xStart() { FunctionFunc curFunc; curFunc = (FunctionFunc)GetProcAddress(libInstance, "?xenoStart@@YAXXZ"); curFunc(); } void xEnd() { FunctionFunc curFunc; curFunc = (FunctionFunc)GetProcAddress(libInstance, "?xenoEnd@@YAXXZ"); curFunc(); } void xUpdate() { FunctionFunc curFunc; curFunc = (FunctionFunc)GetProcAddress(libInstance, "?xenoUpdate@@YAXXZ"); curFunc(); } void xMakeRigidBodyStaticBox(int objid) { FunctionFuncInt curFunc; curFunc = (FunctionFuncInt)GetProcAddress(libInstance, "?xenoMakeRigidBodyStaticBox@@YAXH@Z"); curFunc(objid); } void xMakeRigidBodyDynamicBox(int objid) { FunctionFuncInt curFunc; curFunc = (FunctionFuncInt)GetProcAddress(libInstance, "?xenoMakeRigidBodyDynamicBox@@YAXH@Z"); curFunc(objid); } void xSetRigidBodyPosition(int objid, float x, float y, float z) { FunctionIntFloatFloatFloat curFunc; curFunc = (FunctionIntFloatFloatFloat)GetProcAddress(libInstance, "?xenoSetRigidBodyPosition@@YAXHMMM@Z"); curFunc(objid, x, y, z); } void xSetGravity(float grav) { FunctionFuncFloat curFunc; curFunc = (FunctionFuncFloat)GetProcAddress(libInstance, "?xenoSetGravity@@YAXM@Z"); curFunc(grav); } }; extern XENOWRAPPERWIN32_API int nxenowrapperwin32; XENOWRAPPERWIN32_API int fnxenowrapperwin32(void); and here is how I use it in C#.Net class xeno { [DllImport("C:\\Users\\hayer\\Documents\\Visual Studio 2008\\Projects\\xeno wrapper win32\\Debug\\xeno wrapper win32.dll", EntryPoint = "?LoadLib@Cxenowrapperwin32@@QAEXXZ")] public static extern void xLoadLib(); public void LoadLib() { xLoadLib(); } [DllImport("C:\\Users\\hayer\\Documents\\Visual Studio 2008\\Projects\\xeno wrapper win32\\Debug\\xeno wrapper win32.dll", EntryPoint = "?UnloadLib@Cxenowrapperwin32@@QAEXXZ")] public static extern void xUnloadLib(); public void UnloadLib() { xUnloadLib(); } [DllImport("C:\\Users\\hayer\\Documents\\Visual Studio 2008\\Projects\\xeno wrapper win32\\Debug\\xeno wrapper win32.dll", EntryPoint = "?xStart@Cxenowrapperwin32@@QAEXXZ")] public static extern void xStart(); public void Start() { xStart(); } [DllImport("C:\\Users\\hayer\\Documents\\Visual Studio 2008\\Projects\\xeno wrapper win32\\Debug\\xeno wrapper win32.dll", EntryPoint = "?xUpdate@Cxenowrapperwin32@@QAEXXZ")] public static extern void xUpdate(); public void Update() { xUpdate(); } [DllImport("C:\\Users\\hayer\\Documents\\Visual Studio 2008\\Projects\\xeno wrapper win32\\Debug\\xeno wrapper win32.dll", EntryPoint = "?xEnd@Cxenowrapperwin32@@QAEXXZ")] public static extern void xEnd(); public void End() { xEnd(); } [DllImport("C:\\Users\\hayer\\Documents\\Visual Studio 2008\\Projects\\xeno wrapper win32\\Debug\\xeno wrapper win32.dll", EntryPoint = "?xMakeRigidBodyDynamicBox@Cxenowrapperwin32@@QAEXH@Z")] public static extern void xMakeRigidBodyDynamicBox(int objid); public void MakeRigidBodyDynamicBox(int id) { xMakeRigidBodyDynamicBox(id); } [DllImport("C:\\Users\\hayer\\Documents\\Visual Studio 2008\\Projects\\xeno wrapper win32\\Debug\\xeno wrapper win32.dll", EntryPoint = "?xMakeRigidBodyStaticBox@Cxenowrapperwin32@@QAEXH@Z")] public static extern void xMakeRigidBodyStaticBox(int objid); public void MakeRigidBodyStaticBox(int id) { xMakeRigidBodyStaticBox(id); } [DllImport("C:\\Users\\hayer\\Documents\\Visual Studio 2008\\Projects\\xeno wrapper win32\\Debug\\xeno wrapper win32.dll", EntryPoint = "?xSetGravity@Cxenowrapperwin32@@QAEXM@Z")] public static extern void xSetGravity(float grav); public void SetGravity(float g) { xSetGravity(g); } [DllImport("C:\\Users\\hayer\\Documents\\Visual Studio 2008\\Projects\\xeno wrapper win32\\Debug\\xeno wrapper win32.dll", EntryPoint = "?xSetRigidBodyPosition@Cxenowrapperwin32@@QAEXHMMM@Z")] public static extern void xSetRigidBodyPosition(int obj, float x, float y, float z); public void SetRigidBodyPosition(int id, float q, float w, float e) { xSetRigidBodyPosition(id, q, w, e); } } And in the main C#.Net program I do xeno tx = new xeno(); tx.Start(); tx.SetGravity(-1); tx.MakeRigidBodyStaticBox(ground.Id); tx.MakeRigidBodyDynamicBox(cube.Id); tx.SetRigidBodyPosition(cube.Id, 0, 50, 0);

