extended code to advanced input functionality

OS/C/theory/sync/semaextraposts.c

@@ -1,23 +1,28 @@
 #include <stdio.h>
 #include <pthread.h>
 #include <semaphore.h>
-#include <sys/semaphore.h>
+#include <fcntl.h>
+#include <stdatomic.h>
 
-sem_t my_semaphore;
+atomic_int semaphore_value = 5;
+sem_t *my_semaphore;
 
 int main(){
-    sem_init(&my_semaphore, 0, 5);
+    my_semaphore = sem_open("/my_sem", O_CREAT, 0644, atomic_load(&semaphore_value));
-    int sem_val;
+    int sem_val = atomic_load(&semaphore_value);
-    sem_getvalue(&my_semaphore, &sem_val);
+    printf("Initial semaphore value: %d\n", sem_val);
+
+    sem_post(my_semaphore);
+    atomic_fetch_add(&semaphore_value, 1);
+    sem_post(my_semaphore);
+    atomic_fetch_add(&semaphore_value, 1);
+    sem_post(my_semaphore);
+    atomic_fetch_add(&semaphore_value, 1);
+
+    sem_val = atomic_load(&semaphore_value);
     printf("Semaphore value after extra posts: %d\n", sem_val);
 
-    sem_post(&my_semaphore);
+    sem_close(my_semaphore);
-    sem_post(&my_semaphore);
+    sem_unlink("/my_sem");
-    sem_post(&my_semaphore);
-
-    sem_getvalue(&my_semaphore, &sem_val);
-    printf("Semaphore value after extra posts: %d\n", sem_val);
-
-    sem_destroy(&my_semaphore);
     return 0;
 }

OS/C/theory/sync/withoutsemaphores.c

@@ -4,8 +4,8 @@
 int counter = 0;
 
 void* increment(void* arg) {
-    for (int i = 0; i < 100000; i++) {
+    for (int i = 0; i < 1000000; i++) {
-        counter++;
+        counter++; // No synchronization, will lead to race condition
     }
     return NULL;
 }

OS/C/theory/sync/withsema.c

@@ -1,32 +1,33 @@
+#include <stdatomic.h>
 #include <stdio.h>
 #include <pthread.h>
 #include <semaphore.h>
-#include <sys/semaphore.h>
+#include <dispatch/dispatch.h>
 
-int counter = 0; // shared resource
+atomic_int counter = 0; // shared resource
-sem_t semaphore; // semaphore declaration
+dispatch_semaphore_t semaphore; // semaphore declaration
 
 void* increment(void* arg) {
     for (int i = 0; i < 100000; i++) {
-        sem_wait(&semaphore); // lock
+        dispatch_semaphore_wait(semaphore, DISPATCH_TIME_FOREVER); // lock
-        counter++; // critical section
+        atomic_fetch_add(&counter, 1); // critical section
-        sem_post(&semaphore); // unlock
+        dispatch_semaphore_signal(semaphore); // unlock
     }
     return NULL;
 }
 
 int main() {
     pthread_t t1, t2;
-    sem_init(&semaphore, 0, 1); // initialize semaphore with value 1
+    semaphore = dispatch_semaphore_create(1); // initialize semaphore with value 1
 
     pthread_create(&t1, NULL, increment, NULL);
     pthread_create(&t2, NULL, increment, NULL);
     pthread_join(t1, NULL);
     pthread_join(t2, NULL);
 
-    sem_destroy(&semaphore);
+    dispatch_release(semaphore);
 
-    printf("Final Counter Value (with semaphores): %d\n", counter);
+    printf("Final Counter Value (with semaphores): %d\n", atomic_load(&counter));
 
     return 0;
 }

OS/C/theory/sync/withsema4.c

@@ -2,14 +2,15 @@
 #include <pthread.h>
 #include <semaphore.h>
 #include <fcntl.h>
+#include <stdatomic.h>
 
-int counter = 0; // shared resource
+atomic_int counter = 0; // shared resource
 sem_t *semaphore; // semaphore declaration
 
 void* increment(void* arg) {
     for (int i = 0; i < 100000; i++) {
         sem_wait(semaphore); // lock
-        counter++; // critical section
+        atomic_fetch_add(&counter, 1); // critical section
         sem_post(semaphore); // unlock
     }
     return NULL;
@@ -37,7 +38,7 @@ int main() {
     sem_close(semaphore);
     sem_unlink("/mysem");
 
-    printf("Final Counter Value (with semaphores): %d\n", counter);
+    printf("Final Counter Value (with semaphores): %d\n", atomic_load(&counter));
 
     return 0;
 }