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  • easiest and best way to make a server queue java

    - by houlahan
    i have a server at the moment which makes a new thread for every user connected but after about 6 people are on the server for more than 15 mins it tends to flop and give me java heap out of memory error i have 1 thread that checks with a mysql database every 30 seconds to see if any of the users currently logged on have any new messages. what would be the easiest way to implement a server queue? this is the my main method for my server: public class Server { public static int MaxUsers = 1000; //public static PrintStream[] sessions = new PrintStream[MaxUsers]; public static ObjectOutputStream[] sessions = new ObjectOutputStream[MaxUsers]; public static ObjectInputStream[] ois = new ObjectInputStream[MaxUsers]; private static int port = 6283; public static Connection conn; static Toolkit toolkit; static Timer timer; public static void main(String[] args) { try { conn = (Connection) Mysql.getConnection(); } catch (Exception ex) { Logger.getLogger(Server.class.getName()).log(Level.SEVERE, null, ex); } System.out.println("****************************************************"); System.out.println("* *"); System.out.println("* Cloud Server *"); System.out.println("* ©2010 *"); System.out.println("* *"); System.out.println("* Luke Houlahan *"); System.out.println("* *"); System.out.println("* Server Online *"); System.out.println("* Listening On Port " + port + " *"); System.out.println("* *"); System.out.println("****************************************************"); System.out.println(""); mailChecker(); try { int i; ServerSocket s = new ServerSocket(port); for (i = 0; i < MaxUsers; ++i) { sessions[i] = null; } while (true) { try { Socket incoming = s.accept(); boolean found = false; int numusers = 0; int usernum = -1; synchronized (sessions) { for (i = 0; i < MaxUsers; ++i) { if (sessions[i] == null) { if (!found) { sessions[i] = new ObjectOutputStream(incoming.getOutputStream()); ois[i]= new ObjectInputStream(incoming.getInputStream()); new SocketHandler(incoming, i).start(); found = true; usernum = i; } } else { numusers++; } } if (!found) { ObjectOutputStream temp = new ObjectOutputStream(incoming.getOutputStream()); Person tempperson = new Person(); tempperson.setFlagField(100); temp.writeObject(tempperson); temp.flush(); temp = null; tempperson = null; incoming.close(); } else { } } } catch (IOException ex) { System.out.println(1); Logger.getLogger(Server.class.getName()).log(Level.SEVERE, null, ex); } } } catch (IOException ex) { System.out.println(2); Logger.getLogger(Server.class.getName()).log(Level.SEVERE, null, ex); } } public static void mailChecker() { toolkit = Toolkit.getDefaultToolkit(); timer = new Timer(); timer.schedule(new mailCheck(), 0, 10 * 1000); } }

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  • Android sqlight problem always null

    - by yoav.str
    every time i am using the db its null and i just dont get it i use this code for the SQL when I have quarry : public class GameSQLHelper { static final String[] COUNTRIES = new String[] { "Afghanistan", "Albania", "Algeria", "American Samoa", "Andorra" }; private static final String DB_PATH = "/countryCityGame/databases/"; private static final String DATABASE_NAME = "events.db"; private static final int DATABASE_VERSION = 1; private final Context mCtx; // Table name public static final String TABLE = "myDataBase"; // Columns public static final String LETTER = "letter"; public static final String TYPE = "type"; public static final String VALUE = "value"; //my database SQLiteDatabase myDataBase; private static class DatabaseHelper extends SQLiteOpenHelper { private static final String TAG = null; DatabaseHelper(Context context) { super(context, DATABASE_NAME, null, DATABASE_VERSION); } @Override public void onCreate(SQLiteDatabase db) { String sql = "create table " + TABLE + "( " + BaseColumns._ID + " integer primary key autoincrement, " + LETTER + " text not null, " + TYPE + " text not null," + VALUE + " text not null );"; Log.d("EventsData", "onCreate: " + sql); db.execSQL(sql); insertValuesToDB(db); } private void insertValuesToDB(SQLiteDatabase db) { if (db == null){ } else{ db.execSQL("INSERT INTO " + TABLE + " ("+LETTER+","+ TYPE +"," + VALUE +")" + " VALUES ('A', 'country', 'Angola');"); ContentValues initialValues = new ContentValues(); for (int i = 0 ; i < COUNTRIES.length ; i++){ Character tmp = (Character)COUNTRIES[i].charAt(0); initialValues.put(VALUE, COUNTRIES[i]); initialValues.put(TYPE, "country"); initialValues.put(LETTER,tmp.toString(tmp)); db.insert(TABLE, null, initialValues); } } } @Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { Log.w(TAG, "Upgrading database from version " + oldVersion + " to " + newVersion + ", which will destroy all old data"); db.execSQL("DROP TABLE IF EXISTS notes"); onCreate(db); } } /** * Constructor - takes the context to allow the database to be * opened/created * * @param ctx the Context within which to work */ public GameSQLHelper(Context ctx) { this.mCtx = ctx; } public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { if (oldVersion >= newVersion) return; String sql = null; if (oldVersion == 1) sql = "alter table " + TABLE + " add note text;"; if (oldVersion == 2) sql = ""; Log.d("EventsData", "onUpgrade : " + sql); if (sql != null) db.execSQL(sql); } public void openDataBase() throws SQLException{ //Open the database String myPath = DB_PATH + DATABASE_NAME; myDataBase = SQLiteDatabase.openDatabase(myPath, null, SQLiteDatabase.OPEN_READWRITE); } public boolean existInDataBase(String serchStr ){ Cursor c = null ; try{ openDataBase(); c = myDataBase.query(true, TABLE, new String[] {TYPE }, VALUE + "=" + serchStr, null, null, null, null, null); } catch(Exception e){ Log.d("sqlExacption", e.getMessage()); } if (c == null) return false; return true; } } whenever i call this class (i hold an instace of him initialized : mDbHelper = new GameSQLHelper(this); where this is an activity ) i always get my mDbHelper as null how can i change it , its my first time working with sql outside of mysql platform so i am kind of having problmes understanding tje concept , and the android notepad example didnt help me .