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• I don't understand how work call_once

  - by SABROG

  Please help me understand how work call_once Here is thread-safe code. I don't understand why this need Thread Local Storage and global_epoch variables. Variable _fast_pthread_once_per_thread_epoch can be changed to constant/enum like {FAST_PTHREAD_ONCE_INIT, BEING_INITIALIZED, FINISH_INITIALIZED}. Why needed count calls in global_epoch? I think this code can be rewriting with logc: if flag FINISH_INITIALIZED do nothing, else go to block with mutexes and this all. #ifndef FAST_PTHREAD_ONCE_H #define FAST_PTHREAD_ONCE_H #include #include typedef sig_atomic_t fast_pthread_once_t; #define FAST_PTHREAD_ONCE_INIT SIG_ATOMIC_MAX extern __thread fast_pthread_once_t _fast_pthread_once_per_thread_epoch; #ifdef __cplusplus extern "C" { #endif extern void fast_pthread_once( pthread_once_t *once, void (*func)(void) ); inline static void fast_pthread_once_inline( fast_pthread_once_t *once, void (*func)(void) ) { fast_pthread_once_t x = *once; /* unprotected access */ if ( x _fast_pthread_once_per_thread_epoch ) { fast_pthread_once( once, func ); } } #ifdef __cplusplus } #endif #endif FAST_PTHREAD_ONCE_H Source fast_pthread_once.c The source is written in C. The lines of the primary function are numbered for reference in the subsequent correctness argument. #include "fast_pthread_once.h" #include static pthread_mutex_t mu = PTHREAD_MUTEX_INITIALIZER; /* protects global_epoch and all fast_pthread_once_t writes */ static pthread_cond_t cv = PTHREAD_COND_INITIALIZER; /* signalled whenever a fast_pthread_once_t is finalized */ #define BEING_INITIALIZED (FAST_PTHREAD_ONCE_INIT - 1) static fast_pthread_once_t global_epoch = 0; /* under mu */ __thread fast_pthread_once_t _fast_pthread_once_per_thread_epoch; static void check( int x ) { if ( x == 0 ) abort(); } void fast_pthread_once( fast_pthread_once_t *once, void (*func)(void) ) { /*01*/ fast_pthread_once_t x = *once; /* unprotected access */ /*02*/ if ( x _fast_pthread_once_per_thread_epoch ) { /*03*/ check( pthread_mutex_lock(µ) == 0 ); /*04*/ if ( *once == FAST_PTHREAD_ONCE_INIT ) { /*05*/ *once = BEING_INITIALIZED; /*06*/ check( pthread_mutex_unlock(µ) == 0 ); /*07*/ (*func)(); /*08*/ check( pthread_mutex_lock(µ) == 0 ); /*09*/ global_epoch++; /*10*/ *once = global_epoch; /*11*/ check( pthread_cond_broadcast(&cv;) == 0 ); /*12*/ } else { /*13*/ while ( *once == BEING_INITIALIZED ) { /*14*/ check( pthread_cond_wait(&cv;, µ) == 0 ); /*15*/ } /*16*/ } /*17*/ _fast_pthread_once_per_thread_epoch = global_epoch; /*18*/ check (pthread_mutex_unlock(µ) == 0); } } This code from BOOST: #ifndef BOOST_THREAD_PTHREAD_ONCE_HPP #define BOOST_THREAD_PTHREAD_ONCE_HPP // once.hpp // // (C) Copyright 2007-8 Anthony Williams // // Distributed under the Boost Software License, Version 1.0. (See // accompanying file LICENSE_1_0.txt or copy at // http://www.boost.org/LICENSE_1_0.txt) #include #include #include #include "pthread_mutex_scoped_lock.hpp" #include #include #include namespace boost { struct once_flag { boost::uintmax_t epoch; }; namespace detail { BOOST_THREAD_DECL boost::uintmax_t& get_once_per_thread_epoch(); BOOST_THREAD_DECL extern boost::uintmax_t once_global_epoch; BOOST_THREAD_DECL extern pthread_mutex_t once_epoch_mutex; BOOST_THREAD_DECL extern pthread_cond_t once_epoch_cv; } #define BOOST_ONCE_INITIAL_FLAG_VALUE 0 #define BOOST_ONCE_INIT {BOOST_ONCE_INITIAL_FLAG_VALUE} // Based on Mike Burrows fast_pthread_once algorithm as described in // http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2444.html template void call_once(once_flag& flag,Function f) { static boost::uintmax_t const uninitialized_flag=BOOST_ONCE_INITIAL_FLAG_VALUE; static boost::uintmax_t const being_initialized=uninitialized_flag+1; boost::uintmax_t const epoch=flag.epoch; boost::uintmax_t& this_thread_epoch=detail::get_once_per_thread_epoch(); if(epoch #endif I right understand, boost don't use atomic operation, so code from boost not thread-safe?

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• JavaEE : "Access to default session denied" when sending mail using smtp.gmail.com

  - by Harry Pham

  I am trying to write email authentication feature for my website and I encounter some issues. I got java.lang.SecurityException: Access to default session denied, when I try to do Session.getDefaultInstance. Here are my codes: private static final String SMTP_HOST_NAME = "smtp.gmail.com"; private static final String SMTP_PORT = "465"; private static final String emailSubjectTxt = "Email Confirmation"; private static final String emailFromAddress = "[email protected]"; private static final String SSL_FACTORY = "javax.net.ssl.SSLSocketFactory"; ... String sendTo = "[email protected]"; boolean debug = true; Properties props = new Properties(); props.put("mail.smtp.host", SMTP_HOST_NAME); props.put("mail.smtp.auth", "true"); props.put("mail.debug", "true"); props.put("mail.smtp.port", SMTP_PORT); props.put("mail.smtp.socketFactory.port", SMTP_PORT); props.put("mail.smtp.socketFactory.class", SSL_FACTORY); props.put("mail.smtp.socketFactory.fallback", "false"); //It dies at the next line Session session = Session.getDefaultInstance(props, new javax.mail.Authenticator() { @Override protected PasswordAuthentication getPasswordAuthentication() { return new PasswordAuthentication("myUserName", "myPassword"); } }); session.setDebug(debug); //Set the FROM address Message msg = new MimeMessage(session); InternetAddress addressFrom = new InternetAddress(emailFromAddress); msg.setFrom(addressFrom); //Set the TO address InternetAddress[] addressTo = new InternetAddress[1]; addressTo[0] = new InternetAddress(sendTo); msg.setRecipients(Message.RecipientType.TO, addressTo); //Construct the content of the email confirmation String message = "Test Content" // Setting the Subject and Content Type msg.setSubject(emailSubjectTxt); msg.setContent(message, "text/plain"); Transport.send(msg);

