I am a student Just learning c++ so I am sure there are much more efficient ways of doing this; with that said I would really appreciate some help figuring out why my program crashes. I have narrowed it down the a strcpy function that crashes everything and breaks it, which I have commented out and labeled. I have obviously used the strcpy function multiple times in the program with similar parameters, so I don't understand why that specific one crashes. I have tried everything I can think of and really appreciate the help. As of now I have a lot commented out so it should run with the right text file named "bookdb" my text file currently has this in it
Active Learning Approach,Randal Albert,9780763757236,1,650,1,<br>
Technical Communications,John Lannon,9780321899972,2,724,0,
to see the error you will have to un-comment strcpy(bookArray[num_books].author_name, temp_authorName);
#define _CRT_SECURE_NO_WARNINGS
#include <iostream>
#include <iomanip>
#include <fstream>
#include <cstring>
enum Genres {HORROR=1, SCIFI, COMEDY, DRAMA, ACTION};
struct Book
{
char title[100];
char author_name[50];
char isbn[14];
Genres genre;
int num_pages;
bool paperback;
};
//Function Declarations
unsigned short ReadBooks(Book * bookArray, unsigned short & num_books);
void DisplayBooks(Book * bookArray, unsigned short num_books);
void ResizeArrays(Book * bookArray, unsigned short num_books);
int main ()
{
unsigned short num_books = 0;
Book * bookArray = new Book();
num_books = ReadBooks(bookArray, num_books);
}//End Main
unsigned short ReadBooks(Book * bookArray, unsigned short & num_books)
{
ifstream readBooks("bookdb.txt");
char temp_title[100] = "0";
char temp_authorName[100] = "0";
char temp_isbn[14] = "0";
char temp_genre[50] = "0";
char temp_numPages[50] = "0";
char temp_paperback[50] = "0";
int genreNumber = 0,
numPages = 0,
paperback = 0;
if (readBooks.is_open() )
{
cout << "The file was successfully opened\n" << endl;
readBooks.getline(temp_title, 100, ',');//Reads into temp cstring
strcpy(bookArray[num_books].title, temp_title); //copies to dynamic cstring
//cout << bookArray[num_books].title << endl; //displays part of structure to make sure it worked!!
readBooks.getline(temp_authorName, 100, ',');
strcpy(bookArray[num_books].author_name, temp_authorName);
//cout << bookArray[num_books].author_name << endl;
readBooks.getline(temp_isbn, 14, ',');
strcpy(bookArray[num_books].isbn, temp_isbn);
//cout << bookArray[num_books].isbn << endl;
readBooks.getline(temp_genre, 50, ',');//Get the genre as a char
genreNumber = atoi(temp_genre);//converts char to an int
bookArray[num_books].genre = static_cast <Genres> (genreNumber);//converts int to ENUM
//cout << bookArray[num_books].genre << endl;//Displays ENUM to make sure it worked!!
readBooks.getline(temp_numPages, 50, ',');
numPages = atoi(temp_numPages); //converts char to an int
bookArray[num_books].num_pages = numPages; //assigns int to structure
//cout << bookArray[num_books].num_pages << endl; //Displays part of structure to make sure to works!!
readBooks.getline(temp_paperback, 50, ',');
paperback = atoi(temp_paperback); //converts char to an int
bookArray[num_books].paperback = static_cast <bool> (paperback);
//cout << bookArray[num_books].paperback << endl;
num_books++;
//DisplayBooks(bookArray, num_books);
ResizeArrays(bookArray, num_books);
cout << "The number of books is: " << num_books << endl;
//while (!readBooks.eof() )
//{
readBooks.getline(temp_title, 100, ',');//Reads into temp cstring
strcpy(bookArray[num_books].title, temp_title); //copies to dynamic cstring
cout << bookArray[num_books].title << endl; //displays part of structure to make sure it worked!!
readBooks.getline(temp_authorName, 100, ',');
cout << temp_authorName << endl;
//strcpy(bookArray[num_books].author_name, "0");
///THIS BREAKS MY CODE////strcpy(bookArray[num_books].author_name, temp_authorName);
//cout << bookArray[num_books].author_name << endl;
readBooks.getline(temp_isbn, 14, ',');
//strcpy(bookArray[num_books].isbn, temp_isbn);
//cout << bookArray[num_books].isbn << endl;
readBooks.getline(temp_genre, 50, ',');//Get the genre as a char
//genreNumber = atoi(temp_genre);//converts char to an int
//bookArray[num_books].genre = static_cast <Genres> (genreNumber);//converts int to ENUM
//cout << bookArray[num_books].genre << endl;//Displays ENUM to make sure it worked!!
