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• C# Web Service gets stuck waiting for lock, does not return

  - by blue

  We have a C#(2.0) application which talks to our server(in java) via web services. Lately we have started seeing following behavior in (ONLY)one of our lab machines(XP): Once in a while(every few days), one of the webservice request will just get stuck, will not return or timeout. Following is the stacktrace where it seem to be stuck. Have no clue what is going on here. Any pointer would be of great help. ESP EIP 05eceeec 7c90eb94 [GCFrame: 05eceeec] 05ecefbc 7c90eb94 [HelperMethodFrame_1OBJ: 05ecefbc] System.Threading.Monitor.Enter(System.Object) 05ecf014 7a5b0034 System.Net.ConnectionGroup.Disassociate(System.Net.Connection) 05ecf040 7a5aeaa7 System.Net.Connection.PrepareCloseConnectionSocket(System.Net.ConnectionReturnResult ByRef) 05ecf0a4 7a5ac0e1 System.Net.Connection.ReadStartNextRequest(System.Net.WebRequest, System.Net.ConnectionReturnResult ByRef) 05ecf0e8 7a5b1119 System.Net.ConnectStream.CallDone(System.Net.ConnectionReturnResult) 05ecf0fc 7a5b3b5a System.Net.ConnectStream.ReadChunkedSync(Byte[], Int32, Int32) 05ecf114 7a5b2b90 System.Net.ConnectStream.ReadWithoutValidation(Byte[], Int32, Int32, Boolean) 05ecf160 7a5b29cc System.Net.ConnectStream.Read(Byte[], Int32, Int32) 05ecf1a0 79473cab System.IO.StreamReader.ReadBuffer(Char[], Int32, Int32, Boolean ByRef) 05ecf1c4 79473bd6 System.IO.StreamReader.Read(Char[], Int32, Int32) 05ecf1e8 69c29119 System.Xml.XmlTextReaderImpl.ReadData() 05ecf1f8 69c2ad70 System.Xml.XmlTextReaderImpl.ParseDocumentContent() 05ecf20c 69c292d7 System.Xml.XmlTextReaderImpl.Read() 05ecf21c 69c2929d System.Xml.XmlTextReader.Read() 05ecf220 6991b3e7 System.Web.Services.Protocols.SoapHttpClientProtocol.ReadResponse(System.Web.Services.Protocols.SoapClientMessage, System.Net.WebResponse, System.IO.Stream, Boolean) 05ecf268 69919ed1 System.Web.Services.Protocols.SoapHttpClientProtocol.Invoke(System.String, System.Object[])

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• Drawing an image is completely out

  - by ct2k7

  Hi I'm using this code below to let a user "draw" their signature on a UIView component on my app: UIGraphicsBeginImageContext(signature.frame.size); [drawImage.image drawInRect:CGRectMake(0, 0, signature.frame.size.width, signature.frame.size.height)]; CGContextSetLineCap(UIGraphicsGetCurrentContext(), kCGLineCapRound); CGContextSetLineWidth(UIGraphicsGetCurrentContext(), 5.0); CGContextSetRGBStrokeColor(UIGraphicsGetCurrentContext(), 1.0, 0.0, 0.0, 1.0); CGContextMoveToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y); CGContextAddLineToPoint(UIGraphicsGetCurrentContext(), lastPoint.x, lastPoint.y); CGContextStrokePath(UIGraphicsGetCurrentContext()); CGContextFlush(UIGraphicsGetCurrentContext()); drawImage.image = UIGraphicsGetImageFromCurrentImageContext(); UIGraphicsEndImageContext() The issue I am having is that the drawing is not only is the drawing not in line with the pointer when in use in the simulator, the image is going outside of the designated UIView compontent and is getting smaller/out of focus the more I draw, as you can see in this image: And after a few lines, showing the boundaries of the exact are of where I can draw: Any ideas on what's happening here? lastPoint.y is defined as: lastPoint.y -= 20; Any ideas on what on earth is happening here?

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• List local printers

  - by vladimir

  hi all, i am using this routine to list the local printers installed on on a machine... var p: pointer; hpi: _PRINTER_INFO_2A; hGlobal: cardinal; dwNeeded, dwReturned: DWORD; bFlag: boolean; i: dword; begin p := nil; EnumPrinters(PRINTER_ENUM_LOCAL, nil, 2, p, 0, dwNeeded, dwReturned); if (dwNeeded = 0) then exit; GetMem(p,dwNeeded); if (p = nil) then exit; bFlag := EnumPrinters(PRINTER_ENUM_LOCAL, nil, 2, p, dwneeded, dwNeeded, dwReturned); if (not bFlag) then exit; CbLblPrinterPath.Properties.Items.Clear; for i := 0 to dwReturned - 1 do begin CbLblPrinterPath.Properties.Items.Add(TPrinterInfos(p^)[i].pPrinterName); end; FreeMem(p); TPrinterInfos(p^)[i].pPrinterName returns a 'P' for printer name. i have a PdfCreator installed as a printer. TPrinterInfos is an array of _PRINTER_INFO_2A. how can i fix this?

