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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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  • 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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  • Warning: cast increases required alignment

    - by dash-tom-bang
    I'm recently working on this platform for which a legacy codebase issues a large number of "cast increases required alignment to N" warnings, where N is the size of the target of the cast. struct Message { int32_t id; int32_t type; int8_t data[16]; }; int32_t GetMessageInt(const Message& m) { return *reinterpret_cast<int32_t*>(&data[0]); } Hopefully it's obvious that a "real" implementation would be a bit more complex, but the basic point is that I've got data coming from somewhere, I know that it's aligned (because I need the id and type to be aligned), and yet I get the message that the cast is increasing the alignment, in the example case, to 4. Now I know that I can suppress the warning with an argument to the compiler, and I know that I can cast the bit inside the parentheses to void* first, but I don't really want to go through every bit of code that needs this sort of manipulation (there's a lot because we load a lot of data off of disk, and that data comes in as char buffers so that we can easily pointer-advance), but can anyone give me any other thoughts on this problem? I mean, to me it seems like such an important and common option that you wouldn't want to warn, and if there is actually the possibility of doing it wrong then suppressing the warning isn't going to help. Finally, can't the compiler know as I do how the object in question is actually aligned in the structure, so it should be able to not worry about the alignment on that particular object unless it got bumped a byte or two?

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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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  • 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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  • making an array controller the target of a button

    - by ian
    I am working through a chapter of COCOA PROGRAMMING FOR MAC OS X (3RD EDITION) on NSArrayController and it tells me to: Control-Drag to make the array controller become the target of the Add New Employee button. Set the action to add: However when I drag over the array controller it does not highlight so I get no target options. How do I do this correctly in the new XCode full size image document.h: // // Document.h // RaiseMan // // Created by user on 11/12/11. // Copyright (c) 2011 __MyCompanyName__. All rights reserved. // #import <Cocoa/Cocoa.h> @interface Document : NSDocument { NSMutableArray *employees; } @end document.m: // // Document.m // RaiseMan // // Created by user on 11/12/11. // Copyright (c) 2011 __MyCompanyName__. All rights reserved. // #import "Document.h" @implementation Document - (id)init { self = [super init]; if (self) { employees = [[NSMutableArray alloc] init]; } return self; } - (void)dealloc { [self setEmployees:nil]; [super dealloc]; } -(void)setEmployees:(NSMutableArray *)a { //this is an unusual setter method we are goign to ad a lot of smarts in the next chapter if (a == employees) return; [a retain]; [employees release]; employees = a; } - (NSString *)windowNibName { // Override returning the nib file name of the document // If you need to use a subclass of NSWindowController or if your document supports multiple NSWindowControllers, you should remove this method and override -makeWindowControllers instead. return @"Document"; } - (void)windowControllerDidLoadNib:(NSWindowController *)aController { [super windowControllerDidLoadNib:aController]; // Add any code here that needs to be executed once the windowController has loaded the document's window. } - (NSData *)dataOfType:(NSString *)typeName error:(NSError **)outError { /* Insert code here to write your document to data of the specified type. If outError != NULL, ensure that you create and set an appropriate error when returning nil. You can also choose to override -fileWrapperOfType:error:, -writeToURL:ofType:error:, or -writeToURL:ofType:forSaveOperation:originalContentsURL:error: instead. */ NSException *exception = [NSException exceptionWithName:@"UnimplementedMethod" reason:[NSString stringWithFormat:@"%@ is unimplemented", NSStringFromSelector(_cmd)] userInfo:nil]; @throw exception; return nil; } - (BOOL)readFromData:(NSData *)data ofType:(NSString *)typeName error:(NSError **)outError { /* Insert code here to read your document from the given data of the specified type. If outError != NULL, ensure that you create and set an appropriate error when returning NO. You can also choose to override -readFromFileWrapper:ofType:error: or -readFromURL:ofType:error: instead. If you override either of these, you should also override -isEntireFileLoaded to return NO if the contents are lazily loaded. */ NSException *exception = [NSException exceptionWithName:@"UnimplementedMethod" reason:[NSString stringWithFormat:@"%@ is unimplemented", NSStringFromSelector(_cmd)] userInfo:nil]; @throw exception; return YES; } + (BOOL)autosavesInPlace { return YES; } - (void)setEmployees:(NSMutableArray *)a; @end person.h: // // Person.h // RaiseMan // // Created by user on 11/12/11. // Copyright (c) 2011 __MyCompanyName__. All rights reserved. // #import <Foundation/Foundation.h> @interface Person : NSObject { NSString *personName; float expectedRaise; } @property (readwrite, copy) NSString *personName; @property (readwrite) float expectedRaise; @end person.m: // // Person.m // RaiseMan // // Created by user on 11/12/11. // Copyright (c) 2011 __MyCompanyName__. All rights reserved. // #import "Person.h" @implementation Person - (id) init { self = [super init]; expectedRaise = 5.0; personName = @"New Person"; return self; } - (void)dealloc { [personName release]; [super dealloc]; } @synthesize personName; @synthesize expectedRaise; @end

