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  • Deserialize jSON Google AJAX Translation API

    - by Chris Porter
    I've got the JSON coming back like this: {"responseData": [{"responseData":{"translatedText":"elefante"},"responseDetails":null,"responseStatus":200},{"responseData":{"translatedText":"Burro"},"responseDetails":null,"responseStatus":200}], "responseDetails": null, "responseStatus": 200} And I need to parse it into a ResponseData object I have set-up: public class ResponseData { public string translatedText = string.Empty; public object responseDetails = null; public HttpStatusCode responseStatus = HttpStatusCode.OK; public List<ResponseData> responseData { get; set; } } I Deserialize it like this: JavaScriptSerializer serializer = new JavaScriptSerializer(); ResponseData translation = serializer.Deserialize<ResponseData>(responseJson); But no matter what the translated text is always empty.

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  • mysql query performance help

    - by Stefano
    Hi I have a quite large table storing words contained in email messages mysql> explain t_message_words; +----------------+---------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +----------------+---------+------+-----+---------+----------------+ | mwr_key | int(11) | NO | PRI | NULL | auto_increment | | mwr_message_id | int(11) | NO | MUL | NULL | | | mwr_word_id | int(11) | NO | MUL | NULL | | | mwr_count | int(11) | NO | | 0 | | +----------------+---------+------+-----+---------+----------------+ table contains about 100M rows mwr_message_id is a FK to messages table mwr_word_id is a FK to words table mwr_count is the number of occurrencies of word mwr_word_id in message mwr_message_id To calculate most used words, I use the following query SELECT SUM(mwr_count) AS word_count, mwr_word_id FROM t_message_words GROUP BY mwr_word_id ORDER BY word_count DESC LIMIT 100; that runs almost forever (more than half an hour on the test server) mysql> show processlist; +----+------+----------------+--------+---------+------+----------------------+----------------------------------------------------- | Id | User | Host | db | Command | Time | State | Info +----+------+----------------+--------+---------+------+----------------------+----------------------------------------------------- processlist | 41 | root | localhost:3148 | tst_db | Query | 1955 | Copying to tmp table | SELECT SUM(mwr_count) AS word_count, mwr_word_id FROM t_message_words GROUP BY mwr_word_id | +----+------+----------------+--------+---------+------+----------------------+----------------------------------------------------- 3 rows in set (0.00 sec) Is there anything I can do to "speed up" the query (apart from adding more ram, more cpu, faster disks)? thank you in advance stefano

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  • Change Titlewindow close button

    - by Cameigons
    I'm working with Flex 3.4 SDK. I need to change the default close button image from a TitleWindow. So what I'm doing is defining a CSS selector, like this: TitleWindow{ close-button-skin: Embed('assets/close.png'); border-color: #FFFFFF; corner-radius: 10; closeButtonDisabledSkin: ClassReference(null); closeButtonDownSkin: ClassReference(null); closeButtonOverSkin: ClassReference(null); closeButtonUpSkin: ClassReference(null); } The problem is: the result image is totally squeezed beyond recognition. Probably because the image dimensions are 55x10 pixels (much wider than the default closebutton square-like dimensions) and flex forces it to fit that size. Would anyone know how to go about fixing that?

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  • iPhone Twitter Integration: Validating login.

    - by Mr. McPepperNuts
    The following code posts to twitter: NSString *compoundLoginString = [NSString stringWithFormat:@"http://%@:%@@twitter.com/statuses/update.xml",extractedUsername, extractedPassword]; NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL: [NSURL URLWithString:compoundLoginString] cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:20.0]; // The text to post NSString *msg = tweetText; [request setHTTPMethod:@"POST"]; [request setHTTPBody:[[NSString stringWithFormat:@"status=%@", msg] dataUsingEncoding:NSASCIIStringEncoding]]; NSURLResponse *response; NSError *error; if ([NSURLConnection sendSynchronousRequest:request returningResponse:&response error:&error] != nil){ [self postSuccessfulAlert]; }else{ [self postNotSuccessfulAlert]; } I am curious as to how I could check if the username and password is correct before proceeding to the above piece of code. I found the following code in a tutorial, but am unsure how I would implement or call this function. - (void)connection:(NSURLConnection *)connection didReceiveAuthenticationChallenge:(NSURLAuthenticationChallenge *)challenge { if ([challenge previousFailureCount] == 0) { NSURLCredential *newCredential; newCredential=[NSURLCredential credentialWithUser:[self username] password:[self password] persistence:NSURLCredentialPersistenceNone]; [[challenge sender] useCredential:newCredential forAuthenticationChallenge:challenge]; } else { [[challenge sender] cancelAuthenticationChallenge:challenge]; // inform the user that the user name and password // in the preferences are incorrect NSLog(@"Invalid Username or Password"); } } Any ideas? Please note, I have taken snippets of code from both of the following tutorials. http://iphonedevelopertips.com/networking/post-to-a-twitter-account-from-the-iphone.html and http://icodeblog.com/2009/07/09/integrating-twitter-into-your-applications/