readBooks.getline(temp_numPages, 1000, ',');
//numPages = atoi(temp_numPages); //converts char to an int
//bookArray[num_books].num_pages = numPages; //assigns int to structure
//cout << bookArray[num_books].num_pages << endl; //Displays part of structure to make sure to works!!
readBooks.getline(temp_paperback, 50, ',');
//paperback = atoi(temp_paperback); //converts char to an int
//bookArray[num_books].paperback = static_cast <bool> (paperback);
//cout << bookArray[num_books].paperback << endl;*/
num_books++;
//ResizeArrays(bookArray, num_books);
//}//End while
readBooks.close();
}//End if
else
{
cout << "There was not an existing book file, so one will be created" << endl;
}//End else
return 0;
}//End ReadBooks
void DisplayBooks(Book * bookArray, unsigned short num_books)
{
for (unsigned short i = 0; i < num_books; i++)
{
cout << setw(30) << left << bookArray[i].title << left << setw(20) << bookArray[i].author_name << left << setw(15) << bookArray[i].isbn
<< left << setw(3) << bookArray[i].genre << left<< setw(6) << bookArray[i].num_pages << left << setw(4) << bookArray[i].paperback << endl;
}//End For
}//ENd Display Function
void ResizeArrays(Book * bookArray, unsigned short num_books)
{
Book * temp_bookArray = new Book[num_books + 1];
for (int i = 0; i < num_books; i++)
{
strcpy(temp_bookArray[i].title, bookArray[i].title);
//cout << temp_bookArray[i].title << endl; //For Debugging
strcpy(temp_bookArray[i].author_name, bookArray[i].author_name);
//cout << temp_bookArray[i].author_name << endl; //for Debugging
strcpy(temp_bookArray[i].isbn, bookArray[i].isbn);
//cout << temp_bookArray[i].isbn << endl;//for debugging
temp_bookArray[i].genre = bookArray[i].genre;
//cout << temp_bookArray[i].genre << endl;//for debugging
temp_bookArray[i].num_pages = bookArray[i].num_pages;
//cout << temp_bookArray[i].num_pages << endl;// for debugging
temp_bookArray[i].paperback = bookArray[i].paperback;
//cout << temp_bookArray[i].paperback << endl; //for debugging
}//End for
delete [] bookArray;
bookArray = temp_bookArray;
DisplayBooks(bookArray, num_books); //debugging to make sure bookArray is reassigned
}//End Resize Function
strlen gets all elements without '\\0',so if you have str = "1234"; the str length is 5,(1234 + '\\0) but return 4.Strcpy take all 5 elements + '\\0' .
There are problems with the ResizeArrays:
Just to fix this to the point where it will work, you can do something like:
Book* ResizeArrays(Book * bookArray, unsigned short num_books)
{
....
return bookArray;
}
Then use the function in this way
bookArray = ResizeArrays(bookArray, num_books);
However, as you use an array delete, for your first allocate, you need to use an array allocation in main() as well,
Book * bookArray = new Book[1];
Even though its only allocating one book, it should be done as an array, so it is compatible with the delete [] used in ResizeArrays.
I assume this is a learning exercise. In normal use of C++ you wouldn't use naked new and delete operators. Either you would simply use std::vector or similar, or to create an object that will manage the memory, with the new and delete in the constructor and destructor respectively.
Problems that I see:
Problem 1
There isn't enough space to hold the ISBN properly. The length of ISBN in your input file is 14 characters long. To hold them in a null terminated string, you need to have an array that can hold 15 or more characters.
As a result, the line
readBooks.getline(temp_isbn, 14, ',');
will stop reading after 13 characters since it has to use the 14-th character to store '\\0'
.
Problem 2
This line doesn't look right.
readBooks.getline(temp_numPages, 1000, ',');
I suspect this was a typo and you meant
readBooks.getline(temp_numPages, 50, ',');
Problem 3
There are problems with handling of memory in ResizeArray
.
void ResizeArrays(Book * bookArray, unsigned short num_books)
{
Book * temp_bookArray = new Book[num_books + 1];
// Here, you are deleting the memory that was allocated in `main`.
// bookArray in the calling function now points to memory that has been
// deleted here.
delete [] bookArray;
// Here, you are changing the value of bookArray but only
// locally in this function. This assignment doesn't
// change the value of bookArray in the calling function.
bookArray = temp_bookArray;
DisplayBooks(bookArray, num_books); //debugging to make sure bookArray is reassigned
}//End Resize Function
If you change ResizeArray
to:
void ResizeArrays(Book*& bookArray, unsigned short num_books)
things will be better.
Problem 4
I see that you have commented out the while
loop in ReadBooks
. If you decide to bring that loop back to life, you'll have to resize bookArray
in each run of the loop.
Suggestion It will be easier to use an std::vector<Book*>
to hold the books instead of allocating memory for arrays of Books
.
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