How can I create a matrix that only has structs, and then to create a thread for each data that is stored in the matrix?

Question

I'm creating a matrix of dimension [10][10], that stores a struct Contentor,I can't change the values inside the matrix nor store them.

I try to check if there is any data with a for loop but can't see what's inside.

When I store data inside the matrix I try to create a thread of each one of them to process the data, but I don't really know how to do it...

I have tried using malloc and calloc, I create the matrix in the rudimentary form but nothing seems to work...

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

struct Contentor {

    char nSerie[36];
    char porto[4];

};

void* direcionaParaDestino(void* arg) {
    struct Contentor *arg_struct = (struct Contentor*) arg;

    char destino[4] = arg_struct->porto;

    if(strcmp(destino, "ANR")) {

    } else if (strcmp(destino, "BUS")) {

    } else if (strcmp(destino, "DXB")) {

    } else if (strcmp(destino, "GUA")) {

    } else if (strcmp(destino, "HAM")) {

    } else if (strcmp(destino, "HKG")) {

    } else if (strcmp(destino, "LAX")) {

    } else if (strcmp(destino, "RTM")) {

    } else if (strcmp(destino, "SHA")) {

    } else if (strcmp(destino, "SIN")) {

    }

    pthread_exit(0);
}


int main() {
    struct Contentor parque[10][10] = malloc(100*sizeof(struct Contentor));


    for(int i = 0; i < 10; i++) {
        for(int j = 0; j < 10; j++) {
            parque[i][j].nSerie = "";
            parque[i][j].porto = "";
        }
    }


    pthread_t tids[10][10];
    for(int i = 0; i < 10; i++) {
        for(int j = 0; j < 10; j++) {
            if(strcmp(parque[i][j].nSerie,"")) {
                printf("Lugar [%d][%d] encontra-se Livre\n", i, j);
                //Criar Thread que espera ate 5 segundos
                                short randomNumber = rand() % 5
                pthread_attr_t attr;
                        pthread_attr_init(&attr);
                        pthread_create(&tids[i][j], &attr, direcionaParaDestino, 1 );
                                sleep(randomNumber);

            } else {
                printf("Lugar [%d][%d] encontra-se Ocupado\n", i, j);

            }
        }
    }
    for(int i = 0; i < 10; i++) {
        for(int j = 0; j < 10; j++) {
            pthread_join(tids[i][j],NULL);
        }
    }

}

I want it to be a matrix of that struct, check if there is any data in each spot, then store it and create a thread for each variable stored that will wait up to 5 secs before processing the information.

Answer 1

You can't initialize arrays from other arrays or pointers. And neither can you assign to arrays.

So

char destino[4] = arg_struct->porto;

is invalid.

There are two ways to solve this problem for you:

1. Rely on the fact that arrays naturally decay to pointers to their first element. That is, if a pointer is expected then arg_struct->porto is equal to &arg_struct->porto[0]. That means you can do

   char *destino = arg_struct->porto;
   

2. Not have any destino variable at all, and pass arg_struct->porto directly to your strcmp calls:

   if (strcmp(arg_struct->porto, "BUS") == 0) ...
   

Also note that strcmp returns zero if the two strings are equal. That's the reason for the equality comparison against zero above.

---

The inability to assign to an array is also why statements like

parque[i][j].nSerie = "";

will fail.

If you want the arrays to act like empty strings, all you need to do is set the first element to the null terminator:

parque[i][j].nSerie[0] = '\0';  // Make string "empty"

If you want to clear all bytes of the array, you need to use the memset function:

memset(parque[i][j].nSerie, 0, sizeof parque[i][j].nSerie);  // "Clear" array