destroy added

kernel/sync/semaphore.h

@@ -33,7 +33,7 @@ class Semaphore {
 	 */
 	explicit Semaphore(unsigned c = 0) : counter(c) {}
 	unsigned counter;
-
+  bool used;
 	/*! \brief Wait for access to the critical area.
 	 *
 	 *  Enter/decrement/wait operation: If the counter is greater than 0, then

kernel/syscall/skeleton.cc

@@ -49,23 +49,38 @@ bool sem_init(Vault &vault, size_t id, uint32_t value) {
   if (id >= vault.MAX_SEMS) {
     return false;             // out‐of‐range id
   }
+  if (vault.sems[id].used==1){
+    return false;  //already in use
+  }
+
   vault.sems[id].counter=value;
 	return true;
 }
 
-void sem_destroy(Vault &vault, size_t id) {
-	(void)vault;
-	(void)id;
+bool sem_destroy(Vault &vault, size_t id) {
+  if (id >= vault.MAX_SEMS) {
+    return false;             // out‐of‐range id
+  }
+  if (vault.sems[id].used==0){
+    return false;  //already in free
+  }
+
+  vault.sems[id].used=0;
+  vault.sems[id].counter=0;
+	return true;
 }
 
-void sem_signal(Vault &vault, size_t id) {
+bool sem_signal(Vault &vault, size_t id) {
 	(void)vault;
 	(void)id;
+
+  return true;
 }
 
-void sem_wait(Vault &vault, size_t id) {
+bool sem_wait(Vault &vault, size_t id) {
 	(void)vault;
 	(void)id;
+  return true;
 }
 
 void exit(Vault &vault) { (void)vault; }

kernel/syscall/skeleton.h

@@ -18,9 +18,9 @@ size_t write(Vault &vault, uint32_t id, const void *buffer, size_t size);
 size_t read(Vault &vault, uint32_t id);
 void sleep(Vault &vault, size_t ms);
 bool sem_init(Vault &vault, size_t id, uint32_t value);
-void sem_destroy(Vault &vault, size_t id);
-void sem_signal(Vault &vault, size_t id);
-void sem_wait(Vault &vault, size_t id);
+bool sem_destroy(Vault &vault, size_t id);
+bool sem_signal(Vault &vault, size_t id);
+bool sem_wait(Vault &vault, size_t id);
 void exit(Vault &vault);
 void kill(Vault &vault, size_t pid);