Question about files

**trekintouretter** · 11-15-2007

I am working on a game where I had too much global data. My current solution is to write the data to a file and then to read it back. Here is some code:

fstream f;
f.open("\\screens.txt", ios::in | ios:: out | ios::binary);
...
int screen0[20][20] = {...
for (int i = 0; i < 20; i++)
for (int j = 0; j < 20; j++)
f.write((unsigned char*)screen0[j][i], sizeof(int));
for (int i = 0; i < 20; i++)
for (int j = 0; j < 20; j++)
f.read((unsigned char*)screen[j][i], sizeof(int));

I have multiple arrays for each screen in the game (screen0, screen1...), and depending on a condition, I want to make the current screen a copy of that certain array. I do this by putting the selected screen in a file and then reading it out as the screen array.

I know it sound kinda wierd, but I have tried a lot of things and nothing has worked yet. The problem with this is that I get error messages in the linking process, such as
Undefined symbol filebuf:: openprot in module.
...

Does anyone have an idea what might be causing this? I would greatly appreciate any help you can offer.

**swoopy** · 11-15-2007

>Does anyone have an idea what might be causing this?
Did you #include <fstream>? You would need to include this in each file which needs the file streams.

**trekintouretter** · 11-17-2007

Originally Posted by swoopy

>Does anyone have an idea what might be causing this?
Did you #include <fstream>? You would need to include this in each file which needs the file streams.

I have included it, and it still gives me those errors. But wouldn't it give me a compiler error anyway?

**Salem** · 11-18-2007

Works for me on cygwin, which compiler are you using?

Code:

#include <fstream>
#include <iostream>
using namespace std;

int main ( ) {
    fstream f;
    f.open( "foo.bin", ios::in | ios:: out | ios::binary | ios::trunc );
    char msg[10] = "woohoo";
    f.write( msg, 10 );
    char test[10];
    f.seekg( 0, ios::beg );
    f.read( test, 10 );
    cout << test << endl;
    f.close();
}

> f.write((unsigned char*)screen0[j][i], sizeof(int));
1. It should be &screen0[j][i]
2. You could write out the whole array in one go with
f.write( (unsigned char*)screen0, sizeof screen0 );

**trekintouretter** · 11-20-2007

Thanks for responding. What does ios::trunc mean? and seekg?

**CornedBee** · 11-20-2007

The trunc flag means the file should be truncated to zero length on opening.

The seekg sets the read position.

You should look up stuff like that in a reference.

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