unable to read struct from a binary file using C when file is not 100% filled as expected -

i have file try read contacts simple contactbook using structure.

typedef struct contact{     char name[80];     char surname[80];     char cellnumber[20];     float length;     int contactid; }contact; 

i use function , call reads 200 times (const int maxcontact = 200;).

for(i2=0;i2<maxcontact;i2++)     person[i2]=load(i2); 

this function given id (the variabile i), returns contact has same i:

contact load(int i){     struct contact person;     file *data;     data=fopen("data.bin","rb");     do{         fread(&person,sizeof(contact),1,data);     }while(person.contactid!=i);     fclose(data);     return person; } 

the problem kind of code is, when there no 200 contacts, function not return contact because contact id can't found.

i had solutions in mind rather complex , wanted know if done better.

1. make installer creates files real installer , create 200 undeclared contacts variabiles equal null.

2. check if program being ran first time , same thing above in program itself.

3. if contact id not found exit searching loop equally , return undecleared contact variabiles set null.

after writing this, 3 questions come mind:

which 1 of these best 1 or easiest work with?

is safe return undecleared contact? (i have keep in mind have work contacts: modefy, print, print contacts)

should have structure , file write down statistics of variabiles not used in contact structure/file?

try following approach, linear complexity, if contact absent, initialized 0.

/* initialize memory */ memset(person, 0, maxcontact * sizeof(contact0);  /* open file */ data=fopen("data.bin","rb");  /* file size */ fseek(data, 0l, seek_end);  /* don't read more allocated array can contain */ int size = max(ftell(data), maxcontact * sizeof(contact));  /* seek beginning of file */ fseek(fp, 0l, seek_set);  /* populate array */ fread(&person,size,1,data);  /* close file */ fclose(data);