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/* ex7

 *

 * Test case that illustrates a timed wait on a condition variable.

 */

#include <errno.h>

#include <stdio.h>

#include <string.h>

#include <pthread.h>

#include <sys/time.h>

#include <unistd.h>

/* Our event variable using a condition variable contruct. */

typedef struct {

    pthread_mutex_t     mutex;

    pthread_cond_t      cond;

    int                 flag;

} event_t;

/* Global event to signal main thread the timeout of the child thread. */

event_t main_event;

void *

test_thread (void *ms_param)

{

    int status = 0;

    event_t foo;

    struct timespec time;

    struct timeval  now;

    long ms = (long) ms_param;

    /* initialize cond var */

    pthread_cond_init(&foo.cond, NULL);

    pthread_mutex_init(&foo.mutex, NULL);

    foo.flag = 0;

    /* set the time out value */

    printf("waiting %ld ms ...\n", ms);

    gettimeofday(&now, NULL);

    time.tv_sec  = now.tv_sec + ms/1000 + (now.tv_usec + (ms%1000)*1000)/1000000;

    time.tv_nsec = ((now.tv_usec + (ms%1000)*1000) % 1000000) * 1000;

    /* Just use this to test the time out. The cond var is never signaled. */

    pthread_mutex_lock(&foo.mutex);

    while (foo.flag == 0 && status != ETIMEDOUT) {

        status = pthread_cond_timedwait(&foo.cond, &foo.mutex, &time);

    }

    pthread_mutex_unlock(&foo.mutex);

    /* post the main event */

    pthread_mutex_lock(&main_event.mutex);

    main_event.flag = 1;

    pthread_cond_signal(&main_event.cond);

    pthread_mutex_unlock(&main_event.mutex);

    /* that's it, bye */

    return (void*) status;

}

int

main (void)

{

  unsigned long count;

  setvbuf (stdout, NULL, _IONBF, 0);

  /* initialize main event cond var */

  pthread_cond_init(&main_event.cond, NULL);

  pthread_mutex_init(&main_event.mutex, NULL);

  main_event.flag = 0;

  for (count = 0; count < 20; ++count)

  {

      pthread_t thread;

      int status;

      /* pass down the milli-second timeout in the void* param */

      status = pthread_create (&thread, NULL, test_thread, (void*) (count*100));

      if (status != 0) {

          printf ("status = %d, count = %lu: %s\n", status, count,

                  strerror (errno));

          return 1;

      }

      else {

          /* wait for the event posted by the child thread */

          pthread_mutex_lock(&main_event.mutex);

          while (main_event.flag == 0) {

              pthread_cond_wait(&main_event.cond, &main_event.mutex);

          }

          main_event.flag = 0;

          pthread_mutex_unlock(&main_event.mutex);

          printf ("count = %lu\n", count);

      }

      usleep (10);

  }

  return 0;

}