msg_queue.c

#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/ipc.h>
#include <sys/msg.h>

#include "msg_queue.h"

queue_t queue_create()
{
    key_t keyval = ftok(QUEUE_NAME, QUEUE_ID);
    return msgget(keyval, IPC_CREAT | 0660);
}

queue_t queue_open()
{
    key_t keyval = ftok(QUEUE_NAME, QUEUE_ID);
    return msgget(keyval, 0660);
}

int queue_send(queue_t qid, message_t *message)
{
    int length = sizeof(message_t) - sizeof(long);

    return msgsnd(qid, message, length, 0);
}

int queue_read(queue_t qid, long type, message_t *message)
{
    int length = sizeof(message_t) - sizeof(long);

    return msgrcv(qid, message, length, type, 0);
}

int queue_peek(queue_t qid, long type)
{
    if (msgrcv(qid, NULL, 0, type, IPC_NOWAIT) == -1) {
        if (errno == E2BIG)
            return 1;
    }

    return 0;
}

int queue_remove(queue_t qid)
{
    return msgctl(qid, IPC_RMID, 0);
}