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  • Obj-C: Passing pointers to initialized classes in other classes

    - by FnGreg7
    Hey all. I initialized a class in my singleton called DataModel. Now, from my UIViewController, when I click a button, I have a method that is trying to access that class so that I may add an object to one of its dictionaries. My get/set method passes back the pointer to the class from my singleton, but when I am back in my UIViewController, the class passed back doesn't respond to methods. It's like it's just not there. I think it has something to do with the difference in passing pointers around classes or something. I even tried using the copy method to throw a copy back, but no luck. UIViewController: ApplicationSingleton *applicationSingleton = [[ApplicationSingleton alloc] init]; DataModel *dataModel = [applicationSingleton getDataModel]; [dataModel retrieveDataCategory:dataCategory]; Singleton: ApplicationSingleton *m_instance; DataModel *m_dataModel; - (id) init { NSLog(@"ApplicationSingleton.m initialized."); self = [super init]; if(self != nil) { if(m_instance != nil) { return m_instance; } NSLog(@"Initializing the application singleton."); m_instance = self; m_dataModel = [[DataModel alloc] init]; } NSLog(@"ApplicationSingleton init method returning."); return m_instance; } -(DataModel *)getDataModel { DataModel *dataModel_COPY = [m_dataModel copy]; return dataModel_COPY; } For the getDataModel method, I also tried this: -(DataModel *)getDataModel { return m_dataModel; } In my DataModel retrieveDataCategory method, I couldn't get anything to work. I even just tried putting a NSLog in there but it never would come onto the console. Any ideas?

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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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  • Can some tell me why I am seg faulting in this simple C program?

    - by user299648
    I keep on getting seg faulted after I end my first for loop, and for the life of me I don't why. The file I'm scanning is just 18 strings in 18 lines. I thinks the problem is the way I'm mallocing the double pointer called picks, but I don't know exactly why. I'm am only trying to scanf strings that are less than 15 chars long, so I don't see the problem. Can someone please help. #include <stdio.h> #include <stdlib.h> #include <string.h> #define MAX_LENGTH 100 int main( int argc,char *argv[] ) { char* string = malloc( 15*sizeof(char) ); char** picks = malloc(15*sizeof(char*)); FILE* pick_file = fopen( argv[l], "r" ); int num_picks; for( num_picks=0 ; fgets( string, MAX_LENGTH, pick_file ) != NULL ; num_picks++ ) { scanf( "%s", picks+num_picks ); } //this is where i seg fault int x; for(x=0; x<num_picks;x++) printf("s\n", picks+x); }

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  • Question about Virtual Inheritance hierarchy

    - by Summer_More_More_Tea
    Hi there: I encounter this problem when tackling with virtual inheritance. I remember that in a non-virtual inheritance hierarchy, object of sub-class hold an object of its direct super-class. What about virtual inheritance? In this situation, does object of sub-class hold an object of its super-class directly or just hold a pointer pointing to an object of its super-class? By the way, why the output of the following code is: sizeof(A): 8 sizeof(B): 20 sizeof(C): 20 sizeof(C): 36 Code: #include <iostream> using namespace std; class A{ char k[ 3 ]; public: virtual void a(){}; }; class B : public virtual A{ char j[ 3 ]; public: virtual void b(){}; }; class C : public virtual B{ char i[ 3 ]; public: virtual void c(){}; }; class D : public B, public C{ char h[ 3 ]; public: virtual void d(){}; }; int main( int argc, char *argv[] ){ cout << "sizeof(A): " << sizeof( A ) << endl; cout << "sizeof(B): " << sizeof( B ) << endl; cout << "sizeof(C): " << sizeof( C ) << endl; cout << "sizeof(D): " << sizeof( D ) << endl; return 0; } Thanks in advance. Kind regards.

