Message_que.cpp

/*
 Message queue implementation—Copyright (c) 2002 J. S. Gray
*/
#include "Message_que.h"
#include <cstdio>

// Message queue constructor.
Message_que::Message_que(const char the_key) {
    ipckey = ftok(".", the_key);
    msqid = -1;
}

// Remove the message queue (if this process created it)
void
Message_que::Remove() {
    if (msgctl(msqid, IPC_RMID, (struct msqid_ds *) 0) == -1)
        exit(5);
}

// Place a message in the message queue.
void
Message_que::Enque(void *msg, int msg_size) {
    if (msgsnd(msqid, msg, msg_size, 0) == -1)
        exit(3);
}

// Return a message from the message queue.
int
Message_que::Deque(void *msg, int msg_size, int msg_type) {
    int n;
    memset(msg, 0x0, msg_size); // clear space
    if ((n = msgrcv(msqid, msg, msg_size, msg_type, IPC_NOWAIT)) == -1)
        exit(4);
    return n;
}

// True if message queue exists else false.
bool
Message_que::Exist(const char the_key) {
    return (msgget(ipckey, 0) != -1);
}

// Generate a new message queue.
void
Message_que::Create() {
    if ((msqid = msgget(ipckey, IPC_CREAT | 0660)) == -1)
        exit(1);
}

// Acquire (gain access to) existing message queue.
void
Message_que::Acquire() {
    if ((msqid = msgget(ipckey, 0)) == -1)
        exit(2);
}