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  • How can I make TextToSpeech to speak a text with max volume and restore original volume after speak end?

    - by HelloCW
    I save the current volume both STREAM_RING and STREAM_MUSIC before sTts.get().speak(s, TextToSpeech.QUEUE_ADD, null), I hope the TextToSpeech can speak a text with max volume, but in fact I find the TextToSpeech speak the text with current volume, it seems that sTts.get().speak is asynchronous. How can I make TextToSpeech to speak a text with max volume and restore original volume after speak end? Thanks! public class SpeechTxt { private static SoftReference<TextToSpeech> sTts; public static void SpeakOut(final Context context, final String s) { final Context appContext = context.getApplicationContext(); if (sTts == null) { sTts = new SoftReference<TextToSpeech>(new TextToSpeech(appContext, new TextToSpeech.OnInitListener() { @Override public void onInit(int status) { if (status == TextToSpeech.SUCCESS) { speak(appContext, s); } else { } } })); } else { speak(appContext, s); } } private static void speak(Context context, String s) { if (sTts != null) { switch (sTts.get().setLanguage(Locale.getDefault())) { case TextToSpeech.LANG_COUNTRY_AVAILABLE: case TextToSpeech.LANG_COUNTRY_VAR_AVAILABLE: case TextToSpeech.LANG_AVAILABLE: { sTts.get().setPitch((float) 0.6); sTts.get().setSpeechRate((float) 0.8); int currentRing=PublicParFun.GetCurrentVol(context, AudioManager.STREAM_RING); int currentPlay=PublicParFun.GetCurrentVol(context, AudioManager.STREAM_MUSIC); PublicParFun.SetRingVol(context, 0); PublicParFun.SetPlayVol(context,1000000); sTts.get().speak(s, TextToSpeech.QUEUE_ADD, null); PublicParFun.SetRingVol(context, currentRing); PublicParFun.SetPlayVol(context,currentPlay); break; } case TextToSpeech.LANG_MISSING_DATA: { break; } case TextToSpeech.LANG_NOT_SUPPORTED: // not much to do here } } } public static int GetCurrentVol(Context myContext,int streamType){ AudioManager mAudioManager = (AudioManager)myContext.getSystemService(Context.AUDIO_SERVICE); int current = mAudioManager.getStreamVolume( streamType); return current; } public static void SetRingVol(Context myContext,int vol){ SetVol(myContext,AudioManager.STREAM_RING, vol); } public static void SetPlayVol(Context myContext,int vol){ SetVol(myContext,AudioManager.STREAM_MUSIC, vol); } private static void SetVol(Context myContext,int streamType,int vol){ AudioManager mAudioManager = (AudioManager)myContext.getSystemService(Context.AUDIO_SERVICE); int max = mAudioManager.getStreamMaxVolume(streamType); if (vol>max){ vol=max; } mAudioManager.setStreamVolume(streamType,vol, 0); } }

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  • 32 bit dllimport generating incorrect format error (0x8007000b) on win7 x64 platform

    - by DFP
    Hello, I'm trying to install and run a 32 bit application on a Win7 x64 machine. The application is built as a Win32 app. It runs fine on 32 bit platforms. On the x64 machine it installs correctly in the Programs(x86) directory and runs fine until I make a call into a 32 bit dll. At that time I get the incorrect format error (0x8007000b) indicating it is trying to load the dll of the wrong bitness. Indeed it is trying to load the 64 bit dll from the System32 directory rather than the 32 bit version in the SystemWOW64 directory. Another 32 bit application provided by the dll vendor runs correctly and it does load the 32 bit dll from the SystemWOW64 directory. I do not have source to their application to see how they are accessing the DLL. I'm using the DllImport function as shown below to access the dll. Is there a way to decorate the DllImport calls to force it to load the 32 bit version? Any thoughts appreciated. Thanks, DP public static class Micronas { [DllImport(@"UAC2.DLL")] public static extern short UacBuildDeviceList(uint uFlags); [DllImport(@"UAC2.DLL")] public static extern short UacGetNumberOfDevices(); [DllImport(@"UAC2.DLL")] public static extern uint UacGetFirstDevice(); [DllImport(@"UAC2.DLL")] public static extern uint UacGetNextDevice(uint handle); [DllImport(@"UAC2.DLL")] public static extern uint UacSetXDFP(uint handle, short adr, uint data); [DllImport(@"UAC2.DLL")] public unsafe static extern uint UacGetXDFP(uint handle, short adr, IntPtr data); }

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  • Why overload true and false instead of defining bool operator?

