Testing fstream files.

[Falco Girgis]

I was working on some advanced debuggery last night (to cancel out some of Marcel's blatant douchebaggery when it comes to loading levels).

At the moment, individual loading functions are using C-style text file manipulation:

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FILE *file = fopen("file.txt", "r");

That's completely sweet and all, and I can test the stream simply by:

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if(!file) printf("Marcel screwed something up.\n");

Now the overall debug system uses C++ fstreams (because it's newer, my older code was all C-style).

I'd like to achieve essentially the same thing:

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ifstream file("file.txt");
if(!file.good()) cout << "Marcel screwed something up.\n";

The problem is that the program shits itself when the file is instantiated, and doesn't even get to the good() or bad() tests (which I do believe is the correct way to check the status of the filestream.)

I'd like to know how I'd make the program continue if the file cannot be openned.

[Falco Girgis]

Wtf, I tried this in dev-cpp real quick:

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#include <iostream>
#include <fstream>

using namespace std;

int main() {
    int dummy;
    ifstream file("nothere.txt", ios::in);
    
    if(!file.good()) cout << "Screwed it.\n";
    else cout << "goooood.\n";
    
    cin >> dummy;
    return 0;
}

and it does exactly what I wanted it to.

I wonder if I have some sort of setting wrong in MSVC++. Maybe it does give some sort of exception error when it quits, so maybe debug quits when exceptions are thrown and not caught?

[MarauderIIC]

You don't need the .good(), it's redundant (afaik, unless msvc does something else with it)

This should work:

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int main() {
    ifstream file("doesNotExist.txt");
    ifstream file2("exists.txt");

    if (!file)
        cout << "Error loading file" << endl; //endls flush output buffer
    while (file) {    //checks for .eof() and other failure conditions
        doStuff();
    }

    if (!file2)
        cout << "Error loading file" << endl;
    while (file2) {    //checks for eof() or other failure conditions
//(say someone deleted file while we were reading it, or is corrupt, or something)
        doStuff();
    }
    //if you want you can do this i guess, i'm not sure if it'd work
    if (!file2.eof())
        cout << "An unexpected error occurred before reaching the eof" << endl;
    return 0;
}

And what, does ifstream throw an exception or something? On the constructor line? Shouldn't do that unless you're out of memory or something...

[Falco Girgis]

Oh, wtf?

So is the logical negation operator overloaded to return false if it's screwed and true if not? Because that file isn't a pointer like it was in C.

But that's really nice, I can stick with the same notation that I'm used to.

edit: Yeah, I believe that it does, because either MSVC++ or Windows gives me some sort of exception thrown error.

[MarauderIIC]

I edited the post, where exactly does it barf? On constructor?

[Falco Girgis]

Yes, I believe so. I'll have to go home and mess with it more. I'll tell you what's happening.

[MarauderIIC]

Hum. (It shouldn't barf there, post the whole code, I guess. d:)

[MarauderIIC]

Neat. You can force it to throw exceptions on certain failures (but it doesn't default to any, of course). http://www.cplusplus.com/reference/iost ... tions.html

Also, instead of checking for individual error states, perror() should work, or so I read (it's amazing the amount of useful stuff that classes miss and the amount of useless stuff they pack in).

[kilgariff]

FILE *file = fopen("file.txt", "r");

Just a thought, are you guys using text files for maps?

Or when you say levels, do you mean something else, like names of items and stuff?

[Falco Girgis]

I was referring to "level" as in everything that needs to be loaded for a new area.

We read/write our maps in binary.