Array of struct from binary file - c

Question

I have to write a function that will read an array of structures of type Product with data from a binary file.This file contains the number of products - nr and a number of articles of type Product. What's wrong? Thank you in advance!
#define SIZE 30
typedef struc{
int id;
char[SIZE] name;
float price;
}Product;
void create(Product *p, FILE *fptr)
{
p = malloc(sizeof(Product));
fread(p, 1, sizeof(Product), fptr);
}
int main(int argc, char* argv[])
{
FILE *fptr = fopen(argv[1],"rb");
Product *p;
create(p, fptr);
return 0;
}

Answer 1

You have to modify it to something like this:
#include <stdio.h>
#include <stdlib.h>
#define SIZE 30
typedef struct{
int id;
char name[SIZE];
float price;
}Product;
int readproducts(Product *p, FILE *fptr, int nr)
{
if(nr != fread(p, sizeof(Product), nr, fptr))
return -1;
return 0;
}
int main(int argc, char* argv[])
{
FILE *fptr = fopen(argv[1],"rb");
int nr = 0;
if(NULL == fptr) return -1;
// First read number of products from file
// Assuming this number is written as 4 byte integer - at the start of file
if(fread(&nr, 4, 1, fptr) != 1)
return -1;
// Now, read the products
Product *p = malloc(nr * sizeof(Product));
if(-1 == readproducts(p, fptr, nr))
return -1;
fclose(fptr);
return 0;
}
The way you had used malloc in your function was wrong, see here why.
PS. That said, binary writing/reading might not be portable across different computers.