CODEWITHSUNDEEP
carraysstruct
guyz92
guyz92

Reputation: 15

Getting number of items from Struct Array in C

I am trying to get the size of a struct array read from a binary file so that I can do a for loop to retrieve all the records.

The code below is able to read the file in binary form and return as a buffer. The buffer is then "Cast" as a features(struct).

I have tried sizeof(features) / sizeof(struct feature_struct), it fails to return a valid count so that I can use it as with for loop.

The code below I have hardcoded the loop limit to below 9. Where 9 have to be dynamically detect by the system.

Thanks in advance !.

#include <stdio.h>
#include <stdlib.h>

/* the maximum length of a feature identifier (including the terminating null) */
#define MAX_ID      12
/* the maximum length of a feature name (including the terminating null) */
#define MAX_NAME    256

typedef int                int32_t;

typedef struct feature_struct {
    char        type;            /* feature type */
    char        id[MAX_ID];      /* unique identifier */
    char        name[MAX_NAME];  /* name */
    int32_t     xloc;            /* x location */
    int32_t     yloc;            /* y location */
    int32_t     xdim;            /* x dimension */
    int32_t     ydim;            /* y dimension */
} FEATURE;

int main(){
    int n;
    struct feature_struct* features;
    FILE *fptr;
    long lSize;  
    FEATURE* buffer;
    size_t result;

    if ((fptr = fopen("structsFile.bin","rb")) == NULL){
       printf("Error! opening file");

       // Program exits if the file pointer returns NULL.
       //exit(1);
    }


    // obtain file size:
    fseek (fptr , 0 , SEEK_END);
    lSize = ftell (fptr);
    rewind (fptr);

    buffer = malloc ( sizeof(struct feature_struct) * lSize );
    result = fread (buffer,1,lSize,fptr);
    if (result != lSize) {
        fputs ("Reading error",stderr); 
    }

    features = buffer;

    for (int i = 0; i < 9; i++){
        printf("%s\n", features[i].name);
    }


    fclose(fptr);

    /*
    for(n = 1; n < 5; ++n)
    {
      fread(&features, sizeof(struct feature_struct), 1, fptr); 
      printf("name: %s\n",features.name);
      printf("location: %c\n", features.type);
    }

    */

   return 0;

}

Upvotes: 0

Views: 463

Answers (1)

Elad Hazan
Elad Hazan

Reputation: 331

lSize/sizeof(struct feature_struct)???

Assuming it contains only data of type struct feature_struct

Upvotes: 1

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