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  • Not able to get IME Input Context through C++ (ImmGetContext)

    - by Prakash
    Hi I am trying to disable the IME on notepad using the following psuedo code: MakeNotepadActiveWindow();//Notepad is already open and set to Japanese IME HWND hwnd = GetTheHWNDForNotepad(); HIMC context = ImmGetContext(hwnd); if(context == NULL) printf("context is null %d ",GetLastError()); and the above code is always giving me the null context. GetLastError() gives 0; Could somebody tell me how to get the InputContext

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  • Android Status Bar Notifications - Opening the correct activity when selecting a notification

    - by Mr Zorn
    I have been having a problem with a notification not opening/going to the correct activity when it has been clicked. My notification code (located in a class which extends Service): Context context = getApplicationContext(); CharSequence contentTitle = "Notification"; CharSequence contentText = "New Notification"; final Notification notifyDetails = new Notification(R.drawable.icon, "Consider yourself notified", System.currentTimeMillis()); Intent notifyIntent = new Intent(context, MainActivity.class); PendingIntent intent = PendingIntent.getActivity(context, 0, notifyIntent, PendingIntent.FLAG_UPDATE_CURRENT | Notification.FLAG_AUTO_CANCEL); notifyDetails.setLatestEventInfo(context, contentTitle, contentText, intent); ((NotificationManager)getSystemService(NOTIFICATION_SERVICE)).notify(NOTIFICATION_ID, notifyDetails); If I click the notification while the application which created the service is open, the notification disappears (due to the FLAG_AUTO_CANCEL) but the activity does not switch. If I click the notification from the home screen, the notification disappears and my app is brought to the front, however it remains on the activity which was open before going to the home screen, instead of going to the main screen. What am I doing wrong? How do I specify the activity that will be pulled up?

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  • GetOleDbSchemaTable Foreign Keys on Sql Server 2005

    - by haxelit
    I'm trying to get the Foreign Keys for a table in my SQL Server 2005 database. I'm using the GetOleDbSchemaTable function right now: DataTable schemaTable = connection.GetOleDbSchemaTable( OleDbSchemaGuid.Foreign_Keys, new object[] { null, null, null, "TABLE" }); This pulls back the right foreign keys, the only problem is that the UpdateRule and DeleteRule are set to "No Action". If I browse to the same table in SSMS I can see that my DeleteRule is "Set NULL". Does the GetOleDbSchemaTable function not return the proper foreign key rules ? Has any one else ran into this problem ?

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  • MySQL + MyISAM table size question

    - by alessandro ferrucci
    Hello, I have a test table. The test table is as follows: CREATE TABLE mytest ( num1 int(10) unsigned NOT NULL, KEY key1 (num1) ) ENGINE=MyISAM DEFAULT CHARSET=latin1; I inserted 50 million rows in this table. When I do show table status the avg_row_length is 7. I was expecting to see 4 since mySQL uses 4 bytes for integers. Does the key have an effect on the avg_row_length? When I look at my .MYD file the size is 334 MB which is exactly what it should be given that the avg_row_length is 7, however I was really expecting to see 190 MB given that I only have an int. +----------------+--------+---------+------------+----------+----------------+-------------+------------------+--------------+-----------+----------------+---------------------+---------------------+------------+-------------------+----------+----------------+---------+ | Name | Engine | Version | Row_format | Rows | Avg_row_length | Data_length | Max_data_length | Index_length | Data_free | Auto_increment | Create_time | Update_time | Check_time | Collation | Checksum | Create_options | Comment | +----------------+--------+---------+------------+----------+----------------+-------------+------------------+--------------+-----------+----------------+---------------------+---------------------+------------+-------------------+----------+----------------+---------+ | mytest | MyISAM | 10 | Fixed | 50000000 | 7 | 350000000 | 1970324836974591 | 600518656 | 0 | NULL | 2010-05-22 09:15:06 | 2010-05-22 19:32:53 | NULL | latin1_swedish_ci | NULL | | | I have included the output of show table status for mytest table. Sorry about the formatting :D Thanks in advance! Alessandro Ferrucci