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• Is there a fundamental difference between malloc and HeapAlloc (aside from the portability)?

  - by Lambert

  Hi, I'm having code that, for various reasons, I'm trying to port from the C runtime to one that uses the Windows Heap API. I've encountered a problem: If I redirect the malloc/calloc/realloc/free calls to HeapAlloc/HeapReAlloc/HeapFree (with GetProcessHeap for the handle), the memory seems to be allocated correctly (no bad pointer returned, and no exceptions thrown), but the library I'm porting says "failed to allocate memory" for some reason. I've tried this both with the Microsoft CRT (which uses the Heap API underneath) and with another company's run-time library (which uses the Global Memory API underneath); the malloc for both of those works well with the library, but for some reason, using the Heap API directly doesn't work. I've checked that the allocations aren't too big (= 0x7FFF8 bytes), and they're not. The only problem I can think of is memory alignment; is that the case? Or other than that, is there a fundamental difference between the Heap API and the CRT memory API that I'm not aware of? If so, what is it? And if not, then why does the static Microsoft CRT (included with Visual Studio) take some extra steps in malloc/calloc before calling HeapAlloc? I'm suspecting there's a difference but I can't think of what it might be. Thank you!

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• Reading serialised object from file

  - by nico

  Hi everyone. I'm writing a little Java program (it's an ImageJ plugin, but the problem is not specifically ImageJ related) and I have some problem, most probably due to the fact that I never really programmed in Java before... So, I have a Vector of Vectors and I'm trying to save it to a file and read it. The variable is defined as: Vector <Vector <myROI> > ROIs = new Vector <Vector <myROI> >(); where myROI is a class that I previously defined. Now, to write the vector to a file I use: void saveROIs() { SaveDialog save = new SaveDialog("Save ROIs...", imp.getTitle(), ".xroi"); String name = save.getFileName(); if (name == null) return; String dir = save.getDirectory(); try { FileOutputStream fos = new FileOutputStream(dir+name); ObjectOutputStream oos = new ObjectOutputStream(fos); oos.writeObject(ROIs); oos.close(); } catch (Exception e) { IJ.log(e.toString()); } } This correctly generates a binary file containing (I suppose) the object ROIs. Now, I use a very similar code to read the file: void loadROIs() { OpenDialog open = new OpenDialog("Load ROIs...", imp.getTitle(), ".xroi"); String name = open.getFileName(); if (name == null) return; String dir = open.getDirectory(); try { FileInputStream fin = new FileInputStream(dir+name); ObjectInputStream ois = new ObjectInputStream(fin); ROIs = (Vector <Vector <myROI> >) ois.readObject(); // This gives error ois.close(); } catch (Exception e) { IJ.log(e.toString()); } } But this function does not work. First, I get a warning: warning: [unchecked] unchecked cast found : java.lang.Object required: java.util.Vector<java.util.Vector<myROI>> ROIs = (Vector <Vector <myROI> >) ois.readObject(); ^ I Googled for that and see that I can suppress by prepending @SuppressWarnings("unchecked"), but this just makes things worst, as I get an error: <identifier> expected ROIs = (Vector <Vector <myROI> >) ois.readObject(); ^ In any case, if I omit @SuppressWarnings and ignore the warning, the object is not read and an exception is thrown java.io.WriteAbortedException: writing aborted; java.io.NotSerializableException: myROI Again Google tells me myROI needs to implements Serializable. I tried just adding implements Serializable to the class definition, but it is not sufficient. Can anyone give me some hints on how to procede in this case? Also, how to get rid of the typecast warning?

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• Expand chaining hashtable. Errors on code.

  - by FILIaS

  Expanding a hashtable with linked lists there are some errors and warnings. I wanna make sure that the following code is right (expand method) and find out what happens that raise these warnings/errors typedef struct { int length; struct List *head; struct List *tail; } HashTable; //resolving collisions using linked lists - chaining typedef struct { char *number; char *name; int time; struct List *next; }List; //on the insert method i wanna check hashtable's size, //if it seems appropriate there is the following code: //Note: hashtable variable is: Hashtable * ...... hashtable = expand(hashtable,number,name,time); /**WARNING**:assignment makes pointer from integer without a cast*/ HashTable* expand( HashTable* h ,char number[10],char* name,int time) /**error**: conflicting types for ‘expand’ previous implicit declaration of ‘expand’ was here*/ { HashTable* new; int n; clientsList *node,*next; PrimesIndex++; int new_size= primes[PrimesIndex]; /* double the size,odd length */ if (!(new=malloc((sizeof( List*))*new_size))) return NULL; for(n=0; n< h->length; ++n) { for(node=h[n].head; node; node=next) { add (&new, node->number, node->name,node->time); next=node->next;//// free(node); } } free(h); return new; }

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• Trouble with Code First DatabaseGenerated Composite Primary Key

