C++ :: Override Few Methods In FILE Class
Oct 30, 2013
I need to override a few methods in FILE class so i defined few methods as
EnCrpt * fp;
fp * fopen(const char * filename, const char * mode);
int fwrite(const void * p,int length,int readLenth,FILE * fpp = NULL);
int fread(void * p,int length,int readLenth,FILE * fpp = NULL);
int fseek(FILE * fpp = NULL,long offset, int whence);
long ftell(FILE * fpp = NULL);
int feof(FILE * fpp = NULL);
int fflush(FILE * fpp = NULL);
int fclose(FILE * fpp = NULL);
I will call fread method in my encrypted file class .. similar to other methods.. is this correct ? can NULL file pointer create issue ?
Because i have so many place where FILE class called i don't want to change everywhere to call encrypted file class so i am override these methods to encrypted file class instead of standrd FILE class
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Feb 27, 2014
how to call the methods of the class.I have an object call v which is an array and I don't how to call the methods of the class. The error is here:
v.readDates(v[a]);
#include "Date.h"
#include <iostream>
using namespace std;
int main(){
int a;
cout << " HOW MANY DATES DO YOU HAVE? " << endl;
[code]....
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Oct 9, 2013
I'm using lua 5.2.2 with luabind 0.9.
I'd like to be able to add additional class-methods through lua for any classes that I've bound in c++, but I'm unsure how to do it.
The problem is that luabind uses a function as the __index-metamethod for any bound classes instead of a table, so I don't see a way to access the class-methods at all.
e.g., I'm binding my classes like this:
luabind::module(lua) [
luabind::class_<testClass>("TestClass")
.def(luabind::constructor<>())
.def("TestFunc",&TestFunc)
];
What I essentially want to do is to add a lua-function to the list of methods for this class, and be able to overwrite existing ones:
local t = tableOfClassMethods
local r = t.TestFunc -- Reference to the c++-function we've bound
t.SomeFunction = function(o) end -- New function for all objects of this class
t.TestFunc = function(o) end -- Should overwrite the c++-function of the same name
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Jul 3, 2013
Creating the methods for class List
main.cpp Code: #include "List.h"
int main( )
{
List la; // create list la
la.push_front( "mom" );
la.push_back( "please" );
la.push_back( "send" );
la.push_back( "money" );
la.push_front( "hi" );
cout << "
la contains:
" << la << '
[code]...
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Jun 17, 2014
I am given 2 methods and they want me to create a stand alone class for sql that will change the sql string.
my question is how can i take these 2 methods and make one class out of them that will used on various other forms.
#1
public string AuthenticateWithDB(CUiPontisDatabaseSpecification pdb, string sUserId, string sPassword,
bool bCreatePersistentCookie)
#2
public static void ChangeConnection(Util.ODBC.ODBCDSN odbcInfo, CPonDatabaseVendorType dbType, string uid, string password)
they want it so they can use it like
CUiHttpSessionManager.SimpleDataConnectionString = SomeNewClass.CreateSimpleDataConnectionString()
where some new class is my new class
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Apr 11, 2014
There is any method to compile a method of a class separately from the other methods and the main.
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Mar 21, 2015
The only difficulty im having is creating a class and methods & being able to access them from my win form app. Can i get a few tips on the do's and donts of creating classes / methods and accessing them from form app.
This is what i have put together so far.
public partial class Form1 : Form {
private Image[] dicePics;
private int[] diceNum;
private Random randomize;
public Form1() {
InitializeComponent();
[code]....
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Jul 11, 2012
I develop add-ons for MS Flight Simulator and I use the poorly documented SDK for this. The SDK provides a .h file in which an interface class is defined (with pure virtual methods only), something like this:
Code:
class IPanelCCallback {
public:
virtual IPanelCCallback* QueryInterface (PCSTRINGZ pszInterface) = 0;
virtual bool ConvertStringToProperty (PCSTRINGZ keyword, SINT32* pID) = 0;
virtual bool ConvertPropertyToString (SINT32 id, PPCSTRINGZ pKeyword) = 0;
};
In my code, I use this interface like this:
Code:
IPanelCCallback* pCallBack = panel_get_registered_c_callback("fs9gps");
...
SINT32 id;
pCallBack->ConvertStringToProperty(propertyName, &id);
Everything works fine, but I don't understand why... I thought the linker would stop with an "undefined symbol" error because the IPanelCCallback methods, such as ConvertStringToProperty, are declared as pure virtual but defined nowhere, and I don't use any library for linking. With such an interface class, I thought I would have to defined a subclass of IPanelCCallback and define the ConvertStringToProperty method.
