1 files changed, 174 insertions, 9 deletions

diff --git a/src/semaphore.c b/src/semaphore.c
index 5447c82..8c9f099 100644
--- a/src/semaphore.c
+++ b/src/semaphore.c
@@ -2,6 +2,7 @@
 #include <stdio.h>
 #include <time.h>
 #include <errno.h>
+#include <string.h>
 
 #include <sys/ipc.h>
 #include <sys/sem.h>
@@ -16,17 +17,26 @@ union semun {
 #endif
 
 
+#define P 0
+#define Q 1
+#define N 2
+
+#define SEMAPHORES 3
+
+
 char *argv0;
 
 
-int main(int argc, char *argv[])
+static int
+create_semaphores(void)
 {
 	key_t key;
-	int id = -1;
+	int id = -1, saved_errno;
+	union semun values;
 
-	(void) argc;
-	argv0 = *argv;
+	values.array = NULL;
 
+	/* Create semaphore array. */
 	srand(time(NULL));
 	for (;;) {
 		double r = (double)rand();
@@ -35,24 +45,179 @@ int main(int argc, char *argv[])
 		key = (key_t)r + 1;
 		if (key == IPC_PRIVATE)
 			continue;
-		id = semget(key, 3, IPC_CREAT | IPC_EXCL | 0600);
+		id = semget(key, SEMAPHORES, IPC_CREAT | IPC_EXCL | 0600);
 		if (id != -1)
 			break;
 		if ((errno != EEXIST) && (errno != EINTR))
 			goto fail;
 	}
 
-	printf("key:%zx, id:%i\n", (size_t)key, id);
-
-	if (semctl(id, 0, IPC_RMID) == -1)
+	/* Initialise the array. */
+	values.array = calloc(SEMAPHORES, sizeof(unsigned short));
+	if (values.array == NULL)
 		goto fail;
+	if (semctl(id, 0, SETALL, values.array) == -1)
+		goto fail;
+	free(values.array);
+	values.array = NULL;
 
+	printf("key:%zi(x%zx), id:%i\n", (ssize_t)key, (size_t)key, id);
 	return 0;
 
 fail:
-	perror(argv0);
+	saved_errno = errno;
 	if ((id != -1) && (semctl(id, 0, IPC_RMID) == -1))
 		perror(argv0);
+	free(values.array);
+	errno = saved_errno;
+	return -1;
+}
+
+
+static int
+remove_semaphores(key_t key)
+{
+	int id = semget(key, SEMAPHORES, 0600);
+
+	if (id == -1)
+		return -1;
+
+	if (semctl(id, 0, IPC_RMID) == -1)
+		return -1;
+
+	return 0;
+}
+
+
+static int
+acquire_semaphore(key_t key, int semaphore, int delta)
+{
+	struct sembuf op;
+	int id;
+
+	id = semget(key, SEMAPHORES, 0600);
+	if (id == -1)
+		return -1;
+
+	op.sem_op = -delta;
+	op.sem_num = semaphore;
+	op.sem_flg = 0;
+
+	return semop(id, &op, 1);
+}
+
+
+static int
+release_semaphore(key_t key, int semaphore, int delta)
+{
+	struct sembuf op;
+	int id;
+
+	id = semget(key, SEMAPHORES, 0600);
+	if (id == -1)
+		return -1;
+
+	op.sem_op = delta;
+	op.sem_num = semaphore;
+	op.sem_flg = 0;
+
+	return semop(id, &op, 1);
+}
+
+
+static int
+zero_semaphore(key_t key, int semaphore)
+{
+	struct sembuf op;
+	int id;
+
+	id = semget(key, SEMAPHORES, 0600);
+	if (id == -1)
+		return -1;
+
+	op.sem_op = 0;
+	op.sem_num = semaphore;
+	op.sem_flg = 0;
+
+	return semop(id, &op, 1);
+}
+
+
+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);
+	if (id == -1)
+		return -1;
+
+	if (r = semctl(id, semaphore, GETZCNT), r == -1)
+		return -1;
+	if (z)
+		*z = r;
+
+	if (r = semctl(id, semaphore, GETNCNT), r == -1)
+		return -1;
+	if (n)
+		*n = r;
+
+	if (r = semctl(id, semaphore, GETVAL), r == -1)
+		return -1;
+	if (v)
+		*v = r;
+
+	return 0;
+}
+
+
+int
+main(int argc, char *argv[])
+{
+	int r = -1, saved_errno, value;
+	key_t key = argc > 2 ? (key_t)atoll(argv[2]) : 0;
+
+	argv0 = *argv;
+
+	if (!strcmp(argv[1], "create")) {
+		r = create_semaphores();
+	} else if (!strcmp(argv[1], "remove")) {
+		r = remove_semaphores(key);
+	} else if (!strcmp(argv[1], "pick-up")) {
+		r = release_semaphore(key, N, 1);
+	} else if (!strcmp(argv[1], "hang-up")) {
+		r = acquire_semaphore(key, N, 1);
+	} else if (!strcmp(argv[1], "listen")) {
+		r = acquire_semaphore(key, Q, 1);
+		if (r) {
+			saved_errno = errno;
+			r = release_semaphore(key, P, 1);
+			if (r)
+				perror(argv0);
+			errno = saved_errno;
+			goto fail;
+		}
+		printf("read here\n");
+		r = release_semaphore(key, P, 1);
+	} else if (!strcmp(argv[1], "speak")) {
+		printf("write here\n");
+		r = read_semaphore(key, N, NULL, NULL, &value);
+		if (r)
+			goto fail;
+		r = release_semaphore(key, Q, value);
+		if (r)
+			goto fail;
+		r = acquire_semaphore(key, P, value);
+	} else
+		return 2;
+
+	if (r)
+		goto fail;
+	return 0;
+
+fail:
+	perror(argv0);
 	return 1;
 }