int shm_common_exists(int key)
{
struct shm_status sm;
int retval;
if (shmdrv_loaded) {
memset(&sm, 0, sizeof(struct shm_status));
sm.driver_fd = shmdrv_driver_fd();
sm.key = key;
sm.flags = 0;
retval = shmdrv_status(&sm);
close(sm.driver_fd);
return retval == 0;
} else {
int shmfd;
char segment_name[LINELEN];
sprintf(segment_name, SHM_FMT, INSTANCE_OF(key), key);
if ((shmfd = shm_open(segment_name, O_RDWR,
(S_IRUSR|S_IWUSR|S_IRGRP|S_IWGRP))) < 0) {
retval = 0;
} else {
close(shmfd);
retval = 1;
}
return retval;
}
}
int _rtapi_shmem_exists(int userkey) {
struct shm_status sm;
sm.key = userkey;
return !shmdrv_status(&sm);
}
int shm_common_new(int key, int *size, int instance, void **shmptr, int create)
{
struct shm_status sm;
int retval;
int is_new = 0;
if (shmdrv_loaded) {
// use shmdrv kernel driver
sm.driver_fd = shmdrv_driver_fd();
sm.key = key;
sm.size = (size == NULL? 0: *size);
sm.flags = 0;
retval = shmdrv_status(&sm); // check if exists
if (retval && !create) {
// didnt exist, but just attach requested, so fail
close(sm.driver_fd);
return -ENOENT;
}
if (retval) { // didnt exist, so create
retval = shmdrv_create(&sm);
if (retval < 0) {
return retval;
}
is_new = 1;
}
// now attach
retval = shmdrv_attach(&sm, shmptr);
if (retval < 0) {
close(sm.driver_fd);
return retval;
}
// if size was passed in as 0 (attach), fill in actual size
if (size && (*size == 0))
*size = sm.size;
close(sm.driver_fd);
return is_new;
} else {
// use POSIX shared memory
int shmfd, mmap_size;
mode_t old_umask;
char segment_name[LINELEN];
if ((size == 0) || (*size == 0))
mmap_size = 0;
else
mmap_size = *size;
sprintf(segment_name, SHM_FMT, instance, key);
old_umask = umask(0); //S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP);
if (create && ((shmfd = shm_open(segment_name,
(O_CREAT | O_EXCL | O_RDWR),
(S_IRUSR|S_IWUSR|S_IRGRP|S_IWGRP))) > 0)) {
// initial creation
if (fchown(shmfd, getuid(),getgid()))
perror("fchown");
if (ftruncate(shmfd, mmap_size))
perror("ftruncate");
is_new = 1;
} else if((shmfd = shm_open(segment_name, O_RDWR,
(S_IRUSR|S_IWUSR|S_IRGRP|S_IWGRP))) < 0) {
// just attach, and that failed:
umask(old_umask);
return -errno;
} else { // shmfd open
if (mmap_size == 0) {
struct stat st;
if (fstat(shmfd, &st)) {
perror("fstat");
return -errno;
}
mmap_size = st.st_size;
}
}
if((*shmptr = mmap(0, mmap_size, (PROT_READ | PROT_WRITE),
MAP_SHARED, shmfd, 0)) == MAP_FAILED) {
perror("shm_common_new:mmap");
close(shmfd);
umask(old_umask);
return -errno;
}
if (size) // return actual shm size as determined in attach
*size = mmap_size;
umask(old_umask);
close(shmfd);
return is_new;
}
}