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Oct 2, 2013
Imagine if there is an abstract class with a method (say output or print) which would be inherited by a few other classes. Later objects are created using the inherited classes, and the user wishes to call the above method twice, for eg (i) output/print to screen and (ii) output/print to a file. What is the best way to achieve that.
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Dec 4, 2014
I am writing my program on C++ language. I have one promblem. I need to set signal handler for my process. As the signal is related with the process on system level I have faced the problem.
My program consists several classes. They are connected together. But it doesn't metter in this case. The problem is that I need to access to member and methods of the class from my signal handler. For instance , I have class named Foo at it has some members and methods.
So from my handler I need to call its function and change members.
I understand that compiler should know that this class instances will exist during all program execution.
I have tried to set static member class Foo instance in another class , but this didn't solve the problem.
What is correct approach to do this. How to correctly implement signal handling in such case.
Here is example of my code
Code:
class MyContainer{
private:
std::vector<Foo> container;
public:
int removeFromContainer(Foo* aFoo) {
[Code] .....
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Feb 15, 2012
I have h-file with definition of 3 classes. And cpp-file with realization methods of this classes. And when I compile the project errors - LNK2019 is apperead... How make that methods become visible?
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Aug 11, 2012
We have a midi.cpp which includes midi_synth.h.
this h file declares a class and this class inlines a open method.
Now the linker doesn't recognize this open method when called by another method inside midi.cpp.
What would I do?
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Sep 9, 2014
see these sample:
Code:
#include <iostream>
#include <string>
using namespace std;
class test{
public:
virtual void ola() {
[Code] .....
Like you see, i don't re-declare the 'ola' function in 'test1' class, only in 'test' class. The compiler tell me the 'ola' isn't member of 'test1'. in 'test' i put it 'virtual', but forgetting that, how can i override it without re-declare it?
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Mar 11, 2014
A quick clarification on virtual methods after reading Jumping int C++ by Alex Allain. If a user wanted to extend a class from someone elses library and override its methods that do not contain virtual methods; how would one call the overridden class if it is referred to by its super type
in other words how would someone override a method from someone elses library that does not have virtual keywords.
ie
something.h
Code:
#include <iostream>
namespace game{
class character{
public:
std::string getName(){return "character";}
};
}
main.cpp
Code:
#include <iostream>
#include <vector>
#include "something.h"
using std::vector
class protagonist : game::character{
public:
virtual std::string getName(){return "protagonist";} };
[Code]...
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Jan 28, 2011
i m working in C"et and get this error message Dispose(boo) no suitable methode found to override
That is my code
protected override void Dispose(bool disposing) {
if (disposing && ( components != null)) {
components.Dispose();
}
base.Dispose(disposing);
}
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May 8, 2012
Using c++11, but I don't think that matters here.
output.displayHeader() must execute before the inherited from ostream (cout) executes streaming data, or bad things happen. It's of course not as simple as in the example below, and I need to make sure displayHeader() is never missed.
I'm thinking I need to override the "<<" operator, having my own function call displayHeader(), then call the base (cout) "<<" operator. What's the proper syntax for doing this?
I can't call displayHeader() in the constructor, and I can't call it right after the object is defined. There are exception case scenarios where displayHeader() must not be called, and other things must happen instead.
I'm aware this will result in many redundant bool comparisons versus the way I'm doing it now, and I'm perfectly OK with that.
Code:
#include <iostream>
using namespace std;
class myOutput : public ostream {
public:
myOutput() : ostream(cout.rdbuf()) {
[Code] ....
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Jun 20, 2013
I'm overriding OnNcPaint to do my own caption painting (in a dialog box). If I call "Default" before I do my painting, the default caption and borders remain (as if I'm not painting at all). If I comment out my call to "Default", my caption looks great, but I get no menu bar (I have a menu on the dialog). If I call "DrawMenu" before or after painting, the dialog is all screwed up (and there is no painting in the nonclient area).
I'm running VS2012, on Windows 7.
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Jan 6, 2014
I have questions about multiple inheritance and virtual methods. I have a class called solid. All objects of this class have hitboxes and can collide with others. I have the following methods:
void testCollision(something begin, something end);
/* This method takes a container's begin and end iterators to test if the object collides with any other object of the list of all the solids currently in the game area. Each time there is a collision, it calls collide(other) and other.collide(*this) */
virtual bool collide(solid& other);
/* This method always returns false and does nothing */
This class will be inherited by another class which will have overloads for a few specific collisions. For example:
class player : public solid{
public:
bool collide(projectile& other);
bool collide(enemy& other);
bool collide(wall& other);
};
My question is quite simple actually. If I have a loop which calls testCollision() with all elements in the list of all solids (a list of pointers to solids to be exact) and there is a collision between the player and a projectile, will testCollision call player::colide(projectile& other) or will it call solid::collide(solid& other). And in any case, did I understand how to use the virtual keyword? If I'm right, it should call the player::colide method if it's there for the specific type, else it will call the solid::colide which only returns 0, ignoring collision.
