using pthreads and callbacks

[robUK2]

Hello,

GCC C99

I have just created a simple program, as this is my first time with threads and callbacks.
However, I am wondering do I really need a callback. Can I just call the timeout_cb() function
after the sleep() as completed? Maybe I don't understand, why a callback is needed at all?

Just one more question. The time could be set for a long as 30 seconds. However, the task might
complete before then. Is there any way to stop the timer. As if the task has been completed before
the 30 seconds, I don't want the call back to be called at all? What is I need is stop_timer.

I was thinking is there anyway to stop the sleep once it has started?

Many thanks for any suggestions,

#include <pthread.h>
#include <stdio.h>

/* call back function - inform the user the time has expired */
void timeout_cb()
{
    printf("=== your time is up ===\n");
}

/* Go to sleep for a period of seconds */
static void* g_start_timer(void *args)
{
    /* function pointer */
    void (*function_pointer)();

    /* cast the seconds passed in to int and 
     * set this for the period to wait */
    int seconds = *((int*) args);
    printf("go to sleep for %d\n", seconds);
    
    /* assign the address of the cb to the function pointer */
    function_pointer = timeout_cb;
    
    sleep(seconds);
    /* call the cb to inform the user time is out */
    (*function_pointer)();
	
    pthread_exit(NULL);
}

int main()
{
    pthread_t thread_id;
    int seconds = 3;
    int rc;

    rc =  pthread_create(&thread_id, NULL, g_start_timer, (void *) &seconds);
    if(rc)
	printf("=== Failed to create thread\n");

    pthread_join(thread_id, NULL);

    printf("=== End of Program - all threads in ===\n");

    return 0;
}

 

[victorv]

hi,
working in inter-process comunication,
(probably with trhread is similar),
when a process "sleeps", you can send a signal()
with WAKE signal:
if the process does not receive signal, programs
continues after sleep statement;
if it receive signal WAKE or Ctrl-C (if it is running in console mode), the program jumps at signal (callback) routine, that you have declared.

ciao
vittorio