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  • Modelling in Agile Development

    - by bertzzie
    I'm writing a bachelor dissertation report where I'm developing a system with Agile methodology. Given that the development is an one man show, of course the "Agile" I did was not really agile at all (from my understanding at least). So I want some perspective from SO crowds, who is of course a professional, real world, developer with tons of experience. I think real world experience is better than the theory and experiments that I did. My question is: Do we model during development time when using Agile? UML? DFD? Or a Functional Specification is enough1? If modelling is not really necessary, what do we use to communicate to the user, as the user almost always won't understand UML or DFD? For my system, I use UI & UX Design with heavy prototyping, but then I don't have time to draw UML any more. Which one is better? 1 http://www.joelonsoftware.com/articles/fog0000000036.html I hope the question's not "subjective and argumentative" as I know this question exist because of my lack of understanding in the agile development. If it is, could someone just give me a pointer or reference about that? Possible duplicate: Do you use UML in Agile development practices?

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  • Merge DataGrid ColumnHeaders

    - by Vishal
    I would like to merge two column-Headers. Before you go and mark this question as duplicate please read further. I don't want a super-Header. I just want to merge two column-headers. Take a look at image below: Can you see two columns with headers Mobile Number 1 and Mobile Number 2? I want to show there only 1 column header as Mobile Numbers. Here is the XAML used for creating above mentioned dataGrid: <DataGrid Grid.Row="1" Margin="0,10,0,0" ItemsSource="{Binding Ledgers}" IsReadOnly="True" AutoGenerateColumns="False"> <DataGrid.Columns> <DataGridTextColumn Header="Customer Name" Binding="{Binding LedgerName}" /> <DataGridTextColumn Header="City" Binding="{Binding City}" /> <DataGridTextColumn Header="Mobile Number 1" Binding="{Binding MobileNo1}" /> <DataGridTextColumn Header="Mobile Number 2" Binding="{Binding MobileNo2}" /> <DataGridTextColumn Header="Opening Balance" Binding="{Binding OpeningBalance}" /> </DataGrid.Columns> </DataGrid> Update1: Update2 I have created a converter as follows: public class MobileNumberFormatConverter : IValueConverter { public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture) { if (value != null && value != DependencyProperty.UnsetValue) { if (value.ToString().Length <= 15) { int spacesToAdd = 15 - value.ToString().Length; string s = value.ToString().PadRight(value.ToString().Length + spacesToAdd); return s; } return value.ToString().Substring(0, value.ToString().Length - 3) + "..."; } return ""; } public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture) { throw new NotImplementedException(); } } I have used it in XAML as follows: <DataGridTextColumn Header="Mobile Numbers"> <DataGridTextColumn.Binding> <MultiBinding StringFormat=" {0} {1}"> <Binding Path="MobileNo1" Converter="{StaticResource mobileNumberFormatConverter}"/> <Binding Path="MobileNo2" Converter="{StaticResource mobileNumberFormatConverter}"/> </MultiBinding> </DataGridTextColumn.Binding> </DataGridTextColumn> The output I got: Update3: At last I got the desired output. Here is the code for Converter: public class MobileNumberFormatConverter : IValueConverter { public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture) { if (value != null && value != DependencyProperty.UnsetValue) { if (parameter.ToString().ToUpper() == "N") { if (value.ToString().Length <= 15) { return value.ToString(); } else { return value.ToString().Substring(0, 12); } } else if (parameter.ToString().ToUpper() == "S") { if (value.ToString().Length <= 15) { int spacesToAdd = 15 - value.ToString().Length; string spaces = ""; return spaces.PadRight(spacesToAdd); } else { return "..."; } } } return ""; } public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture) { throw new NotImplementedException(); } } Here is my XAML: <DataGridTemplateColumn Header="Mobile Numbers"> <DataGridTemplateColumn.CellTemplate> <DataTemplate> <TextBlock> <Run Text="{Binding MobileNo1, Converter={StaticResource mobileNumberFormatConverter}, ConverterParameter=N}" /> <Run Text="{Binding MobileNo1, Converter={StaticResource mobileNumberFormatConverter}, ConverterParameter=S}" FontFamily="Consolas"/> <Run Text=" " FontFamily="Consolas"/> <Run Text="{Binding MobileNo2, Converter={StaticResource mobileNumberFormatConverter}, ConverterParameter=N}" /> <Run Text="{Binding MobileNo2, Converter={StaticResource mobileNumberFormatConverter}, ConverterParameter=S}" FontFamily="Consolas"/> </TextBlock> </DataTemplate> </DataGridTemplateColumn.CellTemplate> </DataGridTemplateColumn> Output:

