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• ruby c extensions: character values over 127

  - by Adrian

  I am trying to make a C extension for Ruby that includes a method returning a string, which will sometimes have character values that need to be in an unsigned char. In http://github.com/shyouhei/ruby/blob/trunk/README.EXT, all of the functions listed for turning C strings into Ruby strings take signed chars. So I couldn't do this: unsigned char bytes[] = {0xf0, 0xf1, 0xf2}; return rb_str_new(bytes, 3); How could I make a method that returns these types of strings? In other words, how would I make a C extension with a method returning "\xff"?

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• using C function in C#

  - by andrew

  i have a dll, built with mingw one of the header files contains this: extern "C" { int get_mac_address(char * mac); //the function returns a mac address in the char * mac } I use this dll in another c++ app, built using Visual C++ (2008SP1), not managed, but plain c++ (simply include the header, and call the function) But now I have to use it in a C# application The problem is that i can't figure out how exactly (i'm new in .net programming) this is what i've tried public class Hwdinfo { [DllImport("mydll.dll")] public static extern void get_mac_address(string s); } When i call the function, nothing happens (the mydll.dll file is located in the bin folder of the c# app, and it gives me no errors or warnings whatsoever)

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• How does sizeof calculate the size of structures

  - by Gearoid Murphy

  I know that a char and an int are calculated as being 8 bytes on 32 bit architectures due to alignment, but I recently came across a situation where a structure with 3 shorts was reported as being 6 bytes by the sizeof operator. Code is as follows: #include <iostream> using namespace std ; struct IntAndChar { int a ; unsigned char b ; }; struct ThreeShorts { unsigned short a ; unsigned short b ; unsigned short c ; }; int main() { cout<<sizeof(IntAndChar)<<endl; // outputs '8' cout<<sizeof(ThreeShorts)<<endl; // outputs '6', I expected this to be '8' return 0 ; } Compiler : g++ (Debian 4.3.2-1.1) 4.3.2. This really puzzles me, why isn't alignment enforced for the structure containing 3 shorts?

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• How come this image won't resize to fit the sprite?

  - by George Edison

  I have this snippet of ActionScript code that is supposed to resize an image to fit the sprite: package { import flash.display.Sprite; import flash.display.Bitmap; import flash.events.Event; public class Main extends Sprite { [Embed(source = 'img.png')] private var TheImage:Class; public static const TheImageWidth:Number = 1300; public static const TheImageHeight:Number = 1300; public function Main():void { if (stage) init(); else addEventListener(Event.ADDED_TO_STAGE, init); } private function init(e:Event = null):void { removeEventListener(Event.ADDED_TO_STAGE, init); // entry point var image:Bitmap = new TheImage(); addChild(image); image.scaleX = width / TheImageWidth; image.scaleY = height / TheImageHeight; } } } Why isn't it working?

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• Is this a valid css?

  - by Pandiya Chendur

  I have a pager in my page with anchors in it... I use the following css... .page-numbers a { color:#808185; cursor:pointer; text-decoration:none;outline:none; } .page-numbers a:hover { text-decoration:underline; } .page-numbers a:visited { color:#808185;outline:none; } But my anchor tag doesn't seem to take the css above instead it uses the css below, a { color:#0077CC; cursor:pointer; text-decoration:none;outline:none; } a:hover { text-decoration:underline; } a:visited { color:#4A6B82;outline:none; } Which i have given in the top of my stylesheet... Any suggestion...

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• Effective methods for reading and writing large files in C

  - by Bertholt Stutley Johnson

  I'm writing an application that deals with very large user-generated input files. The program will copy about 95 percent of the file, effectively duplicating it and switching a few words and values in the copy, and then appending the copy (in chunks) to the original file, such that each block (consisting of between 10 and 50 lines) in the original is followed by the copied and modified block, and then the next original block, and so on. The user-generated input conforms to a certain format, and it is highly unlikely that any line in the original file is longer than 100 characters long. Which would be the better approach? a) To use one file pointer and use variables that hold the current position of how much has been read and where to write to, seeking the file pointer back and forth to read and write; or b) To use multiple file pointers, one for reading and one for writing. I am mostly concerned with the efficiency of the program, as the input files will reach up to 25,000 lines, each about 50 characters long. Thanks!

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• What is the difference between NULL in C++ and null in Java?