    - by Joe Enos
    I've been reading about overloading true and false in C#, and I think I understand the basic difference between this and defining a bool operator. The example I see around is something like: public static bool operator true(Foo foo) { return (foo.PropA > 0); } public static bool operator false(Foo foo) { return (foo.PropA <= 0); } To me, this is the same as saying: public static implicit operator bool(Foo foo) { return (foo.PropA > 0); } The difference, as far as I can tell, is that by defining true and false separately, you can have an object that is both true and false, or neither true nor false: public static bool operator true(Foo foo) { return true; } public static bool operator false(Foo foo) { return true; } //or public static bool operator true(Foo foo) { return false; } public static bool operator false(Foo foo) { return false; } I'm sure there's a reason this is allowed, but I just can't think of what it is. To me, if you want an object to be able to be converted to true or false, a single bool operator makes the most sense. Can anyone give me a scenario where it makes sense to do it the other way? Thanks

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  • Best way to get a single value from a DataTable?

    - by PiersMyers
    I have a number of static classes that contain tables like this: using System; using System.Data; using System.Globalization; public static class TableFoo { private static readonly DataTable ItemTable; static TableFoo() { ItemTable = new DataTable("TableFoo") { Locale = CultureInfo.InvariantCulture }; ItemTable.Columns.Add("Id", typeof(int)); ItemTable.Columns["Id"].Unique = true; ItemTable.Columns.Add("Description", typeof(string)); ItemTable.Columns.Add("Data1", typeof(int)); ItemTable.Columns.Add("Data2", typeof(double)); ItemTable.Rows.Add(0, "Item 1", 1, 1.0); ItemTable.Rows.Add(1, "Item 2", 1, 1.0); ItemTable.Rows.Add(2, "Item 3", 2, 0.75); ItemTable.Rows.Add(3, "Item 4", 4, 0.25); ItemTable.Rows.Add(4, "Item 5", 1, 1.0); } public static DataTable GetItemTable() { return ItemTable; } public static int Data1(int id) { DataRow[] dr = ItemTable.Select("Id = " + id); if (dr.Length == 0) { throw new ArgumentOutOfRangeException("id", "Out of range."); } return (int)dr[0]["Data1"]; } public static double Data2(int id) { DataRow[] dr = ItemTable.Select("Id = " + id); if (dr.Length == 0) { throw new ArgumentOutOfRangeException("id", "Out of range."); } return (double)dr[0]["Data2"]; } } Is there a better way of writing the Data1 or Data2 methods that return a single value from a single row that matches the given id?

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  • how to make an import library

    - by user295030
    a requirement was sent to me below: API should be in the form of static library. company xxx will link the library into a third party application to prevent any possible exposure of the code(dll) could they mean an import library? An import library is a library that automates the process of loading and using a dynamic library. On Windows, this is typically done via a small static library (.lib) of the same name as the dynamic library (.dll). The static library is linked into the program at compile time, and then the functionality of the dynamic library can effectively be used as if it were a static library. this might be what they might be eluding to.....I am not sure how to make this in vs2008 . Additional facts: I have a static lib that i use in my current application. Now, I have to convert my app that uses that static lib into an import lib so that they can use a third party prog to access the API's they providede me which in turn will use that static lib i am using. I hope I am clearly explaining this. I am just not sure how to go about it in vs2008. I am looking for specific steps to do this. I already have the coding done. Just need to convert it into the form they are asking and I have to provide the API they want. Other than that then I need to create a test prog which will act as that third party prog so I can make sure my import library works.

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  • can not access MovieClip properties in flashDevelop

    - by numerical25
    I know there is something I am doing wrong. In my controls I have keydown events that control my hero. As of right now, I am trying to rotate my hero but he refuses to turn . Below is my Hero Class, my control class, and gameobject class. pretty much all the classes associate with the controls class. package com.Objects { import com.Objects.GameObject; /** * ... * @author Anthony Gordon */ [Embed(source='../../../bin/Assets.swf', symbol='OuterRim')] public class Hero extends GameObject { public function Hero() { } } } Here is my Controls class. This is the class where I am trying to rotate my hero but he doesnt. The keydown event does work cause I trace it. package com.Objects { import com.Objects.Hero; import flash.events.*; import flash.display.MovieClip; /** * ... * @author Anthony Gordon */ public class Controls extends GameObject { private var aKeyPress:Array; public var ship:Hero; public function Controls(ship:Hero) { this.ship = ship; IsDisplay = false; aKeyPress = new Array(); engine.sr.addEventListener(KeyboardEvent.KEY_DOWN, keyDownListener); engine.sr.addEventListener(KeyboardEvent.KEY_UP,keyUpListener); } private function keyDownListener(e:KeyboardEvent):void { //trace("down e.keyCode=" + e.keyCode); aKeyPress[e.keyCode] = true; trace(e.keyCode); } private function keyUpListener(e:KeyboardEvent):void { //trace("up e.keyCode=" + e.keyCode); aKeyPress[e.keyCode]=false; } override public function UpdateObject():void { Update(); } private function Update():void { if (aKeyPress[37])//Key press left ship.rotation += 3,trace(ship.rotation ); ///DOESNT ROtate }//End Controls } } Here is GameObject Class package com.Objects { import com.Objects.Engine; import com.Objects.IGameObject; import flash.display.MovieClip; /** * ... * @author Anthony Gordon */ public class GameObject extends MovieClip implements IGameObject { private var isdisplay:Boolean = true; private var garbage:Boolean; public static var engine:Engine; public var layer:Number = 0; public function GameObject() { } public function UpdateObject():void { } public function GarbageCollection():void { } public function set Garbage(garb:Boolean):void { garbage = garb; } public function get Garbage():Boolean { return garbage } public function get IsDisplay():Boolean { return isdisplay; } public function set IsDisplay(display:Boolean):void { isdisplay = display; } public function set Layer(l:Number):void { layer = l; } public function get Layer():Number { return layer } } }

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  • Why MSMQ won't send a space character?

