How to get relative memory address of members of Class or Structure ? I want to auto scan the members of Class/Struct, and show the address/value like the "watch window" in debug mode of popular C/C++ IDE software.
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Suppose I have two classes, MyClassX and MyClassY, each with two member variables, as defined below. I create an object instance of each class, and then create a pointer to each member variable for each object:
Code:
class MyClassX
{
public:
int a;
double b;
MyClassX(int _a, double _b)
[code]....
After converting the hexadecimal to decimal, it appears that with MyClassX, pxb is 8 bytes from pxa, whereas for MyClassY, pya is only 4 bytes from pyb. This makes sense for MyClassY, because the first member variable to be stored is an int, and so will occupy 4 bytes. However, why should this be any different for MyClassX, which also has an int as the first member variable, so shouldn't this also occupy 4bytes?
The reason I have come across this problem is that I am looking into streaming objects to memory and then loading them again. (I know boost can do this, but I am trying it out myself from scratch.) Therefore, this is causing an issue, because I cannot just assume that the size of memory occupied by an object is just the sum of the sizes of its member variables. MyClassX is 8 bytes larger than MyClassY, even though the intuition is that it should only occupy 4 bytes more due to a double being replaced by an int.
Code:
class A
{
std::map<std::string, Unit*> aMap;
class B
[Code] .....
This code snippet results in "A non-static member reference must be made relative to a specific object". When I make callA() static, this error goes away, but there is problem with aMap.
I would like to have a unmodifiable standard of WAVEFORMATEX defined as a member of a class of mine. Something like:
class InputTest {
public:
const WAVEFORMATEX StandardWaveFormat;
public:
void TakeInput(WAVEFORMATEX pFormat);
};
Then in my cpp file to hard-code the values:
WAVEFORMATEX InputTest::StandardWaveFormat {
//Instantiate WaveFormat -- PCM standards
StandardWaveFormat.wFormatTag = WAVE_FORMAT_PCM;
StandardWaveFormat.cbSize = 0; //extra information sent over stream. Usually ignored in PCM format.
[Code] ....
I get the following errors starting with the header file:
Error1error C2146: syntax error : missing ';' before identifier 'StandardWaveFormat'
Error2error C4430: missing type specifier - int assumed. Note: C++ does not support default-int
both associated with the "const WAVEFORMATEX StandardWaveFormat; " line.
Here's a link to the WAVEFORMATEX struct: [URL] .....
Then the cpp source code is probably way off. Let me know if you'd like to see the errors associated with that.
I want to take address of a member function in c++. How to do this.
View 2 Replies View Related#include <iostream>
#include <vector>
using namespace std;
int main() {
int * ptr;
vector<int> data;
data.resize( 1000 );
[Code] ....
So I need container that doesn't rellocate their address, It doesn't need to be like vector that everything is in a single pointer such as
int * a = new int[2000];
I have a pointer pointing to a member of a container and it needs to remain valid... doing
vector<int *> Array;
// allocating
for( int i = 0; i < 1000; ++ i ){
Code] ...
Waste of time, allocating them and deallocate them seem to take some time too
a List is also not efficient enough because I access them based on index
It is not a int it is pointing to but a texture, for the sake of simpler example I pick int
So is there a container that doesn't change member address and allocate when it needs to expand ?
My address book will be simple, and the thing's that I'm expecting to use in it are :
Pointers, Linked Lists
Malloc
Structs
Typedefs
Makefile, header file
Putting functions into different program files
I have started the program trying to create a struct, and getting it working with a couple of entries before going onto user input and splitting it up.
Code:
#include <stdio.h>
#include <stdlib.h>
int main(void) {
// Struct type address book. Just a name, a number and a pointer
[Code] .....
I'm a bit lost at this point... My knee jerk thought is to create a for loop, and cycle through the list.
I'm not sure how this would apply to this though? Without using the familiar type of print loop such as :
Code:
for (i = 0; ;i++) {
printf("%i
", array[i];
}
I'm thinking that I need to create a temporary struct that can be used to assign the value of the next struct in the list, and then somehow print from that....
I'll try and write the logic out :
while temp != NULL (The last node value is assigned NULL to show us where the end of the list is)
create a temporary pointer that can be used to keep track of where we are in the list.
print out the current entry name and number
then assign the temp pointer value to the * next of the current struct. So if we are in entry1 the *next should be the address of entry 2.