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  • Why does autoboxing in Java allow me to have 3 possible values for a boolean?

    - by John
    Reference: http://java.sun.com/j2se/1.5.0/docs/guide/language/autoboxing.html If your program tries to autounbox null, it will throw a NullPointerException. javac will give you a compile-time error if you try to assign null to a boolean. makes sense. assigning null to a Boolean is a-ok though. also makes sense, i guess. but let's think about the fact that you'll get a NPE when trying to autounbox null. what this means is that you can't safely perform boolean operations on Booleans without null-checking or exception handling. same goes for doing math operations on an Integer. for a long time, i was a fan of autoboxing in java1.5+ because I thought it got java closer to be truly object-oriented. but, after running into this problem last night, i gotta say that i think this sucks. the compiler giving me an error when I'm trying to do stuff with an uninitialized primitive is a good thing. I think I may be misunderstanding the point of autoboxing, but at the same time I will never accept that a boolean should be able to have 3 values. can anyone explain this? what am i not getting?

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  • Most efficient way to combine two objects in C#

    - by Dested
    I have two objects that can be represented as an int, float, bool, or string. I need to perform an addition on these two objects with the results being the same thing c# would produce as a result. For instance 1+"Foo" would equal the string "1Foo", 2+2.5 would equal the float 5.5, and 3+3 would equal the int 6 . Currently I am using the code below but it seems like incredible overkill. Can anyone simplify or point me to some way to do this efficiently? private object Combine(object o, object o1) { float left = 0; float right = 0; bool isInt = false; string l = null; string r = null; if (o is int) { left = (int)o; isInt = true; } else if (o is float) { left = (float)o; } else if (o is bool) { l = o.ToString(); } else { l = (string)o; } if (o1 is int) { right = (int)o1; } else if (o is float) { right = (float)o1; isInt = false; } else if (o1 is bool) { r = o1.ToString(); isInt = false; } else { r = (string)o1; isInt = false; } object rr; if (l == null) { if (r == null) { rr = left + right; } else { rr = left + r; } } else { if (r == null) { rr = l + right; } else { rr = l + r; } } if (isInt) { return Convert.ToInt32(rr); } return rr; }

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  • AutoIncrement in SQLite with Subsonic 3

    - by Cooter
    This is probably a simple matter, but when I create a new object, the ID property starts off as 0 rather than null. As I understand it, SQLite takes/needs a value of null for the PK column to do the AutoIncrement. So the short question is how to get the ID in the object to start life as null? Thanks cooter

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  • How should Application.Run() be called for the main presenter of a MVP WinForms app?

    - by Mr Roys
    I'm learning to apply MVP to a simple WinForms app (only one form) in C# and encountered an issue while creating the main presenter in static void Main(). Is it a good idea to expose a View from the Presenter in order to supply it as a parameter to Application.Run()? Currently, I've implemented an approach which allows me to not expose the View as a property of Presenter: static void Main() { IView view = new View(); Model model = new Model(); Presenter presenter = new Presenter(view, model); presenter.Start(); Application.Run(); } The Start and Stop methods in Presenter: public void Start() { view.Start(); } public void Stop() { view.Stop(); } The Start and Stop methods in View (a Windows Form): public void Start() { this.Show(); } public void Stop() { // only way to close a message loop called // via Application.Run(); without a Form parameter Application.Exit(); } The Application.Exit() call seems like an inelegant way to close the Form (and the application). The other alternative would be to expose the View as a public property of the Presenter in order to call Application.Run() with a Form parameter. static void Main() { IView view = new View(); Model model = new Model(); Presenter presenter = new Presenter(view, model); Application.Run(presenter.View); } The Start and Stop methods in Presenter remain the same. An additional property is added to return the View as a Form: public void Start() { view.Start(); } public void Stop() { view.Stop(); } // New property to return view as a Form for Application.Run(Form form); public System.Windows.Form View { get { return view as Form(); } } The Start and Stop methods in View (a Windows Form) would then be written as below: public void Start() { this.Show(); } public void Stop() { this.Close(); } Could anyone suggest which is the better approach and why? Or there even better ways to resolve this issue?

