issue reading in data

Question

I am having trouble reading data from a file into a list in a class. It seems like an extra hexadecimal value is being picked up somewhere.

Data: (what I want output to look like) enter image description here

Output: (extra 0x4463c4 is randomly included) enter image description here

Here is a bit of code i think is relevant. Can anyone advise me of errors I may have made?

Where data is read into program from file (main):

struct filmType { char number[6]; char copy; char title[31]; char rent_id[5]; char rent_date[9]; char return_date[9]; }; orderedList <filmType> orderedList; filmType newItem; //start of struct record filmFile.open("films.txt", ios::in); filmFile >> numFilm; filmFile.get(); while (!filmFile.eof()) { filmData.copy = filmFile.get(); readString(filmFile, newItem.title,30); readString(filmFile, newItem.rent_id,4); readString(filmFile, newItem.rent_date,8); readString(filmFile, newItem.return_date,8); filmFile.get(); orderedList.insert (newItem); readString(filmFile, filmData.number,5); }

orderedlist.insert function:(fills list in class)

void orderedList<elemType>::insert(const elemType& newItem) { int index = length - 1; bool found = false; if (length == MAX_LIST) throw string ("List full - no insertion"); // index of rear is current value of length while (! found && index >= 0) if (newItem < list[index]) { list[index + 1] = list [index]; // move item down --index; } else found = true; list [index + 1] = newItem; // insert new item ++length; }

Orderedlist.display function: (outputs list to console)

void orderedList<elemType>::display() const { int index; if (length == 0) throw string ("List empty"); for (index = 0; index < length; ++ index) cout << list[index] << endl; }

readString:

void readString (fstream & inFile, char * string, int length) { inFile.get (string, length + 1); }

Any help is appreciated, let me know if anything needs to be clarified or if more code from the program needs to be seen. Thanks!

You obviously have a complex program, and you recognized that it was too complex to post in its entirety. Instead of posting bits of a big program, how about posting all of a smaller program? Please reduce your program to the smallest possible program that compiles, runs, and shows your error. See sscce.org for more information about this debugging technique. — Robᵩ
– Robᵩ, Commented Oct 17, 2011 at 22:10
In the alternative, step through you program in a debugger. Stop after each file input operation and examine the data that was input. Where does your program first vary from you expection? — Robᵩ
– Robᵩ, Commented Oct 17, 2011 at 22:13
It's not really obvious from the code, try reducing it and validating each step. UnitTest++ is a great framework for these sorts of projects. And for the love of all that is sacred, don't throw strings. Throw something that inherits from std::exception. std::logic_error or std::runtime_error are obvious candidates. — Tom Kerr
– Tom Kerr, Commented Oct 17, 2011 at 22:15

Marc Plano-Lesay · Accepted Answer · 2011-10-17 22:13:47Z

0

You're passing structs objects to cout, which doesn't know how to display them. The hex values you get are your structs objects addresses.

answered Oct 17, 2011 at 22:13

Marc Plano-Lesay

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6 Comments

FailedDev Over a year ago

If operator << was not overloaded the program would not even compile. Your assumption is wrong.

darko Over a year ago

I thought overloading << addressed that problem. I did so in my header: ostream & operator << (ostream & out, const filmType & a) { out << a.number << " " << out << a.copy << " " << out << a.title << " " << out << a.rent_id << " " << out << a.rent_date << " " << out << a.return_date << endl; return out; } (sorry, how might I format code in comments?)

Marc Plano-Lesay Over a year ago

Oh, I though the compiler would display memory address, like with pointers. Then the problem is probably in his implementation of operator<<

Marc Plano-Lesay Over a year ago

That's it. Remove all your out except the first.

FailedDev Over a year ago

@mwmnj Without knowing how filmType looks like we can't pinpoint your problem, however your problem is definitely located here. Check what you are printing, it seems to me you are printing the address of something.

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Community · Accepted Answer · 2017-05-23 10:29:17Z

End of File in C++

.eof() will not return true until after a read actually fails. Which means for the last loop:

while (!filmFile.eof()) //last read worked ok! { filmData.copy = filmFile.get(); //oh, reached end now. read in nothing

Which means the rest of that loop is incorrect. Generally, the pattern is like this:

filmFile.open("films.txt", ios::in); while (readString(filmFile, filmData.number,5)) { filmFile.get(filmData.copy) readString(filmFile, newItem.title,30); readString(filmFile, newItem.rent_id,4); readString(filmFile, newItem.rent_date,8); readString(filmFile, newItem.return_date,8); filmFile.get(); if (filmFile) //make sure there weren't errors orderedList.insert (newItem); }; fstream& readString (fstream & inFile, char * string, int length) { return inFile.get (string, length + 1); }

Which means as soon as the read fails (from eof), the while condition fails, and breaks out of the loop.

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