Print out entry 2 name and number, assign entry 2 next to the temp value.
I just read and have known for a while that classes are private (members and inheritance) by default and structs are public. But my question then comes what if.. a struct inheriting from a class or a class inheriting from a struct?
View 3 Replies View RelatedI need to take info in the following format (no blank/skipped lines):
last name, first name street address city, state zip code
And dynamically allocate space for it. I need to use structs, and I need to use an array of pointers to structs to point to them. I know I probably have quite a few problems with my code, but so far, I am able to store and print back the data without issue. In the following code, I only make the loop run 3 times just so I can test it with manual input into the console, but eventually the max will be 50, or until end of input (will be doing IO redirection with a txt file).
Like I said, I can store and print the data fine, but am getting a segmentation fault when trying to sort the info.
Code:
#include <stdio.h>#include <stdlib.h>
#include <string.h>
struct addressBook{
char name [50];
char streetAddress [50];
[Code] ....
I was looking at some linked list material and was wondering something. Can you initialize a data member inside a struct like in C++? i.e.
Code:
typedef struct node
{
int data;
struct node * next = NULL; // this is the line in question
} LLnode;
I'm a C beginner trying to assign struct member values to other struct members to create a list.
I've tried dot notation, pointer notation, strcpy, memcpy, memmove and normal assignment.
Nothing has worked.
cust_list.h
Here's the definition of my struct:
struct Speaker {
static int numElem;
string name;
int number; // Phone
string topic;
float fee;
};
// IN main() FUNCTION
Speaker s[10];
The goal is for numElem to keep track of how many of the 10 elements are in use. However, I'm not sure the proper way to access the element, if it's even possible.
The program I'm working on is a very basic relational database. I've isolated my problem for simplicity. I get a segfault right here when I try to access db->relationCount. I tried printing db->relationCount from within loadDB and that worked,
[code]
loadDB(db, configFile);
printf("%d",db->relationCount);
fflush(stdout);
I have the code bellow, and i print the data but cannot assign it to global variable.
struct frequency_data {
char frequency[10];
int32 frequenca_mesatare;
int16 PWM_F;
int32 PR2;
[Code] ....
This is with Linux gcc
Code:
typedef struct _a
{
int id;
} a;
typedef struct _b
{
a my_a;
my_a.id = 1; // error: expected specifier-qualifier-list before "my_a"
} b;
I get error: expected specifier-qualifier-list before "my_a"
I must set the id for the kind of struct created inside the struct def because main() will be casting based on this id. Thats how I will know which structure b contains by it's id, there could be hundards of different structs with different values I will cast to the correct one and know it's members by it's id. How do I ?
I'm trying to assign a value to a member of a struct that I called via an overloaded [] operator. I have the following code for the struct:
typedef struct {
float r, g, b, a;
float operator [](int pos) {
switch (pos) {
[Code] ....
And what I wish to do is
MyStruct a;
a[0] = 0.5;
Is it possible with a struct? How to express this to search engines so I haven't been able to find anything about it. If this is not possible with a struct, is there a way to define something that can do all the following things:
SomeStruct test = {0.5, 0.5, 0.5, 1};
test.g = 1.0;
test[0] = 0.0; // test[0] would be equivalent to calling test.r
float somevalue = test[3]; // test[3] would be equivalent to calling test.a
I hope I've been sufficiently clear.
I work on a system that communicates with other systems via messages. Those messages are defined in a spec and every word must be exactly as defined. To accomplish this Ada allows me to define the fields of my record to specific words in memory.
Code:
word = 4;
type Msg_Type1 is record
x: Some_Type;
y: Another_Type;
z: Another_Type;
end record;
[Code] ....
How to initialize a static member of a class with template, which type is related to a nested class?
This code works (without nested class):
#include<iostream>
using namespace std;
struct B{
B(){cout<<"here"<<endl;}
};
template<typename Z>
[Code] ,....
I am writing a program which is using SDL library. I have two different classes which one of them is Timer Class and the other is EventHandling Class.
