Mmap and structure
- by blid..pl
I'm working some code including communication between processes, using semaphores. I made structure like this:
typedef struct container {
sem_t resource, mutex;
int counter;
} container;
and use in that way (in main app and the same in subordinate processes)
container *memory;
shm_unlink("MYSHM"); //just in case
fd = shm_open("MYSHM", O_RDWR|O_CREAT|O_EXCL, 0);
if(fd == -1) {
printf("Error");
exit(EXIT_FAILURE);
}
memory = mmap(NULL, sizeof(container), PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);
ftruncate(fd, sizeof(container));
Everything is fine when I use one of the sem_ functions, but when I try to do something like
memory->counter = 5;
It doesn't work. Probably I got something wrong with pointers, but I tried almost everything and nothing seems to work. Maybe there's a better way to share variables, structures etc between processes ?
Unfortunately I'm not allowed to use boost or something similiar, the code is for educational purposes and I'm intentend to keep as simple as it's possible.