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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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  • TCP client in C and server in Java

    - by faldren
    I would like to communicate with 2 applications : a client in C which send a message to the server in TCP and the server in Java which receive it and send an acknowledgement. Here is the client (the code is a thread) : static void *tcp_client(void *p_data) { if (p_data != NULL) { char const *message = p_data; int sockfd, n; struct sockaddr_in serv_addr; struct hostent *server; char buffer[256]; sockfd = socket(AF_INET, SOCK_STREAM, 0); if (sockfd < 0) { error("ERROR opening socket"); } server = gethostbyname(ALARM_PC_IP); if (server == NULL) { fprintf(stderr,"ERROR, no such host\n"); exit(0); } bzero((char *) &serv_addr, sizeof(serv_addr)); serv_addr.sin_family = AF_INET; bcopy((char *)server->h_addr, (char *)&serv_addr.sin_addr.s_addr, server->h_length); serv_addr.sin_port = htons(TCP_PORT); if (connect(sockfd,(struct sockaddr *) &serv_addr,sizeof(serv_addr)) < 0) { error("ERROR connecting"); } n = write(sockfd,message,strlen(message)); if (n < 0) { error("ERROR writing to socket"); } bzero(buffer,256); n = read(sockfd,buffer,255); if (n < 0) { error("ERROR reading from socket"); } printf("Message from the server : %s\n",buffer); close(sockfd); } return 0; } And the java server : try { int port = 9015; ServerSocket server=new ServerSocket(port); System.out.println("Server binded at "+((server.getInetAddress()).getLocalHost()).getHostAddress()+":"+port); System.out.println("Run the Client"); while (true) { Socket socket=server.accept(); BufferedReader in= new BufferedReader(new InputStreamReader(socket.getInputStream())); System.out.println(in.readLine()); PrintStream out=new PrintStream(socket.getOutputStream()); out.print("Welcome by server\n"); out.flush(); out.close(); in.close(); System.out.println("finished"); } } catch(Exception err) { System.err.println("* err"+err); } With n = read(sockfd,buffer,255); the client is waiting a response and for the server, the message is never ended so it doesn't send a response with PrintStream. If I remove these lines : bzero(buffer,256); n = read(sockfd,buffer,255); if (n < 0) { error("ERROR reading from socket"); } printf("Message from the server : %s\n",buffer); The server knows that the message is finished but the client can't receive the response. How solve that ? Thank you

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  • Who's setting TCP window size down to 0, Indy or Windows?

    - by François
    We have an application server which have been observed sending headers with TCP window size 0 at times when the network had congestion (at a client's site). We would like to know if it is Indy or the underlying Windows layer that is responsible for adjusting the TCP window size down from the nominal 64K in adaptation to the available throughput. And we would be able to act upon it becoming 0 (nothing gets send, users wait = no good). So, any info, link, pointer to Indy code are welcome... Disclaimer: I'm not a network specialist. Please keep the answer understandable for the average me ;-) Note: it's Indy9/D2007 on Windows Server 2003 SP2. More gory details: The TCP zero window cases happen on the middle tier talking to the DB server. It happens at the same moments when end users complain of slowdowns in the client application (that's what triggered the network investigation). 2 major Network issues causing bottlenecks have been identified. The TCP zero window happened when there was network congestion, but may or may not be caused by it. We want to know when that happen and have a way to do something (logging at least) in our code. So where to hook (in Indy?) to know when that condition occurs?

