Packet_sorting

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

//I cant define functions yet, so unfortunately everything is in main
//I tried to be as clear as possible anyway

int main()
{
    // - 1 -

    // "read_packet_file()"

    /* Here I'm going to get two variables for later use: 
        - total_str: The whole file as a single string, an array of all characters 
        - n_total_chars: The total number of characters */

    FILE *file;
    file= fopen("sample_packets.txt", "r"); //change sample_packets.txt for the name of your file

    if (file == NULL) 
    {
        fprintf(stderr, "Error opening file. %s\n", strerror(errno));
        exit(EXIT_FAILURE);
    }

    //Calculate the total number of chars in the file

    int n_total_chars= 1; //+1 for null char
    char c;

    while ((c = fgetc(file)) != EOF) //reads the chars til end of file
    {
        n_total_chars++;
    }

    /* I had to close and open the file to use the same loop again
    in order to set all the chars to a "string" variable
    
        (I guess there is a much better way to do this) */


    fclose(file);
    
    file= fopen("sample_packets.txt", "r");

    char total_str[n_total_chars]; //string size will be the number of chars in the file
    int i=0;

    while ((c = fgetc(file)) != EOF) //store chars in total_str
    {
        total_str[i]=c;
        i++;
    }
    
    
    //I dont need the file anymore, so I close it

    fclose(file);


    // - 2 - 

    // "parse_mac_dst()"

    /* Using the char index, here is a loop to append the mac dst addresses 
    into a two dimensional array called:
        - mac_array

    I has n_lines mac addresses (1 per line) and each string is 
    the size of the mac address length */

    //(Doesnt actually work as expected)

    char sample_line[]="00:00:5E:00:53:AF_2C-54-91-88-C9-E3_192.158.1.38_192.158.1.41_IPV4";
    char sample_mac[]="2C-54-91-88-C9-E3";  

    // Read sample lines to calculate the size of future strings and index

    int n_c_line=strlen(sample_line)+1; //number of chars per line (+ null char)
    int n_c_mac=strlen(sample_mac)+1; // number of chars in destination mac address
    int n_lines= n_total_chars / n_c_line; //number of lines

    char mac_array[n_lines][n_c_mac]; //array of mac strings     
    
    int mac, j, total_index;
    int i_start=18; //char index of mac address, where the first one starts
    
    //I cant figure out why mac_array[any index] sometimes is twice the size it should be
    
    for (mac=0; mac < n_lines; mac++) //number of addresses 
    {
        for (j=0; j < n_c_mac-1; j++) //loop over each address
        {
            total_index= i_start+(mac*n_c_line)+j; //index of the addresses chars

            mac_array[mac][j]=total_str[total_index];
        }
    }
    
    // - 3 -

    //"filter_mac_list()"

    /* Create new 2d array:
        - filtered_array
    It iterates over the strings in mac_array and skips the ones that have 
    duplicates in a later index and saves the ones that dont have duplicates */

    char filtered_array[n_lines][18]; // n_c_mac= 18
    int a, f, isfalse;
    int f_index=0; // Index of the filtered array

    for (f=0; f < n_lines; f++) // Index of the unfiltered array 
    {
        for (a=1; a < n_lines; a++)
        {
            if (f==n_lines-1) // In case it is the last string, so we end loop 
            {
                strcpy(filtered_array[f_index], mac_array[f]);
                break;
            }
            else
            {
                isfalse=strcmp(mac_array[f], mac_array[f+a]); // 0 If equal

                if (isfalse==0) 
                    break;  /* skip string if it has any duplicate in a later index, 
                                it will not be included in the filtered list */
                else if (a!=n_lines-1)
                    continue; //Check next index if we hadnt checked the last one yet 
                else
                    strcpy(filtered_array[f_index],mac_array[f]);
                    f_index++;

                    /* Store actual string in filtered_array, because it is different to all in the 
                    later index and increment index for the filtered_array */
            }     
        }  
    }
    
    // - 4- 

    //"print_mac_list()"

    /* Display filtered list of mac addresses */

    printf("Filtered destination mac addresses:\n\n%s", "[");
    int h=0;
    for (h=0; h < f_index; h++)    
    {
        if (h==f_index-1)
            printf("%s]\n", filtered_array[h]);
        else
            printf("%s,\n\n", filtered_array[h]);
    }

    return 0;
}