semaphores.c

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#include "sr_communications/ipc/semaphores.h"


int createKey(key_t * semKey, char * semFile)
{
    if (access(semFile, F_OK) != 0) {
        if (creat(semFile, 0777) == -1) {
            perror("createKey() - error creating file keys for semaphore\n");
            fprintf(stderr, "kcreateKey %s\n", semFile);
            return -1;
        }
    }

    if ((*semKey = ftok(semFile, 'S')) < 0) {
        perror("createKey() - error ftok ");
        return -2;
    }

    return (int) *semKey;
}


int getSemID(key_t semKey, int * semID)
{
    *semID = semget(semKey, 1, IPC_CREAT | 0777);
    if (*semID == -1) {
        perror("error semget");
        return -1;
    }

    if (semctl(*semID, 0, SETVAL, 1) < 0) {
        perror("error semctl");
        return -2;
    }

    return (int) *semID;
}


int rmSem(int semID)
{
    struct sembuf arg[] = {0,
                           0,
                           0};

    if (semctl(semID, 0, IPC_RMID, arg) < 0) {
        perror("rmSem() - error semctl");
        return -1;
    }

    return 0;
}


int waitSem(int semID)
{
    struct sembuf opIn[] = {0,
                            -1,
                            0}; /*  opIn.sem_num = 0;
     opIn.sem_op = -1;
     opIn.sem_flg = 0;
     */
    if (semop(semID, opIn, 1) < 0) {
        perror("waitSem() - error semop");
        return -1;
    }

    return 0;
}


int freeSem(int semID)
{
    struct sembuf opOut[] = {0,
                             1,
                             0};

    if (semop(semID, opOut, 1) < 0) {
        perror("freeSem() - error semop");
        return -1;
    }

    return 0;
}