ACE Tutorial 019

ACE Tutorial 019 Sharing your Memories

The client app looks much like the server. We could have included the CREATE flag with no ill effects but note the use of close() instead of remove(). Picking the correct detachment method is rather important!

// $Id$

// Again, the common stuff
#include "shmem.h"

#include "ace/Log_Msg.h"

#if defined(ACE_LACKS_SYSV_SHMEM)
int
main (int, char *[])
{
  ACE_ERROR_RETURN ((LM_ERROR,
                     "System V Shared Memory not available on this platform\n"),
                    100);
}
#else // ACE_LACKS_SYSV_SHMEM
int
main (int, char *[])
{
  /*
    Attach ourselves to the shared memory segment.
    */
  ACE_Shared_Memory_SV shm_client (SHM_KEY, SHMSZ);

  /*
    Get our reference to the segment...
    */
  char *shm = (char *) shm_client.malloc ();

  /*
    If the segment identified by SHM_KEY didn't exist then we'll
    get back a 0 from malloc().  You should do this check even
    if you include the CREATE flag 'cause you never know when it
    might fail.
    */
  if (shm == 0)
    ACE_ERROR_RETURN ((LM_ERROR,
                       "(%P|%t) Could not get the segment!\n"),
                      100);

  /*
    Does this match what your server said?
    */
  ACE_DEBUG ((LM_INFO,
              "(%P|%t) Shared Memory is at 0x%x\n",
              shm ));

  /*
    Show the shared data to the user and convert it all to
    uppper-case along the way.
    */
  for (char *s = shm; *s != '\0'; s++)
    {
      putchar (*s);
      *s = toupper(*s);
    }

  putchar ('\n');

  /*
    Flag the server that we're done.
    */
  *shm = '*';

  /*
    Here, we use close() instead of remove().  Remember, that
    will just remove our attachment to the segment.  Look
    closely at the 'nattch' column of the ipcs output & you'll
    see that this decrements it by one.
    */
  shm_client.close();

  return 0;
}

#endif /* ACE_LACKS_SYSV_SHMEM */

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