//---------------------------------------------------------
// com.msg.cc
//---------------------------------------------------------

#include "check.h" // check

#include <cassert>    // assert
#include <cstring>    // strlen
#include <iostream>   // cout
#include <sys/msg.h>  // msgget, msgsnd, msgrcv
#include <sys/wait.h> // wait
#include <unistd.h>   // fork

//---------------------------------------------------------

int main()
{
    struct msgbuf
    {
        long mtype;
        char mtext[1];
    } msg = {1, {'\0'}};

    int msgid = check(msgget(IPC_PRIVATE, 0600));

    if (check(fork())) // parent/reader
    {
        std::cout << "parent/reader: ";
        do
        {
            check(msgrcv(msgid, &msg, 1, 1, 0));
            std::cout << msg.mtext[0];
        } while (msg.mtext[0] != '\0'); // ¿fin de mensaje?
        wait(nullptr);
    }
    else // child/writer
    {
        std::cout << " child/writer: ";
        for (char c = 'a'; c <= 'z'; ++c)
        {
            msg.mtext[0] = c;
            check(msgsnd(msgid, &msg, 1, 0));
            std::cout << msg.mtext[0];
        }
        msg.mtext[0] = '\0'; // fin de mensaje
        check(msgsnd(msgid, &msg, 1, 0));
    }

    std::cout << std::endl;
}

//---------------------------------------------------------