I have a bit of an issue with my program. I have a function void loadData() which will load the data from a text file customers.txt and store each line of data into a Linked List. My concern is, specifically with how I/O works. I managed to get the data from the text file into and stored into a linked list data member variable. When i call that variable i get the answer i want printed onto the console.
std::cout << "Group Name: " << tempCustomer->groupName << std::endl;
However, i decided to run a console output command later in the function to test if all the variables had the right data, i realize that it was all over the place. I'm not sure why its not working.
Here is the loadData() function
void Groups::loadData(){
fin.open("customers.txt");
char holder[MAX_SIZE];
if(!fin.is_open())
std::cerr << "Could not access file" << std::endl;
else{
while(!fin.eof()){
Customers *tempCustomer = new Customers;
fin.getline(holder,MAX_SIZE,';');
tempCustomer->groupName = holder;
std::cout << "Group Name: " << tempCustomer->groupName << std::endl;
fin.getline(holder,MAX_SIZE,';');
tempCustomer->name = holder;
fin.getline(holder,MAX_SIZE,';');
tempCustomer->email = holder;
fin >> tempCustomer->choice;
fin.get(); //gets the last character, which is '\n'
fin.ignore(); //ignores the next character which is the '\n'
tempCustomer->next = NULL;
std::cout << "What does the temp Node Store?" << std::endl;
std::cout << "Group Name: " << tempCustomer->groupName << std::endl;
std::cout << "Name: " << tempCustomer->name << std::endl;
std::cout << "Email: " << tempCustomer->email << std::endl;
std::cout << "Choice: " << tempCustomer->choice << std::endl;
//addCustomerToLL(tempCustomer);
tempCustomer = NULL;
delete tempCustomer;
}
}
fin.close();
}
Here is the Console out put:
Group Name: Jonathan Group
What does the temp Node Store?
Group Name: vazquez.jonathan#pcc.edu
Name: vazquez.jonathan#pcc.edu
Email: vazquez.jonathan#pcc.edu
Choice: 2
Here is the text file customers.txt
Jonathan Group;Jonathan;vazquez.jonathan#pcc.edu;2
This is a school assignment, i'm to store all the customers from the text file into a linked list. I'm also to use c strings as strings rather than c++ version of strings. Let me know if the other files are necessary, i didnt include them since well nothing in this function utilize anything else outside the func besides the ifstream fin; private variable i have in the class and the const int MAX_SIZE = 256; global variable.
Assuming you're not allowed to use std::string, you need to allocate memory for each string.
So replace this:
fin.getline(holder,MAX_SIZE,';');
tempCustomer->groupName = holder;
with:
fin.getline(holder, MAX_SIZE, ';');
char *s = new char[strlen(holder) + 1];
strcpy(s, holder);
tempCustomer->groupName = s;
You should release the memory you allocate when you no longer need it, so create a destructor for your Customers class:
Customers::~Customers()
{
delete[] groupName;
}
It's because the holder changes when you read a new line,but your all string in your Customer points to the same holder which stores the last line you read.
Change the type of name,email etc to char[MAX_SIZE] may help.
Related
Working on an assignment about Abstract Base classes, I'm running into a segment fault when I execute the getInput function I created in the addRecord function. I've tried a variety of methods for getting the user input for the name of the Employee/Student, however I keep running into issues with it.
getInput:
char* getInput(std::string message)
{
char* name;
std::cout << message << std::endl;
std::cin.ignore(INT_MAX, '\n');
std::cin.getline(name, INT_MAX);
return name;
}
addRecord:
/*
* addRecord(vecotr<base*>& v)
*
* Ask the user which type of record they want to add, an employee or student. Once
* they have made their selection, dynamically create a new pointer of the selected
* type of record and have them fill out the record's members via its set methods,
* then add it to the vector using the vector method .push_back().
