I need to read lines from one file and copy them line by line into another file using dynamic memory allocation. It compiles but gives me a seg fault. Why/How?
Code:
int main(){
FILE *fp1;
FILE *fp2;
FILE *i;
fp1=fopen("file1","r");
fp2=fopen("file3","w+");
[Code] ....
I am working on an OOP assignment (text handler) which part of its description is:
Some lines of text as a story which the delimiter between each story is %%%%%
Each text loaded should only occupy the space needed for the text to fit.
It's required to use dynamic variables of type char*. To be more detailed, the text-handler must contain a vector of such char-pointers (i.e. c-strings), and the parameter in the constructor indicates how many pointers (c-strings) to be contained in the vector. Each loaded text will be represented by a number, so that the first text in the file gets number 0 and the next one gets number 1 ... etc. When you want to access a text, you request the text with a certain number, and then get a pointer in return that may be used to output the text on the screen.
My problem is first to allocate a dynamic memory like char** without defining the number of array elements (Each text loaded should only occupy the space needed for the text to fit. )and then store each story from text file (comprise of a few lines of text) into that dynamically located memory(char **)to be able to do some operation on it later.
I have declared a global variable as pointer. The program performs certain number of iterations. After every iteration, the size of memory required for the pointer changes and this pointer variable is to be accessed by different functions. Now, here is my doubt:If I allocate the memory for this global variable in a function, will the contents of the memory be lost once I exit that function. In my opinion, it should not be the case as the dynamic memory allocation takes place in "heap" and should not be affected by the call of functions.
View 4 Replies View RelatedI have recently bought a copy of "Jumping into C++" and have come to chapter 14 ( dynamic memory location) and have a question.
On page 153-154 an example of dynamic allocation is given for array's of int. How would the code look like for strings or structs ?
The allocation was given by:
Code:
int *growArray (int* p_values, int *size)
{
*size *= 2;
int *p_new_values = new int[ *size ];
for ( int i = 0; i < *size; ++i )
{
p_new_values[ i ] = p_values[ i ];
}
delete [] p_values;
return p_new_values;
}
Sample Code I tried to use this for an array of structs but failed completely....
I used the following struct Code:
struct user{
int days;
string name;
};
and the allocation function (which does not work):
Code:
struct user *growarray (struct user *p_values, int *size) {
*size *= 2;
struct user *p_new_values = new struct user[ *size ];
for ( int i = 0; i < *size; ++i )
[Code].....
I am creating a connect 4 game using dynamic memory allocation the question is;
Write a two-player game of Connect Four where the user can set the width and height of the board and each player gets a turn to drop a token into the slot. Display the board using + for one side, x for the other, and _ to indicate blank spaces.
I have created the board. However I am unsure as how to make a start on getting the players to make moves.
Code:
#include <iostream>
using namespace std;
char **create_table(int width, int height, char blank) {
char **p_p_connect4 = new char*[height];
for(int i = 0; i < height; i++) {
p_p_connect4[i] = new char [width];
[Code]....
I'm having problems with this code:
#include <iostream>
using namespace std;
class Foo {
public:
Foo( int n );// Constructor
~Foo();// Destructor
int *ptr;
int N;
[Code] ....
I'm using Visual C++ 2008 version. The problem arises at the end, after the sentence 'system("pause")' is reached, which makes me think that the problem happens when calling the destructor. The destructor is called twice, the first time it's called is in the function print. The problem seems to be that the destructor can only be called once.
I know I can avoid this situation by defining the function print like this:
void print ( const Foo &f )
...
but I would like to know if there is some way I can do this keeping the definition that I've provided.
I am fairly new to dynamic memory allocation and I keep getting a segmentation fault in this code of mine. This is what the method should do:void sort StringsByReversePoints(char **myWords): This function sorts the char* values (i.e. strings) of myWords in descending order of point value by calling getWordPoints as a helper function and comparing adjacent words. This simple (but inefficient) sorting algorithm starts at the beginning of myWords array and sweeps to the end comparing adjacent values and swapping if they are out of order. After N (length of the array) sweeps the array is fully sorted. Note that efficiency can be improved by a factor of 2 by shortening each successive sweep by one, since the first sweep will have guaranteed the minimum point value word is the last element of the array, the next sweep guarantees the last two elements are correct, and so on....Additionally, if a given sweep results in zero swaps then the array is sorted and you can return immediately.
View 5 Replies View Relatedwe are currently covering double pointers and memory allocation. Currently getScrabbleWords is not working. when I compile with commented code (Main() works fine) I get a segmentation fault.
This is the purpose of getScrabbleWords:
char **getScrabbleWords(char **allWords, char letters[]):
This function takes an array of char* values (i.e. strings) representing all the words read from wordlist.txt. Each of these words is tested by callingcanWeMakeIt as a helper function, and pointers to the words that can be made are put into an array, myWords. Note, copies of the words are not made! In order to indicate the end of myWords, we terminate with a NULL pointer. Thus, if N words can be made from letters then myWords should have length N+1.