  - by Stephano

  I've been trying to figure out why C++ is making me crazy typing NULL. Suddenly it hits me the other day; I've been typing null (lower case) in Java for years. Now suddenly I'm programming in C++ and that little chunk of muscle memory is making me crazy. Wikiperipatetic defines C++ NULL as part of the stddef: A macro that expands to a null pointer constant. It may be defined as ((void*)0), 0 or 0L depending on the compiler and the language. Sun's docs tells me this about Java's "null literal": The null type has one value, the null reference, represented by the literal null, which is formed from ASCII characters. A null literal is always of the null type. So this is all very nice. I know what a null pointer reference is, and thank you for the compiler notes. Now I'm a little fuzzy on the idea of a literal in Java so I read on... A literal is the source code representation of a fixed value; literals are represented directly in your code without requiring computation. There's also a special null literal that can be used as a value for any reference type. null may be assigned to any variable, except variables of primitive types. There's little you can do with a null value beyond testing for its presence. Therefore, null is often used in programs as a marker to indicate that some object is unavailable. Ok, so I think I get it now. In C++ NULL is a macro that, when compiled, defines the null pointer constant. In Java, null is a fixed value that any non-primitive can be assigned too; great for testing in a handy if statement. Java does not have pointers, so I can see why they kept null a simple value rather than anything fancy. But why did java decide to change the all caps NULL to null? Furthermore, am I missing anything here?

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• Why must "stride" in the System.Drawing.Bitmap constructor be a multiple of 4?

  - by Gorchestopher H

  I am writing an application that requires me to take a proprietary bitmap format (an MVTec Halcon HImage) and convert it into a System.Drawing.Bitmap in C#. The only proprietary functions given to me to help me do this involve me writing to file, except for the use of a "get pointer" function. This function is great, it gives me a pointer to the pixel data, the width, the height, and the type of the image. My issue is that when I create my System.Drawing.Bitmap using the constructor: new System.Drawing.Bitmap(width, height, stride, format, scan) I need to specify a "stride" that is a multiple of 4. This may be a problem as I am unsure what size bitmap my function will be hit with. Supposing I end up with a bitmap that is 111x111 pixels, I have no way to run this function other than adding a bogus column to my image or subtracting 3 columns. Is there a way I can sneak around this limitation?

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• QValidator for hex input

  - by Evan Teran

  I have a Qt widget which should only accept a hex string as input. It is very simple to restrict the input characters to [0-9A-Fa-f], but I would like to have it display with a delimiter between "bytes" so for example if the delimiter is a space, and the user types 0011223344 I would like the line edit to display 00 11 22 33 44 Now if the user presses the backspace key 3 times, then I want it to display 00 11 22 3. I almost have what i want, so far there is only one subtle bug involving using the delete key to remove a delimiter. Does anyone have a better way to implement this validator? Here's my code so far: class HexStringValidator : public QValidator { public: HexStringValidator(QObject * parent) : QValidator(parent) {} public: virtual void fixup(QString &input) const { QString temp; int index = 0; // every 2 digits insert a space if they didn't explicitly type one Q_FOREACH(QChar ch, input) { if(std::isxdigit(ch.toAscii())) { if(index != 0 && (index & 1) == 0) { temp += ' '; } temp += ch.toUpper(); ++index; } } input = temp; } virtual State validate(QString &input, int &pos) const { if(!input.isEmpty()) { // TODO: can we detect if the char which was JUST deleted // (if any was deleted) was a space? and special case this? // as to not have the bug in this case? const int char_pos = pos - input.left(pos).count(' '); int chars = 0; fixup(input); pos = 0; while(chars != char_pos) { if(input[pos] != ' ') { ++chars; } ++pos; } // favor the right side of a space if(input[pos] == ' ') { ++pos; } } return QValidator::Acceptable; } }; For now this code is functional enough, but I'd love to have it work 100% as expected. Obviously the ideal would be the just separate the display of the hex string from the actual characters stored in the QLineEdit's internal buffer but I have no idea where to start with that and I imagine is a non-trivial undertaking. In essence, I would like to have a Validator which conforms to this regex: "[0-9A-Fa-f]( [0-9A-Fa-f])*" but I don't want the user to ever have to type a space as delimiter. Likewise, when editing what they types, the spaces should be managed implicitly.