*/
void addRecord(std::vector<Base*>& v)
{
std::cout << "--Records to Create--" << std::endl;
std::cout << "1.) Student Record" << std::endl;
std::cout << "2.) Employee Record" << std::endl;
std::cout << "Please select from the above options: ";
int sel = intInputLoop(1, 2);
clearConsole();
if (sel == 1)
{
char* name;
/*
std::cout << "Record Type: Student" << std::endl;
std::cin.ignore(INT_MAX, '\n');
std::cin.getline(name, INT_MAX);
*/
name = getInput("What is the Student's name? ");
float gradePointAverage = (float)intInputLoop(0, 4);
Student student = Student();
student.setName(name);
student.setGradePointAverage(gradePointAverage);
Base* bp = &student;
v.push_back(bp);
std::cout << "Added Student record for " << name << " with a grade point average of " << gradePointAverage << std::endl;
delete name;
}
else
{
char* name;
std::cout << "Record Type: Employee" << std::endl;
name = getInput("What is the Employee's name? ");
std::cout << "What is the Employee's salary? ";
int salary = intInputLoop(0, 0);
Employee employee = Employee();
employee.setName(name);
employee.setSalary(salary);
Base* bp = &employee;
v.push_back(bp);
std::cout << "Added Employee record for " << name << " with a salary of " << salary << std::endl;
delete name;
}
}
Any input is much appreciated. Thank you in advance.
char* name;
This declares a pointer, to an indeterminate number of char values. Who knows how many of them there are. It could be just one, very lonely char, sitting there, all by itself with nobody to play with. It could be a million, an entire city of chars. It's completely unspecified, nobody knows; that's because the pointer is completely uninitialized. Nothing in C++ happens automatically. If you intend to use a pointer, it must, well, point somewhere valid before you can use that pointer.
std::cin.getline(name, INT_MAX);
This call to getline reads input into a pointer. The pointer must point to valid memory. Since the pointer is uninitialized, this is undefined behavior, and is the reason for your crash.
Since your intent here is to use C++, the simplest solution is to use a C++ class that just happens to handle all the memory management for you: std::string:
std::string name;
std::getline(std::cin, name);
You'll need to replace all old-fashioned char * pointers, which is what you would use if you were writing C code, with std::string. After all: this is C++, not C.
I'm trying to build a program that can register a user to the database (still learning cpp, I hope that in the near future I'll be able to work with database).
What I'm trying to do with this code is to check whether an index of array is empty for the user to store an ID in it. If it isn't empty, I want the program to keep looking for an empty index of array, for the new info to be stored in.
Here is the code:
void registro() {
std::string userid[3];
userid[0] = "Houkros"; // eventually I'll try to have this being read from a file or server database..
std::string userpass[3];
std::string usermail[3];
std::string userkey[3];
std::string getUid[3];
std::string getUpass[3];
std::string getUmail[3];
std::string getUkey[3];
std::cout << std::endl << " >>>> REGISTRATION <<<< " << std::endl;
std::cout << " =============================================== " << std::endl;
std::cout << std::endl;
std::cout << "Please, enter the desired user id: " << std::flush;
if (userid[0].empty())
{
std::cin >> userid[0];
}
else {
std::cin >> userid[1];
}
for (int i = 0; i < 2; i++)
{
std::cout << " Element of array: " << i << " is > " << userid[i] << std::endl;
}
Please consider the following definitions for an "empty" array element:
a) not initialised (unhelpful, cannot be checked)
b) never yet written to (same as a) )
c) contains "" (possible, but means that "" must not be accepted as an actual content)
d) is empty according to a second array in which that info is maintained (this is what I almost recommend)
e) contains a struct with a string and a maintained "empty" flag (this I recommend)
Whatever you do, make sure that you init all variables and array elements before first read-accessing them; i.e. in all cases first write something meaningful to it.
I have such piece of code:
typedef struct reader
{
char name[50];
char card_num[50];
char title[100];
}reader_t;
int main()
{
vector<reader> vec;
ifstream input_file("D:\\lab.txt", ios::binary);
reader_t master[1];
input_file.read((char*)&master, sizeof(master));
for (size_t idx = 0; idx < 1; idx++)
{
reader temp;
strcpy(temp.name, master[idx].name);
strcpy(temp.card_num, master[idx].card_num);
strcpy(temp.title, master[idx].title);
vec.push_back(temp);
cout << "Name: " << master[idx].name << endl;
cout << "Card num: " << master[idx].card_num << endl;
cout << "Title: " << master[idx].title<<endl;
}
cout << vec.size();
getchar();
}
What is does: it reads structures from binary file into an array of structures,copies them into vector and displays structure.And yes, I do need to do like this - I need to store structures from file in vector and this is the only working way to do it I could find(if you can tell, how to read structures to vector directly from file - you are welcome).