    - by cyclotis04
    I'm exploring MSMQ services, and I wrote a simple console client-server application that sends each of the client's keystrokes to the server. Whenever hit a control character (DEL, ESC, INS, etc) the server understandably throws an error. However, whenever I type a space character, the server receives the packet but doesn't throw an error and doesn't display the space. Server: namespace QIM { class Program { const string QUEUE = @".\Private$\qim"; static MessageQueue _mq; static readonly object _mqLock = new object(); static XmlSerializer xs; static void Main(string[] args) { lock (_mqLock) { if (!MessageQueue.Exists(QUEUE)) _mq = MessageQueue.Create(QUEUE); else _mq = new MessageQueue(QUEUE); } xs = new XmlSerializer(typeof(string)); _mq.BeginReceive(new TimeSpan(0, 1, 0), new object(), OnReceive); while (Console.ReadKey().Key != ConsoleKey.Escape) { } } static void OnReceive(IAsyncResult result) { Message msg; lock (_mqLock) { try { msg = _mq.EndReceive(result); Console.Write("."); Console.Write(xs.Deserialize(msg.BodyStream)); } catch (Exception ex) { Console.Write(ex); } } _mq.BeginReceive(new TimeSpan(0, 1, 0), new object(), OnReceive); } } } Client: namespace QIM_Client { class Program { const string QUEUE = @".\Private$\qim"; static MessageQueue _mq; static void Main(string[] args) { if (!MessageQueue.Exists(QUEUE)) _mq = MessageQueue.Create(QUEUE); else _mq = new MessageQueue(QUEUE); ConsoleKeyInfo key = new ConsoleKeyInfo(); while (key.Key != ConsoleKey.Escape) { key = Console.ReadKey(); _mq.Send(key.KeyChar.ToString()); } } } } Client Input: Testing, Testing... Server Output: .T.e.s.t.i.n.g.,..T.e.s.t.i.n.g...... You'll notice that the space character sends a message, but the character isn't displayed.

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  • memcache is not storing data accross requests

    - by morpheous
    I am new to using memcache, so I may be doing something wrong. I have written a wrapper class around memcache. The wrapper class has only static methods, so is a quasi singleton. The class looks something like this: class myCache { private static $memcache = null; private static $initialized = false; public static function init() { if (self::$initialized) return; self::$memcache = new Memcache(); if (self::configure()) //connects to daemon { self::store('foo', 'bar'); } else throw ConnectionError('I barfed'); } public static function store($key, $data, $flag=MEMCACHE_COMPRESSED, $timeout=86400) { if (self::$memcache->get($key)!== false) return self::$memcache->replace($key, $data, $flag, $timeout); return self::$memcache->set($key, $data, $flag, $timeout); } public static function fetch($key) { return self::$memcache->get($key); } } //in my index.php file, I use the class like this require_once('myCache.php'); myCache::init(); echo 'Stored value is: '. myCache::fetch('foo'); The problem is that the myCache::init() method is being executed in full everytime a page is requested. I then remembered that static variables do not maintain state accross page requests. So I decided instead, to store the flag that indicates whether the server contains the start up data (for our purposes, the variable 'foo', with value 'bar') in memcache itself. Once the status flag is stored in memcache itself, It solves the problem of the initialisation data being loaded for every page request (which quite frankly, defeats the purpose of memcache). However, having solved that problem, when I come to fetch the data in memcache, it is empty. I dont understand whats going on. Can anyone clarify how I can store my data once and retrieve it accross page requests? BTW, (just to clarify), the get/set is working correctly, and if I allow memcache to load the initialisation data for each page request, (which is silly), then the data is available in memcache.

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  • java singleton instantiation

    - by jurchiks
    I've found three ways of instantiating a Singleton, but I have doubts as to whether any of them is the best there is. I'm using them in a multi-threaded environment and prefer lazy instantiation. Sample 1: private static final ClassName INSTANCE = new ClassName(); public static ClassName getInstance() { return INSTANCE; } Sample 2: private static class SingletonHolder { public static final ClassName INSTANCE = new ClassName(); } public static ClassName getInstance() { return SingletonHolder.INSTANCE; } Sample 3: private static ClassName INSTANCE; public static synchronized ClassName getInstance() { if (INSTANCE == null) INSTANCE = new ClassName(); return INSTANCE; } The project I'm using ATM uses Sample 2 everywhere, but I kind of like Sample 3 more. There is also the Enum version, but I just don't get it. The question here is - in which cases I should/shouldn't use any of these variations? I'm not looking for lengthy explanations though (there's plenty of other topics about that, but they all eventually turn into arguing IMO), I'd like it to be understandable with few words.

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  • Can I get rid of this read lock?