I need to use some member functions and variables of Timer in some Eventhandling Class member functions, Although I want to define an object of Timer in int main {} and relate it to its member function that has been used in Eventhandling member function in order that it becomes easier to handle it, I mean that I want to have for example two objects of timer and two objects of Eventhandling class for two different users.
I do not know how to relate an object of a class from int main{} to its member function which is being used in another class member function.
Lets have it as a sample code:
class Timer {
private:
int x;
public:
Timer();
get_X();
start_X();
[Code] ....
So I have an ImageManager class, Board class, and Box class. In Board.h I can declare ImageManager imgr; and in Board's constructor I can use imgr and its functions and such. However, in Box.h when I try and declare ImageManager imgr; I get the error "cannot access member declared in class ImageManager". Both declarations are under private, and exactly the same, but one doesn't work. Also, is there a way to only have one instance of ImageManager?
View 19 Replies View RelatedHow can I add the variable adress to a void pointer inside of a class?
class variant2 {
private:
void *Vvariant=NULL;
public:
template<typename b>
variant & operator = (b *adress)
[Code] ....
if possible i want avoid the '&' when i assign the variable address.(variant2 f=varname;//like you see i don't use the '&')
for the moment i just need put the address to Variant pointer. but i receive several errors .
FILE* pFile = fopen ("./myfile.txt","w+");
Is there a way to change what a relative path is referencing after runtime has started?
My specific issue is that I have several existing 100,000+ LOC lua projects. I am building a new back-end in C/C++ for this by wrapping a Lua C library. The lua scripts use io.open("./path/relative/to/project/file") which translates to fopen(...) in C. The project file which this is relative to is opened by the user after the application has started.
I see two solutions, neither are particularly good:
1) Change every io.open() function in every project to be relative to a static location. I lose all flexibility if I do this.
2) Modify the Lua library to prepend a custom path to opened files. Modifying 3rd party libraries suck because you can't update the library without tracking patches.
3?) Ask cplusplus forum if there is a way to change the relative directory.
I have my application database in the AppDataRoaming folder. I'm trying to create a connection string for Telerik reporting, up until now I've had a connection string in a settings class that is put together like this:
The path is:
data source=C:UsersSynlightAppDataRoamingAppNamedataAppDB.sqlite
I've tried files paths like this:
%AppData%RoamingAppDatadataAppDB.sqlite
and
Server.MapPath(@"~App_DataRoamingAppDatadataAppDB.sqlite
(those are not the real directory names, of course). How do I create a connection string that will work on target machines?
Is there any way in sfml version 2 that I can get objects in a graphics window to retain there relative positions and sizes when the window is resized? I have tried looking in the documentation for version 2 but with no luck.
As an example suppose the window is 800x600 and there is a line running right across the window at 3/4 of the way down (i.e at y=450). If the window is then made larger say 1280x1024 how would I keep the line in the same relative position (i.e all the way across 1280 and 3/4 of the y setting down).
For a while, I have been running a Windows 7 Visual Studio 2012 CPP project fine. However, today, all of a sudden, it has stopped being able to read any header files that are in relative directories. I cannot think what I have done to make this happen.
It seems to be an issue with Visual Studio as a whole, rather than my individual project, because I have created a new simple project and I am having the same problem. So, I have a CPP project at `C:/Projects/TestProject`. Then, I have a header file called `test_header.hpp`, which is located at `C:/Headers`. In `TestProject`'s project settings, I have added the directory `../../Headers` to `Additional Include Directories`. Then, my main functions is as follows:
Code:
#include "test_header.hpp"
int main() {
return 0;
}
Which gives me the error:
Code:
Error1error C1083: Cannot open include file: 'test.hpp': No such file or directoryc:projects estprojectmain.cpp11TestProject
Is there some global Visual Studio setting that is responsible for setting up these relative directories? Just in case the relative directory was not correct, I also tried a load of others, such as `../Headers` and `../../../Headers`, but these gave the same errors.
How it make it work for my project. Runtime means I am going to have to give the path at the command line?
Here is how I have to run it, so I can test it against the example inputs and outputs they give us to test our program. I am using putty. Already crated the folders inside my project folder, but don't know how to implement it on my source code.
./movie_stats < ./input/test1.in ./my-output/test1.out
What I'm thinking is to open/create the file test1.out in the my-output folder and open it at runtime?