So,everything works fine, but the problem is that I need to create a function which would be able to do the same, but with dynamic array.I wrote something like this:
void read_structs(int vec_size)
{
ifstream input_file("D:\\lab.txt", ios::binary);
//Here I commented 2 ways how I tried to create a dynamic array of structs
//reader* master = new reader[vec_size];
//reader* master = (reader*)malloc(sizeof(reader) * vec_size);
input_file.read((char*)&master, sizeof(master));
for (size_t idx = 0; idx < vec_size; idx++)
{
reader temp;
strcpy(temp.name, master[idx].name);
strcpy(temp.card_num, master[idx].card_num);
strcpy(temp.title, master[idx].title);
vec.push_back(temp);
cout << "Name: " << master[idx].name << endl;
cout << "Card num: " << master[idx].card_num << endl;
cout << "Title: " << master[idx].title<<endl;
}
}
And that worked fine too unless I tried to run it.VS wasn't higlighting error in my code, it just was throwing an exception right as the moment when the program tried to access master[0].name.
There is absolutely no point in the temp struct. See, the
vec.push_back(temp);
is already using copy constructor, so copy constructor must work and then the set of strcpy is not doing anything different from that, so just go with
vec.push_back(master[0]).
You can't read into vector directly. You do need to read into temporary. So that is correct. Except I suppose you want to read all entries from the file no matter how many of them there are, so you need to put the read itself also into the loop.
There is not much point in creating an array of one element.
reader_t master[1];
input_file.read((char*)master, sizeof(master));
// ^ you *don't* need & here, arrays degrade to pointers automatically
and
reader_t master;
input_file.read((char *)&master, sizeof(master));
// ^ but you do need & here.
are equivalent. I would go with the later.
So we are basically down to:
reader temp; // calling it temp; the master name makes no sense.
while (input_file.read((char*)&temp, sizeof(temp)))
// read returns input_file and input_file is false if last operation failed
{
vec.push_back(temp);
// verify the stored values by reading back vfrom vec.back().
cout << "Name: " << vec.back().name << endl;
cout << "Card num: " << vec.back().card_num << endl;
cout << "Title: " << vec.back().title<<endl;
}
In the second example, you didn't initialize master, so it obviously crashed.
There is a more C++ approach though. First, you define a read operator for the structure:
std::istream &operator>>(std::istream &in, reader &r) {
return in.read((char *)&r, sizeof(r));
}
and then you simply read the vector using the istream_iterator:
vec.assign(std::istream_iterator<reader>(input_file),
std::istream_iterator<reader>());
and the standard library will generate the above loop for you.
I'm having a weird issue. I'm writing a function to delete a line from a list of names created elsewhere, which, after some research, seems like it should be fairly simple. I write the current list of names into a list, display the list, have the user input the name they want to delete, remove the user-inputted name from the list, then display the updated list to the user.
Up to here, everything works perfectly, but when I write the list back into the file, the last name gets a random amount of characters chopped off of it, ranging from a couple of characters to the entire line. Now, this is where it gets strange. If I open the file and look at it without exiting the program, the last line of the file is messed up and continues to be whenever I display it later in the program. But, if I exit the program and then open the file, the last line is back to how it was originally written! That file is not written to again by the program after the list is written in, so I cannot imagine why this is happening.
I almost decided that since the file ultimately comes out of the program correct, I could just ignore the issue, but I want the user to be able to view the list of names after the deletion for various reasons, which is made impossible while the last list item prints incorrectly.
I am still fairly beginner with C++, so I'm kind of hoping that this is just an issue of me not fully understanding lists or something. Regardless, dumbed down explanations would be ace.