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  • How is external memory, internal memory, and cache organized?

    - by goldenmean
    Consider a system as follows:= A hardware board having say ARM Cortex-A8 and Neon Vector coprocessor, and Embedded Linux OS running on Cortex-A8. On this environment, if there is some application - say, a video decoder is executing - then: How is it decided that which buffers would be in external memory, which ones would be allocated in internal SRAM, etc. When one says calloc/malloc on such system/code, the pointer returned is from which memory: internal or external? Can a user make buffers to be allocated to the memories of his choice (internal/external)? In ARM architectures, there is another memory called as Tightly coupled memory (TCM). What is that and how can user enable and use it? Can I declare buffers in this memory? Do I need to see the memory map (if any) of the hardware board to understand about all these different physical memories present in a typical hardware board? How much of a role does the OS play in distinguishing these different memories? Sorry for multiple questions, but i think they all are interlinked.

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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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  • Multi-reader IPC solution?

    - by gct
    I'm working on a framework in C++ (just for fun for now), that lets the user write plugins that use a standard API to stream data between each other. There's going to be three basic transport mechanisms for the data: files, sockets, and some kind of IPC piping system. The system is set up so that for the non-file transport, each stream can have multiple readers. IE once a server socket it setup, multiple computers can connect and stream the data. I'm a little stuck at the multi-reader IPC system though. All my plugins run in threads so they live in the same address space, so some kind of shared memory system would work fine, I was thinking I'd write my own circular buffer with a write pointer and read pointers chassing it around the buffer, but I have my doubts that I can achieve the same performance as something like linux pipes. I'm curious what people would suggest for a multi-reader solution to something like this? Is the overhead for pipes or domain sockets low enough that I could just open a connection to each reader and issue separate writes to each reader? This is intended to be significant volumes of data (tens of mega-samples/sec), so performance is a must.

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  • CSS style submit like href tag

    - by seth.vargo
    Hi all, I have a button class that I wrote in CSS. It essentially displays block, adds some styles, etc. Whenever I add the class to a tags, it works fine - the a tag spans the entire width of its container like display:block should do... However, when I add the button class to an input button, Chrome, Safari, and Firefox all add a margin-right: 3px... I've used the DOM inspector in both Chrome and Safari and NO WHERE should it be adding a extra 3px padding. I tried adding margin: 0 !important; and/or margin-right: 0 !important to my button class in my CSS, but the browser STILL renders a 3px right margin! Is this a known issue, and is there a CSS-based solution (i.e. not jQuery/javascript) CODE FOLLOWS: .button { position: relative; display: block; margin: 0; border: 1px solid #369; color: #fff; font-weight: bold; padding: 11px 20px; line-height: 18px; text-align: center; text-transform: uppercase; cursor: hand; cursor: pointer; }

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  • How to partition bits in a bit array with less than linear time

    - by SiLent SoNG
    This is an interview question I faced recently. Given an array of 1 and 0, find a way to partition the bits in place so that 0's are grouped together, and 1's are grouped together. It does not matter whether 1's are ahead of 0's or 0's are ahead of 1's. An example input is 101010101, and output is either 111110000 or 000011111. Solve the problem in less than linear time. Make the problem simpler. The input is an integer array, with each element either 1 or 0. Output is the same integer array with integers partitioned well. To me, this is an easy question if it can be solved in O(N). My approach is to use two pointers, starting from both ends of the array. Increases and decreases each pointer; if it does not point to the correct integer, swap the two. int * start = array; int * end = array + length - 1; while (start < end) { // Assume 0 always at the end if (*end == 0) { --end; continue; } // Assume 1 always at the beginning if (*start == 1) { ++start; continue; } swap(*start, *end); } However, the interview insists there is a sub-linear solution. This makes me thinking hard but still not get an answer. Can anyone help on this interview question?