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  • Restoring multiple database backups in a transaction

    - by Raghu Dodda
    I wrote a stored procedure that restores as set of the database backups. It takes two parameters - a source directory and a restore directory. The procedure looks for all .bak files in the source directory (recursively) and restores all the databases. The stored procedure works as expected, but it has one issue - if I uncomment the try-catch statements, the procedure terminates with the following error: error_number = 3013 error_severity = 16 error_state = 1 error_message = DATABASE is terminating abnormally. The weird part is sometimes (it is not consistent) the restore is done even if the error occurs. The procedure: create proc usp_restore_databases ( @source_directory varchar(1000), @restore_directory varchar(1000) ) as begin declare @number_of_backup_files int -- begin transaction -- begin try -- step 0: Initial validation if(right(@source_directory, 1) <> '\') set @source_directory = @source_directory + '\' if(right(@restore_directory, 1) <> '\') set @restore_directory = @restore_directory + '\' -- step 1: Put all the backup files in the specified directory in a table -- declare @backup_files table ( file_path varchar(1000)) declare @dos_command varchar(1000) set @dos_command = 'dir ' + '"' + @source_directory + '*.bak" /s/b' /* DEBUG */ print @dos_command insert into @backup_files(file_path) exec xp_cmdshell @dos_command delete from @backup_files where file_path IS NULL select @number_of_backup_files = count(1) from @backup_files /* DEBUG */ select * from @backup_files /* DEBUG */ print @number_of_backup_files -- step 2: restore each backup file -- declare backup_file_cursor cursor for select file_path from @backup_files open backup_file_cursor declare @index int; set @index = 0 while(@index < @number_of_backup_files) begin declare @backup_file_path varchar(1000) fetch next from backup_file_cursor into @backup_file_path /* DEBUG */ print @backup_file_path -- step 2a: parse the full backup file name to get the DB file name. declare @db_name varchar(100) set @db_name = right(@backup_file_path, charindex('\', reverse(@backup_file_path)) -1) -- still has the .bak extension /* DEBUG */ print @db_name set @db_name = left(@db_name, charindex('.', @db_name) -1) /* DEBUG */ print @db_name set @db_name = lower(@db_name) /* DEBUG */ print @db_name -- step 2b: find out the logical names of the mdf and ldf files declare @mdf_logical_name varchar(100), @ldf_logical_name varchar(100) declare @backup_file_contents table ( LogicalName nvarchar(128), PhysicalName nvarchar(260), [Type] char(1), FileGroupName nvarchar(128), [Size] numeric(20,0), [MaxSize] numeric(20,0), FileID bigint, CreateLSN numeric(25,0), DropLSN numeric(25,0) NULL, UniqueID uniqueidentifier, ReadOnlyLSN numeric(25,0) NULL, ReadWriteLSN numeric(25,0) NULL, BackupSizeInBytes bigint, SourceBlockSize int, FileGroupID int, LogGroupGUID uniqueidentifier NULL, DifferentialBaseLSN numeric(25,0) NULL, DifferentialBaseGUID uniqueidentifier, IsReadOnly bit, IsPresent bit ) insert into @backup_file_contents exec ('restore filelistonly from disk=' + '''' + @backup_file_path + '''') select @mdf_logical_name = LogicalName from @backup_file_contents where [Type] = 'D' select @ldf_logical_name = LogicalName from @backup_file_contents where [Type] = 'L' /* DEBUG */ print @mdf_logical_name + ', ' + @ldf_logical_name -- step 2c: restore declare @mdf_file_name varchar(1000), @ldf_file_name varchar(1000) set @mdf_file_name = @restore_directory + @db_name + '.mdf' set @ldf_file_name = @restore_directory + @db_name + '.ldf' /* DEBUG */ print 'mdf_logical_name = ' + @mdf_logical_name + '|' + 'ldf_logical_name = ' + @ldf_logical_name + '|' + 'db_name = ' + @db_name + '|' + 'backup_file_path = ' + @backup_file_path + '|' + 'restore_directory = ' + @restore_directory + '|' + 'mdf_file_name = ' + @mdf_file_name + '|' + 'ldf_file_name = ' + @ldf_file_name restore database @db_name from disk = @backup_file_path with move @mdf_logical_name to @mdf_file_name, move @ldf_logical_name to @ldf_file_name -- step 2d: iterate set @index = @index + 1 end close backup_file_cursor deallocate backup_file_cursor -- end try -- begin catch -- print error_message() -- rollback transaction -- return -- end catch -- -- commit transaction end Does anybody have any ideas why this might be happening? Another question: is the transaction code useful ? i.e., if there are 2 databases to be restored, will SQL Server undo the restore of one database if the second restore fails?