    - by Pieter
    I have the following helper class (simplified): public static class Cache { private static readonly object _syncRoot = new object(); private static Dictionary<Type, string> _lookup = new Dictionary<Type, string>(); public static void Add(Type type, string value) { lock (_syncRoot) { _lookup.Add(type, value); } } public static string Lookup(Type type) { string result; lock (_syncRoot) { _lookup.TryGetValue(type, out result); } return result; } } Add will be called roughly 10/100 times in the application and Lookup will be called by many threads, many of thousands of times. What I would like is to get rid of the read lock. How do you normally get rid of the read lock in this situation? I have the following ideas: Require that _lookup is stable before the application starts operation. The could be build up from an Attribute. This is done automatically through the static constructor the attribute is assigned to. Requiring the above would require me to go through all types that could have the attribute and calling RuntimeHelpers.RunClassConstructor which is an expensive operation; Move to COW semantics. public static void Add(Type type, string value) { lock (_syncRoot) { var lookup = new Dictionary<Type, string>(_lookup); lookup.Add(type, value); _lookup = lookup; } } (With the lock (_syncRoot) removed in the Lookup method.) The problem with this is that this uses an unnecessary amount of memory (which might not be a problem) and I would probably make _lookup volatile, but I'm not sure how this should be applied. (John Skeets' comment here gives me pause.) Using ReaderWriterLock. I believe this would make things worse since the region being locked is small. Suggestions are very welcome.

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  • Patterns: Local Singleton vs. Global Singleton?

    - by Mike Rosenblum
    There is a pattern that I use from time to time, but I'm not quite sure what it is called. I was hoping that the SO community could help me out. The pattern is pretty simple, and consists of two parts: A singleton factory, which creates objects based on the arguments passed to the factory method. Objects created by the factory. So far this is just a standard "singleton" pattern or "factory pattern". The issue that I'm asking about, however, is that the singleton factory in this case maintains a set of references to every object that it ever creates, held within a dictionary. These references can sometimes be strong references and sometimes weak references, but it can always reference any object that it has ever created. When receiving a request for a "new" object, the factory first searches the dictionary to see if an object with the required arguments already exits. If it does, it returns that object, if not, it returns a new object and also stores a reference to the new object within the dictionary. This pattern prevents having duplicative objects representing the same underlying "thing". This is useful where the created objects are relatively expensive. It can also be useful where these objects perform event handling or messaging - having one object per item being represented can prevent multiple messages/events for a single underlying source. There are probably other reasons to use this pattern, but this is where I've found this useful. My question is: what to call this? In a sense, each object is a singleton, at least with respect to the data it contains. Each is unique. But there are multiple instances of this class, however, so it's not at all a true singleton. In my own personal terminology, I tend to call the factory method a "global singleton". I then call the created objects "local singletons". I sometimes also say that the created objects have "reference equality", meaning that if two variables reference the same data (the same underlying item) then the reference they each hold must be to the same exact object, hence "reference equality". But these are my own invented terms, and I am not sure that they are good ones. Is there standard terminology for this concept? And if not, could some naming suggestions be made? Thanks in advance...

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  • DBTransactions between stateless calls using GUIDs

    - by Marty Trenouth
    I'm looking to add transactional support to my DB engine and providing to Abstract Transaction Handling down to passing in Guids with the DB Action Command. The DB engine would run similar to: private static Database DB; public static Dictionary<Guid,DBTransaction> Transactions = new ...() public static void DoDBAction(string cmdstring,List<Parameter> parameters,Guid TransactionGuid) { DBCommand cmd = BuildCommand(cmdstring,parameters); if(Transactions.ContainsKey(TransactionGuid)) cmd.Transaction = Transactions[TransactionGuid]; DB.ExecuteScalar(cmd); } public static BuildCommand(string cmd, List<Parameter> parameters) { // Create DB command from EntLib Database and assign parameters } public static Guid BeginTransaction() { // creates new Transaction adding it to "Transactions" and opens a new connection } public static Guid Commit(Guid g) { // Commits Transaction and removes it from "Transactions" and closes connection } public static Guid Rollback(Guid g) { // Rolls back Transaction and removes it from "Transactions" and closes connection } The Calling system would run similar to: Guid g try { g = DBEngine.BeginTransaction() DBEngine.DoDBAction(cmdstring1, parameters,g) // do some other stuff DBEngine.DoDBAction(cmdstring2, parameters2,g) // sit here and wait for a response from other item DBEngine.DoDBAction(cmdstring3, parameters3,g) DBEngine.Commit(g) } catch(Exception){ DBEngine.Rollback(g);} Does this interfere with .NET connection pooling (other than a connection be accidently left open)? Will EntLib keep the connection open until the commit or rollback?

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  • C++, function pointer to the template function pointer

    - by Ian
    I am having a pointer to the common static method class MyClass { private: static double ( *pfunction ) ( const Object *, const Object *); ... }; pointing to the static method class SomeClass { public: static double getA ( const Object *o1, const Object *o2); ... }; Initialization: double ( *MyClass::pfunction ) ( const Object *o1, const Object *o2 ) = &SomeClass::getA; I would like to convert this pointer to the static template function pointer: template <class T> static T ( *pfunction ) ( const Object <T> *, const Object <T> *); //Compile error where: class SomeClass { public: template <class T> static double getA ( const Object <T> *o1, const Object <T> *o2); ... }; But there is some error... Thanks for your help...