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  • Is there a general-purpose printf-ish routine defined in any C standard

    - by supercat
    In many C libraries, there is a printf-style routine which is something like the following: int __vgprintf(void *info, (void)(*print_function(void*, char)), const char *format, va_list params); which will format the supplied string and call print_function with the passed-in info value and each character in sequence. A function like fprintf will pass __vgprintf the passed-in file parameter and a pointer to a function which will cast its void* to a FILE* and output the passed-in character to that file. A function like snprintf will create a struct holding a char* and length, and pass the address of that struct to a function which will output each character in sequence, space permitting. Is there any standard for such a function, which could be used if e.g. one wanted a function to output an arbitrary format to a TCP port? A common approach is to allocate a buffer one hopes is big enough, use snprintf to put the data there, and then output the data from the buffer. It would seem cleaner, though, if there were a standard way to to specify that the print formatter should call a user-supplied routine with each character.

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  • Getting 404 in Android app while trying to get xml from localhost

    - by Patrick
    This must be something really stupid, trying to solve this issue for a couple of days now and it's really not working. I searched everywhere and there probably is someone with the same problem, but I can't seem to find it. I'm working on an Android app and this app pulls some xml from a website. Since this website is down a lot, I decided to save it and run it locally. Now what I did; - I downloaded the kWs app for hosting the downloaded xml file - I put the file in the right directory and could access it through the mobile browser, but not with my app (same code as I used with pulling it from some other website, not hosted by me, only difference was the URL obviously) So I tried to host it on my PC and access it with my app from there. Again the same results, the mobile browsers had no problem finding it, but the app kept saying 404 Not Found: "The requested URL /test.xml&parama=Someone&paramb= was not found on this server." Note: Don't mind the 2 parameters I am sending, I needed that to get the right stuff from the website that wasn't hosted by me. My code: public String getStuff(String name){ String URL = "http://10.0.0.8/test.xml"; ArrayList<NameValuePair> params = new ArrayList<NameValuePair>(2); params.add(new BasicNameValuePair("parama", name)); params.add(new BasicNameValuePair("paramb", "")); APIRequest request = new APIRequest(URL, params); try { RequestXML rxml = new RequestXML(); AsyncTask<APIRequest, Void, String> a = rxml.execute(request); ... } catch(Exception e) { e.printStackTrace(); } return null; } That should be working correctly. Now the RequestXML class part: class RequestXML extends AsyncTask<APIRequest, Void, String>{ @Override protected String doInBackground(APIRequest... uri) { HttpClient httpclient = new DefaultHttpClient(); String completeUrl = uri[0].url; // ... Add parameters to URL ... HttpGet request = null; try { request = new HttpGet(new URI(completeUrl)); } catch (URISyntaxException e1) { e1.printStackTrace(); } HttpResponse response; String responseString = ""; try { response = httpclient.execute(request); StatusLine statusLine = response.getStatusLine(); if(statusLine.getStatusCode() == HttpStatus.SC_OK){ // .. It crashes here, because statusLine.getStatusCode() returns a 404 instead of a 200. The xml is just plain xml, nothing special about it. I changed the contents of the .htaccess file into "ALLOW FROM ALL" (works, cause the browser on my mobile device can access it and shows the correct xml). I am running Android 4.0.4 and I am using the default browser AND chrome on my mobile device. I am using MoWeS to host the website on my PC. Any help would be appreciated and if you need to know anything before you can find an answer to this problem, I'll be more than happy to give you that info. Thank you for you time! Cheers.

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  • gtk draw "expose-event" and redraw

