diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/cmdline.c | 73 |
1 files changed, 45 insertions, 28 deletions
diff --git a/src/cmdline.c b/src/cmdline.c index ebb5060..a86b81b 100644 --- a/src/cmdline.c +++ b/src/cmdline.c @@ -20,10 +20,11 @@ union semun { #define S 0 -#define P 1 -#define Q 2 +#define W 1 +#define X 2 +#define Q 3 -#define SEMAPHORES 3 +#define SEMAPHORES 4 #define MEMORY_SIZE (2 * 1024) @@ -56,6 +57,7 @@ create_semaphores(void) /* Initialise the array. */ values.array = calloc(SEMAPHORES, sizeof(unsigned short)); + values.array[X] = 1; if (!values.array) goto fail; if (semctl(id, 0, SETALL, values.array) == -1) @@ -141,7 +143,7 @@ remove_shared_memory(key_t key) static int -acquire_semaphore(key_t key, int semaphore, int delta) +acquire_semaphore(key_t key, int semaphore, int delta, int undo) { struct sembuf op; int id; @@ -152,14 +154,14 @@ acquire_semaphore(key_t key, int semaphore, int delta) op.sem_op = -delta; op.sem_num = semaphore; - op.sem_flg = 0; + op.sem_flg = undo * SEM_UNDO; return semop(id, &op, 1); } static int -release_semaphore(key_t key, int semaphore, int delta) +release_semaphore(key_t key, int semaphore, int delta, int undo) { struct sembuf op; int id; @@ -170,7 +172,7 @@ release_semaphore(key_t key, int semaphore, int delta) op.sem_op = delta; op.sem_num = semaphore; - op.sem_flg = 0; + op.sem_flg = undo * SEM_UNDO; return semop(id, &op, 1); } @@ -197,7 +199,6 @@ zero_semaphore(key_t key, int semaphore) static int read_semaphore(key_t key, int semaphore, int *z, int *n, int *v) { - struct sembuf op; int id, r; id = semget(key, SEMAPHORES, 0600); @@ -224,7 +225,22 @@ read_semaphore(key_t key, int semaphore, int *z, int *n, int *v) static int -write_shared_memory(key_t key, const char *message) +write_semaphore(key_t key, int semaphore, int value) +{ + union semun semval; + int id; + + id = semget(key, SEMAPHORES, 0600); + if (id == -1) + return -1; + + semval.val = value; + return semctl(id, semaphore, SETVAL, semval); +} + + +static int +read_shared_memory(key_t key, char *message) { int id, saved_errno; void *address = NULL; @@ -233,11 +249,11 @@ write_shared_memory(key_t key, const char *message) if (id == -1) goto fail; - address = shmat(id, NULL, 0); + address = shmat(id, NULL, SHM_RDONLY); if ((address == (void *)-1) || !address) goto fail; - memcpy(address, message, (strlen(message) + 1) * sizeof(char)); + strncpy(message, address, MEMORY_SIZE); if (shmdt(address) == -1) goto fail; @@ -254,7 +270,7 @@ fail: static int -read_shared_memory(key_t key, char *message) +write_shared_memory(key_t key, const char *message) { int id, saved_errno; void *address = NULL; @@ -263,11 +279,11 @@ read_shared_memory(key_t key, char *message) if (id == -1) goto fail; - address = shmat(id, NULL, SHM_RDONLY); + address = shmat(id, NULL, 0); if ((address == (void *)-1) || !address) goto fail; - strncpy(message, address, MEMORY_SIZE); + memcpy(address, message, (strlen(message) + 1) * sizeof(char)); if (shmdt(address) == -1) goto fail; @@ -306,26 +322,27 @@ main(int argc, char *argv[]) t(remove_semaphores(key_sem)); t(remove_shared_memory(key_sem)); - } else if (!strcmp(argv[1], "listen")) { /* TODO must support cancellation */ - t(release_semaphore(key_sem, S, 1)); + } else if (!strcmp(argv[1], "listen")) { + t(release_semaphore(key_sem, S, 1, 1)); for (;;) { - t(zero_semaphore(key_sem, S)); + t(release_semaphore(key_sem, Q, 1, 0)); + t(zero_semaphore(key_sem, Q)); t(read_shared_memory(key_shm, read_message)); printf("%s\n", read_message); - t(release_semaphore(key_sem, Q, 1)); - t(zero_semaphore(key_sem, Q)); - t(release_semaphore(key_sem, S, 1)); - t(release_semaphore(key_sem, P, 1)); + t(release_semaphore(key_sem, W, 1, 1)); + t(acquire_semaphore(key_sem, S, 1, 1)); + t(zero_semaphore(key_sem, S)); + t(release_semaphore(key_sem, S, 1, 1)); + t(acquire_semaphore(key_sem, W, 1, 1)); } } else if (!strcmp(argv[1], "broadcast")) { - t(read_semaphore(key_sem, S, &value, NULL, NULL)); - if (value) { - t(write_shared_memory(key_shm, message)); - t(acquire_semaphore(key_sem, S, value)); - t(acquire_semaphore(key_sem, Q, value)); - t(acquire_semaphore(key_sem, P, value)); - } + t(acquire_semaphore(key_sem, X, 1, 1)); + t(zero_semaphore(key_sem, W)); + t(write_shared_memory(key_shm, message)); + t(write_semaphore(key_sem, Q, 0)); + t(zero_semaphore(key_sem, S)); + t(release_semaphore(key_sem, X, 1, 1)); } else return 2; |