  - by Nick Fleetwood

  This is a tad complicated, and please, I know all the arguments against natural PK's, so we don't need to have that discussion. using VS2012/MVC4/C#/CodeFirst So, the PK is based on the date and a corresponding digit together. So, a few rows created today would be like this: 20131019 1 20131019 2 And one created tomorrow: 20131020 1 This has to be automatically generated using C# or as a trigger or whatever. The user wouldn't input this. I did come up with a solution, but I'm having problems with it, and I'm a little stuck, hence the question. So, I have a model: public class MainOne { //[Key] //public int ID { get; set; } [Key][Column(Order=1)] [DatabaseGenerated(DatabaseGeneratedOption.None)] public string DocketDate { get; set; } [Key][Column(Order=2)] [DatabaseGenerated(DatabaseGeneratedOption.None)] public string DocketNumber { get; set; } [StringLength(3, ErrorMessage = "Corp Code must be three letters")] public string CorpCode { get; set; } [StringLength(4, ErrorMessage = "Corp Code must be four letters")] public string DocketStatus { get; set; } } After I finish the model, I create a new controller and views using VS2012 scaffolding. Then, what I'm doing is debugging to create the database, then adding the following instead of trigger after Code First creates the DB [I don't know if this is correct procedure]: CREATE TRIGGER AutoIncrement_Trigger ON [dbo].[MainOnes] instead OF INSERT AS BEGIN DECLARE @number INT SELECT @number=COUNT(*) FROM [dbo].[MainOnes] WHERE [DocketDate] = CONVERT(DATE, GETDATE()) INSERT INTO [dbo].[MainOnes] (DocketDate,DocketNumber,CorpCode,DocketStatus) SELECT (CONVERT(DATE, GETDATE ())),(@number+1),inserted.CorpCode,inserted.DocketStatus FROM inserted END And when I try to create a record, this is the error I'm getting: The changes to the database were committed successfully, but an error occurred while updating the object context. The ObjectContext might be in an inconsistent state. Inner exception message: The object state cannot be changed. This exception may result from one or more of the primary key properties being set to null. Non-Added objects cannot have null primary key values. See inner exception for details. Now, what's interesting to me, is that after I stop debugging and I start again, everything is perfect. The trigger fired perfectly, so the composite PK is unique and perfect, and the data in other columns is intact. My guess is that EF is confused by the fact that there is seemingly no value for the PK until AFTER an insert command is given. Also, appearing to back this theory, is that when I try to edit on of the rows, in debug, I get the following error: The number of primary key values passed must match number of primary key values defined on the entity. Same error occurs if I try to pull the 'Details' or 'Delete' function. Any solution or ideas on how to pull this off? I'm pretty open to anything, even creating a hidden int PK. But it would seem redundant. EDIT 21OCT13 [HttpPost] public ActionResult Create(MainOne mainone) { if (ModelState.IsValid) { var countId = db.MainOnes.Count(d => d.DocketDate == mainone.DocketNumber); //assuming that the date field already has a value mainone.DocketNumber = countId + 1; //Cannot implicitly convert type int to string db.MainOnes.Add(mainone); db.SaveChanges(); return RedirectToAction("Index"); } return View(mainone); } EDIT 21OCT2013 FINAL CODE SOLUTION For anyone like me, who is constantly searching for clear and complete solutions. if (ModelState.IsValid) { String udate = DateTime.UtcNow.ToString("yyyy-MM-dd"); mainone.DocketDate = udate; var ddate = db.MainOnes.Count(d => d.DocketDate == mainone.DocketDate); //assuming that the date field already has a value mainone.DocketNumber = ddate + 1; db.MainOnes.Add(mainone); db.SaveChanges(); return RedirectToAction("Index"); }

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• Linux C debugging library to detect memory corruptions

  - by calandoa

  When working sometimes ago on an embedded system with a simple MMU, I used to program dynamically this MMU to detect memory corruptions. For instance, at some moment at runtime, the foo variable was overwritten with some unexpected data (probably by a dangling pointer or whatever). So I added the additional debugging code : at init, the memory used by foo was indicated as a forbidden region to the MMU; each time foo was accessed on purpose, access to the region was allowed just before then forbidden just after; a MMU irq handler was added to dump the master and the address responsible of the violation. This was actually some kind of watchpoint, but directly self-handled by the code itself. Now, I would like to reuse the same trick, but on a x86 platform. The problem is that I am very far from understanding how is working the MMU on this platform, and how it is used by Linux, but I wonder if any library/tool/system call already exist to deal with this problem. Note that I am aware that various tools exist like Valgrind or GDB to manage memory problems, but as far as I know, none of these tools car be dynamically reconfigured by the debugged code. I am mainly interested for user space under Linux, but any info on kernel mode or under Windows is also welcome!

