[НРС] Вежбе 9 (Припрема) - зад 2

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
#include <stdbool.h>
#include <math.h>
#include "ispit.h"

#pragma pack(4)

typedef bool polozeno(char);

char *createBuffer(int, int);
bool validateHex(char *);
int convertHexToBin(char *);
int prebroj(char *, polozeno *);
bool isPassed(char);

int main()
{
    int n,
        m;
    char *buffer;
    printf("Unesite broj studenata: ");
    scanf("%d", &n);
    printf("Unesite broj predmeta studenata: ");
    scanf("%d", &m);
    buffer = createBuffer(n, m);
    printf("\nUkupno polozenih ispita: %d.", prebroj(buffer, isPassed));
    free(buffer);
    return EXIT_SUCCESS;
}

char *createBuffer(int n, int m)
{
    char *buffer = NULL;
    if (n > 0 && m > 0)
    {
        int i,
            j;
        char hexNum[33];
        buffer = (char *)malloc(2 * sizeof(int) + n * m * sizeof(ispit));
        *buffer = n;
        *(buffer + sizeof(int)) = m;
        for (i = 0; i < n; i++)
        {
            printf("Unos podataka o ispitima za %d. studenta: \n", i + 1);
            for (j = 0; j < m; j++)
            {
                fflush(stdin);
                int skip = 2 * sizeof(int) + i * m * sizeof(ispit) + j * sizeof(ispit);
                printf("Unos dana ispita broj %d: ", j + 1);
                scanf("%hd", (short *)&buffer[skip]);
                printf("Unos meseca ispita broj %d: ", j + 1);
                scanf("%hd", (short *)&buffer[skip + sizeof(short)]);
                printf("Unos godine ispita broj %d: ", j + 1);
                scanf("%hd", (short *)&buffer[skip + 2 * sizeof(short)]);
                printf("Unos ocene ispita broj %d: ", j + 1);
                fflush(stdin);
                scanf("%i", buffer + skip + 3 * sizeof(short));
                do
                {
                    fflush(stdin);
                    printf("Unos sifre ispitnog roka za ispit broj %d u HEX formatu: 0x", j + 1);
                    scanf("%s", hexNum);
                } while (!validateHex(hexNum));
                *((int *)&buffer[skip + 3 * sizeof(short) + 2 * sizeof(char)]) = convertHexToBin(hexNum);
                printf("Unos imena profesora za ispit broj %d: ", j + 1);
                scanf("%s", buffer + skip + 3 * sizeof(short) + 2 * sizeof(char) + sizeof(int));
            }
        }
        return buffer;
    }
}

bool validateHex(char *hex)
{
    int i;
    for (i = 0; i < strlen(hex); i++)
    {
        hex[i] = toupper(hex[i]);
        if ((hex[i] < '0' || hex[i] > '9') && (hex[i] < 'A' || hex[i] > 'F'))
        {
            return false;
        }
    }
    return true;
}

int convertHexToBin(char *hex)
{
    int ret = 0,
        i;
    float powIndex = 0;
    for (i = strlen(hex) - 1; i >= 0; i--, powIndex++)
    {
        int tmp;
        if (hex[i] > '0' && hex[i] < '9')
        {
            tmp = hex[i] - '0';
        }
        else
        {
            switch (hex[i])
            {
            case 'A': // znamo da ce sva slova biti velika jer smo ih izmenili u validate funkciji
                tmp = 10;
                break;
            case 'B':
                tmp = 11;
                break;
            case 'C':
                tmp = 12;
                break;
            case 'D':
                tmp = 13;
                break;
            case 'E':
                tmp = 14;
                break;
            case 'F':
                tmp = 15;
                break;
            }
        }
        ret += tmp * pow(16, powIndex);
    }
    return ret;
}

int prebroj(char *buffer, polozeno *function)
{
    int n = *buffer,
        m = *(buffer + sizeof(int)),
        counter = 0,
        i,
        j;
    for (i = 0; i < n; i++)
    {
        for (j = 0; j < m; j++)
        {
            int skip = 2 * sizeof(int) + i * m * sizeof(ispit) + j * sizeof(ispit);
            if (function(*((char *)&buffer[skip + 3 * sizeof(short)])))
            {
                counter++;
            }
        }
    }
    return counter;
}

bool isPassed(char ocena)
{
    return ocena > 6 ? true : false;
}