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• convert int to string for use in allegro function

  - by ace

  I am trying to run the following code using allegro. textout_ex(screen, font, numbComments , 100, 100, GREEN, BLACK); numbComments is an integer, the function prototype of this function is void textout_ex(BITMAP *bmp, const FONT *f, const char *s, int x, int y, int color, int bg); and i cannot, according to my understanding pass this integer in the third position. I therefore need to convert the integer into a string. I did it like this, but it didnt work. Help please? int score = numbComments; string Str; stringstream out; // YOU MUST INCLUDE <sstream> FOR THIS. out << score; Str = out.str(); and then tried to use the string Str, which didnt work

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• C++ input chaining in C#

  - by Monty

  I am trying to learn C# coming from C++. I am writing just some basic console stuff to get a feel for it and was wondering if it is possible to do simple chaining of inputs in C#. For example in C++: cout<<"Enter two numbers: "; cin >> int1 >> int2; You could then just input 3 5 and hit enter and the values will be fine. In C# however I have to split it up(as far as I can tell) like this: Console.Write("Enter the first number: "; int1 = (char)Console.Read(); Console.Writeline(""); Console.Write("Enter the second number: "; int2 = (char)Console.Read(); Maybe I am just missing something.

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• How best to implement publicly accessible constants in C#

  - by DanM

  There seem to be three choices for implementing publicly accessible constants in C#. I'm curious if there are any good reason to choose one over the other or if it's just a matter of personal preference. Choice 1 - private field plus property getter private const string _someConstant = "string that will never change"; public string SomeConstant { get { return _someConstant; } } Choice 2 - property getter only public string SomeConstant { get { return "string that will never change"; } } Choice 3 - public field only public const string SomeConstant = "string that will never change"; Which do you recommend and why?

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• How to obtain Bing maps like InfoWindow in Google Maps?

  - by BillB

  I'm using Google Maps v3. I really like the InfoWindows found in Bing, as opposed to Google. Screenshots & functionality found here comparing the two: http://www.axismaps.com/blog/2009/07/data-probing-and-info-window-design-on-web-based-maps/ Question: How can I replicate Bing like InfoWindows while using Google Maps v3? UPDATE: To be more specific, what I like about Bing's InfoWindows include: - The pointer dynamically changes sides from left/right/bottom/top, as opposed to Google limited to only have the InfoWindow pointer on the bottom - Bing's InfoWindows use less space - You can configure Bing's InfoWindows to pop up outside of the map bounders so that you don't have to autopan the map to display the marker's InfoWindow

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• Win32 api call via C# fails!

  - by user434186

  Hi. I have a C++ function exported as api like this: #define WIN322_API __declspec(dllexport) WIN322_API char* Test(LPSTR str); WIN322_API char* Test(LPSTR str) { return "hello"; } the function is exported as API correctly by the .DEF file, cause i can see it in Dependency Walker tool. Now i have a C# tester program: [DllImport("c:\\win322.dll")] public static extern string Test([MarshalAs(UnmanagedType.LPStr)] String str); private void Form1_Load(object sender, EventArgs e) { string _str = "0221"; Test(_str); // runtime error here! } on calling the Test() method i get the error: "A call to PInvoke function 'MyClient!MyClient.Form1::Test' has unbalanced the stack. This is likely because the managed PInvoke signature does not match the unmanaged target signature. Check that the calling convention and parameters of the PInvoke signature match the target unmanaged signature." i tried many other data types and marshalings, but got nothing! plz help me!

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• Need help with displaying the message correctly in the pole display

  - by SA

  Hi, I am using an HP RS232 pole display with the following setting: Char type: USA/Europe (default) Command mode: EPSON (default) Baud rate: 9600, n , 8, 1 (default?) Passthru None (Default) Here's the code using System.IO.Ports; private SerialPort port; port = new SerialPort("COM2", 9600, Parity.None, 8, StopBits.One); port.Handshake = Handshake.None; Port.WriteLine("Welocome to something something"); It has 2 lines consisting of 20 characters each with a total of 40 characters. I have no control how and where the characters get displayed. I have set it to accept ASCII char set and so I am able to type as is visble in the Writeline message

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• Is there an easy way to make `boost::ptr_vector` more debugger friendly in Visual Studio?