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• .Net Finalizer Order / Semantics in Esent and Ravendb

  - by mattcodes

  Help me understand. I've read that "The time and order of execution of finalizers cannot be predicted or pre-determined" Correct? However looking at RavenDB source code TransactionStorage.cs I see this ~TransactionalStorage() { try { Trace.WriteLine( "Disposing esent resources from finalizer! You should call TransactionalStorage.Dispose() instead!"); Api.JetTerm2(instance, TermGrbit.Abrupt); } catch (Exception exception) { try { Trace.WriteLine("Failed to dispose esent instance from finalizer because: " + exception); } catch { } } } The API class (which belongs to Managed Esent) which presumable takes handles on native resources presumably using a SafeHandle? So if I understand correctly the native handles SafeHandle can be finalized before TransactionStorage which could have undesired effects, perhaps why Ayende has added an catch all clause around this? Actually diving into Esent code, it does not use SafeHandles. According to CLR via C# this is dangerous? internal static class SomeType { [DllImport("Kernel32", CharSet=CharSet.Unicode, EntryPoint="CreateEvent")] // This prototype is not robust private static extern IntPtr CreateEventBad( IntPtr pSecurityAttributes, Boolean manualReset, Boolean initialState, String name); // This prototype is robust [DllImport("Kernel32", CharSet=CharSet.Unicode, EntryPoint="CreateEvent")] private static extern SafeWaitHandle CreateEventGood( IntPtr pSecurityAttributes, Boolean manualReset, Boolean initialState, String name) public static void SomeMethod() { IntPtr handle = CreateEventBad(IntPtr.Zero, false, false, null); SafeWaitHandle swh = CreateEventGood(IntPtr.Zero, false, false, null); } } Managed Esent (NativeMEthods.cs) looks like this (using Ints vs IntPtrs?): [DllImport(EsentDll, CharSet = EsentCharSet, ExactSpelling = true)] public static extern int JetCreateDatabase(IntPtr sesid, string szFilename, string szConnect, out uint dbid, uint grbit); Is Managed Esent handling finalization/dispoal the correct way, and second is RavenDB handling finalizer the corret way or compensating for Managed Esent?

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• WPF - Random hanging with file browser attached behaviour.