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  • Not all symbols of an DLL-exported class is exported (VS9)

    - by mandrake
    I'm building a DLL from a group of static libraries and I'm having a problem where only parts of classes are exported. What I'm doing is declaring all symbols I want to export with a preprocessor definition like: #if defined(MYPROJ_BUILD_DLL) //Build as a DLL # define MY_API __declspec(dllexport) #elif defined(MYPROJ_USE_DLL) //Use as a DLL # define MY_API __declspec(dllimport) #else //Build or use as a static lib # define MY_API #endif For example: class MY_API Foo{ ... } I then build static library with MYPROJ_BUILD_DLL & MYPROJ_USE_DLL undefined causing a static library to be built. In another build I create a DLL from these static libraries. So I define MYPROJ_BUILD_DLL causing all symbols I want to export to be attributed with __declspec(dllexport) (this is done by including all static library headers in the DLL-project source file). Ok, so now to the problem. When I use this new DLL I get unresolved externals because not all symbols of a class is exported. For example in a class like this: class MY_API Foo{ public: Foo(char const* ); int bar(); private: Foo( char const*, char const* ); }; Only Foo::Foo( char const*, char const*); and int Foo::bar(); is exported. How can that be? I can understand if the entire class was missing, due to e.g. I forgot to include the header in the DLL-build. But it's only partial missing. Also, say if Foo::Foo( char const*) was not implemented; then the DLL build would have unresolved external errors. But the build is fine (I also double checked for declarations without implementation). Note: The combined size of the static libraries I'm combining is in the region of 30MB, and the resulting DLL is 1.2MB. I'm using Visual Studio 9.0 (2008) to build everything. And Depends to check for exported symbols.

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  • Some questions about special operators i've never seen in C++ code.

    - by toto
    I have downloaded the Phoenix SDK June 2008 (Tools for compilers) and when I'm reading the code of the Hello sample, I really feel lost. public ref class Hello { //-------------------------------------------------------------------------- // // Description: // // Class Variables. // // Remarks: // // A normal compiler would have more flexible means for holding // on to all this information, but in our case it's simplest (if // somewhat inelegant) if we just keep references to all the // structures we'll need to access as classstatic variables. // //-------------------------------------------------------------------------- static Phx::ModuleUnit ^ module; static Phx::Targets::Runtimes::Runtime ^ runtime; static Phx::Targets::Architectures::Architecture ^ architecture; static Phx::Lifetime ^ lifetime; static Phx::Types::Table ^ typeTable; static Phx::Symbols::Table ^ symbolTable; static Phx::Phases::PhaseConfiguration ^ phaseConfiguration; 2 Questions : What's that ref keyword? What is that sign ^ ? What is it doing protected: virtual void Execute ( Phx::Unit ^ unit ) override; }; override is a C++ keyword too? It's colored as such in my Visual Studio. I really want to play with this framework, but this advanced C++ is really an obstacle right now. Thank you.

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  • Implementing a bitfield using java enums

    - by soappatrol
    Hello, I maintain a large document archive and I often use bit fields to record the status of my documents during processing or when validating them. My legacy code simply uses static int constants such as: static int DOCUMENT_STATUS_NO_STATE = 0 static int DOCUMENT_STATUS_OK = 1 static int DOCUMENT_STATUS_NO_TIF_FILE = 2 static int DOCUMENT_STATUS_NO_PDF_FILE = 4 This makes it pretty easy to indicate the state a document is in, by setting the appropriate flags. For example: status = DOCUMENT_STATUS_NO_TIF_FILE | DOCUMENT_STATUS_NO_PDF_FILE; Since the approach of using static constants is bad practice and because I would like to improve the code, I was looking to use Enums to achieve the same. There are a few requirements, one of them being the need to save the status into a database as a numeric type. So there is a need to transform the enumeration constants to a numeric value. Below is my first approach and I wonder if this is the correct way to go about this? class DocumentStatus{ public enum StatusFlag { DOCUMENT_STATUS_NOT_DEFINED(1<<0), DOCUMENT_STATUS_OK(1<<1), DOCUMENT_STATUS_MISSING_TID_DIR(1<<2), DOCUMENT_STATUS_MISSING_TIF_FILE(1<<3), DOCUMENT_STATUS_MISSING_PDF_FILE(1<<4), DOCUMENT_STATUS_MISSING_OCR_FILE(1<<5), DOCUMENT_STATUS_PAGE_COUNT_TIF(1<<6), DOCUMENT_STATUS_PAGE_COUNT_PDF(1<<7), DOCUMENT_STATUS_UNAVAILABLE(1<<8), private final long statusFlagValue; StatusFlag(long statusFlagValue) { this.statusFlagValue = statusFlagValue } public long getStatusFlagValue(){ return statusFlagValue } } /** * Translates a numeric status code into a Set of StatusFlag enums * @param numeric statusValue * @return EnumSet representing a documents status */ public EnumSet<StatusFlag> getStatusFlags(long statusValue) { EnumSet statusFlags = EnumSet.noneOf(StatusFlag.class) StatusFlag.each { statusFlag -> long flagValue = statusFlag.statusFlagValue if ( (flagValue&statusValue ) == flagValue ) { statusFlags.add(statusFlag) } } return statusFlags } /** * Translates a set of StatusFlag enums into a numeric status code * @param Set if statusFlags * @return numeric representation of the document status */ public long getStatusValue(Set<StatusFlag> flags) { long value=0 flags.each { statusFlag -> value|=statusFlag.getStatusFlagValue() } return value } public static void main(String[] args) { DocumentStatus ds = new DocumentStatus(); Set statusFlags = EnumSet.of( StatusFlag.DOCUMENT_STATUS_OK, StatusFlag.DOCUMENT_STATUS_UNAVAILABLE) assert ds.getStatusValue( statusFlags )==258 // 0000.0001|0000.0010 long numericStatusCode = 56 statusFlags = ds.getStatusFlags(numericStatusCode) assert !statusFlags.contains(StatusFlag.DOCUMENT_STATUS_OK) assert statusFlags.contains(StatusFlag.DOCUMENT_STATUS_MISSING_TIF_FILE) assert statusFlags.contains(StatusFlag.DOCUMENT_STATUS_MISSING_PDF_FILE) assert statusFlags.contains(StatusFlag.DOCUMENT_STATUS_MISSING_OCR_FILE) } }

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  • C# Debug.Assert-s use the same error message. Should I promote it to a static variable?

