/* Make the process sleep for SECONDS seconds, or until a signal arrives
   and is not ignored.  The function returns the number of seconds less
   than SECONDS which it actually slept (zero if it slept the full time).
   If a signal handler does a `longjmp' or modifies the handling of the
   SIGALRM signal while inside `sleep' call, the handling of the SIGALRM
   signal afterwards is undefined.  There is no return value to indicate
   error, but if `sleep' returns SECONDS, it probably didn't work.  */

/* sleep has a signal handler that stops on sigalrm
 * lets check it out:
 * Two threads, one to send events, one to sleep */

#include <unistd.h>
#include <stdlib.h>
#include <pthread.h>
#include <signal.h>
#include <stdio.h>
#include <string.h>

char buffer[2000];
void * sleeping();
void handle_signal(int i);

int main(void)
{
    /* setup thread */
    pthread_t sleeper;
    if(pthread_create(&sleeper, NULL, sleeping, NULL) != 0)
    {
        printf("Could not start sleeper thread\n");
    }

    /* interrupt sleeping thread on user input */
    printf("Send a message to the sleeper\n");
    while(1)
    {
        fgets(buffer, 2000, stdin);
        raise(SIGALRM);
    }

    /* join: this will never happen the way this is implemented */
    pthread_join(sleeper, NULL);
    exit(0);
}

void * sleeping()
{
    /* handle SIGALRM */
    struct sigaction action;
    sigset_t set;
    memset(&action, 0, sizeof(action));
    sigemptyset(&action.sa_mask);
    action.sa_flags = 0;
    action.sa_handler = handle_signal;
    sigaction(SIGALRM, &action, NULL);


    /* sleep until we get signal */
    while(1)
    {
        sleep(100000);
        printf("Woke Up!\n"); // when we run this never prints
                              // which means after the sigalrm
                              // we go back to sleep
                              // while the default handling does not
    }
}


void handle_signal(int sig)
{
    /* exit - make thread exit */
    if(strstr(buffer, "exit") != NULL)
    {
        exit(0);
    }
    else // echo message
    {
        write(1, "your message: ", 15);
        write(1, buffer, 2000);
        write(1, "\n", 2);
    }
}