    - by warem
    I want to use expose-event to draw something then update or redraw. That's to say, there are a drawing area and a button in window. When clicking button, the drawing area will be redrawn accordingly. My problems are Following code worked but it only had a drawing area no button. If I add the button(cancel the comment for button), nothing is drawn. What's the reason? In the following code, if I changed gtk_container_add (GTK_CONTAINER (box), canvas); to gtk_box_pack_start(GTK_BOX(box), canvas, FALSE, FALSE, 0);, nothing is drawn. Usually we use gtk_box_pack_start to add something into box. Why doesn't it work this time? The function build_ACC_axis refreshed drawing area and prepared for new draw. I google it but I didn't know if it worked. Could you please comment on it? If the source file is test.c, then compilation is gcc -o test test.c `pkg-config --cflags --libs gtk+-2.0` The code is below: #include <gtk/gtk.h> #include <glib.h> static void draw (GdkDrawable *d, GdkGC *gc) { /* Draw with GDK */ gdk_draw_line (d, gc, 0, 0, 50, 50); gdk_draw_line (d, gc, 50, 50, 50, 150); gdk_draw_line (d, gc, 50, 150, 0, 200); gdk_draw_line (d, gc, 200, 0, 150, 50); gdk_draw_line (d, gc, 150, 50, 150, 150); gdk_draw_line (d, gc, 150, 150, 200, 200); gdk_draw_line (d, gc, 50, 50, 150, 50); gdk_draw_line (d, gc, 50, 150, 150, 150); } static gboolean expose_cb (GtkWidget *canvas, GdkEventExpose *event, gpointer user_data) { GdkGC *gc; gc = gdk_gc_new (canvas->window); draw (canvas->window, gc); g_object_unref (gc); return FALSE; } void build_ACC_axis (GtkWidget *button, GtkWidget *widget) { GdkRegion *region; GtkWidget *canvas = g_object_get_data(G_OBJECT(widget), "plat_GA_canvas"); region = gdk_drawable_get_visible_region(canvas->window); gdk_window_invalidate_region(canvas->window, region, TRUE); gtk_widget_queue_draw(canvas); /* gdk_window_process_updates(canvas->window, TRUE); */ gdk_region_destroy (region); } int main (int argc, char **argv) { GtkWidget *window; GtkWidget *canvas, *box, *button; gtk_init (&argc, &argv); window = gtk_window_new (GTK_WINDOW_TOPLEVEL); g_signal_connect (G_OBJECT (window), "destroy", G_CALLBACK (gtk_main_quit), NULL); box = gtk_vbox_new(FALSE, 0); gtk_container_add (GTK_CONTAINER (window), box); canvas = gtk_drawing_area_new (); g_object_set_data(G_OBJECT(window), "plat_GA_canvas", canvas); /* gtk_box_pack_start(GTK_BOX(box), canvas, FALSE, FALSE, 0); */ gtk_container_add (GTK_CONTAINER (box), canvas); g_signal_connect (G_OBJECT (canvas), "expose-event", G_CALLBACK (expose_cb), NULL); /* button = gtk_button_new_with_label ("ok"); gtk_box_pack_start(GTK_BOX(box), button, FALSE, FALSE, 0); |+ gtk_container_add (GTK_CONTAINER (box), button); +| gtk_signal_connect(GTK_OBJECT(button), "clicked", GTK_SIGNAL_FUNC(build_ACC_axis), window); */ gtk_widget_show_all (window); gtk_main (); }

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  • How do I build a filtered_streambuf based on basic_streambuf?

    - by swestrup
    I have a project that requires me to insert a filter into a stream so that outgoing data will be modified according to the filter. After some research, it seems that what I want to do is create a filtered_streambuf like this: template <class StreamBuf class filtered_streambuf: public StreamBuf { ... } And then insert a filtered_streambuf<> into whichever stream I need to be filtered. My problem is that I don't know what invariants I need to maintain while filtering a stream, in order to ensure that Derived classes can work as expected. In particular, I may find I have filtered_streambufs built over other filtered_streambufs. All the various stream inserters, extractors and manipulators work as expected. The trouble is that I just can't seem to work out what the minimal interface is that I need to supply in order to guarantee that an iostream will have what it needs to work correctly. In particular, do I need to fake the movement of the protected pointer variables, or not? Do I need a fake data buffer, or not? Can I just override the public functions, rewriting them in terms of the base streambuf, or is that too simplistic?

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  • How can I modified the value of a string defined in a struc?

    - by Eric
    Hi, I have the following code in c++: define TAM 4000 define NUMPAGS 512 struct pagina { bitset<12 direccion; char operacion; char permiso; string *dato; int numero; }; void crearPagina(pagina* pag[], int pos, int dir) { pagina * paginas = (pagina*)malloc(sizeof(char) * TAM); paginas - direccion = bitset<12 (dir); paginas - operacion = 'n'; paginas - permiso = 'n'; string **tempDato = &paginas - dato; char *temp = " "; **tempDato = temp; paginas - numero = 0; pag[pos] = paginas; } I want to modify the value of the variable called "string *dato" in the struct pagina but, everytime I want to assing a new value, the compiler throws a segmentation fault. In this case I'm using a pointer to string, but I have also tried with a string. In a few words I want to do the following: pagina - dato = "test"; Any idea? Thanks in advance!!!

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