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  • Invalid argument when calling linux splice()

    - by benny wallace
    Hi I wanted to try out the splice syscall. I have this function - it should copy content of one file to another: static void test_splice( int in, int out ) { int i = 0, rcvd = 0; int filedes[2]; off_t off = 0; if ( pipe( filedes ) < 0 ) { perror( "Kicha pipe" ); exit( EXIT_FAILURE ); } for ( i = 0; i < NUMLOOPS; ++i ) { if ( ( rcvd = splice( in, NULL, filedes[1], NULL, BUFSIZE, SPLICE_F_MORE | SPLICE_F_MOVE ) ) < 0 ) { perror( "splice" ); exit( EXIT_FAILURE ); } if ( splice( filedes[0], NULL, out, NULL, rcvd, SPLICE_F_MORE | SPLICE_F_MOVE ) < 0 ) { perror( "splice" ); exit( EXIT_FAILURE ); } } } The second call to splice in first iteration returns EINVAL ( invalid argument from perror ) everytime - what could be the reason?

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  • Where is the mistake ?

    - by mr.bio
    Hi ... i am implementing a simple linked list in c++. I have a mistake and i don't see it :( #include <stdexcept> #include <iostream> struct Node { Node(Node *next, int value): next(next), value(value) { } Node *next; int value; }; class List { Node *first; // Erstes Element , 0 falls die Liste leer ist int len; // Laenge der liste Node *nthNode(int index); // Hilfsfunktion : O( index ) public: // Default - Konstruktor ( Laenge 0): O (1) List():first(0),len(0){ } // Copy - Konstruktor : O(other.len) List(const List & other){ }; // Zuweisungs - Operator O(len +other.len) List &operator=(const List &other) { clear(); if(!other.len) return *this; Node *it = first = new Node(0,other.first->value); for (Node *n = other.first->next; n; n = n->next) { it = it->next = new Node(0, n->value); } len = other.len; return *this; } // Destruktor ( gibt den Speicher von allen Nodes frei ): O( len ) ~List(){ }; // Haengt der Liste ein Element hinten an: O( len ) void push_back(int value){ }; // Fuegt am Anfang der Liste ein Element ein : O (1) void push_front(int value){ Node* front = new Node(0,value); if(first){ first = front; front->next = 0; }else{ front->next = first; first = front; } len++; }; // gibt eine Referenz auf das index -te Element zurueck : O( index ) int &at(int index){ int count = 0 ; int ret ; Node *it = first; for (Node *n = first->next; n; n = n->next) { if(count==index) ret = n->value; count++; } return ret ; }; // Entfernt alle Elemente : O(len) void clear(){ }; // Zeigt alle Elemente an: hier : O( len * len ) void show() { std::cout << " List [" << len << " ]:{ "; for (int i = 0; i < len; ++i) { std::cout << at(i) << (i == len - 1 ? '}' : ','); } std::cout << std::endl; } }; /* * */ int main() { List l; // l. push_back(1); // l. push_back(2); l. push_front(7); l. push_front(8); l. push_front(9); l.show(); // List(l). show(); } it works ... but the output is : List [3 ]:{ 0,134520896,9484585}

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  • BST insert operation. don't insert a node if a duplicate exists already