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• UITextView doesn't not resize when keyboard appear if loaded from a tab bar cotroller

  - by elio.d

  I have a simple view controller (SecondViewController) used to manage a UITextview (I'm building a simple editor) this is the code of the SecondViewController.h @interface SecondViewController : UIViewController { IBOutlet UITextView *textView; } @property (nonatomic,retain) IBOutlet UITextView *textView; @end and this is the SecondViewController.m // // EditorViewController.m // Editor // // Created by elio d'antoni on 13/01/11. // Copyright 2011 none. All rights reserved. // @implementation SecondViewController @synthesize textView; /* // Implement loadView to create a view hierarchy programmatically, without using a nib. - (void)loadView { } */ // Implement viewDidLoad to do additional setup after loading the view, typically from a nib. - (void)viewDidLoad { [super viewDidLoad]; self.view.backgroundColor = [UIColor colorWithPatternImage:[UIImage imageNamed:@"uiViewBg.png"]]; textView.layer.borderWidth=1; textView.layer.cornerRadius=5; textView.layer.borderColor=[[UIColor darkGrayColor] CGColor]; [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardWillAppear:) name:UIKeyboardWillShowNotification object:nil]; [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(keyboardWillDisappear:) name:UIKeyboardWillHideNotification object:nil]; } -(void) matchAnimationTo:(NSDictionary *) userInfo { NSLog(@"match animation method"); [UIView setAnimationDuration:[[userInfo objectForKey:UIKeyboardAnimationDurationUserInfoKey] doubleValue]]; [UIView setAnimationCurve:[[userInfo objectForKey:UIKeyboardAnimationCurveUserInfoKey] intValue]]; } -(CGFloat) keyboardEndingFrameHeight:(NSDictionary *) userInfo { NSLog(@"keyboardEndingFrameHeight method"); CGRect keyboardEndingUncorrectedFrame = [[ userInfo objectForKey:UIKeyboardFrameEndUserInfoKey ] CGRectValue]; CGRect keyboardEndingFrame = [self.view convertRect:keyboardEndingUncorrectedFrame fromView:nil]; return keyboardEndingFrame.size.height; } -(CGRect) adjustFrameHeightBy:(CGFloat) change multipliedBy:(NSInteger) direction { NSLog(@"adjust method"); return CGRectMake(20, 57, self.textView.frame.size.width, self.textView.frame.size.height + change * direction); } -(void)keyboardWillAppear:(NSNotification *)notification { NSLog(@"keyboard appear"); [UIView beginAnimations:nil context:NULL]; [self matchAnimationTo:[notification userInfo]]; self.textView.frame = [self adjustFrameHeightBy:[self keyboardEndingFrameHeight: [notification userInfo]] multipliedBy:-1]; [UIView commitAnimations]; } -(void)keyboardWillDisappear:(NSNotification *) notification { NSLog(@"keyboard disappear"); [UIView beginAnimations:nil context:NULL]; [self matchAnimationTo:[notification userInfo]]; self.textView.frame = [self adjustFrameHeightBy:[self keyboardEndingFrameHeight: [notification userInfo]] multipliedBy:1]; [UIView commitAnimations]; } // Override to allow orientations other than the default portrait orientation. - (BOOL)shouldAutorotateToInterfaceOrientation:(UIInterfaceOrientation)interfaceOrientation { return YES; } (void)didReceiveMemoryWarning { // Releases the view if it doesn't have a superview. [super didReceiveMemoryWarning]; // Release any cached data, images, etc that aren't in use. } (void)viewDidUnload { // Release any retained subviews of the main view. // e.g. self.myOutlet = nil; } (void)dealloc { [super dealloc]; } @end the problem is that if load the view controller from a tab bar controller the textView doesn't resize when the keyboard appear, but the SAME code works if loaded as a single view based app. I hope I was clear enough. I used the tabBar template provided by xcode no modifications.

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• css Checkbox Label Selector

  - by HW90

  I'm developing a MVC3 application and need to select the checkboxes label. In ASP MVC3 you have helper methods which creat a part of the code. So the code for a checkbox looks like this: <input id="Jumping_successleicht" type="checkbox" value="true" name="Jumping_successleicht"> <input type="hidden" value="false" name="Jumping_successleicht"> <label for="Jumping_successleicht"> <span>leicht (4)</span> </label> Now I've thought I can use following code to select the label: input[type=checkbox] + label { background: url("../../Images/Controls/Checkbox.png") no-repeat scroll left center transparent; clear: none; cursor: pointer; margin: 0; padding: 5px 0 4px 24px; } But it does not work. It looks like label and input have to be next to each other. Does any ony have a solution how to solve this problem?

