C/C++ :: Returning A Char Pointer?
Mar 24, 2015
I am trying to return a char pointer so that i can re use it again. I am writing a vigenere function that takes a message, a key and an initialization vector where it performs the encryption, prints out the encrypted message and returns the encrypted message. I print out the process step by step and everything works, however i pass the answer and print it out again and only the first letter gets changed. I put my code below and my output right after that.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <time.h>
void decrypt(char *to_encrypt, char *key, char* pct);
enum flag{encryption = 1, decryption = 0};
[code].....
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Apr 25, 2014
I am writing a class Player which has several char arrays as private fields. I am trying to write a method which returns an array as a pointer, but doesn't alter the array in any way, thus the const.
Here is a snippet:
Code: class Player
{
private:
char state[MAX_STATE_CHAR + ONE_VALUE];
int rating;
char last[MAX_NAME_CHAR + ONE_VALUE];
char first[MAX_NAME_CHAR + ONE_VALUE];
int groupNumber = NEG_ONE;
public:
char * GetFirst() const
{
return first;
}
Visual studio is saying that the return type doesn't match.
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Mar 2, 2015
I'm having trouble returning a char array by a function, here's the code. The problem is the 'reverse' function, the purpose of the function is to send two char arrays, 'newline' containing the char array, reverse it and place it in the 'rev' char array then output it back in main, however the output remains blank so I assume there must be something wrong with the reverse function.
Code:
#include <stdio.h>
#define MAXLINE 10
int fgetline(char line[], int maxline);
void copy(char to[], char from[]);
void reverse(char forw[], char rev[], int arrsize);
[Code] .....
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Mar 8, 2015
Code:
charArr = new char[50];
cout << "put in value: ";
cin.getline(charArr, 50);
some_func(charArr);
[Code] ....
Let's say I enter a value: 101
It goes into the if statement but clearly I've enter 1s and 0s. When I debugged, at i = 0, the charArr[i] gives me a value of 49 when assigned to an int variable. But when I cout charArr[i] it gives me 1.
So I'm going to assume 49 is part of the address? How can I correctly check the if statement condition?
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Feb 17, 2014
Ive been getting an odd error with this code when I try to compile it, as well as Im not quite sure as how to return my variable "compType" as a char type.
Main
#include <iostream>
#include "Shape.h"
#include <iomanip>
#include <cmath>
using namespace std;
void inputShape( char shape)
[Code] ....
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May 15, 2014
I want to return a char array to the main() function, but its returning garbage value.
#include<stdio.h>
//#include<conio.h>
#include<string.h>
char* strtrmm();
int main() {
char str1[100],c1[100];
[Code] .....
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Nov 21, 2014
As the title says, i'm using a function which returns a pointer to a struct:
the struct is the following:
Code:
typedef struct POINT
{
uint16_t x;
uint16_t y;
}
Coordinate; the function i'm using:
Code:
Coordinate * Read_XTP2046(void)
{static Coordinate screen;
//calculations to determine the coordinates
screen.x=(temp[1]+temp[2])/2;
screen.y=(temp[0]+temp[2])/2;
// and so on...
return &screen;}
The question is: how do i catch this pointer and make it into a Coordinate struct in which i can read the x and y.
In my main program i would do the following:
Code:
Coordinate cor;
cor = Read_XTP2046();
This does not work, as the function returns a pointer, but how to transform this pointer into a Coordinate struct.
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Apr 24, 2013
I hear all the time about the rule of not returning a local pointer, but I'm not exactly sure what that insinuates. Would this example be classified as violating that rule?
class Foo {
public:
Bar* ReturnBar() {
Bar* temp = &bars.at(0);
return temp;
}
private:
vector<Bar> bars;
};
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May 29, 2014
I have a class which looks like the following:
Code:
class Gadgets {
public:
Data* GetData() const {
return _data.data();
}
const Data * GetDataConst() const {
return _data.data();
}
private:
QSharedPointer<Data> _data;
}
You may ask why i have the second GetData() method that return a pointer to my private member, which will then expose my private member externally. I provide this function just for the case where user can do the following
Code:
Gadgets * myGadgets = new Gadgets();
myGadgets->GetData()->ModifyData(.....);
My question pertains to the use of QSharedPointer of data(), where in the doc, it says
T * QSharedPointer::data () const
Returns the value of the pointer referenced by this object.