    - by Hamish Grubijan
    I love Asserts but not code duplication, and in several places I use a Debug.Assert which checks for the same condition like so: Debug.Assert(kosherBaconList.SelectedIndex != -1, "An error message along the lines - you should not ever be able to click on edit button without selecting a kosher bacon first."); This is in response to an actual bug, although the actual list does not contain kosher bacon. Anyhow, I can think of two approaches: private static readonly mustSelectKosherBaconBeforeEditAssertMessage = "An error message along the lines - you should not ever be able to " + "click on edit button without selecting a something first."; ... Debug.Assert( kosherBaconList.SelectedIndex != -1, mustSelectKosherBaconBeforeEditAssertMessage) or: if (kosherBaconList.SelectedIndex == -1) { AssertMustSelectKosherBaconBeforeEdit(); } ... [Conditional("DEBUG")] private void AssertMustSelectKosherBaconBeforeEdit() { // Compiler will optimize away this variable. string errorMessage = "An error message along the lines - you should not ever be able to " + "click on edit button without selecting a something first."; Debug.Assert(false, errorMessage); } or is there a third way which sucks less than either one above? Please share. General helpful relevant tips are also welcome.

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  • C#. Saving information about events and event handlers and removing handlers using this information

    - by Philipp
    I have an object which is creating several event handlers using lambda expressions, and I need to remove all handlers created in that object in one time. I'm trying to create some unified static object which will 'know' which handler relates to which object and event if event handler was created through this static object. I tried something like code below, but I don't understand how to save events and event handlers objects, to be able remove handlers in one time. class Program { static void Main(string[] args) { var EventSender = new EventSender(); var EventReceiver = new EventReceiver(EventSender); EventSender.Invoke(" some var "); LinkSaver.RemoveEvent(EventReceiver); // ?? Console.ReadKey(); } } public class ObjLink{ public object Event; public object Action; } public static class LinkSaver { public static void SetEvent<T>(object obj, Action<T> Event, T Action) { Event(Action); var objLink = new ObjLink{Event = Event, Action = Action}; if (!Links.ContainsKey(obj)) Links.Add(obj, new List<ObjLink>{objLink}); else Links[obj].Add(objLink); } static Dictionary<object,List<ObjLink>> Links = new Dictionary<object, List<ObjLink>>(); public static void RemoveEvent(object obj){ foreach(var objLink in Links[obj]){ // objLink.Event -= objLink.Action; ??? } } } public class EventReceiver { public EventReceiver(EventSender obj) { LinkSaver.SetEvent<EventSender.TestDelegate>(this, obj.SetEvent, str => Console.WriteLine(str + " test event!")); } } public class EventSender { public void Invoke(string var) { if (eventTest != null) eventTest(var); } public void SetEvent(TestDelegate Action) { eventTest += Action; } public delegate void TestDelegate(string var); private event TestDelegate eventTest; // by the way public void RemoveFromEvent() { foreach (var handler in eventTest.GetInvocationList()) eventTest -= (TestDelegate)handler; } }

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  • Simulating a 2-level If-Else using RewriteCond

    - by hlissner
    Hi! I'm trying to get my head around RewriteCond, and want to rewrite any requests either to a static html page (if it exists), or to a specific index.php (so long as the requested file doesn't exist). To illustrate the logic: if HTTP_HOST is '(www\.)?mydomain.com' if file exists: "/default/static/{REQUEST_URI}.html", then rewrite .* to /default/static/{REQUEST_URI}.html else if file exists: {REQUEST_FILENAME}, then do not rewrite else rewrite .* to /default/index.php I don't seem to have much trouble doing it when I don't need to test for the HTTP_HOST. Ultimately, this one .htaccess file will be handling requests for several domains. I know I could get around this with vhosts, but I'd like to figure out how to do it this way. Here's where I am at now: RewriteCond %{HTTP_HOST} ^(www\.)?mydomain\.com$ [NC] RewriteCond /default/static/%{REQUEST_URI}.html -f RewriteRule . /default/static/%{REQUEST_URI}.html [L,NC] RewriteCond %{REQUEST_FILENAME} !-f RewriteRule . /default/index.php [L,QSA] I'm not too familiar with some of the other flags, will any of them be of use here (like chain|C, next|N or skip|S)? Thanks in advance! UPDATE: I've managed to do it, but would appreciate alternatives: RewriteEngine On RewriteRule ^(.+)/$ /$1 [L] RewriteCond %{HTTP_HOST} ^(domainA|domainB)\.com [NC] RewriteCond %{DOCUMENT_ROOT}/%1/static/%{REQUEST_URI}.html -f RewriteRule (.*)? /%1/static/$1.html [NC,L] RewriteCond %{HTTP_HOST} ^(domainA|domainB)\.com [NC] RewriteCond %{REQUEST_FILENAME} !-f RewriteRule .* /%1/index.php [L,QSA]

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  • What are the linkage of the following functions?

