Reading Shared Multi-Queue

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This example shows how to read a Shared Multi-Queue using the Shared Memory Arena library.

We already ran this program in the last example in Writing Shared Multi-Queue.

Looking at the Source

From examples/tutorial/smq_read.c

#include <unistd.h>    /* for usleep() */
#include <signal.h>    /* for signal() */
#include <shm_arena.h> /* for Shared Memory Arena Library */

static int running = 1;

static void catcher(int sig)
{
  printf("catch signal %d\n", sig);
  running = 0;
}

int main(void)
{
  smq_t q;

  signal(SIGINT, catcher);

  q = smq_get(NULL, sizeof(int), 20, "q_count", O_CREAT);
  if(!q)
    {
      printf("smq_get() failed\n");
      return 1;
    }

  while(running)
    {
      int num;

      num = smq_rdlock(q, 0);

      while(num > 0)
    {
      int *ptr;
      ptr = smq_read(q);
      printf("%d ", *ptr);
      fflush(stdout);
      num--;
    }

      smq_unlock(q);

      sleep(1);
    }

  return 0;
}

We loop: read-lock the Shared Multi-Queue, read all the entries that are there, unlock the Shared Multi-Queue, and then sleep.

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