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• Problems using (building?) native gem extensions on OS X

  - by goodmike

  I am having trouble with some of my rubygems, in particular those that use native extensions. I am on a MacBookPro, with Snow Leopard. I have XCode 3.2.1 installed, with gcc 4.2.1. Ruby 1.8.6, because I'm lazy and a scaredy cat and don't want to upgrade yet. Ruby is running in 32-bit mode. I built this ruby from scratch when my MBP ran OSX 10.4. When I require one of the affected gems in irb, I get a Load Error for the gem extension's bundle file. For example, here's nokogigi dissing me: > require 'rubygems' = true > require 'nokogiri' LoadError: Failed to load /usr/local/lib/ruby/gems/1.8/gems/nokogiri-1.4.1/lib/nokogiri/nokogiri.bundle This is also happening with the Postgres pg and MongoDB mongo gems. My first thought was that the extensions must not be building right. But gem install wasn't throwing any errors. So I reinstalled with the verbose flag, hoping to see some helpful warnings. I've put the output in a Pastie, and the only warning I see is a consistent one about "passing argument n of ‘foo’ with different width due to prototype." I suspect that this might be an issue from upgrading to Snow Leopard, but I'm a little surprised to experience it now, since I've updated my XCode. Could it stem from running Ruby in 1.8.6? I'm embarrassed that I don't know quite enough about my Mac and OSX to know where to look next, so any guidance, even just a pointer to some document I couldn't find via Google, would be most welcome. Michael

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• c++ File input/output

  - by Myx

  Hi: I am trying to read from a file using fgets and sscanf. In my file, I have characters on each line of the while which I wish to put into a vector. So far, I have the following: FILE *fp; fp = fopen(filename, "r"); if(!fp) { fprintf(stderr, "Unable to open file %s\n", filename); return 0; } // Read file int line_count = 0; char buffer[1024]; while(fgets(buffer, 1023, fp)) { // Increment line counter line_count++; char *bufferp = buffer; ... while(*bufferp != '\n') { char *tmp; if(sscanf(bufferp, "%c", tmp) != 1) { fprintf(stderr, "Syntax error reading axiom on " "line %d in file %s\n", line_count, filename); return 0; } axiom.push_back(tmp); printf("put %s in axiom vector\n", axiom[axiom.size()-1]); // increment buffer pointer bufferp++; } } my axiom vector is defined as vector<char *> axiom;. When I run my program, I get a seg fault. It happens when I do the sscanf. Any suggestions on what I'm doing wrong?

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• How perform USort() on an Array of Objects class definition as a method?

  - by user558724

  class Contact{ public $name; public $bgcolor; public $lgcolor; public $email; public $element; public function __construct($name, $bgcolor, $lgcolor, $email, $element) { $this->name = $name; $this->bgcolor = $bgcolor; $this->lgcolor = $lgcolor; $this->email = $email; $this->element = $element; } public static function sortByName(Contact $p1, Contact $p2) { return strcmp($p1->name, $p2->name); } } class ContactList implements Iterator, ArrayAccess { protected $_label; protected $_contacts = array(); public function __construct($label) { $this->_label = $label; } public function getLabel() { return $this->_label; } public function addContact(Contact $contact) { $this->_contacts[] = $contact; } public function current() { return current($this->_contacts); } public function key() { return key($this->_contacts); } public function next() { return next($this->_contacts); } public function rewind() { return reset($this->_contacts); } public function valid() { return current($this->_contacts); } public function offsetGet($offset) { return $this->_contacts[$offset]; } public function offsetSet($offset, $data) { if (!$data instanceof Contact) throw new InvalidArgumentException('Only Contact objects allowed in a ContactList'); if ($offset == '') { $this->_contacts[] = $data; } else { $this->_contacts[$offset] = $data; } } public function offsetUnset($offset) { unset($this->_contacts[$offset]); } public function offsetExists($offset) { return isset($this->_contacts[$offset]); } public function sort($attribute = 'name') { $sortFct = 'sortBy' . ucfirst(strtolower($attribute)); if (!in_array($sortFct, get_class_methods('Contact'))) { throw new Exception('contact->sort(): Can\'t sort by ' . $attribute); } usort($this->contact, 'ContactList::' . $sortFct); } } public function Sort($property, $asc=true) { // this is where sorting logic takes place $_pd = $this->_contact->getProperty($property); if ($_pd == null) { user_error('Property '.$property.' does not exist in class '.$this->_contact->getName(), E_WARNING); return; } // set sortDescriptor ContactList::$sortProperty = $_pd; // and apply sorting usort($this->_array, array('ContactList', ($asc?'USortAsc':'USortDesc'))); } function getItems(){ return $this->_array; } class SortableItem extends ContactList { static public $sortProperty; static function USortAsc($a, $b) { /*@var $_pd ReflectionProperty*/ /* $_pd = self::$sortProperty; if ($_pd !== null) { if ($_pd->getValue($a) === $_pd->getValue($b)) return 0; else return (($_pd->getValue($a) < $_pd->getValue($b))?-1:1); } return 0; } static function USortDesc($a, $b) { return -(self::USortAsc($a,$b)); } } This approach keeps giving me PHP Warnings: usort() [function.usort]: of all kinds which I can provide later as needed to comment out those methods and definitions in order to test and fix some minor bugs of our program. **$billy parameters are already defined. $all -> addContact($billy); // --> ended up adding each contact manually above $all->Sort('name',true); $items = $all->getItems(); foreach($items as $contact) { echo $contact->__toString(); } $all->sort(); The reason for using usort is to re-arrange the order alphabetically by name but somehow is either stating that the function comparison needs to be an array or another errors which obviously I have seemed to pass. Any help would be greatly appreciated, thanks in advance.