Why cant a dynamic memory allocation work with references? I was told that references work with const pointers deep down so shouldn't this be legal code?
int &&a=new int;
My compiler says that a entity of int* cannot be used to initialize a entity of int&&?
Does that mean that the compiler thinks of them as different types except deep down a reference is implemented with a pointer? Is this right?
I am using a pair of pthreads that call a pair of functions for ping-pong dma data transfer that are used in a loop for data transfer from an acquisition board. For a large # of waveforms, I ultimately run out of PC memory and the program stops. At the end of each function I use the delete[] command to clear memory for reuse, but the pointer appears to advance by the array size used for the transfer until the location exceeds the 2 GB I have for memory. I can see this happening using the Task Manager performance button time plot and window of total memory used continuing to increase to the limit. The culprit for one of the functions (2nd) is:
unsigned char* dataBuffer2 = (unsigned char *) (pci_buffer2.UserAddr);
where pci_buffer1 and 2 have been set up and allocated in main. I also had the following line in each function process:
double* Rin = new double[length];
and it used up memory twice as fast. When I transferred the last line to an area just prior to main and used a constant 1024 for length, the program ran twice as far before exceeding system memory, so it appears that both lines were forcing new memory assignments and moving the pointers accordingly. In addition to using the delete[] command to free memory unsucessfuly at the end of each function procedure, I ended up closing the memory at the end of each procedure, then reallocating it again with the idea that the pointer would be set back to the original value, but it still seems to icrement along. So, neither approach appears to allow reuse of the memory because the pointer continues to march along. Using Visual C++ 6.0 to compile.
This is the question; Write a function that builds a two-dimensional multiplication table with arbitrary sizes for the
two dimensions.
This is what I have done. I have allowed the user to input whatever size table they want by arbitrarily choosing what value they can input. However I cannot get the board to have blank squares. I thought the char would do it.
Code: #include <iostream>
using namespace std;
char SQAURE_CHAR = {' '};
const int Board_Size = 14;
[Code] ....
Suppose I wished to reallocate memory (resize) an array of pointers. Why does the following not work?(The program runs, yet yields a faulty segmentation error message. Why?):
Code: char **ptrarr = (char**) malloc(sizeof(char*))
Code: ptrarr = (char**) realloc(ptrarr, (capacity) * sizeof(char*));
I need to use dynamic memory allocation and use pointers to iterate through the arrays that I have already in this program. I am lost, nothing I do works and where to use the pointers. I am just looking for a push in the right direction so I can finish this project and how I can implement pointers in my program.
#include <iostream>
#include <string>
#include <cstdlib>
#include <iomanip>
#include <stdio.h>
using namespace std;
[Code]...
Dynamic memory allocation in array in c programming. I am trying to make the user to choose the size of array they want to engage in the game.
However, i have remove the global variable which contribute the error to my code previously. Now I assigned all the arr individually but not using the global variable. However, i still not get the desired board i want. i still keep getting 9x9 array board.
And i also need limit the board size only from 4 to 9. And how do i do that.
Code:
#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <conio.h>
#include <malloc.h>
#include <ctype.h>
#include <stdbool.h>
[Code] .....
Trying to append a comma to a string. Getting "Segmentation Error" on Solaris when the function is entered the second time.
Code:
// Appends a comma to the given string
void appendComma(char* instring) {
if (instring == NULL) {
instring = realloc(NULL, strlen(","));
strcpy(instring,",");
[Code] .....
I am trying to read a file line by line and then do something with the informations, so my method looks like this:
Code:
void open_file(char *link) {
FILE *file = fopen(link, "r");
if (file == NULL) {
fprintf(stderr, "Could not open file.
");
exit(EXIT_FAILURE);
[Code] ....
1) The first complain of valgrind is at the line where I use fgets and its telling me (invalid write of size x), but I have allocated my line to 56000 and the read line is shorter, why is there a write size error then :S?
2) at the line where I realloc where I try to shrink the space he's telling me: Address .... is 0 bytes inside a block of size 56000, But I know i need only this space so why is there a write over space error :S??
So I'm reading a file line by line and storing it backwards into a list. So if the file has has this format...
1
2
3
4
The code should store each line in a list as such...
4, 3, 2 ,1
Instead the code will store the last variable in all nodes. So the final list will look like this...