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May 7, 2013
I'm writing a sorted vector implementation and trying to do it as simply as possible.
Right now, I'm declaring the sorted vector with a protected subclass of vector, then using the "using" keyword to explicitly inherit all methods that aren't related to adding new elements to the vector (so I can control the order).
Eg:
Code: template<typename T, class Cmp = std::less<T>>
class sorted_vector : protected std::vector<T>{
public:
typedef typename std::vector<T>::iterator;
using std::vector<T>::operator=;
using std::vector<T>::assign;
using std::vector<T>::get_allocator;
using std::vector<T>::at;
using std::vector<T>::operator[];
//...
};
Obviously, this is annoyingly redundant. So what I'd like to do is something using the new "delete" keyword from C++11. Is there any quick, expressive way of deleting specific methods?
Also, it's pretty annoying to have to typedef base_class::type type to inherit a type from a base class. Is there a shorter way to do that?
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Nov 21, 2013
How to i access setter from within a setter?
I know that getter methods can be access like
Code: getAccounts().getAccountNumber();
// for example but for setters how do i do it? this doesnt seem to work though
Code: setAccounts().setAccountNumber(accountNumber);
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Oct 20, 2012
Is it common practice to package methods with other elements(string-s, int-s, float-s, array-s...) of struct?
Than struct acts as a class or is acting similar to class and that have no sense to me? I am new to OOP .
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May 8, 2013
i have been trying to call out the tea algorithm from wikipedia. However i keep getting a segmentation fault. Am i calling it out the wrong way? Below are the snippets
methods taken from wikipedia
void encrypt (uint32_t* v, uint32_t* k) {
uint32_t v0=v[0], v1=v[1], sum=0, i; /* set up */
uint32_t delta=0x9e3779b9; /* a key schedule constant */
uint32_t k0=k[0], k1=k[1], k2=k[2], k3=k[3]; /* cache key */
for (i=0; i < 32; i++) { /* basic cycle start */
sum += delta;
[code]....
i tried to encrypt a test text and casting it to the uinstd32_t type. However it always gives me a segmentation fault.
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Feb 2, 2014
What is a method and what is an object?
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Jan 29, 2012
I know that memory addresses in the stack can contain either values or references to other memory addresses, but do these memory addresses also contain methods or are the methods themselves located in the heap?
The confusion comes from the fact that in C# a delegate variable can be assigned either a method's identifier, an inline function, a lambda expression, or a new instance of the delegate type with the method's identifier passed as an argument to the constructor. My guess is that assigning the method's identifier directly to the delegate variable is just a simplified way of calling the delegate type's constructor with the method's identifier as an argument to the parameter, something that the compiler handles for you.
But even in this last case, the delegate variable is said to point toward the method itself. In that case, does it mean that methods are stored in the heap, just as reference type values are?
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May 17, 2013
Suppose I have a class "A", which has a method "void AMP_call()" that calls paralel_for_each in which another method, "float amp_function(float) restrict(amp)". When I call that method, can it then use members of "A"?
class A {
void AMP_call();
float amp_function(float) restrict(amp); // do something on a device
float allowed_variable;
std::vector<bool> not_allowed;
[Code] ....
Another way to frame my question, perhaps to make it easier to understand what I am after, would be that I want to know what happens if an amp-restricted method is called where the body of the class itself (which is not amp-compatible and afaik doesn't have to be since it's not passed to the device) may contain members that are not amp-compatible.
All of the msdn blogs I could find deal with which functions and methods can be called from within a parallel_for_each loop, but not with which variables are available to the lambda function itself.
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Sep 30, 2014
I need to write a windows form application that allows the user to enter a credit card number and credit card type and then determines whether it is a valid number using the following rules:
1.) the first number is:
a. 4 for visa
b. 5 for master card
c. 37 for american express
d. 6 for discover
2.) passes the mod 10/ luhn check, which is calculated as:
a. from right to left, multiply every other digit by 2. when doubling a digit results in a two digit number, add the numbers to get
a single digit. ( like 6 * 2 = 12 therefore 1 + 2 = 3).
b. add all the single digits from 2a
c. add all the odd places from right to left in the card number
d. sum the results fro steps 2b and 2c
e. if the resulting number in 2c is divisible by 10, the card number is valid otherwise it is invalid.
The chapter is introducing methods so that is the main thing i will be using for each step.
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