There are a few caveats to putting objects into shared memory. The most important ones all deal with pointers:
That's not to say you shouldn't try... Just try carefully and test a lot!
// $Id: page04.html,v 1.4 1999/04/03 21:56:33 jcej Exp $
#include "shmem.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 *argv[])
{
// Be sure the segment is sized to hold our object.
ACE_Shared_Memory_SV shm_server (SHM_KEY,
sizeof (SharedData),
ACE_Shared_Memory_SV::ACE_CREATE);
char *shm = (char *) shm_server.malloc ();
if (shm == 0)
ACE_ERROR_RETURN ((LM_ERROR,
"%p\n\t(%P|%t) Cannot create shared memory segment.\n"
"\tUse 'ipcs' to see if it already exists\n",
argv[0]),
100);
ACE_DEBUG ((LM_INFO,
"(%P|%t) Shared Memory is at 0x%x\n",
shm ));
/*
Use the placement new syntax to stuff the object into the
correct location. I think they generally reserve this for
the advanced class...
*/
SharedData *sd = new (shm) SharedData;
// Use the set() method to put some data into the object
sd->set ();
// Set the 'available' flag to zero so that we can wait on it
sd->available (0);
/*
Another cheesy busy loop while we wait for the object to
become available. The cool way would be to hide a semaphore
or two behind this method call & eliminate the sleep.
*/
while (sd->available () == 0)
ACE_OS::sleep (1);
// Show the user what's in the segment
sd->show ();
// All done.
if (shm_server.remove () < 0)
ACE_ERROR ((LM_ERROR,
"%p\n",
"remove"));
return 0;
}
#endif /* ACE_LACKS_SYSV_SHMEM */
// $Id: page04.html,v 1.4 1999/04/03 21:56:33 jcej Exp $
#include "shmem.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 *[])
{
ACE_Shared_Memory_SV shm_client (SHM_KEY,
sizeof (SharedData));
char *shm = (char *) shm_client.malloc ();
ACE_DEBUG ((LM_INFO,
"(%P|%t) Shared Memory is at 0x%x\n",
shm));
/*
More placement new. The constructor parameter prevents
clobbering what the server may have written with it's show()
method.
*/
SharedData *sd = new (shm) SharedData (0);
// Show it
sd->show ();
// Change it
sd->set ();
// Advertise it
sd->available (1);
shm_client.close ();
return 0;
}
#endif /* ACE_LACKS_SYSV_SHMEM */