    - by jeev
    the following code reads an input array, and constructs a BST from it. if the current arr[i] is a duplicate, of a node in the tree, then arr[i] is discarded. count in the struct node refers to the number of times a number appears in the array. fi refers to the first index of the element found in the array. after the insertion, i am doing a post-order traversal of the tree and printing the data, count and index (in this order). the output i am getting when i run this code is: 0 0 7 0 0 6 thank you for your help. Jeev struct node{ int data; struct node *left; struct node *right; int fi; int count; }; struct node* binSearchTree(int arr[], int size); int setdata(struct node**node, int data, int index); void insert(int data, struct node **root, int index); void sortOnCount(struct node* root); void main(){ int arr[] = {2,5,2,8,5,6,8,8}; int size = sizeof(arr)/sizeof(arr[0]); struct node* temp = binSearchTree(arr, size); sortOnCount(temp); } struct node* binSearchTree(int arr[], int size){ struct node* root = (struct node*)malloc(sizeof(struct node)); if(!setdata(&root, arr[0], 0)) fprintf(stderr, "root couldn't be initialized"); int i = 1; for(;i<size;i++){ insert(arr[i], &root, i); } return root; } int setdata(struct node** nod, int data, int index){ if(*nod!=NULL){ (*nod)->fi = index; (*nod)->left = NULL; (*nod)->right = NULL; return 1; } return 0; } void insert(int data, struct node **root, int index){ struct node* new = (struct node*)malloc(sizeof(struct node)); setdata(&new, data, index); struct node** temp = root; while(1){ if(data<=(*temp)->data){ if((*temp)->left!=NULL) *temp=(*temp)->left; else{ (*temp)->left = new; break; } } else if(data>(*temp)->data){ if((*temp)->right!=NULL) *temp=(*temp)->right; else{ (*temp)->right = new; break; } } else{ (*temp)->count++; free(new); break; } } } void sortOnCount(struct node* root){ if(root!=NULL){ sortOnCount(root->left); sortOnCount(root->right); printf("%d %d %d\n", (root)->data, (root)->count, (root)->fi); } }

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  • Data tweaking code runs fine when executed directly - but never stops when used in trigger

    - by MBaas
    I have written some code to ensure that items on an order are all numbered (the "position number" or "item number" has been introduced only recently and we did not want to go and change all related code - as it is "asthetics only" and has no functional impact.) So, the idea is to go and check for an records that jave an itemno of NULL or 0 - and then compute one and assign it. When executing this code in a query window, it works fine. When putting it into an AFTER INSERT-trigger, it loops forever. So what is wrong here? /****** Objekt: Trigger [SetzePosNr] Skriptdatum: 02/28/2010 20:06:29 ******/ SET ANSI_NULLS ON GO SET QUOTED_IDENTIFIER ON GO CREATE TRIGGER [SetzePosNr] ON [dbo].[bestellpos] AFTER INSERT AS BEGIN DECLARE @idb int DECLARE @idp int DECLARE @pnr int SELECT @idp=id,@idb=id_bestellungen FROM bestellpos WHERE posnr IS NULL OR posnr=0 WHILE @idp IS NOT NULL BEGIN SELECT @pnr = 1+max(posnr) FROM bestellpos WHERE id_bestellungen = @idb print( 'idp=' + str(@idp) + ', idb=' + str(@idb) + ', posnr=' + str(@pnr)) UPDATE bestellpos SET posnr=@pnr WHERE id=@idp SELECT @idp=id,@idb=id_bestellungen FROM bestellpos WHERE posnr IS NULL OR posnr=0 END END

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  • How to: WCF XML-RPC client?

    - by mr.b
    I have built my own little custom XML-RPC server, and since I'd like to keep things simple, on both server and client side, what I would like to accomplish is to create a simplest possible client (in C# preferably) using WCF. Let's say that Contract for service exposed via XML-RPC is as follows: [ServiceContract] public interface IContract { [OperationContract(Action="Ping")] string Ping(); // server returns back string "Pong" [OperationContract(Action="Echo")] string Echo(string message); // server echoes back whatever message is } So, there are two example methods, one without any arguments, and another with simple string argument, both returning strings (just for sake of example). Service is exposed via http. Aaand, what's next? :) P.S. I have tried googling around for samples and similar, but all that I could come up with are some blog-related samples that use existing (and very big/numerous) classes, which implement appropriate IContract (or IBlogger) interfaces, so that most of what I am interested is hidden below several layers of abstraction...

