从包含其他结构的二进制文件中写入和读取结构（C）

Question

I have to write/read from a binary file some structs that I created, but when reading them back in, I get some nasty errors.

Take for example this construction:

typedef struct items
{
    char name[21], power[21];
    int stock;
    double price;
} ITEMS;

typedef struct shop
{
    char name[21];
    int numOfItems;
    ITEMS *arr;
} SHOP;

And now, I can create an array of SHOP and fill everything as is (creating an dynamic array for ITEM, for each SHOP[i]), but I'm not sure if:

fwrite(); actually writes the whole array, with all the info that is filled in for the ITEM's and when i use fread() it gives some access violation error.

What would be the correct approach, aside from using .txt files for I/O.

Here is a code sample: http://pastebin.com/79TtvQ9t

Answer 1

If you want to write structure, it should not have the pointer feilds. In this cases you should not write by structure. Because it write an address only for a pointer field

Answer 2

The problem is that you're writing the pointer to the file, that should end in something like this

21 chars -> coming from the char array "name" from struct shop

4 bytes -> coming from int numOfItems

4 bytes -> coming from the pointer to arr

so, your struct should become something like this

typedef struct shop
{
    char name[21];
    int numOfItems;
    ITEMS arr;
} SHOP;

that would end having something similar to this in the file

21 chars -> coming from the char array "name" from struct shop

4 bytes -> coming from int numOfItems

21 chars -> coming from the char array "name" from struct items

21 chars -> coming from the char array "power" from struct items

4 bytes -> coming from int stock

8 bytes -> coming from double price

The bytes may vary depending on the PC that you're running your app (in some PCs int has 2 bytes, in others 4, etc.)