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• Implementing a c/c++ style union as a column in MySQL

  - by user81338

  Friends, I have a strange need and cannot think my way through the problem. The great and mighty Google is of little help due to keyword recycling (as you'll see). Can you help? What I want to do is store data of multiple types in a single column in MySQL. This is the database equivalent to a C union (and if you search for MySQL and Union, you obviously get a whole bunch of stuff on the UNION keyword in SQL). [Contrived and simplified case follows] So, let us say that we have people - who have names - and STORMTROOPERS - who have TK numbers. You cannot have BOTH a NAME and a TK number. You're either BOB SMITH -or- TK409. In C I could express this as a union, like so: union { char * name; int tkNo; } EmperialPersonnelRecord; This makes it so that I am either storing a pointer to a char array or an ID in the type EmperialPersonnelRecord, but not both. I am looking for a MySQL equivalent on a column. My column would store either an int, double, or varchar(255) (or whatever combination). But would only take up the space of the largest element. Is this possible? (of course anything is possible given enough time, money and will - I mean is it possible if I am poor, lazy and on a deadline... aka "out of the box")

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• Implementing list position locator in C++?

  - by jfrazier

  I am writing a basic Graph API in C++ (I know libraries already exist, but I am doing it for the practice/experience). The structure is basically that of an adjacency list representation. So there are Vertex objects and Edge objects, and the Graph class contains: list<Vertex *> vertexList list<Edge *> edgeList Each Edge object has two Vertex* members representing its endpoints, and each Vertex object has a list of Edge* members representing the edges incident to the Vertex. All this is quite standard, but here is my problem. I want to be able to implement deletion of Edges and Vertices in constant time, so for example each Vertex object should have a Locator member that points to the position of its Vertex* in the vertexList. The way I first implemented this was by saving a list::iterator, as follows: vertexList.push_back(v); v->locator = --vertexList.end(); Then if I need to delete this vertex later, then rather than searching the whole vertexList for its pointer, I can call: vertexList.erase(v->locator); This works fine at first, but it seems that if enough changes (deletions) are made to the list, the iterators will become out-of-date and I get all sorts of iterator errors at runtime. This seems strange for a linked list, because it doesn't seem like you should ever need to re-allocate the remaining members of the list after deletions, but maybe the STL does this to optimize by keeping memory somewhat contiguous? In any case, I would appreciate it if anyone has any insight as to why this happens. Is there a standard way in C++ to implement a locator that will keep track of an element's position in a list without becoming obsolete? Much thanks, Jeff

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• OSMF seek with Amazon Cloudfront

  - by giorrrgio

  I've written a little OSMF player that streams via RTMP from Amazon Cloudfront. There's a known issue, the mp3 duration is not correctly readed from metadata and thus the seek function is not working. I know there's a workaround implying the use of getStreamLength function of NetConnection, which I successfully implemented in a previous non-OSMF player, but now I don't know how and when to call it, in terms of OSMF Events and Traits. This code is not working: protected function initApp():void { //the pointer to the media var resource:URLResource = new URLResource( STREAMING_PATH ); // Create a mediafactory instance mediaFactory = new DefaultMediaFactory(); //creates and sets the MediaElement (generic) with a resource and path element = mediaFactory.createMediaElement( resource ); var loadTrait:NetStreamLoadTrait = element.getTrait(MediaTraitType.LOAD) as NetStreamLoadTrait; loadTrait.addEventListener(LoaderEvent.LOAD_STATE_CHANGE, _onLoaded); player = new MediaPlayer( element ); //Marker 5: Add MediaPlayer listeners for media size and current time change player.addEventListener( DisplayObjectEvent.MEDIA_SIZE_CHANGE, _onSizeChange ); player.addEventListener( TimeEvent.CURRENT_TIME_CHANGE, _onProgress ); initControlBar(); } private function onGetStreamLength(result:Object):void { Alert.show("The stream length is " + result + " seconds"); duration = Number(result); } private function _onLoaded(e:LoaderEvent):void { if (e.newState == LoadState.READY) { var loadTrait:NetStreamLoadTrait = player.media.getTrait(MediaTraitType.LOAD) as NetStreamLoadTrait; if (loadTrait && loadTrait.netStream) { var responder:Responder = new Responder(onGetStreamLength); loadTrait.connection.call("getStreamLength", responder, STREAMING_PATH); } } }

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• Inheritance inside a template - public members become invisible?

  - by Juliano

  I'm trying to use inheritance among classes defined inside a class template (inner classes). However, the compiler (GCC) is refusing to give me access to public members in the base class. Example code: template <int D> struct Space { struct Plane { Plane(Space& b); virtual int& at(int y, int z) = 0; Space& space; /* <= this member is public */ }; struct PlaneX: public Plane { /* using Plane::space; */ PlaneX(Space& b, int x); int& at(int y, int z); const int cx; }; int& at(int x, int y, int z); }; template <int D> int& Space<D>::PlaneX::at(int y, int z) { return space.at(cx, y, z); /* <= but it fails here */ }; Space<4> sp4; The compiler says: file.cpp: In member function ‘int& Space::PlaneX::at(int, int)’: file.cpp:21: error: ‘space’ was not declared in this scope If using Plane::space; is added to the definition of class PlaneX, or if the base class member is accessed through the this pointer, or if class Space is changed to a non-template class, then the compiler is fine with it. I don't know if this is either some obscure restriction of C++, or a bug in GCC (GCC versions 4.4.1 and 4.4.3 tested). Does anyone have an idea?