Note: do not delete the pointer returned by this function or pass it to another function that could delete it, including creating QSharedPointer or QWeakPointer objects.
Whereas, if i were to use
Code:
Data* data as my private member class instead of QSharedPointer;
I will not need to worry if the caller do as follow
Code:
Data * data = new Data();
Data *data2 = myGadgets.GetData();
data2 = data;
delete data;
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Aug 18, 2014
Should i never return a pointer to a local variable. i have seen the following code in the standard text book.
Code:
struct node *add_to_list(struct node *list, int n)
{
struct node *new_node;
new_node = malloc(sizeof(struct node));
// some code here
return new_node;
}
new_node is a local pointer then why is he returning the new_node? Is it wrong or am i failing to understand something?
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Mar 5, 2013
I have a program that is trying to find all factors of an integer given. It needs to be done in a recursion function. Right now i have code similar to just getting the prime factors of a integer.
unsigned int * find_factors_using_recursion(unsigned int x ) {
unsigned int * factor = new unsigned int[];//do i put x in here ?
for(unsigned int i = 2; i < x; ++i) {
if(x % i == 0) {
find_factors_using_recursion(x / i);
*factor = (factor[i] = i);
} }
return factor;
delete [] factor;
}
When i cout the *factor = (factor[i] = i) it gives me the prime numbers of the integer passed into the function but when I return the pointer it only returns one of the prime numbers. I'm new to c++, how to return pointers from functions that would be great with an example to go with it.
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Dec 10, 2014
I know how to pass a 2-D array to a function. The prototype for that is void f(int (*p)[2]) assuming the array is of integers and there are 2 columns in it.
However, if I wanted the same function to return a pointer to a 2-D array, what would be the prototype?
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Jun 22, 2014
So, I've got this class in SDL Player that has, among other things, an SDL_Texture* to hold an image that represents the player on the screen. I'd assume it's good practice to do get() and set() functions for the class; but because textures are handled via pointers, when I write a get() function I end up returning a pointer to an internal resource; which isn't good practice I hear as it "breaks" encapsulation.
Find my code below:
#ifndef PLAYER_H
#define PLAYER_H
#include "SDL.h"
#include "SDL_image.h"
#include "CTexture.h"
class Player {
[Code] .....
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Nov 5, 2014
I'm using fgets which will read a single line at a time, but unlike fgets I don't want it to return the new line char ( ) ?I want to be able to use printf to display the lines next to each other.
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Feb 3, 2013
I thought we needed to allocate memory before assigning a value to a char* and also that we needed to use functions like strcpy() to copy something into it. Then how come this works and does not crash?
Code:
#include <iostream>
using namespace std;
int main()
{
char * buf;
buf = "Hello";
cout << buf << endl;
buf = "World!!!!!!!!";
cout << buf << endl;
return 0;
}
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Aug 31, 2013
I like to use a Pointer to char array. And then I would like to do a Pointer Arithmetic by incrementing the Pointer. Finally I would like to see the Addresses of the Pointer to each of the char Array Elements. I had created a program below, but I am not getting any Addresses from my Pointer.
#include <iostream>
using namespace std;
int main () {
int ArraySize;
char ch[]= "This is a Char Pointer";
char* iPtr = ch;
[Code] ....
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May 4, 2013
#include <iostream>
using namespace std;
int replace(char *ptr, char c1, char c2);
int replace(char *ptr, char c1, char c2){
int count = 0;
int i = 0;
[Code] ......
Segmentation fault (core dumped)
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Jun 12, 2013
Is there a more simple method to copy Buf into str? Buf is a binary string.
Code:
void function(string & str) {
int iWholeSize = 512;
char * Buf = new char[iWholeSize];
.... operations on Buf
string s(Buf, Buf + iWholeSize);
str = s;
}
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Apr 4, 2014
Here is my code. I am combining two words and sorting the merge word in alphbetical order. The compiler giving me warning error
Program:12:4: warning: format '%s' expects argument of type 'char *', but argument 2 has type 'char (*)[100]' [-Wformat] Program:14:4: warning: format '%s' expects argument of type 'char *', but argument 2 has type 'char (*)[100]' [-Wformat]
Code:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
[Code].....
