How to assign a value to an array of structures in C? - c

Question

There is a function load that reads an array of structures from a binary file and returns this array.It works correctly.But the problem is that I can not assign an array of structures the value that the load function returns.
struct tickets
{
char plane [7];
char zona [13];
int rate;
int cost;
};
struct tickets* load(char * filename)
{
FILE * file;
char *symbol;
int m = sizeof(int);
int n, i;
int *pti = (int *)malloc(m);
if ((file = fopen(filename, "r")) == NULL)
{
perror("Error occured while opening file");
}
symbol = (char *)pti;
while (m>0)
{
i = getc(file);
if (i == EOF) break;
*symbol = i;
symbol++;
m--;
}
n = *pti;
struct tickets* ptr = (struct tickets *) malloc(n * sizeof(struct tickets));
symbol = (char *)ptr;
while ((i= getc(file))!=EOF)
{
*symbol = i;
symbol++;
}
fclose(file);
return ptr;
}
int main(void)
{
char * filename = "p.dat";
struct tickets* ticket = NULL;
ticket = load(filename);
}

Answer 1

the following proposed code:
cleanly compiles
performs the desired functionality
properly checks for errors
informs the main() function as to how many instances of struct tickets were read
informs the user when any error occurs
cleans up after itself
eliminates one of the calls to malloc()
uses the function: fread() to avoid problems with little/big Endian
documents why each header file is included
assumes the ticket count (first 4 bytes of file) is in binary
incorporates appropriate horizontal and vertical spacing for readability
caveat: since no example input file posted, this code is not tested
and now, the proposed code:
#include <stdio.h> // perror(), NULL, FILE*, EOF,
// fopen(), fclose(), fread()
#include <stdlib.h> // malloc(), free(), exit(), EXIT_FAILURE
#define MAX_PLANE_LEN 7
#define MAX_ZONA_LEN 13
#define COUNT_LEN 4
struct tickets
{
char plane [ MAX_PLANE_LEN ];
char zona [ MAX_ZONA_LEN ];
int rate;
int cost;
};
struct tickets* load( char * filename, size_t * ticketCount )
{
FILE * fp;
if ( ! (fp = fopen( filename, "r" )) )
{
perror( "Error occured while opening file" );
exit( EXIT_FAILURE );
}
size_t bytesRead = fread( ticketCount, 1, COUNT_LEN, fp );
if( bytesRead != COUNT_LEN )
{
fprintf( stderr, "failed to read count of number of instances of 'struct tickets'\n" );
fclose( fp );
exit( EXIT_FAILURE );
}
struct tickets* ptr = malloc( *ticketCount * sizeof( struct tickets ) );
if( ! ptr )
{
perror( "malloc failed" );
fclose( fp );
exit( EXIT_FAILURE );
}
for( size_t i = 0; i < *ticketCount; i++ )
{
size_t numBytes = fread( &(ptr[i]), 1, sizeof( struct tickets ), fp );
if( numBytes != sizeof( struct tickets ) )
{
perror( "read of a struct ticket failed" );
fclose( fp );
free( ptr );
exit( EXIT_FAILURE );
}
}
fclose( fp );
return ptr;
}
int main( void )
{
char * filename = "p.dat";
size_t ticketCount = 0;
struct tickets* ticket = load( filename, &ticketCount );
// ...
free( ticket );
}