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

const int writingIterations = 3;
const int charsToWrite = 5;

void writeDataInFile();
void readDataFromFile();
void printArr(int *arr,int n);

int main() {
    writeDataInFile();
    readDataFromFile();
    return 0;
}

void writeDataInFile() {
    FILE *fp;
    int n =writingIterations;
    int num = 1;
    char letters[charsToWrite];

    for(int i = 0; i < charsToWrite; i++) {
        letters[i] = 'a' + i;
    }

    if((fp = fopen("nums.txt","wb")) == NULL) {
        printf("Error trying to find file.");
        exit(1);
    }

    //write one int and four chars
    for(int i = 0; i < n; i++) {
        if(fwrite(&num,sizeof(int),1,fp) != 1) {
            printf("Error trying to write num.");
            exit(1);
        }

        num++;

        for(int j = 0; j < 5; j++) {
            if(fwrite(&letters[j],sizeof(char),1,fp) != 1) {
                printf("Error trying to write char.");
                exit(1);
            }
        }
    }

    if(fclose(fp) == EOF) {
        printf("Error trying to close file ");
        exit(1);
    }
}

void readDataFromFile() {
    FILE *fp;
    int n,*arr,num,i,j;
    char letter;

    n = 10;

    if((arr = (int *)malloc(n*sizeof(int))) == NULL) {
        perror("Error allocatting memory");
        exit(1);
    }

    if((fp = fopen("nums.txt","rb")) == NULL) {
        printf("Error trying to find file.");
        exit(1);
    }

    i = 0;
    while(fread(&num,sizeof(int),1,fp) == 1) {
        arr[i++] = num;
        if(i == n) {
            n +=5;
            if((arr = (int *)realloc(arr,n * sizeof(int))) ==NULL) {
                perror("Problem with reallocating memory");
                exit(1);
            }
        }

        for(j = 0; j < 5; j++) {
            if(fread(&letter,sizeof(char),1,fp) != 1) {
                printf("Error trying to read char.");
                exit(1);
            }
            arr[i++] = (int)(letter);
            if(i == n) {
                n +=5;
                if((arr = (int *)realloc(arr,n * sizeof(int))) ==NULL) {
                    perror("Problem with reallocating memory");
                    exit(1);
                }
            }
        }
    }

    printArr(arr,n);

    free(arr);
    if(fclose(fp) == EOF) {
        printf("Error trying to close file ");
        exit(1);
    }
}

void printArr(int *arr,int n) {
    int i,j,k;

    for(i = 0,j = 0; i < writingIterations; i++) {
        printf("%d ",arr[j++]);
        for(int k = 0; k < charsToWrite; k++) {
                printf("%c ",arr[j++]);
        }

        printf("\n");
    }
}