Elaborato_SO/src/custom_shm.c

#include <stdio.h>
#include <sys/shm.h>
#include <sys/stat.h>
#include <custom_shm.h>
#include <errno.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>

#include <errExit.h>
#include <forza4.h>

int _SHMID;

tile_t *shmServerAt();

void setupServerShm() {
    _SHMID = getShmidServer();
    _BOARD = shmServerAt();
    
    for (int i = 0; i < _ROWS * _COLLUMS; i++) {
        _BOARD[i] = EMPTY;
    }
}

void setupClientShm() {
    printf(PCLIENT "Setting up shm\n");
    _SHMID = getShmidClient();
    _BOARD = shmClientAt();
}

int getShmidClient() {
    return shmget(ftok(KEYFILE, SHMKEY), _ROWS * _COLLUMS * sizeof(tile_t), IPC_CREAT | S_IRUSR | S_IWUSR);
}

int getShmidServer() {
    key_t key = ftok(KEYFILE, SHMKEY);
    int shmid = shmget(key, _ROWS * _COLLUMS * sizeof(tile_t), IPC_CREAT | IPC_EXCL | S_IRUSR | S_IWUSR);
    if (shmid == -1) {
        // if errno was set to EEXIST, that means the memory location is alredy allocated
        // the server fork and the child remove the memory
        if (errno == EEXIST) {
            char buf[100];
            sprintf(buf, "The board alredy exit, I'll remove it now\n");
            warningMsg(buf);

            pid_t pid = fork();
            if (pid == 0) {
                char str_key[16];
                sprintf(str_key, "0x%08x", key);
                char *vec[] = {"/bin/ipcrm", "-M", str_key, NULL};

                if ((execv("/bin/ipcrm", vec)) == -1) {
                    errExit("execv", "getShmidServer");
                }
            }
            while (wait(0) == -1 && errno == EINTR);

            return getShmidServer();
        }
        errExit("shmget", "getShmidServer");
    }

    return shmid;
}

tile_t *shmServerAt() {
    tile_t *board = (tile_t *)shmat(_SHMID, NULL, 0); 
    if (board == SHMERR) {
        errExit("shmat", "shmServerAt");
    }
    
    return board;
}

tile_t * shmClientAt() {
    tile_t *board = (tile_t *)shmat(_SHMID, NULL, SHM_RDONLY);
    if (board == SHMERR) {
        errExit("shmat", "shmClientAt");
    }

    return board;
} 

void shmDt(void *shm_ptr) {
    if (shmdt(shm_ptr) == -1) {
        errExit("shmdt", "shmDt");
    }
}

void shmServerRm(int shmid) {
    if (shmctl(shmid, IPC_RMID, NULL) == -1) {
        errExit("shmctl", "shmServerRm");
    } 
}