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Jun 7, 2013
Alright, so I have a code that's not giving me errors, but it doesn't seem to retain what I put into an array. Not sure If I'm missing something...
Code:
#include <stdio.h>
int main (void)
{
const char *pointer;
const char alphabet[] = "ABCDEFG";
pointer = &alphabet[5];
printf("pointing to %c of the alphabet
", pointer);
return 0;
}
Trying to get my pointer to return the letter in the [5] spot or "F". Not receiving any errors when compiling, but I seem to get different answers every time I run it.
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Jan 2, 2014
I'm having a problem understanding something with pointers. I was trying to pass a pointer into a function in MSVC-2013, like
char* charptr;
and then calling
myfunct(charptr);
and then inside the function i would set charptr equal to another char ptr, simply like
charptr = anothercharptr;
But this actually caused a compile failure in MSVC, saying charptr is being used without being initialized. in Code::Blocks it just gives buggy output.
I solved this issue by calling the function like
myfunct(&charptr);
and declaring the function like
myfunct(char**);
and then I had to dereference the charptr in the function when assigning it to another ptr, so
*charptr = anothercharptr;
It seems like you should be able to just pass a ptr into a function and change its address to that of another pointer? My main question is really, what is the value of a pointer? I thought the value of a pointer was just the memory address it contains. But then I had to reference it to pass it into the function.
What is the difference between the value of the char* charptr written as either charptr and &charptr?
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Mar 5, 2013
Here's the code I'm working on:
string* arrayPush(string *array, char **toks){
if(array[sizeofHistory -1].empty()){
//find the next available element
for(int i=0; i < sizeofHistory; i++ ){
[Code] ....
toks is an array of pointers to strings. I need to assign a toks to array[i].
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Feb 5, 2014
I am using a small robotic-car that is controlled by writing C/C++ codes under Linux. I need to use a particular function from the library provided by the manufacturer. The relevant API documentation for the function is:
BASEBOARD_ERROR_KIND ZMP zrc :: :: :: Baseboard GetRS232Data (char * msg )
RS232 data acquisition.
Argument:
[Out] msg Address of the acquired data.
Returns:
BASE_OK RS232 data acquisition success
BASE_BASE_232_GETDATA_ERR RS232 data acquisition failure
I have trouble writing the relevant code in the main program that invokes this function. Here is a snippet of what I have tried:
# include "Baseboard.h"
int main () {
Baseboard _Baseboard; // Class name is Baseboard
char *msg ;
[Code] ......
The part where I am uncertain is how to handle the char pointer "msg" in the declaration, function call and referencing. According to the documentation, the char pointer "msg" is the output of the function so I presume that is is somehow dynamically allocated. Am I handling the char pointer properly in the declaration, function call and referencing parts?
Another related question I have is: I am printing out the value of the variable "dummy". I always get 0 for it. Since the variable "dummy" is an enum of type BASEBOARD_ERROR_KIND which can take on two values (first value represents success and the second failure), it is alright to get a integer value of 0 for it if the function call was successful ? (I do not have much experience with using enums so this is a enum-related question on whether we can get an integer value representing the first enum value) .
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Dec 9, 2013
I have a pointer to an Address is there a way to save that address value (not the content but the actual address) into a char ?
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Sep 19, 2013
I understand you can do
char* charpointer[2];
charpointer = "12";
if (charpointer[0] == '1'){
}
but how can we test for a range? 0-1? so I can compare it to '12'
I wouldn't want to do charpointer[0] == '1' && charpointer[1] == '2' though.
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Oct 6, 2014
how string literal that works with the cin object?
char * str = "This is a string constant";
Is the str stored the address of the first character of the string literal?
But some books just state that the pointer-to-char (char pointer) stores the address of the string literal". So just wonder how it is.
When it is used with cout, cout just treats it like a string and instead of printing the address, it just prints out all characters one by one until it reaches the terminated null character.
If this is the case, then I am just wondering how cin works with it? with a statement like this cin >> str; ?
Does the computer allocate enough memory for it? and then cin stores the first character into the first address and then advances to the next address and stores the next character?
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