  - by Stimul8d

  Hi, I have an attached behavior defined thusly,.. public static class FileBrowserBehaviour { public static bool GetBrowsesOnClick(DependencyObject obj) { return (bool)obj.GetValue(BrowsesOnClickProperty); } public static void SetBrowsesOnClick(DependencyObject obj, bool value) { obj.SetValue(BrowsesOnClickProperty, value); } // Using a DependencyProperty as the backing store for BrowsesOnClick. This enables animation, styling, binding, etc... public static readonly DependencyProperty BrowsesOnClickProperty = DependencyProperty.RegisterAttached("BrowsesOnClick", typeof(bool), typeof(FileBrowserBehaviour), new FrameworkPropertyMetadata(false, new PropertyChangedCallback(BrowsesOnClickChanged))); public static void BrowsesOnClickChanged(DependencyObject obj, DependencyPropertyChangedEventArgs args) { FrameworkElement fe = obj as FrameworkElement; if ((bool)args.NewValue) { fe.PreviewMouseLeftButtonDown += new MouseButtonEventHandler(OpenFileBrowser); } else { fe.PreviewMouseLeftButtonDown -= new MouseButtonEventHandler(OpenFileBrowser); } } static void OpenFileBrowser(object sender, MouseButtonEventArgs e) { var tb = sender as TextBox; if (tb.Text.Length < 1 || tb.Text=="Click to browse..") { OpenFileDialog ofd = new OpenFileDialog(); ofd.Filter = "Executables | *.exe"; if (ofd.ShowDialog() == true) { Debug.WriteLine("Setting textbox text-" + ofd.FileName); tb.Text = ofd.FileName; Debug.WriteLine("Set textbox text"); } } } } It's a nice simple attached behavior which pops open an OpenFileDialog when you click on a textbox and puts the filename in the box when you're done. It works maybe 40% of the time but the rest of the time the whole app hangs. The call stack at this point looks like this - [Managed to Native Transition] WindowsBase.dll!MS.Win32.UnsafeNativeMethods.GetMessageW(ref System.Windows.Interop.MSG msg, System.Runtime.InteropServices.HandleRef hWnd, int uMsgFilterMin, int uMsgFilterMax) + 0x15 bytes WindowsBase.dll!System.Windows.Threading.Dispatcher.GetMessage(ref System.Windows.Interop.MSG msg, System.IntPtr hwnd, int minMessage, int maxMessage) + 0x48 bytes WindowsBase.dll!System.Windows.Threading.Dispatcher.PushFrameImpl(System.Windows.Threading.DispatcherFrame frame = {System.Windows.Threading.DispatcherFrame}) + 0x8b bytes WindowsBase.dll!System.Windows.Threading.Dispatcher.PushFrame(System.Windows.Threading.DispatcherFrame frame) + 0x49 bytes WindowsBase.dll!System.Windows.Threading.Dispatcher.Run() + 0x4c bytes PresentationFramework.dll!System.Windows.Application.RunDispatcher(object ignore) + 0x1e bytes PresentationFramework.dll!System.Windows.Application.RunInternal(System.Windows.Window window) + 0x6f bytes PresentationFramework.dll!System.Windows.Application.Run(System.Windows.Window window) + 0x26 bytes PresentationFramework.dll!System.Windows.Application.Run() + 0x19 bytes Debugatron.exe!Debugatron.App.Main() + 0x5e bytes C# [Native to Managed Transition] [Managed to Native Transition] mscorlib.dll!System.AppDomain.nExecuteAssembly(System.Reflection.Assembly assembly, string[] args) + 0x19 bytes mscorlib.dll!System.Runtime.Hosting.ManifestRunner.Run(bool checkAptModel) + 0x6e bytes mscorlib.dll!System.Runtime.Hosting.ManifestRunner.ExecuteAsAssembly() + 0x84 bytes mscorlib.dll!System.Runtime.Hosting.ApplicationActivator.CreateInstance(System.ActivationContext activationContext, string[] activationCustomData) + 0x65 bytes mscorlib.dll!System.Runtime.Hosting.ApplicationActivator.CreateInstance(System.ActivationContext activationContext) + 0xa bytes mscorlib.dll!System.Activator.CreateInstance(System.ActivationContext activationContext) + 0x3e bytes Microsoft.VisualStudio.HostingProcess.Utilities.dll!Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssemblyDebugInZone() + 0x23 bytes mscorlib.dll!System.Threading.ThreadHelper.ThreadStart_Context(object state) + 0x66 bytes mscorlib.dll!System.Threading.ExecutionContext.Run(System.Threading.ExecutionContext executionContext, System.Threading.ContextCallback callback, object state) + 0x6f bytes mscorlib.dll!System.Threading.ThreadHelper.ThreadStart() + 0x44 bytes Now, I've seen this kind of thing before when doing some asynchronous stuff but there's none of that going on at that point. The only thread alive is the UI thread! Also, I always get that last debug statement when it does hang. Can anyone point me in the right direction? This one's driving me crazy!

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• Why can't Java servlet sent out an object ?