    - by Derui Si
    When I was reading the c++ 03 standard (7.1.1 Storage class specifiers [dcl.stc]), there are some examples as below, I'm not able to tell how the linkage of each successive declarations is determined? Could anyone help here? Thanks in advance! static char* f(); // f() has internal linkage char* f() { /* ... */ } // f() still has internal linkage char* g(); // g() has external linkage static char* g() { /* ... */ } // error: inconsistent linkage void h(); inline void h(); // external linkage inline void l(); void l(); // external linkage inline void m(); extern void m(); // external linkage static void n(); inline void n(); // internal linkage static int a; // a has internal linkage int a; // error: two definitions static int b; // b has internal linkage extern int b; // b still has internal linkage int c; // c has external linkage static int c; // error: inconsistent linkage extern int d; // d has external linkage static int d; // error: inconsistent linkage UPD: Additionally, how can I understand the statement in the standard, " The linkages implied by successive declarations for a given entity shall agree. That is, within a given scope, each declaration declaring the same object name or the same overloading of a function name shall imply the same linkage. Each function in a given set of overloaded functions can have a different linkage, however."

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  • ANDROID SAX Parser issue

    - by Chris Watson
    Since I am new to java programming, I need a bit of help with this. I stuck on this one issue and can't continue until I get this to work. I am trying to make a string from that includes a preference int. I saved the data and can display the int (just sample code): SharedPreferences prefs=PreferenceManager .getDefaultSharedPreferences(this); list.setText(prefs.getString("list", "22")); now, I have a xml parser that is pulling a url correctly as a static string: public static String feedUrl = String.format("http://www.freshpointmarketing.com/iphone/objects/XML/AND.php?ID=%d", 22); Works great... now my issue...... I need to have the preference "int" become the variable in the string, thus making it not static. static SharedPreferences prefs=PreferenceManager.getDefaultSharedPreferences(this); static int myVariable = prefs.getInt("list1", 22); public static String feedUrl = String.format("http://www.freshpointmarketing.com/iphone/objects/XML/AND.php?ID=%d", myVariable); If I take out all static references, I get an error on this: private void loadFeed(ParserType type){ try{ FeedParser parser = FeedParserFactory.getParser(type); long start = System.currentTimeMillis(); messages = parser.parse(); long duration = System.currentTimeMillis() - start; Log.i("AndroidNews", "Parser duration=" + duration); String xml = writeXml(); Log.i("AndroidNews", xml); List<String> titles = new ArrayList<String>(messages.size()); for (Message msg : messages){ titles.add(msg.getTitle()); } ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, R.layout.row,titles); this.setListAdapter(adapter); } catch (Throwable t){ Log.e("AndroidNews",t.getMessage(),t); } } thanks

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  • question about Ackermann function

    - by davit-datuashvili
    i am doing to write recursive program which calculates Ackemann function http://en.wikipedia.org/wiki/Ackermann_function here is code public class Ackermann{ public static long ackermann( long m,long n){ return (m==0)? n+1: (m>0 && n==0)? ackermann(m-1,1): (m>0 && n>0)? ackermann(m-1, ackermann(m,n-1)); } public static void main(String[]args){ long m=4; long n=2; System.out.println(ackermann(m,n)); } } but it shows me mistakes Ackermann.java:7: : expected (m>0 && n>0)? ackermann(m-1, ackermann(m,n-1)); ^ Ackermann.java:7: ';' expected (m>0 && n>0)? ackermann(m-1, ackermann(m,n-1)); ^ Ackermann.java:18: illegal start of expression public static void main(String[]args){ ^ Ackermann.java:18: ';' expected public static void main(String[]args){ ^ Ackermann.java:18: illegal start of expression public static void main(String[]args){ ^ Ackermann.java:18: ';' expected public static void main(String[]args){ ^ Ackermann.java:18: ';' expected public static void main(String[]args){ ^ Ackermann.java:26: reached end of file while parsing } ^ 8 errors please help

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  • How to calculate where bullet hits

    - by lkjoel
    I have been trying to write an FPS in C/X11/OpenGL, but the issue that I have encountered is with calculating where the bullet hits. I have used a horrible technique, and it only sometimes works: pos size, p; size.x = 0.1; size.z = 0.1; // Since the game is technically top-down (but in a 3D perspective) // Positions are in X/Z, no Y float f; // Counter float d = FIRE_MAX + 1 /* Shortest Distance */, d1 /* Distance being calculated */; x = 0; // Index of object to hit for (f = 0.0; f < FIRE_MAX; f += .01) { // Go forwards p.x = player->pos.x + f * sin(toRadians(player->rot.x)); p.z = player->pos.z - f * cos(toRadians(player->rot.x)); // Get all objects that collide with the current position of the bullet short* objs = _colDetectGetObjects(p, size, objects); for (i = 0; i < MAX_OBJECTS; i++) { if (objs[i] == -1) { continue; } // Check the distance between the object and the player d1 = sqrt( pow((objects[i].pos.x - player->pos.x), 2) + pow((objects[i].pos.z - player->pos.z), 2)); // If it's closer, set it as the object to hit if (d1 < d) { x = i; d = d1; } } // If there was an object, hit it if (x > 0) { hit(&objects[x], FIRE_DAMAGE, explosions, currtime); break; } } It just works by making a for-loop and calculating any objects that might collide with where the bullet currently is. This, of course, is very slow, and sometimes doesn't even work. What would be the preferred way to calculate where the bullet hits? I have thought of making a line and seeing if any objects collide with that line, but I have no idea how to do that kind of collision detection. EDIT: I guess my question is this: How do I calculate the nearest object colliding in a line (that might not be a straight 45/90 degree angle)? Or are there any simpler methods of calculating where the bullet hits? The bullet is sort of like a laser, in the sense that gravity does not affect it (writing an old-school game, so I don't want it to be too realistic)

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