Trying to read/write structs to binary files...

[supersumo]

I'm trying to use binary files to save my level data for a game. I had it working fine using text files, but I want to use binary files. The functions save the map array, but not the items or enemy array.
here is the kind of data I want to save:
int map[19][550];
ENEMY *enemy = new ENEMY[MAX_ENEMIES];
ITEM *item = new ITEM[MAX_ITEMS];

here are the functions to save/load:

int load_map(char *s) {
int old_max_items, old_max_enemies, i;
ifstream file_in(s, ios::in | ios::binary);
if (!file_in.is_open()) return 1;
file_in.read((char *)map, sizeof(map));
file_in.read((char *)enemy, sizeof(enemy));
file_in.read((char *)item, sizeof(item));
file_in.close();
return 0;
}

int save_map(char *s) {
ofstream file_out (s, ios:ut | ios::binary | ios::trunc);
if (!file_out.is_open()) return 1;
file_out.write((char *)map, sizeof(map));
file_out.write((char *)enemy, sizeof(enemy));
file_out.write((char *)item, sizeof(item));
file_out.close();
return 0;
}

can anybody tell me why it wont save the enemy/item data, but it will save the map. Does it matter that enemy and item are pointers to struct and that map is a regular array?

 

[palbano]

>> Does it matter that enemy and item are pointers to
>> struct and that map is a regular array?

of course it does. sizeof() only knows that "enemy" and "item" are pointers not how many of them their are. Assuming that ENEMY and ITEM are data structures and not classes, you need to supply the actual size to the write() function:

file_out.write((char*)enemy, sizeof(enemy) * MAX_ENEMIES);

-pete

 

[supersumo]

thanks. That worked.

 

[mseth]

I've found the easiest method to read and write structures in "raw" mode is to use C-style input/output for files.

fread(&structname,sizeof(struct),1,file_in);

fwrite(&structname,sizeof(struct),1,file_out);

You can look these up for further information. Please note: if your struct has pointers to dynamic memory, you will have to handle re-designating the addresses pointed to the next application instance, since it will not be the same.