  - by Frank

  I use the following method to send out an object from a servlet : public void doGet(HttpServletRequest request,HttpServletResponse response) throws IOException { String Full_URL=request.getRequestURL().append("?"+request.getQueryString()).toString(); String Contact_Id=request.getParameter("Contact_Id"); String Time_Stamp=Get_Date_Format(6),query="select from "+Contact_Info_Entry.class.getName()+" where Contact_Id == '"+Contact_Id+"' order by Contact_Id desc"; PersistenceManager pm=null; try { pm=PMF.get().getPersistenceManager(); // note that this returns a list, there could be multiple, DataStore does not ensure uniqueness for non-primary key fields List<Contact_Info_Entry> results=(List<Contact_Info_Entry>)pm.newQuery(query).execute(); Write_Serialized_XML(response.getOutputStream(),results.get(0)); } catch (Exception e) { Send_Email(Email_From,Email_To,"Check_License_Servlet Error [ "+Time_Stamp+" ]",new Text(e.toString()+"\n"+Get_Stack_Trace(e)),null); } finally { pm.close(); } } /** Writes the object and CLOSES the stream. Uses the persistance delegate registered in this class. * @param os The stream to write to. * @param o The object to be serialized. */ public static void writeXMLObject(OutputStream os,Object o) { // Classloader reference must be set since netBeans uses another class loader to loead the bean wich will fail in some circumstances. ClassLoader oldClassLoader=Thread.currentThread().getContextClassLoader(); Thread.currentThread().setContextClassLoader(Check_License_Servlet.class.getClassLoader()); XMLEncoder encoder=new XMLEncoder(os); encoder.setExceptionListener(new ExceptionListener() { public void exceptionThrown(Exception e) { e.printStackTrace(); }}); encoder.writeObject(o); encoder.flush(); encoder.close(); Thread.currentThread().setContextClassLoader(oldClassLoader); } private static ByteArrayOutputStream writeOutputStream=new ByteArrayOutputStream(16384); /** Writes an object to XML. * @param out The boject out to write to. [ Will not be closed. ] * @param o The object to write. */ public static synchronized void writeAsXML(ObjectOutput out,Object o) throws IOException { writeOutputStream.reset(); writeXMLObject(writeOutputStream,o); byte[] Bt_1=writeOutputStream.toByteArray(); byte[] Bt_2=new Des_Encrypter().encrypt(Bt_1,Key); out.writeInt(Bt_2.length); out.write(Bt_2); out.flush(); out.close(); } public static synchronized void Write_Serialized_XML(OutputStream Output_Stream,Object o) throws IOException { writeAsXML(new ObjectOutputStream(Output_Stream),o); } At the receiving end the code look like this : File_Url="http://"+Site_Url+App_Dir+File_Name; try { Contact_Info_Entry Online_Contact_Entry=(Contact_Info_Entry)Read_Serialized_XML(new URL(File_Url)); } catch (Exception e) { e.printStackTrace(); } private static byte[] readBuf=new byte[16384]; public static synchronized Object readAsXML(ObjectInput in) throws IOException { // Classloader reference must be set since netBeans uses another class loader to load the bean which will fail under some circumstances. ClassLoader oldClassLoader=Thread.currentThread().getContextClassLoader(); Thread.currentThread().setContextClassLoader(Tool_Lib_Simple.class.getClassLoader()); int length=in.readInt(); readBuf=new byte[length]; in.readFully(readBuf,0,length); byte Bt[]=new Des_Encrypter().decrypt(readBuf,Key); XMLDecoder dec=new XMLDecoder(new ByteArrayInputStream(Bt,0,Bt.length)); Object o=dec.readObject(); Thread.currentThread().setContextClassLoader(oldClassLoader); in.close(); return o; } public static synchronized Object Read_Serialized_XML(URL File_Url) throws IOException { return readAsXML(new ObjectInputStream(File_Url.openStream())); } But I can't get the object from the Java app that's on the receiving end, why ? The error messages look like this : java.lang.ClassNotFoundException: PayPal_Monitor.Contact_Info_Entry Continuing ... java.lang.NullPointerException: target should not be null Continuing ... java.lang.NullPointerException: target should not be null Continuing ... java.lang.NullPointerException: target should not be null Continuing ...

