Thread: Why would ofstream not work sometimes?

Check out the following code:

Code:

obook.write(reinterpret_cast< const char * >(&newBook), sizeof(Book));

...where obook is an ofstream variable that opens a file using ios::ate and newBook is an instance of a class I made.

The problem is that when I write to the file, around 70% of the time, it will work. There is however, a good 30% of the time where it just writes garbage. Even when I'm entering the exact same data twice (exactly the same except the key field). Why would this happen?

Has anyone ever had this problem? I'd appreciate your insights. Thanks.

No it's not being opened in binary. It's in text mode. Here's how I play with it:

Code:

obook.open("books.dat", ios::ate);
if (obook){
   newBook = Book(isbn, author, title, publisher, pPlace, status, year, copy);
   obook.write(reinterpret_cast< char * >(&newBook), sizeof(Book));
   obook.close();
   newBook.show();
   cout<<"\n\nBook data written successfully.";
   getch();
   }
else{
   cout<<"\n\nCannot open transaction file."<<endl;
   getch();
   return;
   }

That's pretty harmless isn't it? I mean it works most of the time without a problem! I just don't understand why simple code can go rouge sometimes.

As for making sure if it is still good(), to be perfectly honest with you, I was never taught that. What's that?

Thanks again Codeplug.

As Codeplug says, you should open the file in binary mode:

obook.open("books.dat", ios::ate | ios::binary);

I've actually tried that. It doesn't work. And exactly as how you typed it too!

When you say text, do you mean that all of the variables in the class should be of the char* type? or do you mean text as in a literal string like "The quick brown fox was nuked by the lazy dog"?

Gotcha.

Starting afresh... (I wish they told us these things in school and in books)

I just tested it and it works. All the time.

I've come to realise why binary mode wasn't working for me. It was because I used fstream to create the file handler, and not ofstream. ofstream works beautifully. But I find that rather curious though. If you have any Idea why that would happen, please comment. A classmate is reading these posts as well, so it would benefit both of us.

Thanks yet again Codeplug. You are for me now what Prelude was for me last year. You guys rock.

With fstream you might try this:
obook.open("books.dat", ios::ate | ios::out | ios::binary);

And then for reading:
obook.open("books.dat", ios::in | ios::binary);

That's interesting Swoopy, I've never thought of that one. I'll give it a shot.

Got it. It's a shame though that C's implementation of files was so much simpler and more reliable. I get the feeling that somehow they were trying to reinvent the wheel with the text mode and it didn't work out so well - as far as standardisation is concerned anyways.