4, 4, 4, 4
Here is my code...
struct node *head = NULL;
int i;
while(read(in, &i, sizeof(int)) != 0) {
struct node *temp = malloc(sizeof(*temp));
temp->line = &i;
temp->next = head;
head = temp;
}
I have a text file (test.txt) with the following data:
01,05,25,20130728
01,06,25,20130728
01,07,25,20130728
01,08,25,20130728
01,05,25,20130728
01,05,25,20130728
01,05,45,20130728
01,05,65,20130728
01,05,85,20130728
01,05,35,20130728
01,05,25,20130728
01,05,35,20130728
I want to read this to one string called line. So far I have this code:
string line;
ifstream myfile ("/home/Test.txt");
if (myfile.is_open()) {
while (myfile.good()) {
getline (myfile, line);
for (int a = 0; a <= 335; a++) {
cout <<line.at(a);
} }
myfile.close();
}
so far its only printing the first line and then throwing an instance of 'std::out_of_range'
I need to read a text file which has various lines containing integers. I need to write those integers separately in a vector. Example, the first line of the text file contains 3 9 8 7 6 so vector[4]=3, vector[3]=9, vector[2]=8 and so on. Next read the second line 4 1 2 3 4 5 and write to another vector vector[5]=4, vector[4]=1...
I tried the code below but it will write from the second line, the whole line in one vector index.
int str; // Temp string to
cout << "Read from a file!" << endl;
ifstream fin("functions.txt"); // Open it up!
string line;
// read line count from file; assuming it's the first line
getline( fin, line );
[Code]...
Im trying to read from a file, line by line, with no specified number of values in the file. Check out my code:
int main() {
string x;
ifstream fin;
int count = 0;
char ch;
fin.open("CWC_Master.txt");
if(!fin)
[Code] .....
Now, this works great! However, its skipping some lines. And I dont know why. For example: Lets say that the input file is:
superman toy
sm2335
19.99
batman toy
bm5532
25.99
aquaman toy
am6786
26.00
Where it should output the above, instead it outputs every other one. Like:
superman toy
19.99
batman toy
25.99
aquaman toy
26.00
How can I fix my code so that it SIMPLY(i say simply because I am still a beginner coder) can read line by line?
I can able to get the last line ten chars but i cant get if the last line is null.
here is my code
#include <cstdlib>
#include <iostream>
#include <fstream>
#include <sstream>
#include <string>
using namespace std;
int main(int argc, char *argv[]) {
[Code] ....
here with i have enclosed my file where i am pick my last ten chars ...
Attached Files : log.txt (4.8 KB)
I have to read the information about logic gates from a file. The file format is shown below:
Code:
gateOne = NAND(inpA, inpB)
gate2=NAND(1,2)
3 = NAND(23,25,26)
As, it can be seen from the above structure that whitespaces are not same everytime. So, to deal with this situation, i am using boost library to remove all whitespaces from the line which is being read and then try to find the name of gate and its input. My code is given below which is able to correctly find the gate names and its first input...but my code is not able to find the second, third and so on input names.
Code:
//C
#include <stdio.h>
//C++
#include <iostream>
#include <sstream>
#include <fstream>
#include <string>
#include <cstring>
#include <boost/algorithm/string/erase.hpp>
[Code] ....
I have three questions concerning the below code I have written, which is expected to do basically as the attached diagram illustrates:
Code:
#include <stdio.h>
#include <stdlib.h>
double getAverageGrade(int studentGrades[] , int size);
int* getStudentInfo(int * numCourses);
int main()
[Code] ...
(1) How may I display the averages to 2 decimal places, namely why doesn't %.2lf work? The program gives 89.00 for 89 and 90, for instance.
(2) How may I read the number of courses and the relevant grades in a row for each student?
(3) How may I free (de-allocate) my array of pointers, namely grades? Does it suffice to use free(grades)?
How to read a file line by line and then later access them by doing something like
Code:
lines[0] //Line number one
...
lines[100] //Line number one hundred and one
lines[100][0] //L
lines[100][1] //i
lines[100][2] //n
lines[100][3] //e
lines[100][4] //
lines[100][5] //n
...
I have an external file with one column of data. If I have a counter value let say counter =1, and counter++ and so on. How I can write such a c++ code that if the value of counter and value from the external file are same then generate an action let say cout both values i.e. value of counter and value from external file.
for more information, here is an example:
data in file(in one column): 2 6 8 9 10...
value of counter : 1 2 3 4 5 6 7 8 9...
then cout values only if value of counter and value from the file is same.
Here is my code so far, but it does not seem to work;
#include<iostream>
#include<fstream>
using namespace std;
int main() {
const int SIZE = 10; //Size declaration of array
int hours[SIZE]; //Array declaration
[Code]...
I am reading my file (20GB) line by line using boost like this
PHP Code:
boost::interprocess::file_mapping* fm = new boost::interprocess::file_mapping("E:Mountain.7z", boost::interprocess::read_only);
boost::interprocess::mapped_region* mr = new boost::interprocess::mapped_region(*fm, boost::interprocess::read_only);
char* bytes = static_cast<char*>(mr->get_address());
An exception is thrown in the second line while allocating memory for mr.
I use boost because it can also work in Mac which my code will be ported to.