  - by Billy ONeal

  I'm considering using boost::ptr_container as a result of the responses from this question. My biggest problem with the library is that I cannot view the contents of the collection in the debugger, because the MSVC debugger doesn't recognize it, and therefore I cannot see the contents of the containers. (All the data gets stored as void * internally) I've heard MSVC has a feature called "debugger visualizers" which would allow the user to make the debugger smarter about these kinds of things, but I've never written anything like this, and I'm not hugely firmiliar with such things. For example, compare the behavior of boost::shared_ptr with MSVC's own std::tr1::shared_ptr. In the debugger (i.e. in the Watch window), the boost version shows up as a big mess of internal variables used for implementing the shared pointer, but the MSVC version shows up as a plain pointer to the object (and the shared_ptr's innards are hidden). How can I get started either using or implementing such a thing?

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• stl::map insert segmentation fault

  - by Jakub Czaplicki

  Why does this code stop with the segmentation fault : class MapFile { public: /* ... */ std::map <unsigned int, unsigned int> inToOut; }; bool SwitchMapFile::LoadMapFile( const wxString& fileName ) { /* ... */ inToOut.insert( std::make_pair(spmPort,fibreId) ); } but this one works fine : class MapFile { public: /* ... */ }; bool MapFile::LoadMapFile( const wxString& fileName ) { /* ... */ std::map <unsigned int, unsigned int> inToOut; inToOut.insert( std::make_pair(input,output) ); } ?

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• J2ME/Java: Referencing StringBuffer through Threads

  - by Jemuel Dalino

  This question might be long, but I want to provide much information. Overview: I'm creating a Stock Quotes Ticker app for Blackberry. But I'm having problems with my StringBuffer that contains an individual Stock information. Process: My app connects to our server via SocketConnection. The server sends out a formatted set of strings that contains the latest Stock trade. So whenever a new trade happens, the server will send out an individual Stock Quote of that trade. Through an InputStream I am able to read that information and place each character in a StringBuffer that is referenced by Threads. By parsing based on char3 I am able to determine a set of stock quote/information. char1 - to separate data char3 - means end of a stock quote/information sample stock quote format sent out by our server: stock_quote_name(char 1)some_data(char1)some_data(char1)(char3) My app then parses that stock quote to compare certain data and formats it how it will look like when displayed in the screen. When trades happen gradually(slow) the app works perfectly. However.. Problem: When trades happen too quickly and almost at the same time, My app is not able to handle the information sent efficiently. The StringBuffer has its contents combined with the next trade. Meaning Two stock information in one StringBuffer. field should be: Stock_quote_name some_data some_data sample of what's happening: Stock_quote_name some_data some_dataStock_quote_name some_data some_data here's my code for this part: while (-1 != (data = is.read())) { sb.append((char)data); while(3 != (data = is.read())) { sb.append((char)data); } UiApplication.getUiApplication().invokeLater(new Runnable() { public void run() { try { synchronized(UiApplication.getEventLock()) { SetStringBuffer(sb); DisplayStringBuffer(); RefreshStringBuffer(); } } catch (Exception e) { System.out.println("Error in setting stringbuffer: " + e.toString()); } } }); } public synchronized void DisplayStringBuffer() { try { //parse sb - string buffer ...... } catch(Exception ex) { System.out.println("error in DisplayStringBuffer(): " + ex.toString()); } } public synchronized void SetStringBuffer(StringBuffer dataBuffer) { this.sb =dataBuffer; System.out.println(sb); } public synchronized void RefreshStringBuffer() { this.sb.delete(0, this.sb.length()); } From what I can see, when trades happen very fast, The StringBuffer is not refreshed immediately and still has the contents of the previous trade, when i try to put new data. My Question is: Do you guys have any suggestion on how i can put data into the StringBuffer, without the next information being appended to the first content

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• CString error, 'CString': is not a member of 'ATL::CStringT<BaseType, StringTraits>'

  - by flavour404

  Hi, I am trying to do this: #include <atlstr.h> CHAR Filename; // [sp+26Ch] [bp-110h]@1 char v31; // [sp+36Ch] [bp-10h]@1 int v32; // [sp+378h] [bp-4h]@1 GetModuleFileNameA(0, &Filename, 0x100u); CString::CString(&v31, &Filename); But I am getting the compiler error C2039:'CString': is not a member of 'ATL::CStringT' This is a non MFC based dll, but according to the docs you should be able to use CString functionality with the include #include atlstr.h how do I make it work? Thanks