I included the function below, any help is much appreciated.
char act, charname[50];
string namestr;
list <string> c1;
list <string>::iterator c1_Iter;
//write the names from the file into a list
ifstream names("List of Names.txt");
while (std::getline(names, namestr))
{
c1.push_back(namestr);
}
//print the current names
cout << "Registered names:";
for (c1_Iter = c1.begin(); c1_Iter != c1.end(); c1_Iter++)
cout << "\n" << setw(5) << " " << *c1_Iter;
//choose which names to delete and confirm
cout << "\n\nEnter the name you would like to delete: ";
cin.getline(charname, 50);
cin.getline(charname, 50);
cout << "\nAre you sure? Enter 'y' to permanently delete " << charname << ", and any other key to return to the start screen.";
cin >> act;
if (act == 'y' || act == 'Y')
{
//delete a file associated with each name
string strname(charname);
strname.append(".txt");
if (remove(strname.c_str()) < 0)
perror("Error deleting file");
else
{
//delete name from the file only if that person's individual file is successfully deleted
c1.remove(charname);
cout << "\n" << charname << " successfully deleted!\n";
//print the updated list of names
cout << "\nUpdated list of registered names:\n";
for (c1_Iter = c1.begin(); c1_Iter != c1.end(); c1_Iter++)
cout << *c1_Iter << endl;
//write updated list of names over "List of Names" to update the file
ofstream newNames("List of Names.txt");
for (c1_Iter = c1.begin(); c1_Iter != c1.end(); c1_Iter++)
newNames << *c1_Iter << endl;
newNames.close();
}
}
As Mohit Jain mentioned in the comments, you need to call names.close() on the ifstream before opening the file for writing as a separate ofstream. Also, you can use a std::string charname rather than char charname[50].
You could also use an fstream with appropriate seeking. If I'm not mistaken have active ifstream and ofstream objects handling the same file can lead to undefined behavior.
Here's a more C++ friendly solution:
#include <iostream>
#include <string>
#include <fstream>
#include <list>
#include <iomanip>
int main()
{
char act;
std::string charname;
std::string namestr;
std::list<std::string> c1;
std::list<std::string>::iterator c1_Iter;
//write the names from the file into a list
std::ifstream names("names.txt");
while (std::getline(names, namestr))
{
c1.push_back(namestr);
}
//print the current names
std::cout << "Registered names:";
for (c1_Iter = c1.begin(); c1_Iter != c1.end(); c1_Iter++)
std::cout << "\n" << std::setw(5) << " " << *c1_Iter;
//choose which names to delete and confirm
std::cout << "\n\nEnter the name you would like to delete: ";
std::cin >> charname;
std::cout << "\nAre you sure? Enter 'y' to permanently delete " << charname << ", and any other key to return to the start screen.";
std::cin >> act;
if (act == 'y' || act == 'Y')
{
//delete a file associated with each name
std::string strname(charname);
strname.append(".txt");
if (remove(strname.c_str()) < 0)
{
std::cerr << "Error deleting file " << strname << std::endl;
return 1;
}
else
{
//delete name from the file only if that person's individual file is successfully deleted
c1.remove(charname);
std::cout << "\n" << charname << " successfully deleted!\n";
//print the updated list of names
std::cout << "\nUpdated list of registered names:\n";
for (c1_Iter = c1.begin(); c1_Iter != c1.end(); c1_Iter++)
std::cout << *c1_Iter << std::endl;
//write updated list of names over "List of Names" to update the file
names.close(); //Close the ifstream before opening the file for editing
std::ofstream newNames("names.txt");
for (c1_Iter = c1.begin(); c1_Iter != c1.end(); c1_Iter++)
newNames << *c1_Iter << std::endl;
newNames.close();
}
}
return 0;
}
I'm getting a segmentation fault while trying to parse a big text file. The file contains 91 529 mRNA transcripts and details about these transcripts. I've created a RefSeqTranscript object that will take these details. When I parse the file, I create a list of these objects and start putting the details into these lists. It works fine for the first 1829 transcripts and then crashes with a segmentation fault. The method I'm running is:
