// Does the same to attach_shm().
// If shared memory segment is newly created, 'iscreate' is set to 1.
// If shared memory segment already exists, 'iscreate' is set to 0.
void *attach_shm2(const char *shmstr, int defaultkey, int shmsize, int *iscreate)
{
void *shmptr = NULL;
int shmkey, shmid;
shmkey = search_shmkey(shmstr);
if (shmkey < 1024)
shmkey = defaultkey;
shmid = shmget(shmkey, shmsize, 0);
if (shmid < 0) {
shmid = shmget(shmkey, shmsize, IPC_CREAT | 0644);
*iscreate = 1;
if (shmid < 0) {
attach_err(shmkey, "shmget", errno);
return NULL;
}
shmptr = (void *) shmat(shmid, NULL, 0);
if (shmptr == (void *) - 1) {
attach_err(shmkey, "shmat", errno);
return NULL;
}
memset(shmptr, 0, shmsize);
} else {
*iscreate = 0;
shmptr = (void *) shmat(shmid, NULL, 0);
if (shmptr == (void *) -1) {
attach_err(shmkey, "shmat", errno);
return NULL;
}
}
return shmptr;
}
void* attach_shm(char* shmstr, int defaultkey, int shmsize)
{
void *shmptr;
int shmkey, shmid;
shmkey = search_shmkey(shmstr);
if (shmkey < 1024)
shmkey = defaultkey;
shmid = shmget(shmkey, shmsize, 0);
if (shmid < 0)
{
shmid = shmget(shmkey, shmsize, IPC_CREAT | 0640);
if (shmid < 0)
attach_err(shmkey, "shmget", errno);
shmptr = (void *) shmat(shmid, NULL, 0);
if (shmptr == (void *) -1)
attach_err(shmkey, "shmat", errno);
memset(shmptr, 0, shmsize);
}
else
{
shmptr = (void *) shmat(shmid, NULL, 0);
if (shmptr == (void *) -1)
attach_err(shmkey, "shmat", errno);
}
return shmptr;
}
// Finds shared memory key corresponding to 'shmstr'.
// If not found, uses defaultkey instead.
// Then mark the segment to be destroyed.
// Returns result of 'shmctl' (-1 on error).
int remove_shm(const char *shmstr, int defaultkey, int shmsize)
{
int shmkey, shmid;
shmkey = search_shmkey(shmstr);
if (shmkey < 1024)
shmkey = defaultkey;
shmid = shmget(shmkey, shmsize, 0);
return shmctl(shmid, IPC_RMID, NULL);
}
// Finds shared memory key corresponding to 'shmstr'.
// If not found, uses defaultkey instead.
// Tries to get shared memory segment according to key.
// If the shared memory segment does not exist, creates one.
// Finally attaches the shared memory segment to the process.
// Returns the address of the attached shared memory segment,
// NULL pointer on error.
void *attach_shm(const char *shmstr, int defaultkey, int shmsize)
{
void *shmptr = NULL;
int shmkey, shmid;
// Search for shared memory(shm) key. If not found, use defaultkey.
shmkey = search_shmkey(shmstr);
if (shmkey < 1024)
shmkey = defaultkey;
// Get existing shm.
shmid = shmget(shmkey, shmsize, 0);
if (shmid < 0) {
// If shm does not exist, try to create one.
shmid = shmget(shmkey, shmsize, IPC_CREAT | 0640);
if (shmid < 0) {
attach_err(shmkey, "shmget", errno);
return NULL;
}
// Attach shm to the process.
shmptr = (void *) shmat(shmid, NULL, 0);
if (shmptr == (void *) -1) {
attach_err(shmkey, "shmat", errno);
return NULL;
}
// Initialization.
memset(shmptr, 0, shmsize);
} else {
// shm already exists.
// Attach shm to the process. No init needed.
shmptr = (void *) shmat(shmid, NULL, 0);
if (shmptr == (void *) -1) {
attach_err(shmkey, "shmat", errno);
return NULL;
}
}
return shmptr;
}