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• MoveFileEx Problem

  - by rajivpradeep

  int i ; DWORD dw ; String^ Source = "c:\\ProtectedFlash\\Program\\test.exe" ; String^ Destination = "c:\\Program Files" ; // move to program Files Folder //pin_ptr<const wchar_t> WSource = PtrToStringChars(Source); // pin_ptr<const wchar_t> WDestination = PtrToStringChars(Destination); i = MoveFileEx(L"c:\\ProtectedFlash\\Program\\ProtectedFlash.exe",L"c:\\Program Files",MOVEFILE_REPLACE_EXISTING) ; dw = GetLastError() ; return 0; The status dw is valued as 5 , when i run the program. Whats the error

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• make error in re-building ns2

  - by user3702405

  I have implemented a new routing protocol named AODV2 in ns-2.35. I am using ns-2.35 in fedora 13. All .cc files have a .o file with them that means recompilation is done. But I am getting an error in response to the 'make' command. Error is shown below: trace/cmu-trace.o: In function hdr_aodv2::access(Packet const*)': cmu-trace.cc:(.text._ZN9hdr_aodv26accessEPK6Packet[hdr_aodv2::access(Packet const*)]+0x7): undefined reference tohdr_aodv2::offset_2' collect2: ld returned 1 exit status make: * [ns] Error 1 I don't know how to remove this error, Can anyone help me please? Thanks, Naeem

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• warning from Eclipse

  - by lego69

  can somebody please explain what does it mean : passing arg 1 of 'free' discards qualifiers from pointer target type thanks in advance

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• create program in c for permutation combination and showing frequency

  - by Vishal Oswal

  I have 2 strings where I have saved fixed 20 characters and these are “A,B,C,D,E,F,G,H,I,J,K,L,M,N,O,P,Q,R,S,T” and same 20 char in string 2. so I will get 400 combinations of 2 character sets like AA,AB,AC,AD,AE,AF,……………AT BA,BB,BC,BD,BE,BF,…………..BT CA,CB,CC,CD,CE,CF……………CT This way we will get 400 combinations (Which program I have created successfully) but then user will put the value till 31 characters witch will be treated as 3rd string for E.g. “ABCDDAAAB” now I have to check the frequency of user input in the sequence of 12,23,34,45,56,67,78,89 (2 CHAR SET) means AB,BC,CD,DD,DA,AA,AA,AB and need to show the frequency of user input OUTPUT: AB=2 BC=1 CD=1 DD=1 DA=1 AA=2 please its urgent

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• Cocoa multiple threads, locks don't work

  - by Igor

  I have a threadMethod which shows in console robotMotorsStatus every 0.5 sec. But when I try to change robotMotorsStatus in changeRobotStatus method I receive an exception. Where I need to put locks in that program. #import "AppController.h" @implementation AppController extern char *robotMotorsStatus; - (IBAction)runThread:(id)sender { [self performSelectorInBackground:@selector(threadMethod) withObject:nil]; } - (void)threadMethod { char string_to_send[]="QFF001100\r"; //String prepared to the port sending (first inintialization) string_to_send[7] = robotMotorsStatus[0]; string_to_send[8] = robotMotorsStatus[1]; while(1){ [theLock lock]; usleep(500000); NSLog (@"Robot status %s", robotMotorsStatus); [theLock unlock]; } } - (IBAction)changeRobotStatus:(id)sender { robotMotorsStatus[0]='1'; }

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• Delphi Typed Constants in Case Statements

  - by Andreas Rejbrand

  What is the most elegant (or least ugly) way of using typed constants in a case statement in Delphi? That is, assume for this question that you need to declare a typed constant as in const MY_CONST: cardinal = $12345678; ... Then the Delphi compiler will not accept case MyExpression of MY_CONST: { Do Something }; ... end; but you need to write case MyExpression of $12345678: { Do Something }; ... end; which is error-prone, hard to update, and not elegant. Is there any trick you can employ to make the compiler insert the value of the constant (preferably by checking the value of the constant under const in the source code, but maybe by looking-up the value at runtime)? We assume here that you will not alter the value of the "constant" at runtime.

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