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  • CreateDIBSection is throwing, when trying to create cursor on Win

    - by Anaamika
    Hi, I am trying to create Cursor from png, and CreateDIBSection() is throwing. Follwoing is the snippet of code: HDC hdc = GetDC(NULL); void* lpBits = NULL; HBITMAP hBitmap; try { hBitmap = CreateDIBSection( hdc, (BITMAPINFO*)&bi, 0, &lpBits, NULL, (DWORD)0); } ReleaseDC(NULL, hdc); As CreateDIBSection is throwing, the code to release DC is not getting executed. can you please let me know the possible issue behind this?

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  • Parallel Classloading Revisited: Fully Concurrent Loading

    - by davidholmes
    Java 7 introduced support for parallel classloading. A description of that project and its goals can be found here: http://openjdk.java.net/groups/core-libs/ClassLoaderProposal.html The solution for parallel classloading was to add to each class loader a ConcurrentHashMap, referenced through a new field, parallelLockMap. This contains a mapping from class names to Objects to use as a classloading lock for that class name. This was then used in the following way: protected Class loadClass(String name, boolean resolve) throws ClassNotFoundException { synchronized (getClassLoadingLock(name)) { // First, check if the class has already been loaded Class c = findLoadedClass(name); if (c == null) { long t0 = System.nanoTime(); try { if (parent != null) { c = parent.loadClass(name, false); } else { c = findBootstrapClassOrNull(name); } } catch (ClassNotFoundException e) { // ClassNotFoundException thrown if class not found // from the non-null parent class loader } if (c == null) { // If still not found, then invoke findClass in order // to find the class. long t1 = System.nanoTime(); c = findClass(name); // this is the defining class loader; record the stats sun.misc.PerfCounter.getParentDelegationTime().addTime(t1 - t0); sun.misc.PerfCounter.getFindClassTime().addElapsedTimeFrom(t1); sun.misc.PerfCounter.getFindClasses().increment(); } } if (resolve) { resolveClass(c); } return c; } } Where getClassLoadingLock simply does: protected Object getClassLoadingLock(String className) { Object lock = this; if (parallelLockMap != null) { Object newLock = new Object(); lock = parallelLockMap.putIfAbsent(className, newLock); if (lock == null) { lock = newLock; } } return lock; } This approach is very inefficient in terms of the space used per map and the number of maps. First, there is a map per-classloader. As per the code above under normal delegation the current classloader creates and acquires a lock for the given class, checks if it is already loaded, then asks its parent to load it; the parent in turn creates another lock in its own map, checks if the class is already loaded and then delegates to its parent and so on till the boot loader is invoked for which there is no map and no lock. So even in the simplest of applications, you will have two maps (in the system and extensions loaders) for every class that has to be loaded transitively from the application's main class. If you knew before hand which loader would actually load the class the locking would only need to be performed in that loader. As it stands the locking is completely unnecessary for all classes loaded by the boot loader. Secondly, once loading has completed and findClass will return the class, the lock and the map entry is completely unnecessary. But as it stands, the lock objects and their associated entries are never removed from the map. It is worth understanding exactly what the locking is intended to achieve, as this will help us understand potential remedies to the above inefficiencies. Given this is the support for parallel classloading, the class loader itself is unlikely to need to guard against concurrent load attempts - and if that were not the case it is likely that the classloader would need a different means to protect itself rather than a lock per class. Ultimately when a class file is located and the class has to be loaded, defineClass is called which calls into the VM - the VM does not require any locking at the Java level and uses its own mutexes for guarding its internal data structures (such as the system dictionary). The classloader locking is primarily needed to address the following situation: if two threads attempt to load the same class, one will initiate the request through the appropriate loader and eventually cause defineClass to be invoked. Meanwhile the second attempt will block trying to acquire the lock. Once the class is loaded the first thread will release the lock, allowing the second to acquire it. The second thread then sees that the class has now been loaded and will return that class. Neither thread can tell which did the loading and they both continue successfully. Consider if no lock was acquired in the classloader. Both threads will eventually locate the file for the class, read in the bytecodes and call defineClass to actually load the class. In this case the first to call defineClass will succeed, while the second will encounter an exception due to an attempted redefinition of an existing class. It is solely for this error condition that the lock has to be used. (Note that parallel capable classloaders should not need to be doing old deadlock-avoidance tricks like doing a wait() on the lock object\!). There are a number of obvious things we can try to solve this