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• Extension methods conflict

  - by Yochai Timmer

  Lets say I have 2 extension methods to string, in 2 different namespaces: namespace test1 { public static class MyExtensions { public static int TestMethod(this String str) { return 1; } } } namespace test2 { public static class MyExtensions2 { public static int TestMethod(this String str) { return 2; } } } These methods are just for example, they don't really do anything. Now lets consider this piece of code: using System; using test1; using test2; namespace blah { public static class Blah { public Blah() { string a = "test"; int i = a.TestMethod(); //Which one is chosen ? } } } I know that only one of the extension methods will be chosen. Which one will it be ? and why ? How can I choose a certain method from a certain namespace ? Edit: Usually I'd use Namespace.ClassNAME.Method() ... But that just beats the whole idea of extension methods. And I don't think you can use Variable.Namespace.Method()

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• [Java] Nested methods vs "piped" methods, which is better?

  - by Michael Mao

  Hi: Since uni, I've programming in Java for 3 years, although I am not fully dedicated to this language, I have spent quite some time in it, nevertheless. I understand both ways, just curious which style do you prefer. public class Test{ public static void main(String[] args) { System.out.println(getAgent().getAgentName()); } private static Agent getAgent() { return new Agent(); }} class Agent{ private String getAgentName() { return "John Smith"; }} I am pretty happy with nested method calls such like the following public class Test{ public static void main(String[] args) { getAgentName(getAgent()); } private static void getAgentName(Agent agent) { System.out.println(agent.getName()); } private static Agent getAgent() { return new Agent(); }} class Agent { public String getName(){ return "John Smith"; }} They have identical output I saw "John Smith" twice. I wonder, if one way of doing this has better performance or other advantages over the other. Personally I prefer the latter, since for nested methods I can certainly tell which starts first, and which is after. The above code is but a sample, The code that I am working with now is much more complicated, a bit like a maze... So switching between the two styles often blows my head in no time.

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• Loading Files in AppEngine

  - by Chris M

  I've got a tiny bit of code to display a file in app.yaml - url: /(.*\.(gif|png|jpg)) static_files: static/\1 upload: static/(.*\.(gif|png|jpg)) in main.py ... class ShowImage(webapp.RequestHandler): def get(self): rootpath = os.path.dirname(__file__) file = rootpath + "/static/tracker.gif"; fh=open(file, 'r') self.response.out.write(fh.read()) fh.close ... I can see the files gone up by going to my *.appspot.com/tracker.gif (as per the app.yaml) But using *.appspot.com/showimage returns Traceback (most recent call last): File "/base/python_lib/versions/1/google/appengine/ext/webapp/__init__.py", line 510, in __call__ handler.get(*groups) File "/base/data/home/apps/APPNAME/2.341131266814384624/main.py", line 170, in get fh=open(file, 'r') IOError: [Errno 2] No such file or directory: '/base/data/home/apps/APPNAME/2.341131266814384624/static/tracker.gif'

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• Exception handling in biztalk 2006 R2

  - by IB

  Hello I have a Biztalk 2006 R2 project (used with ESB Guidance 1) I am calling from orchstration to a static method in c# code, this method uses a class to load a file data into xlang message body at part 0 When i pass filepath which doesnt exists the inside class catch the exception but dont throw it up (in the static method there is a catch block and in the orchstration there is the real handling of the exception) The static method is : public static XLANGMessage LoadFileIntoMessage(XLANGMessage message, string filePath,Encoding encoding) { try { IStreamFactory sf = new FileStreamFactory(filePath,encoding); message[0].LoadFrom(sf); return message; } catch (Exception ex) { throw ex; } } The Class which load the file stream is : private class FileStreamFactory : IStreamFactory { string _fname; Encoding _encoding; public FileStreamFactory(string fname,Encoding encoding) { _fname = fname; _encoding = encoding; } public Stream CreateStream() { try { StreamReader sr; sr = new StreamReader ( _fname, _encoding ); return sr.BaseStream; } catch (Exception ex) { throw ex; } } } I call the static method from the orchstration and expect to catch the exception in my orchstration after the class and the emthod gets it

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