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• How safe and reliable are C++ String Literals?

  - by DoctorT

  So, I'm wanting to get a better grasp on how string literals in C++ work. I'm mostly concerned with situations where you're assigning the address of a string literal to a pointer, and passing it around. For example: char* advice = "Don't stick your hands in the toaster."; Now lets say I just pass this string around by copying pointers for the duration of the program. Sure, it's probably not a good idea, but I'm curious what would actually be going on behind the scenes. For another example, let's say we make a function that returns a string literal: char* foo() { // function does does stuff return "Yikes!"; // somebody's feeble attempt at an error message } Now lets say this function is called very often, and the string literal is only used about half the time it's called: // situation #1: it's just randomly called without heed to the return value foo(); // situation #2: the returned string is kept and used for who knows how long char* retVal = foo(); In the first situation, what's actually happening? Is the string just created but not used, and never deallocated? In the second situation, is the string going to be maintained as long as the user finds need for it? What happens when it isn't needed anymore... will that memory be freed up then (assuming nothing points to that space anymore)? Don't get me wrong, I'm not planning on using string literals like this. I'm planning on using a container to keep my strings in check (probably std::string). I'm mostly just wanting to know if these situations could cause problems either for memory management or corrupted data.

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• openDatabase Hello World - 2

  - by cf_PhillipSenn

  This is a continuation from a previous stackoverflow question. I've renamed some variables so that I can tell what are keywords and what are names that I can control. Q: Why is the deleteRow function not working? <html> <head> <title>html5 openDatabase Hello World</title> <script src="http://www.google.com/jsapi"></script> <script type="text/javascript"> google.load("jquery", "1"); google.setOnLoadCallback(OnLoadCallback); function OnLoadCallback() { var dbo; dbo = openDatabase('HelloWorld'); dbo.transaction( function(T1) { T1.executeSql( 'CREATE TABLE IF NOT EXISTS myTable ' + ' (myTableID INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT, ' + ' Field1 TEXT NOT NULL );' ); } ); dbo.transaction(function(T2) { T2.executeSql('SELECT * FROM myTable',[], function (T6, result) { for (var i=0; i < result.rows.length; i++) { var row = result.rows.item(i); $('#savedData').append('<li id="'+row.myTableID+'">' + row.Field1 + '</li>'); } }, errorHandler); }); $('form').submit(function() { var xxx = $('#xxx').val(); dbo.transaction( function(T3) { T3.executeSql( 'INSERT INTO myTable (Field1) VALUES (?);', [xxx], function(){ $('#savedData').append('<li id="ThisisWhereIneedHELP">' + xxx + '</li>'); $('#xxx').val(''); }, errorHandler ); } ); return false; }); $('#savedData > li').live('click', function (){ deleteRow(this.id); $(this).remove(); }); } function deleteRow(myTableID) { alert('trying to delete'); dbo.transaction(function(T4) { T4.executeSql('DELETE FROM myTable WHERE myTableID = ?', [myTableID], function(){ alert('Deleted!'); }, errorHandler); }); } function errorHandler(T5, error) { alert('Oops. Error was '+error.message+' (Code '+error.code+')'); // T5.executeSql('INSERT INTO errors (code, message) VALUES (?, ?);', // [error.code, error.message]); return false; } </script> </head> <body> <form method="post"> <input name="xxx" id="xxx" /> <p> <input type="submit" name="OK" /> </p> <ul id="savedData"> </ul> </form> </body> </html>

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• HTC Incredible displaying blank ImageView

  - by Todd

  HI, I have an app that displays an an image in an ImageView using the setImageDrawable(Drawable) method. However, with the release of the Droid Incredible the images are coming up as a blank screen. I am using Drawable.createFromPath(Environment.getExternalStorageDirectory() + "\imagefile") to access the image from the SD card. I don't get any sort of error, just a black screen. I will get a null pointer exception if after trying to load the image I try to access a property of the Drawable. This makes me believe that the Drawable wasn't loaded, but I don't know why or how to make it work. This code as been working on all other Android devices, so I'm not sure what is different with the Incredible. Unfortunately I don't have access to an Incredible to test on, so I've got to rely on others to test and send me the log files. Any help you can offer would be greatly appreciated. If anyone knows how to replicate this issue on the emulator, that would be helpful too. I've configured an emulator with firmware 7 and the correct screen resolution, but I was unable to replicate the issue. Thanks.

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• Endianness and C API's: Specifically OpenSSL.