problem and they basically take three forms: Remove the need for locking. This might be achieved by having a new version of defineClass which acts like defineClassIfNotPresent - simply returning an existing Class rather than triggering an exception. Increase the coarseness of locking to reduce the number of lock objects and/or maps. For example, using a single shared lockMap instead of a per-loader lockMap. Reduce the lifetime of lock objects so that entries are removed from the map when no longer needed (eg remove after loading, use weak references to the lock objects and cleanup the map periodically). There are pros and cons to each of these approaches. Unfortunately a significant "con" is that the API introduced in Java 7 to support parallel classloading has essentially mandated that these locks do in fact exist, and they are accessible to the application code (indirectly through the classloader if it exposes them - which a custom loader might do - and regardless they are accessible to custom classloaders). So while we can reason that we could do parallel classloading with no locking, we can not implement this without breaking the specification for parallel classloading that was put in place for Java 7. Similarly we might reason that we can remove a mapping (and the lock object) because the class is already loaded, but this would again violate the specification because it can be reasoned that the following assertion should hold true: Object lock1 = loader.getClassLoadingLock(name); loader.loadClass(name); Object lock2 = loader.getClassLoadingLock(name); assert lock1 == lock2; Without modifying the specification, or at least doing some creative wordsmithing on it, options 1 and 3 are precluded. Even then there are caveats, for example if findLoadedClass is not atomic with respect to defineClass, then you can have concurrent calls to findLoadedClass from different threads and that could be expensive (this is also an argument against moving findLoadedClass outside the locked region - it may speed up the common case where the class is already loaded, but the cost of re-executing after acquiring the lock could be prohibitive. Even option 2 might need some wordsmithing on the specification because the specification for getClassLoadingLock states "returns a dedicated object associated with the specified class name". The question is, what does "dedicated" mean here? Does it mean unique in the sense that the returned object is only associated with the given class in the current loader? Or can the object actually guard loading of multiple classes, possibly across different class loaders? So it seems that changing the specification will be inevitable if we wish to do something here. In which case lets go for something that more cleanly defines what we want to be doing: fully concurrent class-loading. Note: defineClassIfNotPresent is already implemented in the VM as find_or_define_class. It is only used if the AllowParallelDefineClass flag is set. This gives us an easy hook into existing VM mechanics. Proposal: Fully Concurrent ClassLoaders The proposal is that we expand on the notion of a parallel capable class loader and define a "fully concurrent parallel capable class loader" or fully concurrent loader, for short. A fully concurrent loader uses no synchronization in loadClass and the VM uses the "parallel define class" mechanism. For a fully concurrent loader getClassLoadingLock() can return null (or perhaps not - it doesn't matter as we won't use the result anyway). At present we have not made any changes to this method. All the parallel capable JDK classloaders become fully concurrent loaders. This doesn't require any code re-design as none of the mechanisms implemented rely on the per-name locking provided by the parallelLockMap. This seems to give us a path to remove all locking at the Java level during classloading, while retaining full compatibility with Java 7 parallel capable loaders. Fully concurrent loaders will still encounter the performance penalty associated with concurrent attempts to find and prepare a class's bytecode for definition by the VM. What this penalty is depends on the number of concurrent load attempts possible (a function of the number of threads and the application logic, and dependent on the number of processors), and the costs associated with finding and preparing the bytecodes. This obviously has to be measured across a range of applications. Preliminary webrevs: http://cr.openjdk.java.net/~dholmes/concurrent-loaders/webrev.hotspot/ http://cr.openjdk.java.net/~dholmes/concurrent-loaders/webrev.jdk/ Please direct all comments to the mailing list [email protected].

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  • How to implement "circular side-scrolling" in my game?

    - by Mr.Gando
    I'm developing a game, a big part of this game, is about scrolling a "circular" background ( the right end of the Background Image can connect with the left start of the Background image ). Should be something like this: ( Entity moving and arrow to show where the background should start to repeat ) This happens in order to allow to have an Entity walking, and the background repeating itself over and over again. I'm not working with tile-maps, the background is a simple Texture (400x300 px). Could anyone point me to a link , or tell me the best way I could accomplish this ? Thanks a lot.

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