void TranscriptGBFFParser::ParseFile(list<RefSeqTranscript> &transcripts, const char* filepath)
{
cout << "Parsing " << filepath << "..." << endl;
ifstream infile;
infile.open(filepath);
int num = 0;
RefSeqTranscript *transcript = new RefSeqTranscript();
for(string line; getline(infile, line); )
{
in.clear();
in.str(line);
if (boost::starts_with(line, "LOCUS"))
{
if((*transcript).transcriptRefSeqAcc.size() > 0)
{
cout << (*transcript).transcriptRefSeqAcc << ":" << (*transcript).gi << ":" << (*transcript).gene.geneName << ":" << ++num << endl;
transcripts.push_back(*transcript);
delete transcript;
RefSeqTranscript *transcript = new RefSeqTranscript();
}
}
else if (boost::starts_with(line, " var"))
{
TranscriptVariation variant;
(*transcript).variations.push_back(variant);
}
//Store the definition of the transcript in the description attribute
else if (boost::starts_with(line, "DEFINITION"))
{
(*transcript).description = line.substr(12);
for(line; getline(infile, line); )
{
if(boost::starts_with(line, "ACCESSION "))
break;
(*transcript).description += line.substr(12);
}
}
//The accession number and GI number are obtained from the VERSION line
else if (boost::starts_with(line, "VERSION"))
{
string versions = line.substr(12);
vector<string> strs;
boost::split(strs, versions, boost::is_any_of( " GI:" ), boost::token_compress_on);
boost::trim_left(strs[0]);
(*transcript).transcriptRefSeqAcc = strs[0];
(*transcript).gi = atoi(strs[1].c_str());
}
//Gene information is obtained from the "gene" sections of each transcript
else if (boost::starts_with(line, " gene"))
{
for(line; getline(infile, line); )
{
if(boost::starts_with(line.substr(21), "/gene="))
{
Gene *gene = new Gene();
string name = line.substr(27);
Utilities::trim(name, '\"');
(*gene).geneName = name;
(*transcript).gene = *gene;
delete gene;
break;
}
}
(*transcript).gene.geneID = 0;
}
else if (boost::starts_with(line, " CDS"))
{
(*transcript).proteinRefSeqAcc = "";
}
else if (boost::starts_with(line, "ORIGIN"))
{
(*transcript).sequence = "";
}
}
cout << (*transcript).transcriptRefSeqAcc << ":" << (*transcript).gi << ":" << (*transcript).gene.geneName << endl;
transcripts.push_back(*transcript);
delete transcript;
cout << "No. transcripts: " << transcripts.size() << endl;
cout << flush;
infile.close();
cout << "Finished parsing " << filepath << "." << endl;
}
I'm new to C++ and don't have a great understanding of how to work with pointers etc so I'm guessing I might have done something wrong there. I don't understand why it would work for almost 2000 objects before cutting out though.
The file I'm parsing is 2.1 GB and consists of about 44 000 000 lines so any tips on how to improve the efficiency would also be much appreciated.
This is probably not the only answer, but you have a leak...
if (boost::starts_with(line, "LOCUS"))
{
if((*transcript).transcriptRefSeqAcc.size() > 0)
{
cout << (*transcript).transcriptRefSeqAcc << ":" << (*transcript).gi << ":" << (*transcript).gene.geneName << ":" << ++num << endl;
transcripts.push_back(*transcript);
delete transcript;
// LEAK!
RefSeqTranscript *transcript = new RefSeqTranscript();
}
}
You probably mean:
transcript = new RefSeqTranscript();
It's hard to say anything specific unless you provide some more details:
What line does it crashed in?
Do you really need all of those transcripts at the same time?
But I would suggest you a couple improvements:
Don't use pointer (or at least use smart pointer) for the RefSeqTranscript *transcript;
Don't use pointer for the Gene *gene;
Generally, don't use pointers unless you realy need them;
And you have a bug here:
delete transcript;
RefSeqTranscript *transcript = new RefSeqTranscript();
Since you've laready declared transcript outside the loop's body, here you hide it with new variable with the same name. This causes memory leak, and moreover, you delete an outer transcript and do not replace it with anything. So, you probably get a crash on the next iteration.