  - by Hassan Syed

  I have an algorithm that uses the following OpenSSL calls: HMAC_update() / HMAC_final() // ripe160 EVP_CipherUpdate() / EVP_CipherFinal() // cbc_blowfish These algorithm take a unsigned char * into the "plain text". My input data is comes from a C++ std::string::c_str() which originate from a protocol buffer object as a encoded UTF-8 string. UTF-8 strings are meant to be endian neutrial. However I'm a bit paranoid about how OpenSSL may perform operations on the data. My understanding is that encryption algorithms work on 8-bit blocks of data, and if a unsigned char * is used for pointer arithmetic when the operations are performed the algorithms should be endian neutral and I do not need to worry about anything. My uncertainty is compounded by the fact that I am working on a little-endian machine and have never done any real cross-architecture programming. My beliefs/reasoning are/is based on the following two properties std::string (not wstring) internally uses a 8-bit ptr and a the resulting c_str() ptr will itterate the same way regardless of the CPU architecture. Encryption algorithms are either by design, or by implementation, endian neutral. I know the best way to get a definitive answer is to use QEMU and do some cross-platform unit tests (which I plan to do). My question is a request for comments on my reasoning, and perhaps will assist other programmers when faced with similar problems.

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• scanf segfaults and various other anomalies inside while loop

  - by Shadow

  while(1){ //Command prompt char *command; printf("%s>",current_working_directory); scanf("%s",command);<--seg faults after input has been received. printf("\ncommand:%s\n",command); } I am getting a few different errors and they don't really seem reproducible(except for the segfault at this point .<). This code worked fine about 10 minutes ago, then it infinite looped the printf command and now it seg faults on the line mentioned above. The only thing I changed was scanf("%s",command); to what it currently is. If I change the command variable to be an array it works, obviously this is because the storage is set aside for it. 1) I got prosecuted about telling someone that they needed to malloc a pointer* (But that usually seems to solve the problem such as making it an array) 2) the command I am entering is "magic" 5 characters so there shouldn't be any crazy stack overflow. 3) I am running on mac OSX 10.6 with newest version of xCode(non-OS4) and standard gcc 4) this is how I compile the program: gcc --std=c99 -W sfs.c Just trying to figure out what is going on. Being this is for a school project I am never going to have to see again, I will just code some noob work around that would make my boss cry :) But for afterwards I would love to figure out why this is happening and not just make some fix for it, and if there is some fix for it why that fix works.

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• Approaches to replace cursor in pure AS3 / Flare project?

  - by peteorpeter

  Hi there good lookin, I've got a pure AS3 (no Flex) project that uses Flare to display and interact with a data visualization. I just implemented some panning behavior, so you can click and drag the visualization around, and now I'd like to give the user a visual indicator that this is possible, by switching the arrow cursor with a nice grabby-looking hand icon. The user can click and drag at any time except when the mouse is over a clickable node (at which time the cursor swaps to a pointer - this behavior is already in place). So... 1) Do I need to create my own custom bitmap/sprite or is there a palette of built-in cursors I can use? (I'm not using Flex.) 2) Is there a way to simply replace the default arrow with the pan cursor project-wide, or do I need to attach the swapping to mouse events on display objects? Can I use the stage object to make this behavior apply everywhere? 3) How do I perform the swap? Do I use the Cursor object directly or do I need to get involved with the CursorManager? Any guidance, pseudo-code, or words of wisdom is greatly appreciated!

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• Make an element visible to the user but invisible to events

  - by Acorn

  I'm not quite sure how to describe what I'm looking to do, but I'll do my best. At the moment I have a parent <div>, with absolutely positioned child <div>s within it, and I'm tracking the mouse pointer location coordinates relative to the element your mouse is over. At the moment, when I mouse over my child <div>s, I get the mouse location relative to them, but I want the coordinates to be relative the the parent <div> even when mousing over the child elements. So I basically want the child elements to be visible, but transparent to the mousemove, so I want the mousemove to go straight through to the parent element. How would I do this? Do I maybe need to somehow make the parent <div> be in the forground but still have the child <div>s show through? or make a transparent <div> overlay just to get the mouse coordinates? Here's a link to the page I'm experimenting on: http://acorn.host22.com/mouse.html

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• using string to read file - XCode

  - by Fernando

  The following does not work and gives me a SIGABRT when I run in the debugger: std::ifstream inFile; inFile.open("/Users/fernandonewyork/inputText.txt"); cout << inFile << endl; vector<string> inText; if (inFile) { string s4; while (inFile>>s4) { inText.push_back(s4); } } inFile.close(); The following does: std::ifstream inFile; inFile.open("/Users/fernandonewyork/inputText.txt"); cout << inFile << endl; vector<string> inText; if (inFile) { string s4("This is no lnger an empty string"); while (inFile>>s4) { inText.push_back(s4); } } inFile.close(); I was under the impression I was able to simply use s4 without having to worry about any space considerations, or is something else happening here? This is the full error I get from the top code: malloc: * error for object 0x100010a20: pointer being freed was not allocated * set a breakpoint in malloc_error_break to debug Program received signal: “SIGABRT”.

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